| Anyone who lived in Miami-Dade County in 1992 | | | | to a different material, for example, from wood to |
| experienced first-hand what a Category 5 hurricane | | | | concrete or metal to wood, etc. The weakest link |
| looks like. Although where I lived was not particularly | | | | can expose a whole house to disaster. |
| hard-hit, even though there was a great deal of | | | | Now all the straps that connect from the wood |
| damage to the trees and landscaping, the next day I | | | | trusses to the concrete beam are long and strong |
| was walking around the devastated areas of the | | | | enough to sustain hurricane wind forces. The favorite |
| south side of the county. | | | | construction has become reinforced masonry where |
| Architects, engineers, and the building departments of | | | | the concrete block cells are grouted every 4'-0" or so |
| the area learned much from the experience. As a | | | | with a steel reinforcing bar which goes from the |
| whole almost no gas stations or screen-enclosures | | | | footings to the tie-beam. In addition, all window or |
| were left standing. In most homes which had block | | | | door openings in the exterior walls must have the |
| walls on the ground floors and wood framing on the | | | | same reinforced cells with the steel bars at each side |
| second floors, at least parts of the second floors | | | | of the apertures. |
| were gone. I saw one house where the front | | | | The favorite roof configuration is the hip roof. |
| façade on the second floor was left, but as I | | | | Because of the way it's built, it is naturally |
| walked around the yard to the back, all the other | | | | self-bracing. All gable ends are braced with |
| three walls on the second floor were gone with the | | | | cross-bracing, at a minimum at each of the last two |
| clothes and furniture littered all over the yard. In | | | | trusses at each gable. Many times what kept a gable |
| some areas the majority of house lost all the | | | | end from collapsing during Hurricane Andrew was one |
| windows and doors, in addition to the roof finish. In | | | | 2 x 4 bracing. Imagine such a small piece of wood |
| others, even the roof sheathing and sometimes even | | | | made all the difference. |
| some of the wood trusses were gone. | | | | The code now requires that all new windows, even in |
| For about 6 months it looked as though South | | | | just an addition, must either have shutters or be |
| Miami-Dade had been bombarded continuously and | | | | impact-resistant. Impact resistant windows are a |
| we were in the middle of a war zone. In actuality the | | | | great invention. The glass is laminated in layers, similar |
| houses of the county had gone to war with | | | | to the way plywood is made out of layers. |
| Hurricane Andrew and lost. | | | | Impact-resistant windows are so strong that you can |
| Six months after Hurricane Andrew a report came | | | | take a hammer to them and not break them. |
| out citing the reasons why houses failed during the | | | | However, unlike regular windows, if a piece of glass |
| hurricane. These were simple enough: | | | | should break, the glass alone cannot be replaced. The |
| - Unbraced gabled ends of the roof framing trusses | | | | window must be replaced in its entirety. |
| failed | | | | The way the roofing membrane and the wood |
| - Corners of the house lacked the required steel | | | | sheathing are attached to the wood trusses below |
| reinforcing which were supposed go from the | | | | has been improved as well. |
| foundation to the tie-beam | | | | Where wood to wood connections in a trellis or |
| - The roofing paper and tiles or shingle blew away | | | | pergola prior to the hurricane were installed intuitively, |
| and it rained in the house | | | | the code now requires real structural calculations. So |
| - The wood roofing sheathing was not attached | | | | are calculations required for the connections between |
| corrected and it blew away | | | | each truss and the concrete tie-beam below. Nothing |
| - The roof trusses were not attached correctly to | | | | is left to the imagination. The signed and sealed |
| the time beam and were displaced | | | | calculations are presented along with full structural |
| - The connections between steel members or wood | | | | plans at the time of plan review for permitting. |
| members were inadequate and the structure failed | | | | Although great strides have taken place over the last |
| - The windows and doors were not properly | | | | 16 years, there are still construction techniques which |
| attached to the surrounding concrete block walls and | | | | could be improved. For me there is no better |
| blew away | | | | construction system than a concrete slab roof. |
| - The windows did not have shutters and the glass | | | | Because they are difficult to build on a slope, and |
| was broken, the high winds would get into the house | | | | therefore expensive, we continue to building roofs |
| and do great damage | | | | with wood trusses, sheathing, roofing paper, and |
| - The second floor wood framing was not properly | | | | shingle of tile finish. This system is still very |
| attached to the tie-beam at the top of the ground | | | | susceptible to damage in high velocity wind conditions. |
| floor and was destroyed | | | | Hopefully, someday someone will come up with a |
| So what did we learn from the Andrew experience? | | | | better, practical system which will not succumb to |
| I think the most valuable lesson was the importance | | | | hurricanes that easily. |
| of the attachments or connections from one material | | | | |