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Question 1
ప్రశ్న 1
Which statement best describes the basic design philosophy of the Working Stress Method for reinforced concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Working Stress Method is fundamentally an elastic design method. Structural stresses are calculated under working or service-load conditions rather than from ultimate factored-load combinations. These calculated stresses are required to remain within specified permissible values for concrete and reinforcement. Safety is introduced mainly through the relationship between material strength and the lower permissible stress adopted for design. Therefore Option B is correct.
వివరణ:
Question 2
ప్రశ్న 2
Which statement correctly describes the position of the Working Stress Method within IS 456?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 gives primary emphasis to the Limit State Method for structural design. The code nevertheless retains a complete Working Stress Method framework in Annex B. The Working Stress Method may be used where the Limit State Method cannot conveniently be adopted. This is why Working Stress concepts remain relevant for examination syllabi and particular design contexts. Therefore Option B is correct.
వివరణ:
Question 3
ప్రశ్న 3
Which assumption is used in the elastic Working Stress analysis of an RCC flexural member?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The plane-sections assumption is fundamental to classical flexural theory. It implies that longitudinal strain varies linearly over the depth of the section. Perfect bond between steel and surrounding concrete then makes their strains compatible at the same level. The neutral-axis position is obtained from transformed-section equilibrium rather than being assumed at the gross-section centroid. Therefore Option A is correct.
వివరణ:
Question 4
ప్రశ్న 4
In the usual Working Stress analysis of a cracked singly reinforced beam section, how is concrete in the tension zone treated?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Concrete is relatively weak in tension and cracking is expected in the tension zone of an ordinary reinforced-concrete beam. The usual cracked-section Working Stress analysis therefore neglects the tensile contribution of concrete. The tensile force required for flexural equilibrium is carried by the reinforcement. The compression zone of concrete remains active and is treated using elastic stress distribution assumptions. Therefore Option B is correct.
వివరణ:
Question 5
ప్రశ్న 5
Under the Working Stress Method assumptions for elastic member design, the stress-strain relationship of steel and concrete under working loads is taken as:
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Working Stress analysis is based on elastic theory at service-load stress levels. The stress-strain behaviour of both materials is idealized as linear within the range relevant to the method. This permits use of modular-ratio and transformed-section concepts. It also distinguishes the method from ultimate-strength formulations using nonlinear concrete stress blocks. Therefore Option A is correct.
వివరణ:
Question 6
ప్రశ్న 6
In the IS 456 Working Stress Method, the modular ratio m used for flexural calculations is given by which expression, where σcbc is the permissible compressive stress in concrete in bending in N/mm²?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Working Stress provisions specify the modular ratio as m = 280 divided by 3σcbc. Here σcbc is the permissible compressive stress in concrete due to bending. The expression partly allows for long-term effects such as creep. Consequently this design modular ratio should not simply be replaced by the instantaneous ratio Es/Ec calculated from short-term elastic moduli. Therefore Option A is correct.
వివరణ:
Question 7
ప్రశ్న 7
For M20 concrete, the permissible compressive stress in bending under the Working Stress Method is 7 N/mm². What modular ratio should be used according to m = 280/(3σcbc)?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For M20 concrete, σcbc is 7 N/mm². The modular ratio is therefore 280 divided by 3 times 7. This gives 280/21 = 13.33 approximately. This value is the code-design modular ratio for the Working Stress calculation. Therefore Option C is correct.
వివరణ:
Question 8
ప్రశ్న 8
For M25 concrete, the permissible compressive stress in bending is 8.5 N/mm². What is the corresponding Working Stress modular ratio approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The modular ratio is m = 280/(3σcbc). Substituting σcbc = 8.5 N/mm² gives m = 280/25.5. The result is approximately 10.98. This is lower than the M20 value because the permissible concrete bending stress is higher. Therefore Option C is correct.
వివరణ:
Question 9
ప్రశ్న 9
Under the IS 456 Working Stress provisions, what are the permissible concrete compressive stresses for M20 concrete in bending and in direct compression respectively?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The permissible compressive stress in bending for M20 concrete is 7 N/mm². The permissible stress in direct compression is lower, at 5 N/mm². These are Working Stress permissible values and should not be confused with characteristic compressive strength fck. M20 itself has a characteristic cube strength of 20 N/mm², which is a different material parameter. Therefore Option B is correct.
