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This document, titled "SI: Natech risk assessment of hazardous facilities," discusses the vulnerability of industrial plants to damage from earthquakes and the need for new design and assessment methodologies. The document highlights the importance of Performance Based Earthquake engineering in the field of civil structures and the need for consequence analysis to quantify individual or societal risk. The special issue aims to bring together the latest methodologies and techniques for assessing NaTech risk and resilience in hazardous facilities, with contributions from researchers and industry professionals. The issue covers topics such as hazard assessment, seismic analysis of non-structural components, safety barriers, performance-based design, and resilience of industrial facilities. The document includes summaries of several papers that address these topics, providing insights into seismic design, risk assessment, and mitigation strategies for industrial facilities. The guest editors express their gratitude to the authors and the chief editor for their contributions to the special issue. [Extracted from the article]

This paper proposes the double-endplates replaceable beam-column joint (DEBJ) based on the seismic design concept of replaceable beam. Compared to the common extended endplate bolted joint (CEBJ), the DEBJ is easy to be connected and replaced after earthquakes, and it can achieve plastic hinge outward movement in steel frame. Due to double endplates and different failure modes, the current moment-rotation models for CEBJ cannot be used for DEBJ. Therefore, based on the classical model used for traditional endplate joints, a theoretical moment-rotation model for DEBJ is developed, and the calculation methods on ultimate bending moment and initial rotational stiffness are deduced. A parametric study is performed for DEBJ based on a test-validated finite element (FE) model developed in this paper. The predicted moment-rotation curves calculated from proposed theoretical model is validated by the experimental results on endplate joints and FE results on DEBJ. The results show that the established theoretical model proposed in this paper can predict the moment-rotation relation curves of DEBJ and the common extended endplate bolted joint (CEBJ) accurately, the predicted results by established theoretical model are in good agreement with experimental and FE results according to the comparison. It is revealed that the established model has universality to some extent. [ABSTRACT FROM AUTHOR]

In order to study the effect of the velocity pulse on the dynamic response of the train-bridge system of the high-speed railway simple supported beam bridge, the velocity pulse is simulated by the trigonometric function method and superimposed with the far-field earthquake without pulse to synthesize the pulse with different pulse types, pulse periods and pulse peaks. A 10 × 32m typical high-speed railway simple supported beam bridge is considered an case illustrating study. Then, the dynamic response of train-track-bridge coupling system is calculated by train-track-bridge seismic analysis software TTBSAS. Afterwards, the influence of pulse near-field earthquakes parameters and vertical components on dynamic response of train-bridge system and the safety of the train on the bridge are discussed in detail.The new derailment evaluation index is adopted to evaluate driving safety under earthquakes. The train safety control of simply supported beam bridge under the action of near-field earthquake is studied. The results show that the impact of pulse ground motion on the dynamic response of the train-track-bridge coupling system is significantly higher than that of no-pulse ground motion, especially the impact on the bridge and rail subsystem is more significant than that of train subsystem. Under the excitation of ground motion intensity of 0.05g ∼ 0.15g, the safe speed threshold of pulse near-field ground motion is smaller than that of far-field ground motion. When the ground motion intensity is 0.20g ∼ 0.30g, the safe speed threshold of pulse near-field ground motion and far field ground motion is 200km/h. So, the pulse near-field earthquake poses a greater threat to the safety of the train on the bridge than the far-field earthquake. Therefore, the influence of pulse near-field earthquakes should be considered in the seismic design. The research results of this paper can provide theoretitcal support for the design of a high-speed railway bridge in the near-field area. [ABSTRACT FROM AUTHOR]

The transition from the Uniform Building Code (UBC-97) to the International Building Code (IBC-21) marked a major shift in the definition of seismic hazard. The term "seismic hazard" in the form of peak ground acceleration (PGA) is replaced by spectral acceleration. This paper investigates the effect of using new seismic hazards on the structural performance of reinforced concrete (RC) buildings. It also looks into the financial impact on the capital costs of new buildings. Useful insights are made to understand the structural performance and financial impact of adopting IBC 21 for structural design in contrast to UBC 97. This study was carried out from the perspective of a developing country, Pakistan. Reinforced concrete moment resisting and dual frames are used as the main structural system of a typical 7-story residential building to investigate the aforementioned effect. The frames are assumed to be located in two locations with high and low seismic hazards. The effect on structural performance is investigated via nonlinear pushover analysis. Financial impact is judged mainly through cost estimation for steel and concrete. A detailed discussion is also presented on the seismic design guidelines in both codes. [ABSTRACT FROM AUTHOR]

For bridge columns with link beams, the traditional reinforced concrete beam-column joints are susceptible to damage in near-fault ground motions, which will bring great inconvenience to maintenance and replacement after earthquakes. The dual-replaceable composite link beam (DRCLB) proposed in the previous study can effectively ensure the seismic safety of the beam-column joints and improve the post-earthquake recovery ability of piers. In this paper, a resilience-based optimal design methodology is proposed to more effectively and reliably realize the seismic design of a double-column pier with DRCLB. During the optimization process, seismic resilience is selected as the objective function, and three parameters of double-column pier with DRCLB which contain the section area of angle steel (As), the diameter of CFST (D), and the height ratio of DRCLB and column (α) are taken as the optimization variables. A machine learning model using Gaussian process regression (GPR) is established to obtain seismic resilience and conduct the sensitive analysis of parameters. Then, the particle swarm optimization (PSO) algorithm is selected to solve the optimization problem. Finally, the optimum design scheme of double-column pier with DRCLB can be determined based on the GPR model and PSO algorithm. It is concluded that the parameters D and α can significantly affect the resilience of double-column pier with DRCLB. In addition, the optimization design method proposed in this paper can accurately and reliably determine the optimum design of double-column pier with DRCLB. Meanwhile, the obtained optimal scheme can maximize the resilience of double-column pier with DRCLB through adjusting the damage level of beam-column joints. [ABSTRACT FROM AUTHOR]

Hybrid test is a new seismic test method combining numerical simulation with physical test. It is an advanced test method to evaluate the performance of nonlinear structures and systems. This paper proposes a novel hybrid test control system based on MATLAB-STM32. The system uses the STM32 microcontroller as the main controller and electrodynamic vibrator as excitation source of system. Furthermore, a complete set of hybrid test control system which includes physical hardware test and numerical software simulation is established by using MATLAB-STM32 communication technology, PID control method, displacement sensors, force sensors, etc. It provides a test platform for nonlinear test structures, components that are difficult to model, or components that require performance testing. This system realizes the function of real-time two-way communication between MATLAB and STM32 microcontroller. It uses the finite element software OpenSees to establish the numerical substructure, which solves the problem of the collaborative work between the numerical simulation test and the physical test of the experimental substructure, and can simulate the hybrid dynamic seismic test of the damping structure. To test the control performance of the designed system, this paper selects the viscoelastic dampers as the test substructure, and the performance detection and test analysis are completed for the hybrid test of single-layer frame structure with a viscoelastic damper. The test results show that the data communication between the upper and lower computers is stable and the whole control system performs well on both dynamic and static behaviors. [ABSTRACT FROM AUTHOR]

