Vulnerability Assessment Of Structures Research Articles

Seismic vulnerability assessment of reinforced concrete school building in Nepal

The school building built with reinforced concrete in Nepal confront high seismic risk during past seismic events. The vast extent structural damage and loss of human life’s and property was due to the poor enforcement of the standards, lack of ductile detailing and poor construction materials and practices in Nepal. The effect of earthquake excitation on buildings was ignored after the latest earthquake in 2015. Most of the school structures were used in full-fledged without performing any seismic evaluation. Seeing these situations, especially in Nepal, a vulnerability assessment of such school structures is essential. The seismic risk owing to future earthquake can be minimize by proper vulnerability assessment of the school structures. To this end, the purpose of the study is to evaluate seismic performance of school structure through both vulnerability and fragility assessment. The main research issues are explored through analytical method. For this, structural response parameters are analytically studied through linear and non-linear analyses by finite element program-based software. In dynamic analysis, numerical building models were subjected to three synthetic earthquakes Gorkha, El-Centro and Kobe. The fragility function of case study building structure was plotted with the probability of failure at every 0.1 g interval of PGA, which provided technical base for seismic vulnerability assessment of school buildings. The result indicates that the selected school building is found to be vulnerable compared with the standard international guidelines. The results of this study are more useful for different governmental authorities, emergency response organization who are directly involved for proper planning and implementation.

Analysis of Seismic Fragility Functions of Highway Embankments

Vulnerability assessment of structures is a vitally important topic among earthquake engineering researchers. Generally, their primary focus is on the seismic performance of buildings. Less attention is paid to geotechnical structures, even though information about the performance of these structures (e.g. road embankments, levees, cuts) during an earthquake is essential for planning remediation and rescue efforts after disasters. In this paper the seismic fragility functions of a highway embankment are defined following an analytical methodolgy. The technique is a displacement-based evaluation of seismic vulnerability. Displacements of an embankment during a seismic event are approximated by a 2-D nonlinear ground response analysis using the finite element method. The numerical model was calibrated based on the results of a 1-D nonlinear ground response analysis. The expected displacements were calculated for 3 different embankment heights and Peak Ground Acceleration (PGA) values between 0,05 and 0,35g. Based on the results of the 2-D finite element analysis, the relationship between displacements and different seismic intensity measures (PGA, Arias-intensity) was investigated. Different damage states were considered, and the probability of their exceedance was investigated. The seismic fragility functions of the embankments were developed based on probability of exceedance of these different damage states based on a log-normal fragility function. The legitimacy of using a log-normal fragility function is also examined.

Structural Vulnerability Assessment of Heritage Timber Buildings: A Methodological Proposal

The conservation of heritage structures is pivotal not only due to their cultural or historical importance for nations, but also for understanding their construction techniques as a lesson that can be applied to contemporary structures. Timber is considered to be the oldest organic construction material and is more vulnerable to environmental threats than nonorganic materials such as masonry bricks. In order to assess the structural vulnerability of heritage timber structures subjected to different types of risk, knowledge about their structural systems and configurations, the nature and properties of the materials, and the behavior of the structure when subjected to different risks, is essential for analysts. In order to facilitate the procedure, different assessment methods have been divided into the categories in situ and ex situ, which are applicable for vulnerability assessments at the element and full-scale level of a case study. An existing methodology for structural vulnerability assessments and conservation of heritage timber buildings is reviewed and a new methodology is proposed.

Perceived barriers to access care, anticipated discrimination and structural vulnerability among African Americans with substance use disorders.

