The Experimental Research And Theoretical Analysis Of High Strength Concrete Compression-Flexure Members Under Loading And Elevated Temperature

Since reinforced concrete structures and members are destroyed seriously and even collapse in fire, people put more and more attention to the behaviors of reinforced concrete structure and members under elevated temperature. Considerable experimental research and theoretical analysis are in progression. It is well known that in our country tall building develop quickly in recent years and the fire problems of structure stand out increasingly. As a result of high strength and good endurance of high strength concrete, it has been widely used in engineering structures. Especially in the bottom columns of tall building, C50~C60 high strength concrete are employed at large. So it is of practical meaning to study the behaviors of high strength concrete under loading and elevated temperature.In this thesis, the strength and deformation of high strength concrete under elevated temperature are investigated. From the results of tests, the variational regularities of cubic strength, prismatic strength (peak stress) , peak strain , modulus of elasticity, stress-strainperformance, free thermal strain, temperature strain under stress and transient thermal strain ofhigh strength concrete at elevated temperature are presented, the corresponding formulas are also established. The cubic strength of high strength concrete at elevated temperature is compared with that after elevated temperature, the high-temperature behavioral difference between high strength concrete and normal concrete is also compared. In this thesis, the experimental research of the behavior of high strength concrete axial compression columns and eccentric compression columns under non-uniform temperature field are conducted. From the experimental analysis, the variational regularity of ultimate load capacity and deformationof high strength concrete compression-flexure members under non-uniform temperature field is obtained. The influences of different factors including temperature, stirrup contents, strength grade of concrete, pre-loading level, eccentricity and different loading-temperature paths to refractory capability of members are investigated. The sectional temperature field of members is gained by testing measure.On the basis of experimental research, this thesis applies 2-dimensional non-linear finite element method to the analysis of transient temperature field on the section by means of relatively high precision triangular element of six joints. When the temperature field is analyzed, finite element reseaus are divided in space field and finite difference reseaus are divided in time field, and then the program is compiled. The computing results are in good agreement with the test data. It indicates that the program is stable and precise. The assumption about deformation character and constitutional relationship of high strength concrete and reinforcement under elevated temperature is proposed making use of the general regularity of high strength concrete compression-flexure member. The ultimate load capacity and deformation of high strength concrete compression-flexure members under elevated temperature are analyzed by means of full-range and non-linear analysis method. The computing results and test data are in good agreement.