Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 1 CEE Capstone II Structural Engineering Lecture 10 – Masonry Shear Walls

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 2 Time for a Pop Quiz… You should be familiar with… 1.Differences between unreinforced and reinforced masonry 2.MSJC code 3.Components of masonry 4.Properties/manufacturing of CMU 5.Components of mortar

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 3 Time for a Pop Quiz… You should be familiar with… 6.Types of mortar 7.Proportion and property specifications for mortar 8.Differences between mortar and grout 9.Types of reinforcement 10.Definition of f’ m

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 4 Time for a Pop Quiz… You should be familiar with… 11.Unit strength method vs. prism test method 12.Bond patterns for masonry 13.Gross, bedded, and net areas

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 5 Shear Walls Essentially act as vertical beams that resist gravity and in-plane lateral loads Generally, shear walls must be checked for flexure and shear Deflections (stiffness) may also be critical –difficult, consider both shear and flexural displacements –see text

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 6 Unreinforced Shear Walls Generally not very efficient –Limited tension capability –Work best with high axial loads Basic Design Criteria: –Net Tensile Stress (Flexural – Axial) –Net Compressive Stress (Flexural + Axial) –Shear Stress

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 7 Reinforced Shear Walls Shear provisions are a function of the M/Vd ratio (essentially the h/d ratio) h d H VMVM h H VMVM d Flexure likely to control Shear likely to conrol

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 8 Reinforced Shear Walls – Allowable Shear Stress Provisions (MSJC ) For walls with in-plane flexural reinforcement and no shear reinforcement For walls with in-plane flexural reinforcement and shear reinforcement to resist the full shear

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 9 Reinforced Shear Wall Example Fully grouted 8” (nominal) CMU wall Type S mortar, f’ m =3000 psi The wall has no axial stress (ignore self-weight) Vertical reinforcement is 2#8 at each end Determine the maximum horizontal load H that can be applied to the wall. 8’-0” 6’-8” H (wind) 80” Avg. d=72”

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 10 Reinforced Shear Wall Example (continued) Assume wall has no horizontal shear reinforcement Assume wall is underreinforced (technically must check) M = A s F s jd (Assume j=0.9) M = [(2)(.79)][(1.333)(24)](.9)(72) M = 3275 in.-kips H = M/h = 3275/96 = 34.1 kips M/Vd = 96/72 =1.333 > 1.0 F v = (3000) 1/2 = 55 psi > 35 psi F v = (4/3)(35) = 46.7 psi V max = bdF v = (7.625)(72)(46.7) H = 25.6 kips Shear governs ---> H=25.6 kips 8’-0” 6’-8” H 80” Avg. d=72”

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 11 Reinforced Shear Wall Example (continued) Assume wall has sufficient horizontal steel to take full shear corresponding to flexural capacity M/Vd = 96/72 =1.333 > 1.0 F v = 1.5(3000) 1/2 = 82 psi > 75 psi V max = F v bd = [(4/3)(75)](7.625)(72) = 54.9 kips H = 34.1 kips < 54.9 OK A v /s = V max /F s d = 34.1/[[(1.333)(24)](72)] = sq. in. per inch With 2 #4 bars, A v =0.40 in. 2 s =.40/.0148 = 27.0” -----> Use 24” spacing 8’-0” 6’-8” H 80” Avg. d=72”

Villanova University Dept. of Civil & Environmental Engineering CEE Capstone II Structural Engineering 12 Reinforced Shear Wall Example (continued) Summary Only vertical reinforcement (2#8) –H = 25.6 kips (shear governs) Vertical reinforcement (2#8) and horizontal reinforcement 24”): –H = 34.1 kips 8’-0” 6’-8” H 80” Avg. d=72”