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Failure point)

Posted by on 17/ 11/ 15

In cases for which several stochastic basic variables are involved in a perfor­mance function, the number of possible combinations of such variables satis­fying W (x) = 0 is infinite. From the design viewpoint, one is more concerned with the combination of stochastic basic variables that would yield the lowest reliability or highest failure probability. The point on the failure surface asso­ciated with the lowest reliability is the one having the shortest distance to the point where the means of the stochastic basic variables are located. This point is called the design point (Hasofer and Lind, 1974) or the most probable failure point (Shinozuka, 1983).

Consider that X = (X1,X2,…,XK)t are K uncorrelated stochastic basic variables having a vector mean px and covariance matrix Dx...

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Thermal and Moisture Control

Posted by on 17/ 11/ 15

Foundation Water Management

Dampproofing is used to form a water – resistant barrier on the outside of stem walls where they come into contact with the earth. This treatment is especially important wher­ever there is a crawl space or basement be­low grade. Along with proper grading and perimeter drainage, dampproofing is used as protection against the migration of moisture through the wall. Water migration can result in a damp environment under or inside the home, which can lead to structural deterio­ration of the building. This is a frequent and serious cause of mold infestation throughout the country.

Dampproofing of stem walls is only one component of the creation of an effective water barrier...

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Step 2-Sheathe Gable Ends

Posted by on 17/ 11/ 15

When sheathing gable-end truss, check plans to see if a vent opening is shown.

• Toenail through bottom of truss into plate so gable end is on chalk line IV2" in from outer edge of double plate. (See below.)

Step 3-Set Gable Ends

Toenail 16d nails 24" O. C. to hold

gable end while setting gable-end truss.

IV2" chalk line

Truss

Wall

Steps

1. String line from center of gable ends.

2. Lift single truss into place.

3. Center truss on string line.

4. Nail truss to exterior wall on layout.

5. Nail through temporary spacer support near ridge of truss and on layout marked on temporary spacer support.

6. Set six trusses. Then check gable end for plumb and put permanent brace on gable end...

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RELINING A CHIMNEY

Posted by on 17/ 11/ 15

Подпись: As two unseen helpers on the other side of this double-sided fireplace steady the Franklin stove, the mason tips it upright. She placed heavy sheet metal over the hearth and slid the stove on its back into the fireplace.

image398
Подпись: A simple 2x2 and plywood frame creates a 11/2-in. overhang and a 2-in.-thick edge for this site-built concrete crown. To make frame disassembly easy, use drywall screws to fasten it.

While inspecting a chimney, you may find that it has no flue-tile lining or that existing tiles are cracked or broken and too inaccessible to replace. Because superheated gases can escape

through gaps, such a chimney is unsafe to use. In this case, your options are:

► Seal up the chimney so it can’t be used and add a new, properly lined chimney else­where. Or tear that chimney out and replace it.

► Install a poured masonry liner. In this procedure, a heavy-gauge tubular rubber balloon is inflated inside the chimney, and the void is then filled with a cementitious slurry. After the mixture hardens, the tube is deflated and removed. Poured masonry creates a smooth, easily cleaned lining and can stiffen an old chimney whose strength is suspect...

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Tests of Filler Stiffening Properties Filler stiffening properties may be tested with the following methods

Posted by on 17/ 11/ 15

• Methods of increasing of softening point—ring and ball (R&B) method, according to EN 13179-1 (delta ring and ball), and similar methods

• Rigden’s method, according to EN 1097-4, and Rigden-Anderson’s method

• The method of increasing mortar viscosity

The two European tests cited in EN 13043 (EN 13179-1 and EN 1097-4) are carried out for an added filler and the 0/0.125 mm fraction sieved out of the fine aggregate (or an aggregate of continuous grading with D less than or equal to 8 mm) that contains more than 10% dust. Let us dedicate some time to discussing those tests since under­standing them will help determine the expected values of a good filler.

8.3.3.1 Method of a Softening Point Difference

8.3.3.1.1 Method EN 13179-1 (Delta Ring and Ball)

What is delta ring and ball...

