# Types of Loads on Structures β Buildings and Other Structures

## Types of Loads on Structures and Buildings

In a construction of building two major factors considered are safety and economy. If the loads are adjudged and taken higher then economy is affected. If economy is considered and loads are taken lesser then the safety is compromised. So the estimation of various loads acting is to calculated precisely. Indian standard code IS: 875β1987 and American Standard Code ASCE 7: Minimum Design Loads for Buildings and Other Structures specifies various design loads for buildings and structures. Types of loads acting on a structure are:

The first vertical load that is considered is dead load. Dead loads are permanent or stationary loads which are transferred to structure throughout the life span. Dead load is primarily due to self weight of structural members, permanent partition walls, fixed permanent equipments and weight of different materials. It majorly consists of the weight of roofs, beams, walls and column etc. which are otherwise the permanent parts of the building. The calculation of dead loads of each structure are calculated by the volume of each section and multiplied with the unit weight. Unit weights of some of the common materials are presented in table below.
 Sl. No Material Weight 1 Brick Masonry 18.8 kN/m3 2 Stone Masonry 20.4-26.5 kN/m3 3 Plain Cement Concrete 24 kN/m3 4 Reinforced Cement Concrete 24 kN/m3 5 Timber 5-8 kN/m3
Read: Unit Weight / Density of Different Construction Materials

• Residential buildingsβdwelling houses, hotels, hostels, boiler rooms and plant rooms, garages
• Educational buildings
• Institutional buildings
• Assembly buildings
• Mercantile buildings
• Industrial buildings, and
• Storage rooms.
 Number of floors (including the roof) to be carried by member under consideration Reduction in Total Distributed Imposed Loads in % 1 0 2 10 3 20 4 30 5-10 40 Over 10 50

Wind load is primarily horizontal load caused by the movement of air relative to earth. Wind load is required to be considered in structural design especially when the heath of the building exceeds two times the dimensions transverse to the exposed wind surface. For low rise building say up to four to five stories, the wind load is not critical because the moment of resistance provided by the continuity of floor system to column connection and walls provided between columns are sufficient to accommodate the effect of these forces.Β  Further in limit state method the factor for design load is reduced to 1.2 (DL+LL+WL) when wind is considered as against the factor of 1.5(DL+LL) when wind is not considered. The horizontal forces exerted by the components of winds is to be kept in mind while designing is the building. The calculation of wind loads depends on the two factors, namely velocity of wind and size of the building. Complete details of calculating wind load on structures are given below (by the IS-875 (Part 3) -1987). Using colour code, basic wind pressure βVbβ is shown in a map of India. Designer can pick up the value of Vb depending upon the locality of the building. To get the design wind velocity Vz the following expression shall be used:

Vz = k1.k2.k3.Vb

Where k1 = Risk coefficient k2 = Coefficient based on terrain, height and structure size. k3 = Topography factor The design wind pressure is given by

pz = 0.6 V2z

where pz is in N/m2 at height Z and Vz is in m/sec. Up to a height of 30 m, the wind pressure is considered to act uniformly. Above 30 m height, the wind pressure increases.