CN-117071432-B - Construction method for crossing existing overpass by cast-in-situ box girder

CN117071432BCN 117071432 BCN117071432 BCN 117071432BCN-117071432-B

Abstract

The invention discloses a construction method for a cast-in-situ box girder to span an existing overpass, which comprises the following steps of firstly, construction preparation, namely, foundation treatment, template processing and reinforcement processing, secondly, building and reinforcement construction of a full-span scaffold, firstly, building the scaffold, installing a bottom die and an outer side plate of the box girder after the building of the scaffold is completed, prepressing the scaffold, adjusting the elevation of the bottom die according to the condition after the prepressing is completed and unloading, and finally installing an inner side die and a top plate bottom die of the box girder, thirdly, pouring the box girder, curing the box girder after the full-section pouring of the box girder, tensioning when the concrete strength reaches 85% of the design strength, and finally grouting, and fourthly, dismantling the scaffold. The disc buckle type full-hall scaffold is used for reinforcing the existing highway bridge, and then the disc buckle type full-hall scaffold is erected on the top of the existing highway bridge to serve as a cast-in-place scaffold, so that the disc buckle type full-hall scaffold is convenient to install and dismantle, and the construction period can be saved.

Inventors

XIE WENXIANG
YIN LUJUN
DAI DEYI
ZHANG XIANZHE
WU JIANHUA
WANG SHUQI
LIANG ZHENYE
LIU YIFEI
CHEN JIYAN
FAN YUANPING

Assignees

湖北经济学院

Dates

Publication Date: 20260505
Application Date: 20230420

Claims (7)

1. The construction method for the cast-in-situ box girder to span the existing overpass is characterized by comprising the following steps: the construction preparation stage comprises the treatment of a foundation, the processing of a template and the processing of reinforcing steel bars, wherein when the foundation is treated, a 20-number I-steel is longitudinally paved below a scaffold base on a bridge, a 20cm multiplied by 5cm wood plate is transversely arranged below the I-steel, the wood plate is arranged at a hollow slab web of an existing overpass, an under-bridge scaffold is also supported at the hollow slab web of the existing overpass, so that the existing overpass only bears the pressure in the vertical direction, and the construction load is directly transferred to the under-bridge foundation from the upper part of the bridge; Setting up a full-hall scaffold, installing a bottom die and an outer side plate of a box girder after the scaffold is set up, and carrying out graded loading pre-pressing on the scaffold, adjusting the elevation of the bottom die of the box girder according to the condition after the pre-pressing is finished and unloading, and finally installing an inner side die and a top plate bottom die of the box girder, wherein after the scaffold is set up, a plurality of elevation control points are also measured and discharged, then a wire is taken, a bottom bracket is arranged, a tray buckle scaffold is arranged on the bottom die, and an adjustable top bracket is arranged at the upper opening of a vertical rod of the scaffold, and I-steel is paved on the adjustable top bracket, wherein the adjustable top bracket is used for adjusting the height of the scaffold and dismantling the box girder template, and the adjustable range of the adjustable top bracket is about 35 cm; The third step, pouring the box girder, curing the box girder after pouring the box girder on the full section, tensioning when the concrete strength reaches 85% of the design strength, and grouting; And step four, dismantling the scaffold, wherein the dismantling sequence comprises dismantling the inner mold, dismantling the outer side mold, dismantling the top plate bottom mold, dismantling the falling frame, dismantling the bottom mold and dismantling the scaffold.
2. The construction method for the cast-in-situ box girder to span the existing overpass is characterized in that in the second step, when the scaffold is erected, the structural form of the disc buckle scaffold is determined to be that the scaffold below 10m is provided with a scissor support respectively at every 5 rows of transverse uprights and every 5 rows of transverse uprights, the scaffold above 10m and below 15m is provided with a scissor support respectively at every 4 rows of transverse uprights and every 4 rows of transverse uprights, and the scaffold above 15m and below 20m is provided with a scissor support respectively at every 3 rows of transverse uprights and every 3 rows of transverse uprights.
3. The construction method for crossing an existing overpass by using a cast-in-situ box girder according to claim 1, wherein in the second step, the adjustable range of the bottom bracket is 25cm.
4. The construction method for the cast-in-situ box girder to span the existing overpass according to claim 1, wherein in the second step, the scaffold pre-compaction is carried out by sand bag and sand load.
5. The construction method for the cast-in-situ box girder to span the existing overpass according to claim 1, wherein in the second step, when the inner side mould of the box girder is installed, the concrete process sequentially comprises the steps of binding bottom side plate reinforcing steel bars, installing corrugated pipes, penetrating steel strands, supporting the inner side mould, reserving a manhole and binding a top plate reinforcing steel bar.
6. The construction method for the cast-in-situ box girder to span the existing overpass as claimed in claim 1, wherein in the fourth step, the dismantling time of the scaffold is set to be after the box girder concrete reaches the design strength, the steel strands are tensioned, and the grouting and the sealing of the pore canal are carried out.
7. The construction method for crossing the existing overpass by using the cast-in-situ box girder according to claim 1, wherein in the fourth step, the scaffold is removed as follows: A. Unloading by unscrewing the bolt of the adjustable jacking through a spanner, so that the bottom die is separated from the bottom of the box girder; B. removing connecting bolts between the bottom die and the side die and between the bottom die and the bottom die; C. Removing the flange plate and the side die template by using a crane, manually dividing and moving the bottom die to the position of the flange plate, and then hanging the bottom die to the ground by using the crane; D. Dismantling the I-steel and the adjustable jacking; E. Sequentially removing the scaffold with the disc buckles from top to bottom; F. and moving the removed scaffold to the next construction span for construction.

