Bảng tính cầu Cổ Cò (Co co calculation)

This subsection consists of the design requirements for elevated highway bridge structures, including superstructures, substructures and foundations of the Danang Priority Infrastructure Investment Project (DNPIIP), Danang, Vietnam. The Co Co Bridge, crossing the Co Co river in Cam Le district of Danang City, has a total length of about 90 m. The bridge isdesigned to serve 4 traffic lanes and pedestrian load in both sides. The minimum requirement for the width of the bridge shall be 2+7.5+7.5+2 =19.0 m when the sidewalk width is 2 m and the roadway width is 15 m. Concrete structure shall be designed for the main construction material of the bridge because it is located near the coastal area so the exposed condition shall be considered as severe environment and the steel structure shall be concerned for the corrosion protection that would require higher construction costs, long term inspection and maintenance. The arch structure shall be proposed in design of this bridge since its architecture produces better visual effects and the aesthetic consideration plays an important role in the plan of the bridge construction becausethe site is in the development area of the district.

CDM Project Office for Danang City PIIP

8th Floor of CIENCO 5 Tower

77 Nguyen Du Street, Hai Chau District, Danang City, Vietnam

Tel 05 11 388 6778 | Fax 05 11 388 6998

eMail: danangoffice@cdmvietnam.com 

DANANG PRIORITY INFRASTRUCTURE INVESTMENT PROJECT- DANANG PIIP

PACKAGE: A23+ A24+ B27

- Phase 2- Detailed Design

SUBCOMPONENT C57 : CO CO BRIDGE

CALCULATION

Danang, 29 December 2011

Contents

1 Structural Design Criteria

1.2 Design Standards and Codes of Practice 5

Detailed Design of The Co Co Bridge

1 Structural Design Criteria

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

SUBCOMPONENT C –URBAN ROADS AND BRIDGES

THE SOUTHERN LINK ROAD : BASIC DESIGN OF THE CO CO BRIDGE STRUCTURAL DESIGN OF HIGHWAY BRIDGE

1.1 General

This subsection consists of the design requirements for elevated highway bridge structures, including superstructures, substructures and foundations of the Danang Priority Infrastructure Investment Project (DN-PIIP), Danang, Vietnam

The Co Co Bridge, crossing the Co Co river in Cam Le district of Danang City, has a total length of about 90 m The bridge is designed to serve 4 traffic lanes and pedestrian load in both sides The minimum requirement for the width of the bridge shall be 2+7.5+7.5+2 =19.0 m when the sidewalk width is 2 m and the roadway width is 15 m

Concrete structure shall be designed for the main construction material of the bridge because it is located near the coastal area so the exposed condition shall be considered as severe environment and the steel structure shall be concerned for the corrosion protection that would require higher construction costs, long term inspection and maintenance

The arch structure shall be proposed in design of this bridge since its architecture produces better visual effects and the aesthetic consideration plays an important role

in the plan of the bridge construction because the site is in the development area of the district

INCLINED THROUGH RIGID FRAME TIED CONCRETE ARCH BRIDGE

For through rigid frame tied arch bridge, the arch ribs are fixed to form a rigid frame For a small span bridge, the pier can stand small thrust forces caused by self-weight

of the arch but for a large span, the tied bars shall be used to reduce the horizontal force transmitted to the pier and the foundation The tied cables shall be installed inside the edge tie girders in both side of the bridge Most of this kind of bridge has single span, however, the details at the joint on the top of the pier is so complicated because the arch ribs, the piers, the crossbeam and tie beams are joined together The single span of 90 m for the arch bridge shall be proposed The size of the arch ribs becomes large then they will be located outside the sidewalk to keep the bridge width as per minimum requirement Two arch ribs are designed to be slightly inclined inward about 10º not only strengthen the out-of-plane stability of the arch structure but also give a good aesthetic appearance

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

2) Low probability of resonance

3) Conceptual simplicity and standardization for ease of construction, schematic quality control, fast track construction and higher maintenance reliability

4) Reduction of environmental noise and vibration impact

5) Limited hours available for inspection, maintenance and repair

In addition, the design works shall have a high aesthetic character as recommended

in the following criteria:

 The bridge structures shall be proportioned to present an appearance of slenderness

