A prestressed concrete variable section box bridge and its construction method

Abstract

The invention discloses a prestressed concrete variable cross-section box bridge. An upwardly tilted or bent anchoring plate is arranged in the longitudinal direction of a box beam in the direction from the midspan to a bridge pier in and above the corresponding beam depth position of a bottom plate in the midspan position; the anchoring plate is integrated with the bottom plate at the section from the midspan to the 3L / 8 cross section, and the remaining positions are separated; and a prestressed bottom plate cable is arranged in the anchoring plate in an upward bending way. At the same time, the invention provides a construction method of the bridge, and the construction method comprises the steps as follows: carrying out cantilever cast-in-situ construction on the sections of the anchoring plate and the box beam; or delaying for a construction period and carrying out cast-in-situ construction on a supporting frame or a lifting frame in a box; and applying a transverse prestress force to the transverse reinforcement ribs of the anchoring plate for construction before tensioning the prestressed bottom plate cable. According to the bridge and the construction method provided by the invention, the prestressed bottom plate cable is arranged in an upward bending way to provide an upward radial force for counteracting a downward action force applied by a secondary dead load or the like, so that the deflection deformation caused by the action force after a main beam is closed can be avoided, the construction control process is easy, and the bearing capacity can be increased.

Description

technical field [0001] The invention relates to the technical field of civil engineering bridges, in particular to a prestressed concrete variable-section box bridge and a construction method thereof. Background technique [0002] Long-span prestressed concrete variable-section box bridges are widely used bridge types at present, and continuous beams and continuous rigid frame bridges are the most common, and they are often constructed by hanging basket cantilever casting method. [0003] Such as Figure 1 to Figure 1-2 as shown, figure 1 It is a schematic diagram of the structure of a long-span prestressed concrete variable-section box bridge with floor cables bent down, Picture 1-1 for figure 1 Schematic diagram of the structure of the A-A sectional plane of the bridge shown, Figure 1-2 for figure 1 Schematic diagram of the structure of the B-B sectional plane of the bridge shown. [0004] The commonly used cross-section form of this variable-section box girder b...

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Problems solved by technology

[0013] (2) The downward radial force of the floor cable 05 also directly causes the web 02 in the corresponding section to be stretched, which can easily lead to the main tensile stress cracks in the web 02. Usually, such defects are more common in the range from L / 4 section to L / 2 section. Common, related to this, generally the beam height from L / 4 section to L / 2 section is small, and the vertical prestress is difficult to control. If the vertical effective prestress is unreliable, the disease will be aggravated

[0015] (4) The downward radial force of floor cable 05 directly causes the mid-span deflection

[0016] (5) The positioning of the arched floor cable 05 is difficult, the construction is not easy to control, the prestress loss of the curved cable is large, and it is uneconomical

[0017] (6) The downward radial force of floor cable 05, the dead load of the first and second phases, and the load of the driveway are all downward, which intensifies the shrinkage and creep effect of concrete, resulting in continuous downward deflection during the mid-span operation period

[0021] However, with such a setting, the following problems will arise: (1) The floor cables 15 of the long-span prestressed concrete variable-section box bridge are arranged horizontally and the bending moment of the long-span prestressed concrete variable-section box bridge using the cantilever construction method The envelope diagram cannot be completely matched, and there is a certain deviation

(3) The prestressed concrete variable-section box bridge with floor cables 15 arranged horizontally cannot provide upward component force and cannot balance the downward force of the second phase dead load and driveway load

(4) There is no control method to eliminate or reduce the deflection deformation of the main girder caused by the second-stage dead load, and the deformation of the main span is difficult to control after closing

(5) On bridges with two-way longitudinal slopes in the main span, the downward radial force of the floor cables 15, the first-phase and second-phase dead loads, and the driveway loads are all downward, which intensifies the concrete shrinkage and creep effect, resulting in certain continuous downward

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