DESIGN CRITERIA

DESIGN CRITERIA
FOR BRIDGES IN DUBAI

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DESIGN CRITERIA

TABLE OF CONTENTS

1. INTRODUCTION .................................................................................................................................. 4

2. GLOSSARY.......................................................................................................................................... 5

3. DESIGN REFERENCES AND UNITS ................................................................................................. 5

4. CLEARANCES ..................................................................................................................................... 6
4.1 CLEARANCE FOR ROAD TRAFFIC .......................................................................................................... 6
5. CONSTRUCTION METHODS.............................................................................................................. 6

6. MATERIAL CHARACTERISTICS........................................................................................................ 7
6.1 CONCRETE ......................................................................................................................................... 7
6.2 STEEL REINFORCEMENT ...................................................................................................................... 7
6.3 PRESTRESSING STEEL ......................................................................................................................... 8
6.4 ELASTOMER........................................................................................................................................ 8
7. LOAD CASES ...................................................................................................................................... 9
7.1 DEAD LOAD (DL) ................................................................................................................................. 9
7.2 SUPERIMPOSED DEAD LOADS (SIDL) ................................................................................................... 9
7.3 LIVE LOAD .......................................................................................................................................... 9
7.3.1 Design lanes ............................................................................................................................. 9
7.3.2 Design vehicular live load (LL) ................................................................................................. 9
7.3.3 Pedestrian live load (PL) ........................................................................................................ 11
7.3.4 Dynamic Impact (IM) .............................................................................................................. 11
7.3.5 Centrifugal forces (CE) ........................................................................................................... 12
7.3.6 Braking force (BR) .................................................................................................................. 12
7.4 PRESTRESSING FORCE (PS) .............................................................................................................. 13
7.5 TEMPERATURE (T) ............................................................................................................................ 13
7.6 TIME-DEPENDENT EFFECTS – CREEP (CR), SHRINKAGE (SH), RELAXATION.......................................... 13
7.7 DIFFERENTIAL SETTLEMENT (SE) ....................................................................................................... 13
7.8 W IND ............................................................................................................................................... 13
7.8.1 Wind load on structure (WS) .................................................................................................. 14
7.8.2 Wind load on live load (WL) .................................................................................................... 14
7.9 EARTHQUAKE (EQ) ........................................................................................................................... 14
7.9.1 Site coefficient and seismic zone: .......................................................................................... 14
7.9.2 Monomodal Analysis: ............................................................................................................. 14
7.9.3 Response Modification Factor (R): ......................................................................................... 15
7.9.4 Seismic Direction Combination: .............................................................................................. 15
7.10 COLLISION LOAD ON PIERS OR DECKS (CL) ......................................................................................... 15
7.10.1 Vehicular collision ................................................................................................................... 15
7.11 EARTH PRESSURE (EH)..................................................................................................................... 16
7.12 EARTH LOADS (EH) ........................................................................................................................... 16
7.13 W ATER LOADS (WA) ......................................................................................................................... 18
7.14 PEDESTRIAN RAILING LOADS .............................................................................................................. 18
7.15 CONSTRUCTION LOADS (C)................................................................................................................ 18
8. LOAD COMBINATIONS .................................................................................................................... 19

9. STRUCTURAL CHECKING ............................................................................................................... 21

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9.1 SUPERSTRUCTURES.......................................................................................................................... 21
9.1.1 Service limit state.................................................................................................................... 21
9.1.2 Strength limit state .................................................................................................................. 22
9.1.3 Extreme Event limit state: ....................................................................................................... 34
9.2 SUBSTRUCTURES.............................................................................................................................. 34
9.2.1 Piers ........................................................................................................................................ 34
9.2.2 Bearings .................................................................................................................................. 34
9.2.3 Pier cap ................................................................................................................................... 34
9.2.4 Foundations ............................................................................................................................ 35
10. DEFORMATIONS .............................................................................................................................. 36
10.1 BEARINGS AND JOINTS ...................................................................................................................... 36
10.2 PRECAMBER ..................................................................................................................................... 36
11. DRAINAGE......................................................................................................................................... 36

12. MAIN SOFTWARES FOR STRUCTURAL CALCULATIONS .......................................................... 36

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1. Introduction

This report presents the design basis for the detailed design of the bridge in Dubai.

This document is to be considered as the first reference document when performing design work. It
summarises and clarifies all the design criteria that should be applied. It also lists all the codes and
specification references that should be followed.

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2. Glossary
AASHTO: American Association of State Highway and Transportation Officials;
ACI: American Concrete Institute;
BS: British standards;
CEB: Comité Européen du Béton;
LRFD: Load and Resistance Factor Design;
FIP: Fédération Internationale de la Précontrainte;
ASTM: American Society for Testing and Materials.

3. Design references and units

• AASHTO LRFD Bridge Design specifications (3rd edition, 2004);

• AASHTO LRFD Bridge Construction specifications (1stedition, 1998, with interim revisions 1999 &
2000);
• AASHTO LFD Bridge Design specifications (17th edition, 2002);
• Building Code Requirements for Structural Concrete (ACI 318-95);
• Guide Specifications for Seismic Isolation Design (AASHTO – 2nd edition – 2000).

The following documents can also be used:

• Geometric Design Manual for Dubai Roads - Dubai Municipality - Roads Department;
• British BD 60/94 “Design of Highway bridges for collision loads”;

The main units to be used for the design are: [t], [MN], [m], [mm], [MPa], [°C] and [°].

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4. Clearances

4.1 Clearance for road traffic

Minimum vertical clearance as per “Geometric design manual for Dubai roads” § 6.9 is 5.5 m. This is to
be provided across all trafficked lanes including any shoulder or edge strips. The maintained headroom of
5.3 m must be available at all times; it makes allowance of up to 0.2 m for pavement overlay which may
be applied during the maintenance of the road. Sag curve additional headroom shall also be accounted
for, particularly required when the traffic is parallel to the viaduct.

5. Construction methods
The superstructure consists of a cast in place post-tensioned concrete box girder.

The substructures consist of cast in place reinforced concrete piles, piers, abutments and retaining walls.

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6. Material characteristics

6.1 Concrete

f’c is the specified compressive strength of concrete at 28 days (based on tests of cylinders 150x300 mm
made and tested in accordance with AASHTO LRFD Bridge Construction specifications).

The concrete minimum strength requirements are:

• f’c = 37.5 MPa for prestressed concrete (f’c = 45 MPa on cubes);

• f’c = 33.3 MPa for reinforced concrete (f’c = 40 MPa on cubes);
• f’c = 25 MPa for mass concrete (f’c = 30 MPa on cubes).

