Reinforcing steel
- Why:
- To resist tension and shear in masonry assembly:
- To tie wythes of masonry together:
- Increase axial load carryng capacity.
- Provide ductility under seismic loadings.
- Temperature and shrinkage crack control.
- To resist tension and shear in masonry assembly:
- Types:
- Deformed bars:
- Max size » #11 (UBC '97 2107.2.2.1)
- Grades:
- Grade 40 (recommended for its ductility)
- Grade 50
- Grade 60
- Grades refer to minimum specific yield strength, (fy), in ksi.
- Allowable tensile stress, Fs:
Fs = .5 fy £24,000 psi.(UBC '97 2107.2.11.1.1) - Modulus of elasticity, Es = 29 X 106 psi. (UBC '97 2106.2.12.2)
- Joint reinforcement (wire)(UBC '97 2106.1.5.4)
- Shrinkage crack control.
- Placed within mortar joint.
- Tying wythes together.
- Three wire truss or ladder.
- Types: ladder and truss.
- In single-wythe, two wire ladder or truss appropriate.
- Ladder type causes less interference with vertical rebar.
- Common size: No. 9 = .148" in diameter.
- Yield strengths: fy > 70,000 psi
- Fs = .5 fy £ 30,000 psi. (UBC '97 2107.2.11.1.2)
- A required minimum of 5/8" mortar cover must be provided between join reinforcement and exposed face.(UBC '97 2106.1.8)
- Vertical spacing of joint reinforcement in a wall must be £ 16" o.c.
- Shrinkage crack control.
- Optimum spacing of rebar is at 4' O.C. for better workmanship. If they are too close, the movement of the mason is hindered and could result in poor bed joints.
- Deformed bars:
- Additional reinforcement issues to ensure ductility and strength include:
- Amount complies with code minimum and maximum.
- Proper spacing, both horizontal and vertical.
- Minimum cover.
- Anchorage for flexural and shear.
- Lapping.
- Confinement of bars.
- These issues are of primary concern when specifying your design - e.g. detailing.
- Additional reinforcement detailing requirements will be presented for beams and walls in the following two main class modules.
