suscos m emmc co3 bridges fatigue l3

8/11/2019 Suscos m Emmc Co3 Bridges Fatigue l3

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Pontes I

Luis Borges

L3: 27/10/2013

European Erasmus Mundus Master Course

Sustainable Constructions

under Natural Hazards and Catastrophic Events520121-1-2011-1-CZ-ERA MUNDUS-EMMC

L26 – Fatigue and fracture of steel structures

European Erasmus Mundus

Master Course

under Natural Hazards

and Catastrophic Events

SUSCOS

Conceptual Design of Bridges

Fatigue and Fracture Mechanics

Master Course

Contents

• L26 – Basis of fatigue design in steel structures

– Definitions and application range

• L27 – Fatigue loads and determination of stresses and stress ranges

– Cycles and stress ranges

• L28 – Fatigue strength

– Fatigue strength curves

– Fatigue details

L29 –

Reliability and verification – Application to Road Bridges

– Application to Rail Bridges

• L30 – Brittle fracture

Master Course

L26 – Basis of fatigue design in

steel structures

• Generalities

• Definitions and application range

Master Course

Fatigue of steel structures

• Fatigue: damage of a structural

part by gradual crack growthcaused by repeated stresses.

Master Course

Definitions and application range

FATIGUE

• Crack

• Defect

• Nominal stress range

• Detail category

• Fatigue loading

• Fatigue strength

• Fatigue limit

http://slidepdf.com/reader/full/suscos-m-emmc-co3-bridges-fatigue-l3 7/48L26 – Fatigue and fracture of steel structures

Master Course

Fatigue of steel structures (1)

http://slidepdf.com/reader/full/suscos-m-emmc-co3-bridges-fatigue-l3 8/48L26 – Fatigue and fracture of steel structures

Master Course

Liberty Ship 1943

Master Course

Lully Bridge 1999

Master Course

Premature fracture in automobile leaf springs(Engineering Failure Analysis, Volume 16, Issue 2, 2009, pp. 648-655)

Premature rupure due to

- Bad conception,

- Metallurgical problems,

- e defeitos de fabricação.

Examples of fatigue collapses

Master Course

• Wöhler, 1871, trains wheels

– Cracks initiated from the fabrication marking -

XX Century

Master Course

undetectable

ICE Enschede, 1998.Train crash due to failure of a wheel.

Passengers: 287 (ICE-1 max. is 651)

Train crew: 6

Maintenance crew: 2Fatalities: 101

Severe injuries: 88

Minor or no injury: 106

Master Course

ICE Enschede, 1998.Train crash due to failure of a wheel.

Passengers: 287 (ICE-1 max. is 651)

Train crew: 6

Maintenance crew: 2Fatalities: 101

Severe injuries: 88

Minor or no injury: 106

Master Course

EPFL/ICOM –

Construction métallique A. Nussbaumer

• Pile fatigue Arteplage Neuchâtel (CH), 2000

Master Course

Lack of weld

penetration

Pile fatigue Arteplage Neuchâtel (CH),2000

Master Course

QuickTime™ et undécompresseursont requis pour visionner cette image.

Fatigue corrosion

Offshore platform A. Kielland (1980)

Ekofisk field in the Norwegian sector of the North Sea on March 27 1980.

123 people died

Master Course

Fatigue corrosion

Master Course

I-35W Mississippi River bridge

At 6:05 p.m. CDT on Wednesday,August 1, 2007, with rush hour bridge

traffic moving slowly through the

limited number of lanes, the central

span of the bridge suddenly gave way,

followed by the adjoining spans. The

structure and deck collapsed into

the river and onto the riverbanks

below. Approximately 100 vehicles

were involved, sending their occupantsand 18 construction workers up to

115 feet (35 m) down to the river or

onto its banks. Northern sections fell

into a rail yard, landing on threeunoccu ied and stationar frei ht train

Master Course

This image, from the National Transportation Safety Board's Office of Research and

Engineering, shows a fracture in a gusset plate that played a key role in the collapse of

the Interstate 35W bridge

Master Course

1 year before the collapse:

Fatigue Evaluation and

Redundancy analysis,

July 2006

F i i f h i f

Master Course

Fatigue is, one of the main causes of

damage – Bridges among structures

most often dammaged

Motivação

P. Oehme, for steel structures only

Materials used in German

Master Course

EPFL/ICOM –

Construction métallique A. Nussbaumer

Materials used in German

Railways bridges (DB)

Master Course

Motivation

• Fatigue is, with corrosion and wear, one

of the main causes of damage in metallic

members.

• Note: In Mechanics, up to 90% collapses

are due to fatigue phenomena!

Master Course

Summary

• Fatigue occurs on structural parts due to action

of fluctuating stress

• Cracks grow progressively on specific details

• Global actions are generally weak but localsingularities can lead to high stress

concentrations

Master Course

Fatigue: Progressive degradation of structures condition

under repeated actions. The fatigue phenomenon

shows itself in the form of cracks developing at

particular locations in the structure.

Fatigue Life =

No of cycles to

enucleate acrack

No of cycles to

propagate a crackto collapse

Fatigue of steel structures

Master Course

Material scale

Crack initiation

• Cyclic slip conducting to crack initiation / enucleation

Master Course

Material scale

Crack initiation

Master Course

Growing a micro crack in a copper specimen (Schijve 2001)

Material scale

Crack initiation

Master Course

Material scale

Crack initiation

• During crack initiation, fatigue is a surface

material phenomenon

• Crack initiation depends on:

– Material surface

– Environment

– Cristalography: cristaline system, size of the

grains

– Material properties: anisotropy, elasticity

modulus , tension strength, ductility and

hardening...

– Stress ratio

Master Course

top viewside view

Material scale

Crack propagation

Master Course

Material scale

Crack propagation

After crack initiation, fatigue occurs at a

volume level and not only at a surface scale.

Crack propagation depends on:

environment

Certain material properties: módulo de

elasticidade, resistência à tracção,tenacidade, ...

relação das tensões

Master Course

Fatigue at a material level

Initiation + Crack propagation

Master Course

Fatigue life

4 Important parameters:

• Stress range(Ds)

• Global and local geometry

• Material characteristics

• Environment

Master Course

Stress range and mean stress

Master Course

CHS K joints

Length: 8,6 mHeight: 1,8 m

f = 0.7 hz

Qmin = 60 kN

Qmax = 610 kN

Example: tubular truss test

Master Course

Example: tubular truss test

• Compression joint?

E E M d

Master Course

Examplos local geometry

Global and local geometry

E E M d

Master Course

Material characteristics

Master Course

Environment influence

Actions Environment

Neutral Agressive

Static creep crack growth stress corrosioncracking, SCC

Cyclic pure fatigueFatigue corrosion

corrosion fatigue

Master Course

Fatigue – European Standards

lacborges@gmail.com

http://steel.fsv.cvut.cz/suscos

Master Course

Additional reference

suscos m emmc co3 bridges fatigue l3

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