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Free vibration and bending of laminated plates on Winkler foundations are investigated based on a combination of generalized layerwise theory (LW) for higher-order shear deformation theory (HSDT) a...

A vertical spring had a changeable horizontal stiffness to avoid resonance under a seismic displacement, and a viscous damper had a perfect energy dissipation function to reduce the seismic displacement. They were joined together to achieve a seismic isolation system considerably reducing the seismic acceleration response, however, their displacement should be paid more attentions under an earthquake or in a shaking table test. Because the interface friction in the system affected the scaling process of the system in the shaking table test and the corresponding displacement responses, the system was numerically scaled before a real shaking table test. The comparison between the displacement responses of scaled models and prototype models shows that the spatial friction variation and the gravity distortion are the error sources of the relative and residual displacements of scaled models. The error of scaled relative displacement is reduced by the means of increasing PGA, damping constant, spring constant or reducing vertical spring length with zero stress, however, the error of scaled residual displacement is still chaotic under these means. Only if the error sources above are eliminated fundamentally will the error of scaled models be avoided. The conclusions are validated correct by a real shaking table test.

To evaluate the seismic responses of bundled conductor interconnected electrical equipment, a model of the interconnected system was established. The bundled conductor model was incorporated into the interconnected model, and the electrical equipment was simplified as a 5-degrees of freedom structure. The bending stiffness of the sub-conductor and the constraint effects of the spacer, usually omitted in previous research, are considered in the paper. The iteration method was used to obtain the terminal forces and moments of the bundled conductor. Then, the model was validated by shaking table tests. We investigated the effects of the slackness and bending stiffness of the bundled conductor on the seismic responses of the interconnected system. Considering the bending stiffness of the sub-conductor and the effects of the spacer, the seismic response characteristics of the interconnected electrical equipment were much different from those connected by a flexible conductor without bending stiffness in previous research. Not only the terminal forces, but also the terminal bending moment should also be considered in the seismic performance evaluation of interconnected electrical equipment.

In this study, the dynamic responses of railway track multi-layer beam structure system under a moving load, which is connected by Winkler springs, are analyzed. It is noted that since track structure beams with consistent boundary conditions in mathematical sense have the same mode, the mode decomposition can be carried out in the same way. By adopting this approach, the dynamic coupling equations of track structure multi-layer beam system with the same vibration mode under a moving load can be decoupled. The closed vibration solutions of the displacement of the beams at each layer of the track system are presented and some are obtained by observing the form of solutions. The track structure multi-storey beam system model can be further used in the analysis of track system structural displacement, as well as the high-speed railway system and railway-bridge coupled system dynamics. It is found that the multi-layer system of CRTS-II simply supported beam bridge system and CRTS-II track system can be degenerated into triple simply supported beams with Winkler connection and double free beams on Winkler foundation, which is of great significance to engineering practice.

After an earthquake, a track-bridge system may suffer damage and residual deformation, posing a threat for trains passing over a bridge. However, since railway transportation is an important channe...

Rail irregularity presents a major threat to the high-speed train (HST) safety on a high-speed rail (HSR) bridge. Lateral bridge deformation has a significant impact on geometric parameters of the ...

The near fault (NF) line waves send out signal envelopes that oscillate over lengthy periods of time with periodic impulses. Like train bridges, train tracks demonstrate comparable track-bridge (TB...

Considering that existing shaking table tests on bridge structures have not taken into account the effect of moving trains, this paper takes a multi-span simply supported girder with a CRTSII slab ballastless track system and a Chinese CRH2C high-speed train as its objects of study, builds a reduced-scale model for the bridge and train using a similarity ratio of 1:10, and constructs an on-bridge running test platform based on a four-array shaking table. A running test under seismic action is preformed to explore the effects of train speed and the vertical component of ground motion on structural responses under the combined action of seismic and train loads. According to the findings of this paper, a higher train speed leads to more intense wheel-rail interactions. Train speed and the vertical component of ground motion have significant effects on the vertical deformation of structures and on the transverse deformation of bearings and piers, but their effects on the transverse deformation of track structures are negligible. The vertical component of ground motion may cause vertical separation between girders and bearings. The train may induce disengaging between track structures in the vicinity of girder gaps.

In the dynamic analysis of railway lines, both lateral and vertical track irregularities should be considered. In addition, uncertainties in the bridge structure and train load will have different ...

A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated (LFM) signals generated by heterodyning two free-running laser diodes (LDs) is proposed. The Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM signal. The closed-form solution of the correlation coefficient is given, which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is fixed. Simulation results are also given, which proves the correctness of the theoretical results.

