scholarly journals Enhanced Cloud Method (E-Cloud) for Efficient Seismic Fragility Assessment of Structures

2021 ◽  
Author(s):  
Lujie Zhuang ◽  
Yutao Pang
Keyword(s):  
Linear Regression ◽  
Fragility Curves ◽  
Time History ◽  
Frame Structure ◽  
Seismic Fragility ◽  
Seismic Responses ◽  
Demand Models ◽  
Dynamic Analyses ◽  
Cloud Points ◽  
Cloud Analysis

Abstract Cloud analysis is based on linear regression in the logarithmic space by using least squares, in which a large number of nonlinear dynamic analyses are usually suggested to ensure the accuracy of this method. So, it needs significant computational effort to establish fragility curves especially for the complicated structures. The present paper proposed the Enhanced Cloud Method (E-Cloud) to enhance the efficiency but maintain the accuracy of the Cloud method. The basic concept of the proposed “E-Cloud” aims to utilize both maximum and additional seismic responses with corresponding intensity measures (IMs) from ground motions for the logarithmic linear regression of the Cloud method. Since the nonlinear time-history responses can be transferred to the Engineering Demand Parameter (EDP)-IM curve at the duration when the ground motion is intensifying, the additional seismic responses at different IM levels (i.e., potential Cloud points) can be selected from this EDP-IM curve. These potential Cloud points are combined with maximum seismic responses for the regression so as to reduce the required number of dynamic analyses in Cloud analysis. The proposed “E-Cloud” method is applied for the case study of a typical RC frame structure. By comparison of the obtained probabilistic seismic demand models and fragility curves from “E-Cloud” method to Cloud analysis, it is demonstrated that the E-Cloud method can significantly improve the computational efficiency of the Cloud analysis, which also leads to accurate and stable results for the seismic fragility assessment of structures.

scholarly journals Seismic Fragility Assessment of Base-Isolated Steel Water Storage Tank

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhuo Zhao ◽  
Xiaowei Lu ◽  
Yu Guo ◽  
Xiaofeng Zhao
Keyword(s):  
Storage Tank ◽  
Shear Force ◽  
Fragility Curves ◽  
Water Storage ◽  
Time History ◽  
Seismic Fragility ◽  
Coefficient Of Determination ◽  
Base Shear ◽  
Water Storage Tank ◽  
Demand Models

Steel water storage tanks (WSTs) are among the important components of water treatment industry facilities that are expected to remain functional and applicable after strong earthquakes. In this study, the seismic vulnerability of base-isolated steel WST is investigated. A three-dimensional finite element stick model of the targeted tank is created using OpenSees. This model is capable of reproducing convective, impulsive, and rigid responses of fluid-tank systems. Time-history responses of convective displacement, bearing displacement, and base shear force for base-isolated tank subjected to a typical ground motion are compared. Furthermore, time-history analysis based on a suite of 80 ground motions is conducted. The seismic demand models for various responses are established and the most efficient intensity measure (IM) is determined based on the dispersion and coefficient of determination. Seismic fragility curves for different responses are derived for all three damage states using cloud analysis. The results from this study reveal that (i) the convective displacement is significantly greater than bearing displacement; (ii) peak ground displacement (PGD) is the most efficient and sufficient IM for the targeted tank; and (iii) the characteristic of isolation bearing significantly influences the seismic fragilities of convective displacement and bearing displacement and has a little impact on base shear force, which makes the selection of the proper characteristic parameters for isolation bearing very essential. The analysis technique and procedure mentioned above as well as derived insights are of significance to general liquid storage tank system configuration.

