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The construction of bridge prefabricated components involves many aspects of bridge engineering, and its standardized construction technology must be strictly implemented in the construction process of the project.
What should be done on the specific construction site? Let’s have a look! ▎ the size, quantity and specific erection requirements of precast beams and slabs in the bid section shall be fully considered in the site selection of beam and slab Prefabrication Yard, based on the principles of convenience, rationality, safety, economy and meeting the construction period.
For projects in plain areas, centralized precast beams and slabs are set in precast sections, and the scale of Precast Beam Yard is large.
The site is hardened with cement concrete, the drainage system is perfect, the functional zoning is scientific and reasonable, the large-scale publicity signs are eye-catching and beautiful, the site is clean and tidy, and the construction is orderly.
For mountain projects, restricted by factors such as inconvenient transportation and difficult site selection of large sites, precast beams and slabs are generally prefabricated by their contract sections.
Each contract section shall adjust measures to local conditions and build a Prefabrication Yard in accordance with the “standardized” management regulations.
The functional areas such as reinforcement fabrication area, beam making area, beam storage area and stock yard are well-organized and orderly.
The large precast beam yard is open and tidy, with clear functional zoning and high degree of industrialized construction.
Limited by the terrain, with the approval of the construction unit, the Prefabrication Yard is set on the subgrade, and the layout of the yard is reasonable and orderly.
▎ installation of precast beam reinforcement by moulding bed method process flow of precast beam reinforcement installation by moulding bed method: 1 The jig frame is made according to the design parameters of precast beam and slab reinforcement framework; 2.
Install the top plate and bottom web reinforcement on the jig frame respectively; 3.
Install protective layer cushion block; 4.
Hoist the bottom web reinforcement framework into the formwork; 5.
Install the internal mold and adjust the protective layer cushion block twice; 6.
Hoist the top plate reinforcement framework in place and connect it with the bottom web reinforcement framework as a whole.
The installation of precast beam reinforcement framework by jig frame method has the following advantages: 1 Simple operation and convenient construction; 2.
Uniform specification and quality assurance; 3.
Parallel operation, high construction efficiency; 4.
Do not occupy the prefabricated pedestal, Reduce precast pedestal (especially the pedestal located in the soft foundation area) may be subject to pressure settlement, so as to ensure the accuracy of the preset camber of the precast beam and slab.
The prefabricated small box girder reinforcement is installed by the moulding bed method.
After being installed and formed on the special moulding bed for the top plate reinforcement of the small box girder, it is hoisted and spliced with the bottom web reinforcement skeleton as a whole.
The prefabricated box girder reinforcement skeleton is installed and formed on the moulding bed, and then it is hoisted into the formwork as a whole.
▎ positioning frame method The method of installing precast beam reinforcement positioning frame to install precast beam reinforcement has been widely used in expressway projects under construction in our province.
The positioning frame is made according to the design parameters of prefabricated beam and slab reinforcement, and the reinforcement is installed and bound on the positioning frame.
The operation is simple, the reinforcement position is accurate, and the installation quality of reinforcement framework is guaranteed.
Installation of positioning frame for bottom web reinforcement of prefabricated small box girder.
Install T-beam web reinforcement on precast pedestal with positioning frame.
On the precast pedestal, the positioning frame is used to install the reinforcement at the bottom and web of the small box girder.
▎ the horizontal reinforcement positioning process of roof adopts the pull wire method to install the horizontal reinforcement of precast small box girder or T-beam roof, which can make the surface of roof reinforcement smooth and the side line of horizontal reinforcement neat; During the prefabrication of T-beam, the transverse reinforcement of top plate shall be set at the outer edge of the top of side formwork, and the limit strip shall be installed to ensure the accurate position of transverse reinforcement of top plate.
By adopting the above process, the linear smoothness of embedded reinforcement in wet joint of precast beam and slab is ensured, which is conducive to the accurate installation of subsequent wet joint reinforcement.
The longitudinal plane line shape of embedded reinforcement in precast beam slab flange is controlled by stay wire method.
The top plate reinforcement limit frame is set above the side formwork.
Set the limit reinforcement at the outer edge of the embedded reinforcement of the flange on the precast beam and slab formwork, control the position of the reinforcement in place, and ensure the straightness of the outer edge of the embedded reinforcement of the flange.
The embedded reinforcement of wet joint shall be neat and uniform.
▎ positioning process of embedded reinforcement of precast beam anti-collision guardrail process of embedded reinforcement of precast beam slab anti-collision guardrail: 1 Install the embedded reinforcement framework of the centrally prefabricated anti-collision guardrail in place according to the design requirements; 2.
Bind two longitudinal positioning reinforcements on the upper part of the embedded reinforcement of the anti-collision guardrail to improve the deformation stiffness of the upper part of the reinforcement and ensure the spacing of the reinforcement.
