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From a tectonic perspective, Türkiye is a geographical region known for its high seismic activity, with some of the most active faults in the world. On February 6, 2023, two consecutive earthquakes with magnitudes of Mw 7.7 and Mw 7.6 struck Kahramanmaraş within a remarkably short time span of 9 h. This event stands out as a rare and unprecedented tectonic occurrence in terms of seismicity and tectonic activity over the past 100 years. The impact of these two major earthquakes on the region's reinforced concrete structures was significant, resulting in severe damage and the collapse of numerous buildings. It is of utmost importance to investigate and examine the design flaws and underlying factors that contributed to the damage observed in the reinforced concrete structures affected by these earthquakes. Such research will not only contribute to the improvement of structural design, seismic regulations, and quality control measures during construction but also enhance our understanding of earthquake engineering. In this study, an in-depth field investigation was conducted on reinforced concrete structures in Hatay, one of the regions most affected by the Kahramanmaraş earthquakes. The damages occurring in the buildings were documented through a detailed field survey and analyzed. A total of 540 reinforced concrete structures in the Hatay region were extensively examined, and the damages that occurred in these structures were photographed and interpreted to understand their underlying causes. Subsequently, based on the findings from the field investigation, a structural model was designed that incorporated the most significant design and construction errors responsible for the damages observed in the 540 examined structures. The devised model was subjected to static push-over analysis and nonlinear dynamic analysis using the SAP2000 finite element software, and the results obtained were interpreted. [ABSTRACT FROM AUTHOR]

Seismic performance of steel moment-resisting frames is investigated through the incorporation of U-shaped metallic dampers. The primary objective is to assess the effectiveness of these dampers in mitigating seismic responses by utilizing various analysis techniques. Two representative structural configurations (5 and 10-story) are studied in both damped and undamped states to reveal the impact of dampers on seismic response reduction. The study utilizes the endurance time analysis (ETA) method, known for its efficiency in evaluating structural seismic performance. To validate the analysis results, a benchmark comparison is made through nonlinear time history analysis (NTHA). Incremental dynamic analysis (IDA) is also conducted to assess structures' intensity measures with respect to their damage intensity index. The findings demonstrate that U-shaped metallic dampers substantially reduce inter-story drift and story shear forces. Importantly, a close alignment between the results obtained from ETA and NTHA underscores the reliability of the former in assessing seismic performance with supplemental damping devices. [ABSTRACT FROM AUTHOR]

Inelastic displacement demand is an important part of the performance-based design and it should be estimated realistically to determine a reliable seismic performance of a structure. In this context, the coefficient method is an easy and practical method for this estimation. The coefficient method is a method that is used to estimate inelastic displacement demand by the multiplication of the elastic displacement demand and inelastic displacement ratio. Thus, it is clear that a reliable estimation of inelastic displacement demand depends on a reliable inelastic displacement ratio. After a reliable estimation of the inelastic displacement ratio, it is essential to propose an equation for the usage of engineering practice. Although nonlinear regression analysis is preferred in the literature as a classical method to estimate an equation, the Artificial Neural Network method is a new and modern way that can be used in the estimation of inelastic displacement ratio. In this study, Artificial Neural Network models have been proposed by using data of inelastic displacement ratios of Single Degree of Freedom systems with stiffness and strength degrading peak-oriented hysteretic model and collapse potential by performing nonlinear time history analyses. Firstly, a large number of trials have been conducted to obtain an optimum Artificial Neural Network model. The results of Artificial Neural Network models have been compared to the results of equation estimated by using nonlinear regression analysis and given in the previous studies. According to the results, Artificial Neural Network models give closer values to the inelastic displacement ratios of time history analysis than nonlinear regression analysis. Especially, the Bayesian Regularization Backpropagation model of the Artificial Neural Network method with two hidden layers achieved the best performance among the other Artificial Neural Network models. It can be said that Artificial Neural Network methods can be used to estimate inelastic displacement ratio since it yields better accuracy than previous techniques for different parameters. [ABSTRACT FROM AUTHOR]

Directionality in the representation of earthquake demand for structural seismic design has surfaced as a subject of debate in recent years. Design spectra, as defined in building and bridge codes, account for directionality by considering the peak response in all possible orientations of the motion using the RotDnn measure, where "nn" is the percentile of the peak response. Current seismic hazard maps are based on ground motion models that use the RotD50 spectra (median peak response). However, since 2009, building codes have adopted RotD100 spectra (maximum peak response), raising concern among researchers and engineers. The first objective of this study is to evaluate the impact of design spectra definition, RotD50 or RotD100, on the bidirectional inelastic response of azimuth-independent RC systems. Upcoming updates to seismic hazard maps highlight the need of understanding the implication of this choice in bridge design. While previous research focused on the relationship between RotD50 and RotD100, this work assesses the impact of each definition on the inelastic seismic response of RC circular columns designed following the Direct Displacement-Based Design approach and verified through nonlinear time history analyses (NTHA) using ground motions from shallow crustal active and subduction zone regions. The ratios of NTHA to design displacement confirm that RotD100 spectra should be used to design azimuth-independent RC systems and provide the first known verification of DDBD for bidirectional loading (second objective). These ratios are a function of ductility level, tectonic regime, effective period, and coupling (which is the third objective). Overall results show that RC circular cantilever columns designed to RotD100 spectra show less deviation from the expected design displacement than columns designed to RotD50 spectra. This study presents the first step in resolving the ongoing debate over spectra definition and provides recommendations for displacement demand estimations for response spectra-based design approaches. [ABSTRACT FROM AUTHOR]

