房屋建筑畢業(yè)設(shè)計(jì)外文翻譯---鋼筋混凝土板的拉伸硬化過程分析

1、<p><b>　　畢業(yè)設(shè)計(jì) (論文)</b></p><p><b>　　外文翻譯</b></p><p>　　設(shè)計(jì)（論文）題目： 寧波天合家園某住宅樓 </p><p>　　2號(hào)軸框架結(jié)構(gòu)設(shè)計(jì)與建筑制圖 </p><p>

2、;　　學(xué) 院 名 稱： 建筑工程學(xué)院 </p><p>　　專 業(yè)： 土木工程 </p><p>　　姓 名： 陳紹樑 學(xué) 號(hào) 09404010421 </p><p>　　指 導(dǎo) 教 師： 馬永

3、政、陶海燕 </p><p>　　2012 年 12 月 10 日</p><p><b>　　外文原稿1</b></p><p>　　Tension Stiffening </p><p>　　in Lightly Reinforced Concrete Slabs&l

4、t;/p><p>　　1R. Ian Gilbert1</p><p>　　Abstract: The tensile capacity of concrete is usually neglected when calculating the strength of a reinforced concrete beam or slab, even though concrete contin

5、ues to carry tensile stress between the cracks due to the transfer of forces from the tensile reinforcement to the concrete through bond. This contribution of the tensile concrete is known as tension stiffening and it af

6、fects the member’s stiffness after cracking and hence the deflection of the member and the width of the cracks under ser</p><p>　　CE Database subject headings: Cracking; Creep; Deflection; Concrete, reinforc

7、ed; Serviceability; Shrinkage; Concrete slabs.</p><p>　　1Professor of Civil Engineering, School of Civil and EnvironmentalEngineering, Univ. of New South Wales, UNSW Sydney, 2052, Australia.Note. Associate E

8、ditor: Rob Y. H. Chai. Discussion open untilNovember 1, 2007. Separate discussions must be submitted for individualpapers. To extend the closing date by one month, a written request must</p><p>　　be filed wi

9、th the ASCE Managing Editor. The manuscript for this technicalnote was submitted for review and possible publication on May 22,2006; approved on December 28, 2006. This technical note is part of the</p><p>　

10、　Journal of Structural Engineering, Vol. 133, No. 6, June 1, 2007.</p><p>　　11Professor of Civil Engineering, School of Civil and Environmental Engineering, Univ. of New South Wales, UNSW Sydney, 2052, Austr

11、alia. </p><p>　　Journal of Structural Engineering, Vol. 133, No. 6, June 1, 2007.</p><p>　　1.Introduction</p><p>　　The tensile capacity of concrete is usually neglected when calcula

12、tingthe strength of a reinforced concrete beam or slab, eventhough concrete continues to carry tensile stress between thecracks due to the transfer of forces from the tensile reinforcementto the concrete through bond. Th

13、is contribution of the tensileconcrete is known as tension stiffening, and it affects the member’sstiffness after cracking and hence its deflection and thewidth of the cracks.</p><p>　　With the advent of hig

14、h-strength steel reinforcement, reinforcedconcrete slabs usually contain relatively small quantities oftensile reinforcement, often close to the minimum amount permittedby the relevant building code. For such members, th

15、e flexuralstiffness of a fully cracked cross section is many times smallerthan that of an uncracked cross section, and tension stiffeningcontributes greatly to the stiffness after cracking. In design, deflectionand crack

16、 control at service-load levels are us</p><p>　　The most commonly used approach in deflection calculationsinvolves determining an average effective moment of inertia [Ie]for a cracked member. Several differe

17、nt empirical equations areavailable for Ie, including the well-known equation developed byBranson [1965] and recommended in ACI 318 [ACI 2005]. Othermodels for tension stiffening are included in Eurocode 2 [CEN1992] and

18、the [British Standard BS 8110 1985]. Recently,Bischoff [2005] demonstrated that Branson’s equation grossly overestimates </p><p>　　In this paper, the various approaches for including tensionstiffening in the

