Pre-Board Examination PDF

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Polytechnic University of the Philippines College of Engineering Department of Civil Engineering CEA Bldg. NDC Compound, Pureza St. Sta. Mesa, Manila PREBOARD EXAMINATION DESIGN ANG CONSTRUCTION SET B INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer fo...

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Polytechnic University of the Philippines College of Engineering

Department of Civil Engineering CEA Bldg. NDC Compound, Pureza St.

Sta. Mesa, Manila

PREBOARD EXAMINATION DESIGN ANG CONSTRUCTION SET B INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. SITUATION I 1. Member AC as shown in the figure is subjected to a vertical force of 3 kN. Determine the position x of this force so that the average compressive stress at the smooth support C is equal to the average tensile stress in the tie rod AB. The rod has a cross sectional area of 400 sq.mm and the contact area at C is 650 sq.mm a. 132 mm b. 124 mm c. 150 mm d. 140 mm SITUATION II The inclined member in the figure is subjected to a compressive force of 3000 N. 2. Determine the average compressive stress along the smooth area of contact defined by AB a. 3 MPa b. 1.8 MPa c. 1.5 MPa d. 3.6 MPa 3.Determine the average compressive stress along the smooth area of contact BC a. 2.4 MPa b. .1.8 MPa c. 1.5 MPa d. 1.2 MPa 4. Determine the average shearing stress defined by ABDE a. 0.6 MPa b. 1MPa c. 1.5 MPa d. 2 MPa SITUATION III The small block has a thickness of 5mm. If the stress distribution at the support developed by the load varies as shown in the figure 5. Which of the following gives the force applied on the block a. 7.2 kN b. 14.4 kN c. 36 kN d. 18 kN 6. Determine the distance d a. 120 mm b. 200mm c. 150 mm d. 110 mm SITUATION IV The bar has a cross sectional area A and is subjected to the axial load P. 7. Which of the following gives the normal stress at the shaded plane as shown 𝑃 𝑃 b. 𝑠𝑖𝑛2 𝜃 a. 2𝐴 𝑠𝑖𝑛2𝜃 𝐴 c.

𝑃 𝑠𝑖𝑛𝜃 𝐴

d.

𝑃 2𝐴

𝑠𝑖𝑛2 𝜃

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8. Which of the following gives the value of the shearing stress developed at shaded plane as shown 𝑃 𝑃 b. 𝑠𝑖𝑛2 𝜃 a. 2𝐴 𝑠𝑖𝑛2𝜃 𝐴 c.

𝑃 𝑠𝑖𝑛𝜃 𝐴

d.

𝑃 2𝐴

𝑠𝑖𝑛2 𝜃

SITUATION V Member B is subjected to a compressive force of 3600 N. If A and B are made of wood and are 10 mm thick, 9. Determine the smallest value of h so as not to exceed the allowable shear stress of 2000 kPa a. 45 mm b. 70 mm c. 150 mm d. 100 mm SITUATION VI The eyebolt is used to support the load of 25 kN. As shown in the figure, Allowable normal stress for the bolt is 150m MPa and the allowable shear stress for supporting material is 35 MPa 10. Which of the following gives the nearest value of diameter d to support the washer a. 20 mm b. 10 mm c. 16mm d. 12 mm 11. Which of the following gives the nearest value of h to support the washer a. 20 mm b. 10 mm c. 16mm d. 12 mm SITUATION VII The frame is subjected to the load of 7 kN. Pin A is subjected to double shear, whereas pin B is subjected to single shear, the allowable shear stress at all pin is 40 MPa 12. Determine the required diameter for pin A a. 30.48 mm b. 15.240mm c. 11.663 mm d. 10. 56 mm 13. Determine the required diameter for pin A a. 25mm b. 34mm c. 12.5 mm d. 21 mm SITUATION VIII The rigid beam is supported by pin at A and wires BD and CE. If the maximum allowable normal strain in each wire is 0.002, determine the allowable maximum vertical displacement of the load P 14. Determine the allowable maximum vertical displacement of the load P a. 22mm b. 36 mm c. 34 mm d. 11.2 mm SITUATION IX The lower ends of the three bars in Figure are at the same level before the uniform rigid block weighing 40 kips is attached. Each steel bar has a length of 3 ft, and area of 1.0 in.2, and E = 29 × 106 psi. For the bronze bar, the area is 1.5 in.2 and E = 12 × 106 psi. 15. Determine the length of the bronze bar so that the load on each steel bar is twice the load on the bronze bar, a. 3.72 ft b. 3.5 ft c. 2.76ft d. 5ft

