水体质量对大型梁式渡槽横向抗震性能影响研究

Transverse Seismic Performance of Beam Aqueduct Considering Water Mass Influence

通过对流固耦合动力作用简化方法的研究,用等效的弹簧-质量系统来模拟流体与渡槽结构的动力相互作用,并对某渡槽进行了多种地震波作用下的抗震性能分析,得到了大型梁式渡槽结构的自振特性、地震响应。结果表明:槽内大质量水体对渡槽的横向地震响应有较大的影响,若不考虑槽内的水体将低估渡槽的地震反应;但因水体的晃荡作用减小了水体自身的地震反应,若将水体视为刚体附加到槽体上将严重地夸大水的地震惯性力作用。

To analyze the transverse seismic performance of a large-scale beam aqueduct by consid- ering the water mass influence, the aqueduct of the South to North Water Diversion Project is studied. Through a study of the fluid-structure coupling dynamical action method, we use an e- quivalent of a spring-mass system （simplified using the Housner water model） for simulating the dynamic interaction of the fluid and the aqueduct structure. The ANSYS finite element software is adopted to estimate the performance of a large-scale aqueduct with a beam. With the time his- tory analysis method, we have investigated the transverse seismic response of the large-scale beam aqueduct using a few types of earthquake waves. Then, the natural vibration characteristics and the seismic response of the large-scale beam aqueduct are obtained considering the fluid-struc- ture coupling interaction. The calculation results show that the water shaking function has a con- siderable influence on the dynamic characteristics of the aqueduct. The transverse seismic re- sponse of the beam aqueduct is significantly influenced by the water mass in the aqueduct. The water shaking function can effectively decrease the seismic response of the water itself. The transverse seismic response of the aqueduct is underestimated if the water in the aqueduct is ig- nored; however, if all the water in the aqueduct is regarded as a rigid body and appended to the aqueduct, the seismic inertia action of the water is seriously exaggerated and is unreasonable. Consequently, in the dynamic analysis of the large-scale aqueduct, we must consider the fluid-structure coupling interaction. We compare a case in which the fluid-structure coupling interac- tion is considered and that in which the fluid-structure coupling interaction is not considered; the former＇s maximum top displacement and bottom moment and the shear of piers are far less than those of the latter. Therefore, we conclude that the water mass influence on the seismic response of the aqueduct is limited. We compare the seismic responses of two different conditions of full trough （considering the fluid-structure interaction} and empty trough and find that the former＇s maximum top displacement and bottom moment and the shear of piers are all greater than those of the latter. This is because the thankful water increases the quality of the upper portion of the aq- ueduct structure, which increases the seismic forces acting on the aqueduct. In the aseismic anal- ysis of a large aqueduct, the influence of the water mass should be taken into account. When the water mass remains unchanged, and the aqueduct body changes according to the depth-width rati- o, the natural frequency of the water in the aqueduct and the natural frequency of the aqueduct vi- bration change; however, the changes are not considerable. The change of the largest displace- ment of the piers on the top and the greatest moment and shear of the piers at the bottom depen- ded on the depth-width ratio. Therefore, while selecting an aqueduct section, we should take the depth-width ratio of the seismic response of the piers into account. To some extent, the selection of a reasonable section can reduce the seismic response of the aqueduct. The fluid-structure inter- action of the fluid and the aqueduct should be known for the estimation of both the impulse pres- sure and the convection pressure. The sloshing fluid produces a complex reaction on the aqueduct body; hence, we cannot simply consider all water quality values to be the added mass to the aque- duct body.