Engineer Cafe

HOW TO CALCULATE SAFE BEARING CAPACITY OF SOIL ON SITE?

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
<img alt="How to calculate safe bearing capacity of soil on site" class="aligncenter size-full wp-image-2200" height="224" src="http://civilblog.org/wp-content/uploads/2015/02/How-to-calculate-safe-bearing-capacity-of-soil-on-site.jpg" style="border: 0px; clear: both; display: block; float: none; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; height: auto; line-height: inherit; margin: 1em auto; max-width: 100%; padding: 0px; vertical-align: baseline;" title="HOW TO CALCULATE SAFE BEARING CAPACITY OF SOIL ON SITE?" width="448" /></div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
This simple and quick field test will give you a rough idea of bearing capacity of soil.</div>
<h2 style="background-color: white; border: 0px; color: #2a2a2a; font-family: 'Droid Sans', sans-serif; font-size: 24px; font-stretch: inherit; line-height: 1.4; margin: 0px 0px 12px; padding: 0px; text-transform: uppercase; vertical-align: baseline;">
<span style="border: 0px; color: #00ccff; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">PROCEDURE</span></h2>
<ol style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin: 1.5em 0px 1.571em 1.9em; padding: 0px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Excavate a pit of required depth. (preferably equal to the depth of foundation)</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Take a solid ball or square cube of known weight and dimension.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Drop the ball or square cube several times, from a known height on to the bottom surface of excavated pit.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Calculate the average depth of impression made several times on the bottom surface of the excavated pit. Let “d” is the average depth of impression.</li>
</ol>
<h2 style="background-color: white; border: 0px; color: #2a2a2a; font-family: 'Droid Sans', sans-serif; font-size: 24px; font-stretch: inherit; line-height: 1.4; margin: 0px 0px 12px; padding: 0px; text-transform: uppercase; vertical-align: baseline;">
<strong style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span style="border: 0px; color: #00ccff; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">CALCULATION</span></strong></h2>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
Calculate the ultimate resistance of soil ( R ) using the formula given below.</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
<strong style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">R = (w * h) / d</strong></div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
Where,</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
R = Ultimate resistance of soil (in kg)</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
d = Average depth of impression (in cm)</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
w = Weight of the solid ball or square cube (in kg)</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
h = Height of fall of solid ball or cube (in cm)</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
If “A” is the cross-sectional area of the solid steel ball or cube, then resistance of soil per unit area is calculated using following formula.</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
Resistance of soil per unit area (in kg/cm<span style="border: 0px; bottom: 1ex; font-family: inherit; font-size: 10px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; height: 0px; line-height: 1; margin: 0px; padding: 0px; position: relative; vertical-align: baseline;">2</span>) = R / A</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
Safe bearing capacity (in kg/cm<span style="border: 0px; bottom: 1ex; font-family: inherit; font-size: 10px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; height: 0px; line-height: 1; margin: 0px; padding: 0px; position: relative; vertical-align: baseline;">2</span>) = R / (A * F.O.S)</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
Where,</div>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
F.O.S = Factor of safety</div>
<h3 style="background-color: white; border: 0px; color: #2a2a2a; font-family: 'Droid Sans', sans-serif; font-size: 22px; font-stretch: inherit; line-height: 1.4; margin: 0px 0px 12px; padding: 0px; text-transform: uppercase; vertical-align: baseline;">
<span style="border: 0px; color: red; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">NOTES TO REMEMBER</span></h3>
