DESIGN OF TRUSS USING STAAD PRO

CONTENT :ObjectiveIntroductionCollected DataLoads calculation ResultsFor further Scope

INTRODUCTION :

TRUSSES

What is a truss….?A Framework ,typically

consisting of rafter , posts, and struts , supporting a roof , bridge or other structure.

A truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints refer to as nodes. Members are commonly wooden struct or metal bars Joint connections are formed by bolting or welding the ends.

Different types of trusses

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 . 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 of 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 MembersThe 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 members :

Distribution of loads :The top beams in a truss are called top chords and are generally in compression.

The bottom beams are called bottom chords and are generally in tension.

Application of trusses-

Roof of factory shade.Ware houseRailway platformGarage shedtransmission towers Crane trussBridge TrussSport Stadium Truss

SPARTAK STADIUM - RUSSIA

Moses Mabhida Stadium - South Africa.

ANZ STADIUM - AUSTRALIA

POAND TORUN BRIDGE

TOKYO GATE BRIDGE

CRANE TRUSS

some pictures of trusses:

PRATT TRUSS FINK TRUSS

OBJECTIVE :In the design & analysis of industrial shed, the type of truss used in shed is decided based on Importance of Structure, type of loads and purpose of shed. ● The design we have considered the mechanical engineering workshop of college VIGNAN INSTITUTE OF TECHNOLOGY AND SCIENCE which is FINK FAN TRUSS.● The main aim is designing of two types of truss for the same configuration i.e , span length of truss, spacing of truss & length of shed.

MECHANICAL SHED OF OUR COLLEGE WHICH IS FINK FAN TRUSS

Collected data :Spacing of truss =4.921mSpan length = 22.310mHeight of shed upto crown=7.5mLength of shed =68.89mLocation of shed - VITS, mechanical workshop. Terain condition - Hilly area.Roofing type – AC sheet

CALCULATION OF LOADS :DEAD LOAD

LIVE LOAD

WIND LOAD (OR)SESMIC LOAD

DIFFERENT CODES USED FOR CALCULATING DIFFERENT LOADSDEAD LOAD - code (IS 875-1987 PART-1)

LIVE LOAD - code (IS 875-1987 PART-2)

WIND LOAD - code (IS 875-1987 PART-3)

SNOW LOAD - code (IS 875-1987 PART-4) SESMIC LOAD - code (IS 1893-1984)

SPECIAL LOADS and LOAD COMBINATIONS - code (IS 875-1987 PART-5)

DEAD LOAD :A constant load in a structure (as a bridge, building, or machine) that is due to the weight of the members.

It is also know as SELF WEIGHT.

Dead load is obtained from the code (IS 875-1987 PART-1)

As per code (IS 875-1987 PART-1)

Dead load of ac sheeting = 0.17 KN/M2 For fixing = 0.025 KN/M2As followed according to code we get dead load on each nodal point dead load on nodal point = 1.37KN (at intermediates) = .0685 KN (at ends).

LIVE LOAD :Weight of everything superimposed on, or temporarily attached to, a structure (people, machinery and equipment, furniture, appliances, etc).

Live load is obtained from the code (IS 875-1987 PART-2).

Live load obtained after calculating according to code is 0.552 KN.

WIND LOAD :

WIND means motion of air in the atmosphere.

Wind is caused by air flowing from high pressure to low pressure.

The response of the structure to wind depends on the characteristics of the wind.

Wind load is obtained from the code (IS 875-1987 PART-3).

DESIGN WIND SPEED : (Vz)=Vb.K1.K2.K3 where, Vb – Basic wind speed (m/s). K1 – Risk coefficient K2 –Terrain height and structure size factor k3 – Topography factor

Vb – Basic wind speed (m/s)= 44 m/s

According to code by substituting required values we get :Design wind speed (Vz) = 48.97 m/s .

Design wind pressure (Pz) = 0.6(Vz)² = 1.439 KN/M².

Calculation of wind load on individual members : F=(Cpe-Cpi)A*Pd

where , Cpe – external pressure coefficient. Cpi - internal pressure coefficient. Pd – design wind pressure. A – Surface area of structural unit.

θ = 0◦Wind ward leeward

θ = 90◦Wind ward lee ward

-1.2 -0.4 -0.8 -0.6

-0.92 -0.4 -0.764 -0.6

-0.4 -0.4 -0.7 -0.6

α◦

10

13.56

20

WhereArea = 6.53 m²Cpi = ±0.5Assuming permeability of wind 5-20% of wall area.

Cpe :

Wind angle Wind ward Lee ward0◦ -13.34KN -8.50KN90◦ -11.84 KN -10.33 KN

FORCES obtained by substituting values along respective directions we get :

At intermediate nodes :

Wind angle Wind ward Lee ward

0◦ -6.67KN -4.25KN90◦ -5.92 KN -5.16KN

At end nodes :

RESULT