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Different crumb rubber (CR) particle sizes affect asphalt performance differently. To improve the performance of CR in SBS/CR composite modified asphalt (SBS/CRMA) and to study the enhancement of SBS/CRMA performance with varying ratios of composite CR particle sizes. This study employed three different configurations of SBS/CRMA composite ratios. Several tests and analyses were conducted, Brookfield viscosity measurements, conventional performance tests, storage stability, high- and low-temperature rheology, LAS, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) analysis. The results indicated that, in the composite CR particle size ratio, a finer particle size of CR demonstrated more significant benefits in improving the high- and low-temperature performance of asphalt. However, with aging, the role of a coarse particle size of CR gradually became more prominent. Furthermore, compared to a single CR mesh SBS/CRMA, the 3 S + 5R-6:2:2 composite CR particle size ratio of SBS/CRMA exhibited superior high- and low-temperature deformation and fatigue resistance. Considering the microscopic analysis, it can be observed that the fine particle size of CR exhibited superior compatibility and anti-aging performance compared to the coarse particle size. In the composite CR particle size ratio, adjusting the proportion of coarse and fine CR particle size will improve the performance of SBS/CRMA significantly. Contrary to common belief, it was not necessarily true that a higher ratio of coarse CR particles leads to a better modification effect in SBS/CRMA. On the other hand, the composite CR particle size ratio proved significantly advantageous, thereby providing valuable guidance for enhancing the performance of SBS/CRMA.

Aiming to solve the problems that a wind turbine foundation with a foundation pipe may suffer from grouting, where the concrete around the interface collapses and the interface disintegrates under a long-term wind load, a kind of wind turbine foundation with a constrained structural shear connector is proposed. In this article, the scaling model tests and a finite element simulation of a traditional stud foundation pipe, perforated steel shear connector foundation pipe, and three groups of constrained structural shear connector foundation pipes with different anchored depths are presented. The force transmission mechanism and damage mechanism of constrained structural shear connector wind turbine foundations are revealed, and the shear resistance of a constrained structural shear connector is analyzed. The influences of buried depth and other parameters on the mechanical properties of the shear connector are also investigated. The results show that the constrained structural shear connector has the advantages of stronger interfacial stiffness and significant force transfer and diffusion, and can more effectively connect the foundation pipe and concrete foundation to work together. It can give full play to the material advantages of concrete and reinforcements, and effectively improve the embedded stiffness and durability of concrete foundations. It can solve the problem of cracks in concrete caused by local pressure. At the same time, it is suggested that the diameter of the surrounding concrete should be in the range of 3 to 4 D, and the embedment depth of the stud should not be less than 0.4 D to give full play to the performance of the constrained structural shear connector.

As an important part of the boundary conditions on both sides of the high-speed railway track–bridge system, the seismic response of the subgrade structure is different from that of the bridge structure. This difference has become increasingly significant with the widespread adoption of continuous welded rail technology in bridge construction. Therefore, investigating the seismic response of the bridge system, with a specific focus on the longitudinal constraint effects of the subsequent subgrade track structure, is of paramount importance. Utilizing finite element software, two distinct bridge models are developed: one incorporating the subsequent subgrade track structure and another excluding it. Through nonlinear time history analysis under varying seismic intensities, it is demonstrated that the longitudinal constraint of the subsequent subgrade track structure mitigates the longitudinal displacements and internal forces in critical components of the high-speed railway track–bridge system. Concurrently, acknowledging the heightened complexity and cost associated with post-earthquake repairs of the bridge structure compared to subgrade structure, this study uses a risk transfer connecting beam device. This device can redirect seismic damage from bridge structure to subgrade structure, thereby potentially reducing post-seismic repair expenses for the bridge.