Instantaneous Young modulus for normal weight concrete in MPa is calculated using the following
equation:
Ec  5375 f 'c

Long time (differed) modulus is taken equal to half the instantaneous modulus.

• Poisson’s ratio is taken as  = 0.2 for non cracked components;

• Poisson’s ratio is neglected for components expected to be subject to cracking.

Shear modulus of concrete, G, is calculated using the following equation:

Ec
G
21   

The coefficient of thermal expansion and contraction for normal weight concrete is taken as 1.08x10-5 /°C.

Scientific calculations of time dependent effects on concrete shall be considered when designing
prestressed bridges as stated below:

• For shrinkage calculations purposes, the average humidity ratio shall be taken at 70%;
• Creep calculations are done at horizon 2050 (= at 16500 days);
• Creep and shrinkage effects on concrete are taken into account in accordance with the
FIP-CEB 1990 regulation.

No provision shall be made for creep when the long-term modulus of elasticity of the concrete is
considered in the structural calculation.

6.2 Steel reinforcement

The specified yield strength of the steel reinforcement is f y = 460 MPa (grade 460 complying with the
requirement of BS 4449:1988 specification).

The modulus of elasticity of reinforcement Es for non-prestressed steel is taken as 200 000 MPa.

The nominal concrete clear cover (decorative finishes excluded) to be provided for steel reinforcement is:

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• For the viaduct superstructures: 50mm;

• For exposed faces of walls and piers: 50 mm;
• For backfilled areas above groundwater and capillary rise zones: 60 mm ;
• For piers and walls within the groundwater and capillary rise zone: 75mm;
• For exposed faces to marine environment or in direct contact with the soil: 100 mm;

This cover for foundations could be reduced when protective coating (such as bituminous coating,
waterproofing membranes…) is provided (depending on Manufacturer’s specifications).

6.3 Prestressing steel

The characteristics of the prestressing strands are:

• Nominal area: As = 140 mm² for T15 strands and 150 mm² for T15S strands;
• Nominal ultimate stress: f’s = 1860 MPa;
• Jacking stress: 1395 MPa (0.75 f’s);
• Nominal mass: 1.10 kg/m for T15 strands and 1.18 kg/m for T15S strands;
• Young modulus: Ep = 197 000 MPa.

Additional characteristics for the computation of the losses for internal tendons:

• Anchorage pull-in: g = 6 mm;

• Friction coefficient of tendon in duct: K = 0.003 m-1 and μ = 0.2 rad-1;
• Relaxation Loss at 1000 hours under 0.70 fpu: ρ1000 = 2.5 %.

And for external tendons:

• Anchorage pull-in: g = 6 mm;

• Friction coefficient of tendon in duct: K = 0 m-1 and μ = 0.15 rad-1 (polyethylene pipe);
• Relaxation Loss at 1000 hours under 0.70 fpu: ρ1000 = 2.5 %.

Supplementary requirements:

• Minimum concrete cover for prestressing ducts shall not be less than one half the diameter of the
duct or 80 mm;
• Minimum clear spacing of prestressing ducts shall be 40mm;
• Minimum concrete compressive strength at tensioning: 30 MPa;
• Maximum size of the aggregate shall be limited to 40/1.5=27mm.

Relaxation effects of prestressing shall be taken into account in accordance with the FIP-CEB regulation.

6.4 Elastomer

If reinforced elastomeric bearings are used, the following values of shear modulus shall apply:
• G = 0.9 MPa for static calculations (long term);
• G = 1.2 MPa for earthquake calculations;
• G = 1.8 MPa for calculations under short term loading (Live load).

The nominal hardness of the elastomer shall not be greater than 60.

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7. Load cases

7.1 Dead load (DL)

For assessment of Dead Load, the following mass density shall be considered:

• Reinforced concrete 2.5 t/m3;

• Plain concrete 2.4 t/m3;
• Backfill 2.0 t/m3;
• Unit weight of soil above water table 1.9 t/m3;
• Unit weight of soil below water table 0.9 t/m3.

7.2 Superimposed dead loads (SIDL)

For assessment of SIDL, the following mass density shall be considered:

• Wearing surface (50 mm asphaltic concrete, 2400 kg/m3 density) 0.12 t/m2;
• Utilities and services 0.075 t/m2;
• Sidewalk (plain concrete) 2.30 t/m3;
• Lateral barrier 0.51 t/m;
• Pedestrian railing 0.1 t/m/side.

7.3 Live load

7.3.1 Design lanes

Number of design lanes should be taken equal the integer part of the ratio w/3,6, where w is the clear
roadway width between curbs and/or barriers. In cases where traffic lanes are less than 3,6 m wide, the
number of design lanes shall be equal to number of traffic lanes.

In order to account for the probability of simultaneous lane occupation by the design load, the number of
loaded lanes shall be multiplied by the presence factor detailed in the next table:

Number of loaded lanes 1 2 3 >3

Multiple presence factor 1.2 1 0.85 0.65

For the purpose of determining the number of lanes when the loading condition includes the pedestrian
loads combined with one or more lanes, the pedestrian loads may be taken to be a loaded lane.

7.3.2 Design vehicular live load (LL)

The vehicular live load, designated HL-93, consist of a combination of design truck (or design tandem)
and design lane load.

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Each loaded design lane shall be occupied by either one 1 design truck or one tandem, coincident with the
lane load. The effects of the axle sequence and the lane load are superposed in order to obtain extreme
effects.

The HL-93 loads are multiplied by 1.5 in order to take into account the particularities of Dubai roadway
traffic.

7.3.2.1 Design truck

The weights (already multiplied by 1.5) and spacing of axles and wheels shall be as specified in the next
scheme. This load shall be multiplied by the dynamic impact factor.

Longitudinal distance between the two rear axles shall be taken equal to 4.3 m.

The design truck shall be positioned transversally such that the center of any wheel load is not closer
than 0,3 m from the face of the curb or railing when designing deck overhang; and 0,6 m from the edge of
the design lane for designing all other components.

Where sidewalk is not separated from the roadway by a crashworthy traffic barrier, consideration should
be given to the possibility that vehicles can mount the sidewalk.

7.3.2.2 Design tandem

The design tandem shall consist of a pair of 165 kN
axles (1.5 coefficient already included) spaced 1.2 m
apart. The transverse spacing of wheels shall be
taken as 1.8 m.

This load shall be multiplied by the dynamic impact

factor.

The design tandem shall be positioned transversally

such that the center of any wheel load is not closer
than 0.3 m from the face of the curb or railing when
designing deck overhang; and 0,6 m from the edge
of the design lane for designing all other
components.

1
For both negative moment and reaction at interior piers, 90% of the effect of two design trucks spaced (a
minimum) of 15 m between the lead axle of one truck and the rear axle of the second truck, combined with 90% of
the design lane load.

