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This research innovatively presents a multi-parameter seismic fragility analysis methodology anchored on Blending ensemble learning tailored for the high-speed railway track-bridge (HSRTB) system. Leveraging ensemble machine learning models, a seismic demand model encapsulating multiple earthquake intensity measures (IMs) is formulated. The research progresses to deduce the mean seismic fragility representations for single, dual, and composite earthquake parameters. Key findings of this investigation underscore that the advanced methodology aligns well with the Monte Carlo (MC) fragility, signifying its robustness. Crucially, earthquake IM parameters, Sa(0.5) and Sa(0.3)_ASI, emerged as the optimal choices for singular and dual-parameter seismic fragility delineations. Further enriching this research, a composite parameter optimization technique rooted in multi-CPU genetic algorithms is proposed. This avant-garde method remarkably minimizes the fragility estimation error, emphasizing its unparalleled efficacy in enhancing the precision of fragility evaluations. [ABSTRACT FROM AUTHOR]

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]

The accurate assessment of soil conditions is crucial for ensuring the seismic safety of buildings and structures. The existing classification of soils in the building code of Uzbekistan has several drawbacks that affect the accuracy of the input parameters of soil properties, the determination of the seismic intensity of the ground, and the underestimation of external environmental factors that affect seismic intensity. In response to these shortcomings, this paper presents the results of long-term engineering geological, macroseismic, and geophysical studies conducted to assess the influence of ground conditions on seismic intensity parameters. Based on the findings, a new classification of soils according to seismic properties is proposed. The classification system considers the unique characteristics of each soil type and provides a more accurate representation of their seismic properties. The proposed classification system is expected to provide valuable insights for seismic hazard assessment and earthquake-resistant design of structures. [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]

Ancient timber structures have a high cost for conducting dynamic time-history response analysis due to the presence of many nonlinear components, such as mortise-tenon joints and Dou-Gon. To enhance the efficiency of evaluating the seismic performance of ancient timber structures through dynamic analysis, a simplified dynamic response analysis method based on SPO2IDA was adopted to evaluate the seismic performance of a timber frame palace with nine-purlin in Qing Dynasty of China and the results were compared with those obtained using the traditional pushover analysis method. The results showed that there were only slight differences in the seismic response of the ancient timber structure determined by the two methods when the structure was in a nonlinear stage. During a Ⅸ degree rare earthquake, the displacement response differed by 0.004 m, while the median seismic intensity during the third level of damage limit state differed by 0.079 g. The traditional pushover analysis method may underestimate the seismic resistance of the ancient timber structure, but the SPO2IDA algorithm can better capture the uncertainty of the structural vulnerability model at different limit stages caused by ground motion input, achieving the goal of quickly evaluating the seismic performance of the ancient timber structure with acceptable accuracy. [ABSTRACT FROM AUTHOR]

To estimate the connectivity of a road network, it is crucial to evaluate the correlation of hazard intensities among individual bridge locations since the probability of multiple bridges being damaged simultaneously depends on the degree of this correlation. However, research on connectivity assessment of bridge networks considering spatial correlations associated with flood intensities is scarce in the literature. When quantifying the spatial correlation of flood intensities, modeling based on the stream distance rather than the Euclidean distance is required, taking into account that river flow is restricted only within the stream network. To achieve this purpose, a novel methodology is proposed to evaluate the spatial correlation of a stream network based on a geostatistical linear model and stream network covariance models. In addition, this study considers the spatial correlation of seismic hazard intensity. With the proposed method, it is possible to identify which bridges play an important role in ensuring the connectivity of the road network under multiple hazards, i.e. flood and seismic. As an illustrative example, the proposed method is applied to a hypothetical bridge network in Kumamoto Prefecture, Japan. The results demonstrate that improved network connectivity can be achieved by implementing a relevant retrofitting strategy for important bridges. [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]

Fires and earthquakes can be present simultaneously. One primary scenario comes from strong earthquakes, followed by aftershocks, and sometimes causing post-earthquake fires. Another primary scenario starts with a fire, and followed by an earthquake. This study explored the effects of horizontal earthquakes on the structure and behaviors of free-burning fires. The horizontal seismic condition was simulated using a vibrator, with wood cribs as the fuel. Experimental results indicate that the heat release rate increased with the increased seismic intensity, given that the fires encountering horizontal earthquakes burned faster than the free-burning ones. The HRR rise was a result of the earthquake enhancing the combustion efficiency and the surrounding air entrainment. Additionally, the induced vibration changed the structure of the fire, reduced the flame height and increased the fire-base diameter. Furthermore, this study proposed a HRR and a flame height correlations under horizontal seismic conditions. [ABSTRACT FROM AUTHOR]