The application of the structural vulnerability construct in medicine addresses social structures as the source of health inequities. Evidence demonstrates structural vulnerability as the meta-problem that underlie health disparities faced by underrepresented minorities who are less likely to access care and face stigma for substance use disorders (SUDs). The objective of this study is to assess perceived vulnerability at the structural and interpersonal levels depicted by barriers to care, treatment-related stigma and anticipated discrimination among African Americans with SUDs. Participants were 58 consecutive African American patients receiving treatment at an acute inpatient substance use service of a teaching hospital from September to November 2019. Structural vulnerability, barriers to care and anticipated discrimination were assessed using the structural vulnerability assessment tool, Barriers to Access Care Evaluation (BACE) and the Questionnaire on Anticipated Discrimination (QUAD) surveys, respectively. The total mean scores for the BACE-3, BACE-3 stigma subscale and QUAD were 1.0, 1.15 and 1.51, respectively. No statistically significant differences are found in the stigma subscale based on gender and psychiatric diagnosis (p > .05). Furthermore, there were also no gender, age or differences based on psychiatric diagnosis across both the BACE and QUAD scales. Structural and interpersonal factors remain sources of vulnerability, stigma and anticipated discrimination for African Americans with SUDs and comorbid mental illness.

Member and structural fragility of reinforced concrete structure under fire

Purpose Despite recognizing the significance of risk-based frameworks in fire safety engineering, the usual approach in structural fire design is largely member/component level, wherein effect of uncertainties influencing the fire resistance of structures are not explicitly considered. In this context, a probabilistic framework is presented to investigate the vulnerability of a reinforced concrete (RC) members and structure under fire loading scenario. Design/methodology/approach The RC structures exposed to fire are modeled in a finite element (FE) platform incorporating material and geometric nonlinearity, in which the transient thermo-mechanical analysis is carried out by suitably incorporating the temperature variation of thermal and mechanical properties of both concrete and steel rebar. The stochasticity in the system is considered in structural resistance, thermal and fire model parameters, and the subsequent fragility curves are developed considering threshold limit state of deflection. Findings The fire resistance of RC structure is reported to be significantly lower in comparison to the RC members, thereby illustrating the current prescriptive design approaches based on studies of structural member behavior to be crucial from a safety and reliability point of view. Practical implications The framework developed for the vulnerability assessment of RC structures under fire hazard through FE analysis can be effectively used to estimate the structural fire resistance for other similar structure to enhance safety and reliability of structures under such extreme threats. Originality/value The paper proposes a novel methodology for vulnerability assessment of three-dimensional RC structures under fire hazard through FE analysis and provides comparison of the structural fragility with fragility developed for structural members. Moreover, the research emphasizes to assume 3D behavior of the structure rather than the approximate 2D behavior.

Land Subsidence risk maps and InSAR based angular distortion structural vulnerability assessment: an example in Mexico City

Abstract. Land subsidence is a phenomenon present in several cities in central Mexico, and results from a combination of groundwater resources' overexploitation and the local stratigraphic nature. Furthermore, subsidence occurs inhomogeneously in space, producing differential vertical displacements, which affect both the natural media, as well as human-built structures. Subsidence associated structural-vulnerability assessments usually rely on direct field measurements to determine parameters such as angular distortion. However, the large areas in which land subsidence occurs (city-scale) in Mexico City hinders a direct quantification of differential displacements for all buildings and structures present in it. A Sentinel-1 based subsidence analysis shows that the highest velocities are located on the eastern sector of the city. This velocity map was used as the basis for a population density weighted land subsidence correlation analysis. Our Land Subsidence Risk assessment indicates that 15.43 % of the population of Mexico City live in intermediate, high and very-high risk zones which corresponds to 1 358 873 inhabitants. Therefore, a significant percentage of Mexico City's population is vulnerable to suffering damage in their housing structures due to land subsidence. Furthermore, the lower income inhabitants share a proportionally greater economic cost due to land subsidence and associated shallow faulting. The structural vulnerability analysis of the civil structures in the city was performed using angular distortion maps derived from the subsidence velocity gradient between October 2014–October 2017 period. These maps indicate that within this time window, ∼12 % of the total urbanized area in Mexico City had already exceeded a 0.002 radian angular distortion threshold; above which damage in civil structures is more likely to occur. In fact, more than 1 million people have already suffered damages in their houses due to the differential ground subsidence and the resulting structural angular distortion. With these results, we can evaluate correspondence between angular distortion map and critical infrastructure of the city, as a result, we found that between 0 % and 12.84 % of these buildings have undergone over 0.002 radian angular distortion.