వివరణ:
Question 10
ప్రశ్న 10
For M30 concrete under the Working Stress Method, which pair gives the permissible compressive stresses in bending and direct compression respectively?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For M30 concrete, the permissible compressive stress due to bending is 10 N/mm². The corresponding permissible direct compressive stress is 8 N/mm². These values are taken from the Working Stress permissible-stress provisions rather than from the Limit State stress block. The distinction between bending compression and direct compression is therefore important. Hence Option B is correct.
వివరణ:
Question 11
ప్రశ్న 11
What is the permissible tensile stress in Fe415 high-yield-strength deformed reinforcement for flexural tension under the IS 456 Working Stress provisions?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Working Stress permissible tensile stress for Fe415 high-yield-strength deformed reinforcement is 230 N/mm². This value applies to the flexural tensile reinforcement covered by the relevant permissible-stress table. It is not equal to the characteristic yield strength of 415 N/mm². The difference reflects the permissible-stress philosophy of designing at service-load stress levels with a margin against material strength. Therefore Option C is correct.
వివరణ:
Question 12
ప్రశ్న 12
For Fe500 reinforcement under the IS 456 Working Stress provisions, what permissible stress is specified for direct tension and flexural tension?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For Fe500 reinforcement, the permissible stress in direct and flexural tension is specified as 0.55fy. With fy = 500 N/mm², the value is 0.55 × 500 = 275 N/mm². This special tensile-stress provision should not be indiscriminately applied to all compression and shear reinforcement cases. The Working Stress table retains separate provisions for those situations. Therefore Option D is correct.
వివరణ:
Question 13
ప్రశ్న 13
For Grade I mild-steel reinforcement under Working Stress flexural tension, what are the permissible tensile stresses for bar diameters up to and including 20 mm and for diameters over 20 mm respectively?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For Grade I mild-steel bars up to and including 20 mm diameter, the permissible tensile stress is 140 N/mm². For bars over 20 mm diameter, the permissible value is reduced to 130 N/mm². This diameter distinction applies to the mild-steel category in the Working Stress table. It does not apply in the same way to Fe415 flexural tensile bars, for which the listed value is 230 N/mm². Therefore Option B is correct.
వివరణ:
Question 14
ప్రశ్న 14
Why should the Working Stress modular ratio m = 280/(3σcbc) not automatically be replaced by the short-term elastic-modulus ratio Es/Ec?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The code-prescribed Working Stress modular ratio is not merely an instantaneous ratio of elastic moduli. Its formulation partly accounts for long-term effects, particularly creep of concrete. These effects increase the effective relative deformation of concrete with time. Therefore a short-term Es/Ec value and the WSM design modular ratio need not be identical. Hence Option A is correct.
వివరణ:
Question 15
ప్రశ్న 15
A concrete cross-section excluding reinforcing steel has an area of 149000 mm². It contains 1000 mm² of steel and the modular ratio is 13. What total equivalent concrete area is obtained for the uncracked transformed section?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
In an equivalent-concrete transformed section, the actual concrete area is retained and the steel area is replaced by m times its area. The transformed steel area is therefore 13 × 1000 = 13000 mm². Adding this to the concrete area of 149000 mm² gives 162000 mm². If the gross geometric area including the steel location had instead been used initially, the equivalent correction would be based on (m - 1)Ast. Therefore Option C is correct.
వివరణ:
Question 16
ప్రశ్న 16
A singly reinforced rectangular beam has b = 300 mm, effective depth d = 500 mm, Ast = 1200 mm² and modular ratio m = 13.33. Neglecting tensile concrete, the neutral-axis depth x satisfies bx²/2 = mAst(d - x). What is x approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For the cracked transformed section, the first moment of the compression-zone concrete about the neutral axis is balanced by that of the transformed steel. Substitution gives 300x²/2 = 13.33 × 1200 × (500 - x). Solving the resulting quadratic equation gives x approximately 183.7 mm. Rounding to the nearest offered value gives 184 mm. Therefore Option C is correct.