At present, specific earthquake motion is often used for analyzing the influence of trains on high-speed railway structure; however, the uncertainty of earthquake motion is rarely taken into consideration. In this study, on the basis of considering the uncertainty of earthquake motion, and taking a simply-supported beam with CRTS II track system and CRH2 high-speed train in China as the research objects, a finite element analysis model of vehicle-bridge coupled model was established and verified by tests. The influencing mechanism of the trains on structural response under the action of uncertain earthquake was analyzed, and the range of the influence levels of trains on seismic response of structure was calculated. The research findings show that under the effect of earthquake, the presence of trains decreases the responses of piers and bearings, while increases the response of track structure. With increasing peak ground acceleration, the effect of trains on the track structure deformation increases, while that on the bending moment of piers, shearing force, and bearing deformation all decrease. The increase in train speed will not significantly affect the seismic response of structures. The ratio of seismic response between the operating conditions with and without vehicles was kept within a certain range, so that the demand range for seismic response under the operating condition with vehicles can be approximately simplified.

Due to the wide railway network and different characteristics of many earthquake zones in China, considering the running safety performance of trains (RSPT) in the design of high-speed railway bridge structures is very necessary. In this study, in order to provide the seismic design and evaluation measure of the bridge structure based on the RSPT, a calculation model of RSPT on bridge under earthquake was established, and the track surface response measure when the derailment coefficient reaches the limit value was calculated by referring to 15 commonly used ground motion (GM) intensity measures. Based on the coefficient of variation of the limit value obtained from multiple GM samples, the optimal measures were selected. Finally, the limit value of bridge seismic response based on RSPT with different train speeds and structural periods was determined.

Herein, an approach for the dynamic response of a four-beam system with arbitrary boundary conditions when subjected to successive moving loads is proposed. Based on the proposed method, the resona...

Friction pendulum bearing (FPB) is a sliding-based isolator, widely used in the seismic design of the bridge structure. However, there is neither unified standard nor complete evaluation system to evaluate the specific isolation effectiveness of FPB-isolated bridges with different pier heights. In this paper, the prototype bridge finite element models (FEM) of the typical simply supported girder bridges on the double-track railway in China, are established and studied. These bridge FEM differ in the pier height range of 4–60 m. Each FEM adopts two types of bearing: FPB (isolated bearing) and spherical steel bearing (non-isolated bearing). The nonlinear time history analysis is carried out to compare the seismic responses of FPB-isolated and non-isolated bridges. Based on the comparison results, the seismic isolation ratios of FPB are defined and obtained. In addition, a new criterion index is presented to quantifiably measure the effectiveness of the seismic isolation of FPB-isolated bridges with different pier heights, which is beneficial to the further popularization and application of FPB in the seismic design of bridge engineering.

Though seismic vulnerability analysis of highway bridges is mature, there is little corresponding research on high-speed railway (HSR) bridges. The seismic vulnerability analysis of HSR bridges is very different to and more difficult than for highway bridges because the multiple components of the track structure are very complex. To fill this research gap, the authors establish a finite element (FE) model of an HSR bridge with the China railway track system II (CRTS II), which includes sliding layers, cement asphalt (CA) layers and fasteners, base plates, track plates and rails. Analytical results show that seismic responses of multiple bridge components have a linear correlation. Thus, the overall track-bridge system can be assumed to operate like a serial system. Here, the seismic response and vulnerability of various bridge components are first analyzed using the incremental dynamic analysis (IDA) method. Afterwards, the failure sequence is found by comparing the seismic vulnerability of critical bridge components. Finally, the seismic vulnerability of the overall track-bridge system is evaluated according to the upper and lower first-bounds. Results illustrate that the system vulnerability of HSR bridges, which is very different to that of highway bridges, is mainly determined by the sliding layers and fixed bearings. In particular, the serious damage of a sliding layer is caused by the uncoordinated deformation of beam ends, and fixed bearings may break down when they are exposed to strong earthquakes. The overall track-bridge system is prone to severe seismic damage when peak ground acceleration (PGA) is larger than 0.2 g.

The seismic vulnerability of high-speed railway (HSR) bridges may be overestimated or underestimated when the track structure is oversimplified in a finite element model. Thus, the author establish...

