TIMBER ENGINEERING

AKRUTI GUPTA, ARTI GAURKHEDE, CHANDNI AGRAWAL , RUJUTA PATHAK, SHIKHA CHANDAK

AD. CONST. II VIII SEM. B.ARCH B.D.C.O.A. SEW.

Introduction -NEED OF TIMBER AS A CONSTRUCTIONAL MATERIALTimber as a BUILDING material. - TIMBER IN FOUNDATION - TIMBER IN FLOORING - TIMBER IN SOLE PLATES - TIMBER IN FRAMEWORK - TIMBER IN ROOFING - TIMBER IN WINDOWS - TIMBER IN CLADDINGTypes of timber used - SHORT LENGTH TIMBER - LAMINATED TIMBER

Contents :

Methods used for roofing -Lamella roofing -Portal framesSolid beams and web beams

-METHODOLOGY-JOINERY DETAILS

TIMBER IS ONE OF THE EARLIEST MATERIALS TO BE USED FOR STRUCTURAL PURPOSES.

TIMBER CONSTRUCTIONS USUALLY DONE WITH THE HELP OF A FRAMEWORK OF STRUCTURAL TIMBER.

Frameworks are mostly prefabricated & assembled in sections on the ground.

Timber has a low weight in relation to strength, whichis advantageous for transport, erection and production.

It is an environmentally friendly, easily recyclable material.

The energy consumption during production is very low comparedto that of other building materials.

wood has aesthetic qualities, which give great possibilities in architectural design.

INTRODUCTION

Types of timber used

1. SHORT LENGTH TIMBER

This is a type of timber derived from the waste pieces of wood left after sawing of the logs in a mill used for timber construction.

CHARACTERISTICS-

-The product of timber cut into board is referred as lumbers.-Each piece is not more than 2m in length.-The moisture content in timber is above 25% & wood with less than 25% moisture remains free from fungi for centuries.

USES-

-Bow string arch-Portals & girders-Trusses & stanchions-Lamella roofing-Formwork, temporary structure,-Post & frames

The standard lengths of lumber are 6,8,10.12.14.16.18,20,22,24 feet.

2. GLUED LAMINATED TIMBER

Glued laminated timber also called as glulam which is a type of structural timber product composed of several layers of dimensioned timber glued together.Usually their thickness is not more than 2”.Created from 2”×4” or 2”×6” stock by gluing the faces together to create beams such as 4”×12” or 6”×16”. By gluing multiple, common sized pieces of lumber together, they act as one larger piece of lumber

CHARACTERISTICS-

-Glulam is stronger & stiffer than similar sized members made of solid wood. This is achieved by grading during manufacture.-By laminating several smaller pieces of timber a single large, strong structural member is manufactured from smaller pieces.

- glulam is an ideal material to create structures for large spans. - By bending the laminations before gluing, it can be produced in curved shapes.

Structural systems for glulam

A variety of structural systems basedon straight and curved glulam members has been developed for roofs with spans of up to 100 m

For making straight and tapered beams, spans of 30 m and more can be achieved.

Spans of up to 100 m can be realised by three hinge frames built up by two curved glulam elements.

Three-hinged glulam curved frame.

Glulam arch structure made from two curved glulam elements.

Roof structures with straight glulam beams can be used for spans of up to 30–40 m. Steel wires are used for diagonal wind bracing

Glulam arch roof for Stockholm central railway station, built 1925.

USES-

-Trusses and stanchions-Portal frames and girders-Temporary structures-Laminated timber bridges-Lamella roofs-Laminated beams & arches

Methods used for roofing

1.LAMELLA ROOFING-It is the form of curved grid system, which utilizes a large number of identical members called lamellas.

-Each lamella is two ‘bays’ in length and overlapping the adjacent lamella to form a continuous grillage.

CONSTRUCTION OF LAMELLA ROOFING

-First the load bearing walls are constructed with 350mm thickness .

-Brassumer a long member of 150mmx200mm is provided running over wall length.

-Short length timber lamella having saw mill texture is used and they have wedge end on both side with preservative coat.

-A movable centering on 1m gauss rails on which short length timber positions are provided.

-Lamella is carefully jointed with brassumer with special wooden block.

-During fire , only the part is affected and the whole roof does not collapse.

-Cost of construction is less.

-Due to its rectangular voids or coffers, it has good acoustical properties.

-The roof is evenly distributed over the span.

