Effects of mix property on time dependent behavior of reinforced concrete slabs

الملخص EN

A nonlinear, layered, finite element model for predicting the time dependent behavior of reinforced concrete slabs under sustained transverse loading is presented.

The effects of biaxial creep and shrinkage are considered by using the provisions of ACI Committee 209.

Both elastic- perfectly plastic and strain hardening plasticity approach have been employed to model the compressive behavior of the concrete.

The yield condition is formulated in terms of twostress invariants.

The movement of the subsequent loading surfaces is controlled by the hardening rule, which is extrapolated from the uniaxial stress-strain relationship defined by a parabolic function.

Concrete crushing is a strain controlled phenomenon, which is monitored by a fracture surface similar to the yield surface.

A smeared fixed crack approach is used to model the behavior of the cracked concrete, coupled with a tensile strength criterion to predict crack initiation.

An attention is given also to the post-cracking shear strength.

The steel is considered either as an elastic perfectly plastic material or as an elastic-plastic material with linear strain hardening.

Steel reinforcement is assumed to have similar tensile and compressive stress-strain relationship.

A computer program coded in FORTRAN77 language is written to implement the present study.

This program is arranged to give a complete listing of stresses and deformations in every concrete or steel layer.

Several examples for which experimental results are available are analyzed, using the proposed model .The comparison showed very good agreement especially for the maximum deflection, the different about 1%.