漂浮体系斜拉桥的桥塔和主梁之间通常设置纵桥向粘滞阻尼器来控制梁端位 移，合理的阻尼器参数需通过全桥有限元模型进行反复试算得到． 文中基于此类桥梁的显 著动力响应特点，即主梁纵漂振型的贡献占绝对优势，利用结构动力学基本原理提出了考 虑附加粘滞阻尼器的漂浮体系斜拉桥三质点简化动力模型． 修正了两质点模型在力学模 式上的缺陷，并推导出在近断层脉冲型地震作用下的动力响应计算公式，最后以一实际桥 梁工程为例，通过比较各简化模型与全桥模型的差异，证明了三质点简化模型不仅可以有 效地计算出脉冲型地震作用下斜拉桥的动力响应，还能提供塔梁之间更为精确的相对位 移差和速度差，有利于更合理和准确地设计阻尼器参数，验证了三质点模型的合理性．

Longitudinal viscous dampers are usually installed between tower and girder to control the girder＇s longi- tudinal vibration，which is the dominated mode to the dynamic reactions of a floating-system cable-stayed bridge， and the rationale damper parameter has to be determined through complicated FEM analysis． In the light of the dominated vibration mode contribution in floating system，a 3 DOFs simplified dynamic model considering the su- pplemental viscous damper that improves the mechanical behavior of 2 DOFs model was proposed，and the formula- tions for calculating the dynamic responses subjected to pulse dominated near-fault ground motions were deduced． Finally，with an actual bridge project as an example，through comparing the difference between the various simpli- fied model and the whole bridge model，it was proved that the 3 DOFs simplified dynamic model can not only effec- tively calculate the seismic dynamic response of cable-stayed bridge under the action of impulsive earthquake，but also provide a more accurate relative displacement difference and velocity difference between the tower and girder． It is conducive to a more reasonable and accurate design damper parameters，and the rationality of the model is verified．