Pulse-type Ground Motions Research Articles

Response of Base-Isolated Building with Secondary System under Earthquakes and Pulse-Type Ground Motions

Response of Base-Isolated Building with Secondary System under Earthquakes and Pulse-Type Ground Motions

Pulse-type seismic response prediction for uncertain structures based on the attention mechanism and wavelet decomposition augmented decomposition learning

Accurate prediction of structural responses under seismic action is important for the performance assessment of structures. However, depending on the variability of the structure (e.g., the design information) or ground motion characteristics (e.g., the presence of pulses), the seismic response characteristics of the may be significantly different. To overcome this problem, this study proposes a novel structural feature attention mechanism and wavelet decomposition augmented decomposition learning method (SFA-WD-DL) for predicting the time-series of the structural response under pulse-type ground motions. Unlike previous studies, the proposed method can be applied to structures with different shapes. Innovatively, a structural feature attention mechanism is embedded within a neural network model, enabling the consideration of different structural parameters. In addition, a wavelet decomposition-based velocity pulse identification method is combined with decomposition learning, using decomposed pulses and high-frequency features as inputs to the neural network model. This process simplifies pulse feature recognition task of the model. To avoid an unbalanced distribution of ground motion features affecting model performance, a balanced sampling strategy for ground motion datasets combining ground motion clustering and category reorganization methods is proposed, which effectively improves the model robustness. The accuracy and applicability of the proposed method are validated using a dataset containing reinforced concrete frame structures of different shapes and a pulse-type ground motion dataset containing 148 records. In addition, the importance levels of the structural features are obtained through the weight distribution of the structural feature attention mechanism. This indicates that the proposed SFA-WD-DL method is easily interpretable and can extract key features affecting the structural response.

Influence of velocity pulse directivity on seismic response of cross-fault bridges

Pulse-type ground motions have special destructive effects on structures, and directivity is one of the fundamental characteristics of velocity pulses. In this paper, the impact of the velocity pulse directivity of seismic motions on both sides of the fault on the seismic response of fault-crossing bridges was quantified using the original records from the Chi-Chi earthquake in Taiwan. First, an automatic baseline correction method was applied to restore the permanent ground displacement, and the direction corresponding to the strongest pulse energy on both sides of the fault was identified based on continuous wavelet transformation. On this basis, the variability of the peak intensity of ground motions on the hanging wall and footwall in different directions, as well as the differences in pulse characteristics between the strongest pulse component and the two initial horizontal components, were analysed. Finally, a typical 5 × 30 m continuous girder bridge was considered as the research object to reveal the influence of the velocity pulse directivity on the seismic response of key parts on both sides of the fault. The results showed that the variability in the peak ground-motion intensity on the hanging wall of the fault was higher than that on the footwall. The displacement variability was up to 863 %, velocity was 262 %, and acceleration was 124 %. The pulse characteristics of the strongest pulse component were stronger than those of the parallel and vertical fault components, and its acceleration, velocity, and displacement response spectra were larger. The amplification effects of the velocity pulse directivity on the transverse bending moment, longitudinal bending moment, and torque of the pier bottom reached 1.3, 1.1, and 1.6, respectively. However, the amplification effect of the velocity pulse directivity on the relative displacement of the pier top, displacement of the main beam, and displacement of the bearing was more than 1.6 times, which was more significant than the internal force of the pier bottom.

Inelastic Spectra to Predict Constant-Damage Energy Factor of Structures Under Near-Fault Pulse-Type Ground Motions

ABSTRACT A simple relationship is proposed to construct constant-damage energy factor (γ DI) spectra of single-degree-of-freedom (SDOF) oscillators with different levels of damage, expressed by the Park-Ang damage index. γ DI is computed for SDOF oscillators with four hysteretic models when subjected to 80 pulse-like ground motions. The statistical dependence of γ DI on initial period, damage index, postyield stiffness ratio, and ultimate ductility factor is investigated. In comparison with the non-pulse-type ground motions, the near-fault pulse-type ground motions can significantly increase the γ DI of structures, and the magnitude of the increase can reach about 200%. Conservative estimates of mean γ DI of SDOF oscillators are proposed taking into account the combined effect of period, damage level, and ultimate ductility factor.

