| The rectangular hollow section (RHS) steel tubular truss with the concrete-filled in chord is a kind of novel structural system, which chord members are concrete-filled rectangular section steel tube and its web members with rectangular section steel tube are welded on the surface of chords. Supported by the Program for West Transport Construction Science and Technology(2006319812112), and Applied Basic Research Programs of ministry of transport of China (2006319812130), the mechanical behaviors and design method of the trusses were studied in this paper, provided a theoretical basis for its application in bridge structure. The main achievements are summarized as follows:1. Test on two types RHS steel tubular trusses under static point loading at middle span were carried. The failure mode of trusses was due to the joints failure, but the failure modes were different, the concrete-filled in chord changed the failure mode.2. Test on trusses made with RHS and circular hollow section (CHS) steel tube were carried. The trusses of RHS and CHS have not much difference in the bearing capacity and deformation, but with chord concrete-filled, the CHS trusses have the higher bearing capacity of the overall truss and joints, better deformability than the corresponding RHS trusses, and the less proportion of joints deformation in the total deformation.3. Based on experimental results, the influence from concrete-filled in chords on chords members, branch members, joints stress and the overall stiffness of truss were obtained. The concrete-filled in compression chord can help compression chord members very well, and reduce the steel tube strain; The concrete-filled in tension chord do not effect the tension chord members obviously at start state, but can prevent the contraction deformation of tension steel tube at late stage, so increse the bearing capacity; The concrete-filled in chords do not effect the branchs obviously; The concrete-filled in chords can greatly enhanced the strength and rigidities of compression joints, reduce the deformation and increase the strength of tension joints,4. The nonlinear finite element model according to ANSYS program of RHS steel tubular trusses with concrete-filled chord was also built up, the calculating results of nonlinear finite element method kept in with those from tests. The mechanism of trusses with branch and chord section width equal were studied by FEA, the joints gap is the weak positon, the trusses failure were due to the chord shear failure, the concrete-filled chord can improve the shear capacity.5. The rigidity of concrete-filled in compression chord effect on trusses mechanical behavior was analyzed. The compressive stiffness of concrete-filled in compression chord does a greater effect than the bending rigidity. When in the calculation of compression chord stress, the suggestion value of compression stiffness is EA=EsAs+EcAc, as to the trusses deformation calculation, for the effect of joints deformation, the bending rigidity and compression rigidity should be reduced, but reduce method and reduce coefficient should be further discussed.6. The mechanical behavior and failure mode of joints were analyzed, the failure mode of trusses with branch and chord section width equal were provided, and the corresponding formula to calculate ultimate bearing capacity. The mechanism and failure path of overall trusses were studied, the effective length coefficient of compressive member were provided, as to compressive chord, it is 1.0, as to compressive branch, it is 0.75. the amplification factor method of calculation the overall deformation were provided, the amplification factor for RHS truss and RHS truss with concrete-filled in the compression chord is 1.15, and amplification factor for RHS truss with concrete-filled in both compression and tension chords is 1.2. |
PDF Full Text Request