Quick questions on Dead, live and environmental loads on structures for QCE Engineering Unit 3

The dead load is the permanent, unchanging weight of the structure itself plus everything fixed to it: the beams, columns, slabs, cladding, roofing, ceilings and built-in services. Because it does not move or vary, the dead load is the most predictable load and is calculated directly from the volume and density of the materials. The weight of any body is:

Live loads, also called imposed loads, are the variable loads that come from using the structure: people walking on a floor, vehicles crossing a bridge, furniture, machinery and stored materials. They move and change over time, so codes specify conservative design values (for example a crowd loading per square metre). Live loads are inherently less certain than dead loads, which is one reason a factor of safety is applied later.