I'm trying to develop a computer program to analysis frame including p-delta effect using secant stiffness method but i have problems to understand the procedure mentioned in the attached file
1.Set up the member stiffness matrices for all members and assemble them in structure stiffness matrix [K] = [Ke] + [Kg].
2.At the beginning of the calculations, applied loads are taken as zero.
3.Carry out the linear analysis under zero loads and obtain the response of the frame, which is an initial estimate for the nonlinear analysis.
4.Solve the equation [Ke + Kg]{dΔ} = {dP} for {dΔ} and then determine the incremental member end forces.
5.Solve the equation [Ke + Kg]{dΔ} = {dP}iteratively by a sequence of linear steps.
6.The unknown nodal displacements and member end forces are obtained according to the zero applied loads.
7.Update the terms in member stiffness matrices, member forces and structure geometry.
8.Repeat steps 3 to 7 until convergence is attained.
9.Calculate accumulated displacements and member end forces at convergence.
The problem is why at the beginning of the calculations, applied loads are taken as zero!
and why we dont took just the final displacement as solution at the place of accumulated displacements and member end forces
and why in the application example the apply load is not devided in small load increment
thanks
1.Set up the member stiffness matrices for all members and assemble them in structure stiffness matrix [K] = [Ke] + [Kg].
2.At the beginning of the calculations, applied loads are taken as zero.
3.Carry out the linear analysis under zero loads and obtain the response of the frame, which is an initial estimate for the nonlinear analysis.
4.Solve the equation [Ke + Kg]{dΔ} = {dP} for {dΔ} and then determine the incremental member end forces.
5.Solve the equation [Ke + Kg]{dΔ} = {dP}iteratively by a sequence of linear steps.
6.The unknown nodal displacements and member end forces are obtained according to the zero applied loads.
7.Update the terms in member stiffness matrices, member forces and structure geometry.
8.Repeat steps 3 to 7 until convergence is attained.
9.Calculate accumulated displacements and member end forces at convergence.
The problem is why at the beginning of the calculations, applied loads are taken as zero!
and why we dont took just the final displacement as solution at the place of accumulated displacements and member end forces
and why in the application example the apply load is not devided in small load increment
thanks
