Load Rating Statement of Qulaifications

Statement of Qualifications

Buried Structure Evaluation & Load Rating

Submitted By:

CBC Engineers & Associates, Ltd. 125 Westpark Road

Centerville, OH 45459 (937) 428-6150

Statement of Qualifications Buried Structure Evaluation & Load Rating

QUALITY OF FIRM AND PERSONNEL

CBC Engineers & Associates, Ltd. (CBC) is a civil, geotechnical & environmental engineering and field services’ firm

with offices in southwest Ohio, West Virginia, Kentucky and Illinois. The company has been providing engineering

design, field inspection and construction materials testing services for almost twenty (20) years to industrial,

commercial and governmental clients in the Midwestern USA, as well as nationally.

The firm specializes in the evaluation, load rating and remediation of buried culverts, storm sewers and buried

bridges. CBC has been the third party design, evaluation and remediation partner to CONTECH Engineered Solutions,

LLC. for almost 20 years. As such, CBC performs designs, field inspections, evaluations, load ratings and remediation

for hundreds of buried flexible culverts around the country every year for CONTECH and other clients such as

LADOTD, MDT, NYSDOT, NCDOT, ODOT, FDOT, and other county and local government agencies. CBC’s approach to

culvert, storm sewer and buried bridge evaluation uses AASHTO LRFR methodology combined with specialized

equipment and procedures developed internally to aid in the necessary data collection to provide a comprehensive

and measureable assessment of the structure being evaluated. The combined experience of the personnel in CBC

who specialize in this service exceeds 100 years.

Our clients include state, local and federal government agencies, mining companies, manufacturers, utility

companies, commercial, residential, industrial and institutional clients, as well as local and national chain land

developers.

Related Experience Our projects vary in size from a single municipal buried bridge evaluation to complex multi-location culvert

inspection and load rating programs for state DOTs. The following project discussion and project list illustrates CBC’s

recent and ongoing projects that have required a wide range of detailed technical knowledge, experience and

qualifications.

The Louisiana Department of Transportation and Developement – Load Rating Program

The Louisiana Department of Transportation and Development (LADOTD) decided with the urging of their local

FHWA liaison to develop a buried bridge inspection program and then to use the program to load rate their buried

bridge and culvert inventory of some 2500 structures. These buried bridges were both concrete and metal of all

shapes and sizes.

CBC Engineers & Associates, Ltd. was awarded the project on August 30th, 2011. The project consisted of developing

the field evaluation and the load rating process for all the different materials, shapes and sizes. The original contract

had some 270 buried bridges of both concrete and metal materials located all across the state.

CBC developed the field evaluation procedure for both the concrete and metal buried bridges as well as the load

rating procedures complete with software suggestions for each. Brass Culvert was selected to load rate the buried

concrete boxes and CBC developed a spreadsheet solution using NCSPA Data Sheet 19 specific for LADOTD and their

15 load combinations for the metal buried bridges.

In February 2014, CBC was awarded a contract extension adding an additional 70 buried metal bridges. LADOTD

decided through the process that they could more easily evaluate and rate in–house the buried concrete boxes


because the required site data is significantly less than that required to complete the buried metal bridges.

Therefore resources were appropriated to CBC to finish the majority of their buried metal bridges in inventory.

Interestingly the load rating of these structures using AASHTO LRFR methodology has proven to be a challenge as

most all of the structures were designed 40 and 50 years ago. The buried metal bridges as a percentage have load

rated much better than their rigid concrete counterparts. As it has turned out many DOT's are having trouble with

their older buried concrete boxes not checking the LRFR load rating like LADOTD. LADOTD is researching a new

process to use when this becomes a problem. This may include some finite element modeling like CANDE and some

non-destructive on site loading and measurement.

The Montana Department of Transportation – The Watch List

The Montana Department of Transportation (MDT) had been monitoring some 30 locations of known Buried Metal

Bridges across their state. These buried bridges became known as the "watch list" as it was apparent to MDT that

these locations were showing signs of potential movement and corrosion. They carefully watched over these

structures until observations in the roadway above and in the embankment around these buried bridges also started

showing signs of distress. At this point MDT knew that these structures would require replacement or rehabilitation

as they were all installed in the 1960's and 1970's and may have reached their useful life after some 40 plus years.

