Structural layering of plastic bellows


   Due to the low strength and elastic modulus of plast […]

   Due to the low strength and elastic modulus of plastic itself, there is no adhesion between plastic and cement slurry and concrete, so there is an objective weak layer along the bellows interface in the structure. For structures with densely distributed linear prestressed beams at the same height of the cross-section, structural delamination will occur at the height of the cross-section.
  In the construction of plastic bellows, if the prestressed beams deviate in the length direction, a large transverse tensile stress will occur.
  During pre-stressing, if the pre-stress is large during the construction phase, transverse tensile stress will also occur due to the influence of the material Poisson's ratio u. When these two stresses are superimposed, it is very likely that the concrete cross-section will be separated along the plane and cracks will occur. In severe cases, the surface concrete may peel off.
  The prestressed holes were vibrated, displaced and floated during construction, and the placement of the common steel reinforcement bars on the upper and lower layers was seriously insufficient. The surface of the exposed corrugated pipe is clean after peeling off the concrete, and the unbonded concrete shows that the prestressed plastic bellows and the concrete have basically no adhesion. The combination of the above factors causes the local transverse main tensile stress of the concrete on the floor to exceed the ultimate tensile strength of the concrete, causing the concrete to burst downward. Later, the bridge was repaired by vertically implanting anti-collapse transverse steel bars, pouring C60 grout, and supplementing prestressed beams.

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