 The bridge structures shall be harmonized with the surrounding landscape and visual intrusion shall be reduced as far as practical

 All visible longitudinal lines shall be smooth without any appearance of sagging or interruption at piers

 Aesthetic and visual continuity shall be maintained within the whole project

 The edge to the viaduct (and any features) shall be detailed to a high standard

to complement and emphasize the horizontal line The edge shall be also detailed to avoid water or other unsightly staining

 Exposed pipe work, ducts and cables shall be avoided as far as practical If unavoidable, they shall be masked by covers in recesses, blended with the background of structure

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

 iiQi   Rn  Rr

95 0

1 



I R D

i   



Design Limit States

General

Each component and connection shall satisfy Equation 1.1 for each limit state, unless

otherwise specified For service and extreme event limit states, resistance factors shall be taken as 1.0, except for bolts, for which the provisions of Art.6.5.5 shall apply All limit states shall be considered of equal importance

D = a factor relating to ductility (1.0 for all limit states)

I = a factor relating to operational importance (1.0 for all limit states)

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

The structures shall be designed and checked at every stage of construction until the completion of the bridge for specified limit states to achieve the objectives of constructability, safety and serviceability:

1) Ultimate limit state or strength design shall ensure that strength and stability,

both global and local, are provided to resist specified statistically significant load combinations that the viaduct is expected to experience in its design life

2) Service limit state shall ensure durability and set restrictions on stress,

deformations and crack width under regular service conditions

3) Extreme Event limit state shall be taken to ensure the structural survival of a

bridge during a major earthquake or flood, or when collided by a vessel or vehicle, possibly under scoured conditions

4) Fatigue limit state guarantees the safety of the structure and limits the crack

growth against damage due to repetitive loadings It ensures the reference stress range is below the truncated limit for different classes of details Fatigue damage shall be assessed over the designated service life of 100 years Fatigue design for concrete structures shall be based on ACI 358

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

The bridge structures shall be designed in accordance with all applicable portions of the following standards and codes:

Vietnam : 22 TCN 272 – 2005, Bridge Design Standard

: TCXDVN 356 – 2005, Design Standard for Reinforced Concrete

Structures : TCXDVN 375 – 2006, Design of Structures for Earthquake Resistance

: ACI 318-05, Building Code Requirements for Structural Concrete : ACI 336.3R-93, Design and Construction of Drilled Piers

: ACI 341.2R-97, Seismic Analysis and Design of Concrete Bridge

Systems : ACI 343-95 (Reapproved 2004), Analysis and Design of Reinforced

Concrete Bridge Structures : ACI 358.1R-92 Analysis and Design of Reinforced and Prestressed

Concrete Guideway Structures : ACI 435R-95 (Reapproved 2000), Control of Deflection in Concrete Structures

AASHTO: AASHTO, LRFD Bridge Design Specifications – SI Units (2005

: AASHTO, Guide Specifications, Thermal Effects in Concrete Bridge Superstructures

ASCE : ASCE 7-05, Minimum Design Loads for Buildings and other Structures

Steel Buildings, March 9, 2005 ASTM : American Society for Testing and Materials Standards

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

The edition of each standard used shall be that current at the date of signing the Contract Later editions that become available during the course of the Contract may

be used upon receipt of written statement of “No Objection” from owner

In the event of conflicting requirements between the Local Design Specifications and other standards and codes of practice, the Local Design Specifications shall take precedence For requirements which have not been included in the Design Specifications, the order of code adoption shall follow the sequence of American standards and others

1.3.1 Navigational

This river shall not be in class I to class VI of waterway therefore no requirement for navigational horizontal and vertical clearance shall be applied However the minimum vertical clearance between highest water level and bridge soffit shall not be less than 500 mm

1.3.2 Highway

1.3.2.1 Highway Vertical

The vertical clearance of highway structures shall be in conformance with the Highway Design Standard TCVN 4054-2005 Possible reduction of vertical clearance, due to settlement of an overpass structure, shall be investigated If the expected settlement exceeds 25 mm, it shall be added to the specified clearance

The vertical clearance to sign supports and pedestrian overpasses should be

300 mm greater than the highway structure clearance, and the vertical clearance from the roadway to the soffit of bridge structure should not be less than 4750 mm

