19-104208-Structural Letter-06-26-2020-V1Envirotech EngineeringEnvirotech EngineeringEnvirotech EngineeringEnvirotech Engineering, PLLC., PLLC., PLLC., PLLC.
Geotechnical ◦ Environmental ◦ Drainage ◦ Roadway
PO Box 984
Belfair, Washington 98528
Off: 360-275-9374
Cell: 360-689-6045
envirotech@geotechnicalinfo.com
June 20, 2020
Amy Grealish
212 SW 292nd Street
Federal Way, Washington 98023
Reference: Bulkhead Calculations Report
212 SW 292nd Street, Federal Way, Washington
Dear Ms. Grealish,
Envirotech Engineering, PLLC has completed a bulkhead design of a 7.5 ft in height reinforced concrete
bulkhead located at the referenced address. Per the calculations below, the wall is sufficiently stable with
relation to overturning, sliding, and integrity.
Soil Parameters Structural Parameters
γ = 134 psf Wall Support: Fixed-fixed
φ = 35 ° 0.5 in wall flexural rebars vertical, diameter
ca = 0 psf 0.19635 in2 wall flexural rebars vertical, area
Pore Pressure: No 0.5 in
#4 wall temperature rebars horizontal,
diameter
Earth Pressure: At-rest 0.19635 in2 #4 wall temperature rebars horizontal, area
β = 5 ° 0.5 in #4 footing rebars, diameter
γw = 62.4 psf 0.19635 in2 #4 footing rebars, area
0.9 strength reduction factor, flexural
0.85 strength reduction factor, shear
fy = 60 ksi yield stress in steel reinforcement
Load Inputs 0.0018 yield stress ratio
q 10 psf f'c = 2500 psi concrete compressive strength
DL 0 lb/ft 3 in reinforcement steel cover
LL 0 lb/ft γc = 150 pcf concrete unit weight
w 0 lb
Soil Conclusions
K 0.46
Wall Geometry Ke 0.26
B = 66 in δ 23.33
h = 12 in Ψ 0.00
b = 12 in Rs1 1747.15
H = 7.5 ft RsH1 1604.26
t = 8 in RsV1 692.01
Page 2 of 4
D = 0 in Rw 0.00
n = 6 in Rq 34.77
Key: No RqH 31.93
RqV 13.77
Re 730.15
Rs2 0.00
RsH2 0.00
RsV2 0.00
Sliding
Fr = (ΣWi + RsV1 + RqV)tanδ + cA + RsH2 + RsV2 2540 lb/ft
Fs = RsH1 + RqH + Re + Rw 1636 lb/ft
F.S.static = Fr / Fs 1.6 o.k.
F.S.dynamic = Fr / (Fs + Re) 1.1 o.k.
Overturning
Mr = ΣWixi + RsH2y2 + RsV2xsV2 + RsV1 + RqVxsV1 16198 lb
Mo = RsH1y1 + Rwy1 + RqHyq 4130 lb
F.S.static = Mr / Mo 3.9 o.k.
F.S.dynamic = Mr / (Mo + Reye) 2.2 o.k.
Flexural Steel in Wall (vertical)
Wall load from resultant earth pressure = 1.4*(Rs1 + Rw + Rq +Re) = 3516.9 lb/ft
Mu = (Rs1 + Rw + Rq)*(H-h)^2/20 = 3764.3 ft-lb
As = Mu*12/(strength reduction factor, shear*fy*1000*(t - 3 - 0.1*(t-
3))) = 0.19 in2
Ac = fy*1000*As/0.85/f'c = 5.2 in2
Mn = As*fy*1000*(t - 3 - 0.1*(t - 3)) = 50190.7 in-lb
φMn = strength reduction factor, flexural*Mn/12 = 3764.3 ft-lb
As2 = As*Mu/φMn = 0.19 in2
Number of rebars per foot 0.95
rebar spacing 12.68 in
Temperature Steel in Wall (horizontal)
As = yield stress ratio*b*dc = 0.6669 in2
Number of rebars per foot = As/#4 footing rebars, area = 3.40
rebar spacing = 12/number rebars per foot = 23.08 in
Wall Footing
Pu = 1.4*DL/12 + 1.7*LL/12 + RsV1/12 + RsV2/12 + (γH(B/12 - t/12 - n/12))/12 + q/12 = 421.42 lb/in
qu = Pu/B = 6.39 psi
Vc = 2*f'c1/2 = 100.00 psi
d = h - reinforcement steel cover - 1.5*#4 footing rebars, diameter = 8.25 in
Page 3 of 4
Vu = qu/d*((B-t)/2-d) = 16.06 psi
oVc = Vc*strength reduction factor, shear = 85.00 psi
oVc > Vu o.k.
