Although there are various design options for beam or structural cross sections, what I am proposing is to use voids in the structural member to house utilities for mechanical or electrical purposes (low voltage, communications, control or AV) . Lighting services could even be routed. These voids will also help to determine thermal and acoustical properties for occupied spaces that utilize this type of material base for wall/ceiling construction.
Hi Joe, the design of a structural member with voids to accommodate mechanical, electrical, plumbing, etc. utilities may be challenging because of the fire aspects. Wood has self-insulating properties; therefore, exposed members of heavy timber construction meet the minimum fire code requirements just because they are designed with large cross-sections. Any void in the structural member would jeopardise the fire safety of the structure. Non-exposed structural members are contained by use of type X gypsum board. In this case, however, containment of the structural member also means full containment of all the utilities which may not be desirable for practical purposes.
Incorporating devices into building structures to monitor and record/transmit signals about structural and serviceability performance of the building is a viable idea.
GOod review comments. I am especially interested in the monitoring and sensing scheme. As building information and management systems evolve in commercial applications, there could be a robust IT based integrated solution in the making. Back to the voids, do you think that fire-blocking in critical transitions weighs more than fire spread? The box girder scheme could be designed to minimize spread while at the same time, double as utility routes. The transitions and blocking are built in factory settings and all services installed in the factory as well. I know that cost will prohibit, but in the same way thermal and insulating double pane glass windows have an inert gas that separates the panes, the voids in a wood panel for thermal and insulation could incorporate a similar logic…..
RE: Prefabricated systems with factory installed utilities
The idea of prefabricated systems with factory installed utilities is promising and I think similar systems are already available in Europe. Here is a link to a paper presented at WCTE 2012 on improving shear and acoustic performance of CLT by creating voids within the cross plies (http://www.ewpa.com/Archive/2012/july/Paper_022.pdf?PHPSESSID=pb71ovlu7). Fact is that even though this may work for acoustics, it greatly reduces structural fire resistance of the system.
RE: Fire issues (with input from my colleague in Fire)
Any concealed spaces made of combustible construction having a flame spread greater than 25 are required by the Code to be separated with fire blocks into smaller compartments (not larger than those stipulated in section 220.127.116.11 from Division B of NBCC). Most requirements in fire blocking of concealed spaces are related to flame spread rating where 25 is the target rating, whereas typical wood and wood-based products have a flame spread rating around 100.
The sprinkler design standard (NFPA 13) requires that any combustible concealed spaces be protected by automatic sprinklers. There are various exemptions to this requirement, but generally, any cavity more than 6 inches deep needs to be sprinklered.
Heavy timber construction, as defined in NBCC, should be exempted from any concealed spaces (quoted from NBCC “Heavy timber construction means that type of combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on the thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs”).
Fire risk related to combustible concealed spaces is currently being discussed in codes and standards technical committees.