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Preparing Pavement Facilities

Posted by on 18/ 11/ 15

The existing pavement facilities should be prepared prior to placing the mixture of a wearing course. This preparation should result in the following:

• Appropriate, tight, and durable bonding between asphalt course and facilities (e. g., with the use of suitable polymer modified asphalt tapes [Figure 10.7])

• Protection against damage or infiltration of excess asphalt mixture (e. g., around a drain or manhole)

10.2.5 Preparing Edges of the Courses

The edges of the course should also be prepared. The selected method should ensure durable joints at the transverse and longitudinal edges. Most previous experiences have proved the poor effectiveness of traditional methods like applying hot binder,

Preparing Pavement Facilities

image100FIGURE 10...

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REPLACEMENTS FOR BRIDGES

Posted by on 18/ 11/ 15

5.9.1 Introduction

America’s transportation infrastructure—particularly the Interstate Highway System— is past its original anticipated design life and its age is showing. The age of the system coupled with high user demand and limited financial resources requires innovative thinking from the design engineer. One solution frequently utilized is the replacement of deficient bridges with prefabricated structures. The prefabricated alternative is typi­cally less expensive to construct, easier to maintain, and can be built with significantly less service disruption to the traveling public.

This approach can be utilized for stream crossings and for grade separation struc­tures. The systematic approach for selecting an appropriate structure is similar for both applications...

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Proportion

Posted by on 18/ 11/ 15

If these principles are starting to seem a lot like common sense, it is be­cause they are. It is in our nature to seek out the sort of order that they prescribe. Honest structure and simple forms strike a chord with us because they are true to nature’s law of necessity. Sound proportions strike a chord, too. Certain proportions seem to appear everywhere — in sea shells, trees, geodes, cell structure, and all of what is commonly called "the natural world.” That these same proportions continually turn up in our own creations should not seem too surprising or coincidental. We are nature, after all, and so our works are bound to contain these natural proportions.

Proportioning is one of the primary means by which a building can be made readable...

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Tunnel Liner Plates and Rib and Lagging

Posted by on 18/ 11/ 15

Steel tunnel liner plate and steel rib and lagging are flexible structures placed by a tunneling operation. Like other flexible structures, they are designed to deflect verti­cally under load so that the lateral side pressure will be established and essentially uniform radial pressure will develop about the perimeter of the structure. Because these structures are used in tunneling operations, however, under most circumstances it is not necessary to design for the complete prism load. The AASHTO Standard

TABLE 5.27 Average Values of Modulus of Soil Reaction E’ for Deflection Calculations for Flexible Pipe

E’ for degree of compaction of bedding, lb/in2

Slight,

Moderate,

High,

Soil type—pipe bedding

< 85% Proctor,

85-95% Proctor,

> 95% Proctor,

material (Uni...

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Redox Potential (in-situ)

Posted by on 18/ 11/ 15

The redox potential, i. e. a measure (in volts) of the affinity of a substance for elec­trons compared with hydrogen, may also be determined in the field using electrical, hand-held equipment, this time employing an inert oxidation-reduction electrode.

7.5.2 Electrical Conductivity

Electrical conductivity is typically measured in-situ, being an important, yet sim­ple, indicator of pollution since the ability of water to conduct electricity increases as the proportion of dissolved ions increases. It can be measured directly through the insertion of probes and the resistance (or conductivity recorded) or indirectly through air-coupled “aerials”. However, because there are so many factors that affect electrical conductivity (e. g...

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Chapter Seven

Posted by on 18/ 11/ 15

LAYOUT

Layout is the written language of the framer. If the lead framer on the job “writes" clearly, then the framers reading the layout will be able to understand and properly perform the work. It’s important to include enough information in the layout so that there aren’t any questions. Layout language has been developed by framers over the years, and there are some variations. The version described in this book is quite typical. Feel free to make any changes that reflect practices in your area. If you need to explain something about the layout that isn’t shown in this chapter, either write it out on the plates in plain language, or explain it to the person who will do the framing.

Layout for framing requires bringing together the desires of the owner, the written instructions of the a...

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Divide Circumference for Treads

Posted by on 18/ 11/ 15

Draw lines from points A & B to the point where the bisecting line intersects the circumference (at point C) creating half lines.

2. Draw line from the radius origin to the circumference (at point D) passing through the mid point of the half line.

Stair wall lines Two established points Radius origin

3. Draw quarter lines by drawing lines from points B and C to point D.

4. Continue dividing lines in half until all tread widths are found.

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In-situ Measurements

Posted by on 18/ 11/ 15

To measure pH in-situ, so-called pH testers (for a rough estimate of the pH value) and pocket (portable) pH meters are used (Fig. 7.9). Periodic calibration of the in­strument is required.

The determination of pH is very fast and reliable when a combined glass elec­trode is used. It enables an automatic measurement over long time intervals with the accuracy of ± 0.01 pH units. The glass electrode can be used even in strongly acidic and alkaline solutions, and also in the presence of oxidizing or reducing substances. It must be constantly immersed in water. With time, all glass electrodes deteriorate due to alkali leaching from the surface layers.

7.5.1 Introduction

When collecting a sample of water, certain principal variables that are prone to more or less rapid change upon sample stor...

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Choosing an Electrical Tester

Posted by on 18/ 11/ 15

Testing to see if an outlet is energized is so critical to professional electricians that there are scores of specialized testers to choose from, some of which cost hundreds of dollars. Fortunately, amateur electricians can get a reliable tester for less than $30. Here are five types:

► Neon voltage testers are inexpensive and versatile. Insert the probes (prongs) into the receptacle slots or touch them to the screw terminals or to a metal outlet box to see if the unit is hot (energized). Buy quality: Better neon testers have insulated handles, whereas cheapies have bare metal probes so short that you risk shocking yourself when using them.

► Plug-in circuit analyzers can be used only with three-hole receptacles, but they quickly tell you if a circuit is correctly grounded and, if not, wha...

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AND TRIMMERS

Posted by on 18/ 11/ 15

Now it’s time to cut some of the parts that make up the wall, beginning with the window and door headers and the rough sills. Recall from Chapter 3 that headers are needed at window and door openings to transfer the load of the building around these elements to the foundation. This wasn’t always done in old houses, so walls often

Подпись: HEADERS, CRIPPLES, ROUGH SILLS, AND TRIMMERS

sagged and doors and windows became hard to open because of all the weight put on them. Frequently, part of a remodeler’s job is to open up old walls and cut in solid headers over every door and window.

Ordinarily, the distance from the floor to the bottom of the door or window header is б ft. 10 in...

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