Vulnerability assessment of irregular steel structures under traveling fires

SummaryThis paper investigates the response of tall setback irregular steel moment resisting structures under traveling fires. A seven‐story steel regular structure (RS) is first designed for gravity and seismic loads and then it is fireproofed for a fire resistance rating (FRR) of 120 min based on the ISO834 fire. Some architectural changes are then imposed on the RS to make it a setback irregular structure (SBS). Based on the traveling fire methodology, both structures are then subjected to fire curves ranging from 1% to 100% for the fire load density (qf) of 570 MJ/m2. As in the SBS, the distribution of gravity loads is not uniform; the structural fire analyses are performed twice: when the fires start from left to right and then vice versa. The results show the FRR of the RS is minimized under the fire size of 22% with the collapse time of 87.0 min. In the SBS, when the fires start from left to right and then from right to left, the FRR is minimized under the fire size of 20% with the collapse times of 75.0 and 79.0 min, respectively. This shows that the SBS is more vulnerable toward traveling fires than the RS. In order to monitor the role of qf in the FRRs of the structures, qf is then reduced, and the required analyses are repeated. This process continues to where no collapse is observed under all the fire sizes. The results indicate that the RS would remain stable if the qf is decreased to 480 MJ/m2, implying that a 16% increase should be considered to the required FRR. As for the SBS, the qf should be decreased to 440 MJ/m2 to make it stable, meaning that a 25% increase should be considered to the required FRR.

Seismic Vulnerability Assessment of Typical Stone Masonry Building

Masonry, the most commonly used building typology is the building of structures from individual units, which are often laid in and bound together by mortar. Masonry structures are the most vulnerable with external forces. Nepal is disaster prone zone and get frequently attack by various hazard such as earthquake, wind storms, flash-floods, fire, landslides, heavy rain fall, lightening and many more. So, in order to maintain resistive structures, seismic vulnerability of structure should be examined. Nepal Population and housing Census 2011, total 3350143 (2,397,441 –Mud bonded bricks/stone and 952,702- Cement Bonded bricks/ stone) houses out of 5423297 (61.77%) are found to be have masonry foundations. So, to link the context of Resistance structures in Nepal’s context first of all, the predominating stone masonry spread widely over Nepal must be checked for their seismic vulnerability. So, a typical residential stone masonry building is taken for this study. Seismic Vulnerability of the Building is examined in accordance with guidance provided by Government of Nepal- Ministry of Physical Planning and Works, 2011 in their guideline which describe the procedure for qualitative and quantitative assessment of structural earthquake vulnerability of public and private buildings in Nepal. Furthermore, Building is modelled and analyzed by using ETABS software. The outcome obtained from ETABS software are used to find the condition of building and to propose method for its strengthening.

Static force-based seismic analysis of reinforced concrete frames having weaker beam-column joints

Shake table tests were conducted on three 1:3 reduced scale two-story RC frames having weaker beam-column joints. The models were subjected to multi-levels input acceleration time histories to understand the seismic behaviour of test models. The models incurred severe damages in beam-column joint panels, forming shear hinging in joint panels, and were found in the incipient collapse state under input excitation below the design level excitation. Elastic hypothetical structures were considered having fundamental frequency that of test structures, which were subjected to actually recorded input excitation, in order to assess the seismic demands (base shear force and lateral roof displacement) using simplified analytical static procedure. The analytically predicted demands were correlated with the measured inelastic response, in order to calculate seismic response parameters (force reduction factor R and displacement modification factors Cd ). On average, R = 2.0 and Cd = 1.86 were obtained for the considered structures. The derived seismic response parameters can be employed in the analytical static force-based procedure for the seismic vulnerability assessment of RC frame structures having weaker beam-column joints. Example study is presented for the vulnerability assessment of considered structure using the proposed analytical static force procedure and the derived seismic response parameters.