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Prestressing strands shall be seven wires low relaxation strands conforming to

ASTM A416M, Grade 270 Prestressing strand properties are shown in Table 1.4-2

Table 1.4-2: Properties of Prestressing Strand

Table 1.4-3: Friction Coefficient for Posttensioning Tendons

Values of K and  should be based on experimental data for the materials specified

and shall be shown in the contract documents In the absence of such data, a value

For tendons confined to a vertical plane,  shall be taken as the sum of the absolute

values of angular changes over length x

For tendons curved in three dimensions, the total tridimensional angular change  shall

Effective prestressing force is calculated as: P(x) = P0* e – µ(α+kx)

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

For external tendons the wobble factor is only considered over the embedded sections in the diaphragms and deviators

The wedge draw-in shall be: 5 mm for less than 10 strands

6 mm from 10 strands to 15 strands

8 mm from 15 strands and up

Anchorage strength shall not be less than the ultimate tensile load of the prestressing steel to be used, and no harmful deformations shall occur under this load The ultimate tensile load of the prestressing steel shall be the ultimate tensile strength specified in ASTM multiplied by the sectional area and numbers of the wires, strands or bars

High strength tensile bars shall be ASTM A722-98 Grade 150 Tensile strength of

M215 method

Wire shall be uncoated, stress-relieved, cold-drawn, high-tensile steel wire conforming to ASTM A421-05

1) Sheathing for internal tendons shall be formed from thin galvanized steel sheeting

2) External prestressing shall be protected from corrosion by the use of high density polyethylene (HDPE) sheathing which shall be continuous between anchorages

3) The internal cross section area of the sheath shall be at least 2.5 times the strand area The sheath shall have an external diameter to wall thickness ratio of 21 or less

4) At deviators, a double sheathing system shall be used

5) At anchorages, the sheathing shall be a double sheathing system (replaceable system)

6) The radius of curvature of tendon ducts shall not be less than 6000 mm, except

in the anchorage areas where 3600 mm may be permitted

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

7) The inside diameter of ducts shall be at least 6 mm larger than the nominal

diameter of single bar or strand tendons For multiple bar or strand tendons, the inside cross-sectional area of the duct shall be at least 2.0 times the net area of the prestressing steel with one exception: where tendons are to be placed by the pull-through method, the duct area shall be at least 2.5 times the net area of the prestressing steel

8) The size of ducts shall not exceed 0.4 times the least gross concrete thickness

at the duct

1.5 Loads

Dead loads include the weight of the entire structure and all permanently installed

elements such as walls and other fixed service equipments

1) Self Weight (SW)

The unit weights in Table 1.5.1-1 shall be used

Table 1.5.1-1: Self Weights

2) Superimposed Dead Loads (SDL)

Superimposed dead loads shall include barriers, hand rails, utilities attached to the structure, wearing surface, future overlays and planned widening

1) Standard Vehicle Load (LL)

Vehicular live loading on the roadways of bridges, designated HL-93, shall consist of a combination of the:

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

a) Design truck or design tandem

The weight and spacing of axles and wheels for the design truck shall be as specified in Figure 1.5.2-1 The spacing of the two 145 kN axles shall be varied between 4300 and 9000 mm to produce extreme force effects The tire contact area of a wheel consisting of one or two tires shall be assumed to be a single rectangle, whose width of 510 mm and tire length shall be

N for the design tandem

The design tandem shall consist of a pair of 110 kN axles spaced 1200 mm apart The transverse spacing of wheels shall be taken as 1800 mm

b) Design lane load

The design lane load shall consist of a load of 9.3 N/mm uniformly distributed in the longitudinal direction Transversely, the design lane load shall be assumed to be uniformly distributed over a 3000 mm width The force effects from the design lane load shall not be subjected to a dynamic load allowance

c) Application of design vehicular live load

The extreme force effect shall be taken as the larger of the following :

 The effect of design tandem combined with design lane load

 The effect of one design truck with the variable axle spacing combined with the effect of design lane load