Effects of rotational component of ground motions on seismic responses of asymmetric base-isolated structures

Asymmetric base-isolated structures installed on lead rubber bearings (LRBs) and laminated rubber bearings (LNRs) may suffer severe torsion due to the presence of the eccentricity ratio of the isolation system (eb/r). It is also recognized that the rotational component of ground motions can markedly increase torsional responses in structures, which may further amplify the adverse effect of torsion on asymmetric structures. Therefore, understanding how these rotational motions affect asymmetric base-isolated structures on LRBs and LNRs is crucial. Surprisingly, existing literature overlooks the impact of the structural parameter (eb/r) and the ground motion’s pulse period (Tp) on these effects. To fill this gap, numerical analyses are conducted on typical U-shaped planar asymmetric base-isolated structures. These structures, having 5 and 8 stories, are examined using MATLAB programming. Firstly, the translational and rotational responses of the selected cases under coupled rotational and translational components of ground motions are compared with those under the translational components. The responses are also compared to those of the associated, asymmetric fixed-base structures. Then, the role of eb/r in amplifying the negative effect of rotational excitations on selected cases is examined by varying eb/r from 0 to 0.3. The study compares the responses of selected cases subjected to coupled rotational and translational components of fourteen pulse-type ground motions (with Tp ranging from 0.728 to 8.043 s) to those subjected only to the translational components. The results reveal that seismic isolation effectively mitigates the adverse effects of the rotational component of ground motions on asymmetric structures. While rotational components can increase torsion in asymmetric base-isolated structures, the adverse effects are relatively minor and are not exacerbated by eb/r. However, when facing pulse-type ground motions with substantial Tp values, these structures exhibit at least a 200% increase in maximum interstory rotation and a 28% increase in maximum isolator displacement. These increases significantly exceed those observed for the structure subjected to non-pulse-type ground motions. Consequently, structural engineers should take these findings into account when designing and evaluating asymmetric base-isolated structures installed on LRBs and LNRs, particularly in regions where pulse-type ground motions are typical.

Shaking table test of prestressed high-strength concrete pipe piles reinforced with non-prestressed steel reinforcement

Prestressed high-strength concrete piles reinforced with non-prestressed steel reinforcement (PRHC piles) have been developed to improve their seismic performance. In this study, the seismic response and failure mechanism of PRHC piles was investigated using a shaking table test. The dynamic characteristics, dynamic soil pressure, superstructure response, acceleration magnification factors, maximum curvature ductility demand, bending moment response, and failure mode identification of the PRHC piles were determined. The performance of PRHC piles was compared with that of prestressed high-strength concrete pipe (PHC) piles, which showed that the PRHC piles experienced higher energy dissipation and lower maximum curvature ductility demands than PHC piles. In addition, the PRHC piles suffered bending failure at the upper-middle positions, and the plastic zones were higher than those of the PHC piles. The adverse effects of long-period and pulse-type ground motions on pipe piles should be considered in designing for strong seismic events. The addition of non-prestressed reinforcement to a pipe pile allows longer segments of the pipe pile to be involved in providing resistance.

Seismic response of two-storey steel frame equipped with metallic yielding and viscous dampers under far- and near-field earthquakes: Shaking table tests and numerical investigations