The combination of the surrogate model and optimization algorithm to solve structural optimization problems is an efficient way to lower computational costs and reduce time consumption. However, the development of surrogate models for structural analysis frequently faces challenges due to limited datasets. To tackle this issue, this paper presents a surrogate model capable of training on limited datasets while simultaneously predicting multiple concerned indicators, and demonstrates its effectiveness in performance assessment and design optimization through two seismic design case studies. Specifically, an improved model architecture based on the conditional Generative Adversarial Network (cGAN) is proposed. The feasibility of this surrogate model for seismic response analysis and optimization is initially demonstrated using an existing planar frame case. Subsequently, to validate the suitability of the surrogate model for Nonlinear Time History Analysis (NTHA) tasks, the proposed approach is applied to optimize a 3D steel frame equipped with nonlinear viscous dampers. Herein, a three-objective optimization problem is formulated, employing the Non-Dominated Sorting Genetic Algorithm (NSGA-II), driven by the trained rcGAN, to identify the Pareto front. The optimum design is subsequently selected from this front utilizing a multi-criteria decision-making technique. The outcomes from three optimization tests indicate that our approach effectively enhances the seismic performance of the frame while achieving substantial economic benefits, ultimately reducing the construction cost of the benchmark structure by up to 31.1 %. • An rcGAN-based surrogate model is applied to a nonlinear seismic response analysis and optimization task of steel frames. • The proposed surrogate model is able to learn from small datasets and predict multiple targets concurrently. • The large-population optimization algorithm consisted of the trained model and NSGA-II can effectively identify the optimum design. • The optimization algorithm based on the surrogate model has advantages in evaluation speed and optimization efficiency. • The selected optimum design can effectively save the construction cost, thus providing economic benefits to structural seismic design. [ABSTRACT FROM AUTHOR]

For structural engineers, existing surrogate models of buildings present challenges due to inadequate datasets, exclusion of significant input variables impacting nonlinear building response, and failure to consider uncertainties associated with input parameters. Moreover, there are no surrogate models for the prediction of both pushover and nonlinear time history analysis (NLTHA) outputs. To overcome these challenges, the present study proposes a novel framework for surrogate modelling of steel structures, considering crucial structural factors impacting engineering demand parameters (EDPs). The first phase involves the development of a process by which 30,000 random steel special moment resisting frames (SMRFs) for low to high-rise buildings are generated, considering the material and geometrical uncertainties embedded in the design of structures. In the second phase, a surrogate model is developed to predict the seismic EDPs of SMRFs when exposed to various earthquake levels. This is accomplished by leveraging the results obtained from phase one. Moreover, separate surrogate models are developed for the prediction of SMRFs' essential pushover parameters. Various machine learning (ML) methods are examined, and the outcomes are presented as user-friendly GUI tools. The findings highlighted the substantial influence of pushover parameters as well as beams and columns' plastic hinges properties on the prediction of NLTHA, factors that have been overlooked in prior studies. Moreover, CatBoost has been acknowledged as the superior ML technique for predicting both pushover and NLTHA parameters for all buildings. This framework offers engineers the ability to estimate building responses without the necessity of conducting NLTHA, pushover, or even modal analysis which is computationally intensive. • Generated 30,000 random steel buildings for surrogate model development. • Established novel design of experiment framework for surrogate modelling. • Used material, geometry, seismic, and pushover factors for surrogate development. • Developed GUIs for pushover and time history analysis prediction. • Used 13 ML methods for building response prediction with advanced feature selection. [ABSTRACT FROM AUTHOR]

Until recently, the viscous damping ratio pervasively assumed has been ζ = 5 %. However, the dynamic identification of the experimental response recorded in recent large-scale shake-table tests shows that lower levels of viscous damping are more appropriate when material nonlinearities are explicitly accounted for. This paper investigates a hybrid constant-ductility inelastic displacement ratio, C μ 2 , which identifies the inelastic demand for a viscous damping ratio ζ = 2 % when the elastic demand for ζ = 5 % is known. A comprehensive statistical analysis is developed, and analytical estimates are provided, for inelastic single-degree-of-freedom systems with a wide variation of the constitutive parameters and a large earthquake database. [ABSTRACT FROM AUTHOR]

All around the world, non-engineered masonry constructions (NECs) typically have high vulnerability to seismic ground motion, resulting in heavy damage and severe casualties after earthquakes. Even though a number of computational strategies have been developed for seismic analysis of unreinforced masonry structures, a few studies have focussed on NECs located in developing countries. In this paper, different modelling options for finite element analysis of non-engineered masonry buildings are investigated. The goal of the study was to identify the modelling option with the best trade-off between computational burden and accuracy of results, in view of seismic risk assessment of NECs at regional scale. Based on the experimental behaviour of a single-storey structure representative of Indian non-engineered masonry buildings, the output of seismic response analysis of refined 3D models in ANSYS was compared to that of a simplified model based on 2D, nonlinear, layered shell elements in SAP2000. The numerical-experimental comparison was carried out under incremental static lateral loading, whereas nonlinear time history analysis was performed to investigate the dynamic performance of the case-study structure. Analysis results show that the simplified model can be a computationally efficient modelling option for both nonlinear static and dynamic analyses, particularly in case of force-based approaches for design and assessment of base isolation systems aimed at the large-scale seismic vulnerability mitigation of NECs. [ABSTRACT FROM AUTHOR]

In this study, the effects of pounding on seismic behavior of mid-rise reinforced concrete (RC) adjacent buildings with insufficient separation distance were investigated. 5, 8, 10, 13 and 15-storey RC building models were created to represent mid-rise buildings. The nonlinear behavior properties of these models are reflected by plastic hinges defined at the column and beam ends. The buildings are modeled as a three dimensional (3D) column-beam frame system. Adjacent building models are derived, which are connected from floor to floor level using Kelvin contact elements. Total of 30 different adjacent building models were created with the use of buildings having different number of floors. The "0" m gaps reflect inadequate separation distance between adjacent buildings while the "5" m gap is used for the reference building without collision. In order to investigate the pounding effects between adjacent buildings, 22 real acceleration records compatible with TBEC-2018 were selected and scaled. Total of 660 3D nonlinear time history analyses were carried out and the roof displacement demands obtained from these analyses were compared for collision and without collision cases The outcomes of this study show that significant changes may occur in the building displacement demands due to the collision of the mid-rise RC neighboring buildings with insufficient seismic gap. Based on the findings obtained on significant number of adjacent building pairs with different period ratios, the displacement amplification factors (β) are proposed for the mid-rise RC buildings. [ABSTRACT FROM AUTHOR]

