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Although it was claimed that the MKR-α method can improve the overshoot and nonlinear stability characteristics of the KR-α method, it seems that it still has a high frequency overshoot in steady-state responses and a weak instability. Three examples are applied to numerically illustrate the two adverse properties. A loading-correction term is introduced into the displacement difference equation to remove the adverse overshoot in high frequency steady-state responses. Besides, it is analytically verified that the MKR-α method has an adverse weak instability. Although the problem of high frequency overshoot in steady-state responses can be overcome, there is no way to eliminate the adverse weak instability for both the KR-α method and MKR-α method. Thus, the applications of the two families of integration methods are very limited. It is demonstrated that a high frequency numerical damping is incapable of mitigating the overshoot caused by a weak instability. [ABSTRACT FROM AUTHOR]

The reciprocal of the condition number of the stiffness matrix was determined to be Graph HT ht . The authors have conducted the same analysis and found that I the result for the MKR- i Graph HT ht I method in Figure 1(c) of the discussion paper is wrong i . The authors have conducted the same analysis and found that I the results for the MKR- i Graph HT ht I method in Figure 3 of the discussion paper are again wrong i . [Extracted from the article]

This paper presents a modified evaluation approach for the structural-capacity-reserve (SCR) based on the static stability behavior of single-layer spherical lattice shells to achieve more accurate assessment results of seismic damage endurance. The SCR index in this paper is calculated by integrating the redefined residual structural capacity (RSC) ratio based on post-earthquake static stability behavior within the range of damage degrees caused by strong earthquakes. Compared with the assessment work for seismic damage endurance in the existing literature, the proposed RSC ratio in this paper could take into account both ultimate load-bearing strength and residual deformation. Additionally, the specific quantitative indicator in the proposed assessment method should also be determined according to whether the residual nodal displacement of the lattice shell after an earthquake exceeds the limit value state specified by the design code. The numerical results in the case study indicate that the residual load-bearing strength of the lattice shell remains relatively constant under the same damage state induced by different earthquakes, with residual deformation significantly impacting the assessment of seismic damage endurance. Thereby, the required RSC can be controlled by reducing the residual nodal displacements of the lattice shell under strong earthquakes to achieve a well-balanced design scheme. [ABSTRACT FROM AUTHOR]

A new cable-damper stopper equipped for Coal-Fired Thermal Power Plants (CFTPPs) was proposed in our previous paper, where a series of shaking table tests were carried out to investigate its seismic performance, so this paper aims to reveal the working mechanism of the stopper from the theoretical and numerical simulation aspects. The stopper is composed of three main components, i.e. a steel cable, a steel block and a viscous damper. First, the nonlinear restraint stiffness of the steel cable to the boiler was derived; second, the critical damping of the stopper, which makes the vibration of the boiler decay exponentially with no oscillation, was derived; third, an iterative method was proposed to globally tune the CFTPP structure, which makes it possible to obtain the optimal parameters of the cable-damper stopper, including the diameter of the steel cable and damping coefficient of the damper. Finally, finite element models were built and time history analyses were conducted to verify the proposed optimization approach. Firstly, the finite element models were proved valid through the comparison between the results of the simulations and the experiments. Then, based on the results of the simulations, the theoretical procedure was validated. The results revealed that the proposed cable-damper stopper reduced the seismic responses of displacements of the top floor and the boiler significantly, about 30.18% and 60.01% respectively compared with their counterparts of CFTPPs without stoppers. [ABSTRACT FROM AUTHOR]

A pulse-like ground motion identification method is proposed based on the Siamese Convolutional Neural Networks (SCNNs). The wavelet coefficient graphs of pulse-like ground motions are used as the input data, and the features extracted by the SCNNs are used for the identification. Based on the time-domain features, pulse-like and non-pulse-like ground motions are classified into several classes. The results indicated that all the identified pulse-like ground motions have similar pulse features to the pre-selected training data. The principal advantage of the method is that the misclassification problem can be minimized by an updating procedure proposed by this paper. [ABSTRACT FROM AUTHOR]

The dynamic analysis of the out-of-plane response of masonry walls, with different reinforcing systems and hit by sequences of pulses alternating in sign, representative of the seismic action, is the aim of the paper. The analysis is done in the context of the Heyman model of the no tension masonry structures. We consider the wall of the last story of a simple masonry house, commonly reinforced at its head by a ring beam, usually in a reinforced concrete. It has also been considered the retrofitting of the wall by applying, on both its sides, vertical bands in FRP, or similar. The dynamics of the wall, activated by sequences of pulses, is analyzed in detail, considering the change of geometry occurring in the mechanism during the motion. The corresponding differential equation is integrated in a closed form. It is shown that, under the alternating sequence of shocks, the dynamical collapse of the wall takes place immediately after the occurrence of an accumulation of out-of-plane deformation of the wall that drags it into the configuration of zero strength, where any resistance, due to the weight, has been lost. The collapse takes place right after when the subsequent incoming pulse pushes the wall to go further beyond this configuration. The check of the seismic safety of the masonry wall concludes the paper. The smallest limit static strength of the wall required in order the wall, having pulsation p, could be able to sustain, at the limit of the dynamical collapse, the action of the asymptotic pulse sequence with acceleration intensity PGA and specific duration p TE/2 of the expected earthquake. It is shown that the wall, reinforced by a top ring beam, with the addition of vertical bands of glass or similar, of suitable length, pasted with lime mortar, can reach the required level of seismic safety. [ABSTRACT FROM AUTHOR]