19、 design of concrete structures, including the ACI318, Eurocode 2, and BS8110 models, are evaluated critically andempirical predictions are compared with measured deflections.Finally, recommendations for modeling tension

20、stiffening instructural design are included.</p><p>　　2.Flexural Response after Cracking</p><p>　　Consider the load-deflection response of a simply supported, reinforcedconcrete slab shown in Fi

21、g. 1. At loads less than thecracking load, Pcr, the member is uncracked and behaves homogeneouslyand elastically, and the slope of the load deflection plotis proportional to the moment of inertia of the uncracked transfo

22、rmedsection, Iuncr. The member first cracks at Pcr when theextreme fiber tensile stress in the concrete at the section of maximum moment reaches the flexural tensile strength of the co</p><p>　　If the tensil

23、e concrete in the cracked regions of the beam carried no stress, the load-deflection relationship would follow the dashed line ACD in Fig. 1. If the average extreme fiber tensile stress in the concrete remained at fr aft

24、er cracking, the loaddeflection relationship would follow the dashed the actual response lies between these two extremes and is shown in Fig. 1 as the solid line AB. The difference between the actual response and the ze

25、ro tension response is the tension stiffening e</p><p>　　As the load increases, the average tensile stress in the concrete reduces as more cracks develop and the actual response tends toward the zero tension

26、 response, at least until the crack pattern is fully developed and the number of cracks has stabilized. For slabscontaining small quantities of tensile reinforcement [typicallytension stiffening may be responsible for mo

27、rethan 50% of the stiffness of the cracked member at service loads and remains significant up to and beyond the point where the s</p><p>　　3.Models for Tension Stiffening</p><p>　　The instantan

28、eous deflection of beam or slab at service loads may be calculated from elastic theory using the elastic modulus of concrete Ec and an effective moment of inertia, Ie. The value of Ie for the member is the value calculat

29、ed using Eq. [1] at midspan for a simply supported member and a weighted average value calculated in the positive and negative moment regions of a continuous span</p><p><b>　?。?）</b></p>&

30、lt;p>　　where Icr=moment of inertia of the cracked transformed section;Ig=moment of inertia of the gross cross section about the centroidal axis [but more correctly should be the moment of inertia of the uncracked tran

31、sformed section, Iuncr]; Ma=maximum moment in the member at the stage deflection is computed; Mcr=cracking moment =(frIg / yt); fr=modulus of rupture of concrete (=7.5 fc in psi and 0.6 fc in Mpa); and yt=distance from t

32、he centroidal axis of the gross section to the extreme fiber in tensio</p><p>　　A modification of the ACI approach is included in the Australian Standard AS3600-2001 (AS 2001)to account for the fact that shr

33、inkage-induced tension in the concrete may reduce the cracking moment significantly. The cracking moment is given by Mcr=(fr? fcs)Ig / yt, where fcs is maximum shrinkage-induced tensile stress in the uncracked section at

34、 the extreme fibre at which cracking occurs（Gilbert 2003）.</p><p><b>　?。?）</b></p><p>　　where distribution coefficient accounting for moment level and degree of cracking and is given

35、 by</p><p><b>　?。?）</b></p><p>　　and 1=1.0 for deformed bars and 0.5 for plain bars; 2=1.0 for a single, short-term load and 0.5 for repeated or sustained loading; sr=stress in the t

36、ensile reinforcement at the loading causing first cracking (i.e., when the moment equals Mcr), calculated while ignoring concrete in tension; s is reinforcement stress at loading under consideration (i.e., when the in-se

37、rvice moment Ms is acting), calculated while ignoring concrete in tension; cr=curvature at the section while ignoring concrete in t</p><p>　　For slabs in pure flexure, if the compressive concrete and the rei

