Numerical Analysis of Axisymmetric Solids by the Finite Element Method: Use in Concrete, Steel and Mixed Steel-Concrete Elements



<big>'''Numerical Analysis of Axisymmetric Solids by the Finite Element Method: Use in Concrete, Steel and Mixed Steel-Concrete Elements'''</big>

<span style="text-align: center; font-size: 75%;">
[[Image:Draft_Ferreira_761749235-picture-Text Box 3.svg|center|230px]]
</span>
[[Image:Draft_Ferreira_761749235-picture-Text Box 2.svg|center|600px]]

'''1 INTRODUCTION'''

According to Vicente and Oliveira (3) the term Finite Elements was used for the first time in literature in 1960 by Clough, in an Engineering paper on the application of plane elasticity, although the basic idea of the method was already being used by mathematicians, physicists and engineers for some years. Because of its simplicity, efficiency and good accuracy,  the method became one of the main tools of structural analysis for obtaining displacements, stresses and strains in the domain and contour of structures in the last years.

The objective of this paper is to present the numerical results of the implementation of a mathematical formulation based on the Finite Element Method for the analysis of axisymmetric structures characterized by a cross section with an axis of revolution (see Figure 1), under axisymmetric loading and with materials in linear elastic regime. Fortran 90/95 (1) programming language was used to implement this formulation which allows obtaining stress, strain and displacement values along the axisymmetric structure. Finite triangular elements with three nodes called CST (Constant Strain Triangle) were used to discretize the structure and as the FEM formulation adopted allows assessing stresses, strains and displacements only at the centroid of the element, a Lagrange polynomial interpolation was used to determine those magnitudes at the nodes of the elements or at any other point of the structure. It is worth to note that the implemented computer program was called Prograxisymmetric.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image1.png|246px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 1'''</span>. Axisymmetric solid<span style="text-align: center; font-size: 75%;">.</span></div>

=2 FORMULATION=

Problems involving three-dimensional axisymmetric solids or solids of revolution under axisymmetric loading, can be reduced to simple two-dimensional problems. Due to the symmetry of the structure’s geometry and  load around the z axis, all strains and stresses are independent from the rotation angle,  θ. Therefore, the problem can be seen as two-dimensional in the plane rz, defined by the rotation area of the cross section as illustrated in Figure 1.

The axisymmetric solid under axisymmetric loading is subjected to radial (u) and axial (w) displacement and, due to axial symmetry, has circumferential displacement equal to zero. Thus, the displacement vector is given by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{u}=\left[\begin{array}{c}
\mbox{u}\mbox{ }\mbox{(r,z)}\\
\mbox{w}\mbox{ }\mbox{(r,z)}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(1)
|}


Therefore, a two-dimensional region defined by the rotation area of the axisymmetric solid is divided into triangular elements. These triangles, which altogether form the region under analysis are called elements and have 3 nodes and 2 degrees of freedom per node, one in the r direction and another in the z direction, as shown in Figure 2.

In turn, the nodal displacement vector at the nodes of the element is given by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{q}\mbox{ }={\left[\begin{array}{cccccc}
\mbox{q}_\mbox{1} & \mbox{q}_\mbox{2} & \mbox{q}_\mbox{3} & \mbox{q}_\mbox{4} & \mbox{q}_\mbox{5} & \mbox{q}_\mbox{6}
\end{array}\right]}^\mbox{T}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(2)
|}


where the components of the nodal displacement q<sub>1</sub>, q<sub>3</sub>and q<sub>5</sub>are in the r direction and  q<sub>2</sub>, q<sub>4</sub>and q<sub>6</sub>in the z direction, as indicated in Figure 2.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">''' [[Image:Draft_Ferreira_761749235-image4-c.png|270px]] '''</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 2:'''</span>  <span style="text-align: center; font-size: 75%;">Displacement components of a triangular finite element </span></div>

To exemplify, Figure 3 represents a discretized structure with 5 triangular elements and 6 nodes..

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
''' [[Image:Draft_Ferreira_761749235-image5.png|264px]] '''</div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 3:'''</span> <span style="text-align: center; font-size: 75%;">Discretization of a structure with 6 nodes and 5 triangular elements. </span></div>

The connectivity or incidence indicates the nodes that represent each element of the discretized structure. To this end, we adopted the counterclockwise direction. Table 1 illustrates the connectivity of the elements of the discretized structure shown in Figure 3.

{| style="width: 51%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element connectivity</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  colspan='3'  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Three nodes</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 1:''' Connectivity of discretized finite elements </span></div>

'''2.1 Discretization of Displacement Field'''

Displacements at the elements’ centroid can be calculated through the  nodal displacements of the elements themselves and, to this end, in FEM, the shape functions are used, which in the case of CST elements are linear. The shape functions N<sub>1</sub>, N<sub>2</sub>and N<sub>3</sub> correspond to nodes 1, 2 and 3 of the  element. As an example,  N<sub>1</sub>function assumes the unit value at node 1, and decreases linearly to the null value at nodes 2 and 3, defining a flat  surface as indicated in Figure 4. Thus, as function of the natural coordinates  ξ and η, the shape functions can be written as N<sub>1</sub>= ξ, N<sub>2</sub>= η and N<sub>3</sub>=1- ξ- η  (5).

