Installed within the plane of the roof beam's top or bottom flange in an "X" (cross) configuration, Horizontal Structural Steel Bracing Systems are critical for the spatial stability of industrial buildings. They function primarily in tension rather than compression and work in conjunction with tie rods and knee braces to form the roof's lateral resistance system.
Transfers wind loads from gable walls and horizontal seismic forces to the tie rods at the column tops, subsequently channeling them down to the inter-column bracing and into the foundation; restrains the lateral displacement of roof steel beams, preventing overall lateral tipping or instability of the roof structure.
1). Standard applications: Equal-leg angle steel (L50×5, L63×5, L70×6);
2). Long-span, heavy-load, or seismic-resistant facilities: Small-diameter circular hollow sections (CHS); standard material is Q235B, with Q355B used for heavy-load applications.
Installed in the end bays of the roof and the bays flanking expansion joints to create a rigid structural diaphragm.
Cross-bracing members (angle steel or CHS) supplied as individually fabricated units; a pair of diagonally crossing members within a single bay constitutes one complete horizontal bracing set.
1. End connection plates: 8–14mm steel plates factory-welded to both ends of the bracing member, featuring pre-drilled bolt holes for bolting to the steel beam flanges;
2. Central cross-splice plate: A shared splice plate at the intersection point of the "X" configuration, where the two diagonal braces overlap and are secured.
3. Matching Fasteners
Standard Grade 4.8 bolts (M16/M20) for general use; Grade 8.8 high-strength bolts (with flat washers and spring washers) for seismic-resistant structures or facilities housing overhead cranes.
4. Corrosion Protection Specifications
1). Standard: St3 manual surface preparation + primer and topcoat (dry film thickness: 60–90 μm);
2). Corrosive industrial areas / Coastal regions: Full hot-dip galvanizing.
5. Fire Protection Specifications
Application of 0.5-hour rated thin-film intumescent fire-retardant coating within designated fire compartments; anti-corrosion treatment only for areas without fire protection requirements.
1. Conventional Angle Steel Horizontal Bracing: Angle steel main member + end connection plates + intermediate splice plates + anti-corrosion treatment + matching bolts
2. Heavy-duty Circular Hollow Section (CHS) Horizontal Bracing: CHS member + thickened end plates + cruciform gusset plates + high-strength bolts
3. Simplified Light-duty Bracing: Slender angle steel, no thickened stiffeners; typically used for small light-steel industrial buildings
Horizontal bracing (transverse wind resistance) + tie rods (longitudinal tension connection) + knee braces (lateral restraint for beams) form an integrated, stable roof bracing system. Key Advantages
1. Effectively counteracts horizontal forces, providing robust wind and seismic resistance while preventing overall roof swaying or shifting.
2. Tightens the spacing between frame components, preventing misalignment or deformation of steel beams and purlins.
3. Features a simple structural design with flexible installation layouts, facilitating convenient construction.
4. Made from robust, high-tensile material that resists loosening or deformation over long-term use.
5. Undergoes comprehensive anti-corrosion treatment, ensuring high durability for outdoor or exposed industrial facilities.
6. Highly compatible; perfectly integrates with complete steel structural systems, such as portal rigid frames and long-span industrial buildings.
1. The horizontal structural steel bracing system utilizes an X-shaped cross-configuration specifically designed to transmit lateral horizontal forces. It operates under unidirectional loading—acting only in tension and not compression—resulting in a short load path and high overall rigidity. In contrast, tie rods are longitudinal axial members that limit longitudinal movement but cannot resist lateral forces; knee braces and sag rods only provide local restraint for purlins and steel beams and cannot bear the building's overall horizontal loads.
2. It creates a rigid roof diaphragm by concentrating the bracing within specific bays, effectively linking individual rigid frames into a unified, rigid roof structure. Wind loads from the gable ends are rapidly transmitted via the bracing and tie rods down to the columns and foundations. It serves as a core component for preventing lateral roof instability—a capability that other accessories lack.
1. The primary material is typically equal-leg angle steel, which is readily available and cost-effective. Angle steel is a standard market commodity that is easy to cut and weld; compared to round-tube tie rods or load-bearing steel beams, it uses less material, keeping costs manageable for large-scale installations. Conversely, custom box girders or H-beam components entail high costs and are unsuitable for mass use as bracing.
2. Material selection is graded according to specific needs: standard angle steel is used for ordinary light-steel industrial buildings, while smaller round-tube bracing is employed for long-span, seismic-resistant, or crane-equipped facilities. This allows for flexible load matching and prevents material waste.
1. Split prefabrication and on-site bolting; no on-site welding required for standard members. Factory-prefabricated members feature end connection plates for rapid on-site bolted assembly at cruciform joints; however, some tension members require on-site drilling and welding, resulting in lower construction efficiency.
2. Modular, standardized component sets. Single-span bracing sets are mass-produced with uniform hole diameters and interchangeable bolts, facilitating inventory stocking and on-site replacement or maintenance.
1. Lateral stability relies on horizontal bracing, while longitudinal stability relies on rigid tie rods; the two functions complement each other and are indispensable:
Horizontal Bracing: Provides lateral wind and seismic resistance; installed in specific bays.
Longitudinal Tie Rods: Provide continuous longitudinal tying; distributed throughout the structure. Eave braces and sag rods are minor components associated with the building envelope and do not participate in the primary lateral force-resisting system.
