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It is considered thatpropagation of crack width was mitigated because some crackswere developed in different parts of slabs near the interiorsupport. Accordingly, it is considered that the appropriate crackwidth control initially at transverse joints is more important.Load–relative slip curves were also measured experimen-tally through the static loading test performed up to 900 kNafter the repeated loading test (Fig. 24). The increase of rela-tive slip provokes the increase of deflection and the occurrence of cracks in the concrete deck at the internal support may alsoaffect the increase of deflection. Also, the difference of longi-tudinal stiffness in bridges due to the development of cracksin the deck may influence the occurrence of relative slip. Fur-ther analytical researches are expected to help the examinationof this subject. In general, it is considered that the test spec-imen could be also assumed with full composite action until900 kN loading after one million cyclic loading, because moni-tored slips were relatively smaller than ultimate slip of the shearconnection [6,7].Fig. 21. Load–deflection curves under static loading up to 900 kN.Fig. 25 plots the maximum strains (strain at the bottomflange) in the maximum positive moment section and in thenegative moment section of the girder measured until 900 kN.In view of the level of the developed strains, the girder remainsin the elastic range up to the load of 900 kN. In the result, thenonlinear behaviour of the whole bridge can consequently beunderstood as caused mainly by the cracking developed in theconcrete deck. Moment curvature relationship of the bridge model up to900kN loading was also reached as shown in Fig. 26. Inthe maximum negative moment section, the propagation ofcracking in the slab on the interior support makes the stiffnessdecrease. Although cracking of bottom slabs happens at loadingpoints and top slabs on the interior support, the curve of themaximum positive moment section was nearly maintained asthe curve of uncracked composite section (Fig. 26) where girderdid not reach yielding (Fig. 25). In the maximum negativemoment section, the stiffness of the bridge model decreasedgradually and similarly traced the curve evaluated by Eurocode4-2 after design cracking load. However, with moment increase,the stiffness of the composite girder was largely decreasedand eventually became equal to that of cracked compositesection as shown in Fig. 26. It can be observed that the flexuralstiffness of the negative moment section in the test modellargely decreased compared to the effective stiffness calculatedusing Eurocode 4-2 as a result of cyclic loading. It is suggestedthat bonding between reinforcement and concrete becomesweak due to repeated loading effects and thus tension stiffeningeffects decrease. Nevertheless, it is considered that momentcurvature relationship or the flexural stiffness by Eurocode 4-2is still useful for estimation of the effective stiffness consideringtension stiffening effects in the composite bridge with loopjoints prefabricated slabs.
摘要为研究裂缝控制,选取了一个带有预制板的两跨连续组合双肋梁的足尺模型,并对其进行试验及观察。在试验中,第一次荷载加到360kN,然后进行疲劳荷载试验。最后静力加载至900kN。试验结果证实了带预制板的双肋连续组合梁显示出了在静力疲劳荷载作用下的组合截面的强度和刚度特性。然而,在负弯矩作用区域,裂缝集中在内部支撑之上的桥面之间的接缝部位,初始的裂缝间距由接缝处间的距离决定,在使用荷载作用下,带有预制板的组合桥梁的桥面和横向接缝的裂缝宽度可以被控制在一个容许裂缝宽度之内。弯矩曲率曲线或者由欧洲规范4-2中规定的抗弯刚度仍可被用于评估考虑到在这种桥梁上拉伸硬化作用的有效刚度。源:自*751~·论,文'网·www.751com.cn/
c 2007 Published by Elsevier Ltd
毕业论文关键词：裂缝控制；连续组合双梁桥；预制板；环缝；横向接头；静力疲劳载荷；组合截面复合截面的负弯矩区；裂缝宽度；抗弯刚度