that take into account the load's originating cause, recurrence, distribution, and static or dynamic nature. Dead load The dead load includes loads that are relatively constant over time, including the weight of the structure itself, and immovable fixtures such as walls, plasterboard or carpet. The roof is also a dead load. Dead loads are also known as permanent or static loads. Building materials are not dead loads until constructed in permanent position. IS875(part 1)-1987 give unit weight of building materials, parts, components. Live load Live loads, or imposed loads, are temporary, of short duration, or a moving load. These dynamic loads may involve considerations such as impact, momentum, vibration, slosh dynamics of fluids and material fatigue. Live loads, sometimes also referred to as probabilistic loads, include all the forces that are variable within the object's normal operation cycle not including construction or environmental loads. Roof and floor live loads are produced during maintenance by workers, equipment and materials, and during the life of the structure by movable objects, such as planters and people. Bridge live loads are produced by vehicles traveling over the deck of the bridge. Environmental loads Environmental loads are structural loads caused by natural forces such as wind, rain, snow, earthquake or extreme temperatures. Wind loads Snow, rain and ice loads Seismic loads Hydrostatic loads Temperature changes leading to thermal expansion cause thermal loads Ponding loads Frost heaving Lateral pressure of soil, groundwater or bulk materials Loads from fluids or floods Permafrost melting Dust loads Other loads Engineers must also be aware of other actions that may affect a structure, such as: Foundation settlement or displacement Fire Corrosion Explosion Creep or shrinkage Impact from vehicles or machinery vibration Construction loads Load combinations A load combination results when more than one load type acts on the structure. Building codes usually specify a variety of load combinations together with load factors (weightings) for each load type in order to ensure the safety of the structure under different maximum expected loading scenarios. For example, in designing a staircase, a dead load factor may be 1.2 times the weight of the structure, and a live load factor may be 1.6 times the maximum expected live load. These two "factored loads" are combined (added) to determine the "required strength" of the staircase. The size of the load factor is based on the probability of exceeding any specified design load. Dead loads have