Research On Prestressed Friction Loss Of PC Bridge Holes

Modern prestressed technology develops rapidly and is widely used in bridge structures.However,it is affected by construction and environment factors.And the prestress applied in bridge prestressed structure will decrease gradually.This phenomenon of the gradually reduction of prestressing is called prestressed loss.The accuracy of prestress loss calculation is closely related to the performance of the bridge.At present,many prestressed concrete bridges that have been built and put into use have problems such as cracking of box girder and abnormal downward deflection in mid-span,have caused premature failure of some bridges.It is a great threat to the safe use of bridges and the safety of people's property.Therefor,it is of great significance for the safety of bridge structure to discuss and analysis the prestress loss and work out the accurate calculation method of prestress loss.Based on the calculation method of prestressed friction loss in the existing bridge design code,the theoretical formula and finite element simulation analysis of the prestressed friction loss in curved tunnel are carried out in this paper.By analyzing the derivation process of the formula of friction loss of the prestressed pore,the formula of friction loss of the prestressed pore is obtained,which makes the fitting result of friction loss parameters more accurate.The main research contents of the thesis are as follows:(1)Based on the non-uniform distribution of contact pressure,the prestressed friction loss of curved channel is analyzed.Based on the analysis and discussion on the assumption that contact pressure is considered as uniform distribution in the formula of friction loss of prestress in the existing bridge design specifications,it is put forward that the non-uniform distribution of contact pressure is more consistent with the actual distribution of contact pressure.The contact pressure is assumed as a possible non-uniform distribution form,and the formula for calculating the frictional loss of the prestress of the curved channel under the non-uniform distribution of the contact pressure is derived after the static equilibrium analysis of the curved channel.The difference between the theoretical values of friction loss calculated by the formula of friction loss of different curved channels in the form of continuous and discontinuous arrangement is compared,and the influence of the formula on the theoretical calculation of friction loss of curved channels in the form of continuous and discontinuous arrangement is discussed.(2)The finite element simulation analysis of the contact friction between theprestressed steel beam and the concrete in the curved tunnel is carried out.The finite element analysis software is used to simulate the contact force characteristics of prestressed steel bundles and concrete in curved tunnels,and the numerical solution of prestressed frictional losses of curved tunnels is calculated.In addition,the friction loss formula of the standard curved channel and the theoretical solution of the friction loss formula derived in this paper are compared with the numerical solution of the friction loss obtained by the finite element analysis,so as to verify the applicability of the friction loss formula derived in this paper.(3)The calculation formula of the hole friction loss which makes the friction resistance parameter fitting more accurate is analyzed and derived.Through the analysis and study of the derivation process of the standard pore friction loss formula,it is found that the static equilibrium analysis of the prestressed rigid beam micro-segment ignores the influence of the high-order differential change caused by the friction force to the prestressed rigid beam.After taking this influence into account,this paper reanalyzes and derives a formula for the friction loss of the orifice,which can make the fitting result of the friction loss parameters more accurate.At last,the parameter fitting of the measured test data obtained from the friction loss test of the prestressed concrete continuous beam bridge is carried out,and the comparative analysis of the fitting results verifies the practicability of the friction loss formula derived in this paper.