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7.3.2.3 Design lane load

The design lane load shall consist of a load of 13.95 kN/m (already multiplied per 1.5) uniformly
distributed in the longitudinal direction. Transversally, the load shall be assumed to be uniformly
distributed over a width of 3 m.

Only those areas or parts of areas that contribute to the same extreme being sought should be loaded.
The loaded length should be determined by the points where the influence surface meets the centreline of
the design lane. This condition has to be automatically integrated in the computing model.

The lane load is not interrupted to provide space for the axle sequences of the design tandem or the
design truck; interruption is needed only for patch loading patterns to produce extreme force effects.

The force effects from the design lane load shall not be subject to a dynamic load impact.

7.3.2.4 Tire contact area

Tire contact area is needed when investigating local effects or deck transverse flexure, due to the design
truck or the design tandem.

In case of a wheel consisting of one or two tires, the contact area shall be assumed to be a single
rectangle, whose width is 0.51 m and whose length is 0.25 m. Consider then a diffusion angle of 45°
through the wearing surface and the concrete to centroid of the slab.

For the distribution of wheel loads through earth fills, the distribution of live load shall be neglected where
the depth of fill is less than 0.6 m.

Where the depth of fill exceeds 0.6 m, wheel loads may be considered to be uniformly distributed over a
rectangular area with sides equal to the dimension of the tire contact area, and increased by either 1.15
times the depth of the fill in select granular backfill, or the depth of the fill in all other cases.

Where such areas from several wheels overlap, the total load shall be uniformly distributed over the area.

7.3.3 Pedestrian live load (PL)

A pedestrian load of 3.6 kN/m² shall be applied to all sidewalks wider than 0.6 m and considered
simultaneously with the vehicular design live load.

When the loading condition includes the pedestrian loads combined with one or more vehicle traffic lanes,
the pedestrian loads may be taken to be a loaded lane.

7.3.4 Dynamic Impact (IM)

The static effects of the design truck or tandem, other than centrifugal and braking forces, shall be
increased by the percentage of dynamic impact.

The dynamic impact shall not be applied to pedestrian loads or to the design lane loads.

7.3.4.1 Longitudinal dynamic impact

The percentage of dynamic impact is detailed below for each component:
• Deck expansion joints: 75 %,
• All other components:
- All limit states: 33 %.

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Dynamic impact shall not be applied for foundation components that are entirely below ground level, and
for retaining walls that are not subject to vertical reactions from the superstructure.

The dynamic impact for buried structures, in percent, shall be taken as:

IM = 33 (1-0.4DE) ≥ 0%

Where:
• DE : minimum depth of earth cover above the structure (m).

7.3.4.2 Transverse dynamic impact

Transverse dynamic impact can be taken equal to the longitudinal impact (33%).

7.3.5 Centrifugal forces (CE)

Centrifugal forces shall be taken as the product of the axle weights of the design truck or tandem and the
factor C, taken equal to:

4 v2
C
3 gR

Where:
• v: highway design speed (variable with a maximum of 80 km/h=22.22m/s) (m/s);
• g: gravitational acceleration (m/sec²);
• R: radius of curvature traffic lane.

Lane load is neglected in computing the centrifugal force, as the spacing of vehicles at high speed is
assumed to be large, resulting in a low density of vehicles following and/or preceding the design truck.

Centrifugal forces shall act radially (perpendicularly to the traffic lanes) at a distance of 1.8 m above the
roadway surface.

The multiple presence factors specified in §7.3.1 shall apply.

7.3.6 Braking force (BR)

The braking force shall be taken as the greater of:

• 25% of the axle weights of the design truck or design tandem or;
• 5% of the design truck plus lane load or 5% of the design tandem plus lane load.

This braking force shall be placed in all design lanes which are considered to be loaded, and which are
carrying traffic headed in the same direction.

These forces shall be assumed to act horizontally at a distance of 1.8 m above the roadway surface, in
either longitudinal direction to cause extreme forces effects.

The multiple presence factors specified in §7.3.1 shall apply.

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7.4 Prestressing force (PS)

Prestressing losses due to friction, creep, shrinkage and taking into account the construction stages…
shall be considered in computation models.

Prestressing force shall be separated into direct (isostatic), and secondary (hyperstatic) prestress effects
when computing flexural strength of the structure.

Secondary forces from post-tensioning are also included in the EL load case.

7.5 Temperature (T)

Provisions shall be made for stresses and movements resulting from temperature variations: uniform
variation (Tu) and thermal gradient (Tg). The expected values are:

• Temperature range: 75 °C;

• Temperature rise: +43 °C
• Temperature fall: -32 °C
• Thermal gradient: 20 °C

For thermal expansion coefficient of concrete, please refer to section 6.1.

7.6 Time-dependent effects – Creep (CR), shrinkage (SH), relaxation

Creep calculations shall be done at horizon 2050 (at 16500 days).

Structural calculations shall take into account the time dependent effects on materials, i.e. creep,
shrinkage of concrete and prestressing losses (instantaneous and long term losses).

Average ambient relative humidity shall be equal to 70%.

7.7 Differential settlement (SE)

For the design of continuous structures a differential settlement of 5 mm shall be considered as a short
term settlement. This value may be modified when further geotechnical data become available.

Combination of differential settlements shall be considered on one or more piers in order to produce the
maximum forces in the deck.

7.8 Wind

The superstructures shall be designed for wind-induced horizontal loads. Wind-induced vertical drag
loads shall also be considered when checking the stability of the deck.

The wind should be considered to act in a direction such that the resulting force effects are maximised on
a structure in plan. For a structure that is straight in plan, the wind direction should be assumed to be
perpendicular to longitudinal axis.

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The basic wind speed is taken equal to 160 km/h.

7.8.1 Wind load on structure (WS)

The net exposed area is the area as seen in elevation including barriers where relevant.

The intensity of transverse horizontal wind load onto the superstructure is equal to 0.24 t/m² applied on
the net exposed area. Longitudinally the intensity decreases to 0.09 t/m².

The overturning upward force shall be applied at quarter point (transversally) with an intensity of 0.1 t/m².
The exposed plan area to be considered is the net area of the structure as seen in plan from above.

The intensity of horizontal wind load onto the substructure (applied on the net exposed area) is 0.19 t/m²
applied in any direction.

The substructure should be designed for wind-induced loads transmitted from the superstructure and
wind loads acting directly on the substructure. Loads for wind directions both normal and skewed to the
longitudinal centreline of the superstructure shall be considered.