<ol style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin: 1.5em 0px 1.571em 1.9em; padding: 0px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">F.O.S varies from 2 to 3 depending upon the type of structure and site condition.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">In order to get reliable test result, perform this test on different types of soil and then use your judgment to reach at any conclusion.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Instead of using solid steel ball or square cube, we can also use CBR test plunger, or Cone (used for cone penetration test)</li>
</ol>
<h2 style="background-color: white; border: 0px; color: #2a2a2a; font-family: 'Droid Sans', sans-serif; font-size: 24px; font-stretch: inherit; line-height: 1.4; margin: 0px 0px 12px; padding: 0px; text-transform: uppercase; vertical-align: baseline;">
<strong style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span style="border: 0px; color: #00ccff; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">PRESUMPTIVE BEARING CAPACITY</span></strong></h2>
<div style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin-bottom: 20px; padding: 0px; vertical-align: baseline;">
The table given below shows the presumptive bearing capacity values for different types of soils. This table will guide you to reach at any conclusion after conducting the test.</div>
<table style="background-color: white; border-collapse: collapse; border-spacing: 0px; border: 1px solid rgb(221, 221, 221); color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin: 0px 0px 25px; padding: 0px; vertical-align: baseline; width: 621px;"><tbody style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399"><strong style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Type of Soil / Rock</strong></td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399"><strong style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Safe / Allowable Bearing Capacity (kg/cm<span style="border: 0px; bottom: 1ex; font-family: inherit; font-size: 10px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; height: 0px; line-height: 1; margin: 0px; padding: 0px; position: relative; vertical-align: baseline;">2</span>)</strong></td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Rock</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">32.40</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Soft rock</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">4.40</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Coarse sand</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">4.40</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Medium sand</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">2.45</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Fine sand</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">4.40</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Soft shell / Stiff clay</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">1.00</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Soft clay</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">1.00</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">Very soft clay</td><td style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 7px 15px; vertical-align: baseline;" width="399">0.50</td></tr>
</tbody></table>
<h3 style="background-color: white; border: 0px; color: #2a2a2a; font-family: 'Droid Sans', sans-serif; font-size: 22px; font-stretch: inherit; line-height: 1.4; margin: 0px 0px 12px; padding: 0px; text-transform: uppercase; vertical-align: baseline;">
<span style="border: 0px; color: red; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">NOTES TO REMEMBER</span></h3>
<ol style="background-color: white; border: 0px; color: #555555; font-family: 'Droid Sans', sans-serif; font-size: 14px; font-stretch: inherit; line-height: 23px; margin: 1.5em 0px 1.571em 1.9em; padding: 0px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">For non-cohesive soils the values should be reduced by 50% if the water table is above or near base of footing.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">These values should be used only for preliminary design. The actual bearing capacity of soil should be calculated as per the standard codes.</li>
</ol>
<div>
<span style="color: #555555; font-family: Droid Sans, sans-serif; font-size: xx-small;"><span style="line-height: 23px;">Main post from: http://civilblog.org/</span></span></div>
</div>