This paper proposes probabilistic demand models to assess fragilities for high-rise buildings with three types of outrigger systems under seismic and wind loads. Parameters of the structural model are determined based on the structural material and geometric conditions. Parameters of the excitation model are determined based on the hazard characterization that varies with the hazard type. This paper involves three types of hazards: high-frequency ground motions, near-fault ground motions, and stochastic wind loads. With the input information from the structural model and the excitation model, 3D finite element models are built and computed using ANSYS to obtain structural responses (output information). Based on a database with the input-output pair obtained, we formulate probabilistic demand models for high-rise buildings with three types of outrigger systems under three types of hazards. These probabilistic models are proposed to estimate three response quantities of interest, the maximum inter-story drift, the maximum top acceleration, and the maximum top displacement. They, therefore, include univariate, bivariate, and tri-variate models. The probabilistic demand models account for both aleatory and epistemic uncertainties and provide unbiased estimates. With a direct and parsimonious formula, they have high accuracy and are extremely convenient to be used in practical engineering. They are finally used to formulate fragility estimates with bounds for an example high-rise building with three types of outrigger systems under three types of hazards. The results indicate that damped outrigger systems can effectively reduce fragilities for high-rise buildings under three types of hazards. [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]

After the May 12 earthquake in Wenchuan, numerous debris flow disasters occurred due to heavy rainfall. After the earthquake, disaster prevention and mitigation projects, such as the sand dam, played an essential role in safety. However, when the outflow of solid material exceeds the designed storage capacity of the sand dam, the debris flow overtopping the dam intensifies the scraping effect on the source material of the gully channel. This paper takes the "8.20" debris flow in the Chutou gully as the research object. A transport mode of the debris flow after dam overtopping is studied through comprehensive field investigation, theoretical analysis, and indoor model tests. A quantitative evaluation model is established for the scraping depth and scraping volume of dam-overtopping debris flow. The study results showed that once the debris flow overtops a dam, the loose source carried by the channel is involved in the entire migration process, enlarging the fluid scale and intensifying the damage along the channel. The results agree with the measurements and observations, with maximum relative errors of 5.81% and 14.70%, respectively. This shows model validity. Furthermore, the test results show that the debris flow scarping phenomenon in the γ=[1.4 t/m3, 1.6 t/m3] interval is the most significant. Overall, this study will help improve future engineering decisions, design strategies, and finding the best design solutions to minimize the risk of dam-overtopping debris flow disasters. [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]

This paper presents a comparative study on the size effect behaviors of shear performances of concrete shear walls reinforced by steel bars and Basalt Fiber Reinforced Polymer (BFRP) bars. All the works are conducted through a two-dimensional meso-scale numerical simulation model representing the concrete shear wall. The horizontal reinforcement ratio and the sectional size are the main parameters concerned by the present study. Both the seismic behaviors under cyclic loading and the size effect behaviors of the shear performances were simulated and investigated. It can be concluded from the simulation results, (1) the use of steel bars or BFRP bars as horizontal reinforcement does not change the shear failure modes of concrete shear walls, (2) the size effect on the nominal shear strength of BFRP reinforced concrete (BFRP-RC) shear wall is more significant compared to that for steel-RC shear wall, (3) the increase of horizontal reinforcement ratio improves the shear capacity of the concrete shear wall, while weakens the size effect on the nominal shear strength, and (4) the size effect law for the nominal shear strength of steel-RC shear wall is applicable to BFRP-RC shear wall. Finally, the importance of considering size effect in the evaluation of shear performance of steel-/BFRP-RC shear wall is manifested by comparing the predictive results of several popular design codes with the simulation results. [ABSTRACT FROM AUTHOR]

The central difference is a popular algorithm used to integrate the equations of motion, yet suffers from two drawbacks: (1) it is only conditionally stable and requires a small-time step to maintain numerical stability; (2) it is non-dissipative, and high-frequency spurious oscillations may appear and compromise the accuracy of the solution. These drawbacks are detrimental to applying the algorithm to the real-time hybrid simulation of large, complex nonlinear structural systems. In this paper, the conventional central difference algorithm is modified to overcome these drawbacks, and the modified algorithm is applied to the real-time hybrid simulation of complex structural systems. [ABSTRACT FROM AUTHOR]

This paper studies the effects of spatial correlation between the structural components on probabilistic seismic performance of steel moment resisting frames, using extended incremental dynamic analysis (IDA) method to consider the effects of aleatoric uncertainties caused by ground motion records. In this probabilistic assessment, a combination of Latin hypercube sampling (LHS) and Cholesky decomposition (CD) methods are utilized to take the epistemic uncertainties of the numerical model into account. In case the target correlation matrix is not positive definite, two powerful optimization algorithms are employed to find the closest positive definite correlation matrix. [ABSTRACT FROM AUTHOR]

As a new type of station structure, the seismic research of long-span column-free metro station is relatively weak compared with the traditional column station, and the seismic characteristics and failure phenomena of these two types of structures are quite different. Therefore, it is necessary to compare the seismic performance of the two structures. In this paper, a large-scale shaking table test was carried out on the large-span column-free metro station structure and the two-layer island subway structure for the typical soil-rock combination stratum in Jinan, and the parameters such as soil-structure acceleration, soil pressure distribution and strain were obtained by numerical simulation. The results show that the maximum acceleration difference between the two types of structures at the middle plate is 13.8%, and the maximum tensile stress at the connection between the bottom plate and the side wall is 11.6%. Under the same geological conditions and seismic waves, the difference of soil-structure seismic response is related to the overall stiffness of the structure. The columns station is more affected by high-frequency seismic waves, while the column-free station is the opposite. Both types of structures meet the general seismic response law, but the column station shows stress concentration at the column-plate connection, which has a better inhibitory effect on the lateral displacement of the surrounding soil. In general, the seismic performance of the column station is about 1/10 stronger than that of the column-free station, but the column-free station can also meet the basic seismic requirements. A model test was designed for the soil-rock-underground structure interaction system. The interaction characteristics of underground structures in soil-rock strata are studied. The seismic response characteristics of subway stations with different structural types in soil and rock strata are compared. [ABSTRACT FROM AUTHOR]

In this study, theoretical and numerical methods were used to research seismic shear distributions of frame-shear wall structures under elasto-plastic conditions. The shear distributions of frame-shear walls were analyzed based on a simplified elasto-plastic analysis model of flexural shear. Based on a preliminary project, three groups of 2D models with different stiffness eigenvalues were designed and used to compare the shear distributions of whole structures and frames. The characteristics of the shear distributions of structures and frames and the development of plastic hinges were analyzed, and the rationality of shear adjustment based on Chinese standards was discussed from the perspectives of structural design, seismic performance and collapse resistance. The results revealed obvious differences between shear distributions of structures caused by strong vs. frequent earthquakes. For strong earthquakes, the shear distributions tended to be evenly distributed with respect to height, while the shear force of the bottom story was significantly larger than that of the upper stories. This was mainly caused by the redistribution of plastic internal forces due to the development of plastic hinges. The shear adjustment of the frame usually affected the reinforcement in the beams rather than in the columns, which contradicted the design concept of strong columns – weak beams. Additionally, shear adjustment had little effect on the seismic performance and collapse resistance of structures. This paper suggests that by ensuring the ability of strong columns, weak beams and plastic hinges to rotate, shear force adjustment can be prevented. [ABSTRACT FROM AUTHOR]

This paper develops the probabilistic seismic demand models of circular tunnels under the transversal seismic load. The uncertainties of ground motion, soil profile, tunnel depth, and lining size are considered. Since the quasi-static analyses may significantly underestimate the seismic responses of tunnels, the results of dynamic numerical analyses are adopted to construct probabilistic models that are more accurate. The constructed model is unbiased and can facilitate the fragility analysis of tunnels. As a demonstration, the proposed probabilistic models are used to estimate the seismic fragility curves of a particular tunnel. [ABSTRACT FROM AUTHOR]

On a global scale, most earthquake casualties are the result of non-engineered buildings (N-EBs) collapsing in developing regions of the world. This is because developing countries present the unfortunate combination of high population densities, lack of resources, corruption, and a lack of design and construction knowhow needed in seismic regions. Over the last decades, a significant research effort has been dedicated to introducing low-cost seismic protection strategies that could be implemented on a large scale in developing regions of the world. This paper presents those state-of-the-art technologies. The purpose of this paper is to provide an overview of the many available systems, and underline the characteristics of these technology, to expand the range of applicability of each system, and to contribute to its state of development. [ABSTRACT FROM AUTHOR]

With critical lessons drawn from past major earthquakes, the engineering community is appealing for a fundamental shift in the existing design philosophy for structures in seismic zones. One strategy is to endow structures with self-centering (SC) capability. While the concept of SC structures is not new, many novel technologies have been recently emerging that are more efficient, compact, and cost-effective; on the other hand, growing controversy and dispute have also been appearing with deepening investigations. This paper presents a critical review of the evolution of SC technologies and systems for both researchers and practitioners, with an emphasis on post-tension (PT), high-performance spring, and shape memory alloy (SMA) strategies. These SC technologies, together with various energy dissipation options, form the basis of a large part of the newly proposed SC philosophies. This review also includes typical SC structural members such as beam-to-column connections, braces, dampers, shear walls, bridge piers, and isolation bearings, followed by a discussion on the dynamic behavior from a system-level point of view. Available design approaches for SC structures are also touched upon, and practical applications that have emerged over the past decades in several countries including Canada, China, New Zealand, and the US are presented. This paper concludes with an executive summary that covers technological advances, knowledge gaps, and future research directions. [ABSTRACT FROM AUTHOR]

The present paper discusses similitude laws employed for the shaking-table tests of masonry structures with flexible diaphragms. Two tasks are tackled. First, the paper presents a literature review on similitude laws. The discussion focuses on Cauchy and Cauchy-Froude laws. Second, numerical analysis is performed to examine the accuracy and adequacy of the aforementioned two laws. Two previously performed shaking-table tests are taken advantage of as the case studies. The paper explores the ideal applications of similitude laws to the shaking table tests of masonry structures with flexible diaphragms by comparing the behaviour between full-scale prototypes and reduced-scale models. [ABSTRACT FROM AUTHOR]

This paper presents empirical models for the frequency content parameters of offshore ground motions in the Japan Trench area based on the S-net dataset, comprising 6,436 recordings from 496 events. Significant variations in frequency content among shallow crustal, upper-mantle, subduction interface and subducting slab are revealed. Empirical models for To, Tavg, and Tm are proposed, considering moment magnitude, source distance, focal depth, and tectonic types. A comparative analysis with four existing land models highlights differences. Total residual results indicate that land models, based on shallow crustal datasets, tend to overestimate observed frequency content parameters in the Japan Trench area. [ABSTRACT FROM AUTHOR]

This paper provides new and useful insights into the performance and efficiency of geotechnical seismic isolation (GSI) systems with gravel-rubber mixtures containing 10%, 25% and 40% volumetric rubber content (VRC). Finite element numerical models were developed in OpenSees and subjected to sinusoidal ground motions with varying input base acceleration and frequency. The best seismic performance was attained for VRC = 40% at a frequency of 8 Hz. Using a newly developed GSI efficiency index, the energy dissipation efficiency of VRC = 40% was found to vary between good to excellent, while that of VRC = 10% and 25% is poor. [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]

This paper investigates the linear equivalence of the PT-SKID frames based on Jacobsen's method for estimating peak seismic displacement response. Such linearisation is at the base of the DDBD of such systems. First, a simplified model capturing the hysteretic properties of the PT-SKID frames is proposed. Then, the linear equivalent system of the PT-SKID frame is constructed by its secant stiffness and the equivalent damping ratio. Finally, the accuracy of the linear equivalence to assess the peak seismic displacement response is evaluated by numerically testing 5,880 frames. The results show that the linear equivalence frequently underestimates the peak displacement response. [ABSTRACT FROM AUTHOR]

Ensuring resilience through rapid buildings recovery in seismic zones has been placed at the forefront of recent studies. However, studies that compare the relative resilience of buildings constructed with different materials are lacking. This paper focuses on a comparative resilience analysis of concrete moment frames where beam-column connections are made with varying types of concrete mixtures. The connections are made with normal strength concrete (NSC), rubberized concrete (RbC), steel fiber rubberized concrete (STFRC), synthetic fiber rubberized concrete (SYFRC), and high strength concrete (HSC). Nonlinear static pushover and incremental dynamic analysis (IDA) are utilized to understand system response and the level of damage sustained following an earthquake. Subsequently, seismic fragility functions are constructed for the five considered frame types. The frames are subjected to different seismic scenarios, and the corresponding losses, recovery time, and resilience are quantified. A comparison between the five frame types is carried out to examine the optimal concrete mixture to be used to reduce damage probabilities, total direct losses, and recovery time and subsequently enhance resilience. The results show that rubberized concrete strengthened with steel and synthetic fibers can reduce economic losses by up to 19% and increase building resilience by up to 37% compared with the frames constructed with normal strength concrete. [ABSTRACT FROM AUTHOR]

The implementation of fluid viscous dampers has been proven as a feasible method to improve the seismic performance of buildings. However, the different variables involved in the damper's design affect the structural response, especially in terms of seismic demand on non-structural elements. This paper presents a parametric study on the floor acceleration response of three case study buildings equipped with fluid viscous dampers through nonlinear time-history analysis. The results show that the different design parameters of fluid viscous dampers significantly modify the floor acceleration response, with some damper configurations yielding floor accelerations larger than those of the buildings without dampers. [ABSTRACT FROM AUTHOR]

Ground motion prediction equations (GMPEs) play a key role in seismic hazard assessment (SHA). Considering the seismo-tectonic, geophysical, and geotectonic characteristics of a target region, all the GMPEs may not be suitable in predicting the observed ground motion effectively. With a fairly large number of published GMPEs, the selection and ranking of suitable GMPEs for the design of logic trees in SHA for a particular target region have become a necessity of late. This paper presents a detailed quantitative evaluation of performance of 16 GMPEs against recorded ground motion data in two target regions, characterized by distinct seismo-tectonic, geophysical, and geotectonical nature. The dataset comprises 465 three-component spectral accelerograms corresponding to 122 earthquake events. The suitability of a GMPE is tested by two widely accepted data-driven statistical methods, namely, likelihood (LH) and log-likelihood (LLH) method. Different suites of GMPEs are shown suitable for different periods of interest. The results will be useful to scientists and engineers for microzonation and estimation of seismic design parameters for the design of earthquake-resistant structures in these regions. [ABSTRACT FROM AUTHOR]

Axial forces are generated in the plates of ADAS-yielding dampers when subjected to lateral loading due to their boundary conditions. This on one hand can lead to an increase in strain level of the plates and accelerate the damage process, while on the other hand, the interaction of the bending moment with the tensile axial force leads to increasing strength, which is undesirable in the performance of ductile members. In this paper, a modified ADAS device (MADAS) is introduced to prevent undesirable interaction of axial forces, and its cyclic behavior is evaluated both experimentally and numerically. To this end, in the first step, two test specimens with different number of connection pins were prepared and subjected to cyclic loading in a rigid frame. Experimental and numerical results have shown that due to the removal of the constraint in the vertical direction, the level of forces produced by the damper is almost constant and the X-shaped plates have been able to tolerate significant number of cycles before crack initiation. Afterwards, the cyclic performance of ADAS and MADAS dampers was numerically compared individually and also when placed in the frame. Furthermore, in the frame equipped with ADAS damper, the increase in the level of forces produced by the damper led to the buckling of the braces, while the level of generated forces was totally in the expected range in the frame equipped with MADAS damper. [ABSTRACT FROM AUTHOR]