38、nforcement are both linear and elastic, the ratio sr /s in Eq.(3) is equal to the ratio Mcr /Ms. Using the notation of Eq.（1）, Eq.(2) can be reexpressed as</p><p><b>　?。?）</b></p><p>

39、;　　For a flexural member containing deformed bars under shortterm loading, Eq. (3) becomes =1?（Mcr /Ms）2 and Eq.（4）can be rearranged to give the following alternative expression for Ie for short-term deflection calculati

40、ons [recently proposed by Bischoff (2005)]: (5)</p><p>　　This approach, which has now been superseded in the U.K. by the Eurocode 2 approach, also involves the calculation of the curvat

41、ure at particular cross sections and then integrating to obtain the deflection. The curvature of a section after cracking is calculated by assuming that (1) plane sections remain plane; (2) the concrete in compression an

42、d the reinforcement are assumed to be linear elastic; and（3）the stress distribution for concrete in tension is triangular, having a value of zero at the</p><p>　　4.Comparison with Experimental Data</p>

43、<p>　　To test the applicability of the ACI 318, Eurocode 2, and BS 8110 approaches for lightly reinforced concrete members, the measured moment versus deflection response for 11 simply supported, singly reinforced

44、 one-way slabs containing tensile steel quantities in the range 0.0018<<0.01 are compared with the calculated responses. The slabs (designated S1 to S3, S8, SS2 to SS4, and Z1 to Z4) were all prismatic, of rectangu

45、lar section, 850 mm wide, and contained a single layer of longitudinal tensile </p><p>　　The predicted and measured deflections at midspan for each slab when the moment at midspan equals 1.1, 1.2, and 1.3 Mc

46、r are presented in Table 2. The measured moment versus instantaneousdeflection response at midspan of two of the slabs (SS2 and Z3) are compared with the calculated responses obtained using the three code approaches in F

47、ig. 2. Also shown are the responses if cracking did not occur and if tension stiffening was ignored.</p><p>　　5.Discussion of Results</p><p>　　It is evident that for these lightly reinforced sla

48、bs, tension stiffening is very significant, providing a large proportion of the postcracking stiffness. From Table 2, the ratio of the midspan deflection obtained by ignoring tension stiffening to the measured midspan de

49、flection (over the moment range Mcr to 1.3 Mcr)is in the range 1.38–3.69 with a mean value of 2.12. That is, on average, tension stiffening contributes more than 50% of the instantaneous stiffness of a lightly reinforced

50、 slab aft</p><p>　　For every slab, the ACI 318 approach underestimates the instantaneous deflection after cracking, particularly so for lightly reinforced slabs. In addition, ACI 318 does not model the abrup

51、t change in direction of the moment-deflection response at first cracking, nor does it predict the correct shape of the postcracking moment-deflection curve.</p><p>　　The underestimation of short-term deflec

52、tion using the ACI318 model is considerably greater in practice than that indicated by the laboratory tests reported here. Unlike the Eurocode 2 and BS 8110 approaches, the ACI 318 model does not recognize or account for

53、 the reduction in the cracking moment that will inevitably occur in practice due to tension induced in the concrete by drying shrinkage or thermal deformations. For many slabs, cracking will occur within weeks of casting

54、 due to early drying</p><p>　　By limiting the concrete tensile stress at the level of the tensile reinforcement to just 1.0 MPa, the BS 8110 approach overestimates the deflection of the test slabs both below

55、 and immediately above the cracking moment. This is not unreasonable and accounts for the loss of stiffness that occurs in practice due to restraint to early shrinkage and thermal deformations. Nevertheless, the BS 8110

56、approach provides a relatively poor model of the</p><p>　　postcracking stiffness and incorrectly suggests that the average tensile force carried by the cracked concrete actually increases as M increases and

57、the neutral axis rises. As a result, the slope of the BS 8110 postcracking moment-deflection plot is steeper than the measured slope for all slabs. The approach is also more tedious to use than either the ACI or Eurocode