Predictive models for spatial correlation play an effective role in the assessment of seismic risk associated with distributed infrastructure and building portfolios. However, existing models often rely on simplified approaches, assuming isotropy and stationarity. This paper verifies these assumptions by presenting a comprehensive study using a database of 3D physics-based simulated broadband ground motions for Istanbul, generated by the SPEED software. The results reveal significant event-to-event variability and nonstationary and anisotropic characteristics of spatial correlation influenced by source, path, and site effects. The development of nonstationary correlation models requires exploring influential metrics beyond spatial proximity and gaining a deep understanding of their impact, which is the focus of this study. Analysis of the spatial correlations of peak ground displacement, peak ground velocity, peak ground acceleration, and response spectral accelerations at different periods, employing both stationary and nonstationary correlation modelling methods and considering the finite fault model, indicates that the slip distribution pattern, direction and distance of station pairs relative to earthquake rupture, soil softness, and homogeneity of soil properties significantly influence the spatial correlations of near-field earthquake ground motions. Implementation of the introduced parameters in predictive spatial correlation models enhances the precision of regional seismic hazard assessments. [ABSTRACT FROM AUTHOR]

In this paper, the seismic performance and reliability of steel buildings with Chevron-Braced frames are studied integrating a novel probabilistic approach and the performance-based seismic design concept. The seismic response of models is extracted using response history analyses with the help the commercial software SAP2000. In this sense, three variables associated with the seismic response of the structure are studied: overall lateral displacement, rotation of connections, and inter-story drift. Those responses are evaluated by exciting the structure with eleven characteristic ground motions of the zone with respect to three performance levels: immediate occupancy, life safety, and collapse prevention. Once the seismic response is extracted for every performance level, the reliability of the models is calculated with respect to inter-story drift as described next. First, considering the seismic response in terms of inter-story drift for every ground motion, the associated histogram is constructed. Then, using 13 Probability Density Functions (PDFs), a Chi-square test is performed to identify the best-fitted PDF associated to the histogram of inter-story drift. Afterwards, with the best-fitted PDF of inter-story drift, the probability of failure and reliability index are extracted considering serviceability limits for every performance level. This represents a unique approach to extract the risk of structures subjected to ground motions associated to different performance levels. In addition to the structural reliability, a study about the cost of the structures with and without Chevron braces is developed, and then, it is documented the best option. Finally, based on the results reported in this paper, it is demonstrated that steel buildings with Chevron-braced frames present a better seismic performance than steel moment resisting frames without any bracing system. In summary, overall lateral drifts are reduced between 40 and 60% when Chevron braces are implemented in comparison to steel moment resisting frames without braces. On the other hand, if Chevron bracing systems are not used, i.e., in steel moment resisting frames, the inter-story drifts are about 300% higher than those of steel structures with Chevron braces. Hence, structural damages can be considerably reduced if Chevron-braced frames are implemented in steel structures that may be excited by characteristic ground motions of the zone where they are located. [ABSTRACT FROM AUTHOR]

This paper demonstrates the enhanced resilience performance of steel structures with viscoelastic friction dampers (VEFDs) based on numerical simulations of building responses. Velocity-dependent dampers, which are widely used to increase seismic resilience, may increase the axial force of the column under strong earthquake conditions because the generated force depends on the interstory velocity. This often leads to plastic hinges being placed on the columns of the structure, which can lead to structural collapse via weak-layer failure. In addition, while viscoelastic dampers are effective in reducing story drift, peak acceleration, and peak velocity, the proposed hybrid VEFD offers the additional benefit of reducing base shear via the friction damper. Simulation results for 10- and 20-story buildings with the novel VEFDs show that the proposed dampers can control drift and plastic deformation in structural members. Nonlinear dynamic analysis of 20 far-fault seismic ground motion records conducted using OpenSees also reveals lower peak absolute floor acceleration and velocity. Overall, the results suggest that the proposed VEFD has excellent potential for use in the performance-based seismic design of structures because it can reduce both structural and nonstructural damage. The results verify the damper's effectiveness in controlling story drift without a significant increase in the base shear. Collapse probability assessment also demonstrates the collapse resistance of moment-resisting frames when used in conjunction with VEFDs. [ABSTRACT FROM AUTHOR]

Sustainable development in urban areas requires a wide variety of current and theme-based information for efficient management and planning. In addition, researching the spatial distribution of earthquake (EQ) clusters is an important step in reducing seismic risks and EQ losses through better assessment of seismic hazards, therefore it is desirable to acquire an uncontaminated database of seismic activity. Quarry blasts (QBs) conducted over the mapped area have tainted the seismicity inventory in the northwestern region of Egypt, which is the focus of this paper. Separating these QBs from the EQs is hence preferable for accurate seismicity and risk assessments. Consequently, we present a highly effective ML model for cleaning up the seismicity database, allowing for the accurate delineation of EQ clusters using data from a single seismic station, "AYT", which is part of the Egyptian National Seismic Network. The magnitudes ≤ 3 that are very uncertain as EQs or QBs and need a significant amount of time to analyze are the primary focus of the model. In order to find the best way to classify EQs and QBs, the method looks at a number of ML models before settling on the best one using eight features. The results show that the suggested method, which uses the quadratic discrimination analysis model for discriminating, successfully separates EQs and QBs with a 99.4% success rate. [ABSTRACT FROM AUTHOR]

In designing control systems, it is known that fractional-order proportional integral derivative (FOPID) controllers often provide greater flexibility than conventional proportional integral derivative (PID) controllers. This higher level of flexibility has proven to be extremely valuable for various applications such as vibration suppression in structural engineering. In this paper, we study the optimization of FOPID controllers using twelve well-established algorithms to minimize structural responses under seismic excitations. The algorithms include crystal structure algorithm (CryStAl), stochastic paint optimizer, particle swarm optimization, krill herd, harmony search, ant colony optimization, genetic algorithm, grey wolf optimizer, Harris hawks optimization, sparrow search algorithm, hippopotamus optimization algorithm, and duck swarm algorithm. In addition to highlighting the benefits of fractional calculus in structural control, this study provides a detailed analysis of FOPID controllers as well as a brief description of the algorithms used to optimize them. To evaluate the efficiency of the proposed techniques, two building models with different numbers of stories are examined. FOPID controllers are designed based on oustaloup's approximation and the El Centro earthquake data. Using five well-known metrics, the performances of the developed methods are evaluated against five earthquake scenarios, including the recent earthquake in Turkey. A non-parametric (Friedman) test is also employed to compare the algorithms based on their corresponding vibration reduction. The findings of this analysis show that CryStAl consistently performs better than the other algorithms for both building models, thus resulting in superior vibration suppression. [ABSTRACT FROM AUTHOR]

This paper compares two methods for retrofitting an existing hospital concrete structure to improve its seismic performance: internal and external retrofitting. Internal retrofitting involves adding chevron braces, reinforcing shear walls with Fibre-reinforced plastic coating, and wrapping the walls, columns, and beams using steel jackets. External retrofitting uses two braced exterior steel frames connected to the concrete building using dampers. The paper also proposes a new design objective for hospital structures that ensures immediate occupancy performance level under earthquake hazard level-1 and prevents collapse under higher ground motion intensity. The paper evaluates the base structure, the two retrofitting schemes, and the proposed design method using pushover and nonlinear dynamic analyses under 20 selected earthquake records. The paper then compares the probabilistic seismic risk models using fragility curves. The results show that external retrofitting is more effective and economical than internal retrofitting and that the proposed design objective can significantly reduce the seismic risk of hospital structures. [ABSTRACT FROM AUTHOR]

