Analytical Models

Posted by on 20/ 11/ 15

A few material models have been proposed for the development of plastic strains in unbound granular materials in a pavement structure. Lashine et al. (1971), and Barksdale (1972) tested unbound granular material in a repeated load triaxial test for 100 000 cycles. They found that the permanent axial deformation, єpb at different

Fig. 9.4 Example of stress-strain cycles obtained in a repeated load triaxial test on a granular material (Hornych et al., 1998)

stress states is proportional to number of load cycles, N (Fig. 9.4). Since 1971, many analytical models have been developed and most of them are listed by Lekarp and Dawson (1998).

However, these models have never been used with finite element (FE) calcula­tions except the Hornych model (Hornych et al., 1993) which has been used with a simplified finite element calculation by de Buhan (Abdelkrim et al., 2003) for a railway track construction and by Hornych et al. (2007) for a full scale flexible pavement.

The mechanical processes that form the basis of a flexible pavement’s perfor­mance and of a flexible pavement’s deterioration can be separated into two cate­gories, namely:

(i) short-term mechanical processes; and

(ii) long-term mechanical processes.

The first category concerns the instantaneous behaviour of a flexible pavement, as activated during the passage of a vehicle, thus the flexible pavement behaviour can be studied by means of (visco)elastic models. de Buhan (Abdelkrim et al., 2003) and Hornych et al. (2007) use, respectively, linear moduli with a Boussinesq stress analysis and the modified Boyce models with a simple FE analysis for the short term behaviour. The second category concerns the mechanical processes, typically characterized by a quasi-static time-dependency, such as long-term settlements un­der a large number of vehicle axle passages. Together, the approach requires the following parameters:

• Elastic behaviour: E, v or Ka, Ga, у and n.

• Plastic behaviour:

о Rupture (i. e. shear failure) parameters: m, s.

p0

о Plasticity parameters: e B and n.

The Hornych model is another formulation of the Paute model (Paute et al., 1988) which was adopted also in an European norm – EN 13268-7 (CEN, 2000). Some other alternatives were suggested in Lekarp and Dawson (1998), but no overall framework has been established yet to explain completely the behaviour of unbound granular materials under complex repeated loading.

When Two Beams Meet Over a Post

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Where any two beams meet over a post, there are many ways, short of matrimony, to join them together. Traditional timber framers have a variety of joints to use in this situation, including an assortment of “scarf” and “dovetail” joints — these take practice — and half-lap joints, as in Fig. 4.14. Lap joints are not too difficult to make with common tools, and you may like to have a go at them. A drawback, however, is that shear strength of the beam is diminished when it is cut half way through. In fact, weakening of structural members is almost always the case with any traditional joint. Another example of this would be an eight-by-eight-inch beam with a tenon of two-by-eight-inch cross-section carved into its end for insertion into the mortise of an adjacent post. Shear strength is reduced by 75 percent in this case. This is not a problem for timber framers because the structures are so extraordinarily over-built in the first place, and good tight-fitting joints and pegs go a long ways towards promoting strong joints.

The rest of us have several choices:

1. Truss plates on the top. I used this method to join the tops of the post-supported octagonal ring beam at Earthwood. This octagon, halfway between the center pillar and the external walls, cuts the floor joist spans in half on the first floor, and the roof rafter span in half on the second story. When you cut its span in half, you make a beam — remember? — four times stronger on bending. The truss plates are out of the way and out of view, so this was an effective solution. See Fig. 4.23.

2. Подпись: Fig. 4.23, above: Truss plates tie the girders together at the octagonal internal frame at Earthwood. This frame cuts the radial floor joist spans in half.image64Подпись: Fig. 4.24, right: Two four-by-ten (10.1- by 25.4-centimeter) girders meet over a four-by-four post, the joint made strong by the use of a pair of galvanized metal connectors.image65Toe-nailing or toe-screwing from the top of one horizontal timber, diagonally into the end of the adjacent member. Not quite as rigid as the truss plate

method, but quite strong just the same, and useful where truss plates will either be seen or be in the way of fastening another post or beam.

