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Ministry of Public Works

Roads Administration

PART 2Kuwait Bridges & Highway Structures Design Manual

Edition 2

January 2011

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Kuwait Bridges and Highway Structures Design Manual Table of Contents

Part 2 Kuwait Bridges and Highway Structures Design Manual

Page i

TABLE OF CONTENTS

1 INTRODUCTION ................................................................................................................... 1-1

1.1 General ....................................................................................................................... 1-1

1.2 Additional References .................................................................................................... 1-1

2 GENERAL FEATURES OF DESIGN ......................................................................................... 2-1

2.1 Design Life .................................................................................................................. 2-1

2.2 Vertical Clearance ......................................................................................................... 2-1

2.3 Approach Slabs ............................................................................................................ 2-1

2.4 Deck Drainage ............................................................................................................. 2-1

2.5 Architectural Consideration ............................................................................................ 2-2

2.6 Utility Requirements ...................................................................................................... 2-2

2.7 Maintenance Requirements ................................ .................................................. ........... 2-3

3 LOADS ............................................................................................................................... 3-1

3.1 Design Live Loading ...................................................................................................... 3-1

3.2 Dead Loads ................................................................................................................. 3-1

3.3 Wind Loads ................................................................................................................ 3-1

3.4 Thermal Forces ............................................................................................................ 3-1

3.5 Uplift .......................................................................................................................... 3-2

3.6 Seismic Loading ........................................................................................................... 3-2

3.7 Movement Rating ......................................................................................................... 3-2

3.8 Bearing Friction Forces .................................................................................................. 3-2

3.9 Differential Settlement .................................................................................................. 3-2

3.10 Floating Debris............................................................................................................. 3-23.11 Distribution of Loads ..................................................................................................... 3-3

3.12 Load Combinations....................................................................................................... 3-3

4. FOUNDATIONS ..................................................................................................................... 4-1

4.1 Design Method ............................................................................................................. 4-1

4.2 Superficial Soils ............................................................................................................ 4-1

4.3 Ground Water and Sulfates ............................................................................................ 4-1

5 RETAINING WALLS ............................................................................................................... 5-1

5.1 General....................................................................................................................... 5-1

5.2 Factors of Safety .......................................................................................................... 5-1

5.3 Expansion and Contraction Joints .................................................................................... 5-1

6 CULVERTS .......................................................................................................................... 6-1

7 SUBSTRUCTURE ................................................................................................................... 7-1

7.1 Live Load Surcharge ..................................................................................................... 7-1

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8 REINFORCED CONCRETE ......................................................................................................... 8-1

8.1 Concrete ............................................................................................................................... 8-1

8.2 Concrete Protection Against Aggressive Soils..................................................................... 8-1

8.3 Reinforcement ............................................................................................................. 8-1

8.4 Slab Design ................................................................................................................. 8-18.5 Slab Thickness ............................................................................................................. 8-2

8.6 Protection Against Corrosion .......................................................................................... 8-2

8.7 Minimum and Maximum Design Values ............................................................................ 8-2

8.8 Concrete Durability ....................................................................................................... 8-3

9 PRESTRESSED CONCRETE ....................................................................................................... 9-1

9.1 General ....................................................................................................................... 9-1

9.2 Allowable Stresses........................................................................................................ 9-1

9.3 Shear ......................................................................................................................... 9-1

9.4 Concrete ..................................................................................................................... 9-1

9.5 Precast Pre-tensioned I-beams ....................................................................................... 9-1

9.6 Prestressed Voided Slab ................................................................................................ 9-4

9.7 Prestressed Box Beams ................................................................................................. 9-5

10 STRUCTURAL STEEL ............................................................................................................ 10-1

10.1 Design Method ........................................................................................................... 10-1

10.2 Materials ................................................................................................................... 10-1

10.3 Detail Categories ........................................................................................................ 10-1

10.4 Charpy V-Notch Impact Requirement ............................................................................ 10-1

10.5 Stiffeners and Connections .......................................................................................... 10-1

11 EXPANSION AND CONTRACTION ............................................................................................ 11-1

11.1 Movement Criteria . .................................................................................................... 11-1

12 DECK JOINTS .................................................................................................................... 12-1

12.1 Movement Rating........................................................................................................ 12-1

12.2 Common Deck Joint Types ........................................................................................... 12-2

13 BEARINGS ........................................................................................................................ 13-1

13.1 Movement Criteria ...................................................................................................... 13-1

13.2 Types of Bearings Recommended .................................................................................. 13-1

13.3 Bearing Schedule........................................................................................................ 13-4

14 RESTRAINING DEVICES ....................................................................................................... 14-1

14.1 Vertical Fixed Restrainers ........... .................................................. ................................ 14-1

14.2 Vertical Expansion Restrainers ...................................................................................... 14-1

14.3 Shear Keys................................................................................................................ 14-1

14.4 Keyed Hinge .............................................................................................................. 14-1

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Page iii

15 SIGN SUPPORT STRUCTURES ................................................................................................ 15-1

16 PEDESTRIAN BRIDGES......................................................................................................... 16-1

16.1 Design Loads ............................................................................................................. 16-1

16.2 Design Details ............................................................................................................ 16-1

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Kuwait Bridges and Highway Structures Design Manual Chapter 2

Part 2 Kuwait Bridges and Highway Structures Design Manual General Features of Design

Page 2-1

2. GENERAL FEATURES OF DESIGN

The general features of design shall be as specified in Section 2 of AASHTO except as clarified or modified in

this manual.

2.1 DESIGN LIFE

The design life of structures shall not be less than 100 years.

2.2 VERTICAL CLEARANCE

The following are recommended design minimum vertical clearances for structures:

Structure Type Minimum Clearance (m) Posted Clearance (m)

Highway Traffic Structures passing

over Motorways, Expressways, Rural

and Urban Arterial)

5.5 minimum*

6.0 preferred*

over the entire roadway width

5.2

Pedestrian Overpasses 6.0 5.2

Tunnels 5.5 5.0

Sign Structures 6.0 -

* The preferred Vertical Clearance under highway bridges is 6.0m. However, in urban areas

where it is difficult to physically provide this clearance, 5.5m shall be the absolute minimum

Other structures may be identified by Ministry of Public Works for special clearance requirement.

The vertical clearance above water streams and wadis shall be as follows. The minimum vertical clearance

for the bridge deck soffit above the flood level corresponding to 100-year return period (freeboard) is

recommended to be 1 m minimum. In addition, the minimum vertical clearance between the highest ground

level and the deck soffit is recommended to be not less than 3 m regardless of the flood level. This latter

limit is set for inspection and maintenance purposes.

2.3 APPROACH SLABS

Concrete approach slabs shall be used on all structures. Approach slabs serve a dual purpose of providing a

transition structure from the bridge to the approach roadway should the roadway embankment settle and of

eliminating the live load surcharge of the abutment back wall when the conditions specified in AASHTO

LRFD 3.11.6.5 are satisfied. Approach slabs are to be designed to the Service Limit State in accordance with

AASHTO LRFD 5.5.2, with a crack width not exceeding 0.25 mm and shall cover the entire roadway width

including the shoulders, from wing wall to wing wall.

2.4 DECK DRAINAGE

On grade separation structures, roadway drains shall not discharge water into unprotected embankment

slopes or within 5m of the traveled roadway below, nor shall drains be located less than 1.5m from the

centerlines of abutments or piers. In urban areas collection of deck drainage in a pipe system may berequired, with down drains in or on pier columns discharging into storm drainage collector systems.

Consideration should always be given to provide collector drains and discharge systems on the approach

roadway gutter rather than on the bridge.

For bridges with sidewalks, expansion joints shall be turned up at the curb line to prevent roadway water

from entering sidewalk areas. Appropriate means shall be taken to ensure that sidewalk drainage does not

pond and that the water does not escape around the wing walls and erode the embankment.

