Journal of Performance of Constructed Facilities

The paper reports the results of a research aimed at analyzing and interpreting the cracking pattern on the Cappella dei Principi (Prince’s Chapel, the Medici’s mausoleum) in the Basilica of San Lorenzo (Florence, Italy). The research was motivated by the sudden collapse of a keystone of an internal barrel vault sustaining one of the lateral apses. After a brief description of the geometry of the structure, the principal results obtained from in situ surveys (flat-jack tests and cored samples) are described; then the numerical analyses developed both to obtain the static identification of the monument and to assess the possible causes leading to the observed failure are illustrated. The numerical modeling operation has been performed step by step, from linear and quite simple models built with plane elements up to a nonlinear model with three-dimensional elements. The nonlinear FEM, which has been tuned by utilizing the results of the in situ measures, is allowed to both qualitatively and quantitatively reproduce the behavior of the structure and its static problems in the area of the barrel vault over the side apses, allowing for justification of the manifested damage. The comprehension of the structural behavior allows identification of a proper retrofitting strategy.

A full three-dimensional finite-element (FE) homogenized modeling computer program for the evaluation of the nonlinear static behavior of entire masonry structures subjected to horizontal actions is presented and tested on four large-scale masonry churches located in the central region of Italy. At the structural level, masonry is modeled as a homogeneous, orthotropic material featuring softening in tension, shear, and compression. Rigid, infinitely resistant triangular elements connected by elastoplastic interfaces are used to perform full-scale nonlinear analyses. To reduce further processing time needed for the simulations, preliminary FE limit analyses were conducted to identify the failure mechanisms, and hence the interfaces that undergo plasticization during the deformation process. In this way, it is possible to concentrate nonlinearity exclusively on those interfaces that prove active in the limit-analysis problem. Finally, full nonlinear pushover curves are compared with collapse loads; the latter is provided by a limit analysis that assumes a limited number of possible preassigned failure mechanisms, as required by the recent Italian Building Code guidelines on monumental buildings.

Progressive collapses of arch bridges have repeatedly occurred in recent years, resulting in many casualties and significant property losses. Based on an actual recent and serious progressive collapse of a stone arch bridge, this paper simulated the complete progressive-collapse process using the general-purpose finite-element (FE) program, MSC.Marc. The simulation adopted a three-dimensional (3D) FE model and performed a nonlinear analysis using the contact algorithm in conjunction with the element-deactivation technique. The potential causes of the progressive collapse of the stone arch bridge were also evaluated. Furthermore, the importance of different components of the stone arch bridge was determined with the conception of generalized structural stiffness; thus, the most critical and vulnerable regions of the bridge were identified. The results of the simulated progressive-collapse process agreed well with the actual process, and the predicted critical regions were both correct and realistic. This study also provides important references for the analysis and prevention of progressive collapses of stone arch bridges.

Masonry remains the most used material for enclosure and partition walls. However, cracking often occurs in unreinforced masonry walls under service conditions, and little information can be found about systemic approaches in real case studies. Here, attention is given to a large building faced with a fired clay brick masonry veneer that exhibited significant out-of-plane movements only 1.5 years after construction. During the operation of dismounting part of the veneer, partial collapse occurred. The veneer wall, with an elliptical shape, 240 m length and 15 m height, presented no movement joints and insufficient tying. Irreversible expansion of the fired clay brick masonry was expected to be the main reason for the damage. The combination of inspection work (visual inspection, pull-out tests, and topographic survey) and advanced structural analysis with finite elements allowed an understanding of the damage and a repair solution at a fraction of the cost of demolishing and rebuilding a new veneer.

This paper presents the analysis of a failure involving the partial collapse of a masonry wall made of precast concrete blocks in an industrial building as a result of the action of the wind. A field survey was carried out to investigate the origin of the failure, which pointed to defective building practices as the possible cause. At the same time, complementary numerical modeling was performed to simulate the coupled fluidstructure behavior, as well as a parametric study and optimization based on Design of Experiments (DOE) to determine the influence of the principal variables in the wall behavior in the presence of wind loads. The lessons learned in the course of the study are explained in the final section.

