| Due to the unique advantages of special-shaped column structure, it is not only welcome by users and real estate developers, but also supported by government. By now, in practical engineering the most applications are reinforced concrete (RC) column structure. But in the past 20 years of research and application, some shortcomings of such structure are gradually exposed, such as low bearing capacity, weak seismic performance and steel bars are too crowded to pour concrete densely well. These disadvantages directly affect their applications in high-rise and high-intensity area. In order to improve the shortcomings of RC special-shaped column-beam joints and expand its scope of application, at the same time enrich the system of steel reinforced concrete structures (SRC) and improve the SRC special-shaped column structure system, the following work was done on the basis of existing research.(1) In order to investigate the failure modes and seismic behavior of SRC special-shaped column-beam joints,17 specimens were tested under low cyclic reversed loading. The failure process and patterns were obtained. The failure characteristics, mechanical behaviors such as the loading-displacement hysteretic loops, load bearing capacity, story drift rotation, energy dissipation, displacement and rotation ductility of the joints are analyzed. It is shown that the main failures of the column-beam joints are those of shear diagonal compression in the core zone of the joint and shear-bending at the beam root. The hysteretic loops of the joints are plump. The ductility factors of the story drift and the rotation are between 1.80 and 5.63. The ultimate elastic-plastic story drift rotation is about 0.015 to 0.036 and the energy dissipative factor is about 0.150 to 0.293. The shear deformation of joint core is about 0.025 to 0.042 as the joint failed.(2) By analyzing the test loading-displacement hysteretic curves and skeleton curves, the restoring force model of SRC special-shaped column-beam joint was presented. It was three-line model of stiffness degradation considering yielding, ultimate and damage. Through the regression of test data, the stiffness formula of various stages of skeleton curves as well as the stiffness degradation laws for the unloading stiffness were given. And on the analysis of the hysteresis curve the loading and unloading hysteresis rules were given.(3) To make up for the lack of testing, such as the internal stress condition can not be observed as well as the performance of the specimen under other operating conditions, making use of non-linear finite element software ABAQUS 6.8 to simulate and analyze the test specimens, the deformation figure, stress distribution figure and the load-displacement skeleton curves were obtained. The calculation results are in good agreement with the experimental results. At the same time, some factors which affect the bearing capacity and ductility, such as the flange is configured with steel or not, the extending length of the flange, and axial compression ratio, were further analyzed. The calculation results showed that the specimens flange configured with steel or not has little influence to the corner joints and exterior joints, but has a certain influence to the interior joints, and the ductility of specimens whose flange configured steel are better than the specimens without steel. With the extended length of the flange increases the bearing capacity of the specimen is gradually increased, but the increase rate is gradually reduced, at the same time the influence factors of the flange extended length are also presented. And the deformation behavior of specimens increases gradually with the increase of extended flange length. With the axial compression ratio increases, the bearing capacity of the specimen increase with low rate, but the ductility of the specimen gradually worse, and especially when the axial compression ratio is greater than 0.6, the deformation behavior dropped sharply.(4) Based on the test results, the shear force and torque of joint core were analyzed. And shear mechanism was presented and bearing capacity of the resistance elements on characteristic points was analyzed. Through the regression of test data, the crack as well as the shear strength formulas of SRC special-shaped column-beam joint was obtained. For the corner joint, the shear and torsion bearing capacity formulas were also presented under the action of shear-torsion. And the simplified way of shape steel in lattice and solid steel member for shear-torsion member.(5) Based on the test, the connection construction measure of SRC special-shaped column-beam joints were presented, including SRC column (lattice and solid steel) with RC beam, SRC beam and S beam. The construction measure of anti-torsion and coordination for internal force were also presented.
|
PDF Full Text Request