Math Problem Statement
Solution
To determine the displacement of each node and the stress at each element for the given two-member truss, we need to follow these steps:
Step-by-Step Solution
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Identify the Geometry and Properties of Each Member:
- Member 1 (Horizontal):
- Length, inches
- Cross-sectional area,
- Young's Modulus,
- Member 2 (Diagonal):
- Length, inches
- Cross-sectional area,
- Young's Modulus,
- Member 1 (Horizontal):
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Determine the Global Stiffness Matrix: Each member has a stiffness matrix, which in global coordinates can be expressed as:
\begin{bmatrix} c^2 & cs & -c^2 & -cs \\ cs & s^2 & -cs & -s^2 \\ -c^2 & -cs & c^2 & cs \\ -cs & -s^2 & cs & s^2 \end{bmatrix}$$ where $$c = \cos \theta$$ and $$s = \sin \theta$$. For member 1, $$\theta = 0^\circ$$ and for member 2, $$\theta = 45^\circ$$. -
Calculate the Element Stiffness Matrices:
- For Member 1 (Horizontal): \begin{bmatrix} 1 & 0 & -1 & 0 \\ 0 & 0 & 0 & 0 \\ -1 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 \end{bmatrix}$$ $$k_1 = 1.5 \times 10^6 \begin{bmatrix} 1 & 0 & -1 & 0 \\ 0 & 0 & 0 & 0 \\ -1 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 \end{bmatrix}$$
- For Member 2 (Diagonal, ): \begin{bmatrix} 0.5 & 0.5 & -0.5 & -0.5 \\ 0.5 & 0.5 & -0.5 & -0.5 \\ -0.5 & -0.5 & 0.5 & 0.5 \\ -0.5 & -0.5 & 0.5 & 0.5 \end{bmatrix}$$ $$k_2 = 0.8485 \times 10^6 \begin{bmatrix} 0.5 & 0.5 & -0.5 & -0.5 \\ 0.5 & 0.5 & -0.5 & -0.5 \\ -0.5 & -0.5 & 0.5 & 0.5 \\ -0.5 & -0.5 & 0.5 & 0.5 \end{bmatrix}$$
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Assemble the Global Stiffness Matrix: Combine and into the global stiffness matrix, considering the degrees of freedom at each node.
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Apply Boundary Conditions:
- Node 1 and Node 3 are fixed, meaning their displacements are zero.
- This will reduce the global stiffness matrix, leaving us with only the equations for Node 2.
-
Solve for Displacements: Use the reduced global stiffness matrix and the applied load vector to solve for the displacements at Node 2.
-
Calculate Stresses in Each Member: The stress in each member is given by:
where is the change in length of each member.
I can perform the numerical calculations if you want, or provide further details on any step. Let me know how you'd like to proceed!
Relative Questions:
- How is the global stiffness matrix constructed in a truss analysis?
- What are the boundary conditions for this truss problem?
- How do you calculate the displacement at a node in a truss structure?
- How is stress in a truss member related to its strain and Young's modulus?
- Why is it important to know the cross-sectional area and material properties of truss members?
Tip: Always ensure you consider boundary conditions and constraints when setting up your global stiffness matrix in structural analysis problems.
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Math Problem Analysis
Mathematical Concepts
Truss Analysis
Statics
Finite Element Method
Linear Algebra
Formulas
Global Stiffness Matrix k = (AE/L) * [c^2 cs -c^2 -cs; cs s^2 -cs -s^2; -c^2 -cs c^2 cs; -cs -s^2 cs s^2]
Stress σ = (E * ΔL) / L
Theorems
Hooke's Law
Equilibrium Equations in Structural Analysis
Suitable Grade Level
College Level (Engineering)
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