Probabilistic Seismic Demand Analysis Research Articles

Seismic fragility functions for earthquake-induced landslide risk assessment using identified optimal earthquake intensity measures

Seismic fragility analysis can relate the probability of unsatisfactory performance of slopes with increasing intensity of ground motions, which is the basic component of landslide hazard risk assessment. Determination of the optimal earthquake intensity measure (IM) is one of important prerequisite for seismic fragility analysis. Although a small number of studies have already performed seismic fragility analysis of slopes, the optimal IM for seismic fragility analysis of slopes have not been discussed and researched. In the present study, 15 IMs and two different engineering demand parameters (EDPs), including factor of safety (FOS) and Newmark permanent displacement (NPD), are selected for probabilistic seismic demand and seismic fragility analysis of slopes. The metrics of correlation, practicality, efficiency, and proficiency are adopted to identify the optimal earthquake IMs among the studied 15 IMs for two EDPs in seismic fragility analysis of slopes respectively. The results have found that the optimal IM is different for slope fragility analysis when different EDPs are selected. Acceleration spectrum intensity is the most optimal IM among the examined 15 IMs for seismic fragility analysis of slopes when FOS is adopted as the EDP. When NPD is selected as the EDP, root mean square of acceleration and velocity spectrum intensity are in general more appropriate than other IMs. In the last, the seismic fragility curves with regard to two EDPs and corresponding optimal IMs are derived for interpreting more properly slope seismic performance and earthquake-induced landslide risk.

Optimal intensity measure selection and probabilistic seismic demand model of pile group supported bridges in sandy soil considering variable scour effects

Scour of pile group foundations is a common hazard for cross-river bridges and can produce considerable damage to piles in earthquake-prone regions. The fragility-based performance assessment for pile group supported bridges subjected to earthquake and scour hazards has drawn increasing attention from engineering practice and academic communities. Such assessment requires numerical models that are computationally efficient and accurate in describing the mechanical behavior associated with the complex soil-pile interaction of these soil-bridge systems. Additionally, selecting an optimal ground motion intensity measure (IM) is generally required for such assessments. However, modeling the pile group effect for seismically excited pile groups and the optimal IM for the scoured bridges have not been well addressed in previous related studies. To this end, a practical pile group effect modeling approach is adopted in this study and validated by a set of shake table tests on scoured pile group bridge available in the literature. Based on the validated numerical modeling approach for the soil pile interaction, a series of coupled soil-bridge models are generated considering the structural and soil parameter uncertainty and analyzed in the OpenSees platform. The optimal IM for various engineering demand parameters (EDPs) is identified from thirty-nine scalar IM candidates through the criteria of efficiency, practicality, sufficiency, and hazard computability. Finally, a straightforward form of probabilistic seismic demand model (PSDM), incorporating the effect of scour depth changes, is developed for pile group supported bridges. Results show that the increase of scour depth significantly increases the curvature demand of a pile group and statistically reduces the embedded depth of the belowground plastic hinge of the pile shaft. The rank of optimal IM candidates directly depends on the selection criteria of an optimal IM and the selection of EDP. In addition, the scour depth slightly affects the rank of optimal IMs. Generally, VSI, PGV, and Sv,1.0 are recommended for the probabilistic seismic demand analysis of pile group supported bridges in sandy soils with scour potentials.

Evaluation of ground motion intensity measures for time-history dynamic analysis of isolated bridges

The ground motion intensity measure (IM) is an important part of probabilistic seismic demand analysis and is used to predict the seismic response of structures. In this study, two typical isolation bridges are selected as cases, and 80 far-fault and 40 near-fault ground motions are used as inputs for the time-history analysis. By performing a comparison with 19 common IMs, it is proved that the IM based on the geometric mean of the response spectrum is an optimal choice for isolated bridges. The effects of response spectrum type and period range on this form of IM are investigated. The results show that the response spectrum type has a slight effect on the IM based on the geometric mean of the response spectrum, and the period range has a greater impact on the IM. The effects of the upper and lower limits of the period range of this IM are illustrated. The applicability of the IM to the far-fault ground motions and the near-fault ground motions is finally discussed. It can be concluded that when only near-fault ground motions are considered, the period range of the IM should be appropriately increased.

