Lapping of Column Reinforcement

Lapping of Column Reinforcement:

Clear cover to main reinforcement in
Footings : 50 mm
Raft foundation Top : 50 mm
Raft foundation Bottom/ sides : 75 mm
Strap Beam : 50 mm
Grade Slab : 20 mm
Column : 40 mm (d>12mm) 25 mm (d= 12mm)
Shear Wall : 25 mm
Beams : 25 mm
Slabs : 15 mm or not less than diameter of the bar.
Flat Slab : 20 mm
Staircase : 15 mm
Retaining Wall on Earth : 20/ 25 mm
Water retaining structures : 20 / 30 mm
Sunshade (Chajja) : 25 mm

Hook for stirrups is 9D for one side

No. of stirrups = (clear span/Spanning) + 1

For Cantilever anchorage length for main steel is 69D

“L” for column main rod in footing is minimum of 300mm

Chairs of minimum 12 mm diameter bars should be used.

Minimum diameter of dowel bars should be 12 mm

Lap slices should not be used for bar larger than 36 mm.

In steel reinforcement binding wire required is 8 kg per MT.

Lapping is not allowed for the bars having diameters more than 36 mm.

Minimum number of bars for a square column are 4 and for circular column are 6.

Longitudinal reinforcement should not be less than 0.8% and more than 6% of gross C/S.

Weight of rod per meter length = d²/162 where d is the diameter in mm

All reinforcement shall be free from mill scales, loose rust & coats of paints, oil or any other substances.

Main bars in the slabs shall not be less than 8 mm (HYSD) or 10 mm (Plain bars) and the distributors not less than 8 mm and not more than 1/8 of slab thickness.

In case of spacing of bars
Provide the diameter of the bar, if the diameter of the bar are equal.
Provide the diameter of the larger bar, if the diameter are unequal.
5mm more than the nominal maximum size of the coarse aggregate.

Drying Shrinkage of Cement and Concrete

Drying Shrinkage of Cement and Concrete:

Reducing concrete drying Shrinkage Some of the measures that can be taken to reduce the drying shrinkage of concrete include: n Use the minimum water content (consistent with placing and finishing requirements). n Use highest possible volume fraction of good quality aggregate and maximum possible aggregate size. n Use Shrinkage Limited Cement (Type SL) where available. n Do not use admixtures known to increase drying shrinkage, eg those containing calcium chloride. n Ensure concrete is properly placed, compacted and cured.

Creep of Concrete

Creep of Concrete:

Creep
When concrete is loaded, the structure undergoes elastic and inelastic deformations. Elastic deformations occur immediately after the concrete is subjected to a given load, according to Hooke’s Law. Inelastic deformations increase with time as the concrete experiences a sustained load. This inelastic deformation, also known as creep, increases at a decreasing rate during the loading period. During the first month of sustained loading, approximately one-fourth to one-third of the ultimate creep takes place. As time proceeds, usually one-half to three-fourths of the ultimate creep occurs during the first half year.
The amount of creep that the concrete undergoes is dependent upon 1) the magnitude of the sustained loading, 2) the age and strength of the concrete when the stress is applied, and 3) the total amount of time that the concrete is stressed. When the concrete is loaded, the specimen undergoes internal properties such as closure of voids in the concrete, viscous flow of the cement-water paste, crystalline flow in aggregates, and water flowing out of the cement "gel" due to drying and loading. Aggregates play an important role in both creep and shrinkage. A well graded, coarser aggregate with a low voids content decreases the effects of creep and shrinkage. Also, hard, dense aggregates that are not absorptive and have a high modulus of elasticity are desirable for low shrinkage and creep rates. Another important aspect to reducing creep is the type of curing procedure performed prior to loading. Very little creep occurs when a high-pressure steamed curing procedure is used. Atmospheric and high-pressure steam curing produces little creep when compared to the seven-day moist curing method. These two types of curing reduce the drying shrinkage by half as much as they reduce creep. Other factors affecting creep include type of cement, amount of cement paste, size and shape of concrete, amount of reinforcement (rebar), volume-to-surface ratio, temperature, and humidity.

Definition of Civil Engineering

Definition of Civil Engineering

1. Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings.