Examination of the Effective Coefficient of Friction for Shear Friction Design

Since the introduction of the effective coefficient of friction μe approach to the PCI Design Handbook: Precast and Prestressed Concrete, several studies have provided additional test results that can be used to compare and validate the shear friction design provisions. This paper presents a database of shear friction test results collected from the literature that was analyzed for the effective coefficient of friction approach used in the PCI Design Handbook (Eq. [5-32b]), and the coefficient of friction approach used in the PCI Design Handbook (Eq. [5-32a]) and the ACI Building Code Requirements for Structural Concrete (ACI 318- 14) and Commentary (ACI 318R-14) (Eq. [22.9.4.2]). The database was limited to push-off specimens subjected to monotonic loading and without external normal forces. The data were categorized in terms of concrete type, interface condition, compressive strength of concrete, clamping stress, and area of shear interface to help identify gaps in the literature. Analysis of the database showed that PCI Eq. (5-32b) is more accurate and has a lower standard deviation than both PCI Eq. (5-32a) and ACI 318-14 Eq. (22.9.4.2) for normalweight, sand-lightweight, and all-lightweight concrete with monolithic uncracked, monolithic precracked, and cold-joint roughened interface conditions. For the cold-joint smooth interface condition, the authors recommend removing the modification factor λ in the coefficient of friction μ to provide more accurate and economical designs