Simply-supported Girder Bridge Research Articles

Discrete Element Analysis of the Dynamic Mechanical Characteristics of Ballasted Track on Bridges Under Train Loading

The operation and service performance of ballasted track on bridges face significant challenges due to high-speed railway train operations. To investigate the mechanical characteristics of ballasted track on bridges, field experiments were conducted. A coupling model of ballasted track on a simply-supported girder bridge was established using the coupling method of discrete element and multi-flexible body dynamics and analyzes the changes in ballast bed settlement deformation, stiffness and energy with increasing load cycles. The findings reveal that dynamic loading alters the original contact state of ballast particles, displaying notable anisotropy vertically and longitudinally and isotropy horizontally. The vibration of ballast particles on bridges is more pronounced than on the subgrade, with vibration acceleration under the sleeper at 150[Formula: see text]mm depth on the bridge being 2.89 times that on the subgrade foundation. As the system stabilizes, the interlocking effect among granular ballast particles strengthens, reducing mutual sliding and increasing ballast bed stiffness by approximately 7.8–9.5% compared to the initial state, while total energy and dissipated energy gradually decrease. It is recommended to monitor the quality of ballast particles under the sleeper of ballasted tracks on bridges, implement vibration mitigation measures, or periodically replace ballast particles.

Seismic Fragility Analysis of Reinforced Concrete Simply Supported Girder Bridges Resting on Double-Column Piers for High Speed Railway

Seismic Fragility Analysis of Reinforced Concrete Simply Supported Girder Bridges Resting on Double-Column Piers for High Speed Railway

Effects of Track Structure Nonlinearity on Running Safety of Simply Supported Girder Bridges during Earthquakes

Effects of Track Structure Nonlinearity on Running Safety of Simply Supported Girder Bridges during Earthquakes

Seismic performance of railway bridges with novel ductile piers under near-fault earthquakes

The destructive force of near-fault earthquakes presents a significant challenge to railway bridges. To enhance the seismic resilience of railway bridges under such conditions, a novelly designed ductile pier is introduced herein, accompanied by a analysis of its stiffness, damping characteristics, and shear capacity. The analysis reveals that the ductile pier exhibits reduced stiffness and increased viscous damping ratio when compared to the traditional pier. Subsequently, a finite element model of a typical railway simply-supported girder bridge is established and verified through shaking table tests. Furthermore, the near-fault seismic wave synthesis method is introduced, and the synthesized near-fault seismic waves are input into the traditional pier model and the ductile pier model for seismic analysis. The findings demonstrate that the ductile pier effectively diminishes girder acceleration and bearing displacement while enhancing pier energy dissipation. Additionally, the ductile pier is proved effective in safeguarding the core concrete during significant seismic events.

Structural demand assessment of exceptional road transport actions on existing Italian simply-supported girder bridge decks

In the present work an in-depth analysis of the structural demand induced by several configurations of exceptional road transports has been carried out with the aim to quantify bending moment and shear demands over different geometrical layouts of simply-supported girder bridge decks and compare them with those deriving by the application of the traffic load models in force at the time of the design. On such bases, a structural demand coefficient has been computed in analogy to the Level 3 assessment suggested by the new Italian Guidelines for assessing the Risk of existing bridges. In this way, this structural demand index can be easily used by infrastructure owners for a fast assessment of the effects of exceptional road transport configurations potentially travelling over a bridge on its structural elements, if compared to the load models originally considered for its design, thus making possible a preliminary screening on the transitability of the infrastructure and the identification of potential road network bottlenecks.

Deflection Monitoring Method for Simply Supported Girder Bridges Using Strain Response under Traffic Loads