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image6-c.png|402px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 4: '''Representation of shape functions at the element’s nodes </span></div>

Using the shape functions  N<sub>1</sub>, N<sub>2</sub> and N<sub>3</sub>, the displacement vector  ('''u''') is defined from the nodal displacements of triangular element ('''q''') as:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{u=N}\mbox{ }\boldsymbol{q}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(3)
|}


where '''q''' is the nodal displacement  vector (shown in Equation (2)), and '''N''' is a matrix of shape functions given by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{N}=\left[\begin{array}{cccccc}
\mbox{N}_\mbox{1} & \mbox{0} & \mbox{N}_\mbox{2} & \mbox{0} & \mbox{N}_\mbox{3} & \mbox{0}\\
\mbox{0} & \mbox{N}_\mbox{1} & \mbox{0} & \mbox{N}_\mbox{2} & \mbox{0} & \mbox{N}_\mbox{3}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(4)
|}


Therefore, organizing Equations (2), (3) and (4) in matrix form, results:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\begin{array}{c}
u=\mbox{ }N_1\mbox{ }q_1+N_2\mbox{ }q_3+N_3\mbox{ }q_5\\
w=\mbox{ }N_1\mbox{ }q_2+N_2\mbox{ }q_4+N_3\mbox{ }q_6
\end{array}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(5)
|}


Coordinates r and z can also be represented in terms of natural coordinates using the same shape functions. This is the so-called isoparametric representation. Isoparametric representations relate Cartesian coordinates r and z with natural coordinates η and ξ. The isoparametric representations allow verifying that u, w, r and z are functions of  η and ξ. Thus, they may be represented by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">u\mbox{ }=\mbox{ }u\left[r\left(\xi ,\eta \right),~z\left(\xi ,\eta \right)\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(6)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">w\mbox{ }=\mbox{ }w\left[r\left(\xi ,\eta \right),~z\left(\xi ,\eta \right)\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(7)
|}


Using the chain rule for derivatives of u and w, we obtain:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\left[\begin{array}{c}
\frac{\partial \mbox{u}}{\partial \mbox{ξ}}\\
\frac{\partial \mbox{u}}{\partial \mbox{η}}
\end{array}\right]=\left[\begin{array}{cc}
\mbox{r}_{\mbox{13}} & \mbox{z}_{\mbox{13}}\\
\mbox{r}_{\mbox{23}} & \mbox{z}_{\mbox{23}}
\end{array}\right]\left[\begin{array}{c}
\frac{\partial \mbox{u}}{\partial \mbox{r}}\\
\frac{\partial \mbox{u}}{\partial \mbox{z}}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(8)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\left[\begin{array}{c}
\frac{\partial \mbox{w}}{\partial \mbox{ξ}}\\
\frac{\partial \mbox{w}}{\partial \mbox{η}}
\end{array}\right]=\left[\begin{array}{cc}
\mbox{r}_{\mbox{13}} & \mbox{z}_{\mbox{13}}\\
\mbox{r}_{\mbox{23}} & \mbox{z}_{\mbox{23}}
\end{array}\right]\left[\begin{array}{c}
\frac{\partial \mbox{w}}{\partial \mbox{r}}\\
\frac{\partial \mbox{w}}{\partial \mbox{z}}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(9)
|}


the square matrix (2x2)known as Jacobian of the transformation, thus:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{J}=\left[\begin{array}{cc}
\mbox{r}_{\mbox{13}} & \mbox{z}_{\mbox{13}}\\
\mbox{r}_{\mbox{23}} & \mbox{z}_{\mbox{23}}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(10)
|}


where the simplified indicial notation, represented by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <span style="text-align: center; font-size: 75%;"> <math>\mbox{r}_{\mbox{ij}}\mbox{=}\mbox{ }\mbox{r}_\mbox{i}-</math><math>\mbox{ }\mbox{r}_\mbox{j}</math> </span>
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(11)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\mbox{z}_{\mbox{ij}}\mbox{=}\mbox{ }\mbox{z}_\mbox{i}-</math><math>\mbox{ }\mbox{z}_\mbox{j}</math>

was used.
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(12)
|}


'''2.2 Discretization of Strain and Stress Fields '''

The stress vector can be represented by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{\sigma }={\left[\begin{array}{cccc}
{\mbox{σ}}_\mbox{r} & {\mbox{σ}}_\mbox{z} & {\mbox{τ}}_{\mbox{rz}} & {\mbox{σ}}_{\mbox{θ}}
\end{array}\right]}^\mbox{T}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(13)
|}


where <math>{\mbox{σ}}_\mbox{r}</math> ,  <math>{\mbox{σ}}_\mbox{z}</math> ,  <math>{\mbox{τ}}_{\mbox{r}\mbox{ }\mbox{z}}</math> and  <math>{\mbox{σ}}_{\mbox{θ}}</math> are, respectively, the radial, axial, tangential and circumferential stresses  acting on an elemental volume as indicated in Figure 5.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
''' [[Image:Draft_Ferreira_761749235-image22.png|354px]] '''</div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 5:''' Stresses on the differential volume of an axisymmetric solid subjected to axisymmetric loads. </span></div>

Stress values must be calculated for each element, using the specific strain-element displacement relations, given in the usual form, as Bathe (4).

