Correct Answer: none of the above
Explanation: Buckling can occur in columns, especially in long columns, due to the lateral instability. It is not limited to columns that are either “great” or “too great” in a specific sense.
Correct Answer: 300 mm
Explanation: The maximum spacing between longitudinal bars in a column is typically limited to ensure proper distribution of reinforcement and to enhance the column’s load-carrying capacity.
Correct Answer: least of the above
Explanation: The pitch of the ties in a column is determined by the least of the provided options, which includes the least lateral dimension of the column, 16 times the diameter of the smallest longitudinal bar, or 48 times the diameter of the transverse reinforcement.
Correct Answer: 5% more
Explanation: Helically reinforced columns generally have a higher load-carrying capacity compared to tied columns, and the difference can be around 5% more.
Correct Answer: 25 mm
Explanation: According to standards like IS 456:2000, the minimum cover for a longitudinal reinforcing bar in a column should not be less than the diameter of the bar or 25 mm, whichever is greater.
Correct Answer: 30 cm
Explanation: The spacing of longitudinal bars measured along the periphery of the column is subject to limits defined by standards such as IS 456:2000. In this case, the spacing should not exceed 30 cm.
Correct Answer: plane sections transverse to the center line of the beam before bending remain plane sections after bending
Explanation: In a singly reinforced beam, plane sections transverse to the center line of the beam before bending remain plane sections after bending. This is a fundamental assumption in the theory of flexural (bending) behavior.
Correct Answer: tensile reinforcement
Explanation: The effective depth in a singly reinforced beam is measured from its compression edge to the center of the tensile reinforcement.
Correct Answer: 25%
Explanation: Over-reinforcing a beam can increase its moment of resistance, but there are limits to this increase. Generally, increasing the reinforcement beyond a certain point does not lead to a proportional increase in the moment of resistance.
Correct Answer: all of the above
Explanation: In the steel beam theory of doubly reinforced beams, tension is resisted by tension steel, compression is resisted by compression steel, and the stress in tension steel equals the stress in compression steel. This reflects the balance of forces in a doubly reinforced beam.
Correct Answer: a parabolic curve
Explanation: The distribution of shear intensity over a rectangular section of a beam follows a parabolic curve. This is a characteristic pattern that represents the variation of shear stress across the depth of the beam.
Correct Answer: all of the above
Explanation: The spacing of transverse reinforcement in a column is decided by considering the least lateral dimension of the column, sixteen times the diameter of the smallest longitudinal reinforcing rod, and forty-eight times the diameter of transverse reinforcement. All of these factors play a role in determining the appropriate spacing.
Correct Answer: 30 θ
Explanation: The minimum embedment of reinforcement in a concrete flexural member is typically specified as a certain multiple (such as 30 times) of the diameter of the reinforcement.
Correct Answer: bending moment
Explanation: Main reinforcement in an RCC beam is primarily used for resisting bending moments. It helps to withstand tensile stresses induced by bending.
Correct Answer: shear force
Explanation: Shear reinforcement in an RCC beam is provided to resist shear forces and prevent shear failure. It helps in enhancing the shear capacity of the beam.
Correct Answer: tension
Explanation: Bottom reinforcement in a beam is subjected to tension. It helps to resist the tensile forces induced by bending.
Correct Answer: increased stiffness of the section
Explanation: Increased depth of a beam leads to increased stiffness of the section. This can contribute to the overall strength and performance of the beam.
Correct Answer: 1.33
Explanation: In a rectangular R.C.C beam, the ratio of the maximum shear stress to average shear stress is typically around 1.33.
Correct Answer: 750 mm
Explanation: Side face reinforcement is provided in a beam when the depth of the web exceeds a certain threshold, often around 750 mm. This helps in preventing shear failure.
Correct Answer: 300 mm
Explanation: The maximum spacing of side-face reinforcement in a beam is typically specified to ensure effective distribution and anchorage, and it is commonly around 300 mm.
Correct Answer: F/bxd
Explanation: The maximum shear stress (τ_max) in a singly reinforced beam subjected to shear force (F), with depth (d) and width (b), is given by the formula τ_max = F/(b * d).
Correct Answer: centroid of steel
Explanation: In a singly reinforced beam, the effective cover is measured from the centroid of the steel reinforcement to the outer face of the outermost layer of concrete.
