Influence Of Ground Motion Duration Research Articles

Shake table test and seismic fragility analysis of transmission tower-line system considering duration effect

Although extensive attention has been devoted to the influence of ground motion duration on the seismic performance of various structures, the integration of the duration effect into the seismic analysis of transmission tower-line systems (TTLSs) has been rarely studied, leading to a lack of understanding regarding the relationship between the ground motion duration and the seismic response of TTLSs. This paper aims to quantify the duration effect on the structural performance and seismic fragility of a TTLS through shake table tests and numerical simulations. To achieve this goal, a reduced-scale experimental model of a TTLS is carefully designed and fabricated, and a group of ground motions with contrasting durations is chosen using a spectral matching method. Subsequently, shake table tests are conducted to examine the duration effect on the seismic responses of the TTLS. The recorded data indicates that long-duration ground motions (LDGMs) significantly amplify the seismic responses and have the potential to degrade the structural performance. Furthermore, a validated finite element model of the TTLS is employed to compute its nonlinear responses from elastic behavior to complete plasticity utilizing incremental dynamic analysis. Probabilistic assessments are also conducted to investigate the seismic fragility and loss of the TTLS. The findings reveal higher damage probabilities and more severe losses caused by LDGMs, emphasizing the importance of considering the duration effect in the seismic performance assessment of TTLSs. This investigation contributes to a meaningful exploration for reliably assessing the seismic capacity of TTLSs while accounting for the duration effects.

Mitigating ground motion duration impact on steel moment-resisting frames using viscous dampers

This paper explores the significant influence of ground motion duration on the seismic performance of steel moment resisting frames. It demonstrates that during long-duration strong earthquakes, the structural response of such frames can be substantially larger than under short-duration ground motions. To address this challenge, viscous dampers, known for their stable hysteretic behavior and resistance to degradation under cyclic loading, are introduced as a retrofitting solution. To evaluate the effectiveness of viscous dampers, incremental dynamic analysis was conducted on three prototype steel moment-resisting frames of varying heights, both before and after retrofitting with viscous dampers. A total of 44 pairs of short-duration and long-duration spectrum-matched ground motions were employed as seismic inputs to isolate the effects of seismic motion duration from those arising from seismic amplitude and acceleration spectral shape. The findings underscore the potential of viscous dampers to significantly enhance the seismic performance of steel moment-resisting frames. Furthermore, these dampers effectively mitigate the impact of ground motion duration, reducing the uncertainty in structural response and facilitating more accurate evaluations of seismic performance.

Statistical investigation of the influence of ground motion duration on concrete gravity dam responses by proposing a quantitative index

This study aims to investigate the influence of ground motion duration on the seismic performance of concrete gravity dams seeking a quantitative correlation between ground motion durations and structural responses at several seismic intensity levels. In this regard, the Koyna gravity dam, located in India, is selected as the case study. In order to analyze the cumulative damage of the dam body, incremental dynamic analysis with 30 earthquake records with a broad range of durations has been implemented. All selected ground motion records have been spectrally matched to a target spectrum to isolate the contribution of duration from the effects of other ground motion parameters. The first mode spectral acceleration of the structure is considered the intensity measure, and the relative crest displacement and damage dissipation energy are chosen as the damage measure in this paper. Unlike previous studies in this field which are based on central measures of responses such as absolute mean value, in this study confidence intervals of the mean value of responses have been calculated in order to reach a quantitative relationship considering the uncertainty of results. Also, a duration influence index is developed. The obtained results revealed that there is a positive correlation between the ground motion duration and the cumulative damage of the concrete gravity dams so that long-duration motions can cause about 25% higher responses in relative crest displacement and about 70% higher responses in damage dissipation energy in comparison to short-duration ground motions at the same intensity.

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.