CBC Engineers & Associates, Ltd. was contacted by MDT in 2005 for our consultation on how to handle the 30

locations. We first advised them that we needed to go and evaluate each of the 30 buried bridges to see the

structure condition at each location. As it turned out, corrosion was not as much of a problem as the change in

shape geometry. Of the 30 locations that were measured, and in some cases several different times to track

movements, only 13 of the buried bridges were deemed necessary to have some rehabilitation performed to extend

their useful service lives.

Nine of the 13 buried bridges were repaired in-place using CBC's structural design of reinforcing the structures with

curved stiffeners and pouring new concrete floors to provide smooth hydraulics at the invert for low flow and for

animal/pedestrian crossing under the highways. MDT felt that the in-place repairs cost about 20% of the

replacement cost without closing down major roadways and affecting the traveling public. MDT also felt that these

repairs added significant service life to these buried bridges that were once thought to be in need of replacement.

Most recently in 2013, CBC aided MDT on a wildlife crossing in Missoula County, Montana where there was some

apparent movement of a Horizontal Ellipse Super-Span away from the southern end headwall. Upon inspection it

was determined that settlement of the structure had occurred since the installation was completed and CBC

designed a repair to allow the structure to stay in service.

On June 4th, 2014, CBC was selected for the 2014-2015 Steel Culvert Evaluations and Retrofit Contract by the

Montana Department of Transportation. We anticipate this program to start in the upcoming month.

The following table lists some of the relevant recent projects performed by CBC Engineers and Associates, Ltd.


Sample List of CBC Projects CLIENT DESCRIPTION OF WORK

Collin Creek Mall, LLC/Roush Properties/ City of Plano,

Texas

Inspect and evaluate triple 35’-9” x 15’-3” Super-Span Low Profile Arches 2350 feet long installed in 1980 at the Collin Creek Mall; Plano, Texas

Contech Engineered Solutions LLC

Evaluation of Foundation Settlement for BEBO C54T/6; Evaro Hill Wildlife Crossing, MDT Project NH5-1(30)16; Missoula County, Montana


Site Visit and Evaluation of Existing Condition of Multi-Plate Arch Tunnel and Concrete Foundation; Taggart Global Prep Plant, Musselshell County,

Montana


Shape Technician for Triple Barrel 35’ Span Horizontal Ellipse Super-Span River Crossing, Tucuy River, Colombia


Shape Observation of 102A15-24 SS High Profile Arch; Kodiak Rocket Motor Storage; Kodiak, Alaska


Design (CANDE Analysis) & Installation Shape Monitoring for a 48S (24'-4" Span x 15'-3" Rise) BridgeCor Horizontal Ellipse; NW 25th Street; Miami-Dade

County, FL

Foothills Contracting, Inc. Field Measurement and Evaluation of Current Shape of Super-Span #126A33-39; I-90 and South Dakota Highway 79 Over Black Hawk Creek; Meade County,

SD

Hidalgo County / City of McAllen, Texas

Evaluate and provide remediation for a 24’ span x 12’ rise ALSP Single Radius Arch that was exposed to a car fire; McAllen, Texas

Kinder Morgan Terminals Evaluate and provide repair methodology for twin 16’-0” Diameter coal conveyor tunnels approximately 1800 feet long each.

LADOTD State Project No. H.00541, F.A.P. No. STP-9910(552); Evaluate and Load Rating of 270 Metal and Concrete Bridge Culverts Statewide.

Mingo Logan Coal Co. Yearly Measurements of 15 Foot Diameter Steel Culvert Stream Enclosure at the Mountain Laurel Complex, Near Sharples, West Virginia. Proposed repairs

for a badly distorted 5000 feet long structure.