Evaluation of the seismic performance of two historical stone arch bridges of the Iranian rail network is presented using a discrete element method. The total length of the bridges is 66.7 m and 106.1 m. The bridges consist of multi-span arches changing from 5 m to 48.6 m. The incremental dynamic analysis method is used to determine the damage, failure patterns, and acceleration of the collapse threshold. Using the discrete element method after static analysis under gravity load, dynamic analysis of bridges under both horizontal components of the earthquakes was performed simultaneously for different earthquake intensities until collapse. The results showed that the most extensive damage occurred in the smaller bridge with the onset of failures in the top spandrels of the arches and then the piers of the bridge, while in the larger bridge which had a large central arch span, damage and failure occurred more in the central arch and its spandrels. The collapse spectral acceleration of the larger bridge is considerably smaller than the smaller bridge such that the ratio of collapse spectral acceleration of the larger to smaller bridge varies only between 45% to 61%. The low spectral acceleration intensity of collapse indicates more seismic vulnerability of the larger bridge. [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]

To expand the inclusiveness of hybrid test platform research, enhance the flexibility of hybrid test platforms using various control strategies, and promote the development of hybrid test techniques, a low-cost user-configurable electric actuator hybrid test platform is established in this paper. This platform can be transferred to other medium or large electric actuator hybrid test platform, the research applications of this platform cannot be limited by their proposed setup. Firstly, the hardware system design including hybrid test facility integrated control system core architecture and all related signal routings are carried out. Then, the improved equivalent force control feedback method based on force-loading control is proposed, and the software system development including hybrid test process control system software and user-configurable STM32 microcontroller (UCSM) software are conducted. Next, the mechanical performance of viscoelastic damper is tested, and the mechanical model parameters of viscoelastic damper are regressed. The accuracy of electric actuator force control (inner control loop), of which the control tasks get executed on the UCSM is verified using the experimental substructure of viscoelastic damper. The hybrid test of viscoelastic damping system verifies the reliability and robustness of hybrid test platform (outer control loop). Finally, the developed hybrid test platform implements various hybrid tests of viscoelastic damping system under broad temperature range and different seismic intensities. The test results reveal the influence of temperature and seismic intensities on the seismic control effect of viscoelastic damper. [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]

Examining the progression of fire in wood and wood-based materials on a laboratory scale is a challenging endeavour owing to practical constraints inherent to real fire scenarios. Factors such as the rate of fire spread, its intensity, duration, and the extent of its impact on timber structures are notably influenced by the quantity of timber surfaces exposed within a given building. Non-structural timber surfaces encompass decorative or flat linings on walls, ceilings, and flooring. The objective of this research was to devise a methodology that combines X-ray computed tomography (CT) scanning with concurrent fire testing of wood, enabling the assessment of the fire's course and its deleterious effects on timber materials. The overarching goal of this novel tool is to expand our understanding of the fire behaviour exhibited by emerging and modified wood materials. To achieve this, a specialized fire chamber was integrated with an X-ray CT scanner to enable simultaneous fire testing and scanning procedures. In this study, one transversal and one cross-sectional surface of Norway spruce wood were subjected to fire, and the progression of the fire was scrutinized using CT scanning. As the density of the combusting wood material substantially decreased due to carbonization induced by pyrolysis, the advancement of the carbonized front was thoroughly investigated throughout the entire material volume. Ultimately, the findings indicate that CT scanning holds promise as a valuable tool for investigating the behaviour of solid wood, wood-based products, or other lignocellulosic materials when subjected to fire conditions. [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]

Seismic risk assessment requires fragility functions derived using non-linear time-history analysis with earthquake records compatible with the site hazard and characterised via a suitable intensity measure (IM), which poses a challenge given the wide variety of structural characteristics found in bridge inventories. Given the lack of consensus on a suitable IM, regional studies often use peak ground acceleration (PGA), which despite being recognized as a poor indicator of structural performance, has persisted in earthquake response characterisation. Average spectral acceleration (AvgSa) has recently gained popularity since it describes earthquake intensity over a range of pertinent periods of vibration; however, its suitability as an IM has not been demonstrated on real bridge inventories with a wide variety of structural characteristics. In this study, hazard-consistent records selected for both PGA and AvgSa are used to evaluate the response of a large inventory of existing bridges with varying structural characteristics, from the Italian roadway network. The results indicate that AvgSa is a more accurate IM compared to PGA when applied to the regional assessment of RC bridges. [ABSTRACT FROM AUTHOR]

