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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 crosssection (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 crosssection, 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 crosssection is reinforced by a 1 in by 0.5 in steel plank to
form the composite crosssection 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 crosssection. _ _ 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, ' _gf :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.
 Spring '09
 MOORTHY

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