Near-fault ground motions (NFGM) may have a significant component of the long period velocity pulse (LPVP) due to the directivity effect. The structures subjected to such ground motions are prone to experience large displacements. In this paper, the damage potential of such motions is compared with NFGM (without LPVP) and far-field motions in terms of seismic demand (inter-storey drift and inelastic displacement). Due to the lack of site-specific recorded NFGM, the synthetic ground motions are generated and used in this study. For this purpose, first the bedrock motions are obtained through stochastic simulation approach in which the Specific Barrier Model (SBM) is used as source spectrum and then these motions are transferred to the ground surface using one-dimensional ground response analysis. In order to obtain the NFGM with pulse, the bedrock motions are superimposed with the LPVPs and then transferred to the ground surface. To illustrate, the case of a ten-storey reinforced concrete (RC) building is considered in Delhi region (India) which falls under the seismic zone-IV. The main finding of this study is the observation that the NFGM with LPVP impose almost double seismic demand compared to the NFGM without LPVP, specially for the structures lying in the velocity-region of the response spectrum. In this study, the effect of depth of bedrock on seismic demand is highlighted and recommended to be included in the design seismic demand of NFGM. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the dynamic response characteristics of subway station under earthquakes. To this end, seismic waves are transformed into equivalent nodal loads on viscoelastic artificial boundaries using theories and methods of wave motion. The calculation formulas for equivalent nodal loads of SV waves incident at any angle are established, and ANSYS' APDL program compiles to automatically generate the viscoelastic artificial boundary and input the seismic loads. A finite element model of soil-subway station interaction was established, and the seismic response characteristics of a two-story three-span subway station under different incidence angles of SV waves were investigated using the above seismic input method. The results indicate that the incidence angle of seismic waves has a significant impact on the seismic response of subway station. Inclined incidence of seismic waves causes non-uniform loading and deformation of the subway station. Specifically, a small angle leads to predominantly transverse shear deformation, while a large angle causes mainly vertical shear deformation. The inclined incidence of seismic waves significantly increases the vertical acceleration of the subway station, with the effect becoming more pronounced as the angle increases. Additionally, special attention should be given to the joints between the structural slab and the side wall, slab and center column, as well as the two ends of the center column as they are vulnerable areas during earthquakes and require careful consideration in seismic design. [ABSTRACT FROM AUTHOR]

Three scale models of prefabricated piers were designed and manufactured to investigate the impact of staggered longitudinal reinforcement—ultra-high performance concrete (UHPC) connections on seismic performance. The failure modes, hysteresis curves, backbone curves, ductility, stiffness degradation, and energy dissipation capacity of each model were compared and analyzed through quasi-static testing and numerical simulation. The test results demonstrate that the precast assembled pier, incorporating staggered longitudinal reinforcement-UHPC connections, exhibits high bearing capacity and stiffness, effectively enhancing its overall and seismic performance during the early and middle stages; The primary factor contributing to the bond failure of staggered longitudinal reinforcement is the cracking and spalling of UHPC, which directly impacts the ductility and energy dissipation capacity of piers. This paper establishes a prediction formula for the horizontal peak bearing capacity of compression-bending failure piers, based on the strut-and-tie model. The formula takes into account the strength of the staggered longitudinal reinforcement-UHPC connection area, the staggered spacing of the longitudinal reinforcement, the spacing of the stirrups, and the axial compression ratio. By variable parameter analysis and a comparative assessment with the ACI318-19 standard formula, it is evident that the formula proposed in this paper demonstrates desirable accuracy and applicability, offering valuable guidance for the seismic design and structural optimization of prefabricated piers. [ABSTRACT FROM AUTHOR]

Empirical and probabilistic risk analysis methods can relatively accurately predict the seismic vulnerability of reinforced concrete (RC) structures. Using various intensity measures to estimate and forecast the seismic hazard of RC structures can contribute to the development of typical structural seismic resilience and vulnerability models. However, traditional empirical and analytical vulnerability studies rely more on field observation data and seismic risk algorithms and less on numerical simulation analysis for validation and optimization, resulting in limitations and fuzziness in the accuracy of the developed structural risk models. To explore the damage modes of RC frame structures under different intensities, this paper innovatively combines numerical model algorithms with empirical vulnerability methods to conduct empirical vulnerability and numerical simulation analyses on RC structures. Using probability statistics and nonlinear regression analysis methods, a prediction model for estimating the fragility of RC structures was proposed, and 858 RC structure damage samples from a typical city (Dujiangyan) during the Wenchuan earthquake in China on May 12, 2008, were used for model verification and comparative analysis. Using seismic response analysis theory, 901,530 acceleration records of the Wenchuan earthquake detected by eight actual seismic stations were selected, and nonlinear dynamic time history analysis was conducted. A four-story RC structural model was established using finite element software, and numerical simulation analysis was conducted on the model using 117,863 real earthquake acceleration data points obtained from actual monitoring stations during the Wenchuan earthquake. The acceleration time history curves and incremental dynamic analysis curves of the RC structure under different intensity measures were generated. By combining the moire algorithm and numerical simulation technology, damage stress clouds of steel bars and concrete under different intensity measures were generated, and the accuracy of the developed empirical vulnerability model was verified via numerical simulation results. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to discuss the feasibility of utilizing the non-explosive source green seismic exploration technology to detect mineral resources in the deep of complex mountainous areas of western and southern China as well as to provide a feasible detection scheme. Based on seismic illumination analysis and prestack depth-domain migration experiments, a viable active-source seismic detection system was designed for the Zhuxi mining area of Jingdezhen. Geophysical models were established according to the combined drilling profile of L42 and the corresponding petrophysical measurements of rocks based on geological findings, drilling results, and site investigations. Since the single-component p-wave seismometers would be primarily utilized for the subsequent seismic data acquisition, the viscous-acoustic wave equation was selected to simulate the propagation of the seismic wave. Meanwhile, the acoustic-elastic boundary approach (AEA) was used to solve the irregular free-surface problem caused by the rugged Earth's surface. Seismic source-receivers bidirectional illumination analysis and prestack depth-domain reverse time migration experiments were performed on simulated seismic data with 20 dB high SNR (signal-to-noise ratio) and 6 dB low SNR, respectively. The results of this study showed that by adopting a dense exciting-receiving seismic detection system, the eco-friendly non-explosive seismic source technology could reveal the spatial distribution of the main strata underneath the target area and the ore-controlling structures like faults and overthrust nappes. Based on this study, the next step of seismic data acquisition was implemented. The first-hand non-explosive source seismic profiles of the Zhuxi mining area demonstrated that the detection scheme designed was feasible and effective. By constantly improving the technical system, the eco-friendly non-explosive active-source technology would provide a safe and efficient approach, which could be used in the research fields of deep mineral resource prospection, buried faults exploration, urban underground space detection, etc. Finally, the proposed design and demonstration of an active-source seismic detection system based on illumination analysis and migration experiments merits further study and applications. [ABSTRACT FROM AUTHOR]

Quantification of seismic damage to reinforced concrete (RC) members in terms of damages states is important for condition assessment and performance-based seismic design. This paper presents a classification for axially-loaded flexural-dominant well-detailed RC members into clearly-differentiated damage states based on change in failure mode, principles of mechanics, and loss in lateral load capacity. The paper considers extreme fiber compressive strain as the Engineering Response Parameter (ERP) for classification of the damage states. The identification of member damage states based on compressive strain can be very useful for seismic assessment of the existing buildings and performance-based design of new buildings. Published experimentally observed cyclic force–displacement relationships of RC columns have been numerically simulated and are used to develop statistics of compressive strain. These are further used to develop semi-empirical expressions for extreme fiber compressive strain in terms of RC member properties, viz. axial load ratio, longitudinal reinforcement ratio, and confinement reinforcement ratio. It is shown that the proposed expressions accurately predict experimentally observed compressive strain at different damage states. The fragility functions of damage states, that provide the probability of occurrence of the strain limits, are also presented. It is seen that the proposed expressions for strain and their limits accurately identify the damage states on the monotonic stress–strain relationship of confined concrete and validate the use of strain as an ERP. The present study also provides strain limits for different damage states with consistent level of conservatism. [ABSTRACT FROM AUTHOR]

