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Seismic intensity measures (IMs) provide a link between the seismic hazard and the dynamic response of structures subjected to earthquake shaking. The spectral acceleration at the first and usually dominant vibration mode, Sa(T1), is a popular choice for building structures. Meanwhile, the IM selection for bridges is non-trivial since they do not typically possess a single dominant mode. Even for ordinary bridges with a dominant mode, the behavior can change significantly in each principal direction through the activation, or yielding, of its different components. This study examines the performance of a novel IM that incorporates ground motion directionality and structure non-linearity in this context: the nnth percentile of all rotation angles of the inelastic spectral displacement, Sdi,RotDnn. This evaluation is carried out within the context of an ordinary bridge structure and is compared with other conventional IMs used in regional risk assessment of bridges. The case study bridge utilized is a highway overcrossing located in California with two spans and a continuous prestressed reinforced concrete box girder deck section. A large ground motion set was selected from the NGA-West2 database, and incremental dynamic analysis was carried out on the structure to assess the IM performance to characterize collapse. The results indicate that Sdi,RotDnn performs very well compared to other IMs for the bridge structure and could be a prudent choice to characterize inelastic response of bridges with several possible mechanisms in different principal directions. Also, using the RotD50 definition, typically used in ground motion models, showed a 17.3% increase in efficiency compared to RotD100 definition typically used in engineering practice. [ABSTRACT FROM AUTHOR]

Seismic intensity measures (IMs) quantify the severity of ground motions and their impacts on structures. They play a vital role in many aspects of earthquake engineering. This paper proposes a novel method, namely the express iteration method (EIM), for constructing effective vector-valued IMs based on dozens of existing scalar ones given a specific engineering structure or a class of them. Taking advantage of the sophisticated while efficient mapping between scalar IMs and engineering demand parameters (EDPs) via a machine learning model, EIM iteratively eliminates less important scalar IMs from a pool of candidates to find the most effective combinations for a vector-valued IM and achieves superior computational efficiency by avoiding updating the nonlinear mapping during the process. Taking a base-isolated structure and its non-isolated counterpart for a demonstrating case study, the performance of the vector-valued IMs determined by EIM is compared with those by other existing methods in the literature for the task of selecting the most unfavorable ground motions. The results show that EIM prioritizes records with the largest peak inter-story drift PIDs and thus leads to the smallest subset that imposes most severe structural damage, while its computational cost was two orders of magnitude smaller as compared to the existing methods of similar effectiveness. Such superior performance can also be expected in all tasks that involve vector-valued IMs, including but not limited to multi-dimensional fragility analysis, incremental dynamic analysis, and real-time seismic damage prediction. [ABSTRACT FROM AUTHOR]

Recently, experimental studies on failure conditions of buildings equipped with curved surface sliding isolators have shown that when no displacement restraining elements are employed and the concave plates feature a flat rim, the inner slider can run on the edge of the sliding surfaces producing lateral displacement larger than the nominal isolator capacity. The over-stroke displacement capacity reduces the probability of seismic collapse of code-conforming base-isolated buildings for earthquake stronger than the design one. In order to quantify the benefit of the over-stroke displacement capacity of double concave curved surface slider (DCCSS) bearings on the seismic fragility of base isolated buildings, four case studies of six-storey reinforced concrete framed structures, consisting of new constructions and retrofit of existing structures located in high and medium hazard seismic sites, have been investigated in this paper. In all cases, two configurations of the isolation system have been considered, with end-stop displacement or with over-stroke displacement capacity. The seismic performance of the buildings has been investigated by multi-stripe nonlinear time-history analysis. The results of the nonlinear dynamic analysis at the collapse limit state have been compared with nonlinear static analysis in terms of maximum displacement and corresponding base shear. Fragility curves highlight a higher safety margin against collapse for seismic intensities beyond the design limit state of the isolation system with over-stroke capacity. [ABSTRACT FROM AUTHOR]

A new scenario-based method is proposed to determine the performance range of structural systems. The advantage of this method is using inter-storey drift as a damage index, while exploiting local damage indices of the main structural members without the need for detailed analytical models and computationally expensive non-linear dynamic analyses. A new damage function is proposed by linking the local (plastic hinge rotations) and global (inter-storey drifts) damage levels. The accuracy of the proposed function is evaluated and compared with the indices in ASCE41–06, ATC-13, and HAZUS for a set of steel moment-resisting frames subjected to earthquakes of varying intensities. [ABSTRACT FROM AUTHOR]

A new damping control method for the adjacent liquid storage tanks (LSTs) based on vibration barrier (ViBa) is proposed. Considering liquid-solid-soil coupling and structure-soil-structure interaction, a three-dimensional numerical calculation model is established by ADINA. The seismic control effect of ViBa is investigated, and parametric analysis is carried out. The results show that ViBa has a significant control effect on seismic responses and wave height, and the reduction factor of base shear force reaches the maximum value of 49.26%. The larger the seismic intensity, the liquid storage height and the height-radius ratio, the larger the reduction factor of the ViBa. [ABSTRACT FROM AUTHOR]

One of the primary concerns in the field of seismic risk assessment for underground structures is establishing an accurate connection between seismic intensity and structural responses. The objective of this work is to conduct a rational support vector machine (SVM) model for generating mass data and improved fragility curves of cross-fault hydraulic tunnels (CFHTs). The results highlight that the 900 sets, multiple earthquake intensity measures, and cubic polynomial kernel function of the SVM model can improve reliability in evaluating structural performance. Additionally, the improved Cloud analysis method is more suitable for seismic performance than the typical Cloud analysis. [ABSTRACT FROM AUTHOR]

