Traditional Danish West Indian hip roofs are constructed with truss rafters. I would strongly urge building suppliers to discontinue stocking this type of post base altogether. This frame is strengthened by diagonal bracing (called let-in bracing) at each corner. (See guide specifications on back cover). However, I have seen masonry structures, which were improperly constructed which collapsed, whereas properly constructed wooden structures survived. As we travel around the islands we see that it is these traditional buildings, that as a group, have survived the storm best. Any similar base produced by other manufacturers is also suitable. 14). The first European settlers in the Caribbean built buildings that were similar to the kind of building they were used to in their homeland. Two such examples are Simpson CB Series Column Base and Simpson EPB Series Elevated Post Bases. A strong continuous load path is critical to holding the roof, walls, floors, and foundation together during a strong wind event of winds of over 200 mph. (Fig. If you are dealing with wooden walls, the bottom plates should be strapped to the studs and securely attached to the floor. The whole island suffered devastation. Wall systems constructed with Fox Blocks insulated concrete forms (ICFs ) ensure a wind-resistant structure with a strong continuous load path that holds the roof, walls, floors, and foundation together during an intense wind event. Types of bases recommended are integral units, which are cast into concrete with a minimum of 12 Ga. with a 7 Ga. thickness in high wind exposure areas. Over the last several hundred years these buildings have been modified due to environment and climactic conditions so that they are functional in a tropical climate and we can see a “Caribbean Style” emerging with a distinct character of its own. The building type, which, by observation, suffered the most damage, is the rigid frame, large span metal warehouse type of structure. (Fig. St. John, St. Thomas, U.S. Virgin Islands. A best practice for protecting a structure and its occupants from flying debris are walls constructed with ICF. In situations where galvanized roofing has blown off and left the wooden framing intact, it appears that it is the perlins to which the galvanized is nailed that is breaking away from the wooden rafters. 13), NOT recommended is the adjustable type post base, which is attached to an anchor bolt set in the slab after it has been poured. ICF provides greater resistance to damage from flying debris than wood-framed walls. There is no ridge beam in this type of construction and literally hundreds of these roofs survived the storm. (Fig. Traditional wooden buildings survived the storm amazingly well. A wind-resistant structure should re… Consideration should be given to increasing wind design loads and “x” bracing requirements when designing these structure for use in the Virgin Islands. The basic concept behind the shed roofs in relation to the main roof before Hugo was that of a breakaway roof. 10). MASONRY WALLS In conjunction with this failure, as the shed roof blows away, its connection to the flashing between the galvanized shed and main roof becomes a significant detail. West Indian buildings also tend to have smaller, individual roofs, often as a result of the structure being built over a long period of time with additions added here and there. Most foundations in the Virgin Islands are poured concrete and are usually integrally related to cistern construction thus making a massive base to which the rest of the structure is attached. Mandated in higher wind regions are ring-shank nails. These design guidelines were produced in the aftermath of Hurricane Hugo, which devastated the U.S. Virgin Islands in September of 1989. All window and door openings should have 2 #4 re-bars extending vertically, filled with concrete on each side of the opening. A category one hurricane can destroy mobile homes. After the roof sheathing, the roof framing is the next element found within the load path of a building. Obviously a masonry building should be stronger than a wooden building. As a result of this storm I have some very specific recommendations as to the type of column bases which should and should not be used. The rafters of a roof’s frame must be sized to resist the weight of the roof system, and also the loads caused by wind. Quite often we have seen indications that the buildings themselves appear to withstand the storm until hit by debris from adjacent buildings which then triggered the destructive chain reaction. Floor framing typically consists of dimensional lumber, or floor joists, spanning an open area. So it is important to be aware that it is not so much what material you build with, but how the whole structure is fastened together that becomes the key issue in the survival of a storm. When designing a wind-resistant building, engineers can choose various structural components and combine them into what the building code calls a main wind-force resisting system. All Rights Reserved. They are intended to be used as a guide to provide the general public with more information on building design and hurricanes and to foster the construction of structures which are better capable of withstanding hurricane force winds. (Fig. For wind-resistant building design, a continuous load path is the best protection against strong winds. 2.3. The galvanized roof is then screwed to the perlins. The reasons for this will be discussed here in detail. Here are a … If the porches and galleries were to blow away in a storm, they could be attached so as not to take the main roof with them. Installation of wood structural panels or … Buildings constructed with ICF walls protect the building and its occupants during extreme wind events of over 100 mph. Wind-resistant construction is essential for protecting a building and its occupants from disastrous outcomes during strong wind events. Again and again we have seen examples of both islands where this material is still intact. Since climactic conditions have changed little over the last several hundred years this type of construction is still a valid way of building today. The roof framing transfers lateral loads to the shear walls. Traditional West Indian hip roofs have no overhangs. (Fig. In fact, I have inspected some structures that are so complex that it is difficult to conceive how they were constructed in the first place. INTRODUCTION The floor system is part of the continuous path that transfers the loads to the shear walls in the floors below or to the foundation. It is also important to be aware of the lateral loads (wind loads) which act on walls during a storm (Fig. Design Wind Speed and Pressures The basic wind speed is reduced or enchanced for design of buildings and structures due to following factors: (i) The risk level of the structure measured in terms of adopted return period and life of structures. Still, there are many factors that influence whether or not a building has vulnerabilities that can lead to structural failure during strong winds. The lower part contains the typical reinforcing required for the ring beam. It is strongly recommended that anyone constructing or undertaking major repairs to a building should consult with their local architect for professional guidance before proceeding.