Hollow Circular Beam with Known Cracking Moment

A concrete beam with cross section in Figure CO4-2B is simply supported over a span of 4 m. The cracking moment of the beam is 75 kN·m.



1.   Find the maximum uniform load that the beam can carry without causing the concrete to crack, in kN/m.

A.   35.2 C.   33.3
B.   37.5 D.   41.8

2.   Find the modulus of rapture of the concrete used in the beam.

A.   4.12 MPa C.   3.77 MPa
B.   3.25 MPa D.   3.54 MPa

3.   If the hallow portion is replaced with a square section of side 300 mm, what is the cracking moment of the new section in kN·m?

A.   71.51 C.   78.69
B.   76.58 D.   81.11


Solution to Problem 234 Statically Indeterminate

Problem 234
A reinforced concrete column 200 mm in diameter is designed to carry an axial compressive load of 300 kN. Determine the required area of the reinforcing steel if the allowable stresses are 6 MPa and 120 MPa for the concrete and steel, respectively. Use Eco = 14 GPa and Est = 200 GPa.

Solution to Problem 110 Normal Stress

Problem 110
110-footing-wooden-post.gifA 12-inches square steel bearing plate lies between an 8-inches diameter wooden post and a concrete footing as shown in Fig. P-110. Determine the maximum value of the load P if the stress in wood is limited to 1800 psi and that in concrete to 650 psi.

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