Theory Of Structural Vulnerability Research Articles

Collapse analysis and robustness assessment of dropped-story steel frame structures based on structural vulnerability theory

ABSTRACT This paper proposes an improved analysis method based on the theory of structural vulnerability, which incorporates structural redundancy and comprehensively analyzes structural vulnerability and robustness by considering the changes in structural stiffness and redundancy after damage to structural members under conventional loading. The improved method takes into account the changes in the strain energy of the structure after the damage of the structural members, which can be more in line with the actual situation of continuity collapse, and solves the complex process of traditional structural vulnerability theory that requires clustering and unclustering, greatly reducing the workload as well as solving the problem of not being able to find the critical members of the structure. The improved method is used to analyze the vulnerability of a 5-story dropped-story steel frame structure, to find the critical members of the structure based on the test data simulated by ABAQUS, to evaluate the robustness, and to propose improvement measures. The results show that the improved vulnerability assessment method is more reasonable and effective and can be applied to different steel frame structures.

Intra-Lagos migration and spread of COVID-19: revisiting the structural vulnerability theory

Intra-Lagos migration and spread of COVID-19: revisiting the structural vulnerability theory

The structural impacts of enforcement policy on Latino immigrant health.

As evidence of the negative health impact of immigration enforcement policy continues to mount, public health research has focused primarily on the psychosocial health mechanisms, such as fear and stress, by which immigration enforcement may harm health. We build on this research using structural vulnerability theory to investigate the structural processes by which enforcement policy may shape Latino immigrants' health. We conducted qualitative analysis of testimonios from a purposive sample of Latino immigrants (n=14) living in Southern California in 2015, a period of significant federal, state, and local enforcement policy change. Testimonios are a narrative methodology used across the social sciences and humanities to center the voices of marginalized people. Through unstructured testimonio interviews, we sought to understand Latino immigrants' experiences with immigration enforcement and identify specific structural factors by which those experiences may influence health. Respondents' narratives revealed that singular enforcement experiences were not viewed as the sole manifestation of enforcement, but as part of a system of intersecting physical, legal, institutional, and economic exclusions which shaped the social and economic conditions that influence health. These exclusions reinforced respondents' marginalization, produced instability about the future, and generated a sense of individual responsibility and blame. We discuss how physical, legal, institutional, and economic processes may influence health and propose a framework to inform population health research on intersecting structural health mechanisms.

Crime in the new U.S. epicenter of COVID-19

In the latter half of 2020, Los Angeles was dubbed by the media and academicians as the latest epicenter of COVID-19 in the United States. Using time-series analysis on Los Angeles Police Department crime data from 2017 through 2020, this paper tests the economic theory of crime, routine activities theory, social isolation theory, and structural vulnerability theory to determine whether they accurately predicted specific crime rate movements in the wake of COVID-19 in the city of Los Angeles. Economic theory of crime was supported by the data, and social isolation theory and structural vulnerability theory were partially supported. Routine activities theory was not supported. Implications for policymakers and academics are also discussed.

The most adverse fire scenario research of steel frame structure fire-resistant design based on structural vulnerability analysis

The complex responses of the building under fire condition lead to difficult realization of structural fire-resistance design. By identifying the weakness areas, the defined most adverse scenario of the structural fire-resistance design has practical significance. In this paper, the characteristics of fire load, steel at elevated temperature and failure modes of steel beam and column in fire test, were discussed to determine that the damage consequences of steel components under fire were equivalent to component fracture. Meanwhile, the calculation method of joint well-formedness after component failure was given to recognize the failure mode of steel frame structure under fire condition based on structural vulnerability theory (SVT). Then, the most adverse fire scenario of the steel frame structure fire-resistance design under the conditions of single component failure and component failure continuously were analysed. The calculation method of the most adverse fire scenario based on the structural SVT was proposed. According to the failure mode identified by the SVT, the most adverse fire scenario was that the component with the minimum damage pattern subjected to fire in the condition of a single component failure occurred. When the component failed continuously, the components induced the maximum damage pattern (the vulnerability index was the largest) were the key components and such components exposed to fire was the most adverse fire scenario. Finally, two calculation models-6-story 4-span planar steel frame and 3D CFS composite shear wall structures-were selected to verify the proposed calculation of the most adverse fire scenarios. It was concluded that the proposed calculation method could reduce the number of fire scenarios that need to be calculated for design and was suitable for application to performance-based fire resistance design.