It is generally recommended practice to place a gully upstream of expansion joints so as to prevent the flow

of water over the expansion joints.

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Page 2-2

2.5 ARCHITECTURAL CONSIDERATION

Bridges and other highway structures last for a long life span and are seen by observers on a daily basis.

They should be esthetically pleasing. Attention should be paid to the architectural design along the following

principles:

Bridges and other highway structures should complement their surroundings, be graceful in form andpresent the appearance of adequate strength.

Form should follow the flow of forces. Extraordinary and non-structural embellishments should be

avoided.

The bridge should be seen as a whole, with all members consistent and contributing to that whole; the

bridge as an entity, should have a clear and logical relationship to its surroundings.

Structures should be transparent: components should be slender and widely spaced preserving views

through the structure.

Transparency should, however, be balanced with strength to give a feeling of safety, that the structures

are well anchored in the ground. Observers should not feel alarmed or alerted when crossing on or under

the structure.

Architectural design of Kuwaiti highway structures should marry tradition and modernity via:

o Forms and lines should reflect Kuwaiti characteristics throughout the ages, including the current,

cultural heritage, lifestyle, activities,o Design should also be indicative of the age of its construction.

Each structure should have individuality. However, structures in the same project or along the same

corridor should possess continuity in forms and features. There should be a combination of unified and

unique features. Unified features reflect continuity while distinctive features are meant to avoid monotony

and give a sense of placement. The proper balance rests with the architectural designer with due

consideration of placement and conditions at each particular location.

Components should be shaped to respond to the structural function. They should be thick where the

stresses are greatest and thin where the stresses are smaller.

The function of each part and how the function is performed should be visible. The size of each member

compared with the others is clearly related to the overall structural concept and the job the component

does.

The designer should be aware of the difference between rural and urban settings. In a rural setting, the

structures can generally be seen from very far distances in a panoramic view. In an urban setting,structures can be seen from very close range, particularly if they are close to signal controlled junctions.

Accordingly, while the form and proportions are the main focus for rural structures, details and finishes

are at least equally important for an urban structure.

Designers are encouraged to endeavor in creative use of architectural finishes that suit the nature of the

project and its environment.

2.6 UTILITY REQUIREMENTS

Viaducts, overpasses, bridges over underpasses and animal crossings and other bridge decks shall be

equipped with provision for accommodating crossing of utilities on them.

Sidewalks and emergency walkways will house the electric and telephone cables. One side will be dedicated

for electric cables and the other for telephone cables. Electric cables include those that supply power to the

lighting posts on the bridge deck. These, however, will be on both sides if needed.If required, pipes for water, sewage, stormwater or other wet utility will be hanging below the deck slab.

The number and size of pipes will be as required for the particular location. In case of beam and slab

bridge, the pipes will be hanging from the slab between two beams such they are not seen in the bridge

elevation; they will be accessible from underneath. In case of box girder bridge, the pipes will pass inside

the box; they will be accessible from inside the box girder (see Sub-Section 2.7 below).

High voltage electric cables should be treated as a special case not covered in this typical detail. A vibration

study of the bridge under traffic load should be conducted and its effect on the cables evaluated.

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Page 2-3

2.7 MAINTENANCE REQUIREMENTS

All parts of the structures should be easily accessible for inspection particularly the following elements:

Steel bridge superstructure,

Concrete Bridge Superstructure

Bearings, Expansion joints,

Prestressing anchorages and anchor zones,

Underpass retaining walls.

All end and intermediate diaphragms in concrete, steel and composite box girder bridges shall have an

opening of 1000x2000mm (at least 600x1000mm) to allow for passage of inspectors inside the box. The

inside of the box shall be accessible from the outside through openings in the deck soffit and/or at the

abutment behind the end diaphragms. The openings shall be free of any utility pipes or ducts.

Where there is a joint between the abutment and the superstructure, a gallery shall be provided between

the abutment back wall and the superstructure end diaphragms to allow for inspection of the bearings,

expansion joint, end diaphragm, prestressing anchorage, steel diaphragm, etc. The gallery should be

accessible from the outside through an opening in the abutment side wall.

All bearings shall be replaceable. The design shall show the location of the jacking points on the

substructure and superstructure drawings. The design of the bridge superstructure shall account for the

amount of lifting necessary for the bearing replacement.

Where cladding walls are used on underpass walls, the space behind the cladding walls should be accessible

to allow for inspection for ground water leakage and other damages.

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Kuwait Bridges and Highway Structures Design Manual Chapter 3Part 2 Kuwait Bridges and Highway Structures Design Manual Loads

3. LOADSLoads shall be as specified in Section 3 of AASHTO LRFD except as clarified or modified in this manual.

3.1 DESIGN LIVE LOADING Highway Load:(AASHTO LRFD Article 3.6.1.2): Vehicular live loading HL-93 magnified as follows:

o Design Truck (Art. 3.6.1.2.2) multiplied by 1.25,o Design Tandem (Art. 3.6.1.2.3) multiplied by 1.25o Design Lane Load (Art. 3.6.1.2.4) no magnification

Exceptional Load: In addition to the above, design shall be adequate to carry infrequent overload of90 Tonne, 5-axle Military Vehicle. No dynamic allowance shall be applied to the Military Vehicle.

One single Military Vehicle in one direction only shall cross the bridge at any one time, occupying any traffic

lane without concurrent loading in the rest of this lane (no other normal traffic). The rest of the bridge (all

other lanes) can be loaded with normal traffic in both directions. Military Vehicles in convoys shall be spaced

a minimum of 100m.

The Military Vehicle shall be used only in the STRENGTH II Load Combination as defined in AASHTO LRFD

Table 3.4.1-1.

Overload Vehicle

(Dimensions in mm, Weight in Tonnes)

3.2 DEAD LOADSDead loads and dead load combinations shall be as per AASHTO. However, all bridges shall be designed for

additional load:

Future Wearing Surface: 1.2kN/m2 applied over the entire width of roadway from curb to curb to allowfor future wearing surface. This load is in addition to any wearing surface applied at time of construction.

However, the weight of Future Wearing Surface shall be excluded from deflection calculations.

Utilities: shall be as per specific bridge requirements. The design shall allow for a 5kN/linear metre ofbridge for future utilities distributed over all the beams uniformly.

When concrete deck slabs are used as wearing surface, the top 15mm shall not be considered part of thestructural member when computing strength but it shall be included in dead load computation.

3.3 WIND LOADSWind loads shall be applied to structures as per AASHTO. To compute wind load intensities, wind speed shall

be taken as 110kph with gusts of 150kph.

3.4 THERMAL FORCESThermal forces shall be considered in accordance with AASHTO using the following parameters:

Ambient temperature range from + 5C to + 55C Assuming a construction temperature range of 15 C to 39 C Temperature rise (15 C to 55 C) = 40C

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Part 2 Kuwait Bridges and Highway Structures Design Manual Loads

Page 3-2

Temperature fall (39 C to 5 C) = 34C

Mean relative humidity: 20% to 60%.

3.5 UPLIFT

Provisions shall be made to attach the superstructure to the substructure by ensuring that the calculated

uplift is resisted by tension members capable of resisting the largest force developed under the followingconditions:

100% of calculated uplift caused by combination of loadings in which live load plus impact loading is

increased by 100%.

150% of the calculated uplift at working level.

100% of calculated uplift at Load Factor level.

3.6 SEISMIC LOADING

As a minimum, bridges have to be designed to AASHTO LRFD Section 3.10 Earthquake Effects, for

Acceleration of Coefficient 9% or 0.09 (Seismic Zone 1) and Importance Classification: Essential Bridges.

3.7 MOVEMENT RATING

Provisions shall be made in the design of structures to resist induced stresses or to provide for movementresulting from the variation in temperature and anticipated shortening due to creep, shrinkage or pre-

stressing.

Accommodation of thermal and shortening movements will entail consideration of deck expansion joints,

bearing systems, restraining devices and the interaction of these three items.

