【作者】 曹国辉；

【导师】 方志；

【作者基本信息】 湖南大学 ， 结构工程， 2007， 博士

【摘要】 体外配置碳纤维（CFRP）筋预应力混凝土薄壁箱梁将成为新建桥梁结构修建和现有桥梁结构加固的一种较好的结构形式，而国内外有关该方面的研究尚未见文献报道。目前对混凝土连续箱梁的受力性能研究多局限在短期弹性受力阶段，有关混凝土连续宽箱梁开裂后的结构内力重分布和长期受力性能等方面的研究很少。针对目前很多混凝土薄壁箱梁普遍存在开裂严重等病害现象，本文对混凝土薄壁箱梁的短期与长期受力性能进行了深入研究，以探求混凝土薄壁箱梁的长期受力性能，本文完成了以下主要工作：（1）对配置体外CFRP筋预应力混凝土薄壁箱梁进行了短期受力性能试验，根据换算截面法和变分原理，推导了开裂混凝土简支箱梁均布荷载作用、集中荷载作用下截面的剪力滞系数分布规律。分析表明：考虑混凝土开裂引起跨中截面翼缘有效分布宽度系数的变化在5％以内。（2）对钢筋混凝土连续箱梁进行了短期受力性能试验，由于混凝土开裂和橡胶支座不均匀沉降将引起连续梁结构内力重分布。运用变分原理采用解肢法和换算截面法对连续箱梁均布荷载作用下的剪力滞效应进行了分析。分析表明：边跨边支座至反弯点间的简支梁段、反弯点之间的简支梁段在混凝土开裂后，开裂点附近均出现负剪力滞效应，混凝土开裂引起中间支座截面翼缘有效分布宽度系数较弹性状态偏大，按变分原理偏大9.1％～14.8％，按试验结果偏大7.7％～13.7％。混凝土开裂引起跨中截面翼缘有效分布宽度系数的变化在4％以内。（3）对10根混凝土矩形截面梁，包括6根普通钢筋混凝土梁和4根CFRP片材加固梁进行了673d的长期受力性能试验，运用徐变换算截面法预测了长期挠曲变形。研究表明：碳纤维片材对混凝土梁的长期挠曲变形影响很小；对CFRP片材加固梁进行了参数分析；对钢筋混凝土梁的截面应力进行了分析，与实测结果吻合较好；按现行设计规范能较好地预测混凝土矩形截面梁的长期挠曲变形。（4）对体外配置CFRP筋预应力混凝土薄壁箱梁均布荷载作用下的长期受力性能进行了1001d的试验研究。长期荷载作用引起受拉钢筋的应变变化相对较小，受压钢筋的应变变化相对较大，顶板压应变分布呈均匀分布趋势。按现行规范JTGD62-2004计算薄壁箱梁特征裂缝宽度时，建议取与构件受力性质有关的系数C₃=1.25，采用规范GB 50010-2002计算最大裂缝宽度时，建议取构件受力特征系数α_cr=2.7，此时裂缝宽度理论值与实测值吻合较好。采用徐变换算截面法分析了预应力混凝土箱梁持续荷载作用下的截面应力应变分布规律，理论计算值与实测结果吻合较好。运用双线形法和截面曲率法分别对预应力混凝土箱梁的长期挠曲变形进行预测，持荷1001d实测跨中挠度增大系数较现行规范规定值偏大18.5％，建议取长期挠度增长系数η_θ=2.45，此时长期挠度变形理论预测值与实测结果吻合较好。（5）对钢筋混凝土连续箱梁均布荷载作用下的受力性能进行了1006d的试验研究，受拉钢筋的应变增长相对较小，受压钢筋和受压混凝土的应变增长相对较大，且跨中截面的压应变增长较中间支座截面显著，受压翼板应变分布呈均匀分布趋势。对试验模型持荷1006d的内力重分布规律进行了试验观测，与理论预测结果吻合较好。现行设计规范经参数修正后能较好的预测连续箱梁各控制截面的裂缝宽度，跨中长期挠曲变形实测值较理论计算值偏大约11.4％。更多还原

