Fragility curves and seismic demand hazard analysis of rocking walls restrained with elasto‐plastic ties

The complex characteristics of explosion load as well as its increasingly high frequency in the civil environment highlight the need to develop models representing the behavior of structures under blast load. This work presents a probabilistic study of the performance of framed reinforced concrete buildings designed according to the current Italian NTC18 and European EC8 technical standards. First, a simplified single degree of freedom model representing the structural system under blast load has been developed. Then, a probabilistic approach based on Monte Carlo simulation analysis highlighted the influence of seismic demand on the behavior of Reinforced Concrete RC buildings subjected to blast load.

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Analysis of the Seismic Demand of High-Performance Buckling-Restrained Braces under a Strong Earthquake and Its Aftershocks

Advances in Civil Engineering ◽

10.1155/2019/1482736 ◽

2019 ◽

Vol 2019 ◽

pp. 1-14 ◽

Cited By ~ 5

Author(s):

Luqi Xie ◽

Jing Wu ◽

Qing Huang ◽

Chao Tong

Keyword(s):

Plastic Deformation ◽

Ground Motion ◽

Strong Earthquake ◽

High Performance ◽

Hazard Analysis ◽

Ground Motions ◽

Threshold Value ◽

Seismic Demand ◽

Near Fault ◽

Probabilistic Seismic Demand

The analysis of the ductility and cumulative plastic deformation (CPD) demand of a high-performance buckling-restrained brace (HPBRB) under a strong earthquake and its aftershocks is conducted in this paper. A combination of three continuous excitations with the same ground motion is used to simulate the affection of a strong earthquake and its aftershocks. A six-story HPBRB frame (HPBRBF) is taken as an example to conduct the incremental dynamic analysis (IDA). The seismic responses of the HPBRBF under one, two, and three constant continuous ground motions are compared. The IDA result indicates that the ductility and CPD demand of the BRBs under the three constant continuous ground motions are significantly larger than that excited by only one. Probabilistic seismic demand analysis (PSDA) is performed using seven near-fault ground motions and seven far-fault ground motions to consider the indeterminacy of ground motion. The probabilistic seismic demand curves (PSDCs) for the ductility and CPD demand for the HPBRB under the strong earthquake and its aftershocks are obtained in combining the probabilistic seismic hazard analysis. The results indicate that the AISC threshold value of the CPD with 200 is excessively low for a HPBRBF which suffers the continuous strong aftershocks with near-fault excitations, and a stricter threshold value should be suggested to ensure the ductility and plastic deformation capacity demand of the HPBRB.

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Fragility Analyses of Bridge Structures Using the Logarithmic Piecewise Function-Based Probabilistic Seismic Demand Model

Sustainability ◽

10.3390/su13147814 ◽

2021 ◽

Vol 13 (14) ◽

pp. 7814

Author(s):

Yinghao Zhao ◽

Hesong Hu ◽

Lunhua Bai ◽

Mengxiong Tang ◽

Hang Chen ◽

...

Keyword(s):

Fragility Curves ◽

Statistical Significance ◽

Seismic Intensity ◽

Fragility Analysis ◽

Seismic Demand ◽

Demand Model ◽

Intensity Measure ◽

System Fragility ◽

Probabilistic Seismic Demand ◽

Seismic Demand Model

Seismic fragility analysis is an efficient method to evaluate the structural failure probability during earthquake events. Among the existing fragility analysis methods, the probabilistic seismic demand model (PSDM) and the joint probabilistic seismic demand model (JPSDM) are generally used to compute the component and system fragility, respectively. However, the statistical significance behind the parameters related to the current PSDM and JPSDM are not comparable. Aside from that, when calculating the system fragility, the Monte Carlo sampling (MCS) method is time-consuming. To solve the two flaws, in this paper, the logarithm piecewise functions were used to generate the PSDM and the JPSDM, and the MCS was replaced by the univariate conditioning approximation (UCA) method. The concepts and application procedures of the proposed fragility analysis methods were elaborated first. Then, the UCA method was illustrated in detail. Finally, fragility curves of a steel arch truss case study bridge were generated by the proposed method. The research results indicate the following: (1) the proposed methods unify the data sources and statistical significance of the parameters used in the PSDM and the JPSDM; (2) the logarithmic piecewise function-based PSDM sensitively reflects the changing trend of the component’s demand with the fluctuation of the seismic intensity measure; (3) under transverse seismic waves, major injuries happen on the side bearings of the bridge, while slight damage may occur on each pier, and as the seismic intensity measure increases, the side bearings are more likely to be damaged; (4) for the severe damage and the absolute damage of the studied bridge, the system fragility curves are closer to the upper failure bounds; and (5) compared with the MSC method, the accuracy of the UCA method can be guaranteed with less calculation time.