3. T-straps. (Figs. 4.13, 4.24 and 4.25) You can buy a variety of these at the building supply, and their esthetic qualities vary. My friend Steve in Hawaii used the off-the-shelf connectors shown in Fig. 4.24 to join two four-by-ten girders over a four-by-four post. This pair of connectors does everything in one shot: it connects the two girders, and connects the girders to the post. It is not beautiful, but the detail is down in the garage, under the living space, so esthetics matter less. Fsthetically, the best T – straps I have seen are homemade as shown in Fig. 4.13 and use lag screws instead of nails. Several acquaintances have made their own attractive T – straps from one-eighth-inch stock or better, and painted them black. Whenever this method is used, full strength comes from using them on both sides of the joint. Some manufacturers make decorative heavy strap connectors, too.

image66Подпись:

When Two Beams Meet Over a Post

4.28.

Maintain a whole toolbox of these joining methods and have them all available for use as needed. Sometimes one method won’t work but another will. Redundancy of methods is not necessarily a bad thing, either. With large projects, in fact, good engineers deliberately incorporate structural redundancy into buildings to allow loads to be carried by more than one path.

ALERT

Posted by on 20/ 11/ 15

Dielectric unions have insu­lators inside that will not con­duct electricity. If your electrical system is grounded to the water main and you install a dielectric union to join copper pipe to a galvanized steel service pipe, for example, install a bonding jumper to ensure continuous grounding.

llllll

Water-supply pipe supports. Clockwise from upper/eftvtwo Acousto-Plumb® clamps (which reduce pipe noise by cushioning vibrations), a copper pipe strap, a 3A-in. by 6-in. plastic-coated wire hook, two plastic suspension clamps, and a felt-lined J-clamp.

Подпись: After running DWV branch drains to fixtures, install supply-pipe assemblies and solder stub-outs to perforated strap.image599

less. Support horizontal runs of CPVC supply pipe every 3 ft.; vertical runs should be suported every 10 ft., with clamps or plumber’s strap attached to blocking. Support PEX tubing every 32 in. on horizontal runs and every 10 ft. on verti­cal runs (with mid-story guides).

Keep hot and cold pipes at least 6 in. apart. They should never touch. To conserve energy, reduce utility bills, and get hot water sooner at fixtures, install closed-cell foam insulation sleeves on hot-water pipes, as shown in the photo on p. 224. As noted earlier, water-supply stub – outs should protrude at least 6 in. into living space. To hold stub-outs in place, solder them to perforated copper straps nailed or screwed to studs.

Code requires shutoff valves for every fixture riser. Supply pipes to outdoor spigots or unheated rooms should have shutoff valves and unions within the main basement so pipes can be drained. Install water-hammer arrestors on branch lines to appliances such as washers or dishwashers, whose solenoid valves stop water flow so abruptly that pipes vibrate and bang against the framing.

To test the supply system before installing dry- wall, solder caps onto fixture stub-outs and turn on the water. (If you’re installing CPVC supply,

cement caps onto stub-outs.) If there are no leaks, install steel nail-protection plates over any pipes that lie within 114 in. of a stud edge, or use steel stud shoes over notched studs. Then install finish surfaces.

image600Подпись: I Lavatory AssemblyПодпись:Подпись: When connecting supply lines to fixtures, code requires hot on the left, cold on the right. When your eyes are shut tight against soapsuds and you're fumbling for a faucet, it's reassuring to know which spigot is which.Подпись: llll Lavatory or sink supply pipes may have unions that can be disconnected using two pipe wrenches. Otherwise, water-supply nuts (water nuts) will connect the tops of supply risers to threaded faucet stems on the underside of the basin. To loosen water nuts, use a basin wrench, which has a shaft 10 in. to 17 in. long and spring-loaded jaws set at a right angle to the shaft. If the lav isBefore you can install a new fixture, there’s often an old one to remove. If it’s necessary to shut off water to several fixtures during installation, capping disconnected pipes will allow you to turn the water back on.

Before disconnecting supply pipes, shut off the valves that control them. As mentioned, code requires a shutoff valve on each fixture riser, but older systems may have only a main valve that shuts off water to the whole house. After shutting off the controlling valve, open the faucets to drain the water.

old and you intend to reinstall it, save the water nuts because the threaded faucet stems may be nonstandard.

To disconnect a fixture’s drainpipe, use two pipe wrenches to loosen the slip-nut coupling of the P-trap. If older galvanized couplings have seized up, heat them with a MAPP gas torch and tap them lightly with a hammer to free the joint. Then try again with wrenches. Be sure to wear a respirator mask to avoid inhaling smoke from gaskets and such.

