By excessively over-reinforcing a concrete beam, the moment of resistance can be enhanced by no more than________________?
Show answer Hide answer
Answer: D. 25 %
Explanation
Excessively over-reinforcing a concrete beam yields diminishing returns, enhancing its ultimate moment of resistance by no more than 25%. Adding steel beyond balanced design limits causes concrete to crush prematurely before the steel can develop its full strength. Because concrete fails suddenly in compression, extra steel contributes very little additional moment capacity to the section. Over-reinforced beams contain more tensile steel than required for balanced failure, leading to brittle compression-dominated behavior. Moment of resistance depends heavily on the compressive strength of concrete once the steel reinforcement ratio exceeds optimal limits. Design codes discourage excessive over-reinforcement due to the hazard of sudden, catastrophic structural failure without warning.
Option A underestimates the potential capacity increase by setting the maximum enhancement limit at an unrealistically low percentage. Option B represents an intermediate value that still falls short of the maximum possible theoretical moment resistance gain. Option C suggests a 20 percent cap which is lower than the standard empirical limit established for over-reinforced beams.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. As the proportion of steel reinforcement in a concrete member rises________________?
Show answer Hide answer
Answer: B. Depth of neutral axis increases
As the proportion of steel reinforcement increases in a concrete section, the total tensile force capacity rises accordingly. Higher steel area requires a larger compressive force in the concrete to maintain internal equ...
Q2. In accordance with I.S. 456 – 1978, the mixing water pH level must fall within_______________?
Show answer Hide answer
Answer: C. Not less than 6
IS 456 standards dictate that the pH level of mixing water used for reinforced concrete must not be less than six. Acidic water with a pH below six can interfere with cement hydration and corrode embedded steel reinforce...
Q3. An R.C.C. roof slab is analyzed and designed as a two-way slab under the condition that________________?
Show answer Hide answer
Answer: B. The ratio of spans in two directions is less than 2
An R.C.C. roof slab is designed as a two-way slab when the ratio of its longer span to shorter span is less than 2. When this span ratio remains below two, significant bending occurs along both orthogonal directions simu...
Q4. An under-reinforced structural concrete section implies that_________________?
Show answer Hide answer
Answer: D. Steel will yield first
An under-reinforced structural concrete section is designed such that the tensile steel yields first before the concrete crushes. Providing less steel than the balanced amount ensures that the reinforcement reaches its y...
Q5. An R.C.C. beam with a 6 m span, 30 cm width, and 55 cm lever arm carries a 12 t/m U.D.L. Given an allowable shear stress of 5 kg/cm2, evaluate if the beam________________?
Show answer Hide answer
Answer: D. Needs revision of section
When calculated shear stress significantly exceeds the allowable limits of the concrete grade, the beam section dimensions must be revised. High transverse loads combined with small cross sectional areas generate shear s...
Q6. A pile of length L subjected to a uniform load per unit length is suspended at two points; compute the maximum bending moment occurring either at the center or at the suspension points_________________?
Show answer Hide answer
Answer: C. WL²/47
For a pile of length L suspended at two specific optimal points under a uniform load, the maximum bending moment equals WL²/47. Suspending a long pile at calculated optimal locations minimizes the peak bending moments de...