Feasibility Study and Detailed Design of Kandy
Suburban Railway Project (KSRP)
Comprehensive Structural Appraisal of the 20m Span
Simple Railway Bridge Comprising Precast-
Prestressed Beam and Slab Deck and Abutments
with Spread Footing Proposed at 107.17km of
Kadugannawa – Peradeniya Section.
21-09-2023
Contents
Chapters Page Numbers
1. Introduction
2. Specific Design Standards & References
3. Design Basis & Basic Design Data
4. Superstructure & Substructure Selection
5. Design Method
6. Girder Properties
7. Composite Action
8. Wind Load
9. Temperature Effects (Restraints / Stresses)
10. Shrinkage Effects (Restraints / Stresses)
11. Loading Calculation
12. Superstructure Arrangement
13. Deck Parameters
14. Deck Analysis (Live Load Distribution)
15. Girders Weightage Ratio
16. Structural Appraisal of Girders (Beams)
17. Prestress Tendons
18. Detailed Girder Design
19. Slab Design
20. Derailment Check
21. End Diaphragm-Beam
22. Bearings
23. Expansion Joint
24. Substructure Design (Abutments)
25. Fatigue Issues
26. Summary
27. General Arrangement Sketches
1. Introduction
1.Introduction
This report is a part of the KSRP- BRIDGE assessments and proposals schedule. This
part assesses a proposed 20m span bridge, carrying dual track, comprising nine UK
(Europe) standard size precast prestressed-beam, that is locally producible, with in-situ
slab, structurally acting compositely.
The proposed structural system is a well-established form with a proven record of
versatile structural performances locally and internationally. This proposed
superstructure comprises Y8 model prestressed girders with 250 mm thick in-situ
concrete slabs designed and constructed to act compositely in service.
The structural assessment complies with the recommendations of BS 5400 and other
relevant codes of practice.
Background
The proposed structural form falls in the category of a well-established type of structural
arrangement with standard application and subjected to normal conditions where a
currently serving bridge structure has been more than 100 years. Thus, carrying out
every step of design calculations for trivial components is only a little use for the project.
Making critical checks to establish required parameters will be, for practical purposes,
sufficient to make an adequate bridge structure for the intended use.
Two previous comprehensive feasibility studies of a similar nature were carried out in Sri
Lanka: 1) the Outer Circular Highway to the City of Colombo (OCH) by the JICA study
team and 2) the Proposed Colombo Suburban Railway Project (CSRP) by the DOHWA
Engineering Co. Ltd made recommendations for similar PSC girder structural schemes,
pointing out that it’s merit on reliability, economy, maintenance, and constructability.
The workforce and technology required have been locally available for decades with a
sound record for its’ production quality and speed. These can produce these PSC girders
at the site relatively easier than post-tension products which require more expertise in
tensioning and grouting works.
5. Design Method
An orthotropic plate is one which has different stiffnesses in two directions. Thus, a beam
and slab deck, when analyzed by means of plate analogy, is also orthotropic. It is
emphasized that bridge decks are generally orthotropic due to geometric rather than
material differences in two orthogonal directions.
(1) Forces in a Plate Element
(2) Idealized Deck Action
If a plate element subjected to an intensity of loading of p is considered in rectangular
co-ordinates x and y which coincide with the directions of principal orthotropy, then the
bending moments per unit length (Mx & My), twisting moments per unit length (Mxy & Myx),
and shear forces per unit length (V x & Vy) which act on the element are shown in the
figure (1) above. And Figure (2) shows an idealized action of the deck modelled as
orthotropic plate.
The series solution for bridge decks was originally due to Guyon and Massonnet, and
then developed by Morice and Little who, together with Rowe, produced design charts
which enable the calculations carried out by hand.
In this bridge assessment, Morice-Little method was used to analyze the proposed deck.
Since this nature of simplified methods will not only shorten time spent on analysis, but
will also permit the designer to retain a “feel” of behaviour of the bridge which is usually
lost in some other method of analyses. The results from the proposed method do not
deviate significantly from those obtained by other analysis methods including computer
aided ones. These kind of simplified methods for bridge design have been allowed to use
for many years by various North American bridge design codes.
(3) Structural Behaviour of the Beam-Slab Deck
16. STRUCTURAL APPRAISAL OF THE GIRDERS
DESIGN MOMENT (ULS & SLS)
(Without Prestressing)
Load Component Nomina SLS ULS
Case l
Moment
(KNm)
Comb - 1 Comb-3 Comb-1
ϒfl Factored ϒfl Factored ϒfl x ϒf3 Factored
Moment Moment Moment
Dead PSC 830 1.0 830 1.0 830 1.2 x 1.1 1096
Load beam
Slab 443 1.0 443 1.0 443 1.2 x 1.1 585
SDL SDL 954 1.2 1145 1.2 1145 1.75 x 1836
1.1
Live RU 1.1 3176 1.0 2887 1.4 x1.1 4042
Load
DESIGN STRESS (SLS)
(Without Prestressing)
Component Comb – 1 – SLS Comb – 3 - SLS(N/mm2)
(N/mm2)
Section Load Case σtslab σtbeam σbbeam σtslab σtbeam σbbeam
PSC PSC beam 0 5.32 -4.46 0 5.32 -4.46
beam Slab 0 2.84 -2.40 0 2.84 -2.40
Composite SDL 2.81 1.98 -4.1 2.81 1.98 -4.1
Section RU 7.8 5.49 -11.3 7.1 5.0 -10.3
Positive 3.2 (-0.9)1 (1.47)1
Temperature
Reverse (-1.93)1 0.9 -2.07
Temperature
Shrinkage -0.5 1.27 -0.55 (-0.5)1 1.27 -0.55
Total 10.11 16.9 22.81 13.11 17.31 -23.9
2
Limiting N/mm <16 <20 >0 <16 <20 >0
Stress 0.4 fcu 0.4 fcu 0.4 fcu 0.4 fcu
1 Relieving Effects
17. PRESTRESS TENDONS
FIRST APPROXIMATE ESTIMATION OF PRESTRESSING FORCE
Tensile Stress at bottom of the beam = 23.9 N/mm2
Assume a total Prestress loss of 30% from the initial stress.