Montana DOT Provide Inspection and Evaluation of Structures at Mile Posts 51.4, 55.1, 60.6, 119.3, 122.1, 191.3, 238.8, 243.3 on I-94, Mile Post 395.4 on I-90, Mile Post

21.0 on SR 323, Mile Post 94.5 on US 212, and Mile Posts 131.8, 133.4 on I-15 in Montana

Montana DOT Provide Inspection and Evaluation of Structures at Mile Post 243.4 on I-94; MP.21.0 on SR 323; MP.85.3 and 94.5 on US 212 in Montana

Montana DOT Measurements and Recommendations Relative to Remedial Actions for Seven New Facilities (Eight (8) Structures); Interstate I-15 and I-90; State of Montana

Montana DOT Provide Remedial Action Design of Structural Steel Plate Pipe Arches (SSPPA) as Identified in CBC Engineers and Associates, Ltd. Report #7954-1-0906-05

Dated September 14, 2006; Interstate 94, Montana

Montana DOT Shape Measurements of Existing SS Horizontal Ellipse Structure at Proposed Stiffener Locations; P-5 Wildlife Underpass at RP10, Missoula Co., Montana


Qualification, Experience and Training of Personnel CBC is a privately owned company that is dedicated to staying lean, innovative, and current on engineering practices, technologies and regulations. CBC endeavors to deliver high quality, cost effective engineering solutions and services on schedule and on budget by supporting the motivated, flexible, and focused teams of experienced employees. CBC values the importance of client relationships and will strive to continue to offer the best client-consultant experience in the business.

CBC’s project managers and project engineers will be supported by a team of staff engineers, geologists,

environmental scientists, biologists, technicians, CADD operators, word processor operators, secretaries, and

draftspersons, who will provide the expertise and manpower to complete the project.

The following personnel will be performing specific functions as listed on the organization in fulfilling this contract:

Mitchell T. Hardert, P.E.

Chief Engineer & V.P.

Mr. Hardert will be the engineer-in-charge for these type projects and is registered in 48 states in the US. Mr.

Hardert manages the daily engineering and field operations for all CBC’s projects. This includes both new and

retrofit structure design as well as the installation and or evaluation of buried culvert structures. He also prepares

evaluation plans for existing distressed structures where CBC’s field inspectors gather information during field

evaluation. This information is used to evaluate the structure in its insitu shape, load rating and remediation if

required. Under Mitch’s leadership, CBC designs, evaluates, load rates and remediates hundreds of buried

structures, both flexible and concrete every year. CBC has worked with Montana, Ohio, Louisiana, and New York

DOT’s (to name a few) to aid their development of both their culvert inspection programs and load rating processes

as well as many other county and city agencies.

Joseph A. Dennis, Jr.

Director & Sr. Project Manager

Mr. Dennis manages some of CBC’s larger projects especially when related to buried culvert evaluations. He has

successfully managed a culvert inspection and load rating program for LADOTD where CBC is responsible for

developing a routine culvert inspection program as well as load rate 270 buried structures, both concrete and metal.

He has managed the evaluation of a triple barrel 35’-9” x 15’-3” Super-Span structures which were installed in 1980

and were 2300 feet long each for the City of Plano, Texas. Mr. Dennis recently managed the evaluation and

remediation of twin 16’-0” coal conveyor tunnels measuring approximately 1800 feet each. These tunnels are badly

corroded from the coal dust and in need of rehabilitation in place to keep the owner in the international coal load

out and shipping business in Newport News, Virginia. Mr. Dennis is also managing/coordinating the field repairs to

these tunnels.

Location Years of Experience Percentage Available

Dayton, OH 18 20%


Dayton, OH 25 35%


John Corda, P.E. Sr. Geotechnical Project Engineer

Mr. Corda has over 30 years of experience with Finite Element Modeling which is used in many areas of geotechnical

engineering. He is an expert in modeling soil-structure interaction used in buried flexible and rigid structure design

and evaluation. Mr. Corda has designed buried structures in the U.S., Canada, Colombia, Chile, Mexico, Turkey,

South Africa and other countries using his vast knowledge of both flexible corrugated metal pipe structures as well

as rigid concrete structures.

Deepa Nair, P.E.

Geotechnical Project Engineer

Ms. Nair has 7 years of experience across all of CBC’s engineering service offerings. She has become an expert in

evaluating and load rating buried structures using finite element analysis and BRASS Culvert. Ms. Nair’s

responsibilities include the evaluation, design and load rating of flexible and rigid buried structures. She is currently

managing all engineering aspects of a 4 year $700,000 buried bridge load rating program for the Louisiana Department of

Transportation & Development (LADOTD) consisting of inspection and load rating over 300 buried metal and concrete

structures. She has become an expert in evaluating and load rating buried structures using NCSPA Data Sheet 19 analysis,

BRASS Culvert and Virtis.