Earthquake-induced pounding in bridges is a complex contact phenomenon in which the dynamic responses of structures, including collisions between deck and abutments, are strongly related to structural properties and earthquake excitation. The goal of this study is to develop and compare the seismic fragility curves of overall system and individual components of regular and irregular box-girder highway bridges in two cases: with pounding and without pounding. For this purpose, four levels of altitudinal irregularity, ranging from regular to highly irregular, are considered. To extend the results for all bridges in the same class, different sources of uncertainties related to earthquakes, structural geometries, and material properties are taken into account. The analytical fragility curves have been developed based on nonlinear time history analyses in OpenSees finite element software for the cases with and without pounding effects. The process has been repeated for each two-, three-, and four-span classes at four irregularity levels. The fragility function parameters for the two cases with and without pounding have been compared for all classes considered in this study. Using fragility functions, this paper clarifies the interactive roles of irregularity and pounding between deck and abutments for seismic vulnerability of multi-span box-birder highway bridges. The results indicate that collisions often show an adverse effect on all structural components. It has also been observed that the detrimental effect of pounding on seismic fragility is more apparent in irregular bridges when compared with regular ones. In addition, the study introduces a conversion coefficient to clarify the effects of pounding on the fragility of bridge components and the overall system. This coefficient can be applied in both conventional analytical methods like static or simplified analysis and technical earthquake models like HAZUS, adjusting fragility values for pounding and irregularity effects. [ABSTRACT FROM AUTHOR]

This paper evaluates the effectiveness of a novel capacity-design based retrofit for improving both the local and global behaviour of existing reinforced concrete buildings using fibre-reinforced polymers. The approach was previously tested on beam-column joints and is here extended to the building level. A new fibre-element model for the global retrofit is proposed and validated against full-scale experiments. Non-linear push-over analyses confirm the adequacy of the retrofit and fragility analyses are used to compare it to a simpler local retrofit. Finally, cost-benefit analyses for three levels of seismicity highlight the cost-effectiveness of the global retrofit for moderate to high seismicity. [ABSTRACT FROM AUTHOR]

The paper investigates the seismic performance of a novel passive vibration isolation and damping device termed Extended KDamper (EKD). The concept is applied to a representative two-span highway bridge, initially designed on conventional seismic isolation (CSI) bearings. An optimization process is developed and executed to design the EKDs, underscoring the importance of accounting for seismic motion variability. Compared to CSI, the incorporation of EKDs leads to a 40% to 70% reduction in deck drifts. In contrast to the CSI bridge, which may sustain excessive bearing shear strains when subjected to the most adverse seismic motions within the examined set, the bearings of the EKD bridge never exceed the 200% threshold. Through the use of nonlinear 3D time-history analyses, it is demonstrated that the nonlinearity of the EKD elements may result in residual deck drifts. The nonlinear EKDs exhibit a variation in maximum drifts and accelerations on the order of ±20% compared to the preliminary (linear elastic) design for the examined set of spectrum-compatible motions. The increased accelerations result from the stiffening of the negative stiffness elements (NSEs), being more pronounced for seismic motions that entail large displacement demands. With the aid of a fully nonlinear 3D model of the entire soil – foundation – structure system, the effects of soil-structure interaction (SSI) are explored and shown to significantly influence the seismic response of the system. Deck collision with the abutments restricts the movement of the deck and pier; however, it compromises the performance of the EKDs and leads to a substantial increase in deck accelerations. Overall, EKDs may facilitate a more economical design and enhanced seismic performance, particularly for displacement-sensitive structures like rail bridges. [ABSTRACT FROM AUTHOR]

This paper estimates a correlation model and joint distribution model of spectral accelerations of vertical ground motions based on the NGA-West2 ground motion database. The correlation model calculated via BC16 vertical GMPE in this study is compared with those published models via other vertical NGA-West2 GMPEs. It is verified that the calculated residuals of vertical ground motions at multiple periods follow the multivariate normal distributions via both a qualitative validation method and a set of quantitative validation methods. The correlation model and the joint distribution model of vertical spectral accelerations are the theoretical basis for research on the joint occurrence of spectral accelerations of vertical ground motions, and an example of applied research on joint occurrence of spectral accelerations of vertical ground motions is studied: the conditional mean spectrum of vertical ground motions. Finally, the effects of different vertical correlation models and ground motion prediction equations on vertical conditional spectra are investigated for wide application of the correlation model and the joint distribution model of spectral accelerations of vertical ground motions. [ABSTRACT FROM AUTHOR]

Earthquakes have caused catastrophic results in cities since the beginning of settled life, and the cumulative experience of these events has indicated that the lack of seismic resilience brings enormous economic losses and threatens human life. Consequently, the importance of seismic risk mitigation of earthquake-prone structures has arisen to reduce the primary and secondary losses resulting from seismic events in the last decades as developments in the earthquake engineering field occur. The first step for ensuring seismic resilience is the identification of risky buildings, which is a difficult challenge for metropolises like Istanbul since the building stock consists of over a million buildings. Applying code-based detailed assessments to so many buildings is not practical in terms of time and cost. Moreover, the current code-based detailed assessment methodologies such as Provisions for the Seismic Risk Evaluation of Existing Buildings under Urban Renewal Law (2019) and Turkish Building Earthquake Code (2018) provide discrete predictions for existing buildings as either risky or non-risky or satisfying life safety/controlled damage or not. However, a ranking system based on a reliable and realistic risk classification to prioritize the buildings is needed. Therefore, as a pilot project, nearly 23,000 reinforced concrete buildings in 37 different districts of Istanbul have been investigated by Istanbul Metropolitan Municipality (IMM) through PERA2019 performance-based rapid assessment methodology by considering the Design Level and Scenario-Based Earthquake cases. This is the most up-to-date and comprehensive site survey and analysis conducted in Istanbul up to now. In this paper, the characteristics of the building stock in Istanbul based on the conducted site work and the outcomes of the rapid seismic safety assessment efforts are summarized. Then, a discussion on the seismic risk evaluation of the existing residential buildings based on the prioritization of the examined buildings is presented through the results obtained for the Design Level and Scenario-Based Earthquake cases. [ABSTRACT FROM AUTHOR]

