Abstract
The free vibration characteristics of steel-concrete composite continuous beams (SCCCBs) are analyzed based on the Euler–Bernoulli beam theory. A modified dynamic direct stiffness method has been developed, which can be used to analyze the SCCCBs with some lumped masses and elastic boundary conditions. The results obtained by the proposed method are exact due to the elimination of approximated displacement and force fields in derivation. The proposed method is verified by comparing its results with those obtained by ANSYS software and laboratory tests. Then, the influencing factors on the reduction of natural frequency are analyzed and discussed in detail using the proposed method. The results show that stronger interfacial interaction results in higher values of natural frequency as well as larger steel subbeam and thinner concrete slab. The smaller the natural frequency of the SCCCBs is, the more significant effect the interfacial interaction on the natural frequency is. The reduction of natural frequency is not affected by the different numbers of spans but the equal single-span length and various ratios of the side span to the main span but equal total length, but it is influenced by the extra single-span length and different ratios of the side span to the main span but equal main span length. And it is only affected by bending stiffness. Furthermore, the reasonable ratio of the side span to the main span is 0.9∼1.0.
Highlights
Fang et al [25] presented a simplified calculation model and developed the Mode Stiffness Matrix to investigate the dynamic characteristics of steelconcrete composite continuous beams (SCCCBs). en, using this method, the influence of span ratios and shear connection stiffness on natural frequencies was analyzed based on two-span SCCCBs. e results indicated that the natural frequency reduction ratios were totally the same for two-span steelconcrete composite beams (SCCBs) with different span ratios but uniform shear connection stiffness
Example 1: Experimental Verification. is section focuses on the verification of the proposed method by a twospan SCCCB in the laboratory. e natural frequencies obtained by the proposed method were compared with those by ANSYS software and laboratory tests. erefore, the proposed method was verified
The dynamic behaviors of SCCCBs are analyzed using a modified dynamic direct stiffness method based on Euler–Bernoulli’s beam theory. e main advantages of the proposed method are that it is suitable for the SCCCBs with some lumped masses and variable bending stiffness along the x-direction
Summary
Due to the clear advantages of larger spans, higher loadbearing capacities, and more convenient construction, steelconcrete composite beams (SCCBs), especially the steelconcrete composite continuous beams (SCCCBs), are widely applied in railway bridges with the development of the highspeed railway. e SCCCBs are compared with a concrete slab in the compressive portion and a steel subbeam in the tensile portion and connected by shear studs which can transfer the shear force. erefore, the overall mechanical performance of the SCCCBs depends on the material properties of steel subbeam and concrete slab and, to a large extent, on the connection performance of shear studs. e interfacial shear slip will occur between the subcomponents owing to the flexibility of shear studs, which can reduce the natural frequencies of SCCCBs significantly. Fang et al [25] presented a simplified calculation model and developed the Mode Stiffness Matrix to investigate the dynamic characteristics of SCCCBs. en, using this method, the influence of span ratios and shear connection stiffness on natural frequencies was analyzed based on two-span SCCCBs. e results indicated that the natural frequency reduction ratios were totally the same for two-span SCCBs with different span ratios but uniform shear connection stiffness. E purpose of this paper is to present a modified dynamic stiffness matrix method to obtain the exact natural frequencies of SCCCBs with lumped masses and elastic boundary conditions based on the Euler–Bernoulli beam theory. Utilizing the proposed modified method, a number of influencing factors upon the natural frequencies of SCCCBs, namely, interfacial interaction, cross-sectional stiffness ratio, number of spans, single-span length, the ratio of the side span to the main span, and lumped masses, are analyzed and discussed in detail
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