The required movement rating is equal to the total anticipated movement. The calculated movements used

in determining the required movement rating shall be as per AASHTO LRFD except as modified below:

Mean Temperature: 27C.

To allow for the effect of long-term creep and shrinkage in prestressed concrete members, additional

shortening shall be considered. Follow AASHTO LRFD Articles 3.12.5, 3.12.6 and 5.4.2.3 together with

the recommendations of CEB-FIP MC90 for the assessment of creep and shrinkage strains.

3.8 BEARING FRICTION FORCES

Friction forces due to elastomeric bearing pads or PTFE surfaces shall be based on the manufacturers data

for the bearing used but not less than 4% shall be used in the calculations.

3.9 DIFFERENTIAL SETTLEMENT

Differential settlement shall be considered in the design when indicated in the Geotechnical Report. The

Geotechnical Report should provide the magnitude of differential settlement to be used in the design. If no

such calculations are reported, the cumulative effect of at least 25 mm differential settlement of individual

foundations shall be considered.

3.10 FLOATING DEBRIS

Wadi bridge piers shall be designed for impact from floating debris. The equivalent static horizontal force H

generated by floating debris (such as logs, trees, loaded boats etc.) strike the pier at the high flood level atthe speed of flood. This force may be estimated as follows:

H = wv2 / 2gd

Where w = weight of the striking object (kg)

v = Maximum flood velocity (= 1.41 times maximum mean velocity of flood) (m/sec)

g = acceleration due to gravity (m/sec2)

d = distance through which w moves upon hitting the pier (usually taken as 0.05 to 0.10 m)

H = Kg.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Loads

Page 3-3

3.11 DISTRIBUTION OF LOADS

The Designer shall determine distribution of Live Loads from analysis based on the grillage or finite element

methods.

3.12 LOAD COMBINATIONS

Load combinations shall be as per AASHTO LRFD Article 3.4 for the limit states: Service Limit State, Fatigue

and Fracture Limit State, Strength Limit State and Extreme Event Limit State.

Load Combinations EXTREME EVENT I and EXTREME EVENT II are interpreted as follows:

EXTREME EVENT I includes earthquake and water loads of static pressure and buoyancy but does not

include general and local scour for wadi and water stream bridges unless specific site conditions dictate

otherwise.

EXTREME EVENT II includes scour, force effects due to superimposed deformations and collision load CT

but does not include earthquake. The live load factor for this combination is 0.50 to reflect the low

probability of the concurrence of the maximum vehicular live load (other than CT) and the extreme

events.

The load combinations should be applied judicially.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Foundations

Page 4-1

4. FOUNDATIONS

Foundation design shall be based on soil investigation specific to the location under design. An Interpretive

Geotechnical Report should be submitted as part of design calculations.

Soil survey test results shall be included with contract documents.

4.1 DESIGN METHOD

Foundations shall be designed for the allowable soil bearing capacity and settlement criteria, satisfying the

stability and serviceability conditions as per the applied loads and soil conditions, according to International

Standards.

Service Load Design method shall be used for designing foundations. If Load Factor method is to be used by

the Consultant, prior written permission is required form MPW.

4.2 SUPERFICIAL SOILS

In most areas, the geology of Kuwait City comprises of Eocene Limestone at depth completely obscured by

superficial deposits.

The superficial deposits comprise of a lower marine sand, known locally as Gatch, overlain by windblown

sands, made ground or a combination of both. This superficial windblown sands/made ground was found toextend to depths of up to 6m though generally in the range 1.5m to 2m.

These materials are highly variable with recorded SPT N values in the range from 4 to in excess of 50.

Due to the generally weak and variable nature of these materials, no structures are to be founded in them.

Any loose layers, soft spots and any inferior material such as broken rocks or gypsum at the excavation

level shall be totally removed and replaced by cyclopean/blinding concrete, as directed by the engineer.

Subgrade preparation, compaction and backfilling for foundation and slabs on grade construction shall

conform to Section 2 Earthworks Specification.

4.3 GROUND WATER AND SULFATES

Ground water is present at many locations at shallow depth depths. If dewatering will be required during

the construction of such structures, the designer shall address the issue of the effect of dewatering on soil

and adjacent foundation. Remedial measures shall be specified to protect adjacent structures.

The groundwater is generally sulfate rich due to the presence of gypsum and other minerals within the soils,

and will therefore be aggressive towards concrete. Thus it will be necessary to design any concrete

structure below or close to the groundwater to withstand sulfate attack. The designer shall refer to

recognized codes of practice to address this important issue. See Clause 8.2 (Concrete Protection against

Aggressive Soils) for additional details.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Retaining Walls

Page 5-1

5. RETAINING WALLS

5.1 GENERAL

Retaining walls shall be designed in accordance with Section 11 of AASHTO LRFD.

On the Kuwait Motorway System, two types of retaining walls have been successfully used: Non-Gravity Cantilevered Walls (reinforced concrete).

Mechanically Stabilized Earth.

For mechanically stabilized earth, if proprietary systems are to be specified, the supplier shall be requested

to submit full documentation of successful application of the system in similar conditions. Relevant material

test results shall be requested.

As a minimum the following should be included in shop drawing:

The minimum factor of safety against overturning

The minimum factor of safety against sliding

Maximum coefficient of friction against sliding

Phi angle of the backfill

Allowable bearing pressure Minimum design life

Water table level

Elevation of footing bottom

Maximum tolerable deflection

Foundation preparation, compaction, etc. shall comply with Section 2 Earthworks.

Where utilities are to be placed near the retaining walls, the strips or bars forming the reinforcement to the

mechanically stabilized earth shall be carefully detailed to ensure that access to the utilities is provided

without interference to or from the reinforcement.

Special considerations shall be made for appropriate drainage measures if needed.

All retaining structures shall be checked for settlement / differential settlements criteria.

5.2 FACTORS OF SAFETY

Retaining Walls shall be designed for a minimum Factor of Safety as follows:

Sliding: 1.5

Overall stability 1.5.

Bearing capacity 3.0

Overturning: 2.0

For Mechanically Stabilized Earth Wall:

Sliding: 1.5

Overturning: 2.0

Pullout Resistance: 1.5 for wall heights equal or less than 11m

2.0 for wall heights over 11m

Bearing Capacity: 3.0

Slope Stability: 1.5

Mechanically stabilized earth wall shall be also checked for internal stability (critical slip surfaces) as well as

for the maximum tensile forces in the reinforcement layers and connections.

5.3 EXPANSION AND CONTRACTION JOINTS

For reinforced concrete walls, construction joints shall be provided at a distance not exceeding 9m and

expansion joints at a distance not exceeding 36m unless otherwise proven by analyses. All joints shall be

filled with appropriate joint filler.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Substructure

Page 7-1

7. SUBSTRUCTURE

The substructure shall be designed in accordance with Section 11 of AASHTO LRFD.

The substructure shall be designed to allow easy inspection.

Abutments on mechanically stabilized earth shall not be allowed except with prior permit in writing form the

MPW.

Abutments shall have an inspection gallery for bearings as shown in Figure 7.1.

7.1 LIVE LOAD SURCHARGE

Where live load is present near retaining walls or abutment, a live load surcharge load equivalent to 1m of

soil as a minimum shall be added.

Figure 7.1: Typical Cross-Section of Abutment Showing Inspection Gallery for Bearings

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Part 2 Kuwait Bridges and Highway Structures Design Manual Reinforced Concrete

Page 8-1

8. REINFORCED CONCRETE

Reinforced concrete design criteria shall be as specified in Section 5 of AASHTO LRFD except as clarified or

modified in this manual.