Deflection measurements are usually used as a key index in civil engineering for performing structural assessments of bridge safety. However, owing to technical or cost issues, it may be difficult to implement long-term monitoring of bridge deflection, especially for short- or medium-span bridges. Therefore, this study presents a novel method for measuring the deflection of simply supported girder bridges. In the proposed method, the strain measurement was implemented under traffic loading at only one position, such as middle span, and then the strain distribution along the girder was reconstructed to calculate the girder deflection with basic structural mechanical theory. To implement the method, the theory was constructed based on the displacement reciprocal theorem at first to assess the strain distribution along the girder from the strain measurement at some position during traffic loads passing across the bridge. Second, a strain measurement method, namely long-gauge fibre Bragg grating (FBG) sensing technology, was introduced to take strain measurements for a concrete bridge. Third, various finite element (FE) bridge models were developed to validate the proposed method’s accuracy, the results from which indicated that the method accurately implemented deflection measurement with an approximately 5% calculation error. In addition, the influence of some key parameters, such as vehicle type, vehicle speed, and structural damage, was investigated. The simulation results revealed that damage to the hinge joint in the middle location could significantly influence the proposed method’s accuracy such that the error may exceed 10%. Finally, on-site experiments were conducted on a simply supported girder bridge to further validate the proposed method’s accuracy, and an approximately 8% deflection assessment error was found. Considering the additional advantages of FBG sensing technology, the proposed method can also be effective for long-term deflection measurements of short- or medium-span bridges.

Shaking table test of the seismic performance for railway simply-supported girder bridge isolated by self-centering bearing

In order to solve the problem of the residual displacement of a railway simply-supported girder bridge and realize the aim of a rapid recovery in traffic after earthquake events, we designed a self-centering seismic isolation bearing and created a typical simply-supported girder bridge model with 1/10 ratio. Three peak ground acceleration (PGA) shaking table tests were performed, with the test procedures further described in detail. The test results show that the bearing provides an overall good self-centering performance. Other than the case of a 0.5 g transverse earthquake, where the bearing remains outside of the sliding surface and therefore cannot be self-centering, all the tests show that the bearing is completely self-centering. At the same time, during all the earthquake scenarios, the main structure of the bridge was not damaged in any discernable way, the longitudinal frequency did not change, and the transverse frequency decreased given that the bearing remained outside of the sliding surface. In addition, it was found that the large bearing displacement in the longitudinal direction may lead to a collision of adjacent girders, resulting in a sharp increase in the acceleration of the girders. In cases without collisions between the girders, the acceleration of the girder is effectively reduced compared with the acceleration of the pier top. The results also show that the pier can be effectively protected by the self-centering bearing, as well as indicating that the reinforcement strain of the pier does not reach the yield value under all tests. Due to the large displacement of the bearing, it is necessary to increase the allowable displacement or install a limiting device. Finally, the finite element model (FEM) of the test model is established, with the calculation results compared with the test results, in this way proving the correctness of the FEM and providing a reference for designing the seismic isolation of the railway simply-supported girder bridge.

Exceeding probability analysis for rail of high-speed railway under seismic excitations

PurposeThe smoothness of the high-speed railway (HSR) on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges, which may threaten the safety of running trains. Indeed, few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard. The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approachIn order to investigate the exceeding probability of the rail displacement under different seismic excitations, the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis (IDA) is proposed, and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined. Then a finite element model (FEM) of an assumed HSR track-bridge system is constructed, which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track. Under different seismic excitations, the seismic displacement response of the rail is calculated; the character of the rail displacement is analyzed; and the exceeding probability of the rail vertical displacement exceeding the allowable standard (2mm) is investigated.FindingsThe results show that: (1) The bridge-abutment joint position may form a step-like under seismic excitation, threatening the running safety of high-speed trains under seismic excitations, and the rail displacements at mid-span positions are bigger than that at other positions on the bridge. (2) The exceeding probability of rail displacement is up to about 44% when PGA = 0.01g, which is the level-five risk probability and can be described as 'very likely to happen'. (3) The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge, and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/valueThe work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.

Influence of soil liquefaction effect on seismic failure mechanism of river-crossing simply-supported girder bridges subjected to near-fault ground motions

Soil liquefaction induced by strong earthquake could cause severe failure to bridges, particularly for river crossing simply-supported girder bridges. Consequently, it is an urgent task to clarify the influence of soil liquefaction on the seismic failure of this bridge-ground system. To this end, two-dimensional finite element (FE) simulation method focusing on liquefiable site-structure was validated based on a published centrifuge test at first. Then 2 refined FE models were established for a typical river-crossing simply-supported girder bridge with the only difference whether considering site liquefaction. Near-fault ground motions were selected for nonlinear dynamic analysis. Seismic responses of two models were compared to investigate the influence of soil liquefaction on bridge failure mode. The comparison results indicated that soil liquefaction significantly changed seismic response of bridge-ground system, such as site displacement performance, pile–pier displacement demand, pile–piers bending mode, sliding bearing deformation, leading to higher bridge failure risk and change of failure mode.

