Blog Archives

Retrofits

Posted by on 17/ 11/ 15

■ BY DANIEL S. MORRISON

RetrofitsПодпись:Подпись: Climate zonesПодпись: 4, 5: R-10 Climate zone

F

inished basements are a great way to add living space to a house without adding on. You often can add almost as much living space as the main floor offers. Before thinking about flooring choices and paint colors, though, think about the basics. Moisture, insulation, and air infiltration must be tackled before any finish materials are installed. In new construction, these issues are addressed from the outside before the basement is backfilled. Retrofits mean that you have to work from the inside. In either case, it is important to consider the climate before work begins.

Start with Water Management

Because basements are mostly buried in the ground, they are sometimes wet, are usually damp, and are seldom dry...

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BRIDGE BEARINGS

Posted by on 17/ 11/ 15

For concrete-slab bridges where expansion is not provided, the slab is normally sup­ported directly on the substructure, concrete on concrete. A “centerline of bearing (singular)” is denoted on plans at each support. (Some states do not identify a centerline of bearing at the end bent of a slab bridge. Instead, they measure the end span to the end of the slab.)

In other types of bridges, individual bearings are used to support the superstructure. The centerline of these devices is denoted as the “centerline of bearings (plural).” AASHTO requires that steel bridges with spans of 50 ft (15 m) or greater have a type of bearing employing a hinge, curved bearing plates, elastomeric pads, or pin arrangements for deflection (rotation) purposes...

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Portable Sawmills

Posted by on 17/ 11/ 15

Jim, my next-door neighbor, recently built a major addition to his house, using the kinds of timber-framing methods described in this book. He hired a local fellow with a portable bandsaw mill to come up and cut all of the timbers from logs that Jim had hauled out of his own woods. The timbers were cut straight and were of good regular dimensions.

Some of these portable mill operators charge by the hour, some by the board foot, some will do it either way. With heavy timbers, you are probably better off paying by the hour. This is what Jim did, and what he advises. He paid $35 an hour and all the heavy timbers and boards for his addition were cut in about six hours; his addition is fourteen by twenty-four feet, two stories...

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DECK DRAINAGE

Posted by on 17/ 11/ 15

Adequate drainage of the deck is important for safe operation during rainstorms, to prevent accumulation of rainwater or snowmelt that could freeze and cause skidding, and to prolong the life of the deck by removing standing water, which would otherwise contribute the water element necessary for corrosion. Transverse drainage of the deck should be provided by cross-slope whereas zero gradients and sag curves on bridges should be avoided.

Design of the drainage system is frequently one of the last items listed in the scope of ser­vices for a bridge design project. This implies a secondary importance, but that is certainly not the case...

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Vacuum, pressure, and the first hydrodynamic devices

Posted by on 17/ 11/ 15

The writings of our 3rd century BC authors have unfortunately been lost for the most part. We know them primarily through citations and references contained in the writings of the subsequent period, in particular those of the Roman Vitruvius (about 25 BC) and of Heron of Alexandria (around 60 BC). It is thought that Straton of Lampasaque con­ducted the first studies of a vacuum and may be at the origin of the concept reported by Heron that “an absolute vacuum does not exist, but one can artificially produce vacuum in opposition to nature.” Straton was the private tutor of the future Ptolemy II Philadelph in about 290 BC, and, after 286 BC, he was the successor of Theophraste as the head of the Academy of Athens...

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The influence of Alexandria in the 3rd and 2nd centuries BC Mathematicians and inventors[165]

Posted by on 17/ 11/ 15

Is it to increase their prestige that the first Ptolemites set themselves up as protectors of the sciences, techniques and arts? Ptolemy I created the Library of Alexandria – more of a personal collection than a true institution. The Library is then completed by the Museum, either by Ptolemy I himself, or by his successor Ptolemy II Philadelph, who reigned from 285 to 246 BC. The Library is dedicated to the acquisition[166] and conserva­tion of books, whereas the Museum was what one would call today a research institute. The director of the Library and the members of the Museum are supported by the Ptolemites and in general, the financing of the two institutions is entirely assured by the state...

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REPAINTING OF EXISTING BRIDGES

Posted by on 17/ 11/ 15

Repainting of bridges over highways or railroads may necessitate use of protective covers, or require traffic lanes to be diverted or work interrupted during passage of trains, while existing paint is removed and new paint applied. These factors all favor use of a bridge material or protection system that does not require maintenance reapplication of a coating. (See Art. 4.13.)

Removal of Existing Paint. Complete removal of the existing paint on a bridge that is to be recoated with a paint system that requires it can be extremely expensive, particularly if the existing paint contains lead. Lead-based paints were used extensively in the past because they provided good protection...

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Tool Talk MAKING A PLUMB STICK

Posted by on 17/ 11/ 15

Tool Talk MAKING A PLUMB STICK

TO PLUMB WALLS, you can use a wall-high level that costs hundreds of dollars or you can make a plumb stick from any 2-ft. level and a straight 2×4 stud. Even a

battered, inaccu­rate level can be used. Select the straightest stud you can find and nail a 16-in. 1×2 strip onto each end, letting the strips overhang the stud ends by about 3 in. Use some duct tape to attach a 2-ft. level to the opposite edge of the 2×4 (near the center) and your plumb stick is nearly ready to use (see the photo above).

It’s important to check your plumb stick for accu­racy. To do so, hold it veilical and flat against a wall. Keep the bottom end fixed in place as you move the top end back and forth until the bubble is exactly cen­tered in the vial...

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Chemical Processes

Posted by on 17/ 11/ 15

The road construction is a multi-component system which is not isolated but open to physical, chemical and biological interaction with its surroundings. Reactions taking place in the road construction thus influence and are influenced by adjacent systems. For instance, the washing of the road surface by run-off brings organic and inorganic compounds (from sources mentioned in Section 6.2) to road shoulder materials and to neighbouring soils with which they may interact when water infiltrates. Seepage from the road surface into the road structure will also lead to chemical reactions with materials in the various road layers and the underlying soil.

Chemical reactions occurring in the road construction and adjacent soil systems commonly involve the solid and the liquid phases, but the gas ph...

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Rough Carpentry

Posted by on 17/ 11/ 15

Sill Plates

Sill plates or mudsills are decay – and insect – resistant wood members used in frame con­struction wherever wood comes into contact with concrete or soil. For many centuries be­fore toxic petrochemicals came to be used, builders had devised natural means for avoid­ing rot and insect infestation. They commonly charred the portions of wood that were to be placed in the ground or else used naturally re­sistant woods. From about 1974 to 2003, the standard building practice was to use lumber pressure treated with chromated copper ar­senate (CCA) or ammoniacal copper arsenate (АСА). CCA and АСА contain arsenic salts and chromium compounds that can leach out onsite and be absorbed through the skin or in­gested by mouth. They are extremely toxic to

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both humans and the en...

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