Study On Seismic Performance Of The Precast And Partial Steel Reinforced Concrete Frame

A new concept of Precast and Partial Steel Reinforced Concrete (PPSRC) frame structure is put forward. The PPSRC frame structure consists of column and beam precast members. Non-reinforced and reinforced steel skeletons are set in the connection region and the core region of beam and column joints, respectively. Other regions are reinforced concrete structure. The assembly in site and factory production of reinforced concrete structure can be realized by this kind of structure. The concept of partial steel skeleton is raised in this paper. Steel skeletons are not continuous and set in several regions. With the development of structure technology, Steel Reinforced Concrete (SRC) structure has more extensive research and application than common Reinforced Concrete (RC) structure due to its good bearing capacity and good seismic performance. However, research on PPSRC frame structures of non-continuous steel skeleton is lack. In order to perform the further study on the seismic performance of PPSRC frame structures, low cyclic loading tests and seismic performance analyses of specimens, which include four interior joints and four exterior joints of PPSRC frame and three interior joints and three exterior joints of RC frame, are carried out. Nonlinear finite element analyses of seismic performance of PPSRC frame structures in 38 working conditions are implemented. Based on the test results and the finite element analysis results, suggestion of design and calculation and economic research results of PPSRC frame structures are given. The details and conclusions are introduced as follows:1. Low cyclic loading comparison tests of eight PPSRC joints and six RC beam and column joints are developed, respectively. Test results show that the bearing capacity of PPSRC beam and column joints is higher than that of RC beam and column joints. The degradation of bearing capacity and stiffness of PPSRC structure is slower than that of RC structure. The ductility of PPSRC beam and column joints is good. The steel skeletons and reinforcing bars in the beam and column connection region and joint core region have not been yielded. Experiments indicate that the prefabricated connection method designed by in this paper is reliable and is in line with the seismic design concept that joints and columns should be strong, and members and beams should be weak.2. Finite element analysis on the relevance between the seismic performance of beam and column joints of PPSRC and the effect factors, such as ratio of axial compression stress to strength, strength grade of concrete, yield strength of steel, is performed. Analysis results are compared with the test results in failure mode, deformation energy, and stress distribution. Comparison results show that the axial compression stress to strength is proportional to the resistance capacity to deformation of beam and column exterior joints of PPSRC frame. The strength grade of concrete and steel yield strength are proportional to the carrying capacity of PPSRC specimens. Failure form of finite element simulation is basically consistent with that of test, which states that the finite element model given in this paper could simulate the mechanical properties of PPSRC structure well.3. The effect of carrying length of reinforced concrete beam on the bearing capacity of PPSRC structure is analyzed. The finite element analyses of eight beam lengths including four exterior joints and four interior joints have been carried on. The results show that with the increase of carrying length of RC beam, the limit stress of structure is firstly generated in the RC beam section and the failure mode of RC beam is gradually transformed from shear failure into flexural failure. The maximum values of shear stress and the bending tensile stress are appeared in the beam steel ends which are the positions of shear strength mutation and beam stiffness mutation.4. Low cyclic loading of whole PPSRC and RC frame structures are simulated using the finite element analysis. The comparisons of these two structures are implemented on the stress distribution, hysteretic curve, strength and stiffness degradation, and energy dissipation. Comparison results show that PPSRC frame and RC frame have the same seismic energy dissipation capacity. PPSRC frame has the better maintain capacity on strength and stiffness and has the high bearing capacity, which states that PPSRC structure can satisfy the design requirement of precast connection of RC frame structure.5. After analyzing the stress mechanism of PPSRC beam and column joints and optimizing the formulae in Steel Reinforced Concrete Composite Structure Technology (JGJ138-2001) and Steel Reinforced Concrete Structure Design Specification (YB9082-2006), the calculating formulae of bearing capacity of PPSRC frame structure are put forward.6. Through the engineering economy correlation between PPSRC and RC frame structures, the engineering direct cost of PPSRC frame structure is about 18.6%higher than that of general RC frame structure. The indirect cost of PPSRC frame structure is basically the same as that of general RC frame structure. Due to the decrease of the construction period, the acceleration of the fund flow, and the reduction of the project financial cost, the total investments of two types of structures are basically the same.