Trusses

Trusses

Date : 20th May 2012

Name Of Professor : Mr. Sanjay

Subject : Building Construction III

Submitted By : Fairuz , Barch/8008/10

Truss & Its Characteristics: A truss is a structure comprising one or more triangular units .  

A triangle is the simplest geometric figure that will not change shape when the lengths of the sides are fixed.[

It is constructed with straight members

Ends are connected at joints referred to as  nodes.

External forces and reactions to those forces are considered to act only at the nodes

Force acting on the members can either be tensile or compressive.

Moments are excluded because all the joints in a truss are treated as Hinges or Revolute.

Straight Members

Triangular unit

Hinges

Nodes

Heel - The point on the truss where the top and bottom chords intersectSlope - The vertical rise in inches for every 12 inches of horizontal run.Panel Length - The horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.Peak - The point on the truss where the sloped chords meet.Top Chord - Horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.Continuous Lateral Brace - Members installed at right angles to a chord or web member of a truss to provide stability to the truss. All lateral braces must be stabilized.Overall Height - Vertical distance between bearing and the uppermost point of the peak.

Truss & Its Component:

Wedge - The triangular piece of lumber inserted between the top and bottom chords, usually to allow the truss to cantilever.Bottom Chord - The incline or horizontal member that establishes the bottom of a truss, usually carrying combined tension and bending stress.Splice - The location at which two chord members are joined together to form a single member. It may occur at a panel point or between panel points.Panel Point - Also called a joint, it's the location on a truss where the web members and top or bottom chords intersect and are connected by metal connector plates.Web - The members that join the top and bottom chords to form the triangular patterns typical of trusses.

Truss & Its Component:

Bearing - Structural support, usually a beam or a wall that is designed by the designer to carry the truss reaction loads to the foundation.Overhang - Extension of the top chord of a truss beyond the outside of the bearing support.Span - The horizontal distance between the outside edges of the exterior bearing supports, or the bottom chord length, whichever is greater.Bottom Chord Length - Usually the same as the span.Cantilever - The part of the truss that extends beyond its support, not the same as an overhang.Truss Plate – Are plates which are used to connect the members together in the truss manufacturing process.

Truss & Its Component:

There are 4 main assumptions made in the analysis of Truss system :

Truss members are connected together at their ends

Truss are connected together by frictionless pins

Truss structure is loaded only at joints.

Weight of the truss members may be neglected.

Analysis Of Truss:

Different Types Of Trusses:

Flat Truss Bowstring Truss King Post Truss

Queen Post Truss Town Lattice TrussLenticular Truss

Also known as Flat truss

Has parallel top chord and bottom chord.

The top and bottom chord must be correctly positioned during installation to ensure structural integrity is maintained.

Are usually designed to be supported at the ends only

Often used for floor construction.

Parallel Chord Truss:

Also known as Crescent Truss

Is a truss consisting of curved top chord meeting bottom chord at each end.

Has diagonal load-bearing members.

Often confused with tied arch bridges

Bowstring Truss:

A king post is also known as crown post truss

It is the simplest form of truss .

Is used for simple roof trusses and short-span bridges.

Truss consists of two diagonal members that meet at the apex of the truss,.

Consists of one horizontal beam that ties the bottom end of the diagonals together

The king post connects the apex to the horizontal beam below.

King Post Truss:

Is similar to a king post truss

Is used for simple roof trusses and short-span bridges.

Is a supporting post designed to span longer openings than a king post.

A king post uses one central supporting post, whereas the queen post uses two.

Queen Post Truss:

A lenticular truss bridge includes a lens-shape truss.

It has trusses between an upper arch & lower arch.

Upper curves up and then down to end points while lower arch curves down and then up to meet at the same end points. where the arches extend above and below the roadbed.

Mainly used in the construction of stadium.

Lenticular Truss:

Was an alternative to heavy-timber bridges.

Truss consists of parallel top chord & bottom chord

Consists of planks which are arranged diagonally with short spaces in between them.

 Treenails, or wooden pins, connect the bridge's timbers at each intersection of the truss system.

Mainly used in the construction of bridges

Town Lattice Truss:

Advantages Of Truss :

Are Cost effective.

Can be installed quickly even without heavy equipment to lift it into place.

Unique properties of a triangular object allow trusses to span across longer distances. 

A triangular truss maintains its shape, preventing shift and sag. Thus giving stability to the structure.

The shape of a triangle allows all of the weight applied to the sides to be redistributed down and away from the center. 

THANK YOU