3.
Bind and fix the longitudinal positioning reinforcement on the transverse tie rod at the top of the side formwork to prevent the displacement or even dumping of the cast beam and slab concrete reinforcement.
By adopting this process, the common quality problems of large displacement and poor spacing of embedded reinforcement of anti-collision guardrail are effectively eliminated.
The embedded reinforcement of prefabricated side beam anti-collision guardrail is neat and uniform, which ensures the accuracy of the installation position of structural reinforcement of subsequent anti-collision guardrail from the source.
Bind two longitudinal positioning reinforcements on the upper part of the embedded reinforcement.
Tie and fix the longitudinal positioning reinforcement on the transverse tie rod at the top of the side formwork.
The embedded reinforcement of anti-collision guardrail shall be neat and uniform.
▎ the embedded reinforcement of the top plate of the hollow slab is positioned in the prefabrication construction of the hollow slab, and the positioning frame of the embedded reinforcement of the hinge joint and the embedded shear reinforcement of the top plate are set to prevent the embedded reinforcement from deformation or displacement during the concrete pouring of the beam and slab, so as to ensure the accuracy of the embedded reinforcement, so as to ensure that the subsequent deck slab and hinge joint reinforcement can be accurately placed according to the design requirements.
Positioning of embedded reinforcement on top plate of hollow slab.
The position of embedded reinforcement on the top surface of beam and slab shall be accurate to ensure that the reinforcement in the integral layer of bridge deck can meet the design requirements.
▎ accurately place the prefabricated beam roof construction platform.
A detachable construction platform is set on the top of the prefabricated small box girder or T-beam side formwork to facilitate the concrete pouring, vibration and slurry collection of the web and roof, and effectively solve the problem that workers trample on the roof reinforcement during the concrete pouring of the web and roof, resulting in the deformation of the reinforcement skeleton and even footprints on the roof surface.
Carry out roof concrete pouring and surface slurry collection on the platform.
Precast beam construction platform.
The precast beam construction operation platform is convenient for loading and unloading.
▎ high quality stainless steel plate is pasted on the steel formwork of precast beam and slab, which effectively improves the appearance quality of concrete and makes the concrete surface smooth and less bubbles.
The composite steel plate bottom mold pressed by ordinary steel plate and stainless steel plate not only ensures the smoothness of the bottom surface of the beam plate, but also solves the problem of bulging of the stainless steel plate; An adjustable bottom formwork is set at the end to meet the requirements of the length change of the inner and outer side beams of the curve and the angle change of the bottom surface of the support leveling wedge, which is convenient and practical.
Design drawing of adjustable bottom formwork at the end of the base.
Solid drawing of adjustable bottom formwork at the end of the base.
Stainless steel formwork outside the prefabricated beam web.
The prefabricated small box girder is assembled with stainless steel formwork.
▎ hydraulic movable side formwork prefabricated box girder side formwork adopts hydraulic movable integral formwork, which is accurately assembled in place and closely pasted with joints; The use of hydraulic movable side formwork not only improves the efficiency of formwork installation, but also greatly reduces the safety risk in the installation process compared with the traditional hoisting side formwork.
60m box girder hydraulic movable formwork.
Hydraulic movable side formwork.
The small box girder is assembled by hydraulic movable side formwork.
▎ on the basis of implementing the “three centralization” system, the prefabricated beam and slab have achieved the quality goal of “excellent inside and beautiful outside” by using high-quality formwork and improving the construction process.
The prefabricated box girder has beautiful appearance, obvious mirror effect on the outer surface of the web, and the flange edge line and the outer edge line of the reserved reinforcement are straight.
The precast beam bottom plate shall be flat, smooth and uniform in color.
The concrete in the inner cavity of the beam and slab shall be flat and dense, and the edges and corners shall be clear.
The top surface of beam and slab shall be flat, with uniform roughening and moderate roughness.
The concrete at the beam end is dense without slurry leakage.
The tensioning gear plate under the top plate has dense concrete and clear edges and corners.
▎ the anchor sealing process at the end of precast T-beam improves the anchor sealing structure of prestressed anchor head at the end of precast T-beam: 1 According to the technical requirements of anchor sealing, a circular anchor sealing slot hole with a depth of about 10cm shall be reserved at the anchor head at the beam end, and its diameter can meet the needs of tensioning jack operation; The integrated end template with anchor head mold is customized according to the size of anchor sealing slot hole.
2.
Pour T-beam body concrete at one time.
3.
After the completion of prestressed tensioning and duct grouting, the concrete around the anchor sealing slot hole shall be carefully roughened to ensure the bonding performance between the anchor sealing concrete and the beam body.
4.
Use concrete with the same strength grade as the beam body to seal the anchor..
