16.17: N‐M‐Q interaction of cross sections in steel‐concrete double composite girder bridges

Abstract

ABSTRACTRecently, a double composite structure is watched in Japan. This is a structure of composite I girder bridges with lower concrete slab which is one of the major characteristics of double composite structures. That can be considered as an effective cross section, that is, moments of inertia drastically increases in comparison with usual one. Additionally, by adopting the composite action between steel girder and lower concrete slab in the region of the intermediate supports, it is not necessary to take into account of the local buckling. Moreover, the hybrid rigid frame bridge between steel girder and reinforced concrete(RC) pier has some advantages for the seismic design and also maintenance. However, this type of structures hasn't yet been researched so well in Japan. Before applying the limit state design method, for designing this structure, under the action of normal force(N), shear force(Q), bending moment(M) and each combination should be confirmed at which all cross section is in full plastic. So, in this paper, the interaction relationships among bending moment and shear force, normal force and bending moment and normal force, shear force and bending moment are discussed are reported. One of numerical results in case of applying N‐M‐Q is shown that the safety area regarding a verification of the ratio of Q/Qpℓ= 0.7 and Q/Qpℓ= 0.9 decrease about 11% and 24% compared with that of Q/Qpℓ= 0.0, respectively.