Regional seismic risk assessment is necessary for designing effective seismic risk mitigation measures. In general, such risk assessment studies consist of three components: hazard, vulnerability, and exposure modelling. This paper lays the foundations for regional seismic risk assessment of the residential building stock in Serbia and addresses each of the three seismic risk assessment components, either by reviewing the existing or proposing novel models. First, a review of seismic hazard models and seismic design codes used in Serbia in the past 70 years was presented. Next, an overview of Serbia's population metrics and historical development of Serbian's residential building stock was presented to provide the context for the exposure model. Furthermore, the paper proposed a novel building classification for Serbia's residential building stock, which is based on the existing building taxonomies, but it has been adapted to account for the local building characteristics. Building damage patterns reported in past earthquakes in Serbia and neighbouring countries were reviewed as a basis for damage classification pertaining to building typologies included in the proposed classification. Finally, the results of a preliminary vulnerability model were presented in the form of expert-based fragility functions derived for buildings typical of Serbia's residential building stock. [ABSTRACT FROM AUTHOR]

Bridges are vital to modern transportation infrastructure, providing convenient and efficient access to different locations. However, these structures are susceptible to forces that can cause significant damage and pose a hazard in the event of seismic activity. A country's economy relies heavily on its bridge infrastructure, but many older bridges built before 1970 are showing signs of deterioration due to climate change and other factors. At the time of their construction, seismic design codes did not provide sufficient guidance on proper design and detailing to ensure ductility and capacity, resulting in deficient bridges. This paper provides a brief overview of the literature on the seismic behaviour of bridges and the analytical methods used to evaluate their performance. Various factors that influence the behaviour of different types of bridges are also discussed. This paper aims to establish a theoretical foundation for selecting appropriate methods to analyze bridge structures, prioritizing retrofitting, pre-earthquake planning, and loss measurement tools. The seismic design philosophies and analytical methods are elaborated in-depth, including the methodology to develop fragility curves. The paper also discusses the fragility analysis of retrofitted bridges. [ABSTRACT FROM AUTHOR]

This research paper provides a simple and original approach to extend the resonant frequency tuning range for achieving high-to-low frequencies in electrostatically actuated microelectromechanical systems (MEMS) based resonators. In microstructures, low frequencies are usually achieved by increasing the effective mass or decreasing the mechanical stiffness. However, this work intends, assuming a double-sided electrodes design, to control the excited mode of the micro-system in order to achieve low frequencies through DC bias voltage variations and possibly eliminate the displacement dependency in capacitive micro-bridges-based structures. The design consists of a flexible microbeam where its equations of motion are derived within the framework of the nonlinear Euler–Bernoulli beam theory. The equations are then solved using the reduced-order modeling based on the Galerkin modal decomposition while considering the couple-stress theory. Simulation results show an improved performance of the proposed structure compared to previous studies. According to these results, a wide frequency tuning range has been achieved through a proper DC bias voltage arrangement. In addition, the outcomes of the numerical analysis were validated by comparing them with FEM results obtained by COMSOL software. [ABSTRACT FROM AUTHOR]

Previous research has shown that using buckling-restrained braces (BRBs) at hinged wall (HW) base (HWBB) can effectively mitigate lateral deformation of steel moment-resisting frames (MRFs) in earthquakes. Force-based and displacement-based design methods have been proposed to design HWBB to strengthen steel MRF and this paper comprehensively compares these two design methods, in terms of design steps, advantages/disadvantages, and structure responses. In addition, this paper investigates the building height below which the HW seismic moment demand can be properly controlled. First, 3-story, 9-story, and 20-story steel MRFs in the SAC project are used as benchmark steel MRFs. Secondly, HWs and HWBBs are designed to strengthen the benchmark steel MRFs using force-based and displacement-based methods, called HWFs and HWBBFs, respectively. Thirdly, nonlinear time history analyses are conducted to compare the structural responses of the MRFs, HWBBFs and HWFs in earthquakes. The results show the following. 1) HW seismic force demands increase as structural height increases, which may lead to uneconomical HW design. The HW seismic moment demand can be properly controlled when the building is lower than nine stories. 2) The displacement-based design method is recommended due to the benefit of identifying unfeasible component dimensions during the design process, as well as better achieving the design target displacement. [ABSTRACT FROM AUTHOR]

High-quality seismic data is key to determining the success or failure of oil and gas exploration in complex mountain fronts. Observation systems are important factors affecting the quality of the seismic collection. Currently, the seismic collection design of piedmont zones is mainly based on optimizing and analyzing a single collection parameter. The multiparameter optimization is not performed as a whole. Moreover, the collection parameters that significantly impact the imaging quality of piedmont zones are not deeply excavated. This paper first uses the relationship between the acquisition parameters and the signal-to-noise ratio of a previous seismic data analysis to solve this problem and then obtains the prestack offset profiles of different acquisition parameters through forward modeling and prestack offset methods, further analyzes the acquisition parameters that have a more significant impact on imaging quality, uses the degenerative treatment method to process and analyze the newly collected seismic data, and delves into the most sensitive acquisition parameters for imaging quality. The results show that the influence of the gun line distance is the largest, and the influence of the receiving line distance, the number of receiving lines, and the number of receiving channels is reduced. Therefore, the effect of each acquisition parameter on the imaging quality is different, and different acquisition parameters should be selected according to the depth of the target layer. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard assessment of North-East India is carried out considering the GMPE rule and framework developed in the companion paper to account for the propagation of epistemic uncertainty. Seismic hazard is characterized in terms of weighted mean and fractile representation using a logic tree approach. Target conditional spectra with different conditional time periods are estimated by two methods: considering GMPE-specific generalized causal rupture and all contributing causal rupture scenarios. Results are reported with 2475- and 475-year return periods. The ratio of fractile to weighted mean representation of hazard is proposed as an alternative viewpoint of the importance factor used in seismic design. [ABSTRACT FROM AUTHOR]

A large-scale shaking table test of a living stump slope with a geometric similarity ratio of 1:7 was designed and completed. The peak acceleration, acceleration amplification factor, and displacement response patterns of living stumps slopes under different types of seismic waves and excitation intensities were obtained. The time-frequency and energy variation characteristics were analyzed using the Hilbert-Huang Transform (HHT). The results showed that: (1) Regardless of the type of seismic wave, the peak acceleration and acceleration amplification factor of the living stumps slope surface are positively correlated with relative height and seismic excitation intensity. When the excitation intensity is ≤ 0.4 g, the acceleration amplification effect is more pronounced; when the excitation intensity is > 0.4 g, the acceleration amplification effect weakens. (2) Under the action of different seismic waves, the peak displacement of slope surface shows amplification effect along the elevation, and increases with the increase of excitation intensity. In addition, the incremental displacement gradually decreases from the toe to the top of the slope, which is expressed as D2 > D3 > D1 > D4 > D5. The peak displacement at the top of the slope is the greatest, but the incremental displacement is the smallest; the peak displacement at the toe of the slope is the smallest, but the incremental displacement is relatively large. (3) Regardless of the type of seismic wave, living stumps slope shows the characteristics of filtering the low-frequency components of the seismic waves and amplifying their high-frequency components. At the same time, the seismic Hilbert energy gradually accumulates along the elevation. PSHEA and PMSA significantly increase with elevation and excitation intensity, and they reach the maximum at the top of the slope. (4) The seismic Hilbert energy is positively correlated with the relative height and excitation intensity, and reaches the maximum at the top of the slope. With the accumulation of seismic Hilbert energy increases, the dynamic response parameters such as peak acceleration, acceleration amplification coefficient and displacement also increase synchronously, reaching the maximum at the top of the slope. The research conclusions can provide an experimental basis for the seismic design of living stumps slopes. [ABSTRACT FROM AUTHOR]

