RESUB 2-BLD2022-1556+Large Vehicle Analysis Report+3.15.2024_9.52.10_AM+41373240 0 1
A.
LARGE VEHICLE ANALYSIS REQUEST FORM
Proper strucutural evaluation of the proposed vehicle loading requires completion and
submission of this form to ADS Engineering Services:
PROJECT INFORMATION:
Protect Name and Location: 2121" Street SW Commercial - Glacier
Engineer/Contractor Information: Ceko
Product Information: StormTech SC740
❑ SC-160LP ❑ SC-310 ❑X SC-740 ❑ MC-3500 ❑ MC-4500
❑ HP Storm ❑ N-12 ❑ HP Sanitite ❑ Other:
Pipe Diameter:
Cover Information:
❑X Flexible:
Cover Depth During Loading (to top of grade):
Pavement Thickness: 12"
❑ Rigid:
Cover Depth During Loading (to top of grade):
Slab Thickness:
❑ N/A:
Cover Depth During Loading (to top of grade):
VEHICLE INFORMATION:
Vehicle Make and Model (if applicable):
Vehicle Loading Information:
Total Front Axle Load:
Number of Rear Axles: ❑ 1 ❑ 2 ❑ 3 ❑ 4
(Vehicles with multiple rear axles will require a vehicle cut sheet/loading diagram to be
properly analyzed over ADS products)
Form Updated: 1126121 Our reason is water.
Advanced Drainage Systems, Inc, 4640 Trueman boulevard, Hilliard, OH 43026 Tel (614) 658-0050 IW9pipeeom
Load per Rear Axle: Click or tap here to enter text.
(This load should reflect the worst -case project loading scenario and should be supplied
by the vehicle manufacturer or project engineer to Engineering Services)
Axle SDaciniz Information:
Spacing Between Front and Rear Axles: 120
(This value will be assumed to be 120 inches if not provided)
Spacing of Wheels Across Single Axle: 72
(This value will be assumed to be 72 inches if not provided)
Spacing of Wheels Between Tandem Axles: 52
(This value will be assumed to be 52 inches if not provided)
Vehicle Tire Information:
Maximum Tire Pressure: 100 psi
(This value will be assumed to be 100 psi if not provided)
Vehicle Outrigger Information:
Outrigger Type: ❑X Rectangular ❑ Circular
Outrigger Dimensions: 24"x24"
Maximum Outrigger Load: 43,000 pounds
(This load should reflect the worst -case project loading scenario and should be supplied
by the vehicle manufacturer or project engineer to Engineering Services)
Load Duration:
Length of Time Load Will be Over Product: 8 hours
Will the load be removed at night if loading persists for longer than 8 hours?
❑X Yes ❑ No
Form Updated: 1126121 Our reason is water.
Advanced Drainage Systems, Inc. 4640 Trueman Boulevard, Hilliard, OH 43028 Tel (614) 658-0050 adspipe com
Project Name:
Project Number:
Date:
Project Engineer:
Lynnwood 212th St SW Commercial
281702
3/4/2024
Henry Kirk
BOUSSINESQ LIVE LOAD ANALYSIS - FIRE TRUCK / LARGE SERVICE VEHICLE
Calculation Notes:
This load analysis represents the minimum cover needed (19" to bottom of flexible
pavement) in order for outrigger loading to be acceptable for no more than 8 hours.
LOAD INPUTS
IPRODUCT INPUTS
Load per Axle:
24000
Ibs
Product: Chamber dim
0 Triple
Axle Mode Size: SC-740 dim
Axle Spacing:
4.3
ft
Cover: 19 in
Wheel Spacing (on axle):
6.0
ft
Average Tire Pressure:
100.0
psi
PAVEMENT INPUTS
Mult. Presence:
1.0
dim
Pavement: Flexible dim
Impact Factor
1.26
dim
Outrigger Type:
Rectangular
dim
Dim A:
24
in
NOTE: Site design revised to increase
Dim B:
24
in
Cover (H) from 19-inches to
Max Outrigger Load:
43000
Ibs
21-inches, with 3-inches of HMA.
