Blog Archives

Water and Alternative Materials

Recycled and alternative materials are finding increased use in the construction of road pavements and embankments. Environmental concerns are leading to con­straints on quarrying of the materials that have, conventionally, been used while tax incentives and legislative limitations are encouraging the uptake of wastes, by-products and recycled elements in their place. These materials do not, nec­essarily, behave in the same manner in the presence of water as many conven­tional materials do. Self-cementation due to pozzolanic activity may help to sta­bilise some, others may exhibit undesirable leaching, yet others may have much higher permeability than the material they replace...

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Power Tools

Although power tools can’t replace hand tools, they sure do make construction work easier and more efficient. It can be a real timesaver to not have to drag a cord behind you and yet have a tool with enough power to do a professional job. Nowadays there are numerous cordless tools powered by lithium-ion batteries that would be an asset when constructing a house. These include screwdrivers, reciprocating saws, and even circular saws. For years such tools were de­signed primarily for homeowner use, but today they are used on almost every jobsite. I wouldn’t want to be without them.

Подпись:Circular saws

The circular saw has been around since the 1920s, but it didn’t really catch on until the housing boom began after World War II.

Direct-drive saw...

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Overall View of Reliability Analysis Methods

There are two basic probabilistic approaches to evaluate the reliability of an in­frastructural system. The most direct approach is a statistical analysis of data of past failure records for similar systems. The other approach is through relia­bility analysis, which considers and combines the contribution of each factor po­tentially influencing failure. The former is a lumped-system approach requiring
no knowledge about the internal physical behavior of the facility or structure and its load and resistance. For example, dam failure data show that the overall average failure probability for dams of all types over 15 m in height is around 10-3 per dam per year (U. S. National Research Council, 1983; Cheng, 1993)...

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How to Hire a Qualified Auditor

As home-energy audits become a more important part of building and owning a home, more and more auditors are enter­ing the field. Free audits are available from local utility companies, but this avenue has its pros and cons (see the sidebar on the facing page). Independent auditors tend to offer various packages that can be tailored to your home’s needs and your goals. Look for
an auditor who has been certified by CMC Energy Services, Building Performance Insti­tute® (BPI; www. bpi. org), or RESNET.

Although they don’t provide diagnostic testing of a home, CMC Energy Services auditors are screened and complete energy – inspector training...

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Measures of Reliability

In engineering design and analysis, loads usually arise from natural events, such as floods, storms, or earthquakes, that occur randomly in time and in space. The conventional practice for measuring the reliability of a hydrosystems engineering infrastructure is the return period or recurrence interval. The return period is defined as the long-term average (or expected) time between two successive failure-causing events. In time-to-failure analysis (Chap. 5), an equivalent term is the mean time to failure. Simplistically, the return period is equal to the reciprocal of the probability of the occurrence of the event in any one time interval...

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Acute Exposure to Pesticides with Long-Term Consequences

Louise Pape’s life changed drastically in 1993. On a warm spring day, she and her husband were slowly driving home with the windows rolled down to en­joy the cool breeze. At the roadside she spotted a man from a tree care company wearing a gas mask and spraying pesticides on the trees with a large hose. Louise suddenly felt a shower of chemicals on her face, in her eyes, nose, and mouth, as the sprayer overshot his target. She later learned that the pesticide was a mixture of malathion and car – baryl (Sevin).

That incident was the beginning of a night­mare illness for Louise, an environmental planner who, ironically, had just finished developing a safe pesticide plan for her employer, a transnational corporation...

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Biohazards of Lead

A bioaccumulative substance such as lead can be stored in various organs and tissues of the body. As lead-containing tissues are consumed by larger organisms in the food chain, a cumulative effect occurs in each subsequent organism. For example, a fish in a lead-contaminated environment may be exposed to lead in the water and in the organ­isms that it eats, which have accumulated lead from their food source, and so on down the chain. Organisms at the top of the food chain are, therefore, exposed to higher con­centrations of lead.

In humans, long-term exposure can result in brain and nerve disorders, anemia, elevate blood pressure, reproductive problems, decreases in red blood cell formation, and slower reflexes...

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Toxic Byproducts of Combustion

Gas, oil, coal, wood, and other fuels burned in­doors consume valuable indoor oxygen unless air for combustion is supplied from the out­doors. In tight, energy efficient buildings, these fumes can cause serious health consequences.

Подпись: Plastered walls, recycled wood flooring over radiant floor heating and specialty finishes are used in this straw bale home in New Mexico. Interior view shows deep window seat in the country kitchen. Architect: Baker-Laporte and Associates; Builder: Prull and Associates; Photo: Julie Dean.

Indoor combustion is found in fireplaces; woodstoves; gas-fired appliances such as ranges, clothes dryers, and water heaters; fur­naces; gas – and kerosene-fired space heaters; and oil and kerosene lamps. Some of the po­tentially harmful emissions include nitrogen dioxide, nitrous oxide, sulfur oxides, hydro­gen cyanide, carbon monoxide, carbon di­oxide, formaldehyde, particulate matter, and hydrocarbons from natural gas fumes such as butane, propane, pentane, methyl pentane, benzene, and xylene...

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Sources of Indoor Pollution

Indoor air pollutants can be classified into five main categories: volatile organic compounds, toxic byproducts of combustion, pesticides, electromagnetic fields, and naturally occur­ring pollutants. Each category of pollutant is described in a following section.

Volatile Organic Compounds

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Sources of Indoor Pollution

Organic compounds are chemicals contain­ing carbon-hydrogen bonds at the molecular level. They are both naturally occurring and

manufactured. Most synthetic organic com­pounds are petrochemicals derived from oil, gas, and coal. Organic compounds can exist in the form of a gas, a liquid, or solid particles...

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WORKING SAFELY ON A CONSTRUCTION SITE

Подпись: SAVING YOUR BACK WHEN LIFTING A LOAD Подпись: Start off squatting, with your back straight and your knees bent, then grasp the load.Подпись: Begin to lift, keeping your back straight, and gradually straighten your legs.Подпись: Finish with both your back and your knees straight, but don't lock your knees.WORKING SAFELY ON A CONSTRUCTION SITEПодпись: One of the reasons so many carpenters have lower back pain is that they never learned to lift heavy loads properly.

Working on a construction site is not a sunny stroll in the park. There are all kinds of unusual, uncomfort­able, and potentially hazardous conditions you may encounter—uneven ground, troublesome weather, boards with protruding nails, and sloped roof sur­faces that challenge your balance. Learning how to work safely and effectively in a construction environ­ment is just one more skill that you need to acquire, such as hammering a nail or sawing a board. Here are some basic suggestions to keep you safe and productive:

■ Wear good shoes, clothes that fit well, long­sleeved shirts, long pants, a hat with a brim, and sunscreen. (see Resources on p. 279). Leave jewelry at home, and bunch up long hair, so it doesn’t get caught in a power tool.

■ Protect your eyes with safety glasses or go...

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