Correct Answer: over-reinforced section
Explanation: If the concrete in a singly reinforced beam reaches its allowable stress before the steel, the section is considered over-reinforced.
Correct Answer: steel provided is insufficient
Explanation: An under-reinforced section means that the amount of steel provided is insufficient, and it will lead to premature failure of the steel before the concrete reaches its full capacity.
Correct Answer: matches with the critical neutral axis
Explanation: In a balanced failure, the stress in concrete and steel reaches their permissible values simultaneously, and the neutral axis location matches with the critical neutral axis.
Correct Answer: increases
Explanation: If the amount of steel in an RCC beam increases, the depth of the neutral axis (N.A.) increases as well.
Correct Answer: development length
Explanation: The minimum length of the bar that must be embedded in concrete beyond any section to develop bond is known as the development length.
Correct Answer: twice the development length or 30 times the diameter of the bar
Explanation: The lap length of a direct tension reinforcement bar should be more than twice the development length or 30 times the diameter of the bar, whichever is greater.
Correct Answer: 15 times the diameter of the bar or 200mm
Explanation: The minimum straight lap length in tension bars with hooks is typically specified as 15 times the diameter of the bar or 200mm, whichever is greater.
Correct Answer: 24 times the diameter of the bar or lap length
Explanation: The minimum lap length at the splice of compression reinforcement is generally specified as 24 times the diameter of the bar or lap length, whichever is greater.
Correct Answer: maximum size of the bar or 2/3 maximum size of the aggregate
Explanation: The minimum vertical spacing of the main bars in an RCC beam is generally specified as the maximum size of the bar or 2/3 of the maximum size of the aggregate.
Correct Answer: 8.5 N/mm2
Explanation: not available
Correct Answer: maintain cover between steel and formwork
Explanation: Cover blocks are used to maintain the specified cover on the sides and below the reinforcement in concrete.
Correct Answer: 25mm or diameter of the bar
Explanation: The minimum cover to the main bars in an RCC beam is typically specified as 25mm or the diameter of the bar, whichever is greater.
Correct Answer: 25mm
Explanation: The minimum thickness of the cover at the end of a reinforcing bar is generally specified as twice the diameter of the bar or a minimum of 25mm.
Correct Answer: bond stress
Explanation: Number-supported beams are provided to resist bond stress and ensure proper development of bond between concrete and reinforcement.
Correct Answer: bending moment
Explanation: The decision between singly reinforced and doubly reinforced beams is primarily based on the bending moment requirements.
Correct Answer: when the depth and width of the beam are restricted
Explanation: Doubly reinforced beams are often used when there are restrictions on the depth and width of the beam, and additional strength is required.
Correct Answer: the deformations in concrete and steel on both sides remain proportional to their distance from the neutral axis
Explanation: In the analysis of a doubly reinforced beam, the assumption is made that the deformations in concrete and steel on both sides remain proportional to their distance from the neutral axis.
Correct Answer: compressive steel is under-stressed
Explanation: A doubly reinforced beam is economical because it allows compressive steel to be under-stressed, leading to efficient use of materials.
Correct Answer: on planes between the neutral axis and the compressive reinforcement
Explanation: In a doubly reinforced beam, the maximum shear stress occurs on planes between the neutral axis and the compressive reinforcement.
Correct Answer: doubly reinforced beams ignoring compressive stress in concrete
Explanation: Steel beam theory is often used for the analysis of doubly reinforced beams, especially when compressive stress in concrete is ignored.
Correct Answer: 0.40 d
Explanation: The depth of the neutral axis for a singly reinforced balanced beam is typically around 0.40 times the effective depth (d).
Correct Answer: 3.5m
Explanation: The maximum span to satisfy vertical deflection limits for a cantilever beam with an effective depth of 50cm is 3.5m.
Correct Answer: θσs / 4rbd
Explanation: The development length of bars in tension is given by the formula θσs / 4rbd as per I.S: 456.
Correct Answer: one-eighth of the least dimension of the beams
Explanation: The maximum diameter of bars in a beam is generally limited to one-eighth of the least dimension of the beams.
Correct Answer: open or closed loops
Explanation: Transverse shear reinforcement in RCC beams can be provided as open or closed loops, in addition to other forms like ties or helical loops.
