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預(yù)應(yīng)力混凝土受彎構(gòu)件長(zhǎng)期反拱和撓度的合理估算方法

徐金聲，薛立紅(中國(guó)建筑科學(xué)研究院，北京 100013)

［摘要］回顧了對(duì)預(yù)應(yīng)力混凝土構(gòu)件長(zhǎng)期反拱變化規(guī)律的研究及認(rèn)識(shí)過(guò)程；提出了一個(gè)經(jīng)驗(yàn)公式，大大簡(jiǎn)化了預(yù)應(yīng)力混凝土構(gòu)件長(zhǎng)期反拱的精確計(jì)算工作。該經(jīng)驗(yàn)公式既能適用于“全”預(yù)應(yīng)力，也能適用于“部分”預(yù)應(yīng)力混凝土構(gòu)件長(zhǎng)期反拱值的計(jì)算。同時(shí)，對(duì)預(yù)應(yīng)力混凝土構(gòu)件長(zhǎng)期撓度的估算也提出了一個(gè)經(jīng)驗(yàn)公式。長(zhǎng)期反拱和撓度的兩個(gè)經(jīng)驗(yàn)公式都考慮了四個(gè)主要影響因素作為自變量(即鋼筋的配筋率及其位置與混凝土的徐變和收縮)。用試驗(yàn)數(shù)據(jù)全面地進(jìn)行了對(duì)比，給出長(zhǎng)期反拱系數(shù)θp（t→∞）的終極值的可變范圍為-3～+3.5，其通常變動(dòng)范圍是-0.5～+2.8，而不是固定的值+2.0。長(zhǎng)期撓度也不能簡(jiǎn)單地簡(jiǎn)化為短期撓度的2倍。給出了實(shí)際工程的檢測(cè)結(jié)果和計(jì)算例題并提出了對(duì)現(xiàn)行《混凝土結(jié)構(gòu)設(shè)計(jì)規(guī)范》第8.2.5條和第8.2.6條的修改建議。

［關(guān)鍵詞］預(yù)應(yīng)力混凝土；長(zhǎng)期反拱系數(shù)；長(zhǎng)期撓度系數(shù)；試驗(yàn)數(shù)據(jù)；經(jīng)驗(yàn)公式；非預(yù)應(yīng)力筋；配筋率；鋼筋位置

中圖分類號(hào)：TU378文獻(xiàn)標(biāo)識(shí)碼：A文章編號(hào)：1002-848X(2011)01-0095-08

Rational method for estimating long-term camber and deflection of prestressed concrete flexure members

Xu Jinsheng, Xue Lihong

(China Academy of Building Research, Beijing 100013, China)

Abstract:The historical understanding of long-term camber and deflection of prestressed concrete members was described.  An empirical formula, which greatly simplifies the calculation for long-term camber of prestressed concrete members  was presented. It not only applies to the calculation of long-term camber in prestressed concrete members, but also in partial-prestressed concrete members. An empirical formula for estimating long-term deflection was presented. The two empirical formulas of long-term camber and deflection had considered four important independent variables(steel ratio and its position, creep and shrinkage of concrete). A comprehensive comparison of experimental data of long-term camber and results predicted by the formula was also carried out. The range of variation of long-term camber coefficient θp(t→∞) is -3 to +3.5, its normal range is -0.5 to +2.8 and not a constant value+2.0. Even long-term deflection cannot be  simplified with a multiplication factor of 2 over short-term deflection. Suggestions were presented for revisions of section 8.2.5 and 8.2.6 of Code for design of concrete structures.

Keywords:prestressed concrete;  long-term camber coefficient;  long-term deflection coefficient; testing data; empirical formula; non-prestressed steel;  steel ratio; steel position

作者簡(jiǎn)介：徐金聲，研究員，Email:xujinsheng@cabrtech.com。

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