【作者】 王伯昕；

【导师】 黄承逵；

【作者基本信息】 大连理工大学 ， 结构工程， 2008， 博士

【摘要】 上世纪50～90年代我国修建了大量的装配式简支梁桥。随着运营年限的增加及我国经济建设的高速发展,行车数量、载重量和车速的不断提高,大量此类桥梁面临承载能力下降、设计荷载不足的窘境。为了提高此类桥梁的承载能力和安全性能,进行简支转连续的体系转换加固方法是一种比较有效的方法,即针对需加固的简支梁旧桥,将多跨简支梁的梁端连接起来变为多跨连续梁,以达到改善结构受力状况、提高桥梁承载能力、延长桥梁剩余使用寿命、节省资金的目的。随之而来的问题是连接段处于负弯矩区,承受很大的负弯矩作用,一旦开裂,裂缝又出现在桥面,雨水、除冰盐等极易进入结构层使钢筋锈蚀,对于加固后桥梁的耐久性和适用性造成巨大危害。寻找合适的负弯矩区加固材料和提出针对该种材料的合理的加固计算方法,是研究的重点。钢筋钢纤维自应力混凝土是一种新型纤维增强复合材料,由于混凝土基体的自膨胀作用受到钢筋和钢纤维的共同限制从而产生化学预应力,极大地提高混凝土基体的抗拉性能。钢筋、钢纤维和自应力混凝土复合,可以充分发挥三者各自的优势,使复合材料的抗裂性能、抗拉性能、弯曲韧性性能、抗冲击性能和耐久性能明显改善,特别适合作为简支转连续体系加固旧桥负弯矩区的加固材料。目前对钢筋钢纤维自应力混凝土的研究仅限于膨胀增强机理方面和一些基本力学性能,对其结构性能及桥梁加固方面的研究几乎还是空白。本文结合辽宁省交通厅重点科研基金项目《钢筋混凝土简支梁桥转换成连续梁桥加固技术与施工工艺研究》(200514),主要进行了一下研究工作:1.通过研究钢纤维自应力混凝土、钢纤维混凝土、聚丙烯纤维混凝土、大直径合成纤维混凝土、混杂纤维混凝土的配合比、拌合物性能与养护方法、基本力学性能和耐久性能,认为钢纤维自应力混凝土适宜作为简支转连续非预应力法加固旧桥方法中纵向接缝区和负弯矩区后做连续顶板的加固材料,使其满足结构承载力、裂缝控制和耐久性的要求;2.对钢筋钢纤维自应力混凝土限制膨胀性能进行了系统研究,对钢筋和钢纤维对自应力混凝土长期膨胀变形的影响进行了长达9年的试验观测,研究了钢筋和钢纤维对于自应力混凝土的限制膨胀作用,绘制了钢筋钢纤维自应力混凝土的长期限制膨胀变形曲线,并给出了考虑长期变形的钢筋钢纤维自应力混凝土的自应力损失计算方法;3.结合9根叠合T型梁模型试验,主要针对纤维混凝土、自应力混凝土用于后连续体系负弯矩区的抗裂性能、自应力混凝土叠合层自应力的计算方法和负弯矩区混凝土的裂缝开展、截面应变、挠度变形、刚度等抗弯性能进行了研究;4.通过10根两跨后连续叠合T型梁模型试验,研究了简支转连续体系两跨连续T型梁在弯曲作用下的挠度变形、截面应变、裂缝开展和预损伤程度的影响情况、叠合层新老混凝土的粘结情况、加固后连续叠合T型梁负弯矩区混凝土的抗裂计算和极限状态下的抗弯承载力计算;5.通过计算机模拟研究了钢筋钢纤维自应力混凝土的限制应变对桥梁内力的影响,从而确定钢筋钢纤维自应力混凝土允许的限制应变范围、合理的使用位置以及使用效果,为工程应用提供依据。更多还原

【Abstract】 Simply supported bridges are designed to function over long periods of time in China. The incidence of structural deterioration increases with bridge age due to traffic development, such as bearing capacity decreasing, and design capacity shortage. Transforming simply supported into continuous systerm is a feasible way to strengthen the old simply supported bridges in order to enhance the bearing capacity, extend the service life of the bridge and save the maintaining expense. But the concrete in the longitudinal joints and the negative bending moment areas is easy to crack due to the lardge negative bending moment. Once the rain water and Cl~- enter the bridge through the cracks, it’s a hidden trouble to the durability and security of the continuous bridge. So there are an increasing need and a great challenge to search a feasible material and deduce a logical calculated method for old bridge strengthening with this material.Steel fiber reinforcement self-stressing concrete (SFRSSC) is a new type of fiber reinforced composite. The tensile strength of the concrete can be extremely improved by the chemical pre-stressing, which is caused by the restricted expansion of SFRSSC induced by steel bars and steel fibers. The combination of the steel bars, steel fibers and self-stressing concrete enhances the crack resistance, tensile performance, flexural toughness, impact resistance and durability of the composite, and make SFRSSC a wonderful strengthening material to the old bridge rehabilitation. The research on SFRSSC mainly concentrates on reinforced mechanism and mechanical properties. However, there is no literature on structural properties and bridge strengthening applications.Therefore, based on the Liaoning Province Communication Department Key Science Foundation Project (No.200514) Strengthened Technique and Construction Craft of the Continuous Beams after Continuing Simply Supported Beams by Exerting Prestressing Loads, this thesis will focus on the following aspects:1. Based on the experimental investigation of the strengthening materials containing SFRSSC, steel fiber reinforced concrete (SFRC), Polypropylene fiber reinforced concrete, large diameter synthetic fiber reinforced concrete and hybrid fiber reinforced concrete, the mix proportion, the working performance, the fundermental mechanical property and durability are evaluated. The experimental results show that SFRSSC is validated to be a promising material in the longitudinal joints and the negative bending moment areas, satisfying the engineering requirements of the bearing capacity, crack control and durability;2. Based on the experimental observation of SFRSSC during 9 years, the long-term restricted expansion performance is studied. The long-term restricted expansion curves and calculated method of self-stressing loss are given;3. Based on the model experiment of 9 composite concrete inverted T-beams, the crack resistance and flexural performance of SFRC and SFRSSC in negative bending moment areas are evaluated. With the experimental results, the formulas to calculate the self-stressing and crack resistance of the layers are deduced;4. Based on the model experiment of 10 continuous composite concrete T-beams, the deformation, cross-section strain, crack and new-existing concrete bonding are observed. The influence of pre-damage on continuous beams flexural performance is researched and a method to calculate the crack resistance and bearing capacity under ultimate phase of the continuous composite T-beams are carried out;5. Based on the computer analysis, the influence of SFRSSC on the internal force of continuous T-beams are studied. The restricted strain range and the appropriate position of SFRSSC in continuous bridge are deduced for references in bridge strengthening design.更多还原