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Pipe Deflection by the Iowa Formula

Posted by on 18/ 11/ 15

Deflection of flexible pipes is not a design criterion in most specifications, because if pipes are properly installed with approved soil and compaction level, deflections will be within normal limits. However, the deflection for given loading and backfill conditions

Подпись: TABLE 5.26 Values of Bedding Constant K for Deflection Calculations for Flexible Pipe Bedding angle, ° K 0 0.110 30 0.108 45 0.105 60 0.102 90 0.096 120 0.090 180 0.083 Source: From A. P. Moser, Buried Pipe Design, McGraw-Hill, 2001, with permission.

can be approximated for a round pipe. The traditional method of predicting deflection is the Iowa formula introduced by M. G. Spangler and modified by R. K. Watkins:

Подпись: (5.55)DTKWr

AX = ______ _ c______________

Pipe Deflection by the Iowa Formula Подпись: total horizontal deflection, in (mm) deflection lag factor bedding constant vertical load on pipe, lb/in (kN/mm) mean radius of pipe, in (mm) modulus of elasticity of pipe material, lb/in2 (MPa) moment of inertia of pipe wall, in4/in (mm4/mm) modulus of soil reaction, lb/in2 (MPa)

EI + 0.061Er*

Values for the bedding constant may be found in Table 5.26. Because the bedding constant does not vary greatly and the bedding angle is generally not well known, it is often taken as 0.10. Values of the modulus of soil reaction are given in Table 5.27...

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Plastic Pipe

Posted by on 18/ 11/ 15

Introduction. Gravity flow thermoplastic pipes used in highway drainage applications are typically manufactured of high-density polyethylene (HDPE) or polyvinyl chloride (PVC). To a lesser extent acrylonitrile-butadiene-styrene (ABS) pipe is also used but is limited to drain, waste, and vent applications. Plastic pipes are always circular in cross­section. They may be either of a solid wall or profile wall design. These structures are generally designed for ring thrust by a semiempirical method that includes checks for wall area, buckling, and wall stress and strain. A check is also made to ensure the struc­ture has sufficient rigidity to withstand handling and installation forces...

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Using a Voltage Tester

Posted by on 18/ 11/ 15

Two-prong voltage testers are inexpensive, reliable, and available almost everywhere. Whatever tester you use, first test the tester on a circuit that you know is energized.

If the tester doesn’t indicate voltage on that circuit, the tool may be broken.

Testing Receptacles

When testing receptacles, grasp the insulated part of the tester and insert its probes into the receptacle slots. Never touch the bare wire tips of tester probes. If the tester lights up, there’s voltage present. Have a helper at the service panel flip circuit breakers (or remove fuses) till you find the one that controls the outlet and the tester light goes out. Use cell phones to communicate, which sure beats scream­ing between floors.

If the receptacle is faulty or a wire is loose, however, the previous test may not ...

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Corrugated Metal Pipe

Posted by on 18/ 11/ 15

Introduction. Corrugated metal structures are typically manufactured of either steel or aluminum. These structures are generally designed for ring thrust by a semiempirical method that includes checks for wall area, buckling, and seam strength. A check is also

Corrugated Metal Pipe

FIGURE 5.39 Coefficients for calculating moment (M), thrust (N), and shear (V) in concrete pipe under linear pressure distributions. The coefficients used are as follows: M = CmWR, N = CnW, V = CW, where W is total load in each case and R is mean radius. Sign convention: +M is tension on inside face, +N is compression, +V is positive shear for left side. (From J. M. Paris, "Stress Coefficients for Large Horizontal Pipes," Engineering News Record, vol. 87, no. 19, November 10, 1921, with permission)

made to ensure the structur...

