Research on Random Fatigue Load Model of Highway Bridge by Vehicle Traffic Based on GMM

Highway bridges have often suffered accidents due to fatigue damage. This paper studies the influence of vehicle operating state on the fatigue performance of bridges. Based on GMM method and K-S test in information statistics, this paper proposes an improved Gaussian hybrid modelling method, and studies the various parameters of vehicle operating state on beam bridge fatigue, such as the impact of the damage and its fatigue life assessment. On this basis, the fatigue cumulative damage formula of multi-vehicle upper bridge is proposed. The traffic load of Shandong JiNan-QingDao expressway has been GMMly analysed by GMM. The Gaussian mixture model is used to fit the vehicle load probability function by standard fatigue vehicle model. Based on the expressway, the vehicle fatigue has been established to facilitate the fatigue load and evaluate the fatigue life. Gradually this paper helps to improve the accuracy and convenience of the probability model, which is conducive to the establishment of a scientific and efficient load probability model for road vehicles

Flexural Capacity and Behavior of RC Hollow Bridge Beams after a Time Service of 24 Years

The residual bearing capacity of existing bridges has been a controversial topic for engineers and technicians. In order to accurately evaluate the actual bearing capacity of a 24-year-old RC hollow beam bridge, its components with different thickness concrete leveling layer were removed and transported back to the laboratory. The representative static and dynamic responses of the two beams were monitored during the whole procedure. A quick assessment of loading capacity of bridge using crack height and a parameter correction method for the crack width prediction formula in the code were proposed. In addition, comparison of measured and current design codes GB 50010 and ACI 318 predicted behaviour of existing beams was also presented. The results showed that the bending process of the RC hollow beam went through the elastic phase to the elastic-plastic phase and to the final failure. The actual flexural capacity of two beams was 10% larger than the calculated values. The natural vibration frequencies of the beam changed slightly before plastic stage, but the modal amplitude increased with the increase of degree of damage, once the beam entered plastic stage. The predicted deflections according to GB50010 were consistent with the experimental values at about 200 kN; for the code ACI, as the loading force increased, the difference between the two gradually decreased

Depth estimation of surface-opening crack in concrete beams using impact-echo and non-contact video-based methods

Abstract Surface-opening crack is one of the main defects in concrete bridges, which results in degradation in the load-carrying capacity of these structures. Thus, estimating the depth of such surface-opening crack is vital. This study presents impact-echo (IE) and non-contact video-based methods to estimate the surface-opening crack of concrete beams in the laboratory, and the results are compared with visual inspection. Results show that the IE method estimates a considerably larger crack depth than the non-contact video-based method and visual inspection. Although the difference between the depth measured by non-contact video-based method and visual inspection is small, the depth estimated by non-contact video-based method is slightly larger than that measured by visual inspection because it can identify the unrecognizable micro-crack by visual inspection. Moreover, when adopting the IE method, the depth of inclined crack is more overestimated than the vertical crack

Numerical Simulation Study on Exposed Reinforced Anti-Corrosion Layer Damage of the Cross-Sea Bridge Under the Marine Environment

To solve the problem of low precision of numerical simulation of the exposed reinforced anti-corrosion layer damage of the cross-sea bridge, we use the stress ratio between the double slash and the reinforced anti-corrosion layer to analyze the parameters and the damage rate in different qualities of reinforced anti-corrosion layers, use Ansys software to build reinforced finite element model, and analyze the damage degree when the inclination angle was 15 °, 45 ° and 60 °, respectively. The experimental results showed that the proposed method can improve the numerical simulation efficiency, the numerical simulation results, the experimental results, and the theoretical analysis results have good consistency and stability

Experimental Research on Fatigue Behavior of Existing Reinforced Concrete Beams

In order to obtain the law of the fatigue damage development of reinforced concrete hollow beams that has been in service for 24 years, its solid hollow beams were removed and transported to the laboratory for loading test. Two beams were selected for static loading to obtain the ultimate flexural bearing capacity, and three beams were, respectively, subjected to constant-amplitude fatigue loading with different load amplitudes. The static and dynamic behaviors of the beams were monitored in the fatigue test. The fatigue failure of the beams showed that the outermost rebar at the butt weld fractured at first, and the crack width at the fracture position of the steel bar was about 0.3 mm, which was largest in all cracks. After a rebar was broken, midspan deflection and flexibility increased by approximately 20% and 10%, respectively, relative to the initial state. The damage developed rapidly in the following range: (1) the first 10,000 fatigue cycles; (2) after fatigue fracture of the rebar; and in the intermediate stage of fatigue test, the damage development was relatively stable. As the loading amplitude increased, the stiffness degradation and the cumulative damage that occured under the same loading cycle were more significant

Influence of Fluid Viscous Damper on the Dynamic Response of Suspension Bridge under Random Traffic Load