58、 2 approaches.</p><p>　　In all cases, deflections calculated using Eurocode 2[ Eqs.(3)–(5)] are in much closer agreement with the measured deflection over the entire postcracking load range. As can be seen i

59、n Fig. 2, the shape of the load-deflection curve obtained using Eurocode 2 is a far better representation of the actual curve than that obtained using Eq. (1). Considering the variability of the concrete material propert

60、ies that affect the in-service behavior of slabs and the random nature of cracking, the agreement</p><p>　　6.Conclusions</p><p>　　Although tension stiffening has only a relatively minor effect o

61、n the deflection of heavily reinforced beams, it is very significant in lightly reinforced members where the ratio Iuncr / Icr is high, such as most practical reinforced concrete floor slabs. The models for tension stiff

62、ening incorporated in ACI （2005）, Eurocode 2 (CEN 1992), and BS 8110 （1985） have been presented and their applicability has been assessed for lightly reinforced concrete slabs.Instantaneous deflections calculated usi<

63、/p><p><b>　　中文翻譯1</b></p><p>　　鋼筋混凝土板的拉伸硬化過程分析</p><p>　　R. Ian Gilbert</p><p>　　摘 要：混凝土的抗拉能力在計(jì)算鋼筋混凝土梁或板的強(qiáng)度時(shí)通常被忽視,盡管具體的拉應(yīng)力繼續(xù)進(jìn)行，由于拉鋼筋到混凝土之間裂縫的轉(zhuǎn)換力量。這一種混凝土的拉力被稱為混凝

64、土的張力硬化。在開裂后它會(huì)影響鋼筋混凝土的剛度，因此它的撓度和裂縫寬度必須根據(jù)屈服強(qiáng)度負(fù)載。對(duì)輕混凝土，例如樓板，全部裂縫的彎曲剛度比沒有裂縫部分的要小很多，張力加勁有助于剛度。在本文中，ACI方法必須考慮到緊張加勁，歐洲和英國(guó)的方法是嚴(yán)格評(píng)估和預(yù)測(cè)與實(shí)驗(yàn)結(jié)果進(jìn)行比較。最后，建議依據(jù)鋼筋混凝土樓板的建模張力加勁設(shè)計(jì)控制偏轉(zhuǎn)。</p><p>　　關(guān)鍵詞：開裂，蠕變撓度，混凝土，鋼筋，適用性，收縮，混凝土磚。<

65、;/p><p><b>　　1.引言</b></p><p>　　由于拉鋼筋到混凝土之間裂縫的轉(zhuǎn)換力量，拉伸能力在計(jì)算時(shí)通常忽略鋼筋混凝土梁或板的強(qiáng)度,盡管具體的拉應(yīng)力將持續(xù)。這一種混凝土的拉力被稱為張力硬化,它會(huì)影響各部分的剛度，因此必須考慮其撓度和裂縫寬度。</p><p>　　隨著高強(qiáng)度鋼筋的運(yùn)用，增強(qiáng)混凝土板通常使用相對(duì)少量的拉鋼筋，經(jīng)常接

66、近相關(guān)建筑法規(guī)允許的最低允許值。對(duì)于這樣的構(gòu)件，彎曲完全開裂的一個(gè)截面剛度比未開裂的截面小許多倍，張力加勁大大促進(jìn)了開裂后構(gòu)件的剛度。在設(shè)計(jì)中，撓度和裂縫的控制通常是在屈服水平調(diào)整考慮的，并在開裂后剛度的建模精確是必需的。</p><p>　　撓度計(jì)算中最常用的方法包括確定破解構(gòu)件平均有效的轉(zhuǎn)動(dòng)慣量（）。幾種不同的經(jīng)驗(yàn)公式可用于，包括著名的方程開發(fā)Branson（1965）和ACI 318（ACI 2005）。其

