Abstract
Considering precisely the second-order deformation of external tendon, the analytical solution of natural frequencies of 2-span externally prestressed continuous beam was obtained by the energy method. The effect of external prestress compression softening is between the zero effect of unbonded prestress compression and the effect of axial outside compression and is determined by the influence coefficient ranging within 0∼1. The influence coefficient is mainly related to the number of deviators and slightly related to tendon layout. Without deviator, the influence coefficient is 1, and the effect of external prestress compression softening is the same as the effect of axial outside compression. As the number of deviators increases, the influence coefficient gradually decreases from 1 to near 0, and the effect of external prestress compression softening is close to zero effect of unbonded prestress compression. With one or more deviators, the effect of external prestress compression softening is negligible. As the eccentricity and area of tendon increase, only the first symmetric frequency increases obviously, and other frequencies almost remain unchanged. The influence of tendon layout linear transformation on the frequency is negligible.
Highlights
Prestressed concrete structure has been widely used in the strengthening of existing concrete bridges as well as in the construction of various new structures
[1, 2] and Anwar et al [3] studied the static nonlinear behavior of beam externally prestressed with steel tendon and FRP cables, and Fang [4] investigated the friction effect of externally prestressed beam
E analysis of the natural frequencies of externally prestressed supported or continuous beams is of vital importance in dynamic behavior. e natural frequency of a supported beam under axial outside compression is iπ 1 iπ 2 ωi l
Summary
Prestressed concrete structure has been widely used in the strengthening of existing concrete bridges as well as in the construction of various new structures. Hamed and Frostig [17] pointed out zero softening effect of prestress compression of bonded or unbonded tendon. Miyamoto et al [18] presented the dynamic behavior of prestressed supported beam strengthened with external tendon. Shi et al [19] adopted similar method of Miyamoto et al [18] to treat EP effect as N effect and obtained the analytical frequency expression of externally prestressed concrete continuous beam. E prestress compression does not influence the dynamic behavior It conforms with Hamed and Frostig’s [17] conclusion of zero effect of prestress compression on the natural frequencies of bonded or unbonded prestressed beams. Based on energy method, adopting the vibration modes of usual supported beam, considering precisely the second-order effect, Fang [22] analyzed the natural frequencies of externally prestressed supported beam and EP softening effect. Using the method proposed by Fang [22], adopting the vibration modes of usual continuous beam, the natural frequencies of continuous beam were analyzed, and similar conclusions are presented in this paper
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