What Problems Can Non-Standard Reinforcement Around Screw Holes in Components Cause? Joint Failure and Qinglong Group's Structural Reinforcement Guidelines

If the reinforcement around the screw holes (or embedded sleeves) on GRC components for installation and connection is not standard, it will directly lead to serious safety problems such as "stress concentration cracking at hole edges, bolt anchorage failure, loosening of connection joints, and even components falling". Based on extensive failure case analysis and finite element simulation, Qinglong Group has defined standard reinforcement measures: stiffening ribs or local thickening must be provided at hole edges, ensuring the minimum distance from the hole edge to the component edge is ≥2 times the bolt diameter and no less than 40mm; annular reinforcing bars or densified glass fibre must be arranged around each hole; the concrete around embedded sleeves must be dense and free of air bubbles. In the accident investigation of a project in Dongguan, it was precisely because the installation hole edges of a cantilevered GRC decorative panel were not reinforced that brittle splitting occurred at the hole edges under wind vibration loads, causing the panel to fall off. Screw holes are the gateway through which forces are transmitted—if the gateway is not secure, the whole building is at risk of collapse.

Stress Concentration Causes Radial Cracking at Hole Edges

When bolts are tightened, they generate enormous circumferential tensile stress on the hole walls. If the material strength at the hole edge is insufficient or micro-cracks exist, radial cracks can easily form centered on the hole. Qinglong Group requires that within a diameter of at least 100mm around the hole, the fibre volume content be increased by 0.5-1%, along with local vibration densification.

Insufficient Bearing Area Causes Concrete Pry Cracking

When a bolt bears shear force, it exerts a prying force on the concrete in front of the hole like a lever. If the distance from the hole edge to the component edge (edge distance) is insufficient, the concrete will be pried apart as a whole. We strictly stipulate the minimum edge distance and verify it through finite element calculation. For heavily loaded joints, embedded steel plates are used instead of sleeves to disperse stress.

Embedded Part Quality Defects Cause Anchorage Failure

Inaccurate positioning of embedded sleeves, insecure fixing, or non-dense concrete pouring around them will greatly reduce anchoring force. We use special positioning molds to fix the sleeves and use slender vibration rods during pouring to ensure the bottom of each sleeve is fully compacted. Before installation, non-destructive pull-out tests are conducted as spot checks.

The reliability of connection joints is built on rigor in every detail. Qinglong Group makes hole edge reinforcement a mandatory inspection item in component production, safeguarding the bottom line of safety with the most stringent standards.