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MAE 241 - Statics

Summer 2009

Dr. Konstantinos A. Sierros

Office Hours: M and W 10:30 – 11:30 (263 ESB new add)

kostas.sierros@mail.wvu.edu

Teaching Blog: http://wvumechanicsonline.blogspot.com

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Determine the force in each member of the truss andstate if the members are in tension or compression. Set P1 

= 2 kN and P2 = 1.5 kN.

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Determine the force in members JI and DE of the K truss. Indicate if the

members are in tension or compression.

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The truck and the tanker have weights of 8000 lb and 20000 lb respectively. Their respective centers of gravityare located at points G1 and G2 .

If the truck is at rest, determine the reactions on bothwheels at A, at B, and at C. The tanker is connected to thetruck at the turntable D which acts as a pin.

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Chapter 7: Internal forces

Chapter objectives• Use the method of sections to determine

internal loadings in a member • Generalize the procedure in order to

formulate equations that can be plotted to

describe internal shear and moment

throughout a member • Analysis of forces and geometry of 

cables supporting a load

 

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7.1 Internal forces developed in structural members

•To design a structural or mechanical member it is necessary to know

the loading acting within a member in order to make sure the materialcan resist this loading• Internal loadings can be determined by using the method of sections• Use section B, separate the beam into two segments. The internal

loadings acting at B will then become external

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7.1 Internal forces developed in structural members

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• NB acts perpendicular to the cross-section and is termed the normal  

force

• VB is tangent to the cross-section and is called shear force• MB is bending moment

• The force components prevent the relative translation between the

two segments. The couple moment prevents the relative rotation

• When analysing forces/moments the right segment is the better choicesince it doesn’t involve the unknown reactions at A

7.1 Internal forces developed in structural members

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7.1 Internal forces developed in structural members

 Normal force (N) is positive when creates

tension

A positive shear force (V) will rotate thesegment clockwise

A positive bending moment will tend to bend

the segment in a concave upward manner 

(smiley face)

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7.2 Shear and moment equations and diagrams

•  Beams are structural members designed

to support loadings applied perpendicular 

to their axes• Simply supported beam is pinned at one

end and roller supported at the other • Detailed knowledge of the variation of 

the internal shear force V and bendingmoment M along the beam axis

• Using the method of sections we can find

these variations

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