TrussesDate : 20th May 2012Name Of Professor : Mr. SanjaySubject : Building Construction IIISubmitted By : Fairuz , Barch/8008/10
Truss & Its Characteristics: A trussis a structure comprisingone or more triangular units .A triangle is the simplest geometric Nodesfigure that will not change shapewhen the lengths of the sides arefixed.[ Triangular Straight unit MembersItis constructed with straightmembersEnds are connected at jointsreferred to as nodes.External forces and reactions tothose forces are considered to actonly at the nodes Hinges Force acting on the members caneither be tensile or compressive.Moments are excluded because allthe joints in a truss are treatedas Hinges or Revolute.
Truss & Its Component: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 pointsalong 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 alongthe top or bottom chord.Continuous Lateral Brace - Members installed at right angles to a chord or web member of atruss 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 toallow 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, its the location on a truss where the web members and top orbottom chords intersect and are connected by metal connector plates.Web - The members that join the top and bottom chords to form the triangular patterns typicalof trusses.
Truss & Its Component:Bearing - Structural support, usually a beam or a wall that is designed by the designer to carrythe 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, orthe 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 trussmanufacturing process.
Analysis Of Truss: There are 4 main assumptionsmade in the analysis of Trusssystem :Truss members are connectedtogether at their endsTruss are connected togetherby frictionless pins Truss structure is loaded onlyat joints.Weight of the truss membersmay be neglected.
Different Types Of Trusses: Flat Truss Bowstring Truss King Post TrussQueen Post Truss Lenticular Truss Town Lattice Truss
Parallel Chord Truss: Also known as Flat truss Has parallel top chordand bottom chord.The top and bottomchord must be correctlypositioned duringinstallation to ensurestructural integrity ismaintained.Are usually designed tobe supported at the endsonly Often used for floorconstruction.
Bowstring Truss: Alsoknown asCrescent TrussIs a truss consistingof curved top chordmeeting bottom chordat each end. Has diagonal load-bearing members.Often confusedwith tied arch bridges
King Post Truss: A kingpost is also knownas crown post trussItis the simplest form oftruss . Is used for simple rooftrusses and short-spanbridges. Truss consists of twodiagonal members that meetat the apex of the truss,.Consists of one horizontalbeam that ties the bottomend of the diagonals togetherThe king post connects theapex to the horizontal beambelow.
Queen Post Truss: Is similar to a king posttruss Is used for simple rooftrusses and short-spanbridges. Is a supporting postdesigned to span longeropenings than a king post.A king post uses onecentral supportingpost, whereas the queen postuses two.
Lenticular Truss:A lenticular truss bridgeincludes a lens-shapetruss. It has trusses betweenan upper arch & lowerarch. Upper curves up andthen down to end pointswhile lower arch curvesdown and then up to meetat the same end points.where the arches extendabove and below theroadbed.Mainly used in theconstruction of stadium.
Town Lattice Truss:Was an alternative toheavy-timber bridges.Truss consists of paralleltop chord & bottom chord Consists of plankswhich are arrangeddiagonally with shortspaces in between them. Treenails, or woodenpins, connect the bridgestimbers at eachintersection of the trusssystem.Mainly used in theconstruction of bridges
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.