The Design Method Of Rectangular Reinforced Concrete Bent-columns Based On Second-order Effect And Fatigue Life

The current design code for reinforced concrete bent column are seldom consideredsecond-order effect and the fatigue life, or incomprehensive. Therefore, adoption offlexural stiffness value by use of second-order effect and the fatigue life effecting on thebent column are studied, applied into the design of bent column.First, for the second-order effect. RC bent column is simplified as cantilever column,and a theoretical formula of flexural stiffness for cantilever column under eccentric loadsis derived in this paper. Flexural stiffness computation for giant scale, large kind of bentcolumns is conducted, which including multiple linear regression analysis, filtering factorsand proposing simplified calculation method for design, in order to summarize the factorsfor flexural stiffness and be convenient to the application of the theoretical formula todesign. The flexural stiffness theoretical result is compared with that calculated on thebasis of current USA and Europe concrete specification, in order to prove that the flexuralstiffness equation proposed in this paper is useful and reliable in bent-columns designing.Second, for the fatigue properties of bent column. The finite element model of bentcolumn is generated by the ANSYS/FE-SAFE. According to the references, design code,and approximate calculation, the fatigue parameters of concrete material and rebarmaterial, which make up of the bent column, are gained. The load spectrum of the bentcolumn is generated through rain-flow counting method, according to the practicalengineering. Then, the fatigue life, FOS values, and safety probability are calculated basedon the S-N curve through FE-SAFE. The bracket slope, concrete mark and load amplitudeeffecting on the above result are taken to comparisons. The sensitivity of each specialparameter to the fatigue life is analyzed. From the above research, the best specialparameters for design bent column are established. At last, according to the fatigueproperties of bent column, the reduction factor of the maximum stress on the bent columnafter a certain period of load is established. This method provides theoretical basis andreference value for the design of the reinforced concrete structure.