Seismic energy dissipation technology is widely used in building structures to mitigate earthquake damage; two typical energy dissipation devices (EDDs), viscous fluid dampers (VFDs) and metallic yield dampers (MYDs), are often used. To investigate the effects of different types of EDDs on seismic performance, shaking table tests were conducted on a two-storey moment-resistance steel frame (MRSF). This study examined three types of damping schemes: VFDs only, MYDs only, and a combination of both. The test results showed that different damping schemes had different effective stiffnesses and damping ratios. The basic frequency and damping ratio of the MRSF with hybrid dampers increased by 36.18% and 38.41%, respectively, compared with those with VFDs only. Compared with the other two controlled MRSFs using a single type of EDDs, the MRSF equipped with hybrid dampers can effectively coordinate the control of interstorey drifts. To further analyse the impact of pulse-type ground motions (GMs) on the dynamic responses of the controlled MRSFs, numerical models were established for all test models, and the nonlinear time-history analysis (NTHA) was performed. The numerical results fitted well with the test results and showed that the hybrid damping scheme can take full advantage of the two types of EDDs. The mean dissipation energy ratio of the dampers was 86% with GMs with an intensity of 0.80 g. There was a significant difference in the seismic damping effect of the controlled MRSFs with different types of seismic excitations. The acceleration control effect of the MRSF with only MYDs was best with near-field pulse-type GMs, with up to a 30% reduction over the MRSF with only VFDs. The acceleration control effect of the hybrid-controlled MRSF was best with near-field non-pulse GMs; the 1st-storey acceleration control of the hybrid damping MRSF was reduced by up to 42.4% compared to the VFD. The displacement reduction rates of the three controlled MRSFs subjected to pulse-type seismic excitation were lower than those of the three MRSFs subjected to non-pulse-type seismic excitations.

Dynamic Response and Running Safety of High-Speed Railway Train–Track–Bridge System Under Near-Fault Pulse-Type Ground Motion

The pulse effect of near-fault ground motion has asevere threat to high-speed railway train running on bridge. Current research generally relies on numerical simulation and lacks physical test data. In this paper, a scale indoor physical test of high-speed train running on bridge is conducted and dynamic characteristics of high-speed railway train–track–bridge system under near-fault pulse-type ground motion are explored. The bridge of the physical test is excited by shaking table with lateral inputs of near-fault pulse-type ground motion, pulse-free ground motion and far-field ground motion. A corresponding numerical model is established and validated by the test data. Then, the influence regularities of pulse effect on system dynamic response and running safety indexes are explored under different peak ground acceleration (PGA) and train speeds using data of the physical tests and the numerical simulation comprehensively. Results suggest that compared to the near-fault pulse-free ground motion and the far-field ground motion, the near-fault pulse-type ground motion leads to larger lateral beam displacement, lateral train acceleration, and running safety indexes in different degrees. And from the data results of this paper, its lateral wheel–rail force and derailment coefficient are the first to break through the limit values. By studying the parameter sensitivity of lateral train acceleration, it was found that under the near-fault pulse-type ground motion, the lateral train acceleration is significantly more sensitive to changes of train speed and PGA. From the perspective of energy, the near-fault pulse-type ground motion results in spectrum intensity (SI) indexes which are larger and improve faster with the increase of PGA than other ground motions. This indicates that it inputs significantly more energy into the high-speed railway train–track–bridge system, although it may not excite larger lateral beam acceleration.

Probabilistic analysis of high-speed train safety on bridges under stochastic near-fault pulse-type ground motions

The safety of high-speed railway trains running on bridges during stochastic near-fault pulse-type earthquakes is of utmost importance in designing railway bridges. This paper presents an efficient and feasible approach for analyzing the train-bridge coupling system (TBCS) during random near-fault ground motions using the number theory method with dimensionality reduction (NTM-DR). The method's validity is demonstrated through Monte Carlo simulations, which calculate the probabilistic maximum of the system response and the derailment coefficient under various conditions, such as different bridge heights, seismic intensities, and train speeds. Additionally, the response sensitivity to changes in seismic randomness is discussed by comparing it with the deterministic maximum. The results show that the proposed method achieves high accuracy and efficiency in analyzing the TBCS under random near-fault earthquakes. The ratio between the probabilistic and deterministic maximum is consistently above 1.3, highlighting the significance of considering earthquake randomness.

