(完整版)房屋建筑毕业设计 4外文翻译.docx

(完整版)房屋建筑毕业设计 4外文翻译 你如果认识从前的我，也许会原谅现在的我。 毕业设计 (论文) 外文翻译 设计（论文）题目：宁波天合家园某住宅楼 2号轴框架结构设计与建筑制图 学院名称：建筑工程学院 专业：土木工程 指导教师：马永政、陶海燕 2022 年 12 月 10 日 外文原稿1 Tension Stiffening in Lightly Reinforced Concrete Slabs 1R. Ian Gilbert1 Abstract: The tensile capacity of concrete is usually neglected when calculating the strength of a reinforced concrete beam or slab even though concrete continues 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 affects the member's stiffness after cracking and 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. This contribution of the tensileconcrete is known as tension stiffening and it affects the member'sstiffness after cracking and amount permittedby the relevant building code. For such members the 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 control at service-load levels are usually thegoverning considerations and accurate modeling of the stiffnessafter cracking is required. The most commonly used approach in deflection calculationsinvolves determining an average effective moment of inertia Iefor a cracked member. Several different empirical equations areavailable for Ie including the well-known equation developed byBranson 1965 and recommended in ACI 318 ACI 2022. Othermodels for tension stiffening are included in Eurocode 2 CEN1992 and the British Standard BS 8110 1985. Recently Bischoff 2022 demonstrated that Branson's equation grossly overestimates thtie average sffness of reinforced concrete memberscontaining small quantities of steel reinforcement and moment reaches the flexural tensile strength of the concrete or modulus of rupture fr. There is a sudden change in the local stiffness at and immediately adjacent to this first crack. On the section containing the crack the flexural stiffness drops significantly but much of the beam remains uncracked. As load increases more cracks form and the average flexural stiffness of the entire member decreases. If the tensile 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 after 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 zero tension response is the tension stiffening effect （ in Fig. 1）. 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 response at least until the crack pattern is fully developed and the number of cracks deflection calculations. 3.Models for Tension Stiffening The instantaneous 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 calculated 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 （1） 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 transformed 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 the centroidal axis of the gross section to the extreme fiber in tension. A modification of the ACI approach is included in the Australian Standard 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 the extreme fibre at which cracking occurs（Gilbert 2022）. （2） where distribution coefficient accounting for moment level and degree of cracking and is given by （3） 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 tensile 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-service moment Ms is acting) calculated while ignoring concrete in tension; cr=curvature at the section while ignoring concrete in tension; and uncr=curvature on the uncracked transformed section. For slabs in pure flexure if the compressive concrete and the reinforcement 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 （4） 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 calculations recently proposed by Bischoff (2022): (5) This approach which . 