Once you’ve disconnected the drain and sup­ply pipes, lift the lav/sink off its wall hanger, pedestal, or cabinet base and set it aside. An old cast-iron lav can be quite heavy, so lift it with the aid of helper. Place a plastic bag over the drain pipe stub and secure it with a rubber band to keep sewer gases at bay. Disconnect fittings care­fully if you want to reuse them.

To remove a toilet, shut off the water by shut­ting the chrome fixture stop near the base of the unit. Flush the toilet and remove the remaining water with a cup or an inexpensive plastic hand pump. Disconnect the tank from the toilet bowl by loosening the bolts that hold the sections together. If the tank is wall hung, use a wide – jawed spud wrench to loosen the slip nut between the tank and the bowl. The toilet bowl is fastened to the floor by two bolts that rise from the floor flange; unscrew the nuts capping the bolts on both sides of the bowl. Rock the toilet bowl slightly to break the wax seal on the bottom.

Then lift up the bowl and immediately block the drainpipe by stuffing it with a plastic bag con­taining wadded-up newspapers.

Tub drain assemblies may be hidden in an end wall or they may exit into a hole cut into the sub­floor under the drain. The drain and overflow assembly is usually held together with slip cou­plings, so use a pipe wrench to loosen them. If the drain is solid piece, cut through it. Supply pipes may be joined with unions or they may be soldered; it’s easiest just to cut through supply risers. With those pipes disconnected, you can move the tub.

If it’s a standard tub (rather than a free­standing tub), you may need to cut into the finish surfaces at least 1 in. above the tub to expose the tub lip, which is often nailed to studs. If you’re discarding the tub and don’t care about chipping its enamel, use a cat’s paw to pull the nails. If the tub is too heavy or tightly fit to slide out of its alcove, you may need to cut the studs of the end wall so you can slide the tub out.

Подпись: It's much easier to attach hardware to the underside of a sink before mounting it. Here, the plumber uses flexible stainless lines to connect hot and cold faucet valves to the spout inlet. The threaded bottom of each faucet tee-one is visible, at right-receives a 7o-in. water-supply riser and a water nut that holds it tight. Подпись: Apply plumber's putty or silicone under the flange of the drain tailpiece, insert it into the drain hole, and then use sliding-jaw pliers to tighten the locknut on the underside of the basin. Подпись:Подпись:Подпись:

INSTALLING LAVATORIES AND SINKS

Lavatory basins and sinks are supported by pedestals, cabinet counters, legs, wall-mounted brackets, or a combination of these. Cabinet-mounted lavs and sinks are particularly popular because they provide storage space.

Preassemble the hardware. Before mounting a sink or lav, attach its hardware, including faucets, spout, and the drain tailpiece. Such connections are easier to make when the fixture is inverted. Insert the threaded faucet stems through pre­drilled holes in the sink or lav body, and tighten the washered nuts on the underside. Many manu­facturers supply a rubber gasket; but when that’s lacking, spread a generous layer of plumber’s
putty between the metal and the porcelain. Don’t overtighten. Once the faucets are secure, you can connect the risers loosely to the threaded faucet stems, allowing you to reposition them if needed when attaching their lower ends to the angle stops.

Set the unit. Sink (or lav) installations vary, depending on whether the unit is surface mounted, under mounted, flush mounted, wall mounted, or set atop a pedestal. Once you’ve attached the hardware, apply a bead of silicone caulk to the sink lip, turn the unit over, and press it flat to the surface (or underside) of the counter. Some sinks need nothing more to secure them, although many have mounting clips similar to

CURBS AND GUTTERS

Posted by on 20/ 11/ 15

Curbs and gutters convey rainfall into storm drainage systems, which are discussed in the next section. There are, however, less costly alternatives to the traditional vertical curb and gutter construction.

Following are guidelines for curbs and gutters:

• Substitute grassy swales for curbs and gutters.

• Where curbs are installed, build rolled curbs rather than traditional vertical curbs.

• Reduce the width of concrete gutters or eliminate them entirely.

• Eliminate reverse-flow curbs and gutters in parking lots, or replace them with asphalt curb, header curb, wheel stops, or integral curb/sidewalks.

• With concrete vertical curbs, use extruded construction rather than formwork.

Подпись: Grassy SwalesПодпись: Typical roadside swaie Grassy swales are depressed areas running parallel to the street that serve in lieu of curbs and gutters to convey stormwater. The grading required to construct a swale. can be completed during the grading of the surrounding lots or during final street grading. Therefore, cost savings are approximately equivalent to the cost of installi ng a curb and gutter.