In order to study the effect of the vertical deformation of continuous beam structure of CRTS Ι slab ballastless track on rail deformation, this paper analyzes the mapping mechanism of the structural vertical deformation-rail deformation. Based on the principle of stationary potential energy, the work derives an analytical expression for a mapping between the vertical deformation of continuous beam structure and rail deformation by considering the effect of the subgrade. Then, the mapping relation between the vertical deformation of various typical bridge structures and rail deformation was calculated using analytical method. The results were compared with those obtained using ANSYS finite element method. The effects of four factors on rail deformation were investigated, namely, pier settlement, staggered steps on girder, rotation angles on beam ends, and number of spans of simply supported beam. The calculation results obtained via analytical method and those obtained using finite element method fit well with each other, verifying the rationality and correctness of the analytical method. The expression for analytical method is concise and can easily obtain the mapping relation between the structural vertical deformation and rail deformation using the displacement boundary conditions. The vertical deformation of the rail was proportional to the vertical deformation of same typical structure. Both inside and outside the rail deformation area, the length of rail deformation section did not change with structural vertical deformation. When there were simply supported beams at both ends of the continuous beam, the number of spans of simply supported beams had no significant effect on the rail deformation caused by the vertical deformation of typical continuous beam structures. When there were no simply supported beams, the settlement of side pier of continuous beam caused rail deformation similar to the staggered step of girder.

Rail irregularity is the leading cause of enhancing train-track coupling vibration and, therefore, should be studied in detail for safety requirements. In this study, the differences between existing rail irregularities without being subjected to an earthquake between different countries were first studied. Results show that existing power spectrum density and time-domain displacement samples of rail irregularities in the American code are the largest, while the irregularities of the Germany railway are higher than those of China in a specific range of rail wavelengths. Afterward, the effects of earthquake intensity, soil site, and duration on the rail irregularity of a Chinese typical high-speed railway bridge were investigated. For this purpose, a finite element model was established and validated by the shaking table test of a 1/12-scaled high-speed railway bridge experimental specimen. The calculation results indicated that the influences of earthquakes on the rail alignment irregularity were evident.

A series of comprehensive parametric studies are conducted on a steel-frame structure Finite-Element (FE) model with the Multangular-Pyramid Concave Friction System (MPCFS) installed as isolators. This new introduced MPCFS system has some distinctive features when compared with conventional isolation techniques, such as increased uplift stability, improved self-centering capacity, non-resonance when subjected to near-fault earthquakes, and so on. The FE model of the MPCFS is first established and evaluated by comparison between numerical and theoretical results. The MPCFS FE model is then incorporated in a steel-frame structural model, which is subjected to three chosen earthquakes, to verify its seismic isolation. Further, parametric study with varying controlling parameters, such as isolation foundation, inclination angle, friction coefficient, and earthquake input, is carried out to extract more detailed dynamic response of the MPCFS structure. Finally, limitations of this study are discussed, and conclusions are made. The simulations testify the significant seismic isolation of the MPCFS. This indicates the MPCFS, viewed as the beneficial complementary of the existing well-established and matured isolation techniques, may be a promising tool for seismic isolation of near-fault earthquake prone zones. This verified MPCFS FE model can be incorporated in future FE analysis. The results in this research can also guide future optimal parameter design of the MPCFS.

A photonics-based approach to multi-frequency phase-coded microwave signal generation is proposed with an increased number of frequencies. Two microwave reference signals are sent to one arm of a dual-drive Mach-Zehnder modulator (DD-MZM), whereas the binary coding signal is sent to the other arm of the DD-MZM. The optical output of the DD-MZM is detected in a photodetector. Due to the nonlinearity in the electro-optic modulation, the generated photocurrent contains the nonlinear intermodulation products of the two reference signals, which are all modulated by the coding signal. An experiment is performed. Multi-frequency phase-coded microwave signals from 1 to 24 GHz with more than twelve different frequency components are generated. The performance of the generated signal including phase recovery accuracy and pulse compression capability is also verified.

The extension of high-speed railway construction to earthquake-prone regions has significantly increased the probability of trains encountering an earthquake while running on a bridge. Therefore, i...

This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom (DOF) for simplifying the treatment of the train system in bridge seismic checking.

In this study, the principle of minimum potential energy has been used to deduce the mapping relationship between beam deformation and rail deformation with consideration of the constraint effects ...

A new nonlinear track-bridge random model was established based on OpenSEES, of which the random seismic responses is systematically studied by using probability density evolution method (PDEM). First, a three-dimensional detail nonlinear random dynamic model of the track-bridge coupled system in high-speed railway is established considering the earthquake as the random excitation. The dynamic model is composed with the rail, CRTS II slab ballastless track, the simple supported bridges, bearing, pier and the pile foundation, from which the random dynamic equation of the random model is formulated. In order to evaluate the seismic performance of track structures from a random perspective, the random seismic responses of high-speed railway bridge under random seismic excitations are investigated and analyzed by using the PDEM. Eventually, the Newmark β integration method and the double edge difference method of TVD format are adopted to obtain the random responses involving the probability functions, which can be translated to get the mean value and the standard deviation of responses. Thus, the abundant probability information of seismic responses of the high-speed railway bridge under random seismic excitations can be obtained. The PDF and CDF of the sliding layer are obtained; thus, the failure probability and reliability of different damage grades of sliding layer are obtained. Discussions and significant conclusions on the random dynamic responses are presented.

