More than Just Lines on a Map: Best Practices for U.S Bike Routes
Presentation on Structural Integrity from the Department of Mines and Petroleum
1. www.dmp.wa.gov.au/ResourcesSafety
Please read this before using presentation
• The Department of Mines and Petroleum (DMP) supports and
encourages reuse of its information (including data), and endorses use of
the Australian Governments Open Access and Licensing Framework
(AusGOAL)
• This material is licensed under Creative Commons Attribution 4.0 licence.
We request that you observe and retain any copyright or related notices
that may accompany this material as part of attribution. This is a
requirement of Creative Commons Licences.
• Please give attribution to Department of Mines and Petroleum, 2015.
• For resources, information or clarification, please contact:
RSDComms@dmp.wa.gov.au or visit
www.dmp.wa.gov.au/ResourcesSafety
1
3. www.dmp.wa.gov.au/ResourcesSafety
What are we going to cover?
• My experience
• What structural failures have happened recently?
• Historical and common knowledge – structural
hazard awareness
• Examples for discussion
• What is often missed and why?
3
6. www.dmp.wa.gov.au/ResourcesSafety
More structural failures on
WA mine sites
• Winder shaft and sheaves
• Rock pass and bin
• Jib crane (above right)
• Take up plinth (left)
• Radial stacker back stay
• 30t gross weight mixing tank
Possibly more but not reported due to no injury and not
deemed critical by the mine management
6
7. www.dmp.wa.gov.au/ResourcesSafety
Ask yourself
• What awareness do we
have of hazards?
• Is this from knowledge,
training and experience?
• Does it change with time?
• Do we learn from near-
miss or other events?
7
8. www.dmp.wa.gov.au/ResourcesSafety
Historical awareness
Importance of structural integrity
recognised for over 3,800 years!
King Hammurabi (1792 – 1750 BC)
Code – if a building collapse kills the
owner, the builder will be put to death.
Structural safety standards are
constantly evolving as failure events
result in loss of life ― standards are
updated to account for learnings from
failures
8
9. www.dmp.wa.gov.au/ResourcesSafety
• Structural collapse can be sudden
• Structural collapse can results in multiple fatalities
• Degree or level of structural integrity and robustness
is not readily observable
– Load cases are not visible
– Loading is probabilistic
– Strength is calculated (can also be proof-tested but this
is uncommon due to each building being unique)
– Latent defects may exist
• Level of integrity and robustness is not immediately
apparent and may not be adequate
Why is structural integrity important?
9
10. www.dmp.wa.gov.au/ResourcesSafety
Summary of awareness – human factors
With so many warnings and centuries of knowledge of
structural robustness requirements, why do structures
continue to fail?
• Misplaced optimism, even complacency
– “It won’t happen here or to me” (we tend to be optimists)
– “It hasn't happened that I can remember” (it’s always too strong)
• Competency
– Management not identifying risk
– Not utilising sufficiently competent persons in all phases of the
life cycle
So what does unacceptable look like ?
10
11. www.dmp.wa.gov.au/ResourcesSafety
• How safe is this?
• Would you sit
under this
structure?
• This is on a site
that is well into its
asset repair
programme!
What is wrong with this?
11
12. www.dmp.wa.gov.au/ResourcesSafety
Discussion
• Is a total catastrophic collapse required to prove that
a structure is in an unacceptable integrity state?
• Would you be happy with structural failures of:
– Aeroplanes, cars, trains?
– Your children's school hall?
– Your house?
• Aircraft are de-commissioned before catastrophic
collapse. Why are mining structures any different?
• Should this state of structure be tolerated?
• Why has it not collapsed yet?
• When will it collapse?
12
13. www.dmp.wa.gov.au/ResourcesSafety
Steel corrosion notes
13
• Corrosion is common in steelwork but can be
exacerbated by poor practice:
– damage of corrosion protection system
– inappropriate corrosion protection specification
– lack of appropriate monitoring and maintenance
– poor housekeeping (spillages not removed)
• Corrosion of high stress areas is commonly
overlooked by asset management teams when
assessors are not competent in design of structures;
for example
– high stress areas are not identified
– structural function (load transfer) is not understood
15. www.dmp.wa.gov.au/ResourcesSafety
• Are bases important to steelwork – how?
• How much strength does this base have?
• What loading condition would result in total collapse?
• How would repairs be undertaken?
Discussion
15
16. www.dmp.wa.gov.au/ResourcesSafety
Concrete damage and degradation notes
• Loss of bond strength between reinforcing and
concrete – spalling
• Loss of concrete strength due to breakdown,
including alkaline aggregate reaction
• Total fracture due to:
– overload
– poor design and detailing
– impact damage
• Lack of loading combination considerations:
– thermal expansion and contraction (Pilbara 45ºC)
16
18. www.dmp.wa.gov.au/ResourcesSafety
Discussion
• More complex problems require intimate knowledge
of
– structural systems and construction techniques
– secondary effects on structures
• Why is competency of asset management personnel
critical?
18
27. www.dmp.wa.gov.au/ResourcesSafety
What parts of mine sites are structures?
