ABSTRACT
3.2 Duc~ili~y of coluan aeaber Figure 4 shows typical relationships between the moment and the relative rotation 6 of the joint which were obtained from cyclic bending tests. Buildings must be able to absorb the energy of earthquake loadings through plastic deformation of the frames. Consequently, ductility of the members should be estimated from the total energy E~s obtained from skeleton curve(see Fig.3) or accumulated energy integrated for each cycle of load-resistance curves.The values of E~s are shown in Table 3, where Mp means full plastic moment calculated from plastic section modulus and the yield stress of the straight side of the column section. 6p is analytically calculated value which corresponds to Mp. E~s satisfies the relation E~s ~ 6.0 which is required for the structural rank I ( in the case of Bit s 23, AIJ(1990) )except specimen No.1. Consequently, it can be concluded that RHS manufactured by cold forming process have enough ductility for practical use. Accumulative plasticity ~s can also be obtained from cyclic bending tests as shown in Table 3. Figure 2 shows the comparison between ~(open mark) and ~s(solid mark). It is clear that ~ could approximate the lowest ~s, and it is also clear that specimen No.8 has less ductility than other specimens.
