Seismic fragility assessment for moment-resisting concrete frame with setback under repeated earthquakes (original) (raw)
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Seismic Fragility Evaluation of a Moment Resisting Reinforced Concrete Frame
2014
This study examines the seismic behavior of a seven-storey moment resisting reinforced concrete frame under 9 different ground motion (GM) records through incremental dynamic analysis (IDA). The IDA results allowed a thorough understanding of changes in the structural response as the intensity of the GM increases. The selected earthquake hazard is based on maximum considered earthquake ground motions. The seismic performance is quantified through nonlinear collapse simulation on a set of archetype models developed in SeismoStruct. The drift behavior, record-to-record variability of the response and height-wise distribution of drift demand were reported. On the other hand, for collapse evaluation, ground motions are systematically scaled to increasing earthquake intensities until median collapse is established and analyzed the model as a form of IDA. Using collapse data obtained from IDA results, the collapse fragility curve defined through a cumulative distribution function, which r...
The aim of the study is to develop the fragility curves for low-rise, mid-rise, and high-rise concrete moment resisting framebuildings. The concrete moment resisting frame buildings were designed as per Indian seismic design code. The slab elements were modelled as membrane type, shell type and their influence on the probability of damage states obtained from fragility curves is also studied. For the development of the fragility curves, guidelines provided by HAZUS-MH MR4 technical manual has been used. For the analysis, concrete moment resisting frames weremodeled using ETABS. The nonlinear behavior has been incorporated using default plastic hinges in accordance with ASCE 41-13. Spectral demand and spectral capacity curves obtained from the nonlinear static pushover analysis are used for plotting fragility curves. Fragility curves were developed keeping spectral displacement as ground motion parameters.
Vulnerability Assessment of Building Frames Subjected to Progressive Collapse Caused by Earthquake
MATEC Web of Conferences, 2017
Progressive collapse is an initial local failure of the structural component and leading to the additional collapse of the building frames. This study investigated the vulnerability of four-and six-storey moment resisting concrete frame (MRCF) buildings subjected to progressive collapse. The four-and six-storey MRCF buildings were designed based on British Standard (BS) and Eurocode (EC). The differences between these two codes were investigated. Nonlinear static analysis, which is also known as pushover analysis (POA), and nonlinear dynamic analysis or incremental dynamic analysis (IDA), were performed for each model to obtain capacity curve and explore vulnerability measures. IDA was conducted using a sample of ground motion from an earthquake that occurred in Ranau, Sabah in 2015. The four-storey building was more vulnerable than the six-storey building.
Fragility analysis of mid-rise R/C frame buildings
Engineering Structures, 2006
Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The aim of this study is to develop the fragility curves for mid-rise R/C frame buildings in Istanbul, which have been designed according to the 1975 version of the Turkish seismic design code, based on numerical simulation with respect to the number of stories of the buildings. Sample 3, 5 and 7 story buildings were designed according to the Turkish seismic design code. Incremental dynamic analyses were performed for those sample buildings using twelve artificial ground motions to determine the yielding and collapse capacity of each sample building. Based on those capacities, fragility curves were developed in terms of elastic pseudo spectral acceleration, peak ground acceleration (PGA) and elastic spectral displacement for yielding and collapse damage levels with lognormal distribution assumption. To investigate the effect due to the number of stories of the building on fragility parameters, regression analysis has been carried out between fragility parameters and the number of stories of the building. It was observed that fragility parameters change significantly due to the number of stories of the building. Finally, using constructed fragility curves and statistical methods, the maximum allowable inter-story drift ratio and spectral displacement values that satisfy the "immediate occupancy" and "collapse prevention" performance level requirements were estimated.
Incremental Dynamic Analysis and Seismic Fragility Analysis of Reinforced Concrete Frame
Civil and Environmental Engineering
Due to technological developments in last decade, new methods of seismic evaluation are in use like simulation based, algorithm based, probabilistic, software based etc. These developments have enabled researchers to move from linear to non-linear methods of analysis. Incremental dynamic analysis (IDA) is performance evaluation method where a suite of ground motions applied to structure are further scaled to particular levels of seismic intensity. Seismic fragility curves become significant in estimation of structures risk possibility from the point of view of potential earthquakes and helps in predicting the economic consequences for forthcoming earthquakes. The paper reflects IDA and seismic fragility analysis of ground storey + 7 floor (G + 7) reinforced concrete frame subjected to suite of eleven ground motions. Primary objective was to perform equivalent static and linear-dynamic analysis to meet the National and International codal requirements. Then, pushover analysis is carr...