The effectiveness of the tuned mass damper inerter (TMDI) in reducing the vibration of building structures under site-specific earthquake excitation is investigated. The site is Guwahati, Assam, which lies in the most severe seismic intensity zone in India. In this paper, the optimization of the TMDI design parameters is carried out for the site-specific input derived for the building site by a modulated Clough-Penzien (C-P) spectrum fitted to the power spectral density function obtained from a strong motion model of the site. All possible topologies of the TMDI, with one terminal of the inerter being connected to the damper mass attached to the top storey of the example buildings, and the other terminal being connected to any other floor, are investigated. The structure-TMDI system is analyzed both in the frequency-domain and in the time-domain. A numerical study is conducted with two example building structures. Optimization of design parameters of the TMDI is carried out using the technique of simulated annealing in the frequency-domain using the site-specific modulated Clough-Penzien spectrum as input. The performance of the optimal TMDI cases is evaluated by subjecting the example structures to 10 site-specific synthetically generated accelerograms. Results indicate that the TMDI is superior to the TMD for all topologies of the TMDI in case of the 3-storieed structure; and for topologies of the TMDI in which the inerter spans more than 4 floors for the 8-storied structure, with improved reductions in top-floor displacement, acceleration, and stroke length. [ABSTRACT FROM AUTHOR]

Pounding between adjacent structures subjected to earthquake actions can cause significant damage. Due to the many uncertainties inherent to the seismic input and the impact phenomenon, a probabilistic assessment of the occurrence of seismic pounding and of its consequences on the structural performance is necessary. This work analyzes the problem of pounding by considering a single-degree-of-freedom benchmark system surrounded by rigid boundaries and subjected to a stochastic earthquake input. Although simplified, the model is representative of several realistic configurations, such as base-isolated systems surrounded by moat walls or bridge decks near the bridge abutments. The problem is cast in non-dimensional form and a parametric study is carried out to evaluate the influence of the identified non-dimensional input parameters on the statistics of the response. A probabilistic demand model is developed for the impact forces via non-linear regression, with the demand expressed as a function of the identified non-dimensional parameters. This model provides an estimate of median pounding force and of its dispersion given the seismic intensity of the input. Finally, global sensitivity analysis is used to rank the model parameters in terms of their influence on the system performance. [ABSTRACT FROM AUTHOR]

The research attempts to provide a method for evaluating the susceptibility of heritage buildings and potential damage considering local site effects, using as a case study an urban sector situated in Horta, Faial, Azores, Portugal. The physical vulnerability of the investigated structures was appraised using an index-based method devised for structural masonry aggregates to emphasize their likelihood of seismic damage. As a result, a damage scenario based on real accelerograms collected after the 1998 Azores seismic event was developed by using a reliable seismic intensity prediction equation. In addition, the soil amplification, which increases the extent of seismic damage to the examined structures, is assessed by varying the soil conditions using EN 1998–1 Code. Thus, this research emphasises the ground impact in forecasting the expected damage scenarios, enabling optimised risk mitigation strategies in urban settings. [ABSTRACT FROM AUTHOR]

In this work, a total of nine ultra-high performance concrete (UHPC) filled steel tubular columns (UHPCFSTs) were fabricated and tested under cyclic loading. The results indicated that UHPCFSTs mainly exhibited flexural failure mode, compression-flexure failure mode and welding line fracture, and it changed from flexural failure mode to compression-flexure failure mode when the axial compression ratios exceeded 0.3. The elastic and ultimate drift ratios of UHPCFSTs were within the ranges of 1.37–2.05% and 2.38–4.32%, respectively, and the equivalent viscous damping coefficients were within the range of 0.197–0.358 when they failed, UHPCFSTs could sever as good choices in high seismic intensity areas. [ABSTRACT FROM AUTHOR]

Seismic assessment of plain concrete structures like gravity dams is generally conducted based on cracking. The responses of two types of gravity dams, i.e. the conventional and roller compacted concrete (RCC), were investigated in this study using a discrete element tool coupled with special reservoir elements. Using incremental dynamic analysis, the relationship between the seismic intensity measures and crack widths on the U/S face of the monolith was obtained. The damage accumulation on conventional and RCC dams was different: The cumulative cracking on the upstream face of the monolith correlated well to a seismic intensity measure representing base shear. [ABSTRACT FROM AUTHOR]

Early warning systems can estimate the possible-shaking intensity of the earthquake based on the initial P-waves on-site. Researchers have used the following two indicators: the initial peak P-wave displacement ( P d ) and the ground motion characteristic period ( τ c ). In this study, we re-examine the performance of the two indicators by employing ground motion data from the P-Alert low-cost network in Taiwan. We have found that the signal-to-noise ratio of displacement ( S N R d ) is effective for data selection. In addition, we have observed the irregular behavior of τ c in the P-Alert dataset. [ABSTRACT FROM AUTHOR]

Emergency authorities are concerned with how to effectively deliver patients to different hospitals for treatment while not overwhelming any single hospital during emergencies. This study proposes an optimization model for the real-time dispatching and treating schedule to evaluate the seismic resilience of the interdependent transportation-healthcare system. The functionality of the road network, the service of hospitals, and emergency management are comprehensively considered in the model. A series of case studies were used to test the applicability of the method and quantify the resilience under three seismic intensities. [ABSTRACT FROM AUTHOR]