67、他的張力硬化模式包括在Eurocode 2（CEN1992)和（British Standard BS 8110 1985），最近，Bischoff（2005）表明，布蘭森的方程對(duì)含有少量的鋼筋混凝土構(gòu)件鋼筋平均剛度評(píng)估過高，他提出了一個(gè)對(duì)于的替代方程，這基本上是與Eurocode 2方案兼容。</p><p>　　在本文中，包括張力加勁在內(nèi)的各種方法在混凝土結(jié)構(gòu)設(shè)計(jì)，包括在Eurocode 2，ACI 318，

68、BS8110模式，批判性進(jìn)行評(píng)估經(jīng)驗(yàn)預(yù)測(cè)與實(shí)測(cè)撓度進(jìn)行了比較。最后，模擬張力加勁的建議結(jié)構(gòu)設(shè)計(jì)均被包括在內(nèi)。</p><p><b>　　2.開裂后彎曲響應(yīng)</b></p><p>　　考慮一個(gè)簡(jiǎn)支負(fù)載的變形響應(yīng)，鋼筋混凝土板如圖1所示。在負(fù)載小于開裂負(fù)載的情況下，，該構(gòu)件未開裂和表現(xiàn)均勻的彈性，以及撓度斜率是成正比的未開裂的轉(zhuǎn)動(dòng)慣量的換算界面，。該構(gòu)件的第一裂縫在當(dāng)

69、極端纖維在混凝土拉應(yīng)力的最大部分到達(dá)混凝土彎拉強(qiáng)度破裂或時(shí)。</p><p>　　有一個(gè)剛度突變，并立即出現(xiàn)裂紋。在包含了破碎的部分，抗彎剛度顯著下降，但大部分仍然未開裂的梁，隨著負(fù)載的增加，出現(xiàn)更多的裂縫形式和整個(gè)構(gòu)件的平均抗彎構(gòu)件減少。</p><p>　　如果在梁的混凝土開裂區(qū)域內(nèi)施加拉力而沒有壓力，負(fù)載變形關(guān)系將遵循虛線ACD，如圖1。如果平均極端纖維拉伸應(yīng)力在混凝土開裂后留在fr

70、，將遵循虛線AE。事實(shí)上，實(shí)際的反應(yīng)是介于這兩個(gè)極端自建，如圖1所示為實(shí)線AB型。實(shí)際反應(yīng)之間的區(qū)別和零張力反應(yīng)的張力是加強(qiáng)效應(yīng)。</p><p>　　隨著越來(lái)越多的裂縫發(fā)展和實(shí)際響應(yīng)趨向于零緊張反應(yīng)，一般的拉應(yīng)力混凝土減少，至少要等到裂縫模式充分開發(fā)和裂縫的數(shù)量趨于穩(wěn)定。對(duì)于含有少量的拉結(jié)鋼筋磚（通常= As/bd0.003），緊張硬化可能超過50％的鋼筋混凝土的剛度破壞屈服加載而且仍然要達(dá)到和超過的鋼產(chǎn)量和負(fù)

71、荷接近極限地步。依據(jù)在長(zhǎng)期撓度的計(jì)算下，可能是由于綜合作用的拉伸蠕變、蠕變斷裂,收縮開裂，在持續(xù)負(fù)載下張力加勁效應(yīng)隨著時(shí)間而減少。</p><p><b>　　3.加勁的張力模型</b></p><p>　　梁的彎曲或板在使用載重?fù)隙瓤梢运查g從彈性論計(jì)算通過混凝土彈性模量Ec和有效的慣性矩。的價(jià)值對(duì)于構(gòu)件是計(jì)算使用Eq.[1]計(jì)算公式為一個(gè)在跨中簡(jiǎn)支構(gòu)件和加權(quán)平均計(jì)

72、算價(jià)值在正，負(fù)彎矩區(qū)的一個(gè)連續(xù)的跨度。</p><p><b>　　（1）</b></p><p>　　為破碎的換算截面的慣性矩；</p><p>　　為總截面的質(zhì)心軸的慣性矩，但更正確的應(yīng)該是換算截面的未開裂的慣性矩；</p><p>　　為在構(gòu)件的最大彎矩階段的計(jì)算撓度；</p><p>&l