The influence of ground motion duration on the energy based assessment of buildings with infill walls

Infill walls are often used in buildings to divide the residential area in order to meet the architectural requirements and are considered as non-bearing structural elements. In some buildings, infill walls are not used in the frames of the ground floors for commercial or other architectural purposes. Thus, vertical infill wall discontinuity is formed and it appears as an irregularity by earthquake regulations. At the same time, this situation has caused damage to the structures in some earthquakes. Nowadays, traditional seismic design based on strength and resistance is considered not an adequate way to design structures under earthquake effects. Besides, the role of ground motion duration on the seismic performance of building structures has been subject of research recently. One of the methods of defining damage in earthquake resistant design is the energy approach. For this purpose, in this study, the effect of infill walls on the seismic assessment of structures exposed to short and long duration ground motions was performed on dissipated seismic energy approach. Nonlinear time history analyses were performed in two cases, fully infilled and infilled except for the ground floor. Classification of ground motion durations is based on a threshold of 25 s of significant duration (D5-95), and ground motions were evaluated as two different recording pairs of short and long duration. Using spectrally matched short and long duration earthquake records, nonlinear time history analyses were performed for building models and the results were evaluated over hysteretic energy. The analyses showed that the hysteretic energy demands depend on both the ground motion duration and the infill wall placement in the building.

Influence of ground motion duration on seismic behavior of RC bridge piers: The role of low-cycle fatigue damage of reinforcing bars

This paper assesses the influence of ground motion duration on seismic behavior of reinforced concrete (RC) bridge piers using spectrally equivalent short- and long-duration ground motions. Special attention is paid to the role of low-cycle fatigue damage of reinforcing bars. To this end, an experimentally validated nonlinear fiber-based beam-column element considering buckling and low-cycle fatigue of longitudinal bars is adopted for nonlinear dynamic analyses and fragility modeling. An advanced material level damage index is used to account for both the maximum response (strain damage) and cumulative damage (low-cycle fatigue damage of longitudinal bars). The dynamic analysis results indicate that the strain damage is the major failure mechanism for RC bridge piers under short-duration ground motions. Under long-duration ground motions, by contrast, the strain damage is prominent at the early excitation stage, while the low-cycle fatigue damage may dominate the late excitation stage. In particular, the role of low-cycle fatigue is more prominent for RC bridges against long-duration ground motions with significant durations beyond 50 s and peak ground velocities over 30 cm/s. The fragility analysis demonstrates that, ignoring the low-cycle fatigue damage of longitudinal bars will obviously underestimate the seismic fragility of RC bridge piers under long-duration ground motion, and the influences is more significant at more severe damage states. Therefore, the low-cycle fatigue damage of reinforcing bars is one of the main failure modes of RC bridge piers under long-duration ground motion, and should be considered in the seismic design,

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.

Influence of ground motion duration on the seismic vulnerability of aging highway bridges

Despite the potential of long duration earthquakes in subduction zones, little attention has been paid on seismic vulnerability assessment of highway bridges that are simultaneously undergoing prolonged corrosion deterioration. Consequently, this study presents a framework for considering the joint impact of ground motion duration and chloride-induced corrosion deterioration on the lifetime seismic vulnerability of aging highway bridge structures. The proposed framework is then applied to a representative case-study multi-span simply supported highway bridge located in subduction earthquake zone within Seattle, U.S.A. A detailed three-dimensional analytical models are first developed that account for the nonlinear behaviour of different bridge components, including experimentally validated column model capable of capturing cyclic degradation of force–deformation response. Suites of spectrally equivalent short and long duration ground motions are adopted followed by an incremental dynamic analysis-based framework for seismic fragility assessment. Deterministic seismic response assessment reveals a higher seismic demand on multiple bridge components under long duration ground motion record as compared to spectrally equivalent short duration record. Lastly, the bridge components and system fragility curves are developed considering modelling and deterioration uncertainties. Results reveal the significant vulnerability of bridge components and system under the joint impact of long duration earthquake shock and corrosion deterioration.