The façade system is one type of building envelope. It is both acceleration sensitive and displacement sensitive under dynamic loads. However, some novel complex façade systems lack comprehensive study, especially under earthquake excitations, and full-scale shaking table test for both façade system with the main structure is expensive. Thus, a test design procedure is proposed, which includes the input excitations into the façade by using the finite element method (FEM) model, and aims for achieving acceleration and drift demands for acceleration-and-displacement sensitive nonstructural components (NCs). According to this procedure, full-scale shaking table tests for the façade system only are designed and conducted under different earthquake intensity levels. The responses (such as acceleration and displacement) are recorded, and critical damages (such as the relative residual displacement between panels and bolt scratch) are observed. Several key factors that affect the seismic performance, such as the component acceleration amplification factor and the required distance to prevent collision between panels, are discussed. [ABSTRACT FROM AUTHOR]

The code-based response modification factors are mainly developed based on engineering judgments and experiences from past earthquakes, and hence, they may not lead to reliable solutions considering different performance targets and hazard levels. On the other hand, the uncertainties associated with these proposed values are more significant for new lateral load-carrying systems, such as tunnel-form buildings, due to insufficient information about their performance against seismic events. To address these challenges, this study aims to propose a multi-level approach for the estimation of response modification factors for tunnel-form building structures by taking into account the site seismicity and the damage level defined as the target performance. Using the proposed approach, the modification factors corresponding to different ranges of earthquake intensity and damage levels are obtained for 2-, 5-, 7-, and 10-storey tunnel-form buildings. The results are then used to verify the efficiency of the response modification factors proposed by design codes for the preliminary design (code-based factors) of such systems. It is shown that, in general, by adopting a response modification factor between 4 and 6, the tunnel-form structural systems exhibit excellent seismic performance and can satisfy the requirements of the Immediate Occupancy (IO) performance level even under the Maximum Considered Earthquake (MCE). The outcomes of this study could be useful for performance-based design of tunnel-form building structures aligned with the new generation of seismic design codes. [ABSTRACT FROM AUTHOR]

Recent studies showed that while code-compliant structures can generally protect the safety of the occupants, they may exhibit extensive damages during strong earthquake events. On the other hand, structures are generally designed to satisfy the seismic code requirements with the least initial cost regardless of their life cycle cost. In recent years, value-based design has been considered as an effective alternative for code-based design procedures. In this method, as well as the initial cost of the structure, a comprehensive consequence modeling is performed in the design process. In this paper, for the first time, a value-based design optimization method is developed for seismic enhancement of existing RBS steel frames using nonlinear viscous dampers. The efficiency of the method is demonstrated through 4-, 8-, and 12-story frames designed for low, medium, and high earthquake intensity levels, while the life cycle costs are evaluated using FEMA P-58. A time-based approach is carried out to consider different earthquake events and their corresponding probability of occurrence in a specific range of intensities. For dynamic analysis of the structures, the Endurance Time (ET) method is adopted to significantly reduce the computational costs while providing accurate results. The Genetic Algorithm (GA) is then used to optimize the damping coefficient of the viscous dampers for minimum life cycle cost. The results, in general, indicate the efficiency of the proposed method in increasing the total economic value of the studied structures with the least additional cost. It is shown that shorter structures and those designed in high-seismic risk regions benefit more from using optimized viscous dampers, leading to up to 42% lower life cycle costs. The results of this study should prove useful in more efficient strengthening design of existing steel frames. [ABSTRACT FROM AUTHOR]

Shake table tests were conducted on a three-story steel braced frame with pretensioned basalt fiber reinforced polymer (BFRP) under the mainshock and aftershock sequences. The BFRPs were firstly tested to evaluate their dynamic behaviors. Then the self-centering braced frame was excited to a series of scaled earthquakes whose PGAs range from 0.2 g to 1.2 g. Through the pinned connections in the tested frame, the self-centering braces (SCBs) with pretensioned BFRPs were the standalone components to dissipate the seismic energy. The results revealed that the BFRPs with slight performance degradation were suitable to provide the restoring force for SCBs even under the strongest earthquake intensity. SCBs with pretensioned BFRPs were efficient in preventing damage and reducing the residual drift ratios. Although the aftershock slightly amplified the accelerations of the tested frame, the self-centering braced frame with pretensioned BFRPs presented similar drift ratios under the aftershock and separate mainshock with the same PGA. Therefore, the self-centering steel braced frame with pretensioned BFRPs has favorable resilient seismic behaviors and could quickly restore its functions after a strong mainshock-aftershock sequence. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental program involving shake table testing of two full-scale reinforced concrete frame buildings. These tests were conducted to investigate the effectiveness and reliability of a newly proposed servo-hydraulic Active Mass Damper (AMD) that can be designed to enhance the target seismic performance of a building at multiple earthquake intensity levels. The two nominally identical case-study buildings were intentionally designed to exhibit a "soft story" mechanism at the first level when subject to ground shaking of sufficient intensity, but one was equipped with the newly proposed AMD, installed on the roof. The two specimens were then subject to the same loading protocol consisting of a ground shaking sequence of varying intensity, with the seismic input consisting of a selected natural ground motion.The experimental results demonstrated that the proposed AMD is extremely effective at enhancing building seismic performance. Specifically, the AMD provided peak displacement reductions in the order of 70% and was shown capable of absorbing more than 60% of the total input energy. As a consequence, the un-retrofitted structure suffered nontrivial structural and non-structural damage, while the AMD-retrofitted building remained virtually undamaged at all shaking intensities considered. [ABSTRACT FROM AUTHOR]

