1 Introduction
2 Friction Coefficients
2.1 Friction in Post-tensioning System
2.2 Friction Coefficients in Provisions
Provisions | Wobble friction coefficient, k (/m) | Curvature friction coefficient, μ (/radian) |
---|---|---|
Structural concrete design code (KCI 2012) | 0.0015–0.0066 | 0.15–0.25 |
Design code for highway bridges (KRTA 2010) | 0.0015–0.0066 | 0.15–0.25 |
ACI 318-08 (ACI 2008) | 0.0016–0.0066 | 0.16–0.25 |
ACI 318-14 (ACI 2014) | Not specified | |
Standard specifications for highway bridges (AASHTO 2002) | 0.00066 | 0.15–0.25 |
AASHTO LRFD bridge design specifications (AASHTO 2014) | 0.00066 | 0.15–0.25 |
Bridge design manual (PCI 2011) | 0.00066 | 0.20 |
Post-tensioning manual (PTI 2006) | 0.0010–0.0023 (Recommended value: 0.0016) | 0.14–0.22 (Recommended value: 0.18) |
Prestress manual (Caltrans 2005) | 0.00066 | 0.15, 0.20, 0.25, etc. (Related to the length of a strand) |
Canadian highway bridge design code (CSA 2006) | 0.003, 0.005 (Related to the diameter of a sheath) | 0.20 |
BS 8110 (BSI 1997) | Not less than 0.0033 | 0.20, 0.25, 0.30 (Related to rust) |
Eurocode 2 (CEN 2002) | 0.00095–0.0019 | 0.19 |
CEB-FIP model code (CEB 1993) | 0.00095–0.0019 | 0.19 |
fib model code for concrete structures (fib 2013) | 0.0008–0.002 | 0.16–0.20 |
Standard specifications for concrete structures (JSCE 2007) | 0.004 | 0.30 |
Specifications for highway bridges (JRA 2012) | 0.004 | 0.30 |
3 Principle of Smart Strand
4 Full-Scale Test for Friction Coefficient
4.1 Test Specimen and Variables
Category | Test variables | Values |
---|---|---|
Sheath | Diameter (mm) | 66, 85, 100 |
Curvature (sag/length) | 0 (straight), 0.0295, 0.0490, 0.0785 | |
Material | Galvanized metal | |
Strand | Number | 1, 7, 12, 13, 19 |
Nominal diameter (mm) | 15.2 | |
Ultimate strength (MPa) | 1860 | |
Lubrication | Not applied |