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{\sigma =D}\mbox{ }\boldsymbol{\epsilon }</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(14)
|}


where '''D''', is the matrix that relates stress  with strains represented by:  

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{D}=\frac{\mbox{E}\mbox{ }\left(\mbox{1}-\nu \right)}{\left(\mbox{1+}\nu \right)\left(\mbox{1}-\mbox{2}\nu \right)}\left[\begin{array}{cccc}
\mbox{1} & \frac{\nu }{\mbox{1}-\nu } & \mbox{0} & \frac{\nu }{\mbox{1}-\nu }\\
\frac{\nu }{\mbox{1}-\nu } & \mbox{1} & \mbox{0} & \frac{\nu }{\mbox{1}-\nu }\\
\mbox{0} & \mbox{0} & \frac{\mbox{0,5}-\nu }{\mbox{1}-\nu } & \mbox{0}\\
\frac{\nu }{\mbox{1}-\nu } & \frac{\nu }{\mbox{1}-\nu } & \mbox{0} & \mbox{1}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(15)
|}


Strains can be written as: 

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\mbox{ε}\mbox{ }\mbox{=}{\left[\begin{array}{cccc}
{\mbox{ε}}_\mbox{r} & {\mbox{ε}}_\mbox{z} & {\mbox{γ}}_{\mbox{r}\mbox{ }\mbox{z}} & {\mbox{ε}}_{\mbox{θ}}
\end{array}\right]}^{\mbox{ }\mbox{T}}\mbox{ }</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(16)
|}


where  <math>{\mbox{ε}}_\mbox{r}</math> ,  <math>{\mbox{ε}}_\mbox{z}</math> ,  <math>{\mbox{γ}}_{\mbox{r}\mbox{ }\mbox{z}}</math> and  <math>{\mbox{ε}}_{\mbox{θ}}</math> are respectively, the radial, axial, tangential and circumferential strains.

Through mathematical manipulations of Equation (5) and calculating the partial derivatives of displacements u and w in relation to r and z, the strains can be written in the matrix form following Chandrupatla and Belegundu (5):

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| [[Image:Draft_Ferreira_761749235-image30.png|438px]] 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(17)
|}


or in compact form 

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{\epsilon }=\boldsymbol{B}\mbox{ }\boldsymbol{q}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(18)
|}


where the specific strain- displacement matrix of element ('''B'''), with 4x6 dimension, is given by

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{B}=\left[\begin{array}{cccccc}
\frac{\mbox{z}_{\mbox{23}}}{\mbox{det}\boldsymbol{J}} & \mbox{0} & \frac{\mbox{z}_{\mbox{31}}}{\mbox{det}\boldsymbol{J}} & \mbox{0} & \frac{\mbox{z}_{\mbox{12}}}{\mbox{det}\boldsymbol{J}} & \mbox{0}\\
\mbox{0} & \frac{\mbox{r}_{\mbox{32}}}{\mbox{det}\boldsymbol{J}} & \mbox{0} & \frac{\mbox{r}_{\mbox{13}}}{\mbox{det}\boldsymbol{J}} & \mbox{0} & \frac{\mbox{r}_{\mbox{21}}}{\mbox{det}\boldsymbol{J}}\\
\frac{\mbox{r}_{\mbox{32}}}{\mbox{det}\boldsymbol{J}} & \frac{\mbox{z}_{\mbox{23}}}{\mbox{det}\boldsymbol{J}} & \frac{\mbox{r}_{\mbox{13}}}{\mbox{det}\boldsymbol{J}} & \frac{\mbox{z}_{\mbox{31}}}{\mbox{det}\boldsymbol{J}} & \frac{\mbox{r}_{\mbox{21}}}{\mbox{det}\boldsymbol{J}} & \frac{\mbox{z}_{\mbox{12}}}{\mbox{det}\boldsymbol{J}}\\
\frac{\mbox{N}_\mbox{1}}{\mbox{r}} & \mbox{0} & \frac{\mbox{N}_\mbox{2}}{\mbox{r}} & \mbox{0} & \frac{\mbox{N}_\mbox{3}}{\mbox{r}} & \mbox{0}
\end{array}\right]</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(19)
|}


and det'''J ''' is the determinant of the Jacobian matrix ('''J'''), shown in Equation (10).