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16. Determine the length of the bronze that will make the steel stress twice the bronze stress. a. 1.25 ft b. 4.3ft c. 3.4ft d. 2.48 ft SITUATION X A flat steel bar, 1 inch wide by ¼ inch thick and 40 inches long, is bent by couples applied at the ends so that the midpoint deflection is 1.0 inch. Use E = 29 × 106 psi. 17. Determine the magnitude of the couple a. 150.5 lb-in b. 203.3 lb-in c.156.65 lb-in d. 188.3 lb-in SITUATION XI In Figure, assume that a 20-mm-diameter rivet joins the plates that are each 110 mm wide. The allowable stresses are 120 MPa for bearing in the plate material and 60 MPa for shearing of rivet. 18. Determine the minimum thickness of each plate a. 10 mm b. 7.85 mm c. 44 mm d. 3 mm 19. The largest average tensile stress in the plates a. 26.67 MPa b. 18 MPa c. 40 MPa d. 12 MPa SITUATION XII 20. A steel rod having a cross-sectional area of 300 mm2 and a length of 150 m is suspended vertically from one end. It supports a tensile load of 20 kN at the lower end. If the unit mass of steel is 7850 kg/m3 and E = 200 × 103 MN/m2, find the total elongation of the rod. a. 54.33 mm b. 58.66 mm c. 80.33mm d. 32.45 mm SITUATION XIII The rigid bar ABC is originally in a horizontal position. If loads cause the end A to be displaced downwards delta A=0.05 mm and the bar rotates θ=0.2 degrees, 21. Determine the average normal strain in the rod AD a. 1.87 (10-3) b. 0.250(10-3) c. 5.49 (10-3) d. 2.87 (10-3) 22. Determine the average normal strain in the rod BE a. 1.87 (10-3) b. 0.250(10-3) -3 c. 5.49 (10 ) d. 2.87 (10-3) 23. Determine the average normal strain in the rod BE a. 1.87 (10-3) b. 0.250(10-3) -3 c. 5.49 (10 ) d. 2.87 (10-3) SITUATION XIV The steel wires AB and AC support the 200 kg mass. If the allowable axial stress for the wires is 130 MPa. The unstretched length of AB to be 750 mm. E=200 GPa 24.Determine the required diameter of wire AB after the load is applied a. 5mm b. 2.23 mm c. 3.23mm d. 3.54 mm 25. Determine the required diameter of wire AC after the load is applied a. 5mm b. 2.23 mm c. 3.23mm d. 3.54 mm Page 3 of 11

26. Determine the new length of AB a. 760.00mm b. 750.49 mm c. 780. 3mm d. 755.34 mm SITUATION XV 27. A rigid beam is made of steel aluminum and has point F on AB if Take E for steel

AB rests on two short posts shown in the figure. AC and has a diameter of 20 mm, and BD is made of a diameter of 40 mm. Determine the displacement of a vertical load of 90 kN is applied over this point. is 200 GPa, E for aluminum is 70 GPa

a. 0.33mm c. 0.169mm

b. 0.56 mm d. 0.225 mm

SITUATION XVI The A 36 steel column is used to support the symmetric loads from two floors of a building. If A moves downward 3mm and B moves downward 2.3 mm when the loads are applied. The column has a cross sectional area of 0.015 sq.m E of A36 is 210 GPa 28. Calculate load P1 a. 1181.5 kN b.630 kN c. 275 kN d. 905 kN 29. Calculate load P2 a. 1181.5 kN c. 275 kN

b.630 kN d. 905 kN

30. A type of simple stress resulting from the contact pressure of two different bodies, a. Bearing stress b. Principal stress c.Normal stress d. Frictional stress SITUATION XVII If the weight of the pot is 900 lbs 31. Determine the force at FA a. 300 lb c. 344 lb

