Saturday, September 12, 2009

MHS Challenges Natural Disasters-Hurricanes

Perhaps the most powerful of all meteorological forces on the Earth, hurricanes are a steadily increasing threat as larger and larger populations move to coastal regions. Hurricanes mainly present three basic sources of damage to the home; wind, waves, and flooding from storm surges. But one of the added problems with hurricanes is that as they destroy homes the debris created by this destruction becomes projectiles that increase the hazard to other homes. Thus poor quality homes are not just a hazard to themselves; they are hazards to whole communities. This fact has compelled many coastal communities to impose very stringent building codes intended to insure a minimum standard of hurricane resistance for all structures.

Stick frame homes are prone to wind damage from hurricanes for the same reasons they are prone to earthquake damage; nails have a hard time holding things together if they shake or vibrate. Roofing is particularly prone to this problem in response to wind and is one of the greatest sources of debris, commonly being the first part of a house to give-way. The common method of reinforcing homes against hurricane winds is similar to that employed in increasing earthquake resistance -since the root cause of weakness is the same.

Key portions of the structure like the roof are reinforced by adding strapping and gusset plates which are mounted-sometimes- with bolted connections.
In addition, roofing panels may use bolted or screwed attachment rather than nails or may have additional steel strapping, adhesives or adhesive membranes may be added to reduce the tendency of roof shingles to fly off, special kinds of shingles made in continuous strips or with proprietary locking systems may be used, or-perhaps best of all- metal panel roofing with bolted connections may replace conventional roofing altogether.
Here MHS offers the same advantages it offers in respect to earthquake resistance. With positive interface between all components, it simply isn't as likely to come apart under the vibrations induced by wind as nailed construction.
Similarly, with its wall panels held in place continuously along their perimeter they are far less likely to come off and become projectiles, though any nailed siding applied to wall panels is just as likely to come off as on a stick frame structure.
A secondary form of wind damage is impact damage resulting from flying debris. With such extremely high wind speeds, debris impacts the structure of homes with extreme force causing great damage. Penetrations of the walls or roof often lead to subsequent failure of the structure, thus expanding the field of debris.

Stick frame construction has long tended to perform poorly in resistance to such debris impact and much research has gone into trying to find means of reinforcing the wall and roof cladding materials. The use of Structural Insulated Panels for walls has fared well in this respect. SIPs are more monolithic in composition than stud framed wall structure and impacts produce less secondary debris, passing through the SIP like bullets but not causing the SIP panel to come apart whole.
Since it also relies on the use of these, MHS offers the same advantages but improves on this by virtue of the fact that its SIPs have a much more secure and continuous perimeter interface to its overall structure. So while the SIPs of a conventional SIP based or hybrid SIP and stick frame home have the potential to be shaken apart along their nailed connections, a SIP used for walls in an MHS structure could sustain massive amounts of damage before finally coming free.
And when it does, the aluminum post and beam structure itself will remain largely unscathed, whereas the stick frame or SIP based home could be prone to structural failure.

Wave damage is primarily a problem for the few homes that are in direct proximity to the shore. There damage is caused primarily by the subsidence of foundations caused by waves washing sand and earth away or direct damage to home sub-structure by wave impact. Immersion also tends to deteriorate the wood in this structure, making it progressively weaker over time. Considering the environment such sub-structure is subjected to, nailed construction has long ago been abandoned even for structures which are otherwise of conventional stick frame construction. Here MHS is on a roughly equal footing to the conventional structure except that its aluminum composition is immune to the effects of water and thus will not deteriorate over time. However, the elevated substructures used for coastal homes are often based on very large scale timber components. MHS may not be able to approximate this without some kind of compound strut structure or by employing a hybrid of other larger scale aluminum I beam structure. Storm surge damage is essentially the same issue as with flooding and MHS relates to stick frame construction in the same way as noted above.