'''2.3 Method of Potential Energy '''

The potential energy, <math>\prod </math> , of an elastic body is defined as the sum of the internal strain energy (U) and  the potential energy of the external forces (V), that is,

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\prod =\underset{\mbox{U}}{\underbrace{\frac{1}{2}~\int_0^{2\pi }\int_A{\boldsymbol{\sigma }}^\mbox{T}\boldsymbol{\epsilon }\mbox{ }\boldsymbol{r}\mbox{ }\mbox{dA}\mbox{ }\mbox{dθ}}}-</math><math>\underset{\mbox{V}}{\underbrace{\int_0^{2\pi }\int_A\boldsymbol{u}^\mbox{T}\boldsymbol{f}\mbox{ }\boldsymbol{r}\mbox{ }\mbox{dA}\mbox{ }\mbox{dθ}-\int_0^{2\pi }\int_L\boldsymbol{u}^\mbox{T}\boldsymbol{T}\mbox{ }\boldsymbol{r}\mbox{ }\mbox{dl}\mbox{ }\mbox{dθ}-\sum_i\mbox{ }\boldsymbol{u}_i{}^\mbox{T}\boldsymbol{P}_i}}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(20)
|}


where 

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{f}={\left[\mbox{f}_\mbox{r}\mbox{ }{\mbox{,f}}_\mbox{z}\right]}^\mbox{T}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(21)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{T}={\left[\mbox{T}_\mbox{r}{\mbox{,T}}_\mbox{z}\right]}^\mbox{T}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(22)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{P}={\left[\mbox{P}_\mbox{r}{\mbox{,P}}_\mbox{z}\right]}^\mbox{T}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(23)
|}


are, respectively, the body force, surface force  and concentrated load vectors.

The strain energy of the element (U<sub>e</sub>) can be obtained by substituting Equation (18) in the first parcel of Equation (20), and is given by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\mbox{U}_\mbox{e}=\frac{1}{2}\boldsymbol{q}^\boldsymbol{T}\left(2\mbox{π}\int_A\boldsymbol{B}^\boldsymbol{T}\mbox{ }\boldsymbol{D}\mbox{ }\boldsymbol{B}\mbox{ }\boldsymbol{r}\mbox{ }\mbox{dA}\right)\boldsymbol{q}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(24)
|}


where the term within brackets is the stiffness matrix of element  <math>\left(\boldsymbol{K}^\boldsymbol{e}\right)</math> , that is,

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{K}^\boldsymbol{e}=\mbox{2π}\int_A\boldsymbol{B}^\boldsymbol{T}\mbox{ }\boldsymbol{D}\mbox{ }\boldsymbol{B}\mbox{ }\mbox{r}\mbox{ }\mbox{dA}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(25)
|}


As a simple approximation, <math display="inline">\boldsymbol{B}</math> and r can be assessed at the centroid of the triangle and used as representative values for the triangle. 

At the centroid of the triangle, we have that:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\mbox{N}_\mbox{1}\mbox{=}\mbox{ }\mbox{N}_\mbox{2}\mbox{=}\mbox{ }\mbox{N}_\mbox{3}\mbox{=}\frac{\mbox{1}}{\mbox{3}}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(26)
|}


{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\overline{r}=\mbox{ }\frac{\mbox{r}_\mbox{1}\mbox{+}\mbox{ }\mbox{r}_\mbox{2}\mbox{+}\mbox{ }\mbox{r}_\mbox{3}}{\mbox{3}}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(27)
|}


where   <math display="inline">\overline{r}</math> is the distance from the centroid of the element to the z axis. Indicating  <math>\overline{\boldsymbol{B}}</math> as the specific strain- displacement matrix of the element assessed at the centroid, we have:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\boldsymbol{K}^\boldsymbol{e}=2\mbox{ }\mbox{π}\mbox{ }\mbox{     r     ¯}\mbox{ }{\overline{\boldsymbol{B}}}^\boldsymbol{T}\boldsymbol{D}\mbox{ }\overline{\boldsymbol{B}}\int_A\mbox{dA}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(28)
|}


or

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math>\begin{array}{c}
\boldsymbol{K}^\boldsymbol{e}=2\mbox{ }\mbox{π}\mbox{ }\overline{r}\mbox{ }A_e\mbox{ }{\overline{\boldsymbol{B}}}^\boldsymbol{T}\boldsymbol{D}\mbox{ }\overline{\boldsymbol{B}}\mbox{ }\\
\mbox{ }
\end{array}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(29)
|}


With the stiffness matrix <math display="inline">\boldsymbol{K~}</math> and the nodal force vector '''F''' obtained according to equations previously shown, the vector of nodal displacements of structure <math display="inline">\boldsymbol{Q}</math> is calculated by equation:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{K~Q}\mbox{ = }\boldsymbol{F}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(30)
|}


Substituting Equation (18) in Equation (14), we obtain that the stress in each element is given by:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <math display="inline">\boldsymbol{\sigma }\mbox{ = }\boldsymbol{D~B~q}</math> 
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(31)
|}


'''2.4 Method for obtaining the stresses at the nodes of the elements '''

