Blog Archives

FATIGUE LIFE

Posted by on 22/ 11/ 15

Fatigue is an effect consistent with the formation of cracks in material caused by a series of repetitive tensile stress cycles that do not exceed the tensile strength of the material. (For more information on fatigue, refer to the many publications with descriptions of this phenomena [e. g., SHRP Reports A-312 or A-404].)

12.3.1 Test Methods

There are many methods for testing fatigue; for example, the European standard on testing fatigue EN 12697-24 has quoted the following ones:

• Two-point bending test on trapezoidal-shaped specimens (2PB-TZ)

• Two-point bending test on prismatic-shaped specimens (2PB-PR)

• Three-point bending test on prismatic-shaped specimens (3PB-PR)

• Four-point bending test on prismatic-shaped specimens (4PB-PR)

• Indirect tensile test on cylindrical-shaped...

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Drywall over Plaster

Posted by on 22/ 11/ 15

Подпись: Trim Considerationsimage746"Подпись: New drywall over old plaster can reduce the visible profile of existing molding it abuts so much that the molding looks undersize. In this case, you have two alternatives: Use molding to build up (increase the thickness of) trim where drywall abuts it. Or remove the trim and reinstall it over the drywall.Drywalling over plaster is a cost-effective way to deal with plaster that’s too dingy and deteriorated to patch or too much trouble to tear out. But this requires some important prep work.

► If you see discoloration or water damage, repair the cause of the leak or excessive indoor moisture before attaching drywall.

► Locate ceiling joists or studs behind the plaster. Typically, framing is spaced 16 in. or 24 in. on center, but you never know with older houses.

If ceiling joists are exposed in the attic above, your task is simple; otherwise, use a stud finder or drill exploratory holes. Once you’ve located the joists or studs, snap chalklines to indicate the centerlines you’ll screw the drywall into.

► Use screws and plaster washers to reattach loose or sagging plaster sections before you i...

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Ordering Drywall and Associated Supplies

Posted by on 22/ 11/ 15

Ordering Drywall and Associated Supplies

LIKE SHINGLES, SIDING, and insula­tion, drywall amounts are calculated by the square footage of the area to be covered (in this case, the walls and ceilings). Rather than measuring the ceiling and walls in every room, experienced drywallers use a shortcut calculation. They simply multiply the total square footage of a house by 3!! (3.5). For instance, a 24-ft. by 36-ft. house has 864 sq. ft. of floor space, and 864 times 3.5 equals 3,024 sq. ft. of drywall coverage.

DRYWALL IS HEAVY! Carrying a long sheet, like this 12 footer, is definitely a two-person job.

[Photo ® The Taunton Press, Inc.]

Your drywall order

For the modest-size houses that Habitat builds, it s best to make up most of your drywall order with 12-ft. drywall panels...

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WITHIN

Posted by on 22/ 11/ 15

Drywall and Painting

I’m not sure when drywall—also known as gypsum board, wallboard, and Sheetrock®—was first used in construction. I have seen drywall on pre—World War II houses, but we definitely didn’t have drywall in my old prairie home. It wasn’t until the late 1950s in California, where I was working, that drywall be­came the preferred wall covering in residential housing. “Knock on the Wall! Demand Genuine Lath and Plaster!” was the rallying cry of the once-mighty plaster industry, as they struggled against the newcomer—drywall.

Big plaster fought a losing battle. It took two or three weeks to cover walls with layers of plaster, and the process left the house frame waterlogged. In the winter, it could take a month or more for a house to dry out well...

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. The south of Morocco and the Saharan oases

Posted by on 22/ 11/ 15

In 1031 the caliphate of Cordova breaks down, fragmenting into small kingdoms. Alphonse VI of Castilla seizes the opportunity to take Madrid in 1083, then Toledo in 1085. The Andalusians call for help from the only powerful Occidental Arab dynasty of the time, the Almoravides of Morocco. Their chief Youssef ben Tachfin puts an end to the advance of Alphonse VI when he passes through Spain, and he brings Morocco and Andalusia under his unified command. His son Ali, raised in an Andalusian culture, suc­ceeds him in 1106. Andalusian scholars and literati follow him to Marrakesh, capital of the Almoravides. This contact probably explains the appearance of the qanat technolo­gy in Morocco.

