全预应力梁振动频率的理论分析与试验研究

进行了5根全预应力梁的动力试验,试验结果表明:全预应力梁的固有频率随着预应力的增加而增加,这与经典的轴力作用下各向同性材料梁的理论分析结果完全相反。为此,仍将全预应力梁视为各向同性材料,但对梁的计算刚度进行了修正,将预应力筋对梁的作用视为梁的内力,并按一般简支梁频率公式进行梁的频率计算。计算结果表明:提出的计算公式和方法,在进行梁的一阶频率计算时误差较小,而且能很好地反映出梁的频率随预应力的增加而增加的变化趋势,比已有的计算公式和方法更适用;二阶频率的计算误差稍大,也具有一定的适用性;三阶及以上频率的计算尚存在较大误差,这有待今后进一步的开展研究工作。

EXPERIMENTAL AND THEORETICAL RESEARCH ON VIBRATION FREQUENCY OF FULL-PRESTRESSED CONCRETE BEAM

Dynamic tests of five full-prestressed concrete beams were carried out, the results of which indicated that the frequencies of those beams grow in step with prestressing force. It’s opposite to the analysis of dynamic characteristic of isotropic beams subjected to axial compressive force. In this paper, considering those beams as isotropic, the stiffness of full-prestressed concrete beams was modified. Considering prestressing force as internal force of beams, the natural frequency of the beams were calculated using the formula of frequencies for simply-supported beams It indicated that the error of the first frequency calculated by the modified stiffness was small. It also can reflect the variant tendency that frequencies increase with prestressing force, and it is more suitable than other modified stiffness methods. The error of the second frequency is larger than the first frequency, but is still acceptable. Large error exists for the third and high-order frequencies, which deserves further research.