Link to Report: Coming Soon
Background :
Columns are usually the weak links in conventional bridges for seismic design. In current seismic codes, bridge collapse is prevented under rare earthquakes by providing large ductility, but damage of ductile elements including columns is allowed. Reinforced concrete (RC) columns are widely used in seismic regions of the US due to their controlled ductility through confinement and enhanced durability. Damage of RC columns under moderate earthquakes includes cracking, reinforcement yielding, and major spalling. Nevertheless, significant damage is expected under strong earthquakes, which may result in the bridge closure for repair or total replacement. Even though current practice is successful in attaining the no-collapse objective, a new design paradigm is emerging to minimize bridge column damage incorporating low- to no-damage materials and techniques. The benefit can be enhanced if the low-damage details are combined with precast techniques to further promote accelerated bridge construction (ABC). This proposal explores the seismic behavior of a new class of precast bridge columns that are repairable through component replacement. The project goals are achieved by developing new repairable and constructible precast column detailing, performing pre- and post-test analytical studies, large-scale shake-table testing of a top column model, and proposing design and construction recommendations for such columns. Outcomes include dynamic experimental data, design and construction recommendations, and dissemination through technical reports and journal publications. Repairable precast columns may further facilitate the implementation of ABC in high seismic regions of the nation due to their improved performance.
Objectives :
The main objective of the proposed study is to understand the dynamic behavior of repairable precast bridge columns through shake-table testing at the Earthquake Engineering Laboratory (EEL) at the University of Nevada, Reno (UNR) and to better understand the seismic demands on these columns.
Scope :
Task 1 – Literature Review
The project will begin with a comprehensive review of recent advances in repairable, low-damage, and/or self-centering bridge column systems with external dissipaters. The review will focus on experimental and analytical studies of precast, segmental, and rocking column systems that enable rapid post-earthquake repair or replacement of critical components. For example, Lu et al. (2025) presented experimental results on concrete-filled steel tube (CFST) self-centering rocking bridge piers which showed minimal damage and very small residual drift even at large drift ratios. The review will also consider studies on precast segmental columns with unbonded prestressed tendons and external energy dissipaters (e.g., Moustafa & ElGawady, 2020; Zhang et al., 2022).
Task 2 – New and Enhanced Constructible Detailing
As discussed before, new repairable alternatives with better constructability and without pin connections will also be developed in this task. A rating system will be used to determine the top candidates with best seismic performance and constructability for testing.
Furthermore the detailing of one of the test specimens in the pilot phase. The plastic shear forces of the column were transferred to the footing through a pipe-pin connection in which a solid-square steel box was cast with the footing and a matching steel socket was placed in the base of the column. To prevent a soft start, steel bolts were used to fill any gap between the box and socket. Task 2 will analytically explore the feasibility of other types of shear pins to lock the column and footing without any bolts or filler materials. Examples are shafts with angled or curved tips to lock with the socket as the column is lowered during the installation, or the concrete filled steel tubes (CFSTs) shown in We will use finite element software (e.g., ANSYS) to understand the lateral resistance and performance of different shear-pin connections.
Task 3 – Experimental Investigation
The findings of Tasks 1 & 2 will be discussed with the Research Advisory Panel (RAP). Based on their feedback, one column will be selected for large-scale shake-table testing. A reference cast-in-place column from previous UNR experiments will be used as the benchmark model. A precast plant will fabricate the column and ship it to UNR for assembly and testing at EEL. The precast column will be tested at least three times under a 100%-scale near-fault ground motion. After each run, all steel tendons of the column will be cut and replaced with new ones to practice the “repair-by-replacement” method.
Task 4 – Post-Test Analytical Investigation
The PI has performed some pilot studies on the pushover response of repairable precast bridge columns. Figure 4 shows the column model, which was developed in OpenSees (2016). Due to lack of specific elements for such columns, several combinations of materials and elements were used to best replicate the repairable column behavior. Under Task 4, the research team will develop a new column element for repairable precast bridge columns to be compiled in OpenSees. The accuracy and stability of the new element will be evaluated using data from the cyclic (past studies) and dynamic (current project) testing. Subsequently, a comprehensive finite element analysis will be performed to further investigate the repairable column seismic performance. The study will include dynamic analyses of columns with different geometries, tendon lengths, tendon material properties, and single- and multi-column bents.
Figure 4. Analytical Model for Repairable Precast Columns
Task 5 – Recommendations
Based on the experimental and analytical findings, the preliminary design and construction guidelines that were developed in Tazarv et al. (2024) will be updated and reformatted following AASHTO Seismic (2023). The PI has developed AASHTO design and construction specifications for ABC column connections (NCHRP 935). A similar document will be prepared, and the RAP members will be asked to review the document. The guidelines will be updated based on their feedback.
Task 6 – Project Deliverables
At the end of the project, a comprehensive final report will be prepared by the research team in conformance with the center guidelines. The final report will document all aspects of the project including details of the findings for each task. The final report will be reviewed by RAP and will be revised per their comments.
Research Team :
Principal Investigator: Mostafa Tazarv