In past seismic events, earthquakes have often caused significant damage to buildings. It is noteworthy that most of the existing buildings are reinforced concrete structures. Therefore, in order to mitigate the damage caused by earthquakes, it is important to conduct damage assessment of reinforced concrete structures. Considering that damage at the material level is the fundamental cause of component and structural performance degradation, indices based on material damage often have advantages in reflecting and evaluating component and structural damage. This paper proposes a damage constitutive model for concrete based on existing research results. Then, aiming at the shortcomings of current research on steel bar damage constitutive models, a steel bar damage constitutive model under cyclic loading is proposed, reflecting various failure modes of steel bars under seismic actions. Based on this, a multi-level damage index system from materials to components to structures is established. Through multi-level experimental simulations and finite element analysis, the accuracy of the proposed damage indices is validated, and performance indices for components and structures are provided. These indices can effectively reflect the damaged state of components and entire structures and can be used to guide seismic design, damage assessment, and strengthening design. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the seismic risk of the masonry school buildings located in the Tehran metropolis over the next 50 years and to prioritize them for seismic retrofitting toward optimal seismic risk mitigation. Tehran ranks among the world's largest cities facing a significant seismic hazard, and masonry buildings are identified as among the structural types exhibiting the poorest seismic performance. In addition, school buildings, due to their population density, are considered important buildings by many seismic codes; Consequently, it is vital to conduct a comprehensive seismic risk analysis for these buildings and strategically allocate limited resources to their seismic retrofitting. Sensitivity analysis is conducted to rank school buildings here. The sensitivity measures are the derivative of the risk measures with respect to the building retrofit cost. These risk measures are the moments of the probability distribution of the structural and non-structural costs of the building portfolio following risk-neutral and risk-averse decision-making. The risk and sensitivity analyses are conducted employing reliability methods and Rtx software which includes assembling a chain of probabilistic models to represent an earthquake's hazard, the damage caused by it, and the ensuing costs. [ABSTRACT FROM AUTHOR]

In the year 1999, two devastating earthquakes (Mw 7.4 Kocaeli earthquake in August and Mw 7.2 Düzce earthquake in November) occurred in Northwest Türkiye. These two earthquakes led to a very large number of casualties and building collapses. When the 1999 earthquakes occurred, most of the structures in the earthquake-impacted region were not designed according to modern seismic design codes. During the 25 years following those earthquakes, there have been significant advances in building construction in the light of earthquake engineering, including adequate seismic codes, new regulations, and effective code enforcement in the earthquake impacted region. These advances have been reflected in the construction of new structures in the region and the retrofitting of existing ones. As a result, 70–80% of the current building stock in Düzce was designed, constructed, or retrofitted after the 1999 earthquakes. Almost 23 years later, in 2022, an Mw 6.1 earthquake occurred in Düzce, with ground shaking close to the seismic design code life safety performance level. The 2022 earthquake provided a great opportunity to evaluate the effectiveness and consequences of the advances in earthquake engineering and the relevant policy-making and regulations. This paper provides a comparative overview of the 1999 and 2022 earthquakes that struck the city of Düzce in terms of hazard, vulnerability, and consequences. Furthermore, other key lessons learned from the 2022 Düzce earthquake are documented based on field reconnaissance and numerical simulations. The lessons learned are expected to provide useful guidance for the reconstruction efforts after the 2023 Kahramanmaraş Türkiye earthquake sequence or in similar efforts in other parts of the world. [ABSTRACT FROM AUTHOR]

Seismic exploration is an oil exploration method by utilizing seismic information. Useful reservoir parameter information can be gained through inversion of seismic information to effectively carry out exploration work. Prestack data are characterized by large data size and rich information. Rich reservoir parameter information can be obtained through inversion of prestack data. Due to mass prestack seismic data, existing single computer environment cannot satisfy computation requirement of huge data size. Thus, an efficient and fast method is urgently needed to solve the inversion problem of prestack seismic big data. Since local optimum may be easily caught when genetic algorithm is used to optimize elastic parameters, the inversion effect is not obvious. In particular, the optimization effect for the density parameters is not good. An intelligent optimization algorithm is proposed in this paper for elastic parameter inversion of prestack seismic data. The algorithm improves genetic manipulation. The improved algorithm has been used for model trial for log data, and good inversion effect has been achieved. The inverted elastic parameters well fit with the log curve of the theoretical model. The improved algorithm effectively improves the inversion accuracy of density parameters. In this paper, the algorithm has been implemented on Spark model, and the results show that the parallel model can effectively reduce operation time of the algorithm. [ABSTRACT FROM AUTHOR]

This study explores the applicability of the metaheuristic algorithm for calculating the building period. Firefly algorithm (FA) employing the feed-forward (FF) model is applied to an existing period dataset of several wood buildings, whose motions were recorded at ambient conditions. The composition of the considered artificial neural network (ANN) is optimized employing the firefly algorithm, and the fixed weights are determined with the least error for the model. The model's precision is evaluated by comparing the results with the multiple linear regression (MLR) model, the ANN model combined with the genetic algorithm (GA-ANN), particle swarm optimization algorithm (PSO-ANN), and the models existing in building code. The results are also compared with the models presented in the literature for the period estimate required for the seismic design of wood buildings. The paper concludes that the proposed informational model can predict the fundamental period of light-frame wood buildings more accurately than the other available models. [ABSTRACT FROM AUTHOR]

Post-tensioning self-centering walls are a well-developed and resilient technology. However, despite extensive research, the application of this technology has previously been limited to low-rise buildings. A ten-story self-centering wall building has now been designed and constructed using the state-of-art design methodologies and construction detailing, as described in this paper. The building is designed in accordance with direct displacement-based design methodology, with modification of seismic demand due to relevant issues including higher-mode effects, second order effects, torsional effects, and flexural deformation of wall panels. Wall sections are designed with external energy-dissipating devices of steel dampers, and seismic performance of such designed self-centering walls is evaluated through numerical simulation. It is the first engineering project that uses self-centering walls in a high-rise building. The seismic design procedure of such a high-rise building, using self-centering wall structures, is comprehensively reviewed in this work, and additional proposals are put forward. Description of construction detailing, including slotted beams, flexible wall-to-floor connections, embedded beams, and damper installation, is provided. The demonstration project promotes the concept of seismic resilient structures and contributes to the most appealing city planning strategy of resilient cities at present. The paper could be a reference for industry engineers to promote the self-centering wall systems worldwide. [ABSTRACT FROM AUTHOR]

This paper for the first time improved a Robust Multi-Output machine learning regression model for seismic hazard zoning of Turkey, Iraq and Iran using constructed 3-D shear-wave velocity (Vs), seismic tomography dataset model for the crust and uppermost mantle beneath the study area. The focus of this paper's opportunity is to develop a scientific framework leveraging machine learning that will ultimately provide the rapid and more complete characterization of earthquake properties. This work can be targeted at improving the seismic hazard zones system ability to detect and associate seismic signals, or at estimating other seismic characteristics (crust acceleration and crust energy) while traditionally, methods cannot monitor the earthquakes system. This work has derived some physical equations for extraction of many variables as inputs for our developed machine learning model based on a reliable understanding of the tomography data to physical variables by preparing huge dataset from different physical conditions of crust. We have extracted the velocity values of the shear waves from the original NETCDF file, which contains the S velocity values for every one km of the depths of the crust for the study area from one km down to the uppermost mantle beneath the Middle East. For the first time, this study calculated new seismic hazard parameter called Peak Crust Acceleration (PCA) for seismic hazard analysis by considering the transmitted initial seismic energy through the Earth's crust layers from hypocenter. All machine learning algorithms in this study wrote in python language using anaconda platform the open-source Individual Edition (Distribution). [ABSTRACT FROM AUTHOR]