Shake-table test on dynamic response of prestressed high-strength concrete pipe piles under Soil–Structure interaction

This paper presents the results of a shake-table test on a superstructure model supported by a prestressed high-strength concrete (PHC) pipe pile in soft soil. The primary objective is to investigate the dynamic response of the PHC pipe pile in soft soil influenced by soil–structure interaction (SSI). Accordingly, a single PHC pipe pile with iron blocks is constructed and embedded in soft soil. First, the production of the physical model of the PHC pipe pile and experimental details are elucidated. Then, the study focuses on the dynamic response of the soil–pile–superstructure system considering different ground motion types and peak ground accelerations (PGAs). Finally, the inertial and kinematic effects on the dynamic response of the PHC pipe pile are analyzed. The results show that the SSI effect can increase the predominant period of the superstructure. With the SSI effect, the seismic design should consider the adverse effects of long-period and pulse-type ground motions on the pile. The SSI effect caused the rate of increase in the pile bending moment to be gradually higher than the increase in PGA. Moreover, the dynamic response of the PHC pipe pile is mainly dominated by the inertial effect.

Seismic Uplift Effect at End Spans of Long-Span Rigid-Frame Bridges Subjected to Near-Fault and Far-Fault Ground Motions

Miaoziping Bridge, a long-span rigid-frame bridge, uplift appeared at the end spans in the 2008 Wenchuan earthquake. Bearings and pad stones were damaged during the earthquake. In the past, the uplift mechanism and the seismic response under near-fault and far-fault ground motions were not sufficiently recognized. Here, a refined finite-element model of the Miaoziping Bridge was established considering the initial stress state and the nonlinear characteristics of the girder (e.g., cracking of concrete). The Wenchuan strong motion records and other 40 near-fault pulse-type and 40 far-fault ground motions were selected for nonlinear time history analysis. The uplift effect was realized by considering the compressive-only behavior of bearings. The results show that the seismic responses of the bridge under Wenchuan earthquake ground motions are in good agreement with the real seismic damage observed after the Wenchuan earthquake. The excitation of the near-fault pulse-type ground motion along the longitudinal direction is the dominant factor of the uplift at the end spans. When peak ground acceleration of the near-fault pulse-type ground motion is greater than 0.3g, the end spans are prone to uplift, and the maximum uplift displacement responses can reach 50 cm. There is little uplift possibility subjected to the far-fault ground motions. When the pulse period is in the range of 1–3 s, the pulse effect equals or even exceeds the full-wave effect. The end spans can hardly uplift subjected to vertical or transverse excitation individually. There is a slight difference between the uplift displacements subjected to single longitudinal ground motions and three-directional ground motions. The time of maximum uplift displacement is delayed considering the wave-passage effect. When the wave velocity is less than 1,000 m/s, the adverse effects of the wave-passage effect may be considered.

Seismic Performance Comparison of Hybrid, Isolation, and Damping Control Structures through 1/2-Scale Shaking Table Tests Based on Chinese Standard

A hybrid control structure (HCS) using seismic isolation at the base and energy dissipating cladding panel system (EDCPS) in the superstructure was proposed to realize enhanced seismic performance objectives of the main structure and nonstructural walls. To verify the feasibility of the HCS and validate its advantages in controlling the damage of structures compared with a seismic isolation structure (SIS) and a damping structure (DS), 1/2-scale shaking table tests were conducted on a HCS, an SIS, and a DS designed based on Chinese Standard. The seismic performance of the three damage control structures under different earthquake levels and ground motions (i.e., normal and velocity pulse-type ground motions) were investigated, including the damage characteristic, global responses, and isolator and damper behaviors. The test results indicated that the HCS provided the best control effect and remained elastic under the maximum considered earthquake (MCE). In contrast, slight and moderate damage were observed in the main structures of the SIS and DS under the MCE, respectively. Under the service level earthquake, the seismic response of the HCS was similar to or even greater than that of the SIS. While under the design basis earthquake and MCE, the U-shaped steel dampers in the HCS yielded and partially dissipated the earthquake energy; thus, this resulted in an obvious reduction in the drift ratio compared with that of the SIS. No damage to the cladding panels was observed in the HCS and DS, which indicated that the EDCPS was effective in controlling damage to the panels. In addition, a velocity-pulse type ground motion and the peak ground velocity significantly influenced the seismic responses of the HCS, SIS, and DS, particularly under the MCE.

