基于荷载效应的结构抗风设计方法研究

Study on wind-resistant design of structures based on load effects

对等效静风荷载的基本理论进行分析,指出GB 50009—2001《建筑结构荷载规范》的风振系数法给出的等效静风荷载在只考虑1阶振型的前提下,能够实现各种荷载效应的等效;需考虑多阶振型的结构,只有在各阶振型完全相关的条件下,才能得到可满足全部荷载效应等效的静风荷载;一般情况下,包括阵风荷载因子法在内的计算方法,给出的等效静风荷载只能保证单个或多个响应目标的等效,其他荷载效应存在较大不确定性,可能造成据此进行的抗风设计偏于保守或不安全。为克服这些传统抗风设计方法的局限,提出了直接以荷载效应包络值进行结构抗风设计的基本思路:结合风洞试验得到各种荷载效应在不同风向角下可能出现的上、下限值,再将其与其他荷载作用下的效应直接组合进行结构设计。通过工程实例分析表明,采用阵风荷载因子法得出的等效静风荷载值可能导致其他荷载效应被大大高估,而直接采用荷载效应包络值用于结构设计,不但其值准确,且易于操作。

Through a comprehensive analysis on the fundamental theory of the equivalent static wind load （ESWL）, it is pointed out that the ESWL derived from the wind-induced vibration factor in Chinese Load Code will lead to the equivalent results for all the load effects provided that only the first vibration mode needs to be considered. But on the condition that several vibration modes are involved, the ESWL satisfying all the load effects doesn’t exist unless these modes are completely correlated. So in general cases, an ESWL given by different analysis methods including the gust loading factor method is only effective for one or more specific equivalent targets. Other load effects may be overestimated or underestimated under the action of such ESWL. In order to overcome the limit of the conventional methods, a new approach was proposed to make wind-resistant design based on load effects. The envelope of various load effects was obtained first through wind tunnel tests and it was combined directly with the corresponding effects induced by other loads. This design method was demonstrated by an engineering case. It is shown that the ESWL derived from the gust loading factor overestimated significantly some load effects while the wind-resistant design using the load effects envelop is accurate and convenient to carry out.