Flat-Roof Eaves Steel Bar Prefabrication

The construction of flat-roof eaves steel bar prefabrication must strictly adhere to the following key points to ensure structural safety and construction quality:

I. Material Selection and Standards

1. Steel Bar Adhesive: It is essential to use injection-type steel bar adhesive that complies with the GB50367 standard to ensure bond strength and durability.
2. Steel Bars:
   • For eaves reinforcement, HRB400E grade 12mm deformed steel bars with excellent seismic performance should be selected.
   • When connecting prefabricated eaves to the main structure, HRB400 grade steel bars with a diameter range of 12mm-16mm can be used, with specific specifications determined based on design loads.
3. Grouting Material: High-strength grouting material that meets the JG/T408-2019 standard should be used for joint treatment to ensure joint bearing capacity.

II. Steel Bar Installation Process

1. Drilling:
   • Arrange hole positions at a design spacing of 300mm, with a hole diameter 4mm larger than the steel bar diameter (e.g., a 16mm hole diameter for a 12mm steel bar).
   • The hole depth should be 15 times the steel bar diameter (i.e., 180mm for a 12mm steel bar), with a verticality deviation of ≤1°.
   • After drilling, clean the holes at least three times with a high-pressure air pump to ensure no dust or debris remains inside.
2. Adhesive Injection and Steel Bar Insertion:
   • Use injection-type steel bar adhesive, starting from the bottom of the hole and injecting to two-thirds of the depth to avoid uneven adhesive distribution.
   • Insert the steel bar into the hole while rotating it at a speed of ≤20r/min to ensure adhesive overflow at the hole opening and eliminate internal air.
   • Allow the assembly to cure for 72 hours (at an ambient temperature of ≥5°C), during which the steel bar should not be disturbed.
3. Pull-Out Test:
   • Sample one group (3 bars) for every 500 steel bars for on-site pull-out testing, with the tensile strength required to be ≥90% of the design value.
   • If the test fails, double the number of samples for re-inspection. If it still fails, all bars must be reworked.

III. Key Points for Prefabricated Eaves Connection

1. The connecting steel bars must be reliably anchored to the main structure, with the spacing and length of the steel bars determined through structural calculations.
2. Before joint grouting, clean and moisten the bonding surface, and ensure the grouting material is vibrated and compacted in layers.
3. Before construction, assess the current condition of the eaves structure, recording the crack distribution, concrete carbonation depth, and steel bar corrosion degree, and perform reinforcement if necessary.

IV. Safety and Operational Specifications

1. Before construction, erect scaffolding that complies with the JGJ130 standard as an operating platform to ensure personnel safety.
2. Wear safety harnesses for high-altitude work and avoid contact between the adhesive and skin during drilling and injection.
3. In rainy or low-temperature environments (<5°C), take rainproof and insulation measures to prevent affecting adhesive curing.