Need more? Ask Us a Question. This module determines actual soil pressures and required depths for pole footings primarily supporting lateral loads. Such footings are commonly called "flagpole footings". Click here for a video:.
Cases with and without lateral restraint at the ground surface are allowed. Evaluation of actual and allowable pressures is in accordance with the IBC Section entitled "Embedded posts and poles". General Data Tab. Pole Footing Shape. Use this section to specify whether the pole is round or rectangular assumed square. Enter the width or diameter of the pole footing.
Width is measured perpendicular to force direction. If the pole is specified as rectangular, the module will multiply the value entered for footing width 1. Restraint at Ground Surface. Specify whether the footing is free at the ground surface or restrained and cannot translate. A restrained footing indicates that a concrete slab or other rigid element prevents translation of the pole footing at the ground surface, but does not prevent rotation. When specifying a restrained footing, you must assure yourself that the final force required to provide the restraint can actually be developed by the restraining construction.
When ground surface restraint is present, the lateral pressure value at the bottom of the pole will govern the design. Operation Mode.
This setting provides an option to select from two different modes of operation as follows:. Calculate Minimum Depth : In this mode, the module will iterate to determine the minimum embedment depth required to make the actual lateral soil pressure lower than the allowable soil pressure. Find Lateral Pressure for Given Depth : In this mode, the module will calculate the lateral earth pressures caused by the specified pole size, embedment depth and applied loads.
When this option is selected, a Pole Footing Embedment Depth input field will appear as shown below:. Allowable Pressure Limit. Two options are provided as indicated below:. Limit only by "Max.John W.
AndrewP. Course Outline. This course highlights the requirements for determining the embedment depths required and foundation pressures for pole foundations for signs, flagpoles, light poles and pole framed buildings in accordance with Section and Paragraph The course is designed to help architects and structural engineers become familiar with the design criteria for pole foundations.
A copy of the International Building Code is required for this course. This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective. Intended Audience. Benefits to Attendee. The Attendee will learn how to determine the embedment depths and foundation pressures for many pole type structures, including signs, flagpoles, light poles and pole framed buildings.
These pole foundations may be more efficient and easier to install than conventional spread footings in many applications.
Course Introduction. Poles foundations are commonly used for sign, flagpole and light pole foundations and pole framed buildings. A design criteria for pole foundations is indicated in Section and Paragraph This criteria applies to vertical poles considered columns embedded in either earth or in concrete footings in the earth and used to resist lateral loads.
The backfill in the annular space around a column that is not embedded in a concrete footing shall be clean sand thoroughly compacted by tamping in layers not exceeding 8 inches in depth. Course Content. Pole Foundation Design with Spreadsheet. Please click on the above underlined hypertexts to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As You may need to download Acrobat Reader to view and print the document.
Course Summary. This course covered the requirements for determining the embedment depths required and foundation pressures for pole foundations for signs, flagpoles, light poles and pole framed buildings in various types of soil in accordance with the International Building Code. Related Links and References. Q uiz.Fences are fantastic for fixing up a boring yard, creating a private space from peering neighbors or keeping animals in — or out — of your favorite spaces.
A good fence can last for decades, and building a sturdy, durable fence starts at the foundation. Erecting a solid fence is a fairly fast project once the foundation is firmly in place.
Digging a hole seems like the easiest part of the process. Even a kid can get a good-sized hole going in a small amount of time. But the hole is a pretty important part. Too big, and you can jeopardize the structure's ability to hold up to strong winds. A hole that is too small is simply an annoyance as you have to drag everything out and start digging all over again.
The post holes you dig for your fence need to be evenly spaced from top to bottom. When you begin to dig a hole, they tend to be larger on top where the shovel uses the ground for leverage to scoop out the earth. Since we tend to build with a bigger top than bottom, we create v-shaped holes. V-shaped holes just won't do if you fill the hole with concrete. Frost will heave the concrete toward the sky, making room for soil and water to rest beneath the footing and causing your fence to lean and eventually fall over.
Dig the holes but only fill them up halfway with concrete. This will keep them from the hands of frost pulling them up and getting a good grip on the lip of v-shaped concrete blocks. A beautiful fence starts with a well-made hole. To dig a good post hole, you need to go down a third and up to half of the height of the post height above ground. If your post is 6-feet tall, you will dig down at least 2 feet. For the width, you need to make the hole three times the width of the post you intend to use.
