Seismic Behavior Of Cast In-situ Reinforced Concrete Frame Structure With Construction Joints

Construction joints are stopping places in the process of concrete construction and can't be avoid in cast-in-situ concrete structure. Construction joints are an important factor to ensure the security and entirety of construction. It is very disadvantage for the seismic behavior and easier to become the weakness of construction if construction joints were undertreatment. Although reinforced concrete cast-in-situ frame structures with construction joints have been widely used in seismic zones, earthquake resistant tests of frames and frame columns with construction joints had not been done before. So according to the project of Dalian Urban and Rural Construction Committee Scientific Item-"Setting location and treating methods of Cast in-situ Reinforced Concrete Frame Structure with Construction Joints", research work is carried out as follows:Using different joint interfacial treatment method, the bond splitting tensile strength of cubic specimens with construction joints is tested. The test results indicate that the bond splitting tensile strength of modified fly ash mortar is best in joint materials of sorts. Expansive cement paste and joint concrete are next. And the bond splitting tensile strength of joint surface without bond material is least. Using software tool of Photoshop image processing, the compactness and planeness of the fracture surface of bond splitting tensile specimens are evaluated by statistic information of the picture element on luminance value. And the relational formula between them is given. Finally, the effect of joint material is discussed through microscopic and macroscopic analysis.Based on the pseudo static test of 13 frame columns with construction joints and monolithic cast columns, the influences of the axial compression ratio and the treatment methods of construction joints on the seismic behavior of columns are studied. Failure characteristics, bearing capacity, hysteretic curves, skeleton curves, displacement ductility, and stiffness degradations of members are analyzed and compared. Experimental results show that the bearing capacity drops 3%～7% under low axial compression ratio, and the maximum decrease of displacement ductility ratio is more than 30%. The slip of steel bars and rheostriction of hysteretic curves is heaver than monolithic concrete columns. As increasing of axial compression ratio, the effect of construction joints becomes weaken. Under high axial compression ratio, the effect of construction joints for earthquake resistant behavior of columns is indistinctively. Axial compressive force promotes a favorable result for the shear...