超高層建築物施工起重機之耐震需求之探討

Seismic Demand of Construction Cranes during the Erection of High-rise Buildings

超高層建築物由於工期較長，施工期間遭逢地震的機率本較一般工程為高，加上其高度超出一般建築物甚多，因此結構體在不同施工階段之基本振動週期，將隨其高度之變化而出現大幅度變動，而上述變動範圍則往往涵蓋了施工起重機之基本振動週期。若結構本體與起重機之基本震動週期過於接近，則二者在地震中極可能產生共振效應而使起重機所受之地震力大幅增加，並導致起重機結構損壞， 331 地震中台北國際金融大樓所發生之起重機墜落事件便是一例。本研究中根據數筆於實際地震中所取得之地表加速度紀錄，針對一超高層建築物在不同施工階段之結構狀態，進行加速度歷時分析，並根據分析結果，探討地震力對裝設於建築物中之固定式起重機可能造成的影響及施工起重機之耐震需求。為符合工程設計之慣用格式，文中將起重機所受之地震力以其自重之倍數表示，以作為相關法規之修訂參考。

Due to the scale and height reasons, construction of a high-rise building usually takes longer than ordinary projects, which makes it a prime target of seismic attacks. Since the height of the building grows as the constructions proceeds, the dynamic property of the building varies. As a result, it is likely that the fundamental period of the building would come across the period of the crane at a certain stage. When this happens, resonance will become a serious problem in the event of an earthquake. Unfortunately, current regulation have not been able to address this problem and a costly statement was made by the collapse of the construction cranes at the then-inconstruction Taipei International Financial Center during the 2002 Hualian Earthquake. In order to study the seismic effects on the safety of construction cranes during the erection of high-rise buildings, an structural investigation was conducted. In this study, Time-history analyses were carried out on structural models representing different construction stages of an exemplary high-rise building using ground motion records collected at various locations during different earthquakes. Conclusions obtained in this study would provide both engineers and government officials a guideline for the design of construction cranes.