Effects Of Ground Motion Duration Research Articles

Impact of ground motion duration on seismic performance of buckling restrained braced frames

Buckling restrained braced frames (BRBFs) are commonly employed as seismic lateral force resisting system due to their high stiffness and energy dissipation capacity. However, under long-duration strong earthquakes, buckling-constrained braces are susceptible to fracture due to low-cycle fatigue. Previous studies evaluating their seismic performance have not considered the impact of earthquake duration on the results. This study evaluates the impact of ground motion duration on the seismic performance of BRBFs. By employing 44 pairs of spectrally equivalent ground motions with varying durations, the impact of ground motion duration is studied independently from other effects arising from ground motion amplitude and acceleration spectral shape. Nonlinear numerical models considering low-cycle fracture of buckling restrained braces are developed for 4-, 8-, and 12-story archetypes. The effects of ground motion duration on the seismic performance of BRBFs are examined using standard performance and collapse-assessment procedures. The results indicate that under seismic excitations not exceeding the maximum considered earthquake level, ground motion duration does not significantly affect the structural maximum interstory drift, but longer duration generally results in larger cumulative plastic deformation for the buckling restrained brace. Meanwhile, ground motion duration has a significant impact on the results of collapse risk evaluation. In addition, using combined duration- and spectrum-related intensity measure can better evaluate the damage potential of ground motion.

Quasi-static loading procedure of CFS framed shear walls considering ground motion duration

Cold-formed steel (CFS) structures framed with CFS framed shear walls exhibit clear characteristics of strength and stiffness degradation during seismic events, thus the influence of ground motion duration on their seismic responses should not be ignored. The purpose of this study is to construct a quasi-static loading procedure for CFS framed shear walls considering the effect of ground motion duration, which can help to acquire accurate shear performance of the walls and lay a foundation for evaluating the actual seismic performance of the structures. The main research contents and results are as follows: (1) sixty ground motions were selected and adjusted to be spectrally equivalent records, which ensured that the effect of the ground motion duration could be decoupled; (2) nonlinear time-history analysis of eight CFS framed shear wall models were performed, whereafter, considering the influences of both structural responses and the input energy of ground motions, a determination method for the number of loading cycles of the quasi-static loading procedure was proposed, and a prediction model for the number of loading cycles was established; (3) the influence of the amplitude distribution of the quasi-static loading procedure was analysed, and a value range of the amplitude distribution parameter was suggested. Finally, a method to construct the quasi-static loading procedure for CFS framed shear walls was formed and verified.

Effect of ground motion duration on inelastic displacement ratio of SDOF systems

Effect of ground motion duration on inelastic displacement ratio of SDOF systems

Effects of Ground Motion Duration on Seismic Damage of Bridge Isolation Bearings Based on Friction SDOF System

It is generally perceived that ground motion duration has an effect on structural seismic response and damage, despite the neglect of current seismic codes. Based on friction SDOF systems, this paper investigates the duration effect of ground motions on seismic responses and damage of sliding bearings. Ground motions are divided into long-duration (LD) and short-duration (SD) cases, taking the significant duration of 25[Formula: see text]s as the boundary. Each case consists of natural records and spectrally equivalent artificial ground motions to decouple duration from other earthquake characteristics. Results from response history analyses implicate that duration has hardly any effect on seismic responses of the system exhibiting an approximate linear elasticity. Nevertheless, for systems with distinct frictional nonlinearity, selecting LD ground motions as seismic inputs usually leads to a conservative result. By performing incremental dynamic analysis (IDA), nonlinear systems in SD cases bear 10% higher damage risk than those in LD cases without considering the influence of temperature rise. The same is true for systems with a small friction coefficient of 0.005 when earthquakes are in the low intensity range. It was also found that damage exceedance probabilities of these small friction coefficient systems are almost unaffected by the duration as the peak ground acceleration increases to more than 0.6[Formula: see text][Formula: see text]. When the effect of temperature rise caused by friction is considered, the damage exceedance probability in LD cases is higher than SD cases. The damage probability of friction SDOF system under LD earthquake will be underestimated without considering the influence of temperature rise.

