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Unseating prevention
Q-type flexible beam link — image 1
Q-type flexible beam link — image 1

Q-type flexible beam link

Flexible bridge connection for excessive-movement restraint.

This Q-type configuration forms part of the flexible beam-link family. A flexible connection and energy-absorbing arrangement restrain excessive relative movement between bridge components.

Configuration & selection
Q-type connection layout
Free travel, buffer travel and anchorage

For selection, send the design loads, movement requirements and connection drawings. Confirm the model, dimensions and interfaces against your project drawings.

Request product information
Technical information

Applications

Bridge unseating-prevention layouts connecting girders or connecting a girder to an abutment or pier.

Key features

  • Q-type flexible connection limits excessive relative separation.
  • Free movement and restraint engagement are coordinated with normal bridge movement.
  • Connection and anchorage details form part of the bridge seismic load path.

Technical specifications

Select link force, free travel, buffer travel, installation angle and anchorage from the approved bridge design. The catalog recommends distributed, symmetric layouts and, where practical, horizontal girder-to-girder connections.

Detailed technical information

Flexible beam links for unseating prevention

A flexible unseating-prevention device (FUPD) limits excessive movement that could allow the bridge superstructure to leave its pier or abutment. It acts as a final line of defence through flexible connection and buffered energy dissipation.

Features and stated ranges
Item Catalog description
Ultimate capacity Up to 5000 kN, using steel strands or wire ropes
Safety factor ≥1.5
Durability Corrosion-protected steel; stated service life up to 50 years
Free stroke ±200 to ±1200 mm
Buffer stroke ±50 to ±500 mm
Installation angle Type I: ±30°; Types II/III: ±5°
Economy Simple rope/strand and connector construction; standardised selection and batch application
Maintenance Replaceable key components including buffer elements and fork ends

Three product types are illustrated: Q-type beam link, composite energy-dissipating beam link and wire-rope beam link. The quoted ranges describe the family and must be matched to the selected configuration.

Flexible beam links: layout and staged seismic protection

  1. Distribute devices symmetrically. Prefer several symmetric links over one link to avoid excessive anchorage action, damage to the primary structure and asymmetric girder loading.
  2. Between girders, prefer a horizontal girder-to-girder connection, symmetrically below or alongside the girders.
  3. Between girder and abutment, prefer a nearly horizontal connection from the girder underside to the abutment.
  4. Between girder and pier, minimise the inclination. Prefer anchorage into the pier cap where its dimensions permit. Otherwise place pier anchorage at least 200 mm below the pier top.
Three lines of seismic defence
Stage Behaviour
1. Bearings During small/moderate earthquakes, the system remains elastic and bearing movement stays within the intended range
2. Sliding gap As shaking increases, bearings undergo greater sliding within the designed clearance; bearing damage is permitted while other components are intended to remain elastic
3. Restraints and unseating-prevention links The load path changes from girder–bearing–pier to girder–restraint–pier; the pier may enter ductile response