| In recent years, frame structure with special-shaped columns has been widely used in our country. Considering its engineering practice and the seismic requirements of lateral rigidity, this paper proposes a composite structure system with broad-limb special-shaped reinforced concrete columns-small size concrete hollow block wall, in which beams and columns are poured after the masonry walls, the ratio of height to thickness of special-shaped columns is increased appropriately for the combined action of block walls and frame with special-shaped columns, and a number of constructional ring beams are set in the block walls. Therefore, the researches carried out in this paper work have an important theoretical significance and practical value.This paper did some researches on the seismic performance of this structural system by experiment research, theoretical analysis and finite element numerical simulation. A total of 5 specimens with 1:2 reduced scale were tested under cyclic lateral force and a constant axial loading, two of which are single-layer composite structures with broad-limb special-shaped columns-concrete block walls, one of which is four-layer composite structure, and another two are respectively single-layer and four-layer pure frame structures with special-shaped columns. Test results show that the composite structure composed of broad-limb special-shaped reinforced concrete columns with T-shaped cross-section and small size concrete hollow block wall has good teamwork performance; block wall can significantly increase the structural carrying capacity and stiffness, and frame can restrain the deformation of walls to avoid collapse because of cracks; the sequences of cracking and destruction of the samples are concrete block walls, beams and columns, so the block wall can be set as the first seismic defense line of structure, which is also in line with the multi-channel seismic fortification principles. Plastic hinges of special-shaped column frame emerge firstly at the beam ends prior to the columns, which is of typical beam hinge mechanism.Compared to pure frame structure with special-shaped column, the lateral bearing capacity, lateral stiffness, and ductility coefficient of composite structure with broad-limb special-shaped columns-concrete block walls increased significantly. Lateral bearing capacity could be increased by 25% or so, cracking stiffness and yield stiffness increased an average of 2.10 times, and ductility coefficient increased 1.89 times. Additionally this kind of structure had a good seismic performance with plump hysteresis loops.Using elastic-plastic fracture and damage concrete model, the non-linear finite element analysis of one single-storey single-span composite structure with broad-limb special-shaped columns-concrete block walls was carried on in this paper, what focused on the influences of ratio of height to thickness of special-shaped columns and structural high-to-span ratio on the bearing capacity and stiffness.Based on the experimental research and theoretical analysis, six failure modes of composite structure with broad-limb special-shaped columns-concrete block walls were proposed. The formula for calculating shear strength of this kind of composite structures was raised, using a working model of the whole wall to get the formula for calculating the elastic stiffness. The contrast between theoretical results and experimental results showed that the proposed formula could meet the engineering design requirements with better accuracy.The design and construct proposals of papers presented on the composite structure can be referenced by designers.Considering influence of infilled wall on the seismic performance of frame structures, this paper discussed the calculation model of infilled wall stiffness, used three-dimensional analysis program TAT to study influence of period reduction coefficient on the earthquake response of structures, and proposed the seismic conceptual design of infilled wall frame.
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