【Daily Topic】【Civil Engineering Version 20160109】
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Participation reward: 2 Wealth. Reward for correct answer: 9 wealth. For a simply supported reinforced concrete beam with a span of 8 meters and a designed concrete strength grade of C40, the concrete strength must reach at least ( ) N/mm2 before the formwork at the bottom can be removed. A. 28 B. 30 C. 32 D. 34 Answer: B. 30
B. 30. ---------------------------------------------
For a reinforced concrete simply supported beam with a span of 8 meters and a designed concrete strength grade of C40, the formwork at the bottom can be removed only when the concrete strength reaches at least (B. 30) N/mm2.
For a span of 8m, 75% of the strength is required; 40×75% = 30MPa.
For a simply supported reinforced concrete beam with a span of 8 meters and a designed concrete strength grade of C40, the concrete strength must reach at least ( ) N/mm2 before the formwork at the bottom can be removed. A. 28 B. 30 C. 32 D. 34 Answer: (Correct answer) B. This question relates to the regulations regarding the quality management of concrete structure construction. For beams with a span of 8 meters, the concrete must reach 75% of its ultimate strength before the formwork can be removed; 40 × 75% = 30 MPa. Refer to page P439 of the textbook.