8.1 CONCRETE

Concrete for highway structures shall have, as a minimum, the following 28 day Cylinder Strength:

Decks and Barriers f c = 30MPa

Abutments f c = 30MPa

Pier Columns and Shafts f c = 30MPa

Drilled Shafts f c = 30MPa

Retaining Wall Stems f c = 30MPa

Footings f c = 30MPa

For design, Cube Strength and Cylinder Strength can be assumed as follows unless specifically listed

otherwise in the design calculations:

Concrete K-Class

(kg/cm2)

Minimum

Cube Strength(N/mm2)

Cylinder/Cube

Ratio

Cylinder Strength F'c

(N/mm2) (kg/cm2)

250 24.5 0.85 20.8 210

300 29.4 0.85 25.0 255

350 34.3 0.90 30.9 315

400 39.2 0.90 35.3 360

415 40.7 0.90 36.6 370

450 44.1 0.90 39.7 405

475 46.6 0.95 44.3 450

8.2 CONCRETE PROTECTION AGAINST AGGRESSIVE SOILS

Ground water is present at many locations at shallow depth. The groundwater is generally sulfate rich due

to the presence of gypsum and other minerals within the soils, and will therefore be aggressive towards

concrete. Thus it will be necessary to design any concrete structure below or close to the groundwater to

withstand sulfate and other chemical attack.

Concrete mix design and concrete protection requirements shall be in accordance with BRE Special Digest

(Parts 1 to 4) CONCRETE IN AGGRESSIVE GROUND requirements. This guide is published in the UK by

Construction Research Communications Limited.

The designer has to specify in design calculations the following:

Structural Performance Level SPL

DS Class for the Soil

Aggressive Chemical Environment for Concrete (ACEC) Class for the Ground

Concrete Grade and Cement Type

8.3 REINFORCEMENT

Epoxy coated bars shall not be used.

All reinforcement shall be Grade 400 as a minimum.

8.4 SLAB DESIGN

Slabs shall be designed in accordance with the criteria specified in Section 5 of AASHTO LRFD except as

clarified or modified below.

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Page 8-2

All reinforcing bars shall be straight bars top and bottom. The use of truss bars will not be permitted.

For skews less than or equal to 20 degrees, the transverse bars shall be placed parallel to the skew. For Use

of steel stay-in-place forms is discouraged and should be considered only in special conditions and after

obtaining written approval from MPW. Some circumstances that warrant such use include: bridges over

heavily traveled roads that cannot be closed for traffic for a reasonable period and bridges with extremely

difficult access. A discussion on their use shall be made in the design concept report. If use of steel stay-in-place forms is not recommended during design, they will not be allowed during construction due to the

extra dead load. Contractor requests for usage during construction will not be approved.

8.5 SLAB THICKNESS

The thickness of new deck slabs shall be designed in 5mm increments with the minimum thickness as per

Table 2.5.2.6.3-1 of AASHTO LRFD.

8.6 PROTECTION AGAINST CORROSION

The minimum clearance for top reinforcing in new decks shall be 55mm.

8.7 MINIMUM AND MAXIMUM DESIGN VALUES

8.7.1 Minimum Depth of Structural Members

Minimum depth of structural members shall be in accordance with Table 2.5.2.6.3-1 of AASHTO LRFD.

8.7.2 Maximum and Minimum Reinforcement

The maximum and minimum amounts of reinforcement shall as be as per the following AASHTO LRFD

Articles:

Article 5.7.3.3 for maximum and minimum amounts of prestressed and nonprestressed tensile

reinforcement in flexural members.

Article 5.7.4.2 for maximum and minimum amounts of prestressed and nonprestressed longitudinal

reinforcement for compression members.

Article 5.8.2.5 for minimum transverse reinforcement.

8.7.3 Minimum Concrete Cover to Reinforcement

Minimum concrete cover (in millimeters) to reinforcing steel shall be as noted in the listing below:

Concrete exposed to salt water and splash zone 100

Concrete of all substructure elements cast against earth 100

Concrete of all substructure elements exposed to weather 75

Approach slabs 60

Superstructure cast-in-situ concrete exposed to weather 60

Interior faces of superstructure cast-in-place concrete except slabs 40

Cast-in-situ slabs 30

Precast superstructure elements, exposed surfaces 40

Precast superstructure elements, interior faces 30

Precast parapets, concrete barriers, curbs, etc 30

8.7.4 Maximum Deflection

The maximum deflection of structural members shall be in accordance with Article 2.5.2.6.2 of AASHTO

LRFD with due consideration of Article 5.7.3.6.2.

8.7.5 Maximum Crack width

Notwithstanding the measures specified in AASHTO LRFD Article 5.7.3.4 for distribution of reinforcement to

control cracking, the maximum flexural crack width at the tensile face of a concrete section shall not exceed

the following values:

For normal conditions above ground 0.30 mm

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Page 8-3

For normal conditions below ground 0.25 mm

In the coastal zone 0.20 mm

Under sea water 0.10 mm

8.8 CONCRETE DURABILITY

8.8.1 Marine Environment

Structures in the coastal zone characterized by air-borne chloride ions need special attention to durability.

To assure protection of the reinforced and prestressed concrete elements for these structures, all concrete

used for construction will be as per the strengths specified in Clause 8.1 INCREASED by 5 MPa.

8.8.2 Concrete Permeability Requirements (Coastal Zone)

Permeability tests are specified to be conducted on concrete elements as per DIN 1048 and AASHTO T277

Rapid Determination of the Chloride Permeability of Concrete. The acceptance limits are:

DIN 1048

o In-situ construction: less than 25 mm

o Precast units less than 20 mm

AASHTO T277

o In-situ construction 1500 coulombso Precast units 1000 coulombs

Designers may specify more stringent limits if appropriate.

8.8.3 Concrete Surface Protection (Coastal Zone)

Concrete surfaces that are in the sea water below the high sea level and in the splash zone shall be

protected with an epoxy coating.

All exposed concrete surfaces above the splash zone shall be coated with a two-layer protective coating

consisting of:

A silane-siloxane hydrophobic barrier that penetrates the concrete substrate and prevents the passage of

chloride and sulfate ions.

An anti-Carbonation decorative topcoat.

The protective coating shall be supplied, applied and tested in accordance with the Specification. The

acceptance limits of the permeability tests shall be reduced for the coated surfaces as follows:

DIN 1048 results for coated surfaces:

One fifth of the limits for the unprotected surfaces.

Rapid Chloride permeability test results for coated surfaces:

Charge passed should be that specified for the uncoated surfaces minus 500 coulombs

8.8.4 Bridge Deck Protection (Applicable to Coastal and Other Zones)

Concrete bridge decks shall be overlain with a proprietary waterproofing membrane and asphalt wearing

course of minimum thickness 60mm.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Prestressed Concrete

Page 9-1

9. PRESTRESSED CONCRETE

9.1 GENERAL

Prestress design criteria shall be as specified in Section 5 of AASHTO LRFD except as clarified or modified in

Members shall be designed to meet the requirements of all limit states as specified in sub-Section 5.5 of

AASHTO LRFD.

Section properties shall be based on gross area of members. Use of the transformed area of bonded

reinforcement shall only be used for unusual structures and only when approved.

Web reinforcement for shear shall consist of rebars, not welded wire fabric.

The minimum top cover for slab reinforcement shall be 55mm.

9.2 ALLOWABLE STRESSES

The maximum allowable tensile stresses in a pre-compressed tensile zone at service load after losses have

occurred shall be in accordance with AASHTO LRFD except as modified below:

Allowable tension in concrete shall be based on Severe Corrosive Exposure conditions.

For overload group, the allowable tension can be increased up to 0.5 fc (metric units) under service loads.

9.3 SHEAR

Shear design shall be in accordance with AASHTO LRFD.

Prestressed concrete members shall be reinforced for diagonal tension stresses. Shear reinforcement shall

be placed perpendicular to the axis of the member with spacing not-to-exceed three-fourths the depth of

the member.

The critical sections for shear in simply supported beams will usually not be near the ends of the span

where the shear is a maximum, but at some point away from the ends in a region of high moment.

