Test: RCC- 1 - Civil Engineering (CE) MCQ

Reinforcement bars are generally bent by manual levers instead of heating because heating reduces the strength of bar. As Per IS 2502:1963, bending of bars may be done either by improvised means or by hand-operated machines and by power operated bender.

Explanation

• The correct answer, "Compressive steel is under stressed," is considered the crux of why a doubly reinforced beam is less economical than a singly reinforced beam because, in this configuration, the additional steel provided on the compression side does not contribute as effectively as the tensile reinforcement.
• The compressive steel, being under-stressed, implies that it does not work to its full potential, leading to an inefficient use of material which makes the beam design less cost-effective compared to a singly reinforced beam where materials are generally utilized more efficiently.

To economize the design of a flexural member, the tensile bars are curtailed at the section beyond which it is no longer required to resist flexure. In case of Simply Supported slab, alternate bars are curtailed at 1/7 of the span value.

According to IS 456:2000, the width of the flange of a L-beam should be lesser of

i) The breadth of the rib plus half the sum of the clear distances to the adjacent ribs.

ii) The breadth of the rib plus four times thickness of the slab.

The nominal maximum size of coarse aggregate should be as large as possible within the limits specified but in no case greater than one-fourth of the minimum thickness of the member, provided that the concrete can be placed without difficulty so as to surround all reinforcement thoroughly and fill the comers of the form, For most work, 20 mm aggregate is suitable. Where there is no restriction to the flow of concrete in to sections, 40 mm or larger size may be permitted. In concrete elements with thin sections, closely spaced reinforcement or small cover, consideration should be given to the use of 10mm nominal maximum size.

The panel with drops is 1.25 to 1.50 times thicker than the slab beyond the drop. The minimum slab thickness is 125 mm or L/36 for interior continuous panels without drops and end panels with drops or L/32 for end panels without drops or L/40 for interior continuous panels with drops. The length L is the average length of the panel.

Stiffness criteria is associated with A-value and A-value as per IS 456:2000 are:

1. Cantilever beam: 7

2. Simply supported beam: 20

3. Continuous beam: 26

The maximum strain in concrete at the extreme compression fiber is assumed as 0.0035 in flexure.

Most of the loads applied to the buildings are mainly dead and live loads for buildings located in zone II, III etc. But it, Building is located in Zone IV and is multi-storeyed building then effect of earthquake loads and wind loads all also taken in to consideration. Environmental loads are not all time applied to the structure, or they are uncertain in nature

Explanation
 

• Cantilever Span: The effective span of a cantilever slab at the end of a continuous slab is the length up to the face of the support plus half of the effective width. This is because the cantilever slab is supported at one end and extends beyond the support.


• Effective Span Calculation: To calculate the effective span, you need to consider the length up to the face of the support plus half of the effective width of the slab. This will give you the distance that the cantilever slab can effectively span without additional support.


• Importance: Determining the effective span of a cantilever slab is important for structural design and ensuring that the slab can support the required loads without failing.


 

As per IS 456:2000, clause 39.4.1, the ratio of volume of helical reinforcement to the volume of core shall not be less than   So, ratio is 1 × 20/415 = 0.048 

A wall footing or strip footing is a continuous strip of concrete that serves to spread the weight of a load-bearing wall across an area of soil. It is the component of a shallow foundation.

The bridges will not be considered to be carrying any live load when the wind velocity at the deck level exceeds 130 km/hr

Vertical or inclined stirrups provide shear resistance to members. Bent up bars are also used to provide shear resistance upto certain limit. 

The types and formation of cracks depends on the span-to-depth ratio of the beam and loading. These variables influence the moment and shear along the length of the beam. For a simply supported beam under uniformly distributed load, without prestressing, three types of cracks are identified.

1) Flexural cracks: These cracks form at the bottom near the mid-span and propagate upwards.

2) Web shear cracks: These cracks form near the neutral axis close to the support and propagate inclined to the beam axis.

3) Flexure shear cracks: These cracks form at the bottom due to flexure and propagate due to both flexure and shear.

Recent laboratory experiments confirmed that reinforced concrete in beams has shear strength even without any shear reinforcement. This shear strength (τ_c) depends on the grade of concrete and the percentage of tension steel in beams. The maximum shear strength of reinforced concrete depends on the grade of concrete only. (Reference IS 456, clause 40.2.1 and 40.2.3 respectively)