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Summary: The selection of representative input ground motions (IGMs) is important for a proper nonlinear response time history analysis (NLRHA) of modern structures. The prevailing IGM selection procedure requires that the response spectra of selected ground motions are matched with the code‐specified design spectra, while the effect of the frequency contents combination in the time domain on the multimode interactions is not considered. Ignoring the effect of the frequency contents combination in the time domain of IGMs may cause significant variations in the analysis results for selected IGMs, although they are matched to the same design spectrum. In this paper, a modal‐based ground motion selection (MGMS) procedure is proposed as a supplement to spectrum matching‐based IGM selection procedures for selecting proper IGMs that can sufficiently induce the multimode interactions. In the proposed procedure, three equivalent single‐degree‐of‐freedom (ESDOF) systems are developed by pushover analysis. NLRHA is then conducted for these ESDOF systems with a set of 20 seed IGMs chosen by the spectrum‐matching–based selection procedure. Finally, seven IGMs are selected from the seed IGMs for NLRHA in the full structural model. To verify MGMS, seismic demands of high‐rise buildings were computed by NLRHA with seven MGMS‐selected IGMs, seven IGMs with closest spectrum matching, and groups of seven randomly selected IGMs derived from three different sets of 20 seed IGMs. The computed seismic demands with MGMS‐IGMs show very good agreement with the mean demands determined using the whole set of seed IGMs, while the deviation is much lesser compared with those groups of randomly selected IGMs. [ABSTRACT FROM AUTHOR]

The present paper deals with the analytical investigation of representative planar masonry-infilled reinforced concrete (MIRC) frames for seismic fragility, performance and demand. The study includes the effect of various patterns of layout for infills panels along the height of reinforced concrete frames. The analytical investigation has been done using non-linear dynamic time-history analysis under collection of forty SAC near-field ground motions using rational hysteretic models for structural components; the results are presented in terms of parameters such as peak inter-storey drift, residual drift and damage index. The outcomes of study are used to develop seismic fragility curves in probabilistic terms for the generic medium-rise MIRC frames. The developed fragility curves can be useful tools in predicting the life and economic losses in the future seismic event. In the current study, efforts are also made to develop curves demonstrating seismic performance and seismic demand for representative MIRC frames. [ABSTRACT FROM AUTHOR]

• The filtering action of five frames on a suspended ceiling has been analyzed. • Floor response spectra have been numerically defined for five case-study buildings. • Linear and non-linear analyses on suspended ceiling numerical models are performed. • Results obtained from linear and non-linear analyses are compared and discussed. In recent years, scientific interest for the study of Non-Structural Elements (NSE) has significantly increased and the importance of the seismic safety of these elements has become a widely discussed topic. Several technologies able to guarantee the seismic safety of NSE were created. In particular the sector of suspended ceiling has seen the development of different systems for achieving this purpose. Specific internal joints between profiles, perimeter brackets and bracing systems have been created to realize "anti-seismic" suspended ceilings. Several shake table tests, also defined qualifying tests, have been performed to analyze the behaviour of these systems. This work presents new original studies on seismic behaviour of suspended ceilings with an experimental fragility approach. Recently cyclic quasi-static tests have been realized at the University of Padova by means of a specifically developed experimental setup. First, experimental results were processed to define the hysteretic capacity curves of a typical metal T-Grid suspended ceiling. Then, these curves were exploited by means of numerical analyses to determine the elastic and inelastic response of the suspended ceiling installed at various levels of five multi-storey frames characterized by different vibration periods. Linear dynamic analyses of the frames subjected to 7 spectra-compatible artificial seismic signals were performed to obtain floor acceleration signals and spectra. Then three alternative numerical approaches were employed to define the seismic demand on the suspended ceiling. Using a displacement-based approach, capacity curves and elastic floor spectra were compared in the ADRS (Acceleration Displacement Response Spectrum) domain to evaluate the elastic displacements and accelerations of the suspended ceiling (Spectral Analysis). Also, Linear and Non-Linear Time-History analyses of the NSE were performed according to a cascade approach. The comparison of the seismic demands resulting from elastic, inelastic and spectral analyses is reported in the paper for each of the frames. [ABSTRACT FROM AUTHOR]

