Strengthening of Existing Inverted-T Bent Caps -- Volume 2: Experimental Test Program

US Transportation Collection2018PDFTech ReportHurlebaus, StefanMander, John B.Birely, Anna C.Terzioglu, TevfikCui, JilongPark, Sun HeeTexas A&M Transportation InstituteTexas Department of Transportation. Research and Technology Implementation OfficeUnited States. Department of Transportation. Federal Highway AdministrationTexas A&M Transportation InstituteTexasUnited StatesBentsLoad and resistance factor designLoad transferRetrofittingStrengthening (Maintenance)FHWA/TX-18/0-6893-R1-Vol2, Report 0-6893-R1-Vol2Project 0-6893September 2015\u2013August 2018Inverted-T bent caps have been widely used in Texas to provide increased clearance underneath bridges while providing an aesthetically pleasing substructure alternative. The bottom flange (ledge) must have sufficient transverse and punching shear capacity to be able to transfer the applied loads to the web. In this study, retrofit solutions to strengthen the in-service inverted-T bent caps, which have deficiencies with an increased number of lanes, were identified and are discussed in the previous volume. An experimental test program consisting of eight half-scale specimens with hanger, ledge flexure, and punching shear deficiencies was then conducted, with each specimen consisting of external and internal girder locations. Thirty-three individual tests were conducted to investigate six strengthening solutions: end-region stiffener, clamped threadbar with channel, load-balancing post-tensioning, concrete infill with full- and partial-depth fiber-reinforced polymer anchored by steel waling, and large bearing pad. Based on the test results, all retrofit solutions except large bearing pad improved the capacities by 16 percent to 82 percent. The measured ultimate load for all retrofit solutions was greater than the calculated ultimate demands. A capacity analysis based on the 2014 American Association of State and Highway Transportation Officials (AASHTO) LRFD Bridge Design Specifications was also conducted for all tests. The estimated capacities were compared to the measured capacities and determined to be over-conservative in most cases, and rational modifications for the capacity estimations were proposed based on the observed test results. The modified calculations improved the accuracy of the capacity estimations by 8 percent to 28 percent, compared to 2014 AASHTO load and resistance factor design provisions143