Rick Teachey, E.I.T.

Project Engineer

Mr. Teachey’s responsibilities include the derivation of hyperbolic soil modeling parameters from triaxial data for the

finite element analysis of flexible and rigid buried structures in CANDE. Currently he is also developing a new software

tool using more sophisticated meshing techniques than CBC has employed in the past. This tool will not only provide

more accuracy, but also faster means for CBC to analyze buried structures including concrete boxes and arches reducing

the time required to about 10% of what it took just a year ago. CANDE may be required for retrofit designs.

Bill Robertson Director Field Services

Bill has become an expert in using the CBC developed and patented laser measuring device called AccuShape when

evaluating buried flexible structures. CBC has developed a full process of evaluation for buried flexible structures that

depends on accurate and repeatable field measurements. Bill travels across the country performing these field

evaluations for DOT’s, Counties, Cities and private owners. Bill also teaches the process to the rest of the Field Technicians

to keep our people cross trained.


Dayton, OH 50 25%


Dayton, OH 7 25%


Dayton, OH 2 25%


Dayton, OH 14 20%


Capacity and Capability of Firm

Evaluation & Load Rating Discussion

The nation’s bridges can be broadly classified as buried structures and above ground structures. Load rating of the

above ground structures must be performed according to the documented procedure for above ground structures

in AASHTO Manual for Bridge Evaluation, 2nd Edition. The methodology for evaluating buried structures and the loads

to be considered in such evaluations are quite different from above ground structures. All buried structures are a

combination of soil-structure interaction, whether they are concrete or flexible metal. The surrounding soil above,

below and adjacent to the buried culverts may have a large influence on the performance of the buried culverts.

There is not a specific methodology for evaluating the loads on buried culverts in the AASHTO Manual for Bridge

Evaluation, 2nd Edition except for reinforced concrete boxes. The loads and resistance on buried culverts are due to

a combination of foundation soil, backfill around and over the structure, soil material outside the select backfill

envelope, the possibility of drag down adding load to the structure, groundwater conditions, and other forces which

must be evaluated and applied to underground structures. Furthermore, the evaluation of metal culverts is quite

different from the evaluation of concrete culverts. Therefore, each of these is briefly discussed below.

Flexible Metal Structures

Most flexible metal structures are various portions of circles. The behavior of a flexible structure is sensitive to large

side or corner deformations. Any major increase or decrease in side or corner mid-ordinates has been found to be

harmful to overall stability. Based on the type and extent of the select backfill envelope, nature of select backfilling

operations including the lifts of backfill placement and compaction, foundation soil, material outside the select

backfill envelope (original soil or embankment fill) immediately around the structure, there could be possible

flattening of the structure as the sides of the structure move out and the top move down during backfilling

operations and final loading conditions. The actual shape of the structure can therefore be possibly different from

the design shape. The main factor in the load carrying capability of a flexible metal culvert is the shape of the culvert

in place. Therefore, it is prudent to perform the load rating utilizing the actual shape instead of the design shape. It

is reasonably simple to measure chords and mid-ordinates using appropriate methods (manual measurements or

laser measurements) at appropriate intervals along the length of the culvert and compare them with design values.

Another factor influencing the load carrying capability of a structure is the current condition of the structure

determined from visual inspections including any deterioration or loss of section from corrosion, infiltration and loss

of structural backfill through joint separation, presence of any bolt distress/seam issues, evidence of pavement

distress or roadway or structure settlement etc. Ultrasonic thickness readings of the metal wall can be made easily

to determine the extent of deterioration in addition to visual inspection.

All steel culverts will be manually inspected using a tripod mounted laser device called AccuShape, developed and

patented by CBC. CBC developed this device to both speed the gathering of the necessary field shape (geometry)

data and to be able to recreate an accurate cross sectional plot of the pipe being measured. The stability analysis of

any pipe requires the following chords and mid-ordinates of the top arc of the structure to be defined. The

AccuShape laser device allows CBC to quickly record the actual shape in the field on 10 degree increments and then


plot the shape using an AUTO-CAD routine also developed by CBC to generate this required data used in the

MULTSPAN evaluation below.

