Extreme Bridge Loads
Full Session with Abstracts
340050-7 - Seismic Performance Assessment of Bridges incorporating Polyurethane-Enhanced Damage-Resistant Columns through Nonlinear Dynamic Analysis and Large-scale Testing
Friday, April 20
1:30 PM - 5:00 PM
This presentation/paper assesses, via computational and large-scale experimental studies, the seismic performance of a novel bridge substructure design incorporating polyurethane (PU)-enhanced rocking columns. PU-enhanced columns are precast concrete rocking columns that integrate: (i) polyurethane damage-resistant segments at the column ends to accommo-date large rotations without damage, (ii) external replaceable energy dissipating (ED) links, in the form of buckling-restrained yielding elements, to provide supplemental hysteretic damp-ing and flexural stiffness and strength, and (iii) internal unbonded post-tensioning to provide self-centering. Polyurethanes are visco-elastic/visco-plastic polymeric materials, which, com-pared to concrete, exhibit large deformability, low stiffness and large strength, which increas-es with the loading rate, further preventing damage. As a result, under strong earthquakes, damage is mainly concentrated at the (external) ED links, which can be rapidly replaced without bridge operation disruptions, eliminating any residual deformations.
The mechanical properties of polyurethanes of two selected compositions are first quanti-fied through uniaxial testing under various loading paths (monotonic, cyclic) and strain rates (up to 5% /sec). A uniaxial visco-elastic/visco-plastic parallel network constitutive model ca-pable of capturing the observed rate dependency, hysteresis and damage (softening), is de-veloped, calibrated to the experimental data, and implemented in the OpenSees structural analysis software. Using this model, analyses under monotonic and cyclic loading are con-ducted for various PU-enhanced column designs accounting for two PU compositions, vari-ous PU segment geometries (diameter, height) and ED link properties. The obtained responses are compared with those of monolithic reinforced concrete columns and rocking precast con-crete columns. Optimal PU-enhanced column designs are subsequently included in the sub-structure of a two-span bridge, which is subjected to Incremental Dynamic Analyses (IDA) until collapse. These analyses validated the damage resistant properties of PU-enhanced col-umns and showed that replacement of damaged ED links nearly eliminates residual defor-mations.
The presentation will be concluded with the results of a testing program on large-scale (~1:2.5) PU-enhanced cantilever rocking columns subjected to displacement-controlled lateral cyclic loading of increasing amplitude (up to a 20% drift ratio) at several loading rates. Tested columns are retrofitted (via ED link replacement) and re-tested. Rocking-only precast con-crete columns are also tested under the same loading protocols to provide a basis for compari-son. Experimental performance is evaluated in terms of force and ductility capacity, self-centering and energy dissipation capacity, observed damage, and residual strength, before and after retrofit.
• Considering the need for rapid replacement of the aging bridge infrastructure in in the U.S. and worldwide, as well as the poor performance of bridges in recent earthquakes, this presentation will be of national and international interest.
• The target audience will include structural, bridge and earthquake engineers from academia, practice and State Agencies as well as engineers that are interested in use of advanced materials to improve structural performance.
• The audience will be introduced to a bridge substructure design that combines the novel concepts of construction rapidity, damage avoidance and rapid post-earthquake repair, through advanced materials and response mechanisms. These concepts can be extended into various structural systems, such as buildings, and integrated in research efforts and teaching curricula.