Seismic Fragility Analysis of Mid-Story Isolation and Reduction Structures Based Two Directions

2013 ◽  
Vol 739 ◽  
pp. 309-313 ◽  
Author(s):  
Pei Ju Chang
Keyword(s):  
Fragility Curves ◽  
Response Spectrum ◽  
Time History ◽  
Longitudinal Axis ◽  
Seismic Intensity ◽  
Seismic Fragility ◽  
Infill Wall ◽  
Intensity Index ◽  
History Analysis ◽  
Masonry Infill Wall

This study focus on derivation of such fragility curves using classic mid-story isolation and reduction structures (MIRS) in China metropolis. This study focus on derivation of such fragility curves using conventional industrial frames with masonry infill wall. A set of stochastic earthquake waves compatible with the response spectrum of China seismic code selected to represent the variability in ground motion. Dynamic inelastic time history analysis was used to analyze the random sample of structures. MIRS seismic capability of longitudinal and transversal orientation is different. Stochastic damage scatter diagrams based different seismic intensity index are obtained. Seismic fragility of longitudinal axis (Y axis) is larger than transversal axis (X axis) of frames under major earthquake obviously.

Comparative seismic fragility estimates of steel moment frame buildings with or without superelastic viscous dampers

2018 ◽  
Vol 29 (18) ◽  
pp. 3598-3613 ◽  
Author(s):  
Baikuntha Silwal ◽  
Qindan Huang ◽  
Osman E Ozbulut ◽  
Mojtaba Dyanati
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Fragility Curves ◽  
Steel Frame ◽  
Structural Performance ◽  
Seismic Fragility ◽  
Viscoelastic Damper ◽  
Viscous Dampers ◽  
Earthquake Losses ◽  
Demand Models

Superelastic viscous damper is a passive hybrid control device that combines shape memory alloy cables and a viscoelastic damper to mitigate dynamic response of structures subjected to multi-level seismic hazards. In the hybrid device, shape memory alloy cables that exhibit a nonlinear but elastic response are used mainly as re-centering unit, while the viscoelastic damper composed of high-damped butyl rubber compounds is employed to augment the equivalent viscous damping provided by the device. This study evaluates the effectiveness of superelastic viscous dampers in mitigating seismic response of steel frame structures through a probabilistic framework. First, a nine-story steel frame building is designed and modeled with and without superelastic viscous dampers, and extensive nonlinear response-history analyses are conducted. Then, probabilistic demand models are developed for selected engineering demand parameters. To quantitatively compare the performance of the designed buildings, seismic fragility curves and mean annual frequency of exceeding different performance levels are developed. In particular, the structural performance is evaluated using both peak inter-story drift and residual drift responses. Results indicate that superelastic viscous dampers can significantly improve structural performance; thus, it has the potential to lower the post-earthquake losses, as the better structural performance leads to less loss in relocation, rental, and economic loss.

scholarly journals Seismic fragility analysis for tall pier bridges with rocking foundations

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Xu Chen ◽  
Jianzhong Li
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Fragility Curves ◽  
Dynamic Performance ◽  
Time History ◽  
Element Model ◽  
Nonlinear Time History Analysis ◽  
Promising Alternative ◽  
Demand Models ◽  
Rocking Foundations

AbstractCostal bridge systems usually contain tall piers with heights over 40 m, due to the engineering site exposed to deep water circumstances. Note that the conventional seismic isolation devices (e.g., isolation bearings) are not that effective for tall piers, since their dynamic performance is significantly affected by the distributed mass and vibration modes of columns; therefore, base isolation design philosophy could be a promising alternative for mitigating seismic demands of this type of bridges. This paper mainly investigates the efficiency of rocking foundations in improving seismic performance of tall pier bridges, with the results presented in the format of fragility curves. Finite element model of the prototype tall pier bridge is developed, and the responses subjected to near-fault motions are obtained using nonlinear time history analysis. Probability seismic demand models and fragility curves are then developed accordingly, based on which the performance of tall pier bridges are assessed. The results show that employment of rocking foundations could significantly reduce the demands of tall piers and the probability of being damaged. Before the initiation of uplifting at pier base, the behavior of rocking piers resembles that of conventional ones with integrated foundation. While rocking initiates under strong excitations, the demands of rocking piers reduce drastically compared with integrated ones and tend to be similar under different motions, which benefits the post-earthquake performance assessment of these bridges.

scholarly journals Gaussian Kernel Methods for Seismic Fragility and Risk Assessment of Mid-Rise Buildings