Abstract High-speed rail (HSR) has recently expanded its networks globally, but its 350 km/h bridges have not yet been tested for high-level earthquakes. This study tests the typical HSR bridge on a shaking table to assess the seismic performance in high-level earthquakes such as Maximum Considered Earthquake. Based on the model similarity theory, it creates nine round-ended rectangular-shaped cross-section solid RC HSR bridge piers. It employs the orthogonal testing method to conduct experimental design considering four influential factors: aspect ratio, axial load ratio, longitudinal reinforcement rate, and volumetric stirrup ratio. Experimental research was conducted to examine the dynamic response of these piers subjected to varying seismic impacts and design parameters, and the implications of the four factors on the seismic performance of the piers were discussed. After all the earthquake circumstances, the test findings demonstrate that the concrete of the pier specimens has not cracked or spalled much. An earthquake with a peak acceleration of 0.96 g indicates that the pier body of the standard high-speed rail round-end solid pier retains its integrity and stability. The extent of the pier's earthquake damage is not immediately evident. HSR bridges' seismic design may benefit from this research, which examines the impact of dynamic characteristics, including aspect ratio, axial load ratio, and longitudinal reinforcement rate, on HSR bridge piers' seismic performance.

The solar temperature field and its temperature effects on the straddle monorail tourist transportation system (SMTTS) significantly affect its mechanical performance. To investigate the distribution law of the daylight temperature field of the unpaved steel beams, the daylight temperature fields of box-type and I-sectional steel beams in different regions were measured and simulated. With the simulation results, the vertical temperature gradient curves of the unpaved steel girders were determined. Afterward, with the historical meteorological data as variables, the parameters of the extreme value model of generalized extreme value (GEV) distribution were obtained, and the representative values of temperature differences in China, based on the recurrence period, were analyzed. By analyzing the temperature difference values in 34 cities in China, an empirical prediction formula for the representative temperature difference value with three parameters was proposed, and the temperature gradient partition was established. The results indicated that the vertical temperature gradients of closed-section steel box girders are about 2–3 °C greater than that of open-section I-beams. Moreover, there are apparent geographical differences in the temperature difference values of steel girders.

Wind flow over complex terrain is strongly influenced by the topographical features of the region, resulting in unpredictable local wind characteristics. This paper employs numerical simulation to study the wind flow at a towering peak extending out of a steep mountainside and the wind-induced effect on onsite landscape platforms. First, the wind flow from seven different directions is explored via 3D numerical simulations, and the wind load distribution on the platforms is highlighted. Second, a 2D numerical simulation is conducted to evaluate the wind speedup effect at the side peak, examining the influence of the side peak height and the mountainside steepness on the wind speedup factor. The numerical simulations presented in this research were validated by replicating a published numerical and experimental study. The results illustrate the amplifying and blocking effects of the surrounding topography, yielding unpredictable and nonuniform wind pressure distribution on the platforms. The presence of the side peak leads to a significant increase in the speedup factor, and the side peak height and the mountainside steepness have a moderate influence on the value of the speedup factor. Additionally, the speedup factor obtained from this study varies significantly, especially near the surface, from the recommendations of several wind load standards. Consequently, the impact of the local terrain and the wind speedup effect must be thoroughly assessed to ensure the structural integrity of structures installed at a similar topography.

With the increase in the occupancy ratio of bridges and the speed of trains, the probability of trains being located on bridges during earthquakes increases, and the risk of derailment increases. To investigate the influence of unequal-height piers on the dynamic response of high-speed railway train bridge systems, a seismic action model of high-speed train–track–bridge dynamic systems was established based on the in-house code using the finite element method and multi-body dynamics method. It is found that (1) compared to equal-height piers, the peak lateral dynamic response of unequal-height piers (with gradually increasing pier heights) decreases, while the peak vertical dynamic response increases; (2) the peak lateral dynamic response of unequal-height piers (with a steep increase in pier height) increases sharply, while the peak vertical dynamic response decreases; and (3) the safety indicators of equal-height piers are significantly superior to the two unequal-height pier operating conditions.