A = Span = Largest Horizontal Dimension of Structure

B = Rise = Height of Structure Crown above the bottom of the structure

D = Left Side Top Chord Length

E = Right side Top Chord Length

H = Left Side Bottom Chord Length

I = Right Side Bottom Chord Length

K = Top Mid-Ordinate

L = Left Side Top Mid-Ordinate

P = Left Side Bottom Mid-Ordinate

Q = Right Side Bottom Mid-Ordinate

R = Bottom Mid-Ordinate

CBC will decide the intervals of inspection for each structure using the following method once a preliminary

inspection is completed or photos are reviewed. The more distressed (both geometry and corrosion) structures will

have data collected at 10 to 20 feet intervals down the pipe to ensure the worst case is captured. The less distressed

(both geometry and corrosion) structures will have data collected every 20 to 60 feet intervals depending on the

estimated required time to collect the field data.

In addition to the laser readings being recorded at each station, CBC inspectors will visually evaluate the pipe line

geometry, corrosion, alignment, storm connections, and joint integrity; take ultrasonic readings of the pipe wall, and

photos. If warranted, 2” coupons will be taken out of the pipe wall to determine metal loss. When a coupon is

taken, soil samples should be taken through the pipe wall for evaluation. The 2” hole in the pipe will be replaced

with hydraulic cement at the time the sample is taken. This method has been used extensively and provides a

watertight seal that does not degrade the condition of the steel culvert. Water samples should be taken in each line

of pipe and tested in the lab for pH and Resistivity to determine the corrosive nature of the effluent on the metal

pipe. The metal coupons will also be measured in the lab to determine metal loss and compare it to AASHTO design

standards for similar sized culverts.

Once the existing shape is plotted and the chords and mid-ordinates for each shape are graphically determined, a

program titled MULTSPAN will be used to determine the condition of the structure given its deflected shape and to

compare the current shape with the previous AASHTO design shape. This computer program (MULTSPAN)

developed under contract to FHWA and the State of Ohio DOT by former CBC personnel will be used to evaluate the

shortening of mid-ordinates of the structure, and to provide recommendations relative to the degree of "flatness".

The MULTSPAN analysis provides recommendations for remedial action on the basis of the degree of flatness of top

arcs within the structure. MULTSPAN processes the measurements of chords and mid-ordinates to calculate percent

shortening or lengthening then compares the movement to the values in Table 1. Appropriate recommendations

are provided by the program.


TABLE 1

% MID-ORDINATE (K) CHANGE AND REMEDIAL ACTION

MID-ORDINATE

PERCENT CHANGE

DEPTH OF COVER

(Ft)

RECOMMENDED ACTION

<15 Any No action required

15 - 20 Over 6.0 No action required

15 - 20 Under 6.0 Monitor on 6-month interval

20 - 25 Over 6.0 Reduce load to 90% of H-20 and monitor on 6-mo. basis

20 - 25 Under 6.0 Reduce load to 75% of H-20 & monitor on 6-mo. basis

25 - 30 Over 6.0 Reduce load to 75% of H-20 and monitor on 6-mo. basis

25 - 30 3.0 - 6.0 Reduce load to 50% of H-20 and monitor on 6-mo. basis

25 - 30 Under 3.0 Reduce load to 50% of H-20 and do detailed analysis

>30 Close road until detailed analysis is done

Note: Detailed analysis to include soil borings to determine expected additional movement.

After an efficient field reconnaissance including shape and thickness measurements, load rating of the flexible metal

structures must be performed according to NCSPA Design Data Sheet 19 procedures following AASHTO LRFD

methodology. The load rating for ring compression structures including flexible metal arches, round pipes, pipe

arches, and long span culverts is governed by minimum actual wall resistance considering wall area, buckling and

seam resistance (if applicable) compared to the factored actual thrusts from earth and live loads, or minimum cover

requirements as documented in NCSPA Design Data Sheet 19. The minimum wall strength for the structure based

on wall area, buckling resistance and seam resistance (if applicable) must be determined from AASHTO LRFD Bridge

Design Specifications Section 12.7.2 and the factored actual thrust from earth and live loads used in load rating must

be calculated using appropriate load factors obtained from AASHTO LRFD Bridge Design Specifications Section 3,

Table 3.4.1-2 and AASHTO Manual for Bridge Evaluation, 2nd Edition for operating and inventory rating. When load

rating deep corrugated structures, the combined thrust and moment criterion specified in AASHTO LRFD Bridge

Design Specifications Section 12.8.9.5 for deep corrugated structures must also be taken into account in addition to

the usual load rating procedure for ring compression structures.

