Help Needed! Struggling with Structural Analysis Problem

In summary, the student attempted to find the tension in a beam, but did not follow any process that was given in class. The book listed 10.72kN at 21.8 degrees, which the student was close to finding.
  • #1
paul11273
156
0
This is a HW question, and I posted it in the HW section, but no one there seems interested. Perhaps somewhere here would be willing to lend a hand?
See the problem in the attachment.
I basically don't know if I am on the right track.

I started with part a) by trying to find the force (tension) pulling on member AB. I did this by calculating the moment about point D.
Md = 6kN * .3m = 1.8kNm (ccw)

I took this torque and used it to compute the x component of the tension at AB.
Md=Force*distance
Fab=Md / distance
Fab= 1.8kNm * .320m = 5.625kN to the left

Using this tension, I tried to find the x component of the force at point C by using the moment created at E by tension AB.
Me = .460m * 5.625kN = 2.59kNm (ccw)

Fcx = Me / distance
Fcx = 2.59kNm / .300m = 8.63kN

Finally, I try to compute the force along CD using the x component I just found (or think I found). I do this using the right triangle created between D, C and the horizontal from D. This gives me .4 along the horz, and .16 along the vertical. That gives a hypotenuse of 80*sqrt(29). Also, the angle created by DC with the horz is 21.8 degrees. By using similar triangles, I find the force along CD to be
Fcd=(80*sqrt(29)/400) * Fcx = 9.29kN

This answer is wrong. The book has 10.72kN at 21.8 degrees. Atleast I found the angle correctly. I am close, but not correct.
Also, I don't feel like I followed any process that we were given for the analysis of structures. Ofcourse, the class examples were painfully simple, and I left class with a great feeling that this was a piece of cake. This problem is changing my mind. Maybe this is simple too, but I am just not seeing it.

Thanks in advance.
 

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  • #3


Hi there,

It seems like you have put a lot of effort into trying to solve this structural analysis problem. It can be frustrating when you don't get the correct answer, especially when you have put in so much time and effort.

First of all, don't be discouraged. Structural analysis can be a challenging subject and it takes practice to fully understand and apply the concepts. It's also important to remember that there can be different approaches to solving a problem, so even if your method is slightly different from what is taught in class, it doesn't necessarily mean it's wrong.

That being said, it's always a good idea to review the steps and processes that are taught in class for solving structural analysis problems. This can help you identify any mistakes or areas where you may have deviated from the correct method.

In terms of your specific problem, it's difficult to provide a definitive answer without seeing the attached image or knowing the specific instructions and assumptions given in the problem. However, here are a few things that may help you in your analysis:

1. It's always a good idea to start by drawing a free body diagram of the structure and labeling all the forces acting on it. This can help you visualize the problem and also identify any unknowns or assumptions that need to be made.

2. When calculating moments, make sure to use the correct sign convention. It's important to be consistent with your positive and negative directions for moments and forces. In your example, it seems like you may have used a clockwise positive moment convention, but it's important to confirm this with the instructions given in the problem.

3. When calculating the x component of the tension at AB, make sure to take into account the angle between the tension and the horizontal. It seems like you may have overlooked this in your calculation.

4. When calculating the force along CD, it's important to take into account both the x and y components of the force at point C. It's not clear from your explanation if you have considered both components in your calculation.

Overall, it's important to take your time and double check your calculations and assumptions. If you are still struggling, don't hesitate to reach out to your professor or classmates for help. It's always better to ask for clarification rather than trying to figure it out on your own and potentially making mistakes.

Keep practicing and don't give up. With time and effort, you will become more comfortable with structural analysis and be able to solve these types of problems
 

1. What is structural analysis?

Structural analysis is a branch of engineering that involves studying the behavior of structures, such as buildings, bridges, and machines, under various load conditions. It helps engineers ensure that structures are safe, functional, and cost-effective.

2. What are the steps for solving a structural analysis problem?

The steps for solving a structural analysis problem include: 1) defining the problem and gathering all necessary information, 2) determining the type and magnitude of the loads acting on the structure, 3) selecting an appropriate method of analysis, 4) performing the analysis and obtaining results, and 5) interpreting the results and making necessary design modifications.

3. What are the commonly used methods for structural analysis?

The commonly used methods for structural analysis include: 1) Finite Element Method (FEM), 2) Matrix Structural Analysis, 3) Method of Joints, 4) Method of Sections, and 5) Moment Distribution Method. The choice of method depends on the complexity of the structure and the type of analysis required.

4. What are some common challenges faced in structural analysis?

Some common challenges faced in structural analysis include: 1) dealing with complex geometries, 2) accounting for material nonlinearities, 3) considering the effects of time-varying loads, 4) ensuring stability and avoiding failure, and 5) optimizing the design for cost and efficiency.

5. How can I improve my skills in structural analysis?

To improve your skills in structural analysis, you can: 1) study the fundamentals of structural mechanics, 2) practice solving different types of structural problems, 3) familiarize yourself with different analysis methods and software tools, 4) stay updated with the latest developments in the field, and 5) seek guidance and mentorship from experienced engineers.

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