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Seismic Repair of Concrete Wall Piers Using CFRP Active Confinement

项目名称：	Seismic Repair of Concrete Wall Piers Using CFRP Active Confinement
摘要：	Prior to implementation of modern seismic codes, lap splicing of longitudinal reinforcement at the base of wall piers in concrete bridges was a common practice. Figure 1 shows details of lap spliced bars in wall piers; in regions of high seismicity this creates unfavorable conditions. In bridges located in high seismic regions, lap splices located in the critical hinging region of the wall pier experience bond-splitting failure of the spliced bars within the plastic hinge; this leads to stiffness and flexural strength degradation of the pier. Observations after major earthquakes show that structural damage or failure in bridges with concrete wall piers can be attributed to inferior performance of lap-spliced reinforcement at the base of the piers (Mitchell et al. 1994; Priestley et al. 1996). Figure 2 shows typical lap-splice damage from laboratory experiments that includes buckling of vertical and lateral bars (AboShadi et al. 2000). Currently, American Association of State Highway and Transportation Officials (AASHTO) (2010, 2011) prevents splicing of pier longitudinal reinforcement at the base of the pier where plastic hinging could develop. The most common approach for improving the bond strength of spliced reinforcement in existing bridge piers with bond-critical regions is the use of external confinement. Methods studied include the use of steel jackets (Mitchell et al. 1994; Priestley et al. 1996; Aboutaha et al. 1999); and carbon fiber-reinforced polymer (CFRP) jackets (Priestley et al. 1996; Seible et al. 1997; Hawkins et al. 2000; Harries et al. 2006; Ghosh and Sheikh 2007; Harajli and Dagher 2008; Harajli and Khalil 2008; ElGawady et al. 2010; Bournas and Triantafillou 2011; El-Souri and Harajli 2011). A technique using a combination of CFRP jackets and CFRP anchors has also been studied (Kim et al. 2011). All of the above studies reported enhanced bond performance of the reinforcement and improved seismic response. Most of the methods used for seismic bond strengthening use passive confinement techniques - that is, techniques in which the confinement effectiveness is activated once bond-splitting cracks initiate. Because of their passive nature, most of these techniques fall short of achieving their full potential and the seismic performance of the retrofitted wall piers is inferior compared to that of wall piers designed using current codes, such as AASHTO (2011), which stipulate splice-free wall piers that are adequately confined by closely spaced transverse steel ties within the critical hinging region. Typical seismic retrofit recommendations (FHWA 2006) include steel plate encasement and bolts drilled and anchored through the thickness of the wall pier, as shown in Fig. 3; when the steel rods are tightened they provide active confinement of the lap spliced bars. A method similar to the one shown in Fig. 3 has been used with steel anchors but without the steel plate encasement with promising results (Hantouche et al. 2015). The present proposal describes the concept of seismic retrofitting of lap splices in wall piers designed with inferior details similar to those shown in Fig. 1. Active confinement by means of a pretensioned CFRP jacket and CFRP anchor rods is used for bond strengthening of lap-spliced reinforcement thus improving the seismic performance of concrete wall bridge piers. Representative as-built and repaired wall pier specimens with lap-spliced reinforcement within the critical hinging region will be tested under quasi-static cyclic loads. A design approach will be developed to evaluate the active lateral pressure required for adequate bond strengthening and for designing the strengthening system.
状态：	Completed
资金：	145454
资助组织：	Office of the Assistant Secretary for Research and Technology
管理组织：	Mountain-Plains Consortium
项目负责人：	Kline, Robin
执行机构：	Dept. of Civil and Environmental Engineering
主要研究人员：	Pantelides, Chris
开始时间：	20161220
预计完成日期：	20190930
实际结束时间：	20200304