Crime in the New U.S. Epicenter of COVID-19

In the latter half of 2020, Los Angeles was dubbed by the media and academicians as the latest epicenter of COVID-19 in the United States. Using time-series analysis on Los Angeles Police Department crime data from 2017 through 2020, this paper tests the economic theory of crime, routine activities theory, social isolation theory, household bargaining theory, and structural vulnerability theory to determine whether they accurately predicted specific crime rate movements in the wake of COVID-19 in the city of Los Angeles. Economic theory of crime and routine activities theory were mostly supported. Social isolation theory and household bargaining theory were partially supported. Structural vulnerability theory was not supported. Implications and future research are also discussed.

Structural Vulnerabilities, Personal Agency, and Caste: An Exploration of Child Sex Trafficking in Rural India.

The commercial sexual exploitation of children (CSEC) is considered normative and expected among some Indian castes. Focusing on the Bedia specifically, we sought to identify factors responsible for the intergenerational continuation of CSEC as well as opportunities for prevention. To this end, three questions were posed, including: (a) What structural factors perpetuate CSEC among the Bedia? (b) What are the mechanisms by which Bedia children enter the commercial sex industry (CSI)? and (c) To what extent do Bedia women have personal agency in exiting the CSI and in keeping their children from entering? Guided by structural vulnerability theory and a phenomenological approach, in-depth interviews were conducted with 31 Bedia women engaged in (or exited from) the CSI. Results indicate that girls as young as 12 are "selected" to enter the CSI; once involved, they carry the burden of familial financial sustainability and exit only comes when they are no longer able to attract paying clients and younger female kin able to assume the primary breadwinner role. Ability to keep female children from entry is minimal. Implications for future research, practice, and policy are discussed.

Collapse mechanism and shaking table test validation of a 3D mid-rise CFS composite shear wall building

Abstract Structural vulnerability theory (SVT) is a method that identifying the weakness and potential collapse modes of building structures in the finite element (FE) aspect, and the determinant of the global stiffness matrix |K|≤0 is proposed as the judgment of collapse of building structures. Due to the limitation of the SVT in identifying plastic hinge failure modes of the framed structures, this paper proposes the improved SVT (SVT), in which the transformation processes of the connections from rigid ones to pinned ones are considered. Based on the foundations of the ISVT using in planar framed structures, which was conducted by the authors, this paper develops the ISVT from 2-dimension to 3-dimension, and a 5-story cold-formed steel (CFS) building was tested to verify the ISVT. The results show that: the predicted collapse mode with maximum vulnerability index from the ISVT is same with the failure patterns of the test building, the first unzipped elements predicted by the ISVT are same with the most serious damaged components observed form the test. Such two aspects demonstrate the feasibility of the ISVT in revealing the collapse mechanism of the 3D CFS structures. Besides, this paper recommends the expected collapse mode for mid-rise CFS structures, and proposes “strong-frame weak-wall” concept to realize seismic design of the expected collapse mode. The findings can be used for collapse resistance design for mid-rise CFS buildings subjected to earthquakes.

