In this paper, result of tests on 20 simply supported concrete deep beams are presented. All tested beams have dimensions of (150 x 400 x 1100) mm and tested under (1, 2, 4 and 8) point loads. The considered parameters are shear span to effective depth ratio (a/d), concrete compressive strength (fʹc) and longitudinal reinforcement ratio (ρw).The influence of these parameters on cracking and ultimate load, load versus deflection response and concrete strain are investigated.
The results showed that the decrease in the (a/d) ratio from 1.373 to 0.412 leads to a decrease in cracking and ultimate shear strengths by average ratios of 40 % and 57 % respectively, while increasing (fʹc) and (ρw) leads to the increase in the cracking and ultimate shear strengths. The load-deflection response is significantly affected by the (a/d) ratio and becomes appreciably nonlinear as the (a/d) ratio increases, while it is slightly affected by the compressive strength of concrete (fʹc) and steel ratio (ρw). Strain distribution through the depth at mid span is nonlinear even in elastic stage. At the same load level, strain distribution increases as (a/d) increases and decreases as (fʹc) and (ρw) increase. The analytical work has been made on the 20 deep beams plus 62 from literature using the regression analysis. Proposed equation was compared with four equations available in literature and gave less average and coefficient of variation equal to1.04 and 16.98% respectively.