In this presentation, the findings of an extensive testing program investigating the seismic performance of large-scale hybrid-sliding rocking (HSR) bridge columns are presented.
The concept of bridges with HSR columns is an Accelerated Bridge Construction (ABC) technique applicable to high seismic regions. The HSR columns incorporate end rocking joints and intermediate sliding joints over the column height. The end rocking joints, along with the unbonded post-tensioning, provide the HSR columns with self-centering capabilities, while the friction at the sliding joints significantly increases their energy dissipation, reducing their seismic deformation demands.
Preliminary evidence of the damage avoidance capabilities of HSR bridges was obtained through shake table testing and quasi-static cyclic testing conducted at the University at Buffalo on a large-scale HSR bridge, and two HSR columns, respectively. Computational simulation models, which utilized an innovative two-node element formulation to represent the HSR joints, were subsequently developed and validated against the available test data. The simulation models enabled further examination of the effects of various loading conditions and design variables on the seismic performance of HSR columns, leading to an improved HSR column design, which is investigated in this study. Based on observations from an extensive computational parametric study, the new design includes fewer sliding joints with well-controlled sliding properties provided by glass-filled PTFE pads.
This testing program assesses the seismic performance of the new HSR column design under various boundary and loading conditions, and provides data to validate the developed simulation models. Four identical half-scale HSR columns, designed for a five-span bridge located in Los Angeles, CA, are built and tested in the Structural and Materials Testing Laboratory at the Center for Infrastructure Renewal at the Texas A&M University. Each column comprises three hollow precast concrete segments with two sliding joints, post-tensioned together by eight internal unbonded monostrands. The first (cantilever) column is subjected to uniaxial lateral loading. The second column has the top rotation restrained (double curvature member) and is subjected to uniaxial lateral loading. The third (cantilever) column is subjected to biaxial lateral loading, while the fourth (cantilever) column is subjected to combined lateral-torsional loading. Loads are applied using two vertical and two horizontal actuators, under both quasi-static and dynamic conditions to also examine the effect of the rate of loading on the responses. For all tests, peak drift ratios exceeding 10% are achieved. Finally, all tests are simulated using previously-developed 2D and 3D OpenSees models and the computational predictions are compared with the experimental data.
• Given the large number of structurally deficient and functionally obsolete bridges in the US and around the world, the topic of this presentation is of regional, national and international interest.
• This presentation is useful to structural and construction engineers as wells as code developers from academia and practice.
• The audience will be introduced to novel bridge technologies in the framework of seismic ABC, performance advantages of HSR bridges, large-scale experimental testing of HSR columns, and their novel simulation models.