| China is a country with extremely rich offshore petroleum resources,especially in the South China Sea offshore oil and gas resources have yet to be developed. Offshore platform is infrastructure as exploration and exploitation of offshore oil and gas resources; it’s a key problem ensuring the marine safety and personal safety of the platform. According to this condition Zhang Jigang et proposed offshore platform rocking column system. Vibration and displacement of this system can effectively reduce the effect of offshore platform in ice and under the action of earthquake. Rocking column as the important component of offshore platform rocking column structure system, the structure is very important, to ensure not only the swinging column can follow the offshore platform free movement at the same time, but also the stiffness of swinging column meet the capacity of the structural deformation.For studying the structure of rocking column used in offshore platform, 16 Concrete Filled Steel Tubular(CFST) columns subjected to three-point bending test were tested, including a round steel tube, round steel tube with I-cross section, the round steel tube with circular cross section, square steel pipe, square steel tube with I-shaped section, square steel tubes with cylindrical cross section and inside concrete with C50, C70 two kinds of strength. Failure process, failure modes, the bearing capacity and deformation capacity of combination-type CFST columns were done considering different shapes, different section form and different inside concrete strength, and analyzing the internal changes and force characteristics of specimens which had been loaded by local Poisson’s ratio and the local strain.The results show that, when test-piece was loading, steel tubular and concrete as well as internal different cross-section steel has different characteristics and collaborative work mechanisms at different loading stages; circular CFSTs have better ferrule effects, thereby enhancing the bearing capacity and deformation capacity of members; the CFSTs with two cylindrical cross section have best shear performances; to improve the inside strength of concrete can reduce the deformation and confined the sideway of inside concrete; high strength concrete can work well with outside steel tube and make full use of material properties.This paper analyzes C50 strength of inside concrete of concrete filled steel tube. Firstly studying on the constitutive relationship of steel and concrete, using tensile tests for constitutive relation of steel and theoretical derivation in uniaxial compression for concrete constitutive relation. Then six section forms of finite element modals are established, including a round steel tube, round steel tube with I-cross section, the round steel tube with circular cross section, square steel pipe, square steel tube with I-shaped section, square steel tubes with cylindrical cross section. Loading and solving that under the same experimental conditions. The finite element analysis obtain the bearing capacity, failure mode, load-midpoint displacement curve and stress nephogram.Compare with the test results and numerical simulation results, The middle section of concrete filled steel tube can effectively enhance the shear bearing capacity and deformation capacity of member; the failure modes, load-midpoint displacement curve are well simulate by use of the finite element model established in this paper; for concrete filled steel tubular structure of weld, enhancing the weld strength can improve the shear performance of the whole structure; Concrete filled steel tube with built-in section can give full play to the material properties of steel tube and concrete and give full play to the strength of the material; The built-in section member only plays a part under Concrete filled steel tube is loading and not yet reached the limit stress state, having further use of space... |
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