Collapse mechanism analysis of the FIU pedestrian bridge based on the improved structural vulnerability theory (ISVT)

On Mar 152018, a pedestrian bridge on the campus of Florida International University (FIU bridge) collapsed during construction, and 6 victims were identified in this disaster event. This paper investigates the collapse mechanism of the FIU bridge through improved structural vulnerability theory (ISVT). A topological hierarchy model of the FIU bridge is established by the clustering process of the ISVT, and various possible collapse modes are identified by the unzipping process. Besides, the damage event that vibration effects by crane is considered in the computing work. By comparing the collapse mode identified by ISVT and the actual collapse scenario of the FIU bridge, it is found that ISVT could effectively identify the weakness and predicts the possible collapse modes of the FIU bridge by an quantitative vulnerability index. Then, parametric analyses are conducted for the bridge to different unforeseen damage events, and the collapse mechanism of the failure characteristics of the FIU bridge is also revealed by the ISVT. Finally, some suggestions are recommended for the structural design of rigid frame bridge like the FIU bridge.

7.2-O2Keeping healthy and accessing primary and preventive health services in Glasgow: the experiences of refugees and asylum seekers from Sub Saharan Africa

Background and aims: Recent decades have seen material shifts in global migration flows. Migrants now come to the UK for an increasing number of reasons and from an increasing number of countries. This presents a challenge for health services that must provide care to individuals with a broad range of needs. In particular, there is concern that asylum seekers and refugees (ASRs) are at heightened risk of poor wellbeing and of receiving suboptimal healthcare. Concurrent with these shifts in migration, increasing attention is being paid to noncommunicable diseases (NCDs), which are now the most significant drivers of morbidity and mortality in most regions of the world. In the UK, the burden of NCDs is not evenly distributed, with inequalities related to ethnicity and socioeconomic status shaping an individual’s risk of ill health. Little is known, however, about how diverse migrant groups, including ASRs, conceptualise health and respond to health prevention messaging. Against this backdrop, this thesis aims to understand the health-related experiences of one such group – asylum seekers and refugees (ASRs) from Sub Saharan Africa living in Glasgow Scotland. Specifically, it explores: a) perceptions of health, wellbeing, and illness causation, b) experiences of accessing primary and preventive healthcare, and c) the factors influencing these perceptions and experiences. It also seeks to elucidate professional perspectives on ASR health. Methods: To gain an in depth understanding of ASR health perceptions and experiences, as well as professional perspectives, a focused ethnography was undertaken. This approach utilised four qualitative methods: community engagement, participatory focus groups, semistructured interviews, and go- along interviews. In total 12 primary care and public health professionals were interviewed, and 27 ASRs took part in either a focus group, an interview, or both. The thesis took a theoretically informed approach, seeking to determine whether and how two theories – ‘candidacy’ (Dixon-Woods et al 2005) and ‘structural vulnerability’ (Quesada et al 2011) – might deepen our understanding of ASR health. Results: Candidacy enhanced understanding of how ASRs identified and responded to messages about ‘healthy lifestyles’. ASR participants considered keeping healthy to be an individual responsibility, with diet and exercise highlighted as especially important. At the same time, however, perceptions and experiences of health and wellbeing were shaped by a number of structural influences, which limited the capacity of ASRs to engage in health practices. Therefore, while ASRs considered health to be an individual choice in theory, they did not necessarily feel they had the ability to be healthy in practice. The theory of structural vulnerability proved useful in identifying the wider structural determinants that impacted on an individual’s capacity to respond. There were several important structural influences, including poverty, racism, discrimination, and language barriers. The greatest negative influence, however, and one that compounded all the others, was the asylum process. This diminished individuals’ capacity to identify as candidates for prevention messages, engage in preventive health practices, and/ or access care in an optimal fashion. Conclusions: Efforts to engage ASRs in preventive health programmes and practices must take into account the ways in which the immigration and asylum system acts as a determinant of health, affecting both what it means to be healthy and what capacity individuals have to engage. The NHS, together with non statutory bodies, has a role to play in mitigating some of the vulnerabilities to which ASRs are subject.

Bringing a structural perspective to work: Framing occupational safety and health disparities for nursing assistants with work-related musculoskeletal disorders.