For the design of web reinforcement in simply supported members carrying moving loads, it is

recommended that shear be investigated only in the middle half of the span length. The web reinforcement

required at the quarter points should be used throughout the outer quarters of the span if the critical shear

section is included within the design section.

For continuous bridges whose individual spans consist of precast, prestressed girders, web reinforcement

shall be designed for the full length of interior spans and for the interior three-quarters of the exterior span

and based on the critical shear design section.

9.4 CONCRETE

The following concrete strengths are the acceptable. Use of higher strengths may require prior approval of

MPW.

Minimum fc = 40MPa

Maximum fc = 50MPa

9.5 PRECAST PRE-TENSIONED I-BEAMS

9.5.1 Live Load Continuous Beams

To minimize the number of deck joints, girders shall be designed as composite section, simple supported

beams for live load plus impact and composite dead load. The superstructure shall be constructed

continuous with the negative moment reinforcing designed considering continuity over intermediate

supports for live load plus impact and composite dead loads. The positive moment connection may be

designed using the method described in the PCA publication Design of Continuous Highway Bridges with

Precast, Prestressed Concrete Girders. In determining the positive restraint moment, use 30 days as the

length, of time between casting the girders and deck closure. The development length of the strands may

be based on the criteria contained in Report No. FHWA-RD-77-14, End Connections of Pre-tensioned I-

beam Bridges November 1974. In determining the number and pattern of strands extended, preference

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Page 9-2

shall be given to limiting the number of strands by increasing the extension length and alternating the

pattern to increase contractibility.

9.5.2 Debonded Strands

When using strands to pretension, precast beams, the use of de-bonded strands shall be limited to end

blocks.

9.5.3 Deflection

The Release Deflection equals the deflection the prestress girder undergoes at the time of strand release.

The Release Deflection includes the dead load of the girder and the release prestressing force (including the

effects of elastic shortening).

The Initial Deflection equals the deflection the prestress girder undergoes at the time of erection prior to the

diaphragm or deck pours. The Initial Deflection includes the deflection due to the dead load of the girder,

the initial prestressing and the effects of creep and shrinkage up to the time of erection. The time of

erection should be assumed to be 60 days after release.

The Final Deflection equals the deflection due to the dead load of the deck slab, diaphragms and barriers

and the effects of long term creep on the composite girders. The effects of the future wearing surfaces shall

be excluded from deflection calculations.

The tops of the erected girders shall be surveyed in the field prior to placement of the deck forming. If the

tops of the erected girder elevations are higher than the finish grade plus camber elevations minus the deck

slab and buildup thickness, adjustments will have to be made in the roadway profile or in the girder seat

elevations. Encroachment into the slab of up to 15mm will be allowed for random occurrences.

9.5.4 Shear

The value of d to be used in shear calculations shall equal the depth of the beam plus the effective depth

of the slab with a minimum d = 0.80 times the overall depth. The shear shall be calculated assuming full

continuity for composite dead load and live load plus impact.

9.5.5 Method of Analysis

The dead load shall be assumed to be unsupported and carried by the girders only.

9.5.6 Bearing PadsLaminated elastomeric bearing pads should be used for relatively light reactions and moderate

superstructure movements.

Pot type bearings should be used for heavy reactions large superstructure movements and superstructure

on horizontal curve alignment.

Allow for long-term creep and shortening due to prestressing.

Elastomeric bearing pads will be a maximum width of 50mm less than the normal width of the bottom

flange to accommodate the 20mm side chamfer and should be set back 50mm from the end of the girder to

avoid spalling of the girder ends.

9.5.7 Creep Factor

Use a creep factor should be in accordance with AASHTO LRFD when calculating long-term deflections.

9.5.8 Differential Shrinkage

Differential shrinkage should be considered in the design when the effects become significant and when

approved by the Engineer.


The theoretical build-up depth shall be ignored for calculation of composite section properties.

Post-tensioned Box Girder Bridges shall be designed in accordance with AASHTO LRFD. Concrete strength

to be used is similar to Sub-Section 9.4.

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Page 9-3

9.5.10 Bearing Pads

Allow for long-term creep and shortening due to post-tensioning.

9.5.11 Creep and Shrinkage

For restrained members in continuous bridges where shortening due to post-tensioning induces moments

and shears, a shrinkage and creep coefficient of 1.5 shall be used for design of substructure elements with

the total movement equal to 1.5 times the initial shortening. For superstructure elements, no creep factor

should be applied except for long-term deflection considerations.

9.5.12 Flange and Web Thickness Box Girder

Minimum top slab thickness shall be 190mm. Minimum bottom slab thickness shall be 150mm. Minimum

web thickness shall be 300mm (measured normal to girder for sloping exterior webs). Interior webs shall be

constructed vertical.

9.5.13 Diaphragms

Diaphragms shall be placed parallel to abutments and piers for skews less than or equal to 20 degrees and

normal to girders and staggered for skews over 20 degrees. Diaphragms shall be cast integral with girder

webs.

9.5.14 Deflections

The deflection shall be calculated using dead load including barriers, but not the future wearing surface, a

modulus of elasticity Ec = 4800 fc (MPa), gross section properties and calculated final losses. The

additional long-term deflection shall be calculated.

An additional parabolic shaped deflection should be added to the total deflection for simple spans.

The final long-term deflection shall be the sum of the deflection, the additional long-term deflection and the

additional deflection for simple spans. The camber shown on the plans shall be the final long-term

deflection.

9.5.15 Allowable Stresses Prestressing Steel

In calculating the stress in the prestressing steel after seating, the friction and anchor set losses only should

be included. For post-tensioned members, overstressing for short periods of time to offset seating and

friction losses is permitted but the maximum allowable jacking stress for low relaxation strand shall belimited to the limits specified in AASHTO LRFD Table 5.9.3-1.

9.5.16 Allowable Stresses Concrete

In calculating the temporary stress in the concrete before losses due to creep and shrinkage, the friction,

anchor set and elastic shortening losses should be included.

Special consideration shall be given to bridges supported on false work with large openings where

deflections could be harmful to the structure. Unless false work requirements are strengthened or other

means taken to ensure the bridge does not form tension cracks prior to tensioning, the maximum allowable

tension in a pre-compressed tensile zone shall be limited to zero.

9.5.17 Loss of Prestress

If the information of actual system to be used in post-tensioning is not available, the design should be

based on usage of galvanized rigid ducts with K = 0.00066 (per meter) and , = 0.25. Anchor set lossesshould be based on 6mm set.

For creep of concrete, the variable fcds should be calculated using the total dead load applied afterprestressing, including the 1.2 kN/m2 future wearing surface.

9.5.18 Flexural Strength

In determining the negative ultimate moment capacity, the top layer of temperature and shrinkage and

bottom layer of distribution reinforcing may be used. In determining the positive ultimate moment capacity,

the longitudinal flange reinforcing may be used.

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Page 9-4

9.5.19 Shear

The maximum girder web stirrup spacing will be 300mm within 6m from the front face of the abutment

diaphragms. This will eliminate the need for re-spacing the web stirrups at the point of web flare if the post-

tensioning system requires flaring.

The value of d to be used in shear calculations shall be the larger of the calculated d value or 0.8 timesthe overall effective depth.

Calculations shall include the shear due to secondary moment and cable shear. For curved box girder

bridges, the shear due to torsion shall be included.

9.5.20 Flange Reinforcement

Reinforcement in the bottom slab of box girders shall conform to the provisions of AASHTO LRFD 5.14

except that the minimum distributed reinforcement in the bottom flanges parallel to the girders as specified

in AASHTO LRFD 5.14.1.3.2 shall be modified to be 0.30 percent of the flange area.


The superstructure may be designed using the system as described below:

The bottom slab, in the vicinity of the intermediate support, may be flared to increase its thickness at the

face of the support when the required concrete strength exceeds 320 kg/cm2. When thickened, thebottom slab thickness should be increased by a minimum of 50 percent. The length of the flare should be

at least one-tenth of the span length (measured from the center of the support) unless design

computations indicate that a longer flare is required.