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Effect of the Bracing System on the Probability of Collapse of Steel Structures under Maximum Credible Earthquake

Shock and Vibration ◽

10.1155/2021/2323758 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Alireza Kianmehr

Keyword(s):

Residential Buildings ◽

Hazard Analysis ◽

Fragility Curves ◽

Steel Structures ◽

Structural Members ◽

Braced Frame ◽

Ductile Behavior ◽

Bracing System ◽

Eccentric Bracing ◽

Different Characteristics

Simple bracing frames can be divided into two types in terms of concentric or eccentric. Concentric bracing frames are frames that intersect with other structural members at one point in the structure along the bracing members. Otherwise, the braced frame will be eccentric. It is said empirically that due to this type of shaping, eccentric bracing frames exhibit more ductile behavior and concentric bracing frames exhibit more stiff behavior. This behavioral difference caused this study to be numerically computing for five frames, including unique concentric and eccentric bracing frames of 5 and 10 stories and an ordinary 5-story concentric bracing frame. Their tensions and drift ratios should be acceptable for the use of residential buildings. Using the primary two steps of the new PEER probabilistic framework, namely, probabilistic seismic hazard analysis and structural analysis, which leads to the drawing of fragility curves, the probability of collapse is obtained to compare the safety capability of these frames according to their different characteristics against earthquakes. The results show that increasing the ductility or increasing the number of floors or the height of these systems can reduce collapse. Also, according to the results of the probability of collapse obtained in frames with 5-story concentric bracing frames, it can be said that some of the current regulations, which work based on previous approaches of analysis, can lead to unsafe structures with a high probability of collapse.

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Probabilistic seismic demand and capacity models and fragility curves for reticulated structures under far-field ground motions

Thin-Walled Structures ◽

10.1016/j.tws.2019.01.032 ◽

2019 ◽

Vol 137 ◽

pp. 436-447

Author(s):

Jie Zhong ◽

Junping Zhang ◽

Xudong Zhi ◽

Feng Fan

Keyword(s):

Fragility Curves ◽

Ground Motions ◽

Seismic Demand ◽

Far Field ◽

Probabilistic Seismic Demand ◽

Demand And Capacity

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Ground Motion Selection in the Near-Fault Region considering Directivity-Induced Pulse Effects

Earthquake Spectra ◽

10.1193/102517eqs223m ◽

2019 ◽

Vol 35 (2) ◽

pp. 759-786 ◽

Cited By ~ 9

Author(s):

Karim Tarbali ◽

Brendon A. Bradley ◽

Jack W. Baker

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Hazard Analysis ◽

Ground Motions ◽

Seismic Hazard Analysis ◽

Response Analysis ◽

Seismic Demand ◽

Ground Motion Selection ◽

Near Fault ◽

Fault Region

This paper focuses on the selection of ground motions for seismic response analysis in the near-fault region, where directivity effects are significant. An approach is presented to consider forward directivity velocity pulse effects in seismic hazard analysis without separate hazard calculations for ‘pulse-like’ and ‘non-pulse-like’ ground motions, resulting in a single target hazard (at the site of interest) for ground motion selection. The ability of ground motion selection methods to appropriately select records that exhibit pulse-like ground motions in the near-fault region is then examined. Applications for scenario and probabilistic seismic hazard analysis cases are examined through the computation of conditional seismic demand distributions and the seismic demand hazard. It is shown that ground motion selection based on an appropriate set of intensity measures (IMs) will lead to ground motion ensembles with an appropriate representation of the directivity-included target hazard in terms of IMs, which are themselves affected by directivity pulse effects. This alleviates the need to specify the proportion of pulse-like motions and their pulse periods a priori as strict criteria for ground motion selection.

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Near-fault seismic risk assessment of simply supported bridges

Earthquake Spectra ◽

10.1177/8755293020935145 ◽

2020 ◽

Vol 36 (4) ◽

pp. 1645-1669 ◽

Cited By ~ 1

Author(s):

Jian Zhong ◽

Linwei Jiang ◽

Yutao Pang ◽

Wancheng Yuan

Keyword(s):

Seismic Risk ◽

Fault Location ◽

Hazard Analysis ◽

Near Field ◽

Peak Ground Velocity ◽

Seismic Demand ◽

Simply Supported ◽

Directivity Effect ◽

Near Fault ◽

Bridge Models

Bridges tend to sustain excessive seismic demand (e.g. displacement) under pulse-like ground motions attributing to the effect of forward directivity, which is of high likely to occur at locations near the fault rupture. This study tries to incorporate the pulse effect into the probabilistic seismic hazard analysis (PSHA) and probabilistic seismic demand analysis (PSDA) framework, which are combined to quantify the risk of earthquake-induced damage in the near-fault location. The near-fault PSDA and PSHA are established and connected conditioned on peak ground velocity (PGV). Four sets of typical simply supported bridge types with the varying heights, representing the range of the period, are simulated by taking account the strength and stiffness degradation associated with material and geometry nonlinearity. The detailed investigation of the near-fault seismic risk is performed for these bridge models located at representative near-fault sites namely 5, 10, 15, and 20 km, respectively. The results reveal that near-field directivity effect strongly impacts the bridge damage risk with the observation of higher risk at the closer site; the bridges with the period of approximately Tp/2(pulse period) tend to experience the highest seismic risk, and the relative vulnerability of four bridge types is also compared.