An important number of short and medium span bridges in the world were built before 1970. Particularly, in Mexico, the typical structural configuration of these bridges is a simple supported concrete deck on reinforced concrete beams, for two lane roads. Just a few of them have been designed for seismic actions and during their life several increments of the live load amplitudes have been presented. This paper comments the most common procedures to assess the seismic vulnerability of these structures and the techniques used to rehabilitate and retrofit them. Special emphasis is devoted to the importance of the substructure type on the expected damage limit states of the bridges. [ABSTRACT FROM AUTHOR]

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

Given the inherent uncertainty in seismic response, seismic performance assessment of structures should be conducted within a probabilistic framework. One of the most efficient probabilistic approaches is the IM-based probabilistic seismic demand analysis (PSDA). In this method, an intermediate parameter, which is known as the intensity measure (IM), is used to decouple the seismological and structural uncertainties. Two intensity measures of IM oc and (S a) rms were introduced for near-fault pulse-like records in previous research. These IMs are defined based on the optimal combination of spectral displacements and root-mean-square of spectral accelerations at effective periods, respectively. In this research, to consider the efficiency of these IMs under a set of 90 records that contains both near-fault and ordinary ground motion records, we conducted the PSDA for five moment-resisting frames with the number of stories ranges from 3 to 15. Results show that IM oc and the advanced intensity measure of IM 1 I & 2 E exhibit the highest correlation with the expected damage for the most frames, especially moderate and relatively long-period ones. IM 1 I & 2 E is defined based on the inelastic spectral displacement with the higher-mode modification. In addition, comparison of the drift hazard curve of different frames shows that by increasing the structural height, the amount of drift hazard will decrease. However, comparing to other cases, the reduction rate of drift hazard along with increasing the number of stories from three to six is significant. [ABSTRACT FROM AUTHOR]

The objective of this paper was to evaluate the influence of initial flaws in the beam-column connections on the seismic performance of steel frame structures. The finite element models were constructed with different initial flaw lengths by ABAQUS. The initial flaw length was 0, 8, and 16 mm, respectively. The dynamic elastic-plastic time history analysis and the pushover analysis were conducted to obtain the probabilistic characteristics of seismic demand and seismic capacity. Seismic demands are quantified in terms of the maximum drift angle (RDA) and the displacement ductility ratio μ d . Moreover, the peak ground acceleration (PGA) was used for the pushover analysis. Formulas considering the influence of initial flaws on failure probability of a structure were derived for each length using different design basic acceleration of ground motion. The fragility curves were further constructed based on the data of seismic demand and capacity. The results show that the fragility of steel frame structures is similar across different seismic demand parameters. In addition, the analyses of fragility curves obviously indicate that the seismic fragility of steel frame structures increases as flaw length increases. Finally, the fragility of steel frame structures with initial flaws is consistent using different design basic acceleration of ground motion. [ABSTRACT FROM AUTHOR]

Quantifying the higher-mode effects on the seismic demands of buildings may benefit not only the awareness of characteristics of the seismic responses of buildings, but also the development of rapid/simplified methods for the seismic assessment of buildings. This study proposes an approach that is applicable for quantifying the aforementioned effects, covering the full range of building heights and deformation types. The vehicle used in this proposed approach is the generalized building model, which has been modified from the conventional cantilever beam model. In addition to building height and deformation type, the strength ratio of each vibration mode and the site class of buildings are the parameters considered in this study. The higher-mode effects on floor displacements, inter-story drift ratios, floor accelerations, and base shears with relation to the aforementioned parameters are investigated. Finally, the proposed approach is verified via the investigation of the higher-mode effects of a 20-story exemplar building. [ABSTRACT FROM AUTHOR]