Effect of Multi-Components Strong Motion Duration on Seismic Performance of High CFRDs Based on Fragility Analysis

ABSTRACT This paper investigates the influence of multi-components strong motion duration on seismic performance of high concrete-faced rockfill dams (CFRDs) by fragility analysis based on the method of incremental dynamic analysis (IDA). The contributions of all compositions of earthquake excitations are considered by the definition of integrated duration based on the concept of significant duration. The nonlinear finite element model of a 2D 200-m-high CFRD is established as a case study and the vertical and horizontal displacements are selected as damage measures. Fragility curves and probabilities of two sets of 23 and 25 spectrally equivalent as-recorded bi-directional long-duration and short-duration motions are determined under different failure grades and intensities. The results show that the duration of vertical component has a certain effect on correction between strong motion duration and deformation of the dam and fragility analysis indicates that the ground motions with long duration can make more risk of failure of high CFRDs than short duration motions. Therefore, the seismic performance of high CFRDs will be reformed by taking the effect of ground motion duration into seismic design and risk assessment consideration.

Effects of Ground Motion Duration on the Seismic Performance of a Two-Storey Balloon-Type CLT Building

The effects of long duration ground motions on the seismic performance of a newly constructed two-storey balloon-type cross-laminated timber (CLT) building located in Vancouver, Canada, was studied. A three-dimensional numerical model of the building was developed in OpenSees. The connection and shear wall models were validated with test data. Twenty-four pairs of long and short duration records with approximately the same amplitude, frequency content, and rate of energy build-up were used for nonlinear dynamic analyses. Fragility curves were developed based on the results of incremental dynamic analysis to assess the building’s collapse capacity. At design intensity level, ground motion duration was shown not to be a critical factor as the difference in inter-storey drift ratio between the two sets of records was negligible. However, due to the larger number of inelastic cycles, the long duration motions increased the median probability of collapse by 9% when compared with the short duration motions. Further research is required to evaluate the duration effects on taller and platform-type CLT buildings.

Influence of ground motion duration on seismic performance of RC frame isolated by high damping rubber bearings

The high damping rubber bearing (HDRB) is an advanced seismic isolation component currently used in building structures with sound energy dissipation capacity. This study examines the effects of ground motion duration on the seismic performance of reinforced concrete frame isolated by HDRBs. The effect of ground motion duration is isolated from other effects due to ground motion amplitude and acceleration spectral shape by using 44 pairs of short-duration and long-duration spectrally equivalent ground motions. Nonlinear time-history analyses are conducted on a base-isolated building using HDRBs. The numerical analyses considered the calibrated parameters of the HDRB model based on experimental data. The stiffness degradation of the HDRBs due to Mullins’ effect under cyclic loading is accounted into the numerical model. The influence of ground motion duration is evaluated by comparing the seismic responses of the isolator components and the superstructure. The results indicate that the ground motion duration generates a significant influence on seismic responses. The influence varies as the ground motion intensity changes. The stiffness degradation of the HDRB becomes evident with the increase of the earthquake intensity, and the effect of such degradation on the structural responses is more significant when under long-duration ground motions.

Seismic fragility analysis of CFT frames with buckling-restrained braces and steel braces under long- and short-duration ground motions

This study presents the seismic behaviour and the effect of ground motion duration on the probabilistic seismic fragility for the concrete-filled steel tube (CFT) frames with buckling-restrained braces (BRB-CFTF) and conventional steel braces (SB-CFTF). The nine-storey BRB-CFTF and SB-CFTF prototype structures were designed based on the performance-based plastic design method. One scaled single-storey single-bay BRB-CFTF and one buckling-restrained brace (BRB) extracted from the prototype structure were cyclically tested and analyzed. Finite element (FE) models of the two braced frame structures were developed and validated by available test results. The results obtained from nonlinear dynamic analyses showed that the designed two structures achieved expected performance objectives in terms of the inter-storey drift and member energy-dissipating demand. The selection of engineering demand parameter (EDP) quantifying structural response and intensity measure (IM) representing ground motion hazard level was performed to determine optimal indicators for identifying duration effect prior to establishment of fragility curves. The results indicated that the overall damage index (ODI) as the EDP can clearly distinguish the influence of duration effect on structural cumulative damage. The optimal IM relative to ODI was believed to be the combined duration- and spectrum-related INP-D, because of desirable balance among the efficiency, sufficiency and scaling robustness. The BRB-CFTF and SB-CFTF structures were more vulnerable to all limit states under long-duration ground motions than those under short-duration ones at the same seismic hazard level, and the probability of exceedance for a given INP-D of the SB-CFTF was generally larger than that of the BRB-CFTF. The influence of ground motion duration on the cumulative damage for the BRB-CFTF and SB-CFTF structures is suggested to be considered in structural seismic design and analysis.