The engineering communities are mostly interested to a lateral load-resisting system with both ductility and high stiffness against lateral loads while also being repairable after a sever earthquake. For this purpose, the linked column frame system as a new structural system, in which short beams are placed between two close columns, is propsed. The proposed system is a dual system consisting of two parts: the primary lateral load-resisting system composed of linked columns and the secondary moment frame system, which are integrated together to resist lateral loads. These link beams, by providing high ductility capacity, were responsible for absorbing and dissipating energy, thereby significantly increasing the structure's capacity. Moreover, due to the replaceability of the connections, the structure also possesses the ability to quickly return to serviceability conditions after a sever earthquake. In the present research, performance of this system in controlling the vibration of buildings with irregular plan have been investigated. For this purpose, three irregular buildings in plan with a height of 3, 6 and 9-story have been designed as the basic models, then different models have been made by changing the configuration of the linked bays. According to the obtained results under nonlinear time history analysis, it is found that the average percentage reduction of the story's maximum displacement responses for 3-story building is 56%, 6-story building is 36%, and 9-story building with one more linked bay is 44%. • This manuscript presents the effect of linked column frame in controlling vibration of the irregular buildings in plan. • It was seen that until the target displacement of building, only the link beams yield and the moment beams remain elastic. • In this manuscript, the effects of linked bays different configurations on the building's vibration control are studied. [ABSTRACT FROM AUTHOR]

Featured Application: Results from this study indicate that in a 3D time history analysis, without considering the directionality of the records, the actual maximum displacements occur in a random direction and they are around 20% larger than those predicted in the principal axes of the structure, based on the current design practice. When the directivity effects are also considered in the analysis, the difference can increase up to 70% compared to the displacements predicted in the principal X and Y directions. This difference may be more significant for different types of structures, particularly irregular structures. These issues need to be considered in the seismic design and analysis of bridges. Inelastic dynamic analyses were carried out using 3D and 2D models to predict the mean seismic response of four-span reinforced concrete (RC) bridges considering directionality effects. Two averaging methods, including an advanced method considering displacement direction, were used for the prediction of the mean responses to account for different incident angles of ground motion records. A method was developed to predict the variability of the mean displacement predictions due to variability in the incident angles of the records for different averaging methods. When the concepts of averaging in different directions were used, significantly different predictions were obtained for the directionality effects. The accuracy of the results obtained using 2D and 3D analyses with and without the application of the combination rules for the prediction of the mean seismic demands considering the incident angle of the records was investigated. The predictions from different methods to account for the records incident angles were evaluated probabilistically. Recommendations were made for the use of the combination rules to account for the directivity effects of the records and to predict the actual maximum displacement, referred to as the maximum radial displacement. [ABSTRACT FROM AUTHOR]

Concentrically braced frames (CBFs) as one of well-known stiff and common lateral force resisting systems often show limited ductility capacity under severe earthquakes. This study proposes rocking zipper braced frame (RZBF) to improve the drift capacity of CBFs which is based on combination of rocking behavior and zipper columns. In the RZBF system, rocking behavior permit the braced frame to uplift during the earthquake and then restoring force induced through post-tensioned bars self-center the frame to its initial state. Also, zipper columns can decrease the concentration of damage by distributing the unbalance force at the mid bay over the frame's height. To assess the performance of RZBF, a comparison study is carried out considering CBF, rocking concentrically braced frame, zipper braced frame and RZBF. For this purpose, some frames structures are designed and nonlinear time history analysis conduct under a set of earthquake records. Seismic responses such as roof drift ratio, gap opening at the column-base interface, forces of top story braces and post-tensioned bars are taken into consideration. The results show that the proposed RZBF has better performance among the others and zipper columns can improve the behavior of rocking systems. [ABSTRACT FROM AUTHOR]

The effects of combinations of different types of irregularities have not been studied in details in the past and current seismic design codes do not address this issue appropriately. In this research, 76 regular and irregular bridges with irregularities in both superstructure and substructure were designed and evaluated to investigate the impact of combinations of irregularities on the seismic ductility demands. The irregularity parameters considered in this study include irregularities in span arrangement, different lengths of columns, different abutments support conditions and different stiffness of superstructure. The bridges were designed and checked according to AASHTO provisions. Inelastic time history analysis was conducted using OpenSees software and ductility demands in bridge columns for different bridge configurations were predicted. Predictions of ductility demands were based on the mean responses obtained using a number of ground motion records. Finally, the effect of considering displacement directions in predicting the mean bridge response (i.e., using different methods for predicting the mean response) for irregular and regular bridges was investigated. The results indicate that the combinations of irregularities can significantly increase the ductility demands in some cases compared to the case of regular bridges. [ABSTRACT FROM AUTHOR]

This paper presents a study on the behavior of an RC bridge under near-field and far-field ground motions. For this purpose, a dynamic nonlinear finite element time history analysis has been conducted. The near-field and far-field records are chosen pairwise from the same events which are fits to the seismic design of the bridge. In order to perform an accurate seismic evaluation, the model has been analyzed under two vertical and horizontal components of ground motions. Parameters of relative displacement, residual displacement, and maximum plastic strain have been considered and compared in terms of nearfield and far-field ground motions. In the following, in order to decrease the undesirable effects of near-field ground motions, a viscous damper is suggested and its effects have been studied. In this case, the results show that the near-field ground motions increase maximum relative and residual displacement respectively up to three and twice times. Significant seismic improvements were achieved by using viscous dampers on the bridge model. Somehow under the considered near-field ground motion, parameters of residual and relative displacement decrease dramatically even less than the model without damper under the far-field record of the same ground motion. [ABSTRACT FROM AUTHOR]