In order to estimate the seismic demand by using the nonlinear static procedure, different approximate methods have been developed. One of the most useful methods is called displacement coefficient method (DCM), which is based on some modification factors. One of these coefficients denoted C1, concerns the inelastic deformation ratio and usually depends on either the yield-strength reduction factor or the ductility factor. In general the evaluation of the inelastic deformation ratio is based on the response of single degree of freedom (SDOF) systems, where the response of the structure is mainly controlled by the fundamental mode, knowing that the inelastic deformation ratio will not capture the contribution of higher modes in the overall structural response. A developed theoretical approach with the aim of estimating the inelastic deformation ratio for structures, considering contribution of higher modes of vibration, is introduced. In this assessment, the normalized yield strength coefficient (η) and the post-to-preyield stiffness ratio (α) are key factors. The results are compared to the uncoupled modal response history analysis (UMRHA) procedure and some existing formulations for a nine story building subjected to the El Centro 1940 ground motion. It appears that the new theoretical approach leads to enough accurate estimation of the inelastic deformation ratio compared to the UMRHA one. [ABSTRACT FROM AUTHOR]

This study investigated the seismic demand of continuity plates (CP) in Special Moment Frames (SMFs), including built-up I-shape beams. Six reference experiments for SMF connections were considered, including beams with unequal depths on both sides of the column, to compare the seismic demand for CP with the corresponding value of the AISC code formula. The effects of beam shape properties, connection type, shear strain of the panel zone (PZ), different construction detailing and straight/inclined CP in dual/trapezoidal PZ were included in this study. In addition, companion analytical studies were performed to evaluate CP seismic demand. The results of the experiments and numerical analyses showed that the AISC code underestimates seismic demand for CP in joints with beams having sizes outside the geometries of hot-rolled structural sections. Poor seismic performance of the code-designed CP led to premature yielding and out-of-plane local buckling of CP, which were observed in the reference experiments and confirmed by numerical models. Finally, an equation for CP seismic demand was developed based on findings of this research. It was demonstrated that the proposed seismic demand met the required seismic criteria using this equation, and it also kept CP within the safe structural margins. [ABSTRACT FROM AUTHOR]

Taiwan lies in the circum-Pacific earthquake zone. The seabed soil of offshore wind farms in Taiwan is mainly composed of loose silty sand and soft, low-plasticity clay. The seismic demand for offshore wind turbines has been given by the local code. Ground-motion analysis is required to consider the site effects of the soil liquefaction potential evaluation and the foundation design of offshore wind turbines. However, the depth of the engineering bedrock for ground motion analysis is not presented in the local code. In this study, we develop a three-dimensional ground model of an offshore wind farm in the Changhua area, through use of collected in situ borehole and PS (P wave (compression) and S (shear) wave velocities) logging test data. The engineering bedrock is the sediment at the depth where the average shear wave velocity of soil within 30 m, Vsd30, is larger than 360 m/s. In this ground model, the shear wave velocity of each type of soil is quantified using the seismic empirical formulation developed in this study. The results indicate that the engineering bedrock lies at least 49.5–83 m beneath the seabed at the Changhua offshore wind farm. Based on these findings, it is recommended that drilling more than 100 m below the seabed be done to obtain shear wave velocity data for a ground response analysis of the seismic force assessment of offshore wind farm foundation designs.