7.8.2 Wind load on live load (WL)

When vehicles are present, the design wind pressure shall be applied to both structure and vehicles.
Wind pressure on vehicles shall be represented by an interruptible, moving force of 1.5 kN/m acting
normal to, and 1.8 m above, the roadway and shall be transmitted to the structure.

7.9 Earthquake (EQ)

Unless otherwise specified by Nakheel for this project, structures are considered as “essential” bridges
(as per AASHTO LRFD section 3.10.3). These provisions need not to be applied to completely buried
structures.

7.9.1 Site coefficient and seismic zone:

Based on adjacent projects the soil profile type is expected to be between types II and III. Regarding the
site irregularity the site coefficient shall be between 1.2 and 1.5.

An average value of 1.35 will be used for the site coefficient (S).

Dubai is situated in seismic zone 2 with an acceleration coefficient of A = 0.12.

7.9.2 Monomodal Analysis:

The method of analysis that should be used for multispan regular and essential bridges is the single
mode elastic method.

The Elastic Seism Response Coefficient (Csm) is calculated as follows:

Csm = (1.2 x A x S) / (Tm 2/3) ≤ 2.5 x A

Where:

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• A: Seismic Zone coefficient = 0.12;

• S: Site coefficient = 1.35;
• Tm: Period of fundamental vibration mode, (sec).

The determination of the period of vibration T m, should be based on the nominal, unfactored mass of the
component or structure.

The elastic seismic response coefficient Csm, shall be used to calculate the equivalent uniform seismic
load from which seismic force effects are found.

Uniform seismic load is found my multiplying the seismic response coefficient by the permanent loads (DL
+ SIDL).

Seismic loads shall be assumed to act in any lateral direction: seismic forces are calculated for
longitudinal and transverse directions (EQx and EQy).

7.9.3 Response Modification Factor (R):

Elastic seismic force as calculated with Csm shall be divided by R for both orthogonal axes of the
substructure:

• R = 1.5, for wall type piers;

• R = 2, for single columns;
• R = 3.5 for multiple column bents;
• R = 1, foundations and connections.

7.9.4 Seismic Direction Combination:

The seismic forces effects on each of the principal axes of a component resulting from analyses in the
two perpendicular directions, shall be combined as follows:

• ±EQx ± 0.3 EQy

• ±EQy ± 0.3 EQx

The axial load (substructure) shall be taken as that resulting from the appropriate load combination with
the axial load, if any, associated with plastic hinging taken as “EQ”.

7.10 Collision load on piers or decks (CL)

7.10.1 Vehicular collision

a) Unless the piers are protected as specified by AASHTO LRFD § 3.6.5.1, the design shall consider an
equivalent static force of 1800 kN, assumed to act in any direction in a horizontal plane, at a distance of
1.2 m above ground.

For a vehicular collision against the deck, British Code BD 60/94 “Design of Highway bridges for collision
loads” shall be the basis of the design.

b) The force corresponding to a collision load on the concrete barriers, should be taken equal to 240 kN
applied transversally at 0.81 m above the roadway surface.

c) Normal Collision loads on bridge superstructure over highway are defined as follows:

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• 250 kN as a load normal to the carriageway below

• 500 kN as a load parallel to the carriageway below,

The above loads shall be applied on the soffit in any inclination between the horizontal and the vertical.

7.11 Earth pressure (EH)

Lateral earth pressure shall be assumed to be linearly proportional to the depth of earth and taken as:

p  k s gz  10 3

Where:
• p: lateral earth pressure (MPa);
• k : coefficient of lateral earth pressure taken as ko, for walls that do not deflect or move, ka for
walls that deflect or move sufficiently to reach minimum active conditions or k p for walls that
deflect or move sufficiently to reach a passive condition;
• γs: density of soil (t/m3);
• z: depth below the surface of earth (m);
• g: gravitational acceleration (m/s²).

For normally consolidated soils, vertical wall, and level ground, the coefficient of at-rest lateral earth
pressure may be taken as:

ko = 1-sinΦ’f

Where:
• Φ’f : effective friction angle of soil;
• Ko: coefficient of at-rest lateral earth pressure.

For overconsolidated soils, the coefficient of at-rest lateral earth pressure may be assumed to vary as a
function of the overconsolidated ratio or stress history, and may be taken as:

ko = (1-sinΦ’f) (OCR)sinΦ’f

Where:
• OCR: overconsolidated ration.

ka can be determined according to § 3.11.5.3 of AASHTO LRFD and k p with § 3.11.5.4.

7.12 Earth loads (EH)

In lieu of a more refined analysis, the total unfactored earth loads W E acting on the culvert may be taken
as:

For embankement installations: WE  gFe s Bc H

In which:

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H
Fe  1  0.2
Bc

For trench installations: WE  gFt  s Bc H

In which:
C d Bd2
Ft   Fe
HBc
Where:

• g: acceleration of gravity (m/s²);

• W E: total unfactored earth load (kN/m);
• Bc: outside width of culvert as specified in the next figures;
• H: depth of backfill as specified in the next figures;
• Fe: soil-structure interaction factor for embankment installation specified herein;
• Ft: soil-structure interaction factor for trench installations specified herein;
• γs: Density of backfill (t/m 3);
• Bd horizontal width of trench as specified in the next figures;
• Cd: a coefficient specified in the graphic below.

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Fe shall not exceed 1.15 for installations with

compacted fill or 1.4 for installations with
uncompacted fill.

For wide trench installations where the trench

width exceeds the horizontal dimension of the
culvert across the trench by more than 0.3 m, F t
shall not exceed the value specified for an
embankment installation.

7.13 Water loads (WA)

Static pressure of water shall be assumed to act

perpendicular to the surface that is retaining the
water. Pressure shall be calculated as the
product of the height of water above the point of
consideration, the density of water, and gravity.

Design water levels for various limit states shall

be investigated.

Buoyancy shall be considered to be an uplift

force, taken as the sum of the vertical
components of static pressures, acting on all
components below design water level.

The stream pressure is neglected because the

water flow is very low.

7.14 Pedestrian railing loads

The posts of pedestrian railings shall be designed for a concentrated design live load (P LL) applied
transversally at the center of gravity of gravity of the upper longitudinal element:

PLL=0.89+0.73L [kN]

Where L is the longitudinal spacing of posts (3 m for R2 and 5 m for R5).

Design loads, shall not be applied simultaneously with the vehicular impact loads.

7.15 Construction loads (C)

For the cast in situ decks, no particular construction loads are to be considered.

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8. Load combinations
This section specifies the load factors, strength reduction factors, and load combinations to be used in
serviceability and strength design according to AASHTO LRFD.

Group loading combinations are given by:

Q   i  i Qi

Where:

• Q : Total factored force effect;

•  i : Load modifier equal to 1.00;
• Qi : Force effects from loads;
•  i : Load factors specified in the next tables.