Collapse Risks of Fail-Safe RC Frames Due to Earthquakes: Fragility Assessments
Journal of Engineering and Technological Sciences
The objective of this study was to determine the collapse risk of failsafe reinforced concrete (RC) frames due to earthquakes by newly developed fragility curves. The curves were constructed based on the collapse mechanism, instead of measures of lateral drift as customarily adopted. The procedure was applied to RC open frames that were seismic resistant. A fail-safe mechanism was imposed by allowing plastic hinges to be formed mainly in the beams. This automatically satisfied the stronger column-weaker beam requirement; shear failure was neither tolerated anywhere in the columns nor in the beams. Two kinds of fail-safe RC frames were investigated: special moment resisting frames (SMF) and ordinary moment resisting frames (OMF). Their earthquake collapse risk was computed and compared. Inelastic time history (NLTH) and the nonlinear static procedure (NSP) were conducted to assess their structural performance. The results showed among others that the fail-safe OMF had lower collapse risk than the fail-safe SMF. The collapse prevention performance level in NLTH could only be achieved for the fail-safe frames. The non-linear time history analysis should be the only method used for seismic reevaluation/safety checking of building frame structures.
Comparative Probability Based Seismic Safety Assessment of Base Isolated Building Frames
Seismic fragility curves are used to assess the probability of vulnerability of structures at various damage states. This research deals with the effects of different isolation systems on the seismic safety of a two-dimensional reinforced concrete moment-resisting frame. The reference structure was a hotel building in California. A comparative probability-based seismic safety of building components was investigated on the superstructure hypothetically fitted with various isolation systems. In this regard, two categories of isolation systems including, rubber-based and frictionâbased were selected here. The High Damping Rubber Bearings and Friction Pendulum Systems were considered here. Incremental Dynamic Analyses were carried out for a suite of earthquake records to develop the fragility curves considering modeling, demand, and capacity uncertainties. Based on the main results, the influence of seismic isolation systems on the reduction of failure probability of building rather tha...
Vulnerability Assessment of Reinforced Concrete Moment Resisting Frame Buildings
Journal of Structural Engineering, 2007
The objective of this paper is to develop an efficient analytical method for assessing the vulnerability of low-rise reinforced concrete buildings subjected to seismically induced slow-moving earth slides. Vulnerability is defined in terms of probabilistic fragility curves, which describe the probability of exceeding a certain limit state of the building, on a given slope, versus the Peak Horizontal Ground Acceleration (PHGA) at the assumed "seismic bedrock", allowing for the quantification of various sources of uncertainty. The proposed method is based on a two-step, uncoupled approach. In the first step, the differential permanent landslide displacements at the building's foundation level are estimated using a dynamic non-linear finite difference slope model. In the second step, the calculated differential permanent displacements are statically imposed at the foundation level to assess the building's response to differing permanent seismic ground displacements using a finite element code. Structural limit states are defined in terms of threshold values of strains for the reinforced concrete structural components. The method is applied to typical low-rise reinforced concrete frame buildings on shallow foundations with varying strength and stiffness characteristics (isolated footings and continuous slab foundation), standing near the crest of a relatively slow-moving earth slide. Two different slope models are selected representing a cohesive and a purely frictional soil material. The paper describes the method and the derived fragility curves for the selected building and slope typologies that could be used in quantitative risk assessment studies at site-specific and local scales.
Bulletin of Earthquake Engineering, 2021
This paper presents the fragility assessment of non-seismically designed steel moment frames with masonry infills. The assessment considered the effects of multiple earthquakes on the damage accumulation of steel frames, which is an essential part of modern performance-based earthquake engineering. Effects of aftershocks are particularly important when examining damaged buildings and making post-quake decisions, such as tagging and retrofit strategy. The procedure proposed in the present work includes two phase assessment, which is based on incremental dynamic analyses of two refined numerical models of the case-study steel frame, i.e. with and without masonry infills, and utilises mainshock-aftershock sequences of natural earthquake records. The first phase focuses on the undamaged structure subjected to single and multiple earthquakes; the effects of masonry infills on the seismic vulnerability of the steel frame were also considered. In the second phase, aftershock fragility curv...
2008
This report describes a state-of-the-art performance-based earthquake engineering methodology that is used to assess the seismic performance of a four-story reinforced concrete (RC) office building that is generally representative of low-rise office buildings constructed in highly seismic regions of California. This "benchmark" building is considered to be located at a site in the Los Angeles basin, and it was designed with a ductile RC special moment-resisting frame as its seismic lateral system that was designed according to modern building codes and standards. The building's performance is quantified in terms of structural behavior up to collapse, structural and nonstructural damage and associated repair costs, and the risk of fatalities and their associated economic costs. To account for different building configurations that may be designed in practice to meet requirements of building size and use, eight structural design alternatives are used in the performance assessments.