醫療院所耐震補強與性能提升之研究---子計畫：醫療院所結構耐震評估分析與補強設計工法之研究(II)

Abstract

在內政部營建署及教育部的政策推動下，目前全台灣公共建築及各級學校校 舍的結構耐震能力評估工作已全面開展。目前工程界進行建築物耐震詳評工作 時，多將結構視為韌性抗彎構架，且未能將窗台所導致之短柱效應考慮在評估分 析當中。如此不僅無法反映真實的結構行為，且有可能高估結構的耐震能力。耐 震設計強調「強柱弱梁」的觀念立意甚佳，惟因樓板的加勁作用使得梁的勁度大 幅提昇，以致即使在強震下，梁因撓曲變形有限，其斷面主筋無法降伏而未能於 梁端形成塑鉸，對RC 結構而言「強柱弱梁」的設計理想未能實現，導致整體結 構之韌性不如預期。此外，許多中小學校舍的破壞模式幾乎都是沿走廊長向發生 柱剪力破壞，此乃窗台下的填充牆對柱形成局部加勁作用而導致短柱效應所致。 結構分析若未能忠實呈現這些力學行為，後續之耐震詳評結果便不可信。有鑑於 此，本計畫乃提出一套RC 結構耐震詳細評估方法，根據實際之混凝土強度、斷 面尺寸、配筋及填充牆計算結構之極限耐震容量，利用ETABS 推覆分析結果評估 結構之實際耐震能力。結構分析架構係採用剪力屋架以充分反映「強梁弱柱」的 實際結構行為，並以等值斜撐模擬填充磚牆，將其對結構行為的影響反映在分析 模型中。本研究將以典型的醫院建築結構為對象，進行結構耐震能力分析及補強 設計工法之研究。針對耐震能力不足的結構，應考慮功能上有效且對醫院正常運 作影響最少的補強工法，以兼顧醫院之營運及補強工程之順利進行。因此，本計 畫將發展以挫屈連桿及高分子橡膠為核心之兩種斜撐型抗震裝置，經由元件測試 掌握其力學行為以及最佳之設計參數，並利用振動台試驗進行結構耐震性能試 驗，確認其應用於提升結構抗震能力之可行性。

Under the policy moved by Construction and Planning Agency, Ministry of the Interior and the Ministry of Education, the task of seismic capacity assessment of public and school buildings has been conducted nationwide in full scale. Based on experiences gained in reviewing the seismic capacity assessment projects, the applicant finds that the engineers are treating all the structures as moment-resisting frames, and not taking into account, in their analysis, the effect of short-columns caused by window stages. As a result, the analyses are not reflecting the actual behavior of the structures, and may in turn overestimate the seismic capacity. The design target of “strong-column-weak-beam” emphasized in seismic structural design is conceptually correct but impractical for RC structures, since the beams are too stiff to form plastic hinges as their stiffness are substantially enhanced by the concrete floor so that the reinforcing steel bars are not yielding at negligible flexural deformation, even under strong earthquakes. The ductility of the overall structures is much less than expected as a consequence. Furthermore, most of the school buildings were found to be damaged in shear failure of the columns along the corridors. This is due to the “short-column” effect caused by the partially infill brick walls of the window stages. The seismic assessment is not reliable if the actual behavior of the structures is not reflected in the analysis. This project is to propose a seismic assessment procedure for RC structures based on pushover analysis using ETABS by considering the design details of the structural members and infill walls. Typical hospital structures will be considered as the objective in this study. The analytical models are to be considered as shear buildings to reflect the actual structural behavior of “weak-column-strong-beam”, and the infill walls are to be simulated with equivalent bracings. For structures identified as seismically vulnerable, this project is to propose effective retrofit schemes with least impact on the daily operations of hospitals. The task is to develop two types of energy-dissipative braces respectively with buckled strut and polymer rubber inside, respectively. The mechanical behavior and optimal design parameters of the proposed devices will be realized via component tests, while the feasibility of using the proposed devices for seismic retrofit of structures will be verified via seismic performance tests by shaking table.