2>C£ 23/4^
STUDY ON STRUCTURAL ASPECTS OF UNDERPASSES IN 
SOUTHERN TRANSPORT DEVELOPMENT PROJECT
The thesis submitted to the Department of Civil Engineering of the University of
Moratuwa in partial fulfillment of the requirements for the Degree of Master of
Engineering in Structural Engineering Design.
LIBRARY"
!l*IVfrRSIYV Of MORATUWA, SR! LAK.v<
V.QRATUWA
By
V.G. Liyanagamage
Research Supervised By
Prof. M. T. R. Jayasingha
University of Moratu>va
93912
DEPARTMENT OF CIVIL ENGINEERING 
UNIVERSITY OF MORATUWA 
SRI LANKA.
Semptember 2009
93 9/z
(■'
:•I - 4 &
6 >4- i)
93312
Abstract
ABSTRACT
The Colombo-Matara express highway also known as the Southern Lanka Express 
Highways or simply the Southern Expressway is a highway currently under construction 
in Sri Lanka. The 126 km long highway will link the Sri Lankan Capital Colombo with 
Matara, a major city in the Southern Province of the Island. Construction of the highway 
began in 2006 and it is expected to be completed in 2010 at the cost of $600 million. 
When completed, it will reduce the time taken to travel from Colombo to Matara to one 
and a half hours from the current four hours.
It is known fact that the Southern Highway and other subways linked with are normally 
supported by a wide range of different structures which require careful thought in 
selecting a suitable one for each location. In fact, these structures form a vital part of 
transport infrastructure and the smooth running of the network as designed. Even though, 
this study has been narrow down only to underpasses from the vide range of structures 
being used. Therefore, in this research work, it is mainly focused on to the underpasses 
such as metal and concrete underpasses used in and its significant impact on the cost 
initiatives, suitability and the environmental impacts and etc.
The technology used for the metal underpasses on this project is new to Sri Lanka. 
Traditionally in Sri Lanka, pre cast concrete structures are the preferred option, however, 
in this project, metal underpasses has also been used. The introduction of new technology 
requires knowledge of their structural behavior, particularly when used in combination 
with other materials, and their long-term durability. Over the last years, many structures 
have started to show signs of degradation and deterioration as a result of the high chlorate 
content in the air in southern Sri Lanka and some kind of crack failures due to bad 
workmanship as well as lack of adequate supervision. All these issues has been discussed 
and concluded in this report in a precise manner based on physical observation and on 
literature survey.
i
Abstract
Finally, this research concludes that the use of concrete box underpasses in the southern 
highway is mostly substantiated with country like Sri Lanka due to its inherent 
characteristics and with the economy and the durability concerns.
In fact, this report is a part of a post contract analysis which describes important facts that 
had to be emphasized in selection of the structure underpasses for Southern highway 
project and concluded which type of underpasses would have been used with the great 
economic impact to Sri Lanka.
ii
Acknowledgement
Acknowledgement
I would like to make this opportunity to forward my sincere thanks to the project 
supervisor, Prof. M.T.R. Jayasingha who helped me to make this project a success by 
giving advice and looking in to the problems encountered. His guidance and constructive 
criticism helped me o execute the project successfully.
I wish to thank the Vice Chancellor, Dean of the Faculty of Engineering and the Head, 
Department of Civil Engineering for allowing me to use the facilities available at the 
University of Moratuwa.
I am grateful to the RDA for the leave granted to me to follow the postgraduate degree
course.
I wish to thank to Dr. I.R.A.W. Weerasekara, course coordinator and Dr(Mrs) M.T.P. 
Hettiarachchi, the research coordinator of the project for the encouragement given to me 
in completing this study, and all the lecturers of the postgraduate course on Structural 
Engineering Design who helped me to enhanced my knowledge.
Special thanks go to Mr. L.G. Sirisena, Mrs. V.B. Panditha, my loving parents, for the 
support given for my education and learn to be confident throughout the career. I also 
would like to thank my husband for giving valuable support and encouragement to 
complete the study during the period.
Finally, I gratefully acknowledge everybody who helped me in numerous way in 
completing my research study.
V.G. Liyanagamage. 
August 2009.
iii
Declaration
DECLARATION
I, V.G. Liyanagamage, hereby declare that the content of the thesis is the output of the 
original research work carried out at the Department of Civil Engineering, University of 
Moratuwa. Whenever others’ work is included in this thesis, it is appropriately 
acknowledged as a reference.
V V^CXCja.
...Qk/.!flJ. ....
Signature
Name of the Student
Date
Signature
Name of the Supervisor
Date
iv
Contents
Pages
Abstract..................
Acknowledgement 
Declaration............
1
m
IV
Contents.........
List of Figures 
List of Tables.
v
vm
IX
1Chapter 1..........
1.0 Introduction 1
11.1 General....................................................
1.2 Main Objectives..................................... .
1.3 Methodology...........................................
1.4 Main Findings.........................................
1.5 Arrangement of the Report.....................
Chapter 2.......................................................
2.0 Literature Review..................................
2.1 Applications of Corrugated Steel Products
2.2 Description of Corrugations.....................
2.3 Structural Properties of Conduit Wall......
2.4 Pipe Seams.............................................
2.5. Minimum Cover Requirements..............
2.6. Normal Bedding.....................................
2.7. Camber..................................................
2.8. Selection of Structural Backfill...............
2.9. Vertical Deflection.................................
2.10. End Protection......................................
2.11 Failures in Metal structures....................
6
6
7
7
8
8
8
9
11
11
12
12
13
14
15
16
16
v
172.11.1. Buckling of the conduit wall..... ......................
2.11.2. Bolt hole tears............................................. .
2.11.3. Bearing failure at longitudinal seams..............
2.11.4. Excessive deformation of conduit cross section
2.11.5. Collapse of the structure.................................
2.11.6 Remedial measures.........................................
Chapter 3................................................................. .
17
17
17
18
18
19
193.0 FIELD SURVEY
193.1 Introduction.............................................................
3.2 Method and work Procedure.....................................
3.2.1 Metal Structures................................................
3.2.1.1 Filling and Excavation....................................
3.2.1.2. Foundation Preparation..................................
3.2.1.3. Camber at Installation....................................
3.2.1.4. Erection of Structures....................................
3.2.1.5. Backfilling.....................................................
3.2.1.6 Shape Control.................................................
3.2.1.7 End Treatment................................................
3.2.2 Box Culvert......................................................
3.2.2.1 Filling and Excavation...................................
3.2.2.2. Construction of Box Culverts........................
3.3. Failures in Metal Underpasses.................................
3.4 Summary.................................................................
Chapter 4........................................................................
4.0 Analysis of Metal Structure & Results................
4.1 Introduction.............................................................
4.2 Description of Loads on the Metal Structure.............
4.2.1 Dead Load.......................................................
4.2.2. Live Load HB Loading...................................
4.3. Design Calculation as per AASHTO (For HPA 74N)
4.3.1 Description of the Proposed Structure................
4.3.2 Outline Drawing of the Proposed Structure.........
4.3.3. Design Pressure................................................
Chapter 5........................................................................
Analysis of Box Culvert, Results & Design..............
5.1 Introduction.............................................................
5.2 Load Cases........................................................
19
19
19
20
20
20
20
21
21
21
21
22
22
24
25
25
25
25
25
26
26
26
27
27
31
31
...31
31
U4
Vvi
325.3 Loads on the Box Culvert
325.3.1 Loads due to soil..............................
5.3.2 Live Loads......................................
5.3.3. Loads on the top slab.......................
5.3.4. Loads on the side walls...................
5.3.5. Loads on the bottom slab.................
5.3.6 Horizontal Live load due to traction... 
5.3.7. Hydrostatic Pressure.......................
5.4 Modeling of Box Culvert........................
5.4.1 Load Calculation..............................
5.4.1.1 Dead Load Calculation..................
5.4.1.2. Live load calculation....................
5.4.1.3. Super Imposed Dead Load............
5.4.1.4. Reaction from Soil Calculation......
5.4.1.5 Lateral earth pressure calculation ....
5.4.1.6. Traction force...............................
5.4.1.7. Hydrostatic Pressure....................
5.5 Concrete Outline Drawing of Box Culvert
32
33
33
33
33
33
34
34
34
34
35
36
41
42
42
43
435.6. SAP2000 model of the Box Culvert
445.7 Load Combinations
445.8 Deformed Shape for Load Case 4.3...
5.9 Results from the SAP2000 Modeling
Chapter 6........................................
