【作者】 张彦玲；

【导师】 阎贵平； 季文玉；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2009， 博士

【摘要】 连续组合梁桥负弯矩区会产生混凝土受拉、钢梁受压的不利情况,特别是混凝土板的开裂会引起组合梁刚度降低和耐久性下降,因此深入理解组合梁桥负弯矩区的受力性能,有效控制或防止负弯矩区混凝土开裂就成为连续组合梁桥设计中的一个关键问题。本文结合国家自然科学基金资助项目,通过理论推导、模型试验和数值模拟,对短期荷载作用下正常使用阶段组合梁负弯矩区受力性能、混凝土裂缝发展规律及其控制方法开展了深入的研究,所做的主要工作和结论如下:(1)建立了竖向荷载作用下同时考虑组合梁滑移效应、剪力滞效应和Timoshenko梁剪切变形多重影响的荷载效应理论分析方法。对组合梁混凝土翼板的内顶板、悬臂板和宽钢箱梁底板分设了不同的剪滞翘曲形函数,采用能量变分原理,得到了正常使用阶段组合梁在均布荷载、集中荷载和两点对称荷载作用下更为精确的应力和挠度解析解,为后续负弯矩区的相关研究提供了理论分析手段;(2)建立了轴向荷载作用下同时考虑组合梁滑移效应和剪力滞效应双重影响的荷载效应理论分析方法。根据体外预应力组合梁的特点,采用能量变分原理,分别得到了预应力轴力和弯矩作用下截面应力的解析解,发现锚固端和张拉端在预加应力阶段就存在较大的应力集中和滑移变形,根据分析结果给出了预加应力阶段组合梁结合面的相对滑移规律和纵向剪力的计算方法,为连接件的局部加强设计提供了理论依据:(3)对3根反向加载的钢—混凝土简支组合梁和3根2跨连续组合梁进行了静载试验,对混凝土板裂缝发展规律和体外预应力对组合梁裂缝、刚度及承载力等方面的改善作用进行了重点研究,将试验结果和理论推导结果进行了相互验证。通过试验得到了负弯矩作用下组合梁截面的应变分布规律、结合面滑移规律、内力重分布规律及裂缝的发展规律,证实在短期荷载下对组合梁施加体外预应力是控制负弯矩区开裂的一种有效措施;(4)对钢—混凝土组合梁负弯矩区的裂缝宽度和刚度进行了研究。考虑了配筋力比和横向钢筋间距对裂缝间距的影响,根据试验结果对裂缝宽度计算公式进行了修正;提出了采用考虑滑移效应和受拉刚化效应的等效刚度进行正常使用阶段连续组合梁挠度计算的方法;(5)采用能量变分原理得到了沿梁轴仅部分开裂的变刚度组合梁荷载效应的理论解,分析了混凝土开裂对组合梁负弯矩区剪力滞效应和有效翼缘宽度的影响,给出了组合梁负弯矩区有效翼缘宽度的建议修正公式。分析表明:混凝土开裂使组合梁负弯矩区剪力滞系数减小,有效翼缘宽度增大,可在负弯矩区等效跨度范围内按完全开裂的等截面梁进行有效翼缘宽度的计算。在连续组合梁中,等效跨度应充分考虑实际反弯点的位置;(6)根据活性粉末混凝土(RPC)较高的抗拉强度和较小的收缩徐变,提出了钢—活性粉末混凝土组合梁的概念,通过全过程受力性能分析,从理论上表明了采用RPC新材料作为组合梁翼板也是提高负弯矩区抗裂性能的一种有效措施,尤其是采用钢一预应力RPC组合梁时,效果更显著。更多还原

【Abstract】 Continuous composite beams have some disadvantages when the steel girder is in compression while the concrete slab is in tension at the negative moment zone,and the crack of concrete slab will decrease the stiffness and durability,so it is very important to understand the behaviors of negative moment zone deeply,and control or prevent concrete crack at the negative moment zone of continuous composite beams.Combined with the project granted by national natural science foundation of China,the behaviors of negative moment zone,concrete crack mechanics and control method under short-term loads are studied in service stage for composite beams,the main contents and conclusions are as follows:(1) Considering multiple effects of slip,shear lag,and Timoshenko shear deformation,a theoretical method for analyzing load effects under vertical loads is established for steel-composite beams(short for SCBs).With the inner and cantilever concrete top slab and the steel bottom slab set by different shear lag warping shape functions,the more accurate elastic closed-form solutions of stress and flexibility under uniform load,concentrated load,and two-point symmetry loads are deduced in service stage by energy-variational principle.These solutions are used in subsequent study of SCBs’ behaviors at negative moment zone.(2) Considering double effects of slip and shear lag,a theoretical method for analyzing load effects under axial load is established for prestressed SCBs.According to the characteristics of external prestressed SCBs,analytical stress solutions of prestressed SCBs under prestressing axial load and eccentric bending moment are decuced by energy-variational principle.The slip law between concrete slab and steel girder is analyzed,which shows that the stress concentrate and slip are rather greater in prestressing stage.The calculation method of longitudinal shear force is suggested, which can provide a reference for local strengthening design of connectors.(3) Static model tests are conducted on three simply-supported SCBs under negative moment and three continuous two-span SCBs under concentrated loads.The study focuses on the development law of concrete crack and improvement effect due to external prestressing on crack,stiffness,and bearing capacity of composite beams.The law of stress distribution,slip,internal force redistribution,and crack development under negative moment are obtained in the tests.The investigation results show that under short-term loads,applying prestress in concrete slab is an effective measure for crack control under negative moment.At the same time,the theoretical results and test results are verified each other.(4) The crack widths and stiffness of SCBs at negative moment zone are studied. The force ratio and transverse reinforcement spacing are considered in crack spacing, the formula of crack width is modified.Based on the concept of reduced stiffness due to slip effect and the tension stiffening effect,the calculation precision will increase if calculating the deflection of continuous composite beams in service stage by effective stiffness.(5) The theoretical load effect solutions of variable stiffness SCBs which cracked in partial range along the beam are obtained by energy-variational principle.The influence of concrete crack on shear lag effect and effective flange width are investigated,and the verified formula of effective flange width at negative moment zone is suggested.The study results suggest that the concrete crack would lead to smaller shear lag coefficient and larger effective flange width,the effective flange width could be calculated by using a completed cracked beam with a uniform cross-section in the range of equivalent span length corresponding to the negative moment zone.It is also important that the actual position of inflection point should be carefully considered for the continuous composite beams.(6) According to the super tension strength and lower shrinkage and creep of Reactive Powder Concrete(short for RPC),the concept of steel-RPC composite beam is introduced.The full-range analysis shows that adopting RPC as the material of slab is also an effective measure which can increases the crack resistance of composite beams at negative moment zone,especially when the steel-RPC composite beam is applied prestressing load.There are totally 121 graphs,13 tables and 184 references in this paper.更多还原