Sustainability of Infrastructure and the Role of Structural Timber by Keith Crews, Professor of Structural Engineering, University of Technology Sydney.

1. Sustainability of Infrastructure and
the Role of Structural Timber
Keith Crews
Professor of Structural Engineering
Centre for Built Infrastructure Research
University of Technology Sydney
1

2. © 2009 – Keith Crews: keith.crews@uts.edu.au
This presentation may be reproduced for IEAust CPD and
University Educational purposes
But cannot be used for commercial purposes
without the prior written permission of the author

3. Overview
• Sustainability & Structures
• Historical Role of Timber
• Current Challenges
• Techniques & Tools
– Health Monitoring
– Assessment and Impact
– Repair and Rehabilitation
• New Developments and
Opportunities
3

4. Sustainability
• Broadly, is the ability to maintain a certain
process or state, usually with respect to
biological or human systems
• Human sustainability has become increasingly
associated with the integration of economic,
social and environmental spheres
• Involves “meeting the needs of the present
without compromising the ability of future
generations to meet their own needs”
World Commission on Environment and Development (Brundtland Commission) – Report to UNGA 1987
Commission)
4

5. Sustainability & Economics
• Since Industrial Revolution
most Economic systems
are based on growth
• Growth = Prosperity
• Growth = Consume
• Now being confronted:
– Limits to growth
– Limits to resources
– Limits to consumption Source: NOAH / NASA
– Limits to environment 5

6. Getting the Balance Right
• Sustainabilty: improving the quality of human
life while living within the carrying capacity of
supporting eco-systems
• More recently “Triple Bottom line” approach:
– commercially viable development
– enhance community wellbeing
– environmental renewablity and
conservation of resources
• Objective of balancing these is “Sustainability”
6

7. Triple Bottom Line Philosophy
Social
equitable
bearable
sustainable
Environment Economic
viable
Balancing the spheres of influence
Adams, W.M. (2006) quot;The Future of Sustainability: Re-thinking Environment and Development in the Twenty-first Century”

8. Sustainability and Infrastructure
• Economic growth understood
as New = Good
• Political Drivers
– New projects = success
– No votes in maintenance
• Educational Drivers
– Engineers trained to design
new, not sustain existing
• Decisions based on traditional
economic models, rather than
sustainability principles 8

9. Infrastructure Challenges
• “Infrastructure Australia” an excellent initiative
– Highlights problems with planning
– Prioritisation and best value / national interest
– Aims to improve decision making processes
• However, the focus still appears to be on
“new” projects, rather than how we can
improve / maintain existing infrastructure
• Need for a change in mind-set and new
economic / decision making models if we are
to develop sustainable practices
9

10. Infrastructure Challenges
• Declining state of existing infrastructure is
evidenced by the Australian Report Cards
(IEAust & GHD)
– civil infrastructure is barely adequate or poor
– similar situation in US (refer Civil Engineers Aust - Feb 2009)
– e.g: 1 in 4 bridges either deficient or obsolete
• Private investment focuses on new projects
rather than maintaining existing infrastructure
• The Great Challenge of “Aging Infrastructure”
Priority: “Restore and Improve Urban Infrastructure” Nat. Academy of Eng. (July 2008)
10

11. Need for a change in mind-set
• OECD: sustainable infrastructure (structures)
requires 3% of the asset replacem’t value be
budgeted each year for maintenance (on average)
OECD Road Transport Research – Bridges (1992) / OUTLOOK 2000 (1999)
• Obviously this varies with age and use – new
assets would require less, older ones more
• Expenditure in Australia varies between less than
0.5% and 1.5% depending on the asset owner
(ave. for State Governments approx 1.2%; less in LG)
• Creates a cycle of obsolescence
11

12. Degradation Agents
Degradation is caused by one or more of:
• “Normal” wear and tear
• Biological / Chemical / Environmental hazards
• Increased frequency of load events (e.g. more traffic)
• Increased magnitude / severity of loads
– e.g. increasing axle loads from 8t to10t
increases the damage potential by 145%
– Extreme load events
– Climate change
ATSE Report “Assessment of Impact of
Climate Change on Australia’s Infrastructure” (2008)
12