• Improved Machine-Learning (ML) techniques were used to predict Maximum Interstory Drift Ratio (IDR max) and Residual Interstory Drift Ratio (RIDR) of 384 Special Moment-Resisting Frames (SMRFs) considering Soil-Structure Interaction (SSI). • Developed ML algorithms were trained to build a surrogate model for seismic vulnerability and risk assessment of SMRFs. • The performance indicators showed that prediction models had higher performance with acceptable accuracy compared to actual values. • The curve plot ability of methods for estimating Median of IDA curve (IDA Med) and Seismic Failure Probability curve (SFP Curve) was confirmed. Nowadays, due to improvements in seismic codes and computational devices, retrofitting buildings is an important topic, in which, permanent deformation of buildings, known as Residual Interstory Drift Ratio (RIDR), plays a crucial role. To provide an accurate yet reliable prediction model, 32 improved Machine Learning (ML) algorithms were considered using the Python software to investigate the best method for estimating Maximum Interstory Drift Ratio (IDR max) and RIDR of 384 Steel Moment-Resisting Frames (SMRFs). In addition, the curve plot ability of methods was investigated to provide an estimation of Median of IDA curve (IDA Med) and Seismic Failure Probability curve (SFP Curve) considering Soil-Structure Interaction (SSI) effects. It is noteworthy that ML algorithms were improved with a pipeline-based hyper-parameters Fine-Tuning (FT) method followed by forward and backward feature selection methodologies to avoid overfitting and data leakage issues. The improved methods were evaluated to find the best prediction model regarding seismic demands. The results show that proposed methods have higher prediction accuracy and curve fitting ability (i.e. more than 95%) that can be used to estimate IDA Med and SFP Curve of a structure to accelerate the seismic risk assessment. A prediction tool is introduced to use the methods of this study for estimating abovementioned seismic demands. [ABSTRACT FROM AUTHOR]

Users of structural analysis software commonly apply the Rayleigh damping model as a default option for analyzing of structures. When a distributed plasticity model is utilized in the numerical models, the structural responses are not found to be sensitive to the damping models; even the Rayleigh damping model leads to the reasonable seismic results. Moreover, the lower bounds and upper bounds of the demands are sensitive to the type of damping model. In this paper, the effects of viscous damping models in the seismic demands of moment and concentrically braced steel frames are carefully investigated. For this purpose, seven viscous damping models are considered using the different forms of the stiffness matrices in the finite-element modeling. The declared structural systems are modeled against several strong ground motion records in OpenSees environment. Then, the seismic responses such as drifts, accelerations and base shears are compared for the aforementioned damping models. The main result of this research is that applying Rayleigh damping model, as a default option for structural analyzing software will produce underestimated responses. In addition, it is shown that no matter which type of stiffness matrix is used in the stiffness proportional damping model. Therefore, using initial stiffness matrix is cost efficient, particularly in time-consuming nonlinear analyses. [ABSTRACT FROM AUTHOR]

As an alternative to conventional seismic force resisting systems, controlled rocking steel braced frames (CRSBFs) can effectively eliminate permanent structural damage after earthquakes. Together with the rocking action in the braced frame, post-tensioning (PT) elements and fuse members are used to provide self-centering and energy dissipation, respectively. This study firstly aims to assess the influence of design parameters related to the fuse and PT materials on the seismic response of CRSBFs. These factors include the yield strength, initial stiffness, and strain hardening ratio of the fuse, the initial force and modulus of elasticity of the PT strands, and the gravity load on the rocking column. Additionally, different analysis cases are considered to include the effects of frame aspect ratio and earthquake intensity level. Nonlinear response history analyses are performed with factor combinations generated using a design of experiment methodology. The second goal of the study is focused on optimizing the seismic response of CRSBFs with respect to the influential factors identified in the sensitivity analyses. Using a response surface methodology and desirability approach, multiple-response optimization is applied to determine the design variable values needed to simultaneously minimize the maximum transient and residual roof drift ratio and peak floor acceleration. Among other results, it is found that the fuse strain hardening ratio and PT strand modulus of elasticity do not significantly influence the seismic response demands in CRSBFs. The results of the multi-response optimization demonstrate that the initial PT force is most useful for minimizing all three seismic response demand parameters. [ABSTRACT FROM AUTHOR]