 For both negative moment between points of contra flexure under a uniform load on all spans, and reaction at interior piers only, 90 percent of the effect of two design trucks spaced a minimum of 15000

mm between the lead axle of one truck and the rear axle of the other truck, combined with 90 percent of the effect of the design lane load The distance between the 145 kN axles of each truck shall be taken as

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

 For the design of all other components – 600 mm from the edge of design lane

d) Loading for Optional Live Load Deflection Evaluation

If the Owner invokes the optional live load deflection criteria specified in Article 1.7.4, the deflection should be taken as the larger of:

 That resulting from the design truck alone, or

 That resulting from 25 percent of the design truck taken together with the design lane load

Figure 1.5.2-1: Standard Design Truck

The live load effects shall be determined by considering each possible combination of number of loaded lanes multiplied by the corresponding factor specified in Table 1.5.2-1

3500

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Table 1.5.2-1 - Multiple Presence Factors "m”

Number of loaded lanes Multiple presence factor “m”

1 1.20

2 1.00

3 0.85

>3 0.65

2) Dynamic Load Allowance (IM)

The static effects of the design truck or tandem, other than centrifugal and braking forces, shall be increased by the percentage specified by Table 1.5.2-2

Table 1.5.2-2: Dynamic Load Allowance (Impact)

All other components

 Fatigue and fracture limit state

The impact factor shall be applied to the superstructure, supporting columns, legs

of rigid frames and generally those parts of the structure extending down to the main foundation

The impact factor shall not be applied to the following structures:

a) Abutments and retaining walls not subjected to vertical reaction from superstructure

b) Foundations and footings c) Service walkways

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

gR

v f C

2



3) Centrifugal Force (CF)

The centrifugal effect on live load shall be taken as the product of the axle

weights of the design truck or tandem and the factor C, taken as

where

v = highway design speed (m/s)

f = (4/3) for load combination excluding fatigue = 1.0 for fatigue

R = radius of curvature of traffic lane (m)

Centrifugal forces shall be applied horizontally at a distance of 1800 mm above the roadway surface

4) Braking Force (BR)

The braking force shall be taken as :

 25 percent of the axle weights of the design truck or design tandem or,

The braking force shall be placed in all design lanes which are carrying traffic headed in the same direction These forces shall be applied horizontally at a distance of 1800 mm above the roadway surface in either longitudinal direction

to cause extreme force effect

The multiple presence factors specified in Table 1.5.2-1 shall apply

5) Pedestrian Loads (PL)

mm and considered simultaneously with the vehicular design live load

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

6) Wind Load (WS and WL)

Wind loads shall be assumed to be uniformly distributed to the area exposed to the wind The exposed area shall be the sum of areas of all components including floor system and railing as seen in elevation taken perpendicular to the assumed wind direction This direction shall be varied to determine the extreme force effect in the structure or in its components

The design wind velocity, V, shall be determined from:

V = VB S where:

period appropriate to the Wind Zone in which the bridge

is located, as specified in Table 1.5.2-3

S = correction factor for upwind terrain and deck height, as specified in Table 1.5.2-4

Wind zone according to

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

or buildings up to a maximum height of about 10m

Built-up areas with buildings predominantly over 10m high

6.1) Wind Pressure on Structure (WS)

centroids of the appropriate areas, and shall be calculated as:

PD = 0.0006 V2 At Cd  1.8 At (kN) where:

V = design wind velocity determined from Equation 3.8.1.1-1 (m/s)

load (m2)

area in normal projected elevation, without live load, subject to the following provisions:

 For superstructures with solid parapets, the area of superstructure shall include the area of the solid windward parapet, but the effect of the leeward parapet need not be considered

 For superstructures with open parapets, the total load shall be the sum of the loads for the superstructure, the windward parapet and the leeward

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

parapet considered separately Where there are more than two parapets, only those two having the greatest unshielded effect shall be considered

 For truss girder superstructures, the wind force shall be calculated for each component separately, both windward and leeward, without considering shielding

 For piers, shielding shall not be considered

methods:

 For superstructures with solid elevation, of conventional construction with

shall be derived from Figure 1.5.2-2, where:

b = overall width of bridge between outer faces of parapets (mm)

d = depth of superstructure, including solid parapets if applicable (mm)

