Wenfu Zhang

Dimensionless Analytical Solution and New Design Formula for Lateral-Torsional Buckling of I-Beams under Linear Distributed Moment via Linear Stability Theory

Even for the doubly symmetric I-beams under linear distributed moment, the design formulas given by codes of different countries are quite different. This paper will derive a dimensionless analytical solution via linear stability theory and propose a new design formula of the critical moment of the lateral-torsional buckling (LTB) of the simply supported I-beams under linear distributed moment. Firstly, the assumptions of linear stability theory are reviewed, the dispute concerning the LTB energy equation is introduced, and then the thinking of Plate-Beam Theory, which can be used to fully resolve the challenge presented by Ojalvo, is presented briefly; secondly, by introducing the new dimensionless coefficient of lateral deflection, the new dimensionless critical moment and Wagner’s coefficient are derived naturally from the total potential energy. With these independent parameters, the new dimensionless analytical buckling equation is obtained; thirdly, the convergence performance of the dimensionless analytical solution is discussed by numerical solutions and its correctness is verified by the numerical results given by ANSYS; finally, a new trilinear mathematical model is proposed as the benchmark of formulating the design formula and, with the help of 1stOpt software, the four coefficients used in the proposed dimensionless design formula are determined.

Finite element model based test and analysis on ACHC short columns and hoop coefficient

In order to promote the application of angle-steel confined high-strength concrete (ACHC) columns in new construction and reinforcement projects of civil engineering, this paper designs 15 groups of ACHC short columns with a shear span ratio of 1.5 under axial compression by taking the hoop coefficient, strength grade of concrete and yield strength of steel as parameters. Based on the constitutive model of steel and confined concrete and considering hoop effect, the simulation analysis on them was carried out by ANSYS software, and the rationality of finite element modelling is verified by comparing it with the experimental data. The author investigated the influence of different hoop coefficients, different concrete strength grades and different yield strength of steel to the mechanic behaviour of ACHC short columns, and the results show that the influence of hoop coefficient to the bearing capacity and ductility is more significantly than other parameters. Considering the hoop effect of batten plate to concrete, the linear relationship between the influence factor of batten plates and the hoop coefficient is inverted by using 1stopt software. At last, the calculation formula of ultimate bearing capacity of ACHC short columns is gotten, and the design method and suggestion of short columns are put forward.