13. Infrastructure Degradation
Degradation increases with failure to:
• Detail / construct for
durability
• Resource adequately
• Correctly identify
damage
• Understand its impact
• Intervene effectively
– Maintenance
– Repairs Source: Aboura et al – UTS / RTA (2008)
• Strengthen / optimise 13

14. Infrastructure Degradation
Degradation increases with failure to:
• Detail / construct for
durability
• Resource adequately
• Correctly identify
damage
• Understand its impact
• Intervene effectively
– Maintenance
– Repairs Source: Aboura et al – UTS / RTA (2008)
• Strengthen / optimise 14

15. Sustaining Infrastructure
• The issue of aging infrastructure
applies to all structural materials
• The reality is that we cant afford to
replace every structure
• Engineers have a responsibility to
maintain the operational effectiveness
and safety of infrastructure
• Both a challenge and an opportunity!
• Illustrate - specific focus on timber
15

16. Background:
Timber Structures in Australia
• Historic applications
• Current applications
• Development of “tools”
that enable sustainable
practices
– damage detection
– risk assessment
– strategic maintenance
– repair & rehabilitation
16

17. Timber has been an
essential and integral
part of rural Australia’s
buildings and
infrastructure since early
European settlement

18. Structures such as these have
been “out of sight, out of mind”
Yet, despite the fact they are
often not well maintained
Many are still performing well
After 150+ years!

19. Similarly with bridges –
an essential, but under
valued part of our rural
infrastructure

20. Multi-storey timber
warehouses were common
in the 1800’s - many have
been recycled into offices

21. However, lack of
understanding
about detailing,
maintenance and
durability issues can
lead to performance
problems

22. Resulting in the
need for expensive
repairs!

23. Case Study:
Sustaining Timber Bridges
• A main focus of R&D at
UTS since 1990
• Collaborative with RTA,
Industry, Local and Federal
Governments
• Approx $5m of R&D
projects
• Development of new
technologies:
– risk ID / assessment
– repair & rehabilitation
23

24. Timber Bridges - Context
• Approx 40,000+ bridges in Australia
• Approx. 27,000 are aging timber bridges
– most are girder / corbel (spans 8-10m)
– some truss bridges (spanning up to 36m)
• Essential part of our transport infrastructure
– mainly in rural areas / Local Government
– most 70+ years old
– designed for 14 to 18t
– now carrying 44t plus!
• Asset value in excess of $25B
• An important part of our history
with social & cultural significance
24

25. Timber Bridges - Drivers
• Need for bridges with
European expansion
• 1861 decree to use
local materials
• Lack of steel and RC
• Availability of HQ
hardwoods
• 400 truss bridges built
between 1860 & 1936
• 1000’s of girder bridges
25

26. The “stress” of Timber Bridges
• For many Engineers (particularly
in LG), looking after all types of
bridges is a major problem
• The bridges are often “over
stressed” from excessive loads
combined with deterioration
• Engineers looking after them are
“over stressed” in trying
managing these aging bridges
• Compounded by general lack of
confidence / expertise in timber
26

27. Engineering Challenges
• Level of expertise for assessing and / or repairing
bridges varies enormously
– In many councils is virtually non existent
• Consequently, developing and maintaining an
effective BMS is often seen as “too hard”
• Resources are often inadequate
– Funds limited for replacement or rehabilitation
– Need for sustainable practices – they have to last!
• Results in “band-aid” management practices that
react to emergencies
• Bridge maintenance / repairs are not strategic 27

28. Proactive Bridge Management
- Developing Sustainable Practices
Understanding the condition of
the asset involves:
• Developing effective assessment
systems for quantifying safe
capacity / acceptable performance
• Identifying where the greatest
needs / risks are located
• Using this information to develop
and maintain an “information
system” or BMS
• Essential for sustainable
management of infrastructure 28

29. Addressing the “guess work” in strength
assessment of bridges….
One of the biggest
problems has to do with
the assumptions we make
and conclusions we draw
when we assess / model
the bridge structure……
29

30. Uncertainties & Assumptions
• Reliable assessment requires
accurate information about:
– Integrity of member sections
(decay / corrosion / spalling)
– Load history and damage
– Structural interactions
– Material properties
(variability and aging effects)
• Errors can be significant!
• Overly conservative decisions can
be costly!
30

