Abstract
The present study utilizes the finite element method for analyzing the mechanical behavior of singly-reinforced concrete prismatic members with various covering depths. The concrete and the steel bar were represented by the finite elements, and the closely spaced bond linkages similar to those employed by Nilson were used to joint adjacent nodal points of the concrete element and steel element. The nonlinear material properties, nonlinear bond-slip relations, and the influences of progressive cracking and bond failure were taken into consideration in the analysis.
The results are summarized as follows :
(1) The covering depth influences the distribution of stress in steel.
(2) For the reinforced concrete member with a length of 20 cm and a covering depth of 4 cm, a primary transverse crack occurs at the center of the member, and then the secondary cracks initiate midway between the primary crack and the ends of the member. However the secondary cracks initiated near the bar do not spread to the outer side even though the load increases. The bond failure occurs at the primary cracking position and at the ends of the member as soon as the secondary cracks appear.
(3) The minimum space of transverse cracks is about (D+2t), where D is the diameter of the steel bar and t is the covering depth.
(4) The difference between the crack width at the concrete surface and that at the bar surface increases with increasing the covering depth, but the difference does not exceed 30 per cent of the crack width at the concrete surface.
