Applied Mechanics and Materials Vols. 105-107

Abstract: This work presents the dynamic tests on a retrofitted masonry arch bridge. The Gresal Bridge, located in the North-East of Italy, was highly exposed to seismic hazard, due to the slenderness of its high piers. A retrofit intervention has been carried out, and a new rc slab has been built under the pavement, anchored to the piers with high strength vertical ties and restrained at the abutments, to create a new resistance arrangement withstanding inertial forces. The dynamic behaviour has been initially assessed with numerical models comparing the response of the bridge before and after the repair, and has subsequently been tested by the Output-Only technique to detect the variation of the modal response induced by the strengthening intervention. The dynamic tests have shown the structure to be more rigid than expected and, after calibration, a good agreement to exist between the numerical frequencies and the experimental records captured on the retrofitted bridge.

Abstract: The cables in a cable-stayed bridge usually possess low inherent damping and are prone to vibrate by many factors. The wind-rain-induced vibration of the prototype stay cable is a special vibration problem associating with rain and wind. Many methods have been proposed to mitigate wind-rain-induced cable vibrations such as mechanical measures, aerodynamic modification, and control technology. Active control technique has significant control capability because of utilizing the external energy supply but it may not be realistic to large civil engineering structure due to enormous power demand. The two-stage control method has been proposed to control the wind-rain-induced cable vibrations of the prototype stay cable. The studies are carried out to investigate the energy cost features of the control forces as a design guideline.

Abstract: This paper gives a brief explanation of the failure mechanism of rock fragmentation in rock cutting. The JOHNSON_HOLMGIST_CONCRETE is selected as the rock material model in numerical simulation with confining pressure and damage influence introduced. We use the non-linear dynamic finite element software LS/DYNA to simulate the dynamic process of cutting rock. The cutting forces acting on disc cutter are computed. The relationship between cutting forces and penetration depth, confining pressure and damage parameters are obtained. The results show that, the cutting forces increase with the penetration depth. They are larger in equal confining pressure than unequal condition. The forces are amplified with the damage parameters increasing. The conclusion provides a reference for the prediction of the cutting forces.

Abstract: With the large-scale construction of passenger dedicated line, more and more ballastless turnouts were laid as the important infrastructure of passenger dedicated line, and the fastener stiffness of it influenced the vibration and noise of the track. Using the vehicle-turnout coupling dynamic analysis created the method for determining the reasonable fastener stiffness of ballastless track turnout to analyse mutative fastener stiffness's impact on the vibration and noise. Then from three parts of the excitation of wheel-rail roughness, the sound radiation efficiency and the calculation of wheel-rail radiated noise, the noise prediction method for ballastless turnout was stated. Using the above methods, The reasonable fastener stiffness of ballastless turnout can be obtained. The results showed that the stiffness of 25 kN/mm to the fastener of ballastless turnout was reasonable for vibration decrease and noise reduction.

Abstract: A vehicle model and a movable-point simple turnout model were established, and the influences on dynamic responses caused by turnout irregularities when train passes through No.18 turnout was analyzed by using the turnout dynamics simulation software based on finite element method. It shows that turnout dynamic responses are influenced by the combined effects of various types of irregularities, which produce bigger dynamic response than single irregularity. In the turnout devise and use, the distance between slide plate and switch rail or nose rail should be as close as possible, the position arrangements of traction points should be optimized and the insufficient displacement should be eliminated as much as possible; No.18 turnout structure design is reasonable, which can ensure the safety and the stability when train passes over turnout.

Abstract: This paper has the background of JiuJiang bridge recover engineering, and uses the approach that combining submodel method with finite element method to establish the simplified model of the whole steel-concrete composite beam bridge without considering slipping and the refinde model of the typical section with considering slipping. The distribution of slipping of steel-concrete composite beam under the condition of operation is researched. In addition, the deflection as well the stress of typical section between the two kinds of models is contrasted and analyzed. Based on these researches, this article uses the Midas Civil to study the creep effect of steel-concrete composite beam cable-stayed bridge.

Abstract: The finite element model is built by ANSYS, and the distribution of stress is studied. The stress intensity of each layer is computed by Tsai-Wu stress intensity standard. The value computed by Tsai-Wu stress intensity standard under given loads are smaller than 1, and the GFRP bridge deck is in a safe state. The first ply failure is also studied, and the result shows that the first ply failure value is determined by the webs when the webs are very thin. Other circumstances the value is determined by the size of the top and bottom plate. The material utilization is the highest when the thickness of the bottom is equal to the whole webs and a little thinner than the top plate.

Abstract: The tunnel which excavated through the fault fracture zone is still one of the difficulties in the current tunnel construction. Guanjiao tunnel is the longest high-altitude tunnel in the world, and also the longest railway tunnel which is under construction in China. The 9# shaft which located in Erlang fault fracture zone with several faults, complicated geological conditions is difficult to excavate. In the representative section of F3 fault and its influence zone, F22 fault fracture zone, the monitoring tests on contact pressure between surrounding rock and primary support and stress of steel arch is conducted. According to the above monitoring results，the project recommendations are proposed to ensure the smooth construction of tunnel.

Abstract: With China's rapid economic development, transport markets are booming. High way, especially expressway plays a very important role in economic development of today. Asphalt pavement surface is widely used. And with the development of expressway, more and more recycled asphalt concrete will be produced. So how to deal with these waste materials becomes a focus problem among researchers. In this paper, aging rules of asphalt according to the engineering practice and test data was talked about. The aging can be divided into: aging during transport, storage, and heating, aging during hot-mixing and paving, aging during the operation of the pavement. At the same time, the general knowledge about the regenerated asphalt was discussed. In addition, the possible damage of RAP technique to environment was also discussed.

Abstract: The bridges are of much importance to the transportation network system, as they connect key highways at crucial nodes. This paper reviews and discussed risk-based methodologies to assess the risk acceptability and cost-effectiveness of protective measures for bridge under multiple manmade or natural hazards. Three risk acceptance criteria based on fatality risks, failure probabilities and net benefit assessment were described and discussed. The decision support framework accompanying these risk acceptance criteria considers hazard probabilities, value of human life, physical and indirect damages, risk reduction and protective measure costs were studied and an illustrative example was presented.