Nonlinear Time-history Response Analysis Research Articles

Nonlinear dynamic instability and dynamic response of stiffened laminated composite plates subjected to in-plane pulsating patch loading

In this article, the nonlinear dynamic instability of stiffened laminated composite plates is studied in the finite element (FE) framework subjected to uniform in-plane harmonic patch loading. The harmonic load is applied to the two opposite sides of the stiffened plate. The linear and nonlinear time-history response analysis is also studied. The skin and the stiffener are modeled using an eight-node isoparametric degenerated shell element and a three-node curved beam element, respectively. A system of matrices is developed by considering the Green–Langrange strain–displacement relationship. In the linear case, the Bolotin method is used to analyze the dynamic instability region (DIR). The nonlinear instability behavior of the laminated composite stiffened plate is studied by applying the Incremental Harmonic Balance Method (IHB). The Newmark-β method is used to solve the linear and nonlinear time-history response equations to understand the instability behavior of the stiffened plates. The effect of the parameters such as the length of the in-plane loading patch, varying number of stiffeners in -direction and the position of the patch on the nonlinear vibrations and nonlinear dynamic response is examined.

Dynamic stability of single-layer spherical reticulated shell structures under earthquake action

In past decade, earthquake disasters have seriously damaged nonstructural components, so it is very important to study their dynamic stability. However, the existing researches mainly focus on the dynamic stability of multistory and high-rise buildings, and there are still deficiencies in the analysis of dynamic stability of reticulated shell structures under earthquake action. This paper takes the 40 m span K8 single-layer spherical reticulated shell structure with practical engineering significance as the research object, we study its dynamic instability characteristics under earthquake action, and propose a dynamic stability judgment method. The influence of various parameters on the critical loads of emotional stability of reticulated shell structures is systematically analyzed, including the impact of horizontal seismic action, the vertical seismic activity, and the three-dimensional seismic movement, considering the influence of material elastoplasticity; the result of different seismic inputs, the effects of initial geometric imperfections; the effects of varying rise span-ratio. In this paper, to investigate the nonlinear time-history response analysis, we uses the finite-element package ABAQUS. We first analyze the rise-span ratio as the dynamic stability of 1/3 single-layer reticulated shell structure under the action of the El Centro (1940) earthquake to reveal the dynamic loss of reticulated shell structure under earthquake action stable feature. The practical method for determining the proposed dynamic stability has a clear physical meaning and a range of applications. Our findings highlight that the critical load for dynamic stability under horizontal earthquake action is significantly lower than vertical earthquake action, and the critical load is the lowest under three-dimensional earthquake action. Material elastoplasticity influences the critical loads for dynamic stability of reticulated shell structures under different ground motions. The critical load of dynamic stability of single-layer structures with a larger rise-span ratio is lower, while those with a smaller one is higher. The initial geometric defects of the structure should be considered in practical engineering applications. The reticulated shell structure with a larger rise-span ratio needs to consider the dynamic stability problem in the strong earthquake area.

Study on Seismic Response of Staggered Story Isolated Structure Under Long-period Earthquake

The staggered story isolated structure is a new type of isolated structure developed from the base isolated structure. It has great isolation performance under ordinary earthquakes. However, the problem of long-period earthquakes exists in many areas. The prolongation of the natural vibration period of the structure and the resonance caused by the low-frequency part of the long-period earthquakes should not be ignored. The research on the response of the staggered story isolated structure under the long-period earthquake is not perfect. Two finite element models of staggered story isolated structure were established and non-linear time-history response analysis were carried out under ordinary earthquakes and long-period earthquakes, which including near-fault pulse-type long-period earthquakes and far-field harmonic-like long-period earthquakes. Results show that the natural vibration period of the staggered story isolated structure is prolonged, the seismic response is reduced. Under long-period earthquakes, the story drift angle, bearing displacement, story shear, plastic hinges and stress damage of staggered story isolated structure are partly larger than those of ordinary earthquakes. Under the far-field harmonic-like earthquakes, isolation performance is significantly different from those under the near-fault pulse-type earthquakes. And there are significant differences between the two models. The structure has the characteristics of vertically irregular structures and the weak position of the structure is located near the isolation layer, so more attention should be paid to the project.

