Research on Concrete Vertical Precompressive Stress Field at Webs of Box Girder Bridge

Abstract

Based on Fourier series, an analytic formula for analyzing the prestress in the web of box girder with single bar was deduced through simplifying the action of single vertical prestress bar as a couple of concentrated forces with equal value but opposite direction acting on a thin rectangular board with infinite length. The vertical compress stress distribution in the web gotten from the analytic solution basically agrees with that from the ANASYS finite element solution. The analysis result indicates that the vertical compressive stress distribution in the webs meets the normal distribution and small tensile stresses are created aside the tendons. Field tests on a real bridge also demonstrate that the analytic formula is adaptable to the solution of the superposition of vertical prestress in the web. Furthermore, the feature of the vertical prestressing field along the height of the web was analyzed and modifying formula was presented by introducing a compensation factor K. In addition, the μ-K curves of the webs under the action of prestressing tendons with different spacing intervals were presented.