What are Anti-fall Beam Blocks?
Anti-falling beam blocks and embedded plates, are components of Anti-falling Beam Device used to prevent excessive displacement of bridge beams in the event of natural disasters, such as strong winds or earthquakes. They are typically installed on top of bridge piers, abutments, or the sides of beams and are tightly connected to the main bridge structure through specific connection methods, forming an unseating device.
In bridge engineering, anti-falling beam blocks are a crucial seismic-resistant member, and their design and application directly affect the safety and stability of various types of bridges.
Types Of Anti-Fall Beam Blocks – Concrete or Steel
There are 2 types of Anti-fall beam devices coupling type and block type: Coupling devices use prestressed steel bars, steel cables, chains to connect beams and abutments. Block type anti-fall beam device uses a “beam-stopping block.” It is a sturdy barrier placed at the end of the beam’s potential movement path which can be made in 2 forms:
- Reinforced concrete stop block: This type is cast integrally with the cap beam, with sufficient gaps left by calculation.
- Steel stop block: Used when higher strength or more precise clearance control is required.
Anti-fall Beam Blocks in Bridge Steel Structure
- Steel Reasonable Gap: Leave an appropriate gap between the stop block and the bridge beam. If the gap is too small, normal temperature changes and shrinkage will cause the beam to press against the restrainer block, affecting its normal function; for a large gap, the beam will have already undergone excessive displacement, and the bridge bearing may fail before the restrainer block works.
- Sufficient Strength And Toughness: The anti-fall beam block must have sufficient strength to withstand the huge impact force, and it needs to be properly reinforced to give it a certain degree of ductility (deformation ability) to prevent it from breaking. The bearing plates are assembled in the bridge steel structure for various bridges. It is used not only for building railway bridges, highway bridges, and even cross-sea bridges.
Anti-Fall Beam Block And Embedded Plate Fabrication
AGICO supplies cutomized fabrication service of anti-fall beam block and embedded plate for bridge steel structure – unseating prevention devices, check the following specificaitons, if you are looking for steel members for bridge construction, contact us for a free quote now!
Anti-fall beam block and embedded plate supplied by AGICO are fabricated according to Standard: Q/CR749.3-2020 Protective Coating and Paint for Steel Structures and Components of Railway Bridges.
Anti-Fall Beam Block Specification
- Steel Material: Q355D (steel plate), or customized.
- Surface treatment: Multi-alloy powder co-diffusion treatment + passivation + sealing
- Applications: Anti-fall beam devices are set between the bridge beam and the pier. It is used to prevent the unseating of the beam structure from shifting laterally or longitudinally under special loads such as seismic forces. During installation, they are connected with the pre-embedded steel plates, anti-fall beam blocks are usually installed next to the bridge bearing, close to the center line of bridge.
Embedded Steel Plate
- Steel Material: Q355D (steel plate), 45# steel (sleeve), HRB400 (anchor bar)
- Surface Treatment: Multi-element powder co-diffusion treatment + passivation + sealing
- Applications: Pre-embedded in the bottom of high-speed railway bridges. During bridge erection, the anti-fall beam blocks are installed on the inner edge of the recess on the upper part of the pier using bolts to prevent the bridge from collapsing due to vibration during earthquakes.
Dimension of Anti-fall Beam Blocks
Various Types of Anti-fall Beam Block Install
Anti-falling beam blocks are key bridge components used to prevent bridge beams from detaching or overturning under earthquakes or other external forces, the design and installation must strictly adhere to relevant technical standards and engineering requirements.
Dimension: The dimensions of anti-fall beam blocks are typically determined by 3 factors: bridge design, beam dimensions, and installation requirements. AGICO supplies a common size of 740mm*480mm*24mm, or according to the drawing from customer. Besides standard sizes, AGICO also supplies customized anti-fall beam blocks to meet the requirements of each project.
Steel Grades：Commonly used steel grades include Q235B, Q345B, and Q345D, which has excellent mechanical properties and corrosion resistance, or other equivalent steel grades that can meet requirements of bridges in various environments.
Anti-Fall Beam Device Working Principle
The anti-fall beam blocks can be installed in central and side piers, and are designed for continuous beams and single/double track beams. The corrosion protection requirements for the beam blocks adopts zinc impregnation or multi-element alloy co-impregnation.
The anti-fall beam device mainly consists of beam block, pier and abutment blocks, and a ring chain. Both ends of the ring chain are connected to the beam tie rods and the pier and abutment tie rods, and are wrapped with cushioning rubber. Pre-embedded plates are installed on the beam tie rods; this method is not used for steel truss beams. For beam tie rods, single-ear connections have poor stability, insufficient connection strength, and short service life.
AGICO also supplies customized fabrication of high-strength Bolts, if you are interested in bridge unseating prevention solutions, don’t hesitate to send a free quote now!
Fabrication of Anti-fall beam blocks & embedded steel plates
Fabrication Requirements
Install Methods:
The anti-fall beam blocks lay on the supporting pad stones, and shear reinforcement should be pre-embedded. Shear resistance calculations should be performed on the pier top pad stones. During beam fabrication, pre-embedded steel plates are placed in the beam body. After concrete pouring, the beam body is formed, and the welded anti-fall beam blocks are installed using high-strength structural bolts. When processing embedded steel plates and beam blocks, make sure they have accurate opening positions to ensure easier installation later.
Anti-Fall Beam Block & Embedded Plate Supplied by AGICO
9 Tips for Anti-Fall Beam Block Installation
- After the anti-fall beam block is locked in place with the embedded steel plate, tighten the bolts with a wrench.
- When the anti-fall beam device is not working, the upper structure can vibrate freely; when the device is functioning, the upper structure is constrained.
- A hard rubber sheet should be added to the gap between the anti-fall beam block and the pad stone.
- The effective engagement length of the sleeve and bolt threads should be greater than 1.2 times the bolt diameter;
- The bolts are anti-theft type, and appropriate spring washers should be used during bolt installation.
- The dimensions of the bearing pad should be checked before installing the anti-fall beam stop blocks.
- When installing the anti-fall beam block, tighten the bolts continuously while pushing the jack upwards.
- The anti-fall beam blocks and bolts need maintenance over time.
- Clean the sleeve openings of embedded steel plates in the beam before installation.