Seismic response of high-speed railway system under actions of ground motions from deterministic physics-based simulation

In order to investigate the response of a high-speed railway bridge under seismic excitations in the near-fault area, a deterministic physics-based method is used to construct the ground motion field in the near-fault area of a scenario earthquake. A finite element model of an assumed high-speed railway system is established, which consists of a finite length CRTS III ballastless track laid on a 15-span simply-supported girder bridge. The simulated ground motions and a group of three-component as-recorded accelerograms are used to provide non-uniform and uniform excitations at bridge piers, respectively. The seismic response of the rail-track-bridge system is calculated, and the effects of using different types of seismic excitations for the seismic analysis of the high-speed railway bridge in the near-fault area are analyzed. The results show that two end piers of a multi-span simply supported girder bridge could encounter remarkably different excitations in terms of waveform and frequency content for different bridge alignments in the near-fault area. The vertical response of the railway bridge system is more sensitive to the pattern of the excitation than the longitudinal response. Considering the spatial difference of ground motions among piers could increase the difference of the rail vertical displacement between the beam joint and mid-point of span, forming a remarkable periodic vertical irregularity of the rail. Using non-uniform excitation could lead to a reduction in DPeak and APeak which is most significant for DPeak in the vertical direction.

Research on the Mechanical Behavior of a Steel–Concrete Composite Link Slab on a Simply Supported Girder Bridge

Water leakage and debris accumulation caused by the expansion joints in a bridge superstructure reduce the service life of the bridge and increase the maintenance costs. A link slab is an effective means to eliminate the expansion joints, providing a continuous deck system. However, the load-caused concrete cracking of the link slab also leads to problems associated with water leakage and rebar corrosion. In order to solve these problems, a new type of steel–concrete composite link slab (SCC-LS) was designed to continuously subject the bridge deck to a positive bending moment and surface concrete compression, which reduced the cracking damage in the link slab. This paper presents the mechanical performance results of the SCC-LS obtained using full-scale model tests. Furthermore, theoretical calculations and finite element (FE) models of the jointless bridge validated the performance based on the experimental results. The results of this study show that the SCC-LS can effectively solve the problem of concrete cracking on the surface of the bridge deck, which has theoretical reference significance and engineering application value for the structural design, maintenance and transformation of continuous simply supported bridge decks and the promotion of seamless bridges.

Running safety and seismic optimization of a fault-crossing simply-supported girder bridge for high-speed railways based on a train-track-bridge coupling system

Running safety and seismic optimization of a fault-crossing simply-supported girder bridge for high-speed railways based on a train-track-bridge coupling system

Long-Term Monitoring of Local Track Irregularity and Its Influence for Simply Supported Girder Bridge of HSR

By analyzing dynamic track geometric irregularity data of high-speed railway (HSR) with ballast track in China, there is a peak of [5, 11] m wavelength for the longitudinal level at the beam joint of simply supported girder bridges. The difference between the absolute value of track longitudinal level at the beam joint and that at the midspan is one to three mm. Under annual temperature cycle, the ballast at the beam joint loosens because of the bridge–track interaction, which results in the longitudinal level at the beam joint gets larger in winter and smaller in summer, that means the longitudinal level is negatively correlated with temperature, and at the same time, the development of the track longitudinal level and Track Quality Index (TQI) with the temperature are given. In addition, the vertical acceleration of axle box and bogie, and wheel–rail vertical force are larger when the train passes the beam joint than when it passes the midspan, which threatens running safety significantly. This article established a three-dimensional vehicle–track–bridge finite element model (FEM), thus the thresholds of track longitudinal level at the beam joint for simply supported girder bridge with ballast track in 250 km/h HSR were proposed, i.e., the maximum of dynamic track longitudinal level is 14 mm, and the maximum of static value is 11 mm. Once one of the two thresholds exceeds the corresponding limit, the train speed should be reduced to 160 km/h or below.