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Interlocking Metal

Posted by on 17/ 11/ 15

Interlocking metal weatherstripping is an ef­ficient way to seal air leaks around doors. It comes with two different pieces; one attaches to the door, and the other to the jamb and the threshold. When closed, the two pieces interlock to form a seal. This type of weatherstripping is the most difficult to install, a job best left to pros. If your doors already have interlocking metal weather-

stripping, keep it working smoothly by straightening any bends or dents that pre­vent the two pieces from fitting together.

 

Interlocking Metal

 

Durability: excellent Cost: $1.50/ft. to $3/ft.

 

HINGE SIDE

Interlocking Metal

 
Interlocking Metal

On the hinge side of the door, a bronze strip nailed to the jamb slips into a groove cut in the door.

 

LATCH SIDE AND TOP

Saw k...

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Tapes

Posted by on 17/ 11/ 15

These inexpensive tapes come in several varieties: nonporous, closed-cell foam; open-cell foam silicone; and various rub­bers, including a product called EPDM (ethylene propylene diene monomer). It’s worth spending a few extra cents per foot to buy the more-efficient closed-cell foam or higher-quality silicones. Any of these styles can be purchased in various thicknesses and lengths.

Although installation is easy—little more than peel-and-stick—be sure to clean sur­faces using a mild detergent prior to setting the tape in place. In areas that see little use, such as inoperable windows, expect the tape to last roughly three years. On frequently opened windows, you’ll need to replace it in as little as a year. Securing the tape with tacks or staples helps to extend its longevity...

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About Chimney Fires

Posted by on 17/ 11/ 15

Chimney fires occur when imperfectly burned materials in wood smoke condense and stick to the inside of a chimney. The chief culprit in chimney fires is creosote, a sticky brown or black substance that may harden to resemble fragile glass. Incomplete combustion also produces tar, ammonia, methane, carbon monoxide, toluene, phenol, benzene, and eventually, turpentine, acetone, and methyl alcohol.

Подпись: This flue tile and mortar cap were cracked by a chimney fire in a flue overdue for cleaning.Подпись: and attack mortar joints. Above all, never use chimneys whose tiles or mortar joints are cracked or chimneys that have no flue lining. If you're considering buying a house, have its chimney professionally inspected if you see signs of a chimney fire such as creosote flakes on the roof or the ground, scorched or cracked flue liners or chimney crowns, warped dampers or charred studs or joists near a chimney. Many local codes require inspections before homeowners fire up new woodburners. If the chimney isn’t cleaned for a while, creosote accumulates until it’s heated enough to combust in a flash fire, often in excess of 2,000°F. For homeowners, a chimney fire is a terrifying experience, for it may literally roar for extended periods inside the entire flue, flames shooting skyward from the chimney top as though from an inverted rocket...

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Chimneys

Posted by on 17/ 11/ 15

Masonry chimneys are freestanding units that carry exhaust gases out of the house. To prevent superheated gases from escaping, chimneys should be tile lined and free from cracks or gaps, or they should have insulated stainless-steel flues. Annual inspections and maintenance are crucial to chimney health: If you discover mortar or flue tiles that are cracked or missing, the chimney is unsafe. Chimney flashing and roof safety are fur­ther discussed in Chapter 5.

These days, new and retrofit chimneys are often nonmasonry...

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FUNDAMENTALS OF OPEN-CHANNEL FLOW

Posted by on 17/ 11/ 15

The fundamental relationships for hydraulic flow are the same for channels that are physically open at the top, such as roadway channels and curbs and gutters, and for pipes and culverts that have a free water surface. In both cases, hydraulic design is based on open-channel flow. An understanding of these relationships is important for comprehending various design aids subsequently presented.

5.3.1 Types of Flow

Open-channel flow may be categorized by three characteristics: the flow may be (1) steady or unsteady, (2) uniform or nonuniform, and (3) either subcritical, critical, or supercritical. This discussion will begin with the first two categories, and the third will be discussed later.

Steady flow means that at a particular point, there is no change in depth with respect to time...

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