The paper investigates the stiffness and strength of log walls with standard and dovetail bonded corners under lateral loads. The finite element model is developed and validated with experimental work at small-scale and wall-scale levels. The validated wall-scale model was modified by conducting a detailed investigation on assessing the wall behaviour with varying crucial parameters, including coefficient of friction, vertical load, geometric irregularities, and the wall's aspect ratio. The study suggested various techniques for improving the wall's lateral load resistance capacities and initial stiffness, employing steel and wood pins. [ABSTRACT FROM AUTHOR]

This paper presents the concept, design, construction and seismic performance assessment of internal partition walls with novel slotted and bracketed head-track details. In the slotted head-track walls, the anchors connecting the wall to the slab above are intended to slide within the slot to accommodate the desired in-plane drifts. On the other hand, in the bracketed head-track walls, the story-drift demands are accommodated by sliding of the bolt and flexing of the plastic brackets attached to the slots. In this paper, bi-directional behaviour of a novel flexible bracket is experimentally characterised and a number of wall sub-assemblies with the slotted and bracketed connection details are tested under quasi-static cyclic loading to investigate their seismic performance. The walls with slotted details showed the first signs of damage requiring repair at 0.78% drift. In contrast, when brackets were attached to the slots, the wall remained intact up to 4% drift, demonstrating a superior seismic resiliency. [ABSTRACT FROM AUTHOR]

Traditional post-earthquake safety assessment of damaged buildings is always time-consuming and qualitative. This paper proposes a novel quantitative method for evaluating seismic damaged buildings based on 65 RC buildings from the Wenchuan and Lushan earthquakes. The results show that: the uncertainty of the model regression coefficient leads to obvious variability in damage index of the structure (Dz); the residuals do not show obvious trend with the variables; the Pearson correlation coefficient between the calculated and judgment values of test samples is 0.96. Results indicate that the proposed model is feasible for evaluating the safety of damaged buildings on site. [ABSTRACT FROM AUTHOR]

To consider the influence of epistemic uncertainties in both seismic hazard and numerical simulation on seismic risk of subway station structures, the uncertainties mentioned above are uniformly characterized as the epistemic uncertainty of seismic demand of subway station structures from the perspective of uncertainty propagation in this paper. On this basis, the analytical formulations of seismic risk considering simultaneous aleatory and epistemic uncertainties are derived. The validity of the derived analytical formulations is verified by the Monte Carlo simulation and the influences of epistemic uncertainty on the seismic risk of subway station structure are further discussed. [ABSTRACT FROM AUTHOR]

As an effective measure to decrease the residual displacement under earthquakes, unbonded prestressed concrete (UBPRC) columns have been carefully investigated in previous research, while the influence of the complex characteristics of near-fault excitations on the residual displacement of UBPRC is less mentioned. This paper, therefore, focuses on the influence mechanism of the pulse effect and vertical effect of near-fault ground motions on the residual displacement of UBPRC columns. The residual displacement, at first, is formulated as a function of the coupled parameter T1-p (the ratio of the structural period to the pulse period). Then, the effect of near-fault vertical ground motion on the residual displacement is qualified based on the established mathematical model. Further, the model has been applied to investigate the effect of structural properties (dead load axial compression ratio, longitudinal reinforcement ratio, prestressing axial compression ratio, prestressing reinforcement ratio) on the residual displacement of UBPRC columns subjected to the joint action of horizontal and vertical ground motions. This research provides a quantitative methodology to quickly obtain the residual displacement spectra of the UBPRC columns under varying conditions combined with ground motion and structural parameters. [ABSTRACT FROM AUTHOR]

One of the most widely used linear techniques for solving damage identification problems and prediction of the system dynamic behavior is modal testing and analysis. However, most of real structures exhibit nonlinear behavior during their lifetime caused by a number of various reasons. The presence of nonlinearity in a structural system changes its dynamic characteristics; hence, the use of linear techniques is improper for prediction of the system behavior. In this paper, a vibration-based nonlinearity identification technique was proposed to identify early changes in a dynamic system prior to significant damages. This technique combines the time series Autoregressive Moving Average with Exogenous Inputs (ARMAX) modelling, probability theory, and Fuzzy C-Means (FCM) clustering algorithm to categorize the linear and nonlinear dynamic behaviors of a dynamic system. The technique aims to categorize the linear and nonlinear behaviors of a structure, when it is subjected to various levels of excitation source. To show the validity of the proposed method, a series of shake table tests was performed on a six-span steel truss bridge model. The bridge model was excited using different amplitudes of ground motion to control the nonlinearity degree of rubber-based supports. It can be concluded from the analysis results that the new vibration-based nonlinearity identification technique was able to identify nonlinear behavior of the bridge model once it was subjected to different levels of earthquake excitations. This algorithm was able to categorize the linear and nonlinear behaviors of the bridge model and define a specific threshold for different excitation sources. [ABSTRACT FROM AUTHOR]

Estimating the story drift directly from acceleration records is challenging. This paper presents a systematic integration scheme involving the empirical mode decomposition of signals to estimate the earthquake-induced displacement of buildings, including their permanent deformation after an earthquake. A three-phase algorithm is proposed. In phase-1, the displacement waveform without residual displacement is estimated, then in phase-2 the residual deformation is calculated. Combining both phase-1 and phase-2, the displacement waveform is estimated. Three types of acceleration data, namely, shaking table test data, seismic response data for a building, and near-fault ground motion data, were used to validate the proposed method. [ABSTRACT FROM AUTHOR]