In addition to providing savings in initial construction, swales offer continued savings in the form of lower long-term maintenance. Periodic flushing, replacement, or rehabilitation of pipes is eliminated. Swales within the public right-of-way are typically maintained by the home owner. Most swales can be graded to insure easy mowing.

Where runoff can be accommodated by a shallow swale, the depressions can be carried directly across driveways. Where a deeper depression is required for greater runoff capacity, concrete or metal conduits can be installed under driveways. At street intersec – tiohs, stormwater pipe can be installed under the street.

In addition to providing cost savings, swales allow for local retention of moisture from rainfall and melting snow. This is discussed in greater detail in the next section.

Подпись: Types of CurbsCURBS AND GUTTERSCURBS AND GUTTERSThe most common type curb in urban residential settings is the vertical combination curb and gutter.

A less costly alternative is the rolled curb, also called the rollover, roll, or mountable curb. Rolled curbs are typically 6 inches or less in height with a plane sloping face or well – rounded corners with a 2-inch to 3- inch radius which allow vehicles to cross them with varying degrees of ease. They can be sized to meet local hydraulic demands; the slope across the face of the gutter and the height of the curb can be designed to meet the projected capacity.

In many instances, curbs are installed before the type of house to be constructed or a lot is selected, and before driveway placement is decided. Therefore, it is usually necessary to remove the vertical curb, install a curb cut for the driveway, and haul away the old curb. With a rolled curb this is not necessary, saving approximately $300 to $450 per housing unit in the affordable housing demonstrations.

However, if vertical curb is chosen, good planning can reduce the added cost of removing any curb. A simple method gaining in popularity is to leave a space for the driveway and pour a separate entrance later. If possible, the driveway entrance should be installed during construc­tion of the adjacent sidewalk to avoid added labor costs.

Подпись:Concrete gutters, 18 inches to 24 inches wide, are a standard require­ment in many development specifica­tions. In most areas, a 12-inch gutter is sufficient, while in more arid regions, gutters can be elimi­nated entirely by simply extending the asphalt surface to the shoulder or curb. Local weather data should be reviewed, and gutters reduced in size or eliminated where rainfall rates warrant.

Curbs in Alternatives to vertical curbs in off – Off-Street Parking street parking include:

• elimination of curbs and gutters

• header curbs

• asphalt curb construction

• integral curb and sidewalk

• wheel stops

Combination curb and gutter can be eliminated in many parking lots by encouraging the use of sheet flows.

CURBS AND GUTTERS

CURBS AND GUTTERS

CURBS AND GUTTERSMuch of the curb line in parking areas generally consists of reverse flow gutters – that is, gutters that do not convey water as a conventional gutter does, but simply divert water away from the curb. This can usually be accomplished without a curb by proper grading of the parking lot surface.

Подпись: Wheel stops in parking bays
Подпись: STREET

Where curbs are required or chosen, they can often be replaced with header curbs, asphalt curbs, or integral curb and sidewalk, especially in cases where a gutter is not warranted.

Wheel stops are a less expensive alternative to curbs that keep intact the psychological barrier provided by curbs.

Подпись: Construction MethodsInstallation of curbs and gutters traditionally required labor­intensive formwork and preparation. Such construction methods have increasingly been replaced by extrusion or "slip form" techniques in which the operator, following a string line with a machine, "lays" the concrete out in its final form. This technique can be used to construct either a traditional curb or alternative types of rolled curbs. In areas where traditional formwork is still done, builders should check the availability of labor-saving alternatives.

Подпись: Boise, IdahoThe city permitted construction of rolled curbs as a substitute for 6- inch curbs along the residential streets of the Lakewood Meadows development. A total of 3,720 feet of rolled curb was installed at a cost of $16,740. Traditional vertical curbs were required along one collector street; 1,063 linear feet at a cost of $6,112. The rolled curb saved $1.25 per foot or $146 per housing unit.

Подпись: Santa Fe, New MexicoПодпись: EXAMPLES FROM THE DEMONSTRATION PROJECTS
In Fairway Village, the city permitted substitution of a rolled curb for a 6- inch vertical curb. The rolled curb cost $2,00 per foot less to install. Savings were $10,368 or $477 per unit.