6.0 COST ANALYSIS....................
45
47
47
476.1 Introduction..............................
6.2 Cost Estimating Process............
6.3 Cost Analysis of Metal Structure
6.4. Cost Analysis of Box Culvert.... 
6.5 Cost Saving..............................
47
47
49
50
51Chapter 7...............................................................
7.0 CONCLUSIONS AND RECOMMENDATION 51
52REFERENCES
53APPENDIX -A
vii
List of Figures
Page
2Figure 1.1 : View of a Metal Structure.............................................
Figure 1.2 : View of a Box Culvert..................................................
Figure 1.3 : Typical Details of Metal Structures..............................
Figure 2.1 : (a) Longitudinal Stiffeners (b) Transverse Stiffeners
Figure 2.2: Types of Corrugations available....................................
Figure 2.3: Sectional Properties of Selected Corrugation...............
Figure 2.4 : Typical Flat Bedding.....................................................
Figure 2.5 : Typical Vee Shaped Bedding........................................
Figure 2.6 : Cambered pipe...............................................................
Figure 2.7 : Typical Vertical Deflection..........................................
Figure 3.1 : Husker walls are cracked..............................................
Figure 3.2 : Weeds comes through the plates of Metal Structure...
Figure 3.3 : Plates are Corroded......................................................
Figure 4.1 : Concrete Outline of the HPA74N................................
Figure 5.1 : Loads on the Box Culvert.............................................
Figure 5.2 : HB Vehicle Wheel Arrangement..................................
Figure 5.3 : Concrete Outline of Box Culvert..................................
Figure 5.4 : Model of Box Culvert..................................................
Figure 5.5 : Deformed shape of Mode 1..........................................
Figure 5.6 : Deformed shape for Mode 2........................................
2
4
8
10
11
13
13
14
15
22
23
23
27
32
35
43
43
44
45
viii
List of Tables
Page
12Table 2.1 : Ultimate Seam Strength for MP152 Corrugated Structures
Table 4.1 : Description of the Proposed Structure..............................
Table 5.1 : Results from the SAP2000 Modeling...............................
26
46
ix
Chapter 1 Introduction
Chapter 1
1.0 Introduction
1.1 General
Traffic safety concerns, the use of underpasses and Overpasses are now increasingly 
being adopting in the highway construction in Sri Lanka. When the Southern Transport 
Development project is concern, the design professionals have adopted these features 
with a great attention to cater the smooth transport with a safe and without undue delays. 
In this scenario, various types of underpasses have been integrated along with the road 
lines and crossings. Those are bridges, metal structures, box culverts and pipe culverts. In 
the designer’s point of view, there are several issues that have to be concerned in 
selecting a typical underpass to the highway project. Some fundamental issues governing 
under these criteria are type of road users, cost, method of construction, Procurement of 
construction materials as well as availability, durability and the environmental issues.
Metal structures and box culverts occupied in roads play a major role as replacement for 
the bridges as well as the cost significant alternative. Following advantages could have 
been encountered when such a structure is incorporated with the roads.
• No bridge deck deterioration problems.
• Eliminates constant maintenance of bridge approaches and painting of 
superstructure.
• Permits use of constant roadway section in the vicinity of structure.
• Roadway easily widened by simple extension of ends.
• Readily available - components are standard shop items - can be field 
assembled with unskilled labour.
• Less design and construction time - total project completed earlier.
• Environmentally acceptable - permits natural appearance of earth slope and 
vegetation to be utilized.
1
Chapter 1 Introduction
In Southern Transport Development Project we mainly identify two types of underpasses. 
Those are metal structures and box culverts. Fig. la shows the front view of a metal 
structure and Fig. lb shows view of a box culvert.
Figure 1.1: View of a Metal Structure
j
Figure 1.2 : View of a Box Culvert
2
Chapter 1 Introduction
Metal Underpasses
In relation with the Southern Transport Development project, there are five types of metal 
underpasses. Curved corrugated metal plates have mostly used for this metal underpasses. 
Those are MAUP 47N, MAUP 55N, MAUP 67N, HPA 60N, HP A 74N & HES 87N. 
Figure 1.3 shows the typical drawings of metal structures mentioned above. The 
selection of the type depends specially on the maximum span & rise. Moreover, the Span 
& the rise depend on the design elevations of the secondary road which passes through 
the structure and the type of vehicles using that secondary road.
Structural design of metal underpasses is in accordance with the Standard Practice for 
Structural Design of Corrugated Steel Pipe , Pipe Arches and Arches for Storm and 
Sanitary Sewers and Other Buried Applications (ASTM A 796/A 796-01). Dimensions 
and tolerances is in accordance with Standard Specification for Corrugated Steel 
Structural Plate, Zinc - coated, for Field - Bolted Pipe, Pipe - Arches and Arches 
(ASTM A761/A 761M-02).
3
Chapter l Introduction
i
. 50CO
!
\ s I::
2p
/\ ■- wr,i
czzri Mrtm]
MAUP No .4 7N HPA N0.6OM
i i
i
VIg aww-:e S
. Ml* VS i
HPA No.74NMAUP No.55N
SZc 3C0Q
1 I
so
I
MAUP No.67N
Figure 1.3 : Typical Details of Metal Structures
4
Chapter 1 Introduction
Box Underpasses
The size of the box underpasses varies with the fill height and the type of vehicles
traveling on the secondary road. Major material used in box underpasses is ready mixed
concrete - class 30/20. The structural design of the box underpass is in accordance with
BS 8110.
In box underpasses there is a significant moment carried by the surface of the box
underpass.
Need For the Research Work
Southern Transport Development project begins at mid of year 2002. It is important to 
list out following failures based on recent physical observation of site visit,
• Corrosion of metal structures .
• Movements of metal structures plates.
• Absence of Nails used to connect metal structures plates.
• Cracks in box culverts.
• Cracking in husker walls of metal structures.
The above structures have been designed for a life time of 100 years. However, the above 
mentioned defects have been noted with in a period of four years after the construction. 
Road was not opened to traffic during this period (i.e. structures have not subjected to 
design loads)
5
Chapter 1 Introduction
1.2 Main Objectives
To obtain field surveys and analytical research data that can substantiate specification for 
the selection of most effective type of underpasses in modem highways as a means to 
reduce wastage occurred due to use of ineffective type of underpasses by considering the 
structural aspects.
1.3 Methodology
In order to achieve the above objectives, the following methodology was adopted:
1. A literature review was conducted to determine the desirable features that should 
be adopted in construction of metal underpasses and box culverts.
2. Field survey to evaluate current condition of structures.
3. A comparison was made for the structural forms recommended for the 
underpasses by means of reaching compromise solutions.
4. A comparison was made by designing the metal structure manually and box 
culvert in SAP 2000 to find the most effective type of underpass that can be resist 
vertical and horizontal loads.
5. Cost comparison was carried out between metal structure and box culvert
6
Chapter 1 Introduction
1.4 Main Findings
The main findings of this research can be presented with respect to structural forms, 
structural detailing and cost implications.
1 The Construction of Box Culvert is more cheaper than the construction of 
Metal Structure.
2 Box culvert is more durable than the Metal Structure
1.5 Arrangement of the Report
This report is presented in the following manner.
Chapter 2 presents a detailed literature review made to determine the desirable features 
that should be adopted in construction of metal underpasses and box culverts.
Chapter 3 deals with the field visits made and the detail description about the site 
condition.
Chapter 4 presents the design of metal structure and the results
Chapter 5 deals with the analysis of box culvert and the design.
Chapter 6 presents the cost comparison between metal structure and box culvert.
Chapter 7 presents the conclusions made from the research.
7
Chapter 2 Literature Review
Chapter 2
2.0 Literature Review
2.1 Applications of Corrugated steel products
Corrugated steel products have been used for over 75 years play a major role in the 
modem engineering technology for a wide range of important functions. Flexible steel 
conduits play an important role in the form of culverts, storm sewers, subdrains, 
spillways, underpasses , conveyor conduits and service tunnels: for highways, railways, 
airports.
In the late 1960’s , developments were made which involved adding longitudinal and 
circumferential stiffening members to the conventional corrugation structural plate 
structures that permitted the use of larger sizes and increased permissible live and dead 
loads. The above two types of stiffeners are shown in Figure 2.1.
il
• f'
Figure 2.1 : (a) Longitudinal Stiffeners (b) Transverse Stiffeners (Ref. : Design 
and Construction of Soil Steel Bridges, George Abdel - Sayed)
Some of the applications in which these structures are serving are bridges, highway and 
railway overpasses or underpasses, stream enclosures, tunnels, culverts and conveyor 
conduits. These structures have been popular for bridge replacement, and when used as 
such provide the following advantages:
8
Chapter 2 Literature Review
No bridge deck deterioration problems.