Determination of appropriate seismic demand is important for deriving reliable seismic forces for use in structural design and vulnerability assessment. Demand can be defined by either probabilistic or deterministic approaches depending on the use of the assessment. The use of probabilistic or deterministic approaches depends on the level of the assessment since deterministic can mostly be used for single structures whereas probabilistic for city or country level assessment. This paper presents demand characterization which is based on results of existing seismic hazard studies and local tectonic features around Islamabad-Rawalpindi region (study region) in Pakistan. Existing seismic zoning maps and recent probabilistic seismic hazard studies are reviewed, and the findings are used to quantify and compare the demand for a typical low-rise reinforced concrete building. As another option, deterministic demand is defined through spectra using suitable attenuation relationship which is assessed and validated using the Kashmir earthquake and other similar earthquakes data. Deterministic spectra for study region are generated by considering the critical local tectonic features. Federal Emergency Management Agency (FEMA 356) approach is used for smoothening of deterministic spectra, and the new spectral corner periods are calculated. [ABSTRACT FROM AUTHOR]

The seismic reliability of a bridge system is significantly affected by the dependence among typical bridge components. This study demonstrates the process of using a copula technique to describe the nonlinear dependence among component seismic demands isolated from their marginal probability distributions. A suite of 100 bridge-ground motion samples were developed with the Latin hypercube sampling approach and bin approach. Based on the incremental dynamic analysis, the tail dependence among component seismic demands at different intensity levels was analyzed with the best-fitting copula function selected by the minimum distance method. In the longitudinal direction, the dependence increased first and then decreased with the ground motion intensity, while the dependence slightly decreased in the transverse direction. At low-intensity levels, the upper tail dependence among components was strong in both directions. At high-intensity levels, the upper and lower tail dependences were weak in the longitudinal direction, while the upper and lower tail dependences were strong in the transverse direction. Compared to the linear correlation coefficient, the copula technique provides an efficient way to describe the tail dependence among component seismic demands and can be used extensively in the seismic reliability analysis of the bridge system. [ABSTRACT FROM AUTHOR]

This paper evaluates the accuracy of the Modified Fish-Bone (MFB) model for estimating the maximum inter-story drift ratio of irregular moment resisting frame (MRF) structures. To make this model applicable to irregular MRF structures, some modifications are made to the MFB formula. In order to evaluate the accuracy of the MFB model, several irregular frames with different types of irregularities are considered when subjected to different ground motions with different intensities. A local and a global error measure are defined and they are calculated for different frame models subjected to different earthquake records. The effects of different irregularities, ductility demand and frame height on the accuracy of the MFB model are investigated. Based on the results obtained from this evaluation, two simple and effective approaches are suggested to improve the MFB models. [ABSTRACT FROM AUTHOR]