Effects of near-fault pulse-type ground motion on train–track–bridge coupled system with nonlinear supports

Researches have revealed that the excitations of near-fault pulse-type (NFPT) earthquakes lead to significant challenge of high-speed railway. This paper mainly focuses on the dynamic responses of train–track–bridge coupled system (TTBCS) under NFPT ground motions. An innovative effective TTBCS model (TTBCM) considering nonlinearities of supports is proposed herein, and with that model, numerical simulation and data analysis are conducted to reveal the potential effect on TTBCS arisen by NFPT ground motion from both qualitative and quantitative perspectives. Conclusions can be summarized below: The comparison between linear model and nonlinear model reveals the necessity of nonlinearity when conducting TTBCS numerical simulation under NFPT ground motions. Moreover, the analysis of pulse parameters of NFPT ground motions reveals that the relationship between dynamic responses of train group and amplitude of velocity pulse is approximately to the linear positive correlation relationship, while the dynamic responses of train group and period of velocity pulse exhibits negative correlation as inverse proportional function. Based on parameters analysis, a multiple-parameter regression between spectral intensity and pulse parameters is conducted, with the combination of running safety assessment (RSA) criteria including Nadal, wheel unloading, and wheel lift, suggestion from RSA perspective under NFPT ground motions are proposed as well.

Nonlinear seismic response of mid-rise modular buildings subjected to near-field ground motions

In recent earthquakes, structures near seismic sources have suffered severe damage due to near-fault ground motions. When compared with ordinary ground motions, these ground motions create high demands on structures. The presence of a strong energy pulse has been observed in near-fault ground motions. This impulsive motion, propagating towards the site, will result in forward-directivity effects. This study is intended to assess the structural effects of mid-rise steel Modular Building Systems (MBSs) under the near-fault pulse-like and non-pulse-like records and to investigate design procedures that explicitly comprise near-fault effects. The main objective of this paper is the nonlinear seismic responses of MBSs to near-fault forward-directivity (FD) and non-forward-directivity (NFD) ground motions, as well as whether the equivalent pulse present in forward-directivity earthquake ground motions dominate the structural response. This paper discusses the key properties that can be used to characterize near-fault ground motions with forward-directivity effects and non-forward-directivity effects on the engineering demand parameters. For this purpose, using 72 pulse-like ground motions and 120 non-pulse-like ground motions, a Cloud analysis is conducted to obtain statistically significant results. Nonlinear time history analysis is performed using OpenSees based on distributed plasticity approach to develop a finite-element model of a 6-story mid-rise MBS. The results depict that near-field pulse-type ground motions generate larger demands to the MBS compared with the non-pulse ground motions. In addition, when correlated with simple intensity measures such as PGA, PGV, and spectral acceleration at the first mode period, the structural response to forward-directivity ground motions exhibits a higher dispersion than the structural response to non-forward-directivity ground motions. The representative equivalent pulses of the considered forward-directivity ground motions were decomposed using the continuous wavelet transform method to explore their effects on the MBS response. Finally, the influence of the pulse parameters, including period and amplitude of the forward-directivity, are ascertained.

