Experimental Research On Seismic Behavior And Design Methods Of Fiber Reinforced Structure With Specially Shaped Columns

The RC frame structure with specially shaped columns is widely used in field of engineering for the favorable service function. But the existence of weak parts of joints and legs of specially shaped columns in bottom floor restrict the structure height and the further generalization of structure with specially shaped columns. Therefore the method of fiber reinforcement in local area is proposed to make reinforcement to weak parts of structure with specially shaped columns. Fiber reinforcement to the weak parts of structure with specially shaped columns in seismic behaviors is investigated to make this structure generalize further and provide the experiment and research foundation. The detailed work of this paper is stated as follows:According to cyclic loading test of specially shaped columns with leg reinforced by polypropylene fiber and steel fiber, the aspects of failure characteristic, shearing capacity, ductility and seismic behaviors are compared between specimens with and without fiber reinforcement to make the analysis. It is shown in the results that the failure characteristics can be improved and the bearing and deforming capacity can be increased with fiber reinforcement. The conclusion can be drawn from total comparison that the reinforcing effect of steel fiber is better than that of polypropylene fiber.Based on the tests on seismic behaviors of six interior joints and four exterior joints with specially shaped joints reinforced with polypropylene fiber and steel fiber, comparison is made on failure characteristic, shearing and deforming capacity, seismic behaviors and mechanical behaviors in loading to study on the fiber reinforcement on different fiber varieties and fiber using areas. It is shown in the study that fiber could delay the cracking of core area of joint, decrease the width of cracks, alleviate the failure pattern of joint and also improve the bearing capacity, ductility, and seismic behaviors. The best fiber reinforcing effect occurred in that fiber reinforcement on the core area of joints and the area of beam height.On the basis of mechanical mechanism and force transferring process, 52 test results for joints with specially shaped columns are statistically collected to study the changing rule of shearing capacity, based on which the formula of shearing capacity of joints with specially columns is proposed to provide a design calculation method for fiber reinforced joints with specially shaped columns. Calculation and analysis shows that the formula ares rational and save in calculation with security degree.It is shown from the test results and analysis on the constitutive relationship, the compressive strength and peak strain of concrete is influenced little by fiber reinforcement, while the ultimate strain can be increased in large degree, the compressive toughness and tenacity can be improved to make the brittleness of failure characteristics of concrete. The constitutive model of fiber reinforced concrete is established according to the analyzing and test results, which is used in the finite element analysis on the interior joints with specially shaped columns to analyze the influence of fiber using area to the joint bearing capacity in supplement. It is shown from the analysis that the bearing capacity of joints have a maximum with the fiber using area of the core area of joint including half to one times of the beam height.The engineering design suggestions on fiber reinforced joints with specially shaped columns are put forward on the basis of the above test and analysis.