Selection of hazard-consistent ground motions for risk-based analyses of structures

In seismic risk analysis, probabilistic seismic demand analysis (PSDA) is required to determine the probability distribution of structural seismic responses. One of the key steps in PSDA is to select a suite of ground motions that are consistent with seismic hazards at a target site. Current methods for selecting hazard-consistent ground motions only achieve consistency at one or several predefined periods and choose several discrete intensity levels to consider uncertainty of ground motions. To avoid drawbacks of the current methods, this study proposes a novel method for selecting hazard-consistent ground motions. In this method, a scenario earthquake set for ground motion selection is firstly obtained from seismic hazard disaggregation to a hazard level corresponding to a very small value of spectral acceleration at a specific period. Then, a suite of random target response spectra that are consistent with target site seismic hazards are simulated based on the scenario earthquake set. Finally, one suite of hazard-consistent ground motions are selected from a ground motion database. Through a numerical example, this study concludes, a suite of selected ground motions using the proposed method presents very good consistency with the target site seismic hazards. Since hazard-consistent ground motions selected using the proposed method do not depend on the building information, they can be used to accurately perform PSDA of any building and accurately predict structural seismic responses.

Predictive model for seismic displacements of flexible sliding block subjected to near-fault pulse-like ground motions

A post investigation of landslides induced by strong earthquake events in recent years shows that near-fault pulse-like ground motions have a considerable impact on slopes. Accurate evaluation of the stability of slopes under near-fault earthquakes has become a crucial issue in seismic-prone areas. Permanent displacement is widely recognized as an effective index for evaluating the stability of slope. Based on the coupled analysis, an empirical earthquake-induced permanent displacement prediction model was developed. A displacement database of 318 pulse-like ground motions from 50 earthquake events was established. The proposed predictive model is a function of the maximum seismic coefficient-time history (kmax), maximum velocity coefficient of velocity-time history of the k-time history (kv-max), yield acceleration (ky), and period ratio (ratio of the natural period of the slope to the mean period of input motion, Ts/Tm). The dynamic responses (kmax and kv-max) are represented by two different functions. At small period ratios (Ts/Tm≤1.8), it is a function of peak ground acceleration (PGA), peak ground velocity (PGV) and ky. At large period ratios (Ts/Tm > 1.8), it is a function of PGV, Ts and ky. It successfully captured the velocity pulse and long period characteristics of pulse-like ground motions. Compared to the existing model, it is found that the model is more accurate when considering pulse-like ground motions. This prediction model can be used not only for the preliminary evaluation of slope stability but also for probabilistic seismic demand analysis of flexible slopes considering pulse-like ground motion in near-fault regions.

Direct displacement-based design of steel-timber hybrid structure with separated gravity and lateral resisting systems

Steel-timber hybrid structure can bring the benefits of timber and steel together in a more effective way. In this paper, a steel-timber hybrid structure with separated gravity and lateral resisting systems (ST-SGLRS) was proposed, and an iterative direct displacement-based design method was developed for this type of structure. Design examples revealed that the direct displacement-based design method with appropriate iterative steps is feasible for the design of steel-timber hybrid structures with separated gravity and lateral resisting systems. Furthermore, four steel-timber hybrid structures were designed based on the proposed design method, including 6-story, 9-story, 12-story structures with deformable steel-timber connections and a 9-story structure with rigid steel-timber connections, and corresponding OpenSees structural models were generated. Static and dynamic analyses were performed on the models to calibrate the structural performance. Comparing with the analytical result, it is found that the post-yield stiffness of the structure with deformable steel-timber connections decreased less than the structure with rigid steel-timber connections. As the earthquake intensity increased, the inter-story drift of the structure with rigid steel-timber connections increased rapidly. Besides, the residual inter-story drift of the structure with rigid steel-timber connections was generally larger than that of the structure with deformable steel-timber connections, indicating that the deformable connections contribute to the structure's ability to recover after a large earthquake. Finally, the seismic performance of the calibrated structures considering far-field and near-field earthquakes and impulse effect was evaluated via the probabilistic seismic demand analysis method. It is found that the maximum inter-story drift and the residual inter-story drift exceedance probabilities of the structures under near-field pulse-like earthquakes were larger than those under near-field no-pulse and far-field earthquakes. The research outcome aims to provide a fundamental basis for the design and engineering application of steel-timber hybrid structures with separated gravity and lateral resisting systems.

