ACI 440.2R-17 Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures.
This document gives guidance on proper detailing and installation of FRP systems to prevent many types of debonding failure modes. Steps related to the surface prepa- ration and proper termination of the FRP system are vital in achieving the levels of strength predicted by the proce- dures in this document. Research has been conducted on various methods of anchoring FRP strengthening systems, such as U-wraps, mechanical fasteners, fber anchors, and U-anchors. Because no anchorage design guidelines are currently available, the performance of any anchorage system should be substantiated through representative physical testing that includes the specifc anchorage system, installation procedure, surface preparation, and expected environmental conditions. The design equations given in this document are the result of research primarily conducted on moderately sized and proportioned members fabricated of normalweight concrete. Caution should be given to applications involving strength- ening of very large or lightweight concrete members or strengthening in disturbed regions (D-regions) of structural members such as deep beams, corbels, and dapped beam ends. When warranted, specifc limitations on the size of members and the state of stress are given herein.
1.2.1.3 Maximum service temperature—The physical and mechanical properties of the resin components of FRP systems are infuenced by temperature and degrade at temper- atures close to or above their glass-transition temperature T g (Bisby et al. 2005b). The T g for commercially available, ambient temperature-cured FRP systems typically ranges from 140 to 180°F (60 to 82°C). The T g for a particular FRP system can be obtained from the system manufacturer or through testing by dynamic mechanical analysis (DMA) according to ASTM E1640. Reported T g values should be accompanied by descriptions of the test confguration; sample preparation; curing conditions (time, temperature, and humidity); and size, heating rate, and frequency used. The T g defned by this method represents the extrapolated onset temperature for the sigmoidal change in the storage modulus observed in going from a hard and brittle state to a soft and rubbery state of the material under test. This transi- tion occurs over a temperature range of approximately 54°F (30°C) centered on the T g . This change in state will adversely affect the mechanical and bond properties of the cured lami- nates. For a dry environment, it is generally recommended that the anticipated service temperature of an FRP system not exceed T g – 27°F (T g – 15°C) (Xian and Karbhari 2007), where T g is taken as the lowest T g of the components of the system comprising the load path. This recommendation is for elevated service temperatures such as those found in hot regions or certain industrial environments. In cases where the FRP will be exposed to a moist environment, the wet glass-transition temperature T gw should be used (Luo and Wong 2002). Testing may be required to determine the crit- ical service temperature for FRP in other environments. The specifc case of fre is described in more detail in 9.2.1.ACI 440.2R pdf download.