Progressive Collapse Analysis of the Champlain Towers South in Surfside, Florida

Since the Ronan Point collapse in the UK in 1968, the progressive collapse analysis of residential buildings has gradually drawn the attention of civil engineers and the scientific community. Recent advances in computer science and the development of new numerical methodologies allow us to perform high-fidelity collapse simulations. This paper assesses different scenarios that could have hypothetically caused the collapse of the Champlain Tower South Condo in Surfside, Florida, in 2021, one of the most catastrophic progressive collapse events that has ever occurred. The collapse analysis was performed using the latest developments in the Applied Element Method (AEM). A high-fidelity numerical model of the building was developed according to the actual structural drawings. Several different collapse hypotheses were examined, considering both column failures and degradation scenarios. The analyses showed that the failure of deep beams at the pool deck level, directly connected to the perimeter columns of the building, could have led to the columns’ failure and subsequent collapse of the eastern wing of the building. The simulated scenario highlights the different stages of the collapse sequence and appears to be consistent with what can be observed in the footage of the actual collapse. To improve the performance of the structure against progressive collapse, two modifications to the original design of the building were introduced. From the analyses, it was found that disconnecting the pool deck beam from the perimeter columns could have been effective in preventing the local collapse of the pool deck slab from propagating to the rest of the building. Moreover, these analyses indicate that enhancing the torsional strength and stiffness of the core could have prevented the collapse of the eastern part of the building, given the assumptions and initiation scenarios considered

A methodology to quantify debris generation after a seismic event

Seismic damage simulation at the regional scale can potentially provide valuable information that can facilitate decision making, enhance planning for disaster mitigation, and reduce human and economic losses. When an earthquake happens, building damage assessment is one of the important issues in earthquake loss estimation. The amount of debris generated and the effects on related critical infrastructures is also an essential information to evaluate. Indeed, as cascading consequence of debris accumulation, the road network can be interrupted. This entails an overall increase in the average number of people who have difficulty evacuating, with high risk that residents cannot evacuate any areas. This study proposes a method to evaluate the debris affected area and the debris amount as a function of the geometric characteristics and the level of damage of the buildings. The first part of this work is focused on the evaluation of the debris area’s extension by numerical simulations. Comparison of the results with images of real seismic damaged structures allows the validation of the results. Besides, experimental tests on a small shaking table are performed to validate the numerical simulations. A mathematic model based on the results is also proposed

DAMAGE PATTERN ANALYSIS OF THE BASILICA DI COLLEMAGGIO USING AEM MICRO-MODELING

This work focuses on the numerical analysis of the Aspe, Nave, and Transept of the ‘Basilica di Collemaggio’, which was seriously damaged and partially collapsed after the 2009 L’Aquila earthquake. The research team acquired the geometry of the structure through a terrestrial laser scanner. A detailed numerical model was developed using an Applied Element Method micro-modeling technique. The numerical model includes the actual arrangement of walls, arches, vaults, and voids in the masonry. The non-linear behavior of the masonry was modeled through equivalent springs. Non-linear dynamic analyses were performed considering both the in-plane and out-of-plane behavior of the structure. The proposed technique was able to simulate crack development and damage propagation. Comparing the numerical results to the acquired survey data, the model proved consistent and reliable. Therefore, this numerical approach could be used to study the behavior of the structure with different retrofit solutions

Numerical simulations of collapse tests on RC beams

Recent events of bridge collapses, e.g. in Genoa (Italy) on August 14th 2018 and in Kolkata (India) on September 4th 2018, have focused the public interest on the infrastructures' safety for their consequences in terms of fatalities and injuries, but also of economy and social losses. Indeed, focusing on reinforced concrete structural components such as beams, they are subjected during their service life to different loading conditions that may affect their durability and efficiency. This can reduce the structural safety over time until its complete degradation up to the ultimate limit state. In particular, reinforced concrete elements can develop cracking conditions due to tensile stresses that are normally absorbed by the reinforcement. However, such cracking conditions can develop and propagate leading to the exposure of the reinforced concrete element to the aggression of external agents such as chlorides up to collapse. In this work, collapse tests on reinforced concrete beams are reproduced in laboratory through nonlinear numerical simulations. The numerical outcomes will be also compared to available monitoring data collected by distributed fiber optics sensors and image correlation techniques to monitor the state of cracking and its propagation in the thickness

Reliability of collapse simulation - comparing finite and applied element method at different levels

Numerical prediction of progressive collapse of buildings due to extreme loading is still a challenging task. However, increased computational power makes it nowadays possible to analyze not only small-scale connections and mid-size building elements, but also full buildings with considerable height and complexity. The present paper compares the results of Finite Element Method (FEM) and Applied Element Method (AEM) simulations to experimental results when performing blast or earthquake analysis on those three scales. The aim is to highlight which level of physical detail and complexity is required to predict progressive collapse numerically, and which level of accuracy can be expected. For the full scale level, the progressive collapse of the Pyne Gould Corporation Building in Christchurch, New Zealand, was simulated and compared to the final collapse shape. It is shown that the FEM is able to predict the structural response of small scale models well, but fails to achieve realistic collapsed shapes in case of the large structure, whereas the AEM shows convincing results in all cases

DYNAMIC CHARACTERIZATION OF THE CIRCUS MAXIMUS ARCHEOLOGICAL SITE

Monumental structures and archeological sites are often exposed to intense ambient and anthropic vibrations which might compromise their structural integrity. Monitoring these precious assets allows to assess their overall conditions and highlight possible changes in the behavior of the structure. In this paper, the effects of vibrations on the Circus Maximus archeological area are investigated. A wireless structural health monitoring system was used to record accelerations from July 2022 to January 2023. During this period, several concerts and events were held in the area. The acceleration records were used to perform dynamic characterizations of the site. Different numbers of sensors and configurations were used to assess the influence of spatial resolution. The modal properties were obtained through the frequency domain decomposition technique and compared to those from previous studies. Overall, a reduction of the modal frequencies has been observed which requires further investigations