Certified Nursing Assistants (CNAs) experience a high risk of work-related musculoskeletal disorders (WMSDs) and are further made vulnerable by their situation in low levels of workplace and societal hierarchies of power and privilege. This study applies structural vulnerability theory to CNA WMSD experiences in order to identify structural factors that may influence such injuries. A sample of CNAs (n = 26) working in Nursing and Residential Care Facilities (NRCFs) was selected from workers who filed a claim during 2011-2014 for a WMSD of the back, shoulder, knee, or hand/wrist in the Washington State Department of Labor & Industries workers' compensation system. Interviews included questions about workers' injury experiences and work contexts. Qualitative data was analyzed for themes related to structural vulnerability theory and occupational safety and health (OSH) models. Themes illustrate a work environment in NRCFs with major organizational deficiencies for CNA safety and a broader structural environment that appears to mediate them. CNAs described policies and practices that result from management priorities being diverted away from worker safety. These difficulties are compounded by several aspects of CNAs' socio-economic vulnerability. This study demonstrates the utility of a structural perspective for OSH disparities research and points to the need for occupational health intervention on a structural level.

Collapse mechanism analysis of a steel moment frame based on structural vulnerability theory

This paper presents an improved method to analyze the collapse mechanism of steel moment frames based on structural vulnerability theory (SVT), in which the failure processes of the essential components are defined according to the damage characteristics of their ductile and brittle members. The improved method can accurately identify possible collapse modes of steel moment frames, because the transformation processes of such connections as beam-column joints and support joints from rigid connections to pinned ones were considered. Structural vulnerability analysis is performed on a 4-story steel frame structure by using the improved method, the results show that the collapse caused by joint failure in the first story had the maximum vulnerability index, so that the weakness of the steel frame may be located in the first story; while the collapse behaving as a “beam plastic hinge” failure, as an expected failure mode, had the minimum value. Moreover, the improved method was validated by a shaking table test due to the consistence between the experimental results and the collapse modes calculated to have the maximum vulnerability index, which demonstrates that such improved method could be effectively to predict the collapse modes of steel frame structures.

Optimization of domes against instability

Static stability is a decisive factor in the design of domes. Stability-related external factors, such as load and supports, are incorporated into structural vulnerability theory by the definition of a relative rate of joint well-formedness (rr). Hence, the instability mechanism of domes can be revealed. To improve stability, an optimization model against instability, which takes the maximization of the lowest rr (rr,min) as the objective and the discrete member sections as the variables, is established with constraints on the design requirements and steel consumption. Optimizations are performed on two real-life Kiewitt-6 model domes with a span of 23.4 m and rise of 11.7 m, which are initially constructed for shaking table collapse test. Well-formedness analyses and stability calculation (via arc-length method) of the models throughout the optimization history demonstrate that this proposed method can effectively enhance rr,min</sub and optimize the static stability of shell-like structures. Additionally, seismic performance of the optimum models subjected to the same earthquake as in the shaking table test is checked. The supplemental simulations prove that the optimum models are superior to the original models under earthquake load as well.

Structural vulnerability of two traditional Portuguese timber structural systems

In general, the traditional Portuguese buildings show an undesirable deterioration level and, consequently, urgent rehabilitation processes are required. These buildings need maintenance and preservation because they are a valuable Portuguese heritage. Knowing and understanding these buildings is the first step for adequate rehabilitation processes. Usually, these buildings show the same pattern of pathologies and failure sequence. This research work is focused on the study of the roof timber structural systems of these buildings and intends to highlight these aspects. An expedite methodology of structural vulnerability assessment of the traditional Portuguese timber roof structures based on the structural vulnerability theory is presented. Real cases of traditional Portuguese timber roof structures are used. It was concluded that the trussed timber roof system seems less robust than the beamed system.