In this paper, according to the formulation previously presented, the stresses are calculated at the centroid of each triangular finite element. Aiming at determining the stresses at the nodes of the elements or at any other point of the structure, a Lagrange polynomial interpolation was used. Therefore, the polynomial function is represented as:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <span style="text-align: center; font-size: 75%;"> <math>\mbox{P}_\mbox{n}\mbox{(x)=}\sum_{\mbox{k=1}}^{\mbox{n+1}}\left[\prod_{\begin{array}{c}
\mbox{i}\mbox{ }\mbox{=1}\\
\mbox{i¹k}
\end{array}}^{\mbox{n+1}}\frac{\left({\mbox{x-x}}_\mbox{i}\right)}{\left(\mbox{x}_\mbox{k}{\mbox{-x}}_\mbox{i}\right)}\right]\mbox{ }\mbox{y}_k</math> </span>
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(32)
|}


By analogy, the stress at the nodes of each element may be calculated from:

{| class="formulaSCP" style="width: 100%;width: 100%;text-align: center;" 
|-
| 
{| style="text-align: center; margin:auto;width: 100%;"
|-
| <span style="text-align: center; font-size: 75%;"> <math>{\mbox{σ}}_\mbox{n}\mbox{(x)=}\sum_{\mbox{k=1}}^{\mbox{n+1}}\left[\prod_{\begin{array}{c}
\mbox{i}\mbox{ }\mbox{=1}\\
\mbox{i¹k}
\end{array}}^{\mbox{n+1}}\frac{\left({\mbox{x-x}}_\mbox{i}\right)}{\left(\mbox{x}_\mbox{k}{\mbox{-x}}_\mbox{i}\right)}\right]\mbox{ }{\mbox{σ}}_\mbox{k}</math> </span>
|}
|  style="text-align: right;width: 5px;text-align: right;white-space: nowrap;"|(33)
|}

=3 RESULTS AND DISCUSSIONS=

In this section, the applications of the present study are shown. Four examples were analyzed, namely: a hollow sphere subjected to uniformly distributed radial load; a tube subjected to internal radial pressure; a concrete pile subjected to thrust along its shank and to nodal loading  transferred from the foundation block to its top; and finally, a mixed steel-concrete pillar without steel armor subjected to  surface load. The results obtained are compared to literature results and also with those determined using the ANSYS 17 (2) software.

'''3.1 Hollow sphere subjected to Uniformly Distributed Radial Load '''

The hollow sphere considered in this application had an internal radius of 1m and an external radius of 2m, and was subjected to a negative unit pressure P inside, as shown in Figure 6.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image54.png|168px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 6:'''</span> <span style="text-align: center; font-size: 75%;">Hollow sphere</span></div>

A sector of a sphere can represent a complete sphere when the displacement is restricted to the vertical axis. In this manner, the model used for the numerical analysis, as well as the contour conditions used are indicated in Figure 7.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image55.png|210px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 7:'''</span> <span style="text-align: center; font-size: 75%;">Representation of a sphere sector </span></div>

Figure 8 presents the nodal loadings acting inside the hollow sphere. These loads were decomposed as a function of the angles formed with the horizontal.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image56.png|234px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 8'''</span>''':''' <span style="text-align: center; font-size: 75%;">Directions of the nodal loads acting on the empty cylinder subjected to internal radial pressure.</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">.</span></div>

In this example, the domain was discretized with triangular finite elements with three nodes (CST) resulting in a mesh with 96 elements and 63 nodes as shown in Figures 9 and 10.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image57.png|270px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 9'''</span>''':''' <span style="text-align: center; font-size: 75%;">Finite element mesh (node enumeration) – Sphere.</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
''' [[Image:Draft_Ferreira_761749235-image58.png|306px]] '''</div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 10'''</span>''':''' <span style="text-align: center; font-size: 75%;">Finite element mesh (node enumeration) – Sphere.</span></div>

Aiming at checking the efficiency of the numerical implementations performed, the example was also modeled in the ANSYS 17 (2) program adopting the same mesh used in the analysis by Progaxisymmetric. Thus, a two-dimensional finite element with 3 nodes and 2 degrees of freedom per axisymmetric node called PLANE 182 was used to perform the analyses.

Table 2 and 3 present comparisons between the numerical solutions obtained from the computer program developed in this study and those obtained from ANSYS 17 (2) software.

{| style="width: 52%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='5'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Displacement</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Node</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Radius(m)</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">22</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.125</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.559</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.564</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.990</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">24</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.375</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.454</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.460</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.988</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">26 </span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.625</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.407</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.413</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.985</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">28</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.875</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.391</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.937</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.980</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 2:''' Radial displacement (in meters).</span></div>

{| style="width: 45%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Tangential stress</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">96</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.610</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.616</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.990</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">93</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.434</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.439</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.987</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">92</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.378</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.383</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.986</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">90</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.317</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.322</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.985</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">87</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.265</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.270</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.982</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">85</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.239</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.244</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.981</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">84</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.225</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.229</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.981</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">82</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.208</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-0.212</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">0.981</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 3:''' Tangential stress (MPa) at the centroid of some elements.</span></div>

It is noteworthy that the accuracy obtained by the numerical simulation is quite satisfactory.

In this example, the greatest percent differences obtained between the implemented code and the ANSYS 17 (2) software were 1.5% and 1.89%. Those responses correspond to the radial displacements obtained at the nodes and the tangential stresses analyzed in the elements.

It should be noted that the hollow sphere stresses were analyzed at the centroids of the discretized elements.

