Abstract

The Urban Seismic Risk index (USRi) published in a previous article (Carreño et al., Nat Hazards 40:137–172, 2007) is a composite indicator that measures risk from an integrated perspective and guides decision-making for identifying the main interdisciplinary
factors of vulnerability to be reduced or intervened. The first step of the method is the evaluation of the potential physical damage (hard approach) as a result of the convolution of the seismic hazard with the physical vulnerability of buildings and infrastructure.
Subsequently, a set of social context conditions that aggravate the physical effects is also considered (soft approach). According to this procedure, the physical risk index is evaluated for each unit of analysis from existing loss scenarios, whereas the total risk index is obtained by multiplying the former index by an impact factor using an aggravating coefficient, based on variables associated with the socio-economic conditions of each unit of analysis. The USRi has been developed using the underlying holistic and multi-hazard approach of the Urban Risk Index framework proposed for the evaluation of disaster risk in different megacities worldwide. This article presents the sensitivity analysis of the index to different parameters such as input data, weights and transformation functions used for the scaling or normalization of variables. This analysis has been performed using the Monte Carlo simulation to validate the robustness of this composite indicator, understanding as robustness how the cities maintain the ranking as well as predefined risk
level ranges, when compared with the deterministic results of risk. Results are shown for different cities of the world.

Abstract

Abstract

Abstract

This paper deals with the critical issue of structural collapses and introduce a novel interpretation of the concept of Structural Robustness applied to Intact and Damaged Frames in order to quantify the critical load multiplier in each case, by a simple set of mathematical equations.

Abstract

This thesis is divided into two parts: in the first part the collapse of the WTC1, WTC 2 (Twin Towers) and WTC 7 buildings following the terrorist attacks of 11 September 2001 is analysed. In the second part, the collapse type and strength of frame buildings with different topological characteristics. What links the two parts is structural robustness.
Below is an overview of the work with a description of the topic covered in each Chapter.
Chapter 1: description of the structural and fire protection characteristics of the WTC 1, WTC 2 and WTC 7 buildings.
Chapter 2: timeline of the terrorist events of September 11, 2001.
Chapter 3: description of the types of fire, the performance of structures and the behavior of the main building materials (steel, concrete) to fire.
Chapter 4: analysis of the main hypotheses of the collapse of the Twin Towers present in the literature.
Chapter 5: definition of structural robustness, structural toughness, vulnerability. Description of project strategies to prevent progressive collapses.
Chapter 6: measurement of the structural strength of buildings with a reinforced concrete frame structure. through Discrete Element simulations (DEM).
Chapter 7: discussion of progressive collapse due to impacts from an analytical and bibliographical point of view.

Abstract

This thesis is divided into two parts: in the first part the collapse of the WTC1, WTC 2 (Twin Towers) and WTC 7 buildings following the terrorist attacks of 11 September 2001 is analysed. In the second part, the collapse type and strength of frame buildings with different topological characteristics. What links the two parts is structural robustness.
Below is an overview of the work with a description of the topic covered in each Chapter.
Chapter 1: description of the structural and fire protection characteristics of the WTC 1, WTC 2 and WTC 7 buildings.
Chapter 2: timeline of the terrorist events of September 11, 2001.
Chapter 3: description of the types of fire, the performance of structures and the behavior of the main building materials (steel, concrete) to fire.
Chapter 4: analysis of the main hypotheses of the collapse of the Twin Towers present in the literature.
Chapter 5: definition of structural robustness, structural toughness, vulnerability. Description of project strategies to prevent progressive collapses.
Chapter 6: measurement of the structural strength of buildings with a reinforced concrete frame structure. through Discrete Element simulations (DEM).
Chapter 7: discussion of progressive collapse due to impacts from an analytical and bibliographical point of view.

Abstract

Robustness plays a relevant role in the capacity of a structure to sustain abnormal loads
or to deal with unexpected events with large effects, such as explosions and terroristic
attacks. Such situations on dams may have extremely large consequences. For buildings,
the design approach that best implements robustness concepts is represented by the so
called “Consequence Based Design”: even if nothing is known about the cause, selective
element removals and extreme load on the structure are modeled, and their effects are
determined with respect to progressive collapse and damage arrest.
In the paper we try to set-up a “Consequence Based Assessment” of a typical example of
a gravity dam built between the ‘30s and ‘40s of the last century in the northwestern
Italian Alps. A simplified model of the structure is adopted. Removal of parts of the dam
cross-section is assumed to occur: the effects of the extent of damage is discussed on the
bases of the tension generated within the body of the dam.
1

Abstract

Robustness plays a relevant role in the capacity of a structure to sustain abnormal loads
or to deal with unexpected events with large effects, such as explosions and terroristic
attacks. Such situations on dams may have extremely large consequences. For buildings,
the design approach that best implements robustness concepts is represented by the so
called “Consequence Based Design”: even if nothing is known about the cause, selective
element removals and extreme load on the structure are modeled, and their effects are
determined with respect to progressive collapse and damage arrest.
In the paper we try to set-up a “Consequence Based Assessment” of a typical example of
a gravity dam built between the ‘30s and ‘40s of the last century in the northwestern
Italian Alps. A simplified model of the structure is adopted. Removal of parts of the dam
cross-section is assumed to occur: the effects of the extent of damage is discussed on the
bases of the tension generated within the body of the dam.

Abstract

This paper deals with the issue of structural collapse considering an analogy between ductile-brittle transition of materials, taking into account the current literature which also considers the number of fragility and the stress intensification factor in the presence of crack, with extension on a larger scale involving framed structures subjected to increasing vertical loads. It is evaluated the ductile-fragile transition in relation to concrete frames with different structural hierarchy (2x2, 5x5, 11x11).

Abstract