According to AASHTO LRFD section 3.4.1, the components and connections of a bridge shall satisfy the
following equation:

Q  Rn

Where:

•  : Resistance factor specified in § 9;

• Rn : Nominal resistance of the section;
• Q : Factored extreme force effects specified at each of the limit states.

The limit states considered in AASHTO LRFD are:

• Strength limit state;

• Extreme limit state;
• Service limit state.

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The AASHTO LRFD load factors to be taken into account in combinations are given in the following table:

Load DL SIDL LL
( 3) WA WS WL Tu
( 4) Tg SE
( 4) Eq CL
combination EL IM CR
EH BR SH
CE
PL
Limit state
0.9/1.25 0.65/1.5
Strength-I 1.75 1 (1)
( 2) ( 2) 0.5/1.2
0.9/1.25 0.65/1.5
Strength-III 1 1.4 (1)
( 2) ( 2) 0.5/1.2
0.65/1.5
Strength-IV 1.5 1 (1)
( 2) 0.5/1.2
0.9/1.25 0.65/1.5
Strength-V 1.35 1 0.4 1 (1)
( 2) ( 2) 0.5/1.2
0.9/1.25 0.65/1.5
Extreme-event-I ( 2) ( 2) 0.5 1 1

0.9/1.25 0.65/1.5
Extreme-event-II ( 2) ( 2) 0.5 1 1

Service-I 1 1 1 1 0.3 1 (1) 0.5/1(5) 0.5

1/1.2
Service-III 1 1 0.8 1 (1) 0.5/1(5) 0.5
1/1.2
Service-IV 1 1 1 0.7 (1) 0.5
1/1.2

With: Notes:
BR: Braking forces (1)
: The reduced value will be selected when
CR: Creep calculating force effects other than displacements;
CE: Centrifugal force ( 2)
CL: Collision load on pier/deck : The factors shall be selected in order to
DL: Dead load of structural components produce the total extreme factored force effect. For
EH: Earth loads each load combination, both positive and negative
EL: Accumulated locked-in force effects resulting extremes shall be investigated;
( 3)
from the construction process, including the : Combination of loaded lanes shall be
secondary forces from post-tensioning investigated to produce maximum effects;
Eq: Ultimate Earthquake ( 4)
: For continuous units only;
IM: Dynamic Impact (used to compute the (5)
: 1 when live load is not considered and 0.5
Coefficient of Dynamic Amplification)
when live load is considered
LL: Live loads
PL: Pedestrian live load
SE: Differential settlement
SH: Shrinkage
SIDL: Superimposed dead loads
Tg: Temperature gradient loading
Tu: Temperature uniform variation loading
WA: Water loads
WS: Wind load on structures
WL: Wind load on live load

Page 20 / 36
DESIGN CRITERIA

9. Structural checking
Structural components shall be proportioned to satisfy the requirements at all appropriate service,
strength, and extreme event limit states.

9.1 Superstructures

Prestressed and partially prestressed concrete structural components shall be investigated for
stresses for each stage that may be critical during construction, stressing and erection as well as
during the service life of the structure of which they are part.

Stress concentrations due to prestressing or other loads and to restraints or imposed deformations
shall be considered.

9.1.1 Service limit state

9.1.1.1 Temporary stresses before losses:

The compressive stress limit for post-tensioned concrete components shall be 0,6 f’c.

In precompressed tensile zone (any region in which prestressing causes compressive stresses and
service load effects cause tensile stresses) without bounded reinforcement no tensile stress is
allowed.

Tension stress below 0.63 f ' c is allowed in areas with bonded reinforcement sufficient to resist
tensile force in the concrete computed assuming an uncracked section, where reinforcement is
proportioned using a stress of 0.5 fy, not to exceed 210 MPa.

9.1.1.2 Stresses at service limit state after losses:

Maximum compressive stresses allowed in case of cast in situ structures:

• Under only permanent loads (prestressing included) : 0.45xfc’;

• Under live load and one half the sum of effective prestress and permanent loads: 0.4f’c;
• Under permanent loads and transient loads : 0.6f’c.

Concrete tensile stress:

• For components with bonded reinforcement that are subjected to severe corrosive conditions
tensile stress may reach 0.25 f 'c .

Maximum compressive stress for reinforced concrete is 0.6xfc’.

9.1.1.3 Crack control:

The best crack control is obtained when the steel reinforcement is well distributed over the zone of
maximum concrete tension. Several bars at moderate spacing are more effective in controlling
cracking than one or two larger bars of equivalent area.

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DESIGN CRITERIA

The crack width at service limit state is proportional to steel stress. However other significant variables
reflecting steel detailing were found to be the thickness of concrete cover and the area of concrete in
the zone of maximum tension surrounding each individual reinforcing bar.

The following equation is expected to provide a distribution of reinforcement that should control
flexural cracking:

Z
f sa   0,6 f y
d c A1 / 3
Where:

• dc: depth of concrete measured from extreme tension fiber to center of bar located closest
thereto (in mm), the distance of clear cover used to compute d c shall not be taken to be
greater than 50 mm;
• A: area of concrete having the same centroid as the principal tensile reinforcement and
bounded by the surfaces of the cross-section and a straight line parallel to the neutral
axis, divided by the number of bars (in mm²);
• Z: crack width parameter equal to 23 000 MPa for members in severe exposure
conditions.

9.1.2 Strength limit state

The strength limit state issues to be considered shall be those of strength and stability. Factored
resistance shall be the product of nominal resistance per the resistance factor.

9.1.2.1 Resistance factors:

Resistance factor  according AASHTO LRFD §5.5.4.2.1. shall be taken as:

•  = 0.90 for flexure and tension of reinforced concrete;

•  = 1.00 for flexure and tension of prestressed concrete;
•  = 0.90 for shear and torsion;
•  = 0.75 for axial compression with spiral or ties (*);
•  = 0.70 for bearing on concrete;
•  = 0.70 for compression in strut-and-tie models;
•  = 0.80 for compression in anchorage zones;
•  = 1.00 for tension in steel in anchorage zones.

(*) For low values of axial compression,  may be increased linearly to the value for flexure as the
factored axial load decreases from 0.10 f’c Ag to 0 (f’c being the specified compressive strength of
concrete at 28 days and Ag being the gross area of the section).

9.1.2.2 Nominal flexure resistance

The extreme factored bending moment Mu due to the external loading shall include secondary effects
of the prestressing (part of EL) and shall follow this relation:

Mu  Mn

Where Mn is the nominal resistance of the considered section.

