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- Design and construction of an Electric Fish Finder
Dry-floodproofing is permitted by floodplain management regulations and model building codes for some, but not all, flood hazard areas and types of buildings. Specific dry-floodproofing prohibitions are as follows:. Because of potential structural failures, dry-floodproofing of spaces below the DFE is not permitted for buildings in V zones. Because of potential harm to building occupants, dry-floodproofing of spaces below the DFE in A zone buildings is only permitted for non-residential occupancies. Where certificate permitted, one of the requirements of dry-floodproofing is that the dry-floodproofed elements of the building envelope be substantially impermeable to the passage of water.
According to FEMA's FIA Technical Bulletin 3, Non-Residential Floodproofing - Requirements and Certification , substantially impermeable means the walls and floor shall not permit the accumulation of more than 4 inches of water depth during a 24—hour period if there were no devices provided for its removal. However, sump pumps shall be required to control this seepage.
Designers should note that the same requirement would apply to any subgrade portion of the envelope below the DFE, including plazas, tunnels and vaults.
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Designers should calculate the lateral hydrostatic forces and the vertical buoyant forces on a structure containing a dry-floodproofed area. These forces can be quite large, and in the case of small or lightweight buildings, can be sufficient to cause walls to fail or buildings to float out of the ground see photo at right.
Designers should be aware that the use of dry-floodproofing triggers a requirement for a floodproofing certification. A wide variety of materials and devices have been developed to make building walls, floors, openings, penetrations and utilities watertight during flooding.
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Flood shields, panels, doors and gates are typically used to close medium to large openings in building walls. They can be temporary closures that are installed only when a flood threatens, or they can be permanent features that are closed manually or automatically. Key design parameters of these barriers are their height, their stiffness and resistance to hydrostatic forces , their method of attachment or installation, and their seals and gaskets.
As a general rule, flood shields, panels, doors and gates should not be attached to building windows, glazing or doors. Given the potential for large flood loads, they should be attached to exterior walls or the structural frame. Coordination with the design of exterior walls and fenestration is required. Designers planning to incorporate flood shields, panels, doors or gates into a building design are advised to consult with engineers and vendors experienced with the design and installation of these components. Backflow valves are often installed to prevent drains and sewers from backing up into a building, and are an important component of floodproofing.
They are relatively inexpensive to install and simple to operate. Wet-floodproofing is employed commonly in parking garages, building access areas, crawlspaces and similar spaces. Unless dry-floodproofed, enclosed areas below the DFE must be equipped with flood openings capable of equalizing water levels and hydrostatic loads. Since owners usually want to control temperature and moisture in these enclosed areas and prevent rodents, birds and insects from entering , opening covers are often employed. These covers must not interfere with the equalization of water levels in the event of a flood, and should be selected to minimize potential blockage by debris.
There are a variety of commercially available covers, such as grates, louvers and grills see illustration below that allow for control of the enclosed space and the passage of floodwaters. The location, number and size of the openings are specified in Section 2. Two methods of sizing the openings are permitted, a prescriptive non-engineered method and an engineered method.
Both methods have similar requirements related to: openings in multiple walls; the elevation of the bottoms of the openings to be no more than one foot above the adjacent ground level ; minimum opening size three inches in the plane of the wall. However, the two methods use different procedures to calculate the total net area of required openings.
Watertight Concrete System
The prescriptive method calls for one square inch of flood opening for each square foot of enclosed area below the DFE, and is based on conservative assumptions regarding flood characteristics and flow through the openings. The engineered method allows designers to size openings based on site-specific flood characteristics and opening shapes. The engineered method usually results in a smaller total net opening area than the prescriptive method does, however, use of the engineered method triggers a requirement for a flood opening certification. Levees and floodwalls are barriers constructed away from a building as a means of preventing floodwaters from reaching the building.
Permanent barriers are typically constructed of earth, concrete or metal. Temporary barriers are typically installed using sand bags or water-filled tubes.
Permanent barriers will typically require gates or doors at any locations where normal building access vehicular and pedestrian is maintained. Drainage systems will be required inside levees and floodwalls to remove rainfall that is trapped behind the barrier, and to remove floodwaters that enter through leaks in the barrier or seep through the ground. Designers are advised not to rely on temporary barriers for flood protection, and those contemplating use of a permanent levee or floodwall are advised to consult with engineers experienced in the design and construction of these structures.