Accurate running safety assessment of trains under earthquakes is crucial to ensuring the safety of line operation. Extreme contact behaviors such as wheel flange contact and wheel jump during earthquakes will directly affect the running safety of trains. To accurately simulate a wheel-rail extreme contact state, the calculation of the normal compression amount, the normal contact stiffness, and a number of contact points are crucial in wheel-rail space contact modeling. Hence, in order to clarify the applicable algorithms during earthquakes, this paper first introduces different algorithms in three aspects mentioned above. Taking a single CRH2 motor vehicle passing through a ballastless track structure under EI-Centro wave excitation as an example, a comparative analysis of wheel-rail contact dynamics and running safety was conducted. The results showed that adopting the normal compression algorithm based on vertical penetration and the consideration of only single-point contact will result in the maximum calculation error of wheel-rail contact force to reach 339.50% and 35.00%, respectively. This significantly affects the accuracy of train safety assessment, while using the empirical formula for wheel-rail normal contact stiffness has relatively less impact. To ensure the accuracy of running safety assessment of trains during an earthquake, it is recommended to adopt the normal compression algorithm based on normal penetration and consider the multi-point contact in wheel-rail contact modelling.

Abstract 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.

To study the mapping relationship between girder deformation and rail deformation for the CRTS Ⅲ slab ballastless track (SBT) multi-span simply supported bridge, this study derived a simplified analytical solution, and the corresponding ANSYS finite element model (AFEM) was established. Compared with the fine analytical model (FAM) and the AFEM, the calculation results of the three models under the conditions of pier settlement and girder vertical fault were compared, which verified the universal properties of the simplified analytical model (SAM). Based on the verified SAM, the influence of pier settlement, fastener stiffness, girder span, and girder vertical fault on rail deformation was studied. The results show that the rail deformation is approximately proportional to pier settlement and girder vertical fault. With the increase in fastener stiffness, the fastener internal force increases, the rail mapping deformation increases, and the length of the rail mapping deformation area decreases. With the increase in girder span, the rail deformation curve becomes smooth, the length of the rail mapping deformation area becomes longer, and the fastener internal force is significantly reduced.

Corrugated steel plate shear walls (CSPWs) with three different stiffening methods are proposed in this paper, including unstiffened CSPWs (USWs), cross stiffened CSPWs (CSWs) and asymmetric diagonal-stiffened CSPWs (ASWs). A numerical model was established by ABAQUS 6.13 based on the validation of an existing cyclic test on a CSPW. This paper presents an investigation of the lateral performance under monotonic loading, seismic performance under cyclic loading and seismic performance under atmospheric corrosion of USW, CSW and ASW. The results show that (1) Stiffeners can improve the elastic critical buckling load, the initial stiffness and the ultimate shear resistance of CSPWs, and the effect of asymmetric diagonal stiffeners is more significant than that of cross stiffeners; (2) Stiffeners can improve the energy dissipation capacity and ductility, delay stiffness degradation and reduce the out-of-plane deformation of CSPWs, and the hysteretic performance of ASWs is obviously better than that of CSWs; and (3) Under atmospheric corrosion, stiffeners are conducive to inhibiting buckling and improving the seismic performance of CSPWs, while the seismic performance of CSWs is significantly affected by corrosion, so asymmetric diagonal stiffeners are better than cross stiffeners in improving the seismic performance of CSPWs. Meanwhile, the formula of ultimate shear resistance of corroded specimens is also fitted in this paper, which can provide design suggestions for practical engineering.

When solving structural dynamic problems, the displacement algorithm needs only calculating and storing structure’s displacements in the main calculation process, which makes the displacement algorithm have advantages over multivariable algorithms in calculation efficiency and storage requirements. By using a novel approach based on dimensional analysis firstly given by the first author, a one-parameter family of two-step unconditionally stable noniterative displacement algorithms, referred to as the CQ-2x method, is developed. Compared with other unconditionally stable noniterative multivariable algorithms such as the representative KR-α method, the proposed method has advantages in several aspects. The CQ-2x method is unconditionally stable regardless of stiffness hardening or stiffness weakening, while the KR-α method is only conditionally stable in case of stiffness hardening. The CQ-2x method needs only one solver within one time step, while the KR-α method needs two solvers within one time step, which makes the CQ-2x method show higher efficiency. Numerical examples are presented to demonstrate the potential of the proposed method.

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.

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 nonlinear train-track-bridge system (TTBS) considering the random track irregularity and mass of train is discussed. Based on the Karhunen–Loéve theory, the track irregularity is expressed and input into the TTBS, and the result of random response is calculated using the point estimation method. Two cases are used to compare and validate the applicability of the proposed method, which show that the proposed method has a high precision and efficiency. Then, taking a 7-span bridge and a high-speed train as an example, the calculation results of random response of the nonlinear and linear wheel-rail model are compared, and the results show that for the bridge and rail response, the nonlinear and linear models are almost the same. Finally, comparing the calculated probability distribution results with the test results, it shows that the method can be applied to the prediction of actual response range.

