Abstract
In this analysis, the thick-beam theory with transverse shear is adopted. By contrast with previous works, however, the theory proposed herein is enhanced by introducing lateral normal strains and bond-slip characteristics between concrete and reinforcing bar, so as to consider the effects of lateral normal stresses in concrete due to the confinement by stirrups or hoops and of the decreasing stiffness of a structure on the deteriorated bond-slip relationship. Endochronic theory for the multiaxial stress-strain relationship of concrete, the nonlinear model considered the behaviors of strain hardening and Bauschinger effect for reinforcing bar, and the nonlinear model proposed by Morita et al. for the bond-slip relationship between concrete and reinforcing bar are used. A member is divided into several blocks and each block is further subdivided into layers. The stiffness matrix of reinforced concrete structure is derived based on the following basic assumptions : (1) Stresses and strains are constant in an element. (2) The cross section of a member remains plane, but not normal to the deflecting axis, so that shear strain components, ε_<zx> and ε_<xy>, due to bending may be taken into account. (3) Normal strains, ε_<yy> and ε_<zz>, of each element are calculated by using the equilibrium relation on the forces in concrete and lateral reinforcing bar. The longitudinal normal stress increment of a reinforcing bar (⊿_sσ_j) is expressed as follows : ⊿_sσ_j+⊿_sσ_j″=E_<sj>・⊿_cε_j The bond-slip effect of reinforcing bar on the mechanical behavior of reinforced concrete structure can be considered by using the equivalent stress increment due to the bond slippage (⊿_sσ_j″=E_<sj>・⊿_bε_j).