Section properties at the face of the support should be used throughout the support; i.e. the solid cap

properties should not be included in the model.

Negative moments should be reduced to reflect the effect of the width of the integral support.

Dead load forces should not produce any tension in the extreme fibers of the superstructure.

For box girders with severe sloping webs or boxes over 2m deep, transverse flange forces induced by

laterally inclined longitudinal post-tensioning shall be considered in the design.

Single span structures may be jacked from one end only or jacked from both ends as required by the

design. Symmetrical two span structures may be jacked from one end only or jacked from both ends.

Unsymmetrical bridges should be jacked from one end or both ends as required by the design. Three spanor longer structures should be jacked from both ends.

For structures over 120m in length, in determining the c.g. of the strands, the diameter of the ducts should

be oversized by 13mm to allow for ease of pulling the strands.

For horizontally curved bridges, special care shall be taken in detailing stirrups and duct ties. Friction losses

should be based on both vertical and horizontal curvatures. In designing for horizontal curvature, the

exterior web with the smallest radius shall be used. Consideration to the 5% variation allowed per web

shall be included.

9.6 PRESTRESSED VOIDED SLAB

9.6.1 End Blocks

End Blocks should be at least 380mm long or as per design requirement with sufficient steel provided to

resist the tensile forces due to concentrated prestressing loads.

9.6.2 Lateral Ties

At least one lateral tie shall be provided through each diaphragm located at the mid-depth of the section

9.6.3 Shear Keys

After shear keys have been filled with an approved non-shrink mortar, lateral ties shall be placed and

tightened.

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Page 9-5

9.6.4 Barriers

Barriers that are cast-in-situ, shall have 6mm open joints at the mid-span to prevent the barrier from acting

as an edge beam and causing long-term differential deflection of the exterior beam.

9.7 PRESTRESSED BOX BEAMS

9.7.1 End Blocks

End Blocks 450mm long shall be provided at each end and sufficient steel shall be provided in the end

blocks to resist the tensile force due to the prestressing loads.

9.7.2 Lateral Ties

At least one lateral tie shall be provided through each diaphragm located at the mid-depth of the section.

9.7.3 Shear Keys

After shear keys have been filled with an approved non-shrink, low slump mortar, lateral ties shall be

placed and tightened.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Structural Steel

Page 10-1

10. STRUCTURAL STEEL

Structural steel design criteria shall be as specified in Section 6 of AASHTO LRFD except as clarified or

modified in this manual.

10.1 DESIGN METHOD

The Load and Resistance Factor Design (LRFD) method shall be used as the design method for structural

steel.

10.2 MATERIALS

Material shall conform to the requirements of AASHTO LRFD article 6.4 with the selection based on stress

requirements and overall economy.

10.3 DETAIL CATEGORIES

Splices stiffeners, shear connectors and bracing details shall be designed using categories. A through C

details in order to limit the fatigue stress.

Category E details shall not be used.

10.4 CHARPY V-NOTCH IMPACT REQUIREMENT

Where applicable, the Charpy V-Notch impact requirements for structural steel shall be for temperature

Zone 1.

10.5 STIFFENERS AND CONNECTIONS

Intermediate stiffeners shall be placed only on the inside face of exterior girders.

The number and the location of the girder shop and field splices shall be determined so as minimize

fabricated and erected cost of the girders.

All connections except field connections shall be welded. ASTM A325M high strength bolts shall be used for

field connections.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Expansion and Contraction

Page 11-1

11. EXPANSION AND CONTRACTION

11.1 MOVEMENT CRITERIA

Provisions shall be made in the design of structures to resist induced stresses or to provide for movements

resulting from variations in temperature and anticipated shortening due to creep, shrinkage or prestressing.Accommodation of thermal and shortening movements will entail consideration of deck expansion joints,

bearing systems, restraining devices and the interaction of these three items.

The main purpose of the deck joints is to seal the joints opening to obtain a watertight joint while allowing

for vertical, horizontal and/or rotational movement. The bearings are required to transmit the vertical and

lateral loads from the superstructure to the substructure units and to allow for movement in the

unrestrained directions.

Restraining devices are required to limit the displacement in the restrained directions. Improper design or

construction of any of these devices could adversely affect the operation of the other devices.

The required movement rating is equal to the total article movement (i.e. the difference between the widest

and the narrowest opening of a joint). The calculated movements used in determining the required

movement rating shall be as specified in AASHTO LRFD except as modified below:

Mean temperature and temperature ranges shall be as specified in this manual.

To allow for the effects of the long term creep and shrinkage in prestressed concrete members, additional

shortening shall be considered. Follow AASHTO LRFD Articles 3.12.5, 3.12.6 and 5.4.2.3 together with the

recommendations of CEB-FIP MC90 for the assessment of creep and shrinkage strains.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Deck Joints

Page 12-1

12. DECK JOINTS

Kuwait motorway system has utilized several types of joints. Many joints have exhibited problems with

mortar infill adjacent to asphalt pavement. Therefore, for short span bridges, joints at piers shall be

eliminated as much as possible by using continuous deck construction.

When deck joints are used, they shall be designed properly in accordance with Section 14 of AASHTO LRFDBridge Design Specifications and durable deck joints shall be specified.

12.1 MOVEMENT RATING

The movement rating for joints for steel structures shall be based primarily on the thermal expansion and

contraction characteristics of the superstructure, while for concrete structures the effect of shortening due

to creep and shrinkage and where applicable, prestressing shall also be based on the temperature variations

as measured from the assumed mean temperature. Horizontal deflection of piers and abutments due to

earth pressure and/or earthquake should also be considered where appropriate.

Published movements ratings are usually based on the difference between the maximum and minimum

opening without consideration to the required minimum installation width. In determining the movement

rating, consideration must be given to the installation width required to install the seal element.

Other factors, which should be considered in the determining the required movement rating, includeconsideration of the effects of any skew, anticipated settlement and rotations due to live loads and dead

loads, where appropriate.

Items requiring attention include:

The type of anchorage system to be used.

The method of joint termination at the ends.

The method of running joints through barriers, sidewalks and / or medians.

Physical limit of size of joints.

Susceptibility of joint to leakage.

Possible interference with post-tensioning anchorages.

Selection of appropriate modular proprietary systems that meet design requirements.

Forces applied to the surrounding concrete by the joint.

Durability and maintenance requirements.

Comfort of passengers.

Noise due to passing traffic.

Available types of joints include compression seal strip seals, asphaltic plug joints, elastomeric joints and

modular joints. Compression seal joints and strip seal joints are generic and should be detailed on the

plans, by standards and/or covered in the special provisions. Asphaltic plug, elastomeric and modular joints

are proprietary and require that the designer specify allowable joint types and style in the special

provisions. Information concerning specific design parameters and installation details of these joints should

be obtained from literature supplied by the manufacturer of the system. It is the responsibility of the

designer to review the proprietary joint literature and related manufacturers specifications to ensure that

the selected joints types are properly specified and compatible with the design requirements.

The following features of joints should be shown on the plans or shop drawings:

Blockout details showing a second pour, including blockout dimensions and additional reinforcing

required.

Required end treatment in barriers or curbs, including enough details or explanation to accommodate

each of the proprietary systems selected (i.e. cover plates, etc).

Consideration to traffic control in determining section pattern lengths.

Movement rating.

Assumed temperature and opening at time of installation with temperature correction factors.

Actual horizontal length of joint measured from inside of the barrier face to inside of barrier face

corrected for skew.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Deck Joints

Page 12-2

Recesses in deck surface and their details for the case of expansion joints thicker than the wearing

course.

For modular joints, the joints style, gland type, steel edge beam material shall be specified.

12.2 COMMON DECK JOINT TYPES

12.2.1 Compression Seals

The compression seal element should have a shape factor of 1:1(width to height) to minimize sidewall

pressure. The size of the compression seal shall be specified on the plans.

