Statics: pratt truss calculation check

In summary, the person is struggling with a statics problem and has attached a PDF for reference. They are asking for help finding a mistake in their calculations and mention using the joint method. They also mention using RISA for a project in their experimentation class and express frustration with redoing the problem multiple times. Another person responds, pointing out a math error at joint B in calculating BG. The person is hoping to finish the problem by tomorrow for a real-life truss machine test and plans to post pictures if they are successful.
  • #1
mrmotobiker
48
0

Homework Statement



please find it attached as pdf.

Homework Equations



joint method was conducted.

The Attempt at a Solution



please find it attached. i spent so much time on this and i took statics like 1.5 years ago. can you help me find my mistake? i can't seem to find why is my center joints not canceling out.

oh does anyone know how to use RISA? this is for a project in my experimentation class.
 

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  • #2
oh i know i know, I'm a civil and i know statics is a foundation for civil engineering =P but man... I am so pissed off because of this! i redid it like 5 times. i really need to finish this by tomorrow because I'm actually testing a the real thing on the truss machine. will post pics of the testing if i manage to finish this.
 
  • #3
Don't know about RISA, but you made a math error at joint B in calculating BG..otherwise, you're doing good...
 

1. What is a Pratt truss?

A Pratt truss is a type of structural framework commonly used in bridge and building construction. It consists of a series of triangular units connected by vertical and diagonal members, with the top chord typically in compression and the bottom chord in tension.

2. How is a Pratt truss calculated?

To calculate a Pratt truss, you will need to determine the forces acting on each member, such as compression, tension, and shear. This can be done using equations of static equilibrium and the method of joints or method of sections.

3. Why is a Pratt truss used instead of other truss designs?

A Pratt truss is often preferred over other truss designs because it offers a good balance between stability and efficiency. Its diagonal members intersect at a central joint, creating a stable structure, and its configuration allows for the use of shorter and lighter members, making it a cost-effective option.

4. How do you check the stability of a Pratt truss?

To check the stability of a Pratt truss, you can use the method of joints or method of sections to determine the forces acting on each member and then use the equations of static equilibrium to ensure that the structure is in balance. Additionally, you can check for any excessive deflections or buckling, which may indicate instability.

5. Can computer programs be used to calculate a Pratt truss?

Yes, there are several computer programs available that can aid in the calculation of a Pratt truss. These programs use advanced algorithms and numerical methods to quickly and accurately determine the forces and stability of the truss structure.

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