Title:
Development of FRP Retrofit Guidelines for Deficient Reinforced Concrete Horizontal Lateral Force Resisting Systems
Author(s):
Hunter Hutton
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
10/23/2022
Abstract:
This presentation provides an update on an ACI CRC and industry co-funded project to develop retrofit guidelines for strengthening deficient reinforced concrete diaphragms using fiber reinforced polymer (FRP). For reinforced concrete buildings, the horizontal lateral force resisting system (hLFRS) consists of the reinforced concrete diaphragm and associated chords and collectors. These hLFRS can require strengthening for several reasons: a) need to enhance seismic performance, b) inadequate strength or stiffness, c) missing load paths, d) inadequate shear transfer/connections, and e) new penetrations in the slab. Utilizing FRP to remedy these issues is a common practice; however, there are currently no guidelines for the design or detailing of FRP strengthening of deficient hLFRS. The experimental study being conducted at the Virginia Tech Structural Engineering Laboratory consists of cyclic testing of six one-half scale reinforced concrete diaphragms designed to simulate the diaphragm shear zone adjacent to shear walls. The shear behavior of the first two specimens, consisting of a baseline control diaphragm and a diaphragm strengthened with externally bonded CFRP with FRP anchorages, will be discussed and compared. The results of a finite element study, validated by the experimental data, will also be presented to better understand the specimen's experimental behavior. The findings of the experimental and the finite element studies will be used to identify knowledge gaps in current practice and outline the need for improved design principles and limit states. Finally, a preliminary design approach that is consistent with the design principles stated in ACI (2019) and the FRP design philosophy in ACI 440.2R (2017) will be outlined.