Eliminates constant maintenance of bridge approaches and painting of 
superstructure.
Permits use of constant roadway section in the vicinity of structure.
Readily available - components are standard shop items - can be field assembled 
with unskilled labour.
Less design and construction time - total project can be completed earlier.
Less construction engineering and field inspection.
Environmentally acceptable - permits natural appearance of earth slope and 
vegetation to be utilized.
Minimum delay to earth moving or other construction operations.
Least affected by weather and temperature.
1.
2.
3.
4.
5.
6.
7.
8.
9.
2.2. Description of Corrugations
Types of corrugations available are shown in Figure 2.2. Corrugations commonly used 
for pipes are termed circular arcs connected by tangents, and are described by pitch, 
depth and inside forming radius. Pitch is measured at right angles to the corrugations 
from crest to crest. For corrugated plate, the thickness shall be measured on the tangent of 
the corrugations. The thickness shall include both the base metal and the coating.
9
Chapter 2 Literature Review
Figure 2.2: Types of Corrugations available
In Southern Transport Development Project they have used 6 by 2 in (152 by 21mm) 
corrugation. The above corrugation is the Standard of the American Association of State 
Highway and Transportation officials.
10
Chapter 2 Literature Review
2.3. Structural Properties of Conduit Wall
Sectional properties of the arc - and - tangent type of corrugation are derived 
mathematically. Research by American Iron and Steel Institute has shown that failure 
loads in bending and deflection within the elastic range can be closely predicted by using 
computed sectional properties of the corrugated sheet. Figure 2.3 shows the sectional 
properties of selected corrugation for the Southern Transport Development Project.
Ultimate Strength of Bolted Structural 
Plate Longitudinal Seams in kN per m 
__________ of Seam___________
RadiusTangent
Length ,Tl.
Area of
Section/*.
mm2/mm
Tangent
Angle
Moment of 
Inertia.mm 
4/mm
Specified
;Thickness ofGyration
,r,mmA0 2 Bolts per Corrugations
3 Bolts per 
Corrugation
I (mm) 4 Bolts per 
Corrugation
mm
2 82
Hi-
3.29 48.00 44 47 990.06 17 30 613 00
4.24 47.27 44 73 1280.93 17.40 905.00
5.18 46.43 45.00 2575_89
1769.80
17.40 1182.00r 4.79 5.80 45.90 45.18 17.50 1357.00
! 5.54 6.77 45.03 45.47 2Q79.B0 17.50 1634.00
632 7.74 44.15 47.77 2395.25 17.60 1926.00
l 7.11 8.72 43.23 46 09 2717.53 17.70 2101.00 2626.00 2830.00
808 989 41.99 46.47 3113.54 17.70 3430.00
11.88 " 40.169.65 47.17 3801.80 17.90 4159.00
Figure 2.3: Sectional Properties of Selected Corrugation (Ref. : ASTM 
Designation A 796/A 796 M -01, Table 26)
2.4. Pipe Seams
Standard method of shop - fabricating the seams of annular corrugated steel pipe and 
pipe - arches are;
• Riveted Seams
• Spot welded seams
• Bolted Seams and joints
In Southern Transport Development Project they used bolted seams of 3/4in diameter 
(high strength hexagonal bolts meeting ASTM A 449) Following seam strength values 
are based on a seams using 3A” bolts with heavy hex. heads spaced at 13.12 bolts per
11
Chapter 2 Literature Review
meter. These are designed for fitting either the crest or valley of the corrugations, and to 
give maximum bearing area and tight seams without the use of washers. Table 2.1 
describes the ultimate seam strength values for MP 152 corrugated structures.
Specified Thickness (mm) Seam Strength (kg/m)
2.82 63,217
3.56 84,830
6.0 182,061
Table 2.1 : Ultimate Seam Strength for MP152 Corrugated Structures
2.5 Minimum Cover Requirements
Where pipe is to be places under roads, streets or free ways, the minimum cover 
requirements shall be determined. Minimum cover is the distance from the top of the pipe 
to the top of the rigid pavement or to the top of subgrade for flexible pavement.
2.6 Normal Bedding
Pressures developed in the shell by the weight of the backfill and live loads are 
transmitted both to the side fill and strata underling the pipe. The bedding is the portion 
of the foundation in contact with the bottom or invert of the structure. Depending upon 
the size and type of structure, the bedding may either be flat or shaped. With flat bedding, 
the pipe is placed directly on the fine graded upper portion of the foundation. For pipe - 
arches and large span structures, with invert plates exceeding 3700mm in radius, the 
bedding should be shaped to the approximate profile of the bottom portion of the 
structure. Alternatively, the bedding can be shaped to a slight vee shape. Typical details 
of flat bedding and vee shaped bedding are shown in Figure 2.4 and Figure 2.5 
respectively (Ref.: Installation & Backfilling Standards for Armco Structures).
12
:
Chapter 2 Literature Review
o' struojfi; bacMti
:£5J Jo 200 T.r’. Jhick, CCnTOCW*. Mud ACWIWOI &CC<1 ~J &TVnr~*
\
-A ,
-V
H nc^ybf 
SesxWl
3&
3«±S. 1'
T% ** v*' C? SSfsCfc-? -3 O'*
---r,’~£.V~ **fvcJw«? is crrsl-jr.~ 7 • ?
SJniCUl* e^cxJill 
OcntpiCf'J UrttJc* i'.-iur-rr^fi.rine Grtvd««i &iac
Figure 2.4 : Typical Flat Bedding
30
Ro'julnr Backfill
fj.'li .if Slit
l3u«:.V!i-f ”-v ;c 30C sv r.i 
I Ihicfc. C«5tlWJCHrJ 
^ (JCSii Med. A&&»)
4» —
i
i
RyyuUjf 
SackHU or 
’.IS-nj.'IU SchI
0 — ^. 4JII _
---------- -----------|XKJ-*m Mod. AusMc*M ti-'
Corner ^ic.-eSedCinq iiil. utKOdioacS&J
up :g 300 nun thicwvais. fin^odcd 
to :;lidOO of do&orn <*.4 poc-arcx 
f20—fJ5V» Mod. Aasftio)
Figure 2.5 : Typical Vee Shaped Bedding
2.7 Camber
The soil cover above the conduit varies along the pipe because of embankment slopes . 
Due to this uneven cover, the foundation under the pipes settles more under the middle 
length of the conduit than under the outer length. Longitudinal profile of the bedding 
must account for this uneven settlement. Camber is simply a rise at the center of a culvert
13
■
Chapter 2 Literature Review
above a straight line connecting its ends to avoid a sag in the longitudinal profile of the 
culvert. A cambered pipe is shown in figure 2.6 (Ref. : Installation & Backfilling 
Standards for Armco Structures).
Camber
Final Qra.rJe alter settlement
Figure 2.6 : Cambered pipe
2.8 Selection of Structural Backfill
Requirements for selecting and placing backfill material around or near the conduit are 
similar, in some respects , to those for a roadway embankment. However, a difference in 
requirements arises because the conduit may generate more lateral pressure than would 
the earth within the embankment if no structure existed. Therefore soil adjacent to the 
conduit must be compacted densely.
The Structural backfill material should conform to the following classification 
(Installation & Backfilling Standards for Armco Structures);
• Minimum Grading Modulus : (G.M.) 0,8
• Maximum Plasticity Index (P.I) 10 + 3 G.M.
• Minimum CBR at compacted density 15%
• Minimum Compacted Density (MOD. AASHTO) 90%
• Maximum % passing 75 micron sieve 40%
The backfill material should be placed and compacted in layers not exceeding 300mm of 
compacted thickness, with each layer being compacted to the required density at the
14
Chapter 2 Literature Review
optimum moisture content. Backfill material must be placed equally on each side. Each 
layer must be compacted to specified density before adding the next layer. Care must be 
taken to ensure that no more than one layer difference each side of the structure.
Controlling the symmetry of the structure is another important thing during backfill 
operation, by control of the backfill operation. As a general rule, no deflection in any 
direction greater than 2% from original shape should be allowed during the backfill 
operation (Installation & Backfilling Standards for Armco Structures).