Metal box culverts are bending moment design structures due to their large radius crown sections and straight sides,

and therefore the load rating of metal box culverts is governed by the actual plastic moment resistance of the crown

and haunches (based on the plate thickness and type of the exterior/interior ribs and their spacing) compared to the

factored actual crown and haunch moments. The actual moment in the crown and haunches are dependent on the

actual shape of the box and the plastic moment resistances are affected by the degree of deterioration/corrosion in

the metal box walls. Actual shape and condition evaluation of the metal boxes must be performed during field

reconnaissance. The factored dead and live load crown and haunch moments used in load rating must be calculated

as per AASHTO LRFD Bridge Design Specifications Section 12.9.4.2.


Therefore, the methodology for obtaining the load rating for all buried flexible metal structures will be to use

AASHTO (NCSPA) Data Sheet 19 which relates only to metal structures, but to use the actual in place shape of the

structure rather than the design shape to obtain the actual factored loads, and the actual measured wall parameters

than the design parameters to obtain actual wall strengths.

Concrete Box Culverts

Concrete box culverts are rigid structures generally designed for the loads expected to be placed upon them.

However, depending on the structure there may be loads which were not taken into account in the design. If a box

structure is placed on compressible soil, differential settlement between the structure and the surrounding fill can

add large downward forces to the structure. This is particularly true if the structure is supported on piles.

The first step in evaluating a reinforced concrete box culvert should be a determination of whether or not a

geotechnical evaluation was performed, the type of foundation, and any settlement records. In addition to

evaluating the actual loads on the structure, an evaluation of the condition of the structure in-situ must be made.

Such items as spalling, cracking, separation at joints, deterioration of concrete, repair, erosion of invert, and overall

general condition must be made in order to provide an accurate load rating. Both the actual loading on the structure

including self-weight, vertical soil loads, live loads, live load surcharges, lateral earth loads, and the resistances based

on the actual conditions of the structure must be properly evaluated based on the in-situ conditions. Once these

conditions are known, the loads on the structure and the resisting loads are known, the methodology in the AASHTO

Manual for Bridge Evaluation, 2nd Edition can be applied to determine the load rating of the structure.

If an examination shows the box culvert is not cracked or the cracks are minimal, and it doesn't appear that

settlement has been a problem, then the design of the structure can be used for load rating. The culvert design

parameters shall be taken from any available construction documents or standard plans provided by AZDOT. These

include the culvert dimensions, steel and concrete specifications, reinforcing details and installation methods

including soil backfill details and strength parameters for the box culvert. If proper documentation regarding the

specifications and grades of steel and concrete are unavailable, the AASHTO Manual specifies the compressive

strength of concrete per year of construction (Table 6A.5.2.1-1), and yield strength of reinforcing steel per the period

of construction (Table 6A.5.5.5-1) shall be utilized. If a box culvert exhibits considerable spalling or settlement and

cracking, then an evaluation will need to be made based on the actual resistance of the structure applying condition

factors to the design resistance as specified in AASHTO Manual of Bridge Evaluation, 2nd Edition. We propose to

examine the NBI information of those concrete box structures in the inventory presented. We will be able to

determine if there is enough documented information to perform the load rating without going back to the field and

performing another evaluation. Should we have to return to any of the concrete boxes presented, we will make

measurements and estimates of amount of spalling and cracking and any discrepancies from the provided plans if

there are such features, and we will perform the load rating utilizing the methodology of the AASHTO Manual for

Bridge Evaluation, 2nd Edition based on actual in-situ conditions based on condition factors applied to the resistances.

A conservative simplified analytical modeling approach using a two dimensional plane frame model such as the

program VIRTIS developed for AASHTO or the program BRASS CULVERT developed by Wyoming Department of

Transportation shall be utilized in the load rating to obtain consistent, repeatable and efficient load ratings as

recommended in AASHTO Manual for Bridge Evaluation, 2nd Edition Section 6A.5.15 for reinforced concrete boxes.

