High Tunnel Green House

This project is to create a greenhouse that can withstand strong winded areas in the northwest. This project specifically targets Buhl, located near Twin Falls Idaho.

Stand Your Ground
Stand your ground is the design team in charge of the project and it is composed of:

Sponsor
The University of Idaho extension program is the sponsor of this project and Tony McCammon, of the University of Idaho extension program, is the liaison for what the extension program desires for the project.

Interview with Tony McCammon (summarized)

 * The site is located on the north west side of a pond
 * The design is to be a high tunnel greenhouse with rolling up sides to allow for passive ventilation in the summer
 * There has been a history of snow load damage and the end walls blowing in due to wind loads
 * The project is to see if a better design for high tunnel greenhouses can be achieved for high wind speeds and snow loads
 * The minimum specs are for 35 MPH sustained winds with 65 MPH gusts.
 * The design team is free to redesign the greenhouse to whatever is necessary
 * The plastic sheeting for the outside of the greenhouse must last a minimum of 5 years but a 10 year life span is expected if it is possible.
 * The structural frame must last a minimum of 10 years.
 * The orientation of the greenhouse is fixed with winds coming from the north west.

Problem Statement
Given the high wind speeds and average snow loads in the Buhl, Idaho area, the University of Idaho extension's high tunnel greenhouses have been failing. Our project is to design the ideal high tunnel greenhouse to survive the area's environmental conditions.

Design Goals and Specifications

 * Withstand high wind speeds
 * Withstand heavy snow loads
 * Long lifetime
 * Door to fit a small skid-steer loader
 * Roll up sides for passive air ventilation
 * Must fit within a 24 x 40 area

Deliverables

 * Design analysis
 * Cost analysis
 * Prototype
 * Final Design
 * Possible final model

Initial Phase
Collecting data on greenhouse types and environmental conditions, the results of these can be found in Desing Data as: Location Wind Speeds, Wind Loads, Snow Loads, and GreenHouse Design Types. The greenhouse design types have been limited to the two most popular types, Gothic and the Quonset, for the purpose of time limitations.

Current Phase
The current design phase right now is in the process of narrowing down the improved greenhouse designs for the two design selected in the initial phase and to begin math models to eventually start generating cost estimates of various materials, including client specified functions.

Greenhouse Design Types
The two pictures above demonstrate the two most popular design styles for greenhouses.

Location Wind Speeds

 * Latitude: 42.3900
 * Longitude: -114.4439


 * ASCE 7-10 Wind Speeds
 * (3-sec peak gust MPH*):


 * Risk Category I: 105
 * Risk Category II: 115
 * Risk Category III-IV: 120
 * MRI** 10 Year: 76
 * MRI** 25 Year: 84
 * MRI** 50 Year: 90
 * MRI** 100 Year: 96


 * ASCE 7-05: 90
 * ASCE 7-93: 70

Wind speed information is Provided by the Applied Technology Council.

The greenhouse is a risk category I building so all values of velocity will be using the 105 (mph) value.

ASCE 7-10 Velocity Pressure

 * qz10= 00256.0V*Kz*Kzt*Kd*V^2
 * where:
 * qz10 = ASCE 7-10 velocity pressure evaluated at mean roof height (psf)
 * Kz = velocity pressure exposure coefficient
 * Kzt = topographic factor
 * Kd = wind directionality factor
 * V = basic wind speed (mph) from ASCE 7-10 maps referred to as ultimate wind speed maps in 2012 IBC.

Assuming all correction factors K=1 for exposure C and a mean roof height that will be < 30ft and head on wind:
 * qz10=28.224 (psf). This would be assuming a worst case scenario for the greenhouse.

ASCE 7-10 data is provided by the American Wood Council

Velocity Pressure using tables
Using the ASCE 7-10 Table 27.6-1 for exposure C and assuming the maximum height of around 20ft, the wind pressure is read to be between 23-27 (psf). This value will be slightly higher then expected values as the table ends at 110 (mph) instead of the wind velocity provided by the Applied Technology Council of 105 (mph).

Snow Loads
Using the interactive snow load map provided by the University of Idaho, the worst case snow load can be assumed to be about 20 (psf).

Design Documents






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