A relevant percentage of the world population lives in constructions made of sun-dried earth, which are built according to several techniques such as rammed earth, bahareque or adobe. This work specifically focuses on the adobe buildings located in the Historic Centre of Cuenca (Ecuador), recognized as a World Heritage Site since 1999. Although these buildings are characterized by different geometrical and material configurations, all of them have load-bearing façade walls made of adobe. This paper illustrates an analysis of the seismic vulnerability of these adobe façade walls according to different geometrical configurations and considering an out-of-plane loading. This study is based on original in-situ collected data about 45 one and multi-storey buildings. The seismic behaviour of the case studies is investigated through a demand versus capacity analysis based on 5 different failure mechanisms and considering a variable intensity of the seismic action. This procedure has allowed to classify the case studies according to their seismic vulnerability and to identify the most relevant failure mechanisms in such adobe façades. As a main result, some continued fragility curves have been produced to allow replicating this procedure to buildings with similar features. Finally, a repair cost estimation after seismic scenarios is estimated. [ABSTRACT FROM AUTHOR]

This paper studies the influence of degraded connections on dynamic characteristics, seismic response, and seismic fragility behaviors of traditional Chinese timber-framed buildings. Numerical models are developed based on the extended distinct element method, and calibrated with 1:3.52 scaled shake-table test data. The influence of fracture and wood aging on the performance of both mortise-tenon joints and Dougong brackets connections is discussed. A set of 20 ground motion records are selected for an incremental dynamic analysis, seismic behaviors, and fragility assessment. Results indicate that considering 0.75 times and 0.85 times degradation of mortise-tenon joints, natural frequencies are reduced by 8%, and 4%, respectively, and 4%, and 2% for Dougong brackets connections, respectively. The maximum acceleration response is reduced at most by 1.8% and 0.9%, respectively, and the maximum relative displacement is promoted by 7.3% and 5.3%, respectively. In addition, for a peak inter-structural layer drift of 1/442, 1/148, and 1/48, seismic intensities corresponding to median probabilities of exceedance of the structure with 0.75 times degraded performance of mortise-tenon joints are reduced by 32%, 16%, and 9%, respectively, and 14%, 6%, and 3% for Dougong bracket connections. [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]

Puqian Bridge, which spans Puqian Bay in the far South of China, is the largest independent sea crossing bridge project in Hainan Province to date. The construction conditions of the bridge were extremely complex and challenging. The seismic fortification intensity and the basic design wind speed are the highest anywhere in China. In addition, Puqian Bridge is the only bridge in China to cross an active earthquake fault system. At present, the existing seismic design specifications and relevant regulations are not applicable to the structural design and construction of this bridge project. Therefore, a series of the scientific research and technical solutions have been proposed to address the key design and construction issues over the past decade. This technical report introduces the design concepts and seismic fortification criteria. Then, the overall seismic design schemes and configuration details of this project are presented. Thirdly, investigations on wind-resistant design are demonstrated. Finally, studies on the health monitoring system of near-fault and cross-fault bridges in strong earthquake areas are also introduced. [ABSTRACT FROM AUTHOR]

Current approaches to assess the reliability and resilience of water infrastructure subject to seismic hazard typically use Repair Rate (RR) curves for the linear elements (pipelines), which estimate the expected number of repairs needed per unit length after the occurrence of an earthquake of a given intensity. The available RR curves are characterized by high levels of uncertainty being based primarily on expert judgment and on limited data. Also, they provide no distinction between the damage on the segments and on the joints. This paper develops probabilistic physics-based RR curves to quantify the damage to segmented pipelines due to earthquakes. First, a mechanical model for segmented pipelines is proposed. The model is then used to generate a set of synthetic data for the calibration of the model parameters. We compare the proposed RR curves with the ones available in the literature and discuss the advantages of the proposed model. [ABSTRACT FROM AUTHOR]

