Study On The Setting Method Of Transverse Clapboard Of Concrete Thin-walled Hollow High Pier

With the rapid development of highways and the further deepening of the development strategy of the West in our country,the construction of the high pier and long span bridges has stepped into a golden period.According to the preliminary investigation,the bridges with high piers exceeding 40 m and adopting hollow thin-walled structures of high-grade highways which have been built or are in planning and design in the western region,accounted for more than 40% percent of the total number of surveys.At present,for the construction of high pier bridges,it is usually interrupted during the pouring of the transverse diaphragm,and the internal model is re-disassembled,which influence the construction speed.According to statistics,the construction of transverse diaphragm is more than 25% of the total construction duration of the pier.In addition,there is no clear understanding of the action mechanism of the transverse diaphragm on the stability of high piers,as well as the necessity and principle of the transverse diaphragm setting,so that the transverse diaphragm of the practical engineering is only designed by experiential judgment,the location selection is more casual.To ascertain the effect of transverse diaphragm on the stability of high piers,based on the practical engineering,this paper discusses and analyzes the problems of the transverse clapboard setting of six high pier bridges by finite element numerical computation.At the same time,the action mechanism of transverse clapboard on the stability of concrete thin-walled hollow high pier and the feasibility of canceling the diaphragm is investigated by the axial compression experiment and analysis of the concrete thin-walled hollow high pier model.The main research contents and conclusions are as follows:(1)Using ANSYS to analyze the hollow thin-walled high pier of the constructed Donglingdongte bridge and Hezhang bridge(continuous rigid frame bridge)with different conditions of loads,pier heights and wall thickness,linear stability and double nonlinearity stability and linear torsion performance.It is show that the stability coefficient of bridge high piers decreases with the increase of pier height,and increases with the increase of wall thickness.Within the common structural dimensions of the actual project,owing to the large generosity,the problem of local stability of the structure is not prominent,and the first-order stable mode with practical engineering significance belongs to the whole instability.The contribution of transverse diaphragm to the stability,ultimate displacement and torsion resistance of concrete thin-walled high pier is less than 5%.(2)The calculation and analysis of the full-bridge model and pier model of Jinjiang bridge(continuous rigid frame bridge)by Midas/Civil and ANSYS show that,whether the bridge main pier or the handover pier,the first order nonlinear instability modes are the sideways along the direction of the bridge in the top of the pier,and the partial convex in the bottom of the pier.The nonlinear stability coefficient of the main pier and the junction pier with no transverse clapboard is basically the same as that has a clapboard,and the stability coefficient is far greater than the limit of 4.0.Therefore,from the perspective of stability,the high piers of such bridges do not set the clapboard.(3)Through Midas/Civil and ANSYS,the calculation and analysis of three T-girder bridges,like Deep Crossing bridge,Erigeron Stone bridge and Ping Shan bridge,showed that the first-order nonlinear stable modal of the hollow thin-walled high pier in T-beam area is characterized by the instability of the overall instability of lateral inclination of pier top.The nonlinear stability coefficients of main piers without transverse partitions are basically the same as that with,and the stability coefficient is far greater than the limit of 4.0.Therefore,from the perspective of stability,this type of high piers do not set the clapboard either.(4)From the axial compression experiment of 7 hollow thin-walled high pier scale7scaled(20:1)model we know,The failure mode of the model pier with/without transverse clapboard is the whole instability damage;Moreover,the difference of ultimate bearing capacity of the model pier under the same size with/without transverse clapboard is less than5%,and the experimental value agrees with the finite element calculation.However,there is a difference between the local damage pattern and the damage position of the pier model with/without transverse clapboard.The model pier with transverse clapboard is mainly the local transverse and oblique cracks caused by the convex curvature and concave of the intermediate wall plate of the clapboard,and the model pier with no transverse clapboard is dominated by vertical splitting crack cracks in the pier Top.