Fluid viscous dampers (FVDs) are widely used in long-span suspension bridges for earthquake resistance. To analyze efficiently the influences of FVDs on the dynamic response of a suspension bridge under high-intensity traffic flow, a bridge-vehicle coupling method optimized by isoparametric mapping and improved binary search in this work was first developed and validated. Afterwards, the traffic flow was simulated on the basis of monitored weigh-in-motion data. The dynamic responses of bridge were analyzed by the proposed method under different FVD parameters. Results showed that FVDs could positively affect bridge dynamic response under traffic flow. The maximum accumulative longitudinal girder displacement, longitudinal girder displacement, and longitudinal pylon acceleration decreased substantially, whereas the midspan girder bending moment, pylon bending moment, longitudinal pylon displacement, and suspender force were less affected. The control efficiency of maximum longitudinal girder displacement and accumulative girder displacement reached 33.67% and 57.71%, longitudinal pylon acceleration and girder bending moment reached 31.51% and 7.14%, and the pylon longitudinal displacement, pylon bending moment, and suspender force were less than 3%. The increased damping coefficient and decreased velocity exponent can reduce the bridge dynamic response. However, when the velocity exponent was 0.1, an excessive damping coefficient brought little improvement and may lead to high-intensity work under traffic flow, which will adversely affect component durability. The benefits of low velocity exponent also reduced when the damping coefficient was high enough, so if the velocity exponent has to be increased, the damping coefficient can be enlarged to fit with the velocity exponent. The installation of FVDs influences dynamic responses of bridge structures in daily operations and this issue warrants investigation. Thus, traffic load should be considered in FVD design because structural responses are perceptibly influenced by FVD parameters

Monitoring of Daily Temperature Effect on Deck Deformation of Concrete Arch Bridge

Temperature makes greatly differences on concrete in many aspects, including stress, strain and deformation, especially for arch concrete bridge structure. Some software can compute theoretical deformation, stress and bending moment of bridge structure due to temperature load, such as Midas Civil. In recent years, in order to learn about conditions of structure, many bridges have installed the healthy monitoring system. In this research, the monitoring data lasting approach a year was obtained from Haierwa Bridge, a concrete truss arch bridge, in Hebei province. The bridge belongs to Xuanda Highway, which undertook the main traffic flow of coal transportation. The proportion of heavy vehicles, exceeding 50t, ups to 30%, different with common highway. The objective of this paper is to monitor and analyse the deformation of concrete truss arch bridge due to air temperature change. Firstly, results show that the daily tendencies of temperature and bridge vertical deformation at mid-span, L/4 and arch foot in the winter and summer. The linear relationship was calculated between the temperature and deformation of critical sections based on the monitoring data. In addition, the finite element model was established to calculate the theoretical value, and further compared with practice values

Finite Difference Method in Stress Analysis of Anchorage Zone of Highway Extradosed Cable Stayed Bridge

With the development and wide application of extradosed cable stayed bridge, an effective method is needed for simulation of the stress distribution in anchorage zone, which plays a vital role in transferring force from the cable to the pylon and diverting the cable direction. Based on the Finite Difference Method (FDM), an efficient and practical method of stress filed simulation was presented in the paper. First, a plane finite element model was established using ABAQUS, to determine the boundary condition for FDM. Based on this, FDM was used to simulate the stress distribution of the concrete in the anchorage zone. Finally, on the simulation result was calculated and in comparison with finite element model result. It has been found that: The vertical compressive stress of concrete in the anchorage zone gradually reduces from the middle to the two sides, and the stress assumes double peak type in transverse. Compared with the finite element solutions, the approximate solution simulated by FDM improve the computational efficiency with certain accuracy keeping, except the loading area. In vertical orientation, the concrete in the place of H (the width of the pylon) from cable force acting position is in a state of uniform stress

Monitoring of Daily Temperature Effect on Deck Deformation of Concrete Arch Bridge

Temperature makes greatly differences on concrete in many aspects, including stress, strain and deformation, especially for arch concrete bridge structure. Some software can compute theoretical deformation, stress and bending moment of bridge structure due to temperature load, such as Midas Civil. In recent years, in order to learn about conditions of structure, many bridges have installed the healthy monitoring system. In this research, the monitoring data lasting approach a year was obtained from Haierwa Bridge, a concrete truss arch bridge, in Hebei province. The bridge belongs to Xuanda Highway, which undertook the main traffic flow of coal transportation. The proportion of heavy vehicles, exceeding 50t, ups to 30%, different with common highway. The objective of this paper is to monitor and analyse the deformation of concrete truss arch bridge due to air temperature change. Firstly, results show that the daily tendencies of temperature and bridge vertical deformation at mid-span, L/4 and arch foot in the winter and summer. The linear relationship was calculated between the temperature and deformation of critical sections based on the monitoring data. In addition, the finite element model was established to calculate the theoretical value, and further compared with practice values