�B�
L
W = OUTRIGGER LOAD
APPROXIMATE LOAD
DISTRIBUTION
. S
H
O
D�f
Results:
Total Pressure
Peak Wheel Pressure (psi):
9.02
10.34
Wheel Load is OK up to 2 months
Outrigger Pressure (psi):
19.25
20.57
Outrigger Load is OK up to 8 hours
Chamber Results
Min. (psi)
Max (psi) Duration
0.0
6.7 Long -Term
6.7
12.0 2 months
12.0
13.9 1 week
13.9
20.7 8 hours
20.7
Unified Live Load Tool1
Project Name: -inwood 212th St SW Commerc
Date: 3/4/2024
Calculations:
PRODUCT OFFSET & ANGLE COMPUTATIONS - WHEEL LOADS
Axle Spacing A-B: 4.3 Wheel Spacing: 6.0
Triple Axle Mode
Effect of "Axle B" doubled for
Load Cases #1 and #3 to
account for third axle
CONTACT PATCH LOAD CASE #2 -LOAD CASE #1
w
UJ
w
z
z
LONGITUDINAL (TRAVEL DIRECTION
W
� elz
z
0
LOAD CASE
XLE SPACING
W"
AXLE LOADS - LOAD CASES
1
2
13
4
Total Offset, X (in)
Wheel Al
0.0
72.0
52.0
88.8
26.0
76.5
26.0
76.5
36.0
36.0
63.2
63.2
44.4
44.4
44.4
44.4
Wheel A2
Wheel 1131
Wheel B2
Relative Product Angle - Pipe Parallel (deg)
Wheel Al
0.0
90.0
0.0
54.2
0.0
70.2
0.0
70.2
90.0
90.0
34.7
34.7
54.2
54.2
54.2
54.2
Wheel A2
Wheel 1131
Wheel B2
Relative Product Angle - Pipe Transverse (deg)
Wheel Al
90.0
0.0
90.0
35.8
90.0
19.8
90.0
19.8
0.0
0.0
55.3
55.3
35.8
35.8
35.8
35.8
Wheel A2
Wheel 1131
Wheel B2
Offset (in):
Relative Product Angle (deg):
OUTRIGGER LOAD
0.0 Outrigger loads are assumed to be spaced out such that
0.0 interaction of multiple load does not occur. Therefore, the only
outrigger load case is directly below the load (X=O). Wheel loads
are assumed to be negligible when outriggers are loaded
Unified Live Load Tool1
Project Name: ,inwood 212th St SW Commerc
Date: 3/4/2024
FLEXIBLE PAVEMENT BOUSSINESQ COMPUTATIONS
Cover, H =
19
in
Product:
Chamber
[A] Wheel Radius, rA =
7.0
in
Size:
SC-740
[B] Wheel Radius, rB =
7.0
in
Target Width:
50
Outrigger Type:
Rectangular
dim
[A] Wheel Load, PWA =
15176
Dim A:
24
in
[B] Wheel Load, PWB =
15176
Dim B:
24 in
Outrigger Load, Po =
43000
rA -
FPW
* MP
PWA =
\P2AIM
\ /
AXLE - LOAD CASE
1
2 1 3
4
Normalized Depth Factor - H/r
All Wheels
2.734
Normalized Offset Factor - X/r
Wheel Al
0.000
10.359
7.476
12.775
3.738
11.013
3.738
11.013
5.180
5.180
9.095
9.095
6.388
6.388
6.388
6.388
Wheel A2
Wheel B1
Wheel B2
Wheel Al
Wheel A2
Wheel B1
Wheel B2
Wheel Al
Wheel A2
Wheel B1
Wheel B2
Pressure:
Pressure:
Notes
Boussinesq Coefficent for each wheel/outrigger and load case (below) are selected from
Appendix using the normalized factors above.
AXLE LOAD - LOAD CASE
1
2
1 3
4
Average Boussinesq Coefficient, C - Pipe Parallel (dim)
0.085
0.010
0.017
0.003
0.000
0.000
0.017
0.003
0.002
0.010
0.001
0.003
0.000
0.000
0.001
0.003
8.77
2.11
3.56
1.37
Average Boussinesq Coefficient, C - Pipe Transverse (dim)
0.085
0.044
0.004
0.002
0.000
0.000
0.004
0.002
0.005
0.044
0.001
0.002
0.000
0.000
0.001
0.002
9.02
8.72
0.95
0.94
Max Wheel Pressure: 9.02 _ CP Where:
7crz - P = Wheel Load
- C = Avg. Bousssinesq Coefficient
Average Boussinesq Coefficient, C =
Outrigger Pressure:
0.258
19.25
OUTRIGGER LOAD
Rectangular Outrigger. Boussinesq coefficient
deteremined using Rectangular load
approximation. Solution requies
superposition of multiple, intermediate loads.
