Boston Concrete Cutting
288 Grove Street, Unit 110
Braintree, MA 02184


781-519-2456
info@bostonconcretecutting.com
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Concrete Cutting Sawing Abington MA Mass Massachusetts

“We Specialize in Cutting Doorways and Windows in Concrete Foundations”

Are You in Abington Massachusetts? Do You Need Concrete Cutting?

We Are Your Local Concrete Cutter

Call 781-519-2456

We Service Abington MA and all surrounding Cities & Towns

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Concrete cutting and sawing as an extended toe, as is frequently done-with considerable economy and advantage, even that toe must be designed to withstand transverse bending at the concrete wall line, and also shearing at that point. The application of these principles can best be understood by an illustration. Assume that it is required to design a concrete retaining concrete wall to withstand an ordinary earthwork pressure of 20 feet, the earth being level on top. We are at once confronted with the determination of the actual lateral pressure of the earthwork. Unfortunately, this is an exceedingly uncertain quantity, depending upon the nature of the soil, upon its angle of repose, and particularly upon its condition whether wet or dry. The angle of repose is the largest angle with the horizontal at which the material will stand without sliding down. A moment's consideration will show that this angle depends very largely on the condition of the material, whether wet or dry, etc. On this account any great refinement in these calculations is utterly useless. Assuming that the back face of the concrete wall is vertical, or practically so; that the upper surface of the earth is horizontal; and that the angle of repose of the material is 30°, the total pressure of the concrete wall equals 1 w 10-, in which h is the total height of the concrete wall, and w is the weight per unit-volume of the earth. If the angle of repose is steeper than this, the pressure will be less. If the angle of repose is less than this, the fraction will be larger, but the unit-weight of the material will probably be smaller. Assuming the weight at the somewhat excessive figure of 96 pounds per cubic foot, we can then say, as an ordinary rule, that the total pressure of the earth on a vertical strip of the concrete wall one foot wide will equal 16 h2, in which it is the height of the concrete wall in feet.

The average pressure, therefore, equals 16 It; and the maximum pressure at a depth of h feet equals 32 It. Applying this figure to our numerical example, we have a total pressure on a vertical strip one foot wide, of 16 >< 202 = 6,400 pounds. The pressure at a depth of 20 feet equals 32 X 20 = 640 pounds. It is usual to compute the thickness and reinforcement of a strip one foot wide running horizontally between two concrete buttresses. Practically the strip at the bottom is very strongly reinforced by the base- plate, which runs at right angles to it; but if we design a strip at the bottom of the concrete wall without allowing for its support from the base plate, and then design all the strips toward the top of the concrete wall in the same proportion, the upper strips will have their proper design, while the lower strip merely has an excess of strength. We shall assume, in this case, that the concrete buttresses are spaced 15 feet center to center. Then the load on a horizontal strip of face-plate 12 inches high, 15 feet long, and 19 feet 6 inches from the top, will be 15 >< 19.5 X 32, or 9,360 pounds. Multiplying this by 4, we have an ultimate load of 37,440 pounds. The span in inches equals 180. Then 37,440 x 180 equals 842,400 inch-pounds. Placing this equal to 397 bd2, in which b = 12 inches, we find that d2 = 176.8, and d = 13.3 inches. At one-half the height of the concrete wall, the moment will equal one-half of the above, and the required thickness d would be 9.4 inches. The actual thickness at the bottom, including that required outside of the reinforcement, would therefore make the thickness of the concrete wall about 16 inches at the bottom. At one-half the height, the thickness must be about 12 inches. Using a uniform taper, this would mean a thickness of 8 inches at the top. The reinforcement at the bottom would equal .0084 X 13.3 = .112 square inch of metal per inch of height. Such reinforcement could be obtained by using finch bars spaced 5 inches apart.

Are You in Abington Massachusetts? Do You Need Concrete Cutting?

We Are Your Local Concrete Cutter

Call 781-519-2456

We Service Abington MA and all surrounding Cities & Towns

Boston Concrete Cutting | 288 Grove Street, Unit 110, Braintree, MA 02184 | 781-519-2456 | info@bostonconcretecutting.com