Compound intensity measures for improved seismic performance assessment in cross-fault hydraulic tunnels using partial least-squares methodology

Seismic performance assessment of cross-fault hydraulic tunnels is typically expressed in terms of the probability of reaching or exceeding specific damage states related to earthquake intensity measures (IMs) and engineering demand parameters (EDPs). Obviously, this would require determining the appropriate earthquake IMs to reflect the seismological characteristics of ground motions and improving the predictive ability for the EDPs of cross-fault hydraulic tunnels. It is worth emphasising that an unreasonable IM may increase the ground motion uncertainty, which in turn introduces additional uncertainty to the EDP estimates of cross-fault hydraulic tunnels. Hence, this study presents a compound IM, integrating multiple earthquake IMs, to improve the reliability of the seismic fragility analysis of a cross-fault hydraulic tunnel based on the partial least squares methodology. To this end, seven scalar IMs are first determined from the 20 examined earthquake IMs as the fundamental element of the compound IM using four test criteria. Subsequently, a 1080 complete nonlinear dynamic time history analysis of the cross-fault hydraulic tunnel using the incremental dynamic analysis method is conducted to generate a large amount of data. The findings of this study highlight that the compound IM-based probabilistic seismic demand models of the cross-fault hydraulic tunnel incorporate various sources of uncertainties, which enhances the correlation, efficiency, practicality, and proficiency of probabilistic seismic demand analysis and eventually leads to a more reasonable estimation of probabilistic failure. Moreover, the potential of nonlinear polynomial regression of compound IM can further improve the correlation and efficiency of probabilistic seismic demand analysis. Relative to the classical fragility curves utilising a single optimum-IM peak ground velocity, the probability of damage to the cross-fault hydraulic tunnel under a particular damage state related to the compound IM is significantly larger than the corresponding single optimum-IM peak ground velocity. Similarly, the probability of damage to the cross-fault hydraulic tunnel under the Wenchuan seismic event is underestimated, derived from a single optimum-IM peak ground velocity. The abovementioned phenomena demonstrate that a compound IM based on the partial least squares methodology can be suggested for use in estimating the probability of structural damage in performance-based earthquake engineering.

Optimal selection of scalar and vector-valued intensity measures for improved fragility analysis in cross-fault hydraulic tunnels

Seismic intensity measures (IMs) are crucial because they are significantly connected to earthquake hazards and structural responses. It means that selecting appropriate IMs is necessary for underground structures under unfavourable earthquake hazard conditions. The seismic design code and dynamic analysis have conventionally employed the peak ground acceleration (PGA) as an optimal IM, mainly referring to the seismic design code of aboveground structures. However, seismic investigation of underground structures using PGA is still controversial. Simultaneously, directly employing the PGA as an ideal IM may increase the uncertainty associated with ground motions, which in turn increases the uncertainty for probabilistic seismic demand analysis of hydraulic tunnels. As a result, it is important to understand the roles played by different IMs while analyzing the fragility of hydraulic tunnels. This work aims to conduct a comprehensive analysis to identify the optimal scalar- and vector-valued IMs for fragility investigation of cross-fault hydraulic tunnels. Therefore, the 1080 complete nonlinear dynamic time history analysis by surrounding rock-concrete lining-fluid interaction system is conducted to express the earthquake-induced drift ratio of a cross-fault hydraulic tunnel by incremental dynamic analysis. Subsequently, a refinement process is performed to determine the optimal scalar-valued IMs by comparing the correlation, efficiency, practicality, and proficiency of the 7 examined IMs. Meanwhile, the probabilistic seismic demand model of optimum vector-valued IMs is also developed and compared, followed by the three scalar IMs. Eventually, the difference between the fragility curves of the tunnel produced using the optimal scalar- and vector-valued IM is compared. The results demonstrate that compared with scalar two-dimensional fragility curves, the vector three-dimensional fragility surface may increase the reliable probability and minimize the uncertainty in analyzing the structural response hazard curve. The generated vector fragility surface can also estimate the seismic fragility of identical cross-fault hydraulic tunnels in an approximative manner.

Optimal ground motion intensity measure for seismic assessment of high-rise reinforced concrete structures

