Question

Write a one page on design philosophy for concrete buildings for gravity and lateral loads. Why are they important to be designed correctly?

Answer 1

Design philosophy for concrete buildings for gravity and lateral loads are-

1.Lateral loads

Lateral loads are live loads that are applied parallel to the ground which are horizontal forces acting on the structure.

The types of lateral loads are: Wind load.,Seismic load. Water and earth pressure.

Wind load may not be a significant concern for small, massive, low-level buildings, but becomes more importance with high rise buildings.

Buildings in areas of seismic activity need to be carefully designed to ensure they do not fail if an earthquake may occur.

Water pressure tends to exert a lateral load which increases linearly with depth and is proportional to the density of liquid .

Earth pressure can be applied against below-ground structures such as basement walls, retaining walls etc.

Structures must be designed carefully with keeping lateral loads in mind. A structural element that is typically used to resist lateral loads is a shear wall.

Bracing can be used to resist lateral loads. The beams and columns of a braced frame structure carry vertical loads, whilst the bracing carries the lateral loads.

2.Gravity loads

(i) Dead loads

It is also known as permanent or static loads which are predominantly associated with the weight of the structure itself and remain stationary and relatively constant over time.

Dead loads may include the weight of any structural elements, permanent non-structural partitions, immovable fixtures such as plasterboard, built-in cupboards etc.

Dead loads can be calculated by calculating the weights of materials specified and their volume as per drawings. It means that in theory it must be possible to calculate dead loads with a good degree of accuracy.

(i) Live loads

It is also known as imposed loads which are usually temporary, changeable and dynamic.

It includes loads such as vehicle traffic, occupants, furniture and other equipment etc.

The intensity of these loads may vary depending on the time of day, for example an office building may experience increased live loads during week day work hours but much smaller loads during the night or at weekends and on holidays.

Live loads may be concentrated or distributed and may cause impact, vibration , acceleration etc.

They are important to be designed correctly for –

(i) For ensuring safety of the structure.

(ii) For analysing accurate cost of the structure.

(iii) To increase service life of structure.

(iv) To increase durability of structure.