【Abstract】 Thin-walled concrete box girder prestressed with externally CFRP tendons would become a good structural style for the newly built bridges and the structural strengthen of existing bridges, it has no report on the research so far at home and abroad. At present the research on the performance of continuous box girder is only stagnate at short-term and elastic stages, it is almost no research on the structural internal force redistribution and long-term performance of continuous concrete box girder with wide flange after concrete cracking. For too many thin-walled concrete box girders universally cracked, this paper had an indepth experimental study on short-term and long-term, in order to obtain short-term and long-term performance of thin-walled concrete box girder, this paper has finished the following works:（1）Short-term performances of thin-walled concrete box girder prestressed with CFRP tendons were tested. Based on transformed-section method, adopting variational principle, it deduced shear lag coefficient distribution law of simply supported concrete box girder under uniform load and central load. Analyses indicate that effective distribution width coefficient of flange at mid-span section would change within 5% due to concrete cracking.（2） Short-term performance of concrete continuous box girder were tested, it shows that concrete cracking and uneven settlement of latex support would induce structural internal force redistribution of continuous box girder. Applying variational principle, shear lag effect of continuous box girder under uniform load were analysed adopting dismemberment mothed and transformed-section method. The analysis indicate that, after the simply supported beam which begins from the side support to inflection point, and the simply supported beam between the points of inflection, were cracking, it would appear negative shear lag effect nearby cracked point, the influence of concrete cracking on shear lag coefficient would be increased than elastic state at mid-supported section. The value calculated by variational principle would be increased by 9.1%¹4.8%, the value calculated by test results would be increased by 7.7%¹3.7%. The influence on effective distribution width coefficient of flange at mid-span section would change within 4% due to concrete cracking.（3） Long-term behaviors for 673 days were tested on 10 rectangle beams, including 6 ordinary reinforced concrete beams and 4 beams strengthened with CFRP laminates. Long-term deflection of concrete beams were predicted by means of creep transformed-section method, It is found that the existing of CFRP laminates is insignificant to the long-term deflection of concrete beams. Parameters were analysed on beams strengthened with CFRP laminates. The long-term sectional stress were analysed on R.C beams, the theoretical values agree well with the test date. It is preferable to predict the long-term deflection of rectangle concrete beams according to upstate design code.（4） Long-term behaviors were tested for 1001 days on thin-walled concrete box girder prestressed with CFRP tendons under uniform load. The strain of tensile steel bars would change relative small under long-term sustained load, the strain of compressional steel bars would change relative big, strain distribution of top flange would assume uniform trend along with time growth. Calculating the characteristic crack width according to upstate code JTG D62-2004, the property coefficient which related to the members C₃=1.25 is suggested. Calculating the maximum crack width according to upstate code GB 50010-2002, the property coefficient which related to the membersα_cr =2.7 is suggested, so the theoretical crack width would be agree well with the test date. The stress and strain distribution rule of prestressed concrete box girder under sustained uniform load was analyzed by creep transformed-section method, the theoretical predicted values agree well with the test date. By means of bilinear method and the sectional curvature method, the long-term deflection of prestressed concrete box girder was predicted. The actual increscent coefficient of mid-span deflection for 1001 days would bigger than that prescribed by upstate code of 18.5%. The increscent coefficient of long-term deflectionη_θ=2.45 is suggested, so the predicted long-term deflection would be agree well with the test date.（5）Long-term behaviors were tested for 1006 days on reinforced concrete continuous box girder under uniform load. The strain of tensile steel bars would change relative small, the compressional strain of steel bars and concrete would change relative big under sustained load, and the strain increase at mid-span section would bigger than that at mid-supported section. The strain distribution of top flange would assume uniform trend along with time growth. The internal force redistribution laws of the experimental model were tested for 1006 days, the theoretical values agree well with the test date. By modifying the relative parameters to upstate design code, the theoretical crack width at dominant sections would agree well with actual values. The actual long-term deflection at mid-span would be bigger than theoretical values prescribed by upstate design code of 11.4%.更多还原