Numerical simulation of damage and collapse mechanisms suffered by engineering structures can be an effective tool for a quantitative assessment of their causes. Large displacement inelastic analysis may be required in the case of highly flexible structures, such as steel roofs, which frequently experience large failures or even collapse because of buckling. This paper discusses the collapse of a long-span steel roof structure, which fell down suddenly during construction as a result of an out-of-plane buckling phenomenon induced by a gust of wind. Forensic investigations were carried out on behalf of the judicial authority to identify the causes of the accident. Based on detailed information gathered from site surveys and project documents, a three-dimensional numerical model of the as-built structure was created, and buckling analyses were performed to assess the safety level at the moment of the collapse. The as-built structure was braced through some purlins and steel cables fixed at the ground level. Structural stability was also investigated under further modeling assumptions to compare the effectiveness of several bracing systems in preventing the collapse. Analysis results showed that the as-built structure was in an unstable equilibrium condition when the wind breeze occurred. Temporary bracing elements installed on the structure instead of concentric roof braces were not sufficient to ensure the overall stability.

This paper reports the computational results of an investigation of oil storage tanks with the shape of an open cylindrical shell under thermal loads induced by fire. Interest in this problem has arisen as a consequence of a catastrophic fire that affected an oil storage facility in Puerto Rico in 2009 that caused the failure of 21 large tanks. To identify patterns of deformations that could be expected under various fire conditions, computer modeling has been carried out for one tank geometry. It is assumed that fire occurs outside the tank and induces an increasing temperature field affecting part of the external surface in the circumferential direction. The nonlinear shell response is modeled using finite elements under thermal loads and self-weight. The nonlinear behavior is computed to identify thermal buckling of the shell as a limit point. The response is initially computed for empty tanks, and the influence of various factors is investigated, including the liquid stored, a temperature gradient across the thickness, the circumferential zone affected by fire, and the shell thickness. The results for open tanks show that the location of large out-of-plane displacements attributable to thermal buckling coincides with the heated zone. The importance of thermal gradients in the thickness to the buckling load and mode are shown.

The catastrophic earthquake that struck the city of L’Aquila in early April 2009 caused extensive damage to buildings at the University of L’Aquila. Among these edifices are those of the Engineering Faculty, which, in particular, suffered large structural displacements and accelerations that resulted in failures of nonstructural elements (infills, false ceilings, door and window frames), the breakage of wiring and piping systems, and the destruction of furniture and machinery. Of these buildings, the so-called Edifice A presents the most critical damage scenario, requiring a significant rehabilitating intervention. The structural behavior of this building, composed of seven independent RC substructures, is the object of intensive investigation; this is in part because irregularities among these substructures, in terms of geometry, stiffness, and weight distribution, provide a rich case study for interpreting different structural and nonstructural damage scenarios. The paper interprets the observed damage through use of incremental analyses for evaluation of the threshold between linear and nonlinear structural behavior. For this purpose, several finite-element (FE) models are developed with increasing complexity in the geometry and the shear-wall modeling. Capacity curves obtained by the nonlinear pushover analyses are afterward compared with the perceived seismic demands of the structures including site effects. Moreover, based on simplified analyses, numerical evaluations of acceleration-producing failures in the infill walls and the split-face brick walls were performed to achieve an overall description of the structural and nonstructural damage.

This paper presents numerical modeling work as part of a forensic investigation on a catastrophic roadside slope failure in Taiwan. It includes three stages of numerical modeling analysis of the failure slope. Two-dimensional (2D) limited equilibrium analysis numerical modeling is first carried out to check the original design. A series of parametric studies are then introduced to investigate the influences of controlling design factors on slope stability. Finally, three-dimensional (3D) finite-element difference analysis is conducted to further examine possible failure scenarios and the failure states. As a result of this study, the failure mechanism and triggering factors were possibly verified via the numerical analyses. The purpose of the presented study hopefully introduces the applications of numerical modeling in similar forensic investigations, as well as appropriate means of adapting numerical modeling in a forensic investigation.