Influence of ground motion duration on the dynamic deformation capacity of reinforced concrete frame structures

This study investigates the influence of ground motion duration on the dynamic deformation capacity of a suite of 10 modern reinforced concrete moment frame buildings. A robust numerical algorithm is proposed to estimate the dynamic deformation capacity of a structure by conducting incremental dynamic analysis. The geometric mean dynamic deformation capacity of the considered buildings was, on average, found to be 26% lower under long duration ground motions, compared to spectrally equivalent short duration ground motions. A consistent effect of duration on dynamic deformation capacity was observed over a broad range of structural periods considered in this study. Response spectral shape, however, was found to not significantly influence dynamic deformation capacity. These results indicate that the effect of duration could be explicitly considered in seismic design codes by modifying the deformation capacities of structures.

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.

Influence of ground motion duration on the seismic performance of earth slopes based on numerical analysis

Assessing the dynamic stability of earth slopes is an important topic in geotechnical engineering field. In this study, the duration effect on the seismic performance of a multi-layer earth slope is quantitatively investigated, using two pairs of ground-motion suites selected matching a scenario-based response spectrum and a design spectrum, respectively. The four ground-motion suites are selected from the NGA-West2 database, with each pair of suites exhibiting a consistent distribution of response spectra yet different distributions of significant duration. Numerical analyses using the selected ground-motion suites as input are then conducted for the earth slope implemented in FLAC. Comparative results indicate that as compared to the shorter-duration suites, using the longer-duration ground-motion suites generally yields similar topographic acceleration-amplifications but an enlarged distribution of permanent slope displacements. Therefore, the influence of ground-motion duration on seismic-wave amplifications is insignificant; such influence on the earthquake-induced slope displacements is, however, significant. Using the selected longer-duration ground-motion suites, the slope (moderate) damage and failure probabilities exceeding specific displacement thresholds are increased by up to 20% and 50%, respectively. Therefore, when assessing the seismic performance of earth slopes in applications, one should pay adequate attention to the ground-motion duration effect, and input motions shall be selected in such a way that the duration characteristics of ground-motion records are properly constrained.

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.

Ground motion duration effect on responses of hydraulic shallow-buried tunnel under SV-waves excitations

Although intensive research of the influence of ground motion duration on structural cumulative damage has been carried out, the influence of dynamic responses in underground tunnels remains a heated debate. This study attempts to highlight the importance of the ground motion duration effect on hydraulic tunnels subjected to deep-focus earthquakes. In the study, a set of 18 recorded accelerograms with a wide-range of durations were employed. A spectrally equivalent method serves to distinguish the effect of duration from other ground motion features, and then the seismic input model was simulated using SV-wave excitation based on a viscous-spring boundary, which was verified by the time-domain waves analysis method. The nonlinear analysis results demonstrate that the risk of collapse of the hydraulic tunnel is higher under long-duration ground motion than that of short-duration ground motion of the same seismic intensity. In a low intensity earthquake, the ground motion duration has little effect on the damage energy consumption of a hydraulic tunnel lining, but in a high intensity earthquake, dissipation of the damage energy and damage index of concrete shows a nonlinear growth trend accompanied by the increase of ground motion duration, which has a great influence on the deformation and stress of hydraulic tunnels, and correlation analysis shows that the correlation coefficient is greater than 0.8. Therefore, the duration of ground motion should be taken into consideration except for its intensity and frequency content in the design of hydraulic tunnel, and evaluation of seismic risk.

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.