31. Strength Assessment Methods
Various methods, in 4 basic tiers:
1. Visual inspection
2. Desk top analysis
3. Load Testing
4. Health monitoring and damage detection
• Each of these has its place
• Generally speaking, the higher the tier,
the more cost that is involved
• But, with the benefit that the reliability of
the information gained, improves
31

32. Inspection & Assessment
• Most modern asset management systems
involve visual inspection
• Visual systems tend to qualify condition
• Some information can be gathered to quantify
effects of damage - if visible / measurable
• Assumptions must be made about member and
material properties, in order to estimate safety
using “desk top” modelling
• Testing of select elements and load testing can
confirm some of these assumptions
• But - significant damage is often undetected! 32

33. How safe is safe?
33

34. Potential Tools for
Facilitating
Sustainable Practices

35. New Technologies for
Damage Detection
• Significant R&D on NDE technologies for
determining the location and extent of “damage”
• Emerging Technologies (most promising):
– Dynamic / Modal Analysis
– Radiography and GPR
– Stress Wave
• Impact
• Sonic
• Ultrasonic
– Acoustic Emission
• Potential for a “quantum leap” in assessing the
condition of existing structures 35

36. Dynamic / Modal Analysis
• New method developed by UTS in
partnership with IPWEA / RTA
• Provide good “global” indication of
safe response of superstructure
• Quick to perform and cost
effective
• Provides accurate information
about global behaviour of beam
structures (timber, conc & steel)
36

37. Dynamic / Modal Analysis
• Next generation identifies
location and size of damage
(voids / loss of member integrity)
• Development of neural networks
that enable the system to “learn”
• Linked with probabilistic strength
models derived from testing
37

38. Ground Penetrating Radar
• Uses electromagnetic
waves to generate an
image of internal features
• Ideal for investigating
objects with low
conductivity such as
masonry, concrete and
timber
38
Source: W.Muller – QDMR (2008)

39. Ground Penetrating Radar
• Recent developments can create
3D images
• Can be used effectively with other
NDE (e.g. thermal imaging)
39
Source: L. Binda – TU Milano (2008)

40. Ultrasonic Tomography
• Ultrasonic pulse velocity (UPV)
used to create 2D and 3D images
of internal voiding
• Data is analyzed in terms of
propagation velocities and arrival
of the transmitted ultrasonic pulse
Source: De La Haza et al - SFR (2008) 40

41. Acoustic Emission
• AE signals can identify
micro-cracking mechanisms
in reinforced concrete
• Applied to corrosion-induced
cracks due to expansion of
corrosion products
• Potentially effective for
identifying / quantifying
damage accumulation
Estimate of crack depth Image of water filled crack
41
Source: Ohtsu et al - SFR (2008)

42. Engineering Challenges
• Translating R&D into practice
• Key Forums
– SFR Edinburgh
– RILEM TC215
• Training Engineers to interpret
• What is the effect of damage
on structural performance?
• Is it still safe?
• What needs to be done?
Client: How do I fix it? 42

43. Repair & Rehabilitation
of Timber Bridges
• Many councils and road
authorities are now finding it
difficult to secure large
section, durable hardwoods
• This has lead to a number of
alternatives to “adhoc”
replacement being developed
and trialled for future use
• Designed for durability and
high performance to sustain
timber bridges
43

44. Challenges with
Heritage Structures
• Heritage Legislation
means that many old
bridges must be kept
operational
• Tension between
maintaining hist. integrity
(size of members) and
safety for current loads
• Significant R&D projects,
consulting and training
• Development of new
structural systems, design
& detailing methods 44

45. Concrete / Timber Systems
45

46. Engineered Wood Products
• Bridge-Wood decking systems
• Alternative Girder products
– LVL
– Glue Laminated Timber
• Stress Laminated Timber
– Plate decks
– Cellular decks
46

47. Bridgewood
47

48. EWP girder systems
48

49. SLT Systems
49

50. SLT Systems
50

51. SLT Systems
51

52. Hybrid Design Methods
52

53. Modern “best practice” detailing
“Best practice” detailing
methods combined with
careful use of new products
can lead to significant
improvements in durability
and long term performance
of timber bridges – without
the need to replace existing
structures.
53

54. Durable Design Detailing
54

55. Durable Design Detailing
continued
• 8 yr old footbridge
• Detailed for durability
• Excellent – condition 1
• Minimal maintenance required
55

