【正文】 ons. For many slabs, cracking will occur within weeks of casting due to early drying or temperature changes, often well before the slab is exposed to its full service loads. By limiting the concrete tensile stress at the level of the tensile reinforcement to just MPa, the BS 8110 approach overestimates the deflection of the test slabs both below 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 approach provides a relatively poor model of thepostcracking stiffness and incorrectly suggests that the average tensile force carried by the cracked concrete actually increases as M increases and the neutral axis rises. As a result, the slope of the BS 8110 postcracking momentdeflection plot is steeper than the measured slope for all slabs. The approach is also more tedious to use than either the ACI or Eurocode 2 approaches. 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 in Fig. 2, the shape of the loaddeflection 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 properties that affect the inservice behavior of slabs and the random nature of cracking, the agreement between the Eurocode 2 predictions and the test results over such a wide range of tensile reinforcement ratios is quite remarkable. With the ratio of () in Table 2 varying between and with a mean value of , the Eurocode 2 approach certainly provides a better estimate of shortterm behavior than either ACI 318 or BS8110. Although tension stiffening has only a relatively minor effect on 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 stiffening 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 deflections calculated using the three code models have been pared with measured deflections from 11 laboratory tests on slabs containing varying quantities of steel reinforcement. The Eurocode 2 approach （Eq.（5） has been shown to more accurately model the shape of the instantaneous loaddeformation response for lightly reinforced members and be far more reliable than the ACI 318 approach （Eq.（1）.中文翻譯1鋼筋混凝土板的拉伸硬化過(guò)程分析R. Ian Gilbert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。在開(kāi)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。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。關(guān)鍵詞：開(kāi)裂，蠕變撓度，混凝土，鋼筋，適用性，收縮，混凝土磚。這一種混凝土的拉力被稱(chēng)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。對(duì)于這樣的構(gòu)件，彎曲完全開(kāi)裂的一個(gè)截面剛度比未開(kāi)裂的截面小許多倍，張力加勁大大促進(jìn)了開(kāi)裂后構(gòu)件的剛度。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（）。其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(guò)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。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)。在負(fù)載小于開(kāi)裂負(fù)載的情況下，該構(gòu)件未開(kāi)裂和表現(xiàn)均勻的彈性，以及撓度斜率是成正比的未開(kāi)裂的轉(zhuǎn)動(dòng)慣量的換算界面。有一個(gè)剛度突變，并立即出現(xiàn)裂紋。 如果在梁的混凝土開(kāi)裂區(qū)域內(nèi)施加拉力而沒(méi)有壓力，負(fù)載變形關(guān)系將遵循虛線(xiàn)ACD，如圖1。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(xiàn)AB型。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(kāi)發(fā)和裂縫的數(shù)量趨于穩(wěn)定。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(kāi)裂，在持續(xù)負(fù)載下張力加勁效應(yīng)隨著時(shí)間而減少。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)算價(jià)值在正，負(fù)彎矩區(qū)的一個(gè)連續(xù)的跨度。 ACI方法的修改包括在澳大利亞標(biāo)準(zhǔn)AS36002001(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(kāi)裂構(gòu)件這個(gè)事實(shí)。Eurocode 2（1994） 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。 在純彎曲的板，如果抗壓混凝土和鋼筋都是線(xiàn)性和彈性， 等于 ，結(jié)合公式1和2能得 （4）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)] (5)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。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，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)。在每個(gè)板跨中撓度的預(yù)測(cè)結(jié)果與實(shí)測(cè)時(shí)。（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(méi)有出現(xiàn)開(kāi)裂，如果張力加勁被忽略。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（）。對(duì)于每一個(gè)板，在ACI 318的方法低估了瞬間撓度后開(kāi)裂，特別是對(duì)于輕型鋼筋板。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。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(kāi)裂，以及經(jīng)常暴露之前，其板全方位服務(wù)的負(fù)荷。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。因此，BS 8110開(kāi)裂后力矩偏轉(zhuǎn)斜率圖甚至超過(guò)了所有板測(cè)量斜坡。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。考慮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(kāi)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。 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。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。出自：JOURNAL OF STRUCTURAL ENGINEERING 169。 Progressive Collapse。 Steel structures。 the actual values required are normally related to the vertical loading. Figure 1, which is taken from recent US Guidance (SEI 2010), illustrates the principle. The approach is simple to appreciate, requires minimal structural calculation and, in situations where the original provisions are found to be inadequate, can be made to work by providing more substantial connections and/or additional reinforcement in floor slabs In an interesting recent development, that recognizes the link to the generation of catenary action, US Guidance has restricted the use of tying between the structural members to situations in which it can be demonstrated that the associated connections can carry the required forces whilst undergoing rotations of radiance. Where this is not possible, tying should act through the floors and the roof. However, recent studies (Nethercot et al 2010a。 for example, recent thinking in the United States (SEI 2010) makes provision for any of: linear static, nonlinear static or nonlinear dynamic analysis and provides some guidance on the use of each. It may also be used as the basis for more sophisticated numerical studies of particular structures and particular incidents . forensic