To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge, a 3D train–track–bridge coupled model is established for accurately simulating the train–bridge interaction under earthquake excitation, which is made up of a vehicle model built by multi-body dynamics, a track–bridge finite element model, and a 3D rolling wheel–rail contact model. A conditional simulation method, which takes into consideration the wave passage effect, incoherence effect, and site-response effect, is adopted to simulate the spatially varying ground motion under different soil conditions. The multi-time-step method previously proposed by the authors is also adopted to improve computational efficiency. The dynamic responses of the train running on a three-tower cable-stayed bridge are calculated with differing earthquake excitations and train speeds. The results indicate that (1) the earthquake excitation significantly increases the responses of the train–bridge system, but at a design speed, all the running safety indices meet the code requirements; (2) the incoherence and site-response effects should also be considered in the seismic analysis for long-span bridges though there is no fixed pattern for determining their influences; (3) different train speeds that vary the vibration characteristics of the train–bridge system affect the vibration frequencies of the car body and bridge.

This paper focuses on the rapid elastoplastic analyses of light rail vehicle (LRV)- benchmark viaduct system to different seismic scenarios considering the dynamic substructuring method (DSM). Comb...

Seismic loads pose a potential threat to the high-speed railway bridges in China, which have been rapidly developing in recent years, especially for those subjected to the near-fault earthquakes. The previous researches on high-speed railway bridges usually concern the far-field earthquake, and the damage of high-speed railway bridge–track system subjected to the near-fault earthquake has not been well studied. In this article, a seven-span high-speed railway simply supported bridge–track system is selected to explore the seismic damage features under the excitation of near-fault earthquake which possesses characteristics of obvious velocity pulse and high-frequency vibration. First, a detailed finite element model of the selected bridge–track system is established and calibrated by the experimental data and design code. Then the low-frequency pulse-type portion and the high-frequency background portion are separated from the selected eight original near-fault records, and a series of nonlinear dynamic analysis is conducted. The results show that the background portion leads to more serious damage of the bridge–track system than the pulse-type portion. Due to the high stiffness of high-speed railway bridge–track system, the background portion with high-frequency vibration characteristic produces the main part of seismic response of system. As for the damage part of system, the weakest component of the bridge–track system is the sliding layer, followed by the shear alveolar.

A simplified calculation model for the integration of tracks and bridges of multi-span simply supported beam bridge on high-speed railway is proposed by considering the longitudinal connecting effects of adjoining structure. Using this simplified calculation model, the seismic response of multi-span standard simply supported beam bridges of multiple high-speed railways was calculated and compared with the seismic response using the corresponding full-bridge model. Based on the above calculation results, the simplification efficiency and equivalent stiffness of simplified calculation model was studied. Seven earthquake records were selected for calculation, and the growth rates of seismic responses with the increase of number of spans were analyzed in detail. The analysis results show that the seismic response using the simplified calculation model and corresponding full-bridge model are identical with each other; the simplified calculation model greatly reduces the calculation time and the efficiency of reducing calculation time is up to a maximum of 86%. The order of arrangements of interlayer components such as shear teeth and support significantly affects the equivalent stiffness of adjoining structures. The equivalent stiffness of adjoining structures becomes stable with the increase in the number of spans of simply supported beam in adjoining structures. The adjoining structures has an amplification effect on the seismic response of target structures, and the amplification effect becomes stable with the increase in the number of spans of simply supported beam in adjoining structures. Without considering the restraint effect of adjoining structures, the seismic response of multi-span simply supported beam bridge on high-speed railway becomes unsafe, that is, the result is smaller than that of considering adjoining structures.

This paper examines the effect of structural deformation on the unit slab-type ballastless track structure of high-speed railway. The principle of stationary potential energy was used to map the relation between girder vertical deformation and rail deformation considering the effect of subgrade boundary conditions and the nonlinear contact of interlayer. The theoretical model was verified by comparing with the finite element analysis and experimental results. The theoretical model was used to analyze the effects of several key parameters on the rail deformation, such as vertical deformation amplitude, elastic modulus of the mortar layer, and vertical stiffness of the fasteners. The results show that the track slabs suffered significant disengagement, which makes the deformation of the track structure at the position of the beam joint tend to be gentle when nonlinear contact between the mortar layer and the track slabs was considered. The track slabs disengagement mainly occurs near the beam joints (the side of the deformed beam). As the deflection amplitude of the girder increases, the track deformation, the fastener forces and the disengagement length of the track slabs are obviously nonlinear. When the vertical stiffness of the fastener and/or the elastic modulus of the mortar layer increase, the fastener force and the track plate disengagement length increase monotonically and nonlinearly, which will adversely affect the life and safety of the track structure.