1. Restrains out-of-plane buckling of steel beams, significantly reducing the effective out-of-plane length for calculations; optimizes main beam cross-sections and saves steel.
Angle steel members have a regular shape, making rust removal, painting, and hot-dip galvanizing convenient. Compared to open-profile channel steel, there are fewer inaccessible corners, allowing for more thorough anti-corrosion treatment.
1. Horizontal Bracing: Lateral resistance; X-shaped layout in specific bays; primary structural stability component.
2. Tie Rods: Longitudinal tying; continuous layout; capable of resisting both tension and compression.
3. Eave Braces / Sag Rods: Local reinforcement for purlins and minor beams; envelope structural components.
Main material: Q235B round steel. Verify material quality certificates; inspect for bending, cracks, and corrosion (straighten if bending exceeds tolerances); inspect accessory steel plates (lug plates) upon entry to storage.
Cut round steel to drawing specifications using an abrasive saw or CNC saw; grind cut ends smooth and remove burrs.
Option ① Threading (On-site bolted connection)
Roll-thread external threads onto both ends of the round steel bar; thread length must accommodate the nut and backing plate assembly allowance; apply temporary protection to threads to prevent damage.
Option ② Welded Lug Plate (Bolted beam-to-column connection)
Weld connection plates/lugs onto both ends of the round steel bar; use a jig for alignment and tack-weld for positioning.
Full circumferential CO₂ gas-shielded welding; Grade II fillet welds; visual inspection; sampling for flaw detection on critical projects.
CNC drilling of connection plates (hole diameters matched for M16/M20 bolts).
Straighten members to correct welding-induced bending; grind off weld spatter and burrs.
Standard: St3 rust removal → primer + topcoat; dry film thickness 60–90 μm;
Humid plant areas: Hot-dip galvanizing of the entire assembly.
Package with matching nuts, flat washers, and spring washers; label sets and store.
1. Main material: Equal-leg angle steel (Q235B/Q355B); verify material certificates; inspect for bending, twisting, or deformation (straighten if limits are exceeded);
2. Re-inspect appearance of matching steel connection plates.
Cut angle steel to specified lengths per drawings; grind burrs from cut ends; separate layout for long and short members of the cross-brace assembly.
CNC cutting of end connection plates and central cross-splice cover plates.
Position using a jig; center and tightly fit connection plates to both ends of the angle steel; tack-weld to secure; pre-assemble and position the lap plate at the central intersection point.
Full CO₂ welding of seams between connection plates and angle steel; standard Grade II fillet welds; visual inspection; limited sampling for flaw detection on critical projects.
Standardized drilling of connection plates (typically M16 or M20) to ensure precision in hole spacing and edge distances.
Correction of warping or deformation caused by welding; grinding off weld slag and spatter.
·Standard: St3 manual rust removal → primer + topcoat (dry film thickness: 60–90 μm);
·Coastal/Corrosive environments: Hot-dip galvanizing of the entire component.
Component numbers marked by span and assembly set; issued with a matching parts list.
1. Angle Steel Horizontal Bracing (Predominantly rigid tension members)
Common equal-leg angles: L50×5, L63×5, L70×6, L80×6; end connection plate thickness: 8–14 mm; bolt holes: M16, M20; single member length: 3–9 m; member straightness: ≤L/1000.
2. Round Steel Flexible Bracing
Diameter: Φ12–Φ22; threaded ends (40–60 mm) or welded lug plates (8–12 mm); used only for tension bracing in lightweight roofing.
3. Circular Hollow Section (CHS) Heavy-duty Horizontal Bracing
Common sizes: φ89×3, φ114×3.0, φ114×3.5; end plate thickness: 10–16 mm.
|
Material Grade |
Yield Strength |
Tensile Strength |
Application Scenarios |
|
Q235B |
≥235MPa |
375～500MPa |
Horizontal bracing for conventional workshops |
|
Q355B |
≥355MPa |
470～630MPa |
Large-span workshops, crane workshops and seismic areas |
1. Angle Steel / Round Steel Bracing: Tension-only members (cannot resist compression; buckling failure occurs under compression); arranged in an X-pattern; under load, the single diagonal member acts in tension.
2. Circular Hollow Section Bracing: Resists both tension and compression; stable in both directions; used in high-seismic zones and heavy-duty industrial facilities.
3. Function: Transfers gable wind loads and horizontal seismic forces; restrains out-of-plane displacement of steel beams; works with tie rods to form a rigid roof diaphragm. IV. Weld Control
End-connection fillet welds are classified as Grade II welds; they undergo standard visual inspection and, for key projects, spot Ultrasonic Testing (UT) rather than 100% inspection.
1. Standard horizontal structural steel bracing systems: St3 manual surface preparation; primer plus topcoat with a total dry film thickness of 60–90 μm.
2. Coastal corrosive environments: Full hot-dip galvanizing.
Standard: Grade 4.8 ordinary bolts. Seismic-resistant or crane-equipped facilities: Grade 8.8 high-strength bolts, fitted with flat washers and spring washers.
1. Round steel bar bracing: Flexible; tension-only; for lightweight auxiliary applications.
2. Angle steel bracing: Standard primary bracing; tension-only; standard configuration for conventional industrial buildings.
3. Circular hollow section (CHS) bracing: Rigid (resists both tension and compression); specialized for heavy-duty and seismic-resistant applications.
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