The role of ground motion duration and pulse effects in the collapse of ductile systems

SummaryThe seismic collapse capacity of ductile single‐degree‐of‐freedom systems vulnerable to P‐Δ effects is investigated by examining the respective influence of ground motion duration and acceleration pulses. The main objective is to provide simple relationships for predicting the duration‐dependent collapse capacity of modern ductile systems. A novel procedure is proposed for modifying spectrally equivalent records, such that they are also equivalent in terms of pulses. The effect of duration is firstly assessed, without accounting for pulses, by assembling 101 pairs of long and short records with equivalent spectral response. The systems considered exhibit a trilinear backbone curve with an elastic, hardening and negative stiffness segment. The parameters investigated include the period, negative stiffness slope, ductility and strain hardening, for both bilinear and pinching hysteretic models. Incremental dynamic analysis is employed to determine collapse capacities and derive design collapse capacity spectra. It is shown that up to 60% reduction in collapse capacity can occur due to duration effects for flexible bilinear systems subjected to low levels of P‐Δ. A comparative evaluation of intensity measures that account for spectral shape, duration or pulses, is also presented. The influence of pulses, quantified through incremental velocity, is then explicitly considered to modify the long records, such that their pulse distribution matches that of their short spectrally equivalent counterparts. The results show the need to account for pulse effects in order to achieve unbiased estimation of the role of duration in flexible ductile systems, as it can influence the duration‐induced reduction in collapse capacity by more than 20%.

Influence of ground motion duration on ductility demands of reinforced concrete structures

This article investigates the level of influence that strong motion duration may have on the inelastic demand of reinforced concrete structures. Sets of short-duration spectrally equivalent records are generated using as target the response spectrum of an actual long-duration record. The sets of short-duration records are applied to carefully calibrated numerical models of the structures along with the target long-duration records. The input motions are applied in an incremental dynamic analysis fashion, so that the duration effect at different levels of inelastic demand can be investigated. It was found that long-duration records tend to impose larger inelastic demands. However, such influence is difficult to quantify, as it was found to depend on the dynamic properties of the structure, the strength, and stiffness degrading characteristics, the approach used to generate the numerical model and the seismic scenario (target spectrum). While for some scenarios, the dominance of the long record was evident; in other scenarios, the set of short records clearly imposed larger demands than the long record. The detrimental effect of large strong motion durations was mainly observed in relatively rigid structures and poorly detailed flexible structures. The modeling approach was found to play an important role in the perceived effect of duration, with the lumped plasticity multilinear hysteretic models suggesting that the demands from the long records can be up to twice the inferred from distributed plasticity fiber models.

Influence of Ground Motion Duration on the Structural Response at Multiple Seismic Intensity Levels

Influence of Ground Motion Duration on the Structural Response at Multiple Seismic Intensity Levels

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.

EFFECT OF GROUND MOTION DURATION ON SEISMIC FRAGILITY OF RC FRAMES WITH DIFFERENT BEAM-COLUMN JOINT FAILURE MODES

Ground motion duration has great influence on the cumulative fragility and damage of inelastic structures, but the consideration of duration is not clear in current seismic analysis and design. 60 ground motion records with different durations and peak ground accelerations were selected from the PEER strong ground motion database, and categorized as 30 long-and 30 short-duration records. A three-dimensional model of an infilled RC frame teaching building was built via OpenSees. In order to simulate the different failure modes of the beam-column joints, three models were taken, which are the beam-column joints without considering inelastic deformation, with considering the bar bond-slip, and with considering both the bar bond-slip and the shear deformation. Seismic fragility analysis was carried out on the three models under the 60 ground motion records, and the fragility curves for two the kinds of records under different cases were obtained corresponding to five damage levels. Furthermore, the influence of ground motion duration on structural seismic behavior considering the different failure modes of beam-column joints was evaluated. The analytical results show that comparing with the short-duration records, the long-duration records can increase the structural exceedance probability obviously for the corresponding damage levels and beam-column joint cases. Comparing with the case without considering inelastic deformation of beam-column joints, both long-and short-duration records can increase the structural exceedance probability clearly under the same damage level when considering the bar bond-slip or considering both the bar bond-slip and the shear deformation. The effect of long-duration ground motion records on structural seismic performance considering the bar bond-slip and the shear deformation of the beam-column joints is more obvious.