Presentation (truss) by imran khan.

DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF INFORMATION TECHNOLOGY &

SCIENCES

CE 302

Structural Analysis & Design Lab 1

A Presentation Of Civil Engineering Department

Group 3 of Civil Dept. 2014 teamwork

An outlook on

Frame &Truss Analysis

PREPARED BY

MD. IMRAN HOSSAIN (ID:12310177)

FRAME

DEFINITION OF FRAME

A-Frame is a basic structure designed to bear a load in a light weight economical manner.

A frame is a structural system that supports other components of a physical construction.

Multi forced members are generally known as Frames.

Frames are commonly used to support various external loads.

FRAME

FRAME

ANALYSIS OF FRAME

A free body diagram of the complete frame is used to determine the external forces acting on the frame.

Internal forces are determined by dismembering the frame and creating free-body diagrams for each component.

TRUSS

WHAT IS TRUSS ?A truss is a structure comprising one or more triangular units constructed

with straight members whose ends are connected at joints or nodes. If all the bars lie in a plane, the structure is a planar truss.The main parts of a planar truss.

TRUSS ANALYSIS

In other words, Trusses are designed to form a stable structure.

TRUSS ANALYSIS

Following characteristics of Truss* The members of the truss should be in a plane.

* Members are connected at their intersections by means of frictionless pins or hinge.

* Loads and reactions are applied only at joint.

* The centroid of the members must coincide with centroid of the joints.

Truss Members The members which from the outline or perimeter of a truss are

generally called the chord members.

There are two chord members -

01. Top Chord: Top members

02. Bottom Chord: Bottom members

Web Members – The interior members connecting the joints of the chords are called the web members.

There are two members-

01. Diagonal members

02. Vertical members

TRUSS ANALYSIS

TRUSS ANALYSIS

Why are trusses strong?

Trusses derive their strength from the triangle.

The simplest of plane polygons, a triangle is unique in

that it is defined by the length of its sides. That is, one

and only one triangle can be drawn if the length of all

three sides is given.

TRUSS ANALYSIS

Why are triangles used in trusses? Rectangles and squares are not very strong

because the middle of each side would tend to bend or buckle easily. And these are not used in truss.

A truss is a structure made up of triangles. Because triangles are strong because when you define the length of the three sides the relationship between the nodes is fixed. Similarly when you identify any two angles an a side or two sides and a common angle all other properties are fixed. In any other shape there are more degrees of rigidity required to create a fixed structure.

Triangles have sides that reinforce each other. They divide up the load.

TRUSS ANALYSISApplication of trusses-

Roof of factory shade. Ware house Railway platform Garage shed transmission towers Crane truss Bridge Truss Sport Stadium Truss

TRUSS ANALYSIS

TRUSS ANALYSIS

TRUSS ANALYSIS

TRUSS ANALYSIS

TRUSS ANALYSIS

TRUSS ANALYSIS

Joint Method

Determine the Support

Reaction.

Apply Fx = 0 and Fy = 0 to

every node and determine

member force

Dismember the truss and create

a free-body diagram for each

member and pin.

METHOD OF TRUSS ANALYSIS

TRUSS ANALYSIS

SECTI ON METHOD

Determine the Support Reaction.

To determine the force in member

BD, pass a section through the truss

as shown and create a free body

diagram for the left side.

With only three members cut by the

section, the equations for static

equilibrium may be applied to

determine the unknown member

forces, including FBD.

METHOD OF TRUSS ANALYSIS

TRUSS ANALYSIS

Comparison of Trusses and Frames

Trusses Frames

Members are subjected to tension/compression only

At least one member is subjected to bending, shear or torsion

Forces are applied at the joints only.

Forces may act anywhere on the member.

Member does not bend. Members may bend/may not bend.

Composed of rods. Composed of bars.

Used for large loads. Used for small and medium loads.

TRUSS ANALYSIS

Advantages of Truss & Frame

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

TRUSS ANALYSIS

Common Types of Trusses-

King post & Queen post Truss.

Warren Truss.

Howe Truss.

Pratt Truss.

English Truss.

K- Truss.

Baltimore Truss.

Continuous Truss.

Bowstring Truss.

TRUSS ANALYSIS

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-

TRUSS ANALYSIS

King post It is used for simple short-span

bridges.

Fewest number off truss members.- two diagonal members, kingpost braces, that meet at the apex of the truss, one horizontal beam and the king post which connect the apex to the horizontal beam below.

King post & Queen Post Truss-

TRUSS ANALYSIS

Queen post It has two vertical post.

Very strong and stable.

It´s more stable and can support a wider span than a kingpost.

King post & Queen Post Truss-

TRUSS ANALYSIS

It uses equilateral triangles to spread out the loads on the bridges. The equilateral triangles minimize the forces to only compression and tension.

This bridges are often used with verticals to reduce the panel size.

Warren Truss-

TRUSS ANALYSIS

It became very popular and was considered one of the best designs for railroad bridges back in the day.

Wooden beams for the diagonal members, which were in compression. It used iron (and later steel) for the vertical members, which were in tension.

Howe Truss-

TRUSS ANALYSIS

TRUSS ANALYSIS

Very common type but has many variations (Baltimore, Pennsylvania, and the Parker)

The basic identifying features are the diagonal web members which form a V-shape. (Howe truss bridge has a A-shape).

Commonly used for supporting railways.

The Pratt truss’s verticals functioned as compression members and diagonals functioned as tension members.

The Pratt truss required more iron than a Howe truss,

Pratt Truss-

TRUSS ANALYSIS

TRUSS ANALYSIS

The length of members undergoing compression is reduced. This reduction in length enables components of bridges to endure the compressional force.

The design is complicated and it is considered to be one of the

hardest bridges to build.

K- Truss-

TRUSS ANALYSIS

TRUSS ANALYSIS

Roof Truss- Roof trusses, which are

structural components of houses or commercial buildings, support the weight of roof timbers and coverings.

Usually, they are constructed from pieces of timber or steel which are nailed, bolted, or pegged together to form a mutually supporting and strong base for a roof.

TRUSS ANALYSIS

TRUSS ANALYSISDesign of industrial roof truss: Steps of work

1. Selection of truss type.

2. Estimation of loads.

3. Analysis & design of purlin.

4. Analysis & design of sag rod.

5. Dead load(DL) and Wind load(WL) analysis

of truss member.

6. Combination of DL and WL to determine

the design bar forces.

7.Design of member according to the bar forces.

8.Design of bracing system.

9.Design of connection.

10.Detailing.

TRUSS ANALYSIS

We will design a Industrial roof truss

TRUSS ANALYSIS

Design of Purlin Then calculating of purlin number and Purlin

spacing. Then load analysis-

01. Dead load analysis.

02.live load analysis. Then we find out member force by grasp

software. Bracing design-

01. Top chord bracing.

02. Bottom chord bracing.

03. Vertical bracing.

TRUSS ANALYSIS

Types of Truss Connection- 01. Pinned Connection.

TRUSS ANALYSIS

Types of Truss Connection-

02. Gusset plate Connection.