Study on Mechanical Properties of Simply Supported Girder Bridge after Jointless

The jointless bridges includes integral bridges, semi-integral bridges and extended deck bridges. The integral bridges adopts an integral abutment, and its main girder, abutment and pile under abutment are fixed together to bear the force together. The expansion joint and expansion device are cancelled, and the integrity, durability and driving comfort of the bridge are improved. In this paper, a simply supported girder bridge in Fujian Province of China is taken as the research background, and it is transformed into an integral bridge. Midas/Civil software is used to establish the finite element models of the original bridge and the integral bridge, and the mechanical properties of the main girder and the pile under the combined action of dead load and overall temperature rise of 25 °C are analyzed. The results show that due to the consolidation of the main girder and abutment of the integral bridge, the internal force at the girder end under the combined action of temperature and dead load is greater than that of the simply supported beam bridge. The pile deformation of the integral bridge is significant under the combination of temperature and dead load. With the increase of the height-to-thickness ratio of the abutment of integral bridge, the bending moment at the girder end and the mid-span are increasing. Different abutment height-to-thickness ratio has little influence on the horizontal displacement of the girder end of integral bridge. With the increase of height-to-thickness ratio of the abutment of integral bridge, the deformation of pile decreases. The flexible abutment with large height-to-thickness ratio can improve the mechanical properties of pile and achieve the purpose of protecting the pile.

Damage mode and dynamic response of RC girder bridge under explosions

During the whole service life, bridge structures potentially suffered from the threats from military conflicts, terrorist attacks and accidental explosions. The related studies on the damage modes and dynamic responses of entire RC girder bridges subjected to the explosion loadings is very limited, which is addressed through high-reliability numerical simulations. Firstly, by comparing with the experimental overpressure- and acceleration-time histories, as well as the damage modes from the explosion tests on 1/5 scaled two-span girder bridges, the validities of the material models and corresponding parameters, as well as the numerical simulation algorithms are verified sufficiently. Then, three levels of potential explosive threats, i.e., suitcase, sedan, and small moving van (the corresponding equivalent cubic TNT explosive masses are 23 kg, 454 kg and 4536 kg) specified by Federal Emergency Management Agency (FEMA) were selected to analyze the damage modes and dynamic responses of a typical four-span prototype RC girder bridge under both below- and above-deck explosion scenarios. Furthermore, the blast resistance of both simply-supported and continuous girder bridges were examined, and the minimum safe distances were proposed. It derives that, (i) for the below-deck explosion scenarios, total nine damage modes exist from small-scale spalling of concrete at the bottom of pier to the total collapse of the bridge; (ii) for the above-deck explosion scenarios, eight damage modes can be induced, including cratering and opening in deck, flexural failure of the T-girder, etc.; (iii) the continuous bridge exhibits obvious and slight enhanced blast resistance for below- and above-deck explosions than simply-supported girder bridges; (iv) small moving van can lead to the destruction of the entire bridge, the minimum safe standoff distances for suitcase and sedan bombs are 0.5 m and 3.0 m.

RUNNING SAFETY AND SEISMIC DESIGN OPTIMIZATION OF FAULT-CROSSING SIMPLY-SUPPORTED GIRDER BRIDGE OF HIGH-SPEED RAILWAY UNDER EARTHQUAKES WITH DIFFERENT INTENSITIES

An eight-span simply-supported girder bridge of high-speed railway was taken as a research object, which crosses a strike-slip fault. By means of OpenSEES platform, an integrated non-linear model was established by considering bridge-track interaction. The fault-crossing horizontal ground motions were synthesized and inputted. The damage characteristics of bridge and CRTS II slab ballastless track structures were discussed under different earthquake intensities, and the seismic safety of structural components was evaluated quantitatively. With code control criteria of horizontal deformation, the running safety of track was assessed under different speeds, and the optimal design of track structure was discussed. The results show that the seismic responses of the fault-crossing span and its adjacent spans are the largest, and these bridge spans face great risk of damage. The horizontal deformation of track is obvious and the positions imposing potential threats to running safety are mainly the two ends of the fault-crossing span and its adjacent spans. By increasing the number of lateral rail block, the horizontal deformation of track can be effectively reduced. For the case of 6 pairs of rail block per span and line, the deformation can still meet the safety limit with speed of 100 km/h, except for the parallel turning angles of the fault-crossing span under rare earthquakes.