Pushover analysis has become an effective tool for seismic design of high-rise buildings under severe earthquakes. However, the applicability of traditional pushover analysis is often questioned for long-span structures due to their complex dynamic characteristics. In this paper, pushover analysis was adopted to determine the seismic behavior of a long-span steel truss structure under severe earthquakes. Load distributions were determined based on the fundamental modes for vertical and horizontal earthquakes respectively. Pushover curves were obtained by nonlinear static analysis. Target displacements were determined with capacity spectrum method. The maximum displacements and plastic hinge distributions determined by traditional pushover analysis agreed well with those by nonlinear time history analysis for both horizontal and vertical earthquake actions. It was then concluded that the seismic behavior of this kind of long-span steel truss structures can be evaluated by traditional pushover analysis accurately enough for practical design purpose. [ABSTRACT FROM AUTHOR]

Seismic responses of A-frame jumbo-size container cranes are comprehensively studied by exciting them as realistically as practical to evaluate the adequacy of the conventional static approach routinely used for their design. Multiple design earthquake time histories corresponding to the structure and site-specific earthquake design spectra corresponding to specific return periods are selected for the nonlinear time domain dynamic analyses. Cranes are considered to be in service (i.e., boom down), (2) at rest (i.e., boom up or stowed) with a friction contact support condition, and (3) at rest with tie-downs installed conditions. They are represented by finite elements, and appropriate dynamic properties are used following the practices commonly used in the profession. The seismic responses, in terms of base shear force, vertical wheel load, main member stress, portal drift ratio, and uplift, are estimated to define several performance objectives and their corresponding limits. Two container cranes with different dynamic properties and their responses are used to make the final recommendations. The in-service operating condition appears to be the most critical. The variation in the stress responses between the cranes in the at-rest and in-service conditions is about 17 %. However, the uplift in the stowed crane can be about 82 % higher than that in the in-service crane. The commonly used lateral load method using the static concept may not always be conservative, especially for the base shear force and vertical wheel load. For example, the method significantly underestimates the base shear force by about 52 % for the slender crane and 26 % for the relatively stiffer crane. Thus, the nonlinear time domain approach proposed here should always be used. It will satisfy the performance-based seismic design concept under development at present. [ABSTRACT FROM AUTHOR]

Experimental tests have shown that unreinforced masonry (URM) infill walls are affected by simultaneous loading in their in-plane and out-of-plane directions, but there have been few attempts to represent this interaction in nonlinear time history analysis of reinforced concrete (RC) buildings with URM infill walls. In this paper, a recently proposed macro-model that accounts for this interaction is applied to the seismic analysis of RC framed structures with URM infill walls representative of Mediterranean building stock and practices. Two RC framed structures that are representative of low and mid-rise residential buildings are analysed with a suite of a bidirectional ground motions, scaled to three different intensities. During the analyses, the in-plane/out-of-plane interaction is monitored, showing that cracking of the infills occurs predominantly by in-plane actions, while failure occurs due to a combination of in-plane and out-of-plane displacements, with the out-of-plane component usually playing the dominant role. Along the frame height, the bottom storeys are generally the most damaged, especially where thin infill walls are used. These results are consistent with observations of damage to URM infill walls in similar buildings during recent earthquakes. [ABSTRACT FROM AUTHOR]

The design and structural performance of a spent fuel storage system, which plays a role in storing irradiated and damaged fuel assemblies generated during the operation of a reactor, have been regarded as very important issues in relation to nuclear safety. The recent accident at the Fukushima Daiichi Nuclear Power Plant once again highlights the importance of the safe design of such a system. Thus, this paper proposes a new design concept of a spent fuel storage system composed of spent fuel storage racks (SFSR) and a support frame. The design of each SFSR is enhanced by increasing the natural cooling capacity of the pool water. The support frame is newly devised such that it physically prevents the overturning and sliding of racks and collisions among them during an earthquake event. In addition, to verify the structural integrity of the proposed design and evaluate its seismic margin, static analyses, response spectrum analyses and nonlinear time history analyses are conducted. The response spectrum analyses provide the maximum response of the structures during and after seismic events. The nonlinear time history analyses were carried out to predict contact sliding, rocking, twisting, and turning between the floor of the pool bottom and the support frame. The numerical results were analyzed based on the allowable code limits to assess the structural integrity. The possibility of a collision between the support frame and the adjacent pool wall is investigated. The seismic margin of the proposed design is studied within the seismic fragility analysis framework. The analysis results show that the maximum stress values of these SFSRs and their support frame under seismic loads are within the specified code limits. An impact between the support frame and the adjacent pool wall will not occur because the sliding distance calculated from the nonlinear time history analysis is less than the gap between the two elements. These results confirm that they cannot be overturned but will instead slide under an SSE event. Finally, the seismic fragility analysis results demonstrate that the designed spent fuel storage system has a sufficient seismic margin which exceeds the targeted seismic design level. [ABSTRACT FROM AUTHOR]

The present paper investigates the impact of nonlinear soil-foundation-structure-interaction (NLSFSI) on the damage response of 3D R/C buildings supported on different soil types with varying flexibility. The main goal of the paper is to present a first approach towards the possible quantitative differentiation, with respect to fixed base conditions, on the overall damage level when NLSFSI effects are accounted for. To accomplish this purpose nine buildings with various heights and structural systems are studied. For the foundation of the buildings two different soil types are considered, namely cohesive and frictional ones. Moreover, the soil flexibility is taken into account by using two different values of the soil's shear wave velocity. The buildings are subjected to 65 bidirectional earthquake records, for which nonlinear time history analyses are conducted. The accelerograms of each record are scaled to two different seismic intensities corresponding to certain performance levels using appropriate scaling factors. The damage state of the buildings is expressed through the maximum interstorey drift ratio. The assessment of the results revealed that the role of soil-foundation-structure-interaction (SFSI) is not necessarily beneficial. In order to assess the SFSI effects a number of parameters are important as the frequency content of the earthquake ground motion, the building's structural system, the foundation soil flexibility as well as the earthquake intensity. [ABSTRACT FROM AUTHOR]

