**Correct Answer: 7**

**Explanation:** For a cantilever beam, the span to effective depth ratio is generally restricted to a value of 7. This limitation helps maintain the stability and strength of the cantilevered structure.

**Correct Answer: 10 kg/cm²**

**Explanation:** In a Reinforced Brick (R.B.) slab, the permissible compressive stress in bricks is generally taken as 10 kg/cm². This value ensures the safe and efficient performance of the brick material in the slab structure.

**Correct Answer: 1 in 8**

**Explanation:** The slope of weep holes is generally provided at a ratio of 1 in 8. Weep holes with appropriate spacing and slope are used in retaining walls to facilitate drainage and prevent water buildup behind the wall.

**Correct Answer: drain off the water from the fillings**

**Explanation:** Weep holes are provided in retaining and breast walls to facilitate drainage and prevent water accumulation behind the walls. They allow water to escape, reducing the risk of hydrostatic pressure and potential damage to the structure.

**Correct Answer: uniform**

**Explanation:** In the case of the foundation of a rigid base, the distribution pressure on the soil is generally uniform. This uniform distribution helps in preventing excessive settlement and ensures stability.

**Correct Answer: 15 cm**

**Explanation:** The minimum overall depth kept at the edge of Reinforced Concrete (R.C.) footings is typically 15 cm. This depth provides adequate strength and support for the footing structure.

**Correct Answer: use thicker but fewer numbers of bars**

**Explanation:** If a beam fails in bond, one approach to address the issue is to use thicker but fewer numbers of bars. This helps enhance the bond strength between the concrete and the reinforcement.

**Correct Answer: frictional resistance**

**Explanation:** The resistance offered to slipping of steel bars in concrete is primarily due to frictional resistance between the steel and the surrounding concrete. Adhesion and mechanical resistance also play a role in preventing slippage.

**Correct Answer: tensile test**

**Explanation:** When a material is loaded with tensile force at both ends, the test is known as a tensile test. This test is conducted to measure the material’s response to tensile stress and deformation.

**Correct Answer: pull-out test**

**Explanation:** The safe bond stress between concrete and steel is determined by the pull-out test. This test assesses the bond strength between the concrete and the embedded steel reinforcement by applying a tensile force to the bar and measuring its resistance to pull-out.

_{eft}/ b of the column is considered as a long column if its value is

**Correct Answer: 15**

**Explanation:** The ratio l_{eft} / b of a column is considered as a long column if its value is greater than 12 to 15. This indicates that the effective length of the column in relation to its least lateral dimension is significant, leading to a long-column behavior.

**Correct Answer: 25**

**Explanation:** The cover provided in the column with a size less than 200 mm x 200 mm is typically 25 mm. Cover is the protective layer of concrete that separates the reinforcement from the external environment, providing durability and corrosion resistance.

**Correct Answer: diagonal tension failure**

**Explanation:** The types of failure occurring in a beam due to shear force are termed as diagonal tension failure. This failure mode involves the development of diagonal cracks in the tension zone of the beam.

_{415}is taken as

**Correct Answer: 415 N/mm²**

**Explanation:** The tensile strength of Fe_{415} steel is taken as 415 N/mm². This represents the maximum tensile stress that the steel can withstand.

**Correct Answer: 5000 mm²**

**Explanation:** The gross sectional area of the RCC element is 1 m and 0.5 m, m = 0.5 , m². The minimum reinforcement is 1% of this area, which is 0.01 times 0.5 , m² = 0.005 , m² = 5000 , mm².

**Correct Answer: only concrete will resist tension**

**Explanation:** In a singly reinforced beam, as the load increases, the concrete resists tension until it reaches its tensile strength. After that, the steel reinforcement takes over to resist tension.

**Correct Answer: 1.5 to twice bond length**

**Explanation:** The laps in bars, which refer to the overlapping of two reinforcing bars, are generally in the range of 1.5 to twice the bond length. This ensures proper transfer of stresses and maintains the integrity of the reinforcement.

**Correct Answer: maximum bending moment**

**Explanation:** The amount of reinforcement for main bars in a slab is based upon the maximum bending moment. This is because the main bars are primarily designed to resist bending stresses in the slab.

**Correct Answer: 12**

**Explanation:** A column is considered as a long column if its slenderness ratio (\(l / r\)) is more than 12. The slenderness ratio is the ratio of the effective length of the column to its least radius of gyration.