Although many advanced pushover-based models have been developed for the fast prediction of seismic demand of tall buildings, most of these models are only focused on the analysis of moment-resisting frame structures. The seismic behaviour of dual wall-frame structures is very different from that of a moment-resisting frame structure, as structural walls and frames have totally different deflected shapes under the action of lateral loading, thus resulting in a strong structural interaction between the two load-resisting systems. There are few pushover-based models, in which the different structural responses between structural walls and frame structures are included. In this paper, modification of the spectrum-based pushover analysis (SPA) is presented to consider the structural interaction between shear walls and frames and the different damage modes of a dual wall-frame structure. In the modified spectrum-based pushover analysis (MSPA) method, the force vectors applied to the structure and formulations for determining the total roof displacement are changed to take the wall-frame interaction into account. The applicability and accuracy of MSPA in predicting the seismic demand of dual wall-frame structures are investigated through a case study of four 25-storey reinforced concrete wall-frame structures subjected to different levels of the input ground motions. Comparison of the results from nonlinear response time history analysis (NLRHA), several advanced pushover-based models and the proposed MSPA method has been made. It is seen that only MSPA can predict the distribution of the seismic demand along the height of buildings well, and the seismic demand from MSPA shows very good agreement with that from NLRHA. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper the effects of aerodynamic damping and earthquake loads on the dynamic response of flexible‐based wind turbines are studied. A numerical analysis framework (NAF) is developed and applied. NAF is based on a user‐compiled module that is developed for the purposes of the present paper and is fully coupled with an open source tool. The accuracy of the developed NAF is validated through comparisons with predictions that are calculated with the use of different numerical analysis methods and tools. The results indicate that the presence of the aerodynamic loads due to the reduction of the maximum displacement of the tower attributed to the dissipation of earthquake excitation energy in fore‐aft direction. Emergency shutdown triggered by strong earthquakes results to a rapid change of aerodynamic damping, resulting to short‐term instability of the wind turbine. After shutdown of the wind turbine, enhanced dynamic response is observed. For the case where the wind turbine is parked, the maxima displacement and acceleration of tower‐top increase linearly with the peak ground acceleration. With the use of the least‐square method a dimensionless slope of tower‐top displacements is presented representing the seismic response coefficient of tower that can be used to estimate the tower‐top acceleration demand. Moreover, on the basis of the seismic response coefficient, an improved model for the evaluation of load design demand is proposed. This model can provide accurate predictions. [ABSTRACT FROM AUTHOR]

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Liquid storage tanks are critical facilities in petroleum depots that must remain intact and functional following an earthquake. The seismic fragility function is a useful tool for quantifying structural vulnerability. This study accordingly explored the effects of different uncertainties on the seismic fragility of a case study floating-roof storage tank by applying an appropriate approach to seismic fragility analysis. First, an orthogonal sensitivity analysis was performed using a finite element model to determine the random model variables most affecting the seismic responses of the storage tank. Considering the different sources of uncertainty, seismic fragility was subsequently evaluated by combining a cloud analysis with model sampling. Then, the seismic fragility curves of the storage tank system were developed by studying the correlations among multiple failure modes. The results indicate that the computational requirements of the present method were significantly less demanding than those of direct Monte Carlo simulation. Geometric uncertainty was found to exert the greatest impact on the seismic responses. The maximum difference among the fragility function parameters for different sources of uncertainty was 28.9%. The damage assessment of the tank system was shown to be more reasonable when considering the correlations among multiple failure modes. This analysis technique can accordingly provide practical guidance for the seismic design of vertical floating-roof storage tanks. • A seismic fragility analysis procedure was proposed considering different sources of uncertainty. • Sensitivity analysis of seismic responses for floating-roof storage tank was performed. • Difference of fragility curves was calculated considering three sources of uncertainty. • Seismic fragilities of critical failure modes and the whole system were obtained. [ABSTRACT FROM AUTHOR]

In this paper, probabilistic seismic demand analysis is adopted to investigate the seismic fragility of a certain typical irregular highway bridge in the Chinese western mountainous areas. Considering the uncertainties of ground motion and structural parameters, the sample library for seismic fragility analysis is constructed aided by Latin hypercube sampling method, and the nonlinear time history analysis for each sample is implemented to achieve the structural dynamic response under the seismic excitation. Moreover, the curvature ductility ratio and the relative displacement are regarded as the damage indexes for pier and bearing, respectively. Furthermore, the fragility nephograms for the whole piers and fragility curves for various critical sections with different damage states are obtained based on a lognormal distribution assumption and the reliability theory. Finally, the bridge system fragility curves are generated through the first-order reliability analysis method. Fragility curves obtained from the above proposed technique can be used to evaluate the seismic performance of irregular bridges, and it can lay a basis for post-earthquake damage assessment.

