Solved Problems

Bar with Varying Cross-Section

Problem: A stepped steel bar (E=200E = 200 GPa) consists of two segments. Segment AB has area A1=500A_1 = 500 mm2^2 and length L1=1L_1 = 1 m. Segment BC has area A2=200A_2 = 200 mm2^2 and length L2=1.5L_2 = 1.5 m. An axial tensile load of 40 kN is applied at the free end C, and the bar is fixed at A. Determine the total elongation.

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Statically Indeterminate Bar

Problem: A steel bar is fixed at both ends (A and B). The total length is 3 m. A load of 60 kN is applied axially at point C, 1 m from A (and 2 m from B). The area is constant at 300 mm2^2, and E=200E = 200 GPa. Determine the reactions at A and B.

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Rigid Bar Supported by Wires

Problem: A rigid horizontal bar AB of length 3 m is hinged at A and supported by a steel wire at B (L=2L=2 m, A=200A=200 mm2^2, E=200E=200 GPa). A load P=10P=10 kN is applied at C, 2 m from A. Determine the vertical displacement of point B.

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Stepped Bar Fixed at Both Ends

Problem: A stepped bar is fixed at both ends. It has an upper section of length L1=400 mmL_1 = 400 \text{ mm} and area A1=600 mm2A_1 = 600 \text{ mm}^2, and a lower section of length L2=300 mmL_2 = 300 \text{ mm} and area A2=300 mm2A_2 = 300 \text{ mm}^2. A downward load of P=50 kNP = 50 \text{ kN} is applied at the step. Determine the reactions at the fixed supports. Assume E=200 GPaE = 200 \text{ GPa}.

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6 In-Depth Examples of Deformation in Deformable Bodies

The following examples explore the core mechanics of deformation. By expanding on the step-by-step mathematical reasoning, Free Body Diagrams (FBD), and unit analyses, these problems will build a solid foundation in structural response calculations.

Simple Axial Deformation

Problem: A solid structural steel rod of length 2 m2\text{ m} and constant cross-sectional area 500 mm2500\text{ mm}^2 is subjected to a pure axial tensile load of 50 kN50\text{ kN}. Determine the total elongation of the rod. Assume the Modulus of Elasticity is E=200 GPaE=200\text{ GPa}.

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Axial Deformation of a Multi-Segment Bar

Problem: An aluminum stepped bar consists of two segments. The top segment (Segment 1) has a length of 1.5 m1.5\text{ m} and an area of 600 mm2600\text{ mm}^2. The bottom segment (Segment 2) has a length of 1.0 m1.0\text{ m} and an area of 400 mm2400\text{ mm}^2. The bar is suspended from the ceiling. It carries a downward point load of 30 kN30\text{ kN} at the junction between the segments, and a downward point load of 20 kN20\text{ kN} at the free bottom end. Find the total elongation (E=70 GPaE=70\text{ GPa}).

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Deformation Due to Self-Weight

Problem: A vertical heavy steel cable of length 50 m50\text{ m} and cross-sectional area 100 mm2100\text{ mm}^2 hangs freely from a tower. The unit weight of steel is γ=78.5 kN/m3\gamma=78.5\text{ kN/m}^3. Calculate the elongation strictly due to its own weight. Assume E=200 GPaE=200\text{ GPa}.

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Unrestrained Thermal Expansion

Problem: A continuous brass pipeline is exactly 3 m3\text{ m} long at an ambient temperature of 20C20^\circ\text{C}. Find its new length if hot fluid causes the temperature to rise to 80C80^\circ\text{C}. The coefficient of linear thermal expansion for brass is α=19×106/C\alpha=19 \times 10^{-6} /^\circ\text{C}.

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Restrained Thermal Stress

Problem: A steel railroad rail is 10 m10\text{ m} long and is laid securely between two massive concrete abutments at 15C15^\circ\text{C} with absolutely zero gap. Determine the internal compressive stress in the rails if the summer temperature rises to 50C50^\circ\text{C} and the extreme pressure causes the concrete abutments to yield (get pushed outward) by exactly 1.0 mm1.0\text{ mm}. (E=200 GPaE=200\text{ GPa}, α=11.7×106/C\alpha=11.7 \times 10^{-6} /^\circ\text{C})

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Torsional Deformation (Angle of Twist)

Problem: A solid circular steel drive shaft has a diameter of 40 mm40\text{ mm} and a length of 1.5 m1.5\text{ m}. It is subjected to a twisting moment (torque) of 500 Nm500\text{ N}\cdot\text{m}. Determine the angle of twist experienced by the shaft in degrees. Assume the Shear Modulus is G=80 GPaG=80\text{ GPa}.

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