**Correct Answer: plastic and hardened state**

**Explanation:** The states of concrete include the plastic state (during mixing, placing, and compaction) and the hardened state (after curing and gaining strength). The plastic state refers to the moldable, fresh concrete, while the hardened state is the final, cured and set concrete.

**Correct Answer: greatest**

**Explanation:** In a balanced design of a beam, the maximum stresses occurring, whether in concrete or steel, are equal to the permissible stress. This means that both materials reach their maximum capacity simultaneously, resulting in a balanced condition.

**Correct Answer: 420 N/mm²**

**Explanation:** The ultimate tensile strength of structural mild steel is approximately 420 N/mm². This represents the maximum tensile stress that the steel can withstand before failure.

**Correct Answer: more than the permissible stress**

**Explanation:** A reinforced concrete beam will crack if the tensile stress developed in the concrete below the neutral axis exceeds the permissible stress for concrete. Cracking occurs when the tensile stress reaches a critical value.

**Correct Answer: tensile force developed in steel**

**Explanation:** The moment of resistance of an under-reinforced section is primarily computed based on the tensile force developed in the steel reinforcement. The contribution of concrete in compression is also considered, but the tensile force in steel is a critical factor.

**Correct Answer: any one of the above**

**Explanation:** Such a section is known as a balanced section, a critical section, or an economical section. In this condition, both concrete and steel reach their permissible stresses simultaneously, leading to a balanced and efficient design.

**Correct Answer: rigid joints**

**Explanation:** A rigid frame is a structure where the members are connected by rigid joints, allowing minimal rotation at the connections. This characteristic helps distribute moments and provides stability to the frame.

**Correct Answer: all of the above**

**Explanation:** All the mentioned factors—compaction during placement, proper curing after placement, and an appropriate water-cement ratio—influence the strength and durability of concrete. These factors play crucial roles in achieving the desired concrete properties.

**Correct Answer: 7 days**

**Explanation:** Lime concrete in foundations should be kept wet for a minimum period of 7 days without the construction of masonry over it. This ensures proper curing and development of strength in lime concrete.

**Correct Answer: minimum**

**Explanation:** Placing two layers of tensile reinforcement bars in a flexural member in such a way that they are close to the tension face minimizes the effective depth. This arrangement helps in optimizing the use of reinforcement and improving the performance of the member.

**Correct Answer: parabolic above the neutral axis and rectangular below the neutral axis**

**Explanation:** In a reinforced concrete section, the shear stress diagram is typically parabolic above the neutral axis and rectangular below the neutral axis. This distribution of shear stress helps in understanding and designing for the shear forces in the structure.

**Correct Answer: the slab which bends only along one direction**

**Explanation:** A one-way slab is designed to bend primarily in one direction, and its reinforcement is provided to resist the bending stresses in that direction.

**Correct Answer: compression face**

**Explanation:** In an over-reinforced section, where the amount of steel is more than needed for balanced design, failure typically initiates in the compression zone.

**Correct Answer: fy/(1.15Es) + 0.002**

**Explanation:** The maximum strain in the tension reinforcement at failure is determined by the material properties of the steel and is often specified to ensure ductility and proper performance.

**Correct Answer: on columns monolithically built with slab**

**Explanation:** In a flat slab system, the slab is directly supported by columns that are monolithically connected with the slab, eliminating the need for beams.

**Correct Answer: top fibre**

**Explanation:** In a simply supported beam loaded transversely, the maximum compressive stress develops at the top fiber of the beam.

**Correct Answer: safety factor**

**Explanation:** The ratio of ultimate strength to working stress is commonly known as the safety factor, representing the factor by which the design strength is reduced to ensure the safety and reliability of the structure.

_{lim}of singly reinforced section

_{lim}of singly reinforced section

_{lim}of single reinforced section

**Correct Answer: bending moment in excess of M _{lim} of singly reinforced section**

**Explanation:** In a doubly reinforced section, extra compressive reinforcement is provided to handle bending moments beyond the limit of a singly reinforced section.

_{20}for the limit state method of design should be (for plain bars)

**Correct Answer: 1.2**

**Explanation:** The maximum value of bond stress is often limited to ensure the integrity of the bond between the concrete and the reinforcing bars.

