Research On Crack Control For Temperature And Shrinkage Of Prestressed Concrete Beam-Slab Structure Of Extra-length

Accompanying with economic development, applications of prestressed concrete (PC) beam-slab structure of extra-length in Chinese large public buildings are used widely. This dissertation, focusing on characters of PC beam-slab structure of extra-length such as without temperature contraction joint, employing PC construction technique to control cracking, carries out the detailed study, makes reasonable suggestions of such structures design and provided references for code emendation in someday later. The main jobs of this dissertation are as following:It puts forward the necessity of study in this dissertation by disserting the damage of temperature effect on concrete structures of extra-length. At the same time it expatiates the character of temperature stress and requests for value and combination of temperature load.It analyses differences between temperature shrinkage crack and axis tensile crack of member according to analyzing the mechanics of temperature shrinkage crack. Comparing with formulations in different national codes, it disserts calculation methods of average crack width and average crack space caused axial deformation due to effect of temperature shrinkage and discusses the minimal steel ratio to control such crack.It makes a detailed study on analysis temperature shrinkage stress of concrete structure by analyzing and summarizing the research productions home and abroad. It discusses the effect to temperature stress by structural length; provides concepts of subsection-calculation method of temperature stress, restraint coefficient of frame structure and relaxation coefficient of creep stress; based on that sets up a systemic method to analyze temperature shrinkage stress of frame structure. Then it simplifies calculation method and improves calculation precision.It builds the analysis model for PC frame structure of extra-length, analyses the prestress effects and presents fashion of tendon disposition for PC frame structure of extra-length and suggestion for effective flange width of PC beam. It also summarizes the field measured methods of friction coefficient of prestressed tendon duct and analyses the disturbance of data obtained by strain test method employing numerical analysis theory. According to analysis results, author brings forward some advices to treat the test data.By combination with a project example, it disserts how to analyze the temperature and prestress effects of record span structure with general finite element software, then inquires methods to analyze the problems of extra-length structures in practice accurately and presents problems needed to notice in structural analysis.According to the above calculation, analysis and study on temperature shrinkage stress, this dissertation discusses design method of concrete beam-slab structure of extra-length, presents design suggestion and draws conclusion.