Efficacy of 3M-PTGL on low-temperature seismic performance of polyurethane elastomeric bearings for bridges

High-capacity casting polyurethane elastomeric (HCPUE) bearing is a new elastomer isolation bearing that features excellent durability, higher vertical capacity, and a simpler production process compared with traditional rubber isolation bearings. However, HCPUE bearing exhibits significant hardening behavior at low temperatures. To expand the application of HCPUE bearings in cold regional structures, this study developed an improved low-temperature resistant 3M-HCPUE bearing by incorporating 3-methyl tetrahydrofuran copolyether glycol (3M-PTGL) in the elastomer formulation. The low-temperature performance improvement of the 3MHCPUE specimen was verified through characterization and mechanical property tests using six different compounding formulas. HCPUE materials with 15% and 25% 3M-PTGL were selected to prepare improved 3MHCPUE bearings. The shear hysteretic behavior and ultimate deformation performance of the bearings were tested at different temperatures. Seismic fragility analysis of a three-span box girder bridge with 3M-HCPUE bearings was conducted using different isolation periods and ambient temperatures. The 3M-PTGLimproved 3M-HCPUE bearing exhibited excellent low-temperature performance and effectively alleviated the hardening behavior of the HCPUE bearing at low temperatures. The change rate in the equivalent stiffness for the 3MHCPUE bearing with 25% 3M-PTGL was degrees C reduced from 106% to 44% at -20 degrees C compared with that at 23 degrees C. The equivalent damping ratio slightly decreased from 25.2% to 19.6%. The improved 3M-HCPUE bearings effectively reduced the failure probability of the pier at low temperatures, but increases the probability of bearing failure.