73、t;b>　　為開裂力矩（=）；</b></p><p><b>　　為混凝土斷裂模數(shù)；</b></p><p>　　為從質(zhì)心的距離軸的毛截面的纖維在極端的張力。</p><p>　　ACI方法的修改包括在澳大利亞標(biāo)準(zhǔn)AS3600-2001(AS2001)解釋的收縮引起的張力可能會(huì)顯著的降低混凝土的開裂構(gòu)件這個(gè)事實(shí)。開裂的構(gòu)件由

74、公式?jīng)Q定，是纖維在最大收縮引起的拉在未開裂截面應(yīng)力在極端的情況發(fā)生開裂（Gilbert 2003）。</p><p>　　Eurocode 2（1994）</p><p>　　這種方法涉及到在特定的曲率計(jì)算交叉部分，然后結(jié)合取得的撓度。開裂后曲率K的計(jì)算為 (2)</p><p&g

75、t;　　為分配系數(shù)占目前水平和打擊的程度，并給出</p><p><b>　　（3）</b></p><p>　　為變形鋼筋=1.0，光圓鋼筋=0.5；</p><p>　　為單一的，短期負(fù)荷為1.0，重復(fù)或持續(xù)荷載為0.5；</p><p>　　在應(yīng)力加載造成的受拉鋼筋首先開裂，計(jì)算混凝土張力；</p>

76、<p>　　是考慮鋼筋的加載應(yīng)力；</p><p>　　為忽略應(yīng)力混凝土的曲率部分；</p><p>　　曲率的未開裂換算截面。</p><p>　　在純彎曲的板，如果抗壓混凝土和鋼筋都是線性和彈性， 等于 ，結(jié)合公式1和2能得 （4）</p><p>　　對(duì)于一個(gè)包含變形鋼筋受彎構(gòu)件在短期的加載，公式3和公式4

77、可以重新安排，以提供下列替代表達(dá)式短期撓度[最近提出Bischoff(2005)]</p><p><b>　　(5)</b></p><p>　　這種做法，目前在英國(guó)已經(jīng)取代了Eurocode 2的方法，還涉及到在特定的截面曲率的計(jì)算，然后結(jié)合獲得的撓度。開裂后的曲率K計(jì)算假設(shè)（1）、平面為平截面；（2）、壓縮的鋼筋混凝土被認(rèn)為是線彈性；（3）、凝固的混凝土應(yīng)力分布

78、是三角形的，在中性軸和一個(gè)值為零值在1.0 MPa的瞬間強(qiáng)度鋼質(zhì)心，減少至0.55MPa。</p><p>　　4.與實(shí)驗(yàn)數(shù)據(jù)的比較</p><p>　　為了測(cè)試ACI 318，歐洲規(guī)范的適用性和BS 8110輕型鋼筋混凝土構(gòu)件的方法，測(cè)量的力矩與11簡(jiǎn)支的撓度反應(yīng)相對(duì)，單鋼筋單向拉伸板含鋼量計(jì)算結(jié)果在范圍進(jìn)行比較，該板塊（指定S1至S3，S8的，到SS2的SS4型，和Z1到Z4）都是柱狀

79、，矩形截面，850mm，并在一個(gè)有效深度載有縱向拉伸單層鋼筋d(Es=200000MPa和屈服應(yīng)力=500MPa)。每個(gè)板塊的詳細(xì)情況見表1，包括有關(guān)的幾何和材料特性。</p><p>　　在每個(gè)板跨中撓度的預(yù)測(cè)結(jié)果與實(shí)測(cè)時(shí)，在跨中力矩等于1.1，1.2和1.3Mcr列出在表2。與瞬時(shí)變形響應(yīng)的測(cè)量力矩的兩跨中的板。（SS2 and Z3）進(jìn)行比較和計(jì)算結(jié)果獲得圖2，使用三個(gè)代碼方式同時(shí)顯示的結(jié)果，如果沒有出現(xiàn)開