56. Potential of Timber in Structures
• Does timber have a role in
infrastructure?
• Why?
– renewable & sustainable
– we can grow more
• Overview existing uses
• Introduce new timber based
technologies and potential
applications in Australia
56

57. Normal “current” uses
ALL LOADS CARRIED BY TIMBER!

60. Recent developments
• Changes in available resource
– Reduced supplies of native
hardwood
– Increased availability of
plantation timbers such as
radiata pine
– Smaller logs / quicker growing
• Development of new products;
– Engineered Wood Products
60

66. Importance of
collaborative R&D
for design innovation

67. Source: B Hutchings - TimberBuilt P/L (2008)

68. Source: B Hutchings - TimberBuilt P/L (2008)

69. Source: B Hutchings - TimberBuilt P/L (2008)

72. New Building Applications -
Local & O/S developments
• Current R&D in Australia / NZ
• Composite Flooring systems
• Cross laminated timber (CLT)
• Prefabricated Floor, Wall & Roof systems
• Multi-storey Buildings
– commercial
– residential
• Modern Bridges in Europe
72

73. Current R&D – Aust & NZ
• Number of projects focusing on
developing new “engineered” timber
products for non-residential markets
• FWPA projects
– New structural systems (e.g. CLT)
• STIC: 3 Main Programs
– Roof Systems
– Floor Systems
– Wall and Framing Systems
• Collaborative Partnerships:
Research Providers & Industry
73

74. Timber Framing Systems
Internal or external
Rocking motion
dissipation devices
• Recent work at UC
• Use of column & θ imp
Unbonded post-
beam frames for tensioned tendon
U
multi-storey buildings
• Post tensioned LVL
frames that are “self
healing”
• Particular application
in seismic regions
74

75. New floor systems
• Current focus on
non residential
building forms
• New composite
floor systems
• Prefabricated using
CAD/CAM
• High performance
– 8 to 10 m spans
– 3 to 8 storeys
• Use with existing
structural forms 75

78. Cross Laminated Timber (CLT)
• Ability to utilise lower
quality, fast grown
plantation softwoods
• Prefabrication under
factory conditions
• Floors, walls & roofs
• Quick to construct
• Significant uptake &
development in EU
78

81. Prefabricated Building Systems
• Factory Fabrication
– Excellent QA / QC
• Use of CAD / CAM / CNC
• Modular structural system
– material combinations
• Efficient Erection
• “Green building” strong
driver in terms of carbon
store, process and
operating energies
81

83. Multi-Storey Timber Buildings
• Multi-storey timber
framing for buildings in
North America and
Europe well established,
for 4 to 6 storey
• 9 storey residential built
from “cross laminated”
panels in London
• 4 - 6 storey commercial
using glulam frames and
TCC floors in Europe
• Excellent Fire & Acoustic
Performance 83

84. First Storey RC, then Timber

86. 8 storey timber building in Växjö, Sweden

87. 9 storey CLT building in London

88. Examples of Excellence –
Timber Bridges

91. Use with steel
and concrete

92. Conclusions:
Sustainable Infrastructure
• Significant challenges facing Civil and Structural
Engineers
• Urgent need to educate existing & future PE’s:
– Triple Bottom Line “sustainability” principles
– Design of new structures incorporating “renewable” mat’s
– Assessment, protection / enhancement of existing
• Need for us to provide leadership in the community
– Understanding and communicating the need for change
– Lobbying for appropriate resources
– Using our skills & new technologies to create and
implement sustainable practices
92

93. Conclusions:
Timber as a modern material
Viable timber structures are
created by:
• Designing for “whole of life”
value & worth
• Understanding sustainability
processes
• Detailing / const. for durability
• Creative use of new products
• Designers developing
understanding and confidence
in timber & hybrid systems
93

94. Conclusions:
Timber as a modern material
• Structural timber is a truly
sustainable and remarkable
engineering material
• Yet there is a lot of fear, based
on ignorance, about using it
• With professional skills timber
structures can be designed or
rehabilitated for:
– high performance
– stringent environmentally
sustainable design criteria
– and can be both durable and
aesthetically pleasing
structures 94

95. Timber has important role to play in contributing to the Economic,
Environmental and Social aspects of Australia’s Infrastructure
being truly Sustainable. The creative leadership and skills of
Professional Engineers is critical for this to occur.
thank you for your attention