頂層加蓋影響建物耐震能力之分析

Analysis of Effect on Earthquake-Resistant Capacity due to Penthouse-Surcharges on Buildings

翟慰宗(Wei-Chung Chai)

指導教授 ： 簡秋記

中原大學/工學院/土木工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100076

摘要

台灣地區民間住宅，不少住戶為了增加使用空間，而私自變更建築結構，即屋頂頂層加蓋一或二層樓的情形普遍存在；雖然頂層加蓋後，並不會因垂直載重的增加而產生立即性的危險，但加蓋後對原結構體之強度、勁度及耐震能力卻會有顯著不良的影響。1999年台灣921集集地震，不少民宅、校舍或公有辦公室等低層建築因頂樓加蓋，地震時導致房屋塌陷之案例，屢見不鮮。本文即針對此類情況，加以分析探討，即進行推覆法非線性靜力分析，對結構體在地震發生時構架塑鉸產生之順序、屋頂層變位、層間變位、結構整體勁度之減少、正規化基底剪力與屋頂層變位角關係加以分析，另計算結構體頂層加蓋後之降伏地表加速度、崩塌地表加速度，並與原未加蓋結構比較其差異。由本文分析結果得知：當加蓋一層樓時，整體彈性勁度降低的百分比平均為19%，而加蓋二層樓時，降低的百分比平均達35%；當加蓋一層樓時，耐震能力平均降低的百分比平均為25%，而加蓋二層樓時，降低的百分比平均達40%。另外，本研究案例亦進行時間歷程非線性動力分析，在不同的PGA值下，計算結構體加蓋前後產生之最大頂層變位角和層間變位角值，動力分析的結果顯示頂層加蓋後結構體之層間變位角值多無法滿足規範要求。

關鍵字

屋頂頂層加蓋 ； 耐震能力 ； 時間歷程非線性動力分析 ； 推覆法

並列摘要

Numerous buildings with the penthouse-surcharges on top floor are often present for the convenience of utility in Taiwan. Although such illegal structures appear safe under heavy gravity loads, the surcharges will seriously decrease the strength, stiffness and earthquake-resistant capacity of the buildings. The low-rise buildings such as residences, school buildings and town halls with the surcharges are extensively collapsed and damaged for the 921 Chi-Chi Earthquake in Taiwan. Hence, this study mainly includes investigating the effect of earthquake-resistant capacity due to the building with the penthouse-surcharges on top floor through static nonlinear analysis (i.e., the pushover method). The analyses include the seismic response parameters such as plastic hinge locations, roof displacement, interstory drift, stiffness reduction and the normalized base shear-roof drift ratio relationships of the structures. The results to calculate yielding ground acceleration and collapse ground acceleration of the buildings with the surcharges are compared to the original one. The numerical results reveal that for buildings with one or two additional stories upstairs, the structural stiffness drops off 19% and 35%. Furthermore, the earthquake-resistant capacity will drop off 25% and 40%, respectively. We also adopt time-history dynamic nonlinear analysis. The results to calculate the maximum roof drift ratio and interstory drift ratio of the buildings with surcharges are also compared to the original one. The results appear that the deformation of almost illegal structures can not satisfy the specifications on the seismic design code.

並列關鍵字

pushover method ； penthouse-surcharges on top floor ； time-historydynamic nonlinear analysis ； earthquake-resistant capacity

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