The ground motion intensity measure is a key parameter affecting the accuracy of probabilistic seismic demand analysis (PSDA). This paper uses the incremental dynamic analysis (IDA) results of 12 three-dimensional reinforced concrete (RC) high-rise structures to explore the efficiency and sufficiency of a spectral acceleration Sa(T) intensity measure (IM) in a continuous period T (0–8 s). Subsequently, the effects of higher modes and period softening on the results are investigated. Controlling periods – that is, the lower and upper bounds of periods – across the spectrum are also examined in order to propose an optimal IM Sa,GM that considers the effects of higher modes and nonlinear softening on the seismic responses of three-dimensional high-rise buildings. Finally, the proposed optimal IM Sa,GM is compared to the widely used IM of spectral acceleration at the first-mode period Sa(T1) of the structure and the improved IM Sa¯, which considers the first n modes in the field, based on the criteria of efficiency, practicality, sufficiency, proficiency, and scaling robustness. The results indicate that the efficiency and sufficiency of the IM Sa(T) fluctuate with increasing periods T and are affected by higher modes and period softening. Furthermore, the proposed optimal IM Sa,GM exhibits a significant decrease in dispersion with respect to the structural response (efficiency) and scores higher on sufficiency, practicality, proficiency, and effectivity robustness than the IMs Sa(T1) and Sa¯.

Probabilistic seismic performance assessment of offshore jacket structures as a basis for engineering decision-making

Jacket structures play an ever-increasing role in meeting the world’s burgeoning energy demand by providing support structure for exploiting offshore wind energy and oil and gas resources. Many of these structures are past their design lifetimes, and thus may have suffered significant degradation, highlighting the importance of investigating their earthquake response in seismically active regions. This study investigates the seismic performance of a typical offshore jacket platform, denoted as baseline structure, as well as four versions with two longer (25% and 50% larger) and two shorter (25% and 50% smaller) natural vibration periods accounting for two levels of degradation and retrofit effects on structural performance. For each case, eleven ensembles of ground motions compatible with the site’s seismic hazard are selected using the generalized conditional intensity measure methodology. The loading uncertainty is incorporated in the performance assessment procedure via probabilistic seismic demand analysis and the demand hazard is quantified. The results provide valuable information regarding reliability of these structures both at design stage and during service life, which can aid decision-making around rehabilitation of older platforms, the suitability of reusing obsolete platforms beyond service lifetime, and risk-based design of new platforms.

Assessing seismic response equivalency for fixed pile-founded offshore platforms utilizing PSDA and IDA

Detrimental seismic effects on offshore platforms safety and serviceability highlight the necessity of these infrastructures fundamental seismic investigations that contribute to the design and maintenance of reliable structures. To this end, probabilistic seismic response evaluation of fixed pile-founded offshore platforms utilizing probabilistic seismic demand analysis (PSDA) has been employed. Housner Intensity-Drift Ratio as the derived optimal pair -in which engineering demand parameters (EDPs) are calculated, given the ground motion intensity measures (IMs)- is chosen. A selection of optimal IM–EDP pairs is made based on the criteria of practicality, effectiveness, efficiency and sufficiency. In this study, equivalency of the results is evaluated comparing the same IM-EDP pairs against the method of incremental dynamic analysis (IDA). Furthermore, another objective of this assessment is to investigate the appropriate number of required ground motion records according to which structural seismic responses are not over/underestimated. The uncertainties associated with fixed pile-founded offshore platform brace configurations, besides the effect of soil-pile-structure interaction (SPSI) are thoroughly considered, generating more accurate and vigorous results. The findings of this study demonstrate that seismic responses resulted from IDA approach utilizing 12 ground motion records scaled 7 times matches well with those derived from PSDA.

Seismic fragility analysis of concrete pile-supported wharves based on single-degree-of-freedom model

This study proposes a new procedure to predict the seismic fragility curves of concrete pile-supported wharf based on an equivalent single-degree-of-freedom (SDOF) model. The SDOF model is utilized to substitute the practical wharf structure during probabilistic seismic demand analysis for reducing the computational cost and complexity. The trilinear backbone cure and Pivot hysteresis model, whose parameters are determined by the pushover analysis of actual wharf, are incorporated in the SDOF model to represent hysteresis characteristics and strength degradation of wharf. To validate the reasonability of the proposed procedure, two case studies are conducted by comparing the difference of fragility curves developed from actual wharf and its equivalent SDOF model based on the cloud method. The results show that the curves are located very closely on the graph, and the curve of SDOF model is generally above that of actual wharf, which indicates that the SDOF model may provide a conservative assessment for fragility analysis of wharf.

Influence of spiral anchor composite foundation on seismic vulnerability of raw soil structure

A typical single-layer raw soil structure in villages and towns in China is taken as the research object. In the probabilistic seismic demand analysis, the seismic demand model is obtained by the incremental dynamic time history analysis method. The seismic vulnerability analysis is carried out for the raw soil structure of non-foundation, strip foundation, and spiral anchor composite foundation, respectively. The spiral anchor composite foundation can reduce the seismic response and failure state of raw soil structure, and the performance level of the structure is significantly improved. Structural requirements sample data with the same ground motion intensity are analyzed by linear regression statistics. Compared with the probabilistic seismic demand model under various working conditions, the seismic demand increases gradually with the increase of intensity. The seismic vulnerability curve is summarized for comparative analysis. With the gradual deepening of the limit state, the reduction effect of spiral anchor composite foundation on the exceedance probability becomes more and more obvious, which can reduce the probability of structural failure to a certain extent.

