The Analysis Of Mechanical Properties And Engineering Economy Of Partially Prestressed Concrete Beams

With the rapid economic development,the bridge transportation industry is developing at high speed.Part of the bridges design can't meet the requirements of the current vehicle load.During service of bridges,the concrete cracking that caused by reciprocating vehicle load seriously reduce the bridge's bearing capacity.In order to ensure the safety of bridge operation,many bridges need to work out a reconstruction plan to improve the bearing capacity and to achieve safe operation requirements.Reasonable choice of reinforcement,concrete grade,is not only to ensure the design requirements of the bridge reconstruction,but also to effectively save economic costs.The paper study on the static and fatigue tests for improving the reinforced concrete grade of partially prestressed concrete(Partially Prestressed,Concrete,PPC)beams in order to select the most economical and effective grade of reinforced concrete and intuitively analyse the damage process of bridge that caused by reciprocating vehicle load.,then comparing the cost that Glodon Software calculated.The main research contents are as follows:(1)Based on the reconstruction project of 16-meter-span PPC beam(C40,HPB300)in Beijing Hong Kong and Macao expressway(Beijing-Shijiazhuang section).Respectively choose the reinforcement(HRB400)and concrete(C50)that are commonly used in project as variables.There are three schemes on choosing the grade of reinforcement and concrete: The frist one is only improving the concrete grade;The second is only improving the steel grade;The third is improving both of the steel and the concrete grade.(2)Through the analysis of PPC beams' mechanical property such as deflection,stiffness,ductility,the strain of steel and concrete and so on in the flexural test,three schemes can meet the design requirements.Combined with economic and mechanical properties of a comprehensive analysis,the second kind of schemes can be selected for the bridge reconstruction,which can only be subjected to beams which bear static loads or few passing vehicles.(3)Through the analysis of dynamic performance of the test beams with three schemes,it may lead to material waste.Combination of technical and economic analysis for the bridge reconstruction under dynamic load,it's better to choose the first scheme in order to meet the design requirements and increase the safety of the engineering components reserves.(4)According to the experimental data,the curves of stiffness reduction coefficient and fatigue number are obtained.Improving the grade of concrete can reduce the stiffness reduction rate compared the four beams under fatigue load,and it also increases the safety of expansion project.