The elasto-plastic oscillator, representing the basic model for reinforced concrete and steel structures, shows its inadequacy when dealing with masonry structures. The column, resting on a rigid plane with friction, is shown to be particularly appropriate to model the dynamic behaviour of masonry structures. At this aim, this paper investigates the motion of a slender rigid block (SRB), initially resting in its vertical configuration and hit by a seismic input, represented through a single impulse constituted by a rectangular or sinusoidal half-wave or a simplified sequence of horizontal acceleration pulses, having rectangular or sinusoidal shapes. An accumulation of the rotation of the SRB exists under the action of sequences of opposite acceleration pulses. The dynamic collapse is shown to take place when the column is led to its critical configuration – where the restoring moment of the weight is lost – so that the last pulse can further increase the rotation of the column. Expressing the behaviour of the SRB by means of the force reduction factor, the ratio between the magnitude of the collapse horizontal acceleration and the static strength of the column, the difference between the responses of the column decreases with increasing the number of the pulses of the sequence. A simple definition of the asymptotic failure domain can be obtained with a good approximation with a limited number of pulses. It is possible to evaluate the minimum collapse acceleration intensity of seismic sequences of pulses of any assigned duration able to produce the collapse of the rigid block, representing the seismic strength of the SRB. Finally, the results obtained in the theoretical analysis are compared with the outcomes of more accurate and time-consuming non-linear dynamic or incremental analyses (IDA). [ABSTRACT FROM AUTHOR]

For shield tunnels, seismic isolation layer is an effective countermeasure to reduce structural damage during earthquakes. In this paper, the physico-mechanical properties of asphalt-cement (A-C) materials applied to backfill grouting of shield tunnels were investigated by laboratory tests. Then, fragility curves were developed by analytical approach for shield tunnels before and after setting three typical A-C isolation layers (i.e. A-C Iso-layer1, 2, and 3), which were used to express the seismic vulnerability of tunnel lining and evaluate the seismic-reduction effectiveness under earthquakes. The results reveal that A-C isolation layers are effective in seismic-reduction under excitation of low input intensity (less than 0.5 g), while its effect is not significant at high-input intensity. The fragility curves for tunnel lining after setting A-C isolation layers show less vulnerability than not setting one at all seismic intensity levels. From the perspective of damage probability, the seismic-reduction effectiveness decreases with the increasing shear modulus of A-C isolation layer. The probability of minor damage of examined tunnel lining setting up with A-C Iso-layer1 decreased from 23% to 15% at most. [ABSTRACT FROM AUTHOR]

When the high-speed railway (HSR) bridge is subjected to earthquakes, some components in the HSR bridge are damaged, and these components' damages will be reflected in the deterioration of the rail unevenness. In this study, a framework to address the lateral seismic rail unevenness corresponding to the damages of different components in the HSR track-bridge subjecting to earthquakes is developed. In the first place, a benchmark HSR track-bridge system is selected to conduct the nonlinear dynamic analysis, and the distribution law of the seismic residual drifts in the HSR track-bridge system subjecting to different earthquake intensity levels is proposed. Next, a refined mapping model is developed to assess the additional rail unevenness corresponding to the damages of different components in the system. The seismic rail unevenness sample is established by combining the initial and additional rail unevenness. Finally, the assessment method for the power spectrum density (PSD) of the seismic rail unevenness is introduced, and the PSD assessments of rail unevenness corresponding to the seismic damages of different components in the HSR track-bridge system are developed. The proposed methodology provides an innovative approach to assessing the seismic damage status of the HSR track-bridge subjecting to random earthquakes. [ABSTRACT FROM AUTHOR]

The seismic performance of existing RC frame buildings seismically retrofitted by base isolation is examined. Two different types of isolation systems are considered, i.e.: rubber-based and friction-based isolation systems, respectively. Two different performance levels are examined, namely: Global collapse prevention and Usability preventing damage. Seismic performance is assessed by multi-stripe nonlinear time-history analysis, considering earthquake intensity levels with return period ranging from 10 to 100000 years. Results point out that seismic isolation works effectively in limiting damage well beyond the design limit state level while it shows a limited margin with respect to collapse beyond the design limit state level. [ABSTRACT FROM AUTHOR]

Precast structures have become increasingly popular in recent years. However, the low seismic capacity of prefabricated structures is still a fraught issue in high seismic intensity regions. This paper aims to improve the structural seismic capacity of a precast concrete frame by employing a viscous damper. Two precast concrete frame specimens, with and without viscous dampers (PCFV and PCF), were produced and subjected to dynamic reversed cyclic loading tests. The experimental results showed that the viscous damper could improve the dynamic bearing capacity of the frames. [ABSTRACT FROM AUTHOR]