వివరణ:
Question 17
ప్రశ్న 17
What is meant by a balanced singly reinforced rectangular section under the Working Stress Method?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A balanced section represents a limiting condition based on the permissible stresses of both materials. At the balanced working moment, the extreme concrete compression reaches σcbc at the same time that the tensile steel reaches its permissible tensile stress σst. Strain compatibility and the modular ratio determine the corresponding neutral-axis position. Sections with more or less tensile steel than this balanced amount behave differently with respect to which material reaches its permissible stress first. Therefore Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
For a balanced singly reinforced section, the neutral-axis factor k = x/d is given by k = 1/[1 + σst/(mσcbc)]. For Fe415 steel with σst = 230 N/mm² and the IS 456 WSM relation mσcbc = 280/3 N/mm², what is k approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The product mσcbc equals 280/3, or approximately 93.33 N/mm², when the prescribed WSM modular-ratio expression is used. Thus k = 1/[1 + 230/93.33]. The denominator is approximately 3.464. The resulting neutral-axis factor is approximately 0.2887. Therefore Option B is correct.
వివరణ:
Question 19
ప్రశ్న 19
For the balanced Fe415 section in the previous question, what is the lever-arm factor j = 1 - k/3 approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For a triangular elastic concrete compression-stress distribution, the resultant compression acts at x/3 from the compression face. The lever arm between compression and tensile steel is therefore d - x/3. In nondimensional form, j = 1 - k/3. With k = 0.2887, j is approximately 1 - 0.0962 = 0.9038. Therefore Option C is correct.
వివరణ:
Question 20
ప్రశ్న 20
For an M20 balanced rectangular section reinforced with Fe415 steel, take σcbc = 7 N/mm², k = 0.2887 and j = 0.9038. What is the balanced moment coefficient Q in M = Qbd², where Q = 0.5σcbckj?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For a balanced elastic section, the concrete compression resultant is one-half of σcbc times b times x. Multiplication by the lever arm jd gives the moment of resistance. Thus Q = 0.5 × 7 × 0.2887 × 0.9038. This evaluates to approximately 0.913 N/mm². Therefore Option B is correct.
వివరణ:
Question 21
ప్రశ్న 21
Using the balanced moment coefficient Q = 0.913 N/mm² for an M20-Fe415 section, what is the balanced Working Stress moment capacity of a rectangular beam with b = 300 mm and d = 500 mm?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The balanced moment is M = Qbd². Substituting Q = 0.913 N/mm², b = 300 mm and d = 500 mm gives 0.913 × 300 × 500² N·mm. This is approximately 68.5 × 10^6 N·mm. Converting N·mm to kN·m gives approximately 68.5 kN·m. Therefore Option C is correct.
వివరణ:
Question 22
ప్రశ్న 22
For the same M20-Fe415 balanced section, what is the balanced tensile reinforcement percentage Ast/(bd) × 100 approximately, using 0.5σcbcbkd = σstAst?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
At balance, the compressive resultant equals the tensile force in the steel. Thus Ast/(bd) = 0.5σcbck/σst. Substitution gives 0.5 × 7 × 0.2887 divided by 230. This equals approximately 0.00439 as a ratio, or 0.439 percent. Therefore Option B is correct.
వివరణ:
Question 23
ప్రశ్న 23
Compared with a balanced singly reinforced section under the Working Stress Method, which statement best describes an under-reinforced section?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An under-reinforced section contains less tensile steel than the balanced amount for the same section and material combination. Its neutral axis is consequently shallower than that of the balanced section. For a given limiting condition, the steel stress becomes critical while the concrete compressive stress remains below its permissible maximum. An over-reinforced section shows the opposite tendency, with concrete compression governing first. Therefore Option A is correct.
వివరణ:
Question 24
ప్రశ్న 24
Under the Working Stress provisions, when stresses due to wind or earthquake, temperature and shrinkage effects are combined with those due to dead, live and impact loads, the specified permissible stresses may, subject to the code conditions, be exceeded by up to:
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Working Stress provisions permit an increase in the specified permissible stresses for the stated special load-effect combinations. The maximum increase allowed by this provision is 33 1/3 percent. This is a specific Working Stress rule and should not be confused with the load and material partial safety factors used in Limit State design. The associated code conditions, including treatment of wind and seismic effects, must still be observed. Therefore Option D is correct.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about Working Stress Method and Limit State Method:
1. WSM primarily checks elastic stresses under working loads against permissible stresses.
2. LSM uses characteristic loads and material strengths together with appropriate partial safety factors for relevant limit states.