2.9 Vertical Deflection
Corrugated steel pipes functions structurally as a flexible ring which is supported by and 
interact with the compacted surrounding soil. The soil constructed around the pipe is thus 
an integral part of the structural system. Therefore it is important to ensure that the soils 
structure or backfill is made up of acceptable material and well constructed. Typical 
vertical deflection pattern is shown in figure 2.7 (Ref. : Installation & Backfilling 
Standards for Armco Structures).
Fill Load
Original ShapeIFinal Shape
1 Ir—
A U
\ 7
Figure 2.7 : Typical Vertical Deflection
Fill material around the structure should be placed alternatively in layers 150 or 300mm 
thick on both sides. Pipe - arches require that the backfill at the corners (sides) of the 
best material, and be especially well compacted.
15
i
i
Chapter 2 Literature Review
The above book discuss several points we have to consider when erection of the Metal 
Structure.
• Placing backfill around structure
• Shape Control
• Vertical Deflection
• Construction Loadings
2.10 End Protection
This is the case with any water carrying structure, the compacted fill material around an 
Armco structure has to be adequately protected against erosion. This protection can take 
the form of concrete headwall and wing walls, stone pitching, gabion mattresses or 
concrete slab protection of the embankment.
The Standard concrete ring beam recommended for Armco Structures should form an 
integral part of the end protection of a structure. There is no substitute for adequate end 
protection. Which ensures that compacted fill will not be damaged by erosion or 
flooding.
2.11 Failures in Metal structures
Bad construction practice is the main reason for the failure of those structures. The lack 
of understanding of the mechanics of behavior of these structures promotes bad 
construction practice.
Common forms of failures are:
• Buckling of the conduit wall.
• Bolt hole tears.
• Bearing failures at longitudinal seams.
• Excessive deformation of the conduit cross section’
• Lifting of the invert
16
Chapter 2 Literature Review
• Lifting of the pipe ends.
• Distortion of the pipe ends.
• Collapse of the structure.
2.11.1. Buckling of the conduit wall
Buckling can be a result of a local buckling in which the metallic shell buckles in to a 
large number of waves, each of relatively small length. Buckling can occur in the 
compression zone of the wall section. When the conduit wall undergoes large bending 
deformations, this can be usually take place in conduit segments of relatively small radius 
of curvature.
2.11.2. Bolt hole tears
Bolt hole tears are caused by excessive bending of the plates, and that the tendency to 
develop the cracks is directly related to the tension in bolts.
2.11.3. Bearing failure at longitudinal seams
Bearing failure at longitudinal seams can take place due to the yielding of the conduit 
wall directly under the bolts. This type of failure takes place under excessive conduit wall 
thrust.
2.11.4. Excessive deformation of conduit cross section
This is the most common from of failure in metal structures. This result in poorly 
compacted backfill, backfill containing large quantities of clay or organic matter and well 
compacted and good quality backfill not extending on either side of the conduit.
Excessive pipe deformation do not always develop after the structure has been built. It 
deform during the initial stages of the backfilling operation.can
17
Chapter 2 Literature Review
2.11.5. Collapse of the structure
This is the most dramatic failure in these type of structures. The failure of metal 
underpasses is more common than other type of underpass (Design and construction of 
Soil steel Bridges, George Abdel-Sayed ). The failure of the metal underpass could have 
been avoided by careful construction, using good - quality backfill and employing good 
construction practice.
Factors that lead to the collapse of metal structure are as follows:
• Use of poor quality soil,(containing large quantities of clay and organic 
matter, in the backfill)
• Compaction of backfill in very thick layers.
• Compaction of backfill in cold weather.
2.11.6 Remedial measures
The various methods that can be used as follows (Design and construction of Soil steel 
Bridges, George Abdel-Sayed).
• Temporary props.
• Partial concreting inside conduit.
• Internal grouting.
• Shortcreting.
• Partial concreting outside conduit.
18
.
i
UNivtMsrrv if wmimKuw •
■rtQHATUWA
Chapter 3 Field Survey
Chapter 3
3.0 FIELD SURVEY
3.1 Introduction
This chapter describes the observations made during field survey. It describes detail 
description of the backfilling, construction of foundation, installation of metal structure / 
box culvert, backfilling, shape control, end treatment and the failures in the site.
3.2 Method and work Procedure
3.2.1 Metal Structures
3.2.1.1 Filling and Excavation
Filling and excavation width vary with the type of soil, 
a) In Embankment Fill - Firm Foundation
Embankment filling & compaction will be carried out in layers. In fill 
sections, before excavation is begin, the fill shall be constructed for a distance 
of 3 span / diameter and on each side of the metal structure to a minimum 
height of 25% of the vertical dimension of the metal structures.
b) In Embankment Fill - Soft Foundation
The Engineer will be required to issue his instruction. Soft ground treatment 
works will be carried out in accordance with the Engineer’s instructions.
c) In Cut - Firm Foundation (Soil)
The width of the excavation shall be 2m minimum each side of the structure.
d) In Cut - Rock Foundation
Excavation by blasting in accordance with the blasting pattern.
e) In Cut - Soft Foundation
Limits of the excavation shall be 2m minimum each side of the structure.
19
C3S12
Chapter 3 Field Survey
3.2.I.2. Foundation Preparation
• MAUP and HES structures shall be placed on a uniform stable earth or 
granular foundation.
• HPA structures are founded on reinforced concrete footings.
3.2.I.3. Camber at Installation
Cambering shall not be executed for the structures with concrete components (Thrust 
beams / footings) and in such cases foundation shall be constructed so as to avoid 
settlements. That is cambering shall be applicable for MAUP structures only.
3.2.1.4. Erection of Structures
MAUP structures shall be assembled in 4 stages, i.e. bottom, comer, side and top. HPA 
and HES structures can be assembled in 3 stages, i.e. Side, comer and top. In every type 
of structure plate assembling shall be proceeded at one side and the other side 
alternatively.
3.2.I.5. Backfilling
Structural backfill material specified in specifications shall be used as backfill material. 
The main deciding factor for selecting backfilling material shall be the bearing pressure 
of the material compacted to specified density.
Placing of backfill shall be carried out equally on both sides of the structure, in layers of 
compacted thickness of 300mm each layer shall be compacted to specified density before 
placing the next layer.
20
Chapter 3 Field Survey
3.2.1.6 Shape Control
This refers to controlling the shape and symmetry of structure during backfilling by 
control of the backfill operation. Care must be taken while installing the structure.
3.2.1.7 End Treatment
Reinforced concrete shall be provided at the ends of the structure. Protection to the 
embankment shall be provided by concrete headwall and wing walls or gabion mattress 
protection.
3.2.2 Box Culvert
3.2.2.1 Filling and Excavation
Filling and excavation width and the depth vary with the type of soil.
In Embankment Fill - Firm Foundation
The filling distance and height will vary with the structural dimentions and 
existing elevation of the location.
a)
In Embankment Fill - Soft Foundation
Soft ground treatment works will be carried out in accordance with the 
instructions.
b)
In Cut - Firm Foundation (Soil)
For Box culverts in soil foundation, additional excavation of 75mm below the 
bottom level of the culvert is needed for blinding layer.
In Cut - Rock Foundation
Excavate by blasting in accordance with the blasting pattern.
c)
d)
21
Chapter 3 Field Survey
e) In Cut - Soft Foundation
The excavated area will be backfilled with the suitable material and 
compacted up to the 300mm above the bottom of the box culvert.
3.2.2.2. Construction of Box Culverts
Formwork - class 1 will be fixed for placing concrete for base slab of box culvert. The 
formwork of the base slab will be removed 25hrs after concreting. Curing of all exposed 
concrete surface will be carried out for 7 days.
3.3. Failures in Metal Underpasses
Southern Transport Development project begins at mid of year 2002. But there were vide 
variety types of failures can be observed in the site.
Figure 3.1 : Husker walls are cracked.
22 \
Chapter 3 Field Survey
Figure 3.2 : Weeds comes through the plates of Metal Structure.
Piute Discoloured
IMS - HPA74N
[Cha. (a 5+258
02-11-2007
Figure 3.3 : Plates are Corroded..
Most recently Contractor of the Southern Transport Development Project started to 
undergo some rectification methods.
23
Chapter 3 Field Survey
3.4 Summary
To ensure that the steps of the procedure are fully complied with during the activities 
such as setting out, excavation, embankment filling, bedding, erection and backfilling etc. 
certain inspections and verifications will be carried out as described in the above 
procedures.
