Current Projects
Collaborative Research: Resilient Seismic Retrofit by Integrating Selective Weakening and Self-Centering
Many reinforced concrete buildings in the US and around the world were built before the implementation of modern seismic design codes. Existing seismic retrofit methods achieve life safety through permanent damage. This project investigates a new seismic retrofit method which focuses on resiliency by minimizing damage to keep buildings operational following an earthquake.
The new seismic retrofit method integrates the concepts of selective weakening, hinged walls, and self-centering. The method targets reinforced concrete shear walls that have design deficiencies related to confinement, transverse reinforcement, and reinforcement detailing, which have been associated with slender wall failures in past earthquakes. Retrofit is achieved by converting deficient shear walls into self-centering walls by creating a cold joint near the shear wall-foundation interface (weakening) and adding unbonded external post-tensioning. The objective of this research is to understand the change in fundamental response of deficient reinforced concrete buildings when retrofitted with this method and to quantify performance enhancement using reliability concepts.
Lead UB PhD Student: Mr. Sina Basereh
Collaborators: Dr. Sriram Aaleti's research group
University of Alabama, Tuscaloosa
Funding Agency: National Science Foundation
Award Number 1663063
Sample Publications:
Basereh, S., Okumus, P., Aaleti, S. (2020) “Reinforced Concrete Shear Walls Retrofitted Using Weakening and Self-Centering: Numerical Modeling.” ASCE Journal of Structural Engineering, 146(7).
Basereh, S., Okumus, P., Aaleti, S. (2020). “Seismic Retrofit of Reinforced Concrete Shear Walls to Ensure Reparability.”, ASCE SEI Congress, April 5-8, St Louis, MO.
Collaborative Research: Tessellated Structural-Architectural Systems for Rapid Construction, Repair, and Disassembly
This research investigates a new integrated structural-architectural wall system which utilizes tessellated patterns, an arrangement of repetitive elements, to produce buildings that can be efficiently constructed, repaired, reconfigured, and deconstructed. Tessellated Structural Architectural (TeSA) systems can contribute to resilience through rapid repair and reoccupation after an extreme event, as well as to sustainability through reuse and adaptability of materials, structural elements, and buildings.
This project studies and understands fundamental differences of multiple classes of TeSA systems. The structural behavior of diverse classes of tessellated wall systems, including 1D and 2D topologically interlocking tessellations are investigated through validated models. Analytical models, physical experiments, and probabilistic assessments are used to focus on localization of damage in tessellated structures and the effects of repair/replacement of damaged elements at the building scale. Research also creates a decision framework whereby integrated teams of architects and engineers can utilize fragility curves as a visual means of communicating the effects of design decisions concerning materials and building systems.
Lead UB PhD Student: Mr. Mohammad Syed
Collaborators: Dr. Elhami Khorasani
University at Buffalo
Dr. Ross' & Dr. Kleiss' research groups
Clemson University
Funding Agency: National Science Foundation
Award Number 1762899
Sample Publications:
Ross, B, Yang, C., Barrios Hernandez, C., Okumus, P., Elhami Khorasani, N. (in press) “Tessellated Structural-Architectural Systems: A Concept for Efficient Construction, Repair, and Disassembly.” ASCE Journal of Architectural Engineering.
Seismic Vulnerability of Deteriorated Bridges
The goal of this project is to understand the combined impact of corrosion and earthquake hazards on existing bridges. This is achieved by establishing a framework which can then be used to evaluate the impact of using advanced cementitious composites on the vulnerability of bridges to these hazards. Slow deterioration processes such as rebar corrosion degrading the long-term performance of highway bridge components is considered. Corrosion is modelled analytically and its effect on the structure is modeled by calculating material, stiffness and strength loss. Nonlinear dynamic analyses are used to construct seismic fragility curves with the consideration of corrosion effects at discrete times across the life span of bridges. The results can be used to inform repair, retrofit and maintenance decisions.
Lead UB PhD Student: Mr. Hanmin Wang
Collaborators: Dr. Ravi Ranade
University at Buffalo
Funding Agency: Region 2 University Transportation Center (USDOT)
Design and Construction Specifications for Bonded and Unbonded Post-Tensioned Concrete Bridge Elements
Grouted tendons (bonded and unbonded) are predominantly used for post-tensioned concrete bridge elements in the United States. However, because of potential durability issues with grouted tendons, some highway agencies use ungrouted tendons for post-tensioning to facilitate replacement. Combinations of bonded and unbonded tendons as well as internal and external tendons or combinations thereof are used. The AASHTO LRFD Bridge Design Specifications address the design of post-tensioned concrete bridge elements. However, some design aspects pertaining to this variety of tendon applications are not adequately addressed or evaluated (e.g., shear and torsion for elements post-tensioned with unbonded internal tendons, combined unbonded internal and external tendons, or combined bonded and unbonded tendons; and shear and flexure for elements post-tensioned with combined bonded and unbonded tendons). Research is needed to review available information, perform necessary analytical and experimental evaluations, and propose revisions to the AASHTO LRFD Bridge Design Specifications and the AASHTO LRFD Bridge Construction Specifications, if necessary.