SEISMIC ASSESSMENT OF EXISTING BUILDING IN BANGLADESH USING JAPANESE INDEX METHOD

Over the years buildings are constructed in earthquake prone areas without following proper seismic design code. So the structural seismic analysis of existing buildings in the earthquake prone areas will be a prime requirement in the field of civil engineering in near future. Also the structural seismic analysis will lead to the feasibility of application of earthquake retrofitting technique in the vulnerable structures. Currently the urbanization of metropolitan cities in Bangladesh is booming rapidly leading these cities to densely populated area. In the past, there has been vulnerability assessment done for building stock on several metropolitan cities, in most cases using rapid visual screening (RVS) method. But the lacking has always been there on a detailed structural vulnerability assessment. Considering these facts a study has to be done to estimate precisely the possible damage of a building’s structure. In this study an in-depth structural seismic analysis of a medium rise building has been performed using all the 3 levels of Japanese Index Method. The Seismic Index (Is) value of the building is compared with the Seismic Demand Index (Iso) value which is 0.864 for the first level and 0.648 for the second and third level of the area to check vulnerability condition of the building structure. It is observed from this study that Japanese Index Method is developed in a way that it can be used for the seismic analysis of medium rise buildings in Bangladesh.

SEISMIC ASSESSMENT OF EXISTING BUILDING IN BANGLADESH USING JAPANESE INDEX METHOD

Over the years buildings are constructed in earthquake prone areas without following proper seismic design code. So the structural seismic analysis of existing buildings in the earthquake prone areas will be a prime requirement in the field of civil engineering in near future. Also the structural seismic analysis will lead to the feasibility of application of earthquake retrofitting technique in the vulnerable structures. Currently the urbanization of metropolitan cities in Bangladesh is booming rapidly leading these cities to densely populated area. In the past, there has been vulnerability assessment done for building stock on several metropolitan cities, in most cases using rapid visual screening (RVS) method. But the lacking has always been there on a detailed structural vulnerability assessment. Considering these facts a study has to be done to estimate precisely the possible damage of a building’s structure. In this study an in-depth structural seismic analysis of a medium rise building has been performed using all the 3 levels of Japanese Index Method. The Seismic Index (Is) value of the building is compared with the Seismic Demand Index (Iso) value which is 0.864 for the first level and 0.648 for the second and third level of the area to check vulnerability condition of the building structure. It is observed from this study that Japanese Index Method is developed in a way that it can be used for the seismic analysis of medium rise buildings in Bangladesh.

Vulnerability assessment of structures with stochastic properties subjected to random seismic excitation

The present work is concerned with assessing the vulnerability of seismically excited structures using non-deterministic analysis concepts, in order to take uncertainties into account. In this respect, uncertainties in both structural properties and earthquake loads are considered. Hence, the variation characteristics of uncertain material parameters along the length of frame members are modelled using Gaussian stochastic fields. Moreover, non-Gaussian probabilistic earthquake loading is assumed, which is described with the use of random variables based on data obtained from natural ground motion records. This modelling of uncertain-ties using random variables and fields is implemented in the framework of the direct Monte Carlo simulation method, in order to calculate structural response statistics for multi-storey frames with stochastic properties subjected to random seismic excitation.

