How to Determine the Anchoring Depth of Exterior Wall GRC Components?

The anchorage depth of exterior wall GRC components (mainly referring to the anchorage length of post-installed anchors or chemical anchors) is the lifeline of their safe connection to the main structure. It must be determined through scientific calculation and must never be estimated based on experience. Qinglong Group follows national codes such as the Technical Specification for Post-Installed Anchors in Concrete Structures (JGJ 145), performing design calculations based on key parameters including component loads, base material strength, anchor performance, and seismic requirements, to ensure that the safety factor of the anchoring system meets the code requirements (typically no less than 3.0). In the super high-rise GRC curtain wall project of Wuxiang China Resources MixC One in Nanning, we carried out classified calculations and on-site pull-out verification for tens of thousands of anchors, ensuring overall safety.

Key Parameters and Process for Calculating Anchorage Depth

Determining the anchorage depth is a systematic calculation process: 1) Determine the loads: calculate the tensile force, shear force, and possible combined tension-shear forces that each individual anchor must withstand. Loads originate from wind loads, seismic action, self-weight, and thermal deformation. 2) Assess the base material condition: test the strength grade, cracking condition, and reinforcement position of the base concrete, which determines the failure mode of the anchor (concrete cone failure, steel failure, etc.). 3) Select the anchor type: choose a suitable model of chemical anchor or mechanical anchor according to the loading and the environment (e.g., humidity, high temperature), and obtain its performance certification reports (such as ETA and ICC-ES reports). 4) Perform the calculation: based on code formulas, calculate the minimum required anchorage depth hef, and apply reductions accounting for influencing factors such as edge distance, spacing, and cracked concrete. The final design depth must be greater than the calculated value and meet the minimum required by the product manual.

Constructional Requirements and Safety Margin

In addition to calculations, important constructional requirements must also be met: 1) Minimum edge distance and spacing: anchors must maintain minimum distances from component edges and from each other to prevent concrete splitting. 2) Anchorage depth: in concrete base materials, the anchorage depth of chemical anchors is typically no less than 8 times the anchor diameter (8d), and that of mechanical anchors no less than 6d, and under no circumstances should it be less than the limit specified by the product. 3) Seismic fortification: in seismic regions, anchor design must account for repeated loads during earthquakes, which may require deeper anchorage or special seismic-resistant anchors.

On-Site Verification and Quality Control

No matter how perfect the design, on-site verification is still required. Codes require on-site non-destructive pull-out tests for post-installed anchors, with a sampling ratio of typically 1‰ and no fewer than 3 anchors. The test load is taken as approximately 1.2 times the design load. Only after passing on-site verification is the anchoring system accepted. During construction, Qinglong strictly implements the procedure of "design calculation - on-site sampling tests - batch installation", ensuring that every anchoring point is safe and reliable. The scientific determination of anchorage depth is the cornerstone that keeps GRC curtain walls as stable as Mount Tai even when suspended high on the exterior of buildings.