Refer to App. B for an example
dim
dim
in
Ibs
Ibs
Ibs
Unified Live Load Tool1
a road network element that is not needed or required to provide fire
apparatus access to buildings or facilities according to SCC 30.53A.512.
2) The Fire Marshal may require alternative fire protection measures, such as fire
sprinkler systems, in accordance with SCC 30.53A.172 when conditions affect
compliance with fire code requirements.
3) The following are important fire lane specifications for road network design.
Refer to SCC 30.53A.512 for all fire lane requirements.
• Fire lanes shall be installed to within 150 feet of any portion of a facility or
any portion of an exterior wall of the first story of a building;
• Fire lanes shall have an unobstructed width of not less than 20 feet and an
unobstructed vertical clearance of 13 feet, 6 inches in height;
Where a fire lane intersects another road network element using a drop
curb driveway design, the access point shall have a minimum width of 25
feet for a distance of at least 30 feet measured from the face of curb line
(urban) or edge of pavement (rural or urban section without curb) of the
intersecting road network element. This is to allow emergency vehicle
turning movements without driving off pavement.
• Dead-end fire lanes longer than 150 feet shall end in a cul-de-sac
turnaround having a minimum 40-foot outside radius driving surface;
• Where a cul-de-sac planter is installed, the outside radius of the cul-de-sac
shall be a minimum of 50 feet and the inside radius a minimum of 25 feet;
• Fire lane curves and intersections shall have minimum turning radii of 20
feet (inside radius) and 40 feet (outside radius) for emergency vehicle
access;
• Fire lanes shall be constructed of asphalt, concrete or permeable pavement
where feasible. Minimum surfacing requirements are described in Section
4-09. Refer also to Standard Drawings 3-040 or 3-050 and Subsection 3-
04.13 below for cross-section information. The permeable pavement cross-
section shall be an engineered design consistent with Section 11-02.
• The fire lane surface must be capable of supporting a live load of HS-25
(AASHTO Load Factor Design method, LFD) and a fire truck outrigger load
of 43,000 pounds applied to an area of 24 inches by 24 inches located on
16-foot centers;
• Parking lanes or spaces shall not be located within the minimum 20-foot
unobstructed fire lane width;
• The maximum grade for a fire lane shall not exceed 15 percent. Cul-de-sac
bulb grades shall not exceed 6 percent.
3-02 PUBLIC ROAD CLASSIFICATION
See Standard Drawings 3-070, 3-075
Snohomish County classifies public arterial and non -arterial roads in its Comprehensive
Plan. Classifications are provided in Subsections A and B below. Subsection C
Engineering Design and Development Standards 33
January 2016
SIMPSON GUMPERTZ & HEGER
Engineering of Structures
and Building Enclosures
8 September 2016
Mr. David Mailhot
Director, Technical Services
70 Inwood Rd., Suite 3
Rocky Hill, CT 06067
Project 130411.65 — SC-740 Chambers Subject to City of Bellevue, WA Fire Truck Live Load
Dear Mr. Mailhot:
At your request, we calculated the minimum fill depth needed for polypropylene (PP) SC-740
chambers to meet the AASHTO Strength II design requirements when loaded by Vehicle, Fire
Truck, and Apparatus Loading as specified in a City of Bellevue, Washington document dated
January 2010 (Attachment 1). The chambers are assumed to be installed with StormTech
standard installation criteria. This letter describes the details of our analyses and the results of
our structural adequacy calculations.
DESIGN EVALUATION
For this evaluation, we performed design analyses and calculations similar to the AASHTO
Design Truck design analyses described in our 28 June 2011 letter, Structural Evaluation of
StormTech SC-740 and SC-310 Polypropylene Injection Molded Chambers (Attachment 2).
We based our evaluation on the following considerations:
• Chamber geometry and materials match those evaluated in our previous analysis and
design described in our 28 June 2011 letter.
• Chambers are installed in accordance with the StormTech SC-310/SC-740/DC-780
Construction Guide (unless otherwise noted herein).
• The minimum spacing between the adjacent chamber rows is 6 in.
• The minimum fill depth above the top of the chambers for the AASHTO design truck is
18 in. The minimum fill depth for the fire truck loads is 36 in. The fill over the chambers
is well compacted.
• The foundation stone depth below the chamber is a minimum of 6 in., increased as
required in the StormTech SC-310/SC-740/DC-780 Design Manual, based on subgrade
allowable bearing capacity.
SIMPSON GUMPERTZ & HEGER INC.