Fragility analysis of high-span aqueduct structure under near-fault and far-field ground motions

Previous studies have shown that due to the notable characteristics of near-fault pulse-type (NFP) ground motions, such as large velocity pulse, narrow velocity-sensitive region and long period effect, there are significant differences in the seismic response of building structures caused by NFP ground motions and far-field (FF) ground motions. At present, the effect of NFP ground motions on the damage evolution characteristics of the aqueduct is still lacking. In addition, the current seismic design codes do not provide design recommendations for the dynamic response of aqueduct structures under NFP ground motions. The focus of this manuscript is to quantitatively evaluate the fragility of a high-span aqueduct system under NFP and FF ground motions. For this purpose, 10 as-recorded NFP and FF ground motions are considered, and the aqueduct bearing displacements and pier offset ratios are selected as performance evaluation indices. Then, the copula functions are introduced to establish the fragility curve of the high-span aqueduct system considering the seismic demand correlation of the aqueduct bearing and pier components. The results indicate that under same ground motion intensity conditions, the fragility probability of the aqueduct bearings is significantly larger than that of the trough pier under different performance levels, and should be considered in seismic design. In addition, the fragility probability curve of a single aqueduct component is used to describe the fragility probability of the aqueduct system, which overestimates its seismic performance. The fragility probability of a high-span aqueduct system under NFP ground motions is significantly greater than that under FF ground motions. Therefore, seismic safety assessments and seismic designs for the aqueducts should take into account the influence of NFP ground motions.

Dynamic response analyses of long-span cable-stayed bridges subjected to pulse-type ground motions

This paper presents the dynamic response analyses of a special long-span cable-stayed bridge with the main span length of 680 (m) subjected to pulse-type ground motions. The 1/100 scaled shaking table test are developed herein to verify the accuracy and correctness of the 3D finite element (FE) model of the examined long-span cable-stayed bridge on the software platform of SAP2000. To systematically investigate the influence on the seismic responses and on the selection of the nonlinear viscous damper parameters of the employed long-span cable-stayed bridge both the near-fault pulse-type ground motions and the far-field ground motions are selected as the seismic inputs of FE model. Some important conclusions are drawn that the near-fault ground motions usually causes the larger peak responses (e.g., Tower top displacement, girder end displacement, and moment of tower bottom) of the long-span cable-stayed bridge compared with the far-field motions, namely the near-fault ground motions are more destructive to the structures. The displacement responses can be amplified approximately 2–3 times and the damper parameters (Damping coefficient C and damping index α) of nonlinear viscous dampers can be affected by the ground motion characteristics. The damper parameter values are changed from the C = 3000 and α = 0.3 in far-field earthquakes to the C = 6000 and α = 0.2 in near-fault earthquakes, namely the near-fault ground motions obviously increase the demand of energy consumption of general nonlinear viscous dampers.

Seismic response control of building structures under pulse-type ground motions by active vibration controller

Active vibration control systems are commonly reported to be the most robust and effective method for vibration control of structures. However, the type of ground motions and the type of analysis may greatly influence their performances. This study investigates the seismic response of building with and without an active controller under pulse-type ground motions. A 20-story non-linear steel benchmark building is considered. Linear and non-linear analysis is conducted to check the effectiveness of the active control system. Active control with a linear quadratic Gaussian (LQG) control algorithm is applied to the benchmark building for seismic control purposes. Initially, some ground motions are selected following earlier studies from the literature concerning the benchmark building. It is found that the LQG control algorithm is quite effective under the considered earthquakes, and the analysis type does not affect the effectiveness of the controller. Thereafter, a set of additional 69 pulse-type ground motions are considered to check the performance of the LQG control algorithm and to find the suitability of linear analysis. It is noticed that under such pulse-type ground motion, the LQG control algorithm is not much effective if the non-linear behavior of the structure is incorporated in the seismic analysis, whereas in case of linear analysis, the LQG control algorithm is still effective. It is concluded that neglecting the non-linear behavior may lead to unconservative estimates of the seismic response when performing seismic analysis and designing structures equipped with active vibration control systems.