The track irregularity spectrum of longitudinally connected ballastless track (LCBT)-bridge systems of high-speed railway was proposed in this paper. First, a simulation model of an LCBT-continuous girder bridge was established by considering the influences of approach bridges and subgrade with track structure. Further, a large number of sample analyses were carried out by taking into account the uncertainty of LCBT-bridge systems and stochastic behaviors of ground motions based on the simulation model. The damage laws of residual deformation of track-bridge system after earthquake actions were studied. Then, an interlayer deformation coordination relationship (IDCR) considering the track irregularity caused by earthquake-induced damage of bearings was developed, and the superposed track irregularity samples were obtained. Finally, by using the improved Blackman–Turkey method and Levenberg–Marquardt algorithm, the LCBT irregularity spectrum, track irregularity spectrogram, track irregularity limit spectrum, and a fitting formula for the track irregularity spectrum on a bridge after the action of earthquakes were obtained. Results obtained from the fitting formula and IDCR were compared, and they indicated that tracks undergone significant high-frequency irregularity diseases after the earthquake action. It was found that the track irregularity spectrum could be roughly divided into three ranges: high-, medium- and low-frequency wavebands. Consequently, this led to an application of a three-segment power function for the fitting of the track irregularity spectrum after the earthquake action. The track irregularity spectrum after the action of earthquakes provides an important theoretical basis for the establishment of seismic design methods for high-speed railway bridges based on the traffic safety performance.

Based on the finite Fourier series method and the principle of energy variation, a method for calculating the dynamic response of an orbit-girder system is proposed, which is suitable for general spring boundary and nonhomogeneous interlayer stiffness distribution. Two numerical examples are given to verify the effectiveness of the proposed method under different moving load speeds and different stiffness distribution patterns. Based on this method, the influence of boundary conditions, interlayer stiffness degradation mode and degradation amplitude as well as the motion load on the dynamic response of the orbit-girder system is analyzed. A formula for calculating the peak value of additional dynamic response caused by interlayer stiffness degradation is proposed based on the nonlinear fitting method, and the factors affecting the additional response are analyzed. Results show that the variation of boundary conditions does not affect the additional dynamic response of the orbit-girder system. The mode of interlayer stiffness degradation and the degree of nonhomogeneous distribution have a significant influence on the peak of additional dynamic response. The additional dynamic response peak value of the orbit-girder system increases significantly with an increasing degree of nonhomogeneous degradation of the interlayer stiffness. The orbit-girder system has multiple critical speeds under the action of moving load. The magnitude of moving load has an important effect on the additional response peaks of the orbit-girder system. The additional response peaks increase approximately linearly with the increase of the motion load.

When conducting a numerical simulation of a train’s derailment and post-derailment, it is necessary to continuously observe the relative position of the wheel and rail, which is of great significance for the correct evaluation of train safety. In this paper, a non-analytic method is proposed to extend the search range and improve the accuracy of the classical semi-analytical method, i.e. the contact locus method. Based on the point cloud convex hull, a high-density wheel contact locus vertical profile is obtained by projecting the chamfer and internal zone of the flange onto the rail cutting plane. To obtain maximum compression in the normal direction and avoid singularities on both rail head sides in the Cartesian coordinate system the rail surface is interpolated with the polar spline curve. Compared with the classical method used to describe the wheel contact locus, in the proposed hybrid method, potential contact points are provided. Finally, the proposed hybrid method and the classical methods are applied to the wheel track coupling simulation. Numerical results demonstrate the high reliability and effectiveness of the proposed method.

This paper investigated the effects of normal and reinforced beam–column joints on seismic behavior and damages of mid-rise cold-formed steel (CFS) framed buildings, where the reinforced beam–column joint is strengthened by a pair of steel blocks and a gusset plate. Shaking table tests were conducted on a 5-story CFS frame building with normal beam-column joint (CFSM-NJ) and a 5-story CFS frame building with same configurations but with reinforced beam–column joint (CFSM-RJ). Formulae fitted from four damage models were used to assess the seismic damage indexes of these test buildings, and the assessed results were validated by the damage indexes observed from tests. The results show the following: (1) the CFSM-NJ failed due to plastic hinges formed at the column bases and large separate deformation at the beam-column joints; however, the weaken-story failure mode was appeared on the CFSM-RJ; (2) the peak inter-story displacement of the building was reduced about 10–30% due to the reinforced beam-column joints; (3) the Park-Ang model is more appropriate for seismic damage assessment of column bases, but all the damage models overestimates the seismic damages of CFS beams. Finally, the authors comment on the difference between the assessed seismic damage indexes and the observed results, and the maximum damage indexes obtained from the simplified formulae are recommended as the preliminary assessed damages for mid-rise CFS buildings.

