摘要
建立了静风荷载作用下大跨度缆索承重桥梁的非线性扭转失稳模型,导出了求解平衡路径的非线性方程。对于静风扭转平衡路径的稳定性进行了全过程的理论分析。分析了升力矩系数和扭转刚度的非线性特性对于稳定条件、失稳点以及失稳机理的影响。静风扭转失稳的性质为跳跃式极值失稳。发生失稳的条件取决于升力矩系数和扭转刚度的曲线形状。只有当升力矩系数曲线有上凹段或扭转刚度曲线有下凹段存在时,扭转失稳才有可能发生。对于升力矩系数曲线不存在上凹段和扭转刚度曲线不存在下凹段时,平衡路径是稳定的,不会发生静风扭转失稳。扭转刚度的弱化是引起静风扭转失稳的因素之一。升力矩系数的非线性特性将引起等效刚度弱化,也是引起静风扭转失稳的因素之一。当初始攻角较大时,这种等效刚度弱化效应尤其应该给予重视。提出了新的失稳临界风速公式。公式统一,包含了非线性失稳及线性理论的结果;公式简洁,形式上与线性理论的公式相同。对于线性扭转刚度或线性升力矩系数的情形,临界点的物理意义明确、便于图解。新的临界风速公式还反映了初始攻角的影响。初始攻角增大,临界风速减小。
A nonlinear instability mode of torsion for long-span cable-stayed bridges under aerostatic load is proposed, and nonlinear equations to solve equilibrium path are derived out. The theoretical analysis for entire process is made for stability of equilibrium path of aerostatic torsion. The effect of nonlinearity of pitch moment coefficient and module of rigidity of torsion on conditions of stability, instability points and instability mechanism is analyzed. Property of instability for aerostatic torsion is that the instability is extrema instability with jump. The condition of arising instability is related to shape of curves of pitch moment coefficient and module of rigidity of torsion. Only the curve of pitch moment coefficient has concave segments and the module of rigidity of torsion has bulgy segments. The instability of torsion can be perhaps arisen. If there are no concave segments in the curve of pitch moment coefficient and no bulgy segments on the curve of module of rigidity of torsion, the equilibrium path is stabile and the instability of aerostatic torsion can not be arisen. The module of rigidity weaken of torsion is one of causes of instability of aerostatic torsion. The equivalent module of rigidity weaken of torsion brought bythe nonlinearity of pitch moment coefficient is also one of causes of instability of aerostatic torsion. While an initial attack angle is biggish the effect of equivalent module of rigidity weaken ought to be especially noticed. A new formula of critical wind velocity for instability is presented. The formula is uniform because it contains the result of nonlinear instability and linear theory. The formula is compact because it is formally same as the formula of linear theory. For linear module of rigidity or pitch moment coefficient physical significance of a critical point is unambiguous which is expediently obtained by illustrating. The new formula of critical wind velocity reflects the effect brought by the initial attack angle. While the initial attack angle augmentes the critical wind velocity minishes.
出处
《工程力学》
EI
CSCD
北大核心
2007年第z2期145-154,共10页
Engineering Mechanics
关键词
静风稳定性
缆索承重桥
失稳机理
临界风速
升力矩系数
扭转
aerostatic stability
cable-stayed bridges
instability mechanism
critical wind velocity
pitch moment coefficient
torsion