Analisis Riwayat Waktu Nonlinier Struktur Flat Slab dengan OpenSees Navigator

Structural systems that do not use a beam as the main component were first developed by Turner in 1906. This structural system is better known as a flat slab. The flat slab structure is supported by column heads and drop panels, or without drop panels, or without column heads. Several building codes such as IS 456: 2000, ACI 318-08, ACI 318-19, EC 2:2004, and NZS 3101 (Part 1):2006 provide guidance for designing flat slab systems under gravity loads only. However, many flat slab buildings are also built in areas with high earthquakes which can cause the collapse of buildings due to earthquake loads. In this paper the 10-level flat slab building structure design results are analyzed using nonlinear time history response analysis with the help of OpenSees Navigator software using several earthquake records, namely Kobe (Japan, 1995), Imperial Valley (California, 1979) and Tabas (Iran, 1978) which has been adjusted to the design spectra of the city of Yogyakarta. From the results of the analysis using OpenSees Navigator, it was found that the story drift that occurred was still within the limits required in the regulations, so that the building being reviewed was still within the limits of life safety design.

A method to directly estimate the dynamic failure peak ground acceleration of a single-layer reticulated dome

The present paper gives a method to directly estimate the dynamic failure peak ground acceleration of single-layer reticulated domes according to the Chinese earthquake response spectrum. A method given by the Japanese code for seismic design of buildings is presented first, which can be used to estimate the dynamic failure peak ground acceleration of a single-layer dome. However, the existing method cannot be used to calculate the dynamic failure load for a structure in China because of the different codes and methods used for the seismic design of single-layer reticulated domes. Meanwhile, the existing method needs to repeat the finite element method (FEM) elasto-plastic static analysis and FEM nonlinear time–history response analysis to calculate the FEM plasticity adjustment factor and the dynamic ductility index of different domes. Secondly, on this basis, 28 Kiewitt-8 (K8) single-layer reticulated domes with different key structural design parameters are designed using the relevant Chinese specifications, they will be used for the parameter revision of the peak ground acceleration and the dome’s design spectral acceleration, the fitting of the formula to calculate the FEM plasticity adjustment factor, and the statistical analysis of the dynamic ductility index respectively. Thirdly, the peak ground acceleration and the dome’s design spectral acceleration in the existing method are revised according to the Chinese code for the seismic design of buildings. Fourthly, the FEM elasto-plastic static analysis is carried out to get a fitting formula to directly calculate the FEM plasticity adjustment factor with the static safety factor K of the dome. The calculation results of this formula are smaller than that of FEM analysis, which can ensure the safety of the dome. Fifthly, the failure criteria with clear physical meaning are selected from the existing dynamic failure criteria to predict the dynamic failure load of the domes. Then, a FEM nonlinear time–history response analysis is carried out using the FE package ANSYS for the 28 typical domes subjected to 30 different ground motions, and the dynamic failure loads are calculated by the selected failure criteria. It is found that the dynamic failure loads correspond to two different failure modes, one is the local failure caused by the sudden increase of the displacement of the dome’s local node, the other is the global failure caused by the sudden increase of the overall energy of the single-layer reticulated dome. After this, the lower bound failure accelerations with a certain guaranteed rate of those dynamic failure loads are determined using a lognormal distribution. The dynamic ductility index is then revised by the lower bound failure accelerations and the statistical analysis of the dynamic ductility index of the 28 typical domes is conducted to get a lower bound value for it. Finally, a method directly estimating the dynamic failure load of a dome is constructed and verified. The research will provide a new method under a certain degree of reliability to directly estimate the dynamic failure loads of single-layer reticulated shells in the earthquake area of China and contribute to the structural design with more overall confidence.

A Simple Critical Response Evaluation Method for Base-Isolation Building-Connection Hybrid System Under Double Impulse as Representative of Near-Fault Ground Motion

We revisit a unique building system including a base-isolation, building-connection hybrid control system. The base-isolation system withstands pulse-type earthquake ground motions effectively and the building-connection system resists long-duration earthquake ground motions efficiently. A simple smart critical response evaluation method without nonlinear time-history response analysis is proposed for this hybrid building system under near-fault ground motions. An analytical expression of the maximum elastic-plastic deformation of a damped bilinear hysteretic single-degree-of-freedom (SDOF) model under critical double impulse as a representative of pulse-type ground motions derived in our previous paper plays an important role in the development of the simple critical response evaluation method. A two-step transformation procedure into an SDOF model is proposed. The first step is the transformation of the main base-isolated building into an SDOF system and the second step is the reduction of the connecting dampers supported on a sub building to a damper with a sophisticated compensation factor on an assumed rigid wall. The evaluation of damping coefficients with the consideration of yielding of the base-isolation story is a key step in this paper. Different from the previous work, the equivalent damping coefficient is derived depending on the response range before and after yielding of the base-isolation story. This treatment enhances the accuracy of the proposed method. The accuracy and reliability of the proposed response evaluation method is demonstrated by the time-history response analysis of the multi-degree-of-freedom (MDOF) model.

