Reinforced concrete is a composite material that consists of concrete and embedded steel reinforcement (usually bars or mesh). Concrete provides compressive strength, while the steel provides tensile strength. The combination of both materials makes it stronger and more durable.
What is the primary function of shear reinforcement in concrete beams?
A Resist shear forces
B Improve aesthetics
C Increase durability
D Resist bending
Shear reinforcement (such as stirrups) is used in beams to resist diagonal shear forces. Concrete alone is weak in tension, and shear reinforcement helps prevent diagonal cracking, which can lead to structural failure under shear stresses.
What is the typical grade of concrete used in residential buildings?
A M30
B M10
C M40
D M20
M20 grade concrete, with a compressive strength of 20 MPa, is commonly used in residential buildings due to its balanced strength and cost-effectiveness. It is suitable for foundations, slabs, and other structural elements in low to medium-rise buildings.
What is the minimum cover required for reinforcement in a concrete column?
A 10 mm
B 50 mm
C 25 mm
D 20 mm
According to the IS 456 code, the minimum cover to reinforcement in concrete columns is typically 25 mm. This cover helps to protect the reinforcement from corrosion, fire, and other environmental factors, ensuring durability and longevity of the structure.
What does the term ‘development length’ refer to in reinforcement?
A Length of the bar under tension
B Length of the bar in the column
C Length of the bar embedded in concrete
D Length of the bar exposed to air
Development length is the length of the reinforcement bar embedded in concrete to ensure proper bond between the concrete and the steel. It allows for the transfer of stresses between the two materials and helps in preventing the slippage of reinforcement.
Which of the following is a feature of prestressed concrete?
A No need for reinforcement
B Concrete is pre-compressed
C Only tensile forces are applied
D Used for lightweight structures
Prestressed concrete involves applying internal forces to the concrete (typically through tensioning steel tendons) before external loads are applied. This process compresses the concrete, improving its ability to resist tensile forces and reducing the risk of cracking.
What is the purpose of the bond between concrete and reinforcement?
A Increase weight
B Increase concrete strength
C Improve durability
D Transfer stresses between concrete and steel
The bond between concrete and reinforcement allows the two materials to act together as a composite unit. It ensures that stresses are transferred from the concrete to the steel, which carries the tensile stresses, and prevents slippage.
Which of the following is used to resist torsion in concrete beams?
A Stirrups
B Tie bars
C Hooked bars
D Longitudinal bars
Stirrups are used in concrete beams to resist torsional forces, which are twisting forces that can cause failure. They are placed at intervals around the longitudinal reinforcement to help resist these forces and prevent the beam from twisting.
What is the purpose of providing a flat slab in reinforced concrete?
A Decrease weight
B Reduce construction time
C Increase bending strength
D Enhance durability
Flat slabs eliminate the need for beams, providing a simple and faster construction process. This reduces the overall construction time, allows more flexible floor planning, and reduces the number of joints, which can lead to cost savings.
What is the characteristic of a two-way slab?
A Does not transfer loads
B Has a high load-carrying capacity
C Supported on four sides
D Supported on one side
A two-way slab is supported on all four sides and transfers loads in both directions (length and width). It is typically used when the length-to-width ratio of the slab is less than or equal to 2. This helps distribute the load more efficiently.
What is a pile cap used for in foundation systems?
A Transfer loads to piles
B Decrease foundation size
C Increase pile strength
D Protect piles from corrosion
A pile cap is a thick concrete slab that rests on and connects multiple piles. It helps distribute the load from the superstructure evenly to the piles, ensuring that the load is transferred to the deeper, more stable soil layers.
What is the limit state design method?
A Method to control deflection only
B Method to estimate reinforcement quantity
C Method to calculate concrete volume
D Method to check strength and serviceability
The limit state design method ensures that a structure is safe under both ultimate (strength) and serviceability (functional) conditions. It checks that the structure can withstand loads without failing and remains functional during its lifespan without excessive deflection or cracking.
Which of the following concrete grades is best for high-strength applications?
A M10
B M20
C M40
D M30
M40 grade concrete is typically used in high-strength applications like high-rise buildings, bridges, and pavements. It has a compressive strength of 40 MPa and provides better durability and load-bearing capacity compared to lower-grade concrete.
What is the primary purpose of ductile detailing in earthquake-resistant design?
A Decrease cost
B Improve energy absorption
C Increase stiffness
D Reduce weight
Ductile detailing ensures that structures can deform significantly during an earthquake without failing. This improves the structure’s ability to absorb and dissipate seismic energy, reducing the risk of collapse and protecting the building’s occupants.
Which factor influences the durability of concrete the most?
A Water-cement ratio
B Aggregate size
C Concrete age
D Concrete color
The water-cement ratio is the most crucial factor affecting concrete durability. A lower ratio improves strength, reduces porosity, and decreases permeability, making the concrete more resistant to chemical attack, moisture, and freezing-thawing cycles.