Selection of Ground Motion Intensity Measures and Evaluation of the Ground Motion-Related Uncertainties in the Probabilistic Seismic Demand Analysis of Highway Bridges

Probabilistic seismic demand analysis (PSDA) is known as one of the critical intermediate steps in the performance-based earthquake engineering (PBEE) design framework. Accuracy of the PSDA is influenced by various sources of uncertainties and mostly by that stemming from the ground motion-related variabilities. By taking a representative reinforced concrete (RC) continuous girder bridge as the case study, twenty-eight commonly used seismic intensity measures (IMs) were investigated in terms of the effectiveness, efficiency, practicality, proficiency, and sufficiency assessments. Probabilistic seismic demand models (PSDMs) of several critical bridge engineering demand parameters (EDPs) were developed under both the near-field and far-field ground motions through the nonlinear time history analyses (NTHAs). In addition, effects of ground motion-related uncertainties, such as the bin-to-bin (BTB) and record-to-record (RTR) variabilities, on the PSDA of highway bridges were also investigated. It is concluded that (1) IM efficiency contributes significantly to reflecting the RTR variability of ground motions and an efficient IM may reduce the influence of RTR variability in the estimation of structural demands; (2) IM sufficiency reflects the statistical independence of IM and ground motion parameters, and a sufficient IM is helpful in rendering the prediction of structural demands; and (3) uncertainties stemming from both the BTB and RTR variabilities of the seismic records have significant influences on the PSDA and the developed PSDMs of highway bridges.

Probability seismic demand and fragility analyses of novel SMA-based self-centring eccentrically braced frames

This paper performs the seismic assessment of novel shape memory alloy (SMA)-based self-centring (SC) eccentrically braced frames (EBFs) by using probabilistic seismic demand analysis (PSDA) and probabilistic seismic fragility analysis (PSFA). The structural finite element models are established based on a previous prototype building and verified through test results. The PSDA is based on a set of 176 seismic records, and Sa avg is chosen as the proper intensity measure for max inter-storey drift ratio (MIDR) and max inter-storey residual drift ratio (MIRR); whereas peak ground acceleration is more suitable for peak floor acceleration (PFA). After the PSDA results are obtained, time-history analyses and PSFA are conducted. Compared with traditional steel EBFs, the SMA-based SC-EBF shows a slight weakness in MIDR due to the comparatively small energy dissipation capacity but has an apparent advantage in controlling MIRR due to a good SC capacity provided by SMA angles. Furthermore, although the steel EBF with fixed column bases has the smallest MIDR, the fixed bases cause extra damage in column bases, which will bring other problems in post-earthquake rebuild and deviate from the design target of concentrating damage in link beams. The variability of the PFA is small, showing that the influence of structural forms on PFA is not apparent. Considering the overall structural seismic performances in terms of MIDR, MIRR and PFA, SMA-based SC-EBF can be a promising alternative in future seismic-resistant designs.

Seismic Performance Evaluation of Damaged Ancient Timber Structures with Looseness Mortise-Tenon Joints

ABSTRACT In order to investigate the seismic performance of damaged ancient timber structures with looseness mortise-tenon joints, the shaking table test of an intact ancient timber structure was carried out. The experimental model’s failure modes, main modal parameters, and dynamic response curves were investigated. In addition, the finite element models (FEMs) with looseness mortise-tennon joints were built by OpenSees, and the natural periods, acceleration, and displacement time history curves of intact FEM and experimental model are compared. Moreover, incremental dynamic analysis (IDA) of damaged models was performed, where the ground peak acceleration (PGA) and maximum inter-story drift ratio θ max are taken as intensity measure (IM) and damage measure (DM) of the motions of the ground, respectively. The seismic fragility of damaged models was studied by probabilistic seismic demand analysis to evaluate the seismic performance of the damaged structures from the perspective of probabilistic.