The loads typically seen by the concrete boxes including self-weight, vertical soil load, live loads, live load surcharges,

lateral earth loads with minimum and maximum load factors, shall be applied to the two dimensional plane frame


model to obtain the flexure, shear and axial load demands. This modeling approach tends to be highly conservative

in that it provides relatively higher load demands. The concrete box culvert members shall be evaluated for flexure,

shear, and axial thrust at several critical members and sections for the actual load effects and available resistances

using appropriate resistance modifiers to the design resistances based on its actual condition and the minimum

rating factor chosen as the load rating of the structure. Appropriate load factors for dead weights, earth and live

loads to be used to calculate the load demands must be obtained from AASHTO Manual for Bridge Evaluation, 2nd

Edition Section 6A.5.15 for reinforced concrete box culverts.

Based on our past experiences with load rating reinforced concrete boxes, an accurate project specific

standard/design plan of the reinforced boxes or standard plans based on the year of installation including details

such as culvert dimensions, material properties, reinforcing details and soil envelope properties must be made

available for efficient load rating. A lack of such proper documentation can result in underestimation of the material

properties. Underestimation of the material and section properties combined with a conservative modeling

technique as in BRASS CULVERT could possibly result in less than expected load ratings for the culvert. If higher

ratings are required, more sophisticated and complex modeling techniques including CANDE finite element analysis

can be employed that consider soil structure interaction effects also. Also if required, appropriate non-destructive

field tests (NDT techniques) such as x-ray radiography tests and some destructive testing as necessary can also be

utilized to determine any undocumented missing parameters.

Concrete Pipes

Concrete pipes are similar to concrete box culverts; however the methodology for evaluating them is somewhat

different. Concrete pipes also become part of a composite system comprising of reinforced concrete buried section

and soil envelope. Downdrag is less of a consideration with concrete pipes. Two methods of analysis of the concrete

pipes are specified in AASHTO LRFD Bridge Design Specifications, analytically-based Direct Method as in Section

12.10.4.2 and empirically-based Indirect method as specified in Section 12.10.4.3.

Direct method emphasizes the estimation of thrust, moment and shear load demands on the reinforced concrete

pipes based on a comprehensive soil structure interaction analysis and design program developed by AASHTO for

standard installations (if the soil parameters and installation techniques for the pipes are known) and suggests

performing appropriate soil structure interaction analysis to estimate the thrust, moment and shear load demands

for non- standard or unknown installations as in Section 12.10.4.2. The resistance of the reinforced concrete buried

pipe against structural failure shall be determined for flexure, shear, thrust and radial tension. The capacity of the

concrete pipe to carry loads depends on the condition of the pipe. We recommend examining the NBI of the

concrete pipes presented to see if there is enough information to define the load carrying capability. If the

information is not available we recommend field examining the concrete pipes to determine the amount of spalling,

any exposed rebar, damage to rebar, and whether there are openings in the joints between pipes which could allow

infiltration of fines and loss of support of backfill. Any erosion or deterioration of the invert of the pipes should also

be examined. The load rating based on the estimated factored loads and actual field conditions of these structures

utilizing suitable resistance modifiers to the design resistances according to AASHTO Manual for Bridge Evaluation,

2nd Edition with a reformulated load rating equation for buried structures will be made.

The Indirect Method is a commonly utilized method of load rating of the reinforced concrete pipes as suggested in

AASHTO Section 12.10.4.3 based on observed successful past installations. The capacity of the concrete pipe taken


as a three-edge bearing strength of the concrete pipe corresponding to an experimentally observed crack width of

0.01 inch (D-load) shall be compared with the factored earth and live loads on the concrete pipe. These estimated

resistances and factored loads shall be used in a reformulated load rating equation for buried structures according

to AASHTO Manual for Bridge Evaluation, 2nd Edition to come up with a load rating for the reinforced concrete pipes.

The edge bearing strength D–load for the concrete pipe controlled by the least capacities from flexure, thrust, shear

and radial tension based on the dimensions, material properties and reinforcing of the concrete pipes must be

obtained from ASTM standards based on available project specific plans or any available standard plans. The edge

bearing strength D–load for the concrete pipes based on the dimensions, material properties, and reinforcing details

from ASTM standards and modified for the actual structure conditions shall be utilized in load rating.

