On the quantification of collapse margin of a retrofitted university building in Beirut using a probabilistic approach

The scope of this study is to investigate the feasibility and performance of several retrofitting techniques on an existing building in Beirut Arab University (BAU). The implemented retrofitting techniques were adding RC shear walls (SW) and steel bracing systems. Simulation and analysis procedures were performed in a nonlinear platform. Models are designed based on ACI 318-14 and ANSI/AISC 360-10 for concrete and steel, respectively. Non-linear time history analysis (NL-THA), non-linear static analysis (NL-SA) and collapse margin ratio are carried out to evaluate the performance of existing and retrofitted structures. Incremental dynamic analysis (IDA) curves are then generated and used to develop the seismic fragility curves. Three different strong ground motions are used in the analyses by referring to the UBC 1997 requirement. The IDA curves are compared based on five performance levels; operational phase (OP), immediate occupancy (IO), damage control (DC), life safety (LS), and collapse prevention (CP). The fragility curves and the calculated CMRs indicated that the shear wall and steel bracing systems both provide good seismic improvement and are able to achieve strengthening solution targets for an existing building system; however, the performance of RC-SW system under seismic excitation was much better. To this, RC-SW is considered as the most appropriate technique for retrofitting the main building of Beirut Arab University

Development of seismic vulnerability index methodology for reinforced concrete buildings based on nonlinear parametric analyses

This paper presents a simplified method in the seismic vulnerability assessment of reinforced concrete (RC) buildings based on proposed seismic vulnerability index (SVI) methodology. The employed procedure is derived with some modifications from the Italian GNDT and the European Macro-seismic approaches. Eight parameters were modeled in three distinct vulnerability classes to estimate the vulnerability indices of RC structures. The vulnerability classes were categorized based on the earthquake resistant design (ERD) defined as; (Low, Moderate, and High)-ERDs. Nonlinear time history analysis (NL-THA) and nonlinear static analysis (NL-SA) were carried out to define the weight of each parameter in order to calculate the seismic vulnerability index in a specific intensity (PGA) of an earthquake event. Knowing that it ranges from 0 to 1 from less vulnerable to most vulnerable with respect to the seismic intensity. In addition, the engineering demand parameter (EDP) used to determine the vulnerability index as the maximum top displacement of the structure. After determining the (SVI), The mean damage states were developed to evaluate the estimated physical damage of buildings in distinct seismic intensities. • This simplified methodology helps to manage and implements strategies for the safety of the communities before earthquake takes place by investigating the vulnerability classes for each building type. • Modeling the parameters that have an influence on the structural behavior without considering the past-damages observations through an analytical approach. • Developing the seismic vulnerability index can reduce or limit the role of the rapid visual screening methods, which is based on expert opinion decisions, and depends on observations of damages caused by earthquakes, and can be a useful framework criterion in earthquake filed

The seismic vulnerability assessment methodologies : a state-of-the-art review

In the past decades, the research and development of methodologies have received considerable attention which quantified earthquake-related damages to structures. Among these, indices of seismic risk and vulnerability assessment have indeed been developed to quantify the level of damages to structural elements or the whole structural system. In this paper, a detailed investigation has been done on the developed methodologies in the field, and the findings from other works are summarized. The authors have tried to present the most common empirical and analytical methodologies in a concise manner, which would motivate researchers and practicing engineers to use it as a comprehensive guide and reference for their future works

Assessment of seismic scenario-structure based limit state criteria for a reinforced concrete high-rise building

Issues regarding reinforced concrete (RC) high-rise buildings involve different seismic scenarios, such as near- and far-field earthquakes, which can result in different levels and complex seismic scenario structures related to global damage. This study aims to evaluate the seismic scenario structures of a 23-storey RC high-rise building based on different damage measures and to develop a fragility curve with different limit state criteria. Six ground motions are selected to represent two seismic scenarios. Seismic scenario-based global response of the building at increasing earthquake intensity measures is adopted using incremental dynamic analysis (IDA). IDA curves and interstorey drift are used in the parametric study. The structural performance and damage measure of RC high-rise buildings are evaluated with performance-based seismic design limit state. The four performance levels proposed by ATC-43 are operational performance, immediate occupancy, life safety and collapse prevention. The IDA curves showed that near-field effect has a high frequency that gives impact at early intensity measures on building collapse compared with far-field effect. Meanwhile, interstorey drift result indicates that the near-field effect has a larger effect on building damages compared with the far-field effect. Based on the fragility curves, near-field earthquakes have a larger effect towards structural damages than far-field earthquakes

