Why Can Certain Bridges Resist the Tremors of Major Earthquakes?

Environmental experts and engineers analyze lands and their behaviours before building critical infrastructure like bridges. These massive feats of human accomplishment are deceptively sturdy, but how can some be earthquake-resistant bridges? In contrast, others have cables snapping, dropping cars into rivers like a film disaster.

Explore the seismic design of bridges and what goes into ideal strength, configurations, elasticity and damping in a world of rising natural disasters and volatility.

Hybrid Sliding-Rocking (HSR) Columns

HSR columns take traditional bridge construction but make it more flexible. Cast-in-place concrete may not come tumbling down amid a tremor, but it will crack due to its nonexistent fluidity. Repairs for these damages are expensive and labour-intensive, so HSR columns provide an optimistic alternative.

Engineers construct HSR columns from multiple sections instead of one piece. A central cable keeps them together. If a tremor happens, the pieces move around the cable but bounce back to their original positions because of a post-tensioning strand.

They are earthquake-resistant bridges with less headache and taxpayer dollars at risk. Civil engineers may repair damaged columns without closing the entire path, otherwise disrupting citizens’ lives. With these factors in mind, engineers provide an ideal opportunity for skill development and career fulfillment by protecting people and resisting disaster.

Innovations like HSR columns remind industry experts and leaders that the seismic design of bridges is considered more than structural integrity — it keeps citizens and habitats safe while maintaining economic and societal stability.

Eurocode 8 and Compliance

Adhering to compliance and regulatory standards has much to do with whether or not a bridge can resist the terrorizing impacts of an earthquake. Eurocode 8 is one of the most renowned examples of approaching bridge safety and construction to prevent collapse. The recommendations involve bending abutments and piers, which assists their “no-collapse” and “damage limitation” requirements.

According to these guidelines, the bridge must pass safety testing and withstand seismic activity without damage. Every bridge has an importance class, which determines the return period for the most prominent disasters in the area. Some of the world’s most famous bridges, like the Golden Gate Bridge, feel the weight of 39 million cars yearly. Therefore, paying attention to regulations for low mortality and high defenses against earthquakes in prone areas is critical.

Standards in other countries, recommendations from the Federal Highway Administration in the U.S. and AS 1170.4-2007 in Australia detail how to brace earthquake-resistant bridges for seismic activity, like displacement-based seismic design. As innovations surface from industry leaders, these insights will inform future frameworks.

Seismic Dampers

Seismic dampers are ways experts displace intense vibrations from compromising an isolated section of a bridge, which sometimes utilizes hydraulics to disperse energy during inconsistencies. High winds or earthquakes shake the dampers. In the case of fluid-based models, they move the liquid to a piston, where the friction releases as heat. The seismic activity fizzles into the air without causing as much damage to the structure.

The equipment provides resistance against the earthquake’s force, regardless of how much its velocity increases. However, there are a few types of seismic dampers engineers may use in bridges and even in other structures like skyscrapers:

• Base isolation systems: Dampers separate from the main superstructure to severely cut what energy transfers to the bridge.
• Damped outriggers: Devices that provide sturdiness against tremor-induced acceleration, ideal for taller structures.
• Direct-acting damper: Fluid viscous dampers that absorb and move energy.

Smart Retrofitting

Civil infrastructure is decades old and needs upgrades. Retrofitting is one of the best ways to provide holistic defenses against tremors by kicking a structure into the modern age of safety and technology.

Safety standards existed when people first built the bridge, but they were not as strict or informed as now. Professionals must analyze antiquated structures to incorporate necessary modifications, such as:

• Bumper blocks
• Span restrainers
• Braced frames
• Sand cushions
• Infill walls
• Steel jacketing
• Ductile materials

Viewing each bridge based on activity and geography is essential, as not all bridges require the same edits. Projects may view bridges from an expected damage perspective, gauging necessary repairs based on historical data and what that might predict. Alternatively, indices may assign vulnerability levels to determine suggested retrofits.

Retrofits may happen on the earthquake-resistant devices, the foundation or the superstructure. Evaluating them individually and synergistically is essential for well-prioritized enhancements. Then, builders and engineers must advocate for regular auditing and accountability to ensure the longevity of earthquake-resistant bridges.

Reinforcing Seismic Design of Bridges

Constructing earthquake-resistant bridges is non-negotiable in an era of increased urbanization, transportation and climate change-induced surprises. This is critical for areas near tectonic plates and other seismic fixtures, but it will inevitably be best practice for all civil engineers and environmental consultants worldwide.

Normalizing these strategies forces industries to mandate them, witness their benefits and encourage continued research and development to make them even more effective and powerful than they are today.

Emily Newton is Editor in Chief at Revolutionized

Enjoying Sourceable articles? Subscribe for Free and receive daily updates of all articles which are published on our site

Want to grow your sales, reach more new clients and expand your client base across Australia’s design and construction sector?

Advertise on Sourceable and have your business seen by the thousands of architects, engineers, builders/construction contractors, subcontractors/trade contractors, property developers and building industry suppliers who read our stories across the civil, commercial and residential construction sector