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.

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.

This study proposed a dynamic characteristic analytical method (ANM) of a composite box girder bridge with corrugated steel web (CBGCSW) by completely considering the impact of shear lag effect and accordion effect of corrugated steel webs. Based on energy principles and variational principles, a vibration differential equation and the natural boundary conditions of a CBGCSW were developed. The analytical calculation formula for solving the vibration differential equation was then obtained. The results calculated using the ANM agreed well with previous experimental results, which validated the correctness of ANM. To demonstrate the superiority of the ANM, the vibration frequencies of several abstract CBGCSWs with varying ratios of span–width, obtained using the elementary beam theory (EBT) and the finite element method (FEM), were compared with those obtained by ANM. The efficacy of the ANM was verified and some meaningful conclusions were drawn which are helpful to relevant engineering design, such as the observation that a higher natural vibration frequency and smaller span–width ratio significantly magnified the shear lag effect of CBGCSW. The first five-order natural vibration frequencies of the CBGCSW were significantly lower than those of the composite box girder bridge with general steel web (CBGGSW), which indicates that the impact of the accordion effect is significant.

Based on Euler–Bernoulli beam theory, first, partial differential equations were established for the vibration of multiple simply supported beams subjected to moving loads. Then, integral transforms were conducted on the spatial displacement coordinate and time in the partial differential equations, and the frequency-domain response of multiple simply supported beams subjected to moving loads was obtained. Next, by conducting the corresponding inverse transforms on the displacement frequency-domain responses of multiple simply supported beams, the spatial displacement time-domain responses were obtained. Finally, to validate the analytical method reported in this paper, the dynamic response of a typical double simply supported rail-bridge beam system of high-speed railway in China subjected to a moving load was carried out. The results show that the analytical solution proposed in this paper is consistent with the results obtained from a finite element analysis, validating and rationalizing the analytical solution. Moreover, the system parameters were analyzed for the dynamic response of double simply supported rail-bridge beam system in high-speed railway subjected to a moving load with different speeds; the conclusions can be beneficial for engineering practice.

This study establishes the improved element stiffness and mass matrices of the thin-walled box girder, using a cubic Hermite polynomial shape function and based on an improved displacement function for shear-lag warping meeting the axial equilibrium condition of shear-lag warping stress and the consistency requirements of the displacement function. The improved thin-walled box girder element comprehensively considers multiple influencing factors, such as the thin-walled box girder shear-lag effect, shear deformation, and rotational inertia. The element shape function has first-order continuity at the element interface and satisfies the calculation precision with relatively few degrees of freedom. A finite beam element method program that can be used to calculate the natural vibration frequencies of thin-walled box girders was compiled based on the improved thin-walled box girder element. This program was used to calculate the natural vibration frequencies of many thin-walled box girder samples with different span-width ratios, span-height ratios, and boundary conditions. After comprehensively considering the influencing factors, the calculation results obtained from finite beam element method are in good agreement with those obtained from an ANSYS finite element calculation, thus demonstrating the rationality and validity of the improved thin-walled box girder element stiffness matrix and mass matrix proposed in this study. Finally, factors influencing the thin-walled box girder shear-lag effect and shear deformation were analyzed, providing relevant reference for project designers.

Based on Hamilton’s principle, this study has developed a continuous treatment for the steel-concrete composite truss beam (SCCTB). It has also deduced the SCCTB element stiffness matrix and mass matrix, which include the effects of interface slip, shear deformation, moment of inertia, and many other influencing factors. A finite beam element method (FBEM) program for SCCTB’s natural vibration frequency has been developed and used to calculate the natural vibration frequencies of several SCCTBs with different spans and different degrees of shear connections. The FBEM’s calculation results of several SCCTBs agree well with the results obtained from ANSYS. Based on the results of this study, the following conclusions can be drawn. For the SCCTB with high-order natural vibration frequency and with short span, the effect of the shear deformation is greater. Hence, the effect of the shear deformation on the SCCTB’s high-order natural vibration frequency cannot be ignored. On the other hand, the effect of the interface slip on the SCCTB’s high-order natural vibration frequency is insignificant. However, the effect of the interface slip on the SCCTB’s low-order natural vibration frequency cannot be ignored.