41 Seyon Street, Building 1, Suite 500, Waltham, MA 02453 main: 781.907.9000 fax: 781.907.9009 www.sgh.com
Boston I Chicago I Houston I New York I San Francisco I Southern California I Washington, DC
Mr. David Mailhot — Project 130411.65 - 2 - 8 September 2016
• The in situ soil has an allowable bearing capacity of at least 2.5 ksf (to be determined by
the site civil engineerldesigner).
• Figure 1 illustrates the fire truck loading. The front axle and rear axles of the fire truck
are loaded with 19 kips and 48 kips, respectively. The axles are spaced 21 ft on -center.
The wheels on each axle are spaced 8 ft on -center. The contact area for each wheel
(1/2 axle) is 10 in. by 20 in., which is the same contact area as the AASHTO Design
Truck wheel.
Total Load on Front Axle = 19,000 lbs.
Gross Vehicle Weight = 64,000 lbs.
(110-ft. ladder truck)
21 ft.
Total Load on Rear Axles = 46,000 lbs.
(dual -wheel tandem axles)
Figure 1 — City of Bellevue, WA Fire Truck Wheel and Axle Loads (January 2010)
• The maximum reaction (service load) that may occur at a stabilizer outrigger pad for the
fire truck is 45 kips. This load is applied over an 18 in. by 18 in. area for service and
factored design checks. The outrigger pad is also checked with a live load factor of 1.0
(service check) over a 10 in. by 14 in. area.
• The fire truck is acting in its maximum loaded position (the outrigger load) for not more
than 24 hrs of continuous loading.
• The chamber PP material has a short-term tension modulus of 158,500 psi.
• The chamber PP material has a 24 hr tension creep modulus of at least 75,000 psi
at a constant stress of 800 psi (based on StormTech creep test results, TRI Log
No. E2208-77-03).
• The chamber PP material has a long-term creep modulus of at least 27,000 psi at a
constant stress of 500 psi.
As detailed in our 28 June 2011 letter, StormTech SC-740 chambers are designed for AASHTO
Design Truck plus soil loading in accordance with ASTM F2787 — Standard Practice for Structural
Design of Thermoplastic Corrugated Wall Stormwater Collection Chambers. The design
evaluation includes finite element analysis of the chamber response to soil load and the maximum
single -axle load of the AASHTO Design Truck at the minimum and maximum allowable soil fill
depths of 18 in. and 96 in., respectively.
ASTM F2787 adapts the AASTHO LRFD Bridge Design Specifications for thermoplastic pipe
design to open -bottomed chambers. AASHTO allows for a reduction in live load factor from 1.75
Mr. David Mailhot — Project 130411.65 - 3 - 8 September 2016
to 1.35 (Strength II design) when the live load consists of an "owner -specified special design
vehicle." This reduction is based on reduced uncertainty in the total magnitude of load from a
special design vehicle, here the fire truck axle and outrigger loads, compared to the AASHTO
Design Truck, which is a notional or representative vehicle load rather than a specific and known
truck load. Since the fire truck loads differ from the standard design live load, they require
evaluation. We used a live load factor of 1.35 when evaluating the fire truck loads.
The critical axle load for the fire truck is the 48 kip rear axle. Using methods for live load spreading
(live load distribution factor of 1.15) through soil in ASTM F2787, the maximum unfactored
(service) pressure at the top of the chambers due to fire truck axle loading at 36 in. fill depth is
7.6 psi (1.1 ksf). This is based on a surface patch size of 200 sq in. (10 in. by 20 in. wheel). The
factored pressure is 10.3 psi (1.5 ksf). The unfactored pressure at the top of the chambers due to
the AASHTO Design Truck single axle load (32 kips per axle) at fill depth of 18 in. is 12.8 psi
(1.8 ksf) and the factored pressure is 22.4 psi (3.2 ksf). Since the pressure due to the AASHTO
Design Truck is greater than the pressure due to the fire truck axle, and since the load patches
and durations are the same, the fire truck axle does not require further analysis.
For the 18 in. by 18 in. outrigger pad with 45 kip load, the distributed unfactored pressure at the
top of the chambers due to the fire truck outrigger loading at 36 in. fill depth is 12.8 psi (1.8 ksf).