An experimental and numerical research, aimed at evaluating the in-plane seismic performance of an innovative external steel modular system for the strengthening of load-bearing masonry walls, is currently underway at the EUCENTRE Foundation in Pavia. This paper presents, in particular, the results of the experimental part of this research campaign. Solid clay brick and hollow clay "doppio UNI" masonry typologies, representing common solutions in Italian existing buildings, were considered. After the mechanical characterization of the masonry and of the components of the reinforcement system, cyclic in-plane pseudo-static tests on full-scale specimens were performed in order to investigate the influence of the proposed system on the in-plane response of the walls, compared to the unreinforced conditions. The main seismic parameters of the masonry walls (i.e. elastic stiffness, lateral resistance, displacement capacity and energy dissipation) were assessed depending on the achieved damage mechanism. The proposed reinforcement system provided very promising results, improving the in-plane seismic performance of masonry walls at serviceability and especially at ultimate conditions, with a significant increase of deformation capacity above all in the case of shear mechanisms. [ABSTRACT FROM AUTHOR]

Precast concrete members are often connected in the plastic hinge zone by grouting such as shear wall. Precast connection types, different construction methods, and materials will affect the seismic performance of precast concrete structures. This paper experimentally studies the seismic performance of precast concrete shear walls with a new type of grouted sleeve. Furthermore, the sleeves in the connections are grouted by two methods. One is that all of the sleeves are filled from the same grout hole wherein all the sleeves are connected together in the wall-footing joint interface. The other is that each sleeve is separately grouted from their respective grout holes. Therefore, the wall-footing interface materials of 20 mm thickness are high strength grouting material and common mortar in the former and latter case, respectively. The influence of grouted sleeve on the deformation of plastic hinge region is studied. Four full-scale shear wall specimens are designed and manufactured, including one cast-in-situ and three precast specimens. The longitudinal reinforcement of one of the separately grouted precast specimens adopts an unbonded section on the foundation. The failure mode and process, crack pattern, hysteretic performance, energy dissipation capacity, stiffness degradation, and curvature distribution of the plastic hinge area at the bottom of the shear wall are discussed on the basis of the test results. Results show that the precast shear wall with the proposed grouted sleeve has similar seismic performance to the cast-in-situ shear wall. However, the precast grouted-sleeve shear wall with the first grouting method and higher strength of wall-footing interface has a better seismic performance than the other precast specimens. In addition, the grouted-sleeve connection changes the distribution of stress and curvature in the plastic hinge region of the shear wall. [ABSTRACT FROM AUTHOR]

Seismic duration significantly impacts the structural seismic response. In order to obtain a correct time history analysis result of structural seismic design, determining a reasonable seismic duration scheme is imperative. In this paper, a five-span simply supported beam bridge and China Railway Track System (CRTS) II slab ballastless track system is taken as the research focus. A finite-element model for a high-speed railway track-bridge system was developed. The influence mechanism of starting and end threshold on seismic response was analyzed. Different bracketed duration schemes were put forward, and their applicability was assessed. The optimal bracketed duration scheme of time history analysis for a high-speed railway track-bridge system was determined. The results indicate a response curve deviation between the full duration and partial duration in the starting part due to the inconsistent structural movement trends and a deviation in the end part because of the structure entering a free vibration state in advance. When calculating the seismic peak response, the starting threshold A and end threshold B at both ends should be taken as5% of peak acceleration. When calculating seismic residual response, the starting threshold C at the left end should be taken as 25% of peak acceleration. [ABSTRACT FROM AUTHOR]

Seismic resilience has emerged as a trend in the seismic design of buildings, with self-centering components or systems used as an effective method to improve seismic resilience. The outrigger is an essential component for resisting the lateral load in super-tall buildings. However, the diagonal member of the traditional outrigger is prone to buckling, resulting in excessive residual deformation and repair difficulties after earthquakes. A novel self-centering outrigger (SCO) with desirable energy dissipation and self-centering capacity is proposed in this paper. In the SCO, the traditional steel diagonal member is replaced with a new self-centering viscoelastic brace (SCVB). The seismic performance of the SCVB with a total length of 2.2 m is investigated using the low cyclic loading test, with results demonstrating that the SCVB exhibits a flag-shaped hysteretic response. Based on the experiment results of SCVB, a refined finite element model of the proposed SCO is developed to evaluate the seismic performance, then the hysteretic responses of the traditional outrigger and SCO under different load conditions are compared. Results show that the hysteretic curve of the proposed SCO is flag shaped, with stable stiffness and desirable energy dissipation and self-centering capacities. Even at a large loading displacement, a small amount of residual deformation will occur, but it is reduced by 75.52% compared to a traditional outrigger, while the strength is increased by 14.37%. Finally, the influence of the key parameters of SCVB on the hysteretic behavior of SCO are discussed, providing reference for future seismic design of the SCO. [ABSTRACT FROM AUTHOR]

The detection of P-wave is essential for the earthquake early warning system. How to detect the P-wave under noise circumstance accurately and rapidly is a challenge work. Based on the relative power of the seismic signal, a new parameter, the initial power of the P-wave (IPP), is proposed to detect the P-wave. By using the relative power of the seismic signal, the interference of the background noise is eliminated, and the initial power of the P-wave and sigma criterion are both applied to detect the P-wave. Through simulation analysis and example tests whose magnitudes are varied from Ms4.0 to Ms8.0, both the misjudgment and the missing rate of the IPP method are 0, and the time deviation within 0.2 s can reach 78.95%. Comparing with the STA/LTA, STP/LTP and PhaseNet methods, the IPP method proposed in this paper has strong robustness and high accuracy, which represents the initial power characteristic of P-wave and can effectively eliminate the interference of background noise. [ABSTRACT FROM AUTHOR]

