三面圍束磚牆耐震評估模型開發與驗證

台灣很多現存低矮樓層街屋及校舍多為民國70年以前所興建之加強磚造建築物，距今已40年，早已超過使用年限，且老舊加強磚造建築物普遍耐震能力無法達到規範之規定，但全台目前40年以上的老舊加強磚造建築物仍超過30%，目前仍有很多人居住及使用。為避免地震來時造成老舊加強磚造建築物受損倒塌，仍需先對老屋進行耐震評估及補強，故耐震評估工具極為重要，若評估結果能有效掌握既有老舊加強磚造建築物之耐震能力，補強經費對民眾來講也較有說服力。老舊加強磚造建築物因有採光及通風進出需求，需設置高寬比2以上之三面圍束磚牆以利門窗設置，而這些高寬比2以上之三面圍束磚牆於地震來時也能提供強度及勁度來抵抗地震力，然而工程師因為不瞭解高寬比2以上之三面圍束磚牆特性，常將高寬比2以上之三面圍束磚牆忽略不計，導致低估既有老舊加強磚造建築物之耐震能力，進而增加補強經費。為瞭解高寬比2以上之三面圍束磚牆耐震行為，國震中心於2005年起執行一系列高寬比2以上之三面圍束磚牆相關側推試驗及現地試驗。包含有高寬比為2.25至4.5之足尺寸柱側含三面圍束磚牆構件試體、含高寬比為2.25之足尺寸三面圍束磚牆RC構架試體及含高寬比2.72至8.29之足尺寸三面圍束磚牆RC校舍試體，以瞭解高寬比2以上之三面圍束磚牆耐震行為。經試驗結果發現高寬比2以上之三面圍束磚牆不論是在近力側或遠力側皆能提供側向強度及側向勁度。國震中心耐震補強技術手冊TEASPA V2.0三面圍束磚牆耐震評估模型係參考台灣磚構造規範之三面圍束磚牆耐震評估模型所建立，在同時考慮近力側及遠力側三面圍束磚牆下，經驗證高寬比為2.25至4.5含三面圍束磚牆RC構件及RC構架試體側推試驗，強度為試驗值之55%至95%，勁度為試驗值之9%至39%。驗證含高寬比2.72至8.29三面圍束磚牆校舍現地試驗，強度為試驗值110%，勁度為試驗值34%，強度高估及勁度低估原因為TEASPA V2.0三面圍束磚牆耐震評估模型有高寬比不得大於2之限制。國震中心為改善TEASPA V2.0三面圍束磚牆耐震評估模型勁度偏軟問題，提出TEASPA V4.0三面圍束磚牆耐震評估模型，該模型勁度採用ASCE/SEI 41–17複合柱勁度扣掉柱勁度，強度方面比TEASPA V2.0多了一項磚牆劈裂強度，經驗證高寬比為2.25至4.5含三面圍束磚牆RC構件及RC構架試體側推試驗，強度為試驗值之88%至118%，勁度為試驗值之32%至174%。驗證含高寬比2.72至8.29三面圍束磚牆校舍現地試驗，強度為試驗值131%，勁度為試驗值64%。TEASPA V4.0雖然精進TEASPA V2.0三面圍束磚牆耐震評估模型，但對於高寬比大於2.25以上之三面圍束磚牆，仍有強度高估及勁度偏軟問題。為了解決TEASPA V4.0的問題，本文將TEASPA V4.0三面圍束磚牆耐震評估模型單曲率勁度提升為雙曲率勁度，並依照三面圍束磚牆高寬比超過1.5，對角裂縫越少之概念，縮短TEASPA V4.0三面圍束磚牆耐震評估模型水平滑移裂縫及豎向灰縫劈裂裂縫等對角破壞路徑，並給予一個較小的磚牆劈裂強度，本文提出之三面圍束磚牆耐震評估模型，經驗證高寬比為2.25至4.5含三面圍束磚牆RC構件及RC構架試體側推試驗，強度為試驗值之84%至95%，勁度為試驗值之53%至167%。驗證含高寬比2.72至8.29三面圍束磚牆校舍現地試驗，強度為試驗值95%，勁度為試驗值96%，故本文提出之三面圍束磚牆耐震評估模型有效改善TEASPA V4.0強度高估及勁度偏軟的問題，且可適用於高寬比大於2以上之三面圍束磚牆，能有效掌握既有老舊加強磚造建築物之耐震能力，可提供工程師作為套裝軟體評估結果之參考。