The factored pressure is 17.2 psi (2.5 ksf). For the 10 in. by 14 in. outrigger pad with 45 kip load,
the distributed unfactored pressure at the top of the chambers due to the fire truck outrigger
loading at 36 in. fill depth is 15.8 psi (2.3 ksf). Per the City of Bellevue letter, this load is not
increased by a load factor. All outrigger loads are assumed to have a maximum continuous
duration of 24 hrs. The factored outrigger loading on the 18 in. by 18 in. pad is the critical case
for the specified fire truck. The critical distributed pressure is less than the AASHTO Design Truck
single -axle load, but is applied over a greater width. Therefore, it is unclear without analysis which
loading is more critical and the fire truck loads require further evaluation.
To evaluate the effect of the critical fire truck outrigger load, we analyzed the SC-740 chamber
using CANDE soil -structure interaction finite element analysis (FEA) software. We modeled three
adjacent rows of chambers, spaced at 6 in. apart, to capture effects the outrigger load has on the
installed SC-740 chambers through soil -structure interaction. We applied the outrigger load at the
ground surface in three locations: over the top, over the shoulder (quarter span), and directly
above the foot of the center chamber. We considered two live load durations: short-term (<_ 1 min.)
and sustained (24 hr).
The chamber meets the AASHTO Strength II design requirements at 36 in. fill depth (cover over
the top of the chambers) with a soil dead load factor of 1.95 and an outrigger live load factor of
1.35 when installed in accordance with the StormTech installation instructions and loaded by the
fire truck outrigger at maximum load conditions for a maximum of 24 hrs continuous loading.
The safety factor for the bearing pressure on the foundation stone is 2.22. The safety factor for
the bearing pressure on the subgrade soil is 3.61.
SUMMARY
We find that a SC-740 chamber installed with 36 in. minimum fill depth meets the AASHTO
Mr. David Mailhot — Project 130411.65 - 4 - 8 September 2016
Strength II design requirements under the City of Bellevue fire truck axle and outrigger loading
described above, provided the design and installation considerations listed above are met.
Sincerely yours,
esse L. Beaver. P.E. Robert W. Keene
Associate Principal Staff II — Structures
WA License No. 41609
L\BOS\Projects\2013\130411.00-STRM\W P\022JLBeaver-L-130411.65.sco.docx
Encls.
1. Vehicle, Fire Truck, and Apparatus Loading, City of Bellevue, WA, January 2010.
2. Structural Evaluation of StormTech SC-740 and SC-310 Polypropylene Injection Molded
Chambers, 28 June 2011.
A
City of
�=
Bellevue_.
�SMtNG�
Development Services
Handout
Vehicle, Fire Truck, and
_' �F_
The information in this brochure describes the
City of Bellevue's requirements for the structural
design of a condition that may occur with
underground parking facilities or flood control
structures.
Concrete slabs or utility vault lids that are
subject to fire truck or semi -trailer loading must
be designed for additional loading as prescribed
below. This may also include the condition of a
fire truck setting down stabilizer outriggers to
extend a ladder. The project design team should
first contact the Bellevue Fire Department at
425-452-4122 to determine whether the required
fire truck access area may be restricted and
whether the outrigger load is applicable.
Design Loading
Such a concrete slab must be designed for the
following live loads.
• HS20 loading required under the latest
edition of the American Association of
State Highway and Transportation Officials
(AASHTO) publication entitled "Standard
Specifications for Highway Bridges"
• Fire truck wheel and axle loads as indicated:
21 ft.
Total Load on Front Axle = 19,000 lbs.
Gross Vehicle Weight = 64,000 lbs.
(110-ft. ladder truck)
Total Load on Rear Axles = 48,000 lbs.
(dual -wheel tandem axles)
I,E $ ft.
_l
ratus Zoadin
January 2010
Point load of 45,000 lbs. due to the
maximum reaction which may occur at
a stabilizer outrigger. This load must be
applied on an 18x18-inch area (2.25 sf) and
also applied as an unfactored load on a
10x14-inch area (1.0 sf).
The live load conditions given above are to
be applied independent of each other, but in
combination with other loads as required by
AASHTO and the IBC. Each load must be
increased by any factors required by AASHTO or
the IBC unless specifically excepted.
For More Information
Please contact a building plans examiner with
the Bellevue Building Division at 425-452-
4121 or BuildingReview@bellevuewa.gov for
additional design information.
This document is intended to provide guidance in applying certain regulations and is for informational use only. It
cannot be used as a substitute for the Construction Codes or for other city codes. Additional information is available
from Development Services at Bellevue City Hall or on the city website at www.bellevuewa.gov. Assistance for the
hearing impaired: dial 711.
