Research Of Mechanics Behavior For Immersed Tunnel Under Fire Load

With the rapid economic development, more and more immersed tunnel usedacross rivers, seas and lakes,But owning to the characteristics such as long gallery,small room, poor ventilation, once fire occurred in a immersed tube tunnel, it can’t beput out immediately and consequences will be extremely serious. High temperature ofthe fire can hazards the users, and it will lead to the burst and the deterioration of themechanical function of concrete, and do the various degrees of damages to the pipestructure, which will reduce the load capacity and safety of the structure.Main research work of this thesis is as follows:Based on the heat conduction theory, use Large-scale finite element analysissoftware ANSYS, establish a high temperature analysis model of the immersed tunnel.On the basis of reasonably select fire curve and boundary conditions, set the materialsthermal parameter which varies with temperature correctly, carried out temperature fieldsimulation of immersed tunnel when it exposed to fire, research the law of temperaturedistribution of immersed tunnel.Based on the thermal elasticity theory, create the temperature-structure couplingmodel of immersed structure. According to the fire time, corresponding temperatureload is applied into the structure; According to the external conditions of the differentdepths of immersed tunnel, corresponding external loads is applied to the outside of thestructure. Using this model carried out thermal stress calculated for immersed tunnel infire conditions, research the law of thermal stress variation and the resulting structuraldamage depth of immersed tunnel with non-insulated.Based on the immersed tunnel element component model fire tests, Studies thevariation of temperature over time of component model which under the protection oftwo1cm thick (2cm thick) glass magnesium fire board. And usethe variation of thesurface temperature of the component model as temperature load in structuretemperature field calculation.Conduct ing numerical calculation, analysis the law oftemperature distribution of tube which have a heat barrier, And then carrying outthermal stress variation and the resulting structural damage depth of immersed tunnelwith heat barrier.Based on the the ultimate limit state immersed tunnel may reach at hightemperatures, on the basis of considering the temperature distribution within thestructure section as well as the mechanical properties deterioration of the concrete andreinforced, respectively give the high temperature ultimate bearing capacity calculationmethod and the expression of immersed tunnel.