Viscoelastic (VE) dampers, composed of VE layers sandwiched between relative rigid steel plates, have been widely used as dissipation devices to improve performance of structures under dynamic loads. Corresponding analytical and experimental investigations have been carried out by many scholars. However, most of VE dampers studied before are typically traditional dampers applied in regular structures. This paper introduces a new type of VE damper with strong nonlinearity used in the complex and irregular structure of Nanjing Dabaoen Temple. The new VE dampers show obvious nonlinear behavior, improved capacity of dissipation, and larger additional stiffness compared to the traditional ones. Nanjing Dabaoen Temple is a high-rise steel structure by use of 112 new VE dampers. To investigate dissipation characteristics and control effect of the VE dampers in the complex structure, we established a suitable finite element model using SAP2000 software in which the VE dampers were simulated by Maxwell and Wen models connected in parallel, and then nonlinear time history analysis is executed using seven ground motions of moderate earthquakes and three of major earthquakes. Analytical results indicate that control effect of the VE dampers on structural displacement is preferable to that on structural acceleration and shear force due to dampers' additional stiffness. In addition, owing to incremental deformation of VE dampers under major earthquakes, damping effect of the VE dampers on all structural responses under major earthquakes is more obvious than that under moderate earthquakes. Analytical methods and conclusions in this paper will provide significant reference for analysis, design, and application of complex high-rise structures added with VE dampers. [ABSTRACT FROM AUTHOR]

Vertical boundary elements (VBEs) play a key role in seismic performance of steel plate shear wall (SPSW) system and consume major part of the steel material in a structure. The different methods allowed by design standards for computing the force demands exerted on the VBEs yield in widely varied results and are evaluated in this study through a computer-based approach. After elaborating these methods, development of a versatile and user-friendly program is presented that implements various SPSW design algorithms. The program relies on component object model technology and interactively communicates with a component object model supporting program, etabs, as the analysis core. It also benefits from an object-oriented structure. At the next phase, the developed program is utilized to design SPSWs with different heights and extract VBE demands using different methods. Nonlinear time history analyses of the structures, performed in opensees software using a bin of seven ground motion records, have been ultimately used for assessing the precision of different demand estimation methods. The AISC 341-10 capacity-based design method was shown to provide overestimations that reached 90% and 1888%, respectively, for axial and flexural VBE demands of 17-story building. Lower overestimation ratios were found for shorter structures. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Rigid Wall Flexible roof Diaphragm (RWFD) buildings, commonly referred to as “big-box” buildings are the most prevalent type of construction for low-rise industrial and warehouse facilities in the United States (US). These buildings usually incorporate rigid-in plane concrete tilt-up walls and flexible wood roof diaphragms, which is a commonly seen construction technique in the Western United States. Due to their vulnerability in high seismic areas (e.g. California) observed in past earthquakes, an alternative design methodology was introduced in the FEMA P1026 document to account for the response of the flexible roof diaphragm. The FEMA P1026 design approach has been validated through numerical collapse assessment studies. In this study, the Performance-Based Earthquake Engineering framework, introduced by the Pacific Earthquake Engineering Research (PEER) center, is combined with Monte Carlo Simulation to evaluate, in a probabilistic sense, the earthquake-induced economic losses for these structures. The results are presented in terms of expected losses for two hazard intensities: Maximum Considered Earthquake (MCE) and Design Earthquake (DE), while loss disaggregation plots for collapse and no-collapse losses are also presented. The results demonstrate the ability of the FEMA P1026 design approach to reduce earthquake losses compared to current code-conforming RWFD buildings. Additionally, the results can provide damage and loss information for modeling of these types of buildings within a resilient community and other spatially focused analyses. [ABSTRACT FROM AUTHOR]

The paper investigates the structural performance of a seven-story reinforced concrete (RC) building that collapsed during the Van (Turkey) earthquake on October 23, 2011, using nonlinear static and dynamic methods. The selected RC building has two blocks and was designed according to the Turkish Earthquake Code (TEC) in 1975. The site investigation included sections and steel detailing and soil and concrete properties taken after the earthquake. The pushover and nonlinear time history analyses of the building were completed using the existing plan and test and observation data. It is concluded that the building collapses both analysis types. [ABSTRACT FROM AUTHOR]

A simple equation to estimate maximum beam ductility (μθb) of regular steel structures under ordinary (i.e. without near fault effect) earthquakes is proposed. This equation is a function of period, number of span, and global ductility. The proposed procedure enables the rapid assessment of beam plastic rotation of existing buildings and direct deformation-controlled seismic design of new ones. To prepare rational databank, a considerable number of steel MRFs with different geometric configurations were analyzed using nonlinear static and dynamic procedures (NSP and NDP). The NSP is used to evaluate the plastic hinge sequencing, force, and deformation demands over the height of frames. However, the NDP is applied to prepare databank of demands. The proposed relation is based on nonlinear regression of the results of thousands of NDPs. The result of the study shows that μθb is significantly higher than interstory and global ductility. Furthermore, the higher modes effect is completely sensible on increase of rotation ductility in upper stories of high-rise buildings. Finally, the ability of calculating μθb with acceptable precision is the advantage of the proposed relation. The result of the proposed relation, then, could be compared with acceptance criteria of FEMA356 and, therefore, the performance level would be indicated. [ABSTRACT FROM AUTHOR]

