Reinforcement engineering is a crucial aspect of concealed construction, involving reinforcement work in various parts of a building. The quality of this work directly impacts the strength, load-bearing capacity, seismic resistance, and overall performance of reinforced concrete structures, which in turn affects the safety and durability of the entire structure. Therefore, it is essential to pay close attention to steel bar construction in different areas and adopt proper construction methods to ensure high-quality outcomes. Below are key points regarding the construction quality of steel bars in various parts, provided for your reference.
Foundation
(1) The concrete protective layer thickness for longitudinally stressed steel bars in the foundation must meet design specifications and should never be less than 40mm. If no concrete cushion layer is present, this thickness should be at least 70mm.
(2) When binding the base steel mesh, the intersection points of the two rows of steel bars around the perimeter must be firmly tied at every point. Intersection points in the middle rows may be staggered and tied, but it is critical to ensure that all stressed steel bars remain securely in place.
(3) For independent column foundations with two-way reinforcement, steel bars along the short side at the bottom should be placed beneath those on the long side. The steel mesh must be tied firmly at all intersection points.
(4) When using double-layer steel mesh for the foundation bottom slab, steel or concrete support chairs should be placed beneath the upper mesh at intervals of about 1 meter to maintain the correct steel bar position.
Pillars
(1) The bending hooks of longitudinal steel bars should face the center of the column. Positioning clamps or hoops must be installed inside the column to ensure accurate placement without deformation.
(2) For steel bars exposed at the bottom of the column, a tool-type column clamp matching the diameter of the bars should be used to secure them, facilitating proper overlap with the upper column’s steel bars.
(3) If the column’s cross-section changes, the exposed lower column reinforcement must be precisely contracted before binding the beam reinforcement.
(4) Reinforcement connecting cast-in-place columns to foundations must be firmly fixed and accurately positioned to prevent displacement of the column axis.
Walls
(1) When using double-layer steel mesh, braces (hooks) should be installed between the two layers to maintain consistent spacing.
(2) When binding steel mesh for interior and exterior walls, horizontal steel bars should be placed outside the main bars. If steel bars have 90° hooks, the hooks should face inward toward the concrete.
(3) After surveying, the main reinforcement should be bent at a 1:6 ratio according to wall or column boundaries and control lines, adjusted to the BIM model, then stirrup installation and binding can proceed.
(4) Before binding wall (or column) steel bars, high stools must be set up around the wall. All personnel should work from these stools to ensure safety during steel bar binding.
Beams
(1) Once the beam reinforcement is tied, bottom protective cushion blocks (usually made of marble) should be promptly placed. Cushion blocks should be positioned at the intersection of hoop reinforcement and main reinforcement.
(2) At beam-column nodes, where reinforcement is dense, the correct sequence is to first insert bottom reinforcement, then bind the column hoop reinforcement, and finally insert the beam reinforcement.
(3) Intersection points between main reinforcement, waist reinforcement, and hoop reinforcement must be firmly tied using screws oriented in opposite directions for upper and lower rows to prevent deformation of the beam skeleton.
(4) Binding joints are relatively weak under external forces and should be located in low-stress sections of the component. For example, in simply supported beams, tensile steel bar joints should be placed within the outer quarter spans at each end of the beam, with a minimum distance from the bending point of 10 times the steel bar diameter.
Slabs
(1) Before binding slab steel bars, lines should be drawn according to the spacing requirements for the lower steel bars, forming a square grid with an ink marker. Intersection points of the two rows of steel bars around the perimeter must be firmly tied, while those in the middle rows can be staggered and tied, ensuring all stressed steel bars remain securely positioned.
(2) Negative reinforcement on the upper surface of slabs must be protected from foot traffic, especially in cantilevered slabs such as canopies, eaves, and balconies. The positioning of negative reinforcement should be strictly controlled, with cushion blocks and support stools placed as required to avoid damage after formwork removal.
(3) Support stools must not be installed directly on the formwork surface. Instead, they should be placed on the bottom slab reinforcement, with protective cushion blocks positioned at the intersection of bottom reinforcement where stools are installed.
(4) Double-layer steel mesh should have steel reinforcement support feet beneath the upper mesh to maintain correct positioning and alignment of the reinforcement.
Additionally, during steel bar construction, beyond ensuring quality control for the above components, preparatory work is essential. This includes thoroughly reviewing drawings in advance and paying special attention to areas where steel bar diameter or concrete section changes. Inspections and acceptance checks should be conducted, with the next construction phase only proceeding after all quality issues are resolved.
Article source: Architectural Technology Magazine
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