The dynamic response of a simply supported double-beam system under moving loads was studied. First, in order to reduce the difficulty of solving the equation, a finite sin-Fourier transform was used to transform the infinite-degree-of-freedom double-beam system into a superimposed two-degrees-of-freedom system. Second, Duhamel’s integral was used to obtain the analytical expression of Fourier amplitude spectrum function considering the initial conditions. Finally, based on finite sin-Fourier inverse transform, the analytical expression of dynamic response of a simply supported double-beam system under moving loads was deduced. The dynamic response under successive moving loads was calculated by the analytical method and the general FEM software ANSYS. The analysis results show that the analytical method calculation results are consistent with ANSYS’ calculation, thus validating the analytical calculation method. The simply supported double-beam system had multiple critical speeds, and the flexural rigidity significantly affected both peak vertical displacement and critical speed.

Distortional buckling is one of the important buckling models of steel-concrete composite beam in negative moment region. Rotation restraining rigidity and lateral restraining rigidity which steel beam web to bottom plate of steel-concrete composite are the key factors to influence the distortional buckling behavior. A comprehensive and intensive study on rotation restraining rigidity and lateral restraining rigidity which steel beam web to bottom plate of I-shaped steel-concrete composite beam in negative moment region is conducted in this paper. Energy variation principle is adopted to deduce the analytical expressions to calculate the rotation restraining rigidity and lateral restraining rigidity. Combined with the buckling theory of axial compression thin-walled bars in elastic medium, the buckling moment is obtained. Theoretical analysis shows that the rotation restraining rigidity and lateral restraining rigidity of steel beam web appear to have a linear relationship with the external loads and could also be negative. Compared with other methods, the results calculated by the proposed expressions agree well with the numerical results by ANSYS. The proposed expressions are more concise and suitable than the existing formulas for the engineering application.

To evaluate the energy dissipation differences between metal dampers and viscous dampers and to gauge the degree of equivalence between bilinear hysteresis and viscous damping, we studied the equivalence of bilinear hysteresis and viscous damping. Using a MATLAB program and the principle of equal energy dissipation, the energy dissipation effect of bilinear hysteresis was equated based on the effect of viscous damping. Under a state of sinusoidal excitation, the displacement response of the numerical method, which strictly considers the bilinear hysteresis, was compared with the displacement response of the equivalent viscous damping calculation method. The results show that the oscillation periods for the two models demonstrate high consistency, with the displacement curves in the steady-state response stage nearly identical. Because of the lag in hysteresis energy dissipation, the bilinear hysteresis system always reaches the steady-state stage slower than the equivalent viscous damping system, implying that the metal damper responds more slowly to transient energy. In the free vibration stage, the bilinear hysteresis system cannot return to the initial position, while the displacement of the equivalent viscous damping system approaches zero, suggesting that the self-resetting effect of the viscous damper is better. [ABSTRACT FROM AUTHOR]

To study the influence of interlayer stiffness and interlayer damping on the dynamic response of multi-layer beams under moving loads, a method for calculating the dynamic response of a multi-layer beam system considering random interlayer stiffness or random interlayer damping under successive moving loads based on the Karhunen-Lo'eve expansion and point estimation method is proposed. The accuracy of the proposed method was verified by using several numerical examples. The influence of interlayer stiffness, interlayer damping, standard deviation of interlayer stiffness, and standard deviation of interlayer damping on the dynamic response of a girder-rail system was analyzed by using the proposed calculation method. The results show that when the moving load velocity is high, the number of critical velocity of the rail significantly increases with decreasing interlayer stiffness. In addition, dynamic responses of the rail and girder increase with decreasing interlayer damping and the dynamic response of rail at the midspan significantly increases as the standard deviation of interlayer stiffness increases. Neglecting interlayer damping can lead to significant fluctuation in the dynamic response of rail, a significant increase in the number of critical velocity of rail, and increases in the dynamic responses of rail and girder. Changing interlayer stiffness, interlayer damping, standard deviation of interlayer stiffness, or standard deviation of interlayer damping will have no obvious influence on the dynamic response of girder. [ABSTRACT FROM AUTHOR]