關鍵字

三面圍束磚牆；簡易側推分析；現地試驗； TEASPA V4.0 ； ASCE/SEI 41–17

並列摘要

Many existing street houses and school buildings in Taiwan are low-rise buildings and mostly constructed by reinforced brick before 1980, and over its service life. The seismic capacity of these old reinforced brick buildings cannot be confirmed to meet the seismic standards. At present, more than 30% of reinforced brick buildings in Taiwan have been over 40 years old and there are still many people living in and using it., therefore, it is still necessary to retrofited these old reinforced brick buildings to avoid damage or collapse in next earthquake damage or collapse. At this time, the seismic capacity evaluation of these old reinforced brick buildings are very important. If the evaluation results can effectively grasp the seismic capacity of these old reinforced brick buildings, the supplementary funds of government will be more convincing to the public. For lighting, ventilation, and accessibility of this these old reinforced brick buildings, it is necessary to construct a partially confined masonry walls with an aspect ratio of 2 or more. It can also provide on the column side to assist the door and window configuration. These partially confined masonry walls with an aspect ratio of 2 or more can also provide strength and stiffness to resist the earthquake. However, because engineers do not understand the seismic behavior of these partially confined masonry walls with an aspect ratio of 2 or more, they usually ignore it during seismic capacity evaluation. This leads to underestimation of seismic capacity of these old reinforced brick buildings, which increases the retrofit funds. In view of the lack of data of partially confined masonry walls with an aspect ratio of 2 or more, the National Center for Research on Earthquake Engineering(NCREE) in Taiwan carried out a series of pushover tests on partially confined masonry walls with an aspect ratio of 2 or more. The test specimens include a full-size column side with partially confined masonry walls with an aspect ratio of 2.25 to 4.00, a full-size partially confined masonry walls RC frame with an aspect ratio of 2.25 and a full-size low-rise school building with partially confined masonry walls with an aspect ratio of 2.72 to 8.29 for an in-situ pushover test to understand the seismic behavior of partially confined masonry walls during earthquakes. The test results found that partially confined masonry walls can provide lateral strength and lateral stiffness no matter on the near force side or the far force side. In TEASPA V2.0(NCREE) partially confined masonry walls seismic evaluation model is established by design and construction specifications of brick structures for buildings in Taiwan. Under consideration of both the near force side and the far force side of the partially confined masonry walls, the predicted lateral force and lateral stiffness values for pushover tests of a full-size column side and RC frame with partially confined masonry walls with an aspect ratio of 2.25 to 4.00 are 55% to 95% and 9% to 39%, respectively. The predicted maximum base shear and initial stiffness values for an in-situ pushover test of full-size low-rise school building with partially confined masonry walls with an aspect ratio of 2.72 to 8.29 are 110% and 34% respectively. The reasons for overestimation of strength and underestimation of stiffness are that TEASPA V2.0 has a restriction that the aspect ratio of partially confined masonry walls should not be greater than 2. In order to improve the stiffness of the TEASPA V2.0 partially confined masonry walls seismic evaluation model, NCREE proposed the TEASPA V4.0 partially confined masonry walls seismic evaluation model. The partially confined masonry walls model stiffness uses ASCE/SEI 41-17 composite column stiffness and the column stiffness is subtracted. In terms of strength, there is one more brick wall splitting strength than TEASPA V2.0. TEASPA V4.0 predicted lateral force and lateral stiffness values for pushover tests of a full-size column side and RC frame with partially confined masonry walls with an aspect ratio of 2.25 to 4.00 are 88% to 118% and 32% to 174%, respectively. The predicted maximum base shear and initial stiffness values for an in-situ pushover test of full-size low-rise school building with partially confined masonry walls with an aspect ratio of 2.72 to 8.29 are 131% and 64% respectively. Although TEASPA V4.0 upgraded the TEASPA V2.0 partially confined masonry walls seismic evaluation model with an aspect ratio greater than 2.25, but, there are still problems of overestimation of strength and underestimation of stiffness. In order to solve TEASPA V4.0 issues, for the problem of underestimation of stiffness, this paper uses TEASPA V4.0 as the main partially confined masonry walls evaluation model and improve TEASPA V4.0 columns from single-curvature stiffness to double-curvature stiffness. For the problem of overestimation of strength, in accordance with the concept that when the aspect ratio of the partially confined masonry walls exceeds 1.5, the diagonal cracks is are fewer, and the diagonal damage paths of TEASPA V4.0 of partially confined masonry walls can be shortened, such as horizontal slip cracks and vertical gray splitting cracks, and also give a smaller masonry wall splitting strength. The partially confined masonry wall evaluation model proposed in this paper can predict lateral force and lateral stiffness values for a full-size column side and RC frame with partially confined masonry walls with an aspect ratio of 2.25 to 4.00 pushover tests are, 84 to 95% and 53% to 167%, respectively. The predicted maximum base shear and initial stiffness values for full-size low-rise school building with partially confined masonry walls with an aspect ratio of 2.72 to 8.29 for an in-situ pushover test are 95% and 96% respectively. Therefore, the partially confined masonry wall evaluation model proposed in this paper can effectively improve overestimation of strength and underestimation of stiffness of TEASPA V4.0, and can be applied to partially confined masonry walls with an aspect ratio greater than 2. The proposed model can effectively predict the seismic behavior of the old reinforced brick buildings, and also can provide engineers a reference for the evaluation results of the package software.