30 m先张预应力双T梁抗弯性能足尺模型试验研究

Full-Scale Experimental Test on Flexural Behavior of a 30 m-Long Pretensioned Concrete Double-Tee Girder

为研究新型跨径30 m先张预应力混凝土双T梁的力学性能,设计制作了1孔计算跨径28.64 m、梁高1.6 m、顶板宽3.2 m的先张预应力双T梁试件(采用C60高性能自密实混凝土、混合配置了直线与折线预应力筋),同时开展了从预制到加载的全过程抗弯性能足尺模型试验。试验采用先“梁上堆载”、后“跨中千斤顶集中加载”的两阶段加载方案,设置多种内埋、外置传感器,并采用非接触式数字图像相关技术,对梁体内力、梁体竖向位移及腹板全场变形进行测量。试验结果表明:30 m先张预应力双T梁具有良好的抗弯力学性能,以及较好的刚度、抗裂性和承载力,满足规范要求;梁体开裂后抗弯刚度下降不明显,且在卸载后预应力可恢复梁体大部分竖向位移;建议在结构设计中通过加强梁端局部配筋提高抗裂性,还可进一步优化截面形式、配筋形式和高跨比,发挥高性能先张预应力双T梁的经济技术优势。

To study the mechanical behavior of a newly developed 30 m pretensioned concrete double-tee girder,a pretensioned concrete double-tee girder specimen was designed and prefabricated,of which the dimension is 28.64 m in span length,1.6 m in height,and 3.2 m in width of the flange(self-compacting concrete of grade C60 and pretensioning with both straight and deflected strands were used).Meanwhile,a full-scale test on its flexural behavior was conducted from the prefabricated stage to the loading stage.The methods for applying the test load include placing dozens of premade concrete blocks on the top of the beam,and loading with a hydraulic jack at the midspan.The instruments for measuring the stress and the deformation of the girder include a variety of embedded and external strain sensors,and the digital image correlation(DIC) cameras for full-field deformation.The test results show that the pretensioned double-tee girder can meet the requirements of the current bridge design codes in terms of stiffness,crack-resistance,and ultimate flexural strength.In addition,the reduction of flexural stiffness after cracking is not significant,and the major vertical displacement after unloading will be restored due to the prestressing effect.It is suggested that the crack resistance should be increased by adding local reinforcement at the beam end,and the section form,the reinforcement layout and the height-span ratio could be further improved to exhibit the economic and technical advantages of high-performance pretensioned double-tee girders in practice.