In order to examine the dynamic response of a girder-orbit-moving load coupling system considering the constraint effect of the orbit extension, an analytical calculation method for the dynamic response of the girder-orbit system with arbitrary boundary conditions under a moving load is proposed based on the finite Fourier transform. Using the analytical calculation method, the dynamic response of the girder-orbit system with orbit extension at different moving load speeds is calculated, and the calculated results are compared with ANSYS finite element numerical calculation to examine the effect of moving load speed, orbit and girder flexural stiffness, interlayer spring stiffness, and orbit extension length on the dynamic response of the system. Results show that the analytical calculation results are in good agreement with the ANSYS calculation results, verifying the correctness of the analytical calculation method. The amplitude-moving load velocity relationship curve of the girder-orbit system dynamic response is a waveform curve. The interlayer spring stiffness, orbit flexural stiffness, and orbit extension length have significant effects on the dynamic response of the orbital layer, but the effect on the dynamic response of the girder layer is not significant. [ABSTRACT FROM AUTHOR]

In order to study the dynamic characteristics of a simply supported double-beam system under a moving mass, the system of fourth-order dynamic partial differential equations of a simply supported double-beam system was transformed into a system of second-order dynamic ordinary differential equations relative to time coordinates by performing the finite sin-Fourier Transform relative to space coordinates. And the analytical solution of the dynamic response of the simply supported double-beam system under a moving mass was obtained by solving the system of dynamic ordinary differential equations. The analytical method and ANSYS numerical method were used to calculate the dynamic responses of several simply supported double-beam systems under a moving mass at different speeds. The influences of inertial effect, mass movement speed, and Winkler-layer spring stiffness and damping on the dynamic responses of simply supported double-beam systems were analyzed. According to the study results, the analytical calculation results in this paper fit well with the ANSYS finite element numerical calculation results, demonstrating the rationality of the analytical method. The inertial effect has a significant influence on the dynamic response characteristics of the simply supported double-beam system. The simply supported double-beam system underwent several resonant speeds under a moving mass, and the Winkler-layer spring stiffness has a relatively significant effect on the vibration of the first beam. [ABSTRACT FROM AUTHOR]

Although friction-based isolation systems have been studied for many years, their seismic performance and influence factors have not yet been fully analyzed. This paper used a compiled computer program to investigate a rolling friction system under earthquakes. Unlike in other common systems, the relative displacement of the rolling friction system can be larger than the absolute displacement of the ground. Those displacement responses are very sensitive to the wave shape of ground motions. Different ground motion waves, even when generated from the same response spectrum, can result in obviously different displacement responses, and the friction variability on the contact surface provides additional complications for the seismic responses. [ABSTRACT FROM AUTHOR]

Time history analysis is becoming the routine process to quantify the response of the structure under dynamic loads. In this paper, a novel two-step unconditionally stable explicit integration algorithm, named Unconditional Stable Two-Step Explicit Displacement Method (USTEDM), is proposed for vibration analysis of structure. USTEDM is unconditionally stable, requires low memory, produces no overshoot, and is third order accurate. The accuracy and efficiency of USTEDM are presented and compared with other commonly used integration algorithms. The result shows that the proposed algorithm has superior performance and can be used efficiently in solving vibration response of civil engineering structure. [ABSTRACT FROM AUTHOR]

In order to investigate dynamic characteristics of steel-concrete composite box beams, a longitudinal warping function of beam section considering self-balancing of axial forces is established. On the basis of Hamilton principle, governing differential equations of vibration and displacement boundary conditions are deduced by taking into account coupled influencing of shear lag, interface slip, and shear deformation. The proposed method shows an improvement over previous calculations. The central difference method is applied to solve the differential equations to obtain dynamic responses of composite beams subjected to arbitrarily distributed loads. The results from the proposed method are found to be in good agreement with those from ANSYS through numerical studies. Its validity is thus verified and meaningful conclusions for engineering design can be drawn as follows. There are obvious shear lag effects in the top concrete slab and bottom plate of steel beams under dynamic excitation. This shear lag increases with the increasing degree of shear connections. However, it has little impact on the period and deflection amplitude of vibration of composite box beams. The amplitude of deflection and strains in concrete slab reduce as the degree of shear connections increases. Nevertheless, the influence of shear connections on the period of vibration is not distinct. [ABSTRACT FROM AUTHOR]