The prediction of collapse mechanisms for masonry structures affected by ground movements using Rigid Block Limit Analysis

Masonry structures belonged to the Cultural Heritage suffered severe damages in the last decays due to the action of the settlement-induced ground movements. The researchers have been developing numerical tools for the vulnerability analysis and assessment of masonry structures subjected to settlements. Continuous, discrete and rigid block models were proposed in literature. The analysis of both local or global failure modes due to settlement is a still debated topic, involving several questions related to the modelling techniques and to the investigation of the parameters which affect the masonry behaviour against foundation movements. In this framework, the paper focuses on a numerical approach for the settlement analysis based on the rigid block limit analysis. The Italian Code (NTC 2018) also suggests linear kinematic approach for the seismic-induced collapse mechanisms analysis. In such a formulation, the structure is modelled as a collection of polyhedral rigid blocks assuming frictional contact interfaces with infinite compressive strength and zero tensile strength and neglecting the mortar contribution. Originally formulated for the in-plane and out-of-plane mechanisms analysis, the numerical formulation was recently improved in order to analyze blocky-structures subjected to uniform settlement.Numerical case study of a monumental masonry church façade subjected to uniform settlement at the base was presented in this paper aiming at testing the numerical procedure. The results were discussed to evaluate the software capability and accuracy in the settlement-induced collapse mechanisms prediction.

Punch-Through Risk of Jack-Up Under the Dual Uncertainty of Structure and Foundation

Abstract The preload operation of Jack-up in complex multi-layered foundation requires an enhanced understanding of its behavior in punch-through accident and suitable safety analysis tools for the assessment of their reliability in a particular site. In order to evaluate punch-through risk, a risk-consistent method is proposed based on the model of foundation hazard and structural vulnerability. Besides, foundation bearing capacity is evaluated to quantify foundation hazard. Third, to improve the solution efficiency, higher-order moment method (HOMM)-Pushover method has been developed for assessing the structural vulnerability. In addition, case studies are presented to demonstrate the advantages of these techniques and important trends are highlighted by the results of parametric sensitivity studies. More specifically, failure probability analysis has been undertaken using improved method and the punch-through risk is evaluated quantitatively in different hazard levels. The results show that the dual uncertainty of both structure and foundation is crucial for assessment of foundation hazard and structural vulnerability. The randomness of foundation parameters is the dominant factor affecting the punch-through risk, and the risk increases with the increase of preload weight. The time-varying risk in the process of preload operation can be revealed using the risk analysis method mentioned in this paper.

Seismic vulnerability assessment of building stock of Malakand (Pakistan) using FEMA P-154 method

Earthquakes have caused huge infrastructural damages along with loss of lives in the recent past. Continuous subduction of the Indian plate beneath the Eurasian plate has made Pakistan a seismically active region in the world. Malakand, located in the Khyber Pakhtunkhwa Province of Pakistan, is declared at high earthquake risk by the National Disaster Management Authority of Pakistan, warranting a seismic vulnerability assessment study for its existing building stock. Vulnerability assessment of a representative sample of different building use-types was carried out using the rapid visual screening (RVS) procedure of FEMA P-154. The sample size was calculated based on Yamane formula. RVS sheets are used to calculate structural scores, and likely seismogenic damage is depicted as a function of damage grades of European Macro Seismic Scale. Of the building stock inspected, it was observed that almost half of the buildings fall in damage grade 4 and 5, implying a strong probability of heavy structural and non-structural damages in the case of future earthquake occurrence. Government school buildings were found to be less vulnerable than private counterparts. Most of the commercial buildings were not constructed according to building code, making them highly susceptible to damage. Based on the results of vulnerability assessment of building structures, the article recommends implementation of building codes which can lead to a decrease in infrastructural damages and economic losses in the wake of a future seismic event.