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Investigating Efficiency of Vector-Valued Intensity Measures in Seismic Demand Assessment of Concrete Dams

Advances in Civil Engineering ◽

10.1155/2018/5675032 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Mohammad Alembagheri

Keyword(s):

Fragility Curves ◽

Coupled System ◽

Seismic Demand ◽

Spectral Acceleration ◽

Dam Reservoir ◽

Natural Period ◽

Intensity Measures ◽

Structural Responses ◽

Second Period ◽

Vector Valued

The efficiency of vector-valued intensity measures for predicting the seismic demand in gravity dams is investigated. The Folsom gravity dam-reservoir coupled system is selected and numerically analyzed under a set of two-hundred actual ground motions. First, the well-defined scalar IMs are separately investigated, and then they are coupled to form two-parameter vector IMs. After that, IMs consisting of spectral acceleration at the first-mode natural period of the dam-reservoir system along with a measure of the spectral shape (the ratio of spectral acceleration at a second period to the first-mode spectral acceleration value) are considered. It is attempted to determine the optimal second period by categorizing the spectral acceleration at the first-mode period of vibration. The efficiency of the proposed vector IMs is compared with scalar ones considering various structural responses as EDPs. Finally, the probabilistic seismic behavior of the dam is investigated by calculating its fragility curves employing scalar and vector IMs considering the effect of zero response values.

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Seismic Fragility Curves of R.C.Framed Buildings Designed as per is Low, Medium and High Code

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.b6381.129219 ◽

2019 ◽

Vol 9 (2) ◽

pp. 4098-4104

Keyword(s):

Aspect Ratio ◽

Fragility Curves ◽

Pushover Analysis ◽

Seismic Fragility ◽

Seismic Demand ◽

Seismic Loads ◽

Seismic Zone ◽

Rc Buildings ◽

Beam Elements ◽

Technical Manual

In India, the RC buildings codes of gravity and seismic loads have been revised over five decades. The adaptation of gravity and seismic loads combination were rarely taken into design consideration in low and mid-rise building. In the last five decades, low and mid-rise buildings have been constructed high in number in urban cities due to increasing more employment opportunity. The around 56% of the landmass is prone to moderate to severe the earthquake. Also, it evident, in Bhuj 2001 earthquake, many mid and low rise was suffered severely, and more life loss occurred. The seismic zone map has been updated from 1968-2016 and seismic demand increased manifold. The RC buildings have been designed different design philosophy over the period of time, and the urgent need for the assess the vulnerability buildings which have been designed different design codes. In this paper, an attempt made to derive the fragility curves of three and five story RC buildings with aspect ratio and designed as per IS 456-1964 (Low code), IS 456-1978 (Medium code) and IS-13920 (High code). The modelling and pushover analysis are carried out by using a numerical method. User-defined hinge properties for the column as P-M-M and beam as M3 curves have been derived and assigned column and beam elements. The displacement control is applied in pushover analysis. The fragility curves have been derived as per guidelines are given by HAZUS technical manual. Results are compared with design philosophies, aspect ratio and the number of storeys for a given intensity of the acceleration

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Fragility Analysis of a Self-Anchored Suspension Bridge Based on Structural Health Monitoring Data

Advances in Civil Engineering ◽

10.1155/2019/7467920 ◽

2019 ◽

Vol 2019 ◽

pp. 1-19 ◽

Cited By ~ 2

Author(s):

Yuyao Cheng ◽

Jian Zhang ◽

Jiajia Wu

Keyword(s):

Health Monitoring ◽

Hazard Analysis ◽

Fragility Curves ◽

Ground Motions ◽

Suspension Bridge ◽

Monitoring Data ◽

Fragility Analysis ◽

Demand Model ◽

Earthquake Scenarios ◽

Ground Motion Selection

This paper presents an improved fragility analysis methodology to estimate structural vulnerability for probabilistic seismic risk assessment. Three main features distinguish this study from previous efforts. Firstly, the updated fragility curves generated are based on experimental measurements and possess higher accuracy than those produced using design information only. The updated fragility curves take into consideration both the geometry and material properties, as well as long-term health monitoring data, to reflect the current state of the structure appropriately. Secondly, to avoid arbitrariness when selecting ground motions, probabilistic seismic hazard analysis (PSHA) is adopted to provide suggestions for ground motion selection. By considering the uncertainty of the location and intensity of future earthquakes, the PSHA deaggregation result can help to determine the most probable earthquake scenarios for the specific site. Thus, the suggested ground motions are more realistic, and the seismic demand model is much closer to the actual results. Thirdly, this study focuses on the seismic performance evaluation of a typical self-anchored suspension bridge using the form of fragility curves, which has seldom been studied in the literature. The results show that bearing is the most vulnerable part of a self-anchored suspension bridge, while failure probabilities of concrete towers are relatively lower.

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