The response displacement method (RDM) is recommended for the seismic analysis of underground structures in the transverse direction for many codes, including bases for design of structures-seismic actions for designing geotechnical works (ISO 23469) and code for seismic design of urban rail transit structures (GB 50909-2014). However, there are some obvious limitations in the application of RDM. Springs and the shear stress of the soil could be approximately evaluated for the structures having a simple cross section, such as rectangular and circular structures. It is necessary to propose simplified seismic analysis methods for structures with complex cross sections. This paper refers to the idea of RDM and proposes three generalized response displacement methods (GRDM). In GRDM1, a part of the soil surrounding a structure is selected to generate a generalized underground structure with a rectangular cross section, and the same analysis model as RDM is applied to analyze the responses of the structure. In GRDM2, a hollow soil model without a generalized structure is used to compute the equivalent load caused by the relative displacement of the soil, and the soil-structure interaction model is applied to calculate the responses of the structure. In GRDM3, a continuous soil model is applied to compute the equivalent load caused by the relative displacement and shear stress of the soil, and the soil-structure interaction model is applied to analyze the responses of the structure, which is the same as the model used in GRDM2. The time-history analysis method (THAM) is used to evaluate the accuracy of the proposed simplified methods. Results show that the error of GRDM1 is about 20%, while the error is only 5% for GRDM2 and GRDM3. Among the three proposed methods, GRDM3 has obvious advantages regarding calculation efficiency and accuracy. Therefore, it is recommended to use GRDM3 for the seismic response analysis of underground structures that have conventional simple or complex cross sections. [ABSTRACT FROM AUTHOR]

Currently, most of methodologies available to evaluate the seismic performance of buildings use as index maximum interstory drifts. However, recent earthquakes have evidenced the need to develop performance levels that incorporate seismic resilience concepts to evaluate the level of post-seismic functionality of buildings and their capacity to recover functionality. Furthermore, such performance levels should explicitly consider the performance of structural, non-structural elements and contents. For this purpose, this paper proposes a set of six performance limit states for office-type buildings, in which the seismic performance of structural, non-structural elements and contents is explicitly considered. Each of these limit states is associated with a set of probable events that generically determine its recovery of functionality (e.g., post-seismic inspection and management of financial resources). To exemplify the proposed scheme a seven-story reinforced concrete building with unreinforced infill masonry walls and located in Mexico City is evaluated. The results obtained suggest that the building has a significant probability of experiencing loss of functionality due to the damage suffered mainly by the non-structural elements and contents. This indicates that modern seismic design codes, as that used for this study, accomplish their main objective, which is to reduce the probability of collapse and to prevent the loss of human lives. However, these results also demonstrate that the main objective of decision makers when designing such buildings, which is to be functional for one or several needs, is not achieved. [ABSTRACT FROM AUTHOR]

Self-centering shear wall systems (SCSWSs) exhibit superior seismic capacities with low-damage and self-centering features. However, the cumulative effect under long duration earthquakes would diminish robustness of the system and lead to increased unrecoverable damage. Thus, it should be considered in seismic designs for SCSWSs. This paper applies an energy-based design procedure (EBDP) to SCSWSs in accordance with the Chinese code. A step-by-step design procedure is presented to conduct multi-level designs for SCSWSs using EBDP, while detailed explanations are elaborated corresponding to SCSWS features. A design example is presented to verify the applicability of the EBDP in SCSWSs. The performance of the designed SCSWS is then assessed and compared with a SCSWS designed by the direct displacement-based design method. Results show that the EBDP designed structure has 13% enhanced strength capacity with better controllability in the damage development. The damage index equaling to 0.35 and 0.46 are quantified with two groups of earthquakes, which consists with the performance demands. In addition, deformations are in good agreement with the design objectives, implying reasonable application of the EBDP in SCSWSs. [ABSTRACT FROM AUTHOR]

This paper is a review of our work, an experimental study and simulation of seismic fields in volcanic structures using vibrators as sources of elastic waves. We review the results of experimental studies of mud volcanoes carried out by the Institute of Computational Mathematics and Mathematical Geophysics (ICM&MG) of the Siberian Branch (SB), Russian Academy of Sciences (RAS); by the Institute of Physics of the Earth (IPE), RAS; and by the Kuban State University in the Taman mud-volcanic province using vibrators. We have carried out mathematical simulation in heterogeneous geophysical media to refine the information on the structure of the object under investigation, as well as on the distinguishing features of the seismic field. We have developed a mathematical approach to deal with the simulation of vibroseismic probing of mud volcanoes with arbitrary geometries incorporating knowledge of deep-seated faults, overlapping layers, and so on. Numerical techniques were used to solve sets of equations in elasticity theory and to develop parallel algorithms, program packages, as well as carrying out numerical experiments in high-performance computational systems. We present results from calculations of the seismic field for the source zone of the Shugo mud volcano. This paper describes 3D and 2D geophysical models developed for this study and the results of simulation for the seismic field of the Karabetova Gora mud volcano and for the Elbrus magmatic volcano. It is shown that the approach developed here using active vibroseismic techniques can be successfully used in practice to refine the seismic field, the deep structure of geophysical models, and to study the effects exerted by the geometry of a magma chamber and by the presence of erupting channels on data acquired by an observation system on the ground surface. These studies prove that vibroseismic sources with high accuracies of periodic excitation can be used to study volcanic structures and to conduct active monitoring of volcanic activity. [ABSTRACT FROM AUTHOR]

The paper addresses the investigation of the dynamic characteristics of a case study, the Egyptian church of Abu serga. To this aim some in situ investigations have been conducted and related results are discussed. The paper presents interesting and innovative aspects, mainly related to the characteristics of the church investigated, covering a lack of knowledge in the scientific literature due to the typology of the church. The integrated geotechnical and geophysical investigation techniques assessed the level of seismic and other geo-environmental risks that Abu serga church suffers from. It suffers multiple Geo-environmental hazards. The main objectives of this pilot study are as follows: (1) Identifying the shear velocity Vs analysis profile of the subsoil and also the resonant frequency of soil and the historical building of Abu serga church using ambient noise recordings (microtremors) to assess the level of seismic and other geo-environmental hazards. (2) Understanding the damage to the historic building caused by the recent earthquakes. (3) Offering technical support and advice on intervention retrofitting for the historic damaged structure. In this study, ambient noise recordings have been processed through horizontal to vertical spectral ratios to examine the main frequencies and to examine whether the building has its main frequency close to that of the soil in order to identify potential resonance phenomena. Numerous ambient noise recordings were recorded on the soil, in the basement, and at each floor of the buildings. This study suggests moderate level of earthquake activity at Abu serga church and is in a good agreement with the fact that "Egypt is a part of the stable African Shield", but the existence of old structures such as the Abu serga church may reduce the ability to resist any earthquake shaking. [ABSTRACT FROM AUTHOR]

