A new dynamic direct stiffness method for analyzing the natural vibration characteristics of steel–concrete composite beams (SCCBs) is proposed, which considers the effect of partial interaction between the interface of the concrete slab and steel beam. The advantage of the method is that exact solutions can be obtained due to no introduction of approximated displacement and/or force fields in the derivation. Besides, the method is especially useful for the dynamic analysis of SCCBs with axial variable stiffness under four common boundary conditions. The proposed method is validated by comparing with the theoretical and experimental results available in the literature. Finally, the effects of different boundary conditions, shear connection, cross-sectional stiffness ratio, and other parameters upon the frequencies of the beam are discussed in detail.

中文翻译：

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钢-混凝土组合梁的动态直接刚度法的自由振动

提出了一种新的动态直接刚度分析钢-混凝土组合梁（SCCBs）自振特性的方法，该方法考虑了混凝土板与钢梁界面部分相互作用的影响。该方法的优点是由于在推导中没有引入近似位移和/或力场，可以获得精确的解。此外，该方法特别适用于在四种常见边界条件下对具有轴向变刚度的 SCCB 进行动态分析。通过与文献中可用的理论和实验结果进行比较来验证所提出的方法。最后，不同边界条件、剪力连接、截面刚度比的影响，