80、裂，如果張力加勁被忽略。</p><p><b>　　5.討論結(jié)果</b></p><p>　　很明顯，這些輕型鋼筋板，張力加勁非常顯著，提供一個(gè)大比例的開裂后剛度。從表2，跨中撓度的比例得到了加勁，對(duì)測(cè)量張力跨中撓度忽視（在Mcr和1.3Mcr范圍）是在1.38-3.69范圍，取平均值2.12。也就是說(shuō)，平均而言，張力加勁超過50％的一個(gè)輕型鋼筋板在屈服荷載的瞬間開

81、裂。</p><p>　　對(duì)于每一個(gè)板，在ACI 318的方法低估了瞬間撓度后開裂，特別是對(duì)于輕型鋼筋板。此外，在這一時(shí)刻ACI 318突然不成模型，在起初開裂處，突然改變力矩偏轉(zhuǎn)結(jié)果的方向，也沒有預(yù)測(cè)的正確形狀矩?fù)隙惹€。</p><p>　　在短期撓度的低估使用ACI 318模式是經(jīng)化驗(yàn)報(bào)告在這里在表示實(shí)踐中相當(dāng)大的比。不同于Eurocode 2和BS 8110，ACI 318模型不承

82、認(rèn)或?yàn)樵陂_裂的力矩，這將不可避免地減少在實(shí)踐中出現(xiàn)的由于張力引起的混凝土干燥收縮或熱變形。對(duì)于許多板，因早期干燥或溫度變化在數(shù)周內(nèi)將發(fā)生鑄件的開裂，以及經(jīng)常暴露之前，其板全方位服務(wù)的負(fù)荷。</p><p>　　通過限制混凝土拉伸應(yīng)力水平的拉伸筋只有1.0 MPa，BS 8110的方法對(duì)測(cè)試板的上下?lián)隙群土⒓锤哂陂_裂力矩的高估。由于約束的早期收縮和熱變形，這并非不合理和占損失的剛度發(fā)生在實(shí)踐中。不過，BS 8110

83、提供了一個(gè)相對(duì)較差模型剛度，并錯(cuò)誤地認(rèn)為，平均拉力混凝土裂縫進(jìn)行了實(shí)際調(diào)高M(jìn)增大和中性軸的上升。因此，BS 8110開裂后力矩偏轉(zhuǎn)斜率圖甚至超過了所有板測(cè)量斜坡。這種方法使用比Eurocode 2或ACI兩種方式更繁瑣。</p><p>　　在所有情況下，Eurocode 2撓度計(jì)算[EPS.(3)-(5)]是在更接近與實(shí)測(cè)撓度在整個(gè)負(fù)載范圍內(nèi)協(xié)議?？梢钥闯鲈趫D2，荷載—撓度曲線的形狀并使用Eurocode 2是

84、一個(gè)比這更好的代表性實(shí)際曲線結(jié)果，使用EP.(1)?？紤]到具體的變異材料性能影響的板，該協(xié)議Eurocode 2在運(yùn)行特征和對(duì)開裂的隨機(jī)性之間的預(yù)測(cè)和試驗(yàn)結(jié)果在如此廣泛的受拉鋼筋比率是相當(dāng)顯著的。在圖2（）0.80和1.39之間的值平均值為1.07，Eurocode 2的方法提供了ACI 318或BS 8110更好地估計(jì)短期行為。</p><p><b>　　6.結(jié)論</b></p&g

85、t;<p>　　雖然張力加勁只對(duì)重鋼筋梁撓度的影響相對(duì)較小，這是非常重要的對(duì)于Iuncr / ICR的比例很高的輕型鋼筋構(gòu)件，例如作為最實(shí)用的鋼筋混凝土樓板。加勁張力的模型納入ACI(2005)，Eurocode 2(CEN1993)，和BS 8110(1985) 已提交并且輕型鋼筋混凝土樓板的適用性已進(jìn)行評(píng)估。計(jì)算模型的三個(gè)代碼瞬時(shí)撓度進(jìn)行了比較與來(lái)自11個(gè)實(shí)驗(yàn)室測(cè)試測(cè)量撓度在含有不同數(shù)量的鋼筋板。在Eurocode 2