SIMPSON GUMPERTZ & HEGER
Engineering of Structures
and Building Enclosures
28 June 2011
Mr. David Mailhot
National Engineering Manager
ADS/StormTech
70 Inwood Road, Suite 3
Rocky Hill, CT 06067
Project 820342 - Structural Evaluation of StormTech SC-740 and SC-310 Polypropylene
Injection Molded Chambers
Dear Mr. Mailhot:
At your request, we have investigated the structural capacity of StormTech polypropylene (PP)
SC-740 and SC-310 stormwater retention chambers. We provide here a summary of our work
and the findings we draw from this investigation.
OVERVIEW
Polypropylene SC-740 and SC-310
chambers are manufactured by the
injection molding process. The
chambers are arch shaped with a
corrugated profile (three corrugations of
the SC-740 chamber are shown in
Figure 1). SC-740 and SC-310
chambers have nominal widths of 51 in.
and 33 in., respectively, and wall
thicknesses of 0.188 in. and 0.150 in.,
respectively. The chambers are
installed in rows, with clear spacing of
6 in. between the feet of adjacent
parallel SC-740 chambers (3 in.
between rows of SC-310 chambers) and
12 in. clear spacing between
perpendicular chambers.
Our investigation included finite element Figure 1 - Schematic of SC-740
analysis (FEA) of the expected chamber
performance when subjected to earth and live loads with 18 to 96 in, depths of fill. Our
structural evaluation of the chambers is based on meeting the requirements of the AASHTO
LRFD Bridge Design Specifications, 4th Ed., with 2009 Interims, Section 12.12 for thermoplastic
pipe, and ASTM F2787- Standard Practice for Structural Design of Thermoplastic Corrugated
Wall Stormwater Collection Chambers. ASTM F2787 adapts the thermoplastic pipe design
provisions of AASHTO Section 12.12 to open -bottomed chambers.
SIMPSON GUMPERTZ 3 HEGER INC.
al Seyon Street, Building 1, Suite 500
Waltham Massachusetts 02453
me 781.907.9000 m. 781907.9009
www.sgh.com
Boston
Los Angeles
New York
Son frdnClSCO
wostmigton DC
Mr. David Mailhot — Project 820342 -2- 28 June 2011
We monitored shallow- and deep -cover test installations to calibrate and validate our FEA
models. The tests evaluated chamber and end -cap response to static and multiple cycles of
dynamic live loads.
Our evaluation finds that SC-740 and SC-310 chambers meet the AASHTO LRFD
recommended load and resistance factors, when subjected to AASHTO Design Truck (formerly
called HS-20) live loads including AASHTO allowances for impact and multiple presence at
depths of fill between 18 and 96 in. provided:
• PP production resin has a minimum short-term elastic modulus of 135,000 psi,
one -week elastic modulus of 45,000 psi, and a seventy -five-year creep modulus of
24,000 psi.
• PP production resin has a minimum short-term strength of 3,100 psi and a
seventy -five-year strength of 700 psi.
+ Depths of fill are between 18 in. (24 in. if unpaved) and 96 in.
• Structural embedment material is uniform crushed stone with nominal 3/4 to 2 in.
diameter and less than 5% fines (including AASHTO M43 Designations 3, 357, 4, 467,
5, 56, and 57), is classified as subangular or angular, and is placed in accordance with
StormTech installation instructions found in the latest version of the SC-310/SC-740/
DC-780 Design Manual.
• Structural embedment material has a minimum depth of 6 in. below the chambers and
is placed to a minimum depth of 6 in. over the top of the chambers (the minimum depth
below the chamber increases for sites with low bearing capacity), with a minimum clear
spacing of 6 in_ between feet of adjacent rows of SC-740 chambers (3 in. between
rows of SC-310 chambers).
+ Procedures to place and compact backfill minimize chamber distortion.
The StormTech standard installation cross-section for SC-740 and SC-310 chambers (Figure 2)
summarizes the installation requirements. Specific requirements for particular sites may vary;
thus, local engineers must assess project site conditions to ensure installations are completed in
accordance with the requirements of the StormTech SC-310/SC-740/DC-780 Design Manual.
Additional details of our analysis are provided below.
Mr. David Mailhot - Project 820342 - 3 - 28 June 2011
SC-740 OR SC-310
NOMINAL 3/4" -7' (19 mm - 51 mm)
CLEAN CRUSHED, ANGULAR STONE
ADS 601 NON -WOVEN GEOTEXTILE
(OR EQUAL) ALL AROUND CLEAN.
