Resolving forces in 7 member bridge help

In summary: When you enter in lengths and angles, Excel should automatically calculate the angles and then draw the corresponding triangles. If not, you can manually input the angles and then click on the triangle icon to create it.
  • #1
DoctorVictim
3
0
http://imageshack.us/photo/my-images/853/bridgel.png/

I don't answers course just some guidance. I need to find the forces at each joint, and stresses inbetween too. I've calculated the reaction forces by taking moments as 779N at far left and 692.5N at far right.

Now I'm using trig of course to start from the left and work across finding the stresses but I have forgotten how to find the forces at each joint, and I'm not confident my stresses accurate. Could someone point me in the right direction then I can do the rest.

Sorry if my drawing is poor, or if any other info is needed just say

Thanks in advance.
 
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  • #2
You have two options: analysis by sections, or analysis by joints. Analysis by joints may be the simplest and is accomplished by looking at each joint- the forces imparted on each joint by the members must balance to zero for the joint to be static.

Here's a quick rundown of the two analysis methods: http://emweb.unl.edu/negahban/em223/note12/note12.htm
 
  • #3
Right can I throw a few answers at you and see if you agree?

Member of length 19 is undergoing 1164N

Length 24 along the bottom is 865
 
  • #4
You could have posted that image directly here and other members viewing would not then be subject to an advertising barrage.

Why does your truss have no supports?
 
  • #5
That's all I've been giving,it's been done in excel,and is just the members and a total load, with coordinates for each joint. From there I've found all the lengths and angles and now I'm using that to find stresses
 
  • #6
You're going to have to try a little harder on your lengths and angles. For a start, none of your triangles add up to 180 degrees, and because of that I'm guessing your lengths might not match with your angles either.
 

1. How do you determine the forces acting on each member of a 7 member bridge?

To determine the forces acting on each member of a 7 member bridge, you will need to first create a free body diagram of the bridge. This diagram should include all external forces such as the weight of the bridge, the weight of any vehicles or objects on the bridge, and any support reactions. Next, you will need to apply the equations of static equilibrium to solve for the unknown forces on each member. These equations state that the sum of all forces in the x and y direction must equal zero, and the sum of all moments about any point must also equal zero. By solving these equations, you can determine the forces acting on each member of the bridge.

2. What is the importance of resolving forces in a 7 member bridge?

Resolving forces in a 7 member bridge is important because it allows engineers to understand the internal forces within the structure. This information is crucial for ensuring the safety and stability of the bridge. By resolving forces, engineers can identify any potential weak points or areas that may require reinforcement. It also allows for the optimization of materials and design, leading to a more efficient and cost-effective bridge.

3. What factors can affect the forces in a 7 member bridge?

The forces in a 7 member bridge can be affected by a variety of factors. These include the weight and distribution of loads on the bridge, the design and materials used in the construction of the bridge, external forces such as wind or earthquakes, and even temperature changes that can cause expansion or contraction of the bridge. Changes in any of these factors can impact the forces acting on the bridge and must be taken into consideration during design and construction.

4. How do you ensure that the forces in a 7 member bridge are within safe limits?

To ensure that the forces in a 7 member bridge are within safe limits, engineers use various methods such as computer simulations and physical testing. By using mathematical models and simulations, engineers can predict the forces that will act on the bridge under different conditions and make adjustments to the design as needed. Physical testing, such as load testing and strain gauge measurements, can also provide valuable information about the actual forces experienced by the bridge in real-world conditions.

5. Are there any limitations to resolving forces in a 7 member bridge?

There are some limitations to resolving forces in a 7 member bridge. One limitation is that it assumes the bridge is in a state of static equilibrium, meaning that there are no dynamic or changing forces acting on the bridge. This may not accurately reflect the real-world conditions of the bridge, which is constantly exposed to external forces. Additionally, the accuracy of the results may be affected by simplifications or assumptions made in the mathematical models used to solve for the forces. Therefore, it is important for engineers to consider these limitations and use multiple methods to ensure the safety and stability of the bridge.

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