Flexural Steel in Wall Footing
Mu = qu*(B-t)2/8 = 2684.94 in-lb
As = Mu/(strength reduction factor, flexural*fy*900*d) = 0.0067 in2
Ac = As*fy*1000/0.85/f'c = 0.1891 in2
λ = Ac/2/b = 0.0079 in
As2 = Mu/(strength reduction factor, flexural*fy*1000(d-λ)) = 0.0060 in2
As = yield stress ratio*b*hc = 0.1890 in2
Number of rebars per foot = As2/#4 footing rebars, area = 0.9626
rebar spacing = 12/number of rebars per foot = 12.47 in
Temperature Steel in Wall Footing
As = γcBh = 1.43 in2
Number of rebars per foot = As/#4 footing rebars, area = 7.26
Spacing = 1/number of rebars per foot*12 = 1.65 in
As2 = yield stress ratio*B*h = 1.43 in2
Number of rebars per foot = As2/#4 footing rebars, area = 7.26
Minimum spacing = 1/number of rebars per foot*12 = 1.65 in
Maximum spacing = 5*h = 18 in
rebar spacing Choose in
Glossary
γ = soil unit weight q = surcharges
φ = angle of internal friction DL = dead loads on wall
ca =
adhesio
n LL = live loads on wall
Pore Pressure: pressures due to water w =
extra sliding/overturning
resistance
Earth Pressure: active, passive, or at rest
β = angle of backfill
γw = water unit weight fy =
yield stress in steel
reinforcement
f'c =
concrete compressive
strength
B = footing width γc = concrete unit weight
h = footing thickness
b = footing length Fr = resistance against sliding
H = height of wall Fs = sliding forces
t = wall thickness F.S.static = Factor of Safety (static)
D = foodting depth F.S.dynamic = Factor of Safety (dynamic)
Page 4 of 4
n = footing length beyond wall face
Key:
"notched" footing for sliding
resistence Mr =
resistance against
overturning
Mo = overturning forces
F.S.static = Factor of Safety (static)
F.S.dynamic = Factor of Safety (dynamic)
K = earth pressure coefficient Mu = Maximum moment
Ke = earthquake pressure coefficient As = Area of steel
δ = Ac = Area of concrete at stress
Ψ = Mn = Nominal moment capacity
Rs1 = soil partical resultant force
φMn
= Design moment capacity
RsH1 = horizontal resultant force
As2
= New area of steel
RsV1 = vertical resultant force
Rw = pore water resultant force Pu = Factored dead and live loads
Rq = surcharge resultant force qu = Load per unit length of wall
RqH = horizontal surcharge component Vc =
Shear strength capacity of
concrete
RqV =
vertical surcharge
component d = Effective footing depth
Re =
earthquake resultand
force Vu =
Shear stress at critical
section
Rs2 = opposite soil partical relultant force
oVc
=
Reduced shear strength
capacity
RsH2 = horizontal component
RsV2 =
vertical
component
Thank you for the opportunity to work on this project. If you have any questions or need any further
assistance, please contact Michael Staten at 360-275-9374.
Sincerely,
Envirotech Engineering
Michael Staten, P.E.
Project Director
6/20/20