'''3.2 Hollow Cylinder Subjected to Internal Radial Pressure '''

This example presents the results corresponding to an empty cylinder, previously analyzed  by Timoshenko and Goodier (6), with E=20.77x103kN/cm², ð=0.3, internal diameter 5.08cm and external diameter 10.16cm, length equal to 10.16cm and subjected to an internal pressure p=0.616kN/cm², as shown in Figure 11. In this application, the values of the maximum displacements in the piece were assessed and the values of the radial and the tangential stresses at the nodes of the finite elements at the points of maximum displacement were also calculated.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image59.png|180px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 11'''</span>''':''' <span style="text-align: center; font-size: 75%;">Nodal loads acting on the empty cylinder subjected to radial internal pressure.</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">.</span></div>

Figure 12 presents the structured mesh, composed by 40 finite elements and 33 nodes, as well as the contour conditions adopted to obtain the responses by Progaxisymmetric. It must be emphasized that this is the same finite element mesh presented in the literature.

{| style="width: 65%;" 
|-
|  style="text-align: center;width: 50%;"|[[Image:Draft_Ferreira_761749235-image60-c.png|90px]] 
|  style="text-align: center;width: 50%;"|[[Image:Draft_Ferreira_761749235-image61.png|126px]] 
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
'''<br/>'''<span style="text-align: center; font-size: 75%;">'''Figure 12: '''Finite element mesh (element enumeration) and contour conditions (node enumeration) –</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;"> Empty cylinder</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">.</span></div>

The results of displacements and stresses indicated in Figures 14 and 15 were assessed in radial       points of the discretized structure as indicated in Figure 13.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image62.png|318px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 13:'''</span> <span style="text-align: center; font-size: 75%;">Region where the displacement and stress results were </span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">obtained – Empty cylinder. </span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image63.png|258px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 14:'''</span> <span style="text-align: center; font-size: 75%;">Radial displacement in the cylinder.</span></div>

{| style="width: 100%;margin: 1em auto 0.1em auto;" 
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Ferreira_761749235-image64.png|270px]] </span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Ferreira_761749235-image65.png|252px]] </span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 15'''</span>''':'''  <span style="text-align: center; font-size: 75%;">Stresses versus radial position in the cylinder.</span></div>

The numerical responses shown in Figures 14 and 15 were compared with the theoretical results           obtained by  Timoshenko and Goodier (6) corresponding to nodal points in the piece. Radial and      tangential stresses were calculated in the global coordinate system and assessed at the centroid of each triangular finite element. To obtain the stress values in some point out of the centroid, the polynomial       interpolation technique was used with the aid of Lagrange interpolation polynomial.

In this application, the graphs of displacements and stresses at the nodes of the elements show an excellent approximation between the numerical results obtained in this study and the theoretical values found in literature.


'''3.3 Concrete pile'''

This example shows the results of the modeling of a concrete pile as shown in Figure 16.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 [[Image:Draft_Ferreira_761749235-image66.png|462px]] </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 16'''</span>''':'''<span style="text-align: center; font-size: 75%;"> Piles used in deep foundations</span></div>

The concrete pile had  <math display="inline">\mbox{f}_{\mbox{ck}}\mbox{=}\mbox{ }\mbox{25MPa}</math> , Poisson coefficient  <math display="inline">\mbox{ν}\mbox{ }\mbox{=}\mbox{ }\mbox{ }\mbox{0,2}</math> and the concrete elasticity modulus was calculated with the equation  <math display="inline">\mbox{E}_\mbox{c}\mbox{=}\mbox{ }\mbox{5600}\sqrt{\mbox{f}_{\mbox{ck}}}</math> .

The soil considered in this example had specific weight <math display="inline">{\mbox{γ}}_{\mbox{solo}}\mbox{=}\mbox{ }\mbox{18}\mbox{ }\mbox{kN}/\mbox{m}^\mbox{3}</math> , friction angle <math>\phi ={30}^{\circ }</math> and the coefficient of  active soil thrust  <math>\mbox{k}_\mbox{a}\mbox{=}\mbox{ }{\mbox{tg}}^\mbox{2}\left({\mbox{45}}^\mbox{o}-\right. </math><math>\left. \frac{\phi }{\mbox{2}}\right)</math> , that is,  <math display="inline">\mbox{k}_\mbox{a}\mbox{=0,333}</math> .

The block had a height of 2m and the pile had 10m length, that is, the height of the soil massif was  h=12m. Pile diameter was 2m and the axial load to which it was subjected was q=3000kN. Acting pressures on the edges of the pile were calculated by equation <math display="inline">\mbox{p}\mbox{ }\mbox{=}\mbox{ }\mbox{k}_\mbox{a}\mbox{ }{\mbox{γ}}_{\mbox{solo}}\mbox{ }\mbox{h}</math> .

The structure was discretized with 126 nodes and  200 elements, as shown in Figure 17. It is worth emphasizing that the same finite element mesh was used in the analyses by Progaxisymmetric  and       ANSYS (2).

