Title

ELASTIC MODULUS OF PRESTRESSED AND REINFORCED CONCRETE BEAMS IN TAIWAN UNDER DYNAMIC FLEXURAL LOADING

Translated Titles

台灣預力鋼筋混凝土梁受動態撓曲載重作用之彈性模數

DOI

10.6652/JoCICHE.202104_33(2).0001

Authors

Marco Bonopera;張國鎮(Kuo-Chun Chang)

Key Words

concrete beam ; elastic modulus ; flexural vibration ; frequency ; 混凝土梁 ; 彈性模數 ; 撓曲振動 ; 頻率

PublicationName

中國土木水利工程學刊

Volume or Term/Year and Month of Publication

33卷2期(2021 / 04 / 01)

Page #

83 - 92

Content Language

英文

Chinese Abstract

The elastic modulus plays a significant role in the dynamics of Reinforced (RC) and Prestressed Concrete (PC) structures. According to Model B4-TW, the effective elastic modulus of concrete in Taiwan is approximately 80% of that calculated by international standards due to smaller coarse aggregate amount and higher paste volume which reflect its mechanics. This work allowed to verify the influence of such a reduced modulus on the dynamic flexural response of RC and PC beams in Taiwan. Laboratory tests were conducted in distinct days, for a total period of ≈ 2.5 months, on a RC beam made in Taiwan prestressed by a parabolic tendon. The RC beam was short term subjected to free flexural vibrations under prestress losses and different conditions of early-age curing. Simultaneously, its time-dependent daily elastic modulus was determined by Model B4-TW, and experimentally by ASTM C 469/C 469M-14 and the solution proposed by Bonopera et al. tuned on compression test results on cylinders. Subsequently, all test data were compared with prediction formulas based on the beam dynamics of Euler-Bernoulli. The predictions indicated that the fundamental frequency of RC and PC beams in Taiwan is well simulated by the variation of their reduced modulus due to the consolidation/hardening of concrete, according to Model B4-TW. Moreover, the accurate measurement of fundamental frequency was confirmed to be a reliable solution for flexural stiffness evaluation of RC and PC members.

English Abstract

鋼筋混凝土和預力混凝土梁的彈性模數在其結構動態特性扮演很重要的角色。根據B4-TW鋼筋混凝土材料應力應變研究模型顯示,由於台灣相較美國採用較少的粗粒料及較高的漿體體積進行混凝土材料配置,台灣混凝土材料實際有效彈性模數約為美國混凝土設計規範計算值之百分之八十。本研究探討混凝土材料有效彈性模數折減現象對台灣鋼筋混凝和預力混凝土梁之動態撓曲反應的影響。以拋物線型配置鋼腱之預力鋼筋混凝土為實驗試體,試體澆鑄時同步灌注混凝土標準圓柱試體,進行為期約兩個半月,取得混凝土圓柱試體在不同養護齡期天數下之抗壓試驗資料。量測鋼筋混凝土梁試體受短期預力損失和早期養護差異條件之撓曲振動值,同時採用B4-TW模型、ASTM C 469/C 469M-14試驗模型和Bonopera et al.(2018)研究成果,探討每日圓柱試體抗壓試驗所計算得到之混凝土材料彈性模數時變性。接著,將所有試驗資料與Euler-Bernoulli梁動態特性預測計算公式進行比較,結果顯示,台灣鋼筋混凝土和預力鋼筋混凝土梁的基本振動頻率,可有效以B4-TW模型考量混凝土養護過程凝固和硬化,計算得折減的彈性模數進行推估。因此,研究驗證精確量測鋼筋混凝土和預力鋼筋混凝土梁基本振動頻率,是評估其撓曲勁度可靠的方法。

Topic Category 工程學 > 土木與建築工程
工程學 > 水利工程
工程學 > 市政與環境工程