Correct Answer: maximum
Explanation: The spacing of shear reinforcement is typically kept maximum at the center as compared to the end of a beam.
Correct Answer: 2
Explanation: A simply supported beam is deemed to be a deep beam if the ratio of effective span to overall depth is 2 or less.
Correct Answer: 2.5
Explanation: A continuous beam is deemed to be a deep beam if the ratio of effective span to overall depth is 2.5 or less.
Correct Answer: bending moment, shear, and torsion
Explanation: A beam curved in plan is designed for bending moment, shear, and torsion, as it experiences these forces due to its curvature.
Correct Answer: 5wL4 / 384El
Explanation: The formula for the deflection of a simply supported beam with a uniformly distributed load is 5wL4 / 384El.
Correct Answer: deflect upward or downward
Explanation: Due to shrinkage stress, a simply supported beam with reinforcement only at the bottom may tend to deflect upward or downward.
Correct Answer: diagonal tension
Explanation: Shear reinforcement in an RCC beam is provided to resist diagonal tension, which is a common mode of shear failure.
Correct Answer: shear force (SF)
Explanation: A diagonal crack is introduced in a beam primarily due to shear force (SF).
Correct Answer: on the top face of the beam
Explanation: In the case of a cantilever beam, main reinforcement is typically provided on the top face of the beam.
Correct Answer: vertical steel
Explanation: Shear stress is primarily resisted by inclined or diagonal reinforcement, and vertical steel is not as effective in resisting shear.
Correct Answer: shear at the cut-off point does not exceed two-thirds of permissible at that section
Explanation: Tension reinforcement in R.C.C. beams can be cut off when it is no longer needed if the shear at the cut-off point does not exceed two-thirds of the permissible value at that section.
Correct Answer: twice the diameter
Explanation: The radius of the bend to form a hook should not be less than twice the diameter of the bar.
Correct Answer: four times the diameter
Explanation: The length of the straight portion of a bar beyond the end of the hook should be at least four times the diameter of the bar.
Correct Answer: 180°
Explanation: The anchorage value of a standard hook is significant in ensuring the proper development length of reinforcing bars in concrete. When the hook is formed at a 180° angle, it provides optimal anchorage, and its value is considered as 16 times the diameter of the reinforcing bar. This means that the length of the bar, as far as anchorage is concerned, is effectively extended by 16 times its diameter, ensuring adequate bond strength between the steel and the surrounding concrete.
Correct Answer: 16θ
Explanation: In reinforced concrete structures, bars in tension need to be properly anchored to resist forces. The anchorage value of a standard hook for bars in tension is considered equivalent to a straight length of 16 times the diameter of the reinforcing bar. This ensures that the tension forces can be adequately transferred from the concrete to the reinforcing steel without slippage or failure.
Correct Answer: 8θ
Explanation: Similar to hooks, bends in reinforcing bars also contribute to anchorage. The anchorage value of a standard bend, formed at a 90° angle, is considered as 8 times the diameter of the reinforcing bar. This means that the effective anchorage length is increased by 8 times the diameter, providing sufficient bond strength between the steel and the surrounding concrete in tension zones.
Correct Answer: 90°
Explanation: In the construction of reinforced concrete beams, it is common practice to bend the reinforcement bars at a 90° angle at the ends of the beam. This 90° bend helps in proper anchoring of the bars, ensuring that they can effectively resist tension forces. The perpendicular orientation of the bars at the ends facilitates a smooth transfer of forces between the concrete and the reinforcing steel.
Correct Answer: neutral axis
Explanation: In the context of reinforced concrete beams, N.A stands for the neutral axis. The neutral axis is a crucial concept in structural engineering, representing the plane within a beam where the bending stress is zero. Understanding the location of the neutral axis is essential for designing beams that can effectively resist bending moments and distribute loads.
Correct Answer: the depth of the neutral axis increases
Explanation: The depth of the neutral axis in a reinforced concrete beam is influenced by the distribution of steel reinforcement. As the area of steel increases, the neutral axis tends to move towards the tensile face of the beam, resulting in an increase in the overall depth of the neutral axis. This is because the additional steel provides more resistance to tension forces, causing the neutral axis to shift and the beam’s section to effectively become more ductile.
