Blog Archives

The Effect of Temperature

Posted by on 11/ 11/ 15

Pore suctions have the effect of “pulling” the saturated zone nearer the ground surface than it would otherwise have been from where evaporation becomes pos­sible. When evaporation is significant then upward water flow takes place to re­place the water being evaporated. Evapotranspiration by vegetation also introduces an upward water flow towards roots in a similar manner. In hot climates, evap­oration can lead to upward moving water tens of metres above the phreatic sur­face and it can also lead to salts being lifted to the surface where they precipitate out in the soil pores forming calcretes and silcretes (Sabkha soils are an example of this).

Another cause of suction is seasonal ground freezing in high latitudes or at high altitudes...

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Approaches to the Management of Lead-Based Paint on Steel Bridges

Posted by on 11/ 11/ 15

A number of methods have been advanced to effectively contain blasting debris and to min­imize the amount of waste generated from the management of lead-based paint from steel bridges. These methods are discussed in Art. 1.5.5 of this chapter. They can be broadly characterized as follows.

Deferring Maintenance. This approach does not serve to protect the bridge, and is the least satisfactory approach to protecting the large public investment represented by a major steel bridge.

Overcoating. This method consists of applying new layers of nonleaded paint over lead – based paint with the intent of extending the coating system for another 5 years or so. This method may reduce short-term costs and provide an agency more time while new innova­tions in lead paint removal are being developed...

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FILLER

Posted by on 11/ 11/ 15

The term filler means an aggregate that mostly passes through a specified sieve (0.063 mm in Europe, 0.075 mm in the United States). It should be emphasized that the material just discussed, which is generally called filler, denotes all the grains—that is, both those coming from the added filler and those occurring on fine and coarse aggregate grains in the form of dust. Thus if we want to know the behavior of a filler fraction in a given mixture, then all the grains below a specified sieve size in a final mineral blend should be separated, regardless of their source. All that material should be tested. If we only test the added filler, the results do not show the influence of the entire filler fraction on the properties of the mix.

The significant influence of filler on asphalt mixtures...

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Regulatory Framework

Posted by on 11/ 11/ 15

Hazardous waste is regulated under the RCRA if more than 220 lb (100 kg) of hazardous waste is generated each month, as is the case in most bridge paint removal projects. RCRA defines the concentrations of a waste that should be considered hazardous and establishes procedures for handling and disposing of hazardous waste. Disposing of waste is the responsibility of the waste generator. The lead-based paint and blasting grit recovered in bridge paint removal projects may contain concentrations of lead sufficient to classify it as hazardous, waste in all instances, the owner of the structure is considered the generator (in some states the contractor removing the paint may be considered a cogenerator). Subtitle C under RCRA is relevant to lead removal activities. Table 1...

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Reciprocating saws

Posted by on 11/ 11/ 15

Another frequently used tool is the reciprocating saw, also called a sabersaw or a Sawzall®—the name given to Milwaukee’s® popular saw (see the bottom photo on the facing page). This tool allows you to cut in tight places and make curved cuts. Different blades are available for cutting through wood, metal, plaster, and plastic. For general use, I buy 6-in. bimetal blades, which cut through both wood and metal.

Chopsaws

The power-miter saw (generally referred to as a chopsaw) has revolutionized finish carpentry just as the circular saw revolutionized rough­framing carpentry. With a chopsaw, you can make precise square and angled cuts in framing lumber, door and window casings, and base­board trim. These saws are rugged and easy to use...

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FINE AGGREGATE

Posted by on 11/ 11/ 15

Throughout this book the term fine aggregate has been conventionally used as a term for the passive aggregate. Its upper limit depends on us—or more specifically, on

Подпись: (a) (b) FIGURE 3.1 Filling voids among coarse grains of aggregate with passive grains: (a) schematic diagram and (b) an actual example—mastic marked with dark gray color. (Photo courtesy of Krzysztof Blazejowski.)
the type of coarse grain previously in process of SMA design accepted as a skeleton maker. The task of the fine aggregate is to fill voids among the coarse aggregate particles and facilitate their interlocking, though it is likely to be put the other way round; the fine aggregate cannot disturb interlocking of the coarse aggregates. Such a disturbance can best be illustrated by an example of rounded, uncrushed aggregate (e. g., natural sand or uncrushed gravel) with smooth surfaces that allow the coarse aggregates to glide easily...

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The Method and the Madness

Posted by on 11/ 11/ 15

My reasons for choosing to live in such small houses include some envi­ronmental concerns. The two largest of my three, hand-built homes were made with only about 4,800 pounds of building materials each, less than 100 pounds of which went to the local landfill. Each produced less than 900 pounds of greenhouse gases during a typical Iowa winter. And, at 89 square feet, plus porch and loft, each fit snugly into a single parking space.

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In contrast, the average American house consumes about three quarters of an acre of forest and produces about seven tons of construction waste. It emits 18 tons of greenhouse gases annually, and, at more than 2,349 square feet, it would most definitely not fit into a single parking space.