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DESIGN CRITERIA

The box girders can be considered as a flanged section subjected to flexure if the compression flange
depth is less than c. The nominal flexural resistance may be taken as:

 a  a  a  a hf 
M n  Aps f ps  d p    As f y  d s    A' s f ' y  d ' s    0.85 f ' c b  bw 1h f   
 2  2  2 2 2 

Where:

• Aps : area of prestressing steel (m²);

• fps : average stress in prestressing steel at nominal bending resistance (MPa);
• dp : distance from extreme compression fiber to the centroid of prestressing tendons (m);
• As : area of nonprestressed tension reinforcement (m²);
• fy : specified yield strength of reinforcing bars (MPa);
• ds : distance from extreme compression fiber to the centroid of nonprestressed tensile
reinforcement (m);
• A’s : area of compression reinforcement (m²);
• f’y : specified yield strength of compression reinforcement (MPa);
• d’s : distance from extreme compression fiber to the centroid of compression reinforcement
(m);
• f’c : specified compressive strength of concrete at 28 days (MPa);
• b : width of compression flange (m);
• bw : width of web (m);
• β1 : stress block factor ( 0.78 for f’c = 37.5 MPa);
• a : depth of equivalent rectangular stress block equal to c β1 (m);
• c: distance from extreme compression fiber to the neutral axis (m);
• hf : compression flange depth (m).

If the compression flange is not less than c, the following equation shall be used (rectangular
behaviour):

 a  a  a
M n  Aps f ps  d p    As f y  d s    A' s f ' y  d ' s  
 2  2  2

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DESIGN CRITERIA

For components with bonded tendons:

 c 
f ps  f pu 1  k 
 dp 
 
Where fpu is the specified tensile strength of prestressing steel (1860 MPa).

We start by considering a rectangular behaviour of the section:

Aps f pu  As f y  A' s f ' y

c
0.85 f 'c 1bw  kAps f pu d p

Then if c>hf, we consider T section behaviour:

Aps f pu  As f y  A' s f ' y 0.851 f ' c b  bw h f

c
0.85 f ' c 1bw  kAps f pu d p

The stress level in compressive reinforcement shall be investigated by multiplying the compression
stress in the concrete (0.85xf’c) per the ratio Ea/(0.5xEc), and if the compressive reinforcement has
not yielded, the calculated stress shall be used instead of f’y.

f’y = 0.85 x 37.5 x 200 000/(0.5x32 900) = 388 MPa

k can be calculated with the following equation:

 f py 
k  21.04  
 f 
 pu 
With fpy equal to yield strength of prestressing steel (0.9xf pu = 1674 MPa). Then k = 0.28.

We can summarize the calculation methodology with the following manner:

With k and f’y  Calculate c  Calculate fps  Calculate Mn

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DESIGN CRITERIA

For components with unbonded tendons:

dp c
f ps  f pe  6300   f py
 l e 

Where fpe is the effective stress in prestressing steel after all losses and f py is the yield strength of
prestressing steel (1674 MPa).

 2li 
In which: l e   
 2  Ns 

With:

• le: effective tendon length (m);

• li: length of tendon between anchorages (m);
• Ns: number of support hinges crossed by the tendon between anchorages or discretely
bonded points.

For rectangular section behaviour:

Aps f ps  As f y  A' s f ' y

c
0.85 f ' c 1bw

For a T section behaviour:

Aps f ps  As f y  A' s f ' y 0.851 f ' c b  bw h f

c
0.85 f ' c 1bw

In order to solve for the value of fps, the equation of force equilibrium at ultimate is needed. Thus, two
equations with two unknown (fps and c) need to be solved simultaneously to achieve a close-form
solution.

A first estimate of the average stress in unbonded prestressing steel may be made as:

f ps  f pe  103 ( MPa )

We can summarize the calculation methodology with the following manner:

Iterative calculation
if there is a large difference

Estimate fps Calculate c Recalculate fps Recalculate c Calculate Mn

f’y le

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DESIGN CRITERIA

For components with bonded and unbonded tendons:

We proceed with the following manner:

A first estimate of the average stress in unbonded prestressing steel may be made as:

f ps2  f pe2  103 ( MPa )

(Index 2 is for unbonded prestressing and index 1 is for bonded prestressing).

Then we calculate a first value of c with:

For rectangular section behaviour:

Aps1 f pu  Aps2 f ps2  As f y  A' s f ' y

c
0.85 f ' c 1bw  kAps1 f pu d p1

For a T section behaviour:

Aps1 f pu  Aps2 f ps2  As f y  A' s f ' y 0.851 f ' c b  bw h f

c
0.85 f ' c 1bw  kAps1 f pu d p1

Then we calculate f’y (194 MPa), le and a second time fps2:

 d p2  c 
f ps2  f pe2  6300   f py
 le 

With the new calculated value of fps2, we recalculate c and if there is not a significant difference with
the first calculation, we continue to next calculation step; if not, we make an iterative calculation
(recalculate fps2 with the new value of c).

When c is fixed we can calculate fps1 with k = 0.28:

 c 
f ps1  f pu 1  k
 d p1 


And finally the nominal flexural resistance can be taken as:

 a  a  a
M n  Aps1 f ps1  d p1    A ps2 f ps2  d p 2    As f y  d s  
 2  2  2
 a  a hf 
 A' s f ' y  d ' s    0.85 f ' c b  bw 1 h f   
 2 2 2 

And for rectangular section behaviour:

 a  a  a  a
M n  Aps1 f ps1  d p1    Aps2 f ps2  d p 2    As f y  d s    A' s f ' y  d ' s  
 2  2  2  2

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DESIGN CRITERIA

Limits for reinforcement:

The maximum amount of prestressed and non prestressed reinforcement shall be such that:

c
 0.42
de

In which:

Aps f ps d p  As f y d s
de 
Aps f ps  As f y

Where:
• c: distance from extreme compression fiber to the neutral axis (m);
• de: corresponding effective depth from the extreme compression fiber to the centroid of the
tensile reinforcement (m).

If the first equation is not satisfied, the section shall be considered overreinforced. Overreinforced
prestressed members may be used only if it is shown that sufficient ductility of the structure can be
achieved.

The nominal flexural resistance for an overreinforced section may be computed from the following
expressions:

Rectangular section behaviour:  

M n  0.361  0.0812 f 'c bd e2

Flanged section behaviour:  

M n  0.361  0.0812 f 'c bw d e2  0.851 f 'c b  bw h f d e  0.5h f 

Minimum reinforcement:
For investigating the minimum reinforcement, the amount of prestressed and nonprestressed
reinforcement shall be adequate to develop a factored flexural resistance at least equal to lower value
1.2 times the cracking moment (Mcr) or 1.33 times the factored moment required by the applicable
strength load combinations:

Mn > Min(1.2 Mcr; 1,33 Mu)

Mcr is determined on the basis of elastic stress distribution and the modulus of rupture f r of the
concrete:

M cr  S c  f r  f cpe 

Where:

• fr: modulus of rupture of the concrete equal to 0.63 f ' c (MPa);

• fcpe: compressive stress in concrete due to effective prestress forces only at extreme fiber
of section where tensile stress is caused by externally applied loads (MPa);

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DESIGN CRITERIA

• Sc: section modulus for the extreme fiber of the composite section where tensile stress is
caused by externally applied loads (m 3).