Correct Answer: all of the above
Explanation: The neutral axis of a T-beam, which has a flange and a web, can exist in various locations. It may be within the flange, at the bottom edge of the slab, or below the slab, depending on the specific geometry and loading conditions. The neutral axis is a critical parameter in the analysis and design of T-beams, as it influences the distribution of stresses and the overall behavior of the structure.
Correct Answer: remains within the flange
Explanation: The behavior of a T-beam is influenced by the location of its neutral axis. When the neutral axis remains within the flange, the T-beam behaves structurally like a rectangular beam with a width equal to its flange. This simplification is often used in the analysis and design of T-beams, allowing engineers to apply principles similar to those used for rectangular beams.
Correct Answer: 1/12 of the span
Explanation: In the case of T-beams subjected to heavy loads, the overall depth of the rib (or the depth of the web) is typically considered to be 1/12 of the span. This design consideration helps ensure that the T-beam can effectively support and distribute the applied loads while maintaining structural stability.
Correct Answer: 1/7th of the span
Explanation: In the design of simply supported slabs, where bars are provided for reinforcement, alternate bars are often curtailed at approximately 1/7th of the span. Curtailing refers to the intentional shortening or terminating of reinforcement bars in a structural element. This practice is commonly employed to optimize the distribution of reinforcement while considering factors such as construction constraints and material efficiency.
Correct Answer: 30
Explanation: For a slab that is simply supported and spans in one direction, the maximum recommended ratio of span to depth is typically 30. This ratio is an important design consideration to ensure that the slab performs well under the applied loads while maintaining structural integrity.
Correct Answer: 35
Explanation: In the case of a slab that is simply supported and spans in two directions, the maximum recommended ratio of span to depth is generally 35. This ratio takes into account the additional considerations for slabs spanning in two directions, providing guidelines for effective load distribution and structural performance.
Correct Answer: three times
Explanation: To ensure effective load distribution and proper structural behavior in a slab, the pitch of the main reinforcement (spacing between the bars) should not exceed three times the effective depth of the slab. This design criterion helps maintain the integrity of the slab under various loading conditions.
Correct Answer: along the short span
Explanation: In a two-way slab, which spans in both directions, the main reinforcement bars are typically designed and placed along the short span. This comprehensive placement of main bars helps in distributing the loads effectively and provides balanced reinforcement throughout the slab.
Correct Answer: five times
Explanation: The pitch of the distribution reinforcement in a slab (spacing between bars) should not exceed five times the effective depth. This guideline is essential for preventing cracks and ensuring that the distribution reinforcement effectively controls shrinkage and temperature-related stresses in the slab.
Correct Answer: all of the above
Explanation: Distribution reinforcement in a simply supported slab serves multiple purposes. It helps distribute loads, controls temperature-induced stresses, and addresses shrinkage stresses. By providing reinforcement to address these factors, the slab’s overall performance and durability are enhanced.
Correct Answer: maximum bending moment
Explanation: The amount of reinforcement for main bars in a slab is primarily based on the maximum bending moment that the slab is expected to experience. This ensures that the slab can effectively resist bending stresses and provides the required structural strength.
Correct Answer: 15 mm
Explanation: The minimum cover in a slab should be neither less than the diameter of the bar nor less than 15 mm. This minimum cover requirement is crucial for protecting the reinforcement from corrosion and ensuring the durability of the structure.
Correct Answer: one diameter
Explanation: The minimum spacing between horizontal parallel reinforcements of the same size in a slab should not be less than one diameter. This specification is important to maintain proper spacing between bars and to facilitate effective concrete placement.
Correct Answer: one times the thicker bar
Explanation: When dealing with horizontal parallel reinforcements of different sizes in a slab, the minimum spacing should not be less than one times the diameter of the thicker bar. This ensures adequate spacing between different-sized bars and facilitates proper concrete consolidation during construction.
Correct Answer: 7.5cm
Explanation: The minimum overall depth of a continuous slab to satisfy vertical deflection limits depends on various factors, including the span, loading conditions, and material properties. For the given size of the slab (3m x 3.5m), a minimum overall depth of 7.5cm may be required to meet deflection criteria while considering structural stability and performance.
Correct Answer: 1/8
Explanation: The ratio of the diameter of reinforcing bars to the slab thickness is an important consideration in the design of reinforced concrete slabs. A common guideline is to maintain a ratio of 1/8, meaning the diameter of the bars should be no more than 1/8th of the slab thickness. This ratio helps ensure proper concrete cover and adequate reinforcement.