HOW TO CALCULATE SAFE BEARING CAPACITY OF SOIL ON SITE?

This simple and quick field test will give you a rough idea of bearing capacity of soil. PROCEDURE Excavate a pit of required depth....

Design Example: Reinforced Strip Foundation.

0 Design 12:09 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><span style="font-size: 12px; line-height: 18px; text-align: justify;">The load-bearing wall of a single-storey building is to be supported on a wide reinforced strip foundation.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">A site investigation has revealed loose-to-medium granular soils from ground level to some considerable depth. The soil is variable with a safe bearing capacity ranging from 75–125 kN/m2. Also some soft spots were identiﬁed, where the bearing capacity could not be relied upon.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">The building could be supported on ground beams and piles taken down to a ﬁrm base, but in this case the solution chosen is to design a wide reinforced strip foundation  capable of spanning across a soft area of nominal width. </span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">To minimize differential settlements and allow for the soft areas, the allowable bearing pressure will be limited to n</span><span style="font-size: xx-small; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;">a</span><span style="font-size: 12px; line-height: 18px; text-align: justify;"> = 50 kN/m2 throughout. Soft spots encountered during construction will be removed and replaced with lean mix concrete; additionally, the footing will be designed to span 2.5 m across anticipated depressions. This value has been derived from the guidance for local depressions given later on raft foundations. The ground ﬂoor slab is designed to be suspended, although it will be cast using the ground as permanent formwork.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Loadings</b></i></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Design Example: Reinforced Strip Foundation." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEFPUtEg_rdHj-OU-_KybKSXLO0yW_oGWkpP8ou1dcJvus_F-rxG2x8ViqXXtMjAiTrNMqxR2cXaFyalTDoSJFxYxI9HaYe61XQu4YRk6FdX54Hg5OOA36ZdS-rpNiiJkDJ2M4Cz2V_cSx/s1600/38.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Design Example: Reinforced Strip Foundation." /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">If the foundations and superstructure are being designed  to limit state principles, loads should be kept as separate</span><span style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><u style="margin: 0px; padding: 0px;"> </u></span><span style="font-size: 12px; line-height: 18px; text-align: justify;">unfactored characteristic dead and imposed values (as above), both for foundation bearing pressure design and for serviceability checks. The loads should then be factored up for the design of individual members at the ultimate limit state as usual.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">For foundations under dead and imposed loads only,  factoring up loads for reinforcement design is best done  by selecting an average partial load factor, γP, to cover both dead and imposed superstructure loads from</span><b style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"> Fig. 11.22</b><span style="font-size: 12px; line-height: 18px; text-align: justify;"> (this is a copy of </span><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg96-BjjQ7g2YnW9CvKDGH-wk3FY7SBbTvv07TkW27dcNS4LcOMhfKRTYwiaYg9Y2O8oTM78oXRoUg_hCbGg20oSyDI35l6dtGuidtD9jqLetH0ywddjENY0UUC9zXo0neVAI70fxpkg6Yk/s1600/35.gif" style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify; text-decoration: none;"><b style="margin: 0px; padding: 0px;">Fig. 11.20</b> Reinforced concrete strip design conditions.</a><span style="font-size: 12px; line-height: 18px; text-align: justify;">).</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border-collapse: collapse; border: 1px solid rgb(204, 204, 204); font-size: 12px; line-height: 18px; margin: 5px auto 10px; padding: 4px; text-align: center;"><tbody style="margin: 0px; padding: 0px;">
<tr style="margin: 0px; padding: 0px;"><td style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 5px 10px; vertical-align: top;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8s4PFSP181usAMyWFoHVlEToetz9C360cOSvhqKlj0mIHuZXx3nK0KYMl4x3M61aeq4rYYFXtQuwP1bQMbIUZSLvoy8QxqbvRKMOgX8i0Pl6K1GenuX5xBic51RVwdskQBOoynYb-VIhk/s1600/48.gif" imageanchor="1" style="margin: 0px auto; padding: 0px; text-decoration: none;"><span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Combined partial safety factor for dead + imposed loads." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8s4PFSP181usAMyWFoHVlEToetz9C360cOSvhqKlj0mIHuZXx3nK0KYMl4x3M61aeq4rYYFXtQuwP1bQMbIUZSLvoy8QxqbvRKMOgX8i0Pl6K1GenuX5xBic51RVwdskQBOoynYb-VIhk/s1600/48.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Combined partial safety factor for dead + imposed loads." /></span></a></td></tr>
