CE3400_Exam2_Samples - Test 2 CE3400 Strengths, Summer 2005...

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Unformatted text preview: Test 2 CE3400 Strengths, Summer 2005 Closed Book, Closed Notes Mon, Jul 18th 2005, 12:10 P.M—1:10 PM No questions will be allowed once the exam begins. if you need to make an assumption write it down clearly in the blue book. Show all work and proper free body diagrams (FBD’S) for full credit 1) The concrete beam, shown in figure (1), is reinforced with three steel rods placed as shown. The modulus of elasticity of concrete is Ecom = 3 X 106 psi and that of steel is Est : 30 X 105 psi. If the allowable stress for concrete is agfim = 1350 psi calculate (a) The largest allowable positive bending moment and its direction (b) The stress in the steel rods (30 points) 7' . . —8—— m diameter Figure l: 2) The 24 N — m bending moment is acting at B of beam AE. (a) Draw the shear force diagram from B to D (b) Draw the bending moment diagram from C to D (0) Determine the maximum internal bending moment from C’ to D and its position. (d) For the maximum internal bending moment calculated in (0), determine the stresses at points A and B of the cross-section (45 points) (Front View) (Side View) Figure 2: 3) The centroid C of the Cross—section, shown in figure (3), is at a distance 2.74 in from the top. If a vertical shear of 50 kip acts along the cross-section, determine (a) The shear stress at a (b) The position and value of the maximum shear stress along the cross—section. (25 points) Formula sheet 1. Normal stress for a symmetric cross—section under pure bending My Ufi—T 2. Unsymmetric bending w sz Myz P O'w m [Z + 1y +A 3 L7 tan(fl) = ftenw) y 3. Sheer flow and stress due to shear force in beams =KQT_Q 9 P‘s CE 3400(01) and (02) Exam No. 2 04/01/2008 Problem N0. 1 The 1 in by 3 in wooden cross-section is reinforced by a 1 in by 0.5 in steel plank to form the composite cross-section shown in the figure. If the maximum absolute bending stress cannot exceed specified values in the wooden and steel parts of the cross—section, determine the maximum horizontal bending _ moment that can be applied on the composite cross-section. _ _ Wood: E = 2x 103 ksi and can = 1 ksi a) Draw the Shear Force Diagram (SFD) and the Bending Moment Diagram (BMD). b) Determine the absolute maximum bending RA 2 «1480 lb m 3;, stress in the beam. (Refer to formula sheet in the back for structural and geometrical properties for this section) Steel: E 2 30 x 103 ksi and can: 12 ksi .1;- Problem No. 2 3 - ,. For the W12 x 26 beam and the loads shown in IA 7 ;. '1 M5) = 480 3b - {t the figure, ' _g-f :5 Ba x 4891b {1 m- iss 3b 5* RB 11ft Problem N o. 3 A square box beam is constructed from four planks as shown. If each nail can support a shear force of 80 lb, determine the maximum spacing, s, between the nails knowing the beam is subject to a shearing force of V 2 600 lb. Section properties are given and effective I m 27.42 i114. ...
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This note was uploaded on 05/06/2010 for the course CE 3400 taught by Professor Moorthy during the Spring '09 term at LSU.

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CE3400_Exam2_Samples - Test 2 CE3400 Strengths, Summer 2005...

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