A Theory of Vulnerability of Water Pipe Network (TVWPN)

The main objective of this paper is to introduce the proposed theory of vulnerability of water pipe network (TVWPN) and, in particular, its theoretical concepts. These concepts have a basis in the structural vulnerability theory (Agarwal et al., Civ Eng Environ Syst 18(2):141–165, 2001a, J Struct Saf 23(3):203–220, 2001b; Lu et al., Struct Eng 77(18):17–23, 1999; Lu 1998; Pinto 2002; Pinto et al., J Struct Saf 24:107–122, 2002; Yu 1997). The fundamental contribution of this theory is to help design water pipe networks (WPN) more robust against damage to the pipelines. This is achieved through an analysis of the form of the network. The application of the TVWPN is presented through an example of a water pipe network.

Recent developments in robustness and relation with risk

Structural engineering is a mature discipline, but in practice the nature of demands or actions on a structure remains uncertain. It is difficult to foresee where damage, for example resulting from an accident or material degradation, might occur. A structure that is robust will be able to cope with such unexpected demands without disproportionate consequences. There is, however, no satisfactory measure of robustness: not even a widely agreed definition. In this paper an overview of the current guidelines and methodologies to achieve a robust structure is provided. Most of the analytical studies assume a model of loading, but to achieve robustness there is a need to identify potential weaknesses in the form of a structure. In this respect, structural vulnerability theory can be an effective tool to reduce the risk of propagation of failure owing to unforeseen damage or actions. Similar models are already used in the insurance industry to determine the risk to natural and man-made hazards.

The vulnerability of structures to unforeseen events

A structure is vulnerable to an unforeseen event if it is not sufficiently robust. One insight into the lack of robustness is gained through the vulnerability of a structure to disproportionate collapse. In this paper, the importance of assessing the vulnerability of a structure to unforeseen events is highlighted and the nature of unforeseen events examined. A theory of structural vulnerability which examines the form of the structure to determine the most vulnerable sequence of failure events is briefly described. The potential for damage to propagate through a structure is examined through a new measure of hazard potential and vertical pushover analysis. An analysis of an example structure shows that such an approach is able to capture the weaknesses in a structure either due to form or external actions.

Vulnerability of structural systems

A structure is vulnerable if relatively small damage leads to disproportionately large consequences. A structure which is unacceptably vulnerable in any one way is not acceptably robust. A theory of structural vulnerability has been previously reported by the authors. The purpose of the theory is to identify particular failure scenarios by analysing the connectivity of the structural form. In this paper vulnerability theory is applied to three-dimensional frames and, in a preliminary way, to structural dynamics which is crucially important in assessing impact damage in for example progressive collapse. The concepts are illustrated through examples. The vulnerable failure scenarios may then be examined by conventional response analysis and/or by systems reliability theory and risk assessment. The theory is also applicable to structural damage assessment or for assessing structures under unforeseen terrorist attack.

Structural vulnerability, reliability and risk

AbstractA system is robust if it can withstand arbitrary damage. There are many practical ways to design in robustness, but there is as yet no accepted theory of robustness. Reliability theory is a useful tool for examining the probability of failure for a pre‐defined type of loading; however low‐probability–high‐consequence events may be missed. One insight into the lack of robustness is gained by identifying how a system is vulnerable. A system that is vulnerable in any one way is not robust. Like robustness, vulnerability has been defined differently in different contexts. The purpose of this paper is not to argue for particular definitions of robustness, vulnerability or risk, but rather to review a ‘theory of structural vulnerability’ developed by the authors and to show how it can be used in practice to improve the robustness of a system. The theory is one of form and connectivity. The purpose is to identify weak links within a structure as vulnerable failure scenarios. These can then be used with the probability of actions causing them to produce a measure of structural reliability and risk.

The risk of vulnerable failure

There is, as yet, no generally accepted theory of structural robustness or of its corollary, structural vulnerability. The theory of structural vulnerability developed at the University of Bristol is a theory of form that seeks to identify failure scenarios where small damage can lead to disproportionate consequences. In this paper the previously reported theory is combined with a standard response analysis to produce a measure of structural risk which includes the chance of a vulnerable loss of functionality. A simple example of a pin jointed structure is presented.