Prestress Loss Analysis and Overload Early Warning Research of Simply Supported Girder Bridge Based on Embedded Computer and Fiber Grating Sensing Technology

Computer embedded operating system requires the joint development of computer technology, digital technology and communication technology in order to make the embedded operating system more perfect. At the same time, the embedded operating system plays an important role in the development of computer technology. Therefore, we should improve the hardware and software of the embedded operating system to adapt the system to the development needs of the new era. Through the analysis of fiber grating sensing technology, on this basis, the analysis of the prestress loss of the simply supported beam bridge and the research of overload warning are carried out to make it more reasonable.

Effects of fault rupture on seismic responses of fault-crossing simply-supported highway bridges

Past earthquakes have demonstrated that fault-crossing bridges were susceptible to damage or even collapse. This study focused on investigating the effects of fault rupture on seismic responses of a simply-supported highway bridge. Six sets of ground motions with fling-step effect in fault-parallel direction and forward directivity effect in fault-normal direction were selected as the inputs from four strike-slip earthquakes. A simplified baseline correction method was used to recover the permanent ground displacement in these records. A typical simply-supported girder bridge located in China was taken as the prototype bridge and the numerical model of the bridge was generated in OpenSees. Effects of fault crossing angles (from 15° to 165°) and the amplitude of permanent ground displacement on the seismic behaviors of the bridge were evaluated. More specially, two special cases, i.e. contact case and separation case, are considered and compared considering the contact and separation between the girder and abutment in bridge longitudinal direction. Results revealed that the piers and bearings in contact case have larger seismic damage compared to separation case, and the separation case causes the unseating of the bridge spans. It was found that the fault crossing angle has a great impact on the seismic responses of the fault-crossing bridge. The fault crossing angle from 60° to 90° causes the lowest structural seismic responses. The permanent ground displacement is another important influence factor of the bridge. Unlike the bridges without crossing fault, the peak values of the responses of the bridge increase as the pulse amplitudes and pulse periods increase.

Research on the characteristic of seismic damage and seismic design of reinforced concrete simply-supported girder bridge

In previous earthquakes, the bridge in the earthquake zone has been seriously damaged; especially the reinforced concrete simply-supported girder bridge that with poor integrity. In order to study the earthquake damage character and behavior of the reinforced concrete simply-supported girder bridge, according to the survey data of earthquake damage of the reinforced concrete simply-supported girder bridge, that occurred in several major earthquakes in China in recent years, earthquake damage characters of this kind of bridge are classification analyzed. According to the earthquake damage characters, seismic design countermeasures are put forward, which can provide reference for aseismic design of reinforced concrete simply-supported girder bridge.

Experimental study on transverse pounding reduction of a high-speed railway simply-supported girder bridge using rubber bumpers subjected to earthquake excitations

The pounding between shear keys and bearing padstones has been identified as one of critical factors affecting transverse seismic responses of bridges. It is inevitable since the role of shear keys is to limit the excessive displacement of girders during earthquakes. Therefore, it is necessary to perform investigations on reducing the adverse transverse pounding effects on bridges. This paper presents an experimental study on the transverse pounding reduction of a high-speed railway (HSR) simply-supported girder bridge using rubber dampers. A series of shaking table tests were performed on a 1/6-scaled bridge model to investigate the influence of pounding on transverse seismic responses of the bridge model and the pounding reduction effects of rubber bumpers. The fast Fourier transform (FFT) of seismic responses was performed to further discuss the pounding reduction mechanism of rubber bumpers. The experimental results showed that the rubber bumpers are effective on reducing the transverse seismic responses. The pounding between shear keys and bearing padstones evidently increases the high frequency seismic responses of the bridge model. However, the presence of the rubber bumpers can significantly weaken the high frequency responses, and thus mitigates the adverse seismic responses caused by the pounding. In addition, a numerical model incorporating the pounding and rubber bumpers was developed to verify the validity and the accuracy of the numerical modeling. A good agreement between the calculated results and the experimental ones was found.