{| style="width: 59%;margin: 1em auto 0.1em auto;" 
|-
|  style="text-align: center;width: 49%;"|[[Image:Draft_Ferreira_761749235-image75.png|132px]]

<span style="text-align: center; font-size: 75%;">a) Nodes</span>
|  style="text-align: center;width: 50%;"|[[Image:Draft_Ferreira_761749235-image76-c.png|126px]]

<span style="text-align: center; font-size: 75%;">b) Elements</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 17:'''</span> <span style="text-align: center; font-size: 75%;">Finite element mesh of the pile – enumeration of nodes and elements</span></div>

Tables 4, 5, 6 and 7 present the results of radial, axial, tangential and circumferential stresses at the centroid of elements 192 and 200, see Figure 17, compared with those obtained from ANSYS 17(2) software. This example also used the two-dimension finite element with 3 nodes and 2 degrees of freedom per node called PLANE 182 to perform the analyses by ANSYS 17(2).

{| style="width: 51%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Radial stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">192</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">34.860</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">34.842</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">193</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">26.660</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">26.642</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">194</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">125.300</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">125.210</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">195</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">58.070</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">58.036</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">196</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">614.100</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">613.790</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">197</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">573.400</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">573.090</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">198</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-166.100</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-166.020</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">199</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-741.700</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-741.370</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">200</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3196.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3194.800</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 4:''' Radial stresses  (kN/m²).</span></div>

{| style="width: 54%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Axial stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">192</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3039.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3037.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">193</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3126.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3124.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">194</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3101.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3099.400</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">195</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3412.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3410.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">196</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3392.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3390.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">197</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-4016.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-3390.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">198</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-4695.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-4692.400</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">199</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5388.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5385.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">200</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-10700.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-10694.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 5:''' Axial stresses (kN/m²).</span></div>

{| style="width: 54%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Tangential stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element </span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">192</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-7.764</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-7.760</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">193</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">16.250</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">16.242</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">194</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">21.680</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">21.672</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">195</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">47.350</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">47.330</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">196</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">39.020</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">39.002</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">197</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">241.100</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">240.940</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">198</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1198.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1197.700</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0003</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">199</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">601.900</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">601.590</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">200</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4835.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4832.200</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 6:''' Tangential stresses  (kN/m²).</span></div>

{| style="width: 54%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Circumferential stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">192</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-27.130</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-27.115</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">193</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">27.350</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">37.335</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">194</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">99.730</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">99.679</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">195</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">141.900</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">141.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">196</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6.742</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6.739</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">197</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">467.700</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">467.450</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">198</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1750.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1749.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">199</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">140.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">140.690</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0008</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">200</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2086.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2084.900</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 7:''' Circumferential stresses (kN/m²).</span></div>

In this application, when the stresses at the centroid of the element determined by the implemented code were compared with  the results obtained through ANSYS 17 (2) software a maximum percent              difference of 0.08% was obtained.

'''3.4 Mixed Steel-Concrete Pillar '''

This example presents the numerical results of the analysis of a mixed steel-concrete pillar subjected to a designed axial load <math display="inline">\mbox{P}_\mbox{d}=1200\mbox{ }\mbox{kN}</math> . The length of the pillar was 2m and the dimensions of the steel tube were 35.56cmx33.06cmx1.25mm. The tube was filled with concrete whose characteristic strength after 28 days was <math display="inline">\mbox{f}_{\mbox{ck}}\mbox{=30MPa}</math> , the elasticity modulus of concrete was calculated with the equation  <math display="inline">\mbox{E}_\mbox{c}\mbox{=}\mbox{ }\mbox{5600}\sqrt{\mbox{f}_{\mbox{ck}}}</math> , Poisson coefficient for the steel tube was considered  <math display="inline">\mbox{ν}=0,3</math> and for the confined concrete Poison coefficient was equal to  <math display="inline">\mbox{ν}=0,2</math> .

The objective of the analysis was to calculate lateral displacements and radial, axial, tangential and circumferential stresses at different points of the structure and, aiming to validate the results obtained by the computer program developed in the present research, the structure was also modeled through  ANSYS 17 (2) software.

Figure 18 presents a loading scheme acting at the top of the mixed steel-concrete pillar and Figure 19 shows the finite element mesh adopted to solve this example.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
''' [[Image:Draft_Ferreira_761749235-image82.png|306px]] '''</div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 18:'''</span> Mixed Steel-concrete pillar</div>

Figure 20 presents the results of the displacements in the x and y directions at several nodes of the structure located along its length on the mesh right edge compared to those obtained with the aid of ANSYS 17 (2) software.