This paper presents an analytical study used to establish design factors for a new seismic design methodology for precast concrete floor diaphragms. The design factors include diaphragm force amplification factors Ψ and diaphragm shear overstrength factors Ωv. The Ψ factors are applied to the ASCE7-05 diaphragm design forces to produce diaphragm design strengths aligned to different performance targets. These performance targets are based on diaphragm detailing choices, and include: (i) elastic diaphragm behavior or (ii) limiting inelastic deformation demand on the diaphragm reinforcement (connectors between precast units or reinforcing bars in a topping slab) to within their reliable deformation capacities. The Ωv factors provide overstrength relative to the diaphragm bending strength for capacity protection against shear failure. The analytical study was performed by conducting nonlinear time history analyses of a simple evaluation structure, of which the dimensions and structural properties were varied. The analytical model used in the study is constructed and calibrated on the basis of extensive physical testing. The analytically obtained values of the diaphragm design factors are presented as functions of the geometric and structural properties of the building. The design factors presented here have been verified through evaluation of a set of realistic precast prototype structures. The diaphragm design methodology is currently in the codification process. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Diaphragm connector elements were developed for three-dimensional finite element models of precast concrete structures used in nonlinear time history analyses. The use of discrete elements for the diaphragm connectors permits the direct evaluation of local force and deformation demands, information needed in calibrating design factors for a new diaphragm seismic design methodology. This article describes the element formulation. The connector elements consist of assemblages of standard elements readily available in most finite element software libraries. The connector element calibration is based on full-scale testing of common precast diaphragm connectors. In these tests, the connector exhibited hysteretic pinching, stiffness/strength degradation, and slip mechanisms. The diaphragm connector elements were constructed to capture these behaviors to an accuracy sufficient for establishing viable design factors, while still appropriate for insertion into large degree-of-freedom models. The models are validated against the results of simulation-driven tests for critical precast diaphragm joints and a half-scale shake table test. [ABSTRACT FROM AUTHOR]

This article proposes a new approach to predict the plastic drifts and damage states of reinforced concrete frame type structures subjected to monotonic loading. The approach uses plastic energy demand graphs which are determined from nonlinear time history analyses. Plastic energy graphs are obtained by converting the hysteretic moment rotation relations of the structural members to the monotonic behavior. In the study, interstory drift ratio limits are determined from the seismic design codes and used to evaluate the structural damage states of the structures subjected to monotonic loading. The work done by the monotonic type external design loads are expressed by an equation. This plastic energy equation is solved by using the maximum plastic energy values obtained from the plastic energy demand graphs. Plastic design base rotations of the frames are obtained from the plastic energy equalities. Then the total drifts of the stories are determined and assessed by considering the interstory drift ratio limits in Vision 2000 document. Performance levels of the frame type structures may be predicted by comparison of the interstory drifts from the approach in the study with the code-based drift limits. Finally, the accuracy of the approach is evaluated by using the results of nonlinear time history analyses. The total drifts of the structures obtained from energy equalities within the study are checked by the drift results of the nonlinear time history analyses. [ABSTRACT FROM AUTHOR]

The global ductility parameter $$(\mu _{G})$$ , commonly used to represent the capacity of a structure to dissipate energy, and its effects, considered through the ductility reduction factor $$(R_{\upmu })$$ , are studied for buildings with moment resisting steel frames (MRSF) which are modeled as complex multi degree of freedom systems. Results indicate that the $$\mu _{G}$$ value of 4, commonly assumed, cannot be justified, a value between 2.5 and 3 is suggested. The ductility reduction factors associated to global response parameters may be quite different than those of local response parameters, showing the limitation of the commonly used equivalent lateral force procedure (ELFP). The ratio $$(Q)$$ of $$R_{\upmu }$$ to $$\mu _{G}$$ is larger for the models with spatial MRSF than for the models with perimeter MRSF since their ductility demands are smaller and/or their ductility reduction factors larger. According to the simplified Newmark and Hall procedure, the $$Q$$ ratio should be equal to unity for the structural models under consideration. Based on the results of this study, this ratio cannot be justified. The reason for this is that single degree of freedom systems were used to derive the mentioned simplified procedure, where higher mode and energy dissipation effects cannot be explicitly considered. A value of 0.5 is suggested for $$Q$$ for steel buildings with perimeter MRSF in the intermediate and long period regions. The findings of this paper are for the particular structural systems and models used in the study. Much more research is needed to reach more general conclusions. [ABSTRACT FROM AUTHOR]

In recent earthquakes, the observed collapses have been mainly attributed to inappropriate distributions of stiffness and strength of structural members which result from using inefficient seismic lateral load distribution pattern in design phase. Using nonlinear time history analysis under 88 strong ground motions, this paper investigates the seismic lateral load distribution pattern of 3-, 6-, 12- and 16-story buckling restrained steel braced frames, which have been increasingly used during the past decade. Through comparing analytical results with those predicted by IBC-2009 lateral load distribution equation, it can be concluded that except for low-rise structures, code pattern lateral load is quite different from analytical lateral load pattern in particular for taller structures. Therefore, code pattern lateral load would not necessarily lead to efficient distribution of strength and stiffness within the structure; consequently, the structure does not response in a predictable and desirable manner. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simplified models for masonry-infilled RC frames with damping systems were studied. [•] Conventional damping correction factors have significant errors for ductility demand. [•] The errors are more severe for intermediate deformations rather than extensive ones. [•] Equations estimating response reduced by supplemental viscous damping are proposed. [•] Proposed equations are useful for preliminary retrofit design of existing buildings. [Copyright &y& Elsevier]