Buildings in the SFHA must be elevated to or above the DFE using foundations appropriate to the flood hazard zone within which the building is situated. In the case of A zones, the NFIP allows any foundation type—slab, crawlspace, solid foundation walls, piers, posts, piles, columns—provided the foundation meets the requirements of the Authority Having Jurisdiction AHJ building code and regulations , and provided the foundation will resist anticipated design flood conditions and loads.
The NFIP permits buildings to be elevated and supported by fill in A zones, but requires the fill be protected against erosion, if necessary. The intent of the free-of-obstruction and breakaway wall requirements is to minimize the structural elements exposed to breaking waves, high velocity flow and flood-borne debris forces. The NFIP does not permit slab foundations, or crawlspace foundations, or basements, or solid foundation walls in V zones. However, the use non-breakaway walls around building access points stairwells, elevators, etc.
Designers should consult with the AHJ early in the planning process to ascertain what will and will not be allowed. Floodplain management regulations and model building codes both require materials used below the design flood elevation to be flood-resistant. But, what exactly are flood-resistant materials? According to the NFIP, flood-resistant materials are those materials that are capable of withstanding direct and prolonged contact with floodwaters, without sustaining significant damage; direct and prolonged contact means at least 72 hours; significant damage means any damage requiring more than low-cost cosmetic repair such as repainting.
Designers are advised that interior finishes below the DFE must also be flood-resistant. A test protocol was developed to allow the flood-resistance of materials and components to be evaluated. Designers may wish to utilize this protocol if the flood resistance of a particular material is in question.
Several flood-resistance certifications can be required in flood hazard areas. These are discussed generally below, but designers are advised to consult the AHJ to determine exact certification requirements and certification forms. A recent development of the SATRA STM is the introduction of an option for an automatic water detection system, combined with additional shaped elements added to the mechanical footform to aid the detection of water leaks.
On detection of a leak, the test is suspended and the footwear assembly is automatically raised out of the water tank. The introduction of the automatic water detection expands the use of the STM — for instance, allowing tests to be run overnight when manual inspection at intervals would not be practical. The determination of a leak by either manual inspection identified by a damp patch of a prescribed area on tissue contact to the inside of the footwear or the use of any automatic water detection will not precisely correlate.
However, customers will be able to develop their own experience in the use of manual or automatic water detection, depending on footwear type or typical failure mode. The SATRA STM represents a powerful tool for verifying the resistance to water ingress for a wide range of footwear types except high heeled footwear. In the event of water leaks occurring during a test such as when testing to SATRA TM , the manufacturer or brand is able to investigate the failure mode and hence apply corrective actions.
SATRA has test evidence that well-made footwear manufactured with highly water-resistant materials can achieve very high performance values under test in some cases more than 1,, flexing cycles — even with deep immersion levels. Equally, we also see footwear which develops leaks at very low numbers of cycles in low immersion depths.
Admixtures and Type B
In many cases, small attention to the details of construction, design or a material used can make a significant difference to the leak resistance of the footwear. SATRA consultants can provide consultancy for members seeking to improve the water resistance of their footwear. Photograph at top of page shows the mechanical foot fitted with automatic water detection components. Email test. Please contact footwear satra. SATRA offers a wide range of unique member services and products designed to enhance technical knowledge and help improve profitability and global sales.
In many ways, moisture control is one of the unsung heroes of any building. In addition to protecting occupants from adverse health effects, controlling moisture also protects the building and its mechanical systems and its contents from physical or chemical damage. Yet, moisture issues are common.
Design and construction of an Electric Fish Finder
A little bit of water makes for big problems Moisture-related problems are common in U. Between and , the U. The BASE study found that 85 percent of the buildings had been damaged by water at some time, and 45 percent had leaks at the time of data collection. Moisture-related issues such as damp and moldy indoor environments can lead to increased cases of upper respiratory problems, including coughing, wheezing and asthma aggravation, among others, according to the EPA.
Managing moisture through better design For commercial and residential buildings alike, one of the best ways to address moisture-related problems is to attempt to prevent them from happening in the first place. Designing building enclosures to reduce water intrusion is the best place to start. To be effective, these systems must reduce air leakage into the exterior enclosure assemblies during cold weather, and leakage of outdoor air into the exterior enclosure or interior wall, ceiling, and floor cavities during warm weather.
Air sealing an enclosure makes it easier to manage indoor-outdoor air pressure relationships with practical airflow rates. Meanwhile, managing the flow of heat and water vapor through all enclosure assemblies can help avoid condensation on materials inboard of the drainage plane. Insulating materials must also be used to manage heat flow to keep the surface temperature of low permeability materials inside the enclosure above the expected dew point.