鋼筋混凝土平版雙向剪力與撓曲強度之研究

Abstract

鋼筋混凝土平版結構系統(flat plate floor system)為建築常見之結構系統，其優點為能增加結構物整體空間，並減少工期、耗材及人力，以降低建築成本。然而，此類型之結構系統應力易集中於版、柱交界處，造成柱周圍附近之貫穿剪力破壞。因此，平版構件之強度評估為鋼筋混凝土平版結構系統之重要議題。 現今各國規範皆有評估平版構件強度之經驗公式，然而多半是以早期研究之試驗數據作為依據，並採用回歸方式推導出經驗公式作為評估準則，雖然可以提供一定程度之預測結果，然而背後往往缺乏力學機制的考量。 因此，本研究將以內柱支承平版作為研究對象，探討雙向平版構件承受垂直載重之力量傳遞方式與破壞模式，提出一套分析模型以評估平版強度，並透過建立鋼筋混凝土平版試體資料庫，驗證分析模型之準確性與合理性，將驗證結果與ACI 318-19 (2019)規範、Eurocode 2 (2004)規範進行比較。結果顯示，本研究建立之分析模型強度預測值尚稱合理，並能夠掌握大部分平版構件之極限強度(V_test/V_SST平均值接近1)，且分析模型依實際力量傳遞方式與破壞模式作為考量，能提供合理的分析結果。

The flat plate floor system of reinforced concrete is a common floor construction type employed in the construction of the building. There are two main advantages of a flat plate floor system. One is that the larger underfloor spaces and more service areas without the intervention of beams. The other is that the simple formwork can reduce the construction period, building materials and manpower, so as to decrease the construction cost. However, severe stresses concentration around the column will result in punching failure of flat plates. Therefore, the strength evaluation of flat plate is an important issue for flat plate floor system. Currently, there are empirical formulas to evaluate the two-way shear strength of flat plate in design codes. However, most of them are based on the test data of early research and empirical formulas are derived by regression methods. Although codes can provide certain degree of prediction results, there is no consideration of real force transfer mechanism. In this study, the flat plate supported by inner column is taken as the research object. To discuss force transmission and failure mode of two-way flat plate under gravity load, an analytical model considering the influence of critical parameters for estimating the strength of flat plates in shear and flexure is proposed. After the test verification, the proposed analytical model is compared with both ACI 318-19 (2019) and Eurocode 2 (2004) codes. It was found that the analytical model established in this study yields reasonable predictions and the proposed model is able to capture ultimate strength for most specimens (average strength ratio V_test/V_SST is close to one). Besides, it employs the force transfer mechanism and the failure mode into consideration and provides reasonable estimation results.