The McKinley Street Steel Tied Arch Bridge in Corona, California is being built to provide a “grade separation” solution to improve traffic flows where McKinley Street currently crosses a busy railway line, a canal and another road, all at ground level.

The bridge has a span of 87.2 m (286 ft) between bearings, and will raise the driving surface of McKinley Street approximately 9 m (30 ft) at its highest point. With the project’s financing requiring its funds to be utilized within a short timeframe, the urgency to plan and organize the project and to design and construct the new structure was a defining criterion from the outset.

A key consideration in the bridge’s design was the need for it to withstand any earthquakes that might be expected in the area. mageba’s local team was happy to assist in the development of a comprehensive solution incorporating all aspects of the structure’s support and movement. The solution consists of:

• Four RESTON®SPHERICAL bearings, each free-sliding, designed to support vertical loads of 3,694 kips (16,421 kN) – one such bearing at each corner of the bridge’s arch structure, with the entire weight of the structure and any traffic it carries supported by the four bearings alone

• 158 LASTO®BLOCK elastomeric bearings, featuring horizontal movement restraints as required, to support the approach slabs at each end of the main span and cantilevered sidewalks on each side of the bridge

• Eight RESTON®PSD preloaded spring dampers, designed to provide horizontal fixity in service conditions but to permit the kind of seismic movements that would severely damage the structure

• Four RESTON®SA shock absorbers (viscous fluid dampers), designed to accommodate and control movements in service conditions (due to thermal effects etc.)  

• Two TENSA®POLYFLEX®RAPIDCURE (type RC) flexible plug expansion joints – the brand new alternative to the TENSA®POLYFLEX®ADVANCED flexible plug expansion joint, offering even easier installation and shorter curing times to further accelerate construction schedules

With the bridge’s main arch superstructure supported entirely on the four free-sliding RESTON®SPHERICAL bearings, this contributes to the bridge’s protection from earthquakes by means of a seismic isolation strategy, with the superstructure decoupled from any violent movements of the ground beneath the structure.

Should the ground ever move horizontally in an earthquake, the superstructure’s movements will be controlled by the RESTON®PSD preloaded spring dampers and the RESTON®SA shock absorbers. The energy from the seismic event will be dissipated by the shock absorbers (which will allow thermal/SLS movements) and the preloaded spring dampers (which will resist movements except for any large, sudden seismic ones) – with the preloaded spring dampers also ensuring recentring of the superstructure in its original position after the earthquake has passed.

The elasticity of the flexible plug expansion joints makes them compatible with the seismic isolation solution, and even enables them to contribute to it by dissipating some seismic energy as they accommodate the earthquake’s movements in any direction with little or no damage – with any damage being quite easily repairable thanks to the reactivation property of the elastic surface material when fresh material is poured onto or against it.

With this solution quickly developed in close and efficient cooperation with the bridge’s design team, the project is well on its way to meeting its challenging schedule requirements, and the people of Corona can look forward to having this fine new structure at their disposal – even in the wake of any earthquakes that strike southern California in the coming decades.