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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 location of the precast yard of the beam and slab precast yard shall fully consider the size, quantity and specific erection requirements of the precast beam and slab in the bid section, based on the principle of convenience, rationality, safety, economy and meeting the construction period.
For projects in plain areas, precast sections are set up for centralized precast beams and slabs, and the precast beam yard is large in scale.
The site is hardened with cement concrete, with complete drainage system, scientific and reasonable functional zoning, eye-catching and beautiful large publicity signs, clean and tidy site, and orderly construction.
For mountainous projects, due to factors such as inconvenient transportation and difficult site selection for large sites, precast beams and slabs are generally prefabricated by their respective contract sections.
Each contract section shall construct the prefabrication yard according to the local conditions and the “standardization” management regulations.
The functional areas such as the reinforcement fabrication area, beam fabrication area, beam storage area and material storage yard shall be well organized.
Large precast beam yard is open and tidy, with clear functional zoning and high degree of factory construction.
Due to the terrain limitation, 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.
❑ Process flow of installing prefabricated beam reinforcement by jig frame method: 1.
Fabricate jig frame according to design parameters of prefabricated beam slab reinforcement skeleton; 2.
Install the top plate and bottom web reinforcement on the jig frame; 3.
Install protective layer cushion block; 4.
Lift the bottom web reinforcement framework into the formwork; 5.
Install the internal formwork and adjust the cushion block of the protective layer for the second time; 6.
Lift the top plate reinforcement framework in place and connect it with the bottom web reinforcement framework as a whole.
The jig frame method has the following advantages: 1.
Simple operation and convenient construction; 2.
Unified specification and quality assurance; 3.
Parallel operation, high construction efficiency; 4.
Do not occupy the precast pedestal, reduce the possibility of compression settlement of the precast pedestal (especially the pedestal set in the soft foundation area), so as to ensure the accuracy of the preset camber of the precast beam and slab.
Prefabricated small box girder reinforcement shall be installed by jig frame method.
After being installed and formed on the special jig frame for the reinforcement of the top plate of the small box girder, it shall be hoisted and spliced with the reinforcement framework of the bottom web to form a whole.
The prefabricated box girder reinforcement skeleton shall be installed on the jig frame and then hoisted into the formwork as a whole.
❑ Installation of prefabricated beam reinforcement by positioning frame method Installation of prefabricated beam reinforcement by positioning frame method has been widely used in expressway projects under construction in our province.
The positioning frame is made according to the design parameters of the 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 the reinforcement skeleton is guaranteed.
The positioning frame shall be installed for the bottom web reinforcement of prefabricated small box girder.
The T-beam web reinforcement shall be installed on the prefabricated pedestal using the positioning frame.
Use the positioning frame to install the bottom and web reinforcement of small box girder on the prefabricated pedestal.
❑ The horizontal reinforcement positioning process of the top plate adopts the pull wire method to install the horizontal reinforcement of the prefabricated small box girder or T-beam top plate, which can make the surface of the top plate reinforcement smooth and the lateral reinforcement sideline neat; During the prefabrication of T beam, the top plate transverse reinforcement installation limit bar shall be set at the outer edge of the side formwork top to ensure the accurate position of the top plate transverse reinforcement.
By adopting the above process, the embedded reinforcement of the wet joint of the precast beam and slab can be ensured to have a smooth alignment, which is conducive to the accurate installation of the subsequent wet joint reinforcement.
The line drawing method is used to control the longitudinal plane linetype of the embedded reinforcement of the precast beam slab flange.
The top plate reinforcement limit frame is set above the side formwork.
On the prefabricated beam slab formwork, set the limit reinforcement of the outer edge of the embedded reinforcement of the wing slab, control the position of the reinforcement in place, and ensure that the outer edge of the embedded reinforcement of the wing slab is straight.
The embedded reinforcement of wet joint shall be neat and uniform.
❑ Positioning process of embedded reinforcement for precast beam anti-collision guardrail Process of embedded reinforcement for precast beam slab anti-collision guardrail: 1.
Install the embedded reinforcement skeleton of the centrally prefabricated anti-collision guardrail in place according to the design requirements; 2.
Two longitudinal positioning bars shall be bound on the upper part of the embedded bars of the anti-collision guardrail to improve the anti deformation stiffness of the upper part of the bars and ensure the spacing of the bars.
3.
Bind and fix the longitudinal positioning reinforcement on the transverse tie rod at the top of the side formwork to prevent displacement or even toppling of the concrete reinforcement of the cast beam slab.
This process effectively eliminates the common quality problems of large displacement and poor spacing of the embedded reinforcement of the anti-collision guardrail.
The embedded reinforcement of the completed prefabricated side beam anti-collision guardrail is neat and uniform, ensuring the accuracy of the installation position of the structural reinforcement of the subsequent anti-collision guardrail from the source.
Two longitudinal positioning bars shall be bound on the upper part of the embedded reinforcement.
Bind 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 slab of the hollow slab is positioned during the prefabrication of the hollow slab.
The embedded reinforcement of the hinge joint and the positioning frame of the embedded shear reinforcement of the top slab are set so that the embedded reinforcement will not be deformed or displaced during the concrete pouring of the beam slab, ensuring the accuracy of the embedded reinforcement, thus ensuring that the subsequent deck slab and hinge joint reinforcement can be accurately positioned according to the design requirements.
Positioning of embedded reinforcement of hollow slab top plate.
The position of the embedded reinforcement on the top surface of the beam and slab is accurate to ensure that the reinforcement of the integrated layer of the bridge deck can meet the design requirements.
❑ Accurately place the construction platform of precast beam top plate.
A removable construction platform is set on the top of the prefabricated small box girder or T-beam side formwork to facilitate the concrete pouring and vibrating of the web and top plate, as well as the slurry collection on the top plate surface, and effectively solve the problem that workers tread on the top plate reinforcement during the concrete pouring of the web and top plate, causing the deformation of the reinforcement skeleton, and even leaving footprints on the top plate surface.
The roof concrete pouring and surface mortar collection are carried out on the platform.
Prefabricated beam construction platform.
The prefabricated beam construction platform is convenient for loading and unloading.
❑ The formwork is pasted with high-quality stainless steel plate on the steel formwork of the prefabricated beam slab, which effectively improves the appearance quality of the concrete, making the concrete surface smooth and clean, with few bubbles..
