Dynamic Responses Of Train-bridge System Subjected To Collision Loads And Running Safety Evaluation Of High-speed Trains

With the development of science and technology and application of new materials, the bridge span becomes longer and the train speed becomes faster. Meanwhile, as the water, railway and highway traffics become increasingly busy, collisions of vessels, vehicles and ice-floes on bridges crossing rivers and roadways also become more serious. In this dissertation, the bridge vibration induced by collision loads and the related running safety problem of high-speed train on bridge subjected to collision are studied, which is funded by the National Natural Science Foundations "Dynamic responses of railway bridges subjected to collision loads and running safety control of vehicles (Grant No.51178025)" and "Research on mechanism of physical and mechanical properties of river ice action and its effects on railway bridges (Grant No.50878020)". The detailed contents and highlights of the study include:(1) The serious accidents of bridges subjected to collision of vessels, vehicles and ice-floes and the related research situation in China and abroad are reviewed, and the necessity of research toward running safety of high-speed train on bridge subjected to collision load is elaborated. The research contents and general analysis methods of train-bridge dynamic interaction problem are summarized, and the significance and research basis of this doctoral dissertation are introduced.(2) The design methods, numerical simulation and experimental results of collision loads induced by vessels, vehicles and ice-floes are summarized, by referencing the highway and railway bridge design codes and the related researches in China and abroad. The characteristics of collision loads, such as duration time, maximum values and loading positions are analyzed, which provides an important basis to determine the collision loads for dynamic analysis of train-bridge interaction system.(3) The field experiments were carried out to measure temperature fields and ice-floe collision forces at the Jiamusi Songhuajiang Highway Bridge, the Tonghe Songhuajiang Highway Bridge, and several other sites. The relationships between air, water and ice temperature were obtained from the river ice temperature field measurement. The collision loads of ice-floe on bridge piers were obtained from the collision force measurement, which provides experimental data for the dynamic analysis of coupled train-bridge system. The frequency spectrum analysis is done with the FFT method on the measured ice-floe collision data, and then the features of discrete frequency spectra are analyzed.(4) The analysis model of train-bridge interaction system subjected to collision loads is established, and the computer code is written, where the vehicle submodel is established with multi-rigid-body dynamics, the bridge submodel is established with modal superposition method, the vertical wheel-rail force is defined with the wheel-rail close contact assumption, the lateral wheel-rail force is defined with the Kaller's Creep Theory, and the collision force is simulated as nodal dynamic load. Moreover, a new iterative method of whole process is proposed, which is suitable to the time history integral of train-bridge interaction system, and the calculation efficiency is proved through case study.(5) With the analysis model and the computer code, by taking the Jiujiang Yangtze River Bridge as a case study, whose main pier is subjected to vessel collision load, and considering a normal passenger train and the US Grade5irregularity spectrum as calculation conditions, the lateral displacements and accelerations at pier-top and mid-span of the bridge and the running safety indices of the train are calculated through computer simulation. Some of the calculated results are compared with the measured results obtained in the field experiment in2007, which partly proved the proposed method. On the basis, further calculation is performed with the German ICE3train running on the bridge and with irregularity samples measured from the Qinhuang-Shenyang high-speed railway, and the results are compared with the ones from ordinary passenger train, which shows that the high-speed train is more seriously affected than the ordinary train when the bridge pier is subjected to collision load.(6) For the (32+48+32) m continuous PC box girder bridge on the Harbin-Dalian high-speed railway, by assuming one of its piers collided by Jiamusi ice-floe, Tonghe ice-floe and vessel loads, the displacements and accelerations at pier-top and mid-span of the bridge and the derailment factors, offload factors and lateral rail-wheel forces of ICE3high-speed train are analyzed. By further parameter analysis, the influences of collision load types, collision intensities, train speeds and train types on the running safety indices of the train are studied.(7) A preliminary investigation is performed on the control method for running safety of train on high-speed railway bridge subjected to collision load, and the definition for threshold curves between train speed and impact intensity for running safety of train is proposed. Through systematical numerical simulation, the threshold curves between train speed and impact intensity for running safety of several trains including ICE3, Japan E500and China CRH2on the (32+48+32) m continuous PC box girder bridge which is subjected to three types of loads, Jiamusi ice-floe (successive multi-impulse), Tonghe ice-floe (single narrow impulse) and vessel (single wide impulse), are acquired.