摘要
为进一步研究长期荷载作用下预应力混凝土梁徐变应变与应力的关系，对4片预应力度值互不相同的7.5 m跨预应力混凝土简支梁加载600 d，并对跨中截面不同高度处的徐变应变进行了定时测定。通过绘制4片梁跨中截面上边缘徐变应变与相对应力值间的关系图及其徐变度时程曲线图，验证了徐变线性叠加原理。分析试验梁跨中截面不同高度处的徐变应变，指出了预应力混凝土梁在长期荷载作用下平截面假定的适用性，阐明了徐变应力重分布对不同类型的预应力梁横截面中和轴的移动规律：对全预应力梁，中和轴随持荷时间增加由梁身之外向梁身靠近，但仍在梁身之外；对部分预应力梁，中和轴沿截面高度下移，但仍在梁身之内。以平截面假定和混凝土徐变线性叠加原理为基础，建立了不同类型的预应力混凝土梁徐变应变及徐变曲率的几何模型，为工程中精确分析预应力混凝土梁的徐变效应奠定了理论基础。
Abstract
In order to study the relationship between stress and creep strain of prestressed concrete beams under long-term loading , 4 prestressed concrete beams with different prestress values were simply supported and loaded for 600 days, and the creep strain at different height in mid-span cross section of the beams were surveyed at regular time .The time-history curves of creep degree and the relationship diagram between relative stress and creep strain of the mid-span cross section of the top edge were plotted , and the creep principle of linear superposition was verified .With the creep strain measured at different height in midspan section , the assumption of plane section is demonstrated to be true for the beams under long-term loads.Moreover, the neutral axis displacement of prestressed concrete beam was characterized .For full-prestressed concrete beam , the neutral axis was outside the beam in the beginning .Then, the axis moved towards the beam as the stress redistributed due to creep, but it was still outside the beam;for partial-prestressed beams , the neutral axis was at half the height of the mid-span section , and it also moved to the bottom as stress redistributed .Based on the assumption of plane section and creep principle of linear superposition , creep strain and creep curvature geometry models were established according to partial prestressing ratios , and these models are helpful to analyze exact creep effect of prestressed concrete beams .
基金项目
国家自然科学基金(50574148)
河南省教育厅科学技术研究重点项目(12A560009)
NETL
NSTL
维普
万方数据