Abstract
In order to study the effect of prestressed box girder webs stresss state, determining the stress distribution within a web, research and analysis of vertical prestressed box girder, curved beam prestressed sensitivity under the web. Establishing the finite element model of the box girder web vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L / 4 section of the web. Calculation and analysis of curved beam under bending point, different bending angles and bending radius of principal stress effect on the web, Results show that the set of curved beam web when the curved beam bending stress concentration easily, appear the main tensile stress; Increase the bending radius can effectively reduce beam cross-section of web principal tensile stress, along with the rising of the next corner, principal tensile stress peak value increases gradually, thus setting bending beam, should try to reduce the bending angle.
Highlights
Working condition 3: effective vertical prestress is accounted for 30% of tension control; Working condition 4: excluding vertical prestress
Local Calculation Model The main stress of the two sections of the box girder section 2 of the root and the 1/4 sections are drawn in figure 2.Figure 3 shows the main stress vector diagram of the box girder in the area near the L/4 cross section of the bridge under different working conditions
(2) When the effective vertical prestress is kept at more than 60%, the minimum principal stress is basically above 2.0 Mpa, so the calculation formula of vertical prestress in the specification is reasonable by multiplying the reduction factor of 0.6
Summary
Vertical prestress can effectively resist the main tensile stress and shear stress of the box girder. Local Calculation Model The main stress of the two sections of the box girder section 2 of the root and the 1/4 sections are drawn in figure 2.Figure 3 shows the main stress vector diagram of the box girder in the area near the L/4 cross section of the bridge under different working conditions. Main Stress Vector Diagram of Vertical Web under Different Working conditions. (4) In the condition of excluding vertical prestress, The main tensile stress is generated along the entire cross-section of the abdominal plate, If the stress loss of prestressed tendon and the shrinkage creep effect of concrete are considered, the main tensile stress may exceed the limit, which will cause the web to crack. L/4 section web easier to crack, the box girder web plate cracking phenomenon is consistent with engineering practice [7] [8]
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