2021 ◽  
Vol 13 (5) ◽  
pp. 2973
Author(s):  
Somayajulu L. N. Dhulipala
Keyword(s):  
Standard Deviation ◽  
Linear Regression ◽  
Kernel Methods ◽  
Structural Response ◽  
Gaussian Kernel ◽  
Seismic Fragility ◽  
Fragility Functions ◽  
Moment Frame ◽  
Damage States ◽  
Cloud Analysis

Seismic fragility functions can be evaluated using the cloud analysis method with linear regression which makes three fundamental assumptions about the relation between structural response and seismic intensity: log-linear median relationship, constant standard deviation, and Gaussian distributed errors. While cloud analysis with linear regression is a popular method, the degree to which these individual and compounded assumptions affect the fragility and the risk of mid-rise buildings needs to be systematically studied. This paper conducts such a study considering three building archetypes that make up a bulk of the building stock: RC moment frame, steel moment frame, and wood shear wall. Gaussian kernel methods are employed to capture the data-driven variations in the median structural response and standard deviation and the distributions of residuals with the intensity level. With reference to the Gaussian kernels approach, it is found that while the linear regression assumptions may not affect the fragility functions of lower damage states, this conclusion does not hold for the higher damage states (such as the Complete state). In addition, the effects of linear regression assumptions on the seismic risk are evaluated. For predicting the demand hazard, it is found that the linear regression assumptions can impact the computed risk for larger structural response values. However, for predicting the loss hazard with downtime as the decision variable, linear regression can be considered adequate for all practical purposes.

scholarly journals Seismic Fragility Analysis of Structures Based on Adaptive Gaussian Process Regression Metamodel

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yanjie Xiao ◽  
Feng Yue ◽  
Xun'an Zhang
Keyword(s):  
Gaussian Process ◽  
Adaptive Sampling ◽  
Structural Parameters ◽  
Fragility Curves ◽  
Estimation Error ◽  
Time History ◽  
Gaussian Process Regression ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Stochastic Seismic Response

Metamodel-based seismic fragility analysis methods can overcome the challenge of high computational costs of problems considering the uncertainties of earthquakes and structural parameters; however, the accuracy of metamodels is difficult to control. To enhance the efficiency of analyses without compromising accuracy, a metamodeling method using Gaussian process regression (GPR) and active learning (AL) for seismic fragility analysis is proposed. In this method, a GPR metamodel is built to estimate the stochastic seismic response of a structure, in which the record-to-record variability is considered as in the dual-metamodel-based fragility analysis approach. The metamodel can also predict the estimation error. Taking advantage of this ability, we present an AL strategy for adaptive sampling, so that the metamodel can be improved adaptively according to the problem. Using this metamodel and Monte Carlo simulation, seismic fragility curves can be obtained with a small number of calls for time history analysis. To verify its effectiveness, the proposed method was applied to three examples of nonlinear structures and compared with existing methods. The results show that this method has high computational efficiency and can ensure the accuracy of fragility curves without making the metamodel globally accurate.

Dynamic Analyses of Semi-Rigid Connection Low Yield Point Steel Frames

2013 ◽  
Vol 351-352 ◽  
pp. 524-527
Author(s):  
Cui Ling Ma ◽  
Song Dan Sun ◽  
Xian Lei Cao
Keyword(s):  
Steel Frames ◽  
Time History ◽  
Steel Frame ◽  
Frame Structure ◽  
History Analysis ◽  
Dynamic Analyses ◽  
Rigid Connection ◽  
Rotation Stiffness ◽  
Analytic Models ◽  
Steel Frame Structure

Based on the analysis for 10 series (altogether 50) of finite element analytic models, the time-history analysis is discussed in this paper to investigate the relations between frame parameters of semi-rigid steel frames, these parameters include the frame's floor number, the frame's span number, especially the rotation stiffness of beam-to-column connections. Comparing with the steel frame structure, the ductility of semi-rigid steel frame structure is improved with the reduction in the rotation stiffness of connections. Furthermore, semi-rigid steel frame structure under seismic loads has a good seismic performance.