 For truss girder superstructures, parapets and substructures, the wind force

from TCVN 2737 – 1995, Table 6, or from any other recognized source approved by the Owner

testing

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Notes to Figure 1.5.2-2:

1 The values given assume a vertical elevation and a horizontal wind

may be reduced by 0.5% per degree of inclination from the vertical, subject to a maximum reduction of 30%

3 Where the windward face consists of a vertical and a sloping part or two sloping parts inclined at different angles, the wind load shall be derived as follows:

structure

b) For each non-vertical face, the basic drag coefficient calculated above

is reduced in accordance with Note 2

c) The total wind load is calculated by applying the appropriate drag coefficients to the relevant areas

degree of inclination to the horizontal, but not by more than 25%

6 Where a superstructure is superelevated and also subject to inclined wind, the drag coefficient shall be the subject of a special investigation

6.1.2 Longitudinal Wind Load For piers, abutments, truss girder superstructures and other superstructure forms which present a significant surface area to wind loads parallel to the longitudinal centerline of the structure, a longitudinal wind load shall be considered The longitudinal wind loads shall be calculated in a manner similar to those for transverse wind loads

For superstructures with solid elevation, a longitudinal wind load equal to 0.25 times the transverse wind load shall be applied

Longitudinal and transverse wind loads shall be applied as separate load cases and, where appropriate, the structure checked for the effect

of intermediate angles of wind by resolution of forces

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

6.2) Wind Pressure on Vehicles (WL) When considering the STRENGTH III load combination, the design wind load shall be applied to both structure and vehicles Transverse wind load

on vehicles shall be represented by a line load of 1.5 kN/m acting horizontally, transverse to the longitudinal centerline of the structure and

1800 mm above the roadway Longitudinal wind load on vehicles shall be represented by a line load of 0.75 kN/m, acting horizontally, parallel to the longitudinal centerline of the structure and 1800 mm above the roadway In each case the load shall be transmitted to the structure

Longitudinal and transverse wind loads on vehicles shall be applied as separate load cases and, where appropriate, the structure checked for the effect of intermediate angles of wind by resolution of forces

appropriate area, and shall be calculated as:

PV = 0.00045 V2 Av (kN) where:

V = design wind velocity (m/s)

vertical wind load (m2) This load shall be applied only for limit states that do not involve wind on live load, and only when the direction of wind is taken to be perpendicular

to the longitudinal axis of the bridge This load shall be applied in conjunction with the horizontal wind loads

the structure is less than 5 degrees; for inclinations in excess of this, the lift coefficient shall be determined by testing

7) Stream Flow (SF)

The effect of flowing water on piers shall be calculated by the following formulas:

7.1) Longitudinal Direction The pressure of flowing water acting in the longitudinal direction of substructure shall be taken as:

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

2 4

10 4

2 4

10 14

p = pressure of flowing water (MPa)

CD = drag coefficient for piers as specified in Table 1.5.2-5

V = design velocity of water for the design flood in strength and service limit

states and for the check flood in the extreme event limit state (m/s) = 0.71 m/s (V1% based on hydrological report)

Table 1.5.2-5: Drag Coefficient

square-ended pier 1.40

wedged-nosed pier with nose

7.2) Lateral Direction The lateral, uniformly distributed pressure on a substructure due to water flowing at angle  to the longitudinal axis of the pier shall be taken as:

where:

p = lateral pressure (MPa)

CL = lateral drag coefficient for piers as specified in Table 1.5.2-6

Table 1.5.2-6: Lateral Drag Coefficient

Angle  between direction of flow

and longitudinal axis of the pier CL

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Figure 1.5.2-4: Plan View of Pier Showing Stream Flow Pressure

Provisions shall be made for all movements and forces that can occur in the structure

as a result of shrinkage, creep and variations in temperature Load effects that may

be induced by a restraint to these movements shall be included in the analysis Effects due to thermal gradients within the section should also be considered

1) Temperature Rise or Fall Effect (TRF)

The maximum and minimum average bridge temperatures shall be as specified in Table 1.5.3-1.The difference between the maximum and minimum average bridge temperature and the base construction temperature assumed in the design shall be used to calculate thermal deformation effects