Effects of long duration earthquakes on the interaction of inertial and liquefaction-induced kinematic demands on pile-supported wharves

Nonlinear dynamic analyses were performed to evaluate the effects of ground motion duration on the dynamic response of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations. The numerical model was first calibrated using recorded data from a well-instrumented centrifuge test, after which incremental dynamic analyses were conducted using a suite of spectrally matched motions with different durations. The nonlinear dynamic analyses were performed to evaluated three loading scenarios: combined effects of inertial loads from the wharf deck and kinematic loads from ground deformations, deck inertial loads only in the absence of liquefaction (with minimal kinematic loads), and kinematic loads only in the absence of deck mass inertia. The analysis results were evaluated to provide insights on the relative contribution of inertial and kinematic demands on the response of the wharf with respect to motion duration. It was found that the contribution of peak inertial and peak kinematic loads to the maximum total demand increases only slightly with motion duration and intensity. The response of the wharf was found to be primarily governed by kinematic demands when subjected to long-duration motions for the type of foundation analyzed in this study which is commonly used in the port industry.

An Analytical Method for Elastic Seismic Response of Structures Considering the Effect of Ground Motion Duration

The response to earthquake ground motion is composed of three basic elements, namely, amplitude, frequency, and duration. The seismic response of a structure is controlled by the particular combination of these three elements. The seismic response spectra reflect the earthquake ground motion’s frequency-domain features and provide the maximum response amplitude of a single-degree-of-freedom system to a given earthquake ground motion but do not consider the duration factor. However, the analysis of post-earthquake damage shows that the seismic response duration has a strong impact on the damage to structures. Therefore, it is necessary to develop a simple and practical analytical method to account for the seismic response duration. The present study was conducted based on the response spectra theory. We introduce an analytical method of elastic seismic response, which considers its duration by adding the time-domain dimension of earthquakes. The time-domain spectral matrix is used to solve the time-dependent seismic response through the vibration mode decomposition method. The time-domain vibration mode decomposition reaction spectrum not only takes into account the maximum seismic reaction of each vibration mode but also considers the seismic reaction of different vibration modes occurring at the same time, at each moment. The dynamic time duration of the structure’s seismic reaction is quantified by the time-domain seismic reaction spectrum to obtain a more accurate analysis method for the seismic reaction of the structure.

Improvement of energy damage index bounds for circular reinforced concrete bridge piers under dynamic analysis

AbstractAn improvement of energy damage index bounds for circular reinforced concrete (RC) bridge piers under dynamic time history analysis is presented in this study. The energy‐based damage model has been defined as a ratio of hysteresis dissipation energy to input energy for performance evaluation of circular RC bridge pier systems. Based on the energy balance equation, the mentioned damage model can consider all energy aspects, including kinematic energy, strain energy, hysteresis energy, damping energy, and input energy. Additionally, the effect of ground motion duration, amplitude, and frequency content is appropriately considered in this damage model. For this purpose, the damage limit state bounds for two empirical RC bridge piers are statistically evaluated under the 22 far‐field ground motion sets of FEMA‐P695 for simulation of strong‐earthquake motion and consideration of record‐to‐record variability. First of all, appropriate validation between empirical and numerical fiber element models is implemented to estimate accurate results. Then, damage data at each performance level through strain limit states are collected by developing energy incremental dynamic analysis curves. Statistical results on collected damage data are presented in all performance levels to determine damage index bounds by the convolution of fragility curve distribution. Hence, five damage index bounds at five performance‐level are suggested, including very slight, slight, moderate, extensive, and complete damage. Finally, the effect of the other damping ratios on the modified energy damage model is carried out by using the beta coefficient in the formula. In the end, the modified energy damage model is compared with other damage indices to investigate the efficiency of the proposed damage model.