The Almoravides, Berbers from the south, had occupied Sijilmassa, the great cara­
van center of Tafilale...

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Test Results

Posted by on 22/ 11/ 15

A significant impact of mixture type on cracking temperature for newly made mixtures or after a short time of aging has not been observed with TSRST test­ing mixtures of AC, SMA, and porous asphalt (Isacsson et al., 1997). Not until a longer aging period (i. e., more than 25 days) has elapsed has a difference in favor of AC and SMA been observed. Porous asphalt is more susceptible to aging, and the recorded difference of crack temperatures has reached 6°C and 25°C after 25 and 100 days of aging, respectively. Test results (Judycki and Pszczola, 2002) con­cerning a comparison of low temperature properties of various mixtures have not revealed essential differences between AC and SMA. In a U. S...

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Laundry Appliances

Posted by on 22/ 11/ 15

Washers and dryers with porcelain-on-steel or stainless steel interiors are preferable to those with plastic interiors. Although gas dryers are more energy efficient than electric dryers, they cause the same pollution problems as gas ranges. By planning a laundry room with easy access to a drying yard, you can take advan­tage of the most energy efficient of all dryers: the sun.

Dryers should be vented directly to the out­doors. Some heat recovery devices are avail­able that recirculate the hot air from the dryer back into the house. We do not recommend these because they do not sufficiently filter fine particles and, if a gas dryer is being used, combustion gases can be released into the in­door air instead of being vented outdoors.

Vacuum Cleaners

Conventional portable vacuum cleaners...

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Refrigerators and Freezers

Posted by on 22/ 11/ 15

There are many styles of refrigeration units available. Self-defrosting models have a drip pan located somewhere under the unit. Some units have drip pans located in the back or mounted internally, where they are inacces­sible. When purchasing a unit, make sure the drip pan is easily accessible from the front and has adequate clearance underneath for easy cleaning. The pan should be cleaned monthly to prevent odors or the growth of microorgan­isms. It is also important to keep the cooling coils clean of dust. Not only will this improve your air quality but it also will save energy be­cause the unit will not have to work as hard to stay cold.

Cook Tops, Ovens, and Ranges

All electric cook tops, ovens, and ranges produce elevated magnetic fields...

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Time Integration – Solid Mechanics

Posted by on 22/ 11/ 15

For solid mechanics problems, the constitutive law form (Eqs. 11.3 and 11.4) is an incremental one and differs from the ones for diffusion problems (Eq. 11.7). The knowledge of the stress tensor at any time implies that a time-integrated constitutive law is required. The stress tensor is a state variable that is stored and transmitted from step to step based on its final/initial value, and this value plays a key role in the numerical algorithm.

Then, in nearly all finite element codes devoted to modelling, equilibrium is ex­pressed at the end of the time steps, following a fully implicit scheme (t = 1), and using the end of step stress tensor value.

However, integrating the stress history with enough accuracy is crucial for the numerical process stability and global accuracy...

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Thermal Stress Restrained Specimen Test Method

Posted by on 22/ 11/ 15

The TSRST method consists of attaching the ends of a specimen (250 mm long and 60 mm in diameter or 50 x 50 mm cross section) to the frame of a device situ­ated in a cooling chamber. The frame is rigid to keep the length of the specimen unchanged. As the temperature falls (at a rate of -10°C/hr), the specimen contracts and the tensile stress in the specimen rises because it is being held by the frame. The temperature at which the specimen cracks is the test result. This method has been standardized in AASHTO TP 10 and prEN 12697-46.

12.2.3.1 Semicircular Bending Test

The semicircular bend test method is described in prEN 12697-44. A half cylinder sample of compacted asphalt mixture is loaded using a three-point bending scheme...

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