Non linear behavior of steel fibrous prestressed frames under cyclic loads

الملخص EN

This paper presents a numerical model which is capable of predicting the behavior of fibrous prestressed concrete beams and frames subjected to cyclic loads.

The stiffness method with the effective secant stiffness is used here in analyzing plane structures, while the analysis of member cross sections that are subjected to cyclic loads is carried out in combination with the layered section approach.

Material nonlinearity has been taken in to consideration through the analysis of these sections.

This method deals only with axial forces and bending moments neglecting the effect of shear forces.

The study presents a program written with MATLAB language that analyzes structures by the STIFFNESS method and divides the cross sections into small layers in order to utilize the nonlinearity of the stress distribution along the section depth.

The results at each section are moments, curvatures, displacements, forces, stresses and strains under each load cycle.

A cyclic model for fibrous concrete subjected to uniaxial compression or tension has been proposed.

Also the cyclic model of Menegotto and Pinto for conventional and prestressing steel has been adopted.

Full bond between steel and concrete is assumed.

The study shows that the prestresssing force in concrete members has reduced the ductility or capacity of energy dissipation, while a noticeable increase in the member failure load is recorded.

Moreover, the existence of steel fibers in concrete enhances its stiffness, delays the cracks.

The scheme of and then narrows their openings in tension zone and decrease their negative effect.

The layered section presents more reliable stress distribution on the cross section of the concrete members.