Box type baseboard prestress concrete variable cross-section box girder bridge and construction method thereof

Abstract

The present invention belongs to the field of civil engineering bridge technology, and discloses a box-type baseplate prestressed concrete non-uniform box beam bridge. It is characterized by that the rectangular solid baseplate of box beam bridge is remade into the form of box. Said invention also provides its concrete structure characteristics. Its structure includes baseplate box top plate, horizontal anchor plate and box beam, they can be in-situ case together, and formed into one whole body. Said bridge has high structure whole body rigidity, small deflection and strong resistance to shear, and its crossing capacity also can be greatly raised.

Description

technical field [0001] The invention belongs to the technical field of civil engineering bridges, and in particular relates to a prestressed concrete variable-section box girder bridge with a box-shaped floor and a construction method thereof. Background technique [0002] Long-span prestressed concrete variable-section box-girder 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. As shown in Figure 1, it is a schematic structural diagram of a continuous rigid frame bridge. The main girder between the piers 6 and its bottom plate 1 are arched, and the height of the girder at mid-span is smaller than the height of the fulcrum at the 6 piers. [0003] The prior art long-span prestressed concrete variable-section box girder bridges have the following problems of unreasonable structure and stress. The larger the span, the more ser...

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Problems solved by technology

Although the thickening of the web 2 and the bottom plate 1 can solve their stress requirements, the contribution to the stiffness of the beam body does not increase the beam height. After increasing the beam height, the stability of the web 2 will decrease, and the web 2 can be thickened, but Further increase the self-weight, increase the downward radial force of the positive moment bundle in the high span of the beam, and further increase the downward radial force. Therefore, in the existing technology, the large-span prestressed concrete variable-section box girder bridge needs to increase the span by enlarging the traditional box-chamber structure. Beam height, thickened web 2 and bottom plate 1 have relatively large negative effects

[0005] (2) The downward radial force of the floor cable 5 generates shear force along the bridge direction at the corresponding floor 1 position. The bottom plate 1 in the mid-span is relatively thin, generally 25-40 cm. The transverse reinforcement is configured according to the structure. If the radial force is too large, it will easily lead to shear cracks along the bridge direction in the bottom plate 1 of the middle span, which will seriously lead to the cracking and damage of the bridge bottom plate 1.

[0006] (3) The downward radial force of the floor cable 5 directly leads to the tension of the web 2 in the corresponding section, which can easily lead to the main tensile stress cracks in the web 2. Usually, such defects are more common in the range from L / 4 section to L / 2 section , related to this, the beam height in the range from L / 4 section to L / 2 section is generally small, and it is difficult to control the vertical prestress. If the vertical effective prestress is unreliable, the disease will be aggravated

[0007] (4) Because the floor cable 5 needs to be anchored at the junction of the web 2 and the bottom plate 1 due to structural requirements to shorten the force transmission route, the anchorage area of ​​the floor cable 5 of a long-span bridge is usually from near the mid-span to near the L / 8 section. The positive bending moment zone of the variable cross-section box girder bridge constructed by the long-span cantilever pouring method is usually in the interval from the L / 4 section to the mid-span L / 2 section. The bending moment is small or negative. In order to ensure the positive bending moment force in the mid-span and the needs of the anchorage structure, the floor cable 5 arranged between the L / 4 section and the L / 8 section is unfavorable to the force of this section, and the L / 4 section to L / 8 section 8 The cross-section beam is tall, the eccentricity is large, and the downward radial force is the largest, so the negative effect is large

[0008] (5) The downward radial force of the floor cable 5 directly leads to the mid-span deflection

[0009] (6) The positioning of the arched floor cable 5 is difficult, the construction is not easy to control, the prestress loss of the curved cable is large, and it is uneconomical

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