24
Chapter 4 Design of Metal Structure
Chapter 4
4.0 Design of Metal Structure
4.1 Introduction
The designs are carried out to American Standards / Practices as listed below. Traffic 
loading has been calculated according to BS5400 Part 2, HA & HB 30 units as 
requested by Road Development Authority.
Design Calculations are in accordance with following references:
1. Handbook of Steel Drainage & Highway Construction Products ( American 
Iron & Steel Institute)
2. ASTM Designation A 761/A 761M-98 - Corrugated Steel Structural Plate , 
Zinc - Coated, for field - Bolted Pipe, Pipe - Arches and Arches.
3. ASTM Designation A 796/A 796M-01 - Standard Practice for Structural 
Design of Corrugated Steel Pipe, Pipe Arches and Arches for Storm and 
Sanitary Sewers and other Buried Applications.
4. Standard Specifications for Highway Bridges (AASHTO) - Section 12
5. British Standard for Steel, Concrete and Composite Bridges - BS5400 Part 2 : 
1978.
4.2 Description of Loads on the Metal Structure
4.2.1 Dead Load
The following unit weight of materials were used for the design
• Compacted Density of Asphalt Concrete Surfacing - 24.030 kN/m3
• Compacted fill ( Soil) - 19.0 kN/m3
25
Chapter 4 Design of Metal Structure
4.2.2. Live Load HB Loading
As per BS5400;
16 wheels, each 75kN ( 30units of HB ) as shown in Figure 11 of BS5400 with 
innermost axels 6m apart shall be considered. Accordingly the square contact area 
shall be 261mm a side.
4.3. Design Calculation as per AASHTO (For HPA 74N)
4.3.1 Description of the Proposed Structure
(a). Structure Type HPA 74N/ Armco MP152S
Dimensions(b). Max. span 10.58m x rise 5.42m
(c). Top Radius 7.32m
Comer Radius 1.65m(d)
152mm x 50.8mmCorrugation(e)
6.32mm (Armco Nominal Thickness 
6.35mm)(f)
Specified thickness - Top Arc
6.00mm (Armco Nominal Thickness 
6.00mm)
Specified thickness - 
Remainder(g)
Table 4.1 : Description of the Proposed Structure
26
i
Chapter 4 Design of Metal Structure
4.3.2 Outline Drawing of the Proposed Structure
600
7
•* ' ■ •. i
« ■ V• 4*♦ *
4 f *
*4
A v- \m
SLOPE COLLARS
600 600C:
O
ID
'T
LONG BOLT 03/4x6'[r105 ■
0%3%
I.7000
97 30
4565 4365
10576
Figure 4.1 : Concrete Outline of the HPA74N
4.3.3. Design Pressure
The Design Pressure shall be;
P = DL + LL (from AASHTO Section 3.8.2)
L 800mm Pavement
900mm Structural Backfill
27
Chapter 4 Design of Metal Structure
Dead Load (DL) - (0.9 x 19) + (0.8x24.03) 
= 36.32 kN/m2
Live Load
261mm x 261mm
L J
>- 800mm Pavement
900mm Structural Backfill
l
/77Z /777
kN/m275x9.81Live Load (LL)
(0.261+0.7+0.7) x (0.261+0.7+0.7)
= 266.68 kN/m2
Design Pressure
P = DL + LL
= 36.32 + 266.68 = 303.0 kN/m2
The span of the selected type is HPA74N is 10.58m which is more than 6.4m and 
hence this structure falls in to the category of Long - Span Structural Plate Structures. 
Therefore the structure is designed in accordance with Subsection 12.7 of AASHTO 
Section 12. For these structures requirement for buckling and flexibility shall not be
applied.
28
Design of Metal StructureChapter 4
According to AASHTO Section 12.1.4.2.
The thrust in the wall is ; T = P x S/2
For HPA 74N
10.58mMaximum span (>6.4m i.e. long span structural plate structures) 
(ASTM 796 Section 5)
=
9.81m
5.54m
Base span 
Rise =
T = 303.0kN/m2 x (10.58m/2) 
= 1602.87 kN/m
Wall Cross sectional Area (AASHTO Section 12.3.1.) is ;
A = _Tl
(pfy
1602.87 kN/m—
2 x 310 Mpa 
= 26 cm2/m
= 26.0 cm2/mRequired wall area
Area corresponding to the thickness of proposed structure is 74.631 cm2/m. (Thickness 6.00mm)
A = 26.0 <74.631 cm2/m 
Hence ok.
29
Chapter 4 Design of Metal Structure
Check as per AASHTO Section 12.7
I.Table 12..7.2.A Minimum Requirement for Long - Span Structures with Acceptable 
Special Features.
In HES 74N Top Radius 7.32m = 24.01 ft 
Refer Table 12.7.2. A;
Top arc thickness = 0.249 in = 6.32mm
Specified thickness of Top - Arc of proposed structure = 6.32mm 
Hence OK.
II As per Table 12.7.2.A.
The Minimum cover is 4.0ft
(i.e. 1.22m for 23 - 25 ft Top Radius & 0.249in Steel thickness )
III According to AASHTO Geometric Limits
A . Maximum plate radius = 7.32m = 24. ft < 25ft 
Hence OK.
B. Maximum central angle of Top arc = 80°
Central Angle of top arc of proposed structure = 80° 
Hence OK.
C. Minimum Ratio , Top Arc Radius to Side Arc Radius = 2
For Proposed structure
Top Arc Radius = 7.32m 
Side Arc Radius = 1.65m
Therefore Ratio for Proposed Structure = 4.436 > 2 
Hence OK.
Therefore dimensions of the proposed structure satisfied
30
Chapter 5 Analysis of Box Culvert, Results & Design
Chapter 5
Analysis of Box Culvert, Results & Design
5.1 Introduction
Analysis of Box Culvert was performed in SAP 2000. The box culvert should be 
designed considering the following issues.
• It should be able to discharge the volume expected during a design flood.
• The structure of drainage culvert should be designed to be stable against the dead 
, superimposed dead, live and earth pressure.
5.2 Load Cases
Following load cases are to be taken in to account(since culvert is used as underpass)
1. Vehicles at Top - No vehicles at Bottom
1.1 HA only
1.2 HA & HB only
2. No Vehicles at Top - No vehicles at Bottom
2.1 No HA or HB
3. No Vehicles at top - vehicles at bottom
3.1 HA only
3.2 HA & HB only
4. Vehicles at Top & Bottom both
4.1 HA only in top & bottom both
4.2 HA in top & bottom & HB in bottom only
4.3 HA & HB in top & bottom both
4.4 HA in top & bottom & HB in top only
\
:
31
Chapter 5 Analysis of Box Culvert, Results & Design
5.3 Loads on the Box Culvert
Superimposed dead loaduuuuuuuuu
i Live loads
uuuuuuuuu Weight of soil 
Weight of structureuuuuuuuuu
>
Traction
Force Hydrostaticpressure
Soil pressure
<
*
A
tmtttttt tttttttt Reaction of soil
Figure 5.1 : Loads on the Box Culvert
5.3.1 Loads due to soil
Depending on the level of the stream, the box culvert can be either at the road level or 
buried. If it is buried, there will be soil on all four sides. Thus the following loads will act 
due to the soil:
• The weight of the soil between the top slab and the road level acting on the top 
slab.
• The soil pressure acting on the sides of the box culvert.
• If there is soil on the top slab, the soil loads will be transferred on to the side 
walls.
5.3.2 Live Loads
Live loads are generally due to vehicles traveling on the road. Live loads are calculated 
according to BS5400.
32
Chapter 5 Analysis of Box Culvert, Results & Design
5.3.3. Loads on the top slab.
Top slab is loaded due to the weight of soil, super-imposed dead load of the road and live 
loads due to vehicles.
5.3.4. Loads on the side walls
This consists of soil pressure and any surcharge pressure due to live loads.
5.3.5. Loads on the bottom slab
The soil below supports the box culvert. This soil is loaded due to the weight of the soil 
above the box culvert, weight of the soil on the top slab, weight of the box culvert and 
live load on the box culvert. The average upward pressure is assumed on the bottom slab. 
This pressure is equal to all the loads divided by the bottom slab area.
5.3.6 Horizontal Live load due to traction
The structure shall be designed to resist the traction forces. Traction force shall be 
applied perpendicular to the walls of the box culvert. Traction force was calculated as in 
accordance with section 6.6 of BS5400 Part 2.