-The wooden block is used to maintain the angles between Lamellas.

-The slope of roofs is between 22deg. TO 42deg.

CHARACTERISTICS -

Cheap in construction. No caternary work of short length timber is used.

No super skilled labour is required.

Trusses can be made on ground and lifted above to place in position.

They can be dismantled after use in case of temprorary structure and all S.L.T. can be sold to recover 40%.

There is no painting required, just a coat of chemical is used to protect from insects.

DISADVANTAGES –

The volume between truss can not be used.

No safety against fire.

Advantages -

2.PORTAL FRAMES

It is defined as two dimensional rigid frames which have the basic characteristic of a rigid joint between the column & the beam.

CHARACTERISTICS-

-The main objective of this form of design is to reduce the bending moment in the beam thus allowing the frame to act as one structural unit.

-Mainly used in commercial or industrial structures.

-Depending on knee joint and member size timber portals can handle large spans up to and above 50m.

-Timber can be formed into any shape desired creating flexibility for the architect.

Construction Of Timber Portal Frames

RAFTERS

HAUNCH BRACE

FOUNDATION

COLUMN

STRUCTURE OF PORTAL FRAME

-A combination of supporting member and truss of the same material is used.

-Timber portal frames can be built using several different types of sawn timbers Glulam, LVL and plywood box beams, OSB

-The tie member can be of any other material like steel, cable, etc. it is a tensile member.

-Site work of timber portal frame consist of connecting the foot of the supporting member to the metal shoe fixing or to pivot housing bolted to concrete foundation.

-For large span timber portals, steel hinges can be used for efficient erection and added strength.

-Joints are connected at the apex or crown with a bolt fixing or a hinge device.

-most glued laminated timber portal frames are fabricated into 2 halves which eases transportation problem .

-the frames can be linked together at roof level with timber purlins and clad with a light weight sheeting or decking alternatively they may be finished with traditional roof coverings.

-There is a number of different external claddings that can be applied to a timber portal frame some of the popular options are corrugated steel sheet, brick veneer skin and pre cast tilt up concrete panels.

COLUMN

RAFTERS

PURLINS

HAUNCH BRACE

advantages

Constructed from readily available material at an economic cost.

Light in weight . Easy to transport and erect. Can be trimmed and easily adjusted on site. Protection against fungi and or insect attack

can be by surface application. Pleasing appearance either as an natural

timber finish or painted.

solid beam

-using glulam technique for homogeneity span up to 18m with short length timber.

Advantages:

-timber of different tensile strength can be used within the beam.-placed where there is need of more strength.-for curved shape, scantlings of thinner cross-section to be used of 15mm thickness.- No metal brackets are used.

web beam

-web beams are i-beams.

-flange can be made by glulam by screwing, nailing or nut bolting.

-with the weight of the structure concentrated on the frame,The interiors remain largely open and unobstructed.

- Timber I beams consist of timber chords, which is typically solid timber or Laminated Veneer Lumber (LVL), connected with a timber web. The timber web is a sheet material, usually plywood although other materials such as Oriented Strand Board (OSB) are used.

advantages

-The advantages of these systems are:

-longer spans and higher loads are achievable

-more efficient use of the material

-quick installation and light to handle

-fast installation of services

-available in long lengths

-cost advantages

Countersunk head – slotand cross-recessed drive

Raised counter-sunk head –slot and cross-recesseddrive

Round head – slot drive

Flat head nail

Bullet head nail

Hexagon washer head –external hexagon drivePower driven screws provide secure fixing.

Countersunk heads may be appropriate for some applications

Methods used for joining timber members

TIMBER  CONNECTORS

A  timber  connector  is  any  device  used  to  increase the strength and rigidity of bolted lap joints between heavy timbers

Split rings come in diameters of 2 1/2 and 4 inches. The 2 1/2-inch ring requires a 1/2-inch bolt, and the 4-inch ring uses a 3/4-inch bolt.

Shear  plates  connectors  are  intended  for  wood-to-steel  connections

University questions

Briefly enlist the various ways of spanning large span structures with short length timber members and describe with sketches any two types.

Discuss the merits and demerits of covering large span with short length timber. With relevant examples explain the various ways in which slt can be effectively used to cover large spans.

What is laminated/ glultam timber ? List the various roof forms and structural component that can be constructed by using this kind of timber and describe in detail two of such roof forms or structural components.

THANK YOU !!!!!!