The complex characteristics of explosion load as well as its increasingly high frequency in the civil environment highlight the need to develop models representing the behavior of structures under blast load. This work presents a probabilistic study of the performance of framed reinforced concrete buildings designed according to the current Italian NTC18 and European EC8 technical standards. First, a simplified single degree of freedom model representing the structural system under blast load has been developed. Then, a probabilistic approach based on Monte Carlo simulation analysis highlighted the influence of seismic demand on the behavior of Reinforced Concrete RC buildings subjected to blast load.

Modern seismic codes rely on performance-based seismic design methodology which requires from the structures to withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation for various inelastic spectra. The purpose is to investigate the ratio between the inelastic and elastic maximum lateral displacement demands. Three options are considered in the present work to express the inelastic response spectra in terms of the ductility demand, yield strength reduction factor and inelastic deformation ratio. This later, a new non dimensional parameter called inelastic deformation ratio (Cη), depends on the natural period (T), the post-to-preyield stiffness ratio (a), the normalized yield strength coefficient (t) and the peak ground acceleration (PGA). The inelastic deformation ratio (Cη), is not evaluated for a fixed ductility ratio or for a fixed strength reduction factor. Though the ductility demand and yield strength reduction factor differ greatly for given ranges of T and r“ they take close values for systems for any T value when η > 1. It confirms also previous studies stating that they take unity value for periods T ≥ 1sec. [ABSTRACT FROM AUTHOR]

In seismic codes, the acceleration demand of nonstructural components is commonly expressed in terms of floor response spectra and estimated by means of simple predictive equations. By using the latter, response-history analysis of the structure is not required, being floor spectra calculated directly from the peak ground acceleration expected at the site. The price for this simplicity in the method used for the estimation of floor spectra is the generally poor approximation of the obtained predictions. Codes’ equations, in fact, do not explicitly account for important factors influencing floor spectra, such as the contribution of the higher modes of vibration of the structure and the actual value of the nonstructural components’ damping ratio. Alternative spectrum-to-spectrum methods for direct generation of floor spectra have been proposed, which include these factors and improve the accuracy of the predictions. Different approaches have been used and several methods developed. Despite large research effort, however, a comparative evaluation of the currently available proposals is still lacking. The objective of this paper is to fill this gap, by reviewing selected proposals representative of practice-oriented spectrum-to-spectrum methods. A case study consisting in a six-story frame is analyzed and predictions obtained with the investigated methods are compared with exact floor spectra derived from time-history analyses of the structure, as well as spectra calculated using the Eurocode 8 equation. [ABSTRACT FROM AUTHOR]

Response parameters used to estimate nonstructural damage differ depending on whether deformation-sensitive or acceleration-sensitive components are considered. In the latter case, seismic demand is usually represented through floor spectra, that is response spectra in terms of pseudo-acceleration, which are calculated at the floor levels of the structure where the nonstructural components are attached to. Objective of this paper is to present a new spectrum-to-spectrum method for calculating floor acceleration spectra, which is able to explicitly account for epistemic uncertainties in the modal properties of the supporting structure. By using this method, effects on the spectra of possible variations from nominal values of the periods of vibration of the structure can be estimated. The method derives from the extension of closed-form equations recently proposed by the authors to predict uniform hazard floor acceleration spectra. These equations are built to rigorously account for the input ground motion uncertainty, that is the record-to-record variability of the nonstructural response. In order to evaluate the proposed method, comparisons with exact spectra obtained from a standard probabilistic seismic demand analysis, as well as spectra calculated using the Eurocode 8 equation, are finally shown. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A quick and accurate estimate of the seismic demand of tall buildings is one of the important issues in the seismic evaluation of buildings. Nonlinear response time history analysis method (NLRHA) is considered as the most accurate and rigorous method, but the computation requirement of NLRHA for tall buildings can be complex and very time-consuming. Whereas the conventional pushover procedure is not capable of reasonably estimating seismic demand of mid and high rise-buildings, due to the oversimplification of conventional pushover approaches and the complexity of seismic performance of buildings. In this paper, a quick, yet effective, method of analysis, named as a spectrum-based pushover analysis (SPA) method, is proposed to estimate the seismic demand of tall buildings. In the SPA procedure, the very complex and complicated dynamic coupling effect of modes of the nonlinear seismic performance of a building is simplified, and the consecutive pushover technique is adopted to consider the simplified coupling effect. Comparison of the results obtained from NLRHA, the modal pushover analysis method, the consecutive modal pushover analysis method and the proposed SPA method is made. It is seen that the SPA method predicted the seismic demand of buildings well, including the inter-storey drift ratio and hinge plastic rotation, which are very close to those of NLRHA. Owing to its accuracy, effectiveness, and spectrum-based calculation procedure, the proposed SPA procedure is considered to be a very promising tool for predicting the seismic demand of tall buildings. [ABSTRACT FROM AUTHOR]