3. The WSM modular ratio specified as 280/(3σcbc) is not simply the short-term Es/Ec ratio.
4. In ordinary cracked flexural WSM analysis, tensile concrete is normally relied upon to carry the entire tensile force.
Which statements are correct?
1. WSM primarily checks elastic stresses under working loads against permissible stresses.
2. LSM uses characteristic loads and material strengths together with appropriate partial safety factors for relevant limit states.
3. The WSM modular ratio specified as 280/(3σcbc) is not simply the short-term Es/Ec ratio.
4. In ordinary cracked flexural WSM analysis, tensile concrete is normally relied upon to carry the entire tensile force.
Which statements are correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement 1 is correct because Working Stress design is based primarily on elastic service-load stresses and permissible limits. Statement 2 is correct because Limit State design works with characteristic quantities and partial safety factors appropriate to the limit state. Statement 3 is correct because the prescribed WSM modular ratio partly incorporates long-term concrete behaviour such as creep. Statement 4 is incorrect because ordinary cracked flexural analysis neglects tensile concrete and assigns the principal tensile resistance to reinforcement. Therefore Statements 1, 2 and 3 are correct and Option B is the unique answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: B. Stresses produced by service or working loads are limited to specified permissible stresses based on elastic behaviour. సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: B. Limit State Method is normally used, while Working Stress Method provisions are retained in Annex B for situations where Limit State Method cannot conveniently be adopted. సమాధానం: B.
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Question 3 ప్రశ్న 3Answer: A. Plane sections before bending remain plane after bending. సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: B. Its tensile resistance is normally neglected and the reinforcement is taken to resist the tension. సమాధానం: B.
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Question 5 ప్రశ్న 5Answer: A. A straight line within the assumed working range సమాధానం: A.
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Question 6 ప్రశ్న 6Answer: A. m = 280/(3σcbc) సమాధానం: A.
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Question 7 ప్రశ్న 7Answer: C. 13.33 సమాధానం: C.
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Question 8 ప్రశ్న 8Answer: C. 10.98 సమాధానం: C.
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Question 9 ప్రశ్న 9Answer: B. 7 N/mm² and 5 N/mm² సమాధానం: B.
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Question 10 ప్రశ్న 10Answer: B. 10 and 8 N/mm² సమాధానం: B.
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Question 11 ప్రశ్న 11Answer: C. 230 N/mm² సమాధానం: C.
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Question 12 ప్రశ్న 12Answer: D. 275 N/mm² సమాధానం: D.
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Question 13 ప్రశ్న 13Answer: B. 140 and 130 N/mm² సమాధానం: B.
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Question 14 ప్రశ్న 14Answer: A. Because the prescribed Working Stress modular ratio partly accounts for long-term effects such as creep. సమాధానం: A.
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Question 15 ప్రశ్న 15Answer: C. 162000 mm² సమాధానం: C.
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Question 16 ప్రశ్న 16Answer: C. 184 mm సమాధానం: C.
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Question 17 ప్రశ్న 17Answer: A. Concrete and tensile steel reach their respective permissible stresses simultaneously under the limiting working moment. సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: B. 0.289 సమాధానం: B.
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Question 19 ప్రశ్న 19Answer: C. 0.904 సమాధానం: C.
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Question 20 ప్రశ్న 20Answer: B. 0.913 N/mm² సమాధానం: B.
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Question 21 ప్రశ్న 21Answer: C. 68.5 kN·m సమాధానం: C.
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Question 22 ప్రశ్న 22Answer: B. 0.44 percent సమాధానం: B.
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Question 23 ప్రశ్న 23Answer: A. It contains less tensile reinforcement, and the steel permissible stress tends to govern before the concrete reaches its permissible compressive stress. సమాధానం: A.
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Question 24 ప్రశ్న 24Answer: D. 33 1/3 percent సమాధానం: D.
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Question 25 ప్రశ్న 25Answer: B. 1, 2 and 3 only సమాధానం: B.