SUMMARY The concentrically braced frame (CBF) structure is one of the most efficient steel structural systems to resist earthquakes. This system can dissipate energy during earthquakes through braces, which are expected to yield in tension and buckle in compression, while all other elements such as columns, beams and connections are expected to behave elastically. In this paper, the performance of single-storey CBFs is assessed with nonlinear time-history analysis, where a robust numerical model that simulates the behaviour of shake table tests is developed. The numerical model of the brace element used in the analysis was calibrated using data measured in physical tests on brace members subjected to cyclic loading. The model is then validated by comparing predictions from nonlinear time-history analysis to measured performance of brace members in full scale shake table tests. Furthermore, the sensitivity of the performance of the CBF to different earthquake ground motions is investigated by subjecting the CBF to eight ground motions that have been scaled to have similar displacement response spectra. The comparative assessments presented in this work indicate that these developed numerical models can accurately capture the salient features related to the seismic behaviour of CBFs. A good agreement is found between the performance of the numerical and physical models in terms of maximum displacement, base shear force, energy dissipated and the equivalent viscous damping. The energy dissipated and, more particular, the equivalent viscous damping, are important parameters required when developing an accurate displacement-based design methodology for CBFs subjected to earthquake loading. In this study, a relatively good prediction of the equivalent viscous damping is obtained from the numerical model when compared with data measured during the shake table tests. However, it was found that already established equations to determine the equivalent viscous damping of CBFs may give closer values to those obtained from the physical tests. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The global seismic response of 3- and 8-story eccentrically braced frames (EBFs), designed for western and eastern North American locations, is studied using nonlinear time history analysis. Analytical models were built in three computer programs. Similar maximum forces were obtained, but the inelastic deformation predictions at the element and global structural levels showed sensitivity to the modeling employed. This feature should be considered in seismic performance assessment or design. Current design methods failed to predict interstory drifts and plastic link rotations, but the study confirmed the strong correlation between the two parameters associated with rigid-plastic behavior. The influence of yielding and flexural buckling of frame members, other than the links on the global frame performance, was evaluated using the OpenSees model. It was confirmed that the flexural yielding of outer beams is acceptable for EBFs with short and intermediate links, if the combined flexural strength of the braces and beams is at least equal to the expected end-link moments and the braces can resist the associated axial force-bending moment demand. Inelastic response of braces and columns in such frames did not negatively impact the overall frame behavior. [ABSTRACT FROM AUTHOR]

Abstract: In Latin America there is an urgent need for housing; thus, during the last few years a relevant number of mid-height buildings (usually, up to five stories) with thin RC shear–walls have been constructed for low-cost dwellings in Bolivia, Colombia, Ecuador, Mexico, Peru, Venezuela, and other countries located in seismic-prone regions. These walls are 10cm thick and their reinforcement consists mainly of a single layer of welded wire mesh. This construction technology offers two main advantages: economy and rapidity of construction. These buildings do not fulfill the international seismic codes but some national regulations are less demanding, not preventing the use of thin bearing walls. These buildings might be vulnerable to earthquakes because of their low ductility, the insufficiency of the experimental information, the absence of observed damages and, in some cases, poor construction quality. This work describes the initial steps of a wider research aiming at providing reliable seismic design guidelines for thin-wall buildings; the initial objectives are analyzing the seismic performance of these buildings, proposing preliminary design criteria and identifying further research needs. This research focuses on buildings located in Peru, being representative of the situations in the other countries. The vulnerability is numerically evaluated by push-over and nonlinear time history analyses; the structural parameters are obtained from available testing information. The obtained results show that the seismic strength of the analyzed buildings is insufficient; however, minor changes in the structural design might improve significantly their seismic performance. Cheap and easy-to-implement design recommendations are issued. [Copyright &y& Elsevier]

Motivated by the seismic damage observed to reinforced concrete (RC) frame structures during the Wenchuan earthquake, the effect of infill walls on the seismic performance of a RC frame is studied in this paper. Infill walls, especially those made of masonry, offer some amount of stiffness and strength. Therefore, the effect of infill walls should be considered during the design of RC frames. In this study, an analysis of the recorded ground motion in the Wenchuan earthquake is performed. Then, a numerical model is developed to simulate the infill walls. Finally, nonlinear dynamic analysis is carried out on a RC frame with and without infill walls, respectively, by using CANNY software. Through a comparative analysis, the following conclusions can be drawn. The failure mode of the frame with infill walls is in accordance with the seismic damage failure pattern, which is strong beam and weak column mode. This indicates that the infill walls change the failure pattern of the frame, and it is necessary to consider them in the seismic design of the RC frame. The numerical model presented in this paper can effectively simulate the effect of infill walls on the RC frame. [ABSTRACT FROM AUTHOR]

The proposal lateral load pattern for pushover analysis is given in two forms for symmetric concrete buildings: 1-(X/H) 0.5 for low-rise and mid-rise buildings, 2- Sin(ΠX/H) for high-rise buildings. These two forms give more realistic results as compared to conventional load patterns such as triangular and uniform load patterns. The assumed buildings of 4, 8, 12, 16, 20 and 30 story concrete buildings are special moment frame which have been designed according to 2800 standard. Then using conventional load patterns and proposal load patterns, the pushover analysis has been done and results have been compared with the outcomes of nonlinear time history analysis. Results show the accuracy of proposed load pattern in comparing to the load patterns proposed by standards such as FEMA356. [ABSTRACT FROM AUTHOR]

The concept of base isolation is a century old, but application to civil engineering structures has only occurred over the last several decades. Application to light-frame wood buildings in North America has been virtually non existent with one notable exception. This article quantitatively examines issues associated with application of base isolation in light-frame wood building systems including: (1) constructability issues related to ensuring sufficient in-plane floor diaphragm stiffness to transfer shear from the superstructure to the isolation system; (2) evaluation of experimental seismic performance of a half-scale base-isolated light-frame wood building; and (3) development of a displacement-based seismic design method and numerical model and their comparison with experimental results. The results of the study demonstrate that friction pendulum system (FPS) bearings offer a technically viable passive seismic protection system for light-frame wood buildings in high seismic zones. Specifically, the amount and method of stiffening the floor diaphragm is not unreasonable, given that the inter-story drift and accelerations at the upper level of the tested building were very low, thus resulting in the expectation of virtually no structural, non structural, or contents damage in low-rise wood frame buildings. The nonlinear dynamic model was able to replicate both the isolation layer and superstructure movement with good accuracy. The displacement-based design method was proven to be a viable tool to estimate the inter-story drift of the superstructure. These tools further underscore the potential of applying base isolation systems for application to North America's largest building type. [ABSTRACT FROM AUTHOR]