The temperature ranges given in Table 1.5.3-1 apply to bridge decks with a depth

up to 2m and with 100 mm thickness of surfacing in the case of concrete decks and 40 mm in the case of steel decks.Where a deeper deck or different surfacing thickness is used, the temperature ranges should be adjusted accordingly

Table 1.5.3-1- Bridge Temperature Ranges

Climate Zone Concrete

superstructure

Concrete deck on steel girders or box

Steel deck on steel girders or box

* Note : For sites north of latitude 16° N and at an elevation above sea level greater than

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

In this project, the location is the south from Hai Van Pass and the average temperature in Danang city is 26°C

The coefficient of thermal expansion (α) to be used in the analysis are as follows:

11.7x10-6/◦C for steel 10.8x10-6/◦C for normal density concrete

2) Temperature Gradient Effect (TG)

The effects of vertical differential temperature gradients through a bridge superstructure shall be derived for both positive temperature differential conditions (top surface hotter) and negative temperature differentials (top surface cooler)

The vertical temperature gradient in concrete superstructures and steel/concrete composite superstructures with concrete decks may be taken as shown in Figure

positive and negative temperature differentials Dimension “A” in the Figure shall be taken as:

For concrete superstructures that are 400 mm or more in depth – 300 mm For concrete sections shallower than 400 mm – 100 mm less than the actual depth

For steel/concrete composite superstructures, the distance “t” shall be taken as the depth of the concrete deck

For superstructures comprising a steel deck on steel girders or box, temperature gradients shall be determined be a recognized method approved by the Owner The temperature gradients given in Table 1.5.3-2 apply to bridge decks with 100

mm thickness of surfacing Where a different surfacing thickness is used, the values should be adjusted accordingly

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

 0 6

6 0 118

0

0 10 120

58 1 5 3 ) , (

i

i i

f c i

t t

t t t

H k

k t

Table 1.5.3-2 - Temperature Gradients

Parameter Positive temperature

gradient (°c)

Negative temperature gradient (°c)

For transverse design of concrete box section, the differential temperature between inside and outside box for design shall be ± 6°C Linear distribution between outside and inside box is assumed

4) Creep and Shrinkage (CR & SH)

The creep coefficient may be estimated as:

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

for which:

c

f 42

62

where:

component specified in Figure 1.5.3-2

Figure 1.5.3-2 Factor kc for Volume to Surface Ratio

accelerated curing by steam or radiant heat may be taken as equal to seven days

of normal curing

The surface area used in determining the volume to area ratio should include only the area that is exposed to atmospheric drying For poorly ventilated enclosed cells, only 50 percent of the interior perimeter should be used in calculating the surface area

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

3

10 51 0 0 35

s

t 0 55

t k

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

c c

E  0 043 1 5 

Modulus of Elasticity

where:

Poisson’s ratio Unless determined by physical tests, Poisson’s ratio may be assumed as 0.2 For components expected to be subject to cracking, the effect of Poisson’s ratio may

be neglected

1) Collision Force from Highway Vehicles (CL)

Unless protected, abutments and piers located within a distance of 9000 mm to the edge of roadway, or within a distance of 15 000 mm to the centerline of a railway track, shall be designed for an equivalent static force of 1 800 000 N, which is assumed to act in any direction in a horizontal plane, at a distance of

1200 mm above ground

2) Vessel Collision (CV)

The vessel collision forces shall not be considered in the design of the bridge 3) Erection Load (EL)

a) Live Load at Erection Stage (LER) Live load on superstructures at erection

stage for design shall be not less than 6 kN/m2

b) Wind Load at Erection Stage (WER) Wind load at erection stage of each span

of superstructures shall be derived from hourly wind speed as detailed in Table 1.5.4-4:

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

A T

AS C

corresponding to a 10 year return period

corresponding to a 50 year return period

4) Earthquake Load (EQ)

Vietnam lies between the two greatest seismic belts of the planet: the Mediterranean-Himalayan Belt and the Pacific-Ocean Belt Although the seismic hazard is not as great as the countries lying directly on these belts (e.g Philippines, Indonesia), it requires precautions and the major public structures should be properly designed against seismic loads

Earthquake loads shall be taken to be horizontal force effects given by the

structure and adjusted by the response modification factor, R

shall be taken as:

where:

Tm = period of vibration of the mth mode (sec)

A = acceleration coefficient

S = site coefficient

nominal, unfactored mass of the structures

For bridges on soil profiles III or IV and in areas where the coefficient “A” is

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

For soil profile III and IV, and for modes other than the fundamental mode that

mode shall be taken as:

b) Acceleration Coefficient (A) Acceleration coefficient in each seismic zone map shall be assigned in Table 1.5.4-5

Table 1.5.4-5: Acceleration Coefficient and Seismic Zones

Acceleration Coefficient Seismic Zone MSK-64 Class

c) Site Coefficient (S) The site coefficient, S, shall be specified in Table 1.5.4-6 based on soil profile types as follows:

Table 1.5.4-6: Site Coefficients

Site Coefficient I Soil Profile Type II III IV

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Soil Profile Type I

A profile shall be taken as Type I if composed of

 Rock of any description, either shale-like or crystalline in nature, or

 Stiff soils where the soil depth is less than 60000 mm, and the soil types overlying the rock are stable deposits of sands, gravels, or stiff clays

Soil Profile Type II

A profile with stiff cohesive or deep cohesionless soils where the soil depth exceeds 60000 mm and the soil types overlying the rock are stable deposits of sands, gravels, or stiff clays shall be taken as Type II

Soil Profile Type III

A profile with soft to medium-stiff clays and sands, characterized by 9000

mm or more of soft to medium-stiff clays with or without intervening layers

of sands or other cohesionless soils shall be taken as Type III

Soil Profile Type IV

A profile with soft clays or silts greater than 12000 mm in depth shall be taken as Type IV

d) Response Modification Factor (R) The seismic design force effects for the substructures and the connections between parts of structures shall be determined by dividing the force effects resulting from elastic analysis by the appropriate response modification factor, R, as specified in Table 1.5.4-7

e) Combination of Seismic Force Effect The elastic seismic force effects on each of the principal axes of a component resulting from analyses in the two perpendicular directions shall be combined

to form two load cases as follows:

 100% in longitudinal combined with 30% in transverse direction

 100% in transverse combined with 30% in longitudinal direction

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Table 1.5.4-7: Response Modification Factor for Substructure

Substructure

Importance category

Reinforced concrete pile bents

 Vertical piles only

 With batter piles

1.5 1.5

2.0 1.5

3.0 2.0

Steel or composite steel and concrete pile bents

 Vertical piles only

 With batter piles

1.5 1.5

3.5 2.0

5.0 3.0

1) Differential Settlement (DS)

for piles founded in the stable stiff soil For simply supported structures, the differential settlement has little or no structural impact on either the columns or superstructure

impact and shall be a permanent load in both service and ultimate load states It is considered a long-term effect that develops gradually; therefore its effect may be mitigated by concrete creep Therefore, the differential settlement is assumed to occur evenly over a period of 10 years, starting immediately after the structure went into service

Above values are not binding and may be adjusted case by case based on geotechnical analysis

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

2) Earth Pressure (E)

by Coulomb’s Equation However, no structure shall be designed for less

the structure equal to one half its height, a live load surcharge pressure equals to not less than 0.60 meter of earth shall be added

c) Where an adequately designed reinforced concrete approach slab supported at one end by the bridge is provided, no live load surcharge needs to be considered

material by means of weep holes and crushed rock, pipe drains or gravel drains, or by perforated drains

3) Buoyancy (B)

Buoyancy shall be considered wherever it may affect the design of the substructure, including piling, and the superstructure

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Load combinations outlined in the 22 TCN-272-05 are incorporated into the design criteria The final service, strength, extreme event and fatigue load combinations are tabulated in Table 1.6-1 The load factors for all permanent loads shall be as shown

EVENT p 0.50 1.00 - - 1.00 - - - 1.00 1.00 1.00 SERVICE 1.00 1.00 1.00 0.30 1.00 1.00 1.00/1.20 TG SE - - - FATIGUE – LL, IM

& CE only

Notes to Table 1.6-1

1 Where the bridge is to be checked for use by an Owner-specified special vehicle

or by a permit vehicle, the load factor for live loads in combination

STRENGTH-I may be reduced to 1.35

2 Bridges with very high dead load to live load force ratios (eg long span bridges) should be checked for a combination without live loads, but with a load factor of 1.50 applied to all permanent load effects