Correct Answer: 12 mm
Explanation: In the given scenario, where the slab thickness is 100 mm, the maximum diameter of the reinforcing bar placed in the slab is often recommended to be 12 mm. This choice of bar diameter ensures proper structural performance and adherence to design standards.
Correct Answer: the ratio of spans in both directions is less than two
Explanation: An RCC roof slab is designed as a two-way slab when the ratio of spans in both directions is less than two. This design approach is suitable for distributing loads effectively in both directions and ensuring stability under various loading conditions.
Correct Answer: cracks develop near the corners
Explanation: If the corners of a two-way slab are held down firmly, it can lead to stress concentrations, resulting in cracks near the corners. This phenomenon occurs due to restraint, and the development of cracks is a common issue in such situations.
Correct Answer: flat slab
Explanation: A slab that is built integrally with the supporting columns without any beams is referred to as a flat slab. In flat slab construction, the slab directly rests on the columns, and there are no beams providing additional support.
Correct Answer: capital
Explanation: The enlarged head of a supporting column in a flat slab is technically known as a capital. The capital serves to distribute loads effectively from the slab to the column and enhances the overall structural performance.
Correct Answer: drop panel
Explanation: The thickened part of a flat slab over its supporting column is technically known as a drop panel. This drop panel provides additional strength and stiffness to the slab-column connection, improving load distribution and structural performance.
Correct Answer: breadth of the slab
Explanation: In a two-way slab, the main reinforcement is typically provided along the breadth of the slab. This arrangement helps in effectively resisting bending moments in both directions and ensures structural integrity.
Correct Answer: tension at the top
Explanation: In the case of a cantilever slab, the main reason for placing the main reinforcement bars at the top is to resist tension forces. The tension at the top face of the cantilever slab is critical for preventing cracking and ensuring the structural stability of the slab under loading conditions.
Correct Answer: torsional moments on the slab
Explanation: The lifting of corners in a two-way slab occurs due to torsional moments. Torsional moments create twisting effects in the slab, leading to the upward movement of corners. This phenomenon is more prominent in slabs with irregular or unbalanced loading conditions.
Correct Answer: 1/5th of the short span
Explanation: The length of mesh of torsional reinforcement in a slab is typically taken as 1/5th of the short span. This provision helps in effectively resisting torsional forces and enhancing the overall structural stability of the slab.
Correct Answer: both (a) and (b) of the above
Explanation: Torsion steel in a two-way slab is provided both at the top and bottom of the slab. This dual reinforcement is intended to effectively counteract torsional moments and ensure the slab’s resistance to twisting forces.
Correct Answer: 8 mm
Explanation: The minimum diameter of bars for a slab is generally considered to be 8 mm. This minimum diameter is specified to ensure adequate strength and durability of the reinforcement in the slab.
Correct Answer: paraboloid
Explanation: A circular slab, when subjected to external loading, deforms to assume a shape of a paraboloid. The deformation is influenced by the distribution of loads and structural behavior, resulting in a curved shape resembling a paraboloid.
Correct Answer: all of the above
Explanation: A rib slab can be provided for various purposes, including plain ceiling, acoustic insulation, and heat insulation. The ribs in the slab add architectural features, and the voids between ribs can be utilized for insulation or other functional purposes.
Correct Answer: Φσs / 5πbd
Explanation: The development length of bars in compression as per IS 456:2000 is given by the formula Φσs / 5πbd, where Φ is the diameter of the bar, σs is the permissible stress in compression, b is the breadth of the member, and d is the effective depth.
Correct Answer: 200 KN/mm²
Explanation: The modulus of elasticity for steel as per IS 456-2000 is 200 KN/mm². This value represents the stiffness of steel and is an important parameter in structural analysis and design.
Correct Answer: M20
Explanation: The minimum grade of concrete to be used in reinforced concrete as per IS 456-2000 is M20. This specifies the characteristic compressive strength of the concrete mix.
Correct Answer: max. of (a) and (b) above
Explanation: The minimum cover at the end of reinforcement should be the maximum of either 20 times the diameter of the bar (20 Φ) or 25 mm. This ensures adequate protection of the reinforcement from environmental factors and corrosion.
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.