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Information Fusion and Resource Allocation for Accelerated Life Testing-Based Reliability Assessment

Accelerated life testing (ALT) has been widely used to expedite the analysis of a product's failure time when used under normal conditions and calculate its reliability. For engineering systems with multiple components, ALT could be performed at different levels, namely component level and/or system level. Present methodologies in ALT allows for the assessment of system reliability by testing at the system level or single components without considering dependence. This research aims at fusing testing information collected from different levels in order to draw system reliability conclusions. It tackles the dependence between the component failure times of a system, which is caused by unobservable factors. Two novel frameworks are proposed to analyze the reliability of systems with multiple components using ALT. We model the dependency using a Copula function in conjunction with Weibull distributions in the first framework and using shared frailty models with extended hazard model in the second. We present the concept of information fusion which is a method to fuse both component-level ALT data with system-level ALT data to calculate system reliability. An optimization model that is constrained by the cost of testing and bounded ALT design parameters, namely stress levels and number of tests at each stress levels, is developed to find the optimal and cost-effective ALT plans. This research relies heavily on different statistical concepts and Bayesian inference approaches. A four-arm robots and electrical circuit broad of autonomous vehicles examples are used to demonstrate the proposed approaches.PhDCollege of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/167356/1/Kassem Moustafa Final Dissertation.pd

The efficiency of an improved seismic vulnerability index under strong ground motions

This paper examines the seismic performance of a Hospital Building damaged during the Ranau earthquake in Malaysia of intensity level (VIII), through an improved empirical seismic vulnerability index (SVI). The research aims at reducing the limitations and the uncertainties associated with the GNDT and the EMS approaches related to RC buildings, which can possibly be resolved by implementing the analytical techniques via applying nonlinear parametric analysis. Nonlinear time-history analyses were performed by incorporating an array of strong ground motions divided between far-field and near-field sets to assess the influence of each category on the SVI values and then comparing with SVI values obtained from the nonlinear static analysis (NSA). For a better comparison, the results are depicted in terms of collapse fragility curves for the modeled parameters. The proposed approach has been verified through observational fragility curves after Ranau earthquake. Whereas, the obtained SVI values were similar for the near-field and far-field, but with different collapse intensities and mean damage grades

Improved vulnerability index methodology to quantify seismic risk and loss assessment in reinforced concrete buildings

An improved seismic vulnerability index methodology is formulated on the basis of eight modeled parameters that are designed according to earthquake-resistant design concept and derived from the empirical vulnerability index that was initiated by the Group of National Defense against earthquake, named as GNDT Level approach. The results indicated that there is a good correlation between the analytical modeling approach and the observed fragility features during in-situ field investigations. To prove that the proposed methodology is accurate and reliable, the verification of the current methodology is performed through the experimental testing related to school building damages during Ranau Earthquake

Development of a uniform seismic vulnerability index framework for reinforced concrete building typology

This paper presents a uniform framework for seismic vulnerability assessment of selected reinforced concrete (RC) structures in Malaysia based on an improved seismic vulnerability index (SVI) approach. To establish the formulated framework, three stages of validation are applied to two reference buildings damaged during the 2015 Ranau seismic event in Malaysia. Throughout the first stage, field examinations for the addressed building damages (Hospital and School Buildings) are identified, and then a detailed diagnosis of physical damage elements across field visual observation has been performed. In the second stage, a transitioning progress from empirical field examination into an analytical assessment is utilized using finite element simulation to derive an improved seismic vulnerability index (SVI). This is achieved by finding the proper parameters such as beam-column joint connection; support boundary condition; horizontal diaphragm system; type of soil; ductility level; horizontal and vertical mass irregularity, and material strength. To achieve this aim, the buildings have been explicitly modeled using nonlinear parametric analysis (NL-PA) and their vulnerability groups have been categorized based on the earthquake-resistant design (ERD). The improved seismic vulnerability index is used to predict the susceptibility of the structures after performing a nonlinear parametric analysis. Eventually, using probabilistic seismic risk assessment with the compatibility of field real damage and the location of the plastic hinges in the structural members, the modeling verification process is achieved. It is concluded that the use of the new analytical vulnerability index damage indicator can be used as a guidance for earthquake impact assessments in Malaysia and can be applied uniformly to any country irrespective of the differences in construction and seismicity