Calculating constraint reactions

In summary, the conversation discusses calculating constraint reactions on 6 pads using FEM calculations and how to solve statically indeterminate systems. It suggests lumping the constraints together and distributing the forces and moments equally among the pads.
  • #1
Andrea Vironda
69
3
TL;DR Summary
Constraint reactions on a 6 pads system
I would be interested in calculating the constraint reactions on the 6 pads in yellow in the figure, about 300mm apart among them and loaded with F=12500 kN in blue. Since the system is highly hyperstatic, I don't know how to calculate the constraints. Can you give me a hand?

I've made a FEM calculation using Ansys Workbench v18. Do you think it's possible to read those data from there?
Schema RAM.jpg
 
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  • #2
https://en.wikipedia.org/wiki/Statically_indeterminate#Mathematics said:
To solve statically indeterminate systems (determine the various moment and force reactions within it), one considers the material properties and compatibility in deformations.

But if one wants to assume that the forces are well distributed between the different constraints, one can lump the constraints together.

First, find the centroid of the six pads by averaging Xs and Ys to simulate a single reaction pad. The vertical reaction force on that pad will be ##F## and there will be a moment ##M## created to be in equilibrium.

Then draw a line from that pad to each pad. These are your lever arms and the reaction force to the moment for each pad will be perpendicular to these lever arms of length ##R_n## (where ##n## varies from ##1## to ##6##).

Now assume the vertical force and the moment reactions are distributed equally to each pad, thus each pad will have a reaction force that will be a vector composed of ##F/6## and ##M/6/R_n##.
 
  • #3
Thanks, it helped me a lot
 

1. What is the purpose of calculating constraint reactions?

The purpose of calculating constraint reactions is to determine the forces and moments acting on a structure or system. These reactions are essential for analyzing the stability and safety of a structure, as well as for designing and optimizing its components.

2. How do you calculate constraint reactions?

Constraint reactions can be calculated using principles of statics and mechanics. This involves setting up a free-body diagram, applying equilibrium equations, and solving for the unknown reactions. Computer software and simulations can also be used for more complex systems.

3. What are the types of constraint reactions?

The types of constraint reactions include normal forces, shear forces, and moments. Normal forces are perpendicular to the surface, shear forces are parallel to the surface, and moments are rotational forces. These reactions can be either internal or external.

4. How do constraint reactions affect the design of a structure?

Constraint reactions play a crucial role in the design of a structure as they determine the strength and stability of its components. By calculating these reactions, engineers can ensure that the structure can withstand the expected loads and forces, and make adjustments to improve its performance.

5. What are some common challenges in calculating constraint reactions?

Some common challenges in calculating constraint reactions include dealing with complex geometries, non-uniform loads, and dynamic systems. Additionally, ensuring accurate and precise measurements and accounting for all external factors can also be challenging. Using advanced software and techniques can help overcome these challenges.

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