<tr style="margin: 0px; padding: 0px;"><td class="tr-caption" style="border: 1px solid rgb(204, 204, 204); font-size: 9.60000038146973px; margin: 0px; padding: 5px 10px; vertical-align: top;"><span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><b style="margin: 0px; padding: 0px;">Fig. 11.22</b> Combined partial safety factor for dead + imposed loads.</span></span></td></tr>
</tbody></table>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgc92VQhqxOj8n_g2HkAF7Lmot0myHxG_gj5GVplcY8w9Hw4a6hew9d8lO0Knb43GrnAuW7HMlFOV1mqxftY5R7lfnMWnDMHUdN7-166QVSFibM1PaRnpfEJfXVVFMSG0EK9EaSNEzuf-j/s1600/39.gif" imageanchor="1" style="margin: 0px 1em; padding: 0px; text-decoration: none;"><span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgc92VQhqxOj8n_g2HkAF7Lmot0myHxG_gj5GVplcY8w9Hw4a6hew9d8lO0Knb43GrnAuW7HMlFOV1mqxftY5R7lfnMWnDMHUdN7-166QVSFibM1PaRnpfEJfXVVFMSG0EK9EaSNEzuf-j/s1600/39.gif" style="border: 0px; margin: 0px; padding: 0px;" /></span></a></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><span style="font-size: 12px; line-height: 18px; text-align: justify;">From </span><b style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;">Fig. 11.22</b><span style="font-size: 12px; line-height: 18px; text-align: justify;">, the combined partial safety factor for superstructure loads is γ</span><span style="font-size: xx-small; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;">P</span><span style="font-size: 12px; line-height: 18px; text-align: justify;"> = 1.46.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">Weight of base and backﬁll, f = average density × depth</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">                                             = 20 × 0.9</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">                                             = 18.0 kN/m2</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">This is all dead load, thus the combined partial load factor for foundation loads, γ</span><span style="font-size: xx-small; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;">F</span><span style="font-size: 12px; line-height: 18px; text-align: justify;"> = 1.4.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Sizing of foundation width</b></i><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">New ground levels are similar to existing ones, thus the (weight of the) new foundation imposes no additional  surcharge, and may be ignored.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">The minimum foundation width is given by </span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuG0nULO4BMtbkQyoR0aH8NkmmB0Q6Q86QCVIo4BN5mdZKC6K-5eniKxTilp79rQwp2eYbn5RUgx04D4_LMb1HS7gEedOqB6hmCOLb1fvkK6RYC-40cvWjqCcrgC8mMl40MZ1Qj-EVVxlA/s1600/40.gif" style="border: 0px; margin: 0px; padding: 0px;" /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">Adopt a 1.2 m wide × 350 mm deep reinforced strip foundation, using grade 35 concrete (</span><b style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;">see Fig. 11.23</b><span style="font-size: 12px; line-height: 18px; text-align: justify;">).</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: center;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Design Example: Reinforced Strip Foundation." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkBi7o9WxMBkbHWDk1vpf1Lq_eGmX5f-1cPaPTSUv1ap37CBr7FNLk3ccdqo0qDOr4Ei2xfqVOctbJ_tDt1DWUpQ75PIhZmwLdOA_KCWkwK5-1Z1HzhG_Bt5rgxEb8mh8EscsEicT1HzCk/s1600/49.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Design Example: Reinforced Strip Foundation." /></span></div>
<div style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: center;">
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><b style="margin: 0px; padding: 0px;"> Fig. 11.23</b> Reinforced strip foundation design example – loads and bearing pressures.</span></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Reactive upwards design pressure for lateral reinforcement design </b></i></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Design Example: Reinforced Strip Foundation." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMmAuf2u3kNjcHGmTx7xEuBsTG0PBYpCLmDzDWRJjqCtvVu6HHrOuG37vQ0rdkU4mYisSyfA0hopjm8eaX1eR3zcURli5YHhROX5X11k0Dexi0DwCWiHv8QIgQDy6bBzflk0JKk4Dm-nCF/s1600/41.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Design Example: Reinforced Strip Foundation." /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Lateral bending and shear</b></i><span style="font-size: 12px; line-height: 18px; text-align: justify;">b = 1000 mm.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKEmxOWNbfoluQ34BoH0NIKN0sNONSmKsTbQpBkHgcd7dV8ZlvmdRCIHLS0jMOBn3FV68ON_vVOogWiNb8Yn_RMWhOq-mdp6FVohYPzl0-1U4zqgmZC5OmW3zEPnlQ5PcudAocSF-qsjnL/s1600/42.gif" style="border: 0px; margin: 0px; padding: 0px;" /></span></div>
