Technical Standards for PV Flexible Bracket Anchor Cables: Design and Construction Referring to Cable-Stayed Bridge Standards (Issue 9)

Flexible Brackets and Cable-Stayed Bridges: Sibling Structures

Cable-stayed bridges excel in spanning capacity, balanced force distribution, structural stability and material saving. Their structure mainly consists of cable towers, main girders and stay cables (steel strand and anchors). PV flexible brackets share these traits: large span, high clearance, material saving and strong adaptability to terrain. The two are structurally similar — both are cable-anchor engineering structures. Cable-stayed bridge design is rigorous and its construction quality is strictly controlled. This issue focuses on part of the stay-cable structure of bridges.

The Critical Role of Angle Precision

Cable-stayed bridge spans generally range from a few hundred metres to about one kilometre. Whatever the final structural length, a large number of stay cables must be installed, anchored in balance between the cable towers and the main girder, so that the structure is evenly loaded and the bending moment and deflection of the bridge structure are controlled to design standard values. Because each cable is connected at a different position and distance, the angle each cable forms with the bridge deck differs. In this situation, the accuracy of the angular attitude and deflection angle between the stay cable and the anchor at different angles is critical.

Installation Deviation Standards for Anchor Systems

Anchor installation deviation standards are determined by the type of engineering project and are generally divided into several precision grades:

• Ordinary precision — when the relative position and attitude of the anchor have low influence on structural stability: installation deviation within ±10 mm; the angular deviation between strand and anchor attitude within ±1°.
• Higher precision — when the anchor position and attitude have higher influence on structural stability: installation deviation within ±5 mm; angular deviation within ±0.5°.
• Highest precision — when the anchor position and attitude are extremely critical to structural stability: installation deviation within ±2 mm; angular deviation within ±0.2°.

In cable-anchor engineering, if the angular deviation between the strand and the anchor attitude is too large, it can cause under-tensioning, aggravated wear, strand fracture and structural damage. Imagine a cable-anchor structure where the angular deviation between strand and anchor is greater than 10° to 50° — would such a project be safe?

Angle-Adaptive Anchors: A Solution Shown at SNEC

SNEC Shanghai is the world's largest PV exhibition; in 2024 it attracted about 3,500 exhibitors and roughly 500,000 visitors. Among the flexible bracket exhibitors, a Nanjing new-energy company and a Tianjin company each displayed their own articulated angle-adaptive anchors for flexible brackets. The Tianjin company's hinged anchor connects the anchor to a movable pivot pin, functioning like a universal joint: with a cable angle of up to ±45°, the angular precision between strand and anchor can reach 0°. When the strand is prestressed, the strand and anchor adapt to angle changes synchronously. This product is particularly suitable for flexible brackets on mountains and hills. It has already been applied in flexible bracket projects in Guizhou, Yunnan, Zhejiang and Shaanxi. Test results after installation show that the angular deviation between strand and anchor can be kept at 0°, with stable performance — effectively solving the quality problem of excessive angular deviation between strand and anchor caused by mountain terrain with conventional fixed anchors.

Key Takeaways

• Design and build flexible bracket anchor systems by referring to cable-stayed bridge standards.
• Keep installation deviation within ±10 mm (and tighter where stability demands it) and angular deviation within ±1° at most.
• For slope terrain, articulated angle-adaptive anchors maintain 0° strand-to-anchor alignment.