The purpose of this study is to explore the optimum seismic IMs for the probabilistic seismic demand model of subway stations subjected to near-fault seismic excitations with velocity pulses, and establish the seismic fragility curves based on the optimum seismic IMs. A two-storey three-span subway station is used herein as a representative case study for the cut-and-cover rectangular underground structure. Because the dynamic response of underground structure is closely related to the properties of the surrounding soil/rock, four typical classes of engineering sites covering Classes I to IV are selected in accordance with the Chinese code for seismic design of urban rail transit structures. Nonlinear time history analyses considering soil–structure interaction (SSI) are conducted on the two-dimensional numerical model of the subway station embedded in four different engineering sites. An ensemble of 121 near-fault seismic excitations with velocity pulses is used in seismic dynamic analyses so as to define the optimum IMs. Each seismic excitation is converted into the free field load at artificial boundaries of discretized numerical model of SSI system. The efficacy of 21 commonly used ground motion IMs for predicting seismic response of shallowly buried subway stations is discussed in this study. Four different criteria characterizing the adequacy of IMs, including efficiency, practicality, proficiency and sufficiency, are used in identification of the optimum IMs, on account of the statistical regression results of the selected IMs and engineering demand parameters of the subway station structure measured by maximum inter-story displacement ratio. It is concluded that for engineering sites of Classes I and II, the sustained maximum acceleration followed by peak ground acceleration are the optimum IMs, and for engineering sites of Classes III and IV, the velocity spectrum intensity is the optimum IM. Finally, based on the optimized seismic IMs, the fragility curves of subway station embedded in different site classes are developed in this study. [ABSTRACT FROM AUTHOR]

In low-to-moderate seismicity regions, seismic loss functions (SLFs) are barely established due to limited observational data, making it difficult to derive decision-making on disaster prevention and management. Herein, a Bayesian framework is developed to update the SLFs with limited observational data. The proposed point-based Bayesian method updates local probability density function parameters for damage ratios at each seismic intensity, which helps to avoid an unrealistic underestimation of damage ratios in the low-to-moderate range of seismic intensities. The feasibility of the developed framework in a low-to-moderate seismicity region is verified by the comparison between the updated SLF and post-event data. [ABSTRACT FROM AUTHOR]

Two new, highly efficient single-parameter seismic intensity measures (IMs), one structure-specific and one structure-independent, are proposed for use on both bare and infilled reinforced concrete frames. The efficiency of these IMs has been evaluated along with the efficiency of several other IMs and seismic parameters over a group of 1568 bare and infilled frames. The ability of the investigated IMs to predict damage is evaluated on the basis of the correlation between IMs and the seismic damage, the dispersion of this correlation over the considered frames, its consistency across different seismic intensity levels, and its bias towards specific structural types. [ABSTRACT FROM AUTHOR]

This study firstly investigates the seismic intensity measures (IMs) from the existing scalar ones that are suitable for the prediction of seismic response of shallowly buried rectangular underground structures. The peak acceleration and peak velocity at the ground surface are identified as the optimal IMs based on their efficiency, practicality, and proficiency. A series of seismic fragility curves are then developed for a two-story and three-span underground subway station embedded in three different typical engineering sites using nonlinear incremental dynamic analyses. In this study, the input ground motions at the level of engineering bedrock for the underground structure–soil interaction system are obtained through one-dimensional equivalent linear site response analysis according to the one-dimensional wave propagation theory. Comparison of the numerical results in this paper with the previous empirical and numerical fragility curves shows that the fragility analysis method in this paper is feasible, which can quantitatively give the failure probability of structures at different performance levels, and can provide reference for seismic design of underground structures. The numerical results indicate that both the characteristics of ground motions and the site profile have significant influence on the seismic fragility curves of underground structures. Underground subway stations are generally more vulnerable to seismic damage when embedded in engineering sites with lower average shear velocity. Moreover, seismic damage margin ratios are proposed for the underground structure in different site classes to show the confidence levels of its seismic performance when subjected to different levels of earthquake events, and can be used as a preliminary index for the earthquake risk assessment of subway station. [ABSTRACT FROM AUTHOR]

In this paper, a post-earthquake damage assessment method for 11 different structural systems is proposed. The method is mainly based on residual inter-story drift ratios of all structural elements in the building, an important response parameter due to its simplicity of measure after the earthquake. nearly 2000 test specimens representing structural elements characterized by different structural systems (walls, frames, etc.) and materials (masonry, reinforced concrete, and steel) which were tested under quasi-static cyclic loading provided more than 100,000 data points that were used to correlate the residual drift ratio and damage states in structural elements. The damage severity of each structural element was then determined based on the weighted average of each damage state's exceedance probabilities given a residual drift ratio. The method also considers the damage propagation among different structural elements by considering the weighted average overall damage scores in structural elements concerning their load-bearing contribution. The pre-earthquake condition of the building and the level of experienced earthquake intensity is the other input parameters for the proposed method, which finally leads to the building's overall damage score. To verify the accuracy of the proposed method's results, an example building hit by the Ezgeleh earthquake is evaluated, and the results are compared with those of other post-earthquake damage assessment methods. [ABSTRACT FROM AUTHOR]

In this study, a damage survey was conducted on the buildings of two schools located in the town of Abira, where a Japanese seismic intensity of 6 upper was recorded during the 2018 Hokkaido Eastern Iburi Earthquake. The damage classes of the reinforced concrete structural members and residual seismic capacity ratios were examined. Both schools had performed seismic evaluation and retrofitting before the earthquake, and no serious damage occurred, but flexural and shear cracks in columns and walls were observed. Analysis using drone photographs was conducted to perform crack detection and crack width evaluation and create point cloud models. [ABSTRACT FROM AUTHOR]

