Key Engineering Materials Vol. 574

Abstract: This paper presents the results of a study on the early-age cracking behavior of diaphragm in long-span prestressed concrete box girder bridge with cracking control techniques. Based on the three-dimensional hydration heat temperature conduction and humidity diffusion theory, and according to the similarity of differential equation between the humidity diffusion theory and temperature conduction theory, the early-age cracking of diaphragm was simulated by a three-dimensional finite element model with consideration of concrete shrinkage, creep, cement hydration heat and variation of temperature. The numerical simulation accurately predicts the cracking region and size and stress time history of diaphragm, and provides load standard for cracking control techniques of prestressing force. The cracking control techniques of prestressing force effectively avoid the early-age cracking of diaphragm by application of practical engineering.

Abstract: The dynamic response under running vehicle of the bridge includes the static response. The frequency components of simple supported beam dynamic response under the uniform constant force and the harmonic force were discussed. A method using the low pass filter to extract the static displacement from dynamic response curves was proposed and extended to the continuous girder bridge. Simulation analysis describes the process of extracting static displacement. The results show that the method is effective to separate the static and dynamic compositions from the vibration deflection. The dynamic deflection curves of an actual bridge was studied to get the generalized influence lines and then vehicles were laid on them as the static load test program to estimate the static deflection. The results of research show the estimative deflection has high precision and meets the requirements of the bridge inspection. This method can replace the static load test for rapid assessment of the girder bridge.

Abstract: Basalt Fiber Reinforced Polymer (BFRP) bar was deemed as a substitute material of steel bar owing to its strong tensile properties and corrosion resistance which is benefit to enhance the durability of reinforced concrete bridges. Based on the current research findings, the prospects of BFRP bar for the application to bridges were analyzed. It was concluded that BFRP bar had more widely application to bridges than steel bar owing to the advantages of BFRP bar in the mechanical performance of resisting the corrosion. Meanwhile, two key points of whether BFRP bar could be successfully applied to bridges were also discussed, i.e., the bond-anchorage properties between BFRP bar and concrete as well as the manufacturing technique of anchorage device of BFRP bar.

Abstract: As a new structure type, arch bridge of concrete filled steel tube (CFST) has many merits and unique dynamic characteristics. Some present researches indicate that the CFST arch bridge has obvious impact effect, but the research on its dynamic performance due to vehicle is relative backward. In this paper, power spectral density function is selected to simulate the roughness of pavement, the dynamic equation of vehicle-bridge is built with seven degrees of freedom vehicle model. Based on separated iterative method, the parameters’ influence of CFST arch bridge on dynamic performance due to vehicle is carried out systematically. The analysis results are useful and helpful for the design theory of impact effect of CFST arch bridge.

Abstract: Based on the survey of existing highway bridges, there are a large number of flaws induced by moving vehicles. The most important cause of this phenomenon is the lack of design codes on dynamic performance of highway bridges to moving vehicular loads. The existing theory of vehicle-bridge interaction is reviewed. Then the home-code program VBCVA combined with finite element program ANSYS is introduced to analyze the problem of vehicle-bridge interaction. Also, the existing design indexes of dynamic performance are discussed, such as dynamic impact factor, deflection limit, and acceleration. On the basis of above theory and program, the framework of design on dynamic performance of highway bridges to moving vehicular loads is proposed.

Abstract: The main girder and the piers of bridges are generally linked with sliding bearings. Under seismic excitation, pounding effects between the main girder and the abutment, the adjacent girder and the blocking device caused by excessive relative displacements between piers, abutments and the girder are highly probable. The effects can not only damage the structure but also lead to collapsing. Based on a continuous viaduct, the paper studied the disciplines of the pounding response under uniform seismic excitation and the spatial seismic excitation, then put forward that the composite metal damper may reduce the effect of pounding. The research shows that under same seismic intensity, the results, including pounding force, the shear force of the fixed bearings and the plastic hinge on the piers, are amplified under multi-point excitation than under uniform excitation. And composite metal dampers can reduce the seismic responds under frequent earthquakes and prevent or largely reduce the pounding effect under severe earthquakes. Therefore the effect of pounding on the dynamic performance can be lessened. The seismic reduction is widely and well-adapted under both uniform excitation and multi-point excitation.

Abstract: Due to the fire effect, a frame underpass bridge had suffered a huge damage in Changjiang road in Harbin in the direction to Acheng. One span of the bridge was burned in large area, parts of which were burned badly. Many adjacent beams turned black at bottom of roofs; parts decoration of side wall were damaged to some extent. As a result, both directions of the traffic were disrupted, causing traffic jams. To make sure of repairing and restoring the traffic during the shortest period, Harbin municipal committee established the Changjiang road rescue headquarters. Under the precondition of utmost to save money and ensure that the repaired underpasses technology standards meet the design requirements, the research group were about to use steel plate or carbon fiber sheet as the reinforcing material, after detecting and identifying the bridge damage. Through a comprehensive consideration for the ascension of normal section bearing capacity of two reinforcing materials, pasting carbon fiber sheet was adopted to complete repair reinforcement scheme.

Abstract: Bridges are subjected to time-dependent loading and strength degradation processes. The main purposes of the designers and the owners are to keep these processes under control, to real-timely know and predict the structural time-variant reliability indices through health monitoring for bridge structures. The sensors of monitoring systems used in structural engineering provide data used for reliability prediction. But how to make use of monitored data to predict and make assessment of the time-variant reliability indices of bridges has become the bottleneck in the field of structural health monitoring (SHM). Bayesian dynamic models can combine the structural monitoring information with the structural reliability, and also can consider the uncertainty of the mass monitoring information. Therefore, in this paper firstly the bayesian dynamic model is built based on the monitoring information; secondly the monitoring mechanism of the monitoring information is given based on the built bayesian dynamic model; thirdly structural reliability indices are predicted based on the monitoring information and the built bayesian dynamic models; finally an actual example is provided to illustrate the feasibility and application of the built bayesian dynamic models in this paper.

Abstract: This paper investigated an optimal strategy of constructing the tunnel with double-arch section, which the one-cave benching tunneling construction and twin side heading construction were replaced by the center drift combining CRD method and the center drift combining twin side heading method. And the proposed measure was applied to construct the back-turning section of the Clover Park Station which was located in metro line 2 Nanjing, China. The economy and practicality of the proposed method was demonstrated by the application to this practical tunnel