86、方案EP.(5)已被證明是更準(zhǔn)確地模擬了瞬時(shí)負(fù)載變形的加固構(gòu)件輕型鋼筋構(gòu)件的波形和ACI 318（EP.(1)比更為可靠的方法。</p><p>　　出自：JOURNAL OF STRUCTURAL ENGINEERING © ASCE / JUNE 2007</p><p><b>　　參考文獻(xiàn)</b></p><p>　　[1]A

87、merican Concrete Institute （ACI）.（2005）. “Building code requirements for structural concrete.” ACI 318-05, ACI Committee 318, Detroit.</p><p>　　[2]Bischoff, P. H. (2005). “Reevaluation of deflection predicti

88、on for concrete beams reinforced with steel and fiber-reinforce polymer bars.” J.Struct. Eng., 131(5), 752–767.</p><p>　　[3]Branson, D. E. (1965). “Instantaneous and time-dependent deflections ofsimple and c

89、ontinuous reinforced concrete beams.” HPR Rep. No. 7,1, Alabama Highway Dept., Bureau of Public Roads, Ala.</p><p>　　[4]British Standards Institution (BS).（1985）. “Structural use of concrete, Part 2, code of

90、 practice for special circumstances.” BS8100: Part2:1985, British Standard, London, England.</p><p>　　[5]European Committee for Standardization（CEN）. （1992）. “Eurocode 2:Design of concrete structures Part 1-

91、1: General rules for buildings.”DD ENV 1992-1-1, European Prestandard, Brussels, Belgium.</p><p>　　[6]Gilbert, R. I.（2003）. “Deflection by simplified calculation in AS3600-2001—On the determination of fcs.”

92、Australian J. Structural Engineering,5（1）, 61–71.</p><p>　　[7]Standards Australia（AS）. （2001）. “Australian standard for concrete structures.”AS 3600-2001, Sydney, Australia.JOURNAL</p><p><b&

93、gt;　　外文原稿2</b></p><p>　　The Twelfth East Asia-Pacific Conference on Structural Engineering and Construction</p><p>　　Design of Building Structures to Improve their Resistance</p>&l

94、t;p>　　to Progressive Collapse</p><p>　　D A Nethercota</p><p>　　a Department of Civil and Environmental Engineering, Imperial College London</p><p>　　Abstract：It is rare nowadays

95、for a “new topic” to emerge within the relatively mature field of Structural Engineering. Progressive collapse-or, more particularly, understanding the mechanics of the phenomenon and developing suitable ways to accommod

96、ate its consideration within our normal frameworks for structural design-can be so regarded. Beginning with illustrations drawn from around the world over several decades and culminating in the highly public WTC collaps

97、es, those features essential fo</p><p>　　2011 Published by Elsevier Ltd. </p><p>　　Keywords: Composite structures; Progressive Collapse; Robustness; Steel structures; Structural design</p>

98、<p>　　1. Introduction </p><p>　　Over time various different structural design philosophies have been proposed, their evolutionary nature reflecting：</p><p>　　*?Growing concern to ensure

99、adequate performance. </p><p>　　*?Improved scientific knowledge of behaviour. </p><p>　　*? Enhanced ability to move from craft based to science based and thus from prescriptive to quantitativ

100、ely justified approaches</p><p>　　This can be traced through concepts such as: permissible stress, ultimate strength, limit states and performance based. As clients, users and the general public have become

101、 increasingly sophisticated and thus more demanding in their expectations, so it became necessary for designers to cover an ever increasing number and range of structural issues–mostly through consideration of the “reach