Dr. Taehee Lee: April 17, 2025 at 2:00 P.M. – ASE Grad Seminar Series
April 21, 2025
Date/Time: April 17, 2025, 2:00PM
Location: Walker Engineering 320
MS Teams link: Join virtually (Meeting ID: 289 501 747 572; Passcode: mF2mp9cJ)
Speaker: Dr. Taehee Lee, Visiting Scholar
Affiliation: Department of Aerospace Engineering, Mississippi State University
Title: Development of Stiff-type Polyurea Retrofit Material and its Seismic Strengthening Effect on Masonry Structures
Abstract: The construction industry paradigm among OECD countries is shifting from new construction to the maintenance and rehabilitation of existing structures. To meet the rapidly growing need for structure strengthening of a growing number of aged structures, strengthening material with easy to apply and short construction time is needed. In this study, a new strengthening material (Stiff-type Polyurea (STPU)) is developed to meet the rapidly growing demand for the strengthening of aged structures. STPU is developed by modifying components of existing polyurea to have a better strengthening effect. To develop STPU, a high tensile strength and low percent elongation are needed. The mechanical property test results showed that Polymeric MDI as prepolymer with NCO 18% was the best mix proportion for STPU. From the durability tests, STPU shows excellent durability and satisfied the Korean standard requirements. The strengthening effect of STPU on masonry wall structures was evaluated in experimental and numerical methods. To evaluate the strengthening effect of STPU on masonry walls, a flexural strength test and a shaking table test were conducted. From flexural strength test results, the strengthening effect of STPU shows higher in order of BFPF, BFPS, BFP, and BFN. STPU strengthened specimens show ductile behavior after the ultimate load whereas non-strengthened specimen shows brittle fracture. From the shaking table test results, compared to the non-strengthened specimen, the STPU-strengthened specimen shows a 24% decrease in acceleration and improvement in seismic load resistance by 0.3g peak ground acceleration (PGA). To construct a numerical model of STPU-strengthened masonry wall using ABAQUS, the Arruda-Boyce model was applied to STPU, and a detailed micro-model was applied to the masonry wall. The difference ratio between the simulation and experiment results is under 16%. the simulation results show the same crack patterns and tendency in experiment result.
Bio: Dr. Taehee Lee is a Visiting Scholar in the Department of Aerospace Engineering at Mississippi State University. He earned his bachelor’s degree in August 2016 from the Department of Civil and Environmental Engineering at Yonsei University (in Korea). He entered the integrated M.S./Ph.D. program at Yonsei Graduate School in September 2016. Dr. Lee earned his Ph.D. degree in February 2024 from the Department of Civil and Environmental Engineering at Yonsei University, where he specialized in Concrete Structural Engineering under the supervision of Professor Jang-Ho Jay Kim. During his doctoral studies, he conducted research on the development of polyurea-based strengthening materials and the seismic performance evaluation of masonry structures retrofitted with polyurea, contributing to a broad range of studies within the field of concrete structural engineering. His research interests have included the development of systems for strengthening concrete structures using carbon fiber reinforced polymers (CFRP), polyurea materials for seismic retrofit, and the structural behavior of prestressed concrete members under blast loads. Dr. Lee actively participated in multiple national research projects aimed at enhancing the durability and safety of civil infrastructure in Korea. He has been involved in the preparation of research proposals for R&D projects in Korea with annual budgets ranging from approximately USD 75,000 to 2.25 million, thereby gaining valuable experience in large-scale project planning and collaboration. To date, he has published a total of 11 papers in internationally recognized SCI/E-indexed journals, including Engineering Structures (IF: 5.6), Composite Structures (IF: 6.7), and Construction and Building Materials (IF: 7.4), as both first and co-author. In Fall 2024, he taught a graduate course titled “Special Topics in Structural Engineering” in the Department of Construction Systems Engineering at Kook-Min University, contributing to the education of future scholars in the field.