(2) Selection of closing temperature. The relationship between air temperature and beam temperature is tested and analyzed, and the closing time is determined, which provides the basis for selecting the locking mode of closing section. Generally, the low temperature should be turned off, and it should be turned off at night in summer. Cover with straw bags, etc. And strengthen the curing of joint concrete, so that the concrete is in a state of heating and compression in the early hardening process.
(3) Selection of concrete for closure section. The concrete in the closure section is one grade higher than that in the beam, which requires early strength. It is best to use micro-expansive concrete, which requires special mix design. When pouring, it should be carefully vibrated and maintained, and the prestressed tendons should be tensioned in time to prevent cracks in the concrete in the closed section.
(4) The locking of the closed section shall be carried out quickly and symmetrically. First, weld (or bolt-connect) one end of the external rigid support with the embedded part at the beam end, then prop up the internal rigid support for welding, and then quickly connect the other end of the external rigid support with the beam, and the temporary prestressed beam should also be tensioned quickly. After the closure section is locked, the consolidation constraint on one side is immediately released, so that one end of the beam can freely expand and contract along the support under the connection of the closure section.
(5) In order to ensure that the concrete is always in a stable state during the construction of the closure section, if necessary, a counterweight (or ballast) equal to the weight of concrete can be added at each cantilever end before pouring, and the concrete can be loaded and unloaded according to the axis of the beam.
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