EVALUATION OF SHEAR STRENGTH OF PRESTRESSED CONCRETE BEAMS WITH HIGH STRENGTH MATERIALS
Supervisor: Susumu KONO
Shear behavior of prestressed concrete beams has been studied for many years and some equations were already proposed in several codes. However, these equations do not correctly evaluate which resulting in conservative design or dangerous design. One hundred sixty-eight (168) data from 14 papers published in Japan during 1981 to 2004 are used in analysis. Equations provided by Japanese PC standard 1998 and ACI 318-05 are studied using these data. Based on analysis, equation 71.2a of Japan PC standard 1998 was the best design equation to predict shear strength of prestressed concrete beams among six equations. However, the equation has following shortcomings. It is quite conservative for I-section and un-bonded rectangular section. On the other hand, it overestimate shear strength of pre-cast prestressed concrete and rectangular beam using high strength steel as shear reinforcement. To improve its performance, the arch contribution was isolated by choosing beams with un-bonded tendon or specimens without shear reinforcement. Then, the modification was made to; the effect of prestressing force on the compressing strength of concrete strut, confining effect provided by shear reinforcement on the compressive strength of concrete strut and the effective width of the web for I-sections. On the other hand, truss contribution was not modified except for I-section. Proposed modification has produced satisfying results. Average experiment-to-prediction ratio is getting closer to 1.0 and scatter of data is getting small.
|Citation: ||Bulletin of IISEE, 43, 79-84.|