On the 25 February 2018, an earthquake of magnitude Mw7.5 struck the region of Porgera in Papua New Guinea (PNG), triggering numerous landslides. Planetscope images are used to derive a partial inventory of 2941 landslides in a cloud-free area of 2686 km². The average area of landslides in the study area is 18,500 m². We use the Environmental Seismic Intensity (ESI) scale to assess the damage due to the triggered landslides. Local intensity values are assigned to individual landslides by calculating their volume using various area-volume relations. We observe that different empirical relations yield similar volume values for individual landslides (local ESI intensity ≥ X). The spatial variation of landslide density and areal coverage within the study area in cells of 1 km² is investigated and compared to the probability predicted by the USGS model. We observe that high probability corresponds to a significant number of landslides. An ESI epicentral intensity of XI is estimated based on primary and secondary effects. This study represents the first application of the ESI scale to an earthquake in PNG. The Porgera earthquake fits well with past case studies worldwide in terms of ESI scale epicentral intensity and triggered landslide number as a function of earthquake magnitude. [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]

Cu-Al-Mn is one of the shape memory alloys (SMAs), which has been newly studied in recent years. This material can be used instead of typical Ni-Ti SMA since it can reduces material cost and dependence on temperature and loading rate, also, increases machinability and cold workability. In the present study, the seismic application of Cu-Al-Mn bars was evaluated as a part of the steel brace, selecting a 2D two-story split-X braced frame. FEMA P-695 methodology used to compare the collapse performance of two systems in the special concentrically braced frame (SCBF) and Cu-Al-Mn SMA braced frame (SMABF). Then the seismic response of the two systems was investigated at the different levels of earthquake intensity under nonlinear incremental dynamic analysis. The results showed that the SMABF had an allowable and more significant margin collapse compared to the SCBF system. The fragility curve of the two systems showed that the Cu-Al-Mn brace decreased the collapse probability of the frame. The collapse probability of Cu-Al-Mn brace was reduced by 82% and 45% at the maximum considered earthquake (MCE) and 1.5 times of MCE, respectively, compared to the collapse probability of the SCBF system. The SMABF had an allowable maximum inter-story drift ratio, having more distribution over the height of the frame in collapse point under all records but under 21% of records, the maximum inter-story drift ratio of the SCBF reached over 2.5%. The Cu-Al-Mn brace reduced the axial strain demand of the brace and inter-story drift of the 1st floor and residual drift. The result showed that the decreasing percentage of axial strain was 36% on average under the MCE intensity level of earthquakes. Also, the application of Cu-Al-Mn SMA in the braced frame increased the maximum top acceleration about 69% at the MCE level. Therefore, increasing acceleration in this system must be considered in the design of non-structural components. Despite the effectiveness of this new material, low ductility and poor energy dissipation were two weak points of this system. Therefore, this new alloy suggested using with other damping systems, or boundary frame with rigid connections to provide extra energy dissipation. [ABSTRACT FROM AUTHOR]

Strengthened masonry buildings are one of the most common types of old structure usually located in the ancient Algerian urban nuclei. The present study focused on common strengthened masonry buildings. Feedback from seismic experiments has shown that their dynamic behavior is generally nonlinear and highly vulnerable to earthquakes. Also, in order to predict the rate of damage that could occur to this type of structure in the event of earthquakes, empirical fragility curves based on a probabilistic method have been developed. In this study, seismic fragility analysis has been performed using the vulnerability index and the average damage rate. The vulnerability index will belong to one of three vulnerability classes determined by nonlinear dynamic analysis. The average damage is obtained using a deterministic method taking into account the vulnerability index and the seismic intensity. The fragility curves, which give the probability of achieving or exceeding a certain damage level for the three classes of vulnerability considered, have been compared to different studies that developed similar analyses. A seismic scenario was performed using a geographic information system and applied to strengthened masonry buildings located in Algiers city, which was built before the first Algerian seismic regulations of 1981. [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]

One of the most important components of an electrical substation is its power transformer, but this component is vulnerable to earthquakes. Several studies have demonstrated the good potential of base isolation to improve the seismic resistance of transformers. However, cost-effectiveness of a base isolation system is as important to the managers of a power grid as its isolation efficiency. Therefore, to investigate the cost-effectiveness of base isolation for large transformers, the framework of this two-part study comprised: (1) shaking table testing and (2) cost-effectiveness analysis. In the shaking table testing, the isolation efficiency of a friction pendulum system for a 220 kV transformer-bushing system was validated. In the cost-effectiveness analysis, the converter transformers of a typical substation were taken as examples to calculate the expected cost in a single earthquake event and the expected total life-cycle cost with/without the base isolation. The base isolation could impart considerable economic benefits in an extreme earthquake event and significantly reduce the risk of unacceptable earthquake-induced losses during the life period. Together, these two parts demonstrated the great cost-effectiveness of base isolation for large transformers in areas of high seismic intensity, underscoring the importance of further development and applications of this technology. [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]