Purpose: The novel metallic damper device for passive vibration control of structures, which is designed primarily for seismic protection of buildings, is described in this paper. It consists of the base plate, fixed into foundation, with two concentric cycles of vertical components and a middle steel activating plate anchored to the isolated structure. During an earthquake, the middle steel activating plate moves together with main structure causing bending of vertical components. Seismic energy is absorbed due to plastic deformation of the vertical components of the damper. The performance of various vertical components, the key elements of the novel damper is studied in this paper. The advantages of this type of damper reflect in its ability to adapt its own features depending on the intensity of the earthquake and that it has equivalent characteristics in every horizontal direction due to rotational symmetry. Methods: Sixteen experimental tests of the vertical components of the damper, were conducted to obtain their hysteretic behaviour. Numerical models using the finite element method and the Abaqus/Standard software were developed, validated and verified with experimentally obtained results. Results: The experimental results show significant energy absorption of the vertical components of the novel damper. Numerical models can be used in further research instead of expensive experimental tests. Conclusions: The vertical components of the novel damper possess extraordinary hysteretic performance. If the components of the energy dissipation device are properly designed for maximum displacements, the device is not expected to suffer heavy damage or total failure during earthquakes. [ABSTRACT FROM AUTHOR]

Accurate recognition of the type of ground motion is a basic task in the field of seismic engineering. In this paper, the key technologies of detection and recognition of underground seismic signal are studied. The target recognition algorithm is designed to realize the target recognition through denoising the collected target signal and extracting the characteristic quantity. Considering that ground motion signals generated by moving targets on the ground are susceptible to environmental noise, this paper introduces the working principle of wavelet packet denoising and its support vector machine classification model. Wavelet packet was used to transform the signal to denoise first, then zero-crossing rate analysis of the denoised signal was carried out after wavelet packet denoising and extracts the parameters, and the energy of cross-correlation criteria was selected finally. Quantitative indices are combined to construct multi-feature vectors, which are used as input of multi-class support vector machine for training and prediction. In this model, the optimal parameters of support vector machine model are found by genetic algorithm parameter optimization. The experimental results show that the improved model can recognize and classify the ground motion signals caused by people and vehicles correctly and can improve the performance of the classifier. [ABSTRACT FROM AUTHOR]

This paper presents a topology optimization approach for the seismic design of multiple-rocking self-centering concentrically braced frames (SC-CBFs). SC-CBFs have been recently developed as damage-free seismic lateral load-resisting systems. In these systems, rocking sections are potentially designed in several locations over the height due to several modes. The design of multiple-rocking SC-CBFs is a demanding task due to their highly non-linear behavior. The vertical irregularity, caused by the non-continuous stiffness over the height of these systems, makes the prediction of their behavior a challenging task, especially when subjected to dynamic ground accelerations. In this paper, an efficient and general design approach for these systems is developed utilizing gradient-based topology optimization. An optimization problem is formulated such that the construction cost of the SC-CBF is minimized while simultaneously considering the topology of the frame, cables, energy dissipation (ED) material, and the location of the rocking sections. The performance of the building is limited to acceptable limits by formulating the constraints of the optimization problem based on the results obtained from non-linear time history analysis (NLTHA). An efficient numerical integration scheme based on the mixed lagrangian formalism (MLF) was adopted to conduct the NLTHA. The proposed method was used for the design of 5- and 10-story buildings. The results show that efficient designs could be achieved with a reasonable number of iterations using a personal computer. This makes the proposed approach desirable for the design of multiple-rocking SC-CBFs by researchers and engineers. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of the seismic behavior of reinforced concrete (RC) structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure. In this regard, the behavior of six prototype structures (with different heights and plan layouts) is investigated through nonlinear static and time history analyses, implemented in the OpenSees platform. The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages. Moreover, the global response of the buildings is discussed in terms of some parameters, such as lateral overstrength due to the gravity flat slab-column frames. According to the nonlinear static analyses, in structures in which the slab-column connections were designed only for gravity loads, the slab-column connections exhibited a punching mode of failure even in the early stages of loading. However, the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318 (2019) was provided in the slabs at joint regions. Furthermore, despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures, a relatively significant overstrength was imposed on the structures by the gravity frames. [ABSTRACT FROM AUTHOR]

Building code implementation in developing countries is a serious concern due to poorly regulated construction practices. Deficiencies in terms of material strength and structural detailing are found the most in reinforced concrete frames in Pakistan. This paper presents the results of quasi-static cyclic tests performed on reduced-scale RC frames with and without beam-column joint detailing and considering normal and low-strength concrete respectively. Fragility functions and loss curves for the standard/sub-standard frames were derived using an experimentally validated numerical model. Furthermore, the existing RC frames building stock was rehabilitated with various configurations of steel bracing i.e. one way diagonal, one way eccentric, two way diagonal, two way eccentric and concentric. The developed fragility and loss curves for the rehabilitated frames confirmed that the two way diagonal steel bracing system outclasses the other types. Moreover, inter-story drift limits for as-built and rehabilitated frames were proposed under design base earthquakes and maximum considered earthquakes. Maximum considered earthquakes pushed the ductile as-built frame further than the moderate damage state, thus rehabilitation after such an event will be required for the structure. The presented results will help in seismic risk assessment, decision-making and public awareness. [ABSTRACT FROM AUTHOR]

The Greek National Annex for current Eurocode 8 has adopted the seismic hazard zonation map published in 2003 as part of the modifications to the Greek Seismic Code EAK 2000 (EAK 2003). This map, which followed the catastrophic earthquakes that hit the country between 1978 and 2001, includes three seismic hazard zones with peak ground acceleration (PGA) ranging between 0.16 and 0.36 g. In this paper, following the significant progress that has been made worldwide in the last two decades towards the improvement of the definition of seismic actions and the seismic hazard maps using fully probabilistic models, we make a complete proposal for the Greek National Annex of the ongoing revision of Eurocode 8, which includes a new seismic hazard zonation map for Greece, as well as a novel site categorization scheme and related site amplification factors. To this end, we use the results of the European Seismic Hazard Model, ESHM20, as reported by Danciu et al. (The 2020 update of the European Seismic Hazard Model: Model Overview, 2021) which will be adopted as informative reference for the seismic hazard at European level in the forthcoming revision of Eurocode 8 (CEN/EC8). The herein proposed ground shaking zonation for rock conditions includes five zones with PGA values ranging between 0.13 and 0.37 g. For each zone, two newly proposed ground motion parameters, i.e., Sα,475 and Sβ,475, are provided, which are the two parameters used for anchoring the elastic response spectrum as defined in CEN/EC8, along with all the other necessary parameters for the definition of the elastic response spectrum, including site amplification. The proposal for the new seismic zonation is supported by a preliminary investigation of the impact of its adoption on the seismic design of new structures and on the seismic risk of the current building stock in Greece, to help gain a better insight on how important the differences imposed by the new zonation might be for the end-users and the administration. [ABSTRACT FROM AUTHOR]

Slopes have a significant impact on the ground motion characteristics, which can aggravate the damage degree of building structures during a strong earthquake. However, many studies have focused on the design response spectra under flat site conditions and fewer researchers have investigated the impact of slope topography on the design response spectra. In this study, the numerical simulation is used to obtain the seismic response of slopes and the differential evolution algorithm is used to obtain the standardized response spectra of the acceleration time histories along the ground surface behind the slope crest. The impacts of slope height (H), slope gradient (i), average shear wave velocity in the top 30 m (VS30) and distance from the slope crest (x) on the characteristic parameters of the design response spectra are then investigated. The results show that H, i, VS30 and x have a little influence on the normalized second inflection point period (mean(Tg/Tg,ff)) but a great influence on the normalized plateau value (mean(αmax/αmax,ff)). Specifically, both mean(Tg/Tg,ff) and mean(αmax/αmax,ff) show a trend from increasing first to decreasing and stabilizing finally as x increases; the mean(αmax/αmax,ff) shows an increasing trend as H increases, but a decreasing trend as i or VS30 increases. Finally, to provide some guidance for the seismic design of building structures near slopes, two approximate relationships are proposed: (1) between mean(Tg/Tg,ff) and x, and (2) between mean(αmax/αmax,ff) and H, i, VS30, x. The main innovation of this paper is that the relationship between the characteristic parameters of the design response spectra and the slope site characteristic parameters is clearly summarized and quantified for the first time. [ABSTRACT FROM AUTHOR]