The computational complexity and high computational costs are the main obstacles to estimate the seismic demand and capacity of non-linear structural systems and assess their seismic performance under strong earthquake events. On the other hand, the current response modification factors for seismic design of structures are mainly based on a single performance target, and therefore, cannot be directly used in modern performance-based design procedures. In this study, a low computational cost method is adopted for seismic performance assessment of steel moment-resisting frames and development of multi-level modification factors by using the newly-developed Endurance-Time method. The efficiency of the proposed method is demonstrated for 3, 5, and 7-storey frame examples. It is shown that compared to conventional methods using time-history and pushover analysis techniques, the proposed approach can significantly (up to 80%) reduce the computational costs. The results indicate that push-over analyses may lead to inaccurate results, while a good agreement is generally observed between the seismic demands predicted by Endurance-Time and Time-History methods (less than 10% error). The results of Endurance-Time method are then used to develop multi-level response modification factors for steel moment-resisting frames by taking into account the effects of earthquake intensity and the target performance level. It is shown that Endurance-Time method can accurately estimate the response modification factors and the corresponding earthquake intensity levels with significantly less computational cost compared to the conventional methods using incremental dynamic analysis. The proposed multi-level response modification factors should prove useful in performance-based seismic design of steel moment-resisting frames. [ABSTRACT FROM AUTHOR]

In this study a seismic risk analysis of masonry buildings based on damage data of L'Aquila 2009 earthquake is presented. Typological loss curves and Expected Annualized Losses (EAL) values are presented, starting from the data collected into AeDES forms available in the Da.D.O. database. A completion is proposed for improving the sample statistical significance, and correctly including undamaged and not surveyed buildings that suffered low shaking values. Finally, the loss curves proposed permits to economically assess the effectiveness of some local and very frequent interventions (such as chains/ring beams), and their consequent impact in seismic risk mitigation. [ABSTRACT FROM AUTHOR]

A seismic loss-based design framework is proposed. It relies on the introduction of a multi-objective loss-performance matrix that attempts to set an innovative design approach directly associating loss measures to performance levels as a function of the design seismic intensity and the social importance of the building. This approach provides higher awareness about the economic consequences caused by structural and non-structural damage in the aftermath of an earthquake event. The design framework is applied to a case-study-reinforced concrete frame building designed as a traditional cast-in-situ moment resisting frame system, analyzing its performances within the new loss matrix. [ABSTRACT FROM AUTHOR]

Structures on coral reefs are often subjected to the earthquakes. However, few researches have been reported about the seismic response of coral sand site. Shaking table tests of structures supported by pile groups were performed to reveal the seismic response of pile-soil-superstructure system by comparing with quartz sand site. Moreover, the effects of pile number and shaking intensity on the dynamic characteristics were analyzed. The results show that the liquefaction of coral sand site is more difficult than quartz sand site. The pile number and shaking intensity play key roles in the seismic response characteristics of coral sand site. [ABSTRACT FROM AUTHOR]

The present study proposes a statistical methodology to rate the habitability of different types of buildings after an earthquake. The first step was to rank variables that affect the vulnerability of a building and formulate a statistical study with a discrimination index that makes it possible to identify buildings as habitable or non-habitable. This ranking applied the criteria established in various international guidelines that are used to distinguish between habitable (undamaged/no structural damage) and non-habitable buildings (structural damage). The proposed methodology was applied to a database with information about buildings and damage grade experienced following the 2011 earthquake in Lorca. The approach presented could be extended to other regions where neccessary data are available. [ABSTRACT FROM AUTHOR]

Seismic performance of postmainshock buildings considering seismic mainshock-aftershock sequences are studied. The case studies correspond to three SAC steel MRF buildings of three, nine and twenty stories. The 2-D models are able to capture important properties of deterioration of strength and stiffness. Endurance time method is used to predict the response of structures in different hazard levels. Results are compared with those from of nonlinear incremental dynamic analysis. Maximum dynamic seismic responses of structures are captured during synthetic mainshock-aftershock seismic sequences which are produced by endurance time method. Interactional-conceptual curves for different seismic performance levels and residual collapse capacity of post-mainshock damaged buildings are presented. The collapse fragility curves of case studies are extracted. The results show that the residual seismic response of building caused by the mainshock and the direction of applied aftershocks are highly significant factors in evaluation of postmainshock buildings. It is found that in a seismic sequence which has two earthquakes with different intensities, occurrence of the stronger shake before the less intensive one, imposes higher seismic risk to the building. [ABSTRACT FROM AUTHOR]

Many bridges in seismic prone regions suffer from serious foundation exposure caused by scouring of the riverbed. In this study, the seismic performance of a bridge at various scour depths is assessed using a nonlinear static procedure based on the capacity spectrum approach. The performance limit of the bridge is identified in the capacity spectrum. The level of seismic intensity, characterized as peak ground acceleration, required to reach this performance limit is determined accordingly. The influence of riverbed scour on the seismic performance of a bridge is assessed by comparing the seismic intensities correlated to the performance limit at different scour depths. Results emphasize that for a bridge originally equipped with sufficient foundation strength, an improved seismic performance is observed when the scour depth is shallow. Once the scour depth exceeds a critical level, the seismic performance of the bridge is controlled by unexpected damage in the foundation. The seismic intensities correlated to the performance limit of the bridge decreases, and the seismic performance declines rapidly when the scour depth increases. The influence of structural properties and soil profile type on the seismic performance of a bridge at different scour depths is also investigated. The minimum scour depth, which causes the difference in seismic performance limit of a bridge from the original design, reduces with a decrease in the superstructure mass or soil-foundation system strength. The findings of this study help engineers evaluate the need for foundation retrofitting, particularly to ensure satisfactory seismic performance for bridges that undergo riverbed scour. [ABSTRACT FROM AUTHOR]