Effective movement ratings for this type of joint range up to 50mm. Advantages for this type of joint

include its low cost, proven performance and acceptance for use on pedestrian walkways. However, this

type of joint cannot be unbolted and easily raised, generates pressure and it is not good for high skews or

horizontal direction changes.

12.2.2 Strip Seals

Effective movement ratings for this type of joint range up to 100mm. This type of joint is best used when

the movement rating is beyond the capacity of compression seals and for large skews. Strip seals joints will

require cover plates for pedestrian walkways.

12.2.3 Asphaltic Plug Joints

Effective movement ratings for this type of joint range up to 50mm. The advantage of this type of joint is

being durable, noiseless under traffic, practically Maintenance free and easy to install. It is the best choice

for precast girder decks with no continuity top slab and with top slab for an expansion length up to 60 m.

12.2.4 Elastomeric Joints

Effective movement ratings for this type of joint range up to 350mm. It is the best choice for an expansion

length up to 350 m and is particularly suitable for continuous bridge decks.

12.2.5 Modular Joints

Modular joints are very complex joint systems. Effective movements ratings range from 100mm up to

750mm. Modular joints are the best choice for movements ratings over 300mm.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Bearings

Page 13-1

13. BEARINGS

Kuwait motorway bridges built in the early 1980s have exhibited severe bearing deterioration such as

excessive bulging, tearing, and separation of laminated pads.

The following recommendations shall be addressed in design and detailing of bearings for new bridges.

Bearings shall be accessible and easily inspected by providing enough vertical and lateral clearances.

Pot bearings should not be covered and should have permanent marking indicating initial position

(rotation and displacement) and height (when loaded) of bearing.

Bridge seat and beam end diaphragms shall be detailed to allow jacking of bridge from bridge seat

whenever is practical in case of bearing replacement.

Design of fixed bearings should avoid using elastomeric pads with holes for anchor rods as this makes

bearing replacement extremely difficult.

Un-reinforced elastomeric bearing pads shall not be used unless for very light loading.

Reinforced elastomeric pads shall be of neoprene (not natural rubber) and used only for short span

precast beams.

13.1 MOVEMENT CRITERIA

Because bearings must be designed to be installed at temperatures other than the mean temperature, themovement rating should be based on the full temperature range and not the rise or fall from a mean

temperature. Calculation of the movement rating shall include:

Thermal movement, shortening due to creep, shrinkage and prestressed shortening.

For cast-in-place post-tensioned concrete box girder bridges both the elastic and long term prestress

shortening effects shall be considered.

An initial offset of the top sliding surface from the centerline of bearing should be calculated and shown on

the plans or shop drawings so that the top sliding surface will be centered over the bottom sliding surface

and the centerline of bearing after all shrinkage, creep and post-tensioning shortening has taken place in

the superstructure.

13.2 TYPES OF BEARINGS RECOMMENDED

Permissible bearing types include, elastomeric bearing pads, steel bearings, sliding elastomeric bearingsand high- load multi-rotational bearings (pot, disc or spherical).

Because of previous problems with existing bearings, all bearings types including electrometric bearing pads

shall be designed for impact.

13.2.1 Elastomeric Bearing Pads

Elastomeric bearing pads shall conform to the requirements of AASHTO LRFD Section 14 or Eurocode EN

1337. Bearing pads shall be designed and to be constructed using steel laminates. If fiberglass laminates

are needed, this has to be indicated. The following data should be shown on the plans or shop drawings:

Length, Width and Thickness of Pad

Durometer Hardness

Design Methods (A or B)

Design Load Low Temperature Zone (A, B or C)

Elastomer Grade (0, 2 or 3)

Generally, bearing pads shall be Durometer 60-Elastomer with steel reinforcement.

Design of steel-reinforced elastomeric bearings shall be in accordance with AASHTO LRFD Bridge Design

Specifications Method B defined in Article 14.7.5 or Method A defined in Article 14.7.6 where the provisions

of the appropriate article are used. Alternatively elastomeric bearings may be designed in accordance with

Eurocode CEN prEN 1337-3. The specifications shall clearly indicate the required testing and quality control

procedure required.

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Page 13-2

Pads shall have a minimum thickness of 25mm and generally with maximum thickness around 100mm.

Holes will not be allowed in the pads.

Where possible, width and length dimensions shall be detailed in even 50mm increments.

Where used with prestressed I-girders, pads shall measure a minimum width of 50mm less than the

nominal width of the girder base to accommodate the 20mm side chamfer and shall be set back 50mm fromthe end of the girder to avoid spalling of the girder ends.

Elastomeric pads should not be used in cases where deck joints or bearings limit vertical movements, such

as in holder style sliding steel plate joints or widening where existing steel bearings are to remain.

Where elastomeric bearing pads with greased sliding plates are used on post-tensioned box girder bridges

to limit the required thickness of the pad, the pad thickness should be determined based on temperature

movements only, with the initial and long term shortening assumed to be taken by the sliding surface.

Elastomeric bearing pads are the preferred bearing type for new steel girders, precast prestressed girders

and short span post-tensioned box girder bridges.

13.2.2 Steel Bearings

Steel bearings may consist of rockers or fixed or expansion assemblies, which conform to the requirements,

specified in Section 14 of AASHTO LRFD.Steel bearings are not a preferred bearing type and their use should normally be limited to situations where

new bearings are to match the existing bearings type on bridge widening projects.

13.2.3 Sliding Elastomeric Bearings

Sliding elastomeric bearings consist of an upper steel bearing plate anchored to the superstructure, a

stainless steel undersurface and an elastomeric pad with Teflon coated upper surface. The Teflon surface

shall be attached to a 10mm minimum thick plate, which is vulcanized to the elastomeric pad. The bearing

accommodates horizontal movement through the Teflon sliding surface and rotation through the elastomeric

bearing with the thickness of the elastomeric bearing determined by the rotational and friction force

requirements. Keepers may be used for horizontal restraint of the pads. Anchor bolts with slotted keeper

plates may provide vertical restraint or individual vertical restraint as appropriate. The pad dimensions and

all details of the anchorage and restraint systems shall be shown on the plans. The special provisions should

allow for proprietary alternates.

Sliding elastomeric bearings should be considered for applications where regular elastomeric bearing pads

would exceed 100mm in height or where special access details would be required for other proprietary

bearings in such places as hinges.

13.2.4 High Load Multi-Rotational Bearings

High load multi-rotational fixed bearings consist of a rotational element of the Pot-type, Disc-type or

Spherical-type. High-load multi-rotational expansion bearings consist of a rotational element of the Pot-

type, Disc-type or Spherical-type, sliding surfaces to accommodate translation and guide bars to limit

movement in specified directions when required.

Pot bearings consist of a rotational element comprised of an elastomeric disc totally confined within a steel

cylinder. Disc bearings consist of a rotational element comprised of a polyether urethane disc confined by

upper and lower steel bearing plates and restricted from horizontal movement by limiting rings and a shear

restriction mechanism. Spherical bearings consist of a rotational element comprised of a spherical bottomconvex plate and mating spherical top concave plate.

These design criteria were prepared for the broad range of normal applications and the specified limits of

loads, forces and movements. The design and manufacture of multi-rotational bearings relies heavily on the

principles of engineering mechanics and extensive practical experience in bearing design and manufacture.

Therefore, in special cases where structural requirements fall outside the normal limits; a bearing

manufacturer should be consulted.

13.2.4.1 Rotational Requirements

The rotational requirements of these bearings are treated in a new way. Rotational requirements of the

bearings, Rb, are determined by:

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Page 13-3

Rb = Rs + Rc

Where

Rb = Rotation capacity designed into the bearings.

Rs = Anticipated rotation of the structure in service. (Includes live loads and rotations induced by

construction / erection sequences).

Rc = Rotation induced in the bearing by construction tolerances, 0.02 radians maximum.

13.2.4.2 Use of multi - rotational bearings is especially indicated where:

Low profile, high load bearings are required.