{| style="width: 68%;margin: 1em auto 0.1em auto;" 
|-
|  style="text-align: center;"|<span style="text-align: center; font-size: 75%;">''' [[Image:Draft_Ferreira_761749235-image83.png|138px]] '''</span>

<span style="text-align: center; font-size: 75%;">'''a) Elements'''</span>
|  style="text-align: center;"|<span style="text-align: center; font-size: 75%;">''' [[Image:Draft_Ferreira_761749235-image84.png|144px]] '''</span>

<span style="text-align: center; font-size: 75%;">'''b) Nodes'''</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 19: '''Finite element mesh''' '''of the mixed steel-concrete pillar''' '''</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">– enumeration of nodes and elements.</span></div>

{| style="width: 100%;" 
|-
|  style="text-align: center;vertical-align: top;width: 50%;"|[[Image:Draft_Ferreira_761749235-image85.png|294px]] 
|  style="text-align: center;vertical-align: top;width: 49%;"|[[Image:Draft_Ferreira_761749235-image86.png|270px]] 
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 20:'''</span> <span style="text-align: center; font-size: 75%;">Nodal displacements.</span></div>

Tables 8, 9, 10 and 11 present the results of the radial, axial, tangential and circumferential stresses of the elements located at the top of the mixed pillar.

{| style="width: 54%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Radial stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">149</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3665.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3663.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">150</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-7096.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-7092.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-461.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-460.770</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1689.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1687.700</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0008</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1022.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1021.900</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0001</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2875.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2873.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2293.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2291.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-4616.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-4613.200</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">7</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5524.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5521.400</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">8</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-8313.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-8308.900</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 8:''' Radial stresses (kN/m²).</span></div>

{| style="width: 55%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Axial stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This studyANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">149</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-13360.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-13354.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">150</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-22640.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-22626.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2920.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-2918.500</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5608.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5605.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5659.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-5655.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-11710.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-11702.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-11820.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-11815.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-28130.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-28118.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">7</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-28400.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-28385.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">8</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-92310.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-92263.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 9:''' Axial stresses (kN/m²).</span></div>

{| style="width: 55%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Tangential stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">149</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">12610.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">12608.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0002</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">150</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1015.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-1014.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0010</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">614.900</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">614.620</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1467.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1466.500</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0003</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">546.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">546.360</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1506.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1505.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0003</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">353.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">356.420</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1207.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1206.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0008</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">7</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">779.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">778.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">8</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-22.720</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-22.710</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 10:''' Tangential stresses (kN/m²).</span></div>

{| style="width: 55%;margin: 1em auto 0.1em auto;border-collapse: collapse;" 
|-
|  colspan='4'  style="border-top: 1pt solid black;border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Circumferential stresses</span>
|-
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Element</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">ANSYS</span>
|  style="border-top: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">This study/ANSYS</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">149</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6897.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">-6893.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">150</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1283.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1283.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0000</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4714.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4711.400</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1090.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1089.600</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0004</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">10410.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">10403.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0007</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">4</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2408.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">2406.900</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">5</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">25400.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">25384.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3964.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">3961.800</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0006</span>
|-
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">7</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">89730.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">89687.000</span>
|  style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|-
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">8</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6092.000</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">6088.700</span>
|  style="border-bottom: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">1.0005</span>
|}


<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 11:''' Circumferential stresses (kN/m²).</span></div>

In this application the comparison of the stresses at the centroid of the elements obtained by Progaxisymmetric with the results of ANSYS 17 (2)software resulted in a maximum difference of 0.10%. it is worth emphasizing that in this example, a mesh composed by two elements (steel and concrete) was generated.

=4 CONCLUSIONS=

One of the main contributions of this study is the implementation of a sub-routine based on Lagrange polynomial that allows obtaining stress values at any point located along the triangular finite element.

Another significant contribution is that structures composed by more than one material could be analyzed in the present research. As an example, the fourth application, corresponding to a mixed steel-concrete tubular pillar with circular cross section can be mentioned.

In addition, different types of loadings such as body forces, nodal loads or uniformly distributed surface loads, distributed in triangular or trapezoidal form applied on the edges of the elements can be introduced in this computational package. We must also mention that mathematical manipulations were made capable of transforming them into equivalent nodal loads and it is worth remembering that the surface loads can be applied on horizontal, vertical or inclined edges.

Finally, it is important to cite that the examples presented were compared with results from the literature and with numerical modelings performed with  ANSYS 17(2) software aiming at validating the success of the numerical implementations carried out.

Therefore, based on the numerical comparisons conducted, we conclude that the implementation developed was successful; contributing with accurate stress, strain and displacement values in axisymmetric structures subjected to axisymmetric forces.

'''References'''

[1] Chapman, S. J. Fortran 90/95 for Scientists and Engineers. McGraw–Hill, 2003, 2nd ed.

[2]  ANSYS. Inc. theory reference, 2012, (version 12.1).

[3]  Vicente, W. M. and Oliveira, W.C., Análise de Tensões em Placas Circulares Utilizando Elementos Finitos Axissimétricos. Trabalho Final de Graduação de Engenharia Mecânica, 2009, Universidade Federal de Itajubá, Itajubá, MG, Brasil.

[4]  Bathe, K. J., Finite Element Procedures. Prentice Hall, 1996, Englewood Cliffs, New Jersey, 1051 p.

[5]  Chandrupatla, T.R. and Belegundu, A.D., Elementos Finitos. São Paulo: Pearson Education do Brasil, 2014.

[6]  Timosh, S. P. and. Goodier, J. N.,  Theory of Elasticity. Third Edition, 1951, New York, McGraw–Hill Co.