CALCULATION OF INTERNAL FORCES OF STAGGERED TRUSS STRUCTURES SUBJECTED TO VERTICAL LOADS

Iterative formulas of nodal rotational angle and lateral deflection of truss panel and fixed-moment in end-fixing Vierendeel truss subjected to vertical loads are presented in this paper. Iterative formulas of nodal rotational angle and lateral deflection caused by unit rotational angle in one end of end-fixing Vierendeel truss and methods for calculating rotational stiffness and transfer coefficient are provided by use of the conditions that the forces on each node are in equilibrium and that the summation of relative lateral deflection of truss panel is zero. As a result, the staggered truss structure is simplified as a rigid frame with no lateral deflection and iterative formulas of nodal rotational angle including rotational stiffness, transfer coefficient and fixed-moment and methods for calculating member forces are developed. With consistent displacement principle, a calculation model of Pratt staggered truss including three unknown forces and formulas of unknown forces and calculation methods of member forces are proposed. Results show that the number of members involved in interaction is decreased greatly and iterative convergent rate is improved greatly. Thus, the method adopted in this paper needs less computational effort and are convenient for application. The results obtained by the present method are in good agreement with the those of software ANSYS.