We analyze the global and local uncertainties of ground motion-macroseismic intensity conversion equations and derive new probabilistic relationships between the macroseismic intensity and peak ground motion parameters (peak ground acceleration and peak ground velocity) for western China based on the assumption that the peak values of ground motion are randomly distributed for each MMI level, bounded by a normal distribution. For this purpose, a strong ground motion database consisting of 37 moderate- to large-magnitude earthquakes that occurred in western China between 1994 and 2017 is employed along with the corresponding modified Mercalli intensity (MMI) information inferred from isoseismal maps and earthquake damage reports. The mean value and standard deviation parameters in the probabilistic formulas are obtained from the result of the analysis of the local uncertainties of the data compiled for Western China. We propose a method for the rapid assessment of computer-generated intensity maps using the new probabilistic formulas. Our method composed of two steps. (1) According to a Bayesian formula, the possibility, expectation and standard deviation of the seismic intensity are calculated by the ground motion parameters recorded at a site station. (2) Furthermore, expectation and standard deviation maps of the seismic intensity throughout an area are obtained through spatial interpolation. Finally, an application is illustrated to validate this new methodology by presenting rapidly estimated (computed) intensity maps of the 8 December 2016 Hutubi (Ms 6.2) earthquake in western China. [ABSTRACT FROM AUTHOR]

Shake-table tests conducted on three as-built and six haunch-strengthened two-story RC frames were analyzed to develop damage scale; suggest roof drift and base shear coefficient for various performance levels of as-built and haunch-strengthened frames. Nonlinear numerical models were prepared in finite element-based software SeismoStruct, calibrated with the experimental tests. Incremental dynamic analysis of models was carried out using natural acceleration time histories. Seismic fragility functions were derived for both as-built and haunch-strengthened models using a probabilistic method. Damage-to-loss factors were employed to transform structural damages to repair cost ratio, which were correlated with seismic intensity to derive seismic loss curves. [ABSTRACT FROM AUTHOR]

This study is carried out based on field investigation data obtained over more than 20 days after the 20 April 2013 Lushan Ms7.0 earthquake in Sichuan Province, China. The investigation includes detailed seismic damage data from 3,684 buildings in 428 districts. This research summarizes the seismic characteristics of buildings with different structures in this area and systematically analyzes the cause of damage. Based on this analysis, the seismic vulnerability of various structural forms in different intensity regions is systematically assessed. The damage characteristics are summarized for several types of the structures typical in the region: constrained masonry structures designed following current standards, unengineered constrained masonry structures, unreinforced masonry structures, brick-wood structures, brick-concrete structure, traditional Chinese timber frame structures, reinforced concrete frame structures, tall buildings, and industrial plants. Moreover, the causes of damage to these structures are investigated. Furthermore, through statistical analysis, this study develops a vulnerability matrix for the main building types and compares their vulnerabilities of similar buildings in regions with different earthquake intensities. The research results provide an important reference for earthquake engineers to recognize failure modes in different types of structures (especially those reconstructed after the Wenchuan earthquake, Sichuan Province, China), revise seismic design codes, and formulate future disaster-reduction plans. [ABSTRACT FROM AUTHOR]

In this paper, an analytical scheme for the selection of the corner frequency of high-pass filters is proposed based on the minimization of the variations of three characteristic frequencies, which correlate with the energy content of the seismic waves at low frequencies. This goal is achieved via the evaluation of the degree of their sensitivity to the selection of the cut-off frequency based on criteria defined in terms of time integrals of the squared ground motions. The observations of the present study highlight the necessity of the consideration of the impact of high-pass filtering uncertainty in seismic analyses, and the possibilit y of the future use of theoretical models in the systematic processing of recorded ground motions. [ABSTRACT FROM AUTHOR]

Understanding of the soil-foundation-structure interaction (SFSI) is crucial for seismic design. The period-lengthening ratio (PLR) has been studied using both analytical and experimental methods. In this study, to obtain a PLR that reflects the non-linear characteristics of the soil, dynamic centrifuge testing is conducted and the PLR is evaluated for different seismic intensity and frequency characteristics. The results indicate that the PLR of a single-degree-of-freedom (SDOF) structure increases with the peak ground acceleration at the surface. In addition, from the test results, the PLR is affected by the relationship between the excitation and natural frequencies of the structure, which must be considered in future. [ABSTRACT FROM AUTHOR]