**Correct Answer: 1/4 of the minimum thickness of the member**

**Explanation:** The size of the aggregate is limited to avoid issues such as honeycombing and to ensure workability. In no case should the size be greater than 1/4 of the minimum thickness of the member.

**Correct Answer: clear span plus the effective depth of the slab**

**Explanation:** The effective span of a simply supported slab is the clear span plus the effective depth of the slab, taking into account the supporting conditions.

**Correct Answer: long**

**Explanation:** The slenderness ratio is a measure of how slender or stocky a column is. If the slenderness ratio is high, the column is considered long.

**Correct Answer: Bond stress = Bond Load/X-area of rebar**

**Explanation:** Bond stress is the force exerted between the reinforcing bar and the surrounding concrete per unit area of the bar’s surface.

**Correct Answer: increased towards the center of the beam**

**Explanation:** The spacing of stirrups in a rectangular beam is often increased towards the center to provide adequate shear reinforcement where the shear forces are higher.

**Correct Answer: maximum bending moment**

**Explanation:** The amount of reinforcement for main bars in a slab is based on the maximum bending moment to ensure that the slab can resist the applied loads.

**Correct Answer: half the width of the panel**

**Explanation:** The effective width of a column strip in a flat slab is typically taken as half the width of the panel, considering the distribution of loads and moments.

## FAQs on Structural Design MCQs for Civil Engineers

### ▸ What are the fundamental principles of structural design?

The fundamental principles of structural design include understanding the load distribution, material properties, structural analysis, and ensuring stability and safety. Structural engineers must apply principles of statics, dynamics, and material mechanics to design structures that can safely carry loads and resist environmental forces.

### ▸ How do structural engineers ensure the safety of a building design?

Structural engineers ensure the safety of a building design by performing rigorous structural analysis to assess loads and stresses. They use codes and standards to guide their design, conduct safety checks, and often use software tools to simulate various conditions. The design must consider factors such as load-bearing capacity, material strength, and potential environmental impacts.

### ▸ What is the significance of load calculations in structural design?

Load calculations are crucial in structural design as they determine the amount of stress and strain that different parts of a structure will experience. Accurate load calculations ensure that the structure can support the expected loads, including live loads, dead loads, wind loads, and seismic loads, thus preventing potential failures and ensuring safety.

### ▸ How does material selection impact structural design?

Material selection significantly impacts structural design as different materials have varying strengths, durability, and properties. Engineers choose materials based on factors like load-bearing capacity, environmental resistance, cost, and aesthetics. Proper material selection ensures that the structure meets performance requirements and maintains safety and longevity.

### ▸ What role does structural analysis play in designing bridges?

Structural analysis is critical in bridge design as it helps engineers understand how different forces affect the bridge. It involves analyzing the effects of traffic loads, wind, seismic activity, and other factors. Accurate analysis ensures that the bridge can safely support these forces while maintaining stability and durability over time.

### ▸ What are some common structural design software tools used by engineers?

Common structural design software tools used by engineers include AutoCAD for drafting, SAP2000 for structural analysis, ETABS for building design, and STAAD.Pro for multi-disciplinary analysis. These tools help engineers model structures, perform complex calculations, and ensure compliance with design codes.

### ▸ How do seismic codes affect structural design?

Seismic codes affect structural design by providing guidelines to ensure structures can withstand earthquakes. These codes require engineers to incorporate specific design features such as reinforcement, flexible joints, and base isolation to absorb and dissipate seismic energy, minimizing damage and protecting occupants during seismic events.

### ▸ What are the best practices for designing earthquake-resistant structures?

Best practices for designing earthquake-resistant structures include using high-quality materials, ensuring proper reinforcement, designing flexible connections, and incorporating base isolators. Engineers also follow seismic codes and guidelines to enhance the structure’s ability to absorb and dissipate seismic forces, reducing the risk of damage during an earthquake.

### ▸ What factors should be considered when designing multi-story buildings?

When designing multi-story buildings, factors to consider include load distribution, lateral stability, structural connections, and material properties. Engineers must account for the increased loads on lower floors, ensure proper vertical and horizontal load transfer, and address challenges related to wind, seismic forces, and building settlement.

### ▸ How can I find online quizzes and practice questions for structural design?

You can find online quizzes and practice questions for structural design on educational websites such as https://gkaim.com. These resources offer a variety of practice materials to help you test your knowledge and prepare for exams related to structural engineering.