Modal-based ground motion selection procedure for nonlinear response time history analysis of dual wall-frame structures

Modal-based ground motion selection procedure for nonlinear response time history analysis of dual wall-frame structures

Modal-Based Ground Motion Selection Method for the Nonlinear Response Time History Analysis of Reinforced Concrete Shear Wall Structures

This paper presents a modification of the modal-based ground motion selection (MGMS) method for improving the reliability of the nonlinear response time history analysis (NLRHA) of reinforced concrete (RC) shear wall structures. The original MGMS procedure quantified the impact of frequency content combinations in the time domain (FCCTD) of input ground motions (IGMs) on the seismic response of building structures using the level of interaction of the first three modes induced by IGMs. However, previous research found that the first two modes have far larger modal mass coefficients than those of higher modes and dominate the vibration of the RC shear wall structures with a symmetric plan. Therefore, the MGMS procedure should be modified by employing the interaction of the first two modes induced by IGMs to properly account for the effect of the FCCTD of IGMs on the seismic response of structures. In the MGMS procedure for RC shear wall structures, seven IGMs that caused the most significant interactions of the first two modes were selected from a suite of twenty seed IGMs, which were chosen with a conventional spectra-matching-based IGMs selection procedure for the NLRHA of the structure. A comprehensive case study involving three RC shear walls with different heights was conducted to investigate the capability of the MGMS in selecting suitable IGMs for the NLRHA of RC shear wall structures. Sets of seed IGMs were selected, adopting conditional mean spectra and design spectra as the target spectra. It was found that the seismic demands computed using MGMS selected IGMs can ensure a more reliable and reasonable computation of seismic demands compared with conventional spectra-matching-based IGMs selection methods.

Seismic fragility of structures with energy dissipation devices for mainshock-aftershock events

This paper presents a mainshock-aftershock seismic fragility and collapse capacity assessment of reinforced concrete (RC) structures retrofitted with a hybrid damper composed of a steel slit plate and friction pads. Three and eight-story RC buildings are designed and assessed before and after retrofit considering the aftershocks effect. Non-linear time-history response analysis (NLTHA) using twelve natural earthquake sequences are used to produce incremental dynamic analysis (IDA) curves to obtain the median collapse capacity of the structures. Three different damage state (DS) levels are used for the mainshock ground excitation to quantify the scale factors required for conducting the aftershock IDAs. The maximum inter-story drift ratio (MIDR) is used as the main engineering demand parameter. The study shows the importance of considering the aftershock in the seismic assessment process of RC structures. The un-retrofitted structures are found to experience a high level of deterioration under aftershock event which is not considered in the design stage. The findings of the study reveal that the mainshock-aftershock sequence responses of the retrofitted structures show better performance in terms of the median collapse capacity and the seismic fragility compared to the un-retrofitted ones.

Performance-based seismic retrofit of RC structures using concentric braced frames equipped with friction dampers and disc springs

In this study, concentric braced frame installed with a friction damper-disc-springs is proposed to enhance the seismic performance of RC framed structures. The structural configuration of the retrofit is outlined and the analytical model is explained. A performance-based seismic retrofit procedure combined with a genetic algorithm (GA) optimization is proposed to obtain the optimum design variables of the retrofit. 2D and 3D structural models are used as case studies. The effectiveness of the proposed retrofit is assessed through non-linear time-history response analysis (NLTHA), fragility analysis, and seismic life cycle cost (LCC) estimation. To ensure that concrete stresses after retrofit are within acceptable limits, finite element method is used. The results show that the proposed retrofit technique is effective in reducing the maximum inter-story drift ratio and in eliminating the residual drift of the model structures significantly. In addition, the probabilities of exceeding different limit states and the total seismic LCC are significantly reduced compared to the un-retrofitted cases.

Study on failure criterion of thin-walled steel frame structures based on the ESED parameter

The aim of this paper is to propose a new failure criterion for thin-walled steel frame structures based on the sum of the structural exponential strain energy density (ESED) parameters, by analyzing the whole behavior of thin-walled steel frame structures under static and seismic loads. Firstly, the strain energy variation of the thin-walled steel member and structures before and after buckling failure is studied theoretically by introducing the thin-walled theory, after this the ESED failure criterion is proposed to estimate the seismic failure loads of thin-walled steel frame structures. Secondly, a one-story thin-walled steel framework, a five-story thin-walled steel framework and a single-layer spherical reticulated shell separately subjected to different waves were selected on which to carry out the nonlinear time-history response analysis to obtain the ESED model to verify the new failure criterion. Finally, some discussions, comparison between the numerical solution and the analytical solution, the distinction of the ESED between pre- and post-structural failure and failure modes corresponding to the failure load, on the new failure criterion are conducted to a certain extent to prove its rationality. The research on the new failure criterion will provide a new approach to carrying out the structure failure mechanism analysis and contribute to the structural design with more overall confidence.

Self-centering steel slotted friction device for seismic retrofit of beam-column joints

A new self-centering slotted friction device (SC-SFD) is introduced for seismic retrofit and upgrading of beam-column joints. The device can be used for existing or new structures. A framework utilizing a performance-based seismic design procedure combined with a genetic algorithm (GA) optimization is used to obtain the optimum design variables of the device. A 5-story building and one-story industrial structure are used as case studies. The effectiveness of the proposed retrofit is assessed through conducting non-linear time-history response analysis (NLTHA), incremental dynamic analysis (IDA), fragility analysis, and seismic life cycle cost (LCC) evaluation. The obtained results demonstrate that the proposed retrofit is effective in reducing the maximum inter-story drift ratio (MIDR) significantly and in eliminating the residual drift. Additional engineering demand parameters, such as the floor acceleration and the base shear have been investigated to prove the superiority of the proposed retrofit technique compared to the fully rigid joint alternative. A finite element method (FEM) is used to ensure that concrete stresses after retrofit are within the acceptable limits. The retrofitted models show high energy dissipating potential compared to the bare cases. The IDA and fragility analyses show significant improvement in the retrofitted structures in terms of the median collapse capacity and seismic fragility. The probabilities of exceeding different limit states and the LCC of the retrofitted structures have been reduced significantly compared to the bare cases. Based on these findings, the proposed retrofit is recommended for similar structures to improve their resilience against earthquakes and to reduce the total seismic LCC.

Seismic stability of an underground cavern in jointed rock mass based on the discrete fracture network

In the construction of underground structures in high seismic intensity areas, it is inevitable that a fault fracture zone will pass through the construction site. Therefore, it is very important to evaluate and analyze the stability of the unstable block, which is cut by the fault and the dominant joint group. In this study, the discrete element method was used to simulate the seismic response of an underground powerhouse of a hydropower station near a high seismic zone. The discrete fracture network (DFN) model was introduced to simulate the joint group. Moreover, to optimize the number of joints and improve computational efficiency under dynamic conditions, the joints in the DFN with little influence on the stability of the cavity, were deleted by the algorithm, and a nonlinear time-history response analysis method was used for dynamic calculation. Based on the simulation results obtained, it was possible to classify the instability of the unstable block, and corresponding suggestions for construction were provided. Additionally, these results can be used as a reference for the seismic design of similar underground structures.

First-excursion stochastic incremental dynamics methodology for hysteretic structural systems subject to seismic excitation

