Resilient Bridge Rocking Columns with Polyurethane Damage-Resistant End Segments and Replaceable Energy-Dissipating Links

Abstract

This paper introduces a novel low-damage bridge column design for accelerated bridge construction (ABC) in seismic areas. The proposed design integrates (1) polyurethane (PU) damage-resistant segments at the column ends to accommodate large rotations without damage, (2) external replaceable energy-dissipating (ED) links to provide supplemental hysteretic damping and flexural stiffness and strength, and (3) internal unbonded posttensioning to provide self-centering. Polyurethanes are polymeric materials that exhibit large deformability, low stiffness, and large strength, in addition to rate-dependent elastic and inelastic mechanical properties. As a result, PUs can accommodate large deformations with negligible damage. The ED links are external buckling-restrained yielding steel elements, which offer additional stiffness/strength and hysteretic energy dissipation to control seismic-displacement demands. Following strong earthquakes, residual deformations are small and can be fully eliminated upon replacement of the (external) ED links, which are the only elements to experience major damage. Because all ED links are external, replacement can be rapidly performed without operation disruptions. The mechanical properties of a selected PU were first investigated through uniaxial compression tests for various strain rates. The proposed column design was then investigated for various PU-segment geometries and various ED-link properties through three-dimensional finite-element analysis of a bridge column subjected to monotonic and cyclic pushover loading at various loading rates and amplitudes. The proposed column design was found to provide major self-centering and energy-dissipation capabilities with negligible damage. The response was found to be dependent on the geometric properties of the PU segments. Residual deformations significantly decreased with the loading rate. However, the peak column strength only slightly increased with the loading rate.