AS 5104 (ISO 2394) General principles
on reliability for structures
2.1.1 Structure: Organized combination
of connected parts designed to provide
some measure of rigidity
2.1.2 Structural element: Physically
distinguishable part of a structure.
EXAMPLES: Column, beam, plate
2.1.3 Structural system: Load-bearing
elements of a building or civil
engineering works and the way in which
these elements function together
27
Editor's Notes
Vigilance is key – we cannot relax or become complacent.
If it was right before, don’t think it will always be so.
Learning from mistakes is the key issue and the reason why standards are continuously updated.
In answer to the questions:
How are these hazards managed by structural design?
These are the pillars of competency. What we regard as a hazard and how to best design structures to accommodate them comes from understanding of all these.
Yes. Hazard identification is growing and the need to keep up with continued professional development is a key aspect of competency
Yes. We should not shy from reporting these and encouraging investigations.
The hazards associated with structural integrity have been documented for nearly 4,000 years.
Structural integrity is not something that can be managed at lower hierarchy of control levels – one has to design, build and maintain to ensure the hazard is addressed.
Just because it has not yet collapsed does not make it safe. The structure simply has not yet experienced all the loading that it could be subject to.
In answer to the questions:
This is NOT safe – a loss of material means a loss in strength.
You should not “sit under” or be anywhere near an obviously unsafe or otherwise compromised structure.
It is vital to use competent persons to manage structural integrity.
In answer to the questions:
As a society we do not accept catastrophic failure events as these can kill people. Building structures on mine sites are no different than these examples and we do not expect structures to collapse.
A state of severe corrosion and decay cannot be tolerated.
The structure has most likely not collapsed because it has not received the adequate loading, but the structure may experience this any point in time.
A structure may collapse given the right circumstances.
Corrosion is often hidden under spillage, layers of paint and inside connections. We need to investigate failure potential when we see corrosion indicators – this relies on competent persons assessing the state of the structure.
In answer to the questions:
It has failed but not yet collapsed.
Indicators include the efflorescence (salts), build up of spillage at the base, and pieces falling off.
This is nearly impossible to repair – the ingress of salts and level of carbonation is deep in the concrete.
In answer to the questions:
Steelwork reliability relies on the bases – any movement or loss in strength may severely compromise the serviceability and ultimate strength.
This base has a fraction of its original capacity since the reinforcing has nearly no remaining bond strength.
A critical example includes, an uplift case or a free standing column that needs to resist bending.
Repairs could include propping the structure adjacent to this position and a complete rebuild of the base – this is difficult and costly.
Once spalling occurs it is often expensive to fix as it has happened “all over”.
The choice of aggregates and cement used is key to preventing chemical interaction problems – not every aggregate or cement combination is suitable.
Fracture through the member can happen when large loads occur, which the member was not designed for – these include large temperature differentials and vehicular impact.
(Note for presenter: click in sequence with numbered points and animated circles highlighting issue will appear on screen)
In answer to the questions:
1. The permanent decking which has corroded away may be the reinforcing (unless added bars are in the concrete).
2. The cut-out of the beam flange (lower right) to allow the top path of the pipe has compromised the beam’s strength and stability
3. The added lifting points (lower left, far right) add eccentricity and are not ideally constructed
The situation should be assessed by a competent person and the necessary action(s) taken.
Once modifications are introduced, including repairs, the entire structural system can be compromised. Asset management personnel need to be able to identify all the aspects that can compromise structural integrity, not only corrosion.
In answer to the questions:
The added surface bed slab has introduced risk – corrosion under the slab.
Corrosion can be so severe that the strength of the bracing connection is compromised. This in turn compromises the stability of the building, resulting in a collapse.
Often mass concrete is added to “cure the corroded base” – it does the opposite. It promotes further corrosion which results in swelling and the mass concrete falls off.
Apart from the compromised connection and member strength, if this was at height the falling broken pieces would be another introduced hazard.
In answer to the questions:
Crack propagation, poor detailing and incorrect repair techniques.
Not solving the root cause of the problem – not using competent persons to investigate and correct the issue.
(Note to presenter: click for circle and percentage to appear)
(Note to presenter: click for circle to appear)
Over 20 years, and through many repairs where oxy-acetylene sets had been conveyed across this same area.
Understanding why bearer bars need to span between supports is fundamental to the structural integrity of grating.
This was not identified as a critical defect compromising structural integrity.
The structure was not protected by bollards despite this being a known vehicle pathway.
(Note to presenter: click for circle to appear)
The bracket to which the torque arm is attached is bent and rotated – open sections are not suitable to carry torsion loads.
This problem can arise through a lack of competency of any party in the lifecycle of the structure, including the designer, manufacturer and assessor of the plant for integrity and continued use.
Note to presenter: click for circles to appear)
The belt is cutting into the chords of the gantry.
At a certain point there will no longer be adequate remaining strength and the structure will collapse.
Not only are parts supporting moving plant and equipment structures, but structures are in workplaces as well.
The entire assembly, including the bases (underground), is a load-bearing structure.