A novel efficient stochastic incremental dynamics methodology considering first-excursion probability for nonlinear structural systems subject to stochastic seismic excitations in alignment with contemporary aseismic codes provisions is developed. To this aim, an approximate nonlinear stochastic dynamics technique for conducting first-passage probability density function (PDF) based stochastic incremental dynamic analysis is developed. Firstly, an efficient stochastic iterative linearization methodology is devised achieving convergence of the equivalent system damping ratios with the damping premises of the excitation response spectrum leading to a coherent determination of a robust scalable intensity measure (IM) which bears direct relation to its damaging potential. Subsequently, utilizing the stochastically derived time-varying forced vibrational system properties in conjunction with a combination of deterministic and stochastic averaging treatment the first-excursion PDF is efficiently determined for each and every of the considered limit-state rules (LSs). Lastly, an incremental mechanization analogous to the one used in normal incremental dynamic analysis (IDA) is proposed to ensure the necessary compatibility for applications in the fields of structural and earthquake engineering. The back-and-forth twisting pattern of IDA curves which is related with the multiple points satisfaction of the very same limit-state rule encourages the study of the problem from a first-passage perspective considering timing in addition to the intensity of the excitation variable. The selected engineering demand parameter (EDP) of the first-excursion time constitutes an excellent response related variable with twofold meaning; it performs structural behavior monitoring considering intensity and timing information whereas it is inherently coupled with limit-state requirements. The developed stochastic dynamics technique provides with reliable higher order statistics (i.e., PDF) of the chosen EDP. A structural system comprising the bilinear hysteretic model serves as a numerical example for demonstrating the reliability of the proposed first-excursion PDF-based stochastic incremental dynamics methodology. Nonlinear response time-history analysis involving a large ensemble of Eurocode 8 spectrum compatible accelerograms is conducted to assess the accuracy of the proposed methodology in a Monte Carlo-based context.

CFST arch bridge seismic response analysis considering near-fault ground motion pulse characteristics

Based on a long-span CFST arch bridge finite element model, nonlinear time-history response analysis is carried out. It is found that the key section of the connection of arch rib and bridge deck is a particular location with larger seismic response. The fling-step type TCU068-E is more liable to excite a greater seismic response at arch rib sections. Through seismic wave dyadic wavelet analysis, the wavelet component in the structure fundamental frequency band is reconstructed to be a new seismic excitation. The results indicate that the low-frequency component of TCU068-E is strong, and larger structural seismic response is generated accordingly.

Spectrum-based pushover analysis for the quick seismic demand estimation of reinforced concrete shear walls

In the design of medium- and high-rise buildings, the reinforced concrete (RC) shear wall structure is widely used to resist seismic loading. Thus, accurately predicting the seismic demand of this structural form becomes particularly important. However, existing multi-mode pushover analysis methods are mainly applied to predicting seismic demands of frame structures, while few attentions have been paid on other structural forms. In this paper, by revising the equation for predicting the overall roof displacement, the spectrum-based pushover analysis (SPA) of RC shear wall structures for the fast prediction of the seismic demand is presented. The accuracy of the SPA method in the fast prediction of seismic demands of RC shear wall structures was investigated through a case study on two representative RC shear wall buildings. The impact of the input ground motions (IGM) scaling target spectra on the accuracy of the SPA method was studied by selecting and scaling IGMs with the target spectra being the ASCE design spectra and conditional mean spectra. Seismic demands computed by the SPA method, the nonlinear response time history analysis (NLRHA), and the other two advanced methods of multi-mode pushover analysis were compared. It is indicated from the comparison of the seismic demands that the SPA method predicted seismic demands of RC shear wall structures with outstanding and consistent accuracy. Therefore, the SPA method can be considered as a solution for the fast seismic demand prediction of RC shear wall structures for different regions, where different target spectra are used as the seismic intensity representatives.

Seismic performance of RC frame buildings accounting for the out-of-plane behavior of masonry infills

Past earthquakes have repeatedly shown that damage to masonry infills can produce large economic losses and even jeopardize human lives. Nevertheless, in current design practice masonry infills are ignored, while available macro-models for nonlinear analysis focus the attention on the In-Plane (IP) behavior of masonry infills only, while neglecting the Out-Of-Plane (OOP) collapse mechanism. The main objective of this study is to investigate the seismic performance of RC frame buildings accounting for the interaction between IP and OOP behavior of masonry infills. To this end, a suitable nonlinear model, able to capture the IP stiffness and strength reduction due to the OOP displacement demand (and vice versa) is implemented. The selected model incorporates a routine that removes infills from the structural model when either IP or OOP collapse occurs. Different building models, representative of typical residential buildings, realized in Italy (and other European countries) from 50’s to 90’s, are examined through nonlinear response-time history analysis at different earthquake intensity levels, with return period ranging from 30 to 5000 years. Two alternative infill configurations (single layer and double layer with inner cavity) are considered, in accordance with the construction practice of the time. The comparison between the models with and without IP/OOP interaction points out the relevance of the OOP behavior towards an accurate evaluation of the seismic performance of RC frame buildings. A set of fragility curves is tentatively proposed, for different building performance levels, ranging from immediate occupancy to life safety.

