Timber, a truly sustainable resource, can be used to replace steel and concrete structures

in multi-storey building.

John Chapman, Senior Lecturer

School of Architecture, University of Auckland

Introduction to recent timber building research - School of Architecture, University of Auckland

• pinus radiata timber poles as the main structural elements in commercial / industrial building

• research is in response to the advantages of timber as a sustainable material

• 4 separate, but interrelated, studies

Environmental Reasons for radiata poles as structural elements in building

• radiata poles are

- a renewable resource

- require little energy during manufacture

- absorb carbon from the atmosphere and reduce greenhouse gases

Other Reasons for radiata poles as building

structural elements

• Competent structural product

• higher failure stresses than sawn lumber

• cheap timber at NZ$350/cu.m

– Images by Andrew Charleson – senior lecturer Victoria University

Study 1: Radiata Poles as the Columns in Multi-storey Timber Building

Study 2 – Investigating Timber Floor Types for Commercial Building

• floor structure types:– glulam– timber trusses – LVL (linear veneer lumber)

• office live loading of 3 Kpa

• resulting timber floors compared for cost and volumes of timber.

Study 3: Large Industrial Truss

Structures Using Pinus Radiata Poles

Study 4: Six Storey Apartment Building using Radiata Poles for the Beam and

Column Structural Elements

• results of studies 1 to3 led to the proposal that timber poles were very suited for the structural elements in medium storey apartment building

Apartment Plans

• beams and posts can be arranged as simple posts and beams

• resistance to horizontal loads supplied by the frequent party walls

• floor is timber– floor beams are pairs of

radiata poles

Prototype Pole Building-Plan of Units (figure 1)

Prototype Pole Building-Plan of Main Structure ( figure 5)

Apartments Cross Section

• The research considered seven aspects of the prototype pole building

– dimensional stability of the timber

– environmental impact

– building strength

– non destructive testing of poles

– economics

– fire resistance

– sound insulation

Environmental Impact

• Pole building structure– Energy for manufacture

= 0.5 Gj/sq.m.– Total carbon absorbed from

atmosphere= 27.4 Kg/sq.m.

• Equivalent RC structure– Energy for manufacture

= 2.24 Gj/sq.m.

– Total carbon emitted into atmosphere

= 52.5 Kg/sq.m.

Building Strength

• pole members readily available

• for major earthquake zones, column pole diameters increase by 50mm approx

Non Destructive Testing of Timber Poles

• Acousto-ultrasonic based methods relate propagation velocity of the longitudinal wave with wood density and modulus of elasticity

• Acousto-ultrasonic testing detects pole defects.

Economics

• pole/timber structure is 89% the cost of the equivalent reinforced concrete structure– Pole building structure = US$124.40 / sq.m.– Equivalent R.C. = US$208.70 / sq.m.

• timber buildings are significantly lighter than the R.C. alternatives and have reductions in foundation costs. (not considered in above cost analysis)

Fire Resistance

• each residential unit is an independent fire cell– pole structure & party walls are plasterboard lined

• 80mm expected loss of pole diameter in 1 hour fire– Poles will continue to support building after 1 hour fire

Sound Insulation• 50mm thick concrete floor toppings to protect from vertical noise transference

• Horizontal insulation at party walls assisted by fibreglass blanket between two separated timber frames

• Sound transference the main obstacle to timber building. Research occurring at the University of Auckland Acoustics Research Centre and elsewhere in world

Conclusions to Radiata Poles as the Columns in Multi-storey Timber Building

• no impediments to radiata poles as main structural members in multi-storey of up to at least 6 storeys

• 6 storey apartment building most complete project– considered more deeply the

issues and perceived problems

• Further research into this low energy, sustainable, and atmosphere assisting building product is continuing