Abstract

Currently there is an increasing focus on the transmission of low frequency sound in buildings, as sources such as road and air traffic or even home theatre subwoofers become part of everyday life for many people. Hence, development of efficient and accurate methods for prediction of sound in such buildings is important. In the lowfrequency range, prediction of sound and vibration in building structures may be achieved by finite-element analysis (FEA). The aim of this paper is to compare the two commercial codes ABAQUS and ANSYS for FEA of an acoustic-structural coupling in a timber lightweight panel structure. For this purpose, modal analyses are carried out employing a fully coupled model of sound waves within an acoustic medium and vibrations in the structural part. The study concerns the frequency range 50–250 Hz.

Abstract

The behavior and response of pipelines subjected to slip fault movement is studied by numerical simulations as well as experimental setup. A finite element modeling is also developed via ABAQUS software. In this study, an artificial accelerogram is applied to the system and matched against the response spectrum according to the standard No. 2800 (Iranian code of practice for seismic resistant design of buildings, 2014). Three different pipe nominal sizes and thicknesses (1 ½”, 2” and 4”) are considered in the experiments on the shaking table. According to the results, plastic hinge as well as the extremum stress and strain is formed in the fixed soil wedge and at locations close to the fault line. Further, as the pipe D/t ratio increases, the plastic hinge forms further away from the fault line. According to the results, the pipe-soil strain ratio (εp/s) has lower values at larger pipe diameters. Also, the axial strains would be greater for the systems with higher (εp/s) ratios. Document type: Article

Abstract

The present study addresses the retrofitting of running-bond masonry walls through the application of oriented strand board (OSB) timber panels aiming to increase the masonry flexural strength and deformation capacity under out-of-plane actions. This paper presents the numerical analysis of masonry prisms to complement the information provided by the experimental campaign developed on flexural performances of timber retrofitted masonries. The numerical model represents the masonry components (brick and mortar) as a three-dimensional volume via volumetric finite elements, i.e. hexahedral 8-node linear brick elements with reduced integration and hourglass control. The nonlinear properties of the mortar joints and the brick units have been calibrated through information that resorts from experimental characterization tests. The numerical damage pattern and load-displacement capacity curve are compared with the experimental observations. A good agreement has been found and, therefore, the calibrated model can be employed in parametric studies, to further analyse the efficiency of the proposed timber masonry retrofit technique, and to more complex structural study cases.

Abstract

Nowadays, simulation is becoming more and more important in industries. Here we consider a typical industrial application in the field of sheet metal bending. A high number of simulations is necessary during the development process to perform parameter studies and optimizations. On the other hand, simulation tools should be also available for the customers of these machines, e.g., to plan the production of very specific profiles. In such cases, the optimal process parameters only can be found by simulation. Very important in this context are the license costs for commercial simulation software. Frequently, the simulations are not limited by computational power but by the number of available licenses, such that the duration for parameter studies is elongated. Also, with license costs it very expensive to provide a simulation platform to the customers. The presented case study has been carried out with the goal of comparing possible open source alternatives to expensive commercial Finite Element software. Exemplarily, we consider the elasto-plastic bending of a cantilever, using the Johnson Cook constitutive law. For this test case, a three dimensional Finite Element analysis is performed, comparing the results of open-source software (Salome-Meca) and a com mercial counterpart (Abaqus). Different element types and mesh sizes are compared, the usability of both tools, and the computational time. Considering the obvious price difference, both platforms show comparable results. Comparing the functionality of both programs, both are capable for modelling highly detailed and complex models for elasto-plastic material processing. However, for under standing the structure of the user interface of Salome-Meca is far more time consuming. Additionally, the performance of Salome-Meca on different operating systems is com pared: Salome-Meca on Linux, Salome-Meca on Linux, installed in a virtual machine on Windows, and finally Salome-Meca on Windows. All in all, it turned out that depending on the specific application Salome-Meca can be a powerful alternative to Abaqus for the considered industrial application.

Abstract

Improved wood-based materials, on the one hand, and computer-operated machinery, on the other, enable new types of timber-to-timber joints. Furthermore, new materials, such as laminated veneer lumber with cross-layers made of soft- or hardwood offer new possibilities regarding timber-to-timber connections like tenon and mortise. Experimental investigations have shown comparable failure mechanisms in mode I and mode II for tenon and multiple tenon joints, dovetail connections as well as for end-notched beams. In the field of fracture mechanics different concepts exists to describe the fracture behaviour such as the strain energy release rate, the stress intensity factors and the J-integral method for timber-to-timber joints. In this study the J-integral was determined around the crack tip in a finite element (FE) model in timber connections. The failure criterion was defined when the J-integral equals the energy release rate GcI+II in mixed mode of the timber material (Fig. 1a). A sensitivity analysis showed that the failure load Vc was not depending significantly on the initial crack length, the element size, the distance from the crack tip of the chosen contour Γ1 and the size of the chosen contour. In the next step, the model was validated on experimental test results of end-notched beams, tenon connections and multiple tenon connections (Fig. 1b). The experimental and numerical results showed very good accordance for different connection size and up to seven possible crack layers (Fig. 1c). Furthermore, a comparison between different fracture mechanic models with strain energy release rates and cohesive zones showed good performance of the new approach. Afterwards, the FE model using the J-integral failure criterion was used to perform a comprehensive study of geometrical parameters for end-notched beams and tenon connections. Finally, the dataset was used as a basis to develop a engineering model for three types of timber connections. The evaluation of the J-integral allows to determine the failure load due to crack initiation under a mixed mode loading in a linear elastic FE model with pre-defined cracks. The advantage of the J-integral method is the significant decrease of the computing time for extensive parameter studies. The model for end-notched beams, tenon joints and multiple tenon connections is insensitive to common variations of material properties as well as for the choice of the initial crack length. The application on timber structures under pure shear failure or tension failure perpendicular to the grain will be part of future research.