ABSTRACT
Crack formations of SS-1 and SS-5 are sketched in Figure 11. In SS-1, a crack was initiated near the midspan at the load of 39 kN and then the number of cracks increased. When the load reached 157 kN, cracks occurred horizontally at the end of the concrete. This was caused by shear failure of the concrete around the studs. When the load reached 314 kN, the concrete was crushed in conical shape and the sheet pile and the concrete separated from its end. Subsequently, the beam collapsed quickly and buckling of the pile finally occurred. The process of collapse of SS-2 to SS-4 was similar to that of SS-1. In SS-5, a crack was initiated at the load of 90 kN, and then flexural cracks were formed. Finally, shear failure of the concrete around the studs was observed. However, collapse at the end of the concrete like SS-1 was not observed. The ultimate load of SS-5 was the largest among the beams. In SS-6, flexural cracks developed like the other beams, but finally, shear failure of the concrete occurred at the stirrup. In all the beams, destruction
of the studs and the bars did not occur. The calculated ultimate moment of the beam is 120 kNm, which is 307 kN in terms of load. It can be said that SS-1 through SS-6 have higher yield strengths than this value. SS-1 through SS-4, however, did not have sufficient added strengths because of destruction caused by pull-out shearing. Hence, mechanical properties of these beams were not preferable. Therefore, use of long studs or stirrups should be necessary. Strength characteristics of the beams with initial stresses showed no remarkable difference with those without them.
