1. Lead-rubber bearings have higher vertical load capacity than conventional bearings
2. Lead-rubber bearings dissipate energy while lengthening the structure's period
3. Conventional bearings cannot accommodate the horizontal displacements in seismic events
4. Lead-rubber bearings eliminate the need for expansion joints in the superstructure

Explanation

Explanation: Lead-rubber isolation bearings combine period lengthening (reducing seismic forces) with energy dissipation through lead core yielding—critical for structures near active faults where high-energy ground motions occur. Per AASHTO Guide Specifications for Seismic Isolation Design, these bearings typically provide 15-30% damping compared to 5-7% for conventional elastomeric bearings, substantially reducing superstructure accelerations and substructure forces. Vertical capacity (A) is similar between types; displacement capacity (C) can be addressed in both bearing types through proper design; and expansion joint requirements (D) are determined by thermal movements, not bearing type.

Learning Resources:

• Review AASHTO Guide Specifications for Seismic Isolation Design, 4th Edition (2014), Sections 8 and 12 for bearing requirements.
• Study the Benicia-Martinez Bridge (California, 2007) for a notable application of isolation bearings.
• Digital Resource: Explore MCEER's Seismic Isolation Bearing Database (http://mceer.buffalo.edu/research/databases)
• Tip: When designing isolated bridges, carefully consider bearing stability under combined vertical load and lateral displacement, particularly accounting for P-Δ effects during maximum design earthquake (MDE) events.