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  • 學位論文

外加RC構架補強之試驗研究及其於公共建物之應用

Experimental Study on Retrofit with External Reinforced Concrete Frames and Its Applications on Public Buildings

指導教授 : 鍾立來
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摘要


921大地震凸顯臺灣老舊建物耐震能力不足之問題,而全臺灣約有25000棟國中、小校舍,且校舍屬公共設施,於震後需作為學生與附近居民緊急避難場所,因此提升其耐震能力乃當務之急,但若全數拆除重建或進行補強將極度耗時且不經濟,是故國家地震工程研究中心針對校舍提出一系列評估流程及補強方法,評估流程包含簡易調查、初步評估、詳細評估(側推分析),對於校舍耐震能力進行層層篩選,最後再對耐震能力不足之校舍進行結構補強。校舍補強常見工法有:擴柱補強、翼牆補強及剪力牆補強等,然而上述方法雖可有效提升校舍結構耐震能力,但於補強過程中,會影響既有結構物之使用,欲應用於運作功能不能受影響之公共建物(如:醫院)有其難處,本研究遂提出國內較少使用之補強工法,即為外加構架補強工法。 外加構架補強工法,顧名思義,即為於既有建築物弱向兩側各新增一面外加構架進行補強,藉此提升結構物耐震能力,本研究採用外加RC構架,使用植筋補強樓板與既有結構物進行連接,藉由RC樓板將地震力由既有結構物傳遞至外加RC構架。為評估包含校舍在內所有公共建物耐震能力,並對其進行外加RC構架補強設計,本研究使用包含初步評估法、改良極限彎矩平衡法之簡易詳細評估及詳細評估(側推分析)對既有建築物進行耐震評估;於外加構架部分,參考林聖學所提出之外加RC構架補強初步評估方法並進行改良,同時提出外加RC構架補強初步設計方法、改良極限彎矩平衡法之簡易詳細評估、樓板初步設計方法及側推分析時樓板非線性鉸設定方式,將樓板納入詳細評估中,提供使用者對欲使用外加RC構架補強之結構物進行評估與設計的一種選擇。本研究之詳細評估參考國家地震工程研究中心所出版之校舍結構耐震評估與補強技術手冊第三版之建議,使用ETABS輔助進行非線性靜力側推分析,藉此得結構補強後之容量曲線及轉換後之耐震性能曲線,評估結構物於外加RC構架補強後之耐震能力。本研究於提出補強評估及設計方法後,分別使用一棟校舍(後甲國中德育樓既有校舍)及二棟醫院(國軍北投醫院、臺大醫院斗六分院)進行耐震評估及耐震補強作為範例,並證實結構物耐震能力均能有效提升至其耐震需求,盼該補強方法不僅只用於校舍補強,更能將其不影響結構物使用性之優點,推廣至醫院乃至其它公共建物,使其充分發揮其優勢。 由於本研究之外加RC構架補強採取植筋補強樓板傳遞地震力,是故樓板剪力傳遞之能力攸關補強成敗與否,倘若樓板無法順利將地震力傳遞至外加構架,率先發生剪力破壞,將無法發揮預期強效果。由於目前國內少有樓板剪力傳遞相關之試驗,故本研究特設計4座試體(2座植筋補強樓板、2座新建樓板),藉此探討樓板剪力傳遞行為,並探討新建樓板鋼筋配置模式對於樓板之影響,本研究除對試驗結果與樓板設計方式(規範)進行比較,證實規範之樓板設計方式確實保守外,亦對樓板側力位移曲線進行完美彈塑性分析,以校舍補強手冊三版之方法為主軸,修改試體評估曲線,驗證其相較於試驗結果均較為保守。

並列摘要


The Chi-Chi earthquake let people in Taiwan know that the seismic capacities of old buildings are not enough. There are about 25,000 school buildings in Taiwan. They belong to public facility and provide people shelters when their homes are seriously damaged by earthquake. Therefore, school buildings need to raise their seismic ability as soon as possible. However, rebuilding or retrofitting all school buildings will cost a lot and is inefficient. In order to raise the efficiency, National Center for Research on Earthquake Engineering (NCREE) proposed complete procedures for seismic evaluation and seismic retrofit of school buildings. The procedures of seismic evaluation include: simply survey, preliminary evaluation and detailed evaluation (pushover analysis). After screening out school buildings which have less seismic capacity than seismic demand, we need to do seismic retrofit for them. The typical retrofit methods of school buildings are: RC jacketing, adding wing wall and shear wall. All these retrofit methods will affect the function of existing building under construction so they cannot be used for the public buildings such as hospital which the function cannot be affected. In this research, retrofit method with adding external frames, seldom seen in Taiwan, is proposed. Adding external frames is a retrofit method by which two external frames are added along the weak direction of existing building to raise the seismic ability. In this research, external reinforced concrete frames is connected to existing building through reinforced concrete slab. One end of the slab rebar is post-installed to the beam of existing building and the other end is anchored to the beam of external frame. The reinforced concrete slab to transfers the seismic force from existing building to external frames. In order to evaluate the effectiveness of adding external frames, preliminary evaluation method for the retrofitted building is established. Accordingly, external frames can be design preliminarily. In addition, simple detailed evaluation method is extended from the Ultimate Moment Balanced Method. After pushover analysis, shear demand can be acquired for the design of reinforced concrete slab. Moreover, plastic hinge parameters of the slab are developed and incorporated in the pushover analysis so that the design of slab can be checked. From nonlinear static pushover analysis, the capacity curve is achieved and it is turned into performance curve to find out the seismic ability of building after adding external reinforced concrete frames. In this research, we take one school building and two hospitals as example. We hope the method can not only be used for school buildings, but also take the advantage of the method to use for hospitals or other public buildings. The rebars of the slab in the transverse direction are post-installed into existing beam to transfer the seismic force from existing building to external frame so the shear capacity of the slab will influence whether the retrofit is successful. If the slab cannot transfer the seismic force to external frame successfully, shear failure happens at the slab faster than the external beam and column, the retrofit will fail. Since there are few tests about shear force capacity of slab in Taiwan, we design 4 specimens (2 retrofit specimens and 2 newly built specimens) in this research. We use the specimens to discuss how the shear force is delivered and observe how the design of steel bar influences the shear strength of the slab. In addition to comparing the shear strength of specimens with design method (code) to prove the design rule of code is conservative enough, we also turn the curve of lateral force and displacement of specimens into elasto-plastic curve. And we also refer to Hand Book about Seismic Evaluation and Seismic Retrofit of School Building (III) and modify the evaluation curve of lateral curve and displacement to prove that the evaluation curve is more conservative than test result.

參考文獻


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被引用紀錄


賴濤(2017)。既有中高樓層建築之耐震評估與補強—外置RC構架暨剪力牆複合工法〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU201703421

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