Description

Construction method for crossing existing overpass by cast-in-situ box girder Technical Field The invention relates to the technical field of bridge construction, in particular to a construction method for crossing an existing overpass by a cast-in-situ box girder. Background When the cast-in-situ box girder and the existing highway bridge are crossed, the cast-in-situ box girder needs to span the bridge, but cannot damage the existing highway bridge, and an effective method capable of saving resources, reducing energy consumption and saving construction period is needed to be found, so that the problem of crossing the cast-in-situ box girder of the existing highway bridge is solved. The existing main method adopts a few scaffolds of steel pipe piles to span the existing highway bridge, but the method has the defects of higher cost, difficult disassembly (heavier structure), larger temporary structure deflection (larger span) and longer construction period. Disclosure of Invention The invention aims to provide a construction method for crossing an existing overpass by using a cast-in-situ box girder, which solves the problems encountered in the actual use. In order to achieve the above purpose, the present invention provides the following technical solutions: a construction method for crossing an existing overpass by a cast-in-situ box girder comprises the following steps: the construction preparation stage comprises the steps of foundation treatment, template processing and reinforcing steel bar processing; Setting up and reinforcing construction of a full scaffold, namely setting up the scaffold, installing a bottom die and an outer side plate of the box girder after the scaffold is set up, pre-pressing the scaffold, adjusting the elevation of the bottom die according to the condition after the pre-pressing is unloaded, adapting to the construction requirement of the current bridge, and finally installing the inner side die and the top plate bottom die of the box girder; pouring the box girder, curing the box girder after pouring the box girder on the full section, tensioning when the concrete strength reaches 85% of the design strength, and grouting; And fourthly, dismantling the scaffold, wherein the dismantling sequence comprises dismantling the inner mold, dismantling the outer side mold, dismantling the top plate bottom mold, dismantling the bottom mold by falling frames and dismantling the scaffold. Preferably, in the first step, when the foundation is treated, 20I-steel is longitudinally paved below the scaffold base on the bridge, a 20X 5cm wood board is transversely arranged below the I-steel, the wood board is arranged at the web of the hollow slab of the original viaduct, and the scaffold under the bridge is also supported at the web of the hollow slab of the original highway bridge, so that the original highway bridge only bears the pressure in the vertical direction, and the construction load is directly transferred from the bridge to the foundation under the bridge. Preferably, when the scaffold is erected in the second step, the structure form of the disc buckle type scaffold is determined, a scaffold with the diameter of less than 10m is provided with a scissor support respectively in every 5 rows of transverse upright posts and every 5 rows of transverse upright posts, a scaffold with the diameter of more than 10m and less than 15m is provided with a scissor support respectively in every 4 rows of transverse upright posts and every 4 rows of transverse upright posts, and a scaffold with the diameter of more than 15m and less than 20m is provided with a scissor support respectively in every 3 rows of transverse upright posts and every 3 rows of transverse upright posts. Preferably, after the scaffold in the second step is erected, measuring and releasing a plurality of elevation control points, then carrying out wire arrangement, arranging a bottom bracket, installing a tray-buckled scaffold on the bottom bracket, installing an adjustable top bracket at the upper opening of a vertical rod of the scaffold, wherein the adjustable top bracket is used for adjusting the height of the scaffold and removing a template, the adjustable range of the adjustable top bracket used by the scaffold is about 35cm, and the adjustable range of the adjustable bottom bracket is 25cm. And preferably, the scaffold pre-pressing in the second step adopts sand bags and sand carriers to pre-press the load. The concrete process of the method comprises the steps of binding bottom side plate steel bars, installing corrugated pipes, penetrating steel strands, supporting the inner side mold, reserving a manhole and binding top plate steel bars. And preferably, after the prepressing in the second step is finished, the elevation of the bottom die is adjusted in time, and the box girder steel bar and concrete construction is carried out. And (3) the scaffold is removed in the step four, namely, after the concrete of the box