A Deep Dive into the Role of Elastomeric Bridge Bearings
Countries around the world have started to invest massive monetary resources into bridge projects for road transport in a bid to accommodate the enormous numbers of vehicles in transit each day. Such projects require millions of tons in material resources including steel and supporting construction materials to support massive vehicle weights which can account for several hundred tons at any given period of time.
The potential of a bridge failure is one of the most significant threats that builders must contend with. Natural disasters such as earthquakes and material fatigue are some of the more common causes of bridge failures, resulting in hearing of bolts, shifting bridge sections and collapsing decks, potentially putting human lives and valuable property at risk.
To counter such threats, all bridges are designed for moderate flexibility. The bridge is expected to be subject to unexpected external forces such as natural disasters, high wind speeds, heavy traffic, or changes in temperature, which makes bridge bearings crucial to the structure.
The types of bridge bearings include sliding bearings, disk bearings, rocker and pin bearings, pot bearings, curved bearings, roller bearings, curved bearings, and elastomeric bearings.
Elastomeric Bridge Bearings Popular for Flexible Structures
In most cases of constructing bridges, the required flexibility is largely achieved through the use of elastomeric bridge bearings. These components are mostly made from materials such as neoprene, which is a type of heavy-duty industrial standard rubber.
Such bearings are normally placed between bridge superstructures and substructures such as the pier supports and bridge beams, which helps in even distribution of loads of the superstructure, enabling the superstructure to move in a measured manner during exceptional environmental conditions. This eliminates risks of harmful stress, which could reduce the structural integrity of the bridge, raising the possibility of collapse.
Further, elastomeric bridge bearings do not just prevent bridges from collapsing. These components also boost the life of bridges, by minimizing wear and tear stresses on other bridge materials and components. Consequently, elastomeric bridge bearings generate substantial monetary savings for governments in terms of replacing components.
3D Simulations for Elastomeric Bridge Bearing Functions Become Mainstream
Elastomeric bridge bearings are now widely considered as being important for cost efficient and safer bridge designs. Consequently, these components require extensive testing and prototyping prior to usage in real world bridge production efforts.
As a result, construction and infrastructure companies are increasingly making use of 3D simulation software as a key part of the testing process. Bearing pads can be composed of elastomeric materials to be reinforced, and simulations can provide insights on factors such as compression, compression with rotation, and compression with shearing. Such simulations allow observations on the relation and the effects different bridge components have on each other, which is ultimately important in terms of load carrying capacity of bridge bearings.
The production of elastomeric spherical bridge bearings with cutting edge tech are expected to play important roles in terms of longevity, bridge safety, and dependability.
Unlocking Importance of Testing on Performance of Elastomeric Bridge Bearings
In a bid to improve the overall reliability and performance of elastomeric bridge bearings, manufacturers have taken to extensive testing including processes such as shear fatigue tests and compression tests on elastomeric bridge bearings, while being in compliance with local regulations.
According to analysts, testing has proven that the use of elastomeric bridge bearings increased the capabilities of stress handling substantially, where bridge failures only occurred in cases of loads up to 26 times more than permissible limits, consequently proving high levels of reliability in terms of vertical performance.
When it comes to shear rating of elastomeric bearing, these components have been found to be largely dependent on fabrication conditions, while barely meeting performance standards above permissible load limits. According to tests, elastomeric bridge bearings were at a higher risk of failure in cases where internal rubber layers were developed without a single rubber layer.
Elastomeric bridge bearings can be used to complement seismic devices including seismic isolators, which will enable higher shear performance. The widespread practice of stacking multiple rubber pads, has been found to increase the failure rate and has been increasingly discouraged across the industry.
Decoding Customization in Structural Bearing Assemblies
With bridges being built for different purposes and in different configurations, elastomeric bridge bearing manufacturers have also taken to customization in molds, making use of natural rubber and neoprene. These customizations can be primarily classified into non-reinforced, laminated, or sliding options.
Of these, non-reinforced elastomeric bridge bearings are largely used in situations where stresses such as horizontal deflection, load, and rotation are minimal, and are also designed to be more inexpensive.
Further, sliding elastomeric bridge bearings are mainly used for bridge projects which have larger magnitudes of horizontal displacements. In such situations sliding elastomeric bearings provide a cost effective solution, through the addition of a low friction sliding surface, which enables unlimited horizontal displacement without impacting the height of the bearing assembly structure.
The two components of a sliding elastomeric bridge bearing includes the upper component of steel load plates, which is integrated to the superstructure along with a steel sheet fixed to the load plate. The lower half on the other hand, comprises of a low friction polytetrafluoroethylene PTFE bridge bearing surface which is integrated to a steel or carbon base. This is then fixed to the elastomeric bearing, which in turn is fixed to a load plate.
Finally, laminated elastomeric bridge bearings, include wear resistant steel plates internal to the structure, which substantially bolsters the vertical load bearing capabilities, and the amount of horizontal deflection, which is handled by the bearing device. The steel plates are bonded to the rubber by vulcanization to generate alternating layers of the elastomer. Consequently, laminated bearings provide larger scope of customization.
Elastomeric bridge bearings have displayed satisfactory performance in most cases. While the aspect of compressive stiffness has been found to go up with larger axial loads, the factor of shear stiffness continues at a constant level, with hear modulus values remaining below that of the rubber. Consequently, the bridge bearing industry needs to conduct better quantitative investigations to identify solutions to elasticity and economy problems, which will play a self-adaptive role in the years ahead.
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