This paper estimates the joint occurrence of spectral accelerations (SA) between horizontal (HGM) and vertical ground motions (VGM) based on the NGA-West2 ground motion database, which includes the correlation model and joint distribution model. In this study, the correlation model calculated via CB14 horizontal ground motion prediction equation (GMPE) and BC16 vertical GMPE is obtained. It is verified that the joint distribution of residuals follows a multivariate normal distribution via both a set of quantitative validation methods and a qualitative validation method. Conditional mean spectra of VGMs conditioned on SAs of HGMs are studied as an application of joint occurrence of SAV–SAH. [ABSTRACT FROM AUTHOR]

With a view to providing general Storey Loss Functions (SLFs) for existing reinforced concrete (RC) residential buildings in Italy, this paper layouts the procedure and the development of SLFs for different residential building typologies, using post-earthquake observational damage data of the 2009 L'Aquila earthquake. To do so, the addressed building typologies and the cost ratios, with respect to the total construction cost, for structural and non-structural elements were defined according to the Italian price bulletin of building typologies, using the current average construction cost per square meter. Fragility models available in the literature, which had been specifically calibrated for structural and non-structural elements commonly found in Italian and Mediterranean RC buildings, were employed and the assumed repair costs were the ones incurred for repairing the buildings damaged during the 2009 L'Aquila earthquake. The proposed SLFs were then employed to perform loss assessment on a representative portfolio of Italian existing masonry-infilled RC residential buildings, showing the consistency of the results with respect to available research studies. The outcomes therefore denote how the proposed SLFs can be a useful tool as an alternative to the simplified conservative loss assessment guidelines currently employed in Italy, with a view to planning risk mitigation measurements both at a regional and single-building level. [ABSTRACT FROM AUTHOR]

The longitudinal seismic response reduction in railway bridges is worthy of attention because it relates to the engineering cost. It is difficult to further explore the reduction effect because the complexity of traditional analysis model leads to the low efficiency in parametric analysis. In this paper, the track structure was simplified, and a simplified calculation model was established. The parametric analysis considering the span number and pier height on the simplified model seismic responses was carried out. The results showed that the reduction effect was extensive and there was a great internal force transferred to the subgrade-track structure. [ABSTRACT FROM AUTHOR]

This paper presents a reduced-order multi-scale simulation approach for nonlinear analysis of structures with local nonlinearities. Using it, the traditional global structural analysis can be changed to that of a reduced-order system where only nodal displacements of nonlinear elements are solved using the Newton–Raphson method in a single iterative procedure. Meanwhile, two nonlinear force/stiffness correctors are introduced based on the stress decomposition to describe material nonlinearities of frame members. In addition, two simulation ways are used to deal with the nonlinearities of the yielding frame members. Finally, the static and transient structural systems are simulated to verify the approach. [ABSTRACT FROM AUTHOR]

In this paper, the problem of dynamic stress concentration in the process of anti-plane motion caused by a single circular cavity in a strip medium and the non-circular cavity in a porous strip medium is studied. In the case of only a single circular cavity, a numerical calculating example is presented to solve scattering around a circular cavity with a given SH guided wave and describe dynamic stress distribution at the edge of a circular cavity. Then, the results of the finite element method and analytical method are used to verify each other. Firstly, a compatible guided wave is constructed in the elastic strip, which satisfies stress-free conditions in upper and lower boundaries. Secondly, the scattering of waves around a circular cavity is expressed as series form by the employed wave function expansion method, and compatible scattering guided waves resulting from the reflection of waves off the boundaries of the elastic strip is constructed by repeated image superposition. Lastly, the coefficients of the wave function expansion are determined based on the stress-free condition of circular boundaries with pre-given incident guided waves. In the case of the non-circular cavity in the medium, the scattering of guided waves from the cavity is solved by finite element analysis, the dynamic stress distribution factor around the edge of the cavity is given, and to discuss influences of wave frequency and cavity position. The conclusions of this paper are of great reference value to the selection and ultrasonic non-destructive testing of anti-seismic materials. [ABSTRACT FROM AUTHOR]

China is now undergoing the largest and fastest urbanization process in the world, developing various reinforced concrete high-rise buildings during this process. Most high-rise structures are constructed in densely populated and economically active areas and earthquakes pose a potential possibility of serious economic loss and casualties, which cannot be ignored. This paper conducts on-site dynamic tests on 129 high-rise RC buildings in eastern China by utilizing ambient vibration measurement. Fundamental vibration periods, second vibration periods, and third vibration periods are statistically analyzed in translational directions based on two high-rise building types: shear wall slab building and shear wall tower building (including framed shear wall structures and framed tube structures). After fully considering building usage conditions and comparing the fitting formulas in existing codes, fitting empirical formulas of the vibration periods in two translational directions based on the above structural types are given. The ratio distribution ranges of vibration periods are calculated by utilizing the vertex displacement method, concentrated mass method, and Rayleigh-Ritz energy method. In addition, by analyzing the vibration period ratio in horizontal directions of 543 high-rise RC buildings, different ranges are distinguished as well as suggested boundaries are given. The conclusion of this paper provides a reference and convenient method for future on-site dynamic testing and a new proposal is provided to the empirical formula of vibration period in the current building seismic design code. [ABSTRACT FROM AUTHOR]