台灣混凝土彈性模數折減對數項結構相關設計規範的影響

Study of Influences of Reduced Elastic Modulus of Concrete on Related Structural Design Codes in Taiwan

10.6849/SE.201912_34(2).0004

胡瑋秀(Wei-Hsiu Hu)；廖文正(Wen-Cheng Liao)

彈性模數 ； 台灣混凝土結構設計規範 ； 台灣建築物耐震設計規範及解說 ； 鋼結構容許應力設計法規範 ； modulus of elasticity ； design code for structural concrete in Taiwan

結構工程

34卷2期（2019 / 12 / 01）

76 - 89

繁體中文

台灣混凝土彈性模數E_c較現行規範所預估之値有偏低的趨勢，其值約為規範的80%左右，彈性模數的修正將會對版梁柱尺寸設計、設計基底剪力值和其餘與彈性模數相關的規範產生影響，如台灣混凝土結構設計規範、台灣建築物耐震設計規範及解說與鋼結構容許應力設計法規範等。然而上述相關規範沒有對其中受彈性模數影響的公式做出修改。為使設計更為準確，須探討彈性模數修正對規範的影響。本研究檢視前述規範中直接或間接與彈性模數有關的規定，探討其數項受影響的公式，並依據學理提出對應的建議。依據本研究結果，非預力單雙向版規範因應彈性模數的折減，其最小深度需要增加為1.077倍；在柱的長細效應中，當細長比為40時，其彎矩放大係數則需要增加為1.15倍；當混凝土之抗壓強度小於360 kgf/cm^2時，則單一剪力釘容許強度將變為0.89倍，所需剪力釘個數變為1.124倍。以上結果顯示，彈性模數的修正不僅單是修正E_c值公式，規範中直接或間接與彈性模數有關的規定均須要修正。

In Taiwan, the prediction of E_c calculated by current design code is usually overestimated by 20% of that obtained by experimental results. The revision code of E_c =12000 (f'_c)^(0.5) is 80% of current E_c =15000 (f'_c)^(0.5). The reduction of E_c would influent the size of beam and column, design value of base shear and other related structural design codes in Taiwan, such as ＂Design Code for Concrete Structures＂, ＂Seismic Design Specifications and Commentary of Buildings＂ and ＂Allowable Stress Design Specifications and Commentary of Steel Structures＂. The objectives of this research are to clarify those influences on these related structural design codes with reduced E_c and to comment and give suggestions to the engineering society. The results show that because of the reduction of E_c, the minimum thickness of reinforced concrete slab should increase by 7.7％ times, moment magnification factor would increase by 1.15 times (if slenderness ratio of column is 40), number of shear concrete stud would increase by 1.124 times (if compressive strength of concrete f'_c ＜ 360 kgf/cm^2). Structural design codes that directly or indirectly related to E_c should be modified accordingly because of the reduction of E_c.

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