Purpose: The scarcity of flat lands in the hilly region forces the construction of buildings on sloping terrain with foundations constructed at different levels. These buildings are inherently vulnerable to earthquakes due to horizontal and vertical irregularities that are extremely hard to avoid because of the nature of the terrain. Compounding on that fact, a large stock of buildings in the hilly region have been constructed without following the earthquake-resistant design provisions, the consequences of which were evident in past seismic events such as the 2011 Sikkim earthquake and the 2015 Nepal earthquake. Methods: The paper aims to assess the explicit and combined effect of seismic design provisions of Indian Standards on the seismic response of a set of Un-Reinforced Masonry (URM) infilled Reinforced Concrete (RC) buildings on a hill with the prevalent configuration observed. 3D analytical models have been considered for the RC frame elements with infill-frame interaction taken into account by diagonal strut elements. Incremental dynamic analyses have been performed for a realistic assessment of key parameters influencing the seismic performance of such buildings. Results: It has been observed that the seismic response parameters in terms of joint displacement and inter-storey drift ratio are higher for buildings designed considering only gravity loads as compared to buildings designed as Special Moment Resisting Frame (SMRF) as per relevant Indian seismic design standards whereas minor variations were observed in the roof acceleration and Peak Storey Acceleration (PSA). It has also been observed that collapse probability at any given seismic hazard level reduces significantly when the Gravity Load Designed (GLD) RC building is designed and detailed as SMRF. It has further been observed that the collapse probability of the GLD RC building can be reduced by more than 40% at the design seismic hazard level if seismic design and ductile detailing provisions are implemented. [ABSTRACT FROM AUTHOR]

The past few decades have been marked by a rapid acceleration in Municipal Solid Waste (MSW) generation because of industrialization, urbanization, and economic growth combined with a high population growth rate. Thus, the most economically effective alternative to developing new landfills is the construction of reinforced soil walls (RSW) in existing MSW landfills to allow for their vertical expansion. This paper presents a structure for the system reliability-based seismic design optimization (SRBSDO) approach for landfills by incorporating the variability associated with design parameters under seismic conditions. The formulation considers a three-part wedge mechanism based on the pseudo-static limit equilibrium method. The influence of the horizontal seismic acceleration coefficient (kh) on the stability against external and internal modes of failure is studied. A target reliability index of not less than 3.0 is adopted to obtain the optimum dimensions of RSW required to achieve stability against three modes of failure (bearing capacity, sliding, and eccentricity). The dimensions of RSW are presented with respect to vertically expanded heights in the form of design charts. The results of the internal stability analysis of an RSW are provided to obtain the optimum number of geosynthetic reinforcement layers required for the stability of RSW under seismic loading. It is reported that kh has a substantial influence on the reliability of RSW, and higher values of mean and coefficient of variations of kh may cause instability. It is observed that the total length of the reinforcement (B2) should not be less than 0.67 and 0.91 times the height of the RSW (H2) for kh = 0.1 and 0.2, respectively. The minimum required number of reinforcement layers to maintain overall stability are 13 for kh = 0.10 with minimum B2/H2 of 0.66 and 19 for kh = 0.20 with minimum B2/H2 of 0.83. [ABSTRACT FROM AUTHOR]

Seismic losses due to earthquakes have been shown to have significant economic, social and environmental consequences. Over recent years, research to predict potential economic and social impact due to seismic risk has been increasing. Recognizing that the traditional philosophy of life safety design can lead to extensive damage and demolition which has a large environmental cost, incorporating environmental impacts associated with the expected seismic damage over a building's life is a key step as the building industry moves towards both sustainable and seismically resilient design. This paper introduces a framework that uses environmental indicators quantifying losses from seismic response that can then be used to advocate for a change in seismic performance objectives. First, existing literature and previously developed approaches for quantifying potential environmental impact due to seismic damage are summarized. Next, performance based earthquake engineering concepts are used to demonstrate a probabilistic approach to quantify potential environmental impacts using a range of environmental and resource use indicators over the life span of a case study building. In addition, a case study is presented to compare different environmental indicators between a Code Minimum building and the same building redesigned for a higher seismic performance. The majority of the composition of the environmental indicator values are from the inclusion of the non-repairable scenario, and from the repair activities, the majority of the impacts are from damage to drift sensitive components including curtains walls, partitions and elevators. For the Code Minimum building the non-repairable scenario contributes to between 8 to 11% the total seismic cost. For the Stronger Stiffer building, the non-repairable scenario contributes around 3% of the initial impact. Neglecting non-repairable scenarios does significantly reduce the potential environmental impacts when analyzing buildings designed for current code minimum structural standards. [ABSTRACT FROM AUTHOR]

The paper deals with the use of proportional systems in architecture applied to the case study of the "modern" reconstruction of a fifteenth-century cloister heavily damaged during the Second World War bombing in Milan. First detailed analysis of the regulating lines underlying the typical vault spans of the four cloisters composing the architectural complex is carried out. Afterward, a thorough comparison is conducted of the proportional relation of the new span of the reconstruction designed by the rationalist architects Ignazio Gardella and Giovanni Romano in order to emphasize the role of the span as a proportional system that becomes the base "module" of the project. Finally, the correlation between geometrical proportions and structural conception is investigated, highlighting the differences between the existing masonry structures with a cross-vault arch system and reinforced concrete structural frames of the new intervention. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic loss assessment of seismically isolated and non-isolated buildings with steel moment or braced frames, designed by the seismic design standard of ASCE/SEI 7-16. The seismic loss is calculated from the damage to structural and non-structural components, as well as the demolition and the collapse of buildings. This study demonstrates that the expected annual losses for seismically isolated buildings are half or less than half of those calculated for non-isolated buildings. These losses depend on the types of seismic isolation systems and seismic force resisting systems used. Among the cases of isolated buildings studied in this paper, the most cost-effective systems are found to be the buildings designed by minimum strength requirement in ASCE/SEI 7-16 and with isolators which have displacement capacity 1.5 times larger than the minimum required in ASCE/SEI 7-16, in terms of expected annual losses. This study also compares the results obtained from different approaches of selection and scaling of ground motions. The following research finds that when Incremental Dynamic Analysis approach with far-field ground motion set in FEMA P695 is used, the computed expected total annual losses become doubled from the Conditional Spectra approach. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for seismic signal denoising based on the dual-tree complex wavelet transform. The advantages of shift invariance, adequate directions and anti-aliasing enable the dual-tree complex wavelet to effectively represent seismic data. However, the fixed threshold in each sub-band leads to the attenuation of the useful signal or residual noise. In this paper, noise attenuation strategies are discussed for all sub-bands in different directions and scales. In this approach, block matching is combined with singular value decomposition to handle the noisy coefficients in high-frequency scales based on local and non-local similarity. An adaptive threshold is used to divide the signal from the noise at low-frequency scales. The method is applied to synthetic seismic data and field data to verify its performance. The experimental results illustrate that the proposed method improves the signal-to-noise ratio by 3-4 dB compared with fixed threshold denoising in all sub-bands. [ABSTRACT FROM AUTHOR]