b.326 lb d. 230 lb

32. Determine the force at FB a. 300 lb c. 344 lb

b.326 lb d. 230 lb

33. Determine the force at Fc a. 300 lb c. 344 lb

b.326 lb d. 230 lb

SITUATION XVIII The 8 kg lamp is suspended as shown. The undeformed length of spring AB is 0.4 m, and the spring has a stiffness of 300 N/m 34. Determine the deformed shape of the spring a. 0.735m b.0.853 m c. 0.98 m d. 0.678m 35. Determine the length of AC a. 1.178m c. 1.461 m

b.1.527 m d. 1.324 m

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SITUATION XIX The wooden plank resting between the buildings deflects slightly when it supports the 50 kg boy. This deflection causes triangular distribution of load at its end, having a maximum intensities of Wa and Wb. 36. Determine the intensity of Wa a. 1.44 kN/m b.1.11kN/m c. 1.88 kN/m d. 0.45 kN/m 37. Determine the intensity of Wb a. 1.44 kN/m b.1.11kN/m c. 1.88 kN/m d. 0.45 kN/m SITUATION XX The smooth disk D and E have a weight of 200 lb and 100 lb respectively. If a horizontal force of P=200 lb is applied to the center of disk E. 38. Determine the Reaction at point A a. 250 lb b.9.18 lb c. 141 lb d. 121 lb 39. Determine the Reaction at point B a. 250 lb b.9.18 lb c. 141 lb d. 121 lb 40. Determine the Reaction at point C a. 250 lb b.9.18 lb c. 141 lb d. 121 lb SITUATION XXI For the truss loaded as shown 41. Determine the force in Member BG a. 200 lb C b.420 lb C c. 141 lb d. 495 lb T 42.Determine the force in Member BC a. 200 lb C b.420 lb C c. 141 lb d. 495 lb T 43. Determine the force in Member HG a. 200 lb C b.420 lb C c. 141 lb d. 495 lb T SITUATION XXII The 75 kg man in the figure shown attempts to lift the 40 kg uniform beam off the roller support at B. 44. Determine the tension developed in the cable attached to B. a. 300 N b.256 N c. 224 N d. 512 N 45. Determine the normal reaction of the men on the beam a. 300 N b.256 N c. 224 N d. 512 N SITUATION XXIII The frame in the figure supports the 50 kg cylinder. 46. Determine the Reaction at A a. 500.32 N c. 235.2 N

b.884.5 N d. 736 N Page 5 of 11

47. Determine the force at BC a. 245.25 N c. 300 N

b.884.5 N d. 736 N

SITUATION XXIV The wall crane supports a load of 700 lb. The jib ABC has a weight of 100 lb and member BD has a weight of 40 lb. Each member is uniform and has a center of gravity at its center 48. Determine the reaction at pin A a. 2119 lb b.1222 lb c. 3000 lb d. 3212 lb 49. Determine the reaction at pin D a. 2345lb b.2456 lb c. 3500 lb d. 2588 lb 50. Determine the force at Winch W a. 1400 lb b.700 lb c. 175 lb d. 350 lb SITUATION XXV Determine the reactions at the fixed support E and the smooth support A. The pin is attached to member BD passes through a smooth slot at D 51. Determine the Reaction at A a. 183 N c. 256 N

b.350 N d. 124 N

52. Determine the Reaction at E a. 400 N c. 122 N

b.234 N d. 417 N

53. Determine the moment at support E a. 500 Nm b.455 Nm c. 350 Nm d. 300Nm SITUATION XXVI From the figure shown below 54. Calculate the normal force at C a. 400Nm b. 357Nm c. 800 Nm d. 345Nm 55. Calculate the shear at C a. 120 N c. -120 N

b. -96 N d. 96 N

56. Calculate the bending moment at C a. 202 Nm b. -218 Nm c. 144 Nm d. 100 Nm SITUATION XXVII 57. An aluminum bar having a cross-sectional area of 0.5 in2 carries the axial loads applied at the positions shown in Figure Compute the total change in length of the bar if E = 10 × 106 psi. Assume the bar is suitably braced to prevent lateral buckling a. 0.333 in b. 0.0696 in c. 0.0012 in d. 0.05005 in

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