CRUSHED ANGULAR STONE- A
DESIGN ENGINEER IS RESPONSIBLE FOR
ENSURING THE REQUIRED BEARING
CAPACITY OF SUBGRAOE SOILS
GRANULAR WELL -GRADED SOILIAGGREGATE MIXTURES
<35% FINES COMPACT IN B" (152 mm) MAX LIFTS TO 95%
STANDARD PROCTOR DENSITY SEE THE TABLE OF
ACCEPTABLE FILL MATERIALS
PAVEMENT DESIGN (PER
/--ENGINEER'S DRAWINGS)
/'TO BOTTOM OF FLEXIBLE PAVEMENT FOR UNPAVED
INSTALLATIONS WHERE RUTTING FROM VEHICLES
MAY OCCUR INCREASE COVER TO 24" (610 mm)
6' (152 mm) M t SC-740 - 51" (1295 mm)
SC-310 - 34" (W mm)
18 (2438 mm) MAX
(457 mm) MIN
6"(152mm) MIN +
SC-740 - 30" (762 mm)
SC 310 16" (406 mm)
DEPTH OF STONE
TO BE DETERMINED
BY DESIGN ENGINEER
6" (152 mm) MIN
12" (305 mm) TYP
Figure 2 - Stormiech Standard Installation Requirements for SC-740 and SC-310 Chambers
Mr. David Mailhot — Project 820342 - 4 - 28 June 2011
SC-740 AND SC-310 CHAMBERS
The PP chambers have the typical
corrugated profile shown in Figure 3.
Dimensions of specific cross-section
elements vary around the circumference
of the chamber; with the crest narrow at
the crown and wider at the base, just
above the foot (Figure 1). We included
the effects of the drainage slots in crest
of the corrugation near the base of the
chamber in our evaluation. We used
material properties from test specimens
cut from production chambers in our
analysis and calculatsons. Conventional
testing and time -temperature
superposition methods were used to
project long-term modulus and strength
't '
110-1
Soil Side
Cres>
Figure 3 — Corrugation Profile
Web
We used the two-dimensional public -domain finite element computer program CANDE to model
and analyze the chambers with 18 and 96 in. depths of fill while subjected to AASHTO Design
Truck (HS-20) live loads. The end caps were not evaluated in our computer models.
The CANDE models incorporated nonlinear soil behavior using the Duncan/Selig hyperbolic
model. The soil properties were developed by Selig for the SIDD (Standard Installation Direct
Design) concrete pipe installations, which have been adopted by AASHTO as the basis for
concrete pipe and thermoplastic pipe designs. We modeled the embedment soils as coarse -
grained soils with density equal to 95% of maximum density per the standard Proctor test
(SW95). The 95% condition is a conservative representation of the specified embedment soils.
The backfill soils, from the embedment soil to the top of the soil cover, were modeled as
granular, well -graded soil with density equal to 90% of maximum density per the standard
Proctor test (SW90). All sods were assumed to have a density of 120 pcf.
We modeled the chamber with elastic moduli representing the load -duration -dependent stiffness
of the chamber material to evaluate the following load conditions:
short-term live load less than 1 min. in duration
one -week live load to represent a parked vehicle
long-term dead load of seventy-five years in duration
Models at both depths of fill included three adjacent chambers subjected to soil and live load.
Live load consisted of the AASHTO Design Truck positioned over the crown or shoulder
(quarter span) of the center chamber. We increased the live load magnitude for impact (effect
varies with depth) and multiple presence (20% increase) when using a single -loaded lane in
Mr. David Mailhot .-. Project 820342 b - 28 June 2011
accordance with AASHTO and ASTM F2787. Per ASTM F2787, the live load for the one -week
case was not increased for impact or multiple presence, since a static vehicle will not induce
impact effects and there is a low probability of having an overloaded truck parked over the
chambers for a long duration. For deep cover installations, we considered interaction of two
wheels on the same axle as the wheel loads distributed through the soil cover.
Section properties for the chamber beam elements in the models were based on StormTech
three-dimensional solid computer geometries of the chambers. We made section cuts at four
locations around the circumference of the chambers and determined the section properties from
each cut in CAD. We interpolated to find section properties for beam elements between the
section cut locations. We later verified the section cuts were representative of the manufactured
chamber geometry.
We determined flexural bending moments, compressive axial thrusts, and deflections around
the circumference of the chamber in CANDE and used those results in our design evaluation,
discussed below.
TEST INSTALLATIONS
To confirm the analysis results we monitored and evaluated a series of shallow- and deep -cover
test installations conducted at StormTech test facilities. Shallow -cover tests were conducted
with depths of fill from 6 to 24 in over the tops of the chambers. Live loads included static and
dynamic vehicle -axle loads ranging from 25,000 to 36,000 Ibs The test data included chamber
vertical deflections due to static live load and visual evaluation of chamber durability for cyclic
dynamic loading Performance of the chambers in the shallow -cover tests was used to calibrate
and verify the computer model results.
The deep -cover test consisted of burying two SC-740 chambers under 11.8 ft of fill. The
embedment material for the chamber in this test was silty clay (CL-ML). The remaining fill was
silty sand.. The embedment soil was significantly less stiff than the crushed stone embedment
normally required by StormTech. This increased the load on the chambers well above the
design load and to the point of failure. Data collected during the test included strain in the
chamber leg, displaced shape, and visual inspection of the chambers. Chamber performance
correlated well with the deep -cover CANDE models and the AASHTO LRFD design limit states.
By design, chamber failure was achieved in two years in the predicted compression local
buckling mode. The deep -burial test confirmed that the factor of safety was greater than
required by AASHTO.
Both the shallow- and deep -cover tests included end caps. No distress was noted in the
shallow -cover tests, which included conditions more severe than expected in service. In the
deep -cover test, the end caps showed some rib buckling but no stress whitening, cracking, or
buckling of the surface.
DESIGN EVALUATION
We evaluated structural adequacy (chamber capacity to resist compressive axial and flexural
loads while accounting for local buckling) in accordance with the AASHTO LRFD Section 12.12
procedures for structural design of profile wail thermoplastic pipe and ASTM F2787. We
evaluated the structural adequacy using a material compression strain limit of 3.3`?o for PP.
Mr. David Mailhot --' Project 820342 - 6 - 28 June 2011
A structural adequacy of 1.0 or greater means the chamber is capable of supporting the
short-term live loads and long-term soil loads with the safety levels (load and resistance factors)
prescribed by AASHTO. The minimum structural adequacies for the SC-310 and SC-740
chambers are 1.02 and 1.01, respectively The SC-740 and SC-310 chambers meet the design
requirements including load factors of 1.95 for sod load and 1.75 for love load for depths of fell
between 18 and 96 in. when installed in accordance with the requirements of the StormTech
SC-310/SC-740/DC-780 Design Manual as described in this letter.
The shallow- and deep -cover test installations demonstrated that the chambers perform as
anticipated by the computer models and that the chambers and end caps meet and exceed the
load and resistance requirements of ASTM F2787 and AASTHO LRFD specifications for
thermoplastic pipes.
SUMMARY
We have evaluated the expected service performance of the StormTech SC-740 and SC-310
chambers using ASTM F2787 and AASHTO LRFD procedures for loads, structural capacity,
and load and resistance factors. We conducted our analyses using chamber geometry from the
StormTech solid computer geometries confirmed by chamber measurements after manufacture.
Our evaluation consisted of finite element computer modeling of chamber performance at
depths of fill between 18 and 96 in., and field tests with depths of fill between 6 in and 138 in.
Time -dependent material properties for the polypropylene chambers were based on tests
performed on specimens from actual chambers.
The analyses and calculations demonstrate that the factor of safety is equal to or greater than
1.95 for dead load and 1.75 for live load, the minimum values required by ASTM F2787 and by
AASHTO for thermoplastic pipe, when installed in accordance with the requirements of the
StormTech SC-310/SC-74O/DC-780 Design Manual, as described in this letter, at depths of fill
between 18 and 96 in and subjected to live loads of Design Truck (HS-20) magnitude or less,
including allowances for impact and multiple presence. We suggest that the minimum depth of
fill be increased to 24 in. for unpaved installations, where rutting might reduce the depth of fill
over time.
Sincerely yours,
A'
`i
•..�r � *Mf i!1 Y 3 ' y � ..'.y
C. J r •ayC'JIL�� ��•`t
�ao_" K%!II �r?Ao.r'_P .1
aJsiJfi4i2:ff�bti��y
Timothy J. McGrath, Ph.D. 2°a�5 �� Brent J. Bass
Consulting Principal Staff II — Structures
CT License No. 22412
1ABOS\Prolects\2000\20342 OOSTRM\WP\027TJMcGrath-L-820342.00 eac.doc