You need to dig a inch wide hole for a 4-foot wood post.
The Open Civil Engineering Journal
Gates require a hole with a depth of 36 to 40 inches in the ground and with a diameter of at least 12 inches. Before you go around digging on your property, give a buzz to the call center in your state to ensure you won't be knocking out any power, shoveling into sewage or water lines or taking down cable before the big game. Always wear safety goggles when digging as well as a long-sleeved shirt, pants and gloves because digging brings up a lot of loose objects that can be sharp and go flying when hit from above.
As a professional writer she has researched, interviewed sources and written about home improvement, interior design and related business trends. She earned a B.
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Students Click Here. Related Projects. Hi, How do you verify the ground stability for an utility wood pole? But is there a way for more accurate design based on the type of soil and bearing resistance? Calculate the wind moment to be resisted in your locale.
The 5 Limitations of the Pole Foundation Equation
With soil properties known, consider the pole doing a rigid body rotation, then check the permissible bearing stresses against the soil. If using the IBC look at Section The following formula shall be used in determining the depth of embedment required to resist lateral loads where no lateral constraint is provided at the ground surface, such as by a rigid floor or rigid ground surface pavement, and where no lateral constraint is provided above the ground surface, such as by a structural diaphragm.
The following formula shall be used to determine the depth of embedment required to resist lateral loads where lateral constraint is provided at the ground surface, such as by a rigid floor or pavement.
The backfill in the annular space around columns not embedded in poured footings shall be by one of the following methods:. Sign Up. Upgrade to premium. Simplify code analysis. Designs to resist both axial and lateral loads employing posts or poles as columns embedded in earth or in concrete footings in earth shall be in accordance with Sections The design procedures outlined in this section are subject to the following limitations: The frictional resistance for structural walls and slabs on silts and clays shall be limited to one-half of the normal force imposed on the soil by the weight of the footing or slab.
Posts embedded in earth shall not be used to provide lateral support for structural or nonstructural materials such as plaster, masonry or concrete unless bracing is provided that develops the limited deflection required. The depth to resist lateral loads shall be determined using the design criteria established in Sections Equation or alternatively.
The resistance to vertical loads shall be determined using the vertical foundation pressure set forth in Table The backfill in the annular space around columns not embedded in poured footings shall be by one of the following methods: Backfill shall be of concrete with a specified compressive strength of not less than 2, psi The hole shall not be less than 4 inches mm larger than the diameter of the column at its bottom or 4 inches mm larger than the diagonal dimension of a square or rectangular column.
Backfill shall be of clean sand. The sand shall be thoroughly compacted by tamping in layers not more than 8 inches mm in depth. Backfill shall be of controlled low-strength material CLSM.
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About UpCodes. Diameter of round post or footing or diagonal dimension of square post or footing, feet m. Depth of embedment in earth in feet m but not over 12 feet 3.
Distance in feet m from ground surface to point of application of " P. Allowable lateral soil-bearing pressure as set forth in Section Moment in the post at gradein foot-pounds kN-m.Log In. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action. Click Here to join Eng-Tips and talk with other members! Already a Member?
Join your peers on the Internet's largest technical engineering professional community. It's easy to join and it's free. Register now while it's still free! Already a member? Close this window and log in.
Are you an Engineering professional?Concrete anchors
Join Eng-Tips Forums! Join Us! By joining you are opting in to receive e-mail. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Students Click Here. Related Projects. We don't usually do pole barns in our office so I'm not quite sure if the embedment I got is typical or not. So, I wanted to ask if a 8ft embedment for a 20 foot post sounds about right. I know their are other factors that you will need to know for the design, but I was just curious if this sounds about right to you.
How can you ask if the embedment is correct if you don't mention what the loads are? Do we have 80 mph winds or mph wind?
Post Embedment Techniques
You know there are others factors but we don't know what they are. Is you building enclosed or open? Google to see if some of these publications are available.
Soil type, esentailly k value, pole diameter are key parameters to determine the embedment depth, as well. Brom's method gives your some idea.This program will provide the designer with the required pole embedment depth and stress information for his posts.
Great for design of signs or light poles. WinPost has a friendly user-interface, where you can introduce several parameters, such as : wind velocity, number of evenly spaced poles, pole width, pole depth etc.
After you set these parameters, this application will provide you output results like required pole ground embedment, actual pole bending stress, total wind force on attachment etc.
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