5.3.7. Hydrostatic Pressure
The effect of hydrostatic pressure must be taken in to account in the design of box 
culverts, (either the selected structure is vehicular culvert). Because due to heavy rain if 
water table increases to the high flood level in that area it will automatically generate 
high hydrostatic pressure.
33
Chapter 5 Analysis of Box Culvert, Results & Design
5.4 Modeling of Box Culvert
Analysis of box culvert was performed using 2D shell elements of appropriate thickness. 
Soil was modeled as springs. Then the support conditions are taken as simply supported 
at its two ends.
Depending on the SPTN values of each soil type spring constants are calculated and 
tabulated below.
Depth (measured from the culvert 
top level) (in mm)
Spring Constants
2675 8,000
2140 16,000
Below 2140 24,000
5.4.1 Load Calculation
5.4.1.1 Dead Load Calculation
Dead load may be calculated from SAP2000 finite element software automatically.
5.4.I.2. Live load calculation
HA Loading
UDL shall be taken as 30kN per linear meter of notional lane. 
HA loading for the Top Slab 
HA loading for the Bottom Slab
30kN/m
30kN/m
34
Chapter 5 Analysis of Box Culvert, Results & Design
HB Loading
HB loading for the top slab 
HB loading for the bottom slab
30 units each 75kN
20 units each 50kN
<L
axleaxle axleaxle
'I I:1 1
«----T ** — IIit
I m
T it- - ihI m i +- - ---------- »
I m
•i — !J-i----- 4
1.8 m, 1.8 mt*—1— 6 m H
Figure 5.2 : HB Vehicle Wheel Arrangement
5.4.I.3. Super Imposed Dead Load
Assume 60mm surfacing
Compacted Density of Asphalt Concrete =
Loading from the surfacing =
2450kg/m3
2450x0.06x5.35x9.81
7.72 kN/m
35
Chapter 5 Analysis of Box Culvert, Results & Design
5.4.I.4. Reaction from Soil Calculation
Load Case 1.1
Total HA load in top slab 30 x 10.8 
324 kN—
Super imposed load top slab 7.72x10.8 
83.38 kN
Super imposed load bottom 
slab 7.72x10.8 
83.38 kN=
Volume of 
concrete {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2) 
103.148m3
Weight of concrete 103.148x24 
2475.55 kN
Total downward 
load 324 + 83.38 + 83.38 + 2475.55 
2966.31 kN
=
=
274.66 kN/mReaction from soil
Load Case 1.2
30x10.8 
324 kN
Total HA load in top slab
—
75 x 4 x4 
1200 kN
Total HB load in top slab =
=
7.72x10.8 
83.38 kN
Super imposed load top slab
=
Super imposed load bottom 
slab 7.72x10.8 
83.38 kN=
Volume of 
concrete {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2) 
103.148m3
=
=
103.148x24 
2475.55 kN
Weight of concrete
Total downward 
load 324 + 1200 + 83.38 + 83.38 + 2475.55a
36
Chapter 5 Analysis of Box Culvert, Results & Design
= 4166.31 kN
Reaction from soil 385.77 kN/m
Load Case 2.1
Super imposed load top slab = 7.72x10.8 
= 83.38 kN
Super imposed load bottom 
slab = 7.72x10.8
= 83.38 kN
Volume of 
concrete = {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2)
= 103.148m3
Weight of concrete = 103.148x24
= 2475.55 kN
Total downward 
load = 83.38 + 83.38 + 2475.55
= 2642.31 kN
244.66 kN/mReaction from soil
Load Case 3.1
= 30x10.8
= 324 kN
Total HA load in bottom slab
= 7.72x10.8
= 83.38 kN
Super imposed load top slab
Super imposed load bottom 
slab = 7.72x10.8
= 83.38 kN
Volume of 
concrete = {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2)
= 103.148m3
= 103.148x24
= 2475.55 kN
Weight of concrete
Total downward 
load = 324 + 83.38 + 83.38 + 2475.55
= 2966.31 kN
274.66 kN/mReaction from soil
37
Chapter 5 Analysis of Box Culvert, Results & Design
Load Case 3.2
Total HA load in bottom slab = 30x10.8
= 324 kN
Total HB load in bottom slab = 50 x 4 x 4
= 1200 kN
Super imposed load top slab = 7.72x10.8
= 83.38 kN
Super imposed load bottom 
slab = 7.72x10.8
= 83.38 kN
Volume of 
concrete = {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2)
= 103.148m3
Weight of concrete = 103.148x24
= 2475.55 kN
Total downward 
load = 324 + 1200 + 83.38 + 83.38 + 2475.55
= 3766.31 kN
348.73 kN/mReaction from soil
Load Case 4.1
Total HA load in top & bottom
= 30x10.8x2
= 648 kN
slab
= 7.72x10.8
= 83.38 kN
Super imposed load top slab
Super imposed load bottom 
slab = 7.72x10.8
= 83.38 kN
Volume of 
concrete = {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2)
= 103.148m3
= 103.148x24
= 2475.55 kN
Weight of concrete
Total downward 
load = 648 + 83.38 + 83.38 + 2475.55
= 3290.30 kN
304.66 kN/mzzReaction from soil
rj>'
38
Chapter 5 Analysis of Box Culvert, Results & Design
Load Case 4.2
Total HA load in top & bottom
slab 30 x 10.8x2 
648 kN
=
—
Total HB load in bottom slab 50 x 4 x 4 
1200 kN
Super imposed load top slab 7.72 x 10.8 
83.38 kN
=
=
Super imposed load bottom 
slab 7.72x10.8 
83.38 kN
Volume of 
concrete {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2) 
103.148m3
103.148x24 
2475.55 kN
Weight of concrete =
Total downward 
load 648 + 1200 + 83.38 + 83.38 + 2475.55 
4090.30 kN
378.73 kN/mReaction from soil
Load Case 4.3
Total HA load in top & bottom
30 x 10.8x2 
648 kN
slab =
=
75 x 4 x 4 
1200 kN
Total HB load in top slab
=
50 x 4 x 4 
800 kN
Total HB load in bottom slab =
=
7.72 x 10.8 
83.38 kN
Super imposed load top slab =:
Super imposed load bottom 
slab 7.72 x 10.8 
83.38 kN
=
Volume of 
concrete {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2) 
103.148m3
=
S
39
Chapter 5 Analysis of Box Culvert, Results & Design
Weight of concrete = 103.148x24
= 2475.55 kN
Total downward 
load = 648 + 1200 + 800 + 83.38 + 83.38 + 2475.55
= 5290.33 kN
Reaction from soil 489.85 kN/m
Load Case 4.4
Total HA load in top & bottom
slab 30 x 10.8x2 
648 kN
Total HB load in top slab 75 x 4 x4 
1200 kN=
Super imposed load top slab 7.72x10.8 
83.38 kN
=
=
Super imposed load bottom 
slab 7.72 x 10.8 
83.38 kN
=
=
Volume of 
concrete {10.8 x ( 0.75 + 0.60 ) x 5.35} + 9 4.7 x 0.5 x 5.35 x 2) 
103.148m3
=
=
103.148x24 
2475.55 kN
Weight of concrete =
Total downward 
load 648 + 1200 + 83.38 + 83.38 + 2475.55 
4490.30 kN
415.77 kN/mReaction from soil =:
40
Chapter 5 Analysis of Box Culvert, Results & Design
5.4.1.5 Lateral earth pressure calculation
Take Surcharge as 10kN/m2
Take Unclassified Soil
18 kN/m3 
30 dgrees
Y
<P
Consider at Rest condition 
(1 - Sin cp )ko
0.5
Over-burden at top = 10kN/m2
10 + 0.5 x 18 x
Over-burden at 5350mm depth = 10 + koyH = 5.35
58.15 kN/m2~
Pressure Distribution
10.0 kN/m2
5.35m
58.15 kN/m2
:
41
:
Chapter 5 Analysis of Box Culvert, Results & Design
5.4.I.6. Traction force
BS5400 Part 2 Section 6.6 states that
For HA loading:
Traction force = 8 x 10.8 +200 (but minimum 700kN) 
Traction force from HA vehicle = 286.4 kN
For HB loading
Traction force for 30units of HB vehicle = 75 x 25% x 8
= 150 kN
Traction force for 20units of HB vehicle = 50 x 25% x 8 
= 100 kN
From the above calculations Traction force for HA vehicle > HB vehicle
Apply traction force of 286.4kN from HA vehicle at the center of the notional lane.
