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Concrete In Australia : March 2013
Concrete in Australia VolVol 39 No 1 17 the pour. It was also crucial that the dry density of the concrete reached the minimum speci ed limit and wet density tests, correlated to nal dry density, were used to check the concrete prior to placement in the works. All pedestrian tra c on oors apply dynamic forces that cause the oor structure to vibrate. e amplitude of displacement due to these vibrations is usually very small and not visually perceptible or signi cant in terms of structural integrity. However, these vibrations can o en be felt by people and, depending on the magnitude, can be distracting and disconcerting for recovering patients and can also impair the use of sensitive equipment. e vibration performance of the structural oor system is therefore critical to the functional performance of the facility. Areas that required particular attention included the operating theatres, the in-patient ward levels and the laboratories in the Pathology Building and the Human Performance Laboratory in the State Rehabilitation Centre Building. Traditionally, there has been a tendency to design all parts of a building to a uniform, strict vibration criterion. is allows maximum exibility, as the most sensitive equipment can be placed anywhere within the building envelope. However, this is not without signi cant cost and for a facility the size of Fiona Stanley Hospital, this approach was not considered to be cost-e ective. It was therefore important to understand the acceptance criteria related to the area under consideration. For example, laboratories, where acceptance is driven by sensitive equipment performance and ward oor levels driven by human comfort. Vibration performance of oors is related to several properties but most important is the sti ness, mass and damping characteristics of the oor system between supports. Medium to long span, in situ concrete oor systems, whether at plate (in-patient ward levels) or banded slab systems (laboratories and clinical levels), have the bene t of mass, which greatly assists where the sti ness properties of the oor cannot be signi cantly increased due to restrictions in available depth. Acceptance criteria based on the Australian Standard, AS2670.2: Evaluation of human exposure to whole body vibration, part two and ASHRAE curves, were adopted for the relevant areas under consideration. A nite element analysis was performed for the critical areas, where the response of the oor was calculated for pedestrian footfall over a range of frequencies, from 1.8Hz to 2.5Hz, applied within the major corridor zones. e use of an FEA analysis allowed us to ne tune the structural properties, particularly in identifying local areas of the oor plate where the acceptance criteria were exceeded and adjustments in oor depth/mass made to meet prescribed criteria. e structural solutions implemented for the project were well developed by the design team during the early stages of the project and further re ned with the involvement of Brook eld Multiplex. e structural frame of the main hospital facilities was completed almost nine months ahead of schedule and facilitated an early start to the services installation and building t out. In late 2012, the Health Department of WA announced that Fiona Stanley Hospital would be complete in 2014. e project will also be completed to the budget set at that time. is is an outstanding result, considering the complexity and duration of the project. Donald Macmillan is associate director of BG&E, consulting engineers specialising in the fields of building structures, facades, bridgeworks, civil engineering and infrastructure. For more information go to www.bgeeng.com. An edit of this article first appeared in the structural feature of the February 2013 civil edition of Engineers Australia magazine. The finite element analysis output from the vibration modelling.