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Design Example: Reinforced Strip Foundation." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEichc8Q3ngoFES_-5Tm_Dm4Ibvm9i217_Iq1nAsOZmyPVTE71N6qV_ch9TEkRhkHBkU6vzHuhqfTD4D3gZnZ0pGWUv8_sQ1J5OGjtFcBwXQaADiIOv7d2x1kI-28b3u8h5qzxF3-ME3MsvI/s1600/44.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Design Example: Reinforced Strip Foundation." /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">Thus vu < vc , therefore no shear reinforcement is required.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Loading for spanning over depressions</b></i><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">Where a local depression occurs, the foundation is acting like a suspended slab. The ultimate load causing bending and shear in the foundation is the total load i.e. superstructure load + foundation load, which is given by</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWHj31xbSVxaTgo8V8vkts0zVkFH_MGDEaHNVkfN5VOfkjpnsZAGJuEcSXEUt9fRLS1K3bOEaFD6QEABPyDb-U7YhWnl8EQnkVQWSxZSfYBWPuY8T9czEwoglbuQz0PP2wWPogJFnvMo0k/s1600/45.gif" style="border: 0px; margin: 0px; padding: 0px;" /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Longitudinal bending and shear due to depressions</b></i><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">Ultimate moment due to foundation spanning – assumed simply supported – over a 2.5 m local depression is</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj18n-mdSg3LrmTtR2tHEjpYsjuEH5TKsMVWJgVLt7Rb-SMXLYPMxnrk3heEyQtr3KoKkF1AQFyZw8rMXEviSsVmPeTKHY09YjxOYAx0HJEzzxDvEnQf6WypE0qB8Kb_J7fyM00S4CaEkuD/s1600/46.gif" style="border: 0px; margin: 0px; padding: 0px;" /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><span style="font-size: 12px; line-height: 18px; text-align: justify;">Width for reinforcement design is b = B = 1200 mm.</span></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img alt="Design Example: Reinforced Strip Foundation." border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB8xotneR9huxJQKcPAkswsMu6fmhSR4UKxMyIUjQ1HzTIY_M9B5VsBRO9InrLzXjZRd0f00No9Kwhom3NR08cLB0pqSDng4xIJhTrFHTekl1BQug1Aegt-WtVDnaKkk-EJDQnCd9GFzWN/s1600/47.gif" style="border: 0px; margin: 0px; padding: 0px;" title="Design Example: Reinforced Strip Foundation." /></span></div>
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><span style="font-size: 12px; line-height: 18px; text-align: justify;">Thus vu < vc = 0.49 N/mm2, therefore no shear reinforcement is needed.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><i style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: justify;"><b style="margin: 0px; padding: 0px;">Depression at corner of building</b></i><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">The previous calculations have assumed that the depression is located under a continuous strip footing. The</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /><span style="font-size: 12px; line-height: 18px; text-align: justify;">depression could also occur at the corner of a building where two footings would meet at right angles. A similar calculation should then be carried out, to provide top reinforcement for both footings to cantilever at these corners.</span><br style="font-size: 12px; line-height: 12px; margin: 0px; padding: 0px; text-align: justify;" /></span></span><br />
<div class="separator" style="clear: both; font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: center;">
<span style="background-color: white; color: black; font-family: Verdana, sans-serif;"><img border="0" height="135" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRiUJUpaqzuLMJ0oLwUAJUI6GOxoZoMB0PedhW3qdJLcBZ3cveIo4Lv9wEPy-8tV3PNILPF6FnxeqOwNV40ImNtch09kDSyf5RrZpUotL9lKKQ5xJcPu-aKWwRoNKi30pjz3jtrcYJh4zT/s320/50.gif" style="border: 0px; margin: 0px; padding: 0px;" width="320" /></span></div>
<div style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: center;">
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><b style="margin: 0px; padding: 0px;">Fig. 11.24</b> Reinforced strip footing design example – reinforcement.</span></span></div>
<div style="font-size: 12px; line-height: 18px; margin: 0px; padding: 0px; text-align: center;">
<span style="background-color: white;"><span style="font-family: Verdana, sans-serif;"><br /></span></span></div>
<div style="margin: 0px; padding: 0px; text-align: left;">
<span style="background-color: white; font-size: 12px; line-height: 18px;"><span style="font-family: Verdana, sans-serif;">Main post </span></span><span style="font-size: 11.9999990463257px; line-height: 18px; text-align: left;"><span style="font-family: Verdana, sans-serif;">http://www.abuildersengineer.com/</span></span></div>
</div>

Design Example: Reinforced Strip Foundation.

The load-bearing wall of a single-storey building is to be supported on a wide reinforced strip foundation. A site investigation has reveal...

Top Menu

HOW TO CALCULATE SAFE BEARING CAPACITY OF SOIL ON SITE?

Design Example: Reinforced Strip Foundation.

Popular Posts

Blog Archive