Vertical component effects of earthquake and soil-structure interaction on steel gabled frames

With an increase in the width of the steel gabled frame (SGF) span, in general, the structural mass considerably increases, as a result of which the vertical ground motions can exert significant inertial force on the members of a structure. Although numerous studies have confirmed the destructive effects of the vertical component of earthquake on concrete and steel structures, no research has been devoted to the impact of this component on steel gabled structures yet. Hence, the findings of this research will, at best, unveil possible new dimensions of these types of structures. Moreover, the investigation into the behavior of such structures with regard to the effects of soil-structure interaction (SSI) can help gain a more accurate understanding of their behavior. To this aim, in the present paper, an incremental dynamic analysis (IDA) was conducted for the first time on four SGFs with spans of 20 m and 60 m and heights of 6 m and 12 m with and without consideration of the vertical component of earthquake as well as SSI. Results were collected in the form of multi-record IDA curves, summarized IDA curves, fragility curves and probabilistic seismic demand analysis (PSDA) curves, indicating that the vertical component of earthquake had a determinative role on the seismic performance of wide-span SGFs. This component causes the structure to reach the nonlinear region more quickly, raises the stiffness changes in the nonlinear region, enlarges the data dispersion and demand sensitivity, intensifies the softening behavior, reduces the dynamic capacity, raises the failure probability, enhances the uncertainty, increases the mean annual frequency (MAF) and accelerates the damage in such structures. However, SSI does not have any significant role in the seismic performance of SGFs; just partially leading to more conservative results, especially when they have wide spans. Besides, the results of the PSDA analysis showed that under similar conditions, short-period SGFs are more vulnerable than long-period SGFs and should be prioritized for retrofitting.

Estimating seismic demand models of a building inventory from nonlinear static analysis using deep learning methods

Probabilistic seismic demand analysis (PSDA) is the most time- and effort-intensive step in risk-based assessment of the built environment. A typical PSDA requires subjecting the structure to a large number of ground motions and performing nonlinear dynamic analysis, where the analysis dimension and effort substantially increase at large-scale assessments such as community-level evaluations. This study presents a deep learning framework to estimate seismic demand models from nonlinear static (i.e., pushover) analysis, which is computationally inexpensive. The proposed architecture leverages an encoder–decoder model with customized training schedules and a loss function capable of determining demand model parameters and error. Furthermore, the framework facilitates the seamless incorporation of structural modeling uncertainties in PSDA. The proposed framework is then applied to a building inventory consisting of 720 concrete frames to examine its generalizability and accuracy. The results show that the deep learning architecture can estimate demand models by an R2 of 84% using a test-to-train ratio of unity. In addition, the average prediction error is less than 3% and 6% for demand model slope and intercept parameters, respectively, translating into an accurate estimation of fragility functions with a median error of 5.7%, 6.9%, and 6.8% for immediate occupancy, life safety, and collapse prevention damage states. Lastly, the framework can efficiently propagate structural uncertainties into seismic demand models, capturing the implicit relationship of the frames’ nonlinear characteristics and resultant fragility functions.

Demand‐oriented performance assessment using models of different degree of complexity

AbstractThis paper presents a procedure for evaluating performance objectives expressed in terms of the intended exceedance rate of a certain level of seismic demand. With the purpose of keeping the computational effort at a manageable level, the procedure relies on the use of structural models of different degree of complexity: a simplified predictor model that allows conducting hundreds of response history analyzes in a small computational time, and a sophisticated reference model able to realistically simulate overall system response. The former is used for the purposes of identifying a reduced set of ground motions for evaluating the performance objective of interest, which are then used as the input motions in the latter to estimate the level of demand with the specified exceedance rate and obtain additional insight into understanding the system in case performance needs to be improved. By introducing an intermediate structure‐specific predictor model, the so‐called demand‐oriented assessment is able to provide results that are more accurate than those obtained from intensity‐based assessments, while significantly reducing the computational effort associated to rigorous probabilistic seismic demand analysis.

Seismic reliability assessment of a non-seismic reinforced concrete framed structure designed according to ABNT NBR 6118:2014

abstract: Due to the paucity of studies regarding the seismic assessment of buildings in Brazil, this study aims to present and discuss a seismic reliability assessment of a reinforced concrete framed structure designed according to the Brazilian standard ABNT NBR 6118:2014 without the consideration of the seismic design requirements of ABNT NBR 15421:2006. Herein, fragility functions are generated through probabilistic seismic demand analysis, and integrated with hazard curves for Northeastern Brazil to generate regional failure probability maps for three limit-states: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). The results indicated that the building performance is adequate for IO; however, for LS and CP, an unacceptable performance is observed.