With the extension of high-speed railways to high-intensity earthquake regions, it is impossible to avoid structural vibrations due to the joint action of trains and earthquakes. Therefore, it is of great significance to study the influence trains on bridge structures exposed to earthquakes. In this paper, a coupled finite element analysis model of a high-speed railway vehicle-bridge was established by considering a simply-supported beam bridge with the China Railway Track System (CRTS) II plate and the CRH2C high-speed train. The correctness of the model was experimentally verified. By considering the ground motion randomness, the influence of the train on the response of the bridge structure exposed to an earthquake was analyzed. Also, the influence level of the running train on the seismic response of bridge structures with different pier heights was studied. The results revealed that the train dynamic effect significantly reduced seismic responses of piers and supports, and that the effect itself decreased with the pier height increase. Furthermore, the dynamic effect of the train increased the seismic response of the track structure, while the bridge pier height had little influence on the dynamic efficiency of the track structure. For different pier heights, the probability distribution model of the train dynamic effect for the track-bridge system seismic response was considered as the normal distribution. This indicated that the seismic response of the track-bridge system under vehicle condition could be simplified as the product of the seismic response and safety factor under no vehicle condition.

A bolt-connected precast reinforced concrete deep beam (RDB) is proposed as a lateral resisting component that can be used in frame structures to resist seismic loads. RDB can be installed in the steel frame by connecting to the frame beam with only high-strength bolts, which is different from the commonly used cast-in-place RC walls. Two 1/3 scaled specimens with different height-to-length ratios were tested to obtain their seismic performance. The finite element method is used to model the seismic behavior of the test specimens, and parametric analyses are conducted to study the effect on the height-to-length ratio, the strength of the concrete and the height-to-thickness ratio of RDBs. The experimental and numerical results show that the RDB with a low height-to-length ratio exhibited a shear–bending failure mode, while the RDB with a high height-to-length ratio failed with a shear-dominated failure mode. By comparing the RDB with a height-to-length ratio of 2.0, the ultimate capacity, initial stiffness and ductility of the RDB with a height-to-length ratio of 0.75 increased by 277%, 429% and 141%, respectively. It was found that the seismic performance of frame structures could be effectively adjusted by changing the height-to-length ratio and length-to-thickness of the RDB. The RDB is a desirable lateral-resisting component for existing and new frame buildings.

By considering the effect of the constraints of the rails on the subgrade section on both sides of a bridge, analytical expressions are derived to study the mapping relationship between the rail deformation and changes in the condition of the supporting beam(s), based on the principle of minimum potential energy. Rail deformations in a slab track–bridge system induced by the subsidence of piers and beam faults are investigated in detail. Results are compared with the finite element calculations to assess the main factors that influence rail deformation. The results show that the rail deformation curves under different working conditions (single or multiple pier subsidence and beam faults) determined using the analytical model fit well with those from the finite element models. With increasing subsidence of piers, the rail deformed more significantly in the subsidence zone. Moreover, both the maximum downward and upward deformations of the rail changed linearly with the subsidence of piers. Use of fasteners or a mortar layer with greater vertical stiffness caused the rail to become more irregular.

This study establishes an improved analytical method (IAM) to investigate the dynamic characteristics of composite box beam with corrugated webs (CBBCW), and the IAM has comprehensively considered the effects of several factors, such as the shear lag, interfacial slip, shear deformation and rotational inertia of CBBCW in combination with the characteristics of CBBCW. Further, based on the Hamilton principle, the vibration differential equation and boundary conditions for CBBCW have been deduced. Finally, an IAM for calculating the dynamic characteristics of CBBCW was proposed. Based on the IAM developed in this study, the natural frequencies of multiple CBBCW cases with different spans, shear connection degrees and boundary conditions have been calculated. The results calculated by the IAM have been compared with those calculated by the finite element method and by the general beam theory. The comparison verifies the effectiveness of the IAM and obtains some conclusions that are meaningful to engineering design, i.e. the shear lag effect of CBBCW increases with increasing shear connection degree and also increases with increasing order of the vibration mode, the shear lag effect of the CBBCW is up to 6.2% in the first five orders of the vibration modes and the effect cannot be ignored. In the first- and second-order vibration modes of the CBBCW cases, the maximum interface slip effect of CBBCW is 28.42% and therefore cannot be ignored. On the other hand, the shear lag effect of CBBCW is usually lower than those of ordinary composite box beam with the same web thickness.

This paper aims at introducing a novel method to control the lateral vibration of reinforced concrete, lightweight pier railway bridges (LPRBs) with heavy-haul (HH) monorail trains. For this purpos...