• 1232 nonlinear dynamic (time history) analyses are performed using 56 different building pairs. • Minimum required separation distances of adjacent buildings are investigated. • The distances are compared with minimum requirements of codes, provisions and proposed methods. • Two different simple approaches are proposed to estimate the seismic gap distances. • The first approach requires linear static analysis of the buildings while the second simplified approach does not need any analysis. This study aims to investigate the determination of seismic separation gap of adjacent low and mid-rise reinforced concrete (RC) buildings with no structural irregularity using nonlinear time history analysis. The low and mid-rise RC buildings were reflected using 3, 4, 5, 6, 7, 8, 9 and 10-story buildings designed per 2018 Turkish Building Earthquake Code (TBEC-2018). Beam and column elements are modeled as nonlinear frame elements with lumped plasticity by defining plastic hinges at both ends of beams and columns. The adjacent three-dimensional (3D) building models are connected to each other by link elements at the floor levels. 1232 nonlinear dynamic (time history) analyses were performed using 56 different building pairs and 11 different earthquake record pairs (22 records) compatible with TBEC-2018 to obtain the required seismic gap distances. The distances necessary to avoid pounding obtained from the analyses were compared with the minimum seismic gap requirements of the current earthquake codes, provisions (Eurocode-8, ASCE 7-16 and TBEC-2018) and several proposed methods (ABS, SRSS and DDC) in the literature. The outcomes indicate that the ASCE 7-16 and EC-8 significantly overestimate the required seismic gap distances for the buildings with similar dynamic characteristics while they provide reasonable estimates for the buildings with significantly different dynamic characteristics. However, the TBEC-2018 requirements are insufficient for the neighboring building period ratios greater than 1.25. Although both the ASCE 7-16 and EC-8 requirements are acceptable for the design of new buildings as being on safe side, they are not useful for the evaluation of existing buildings. Two different simple approaches were proposed to estimate the required seismic gap distances between neighboring buildings. The first approach requires linear static analysis of the buildings subjected to the reduced seismic design forces while the second simplified approach does not need any analysis. The proposed equations in this study are simple and useful for the evaluation of existing low and mid-rise RC buildings with no structural irregularity. Besides, their estimates are acceptable for the design purposes. [ABSTRACT FROM AUTHOR]

Normally, Laminated Rubber Bearing Pads (LRBPs) are directly placed between girders and piers and their role is to provide the bridge span with horizontal movement, and to transmit the gravity loads from the deck to the piers. Although not designed for seismic loads, they can act as a fuse, partially isolating the substructure from the superstructure and keeping the piers intact during earthquakes. However, recent investigations show that large relative displacement of superstructure against substructure caused by sliding at bearing (sliding between girders and LRBPs) can cause expansion joint failure or even bridge span collapse. Accordingly, proper restrainers should be selected to prevent large displacement. Among all types of restrainers, viscous dampers as passive energy dissipation devices have shown a great capacity in damping earthquake energy. This study investigates the effectiveness of a VD-LRBP system, a viscous damper in conjunction with LRBPs, in dissipating energy and reducing the displacement of the superstructure with reference to the substructure caused by sliding at bearing during a seismic event. A Finite Element (FE) model was first developed and validated using available experimental and numerical results. With the validated model, a 3D Nonlinear Time History Analysis (NTHA) was conducted on a reinforced concrete bridge model under various records of earthquakes using OpenSees, an open-source finite element software. The relative displacement histories were recorded for the bridge in two cases: 1- with only LRBPs and 2- with viscous dampers and LRBPs (VD-LRBP system). The results of this study show that applying viscous dampers can reduce the relative displacement of the superstructure with reference to the substructure for up to 60 percent. As importantly, it can also reduce the residual displacement after the earthquake to near zero. [ABSTRACT FROM AUTHOR]

In this article, effects of ductility level and connection type on seismic responses of fixed-base and base-isolated buildings with steel moment-resisting frames are evaluated using nonlinear time history analyses. In a comparative assessment of responses, a set of twenty-four models is seismically designed, including 3- and 9-story base-isolated and conventional buildings, with ordinary (OMF), intermediate (IMF), and special (SMF) levels of ductility. Each model presents two types of connections, including WUF-W and RBS. Three-dimensional models for all buildings are created in OpenSees software, and seismic responses are assessed for two earthquake scenarios. Seismic responses of buildings, such as peak floor acceleration, peak floor shear force, peak story drift, and residual and maximum displacement of isolators are calculated and analyzed. The results indicate that the ductility levels and connection types significantly affect seismic responses of base-isolated and fixed-based buildings. The RBS connection reduces the peak drift demands compared to the WUF-W connection, and the difference increases with the increment of building's height. The SMF superstructure decreases the peak floor acceleration and peak shear force compared to the IMF and OMF ones. Moreover, the peak floor drift ratio of the OMF superstructures is larger than the IMF and SMF in base-isolated buildings. The maximum difference is computed by about 80% between the OMF and SMF superstructures. • Effects of level of ductility and connection type on seismic responses of isolated moment-resisting steel frame buildings. • Comparative response evaluation of base-isolated and conventional steel moment-resisting frames. • Considering different hazard levels and buildings height in assessment of base-isolated buildings. • Implement and validating 3D models of RBS and WUF-W connections in open source software. [ABSTRACT FROM AUTHOR]