Experimental And Theoretical Study On Cracking Load Of Preflexed Beam

Preflexed beam gets attention of bridge engineers because of its height advantages.This new structure is suitable for urban interchange and highway overpass.It will have good prospects in China.From the beginning of the eighties of last century,China began to carry out related research on preflexed beam,got some achievements and actual projects.However,due to the lack of domestic relevant regulations and standards,promotion in this field is currently in a state of stagnation.Current research has been done in MOHURD,began compiling the national standard "Standard for Preflexed Beam Bridges",to guide the design and construction of preflexed beam bridge.In this paper,the following researches have been done:(1)Based on the elastic design method,starting from the different states of prebeam bridges in the process of construction and use,the computing sections of prebeam are classified.According to the different force state,the stress calculation method and the deflection calculation method of the preflexed beam are given respectively.(2)The fabrication process,the force characteristics and the failure mechanism of the preflexed beam are studied.Through the static load experiment of four preflexed beam,the following experimental objectives are achieved:1)study the mechanical and structural characteristics of the preflexed beam,and understand the specific design and production process of the structure.2)Through the test of beam static load test,study the structural deformation characteristics,determine the cracking load of concrete,to explore its crack distribution,development and crack width development law.And check the correctness of the existing empirical formula.3)Through the test of beam static load test,to explore the advantages and disadvantages of the flexural capacity and construction of this structure.(3)According to the requirements of the new " Standard for Preflexed Beam Bridges ",the preflexed beam calculation software is compiled by Visual C ++ language.On the basis of studying the new specification and design method of the preflexed beam,the core algorithm in the procedure is summarized and refined.Some of the parameters in the calculation software are modified and some new contents are added,which makes the calculation software more perfect,and software can meet the requirements of today's bridge design specifications.The main functions of the calculation software include the calculation of the bearing capacity of the bearing capacity limit state,the stress calculation of the normal use limit state,the deformation calculation of the normal use limit state,the crack resistance and the crack width calculation of the normal use limit state,and the design of the connection calculation.(4)Based on the new technical requirements of" Standard for Preflexed Beam Bridges",according to the structure and requirements in the existing "Highway Bridge Standard Plan",a variable plate thickness preflexed beam bridge suitable for highway traffic engineering is designed.The relevant calculation and checking are carried out,provide a reference for engineering applications.