9.1.2.3 Shear
The nominal shear resistance Vn, shall be determined as the lesser of:

Vn = Vc + Vs + Vp

Vn = 0.25 f’c bv dv + Vp

And satisfy:

Vn > Vu

In which:
Vc = 0.083 β f ' c bv dv

Av f y d v cot 
Vs 
s
Where:

• bv : effective web width taken as the minimum web width measured parallel to the neutral axis
within the depth dv (m) ;
• dv: effective shear depth taken as the distance, measured perpendicular to the neutral axis,
between the resultant of the tensile and compressive forces due to flexure; it need not to be
taken less than the greater of 0.9 de or 0.72 h (m);
• de: effective depth from extreme compression fiber to the centroid of the tensile force in the
tensile reinforcement (m);
• h: overall depth of the member (m);
• s: spacing of stirrups (m);
• β: factor indicating ability of diagonally cracked concrete to transmit tension;
• θ: angle of inclination of diagonal compressive stresses (°);
• Av: area of shear reinforcement within a distance s (m²);
• Vs: shear resistance provided by reinforcement (MN);
• Vc: nominal shear resistance provided by tensile stresses in the concrete (MN);
• Vp: component in the direction of applied shear of effective prestressing force; positive if
resisting the applied shear (MN).

In determining web width at a particular level, one-half the diameter of ungrouted ducts or one-quarter
the diameter of grouted ducts at that level shall be substracted from the web width.

The shear stress on the concrete vu shall be determined as:

Vu  V p
vu 
bv d v

The required transverse reinforcement (in m² within a distance s) shall have an area at least equal to:

bv s
Av min  0.083 f ' c
fy

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DESIGN CRITERIA

For sections containing at least the minimum amount of transverse reinforcement, the values of θ and
β (in this order) shall be as specified in the next table:

In using the above table, εx shall be taken as the calculated longitudinal strain at the mid-depth of the
member when the section is subjected to M u, Nu and Vu as shown below:

If the section contains at least the minimum transverse reinforcement εx can be determined as:

 Mu 
  0.5 N u  0.5Vu  V p cot   Aps f po 
x   v 
d
2E s As  E p A ps 

With:
• Aps: area of prestressing steel on the flexural tension side of the member (m²);
• As: area of nonprestressed steel on the flexural tension side of the member (m²);
• fpo: for usual levels of prestressing, a value of 0.7 fpu can be used (MPa);

Page 29 / 36
DESIGN CRITERIA

• Nu: factored axial force, taken as positive if tensile and negative if compression (MN);
• Mu: factored moment, taken as positive quantity, but not to be taken less than V udv (MNm);
• Vu: factored shear force taken as positive quantity (MN).

As the value of θ has not been yet extracted from the above table, it is necessary to perform an
iterative calculation by supposing for example θ = 28° and the initial value of ε x not be taken greater
than 0.001.

We can summarize the calculation methodology in the following manner:

Iteration if large difference

Assume θ Calculate εx Calculate vu/f’c  New value of θ Calculate Vs & Vc Calculate Vn

AASHTO LRFD 3rd edition is known to underestimate the shear reinforcement: ultimate reinforcement
is ok but service behaviour is not (excessive cracking).

For this reason, shear reinforcement shall be also estimated with AASHTO 17 th edition (with its
specific load combination: 1.3[DL+SIDL] + 2.17[LL+I]) and the maximum shall be used.

Members subject to shear shall be designed so that: (AASHTO 9.20.1.3):

Vu   Vc  Vs 

Where:
• Vu: factored shear force including reduction due to prestress;
• Vc: nominal shear stress provided by concrete;
• Vs: nominal shear stress provided by web reinforcement;
• : strength capacity reduction = 0.9 for shear (AASHTO 9.14).

The reaction of the applied loads introduces compression into the end region of the member. Sections
located at distance less than h/2 from the face of the support may be designed for the same shear as
that computed at a distance h/2. In our case h/2 is variable (AASHTO 9.20.1.4)

Minimum shear strength provided by concrete shall be taken equal to (AASHTO 9.20.2.2):

Vc  0.14 f 'c b' d

• f’c : specified compressive strength of concrete;

• b’ : width of the webs ;
• d : distance from extreme compressive to centroid of prestressing steel.

Shear strength provided by web reinforcement (AASHTO 9.20.3.1)

Av f sy d
Vs 
s
Where:
• Av: area of web reinforcement within a distance s ;
• fsy: yield stress of non-prestressed conventional reinforcement in tension.

Vs shall not be taken greater than:

Page 30 / 36
DESIGN CRITERIA

VsMAX  0.664 f 'c b' d .

Cumulating longitudinal shear reinforcement and transverse flexure reinforcement

When computing web reinforcement due to deck transverse flexure (A trans), the found reinforcement
should be cumulated with web shear and torsion reinforcement (Ashear and Atorsion) to find the total web
reinforcement ( Aweb).

Aweb should be taken as the greater value of the following values:

Aweb1 = (Ashear+ Atorsion) +0.5 Atrans

Aweb2 = 0.5 (Ashear+ Atorsion) + Atrans

Aweb3 = 0.7 (Ashear+ Atorsion) + 0.7Atrans

9.1.2.4 Torsion
Torsional effects shall be investigated where:

Tu  0.25Tcr

In which:

Acp2 f pc
Tcr  0.328 f ' c 1
pc 0.328 f ' c

Where:

• Tu: factored torsional moment (MNm);

• Tcr: torsional cracking moment (MNm);
• Acr: total area enclosed by outside perimeter of cross-section (m²);
• pc: length of the outside perimeter of the concrete section, wings shall be neglected (m);
• fpc: compressive stress in the concrete after prestress losses at the centroid of the section
or at the junction of the web and flange where the centroid lies in the flange (MPa).

The factored torsional resistance Tn, shall satisfy:

Tn > Tu

The nominal torsional resistance shall be taken as:

2 Ao At f y cot 
Tn 
s
Where:

• Ao: area enclosed by shear flow path, including any area of holes therein (m²);
• At: area of one leg of closed transverse torsion reinforcement (m²);
• θ: angle of crack as determined in accordance with the provisions of shear with the
following modifications:

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DESIGN CRITERIA

Usually the loading that causes the highest torsion differs from the loading that causes the highest
shear. Although it is sometimes convenient to design for the highest torsion combined with the highest
shear, it is only necessary to design for the highest shear and its concurrent torsion, and the highest
torsion and its concurrent shear.

