Problem sovling trusses and frames

Question 1

  1. Determine which diagonal CF or DG is working

Diagonal CF is working

The general stress and tension encountered by the diagonal is

problem sovling trusses and frames

Where fy=0,fx=f,vxy=v

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Fpr=stress principal

F= bending stress as found in equation 2

V= the shearing stress as obtained in equation 1

In the above beams, the length in which shear failure occurs or the shear span is more than thee ffective depth, and failure in the diagonal tension shall be more than shear failure. For the longer shear span that is in the concrete beam shall crack –because there is flexural stress tensile due to the diagonal tension.

The tensional stress is acting at an approximate 45 degrees to the effective normal parts that is closer to the support. Due to the low tensile stress the diagonal beam cracks along the perpendicular and hence the need for reinforcement.

ii) Calculate the tension force that this diagonal is carrying

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Calculate the force in the members FG, DC, CG and GH

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Question 2

Indicate on the truss diagram any zero force members

Out of all these joints the none zero joints are 1 and 6 in these joints, joint 6due to the fact that there are four member joints connected to it. On the other hand, joint N there exists a single two joints of non-collinear nature. Indeed, it is concluded that joint N and M are zero member force this indicates that as long as the loading and support conditions are shown as N and M and therefore joint 1 can be eliminated without interfering with the internal loads truss distribution.

If you start at joint A, can you solve for the force in all members of the truss only using method of joints? Why, or why not?

The answer is yes, this is because the support or force has collinear reaction with two or one members. Therefore the non-collinear members has a zero force . It is therefore possible to evaluate the amount of forces.

Determine the force in every member of the truss.

A=3kN+2kN=5kN

PF=4+3+2=9kN

Question 3

3. Find the support reaction

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And
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b) Find the forces in members DE and DL. (7 marks)

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The total Fx=0

Total Fy= Bv+Cv-1000

Sum TB= 1,000N(4ft)(2ft)

Solve these values Cv=6,660 lb and Bv=3,330 lb