An assessment of building vulnerability to a tsunami in the Galle coastal area, Sri Lanka

Tsunami vulnerability assessment is the initial step for effective planning and implementation of tsunami risk reduction. Whilst the high tsunami risk of the Galle coastal area is well known, the structural vulnerability to tsunami hazards has never been assessed. This paper presents tsunami vulnerability for structures, relative vulnerability indexes, and vulnerable areas in Galle city, Sri Lanka. To develop the relative vulnerability index map, data on 705 buildings in terms of attributes of the building, protection of the building, and depth of the water flow at the building location were obtained from field surveys. The results of the structural vulnerability assessment show that if the 2004 Indian Ocean tsunami were to occur today, 35% of the buildings would be affected in the Galle coastal area and when we consider the 100 m buffer zone, this value increases to 56%. Buildings with minor vulnerability constituted around only 3% inside the 100 m buffer zone.

Dempster–Shafer Theory applications in post-seismic structural damage and social vulnerability assessment

ABSTRACT The inherent uncertainty involved in assessments of both post-seismic structural damage and the social vulnerability of those affected motivates the search for a suitable analysis framework. As these risk assessments are subjective in nature and require expert opinion, many common methods such as probability may not provide the most natural mathematical structure. This paper explores how Dempster–Shafer Theory might be used in these applications, as this theory allows the combination of multiple expert beliefs while considering such uncertainties. A post-seismic structural damage assessment survey was used to evaluate combined belief outputs compared to probability outputs. The results computed using the Dempster–Shafer Theory were more consistent than probability when compared to the actual damage of the images shown in the survey. This suggests that Dempster–Shafer Theory may be a suitable framework to represent ignorance and evidence-based assessments.

Shear Failure Capacity Prediction of Concrete Beam–Column Joints in Terms of ANFIS and GMDH

Vulnerability assessment of structures in an earthquake is one of the most important topics in structural engineering. HAZUS instruction is the code widely used for assessment of structures for satisfied damage based on the interstory drift. In a structure, there are several parameters, such as forces and responses in elements, which cause damage to the structure simultaneity, and therefore, the use of only one parameter, such as interstory drift, could be unrealistic. In this paper, reinforced concrete (RC) beam–column joints are studied, with the aim of determining the maximum shear capacity of RC joints as a key parameter in the damage of RC structures. For this purpose, two strong approaches, including group method of data handling (GMDH) and adaptive neuro-fuzzy inference system (ANFIS), were used. The selected models were created based on a large experimental database. The results indicated that the considered methods are capable of determining the shear capacity of RC joints with high accuracy.

Structural Vulnerability Assessment of Multi-energy System Using a PageRank Algorithm

Abstract Severe natural catastrophes may directly cause large-scale cascading failures in energy systems. This paper presents a comprehensive scheme of vulnerability assessment for multi-energy systems, including both electricity and natural gas. Differing from cascading failure theory, this scheme employs PageRank algorithm to measure the structural importance of the integrated system. A modified weighted PageRank methodology is applied to determine the importance of nodes in both natural gas and electricity networks. The effectiveness of this scheme is demonstrated and analyzed via an integrated energy system in the case study. This algorithm can help identify the weakness in the integrate energy system so that purposeful planning and operation strategies can be deployed to increase the security.

A simplified approach to the evaluation of the strength of old concrete

To design the retrofit and/or conservation of existing reinforced concrete structures, an assessment of concrete strength is generally required. The current methodologies consist of destructive tests, based on uniaxial compression performed on concrete cores extracted from a structure, and/or non-destructive tests, in which the strength of the concrete is indirectly estimated by measuring other physical properties (like ultrasonic pulse velocity). Nevertheless, in several situations (e.g. the seismic vulnerability assessment of long-term service structures), the traditional tests cannot be performed. Hence, a new simplified approach is introduced and described in this paper. This can be applied to structures located in a precise geographical area, where the average strength of concrete (and the relative variance) is a function of the year of construction. Such a relationship is summarised by the so-called strength curves statistically computed from a huge database stored in the Department of Structural and Geotechnical Engineering of Politecnico di Torino (Italy). Relating to a concrete dam and a stadium built during the 1950s and in 1967, respectively, the strength predicted by these curves is in good agreement with the measurements of destructive tests.