For combined shear and torsion, εx shall be determined using the equation of § 9.1.2.3 with Vu
replaced by:

2
 0.9 p hTu 
Vu  Vu   
 2 Ao 

The angle θ shall be as specified in table of § 9.1.2.3 with the shear vu for box sections taken as:

Vu  V p Tu p h
vu  
bv d v Aoh

Where:

• ph: perimeter of the centreline of the closed torsion reinforcement (m);

• Aoh: area enclosed by centreline of exterior closed transverse torsion reinforcement
including area of any holes (m²).

The transverse reinforcement shall not be less than the sum of that required for shear and for the
concurrent torsion.

The longitudinal torsion reinforcement shall be proportioned to satisfy:

2 2
M 0.5 N u  Vu   0.45 p hTu 
As f y  Aps f ps  u   cot    0.5Vs  V p    
d v     2 Ao 

We can summarize the calculation methodology with the following manner:

Iteration

Calculate new vu & VuSuppose θ Calculate εx New value of θ Calculate Tn Calculate As

9.1.2.5 Local zones

1) For post-tensioned elements, anchorage zone reinforcement shall be provided as specified in
AASHTO LRFD § 5.10.4 & § 5.10.9. Maximum jacking force shall be multiplied per 1.2.

2) Interface shear transfer shall be considered across a given plane at an existing or potential crack,
or at an interface between two concretes cast at different times according to AASHTO LRFD § 5.8.4.

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DESIGN CRITERIA

For example, corner equilibrium and extremity

bearing location can be checked with the
following manner:
Prec i+1
Avf
Vn  c Acv   f y   Pc  min( 0.2 f Acv ;5.5 Acv )
'

sin 2 
c
Prec i Prec i //
i
Pc   P  R 
rec

app
j 1
i
  Prec
Prec i
// //
Rapp
Avf i  
f y     Prec
j 1
 Vn  cAcv    
 Rapp 
sin 2   
 j 1 
 // i

 Rapp   Prec
//

 i   
sin 2  Rapp//
 Avf    cAcv     Prec  Rapp 
j 1 

    f
 j 1  y
 
  Rapp
Rapp

With:
• Vn: nominal shear resistance (MN);
• Acv: area of concrete engaged in shear transfer (m²);
• Avf: area of shear reinforcement crossing the shear plane (m²);
• c: cohesion factor equal to 1 MPa for concrete placed monolithically;
• μ: friction factor equal to 1.4 for normal density concrete placed monolithically;
• Pc: permanent net compressive force normal to the shear plane, if tensile Pc = 0 (MN).

Same approach can be used for blisters shear friction reinforcement:

 
Pu//   c Acv   Avf f y  Pu 


Pu//    Pu  c Acv
 Avf

 fy

3) Required reinforcement (surface and bursting) shall be provided at bearings location (with design
force x 1.2).

The design forces for jacking in service shall not be less than 1.3 times the permanent load reaction at
the bearing, adjacent to the point of jacking.

4) Where the reaction force or the load introduces direct compression into the flexural compression
face of the member, the tensile capacity of the longitudinal reinforcement on the flexural tension side
of the member shall be proportioned to satisfy:

Mu N V 
As f y  Aps f ps   0.5 u   u  0.5Vs  V p  cot 
d v f c  v 

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DESIGN CRITERIA

Where:
• Vs: shear resistance provided by the
transverse reinforcement at the section
under investigation , except Vs shall
not be taken greater than Vu/Φ (MN);
• θ: angle of inclination of diagonal
compressive stresses used in
determining the nominal shear
resistance of the section under
investigation (°);
• Φf Φv Φc: resistance factors taken as
appropriate for moment, shear and
axial resistance.

The area of longitudinal reinforcement on the flexural tension side of the member need not exceed the
area required to resist the maximum moment acting alone.

At the inside edge of the bearing area of simple end supports to the section of critical shear, the
longitudinal reinforcement on the flexural tension side of the member shall satisfy:

V 
As f y  Aps f ps   u  0.5Vs  V p  cot 
 v 

These equations shall be taken to sections not subjected to torsion. For more explanations please
refer to AASHTO LFRFD § 5.8.3.5.

9.1.3 Extreme Event limit state:

The structure as a whole, and its components, shall be proportioned to resist collapse due to extreme
events. Resistance factor shall be taken as equal to 1.0.

9.2 Substructures

9.2.1 Piers
PCACOL program shall be used for checking bi-axial loads on piers.

9.2.2 Bearings
As the design life of bearings is shorter than the design life of structure, it will be kept in mind that
accessibility and replacement of each part of the bearing are of paramount importance.

The design forces for jacking in service shall not be less than 1.3 times the permanent load reaction at
the bearing, adjacent to the point of jacking.

Elastomeric Bearings or Pot Bearings shall be designed in accordance with AASHTO LRFD.

In case of elastomeric bearings, seismic verification shall be done using the Guide Specifications for
Seismic Isolation Design (AASHTO – 2nd edition – 2000).

9.2.3 Pier cap

The design of the pier cap may consider that any jacking of the deck (e.g. in case of bearing
replacement…) will be undertaken with closed traffic. Thus no live load would be considered.

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DESIGN CRITERIA

9.2.4 Foundations
Unless otherwise specified in this document, the design of foundations for at grade and elevated
sections shall comply with AASHTO LRFD.

Attention is drawn to the fact that concrete cast below ground level has to be properly protected
against chemically aggressive soil.

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DESIGN CRITERIA

10. Deformations

10.1 Bearings and joints

Deck joints and bearings shall accommodate the dimensional changes caused by loads, creep,
shrinkage, thermal changes, settlement and prestressing.

According to the combinations defined above (§8), the displacements due to temperature, creep and
shrinkage effects shall be multiplied per 1.2.

10.2 Precamber

Bridges shall be built with a precamber equal to the sum of the anticipated deflections under Dead
Load & Superimposed Dead Load such that the profile matches the theoretical profile after long-term
losses have occurred.

11. Drainage
We will follow the Drainage System Design Criteria issued by Dubai Municipality: a rainfall rate of
20mm/hour and a minimum velocity of 0.6m/s will be considered.

Wherever possible, longitudinal drainage of viaduct is accomplished by providing a longitudinal slope

to the structure (a minimum of 0.2% shall be provided).

12. Main softwares for structural calculations

The following softwares will be used:

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