The friction pendulum bearings (FPB) begin to be used in railway bridges in China. In one earthquake region in China, the shear pins of FPB are required to be well to provide the enough shear force and stiffness under service loads (such as the vehicle forces being less than 170 kN in the longitudinal direction and 40 kN in the transverse direction) or small earthquake loads with a peak ground acceleration (PGA) being less than 0.1 g, however, are cut off to isolate seismic energy under large earthquake loads with a PGA being larger than 0.2 g. It is necessary to identify the appropriate strength of FPB shear pin to satisfy the above requirements. This paper selected the simply supported bridges on a single-line railway in the above earthquake region as the study object, which had a span length of 32 m and two height types of piers (8 m and 25 m). A prototype finite element model (FEM) and a scaled FEM were numerically analyzed, and a scaled experimental model was tested on shake table for each bridge. The results of them were compared with each other to validate the rationality of all models and to achieve the appropriate strength of FPB shear pin. The results show that the appropriate strengths of FPB shear pins are 540 kN in the longitudinal direction and 300 kN in the transverse direction for the bridge with the pier height of 8 m. Likewise, 350 kN and 270 kN are determined as the appropriate strengths of FPB shear pins for the bridge with the pier height of 25 m in the longitudinal and transverse directions, respectively. The numerical method of FEM is correct based on the experimental validation, and can be used to identify the appropriate strengths of FPB shear pins for other railway bridges.

An iterative framework is introduced in this present study to detect seismic isolation precursors of the shortcut calculation method for the isolated benchmark high-speed railway RC bridge....

Corrugated steel web is folded along the longitudinal direction and has the mechanical properties such as axial compression stiffness corrugation effect, shear modulus corrugation effect, similar to that of an accordion. In order to study the lateral-torsional buckling of box beams with corrugated steel webs (BBCSW) under the action of bending moment load, the neutral equilibrium equation of BBCSW under the action of bending moment load is derived through the stationary value theory of total potential energy and further, along with taking Kollbrunner-Hajdin correction method and the mechanical properties of the corrugated web into consideration. The analytical calculation formula of lateral-torsional buckling critical bending moment of BBCSW is then obtained. The lateral-torsional buckling critical bending moment of 96 BBCSW test specimens with different geometry dimensions are then calculated using both the analytical calculation method and ANSYS finite element method. The results show that the analytical calculation results agree well with the numerical calculation results using ANSYS, thus proving the accuracy of the analytical calculation method and model simplification hypothesis proposed in this paper. Also, compared with the box beams with flat steel webs (BBFSW) with the same geometry dimensions as BBCSW, within the common range of web space-depth ratio and web span-depth ratio, BBCSW’s lateral-torsional buckling critical bending moment is larger than that of BBFSW. Moreover, the advantages of BBCSW’s stability are even more significant with the increase of web space-depth ratio and web depth-thickness ratio.

This article aims to disclose that the deformation and damages of the one-way straight mortise-tenon (OWSMT) joint, the key force transmission connection of traditional wood buildings, lead to a si...

Continuous girder bridges for high-speed railway (HSR) are increasingly used to overcome undulating terrain and to provide a flat surface for high-speed travel. Only a few dynamic experiments have been applied to such bridges, none of them focusing on HSR continuous girder bridges. The aim of this paper is to use experimental results to investigate the earthquake response of bridges of this type constructed in China. To address this aim, a 1/12-scale typical Chinese HSR continuous girder bridge specimen was constructed and the experimental procedures were detailed. From the experimental results it was found that the first natural frequency of piers was obviously decreased after the specimen was subjected to the peak ground acceleration of 0.38 g earthquake excitation. The acceleration response observed at the top of piers increased with the increase of earthquake intensity, and the concrete at the bottom of piers was cracked when the peak ground acceleration exceeded 0.20 g. The results also showed that a fixed bearing installed on the HSR bridge was damaged under 0.32 g earthquake excitation, whereas no damage was found in a girder for all test scenarios (i.e., from 0.15 g to 0.38 g). In addition, compared to unidirectional earthquake excitation, the earthquake response increased under bidirectional earthquake excitation. The experimental procedures and findings can be used as benchmarks for practical applications or for further similar experiments.

A continuous bridge in high-speed railway is close to several known faults in China. Those faults, respectively at different distances from the bridge site, will produce different ground motions with the different ratios of vertical component to the horizontal component at the bridge site. It is necessary to identify the influence of vertical ground motions on the seismic responses and vulnerabilities of the track-bridge system. This paper solved this problem by carrying out an incremental dynamic analysis (IDA) and a further seismic fragility analysis on a widely used continuous bridge in China. The results show that the damage probabilities of most bridge and track components increase along with the increase of vertical part in ground motions. This trend is significant for the sliding layer of track part in the longitudinal direction and the piers of bridge part in any direction, however, insignificant for the bearings of bridge part in any direction. Moreover, this trend is more significant for the track part across the girder gap due to the different seismic responses of adjacent bridges. The seismic design of track-bridge system should rigorously take the vertical part of ground motions into account.

