The Behavior of Shelf Angles Made with Various Connectors
Abstract
Masonry veneer is a very successful external wall design, used in almost all kinds of modern buildings and construction. The building code recommends that the self-weight of the brick veneer must be transferred to the structural backing with the help of shelf angles. The shelf angles are attached to the main structure frame through anchors. The Through bolts are an industry favorite anchor but has some persistent problems that do not comply with the requirements of current building codes. These bolts are uneconomical, time-consuming, and create thermal bridges. Although the Lag screw provides a better alternative to the Through bolts anchor but the availability of data for the design performance of the Lag screw and stand-off specifics is scarce. There is limited previous studies that determined the structural and thermal performance of Lag screws with and without the use of stand-offs. The current research determines the structural and thermal performances of wood-flooring systems where shelf angles are attached to the structure through anchors (Through bolts or Lag screw), with and without various stand-offs. The stand-offs include 2 inch Fiberglass tube, 2 inch C-channel and 2 inch proprietary Fero-fast thermal bracket. Moreover, the study presents the comparison study of key parameters such as the mid-span deflection, rotation in shelf angle, loading capacity of fasteners, failure modes of specimen and U-value for thermal performance between Through bolts and Lag screw with and with-out stand-offs. The result of this study compares the performance of proposed stand-offs and anchors with traditional anchoring systems for shelf angles. Also examines whether these innovative solutions meet the demand for reduction in thermal bridging and provide structural stability in building envelopes.
The thermal analysis conducted in this study revealed that Through-bolt connections demonstrated lower thermal performance compared to Lag screws. However, that through-bolts had a higher structural performance than the Lag screws due to their longer embedment length. The study also concluded that the stand-offs improved the thermal performance of the assembly.