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Volts, Amps, and Watts

Posted by on 18/ 11/ 15

At a power plant or a substation, electricity is multiplied (charged) and given pressure (voltage); in that form, electricity is potential energy, just like a charged battery. When electricity is put to work at an outlet, electrons flow through the wires, and power is delivered as heat or light. Amperes (amp) is the measure of this current flow. The amount of energy consumed at a given point-say, at a toaster or a light bulb-is measured in watts. Volts, amperes, and watts are thus interrelated:

► Voltage: the potential to do work (electrical pressure).

► Amperes: the rate of electrical flow.

► Watts: the rate at which energy is consumed.

Or, expressed as mathematical formulas:

watts = voltage x amperes amperes = watts * voltage

To reiterate briefly, electricity, impelled by voltage, flo...

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Techniques MAKING A PLATFORM FOR ROOF SHEATHING

Posted by on 18/ 11/ 15

Techniques MAKING A PLATFORM FOR ROOF SHEATHINGA SAFE STRATEGY for hoisting sheathing onto a roof is to build a simple staging platform, as shown in the photo at right. Nail the platform’s two horizontal supports (a pair of 2x4s works fine) to the wall framing or, if the wall has been sheathed already, to a 2x cleat nailed through the sheathing and into the studs. The supports must be a couple of feet above the bottom plate of the wall. Space them about 32 in. apart, and make them roughly level. Support the outboard end of the platform with 2x legs firmly attached to the horizontal supports. Nail a 2x on top of the platform near the outer end to provide addi­tional stability. If necessary, install diagonal braces between the supports and the legs or the wall fram­ing for added strength...

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DAY-CARE CENTERS

Posted by on 18/ 11/ 15

Day-care centers, pre-schools, and nursery schools all fall under the same classification when computing minimum needs for plumbing fixtures. Figure 9.6 shows you the formulas for figuring the number of fixtures needed. It’s a simple table. Basically, you supply one toilet and one lavatory for each 15 oc­cupants of the building. If the school will have 30 occupants, you must install two toilets and two lavatories. When 45 people will be in the school, you need three toilets and three lavatories. This is one of the easiest sizing exer­cises going.

ELEMENTARY AND SECONDARY SCHOOLS

Requirements for elementary and secondary schools are a bit more complex than those applying to pre-schools. Even so, the process of sizing the fixture needs is not difficult. Look at the table in Figure 9.7...

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Rigid Pipe

Posted by on 18/ 11/ 15

Introduction. There are two general types of rigid underground structures—those with a curvilinear shape, and those made up of straight walls and flat slabs. A reinforced concrete pipe is an example of the former, while a reinforced concrete box is an example of the latter. Rigid structures built in a curvilinear shape tend to act in compression. However, because of their limited deflection capability, they develop moment as well as compressive stresses. The effect of moment is reduced, however, because the curvilinear shape increases the compression in the member. Structures built with straight structural elements act very differently...

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Surface Preparation

Posted by on 18/ 11/ 15

The rule for SMA surface preparation is the same that as for other binder courses. The surface of the underlying course should be even, clean, and free from dirt that could disturb the appropriate bonding of the laid-down mixture with the layer underneath. Any soiling of the surface (Figure 10.6) should be removed from the pavement. Oil and fuel stains should be cleaned with an absorbent material, and their residue should be washed off. The remains of an old mixture atop an underlying layer should be removed because they may cause partial unevenness of the spread SMA mixture (see Figure 11.33). When placing an SMA course on an old pavement, one should see that patches made of mastic asphalt have been removed and a new patch of asphalt concrete has been made...

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Wind and Rain

Posted by on 18/ 11/ 15

There are additional requirements regarding issues such as wind speed at the laydown site in many national specifications. Let us take the Polish guidelines WT2 2008, for instance, in which the maximum allowable wind speed has been set at 16 m/sec (58 km/hr). The values of wind speed at the construction site are undoubtedly a fac­tor of tremendous significance, especially when placing thin courses of SMA.

Wind and Rain
Frequent rainfall and the necessity of placing an SMA on a wet underlying layer are problems that often beset road builders. Most regulations do not allow SMA laydown on a wet surface or during rainfall (Figure 10.4)...

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