4parison with Experimental Data 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 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 rectangular section 850 mm wide and contained a single layer of longitudinal tensile steel reinforcement at an effective depth d (with Es=200 000 MPa and the nominal yield stress fsy=500 Mpa). Details of each slab are given in Table 1 including relevant geometric and material properties. The predicted and measured deflections at midspan for each slab when the moment at midspan equals 1.1 1.2 and 1.3 Mcr 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 Fig. 2. Also shown are the responses if cracking did not occur and if tension stiffening was ignored. 5.Discussion of Results It is evident that for these lightly reinforced slabs 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 deflection (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 slab after cracking at service load. 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 abrupt change in direction of the moment-deflection response at first cracking nor does it predict the correct shape of the postcracking moment-deflection curve. The underestimation of short-term deflection using the ACI318 model is considerably greater in practice than that indicated by the laboratory tests reported 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 0.80 and 1.39 with a mean value of 1.07 the Eurocode 2 approach certainly provides a better estimate of short-term behavior than either ACI 318 or BS8110. 6.Conclusions Although tension stiffening 11 laboratory tests on slabs containing varying quantities of steel reinforcement. The Eurocode 2 approach （Eq.（5） 并在一个有效深度载有纵向拉伸单层钢筋d(Es=200000MPa和屈服应力=500MPa) 每个板块的详细情况见表1 包括有关的几何和材料特性 在每个板跨中挠度的预测结果与实测时 在跨中力矩等于1.1 1.2和1.3Mcr列出在表2 与瞬时变形响应的测量力矩的两跨中的板 （SS2 and Z3）进行比较和计算结果获得图2 使用三个代码方式同时显示的结果 如果没有出现开裂 如果张力加劲被忽略 5.讨论结果 很明显 这些轻型钢筋板 张力加劲非常显著 提供一个大比例的开裂后刚度 从表2 跨中挠度的比例得到了加劲 对测量张力跨中挠度忽视（在Mcr和1.3Mcr范围）是在1.38-3.69范围 取平均值2.12 也就是说 平均而言 张力加劲超过50的一个轻型钢筋板在屈服荷载的瞬间开裂 对于每一个板 在ACI 318的方法低估了瞬间挠度后开裂 特别是对于轻型钢筋板 此外 在这一时刻ACI 318突然不成模型 在起初开裂处 突然改变力矩偏转结果的方向 也没有预测的正确形状矩挠度曲线 在短期挠度的低估使用ACI 318模式是经化验报告在这里在表示实践中相当大的比 不同于Eurocode 2和BS 8110 ACI 318模型不承认或为在开裂的力矩 这将不可避免地减少在实践中出现的由于张力引起的混凝土干燥收缩或热变形 对于许多板 因早期干燥或温度变化在数周内将发生铸件的开裂 以及经常暴露之前 其板全方位服务的负荷 通过限制混凝土拉伸应力水平的拉伸筋只有1.0 MPa BS 8110的方法对测试板的上下挠度和立即高于开裂力矩的高估 由于约束的早期收缩和热变形 这并非不合理和占损失的刚度发生在实践中 不过 BS 8110提供了一个相对较差模型刚度 并错误地认为 平均拉力混凝土裂缝进行了实际调高M增大和中性轴的上升 因此 BS 8110开裂后力矩偏转斜率图甚至超过了所有板测量斜坡 这种方法使用比Eurocode 2或ACI两种方式更繁琐 在所有情况下 Eurocode 2挠度计算EPS.(3)-(5)是在更接近与实测挠度在整个负载范围内协议可以看出在图2 荷载-挠度曲线的形状并使用Eurocode 2是一个比这更好的代表性实际曲线结果 使用EP.(1) 考虑到具体的变异材料性能影响的板 该协议Eurocode 2在运行特征和对开裂的随机性之间的预测和试验结果在如此广泛的受拉钢筋比率是相当显著的 在图2（）0.80和1.39之间的值平均值为1.07 Eurocode 2的方法提供了ACI 318或BS 8110更好地估计短期行为 6.结论 虽然张力加劲只对重钢筋梁挠度的影响相对较小 这是非常重要的对于Iuncr ICR的比例很高的轻型钢筋构件 例如作为最实用的钢筋混凝土楼板 加劲张力的模型纳入ACI(2022) Eurocode 2(CEN1993) 和BS 8110(1985) 已提交并且轻型钢筋混凝土楼板的适用性已进行评估 计算模型的三个代码瞬时挠度进行了比较与来自11个实验室测试测量挠度在含有不同数量的钢筋板 在Eurocode 2方案EP.(5)已被证明是更准确地模拟了瞬时负载变形的加固构件轻型钢筋构件的波形和ACI 318（EP.(1)比更为可靠的方法 出自：JOURNAL OF STRUCTURAL ENGINEERING (c) ASCE JUNE 2022 参考文献 1American Concrete Institute （ACI）.（2022）. "Building code requirements for structural concrete." ACI 318-05 ACI Committee 318 Detroit. 2Bischoff P. H. (2022). "Reevaluation of deflection prediction for concrete beams reinforced with steel and fiber-reinforce polymer bars." J.Struct. Eng. 131(5) 3Branson D. E. (1965). "Instantaneous and time-dependent deflections ofsimple and continuous reinforced concrete beams." HPR Rep. No. 7 1 Alabama Highway Dept. Bureau of Public Roads Ala. 4British Standards Institution (BS).（1985）. "Structural use of concrete Part 2 code of practice for special circumstances." BS8100: Part2:1985 British Standard London England. 5European Committee for Standardization（CEN）. （1992）. "Eurocode 2:Design of European Prestandard