Finances informed my decision, too...

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PIPING MATH

Posted by on 11/ 11/ 15

This section will profile formulas that can help you when working with pipes. Rather than talk about them, let’s look at them.

What plumber hasn’t had to figure the grading for a drainage pipe? De­termining the amount of fall needed for a drainpipe over a specified distance is no big mystery. Yet, I’ve known good plumbers who had trouble with cal­culating the grade of their pipes. In fact, some of them were so unsure of themselves that they started at the end of their runs and worked backwards, to the beginning, to insure enough grade. Not only is this more difficult and

Подпись: ✓ fast code fact As a rule of thumb, most codes require a minimum of one-quarter of an inch per foot of fall for drainage piping. There are exceptions. For example, large-diameter pipes may be installed with a minimum grade of one-eighth of an inch per foot. Too much grade is as bad as too little grade. A pipe with excessive grade will empty liquids before solids have cleared the pipe. Maintain a constant grade within the confines of your local plumbing code. time consuming, there is still no guar­antee that there will be enough room for the grade. Knowing how to figure the grade, fall, pitch, or whatever you want to call it, for a pipe is essential in the plumbing trade...

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Making the Grade

Posted by on 11/ 11/ 15
Подпись: Upon hearing that I planned to build a timber frame home with an earth roof, the immediate response from the building department supervisor was, "Are you a structural engineer? I'm not." I knew then that I would have to hire an engineer. But another problematic issue soon arose, revolving around the fact that I was felling my own trees (hardwood, no less) and chainsaw-milling them into posts and beams. The issue concerned the use of ungraded hardwood lumber. Finding an engineer was a process by itself, as I encountered resistance to the idea of using native timbers. Many engineers simply don't want to be bothered with "gray" areas when it comes to what they think of as unconventional building. Tracking down someone to grade my homespun hardwood timbers was even more difficult than finding the right engineer. We live in the northern part of Michigan's lower Peninsula. Numerous local sawmills process the fine maple, oak and beech stands in our region, but none of the ones I contacted graded hardwood for its structural properties, but only with respect to veneer lumber, flooring, and the like. I contacted a "certified" hardwood lumber grader through one of the mills, who made a 90-mile round trip to my place only to reveal that he didn't know how to grade posts and beams for structural purposes. So I cast my net further afield. Подпись: The Department of Forestry at Michigan State University referred me to the National Hardwood Lumber Association (NHLA) in Memphis, Tennessee. Through them I connected with a sympathetic inspector who proposed an alternative to having him visit my location and charging me the minimum fee of $470 a day, plus expenses. He volunteered to call the local "certified" inspector — the one who had already visited — and explain to him how to grade hardwood for structure. The grading was done according to guidelines from the Northeastern Lumber Manufacturers Association (NeLMA) in Maine. The inspector charged me $120 and apologized that the bill came to that much. It seemed quite reasonable to me, considering the time he spent educating himself to "make the grade." Incidentally, the building inspector was not the only one who needed the certified grading; my engineer also needed it in order to feel comfortable about assigning values to my timbers. Thankfully, my building inspector is basically on my side and seems to appreciate the lengths I've gone to satisfy code. I've maintained a cordial relationship with all the inspectors I've dealt with, and though it's been mighty frustrating at times, the good will is generally repaid in kind. It pays dividends to treat the building department as a resource, and not an adversary.

Mark Powers, owner-builder, Alonson, Michigan

Author’s note: The two lumber organizations mentioned above, NHLA and NeLMA, are listed in Appendix C.

In short, the grading of lumber can be an expensive proposition, which defeats the advantage of using local rough-cut lumber in the first place. At this time, despite widespread adaptation of the International Building Code, it is possible for most people in rural areas to build with non-graded lumber. Check on this with the town or county building inspector before placing a big lumber order with your local sawmill, or cutting quantities of your own lumber with a chainsaw mill. If evasion is a strategy that you have in mind — I am not advocating this, you understand — then you might want to gain the information anonymously.

My gu...

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. AVOIDING KICKBACK

Posted by on 11/ 11/ 15

When the blade of a circular saw gets pinched by the wood, the power of the motor can force the saw backward—a safety hazard called kickback. In extreme cases, the saw can jump away from the material with the blade still spinning, harming anything in its path. To prevent kickback when using a circular saw, follow these guidelines:

■ Use a sharp, carbide-tipped blade.

■ Cut in a straight line.

■ Let the saw do the cutting—don’t force it. Forcing the cut can cause the blade to bind and kick back.

■ Always provide proper support for the stock. Avoid setups that al­low the material being cut to pinch the blade (see the illustration below).

■

Подпись: When you are cutting wood, support it properly. Unsupported wood can pinch the blade and cause the saw to kick back.

Подпись: Adjust the cutting depth. Always set the cutting depth so that the saw just barely cuts through the material. [Photo © Tony Mason] Подпись:If a kickback does occur, release the saw trigger immediately and let the blade stop...

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