Problems:
①Concrete precast components are damaged during transportation.
②Concrete precast components are not stacked in a standardized manner.
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Analysis:
I. Precast Components Are Damaged During Transportation:
①During the transportation of precast components, the components are not firmly fixed, causing the to move and fall.
②Precast components are stacked with rigid pads during transportation.
③The stacking height of precast components is too high during transportation, causing damage to the components.
④The vehicle speed is too fast during transportation, and the components are broken due to vehicle bumps when encountering uneven terrain.
II. Precast components are not stacked in a standardized manner
①Precast components are stacked randomly, and the position of the horizontal precast component stacking support is unreasonable, resulting in component cracking and damage.
②The stacking rack is not rigid enough and is not firmly fixed, causing the components to fall.
③The precast components are stacked too close, and the finished product protection measures between precast components are improperly set, causing the components and the protruding steel bars to collide with each other and break.
④ The stacking site of prefabricated components at the construction site is not hardened, and there is no isolation fence around it
⑤ The stacking sequence of prefabricated components does not take into account the lifting sequence, and multiple searches affect efficiency
⑥ The stacking support pads of the composite floor are not aligned up and down, and no flexible pads are set.
Solution:
I. Construction Unit Measures To Protect Components During Transportation
① A transportation and stacking plan for prefabricated components should be formulated, and its contents should include transportation time, sequence, stacking site, transportation route, fixing requirements, stacking support pads, and finished product protection measures. There should be special quality and safety assurance measures for the transportation and stacking of large components with super height, super width, and special shapes.
② When transporting components, fixed measures should be taken to prevent the movement, dumping, deformation, etc. of components.
③ When transporting components, measures should be taken to prevent damage to the components, and protective pads should be placed at the corners of the components or where the chains contact the concrete.
④ The number of layers of prefabricated components for transportation and stacking should not exceed the limit number of layers. Generally, the number of layers of composite slabs shall not exceed 6 layers, the number of prefabricated columns shall not exceed 2 layers, and the number of stairs shall not exceed 4 layers.
⑤ The speed of the vehicle should be controlled during transportation. For uneven sections of the road, it is essential to drive at a low speed to prevent the components from being damaged by bumps.
Ii. Measures Of The Construction Unit, Precast Concrete Component Stacking Specifications
① The on-site stacking plan should be formulated in a targeted manner according to the type of prefabricated components. Generally, vertical components are placed upright, and horizontal components are stacked. The form of the stacking frame and the number of stacking layers should be clearly defined.
② The stacking frame should have sufficient strength, rigidity, and stability, and meet the anti-overturning requirements and be verified.
③ A passage with a width of not less than 0.6m should be left between the component stacks. Soft materials should be padded between the steel frame and the components to avoid collision and damage to the components.
④ The yard area should be sufficient to store the number of components on one floor. When the component yard is located on the upper part of the basement roof, the bearing capacity of the roof should be verified. If it is insufficient, the roof support reinforcement measures should be considered.
⑤ The stacking position and order of prefabricated components should take into account the supply plan and hoisting order, and should be reasonably placed according to the principle that the vertical components hoisted first should be placed on the outside and the horizontal components hoisted first should be placed on the upper layer. When the site is limited, the components can also be hoisted directly from the transport vehicle, and the stacking order of the components on the vehicle also needs to be planned in advance.
⑥ The position of the lower shelving point of the composite floor should be consistent with the position of the designed hoisting point. When prestressed horizontal components such as prestressed double T plates and prestressed hollow plates are stacked, interlayer pads should be placed according to the arch position of the components, and independent pads are generally placed at the ends of the components
⑦ The number of layers of prefabricated components is generally not more than 6 layers for composite plates, not more than 2 layers for prefabricated columns, and not more than 4 layers for stairs
