Spherical Bearings: Building‑Steel‑Constructure Vs Bridge‑What Are The Key Differences

For domestic Chinese projects, building‑steel‑constructure spherical bearings comply with GB/T 32836‑2016, mainly for gymnasiums, space trusses, steel connecting corridors and large‑span roofs under the jurisdiction of building codes. Bridge spherical bearings follow GB/T 17955‑2009, which applies to highway bridges governed by transportation specifications. On the international side, EN 1337‑7 covers both building and bridge spherical PTFE bearings. ASTM D5977‑23 specifies high‑load rotational spherical bearings, originally developed for bridge applications, and requires modification when deployed for building‑steel‑constructure.

Both product lines adopt the same core mechanism. A spherical PTFE‑stainless steel pair delivers universal rotation, while a flat sliding pair enables horizontal displacement. The three basic types remain consistent: fixed spherical bearings (GD), unidirectional sliding bearings (DX), and multi‑directional sliding bearings (SX). Despite these similarities, critical differences stem from service loads, displacement demands, anti‑pull requirements, code‑mandated capacity, sealing philosophies and system layout rules.

Load conditions form the root distinction. Building‑steel‑constructure spherical bearings are dominated by static dead loads, with wind and earthquake as primary horizontal actions. Impact and cyclic repeated loads are rare. Tensile vertical forces frequently occur due to wind uplift on large‑cantilever roofs, so anti‑pull bearings are a regular selection for building projects.

By contrast, bridge spherical bearings sustain dynamic vehicle loads, braking forces and heavy cyclic alternating loads. Vertical reactions fluctuate constantly as traffic passes over the superstructure. Horizontal forces include seismic effects, thermal forces and vehicle braking. Fatigue risk for stoppers, welds and sliding interfaces becomes a major design concern. Most bridge supports stay under compression; anti‑pull bearings are only custom‑built for special negative‑reaction piers.

Regarding horizontal load capacity, GB/T 17955‑2009 sets a hard mandatory requirement: non‑sliding‑direction horizontal capacity for fixed and unidirectional bridge bearings shall not be less than 10 % of the vertical design load. For building‑steel‑constructure spherical bearings under GB/T 32836‑2016, the 10 % value is merely advisory. Horizontal resistance shall be calculated from actual wind and seismic demands. Using building‑grade bearings on bridges risks stopper failure under braking loads.

Displacement requirements also diverge. Building‑steel‑constructure bearing movements normally range from ±20 mm to ±120 mm, driven mostly by temperature change and foundation settlement. Bridge bearings need far larger travel, often ±100 mm up to ±400 mm, to accommodate concrete shrinkage, creep, wide temperature swings and large seismic offset.

Sealing and corrosion resistance requirements are stricter for bridge bearings. They operate fully exposed to de‑icing salt, road dust and all‑weather conditions. Building bearings may use simplified seals for indoor installation; full sealing is compulsory only for outdoor roofs and steel corridors.

System layout logic differs greatly. A large‑span building roof system typically uses only one fixed spherical bearing as the immobile reference point. All remaining supports use unidirectional or multi‑directional sliding bearings. Multiple fixed points would trap thermal deformation and induce destructive internal forces. Multi‑span bridges can deploy several fixed bearings divided by expansion joints, without the single‑fixed‑point restriction.

Factory validation tests reflect those practical gaps. Bridge bearings require more cyclic‑load and repeated‑sliding tests simulating traffic cycles. Building‑steel‑constructure bearings focus on static proof load, rotation performance, friction coefficient and PTFE bonding; anti‑pull variants add dedicated tensile tests.