Research on the Pounding Response and Pounding Effect of a Continuous Rigid-Frame Bridge with Fabricated Super-High Piers Connected by Grouting Sleeves

The dynamic characteristics of a continuous rigid-frame bridge with fabricated super-high piers (CRFB-FSP) connected by grouting sleeves and adjacent continuous beam bridges (AB) are significantly different, and they are prone to pounding under earthquake excitation. At present, the pounding response between the CRFB-FSP and AB is still unclear, and the impact of the pounding on the seismic performance of a CRFB-FSP is still in the exploratory stage. In this study, two 1/20 scaled models of a CRFB-FSP (MB) and a cast-in-place AB were designed and manufactured. Then, according to the research purpose and the output performance of the shaking table, three each of non-long-period (NLP) ground motions and near-fault pulse-type (NFPT) ground motions were selected as the inputs of the excitation shaking table test. The peak ground acceleration (PGA) changes from 0.5 g to 1.5 g. According to the similarity ratio (1/20), the initial gap between the MB and AB was taken as 7 mm (prototype design: 140 mm). Furthermore, the longitudinal pounding response between the CFRB-FSP and AB, as well as its influence on the seismic performance of the CFRB-FSP, was systematically investigated through a shaking table test and finite element analysis (FEA). The results showed that the pounding with the CRFB-FSP easily caused a persistent pounding, which may increase the damage risk of the pier. The peak pounding force under the NFPT ground motion was more significant than under the NLP ground motion, whereas the pounding number under the NFPT ground motion was smaller. The peak pounding force increased with the increase in the initial gap, pounding stiffness, span, and pier height. With and without pounding, the CRFB-FSP reflected higher-order mode participation (HMP) characteristics. After pounding, under the NFPT excitation, the HMP contribution increased significantly compared with that of the without pounding condition, while this effect under the NLP excitation was smaller. The peak displacement of the main beam of the CRFB-FSP increased with the increase in the main beam span, pier height and initial gap. The peak bending moment of the pier bottom increased with the increase in the main beam span and initial gap, however, decreased with the increase in the pier height. Moreover, the peak displacement of the main beam and the peak moment of the pier bottom of the CRFB-FSP both reduced. In contrast, the corresponding seismic response of the AB increased under the same conditions.

Effects of near-fault pulse-type ground motions on high-speed railway simply supported bridge and pulse parameter analysis

Based on an innovative high-speed railway simply supported bridge (HSRSSB) model, the potential influence of near-fault pulse-type ground motions on HSRSSB is analyzed. Eighty-five original records of such ground motions are imposed on the simulation model. The dynamic responses of the bridge are calculated, including girder displacement, rail displacement, pier bending moment, bearing deformation, and residual displacement. Linear regression analysis reveals the relationship between the dynamic response and intensity measures (IMs). Moreover, six typical ground motions are chosen from these eighty-five records as prototypes in order to perform a pulse parameter analysis. Through an artificial ground motion synthesis, the effects of parameters, such as pulse amplitude, pulse period, and pulse number, on the behavior of HSRSSB are investigated and discussed. It is concluded that the response of HSRSSB depends on the acceleration-type IMs and presents a strong linear relationship with spectral IMs at the fundamental period of the structure. Regarding the pulse parameters, the HSRSSB dynamic response shows a positive correlation relationship with pulse amplitude, but a negative correlation with pulse period.

A hybrid characterization framework for structure-significant pulse-like features in ground motions

In earthquake engineering and engineering seismology, it is fundamental to identify pulse-type ground motions and characterize their pulse-like features, as seismologists relate them to the fault rupture and engineers relate them to the structural response. Pulse-type ground motions have been observed to exhibit peculiar attributes both in the response spectrum and in the time series. The existing pulse identification methods rarely leverage the distinct feature in response spectrum sufficiently, and consequently only the mimicry in time series sometimes loses the impulsive effect of the original ground motion on the structures. Based on the self-similarity revealed by dimensional analysis, the current study developed a hybrid pulse characterization framework that starts from subregion-to-subregion similarity matching in response spectral space and finally achieves resemblance in time domain, for pulse-like features in either ground velocity or acceleration. The framework directly identifies the pulses that dominate the structural response. The framework is versatile in terms of allowing various pulse waveforms, switching among different types of response spectra, and coping with the ground motions that contain multiple structure-significant pulse-like features.