This paper represents multivariate fragility functions (MFFs) based on sliding displacement of soil slopes for landslide hazard assessment. The MFFs correlate the sliding displacement probability of slopes to earthquake intensity measures (IMs). Conditional distributions are employed to develop MFFs for failure probability analysis of slopes by considering scalar and vector IMs in the absence of any predetermined predictive model for sliding displacement of slopes. Three sliding displacement-based damage states are defined herein as the low, moderate, and high levels of landslide hazard. The results demonstrate that the probability of exceedance from a given damage state strongly depends on the type and the number of IMs chosen for the fragility analysis whereas the predicted failure probabilities resulted from the scalar and multivariate analyses can vary up to three times. Results of this study indicates that the multivariate fragility analyses can lead to landslide damage estimation in more reliable manner, compared with the scalar-valued fragility curves which are commonly used to predict the seismic hazard of earth slopes. [ABSTRACT FROM AUTHOR]

Effective implementation of the static friction of sliding isolators in object-oriented software for structural design has not yet been achieved, and use of the dynamic friction only for design is common practice. A modeling strategy to account for the contribution of static friction under unidirectional ground motion histories has been developed and used to assess its effects on the response of a building isolated with curved surface sliders. Under low-to-moderate intensity earthquakes, disregarding static friction can lead to unpredictable response of the isolation system and result in a non-conservative evaluation of accelerations and forces transferred to the superstructure. [ABSTRACT FROM AUTHOR]

The aim of the present study was to examine the effects of earthquake direction on seismic performance of concrete gravity dams subjected to seismic sequences. For these purposes, two seismic incident directions are applied along horizontal axes to assess the maximum structural demands. Nonlinear dynamic analyses of the dam-reservoir-foundation system subjected to as-recorded mainshock–aftershock sequences are conducted to investigate the effects: 1) direction of single earthquake events; 2) direction of seismic sequences; 3) aftershock polarity; and 4) earthquake intensity. The results indicate that earthquake direction can significantly change the damage propagation processes of concrete gravity dams. [ABSTRACT FROM AUTHOR]

A novel evolutionary power spectrum model of seismic ground motions is formulated. The model consists of an envelope function and a seismic spectrum. The envelope function of the ground motion is derived based on a rectangular fault model in which rupture propagates along the diagonal line. The spectral characteristics of the ground motion are described by the earthquake source spectrum and the transfer function of the medium. The values of the model parameters are obtained by the earthquake source mechanism analysis and the ground motion spectrum identification. For applications, the ground motion records during the Northridge earthquake are modeled and simulated. [ABSTRACT FROM AUTHOR]

This paper discusses and quantifies the minimum requirements of walls and tie-columns in confined masonry (CM) buildings located in earthquake-prone regions. A research database including 238 damaged CM buildings obtained from the 2008 Wenchuan earthquake survey is established and comprehensively examined. The requirements of masonry walls in CM buildings are discussed, and a simplified tie-column density index is proposed for evaluating the potential damage of the structures. Besides, the minimum requirements of reinforced concrete tie-columns and their maximum allowable spacing in CM buildings at different seismic intensity zones are discussed. [ABSTRACT FROM AUTHOR]

Empirical correlations between the frequency-content parameters of earthquake ground motions and amplitude-, cumulative-, and duration-based intensity measures (IMs) are examined in this study. Three commonly used scalar frequency-content parameters are considered, namely the mean period (Tm), the average spectral period (Tavg), and the smoothed spectral predominant period (T0). It is found that the frequency-content parameters have weakly negative correlations with high-frequency IMs such as peak ground acceleration (PGA) and spectral accelerations (SAs) at periods smaller than 0.3 s, low-to-moderate positive correlations with peak ground velocity (PGV) and SA within a period range of 0.5 s–10 s, negligible correlations with cumulative-based IMs, and weakly positive correlations (in the vicinity of 0.1–0.3) with significant durations. Simple piecewise parametric equations are proposed to fit the empirical correlations of Tm, Tavg, and T0 with SA over the entire period range. The presented correlation results and parametric models enable the frequency-content parameters to be easily used in various applications such as ground-motion selection and vector-based probabilistic seismic hazard analysis. [ABSTRACT FROM AUTHOR]

The seismic assessment of a road network depends largely on the characterization of the fragility of its bridge components. The accuracy of bridge seismic demand estimates and the use of proper intensity measures (IM) will significantly influence such task. The available literature has mainly focused on buildings or a limited number of bridge configurations and IMs, which may not be representative for bridge portfolio assessment studies. In this paper, the correlation quality between a larger pool of traditional and innovative IMs and the nonlinear dynamic response of typical Italian RC bridges is investigated to identify the best-performing IMs. [ABSTRACT FROM AUTHOR]

The 2011 great Japan Tohoku earthquake is not only the most devastating but also, one of the best recorded earthquakes in the history of seismology. A thorough study of strong motion characteristics of this earthquake is conducted using 20 well established ground motion parameters (GMPs). The behaviour of these parameters with fault distance and average shear wave velocity is examined and attenuation relationships are developed using the 1172 surface level strong motion records. In addition, all GMPs are categorized on a statistical basis using principal component analysis, which is further used to rate the damage potential of ground motion records. [ABSTRACT FROM AUTHOR]

This paper is aimed at determining the effects of the soil characterization on the seismic input to use for seismic assessment. Three different soil profiles have been assembled to represent the stratigraphies found through a proper experimental investigation, carefully described, and alternative seismic site response analyses have been performed. The surface spectra obtained from the seismic site response analysis (SRA) are very different from each other, thus evidencing the importance of carefully describing soil stratigraphy. Furthermore, the comparison among the surface records found for different return periods has shown a limited sensitivity of the SRA to the seismic intensity. [ABSTRACT FROM AUTHOR]