Rehabilitation of concrete girders with distressed end regions using innovative materials

concrete;concrete bridge girder;end region;strengthening;repair;fiber reinforced polymer (FRP);shape memory alloy (SMA);prestressing;corrosion;durability;finite element analysis

Zhao, Hang

关键词: concrete;    concrete bridge girder;    end region;    strengthening;    repair;    fiber reinforced polymer (FRP);    shape memory alloy (SMA);    prestressing;    corrosion;    durability;    finite element analysis;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/106245/ZHAO-DISSERTATION-2019.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Concrete bridges play an important role in the transportation network. However, there are more than 56,000 bridges that have been identified as structurally deficient in the U.S., especially those bridges located in the Northern part of the U.S. where harsh climate inflicts severe damage to the structural integrity and durability of the bridges. Among all types of damage, the distressing of end regions in bridge girders is very commonly observed. This damage could be in the form of cracking and spalling of concrete and steel corrosion. This research focuses on addressing this type of damage through innovative repair methods using two novel materials, namely fiber reinforced polymers (FRP) and shape memory alloys (SMA). On one hand, FRP has attracted researchers’ attention because of its high strength-to-weight ratio and corrosion resistance. However, the benefits and effectiveness of repairing concrete girders with damaged ends using FRP, especially if the damaged region is localized at the end (i.e. under very short shear span) have not been studied in depth yet. On the other hand, SMA is a new class of material that is capable of restoring its original shape after being excessively deformed simply by heating. This “shape memory” phenomenon offers significant ease when applying prestressing in very localized regions where conventional prestressing technique is not feasible. This research utilizes experimental and numerical approaches to explore the effectiveness of using FRP laminates and precast prestressing plate (PPP) reinforced with SMA, i.e. SMA-PPP, to repair and strengthen concrete girders with damaged ends. Since the specific damage described above is mainly localized at end regions of precast prestressed concrete (PPC) girders where beam theory is no longer applicable, the behavior of end region (D-region) repaired/strengthened with FRP and SMA is studied using strut-and-tie model (STM). The research tasks carried out comprises conducting three-point-bending tests on full-scale PPC girders repaired with FRP laminates. In addition, small-scale experimental tests are carried out to prove the feasibility of applying prestressing using SMA-PPP and to investigate different connection methods to mount the PPP externally on concrete structures. Finite Element Analysis (FEA) and parametric studies are alsoperformed on PPC bridge girders to explore the effect from various repair systems/designs on the capacity and ductility of the PPC girders using both FRP laminate and SMA-PPP. The results from parametric studies are used to generate and calibrate the STM, which is adopted to analyze the shear capacity of PPC girders repaired with both FRP laminate and SMA-PPP. Accelerated aging test is utilized to study the long-term behavior of NiTiNb SMA reinforcement followed by a series of tests including mechanical and microscopic testing. The impact of SMA heating on the mortar material used in the study of SMA prestressing is also investigated experimentally.