3 For bridges over waterways, the consequences of changes in foundation conditions resulting from the design flood for scour shall be considered at the Strength and Service limit states

4 For bridges over waterways, when checking the effects of loads EQ, CT and CV

at the Extreme Event limit state, water loads (WA) and scour depths may be based

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

on the mean annual discharge The structure shall, however, be checked for the consequences of changes in foundation conditions resulting from the check flood for scour at the Extreme Event limit state, with the corresponding water load (WA) applied but without loads EQ, CT or CV applied

5 For checking crack widths in prestressed concrete structures at the Service limit state, the load factor for live load may be reduced to 0.80

6 For checking steel structures at the Service limit state, the load factor for live load shall be increased to 1.30

where:

DC = dead load of structural components and nonstructural attachments

DW = dead load of wearing surfaces and utilities

EH = horizontal earth pressure load

EL = accumulated locked-in force effects resulting from the construction process

including the secondary forces from post tensioning

BR = vehicular braking force

CE = vehicular centrifugal force

CR = creep

CT = vehicular collision force

CV = vessel collision force

EQ = earthquake

IM = vehicular dynamic load allowance

LL = vehicular live load

PL = pedestrian live load

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

WL = wind on live load

WS = wind load on structure

Each combination of limit state is described as follows:

 STRENGTH I Basic load combination relating to the normal vehicular use of the bridge without wind

 STRENGTH II Load combination relating to the bridge exposed to wind velocity exceeding

25 m/s

 STRENGTH III Load combination relating to normal vehicular use of the bridge with wind of 25m/s velocity

 EXTREME EVENT Load combination relating to earthquake, collision by vehicles, vessels, and certain hydraulic events with a reduced live load other than that which is part

of the vehicular collision load, CT

 SERVICE Load combination relating to the normal operational use of the bridge with a

25 m/s wind and all loads taken at their nominal values This load combination is intended to control deflections, crack width in reinforced and prestressed concrete structures, yielding of steel structures and slip of slip critical connections due to vehicular live load This load combination should also be used for the investigation of slope stability

 FATIGUE – LL, IM & CE only Load combination relating to repetitive gravitational vehicular live load and dynamic responses under a single design truck

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Table 1.6-2: Load Factors for Permanent Loads

EH: Horizontal Earth Pressure

 Active

 At Rest

1.50 1.35

0.90 0.90

EV: Vertical Earth Pressure

N/A 1.00 0.90 0.90 0.90 0.90

Load Factors for Construction Loads Load factors for the weight of the structure and appurtenances shall not be taken to be less than 1.25

Unless otherwise specified by the Owner, the load factor for construction loads, for equipment and for dynamic effects shall not be less than 1.5 The load factor for wind shall not be less than 1.25 All other load factors shall be taken as 1.0

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Load Factors for Jacking and Posttensioning Forces JACKING FORCES

Unless otherwise specified by the Owner, 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

Where the bridge will not be closed to traffic during the jacking operation, the jacking load shall also contain a live load reaction consistent with the maintenance of traffic plan, multiplied by the load factor for live load

FORCE FOR POSTTENSIONING ANCHORAGE ZONES The design force for posttensioning anchorage zones shall be taken as 1.2 times the maximum jacking force

The viaduct structure shall be designed in accordance ACI 358.1R-92 and the appropriate highway bridge design codes therein referred to ACI 358.1R-92 is based on the limit state philosophy defined in Section 1.1

Crack widths shall be calculated according to ACI 224.2R-01, reapproved 2004, or

BS 5400 Part 4

The bridge structure shall be designed in accordance with the limit state philosophy

as outlined in Section 1.1 Some further details are listed below:

Design Criteria

Danang PIIP : Component C – Urban Roads and Bridges

Table 1.7-1: General Design Philosophy

Strength design for structural elements, service load for surface crack width

Check of reinforcing bars for bored cast

in situ piles shall be provided as required

Strength design and service load design

Cast In Place Prestressed

Concrete

Strength design and service load design

and service load for surface crack width Further considerations for each component: