Abstract
There have been very few tests on columns with ordinary reinforced concrete sections subjected to axial force and shear action at the same time. No tests at all have been reported on composite sections. In Japan however, we have had many actual cases where columns were subjected to large shear forces due to seismic forces and some of them have been destroyed by the shear. In this investigation the test on Series I is to find the kind of eccentric compression resistance which will be obtained in the case where bending moment changes along the member axis, and in order to find the shearing resistance of columns the test on Series II was held to check the effect of each parameter which governs the shear resistance by changing the parameters independently. In Series I we took the same sections and eccentricity as used under Part 1 to compare with the case where bending moment is constant. Half of the specimens were repeatedly loaded statically. In Series II we changed individually each parameter which governs the resistance. Series I has shown 3 kinds of failure behavior as shown in Fig. 6. (a) shows that the bottom part was crushed by the eccentric compression. (b) shows that the failure was caused by the diagonal tension and the cracks run along the principal stress line. (c) was limited to the specimen of the composite section and it seems that the concrete part was subjected to the punching shear with the slide of the steel. The cracks in Series II were caused by the failure due to the diagonal tension as shown in Fig. 8. Computing the resisting strength in case where the bottom part is subject to eccentric compression failure in Series I by the ultimate strength equation of Part 1, we find that the theoretical values almost coincide with the experimental values. The relations between the elements and shearing strength (3) are shown in Fig. 12〜17. Considering that the effect of the tie plate is about half the effect of hoop, the relation between the amount of shear reinforcement and τ is as shown in Fig. 13. It can be seen that τ becomes larger as the column length becomes shorter.