Impact of ground motion duration on concrete shear walls reinforced with different types of shape memory alloy rebars

The impact of ground motion duration often arises when investigating buildings’ performance in regions susceptible to strong earthquakes, where reinforced concrete (RC) shear walls are typically used as a lateral force-resisting system. Although the seismic performance of these reinforced walls has been improved by the use of self-centering devices and materials, the influence of ground motion duration on self-centering RC walls is not yet well understood. This paper, therefore, examines the effect of ground motion duration on seismic performance and the damage scheme of the self-centering shear wall reinforced with three different types of superelastic shape memory alloy (SE-SMA) in the plastic hinge. A ten-story case study building was analyzed and designed according to the current ASCE 7-16 and ACI-318 practice codes. The maximum inter-story drift ratios (IDR), residual drift ratios (RIDR), shear forces, bending moments, material damages, and collapse margin ratios were examined. The results indicate that IDR and RIDR significantly increased as ground motion duration increased. Meanwhile, the shear forces increased by about 24% on average, which induced only a 6% increase in the bending moments. It was also observed that ground motion duration significantly influenced the scaling factor required to reach the collapse level. Among the examined SE-SMA RC walls, the results indicate that Cu-based SMA RC wall exhibits superior performance in terms of IDR, RIDR, shear forces, and bending moments and performs fairly well in terms of material damage and collapse margin ratio compared to other SMA RC walls. Thus, using Cu-based SMA material in seismically active regions prone to short and long duration ground motions is generally recommended.

Role of strong motion duration on seismic responses of high concrete faced rockfill dams

This study investigates the role of strong seismic motions on the dynamic responses of high CFRDs through elastoplastic analysis. Damage measures (DMs) including vertical and horizontal displacements, plastic shear strain, as well as a face-slab damage index are selected to gauge the deformation, stability of the dam slope and the anti-seepage ability of the face slab, respectively. The selected DMs are key to the safety of high CFRDs. A group of 35 as-recorded ground motions with a wide range of durations are modified to conform to a 5% damped target spectrum are used as input motions for dynamic analysis. A comprehensive understanding of the effects of ground motion duration is obtained through a tri-fold analysis of the ground motion records, the nonlinear dynamic response of CFRDs and the statistics of the results. The definitions of significant duration, bracketed duration and uniform duration, each with consideration to two different thresholds, are selected to characterize strong motion durations. The results suggests that significant duration is the most useful indicator for seismic assessment of high CFRDs and for evaluating the effects of the duration of an earthquake on the integrity of high CFRDs.

Quantifying the effects of long‐duration earthquake ground motions on the financial losses of steel moment resisting frame buildings of varying design risk category

AbstractThis paper investigates the effect of ground motion duration on risks to life safety and costs associated with low‐to‐medium‐rise reference steel moment resisting frame buildings classified as risk categories II and IV. The ductile steel resisting frame buildings are designed in the downtown area of Seattle, Washington, where long‐duration earthquakes are more likely to occur. For this purpose, two sets of spectrally equivalent long‐ and short‐duration ground motions are employed to perform nonlinear dynamic analyses for two‐dimensional nonlinear structural models of the steel frame buildings. It is shown that the consideration of the effects of long‐duration ground motion significantly increases the collapse risk of the steel frame buildings, by a factor of about 5 on average, in comparison to the short‐duration set. The destabilizing P‐Delta effects are found to increasingly aggravate the influence of long‐duration earthquakes on the risk to life safety of the medium‐rise steel frame buildings. For frequently occurring ground motion intensities, reparable damage to nonstructural components holds most of the total expected economic seismic loss in the reference buildings, regardless of the ground motion set and assigned risk category. The influence of ground motion duration on the economic seismic loss in the steel frame buildings starts to become important for strong ground motions associated with design‐level earthquakes or higher.

Influence of ground motion duration and isolation bearings on the seismic response of base-isolated bridges

This study investigates the effect of ground motion duration on the seismic response of base-isolated bridges. Three different isolation bearings are considered in this study, such as lead rubber bearing (LRB), Shape memory alloy wire-based lead rubber bearing (SLRB), and Friction pendulum system (FPS). Each isolation system is designed to provide a similar isolation period so that the seismic response is comparable. Using 20 long-duration motions and 20 spectrally matched short-duration records; the seismic performance of the base-isolated bridges is evaluated and compared using nonlinear time history analyses. Response parameters considered for this study are the base shear in the piers, the acceleration of the bridge deck, maximum and residual displacement of the isolation bearings as well as the energy dissipation capacity. The results indicate that the long-duration motions cause more damage to different bridge components as compared to the short-duration motions in-terms of higher deck acceleration, pier base shear, and residual isolator displacement. It is also observed that ground motions having similar magnitude with different significant durations can significantly affect the isolator as well as the bridge response.

