Part1Lecture6-8 - Functional Features and Design Criteria...

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Fall 2002 Biernbaum, MSU HRT 221, pg 13 Functional Features and Design Criteria (Meeting 6) Ref: AEN 12 Strength and Integrity (see Greenhouse Engineering) The are many different forces acting on the greenhouse structure. An attempt has been made by the National Greenhouse Manufacturers Association to standardize the terminology and the requirements for commercially built greenhouses. (See http://www.ngma.com ) - dead load: weight of the structure + heat and ventilating equipment + long term crops - live load: due to building use such as workers on the roof or short term crops minimum design - 15 lbs per square foot of floor - snow load: weather information, type of snow minimum design at 15 lbs per square foot of floor gutter connected greenhouses may have problem - wind load: the structure must resist both lateral forces and lifting forces which develop must resist 80 mph wind 16-20 lbs per square foot - foundation: must be designed to take vertical load as well as horizontal and lifting forces due to wind base of the foundation below the frost line Structural influence on light transmission - orientation as discussed previously - roof slope influences light transmission 35 o most satisfactory 26 to 28 degrees common (6 - 12 slope) (<26 o decreases condensation runoff and snow removal) - minimize structural members to minimize shading, also minimize overhead equipment for heating, electricity, irrigation, etc. which may shade the crop Structural influence on climate control - roof slope on condensation and snow removal - pad to fan distance for evaporative cooling - adequate passive ventilation - heating efficiency surface area to floor area infiltration rate Structural limitations to access and working height Working height has increased over the years from heights as low as 8 feet to heights of 10 to 12 feet in Dutch designs and newer construction. It is not unusual to see even 14 foot tall gutters at times. May need access for vehicles to remove the crop.
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Fall 2002 Biernbaum, MSU HRT 221, pg 14 Floors for humidity control, collecting runoff and materials handling The greenhouse floor must provide for good drainage to remove excess water. Drainage water should be able to be collected and run to a "legal" drain field or waste
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This note was uploaded on 07/25/2008 for the course HRT 221 taught by Professor Biernbaum during the Fall '04 term at Michigan State University.

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Part1Lecture6-8 - Functional Features and Design Criteria...

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