TTF CPD No1 Engineered Timber - An Overview (for Distribution)

transcript

Engineered Timber – An overview

Deb Turnbull

4 October 2012

www.napier.ac.uk/isc

The need for re-engineering

Timber composites - what are they?

Basic information - Glulam, PSL, LSL, LVL

Massive timber - Brettstapel- CLT

Timber I-beams

Timber trusses - Carpentry- Plate connectors- Metal webs

Timber with other materials - Steel- Cement/concrete- Insulation

Timber frame

Resource - Length- Cross sections

Properties - Structural performance- Species

The need for Re-engineering

Timber Composites

CTS Bridges

Welsh Oak Frame

Dimensional stability- moisture content- cross laminations

Structural performance- more homogenous material- increased lengths

Greater use of resource

Timber Composites

Veneers

Timber Composites

PlanksGlulam

Massive Timber

Timber Composites

Flakes

Laminated Strand Lumber(LSL)

Oriented Strand Board(OSB)

Timber Composites

Saw dust Fibreboards

Chipboard

Timber Replacement

Longer spans

Higher performance

Appearance

Glulam

I-joistsBox

Components and systems

trusseswalls

and floor panels

LVLPlywood

OSBFibreboard

Sawn timber CLT

GlulamManufacture

Stock sizes - 90 to 265 wide and 180 to 2050- square and circular sections available

Bespoke - curved, tapered, portal frames

Species - Spruce is usual, pine and larch also available- Other species have been tried including UK grown

Design - fabricators often have in-house design capability- manufacturers have free software- connections need special consideration

Glulam uses

Beams, Columns

Portal Frames

Space Frames

Geodesic structures

Scottish parliament, Cowley Timberwork Strawberry Lodge, Chiswick, Axis Timber

Acetylated timber in glulam beams

Parallel Strand Lumber (PSL) &Laminated Strand Lumber (LSL)

Only one manufacturer – Weyerhaeuser (was Trus Joist)No longer available

Sizes - stock sizes- special sizes for I-joist systems

Design - manufacturers have free software- connections

Uses - in UK, beams and columns in timber frames

Laminated Veneer Lumber (LVL)

Typical stock sizes - thickness 27, 33, 39, 45, 51, 57, 63, 69, 75- width 200 to 900

Spans - Floors up to 9m- Roofs up to 18m

Design - manufacturers have free software

LVL uses

Rim boards in timber frame

Beams, Columns

Portal Frames

Space Frames

Geodesic structures

Stressed skin panels

Edinburgh Napier University, Cowley Timberwork

Kerto Q monocoque panels, Cowley Timberwork

Massive Timber

Brettstapel - nailed- dowelled

Cross Laminated Timber- glued- dowelled- interlocking

Brettstapel

Can use lower grade timber

Nailed or all timber product

Used for walls and floors

Manufacture

01 October 2010

Higher levels of automation

01 October 2010

Fabrication into panels

2.5 wide and up 18.5m long

Structural design

Flatwise

Stiffness - Emean for all stiffness calculations

Shear deformations not so significant due to span to depth ratio

Material safety factor, k mod x (strength property)ϒm

Connections need careful thought

Edgewise

Racking

Bending

Panel sizes and spans

Typical load span table for timber with MOE of 11,000 N/mm2 Grade C24

LoadThickness(mm)

01 October 2010

Building performance

Airtightness - Relies on additional layer – typically OSB

Thermal performance- 100mm thick panel of 500 kg/m3 U=0.13 W/mK

External wall make-upsPanel profiles

Directly applied plasters

01 October 2010

Brettstapel

Cross Laminated Timber

Typical lay-ups

Panel thickness Layer thickness

51 Metsä 17, 17, 17100 BinderHolz 37, 26, 37126 StoraEnso 42, 42, 4285 Metsä 17, 17, 17, 17, 17147 BinderHolz 41, 22, 21, 22, 41200 KLH 40, 40, 40, 40, 40

CLT Benefits

Airtight - if edges glued

Don’t generally need lintels

Speed on site with large panels

Good replacement for reinforced concrete- 6 times lighter- 1/3 the thickness for similar span

www.napier.ac.uk/isc01 October 2010

Pag 31

Waugh Thistleton Architects BRE Ravenscraig Visitor Centre

Hackney Academy, Eurban

Use of EC5 – multiple connected layers and Appendix B

Fire – charring rate

Structural design

Preliminary sizing

Manufacturers design software

Other Guidance

Dowelled cross laminated timber

TechnoWoodHolz100Nur HolzThoma

Timber Trusses

Cheadle Hume, Cowley Timberwork

with steel

UK Sitka spruce Trusses

Compared to above using plywood gussets

Timber I-Beams

CTS Bridges

Welsh Oak Frame

Timber I joists

CTS Bridges

Welsh Oak Frame

Special uses with connectors

Timber in Combination with other materials

Concrete

Insulation

Timber in Combination with Steel

Flitch beams Bolted Impact nailed

CTS Bridges Forestry Commission

Mechlam bridges Stress laminated bridges

With concrete

Acoustics

Thermal mass

Longer spans than timber alone

Composite

Non-composite

Welsh Oak Frame

Non-composite systems

With I-joist floors

Manufacturers linked with screed suppliers

Timber concrete - composite action

CTS Bridges

Welsh Oak Frame

01 October 2010

Kaufmann Oberholzer, CH

With insulation

Panels

Structural Insulated Panels - SIPs

Sheathing layers

Bonded insulation – injected PUR foam- glued EPS

Joints

- splines-thinner full sections

Fixings- Some straight into OSB

01 October 2010

Composite Insulated Beams (CIBs)

Increased bearing capacity - 18-30%

Heat loss reduced by 56-86%

Most efficient – Box beams with timber or LVL flanges

Beams and CIBs had increased shear and bending strength over I-joists

Timber Frame

Can incorporate many forms of engineered timber

- Improved joists, I joists and timber trusses for walls and floors- For replacement of steel for purlins and rafters- Cassettes- Acetylated timber ground beams

Thank-you

d.turnbull@napier.ac.uk

TTF CPD No1 Engineered Timber - An Overview (for Distribution)

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