Take tendons initial stress is 75% of the characteristic strength = P = 0.75 x Po
Drawn Strand diameter = 15.2 mm (BS 5896, 165 mm2, fpu = 1820 N/mm2)
Initial Force = 0.75 x 165 x 1820 / 1000 = 225 KN (preferrable)
Take eccentricity, ea = 380 mm
Required initial force = 8515 KN
Required No. of Strands =8515 /225 = 38 Nos x φ 15.2 mm
STANDARD PRESTRESSING STRANDS IN COMPLIANCE WITH BS 5896
9. TEMPERATURE EFFECTS (RESTRAINTS / STRESSES)
2. SPEFIC DESIGN STANDARDS AND REFERENCES
1. BS 5400-2: 2006 Steel, concrete and composite bridges- Specification for loads
2. BS 5400-4: 1990 Steel, concrete and composite bridges- Code of practice for design of
concrete bridges
3. ICE Manual of bridge engineering, 2nd Edition
4. E.C. Hambly, Bridge Deck Behaviour, 2nd Edition
5. Derrick Beckett., An Introduction to structural design, (1) Concrete Bridges
6. M.K. Hurst., Prestressed Concrete Design
7. B.A. Nicholson., Simple Bridge Design using Prestressed Beams
8.L.A. Clark., Concrete Bridge Design to BS 5400
9.D C ILES., Design Guide for Steel Railway Bridges
10. The AASHTO-LRFD Bridge Design Specifications
11. RDA Bridge design manual
8. WIND LOAD
Since the bridge is concrete structure located at the normal height above the ground and the
span is around 20 m and width are more than 10m, wind load can’t be the governing factor in
the design of this superstructure.
Further, this proposed substructure has spread foundation at normal height.
6. GIRDER (PSC BEAM) PROPERTIES
7. COMPOSITE ACTION
(COMPOSITE SECTION PROPERTIES)
10. SHRINKAGE EFFECTS (RESTRAINTS AND STRESSES)
(DIFFERENTIAL SHRINKAGE EFFECTS)
18. DETAILED GIRDER DESIGN
22. BEARINGS
(FLOATING DECK MODEL)
Load Rating (SLS) (KN) (per Bearing)
Load Dead Super Primary Longitudinal Transverse
Case Load Dead Live Load Load(a) Load(a)
Load (RU)
Load 240 213 545
Total 1000 25 10
a
Loads shall be considered with vertical loads
23. EXPANSION JOINTS
Expected Effective bridge temperature different = 10 deg. C
Thermal expansion coefficient = 12 x 10^-6 / C
Bridge length = 20 m
Expected Total Movement = 2.5 mm
ULTIMATE SHEAR RESISTANCE
LONGITUDINAL SHEAR
14. DECK ANALYSIS
SUBSTRUCTURE SELECTION (ABUTMENT)
RETAINING WALL TYPE – FREE CANTILEVER MODEL WITH VERTICAL LOAD
GROUND CONDITION IS SUITABLE FOR SPREAD FOOTING
SPT VALUE EXCEEDS 50 (SPT N > 50)
DESIGN ALLOWABLE BEARING PRESSURE = 350 KN / m 2
(Reference – Annexed Site (Soil) Investigation Report – SPT Data)
ESTIMATION OF ALLOWABLE BEARING CAPACITY OF SOIL FOUNDATION
19. SLAB DESIGN
20.DERAILMENT CHECK
(ACCIDENT LOADING)
21. END DIAPHRAGAM BEAM
24. SUBSTRUCTURES (ABUTMENTS)
25. FATIGUES ISSUES
26. SUMMARY
No Item / Requirement Remarks
Component
CONCRETE GRADE 60 N/mm2
(60)
1 TRANSFER STATE 60 N/mm2
PSC BEAM STRENGTH
(Y 8) (60)
47 Nos of 15mm dia.
9 Numbers Strands at mid 1820 N/mm2
19 Nos at End
CRANE PLACEMENT
2 SLAB CONCRETE 50 50 N/mm2
250 mm THICK Min Cover 40 mm
(Cast in-situ)
FORMWORK PERMANENT 20 – 30 mm
3 15 mm diameter
1820 N/mm2
STRANDS Initial Tension Per each strand
(47 Numbers per 225 KN
beam) PRESTRESS LOSS 13 %
AT TRANSFER
FINAL PRESTRESS 36.8%
LOSS AT SERVICE
4 ABUTMENTS CONCRETE 30 N/mm2
(Retaining wall type –
free cantilever model)
BACKFILLING PRIOR TO DECK PLACEMENT
Required Foundation
Bearing Capacity 350 KN / m2
5 BRIDEGE 18 Nos Elastomeric
BEARINGS (FLOATING DECK FUNCTION)
6 Expansion Joint Cover Plate Type
7 CONSTRUCTION CIDA (FORMER ICTAD) SPECIFICATION
SPECIFICATION FOR BRIDGES U/O/S
8 Design and Detailing BRISTISH STANDARDS / EUROPEAN
STANDARDS
EXPANSION JOINT TERMINATION DETAILS
PROPOSAL OF BRIDGE PARAPET MODEL
BRIDGE PARAPET OPTIONS
EXPANSION JOINT TERMINATION DETAILS
27. GENERAL ARRANGEMENT SKETCHES
AND KEY DETAILS