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger cross-section and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model. [ABSTRACT FROM AUTHOR]

Polyimide/silica (PI/SiO2) nanocomposite films with 10 wt % of silica content were prepared by sol–gel process under the conditions with and without additional water. The presence of additional water has great effect on the silica particle size and thus on the properties of the prepared PI/SiO2 films. The results indicated that with additional water, the silica particles formed before the imidization of poly(amic acid) (PAA) and aggregated with the increasing of temperature and degree of the proceeding imidization process. For the nonaqueous process, the hydrolysis condensation reaction of tetraethoxysilane (TEOS) did not occur until the imidization of PAA took place, and no silica particles were found in the unimidized PAA films. The hydrolysis–condensation reaction of TEOS was initiated simultaneously by the trace water released from the imidization reaction, the self‐catalysis mechanism of the approach provide a means of achieving uniformly dispersed silica particles formed in the PI matrix with particle size in the range of 30–70 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1579–1586, 2007 [ABSTRACT FROM AUTHOR]

Silver nanoparticles embedded on silica nanospheres were prepared by using ion-exchangeable poly(acrylic acid) (PAAc) grafted on the silica surface as a soft template followed by chemical reduction. The prepared hybrid nanospheres were characterized using x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, and bactericidal activity measurements. The results suggest that mono-dispersed Ag nanoparticles with controllable diameters can be obtained on the surface of silica nanospheres by varying the concentration of the silver nitrate and the pH value of the suspension, and the hybrid nanospheres have excellent bactericidal activity and potential applications as bactericidal agents in biomedical fields. [ABSTRACT FROM AUTHOR]

Previously, many isolation systems with friction action are designed ignoring the variability of friction coefficient. By taking a rolling-damper isolation system as the study object, this paper analyzed the effects of non-uniform distribution of rolling friction coefficient on its isolation performance through a compiled computer program. The results show that the errors associated with the maximum structural relative displacement, acceleration and residual displacement due to ignoring the friction variability are sequentially growing, and this rule is weakened by the damper. Under the condition of large friction variability and little damper action, the calculation of the maximum structural relative displacement and acceleration should consider the friction variability. When the structural residual displacement is concerned, the variability of rolling friction coefficient should be fully considered regardless of friction variability degree. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

As to analyze the effects of friction pendulum bearings (FPB) on the responses of simply supported bridges on a high-speed railway under longitudinal earthquakes, a spatially integrated track-bridge model with a CRTS II slab ballastless track and FPB was established by using the OpenSEES software. The seismic responses under different ground motions were calculated and compared with those using common spherical steel bearings. The comparison results show that the combination of FPB and the CRTS II slab ballastless track is more reasonable. Namely, using FPB can effectively protect the bridge and track structures. Moreover, the rails, fasteners, CA layer and piers are perfectly protected by multi-layer isolation mechanics, induced by FPB and sliding layer, even under strong earthquakes. Finally, 0.05 is identified to be the best value for the friction coefficient of FPB under longitudinal earthquakes. [ABSTRACT FROM AUTHOR]

The random friction distribution is an objective phenomenon and always leads to great uncertainty in seismic responses of damper-friction isolation systems. As to optimize the seismic performance, this paper artificially made the friction distribution on a contact surface to be concave. When the damper-friction isolation system was subjected to different ground motions, more regular responses, due to the concave friction distribution, were obtained comparing with the responses of the random friction distribution. The concave friction distribution is always conducive to reducing the structural relative displacement and insignificantly increasing the structural acceleration. An optimization design example of an isolation building was carried out. And the results showed that as for a structure only being sensitive to acceleration or force, significant concave friction distribution and little damping constant would be the best design combination. It resulted in a much less acceleration and an acceptable relative displacement on the structure. [ABSTRACT FROM AUTHOR]