Office floor live load- past, present, and future.

Abstract

Buildings and construction industry are estimated to account for nearly 40% related CO2 emissions. The introduction of strict targets for near-zero energy buildings mean that embodied energy is approaching 100% of total energy consumption. One of the Circular Economy strategies aimed at reducing the use of resources is to prolong the life of the product. With a goal of minimum embodied energy in buildings and make them more flexible in adaptation to maximize their life, every step of the design process must be very carefully examined. In structural design codified rules set out how to calculate the design effect of actions (e.g. imposed loads) on an element, which must be less than or equal to the resistance of that element. The U.S., Canada and the UK codes indicate 2.4 or 2.5kN/m2 as live loads for office floors. Despite this, the area weighted average of imposed loading in 95 office buildings completed in the last 20 years was found to be 4.2kN/m2 (including allowance for partitions). This same value was first introduced in 1862 by The Laws of New York State. In the UK it is common practice to assume 5kN/m2 (including allowance for partitions), a value that is equal to that in The London Buildings Acts 1909. Previous studies have shown that loads introduced in current codes are almost impossible to exceed during a building’s life. Furthermore 0.5kN/m2 reduction in design loads could result into a 20% reduction in the building costs and a 14% reduction in the overall embodied carbon of the structure. Research was undertaken to find what causes the decision to assume higher values than codes indicate. It was found that floor load capacity is the one of the factors that is used to grade office space. However, no guidelines introducing load requirements for such classification were found. It might be concluded that the higher load capacity is perceived as a “flexibility” measure and is connected to higher expected rent. It causes over specification and consequently higher energy intensity in construction without clear impact on building life extension