CONSPAN (Concrete Arch-Box) & Concrete Arch Structures

CONSPAN and concrete arch structures are different from pre-cast box culverts in that they are designed to utilize

the resistance of the soil in the overall design. Consequently, the performance of a CONSPAN or concrete arch

structure is related to soil structure interaction. These structures may also experience downdrag similar to box

culverts and some may bear on piles which may exuberate downdrag. We recommend examining the NBI

information to see if there is enough information to define the in-situ conditions. If this information is inconclusive,

we recommend performing a field evaluation of these structures to determine the in-situ conditions, the basic shape

of the structure, and then calculating the loads and resistance. These structures will be evaluated similarly to the

box culverts taking into account the resistance provided by the soil backfill utilizing a sophisticated soil structure

interaction finite element modeling programs such as CANDE. These estimated resistances utilizing resistance

modifiers to take into account the actual condition of the structure and estimated factored loads shall be used in a

reformulated load rating equation for buried structures according to AASHTO Manual for Bridge Evaluation, 2nd

Edition to come up with a load rating for a CONSPAN or concrete arch structure.

Load Rating Software Discussion - BRASS CULVERT vs. VIRTIS

Load rating software is still very limited for buried structures and culverts. A buried structure can still be considered

a bridge by the FHWA definition of any structure above ground or buried with a single span or combined spans

greater than 20 feet. CBC has performed load ratings on both metal and concrete structures meeting this criteria.

Unfortunately, BRASS CULVERT and Virtis are the only software programs able to analyze a buried bridge or culvert

and this is limited to concrete box culverts. The rest of the buried structure types mainly all buried flexible metal

shapes and sizes, concrete pipe and pre-cast concrete arch-box and arches need to use other methods to load rate.

AAHSTO (NCSPA) Data Sheet 19 will load rate the buried flexible metal structures (2 2/3” x ½”, 3”x1”, 5”x1”, 6”x2”

and 9”x2 1/2”corrugation sizes) and CANDE finite element modeling program can be used to load rate Deep

Corrugated Metal Structures (15”x 5 ½” corrugation) as well as both pre-cast concrete arch-box and arch shapes.

CANDE may require more data to set up the model than is currently available in the NBI or project files. Some

assumptions may be required to run these type of load ratings.

BRASS CULVERT and Virtis are both considered two dimensional plane frame models with a simplified finite element

program working in the background. Virtis has more flexibility in the number of barrels that can analyzed, varying

height of cover inputs and more flexibility in setting up the boundaries of the model for analysis. The background

analysis of creating an LRFR load rating for concrete box culverts is the same. CBC is proficient in running either

program and understand that PIMA County would like to use the Virtis program wherever possible.


Staffing Plan – A Diagram showing all personnel specifically assigned to each work element of the

project, their duties, and immediate supervisors.

Al Banner

President & COO

Resource Allocation and Coordination

Mitchell T. Hardert, P.E. Chief Engineer & V.P.

Principal-In-Charge Will Review and P.E. Seal All

Reports and Designs

Joseph A. Dennis, Jr. Director & Senior Project Manager

Project Liaison / Manager Responsible for Contract Execution and

All Coordination with Owner

Ioan "John" Corda, M.S., P.E. Senior Geotechnical Project Engineer Provide Culvert Evaluations and Repair

Designs as Required

Jay Evans CAD Technician

Draw Shapes of every Station of Corrugated Metal Culverts

Word

Processing

Deepa Nair, P.E. Geotechnical Project Engineer

Provide Load Rating Calculations and Culvert Evaluations

Rick Teachey, E.I.T. Project Engineer

Provide Load Rating Calculations and Culvert CANDE Evaluations

Bill Robertson Director Field Operations

Organize and Prepare Inspection Team for all Culvert Inspections

Gene Highlander, P.E. Culvert Inspector

Lead Inspector – May take a helper to record data and move equipment

Bruce Gillespie Culvert Inspector


Don Martin Culvert Inspector


Jeff Floyd, P.G. Culvert Inspector


David Hunt CAD Group Leader

Draw Shapes of every Station of Corrugated Metal Culverts

Load Rating Statement of Qulaifications

Documents

Transcript of Load Rating Statement of Qulaifications