Seismic fragility assessment of bridge piers incorporating high-strength steel reinforcement and concrete under near-fault ground motions

2020 ◽  
Author(s):  
Saif Aldabagh ◽  
Saqib Khan ◽  
M. Shahria Alam
Keyword(s):  
High Strength Steel ◽  
Load Capacity ◽  
Fragility Curves ◽  
Time History ◽  
Inelastic Strain ◽  
High Strength ◽  
The United States ◽  
Bridge Piers ◽  
Seismic Fragility ◽  
Damage States

Design codes in the United States and Canada limit the use of high-strength steel (HSS) and high-strength concrete (HSC) to bridge components that are expected to remain elastic during a seismic event. Although HSS and HSC have higher tensile and compressive strengths, respectively, their lower inelastic strain capacities impose for such restrictions. To assess the seismic performance of HSS and HSC, the pier of an existing bridge is redesigned using concrete compressive strength of 50 and 80 MPa, and reinforcement yield strength of 420, 690, and 830 MPa. Static pushover and nonlinear dynamic time-history analyses were performed to generate force-deformation and seismic fragility curves. Bridge piers incorporating HSS and HSC attained the maximum load capacity yet were the least ductile. They were less seismically vulnerable than those incorporating conventional materials at minimal and repairable damage states, but not at extensive and probable replacement damage states.

scholarly journals Seismic Fragility Assessment of Columns in a Piloti-Type Building Retrofitted with Additional Shear Walls

2020 ◽  
Vol 12 (16) ◽  
pp. 6530
Author(s):  
Hoang Dang-Vu ◽  
Jiuk Shin ◽  
Kihak Lee
Keyword(s):  
Fragility Curves ◽  
Time History ◽  
Shear Walls ◽  
Fiber Reinforced Polymers ◽  
Nonlinear Time History Analysis ◽  
Seismic Responses ◽  
Carbon Fiber Reinforced Polymers ◽  
Urban Structures ◽  
Before And After ◽  
Nonlinear Time History

This study evaluated the influence of additional shear walls, constructed on the first floor, as strengthening methods for a piloti-type building subjected to earthquake loadings. Piloti-type buildings are commonly designed as urban structures in many cities of South Korea. The existence of just columns on the first floor of the building is a feature that is advantageous from an architectural viewpoint, and yet has potential structural disadvantages. Such columns usually exhibit shear–axial failure, due to inherent vertical and horizontal irregularities and insufficient seismic reinforcements. Among several retrofitting methods, including additional braces, carbon fiber reinforced polymers, dampers, and so forth, this research considered reinforced concrete shear walls to improve the seismic responses of piloti buildings. A parametric analysis of the location of the retrofitted shear walls in a typical piloti building was implemented using the Zeus-NL program. Nonlinear time history analysis and incremental dynamic analysis were performed to comparatively evaluate the structure’s seismic responses and fragility curves before and after retrofit.

Seismic Fragility Analysis for Typical Multi-Span Simply Supported Railway Box Girder Bridges

2016 ◽  
Vol 858 ◽  
pp. 137-144 ◽  
Author(s):  
Yun Dan Wu ◽  
Xiao Yao ◽  
Shi Jun Zhou
Keyword(s):  
Fragility Curves ◽  
Eastern China ◽  
Time History ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Simply Supported ◽  
Girder Bridges ◽  
Demand Models ◽  
Concrete Box Girder Bridges ◽  
Bridge System

Fragility curves for typical multi-span simply supported concrete box girder bridges in eastern China are presented. A set of bridge samples, of which five uncertain parameters are considered, is established using the Latin hypercube sampling. Nonlinear time history analyses are conducted to capture the structural response quantities. Probabilistic seismic demand models are formulated by quadratic regression analysis for the capacity/demand ratios. Fragility curves of bridge components are developed and the fragility of bridge system is evaluated using the first-order bound method. The results show that the columns and expansion bearings among bridge members are more fragile under earthquake excitation, and the bridge system is more fragile than any bridge component. The typical bridges have more than 50% probability when subjected to PGAs of 0.46, 0.58, 0.82, and 1.0g for four damage states, respectively. The fragility curves can be used for retrofit prioritization for this type of bridges.

Sign in / Sign up

Export Citation Format

Share Document