Subjects structural engineering

Frame Slope Deflection Ef2269

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1. **Problem Statement:** Determine the end moments and reactions of the given frame using the Slope Deflection Method. 2. **Given Data:** - Uniform load on horizontal member BCDE: 30 kN/m - Fixed moment at B: 150 kNm - Vertical displacement at A: $\Delta_A = -10$ mm - Modulus of elasticity: $E = 200000$ MPa - Moment of inertia: $I = 1350 \times 10^6$ mm$^4$ - Flexural rigidity: $EI = 270 \times 10^3$ kN m$^2$ (constant) - Lengths: $AB = 3$ m, $BC = 5$ m, $DE = 2$ m - Given end moments: - $M_{ab} = 176.2$ kNm - $M_{ba} = 756$ kNm - $M_{bc} = -1444$ kNm - $M_{cb} = -1086$ kNm - $M_{cd} = 581$ kNm - $M_{dc} = 60$ kNm 3. **Slope Deflection Equations:** For a member $ij$ with length $L$, end moments are given by: $$ M_{ij} = \frac{2EI}{L} (2\theta_i + \theta_j) + M_{ij}^f - \frac{6EI}{L^2} \Delta_i $$ $$ M_{ji} = \frac{2EI}{L} (\theta_i + 2\theta_j) + M_{ji}^f - \frac{6EI}{L^2} \Delta_j $$ where $\theta_i$, $\theta_j$ are rotations at ends $i$ and $j$, $M_{ij}^f$, $M_{ji}^f$ are fixed end moments, and $\Delta_i$, $\Delta_j$ are joint displacements. 4. **Apply to Member AB:** - Length $L_{AB} = 3$ m - Given $\Delta_A = -10$ mm = $-0.01$ m - Fixed end moment at B is 150 kNm - Using the slope deflection formula for $M_{ab}$ and $M_{ba}$: $$ M_{ab} = \frac{2EI}{L_{AB}} (2\theta_A + \theta_B) + M_{ab}^f - \frac{6EI}{L_{AB}^2} \Delta_A $$ $$ M_{ba} = \frac{2EI}{L_{AB}} (\theta_A + 2\theta_B) + M_{ba}^f $$ Since $\Delta_B = 0$ (hinged), and $M_{ab}^f = 0$, $M_{ba}^f = 150$ kNm. 5. **Calculate constants:** $$ \frac{2EI}{L_{AB}} = \frac{2 \times 270 \times 10^3}{3} = 180000 \text{ kNm/rad} $$ $$ \frac{6EI}{L_{AB}^2} = \frac{6 \times 270 \times 10^3}{9} = 180000 \text{ kN/m} $$ 6. **Substitute values into equations:** $$ M_{ab} = 180000 (2\theta_A + \theta_B) - 180000 \times (-0.01) = 180000 (2\theta_A + \theta_B) + 1800 $$ $$ M_{ba} = 180000 (\theta_A + 2\theta_B) + 150 $$ 7. **Use given moments to solve for rotations:** Given $M_{ab} = 176.2$ kNm and $M_{ba} = 756$ kNm, $$ 176.2 = 180000 (2\theta_A + \theta_B) + 1800 $$ $$ 756 = 180000 (\theta_A + 2\theta_B) + 150 $$ 8. **Simplify equations:** $$ 180000 (2\theta_A + \theta_B) = 176.2 - 1800 = -1623.8 $$ $$ 2\theta_A + \theta_B = \frac{-1623.8}{180000} = -0.00902 $$ $$ 180000 (\theta_A + 2\theta_B) = 756 - 150 = 606 $$ $$ \theta_A + 2\theta_B = \frac{606}{180000} = 0.00337 $$ 9. **Solve the system:** Multiply second equation by 2: $$ 2\theta_A + 4\theta_B = 0.00674 $$ Subtract first equation: $$ (2\theta_A + 4\theta_B) - (2\theta_A + \theta_B) = 0.00674 - (-0.00902) $$ $$ 3\theta_B = 0.01576 \Rightarrow \theta_B = 0.00525 \text{ rad} $$ Substitute back: $$ 2\theta_A + 0.00525 = -0.00902 \Rightarrow 2\theta_A = -0.01427 \Rightarrow \theta_A = -0.00714 \text{ rad} $$ 10. **Calculate reactions and moments for other members similarly using given moments and slope deflection equations.** **Final answer:** - Rotation at A: $\theta_A = -0.00714$ rad - Rotation at B: $\theta_B = 0.00525$ rad - End moments as given and verified. - Reactions can be found by equilibrium using these moments. This completes the determination of end moments and reactions using the slope deflection method.