Long span, curved, or skewed bridges and other similar structures of complex design are required.

Long slender columns or light frames and members exhibit minimum stiffness or rigidity.

Settlement of the substructure is anticipated.

Self-aligning capabilities are required.

Large movements are anticipated.

Economical, long life, or low maintenance bearings are desirable.

Regular elastomeric bearing pads would exceed 100mm in height.

13.2.4.3 Design Criteria

Since special details are required to allow for access of inspection, repair or replacement of the bearings,

the replacing of joints to eliminate the need for use these bearing types should be considered.

Some structural considerations in use of multi-rotational bearings are listed below. Reference to this

specification refers to the design criteria below.

1. Vertical and horizontal loads shall be assumed to occur simultaneously. All loads are service loads.

Minimum vertical loads are dead loads and superimposed dead loads excluding the future wearing

surface, and live loads and impact.

2. The total recommended clearance between all guiding and guided sliding surfaces shall not excced

1.5mm in order to limit edge stress on guiding interfaces.

3. Avoid specifying total spacing of more than 1.5mm between guides and guided components where

possible.

4. Where feasible provide at last two fixed or guided expansion bearings each able to resist all

horizontal forces at each abutment, column, hinge or pier for design redundancy.

5. Some press-fit guide bar details in common use have proven unsatisfactory in resisting horizontal

loads. When analyzing these designs, consideration should be given to the possibility of rolling of

the bar in the recess.

6. Multi-rotational bearings should not be used at vertical loads less than 20% of their vertical

capacity. Bearings for less than 20% vertical capacity require special design.

7. Special consideration in bearing design shall be given where high horizontal to vertical load (above

0.30) is anticipated.

8. Frictional resistance of bearing slide surfaces should be neglected when calculating horizontal load

capacity.9. The installed alignment of bearing guiding systems relative to the anticipated movement direction

of the structure should be carefully considered to avoid bearing guide system failure. Special

studies or designs may be required on curved or skewed structures to ensure correct installation.

10. The substructure and superstructure should be designed so as to remain rigid under all service

conditions in areas around and in contact with the bearings, paying particular attention to the use

of stiffness at extreme points of movements.

11. The substructure and superstructure design should permit bearings to be removed for inspection or

rehabilitation by minimum jacking of the structure. Jacking points shall be provided in the structural

design.

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Page 13-4

12. The minimum structure rotation, Rs, of bearings covered in the specification is 0.01 radians. Rs

comprises live loads and rotations induced by construction/erection sequences.

13. The maximum construction rotation, Rc (rotation induced by construction tolerances), is 0.01

radians

14. Recommended coefficients of friction for structure design follows:

o Unfilled sheet or woven fiber.

o PTFE/stainless steel 0.04.

o Filled PTFE sheet/stainless steel 0.08.

The above coefficients of friction are based on the average stress and limits of edge stress of

PTFE in this specification, out of level installations within the limits of this specification and

normal in service oxidation of the stainless steel mating surface. Service conditions, where

exceptional corrosion of the stainless steel mating surface may occur, will require special

assessment of the long-term coefficient of friction.

15. Pot, disc and spherical multi-rotational bearings should not be mixed at the same expansion joint or

bent. The differing deflection characteristics and differing rotation characteristics may result in

damage to the bearings and / or structure.

16. Contract drawings and documents should contain a bearing schedule.

17. Some bearing tests are very costly to perform. Other bearings tests cannot be performed because of

the unavailability of test equipment. The following test requirements should be carefully considered

before specifying them:

o Vertical loads exceeding 2,250,000kg.

o Horizontal loads exceeding 225,000kg.

o The simultaneous application of horizontal and vertical loads where the horizontal load exceeds

75% of the vertical load.

o Triaxial test loading.

o The requirement for dynamic rotation of the test bearing while under vertical loads.

13.3 BEARING SCHEDULE

A bearing schedule shall be included in the contract drawings or as built documents and shall contain thefollowing as minimum:

A schedule of all minimum and maximum vertical and horizontal service loads.

Minimum structure and construction rotation requirements.

Magnitude and direction of movements at all bearing support points.

Quantity, type (fixed, expansion or guided expansion).

Plan view, alignment and location of all bearing units.

Allowable upper and lower bearing contact pressure.

Fixing or anchorage details and / or requirements.

Grades, bevels and slopes of all bearings.

Allowable coefficient of friction of slides surfaces.

Surface coating requirements and the appropriate specifications.

Seismic requirements, if any.

Uplift details, temporary attachments or other requirements.

Installation scheme.

Bearing preset details, if required.

The information related to design should be in a bearing schedule based on Table C.14.4.1-1 of AASHTO

LRFD Bridge Design specifications. Design rotation movement and other requirements in the bearing

schedule should only refer to the requirements of the structure where the bearings are to be used.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Restraining Devices

Page 14-1

14. RESTRAINING DEVICES

Restraining devices are meant to prohibit movement in a specified direction. Restraining devices shall be

designed to resist the imposed loads including earthquakes as specified in AASHTO LRFD and as modified in

this manual.

Restraining devices could include concrete shear keys or end blocks, horizontal or vertical cable restrainersor mechanical restraining devices that would be an integral part of bearing or a separate system.

Restraining device to prohibit vertical displacement at expansion ends shall be designed to allow for

inspection and future replacement of bearings.

Allowable restraining devices include, but are not limited to the following: vertical fixed restrainers, vertical

expansion restrainers, external shear keys, internal shear keys and keyed hinges.

14.1 VERTICAL FIXED RESTRAINERS

Vertical fixed restrainers consist of cable and appropriate hardware and are designed to allow rotation but

no translation in either horizontal direction.

14.2 VERTICAL EXPANSION RESTRAINERS

Vertical expansion restrainers consist of cable and appropriate hardware and are designed to allow rotationand longitudinal translation but no transverse translation. Some limited vertical displacement is allowed to

permit replacement of bearing if required.

14.3 SHEAR KEYS

Shear keys are reinforced blocks designed to limit transverse displacement while allowing longitudinal and

rotational movements. External shear keys are preferable to internal restrainers since they are more

accessible for repairs and easier to construction.

14.4 KEYED HINGE

A keyed hinge is a restraining device, which limits displacements in both horizontal directions while allowing

rotation.

For a typical expansion seat abutment where restraining devices are required, the restraining devices will

consist of vertical expansion restrainers and external shear keys.

For a typical seat abutment for a post-tension box girder bridge, restraining devices will consist of vertical

fixed restrainers and external shear keys. For a typical pinned seat abutment for a prestressed girder

bridge, restraining and external or internal shear keys.

For a typical pinned pier, restraining devices will consist of vertical expansion restrainers and internal shear

keys.

For a typical pinned pier, restraining devices will consist of vertical fixed restrainers and internal shear keys

or a keyed hinge.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Sign Support Structures

Page 15-1

15. SIGN SUPPORT STRUCTURES

Sign support structures shall be designed in accordance with AASHTOs Standard Specifications for

Structural Supports for Highway Signs, Luminaries and Traffic Signals.

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Part 2 Kuwait Bridges and Highway Structures Design Manual Pedestrian Bridges

Page 16-1

16. PEDESTRIAN BRIDGES

Pedestrian bridges shall be designed in accordance with AASHTOs Guide Specifications for Design of

Pedestrian Bridges except as clarified or modified in this manual.

16.1 DESIGN LOADS16.1.1 Pedestrian Live Load

Pedestrian Live Load shall be as per AASHTO LRFD Article 3.6.1.6. However, Live Load shall not be less than

4.3kPa for walkway area.

16.1.2 Vehicle Load

When ramps are used the bridge shall be designed for a maintenance vehicle. If not specified by MPW, the

maintenance vehicle shall be:

When the bridge clear deck width is less than 3.00m, H-5 x 1.05 truck shall be used with total weight of

47kN.

dmrb 2011_01_31 part 2

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