Modal‐based ground motion selection procedure for nonlinear response time history analysis of high‐rise buildings

SummaryThe selection of representative input ground motions (IGMs) is important for a proper nonlinear response time history analysis (NLRHA) of modern structures. The prevailing IGM selection procedure requires that the response spectra of selected ground motions are matched with the code‐specified design spectra, while the effect of the frequency contents combination in the time domain on the multimode interactions is not considered. Ignoring the effect of the frequency contents combination in the time domain of IGMs may cause significant variations in the analysis results for selected IGMs, although they are matched to the same design spectrum. In this paper, a modal‐based ground motion selection (MGMS) procedure is proposed as a supplement to spectrum matching‐based IGM selection procedures for selecting proper IGMs that can sufficiently induce the multimode interactions. In the proposed procedure, three equivalent single‐degree‐of‐freedom (ESDOF) systems are developed by pushover analysis. NLRHA is then conducted for these ESDOF systems with a set of 20 seed IGMs chosen by the spectrum‐matching–based selection procedure. Finally, seven IGMs are selected from the seed IGMs for NLRHA in the full structural model. To verify MGMS, seismic demands of high‐rise buildings were computed by NLRHA with seven MGMS‐selected IGMs, seven IGMs with closest spectrum matching, and groups of seven randomly selected IGMs derived from three different sets of 20 seed IGMs. The computed seismic demands with MGMS‐IGMs show very good agreement with the mean demands determined using the whole set of seed IGMs, while the deviation is much lesser compared with those groups of randomly selected IGMs.

Seismic retrofit of RC buildings using self-centering PC frames with friction-dampers

This paper presents the seismic upgrade of existing reinforced concrete (RC) structures by using a self-centering post-tensioned pre-cast concrete frame with friction dampers (SC-PC-FD). The effectiveness of the retrofit is investigated through conducting cyclic loading tests on a single story RC frame before and after the retrofit. The experimental results are used to validate the numerical modeling of the test specimens. A performance-based seismic design procedure is proposed based on a genetic algorithm (GA) to determine the story-wise distribution of the damper friction capacity and the area of post-tensioning steel. Three-, five-, and eight-story RC framed structures are used as case study models for evaluating the effectiveness of the retrofit technique. Non-linear time-history response analysis (NLTHA), incremental dynamic analysis (IDA), and fragility analysis are conducted to investigate the seismic performance of the retrofitted structures. Results of the nonlinear time-history analyses show that the retrofit reduces the maximum inter-story drift ratio (MIDR) and the residual drift of the model structures. IDA and fragility curves show that the collapse capacities of the model structures are increased after the retrofit and the retrofitted buildings have lower probabilities of reaching the design limit states compared to the un-retrofitted ones.

Fragility analysis of nonproportionally damped inelastic MDOF structural systems exposed to stochastic seismic excitation

A novel methodology for conducting efficiently fragility analysis considering nonproportionally damped inelastic multi degree-of-freedom (MDOF) structural systems subject to stochastic seismic excitations defined by an advanced stochastic model consistent with magnitude-epicentral distance earthquake properties is developed. To this aim, an approximate stochastic dynamics technique for determining the system response amplitude probability density functions (PDFs) is developed. Firstly, relying on statistical linearization and state-variable formulation the complex eigenvalue problem is addressed through the time-domain. Secondly, utilizing the forced vibrational modal properties of the linearized MDOF system in conjunction with a combination of deterministic and stochastic averaging treatment, the MDOF system modal response amplitude process PDFs are determined. The modal participation factors are then defined for the complex-valued mode shapes and the total response amplitude process PDFs are provided in physical coordinates. Subsequently, appropriate limit states are related with the higher order statistics of the engineering demand parameters (i.e. that of the PDF) for quantifying structural system related fragilities. Nevertheless, due to the vector-valued nature of the adopted intensity measure, depicting system fragilities takes the form of three-dimensional fragility surfaces. The associated low computational cost renders the proposed methodology particularly useful for efficient structural system fragility analysis and related performance-based engineering design applications. A multi-storey building structure comprising the bilinear hysteretic model serves as a numerical example for demonstrating the reliability of the proposed fragility analysis methodology. Nonlinear response time-history analysis involving a large ensemble of compatible accelerograms is conducted to assess the accuracy of the proposed methodology in a Monte Carlo-based context.