外挑式场馆建筑的动力性能

Dynamic behavior of stadium-type buildings with cantilever structures

通过世博会两个工程实例,建立外挑式场馆建筑非耦联系统的分布参数力学模型。它们的体型空旷而矮胖,质量大都分布在主体框架或剪力墙的外侧,具有相当大的转动惯量。无阻尼自由振动的分析结果表明,扭转往往为第一振型。进一步分析和论述了平扭耦联系统偏心率-e和频率比Ω对地震反应的影响。当Ω=1时,系统对扭转反应相当敏感。对于小偏心系统,当Ω≤0.75或Ω≥1.25时,扭转效应会显著减小。对外挑式场馆建筑,拘泥于限制扭转不为第一振型不一定是完全合适的。它们的抗震性能应该从振型、频率比、位移比、层间位移角等几个方面进行综合评价。

On basis of two EXPO engineering projects,the uncoupled model with distributed mass and stiffness is presented for stadium-type buildings with cantilever structures.The results of free vibration analysis show that torsion will be easy to be the first modal shape of the system,which has properties of the low ratio of building height to planar dimensions and the large gyration radius of mass.For the torsion-coupled system,both eccentricity and frequency ratio Ω are important design parameters.For the system with small eccentricity,whether Ω≤0.75 or Ω≥1.25,the seismic torsion responses will be greatly reduced.As the eccentricity being larger,the modal shape will be coupling each other,especially when Ω=1.It is reasonable for the tall buildings to stipulate that the torsional modal shape must not be the first one to reduce the torsion responses,because the first modal shape will be translational,when it is well designed.However,it may not be necessary to control the order of the modal shapes for the stadium-type buildings with outrigger structures.Their dynamic behavior should be estimated by using the design parameters,such as eccentricity,frequency ratio,lateral stiffness,torsion displacement ratio,and so on.