用能量法分析体外预压力对简支梁动力性能的二阶效应

SECOND ORDER EFFECT OF EXTERNAL TENDON COMPRESSION ON DYNAMIC BEHAVIOR OF SIMPLY SUPPORTED BEAM BY ENERGY METHOD

精细地考虑了体外筋变形中的二阶项,用能量法推导了体外预应力梁的自振频率,阐明了体外预压力对梁自振频率的效应.计算结果表明:体外预压力压缩软化效应的影响系数,主要取决于转向座的数量.无转向座时,体外筋偏心距损失为最大,影响系数为1,体外预压力的效应与外轴力的效应相同.随着转向座数量的增加,偏心距损失减小,体外筋接近于无粘结筋,影响系数降低至接近于0,即接近于无粘结筋预压力的零效应.当梁转向座的数量≥2时,由于影响系数显著地小于1,可以忽略体外预压力的压缩软化效应.随着体外筋面积和偏心距的增加,梁的第1自振频率增大.不过,体外筋对其他阶自振频率的影响很小,可以忽略.

Precisely considering the second order term in externally prestressed beam is derived by energy method. external tendon deformation, the natural frequency of It illustrates the effect of external tendon compression on beam natural frequency. The calculation results also show that the influence coefficient stating the softening effect of the external tendon compression mainly depends centricity loss is maximum, the influence coefficient is 1 on the number of deviators. Without deviator, the ec- and the effect of external tendon compression is the same as that of the external axial force. As the number of deviators increases, the eccentricity loss decreases, external tendon is close to the unbonded tendon, and the influence coefficient decreases to near zero, which is close to nought effect of unbonded tendon compression. For the beam with two or more deviators, due to the influ- ence coefficient significantly less than 1, the external tendon compression softening effect is negligible. With the increase of the eccentricity and tendon area, the first natural frequency grows up, but the effect of the external tendon on other frequencies is negligible.