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The critical section for determining the maximum bending moment for footing supporting a concrete column is located:
Reinforcement bars are generally bent:
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.
A doubly reinforced beam is considered less economical than a singly reinforced beam because:
In doubly reinforced beam we provide some steel in compression zone to reduce the depth of beam. Since steel is 10times costlier than concrete, the beam cost is going to be increased. In general, doubly reinforced beams have a dimensional constraint, as a result of which larger quantities of steel reinforcements are required.
In a simply supported slab, alternate bars are curtailed at:
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.
The width of the flange of a L-beam, should be less than
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 maximum permissible size of aggregates to be used in casting the ribs of a slab, is
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.
For M 15 grade concrete and Fe 415 grade steel the limiting moment of resistance factor is
Limiting moment of Resistance factor for M-15 Grade Concrete and Fe-415 steel is
Mu(lim) = Qu Bd2
Qu → Limiting moment of resistance factor
The minimum thickness of a flat slab is taken
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.
For normal cases, stiffness of a simply supported beam is satisfied if the ratio of its span to its overall depth does not exceed
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
Modular ratio for concrete of Grade M-25 is
As stipulated in IS: 456 – 2000, some assumptions are considered in the computation of ultimate flexural strength of reinforce concrete section. Of the four options given below, the odd one is to be marked.
The maximum strain in concrete at the extreme compression fiber is assumed as 0.0035 in flexure.
Which of the following statements is true?
A. Most of the loads applied to a building are environmental load.
B. Most of the loads are dead followed by live loads.
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
The effective span, of cantilever slab at the end of a continuous slab is:
Which one of the following represents the ratio of volume of helical reinforcement to volume of core if = 1, concrete is M 20 and steel is Fe 415.
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
When a number of columns in a row are provided with a long and narrow combined footing, the footing is termed as
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 highway bridges shall not be considered to be carrying any live load when the wind velocity at deck level exceeds:
The bridges will not be considered to be carrying any live load when the wind velocity at the deck level exceeds 130 km/hr
The shear strength can be ensured in a beam by providing:
Vertical or inclined stirrups provide shear resistance to members. Bent up bars are also used to provide shear resistance upto certain limit.
The stainless steel consists of:
In case of beams in RCC members, the flexural crack is formed at:
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.
The design shear stress in reinforced cement concrete depends on
Recent laboratory experiments confirmed that reinforced concrete in beams has shear strength even without any shear reinforcement. This shear strength (τc) 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)
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