Prefabricated Beam Keyway in Housing
The prefabricated beam keyway in housing is a groove formed when the prefabricated beam is connected to other components, achieving a stable structural connection through precise forming and standardized construction.
Definition and Core Function
A prefabricated beam keyway is a groove structure reserved on the beam body through a mold during the factory prefabrication process. Its core function is to provide space for steel bar insertion, concrete pouring, or mechanical connection, ensuring that the beam forms an overall force-bearing system with walls, columns, floor slabs, and other components. For example, in prefabricated buildings, the combination of keyways and cast-in-place concrete can significantly improve the shear bearing capacity, meeting the strength requirements of the Technical Standard for Prefabricated Concrete Buildings (GB/T 51231 - 2016).
Construction Specifications and Key Parameters
- Dimension Control
The depth of the keyway must strictly follow the design requirements: the depth of an ordinary keyway is 15 - 20mm, and the depth of an end-face keyway should not be less than 30mm. The width should meet the specification of “≥3 times the depth and ≤10 times the depth,” and the spacing is usually equal to the width of the keyway. For example, for a keyway with a depth of 20mm, the width should be between 60 - 200mm, and a spacing of 60mm is appropriate. - Forming Accuracy
The dimensional deviation of the mold should be controlled within ±2mm to avoid affecting the insertion of steel bars or the compactness of the concrete. When demolding, a special release agent or pneumatic device should be used to prevent edge damage. - Surface Treatment
Before forming, the flatness of the beam surface should be checked, and defects such as cracks and oil stains should be removed. After forming, debris should be cleaned up, and the compactness should be verified through ultrasonic testing or the sand filling method, with the void ratio not exceeding 5%.
Type Selection and Application Scenarios
- Rectangular Keyway
Suitable for the connection of vertical components, such as the joints between beams and shear walls. It forms a shear key through steel bar insertion, enhancing the overall structural integrity. - Trapezoidal Keyway
Utilizes a wedge-shaped structure to achieve a self-locking effect and is often used for the joints of horizontal components (such as floor slabs and beams) to improve the connection tightness. - Circular Keyway
Mostly used for the positioning of embedded parts, cooperating with bolts for precise assembly, and is commonly seen in equipment foundations or special node connections.
Maintenance and Quality Assurance
The keyway area should be strengthened with covered moist maintenance to prevent surface cracking caused by concrete shrinkage. The maintenance time should meet the design requirements, usually not less than 7 days. After construction, triple acceptance checks including visual inspection, dimension verification, and compactness testing should be carried out to ensure that the connection nodes meet performance indicators such as earthquake resistance and shear resistance.