5.4.I.7. Hydrostatic Pressure
Take the high flood level at the selected culvert area as 4.28m
Hydrostatic pressure = hpg = 4.28 x 1000 x 10 / 1000 
= 42.8 kN/m2
= 42.8 x5.35x0.5x42.8/42.8 
= 114.49 kN/m
Equivalent UDL
42
Analysis of Box Culvert, Results & DesignChapter 5
5.5 Concrete Outline Drawing of Box Culvert
RFL LINE
5000 :
L • < . • i4-V.4. •
V25C -a
J50mm IHK.
approach slab CORBEL
50mm THKTbIJNDING CONCRETE g
8
------- CONCRETE GRADE 30/20< s
4
500 |
>00
m. <T 4 4<7 . ^ !C03*-------4
| LSCREED CONCRETE 15^C>
____________________ 10500
Figure 5.3 : Concrete Outline of Box Culvert
5.6. SAP2000 model of the Box Culvert
fy<- -Vc o-s 'Vs yVV-
*-L Ss ^ ~
*
‘ifs
Figure 5.4 : Model of Box Culvert
43
Analysis of Box Culvert, Results & DesignChapter 5
5.7 Load Combinations
HA Only
Dead Weight 
Earth Pressure 
Superimposed Dead 
Live Load
= 1.15
= 1.5
= 1.75
= 1.5
HA and HB
Dead Weight 
Earth Pressure 
Superimposed Dead 
Live Load
= 1.15
= 1.5
= 1.75
= 1.3
5.8 Deformed Shape for Load Case 4.3
ggg||§§
•n
i.-1"
- mmhA, ^\7\^ \*\ft®
l1?; ^ * f-4
f r 7 * 
r~hrri—s~
j;—j~ y—f—
y-hf-f-j 
-4—4- i-~i *- 1 -
4 ' * 1 j ; - - 
v ■* # ^ +ib * • > 1 1 1 1—i - > -a- » ' >- >' * '> >i > * *i —i- >
* -i i -r—T V *T
, \ ' ■ ^ s*>
5 , * dp
v -*r \-4^
i i i i 3 «^
s'-
: ' 1 1 
> 1 "if' -V 3’ 1
* i i i I 1
:
3
Figure 5.5 : Deformed shape of Mode 1
44
Kv->»
Chapter 5 Analysis of Box Culvert, Results & Design
: - '©©V
awaM
«!*.' \ >/, . 1 V. SM I
A™
\ 9\t i i \ v,\\ * * -. v.
., ^ V r J 7 _.•* I* ? f f f ? 5 } * 4 4 3 1 i,
^7 hV' ■Ml/'.^r 7 > , 7s 7 - f f -s~ t ? 4—1—a—7—i—i—r—43. w*
r f ri'f f'rtrl 17 \ \ \"\
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5.9 Results from the SAP2000 Modeling
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45
Chapter 5 Analysis of Box Culvert, Results & Design
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-• 46
Chapter 6 Cost Analysis
Chapter 6
6.0 COST ANALYSIS
6.1 Introduction
One of the main objectives of this project is to evaluate the cost effectiveness of metal 
structure when compared with box culvert, to select most appropriate structure type for a 
site under consideration. This chapter provides guidelines for the establishment of basic 
cost to compare the alternatives.
The basic cost used here is taken form currently used for estimating process at Road 
Development Authority.
6.2 Cost Estimating Process
The process stated below is developed for estimating the underpass cost after the 
completion of the preliminary design. Cost for all other items including but not limited to 
the following are excluded from the cost provided in this chapter.
6.3 Cost Analysis of Metal Structure
The basic structural items of the HPA74N metal structure was found to be as follows.
47
Chapter 6 Cost Analysis
Bill of Material for HPA74N Metal Structure
Total
Nos.
Item Width Length Total
Quantity
Description Units Height (m)No. (m) (m)
HPA74N Metal 
Plates Nos.1 119 119
Bolts (3/4” x 3”) Nos.2 5219 5219
Unclassified m33 1 14.58 20.13 2231.07.6Excavation
Structural Backfill 
for Metal Structure
1 10.58 20.13 128.000.6m34 1 3.00 20.13 266.04.4
2 1.0 20.13 18.120.45
m3Foundation5 2 (0.45+0.3)72 3.020.2 20.13
2 0.6 20.13 7.250.3
Cost Calculation
The basic cost presently used in Road Development Authority was used.
Cost of Concrete
1. Grade 30 concrete per m3 with placing
2. Reinforcing Steel (100kg per m3)
Rs. 13,000.00 
Rs. 15,000.00
Concrete cost with r/f per m3 Rs. 28,000.00
Quantity AmountRate (Rs.) 
291,500.00
UnitItem
34,688,500.00119Nos.HPA74N Metal Plates
78,285.00521915.00Nos.Bolts (3/4” x 3”)
1,189,123.002231.0m1 533.00Unclassified Excavation
3,286,992.28Structural Backfill for Metal 
Structure _____
3m 394.08342.62
794,920.0028.39TTTm 28,000.00Foundation
40,037,820.28Total Cost
48
Chapter 6 Cost Analysis
6.4. Cost Analysis of Box Culvert
The basic structural items of the reinforced concrete box underpass at 09+373 were found 
to be as follows.
Bill of Material for Reinforced Concrete Box Underpass
Cross
Sectional
Area
Item Width Length Total
QuantityDescription Units Height (m)No. (m) (m)
(m2)
Grade 30 
Structural 
Concrete
3m1 437.119
Reinforcement Tones 32.3652
Unclassified
Excavation
3m 14.30 20.13 7.0 2015.02 1
20.13 6.05
m2 440.85Formwork 20.13 6.053
20.13 9.8
Cost Calculation
QuantityRate (Rs.) AmountUnitItem
T“Tm 5,682,547.00437.11913,000.00Grade 30 Structural Concrete
32.365 4,854,750.00150,000.00TonnesReinforcement
TTTm 2015.0 1,073,995.00533.00Unclassified Excavation
2 440.85 896,334.532033.21Formwork m
12,507,632.63Total Cost
Note that the above calculated cost is very basic cost not in the actual cost involving the 
construction of metal underpasses and box culvert. For the above cost calculation the cost 
of construction of wing wall, mobilization,
49
Chapter 6 Cost Analysis
6.5 Cost Saving
According to the above basic cost calculation the average cost saving for the structural 
part as follows.
Cost saving Rs. 40,037,820.28- 12,507,632.63 
Rs. 27,530,187.65
Rs. 27,530,187.65 / 40,037,820.28x 100% 
68.7%
% of cost saving
50
Chapter 7 Conclusions & Recommendations
Chapter 7
7.0 CONCLUSIONS AND RECOMMENDATION
According to the cost calculation it is shown that the 74% of cost saving is there by using 
box underpass.
By using box underpass instead of metal underpass Sri Lanka can save billions of money 
from Southern Transport Development Project.
Another useful source of information is the durability of metal underpasses. Sacrificial 
cathodic protection is the effective method of protecting the metallic shell against 
corrosion. In this protective system the steel plate is connected through an electrical 
conductor to a sacrificial zinc or aluminium, plate which acts as anode and corrodes, 
there by preventing the steel plate from corrosion.
51
References
REFERENCES
1. Soil - Steel Bridges, Design and Construction, George Abdel-Sayed, Baidar Bakht, 
Leslie G. Jaeger.
2. BS 5400 Part 2 : 1978, Steel ,Concrete and Composite Bridges, Specification for 
Loads , BSI, London, U.K.
3. BS 5400 Part 4 : 1978, Steel ,Concrete and Composite Bridges, Code of Practice for 
design of concrete bridges , BSI, London, U.K.
4. Armco, Staco, Multi - Plate Super- Span Technical Manual, Access International 
(Pvt) Ltd., Sri Lanka
5. Installation and Backfilling Standards for Armco Structures, Armco Surperlite (Pty) 
Ltd.
6. Handbook of Steel Drainage & Highway Construction Products, American Iron & 
Steel Institute.
7. ASTM Designation A 761/A 761M-98 - Corrugated Steel Structural Plate , Zinc - 
Coated, for field - Bolted Pipe, Pipe - Arches and Arches.
8. ASTM Designation A 796/A 796M-01 - Standard Practice for Structural Design of 
Corrugated Steel Pipe, Pipe Arches and Arches for Storm and Sanitary Sewers and 
other Buried Applications.
9. Standard Specifications for Highway Bridges (AASHTO) - Section 12.
10. User Manual, SAP2000 Nonlinear V8.23, The static and dynamic finite analysis of 
structures Inc, 1995 Berkeley, Califonia, USA.