A photonic-assisted multi-functional radar system for simultaneous distance and velocity measurement and high-resolution microwave imaging is proposed and experimentally demonstrated by using a composite transmitted microwave signal of a single-chirped linearly frequency-modulated (LFM) signal and a single-tone microwave signal. In the system, the transmitted signal is generated via photonic frequency up-conversion based on a single integrated dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM), whereas the echo signals scattered from the target are de-chirped to two low-frequency signals using a microwave photonic frequency mixer. By using the two low-frequency de-chirped signals, the real-time distance and radial velocity of the moving target can be measured accurately according to the round-trip time of the echo signal and its Doppler frequency shift. Compared with the previous reported distance and velocity measurement methods, where two LFM signals with opposite chirps are used, these parameters can be obtained using only a single-chirped LFM signal and a single-tone microwave signal. Meanwhile, high-resolution inverse synthetic aperture radar (ISAR) imaging can also be realized using ISAR imaging algorithms. An experiment is performed to verify the proposed multi-functional microwave photonic radar system. An up-chirped LFM signal from 8.5 to 12.5 GHz and an 8.0 GHz single-tone microwave signal are used as the transmitted signal. The results show that the absolute measurement errors of distance and radial velocity are less than 5.9 cm and 2.8 cm/s, respectively. ISAR imaging results are also demonstrated, which proves the high-resolution and real-time ISAR imaging ability of the proposed system., 16 pages, 9 figures

When an earthquake occurs, due to the high operation speed of the train group, there is still a long distance from braking to stopping, so it needs a large number of bridge spans to calculate the integrated dynamic response, which leads to a large amount of calculation of the train-track-bridge (TTB) system under a seismic event. In order to reduce the amount of calculation, this paper proposed an efficient model called closed-loop model for simply supported railway bridge. The proposed model is realized by coupling the head and end of the rail-slab-bridge system through the utilization of pseudo-element. Simulation comparison of TTB response with and without seismic excitation between conventional TTB model and efficient model indicates that, under the premise of ensuring calculation accuracy, the efficient model shows the advantage of fewer degrees of freedom (DOF) of model and higher computational efficiency. For instance, under El Centro earthquake excitation, the time cost of proposed model is only 6% of conventional model. Meanwhile, six seismic events with different acceleration amplitudes are imposed on the efficient model, and the results of car-body acceleration, wheel-rail force, and wheel load reduction ratio are gathered and discussed; it can be concluded that, except Trinidad earthquake, for other earthquake samples investigated in this paper, with acceleration amplitude larger than 0.8 g, the train operation is at the risk of derailment.

Artificial seismic waves can be easily generated by software, and needs identification if they can be used to evaluate the seismic vulnerability of general bridges. A finite element model of a (48+80+48)m continuous girder bridge in a high-speed railway was built by OpenSEES software, and was calculated by an incremental dynamic analysis (IDA) using both the artificial waves and actual waves. The seismic fragility curves for major structural components under the artificial waves and actual waves were developed assuming lognormal distributions for both the demand and capacity of bridge structure, and then compared with each other. The comparison results show that there is a perfect consistency between the seismic responses under both the artificial waves and actual waves for most components. Although the seismic responses of sliding layer under the actual waves are slightly different from those under the artificial waves, the largest error of damage exceeding probability between them is still acceptable. Therefore, the artificial waves can be used to evaluate the seismic vulnerability for the continuous girder bridges in a high-speed railway under earthquakes.

A specially shaped corrugated steel shear wall (S-CSSW) system was proposed for the application of steel residential buildings. The proposed shear wall system featured a main shear wall with small section concrete filled steel tube (CFST) boundary columns and horizontally corrugated shear plates and side short pier CSSWs in the perpendicular direction. Quasi-static cyclic tests were performed on the S-CSSWs with and without reinforcing beams to investigate the shear strength, failure modes and hysteretic responses. Finite element simulations were introduced to further study the shear bearing mechanisms of S-CSSWs for a comparison with traditional flat plate shear walls with similar wall configurations. An additional parametric simulation was performed to investigate the influence of the corrugated plate width on failure modes. Results indicated that the proposed S-CSSWs possessed good ductility. Compared with the flat plate shear walls, the proposed shear walls had higher initial stiffness and elastic shear strength. The width of the corrugated shear panels was an important factor influencing the failure modes and lateral bearing abilities and needed to be carefully controlled to avoid early buckling occurring ahead of the shear yielding mode. Some design remarks are concluded regarding the design of the corrugated shear panels and stiffening beams.