Pultruded FRP (Fiber Reinforced Polymer) material can be considered as a structural material for civil engineering applications when it guarantees structural reliability and higher efficiency under different loading conditions, dead loads, live loads, wind and seismic actions, during the serviceability state. The overall structural behaviour in static field of FRP members, columns-beams joints and connections and framed structures are well known, while the dynamic response is not yet widely investigated. Through the analysis of modal shapes, resonance frequencies and damping ratios of different pultruded members (beams, columns, beam-column joints) and structures the performance relationships in the dynamic field have been defined. As shown by the experimental and analytical results the dynamic properties of pultruded FRP material are characterized by high periods of vibration, low frequencies and a spontaneous dissipative capacity of the seismic action due to its low mass; in the design approach this latter aspect has to be balanced by the high deformability. The analyses allow to define the performance laws of structural elements made of pultruded FRP material that are preparatory for the final recommendation in the seismic design criteria of all-FRP structure addressed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents two analysis methods for the in-plane seismic response of steel multitiered braced frames (MT-BFs) with three or more tiers: (1) a substructuring technique; and (2) a stiffness analysis method. Both methods are consistent with the 2010 AISC Seismic Provisions and have been developed to estimate column flexural demands and tier drifts to prevent column instability and to mitigate concentration of tier drifts as well as premature brace failure under seismic loading. Both methods account for the progression of brace tension yielding along the frame height as observed in MT-BFs. The substructuring technique is simpler and is limited to regular frames, as it assumes a predefined yielding sequence. The stiffness analysis-based method is more rigorous and can predict the actual frame nonlinear response. It can be applied to both regular and irregular MT-BF configurations. The application of the methods is illustrated for two five-tiered special concentrically braced frame examples. Nonlinear response history analysis is performed to validate the proposed methods for the frames studied. [ABSTRACT FROM AUTHOR]

Masonry infill walls are unavoidable parts of any building to create a separation between internal space and external environment. In general, there are some prevalent openings in the infill wall due to functional needs, architectural considerations or aesthetic concerns. In current design practice, the strength and stiffness contribution of infill walls is not considered. However, the presence of infill walls may decisively influence the seismic response of structures subjected to earthquake loads and cause a different behavior from that predicted for a bare frame. Furthermore, partial openings in the masonry infill wall are significant parameter affecting the seismic behavior of infilled frames thereby decreasing the lateral stiffness and strength. The possible effects of openings in the infill wall on seismic behavior of RC frames is analytically studied by means of pushover analysis of several bare, partially and fully infilled frames having different bay and story numbers. The stiffness loss due to partial opening is introduced by the stiffness reduction factors which are developed from finite element analysis of frames considering frameinfill interaction. Pushover curves of frames are plotted and the maximum base shear forces, the yield displacement, the yield base shear force coefficient, the displacement demand, interstory drift ratios and the distribution of story shear forces are determined. The comparison of parameters both in terms of seismic demand and capacity indicates that partial openings decisively influences the nonlinear behavior of RC frames and cause a different behavior from that predicted for a bare frame or fully infilled frame. [ABSTRACT FROM AUTHOR]