Performance of seismically substandard bridge reinforced concrete columns subjected to subduction and crustal earthquakes

The recent occurrence of highly damaging, long-duration subduction earthquakes in Chile (Maule, 2010) and Japan (Tohoku, 2011), has highlighted the importance of better understanding the effects of ground motion duration on structural performance. With that aim, an experimental program was conducted to study the effects of ground motion duration exhibited by subduction earthquakes on the performance of reinforced concrete bridge columns. The results of shake table experiments on large-scale circular reinforced concrete columns that were subjected to subduction and crustal ground motions are presented. The specimens were chosen to reflect common reinforced concrete bridge columns, which were built prior to mid-1970 in the Pacific Northwest of the United States and thereby designed and constructed using seismic procedures currently considered substandard. The results showed that ground motion duration can affect the displacement capacity and influence the failure mode of these types of bridge columns. Despite achieving similar levels of deformations, more damage was recorded in the specimens subjected to subduction ground motions as compared to crustal. This increased damage was confirmed with visual observations as well as calculated cumulative displacement ductility for each specimen. Measured material strains are also presented and compared to strain limits used in other literature for two-level performance criteria. The results have shown that subduction ground motions can impose higher material strains and result in reinforcement bar buckling that is not necessarily achieved under similar displacement demands from crustal ground motions.

Effects of ground motion duration on the seismic damage to and collapse capacity of a mid-rise woodframe building

This paper studies the seismic performance of a six-story mid-rise woodframe building under long duration ground motions. The prototype structure was designed by using a performance-based seismic design (PBSD) approach and tested on a shake table at full-scale as part of the NEESWood Project. A three-dimensional finite element model of the structure was developed using the Timber3D program and validated using the shake table test data. Two sets of short and long duration records that had approximately the same response spectra were used for nonlinear dynamic analyses. Fragility curves developed by incremental dynamic analysis (IDA) showed the median collapse capacity of the structure was reduced by 18% for long duration motions compared to the capacity for short duration motions. At the maximum considered earthquake (MCE) intensity level, the estimated median Park and Ang damage index of the structure for long duration motions was increased by 36%.

Effect of Ground Motion Duration on Reinforced Concrete Shear Wall Buildings

This paper investigates the effect of earthquake ground motion duration on the design and collapse risk of reinforced concrete shear wall buildings from 6 to 30 stories. Both design and collapse levels of shaking were considered through nonlinear incremental dynamic analysis. At the design level of shaking, it was found that (1) maximum interstory drifts were increased as ground motion duration increased (from <20 s to 35–150 s of strong shaking), though not enough to flag the designs as unacceptable; (2) story forces and moments were not significantly affected; and (3) energy demands were greatly increased by motion duration. When the records were scaled until collapse level, it was found that (1) the median collapse scaling level was greatly impacted by duration, and the median collapse shaking level was almost 20% higher on average when considering shorter records; and (2) long duration records produced both larger probabilities of collapse at the design shaking level and lower collapse margin ratios compared with spectrally equivalent short duration records.

Influence of earthquake duration on the response of steel moment frames

The influence of ground motion duration on the seismic response of steel moment frames is examined is this paper, with due consideration for cyclic degradation effects. A set of 77 spectrally equivalent pairs of short and long records is utilised in detailed nonlinear dynamic assessments in order to isolate the effects of ground motion duration. The influence of duration is firstly evaluated considering degrading and non-degrading idealised bilinear SDOF systems, for various levels of lateral strength representing practical ranges encountered in design. Subsequently, a sensitivity assessment focusing on the main parameters affecting the response of hysteretic degrading models is carried out through comparative incremental dynamic analysis. Whilst the effect of duration becomes more pronounced with the increase in lateral strength demands, particularly when approaching collapse, the cyclic degradation rate is shown to play a significant role even at lower levels typically associated with design. The performance of EC8-compliant frames indicates a higher probability of collapse when long-duration ground motion records are used, with a typical reduction of about 20% in the collapse capacity, in comparison with short-duration cases. The influence of duration is also examined through collapse capacity spectra, based on the seismic performance of 50 steel moment frames, which show that considerable reduction in the structural collapse capacity of structural systems occurs when relatively long duration records are adopted, for a wide range of dynamic characteristics. This becomes particularly evident in the case of buildings with relatively significant cyclic deterioration rates, where collapse capacity reductions up to 40% due to the influence of earthquake duration are obtained.

Effects of Ground Motion Duration on the Seismic Performance and Collapse Rate of Light-Frame Wood Houses

AbstractThis paper studies the effects of long duration ground motion on three conventional low-rise light-frame wood houses with different sheathing configurations. These are two-story residential...