11. Foundation Analysis and Design, Joseph E. Bowles
52
APPENDIX -A
53
CalculationReference Output
DESIGN OF DECK SLAB (TOP SLAB)
Bending moment is critiacl in Load case 4.1. So that consider the loading case 4.1 
for reinforcement design.
Design main reinforcement for mid span of the slab.
Thickness of the slab = 600 mm
Part 4: 1990 
4.2.3 M = 541 kNm/rrDesign bending moment, M design at mid span 541 kNm/m
Assume severe environment condition, 
Cover Cover= 65 mm
= 65 mm
Diametre of main reinforcement = 32 mm
Effective depth, d = 600-65-32/2 d = 519 mm= 519 mm
M = (0.87fy)Asz 
z = (1 -i.lfyAs/fcubdJd
BS 5400 
Part 4: 1990
equation 1 
equation 5 from these two equations
5.3.2.3
z = 0.5d[1+(1-5M/fcubd2)1/2] 
z = 0.5d [1+ (1 -5x541x1 06/30x1 000x5232)1/2 ] 
= 0.908 d < b d
Hence o.k
Z = 0.908 d 
= 0.908x519 = 471 mm
Main reinforcement
As = M / 0.87fyZ
= 541x106 7 0.87x460x471
equation 1
mm2/m As req= 2868 ==
2868 mm2/m
mm2 ) As pro
2925 mm2/m
Use T 32 @ 275 (As = 2925 =
Check for minimum reinforcement required for cantilever slab 
Check for minimum reinforcement
100AS / bad = 100x2925/(1000x519)
BS 5400 
Part 4: 1990 
5.8.4.1
= 0.56 >0.15 Main reinforcement
T 32 @ 275
Hence o.k
fb) DESIGN OF SECONDARY REINFORCEMENT (TOP SLAB)
Requirement for secondary reinforcementBS 5400 
Part 4: 1990 
5.8.4.2 mm2/m(0.12/100)b,d = (0.12/100)x1000x519 = 623
Secondary
reinforcement
T 12 @ 175
mm2 )(As = 64612 @ 175Use T
Calculation OutputReference
Serviceasibility Crack check
At center of bottom slab maximum service moment 450.5 kNm=
's
d= 519 mm 81mrr¥■ /600mm
7
-aep + Njnep(2+aep)x —
d
Es = 14.2857aep =
Ec
As 2925 0.005P = ~
103 x 519bd
aep = 14.286 x 0.005 
= 0.07143
0.31x— —
d
162.56 mmx =
11 xz---- =
d3d
464.81 mmz =
Service stress, fs = M
A,xZ
450.5x106fs =
2925x464.81 
= 331.406 N/mm2
= fses = 331.406 = 0.0017
200x103 
= fh-x 1 x Gs
Es
e1
d - x
x 0.0017600 - 162.564
523 - 162.564
0.002=
■
em = ei ' b(h-x)2
3EsA,(d-x)
= 0.0020336 - 1000 *(600- 162.564 )2
3 x 200 X1000 x 2925 (519 -162.56)
:
!
0.002
OutputCalculationReference
Calculation of aa
Cmin — 81 mm
-163cr = V 975+1002 
= 123.32 mm
3aCP 8mWa =
I + 2[(acr -cm,n)/(h-x)]
Wcr = 3 x I 23.32x 0.002
+ 2[( I 23.32-61 )/(G00-1 62.56)] 
0.19 mm < 0.2mm=
lienee Satisfactory. 0.I9w
<0.2mm 
hence satisfactory
DESIGN MAIN REINFORCEMENT FOR HOGGING MOMENT (TOP SLAB)
Thickness of the slab = 600 mm
BS5400 
Part 4: 1990
M = 586 kNm/nrDesign bending moment, M design at mid span 586 kNm/m4.2.3
Assume severe environment condition, 
Cover Cover65 mm
65 mm
Diametre of main reinforcement = 20 mm
= 525 d = 525 mm= 600-65-20/2Effective depth, d mm
M = (0.87fy)Asz 
z = (1 - l.lfyAs/fcubdJd
equation 1 
equation 5
BS 5400 
Part 4: 1990 from these two equations
5.3.2.3
z = 0.5d[1+(1-5M/fcubd2)1/2l 
z = 0.5d [1+ (1-5x586x106/30x1000x5252)1/2 ] 
= 0.90 d < 0.950 d
Hence o.k
Z = 0.90 d 
= 0.900x525 = 473 mm
Main reinforcement
Ag = M / 0.87fyZ
= 586x10® / 0.87x460x473
equation 1
mm2/m As= 3093 sreq
3093 mm2/m
mm2 ) Agpro(As = 314220 @ 100Use T
3142 mm2/m
Check for minimum reinforcement required for cantilever slab 
Check for minimum reinforcement
100AS / bad = 100x3142/(1000x525)
BS 5400 
Part 4:1990 
5.8.4.1
Main reinforcement= 0.598 > 0.15
20 @ 100T
Hence o.k
OutputCalculationReference
Serviceability Crack Check
466.35 kNmAt corners maximum service moment S3
From the above
0.071
162.56 mm 
464.81 mm
aep = 
x =
z
6= 488.35 x 10
3142x464.81 
= 334.386 N/mm2
fs
= fses = 334.386 = 0.0017
200x103 
= f h-x 1 x es
Es
d - x
162.56 x 0.0017600=
525 162.56
0.002
= ei - b(h-x)2
3EsAs(d-x)
1000 *(600- 162,56 )20.002—
3 x 200 X1000 x 3142 (525 -162.56)
0.0017
Calculation of aCT
^min “ 75 mm
aCr = v 752+50.02
80.14 mm
-10
^cr SmWcr =
I + 2[(aCP -cmin)/(h-x)]
= 3x60.1 4x0.001 7Wcr
I +2[(60.14-75)/(G00-1 G2.5G] 
0.19 mm < 0.2mm=
0.1 9w =
<0.2mm 
hence satisfactory
Hence Satisfactory.
0.18% each face , each wayMinimum Steel
1080 mm2/m0.18 x 103 x 600Area ==
100
(1149 mm2/m)Use Y16 @ 175mm centers
Calculation OutputReference
DESIGN FOR SHEAR
Design shear force, V design = 1257 kN/m
= 525Effective depth, d mm
= V/bd
= (1257x103)/(1000x525) 
= 2.39 N/mm2 
= 0.75x(30)1/2 
= 2.39 < 0.75x(fcu)1/2
Design shear stress, vBS 5400: 
Part 4: 1990 
5.3.3.1 
equation 8
v
= 4.108 N/mm2 
or 4.75 N/mm2
0.75X(fcu)1/2 
Design shear stress, v
2.39 N/mm2
Hence O.K
For uniaxial shear 
Allow, shear resistance 
£svc
Where, depth ratio,
= (0.27/ym)(100As/bwd)1,3(fcu)l,3^sBS 5400:
Part 4: 1990 
5.3.3.2 = (500/d)1/4 
= (500/525)1'4
= 0.99 or 0.7 (greater value)
= (0.27/0.99)x(100x3142/1000x525)v3x(30)1/3x1.25£svc
= 0.89 < v = 2.39 N/mm2
Hence shear r/f is required
DESIGN OF wall
Consider load case 4.3 for design the wall of the culvert.
Design main reinforcement for mid span of the slab.
= 500Thickness of the slab mm
Part 4: 1990
M = 1148 kNm/rr1148 kNm/mDesign bending moment, M design at mid span4.2.3
Assume severe environment condition, 
Cover Cover= 45 mm
= 45 mm
= 32Diametre of main reinforcement mm
= 439 d - 439 mm= 500-45-32/2Effective depth, d mm
1 x'NM = (0.87fy)Asz 
z = (1 ■1.1fyA#/fcubd)d
equation 1 
equation 5
BS 5400 
Part 4: 1990 4 Xfrom these two equations5.3.2.3 ' ftz = 0.5d[1+(1-5NI/fcubd2)1/2]
z = 0.5d [1+ (1-5x1148x10e/30x1000x4392)1/2 ]
= 0.543 d < b d
Hence o.k
Z = 0.543 d 
= 0.543x439 = 238 mm
OutputCalculationReference
Main reinforcement
Ag = M / 0.87fyz
= 1148x10® 7 0.87x460x238
equation 1
mm2/m As= 12032 req
mm2/m12032
(As = 16085 mm2 ) AsUse T 32 @ 50 pro
mm2/m16085
\S\ 16/17
\ W'V-'