Construction Fasteners

Construction Fasteners are standardized hardware components used to fasten and connect various rods (such as steel pipes and profiles) in construction. They are core connectors in structures like scaffolding, formwork supports, and temporary protective facilities. Their role is to combine scattered rods into a stable stress-bearing system through mechanical clamping force, ensuring construction safety and structural stability. They are widely used in housing construction, bridge engineering, municipal construction, and other fields. The following is a detailed introduction from aspects such as classification, performance requirements, application scenarios, and purchasing points:

I. Main Types and Functions

According to connection methods and purposes, building couplers can be divided into three categories:

Right-Angle Coupler (Cross Coupler)

Structure: Composed of two vertically intersecting clamping seats, fastened by bolts.

Function: Used for 90° right-angle connection between vertical rods (uprights) and horizontal rods (crossbars). It is the basic node connector of the scaffolding frame, ensuring rigid fixation of horizontal and vertical rods.

Swivel Coupler (Universal Coupler)

Structure: The clamping seat can rotate around the central axis, supporting arbitrary angle adjustment from 0° to 180°.

Function: Connects inclined or non-right-angle intersecting rods (such as diagonal braces, oblique supports), adapting to the angle requirements of complex structures and enhancing overall stability.

Butt Coupler (Straight Coupler)

Structure: Two coaxial clamping seats, used for straight butt extension of two steel pipes.

Function: When the length of a single steel pipe is insufficient, the span is extended through the butt coupler, maintaining the continuity and stress consistency of the rods.

II. Manufacturing Materials and Processes

The performance of building couplers is closely related to materials and processes. The mainstream types include:

Cast Iron Couplers:

Material: Malleable cast iron (such as KT35-10), formed by casting process.

Characteristics: Low cost, moderate strength, suitable for general load scenarios, but with high brittleness, which may 脆裂 under long-term impact.

Steel Couplers:

Material: Low-carbon steel or alloy structural steel, manufactured by forging and stamping processes.

Characteristics: Good toughness, strong impact resistance, and bearing capacity superior to cast iron couplers. Suitable for heavy-duty scaffolding or high-load projects (such as bridge construction), but with higher cost.

Surface Treatment:

To improve corrosion resistance, the surface of the coupler is usually treated with hot-dip galvanizing, electro-galvanizing, or painting, which can effectively prevent rust in humid and outdoor environments and extend service life.

III. Core Performance Requirements

Construction Fasteners must meet strict industry standards (such as China's GB 15831-2006, international EN 74). Key performance indicators include:

Anti-Slip Performance: The fitting area with the steel pipe after clamping is ≥70%, ensuring no slipping under stress, and the anti-slip coefficient is ≥0.5.

Anti-Destruction Performance: No fracture when bearing 15kN axial tension, and no thread slipping when the bolt tightening torque reaches 65N・m.

Anti-Deformation Performance: Under 7kN load, the deformation at the opening is ≤1.5mm, ensuring effective clamping after long-term use.

Corrosion Resistance: The galvanized layer thickness is ≥85μm (hot-dip galvanizing), and no red rust occurs in the 48-hour salt spray test.

IV. Typical Application Scenarios

Scaffolding System:

When building construction operating platforms, right-angle couplers are used to connect uprights and crossbars, swivel couplers to fix diagonal braces, and butt couplers to extend the length of steel pipes.

Formwork Support:

In the support system of concrete pouring formwork, couplers are used to fix uprights and horizontal tie rods to prevent deformation or collapse of the formwork.

Temporary Protective Facilities:

Protective railings and safety passages at construction sites use couplers to connect steel pipes to form closed protection, ensuring personnel safety.

Emergency Projects:

For quickly building temporary passages and supports during emergency rescue and disaster relief, the convenience of couplers is relied on for rapid assembly.

V. Usage and Maintenance Notes

Installation Specifications:

The bolt tightening torque should be controlled within 40-65N・m (slightly different for different specifications). Too loose may cause slipping, and too tight may lead to bolt fracture.

Ensure that the coupler matches the steel pipe specifications (such as Φ48mm steel pipe corresponding to standard couplers), avoiding "small couplers with large pipes" or "large couplers with small pipes".

Regular Inspection:

Before construction, check whether the couplers have cracks, deformation, bolt slipping, or peeling of the surface coating. Unqualified products are strictly prohibited.

After long-term use, re-tighten the bolts every 3 months to prevent loosening due to vibration.

Storage and Maintenance:

Idle couplers should be stored in a dry and ventilated place, avoiding rain or exposure to the sun; rusty parts need to be derusted and repainted, and severely rusted ones should be scrapped immediately.