Views: 0 Author: Site Editor Publish Time: 2026-09-15 Origin: Site
Seismic bracing assemblies are structural hardware firmly anchored to building main structures, primarily designed to resist seismic loads. A complete assembly consists of anchors, reinforced hang-rods, seismic connection components, lateral seismic braces, longitudinal seismic braces, and pipe connection components.
Anchors serve as connecting hardware linking seismic bracing systems to concrete or steel building substrates. They shall be post-installed undercut anchors with mechanical interlocking effect; ordinary expansion anchors are not permitted.
Two main undercut anchor types are available. The first is mould-set undercut anchors, where special drill bits pre-form undercut holes prior to anchor installation. The second is self-undercut anchors, fitted with hard cutting blades. Undercut hole forming and anchor expansion are completed simultaneously during installation.
Seismic connection components are intermediate fittings that connect anchors with pipeline-side hardware. The plate thickness of these components shall be no less than 5 mm, and surfaces shall be hot-dip galvanized.
Seismic diagonal braces transfer horizontal seismic forces from pipelines to building primary structures. Braces installed parallel to the cross-section of pipelines are defined as lateral seismic braces, while those installed perpendicular to pipeline cross-sections are defined as longitudinal seismic braces. The channel steel used for diagonal braces shall feature a minimum wall thickness of 2 mm.
Pipe connection components clamp pipelines securely and restrict unwanted displacement. Three common configurations are adopted: pipe-clamp type, U-clamp type and Ω-clamp type.
Reinforced hang-rod assemblies clamp main load-bearing hang-rods to improve bending resistance and overall stability. Reinforcement with channel steel shall be implemented when the slenderness ratio of primary suspension threaded rods exceeds 100, or when the slenderness ratio of diagonal brace members exceeds 200.
Indoor water-supply, hot-water and fire-protection pipes with nominal diameter DN65 and above shall be fitted with seismic bracing.
– For rigid-jointed metallic pipes: maximum allowable spacing is 12 m for lateral bracing and 24 m for longitudinal bracing.
– For non-metallic, composite pipes or metallic pipes with flexible joints: maximum allowable spacing is 6 m for lateral bracing and 12 m for longitudinal bracing.
Seismic bracing shall be provided for rectangular ducts with cross-sectional area ≥ 0.38 ㎡ and circular ducts with diameter ≥ 0.7 m. Seismic bracing is mandatory for smoke-control, smoke-exhaust and emergency-ventilation ducts and associated equipment regardless of dimensions. Seismic bracing shall be applied for suspended air-handling units, fans and other equipment with weight exceeding 1.8 kN.
– For rigid-material ducts: maximum allowable spacing is 9 m for lateral bracing and 18 m for longitudinal bracing.
– For non-metallic ducts: maximum allowable spacing is 4.5 m for lateral bracing and 9 m for longitudinal bracing.
Pipes inside critical equipment zones including boiler rooms, chiller plants and heat-exchange stations shall also be equipped with seismic bracing.
Gas pipes with inner diameter ≥ 25 mm shall be protected by seismic bracing. The maximum allowable spacing is 6 m for lateral bracing and 12 m for longitudinal bracing.
Seismic bracing is required for electrical conduits with inner diameter ≥ 60 mm, as well as cable ladders, cable trays and bus-ducts with unit weight ≥ 150 N/m. For metallic electrical components, the maximum allowable spacing is 12 m for lateral bracing and 24 m for longitudinal bracing.
Each horizontal pipe segment shall be equipped with lateral seismic braces at both ends. Additional intermediate lateral braces shall be added if the distance between two lateral braces exceeds the permitted maximum spacing. Lateral seismic braces shall be installed within 0.6 m of pipe elbow sections. Both lateral and longitudinal seismic braces shall be fitted on either side of flexible compensators and expansion joints.
Every straight horizontal pipe run shall have at least one longitudinal seismic brace; bidirectional seismic bracing is generally recommended. Extra longitudinal braces shall be inserted sequentially once the span between adjacent longitudinal braces goes beyond the maximum permitted spacing.
Single-rod seismic bracing consists of one primary load-bearing hanger plus seismic diagonal braces. It is widely used for water-supply, fire-protection and gas pipelines. Portal-style bracing may be adopted where two or more pipelines run side-by-side.
For horizontal pipes connected to risers, the first seismic brace shall be arranged within 0.6 m from the riser joint. Where riser height exceeds 1.8 m, four-way seismic bracing shall be fitted at both top and bottom positions. Extra intermediate seismic bracing shall be added when riser height is greater than 7.6 m.
Portal-style seismic bracing comprises two or more load-bearing hangers, cross beams and seismic diagonal braces. This configuration is frequently used for cable trays, bus-ducts, air-conditioning ducts and smoke-exhaust systems. Each portal-style assembly shall include no less than one lateral seismic brace and two longitudinal seismic braces.
Combined seismic bracing solutions apply to installation zones with multiple overlapping utility pipelines.