CURBS AND GUTTERS

CURBS AND GUTTERS

Santa Fe curb and gutter vs Fairway Village curb and gutter

 

CONVENTIONAL CURB a GUTTER

 

CURBS AND GUTTERS

Elkhart County, Indiana

Elkhart County approved the elimina­tion of curbs and gutters, and substitution of a system of drainage swales. The cost of typical Elkhart streets, including curbs and gutters, averaged $32 per foot. The curbless demonstration project streets averaged $21 per foot. A total of $330 was saved on each 60-foot wide demonstra­tion lot.

Other affordable housing demonstra­tion projects using rolled curbs instead of the typical vertical curbs include: Tulsa, Oklahoma; Oklahoma City, Oklahoma; Birmingham, A labarna; White Marsh, Maryland; an d Sioux Falls, South Dakota.

Demonstrations in Christian County, Kentucky; Mesa County, Colorado; Greensboro, North Carolina; and Lacey, Washington eliminated curbs and gutters.

Long Term Elasto-Plastic Behaviour

Posted by on 20/ 11/ 15

Routine pavement methods are mechanistic-empirical design methods, based on linear elastic calculations. Usually, the only rutting criterion to be used concerns the subgrade soil, and consists in limiting the vertical elastic strains at the top of the subgrade. Rarely is a criterion applied for the unbound granular layers although Dawson and Kolisoja (2004) have shown that in roads with thin bound layers, the road’s rutting will largely be the consequence of plastic deformation in the granu­lar layers. Similarly, it is rare for a plastic criterion to be used in design probably because of the much greater difficulty in computing plastic strain fields.

Advanced pavement models are based on the main tests for unbound granular materials: the monotonic triaxial test and the repeated load triaxial test (this test and the models’ calibrations are presented in Chapter 10).

These models are split in four categories:

• Analytical models;

• Plasticity theory based models;

• Visco-plastic equivalent models; and

• Shakedown models.

TESTING THE DWV SYSTEM

Posted by on 20/ 11/ 15

Once you’ve roughed out the DWV system, but before hooking up fixtures, test for leaks. Filling DWV pipes with water is a common test, which requires that you seal all fixture stub-outs and use a garden hose to fill the largest stack. (All DWV pipes are interconnected, so you need fill only one stack to fill all.) Should you see leaks, drain the system, fix the leaks, and refill. Once

Подпись: SAFETY ALERT Electrical service is often grounded to metal water-supply pipes. Thus they may be energized. To avoid shocks when cutting into such pipes, use a cordless reciprocating saw with a metal-cutting blade, rather than a corded saw. The cordless saw's plastic casing will also insulate against shocks if pipes are energized, as will rubber gloves. Before cutting, shut off the water and open faucets to drain the pipes. llllll Подпись: When filling the DWV system for testing, use a double dynamiter to block the combo fitting at the base of the main drain. Testing plugs. Clockwise, from bottom: 1 ’A-in. test plug, 3-in. test plug, 4-in. test plug, and "jim cap." The first three plugs insert into pipes and expand via a wing nut; the jim cap slips over the outside of a pipe and tightens with a band clamp. you see no leaks, allow the water to stand at least overnight or until the inspector signs off on your system.

There are several types of pipe seals. The most common and least expensive is a glue-on cap that fits inside a DWV pipe stub. Allow pipe cement to dry a day before filling pipes with water. When the test is completed, drain the system by open­ing a cleanout at the lowest point, and cut off the small sections of drainpipe in which caps are

image597

glued. Where a stack is several stories high, this is the only type of cap guaranteed not to be dislodged by a weighty column of water.

Reusable rubber caps or plugs eliminate the need for gluing. A jim cap fits over the end of a pipe and tightens with a ring clamp. Test plugs fit into pipe ends and are expanded by a wing-nut assembly. A third type, known as a double­dynamiter out West, can be rented. It is a spring – loaded device that fits into the combo at the foot of the building drain. As shown in the top photo at left, this tool has two rubber balls that can be expanded or contracted by turn screws on the shaft. Insert the balls so that the forward one lodges in drainpipe, and then expand that ball; the second ball should block the open leg of the combo. To release the water, contract the balls of the double-dynamiter in the order in which you expanded them. Loosened, the forward ball will allow the test water to run down the drain; releasing the second ball allows you to remove the tool. Label the respective turn screws so you don’t confuse them: If you release the second ball first, you may get a faceful of waste water.

If there are finish ceilings in place below new pipes and you don’t want to risk wetting them with a failed connection, use an air-pressure test in which all openings (including stacks) are sealed. Typically, an inflatable bladder attached to a gauge is inserted into a cleanout at the base of the soil stack, and air is pumped into the DWV system. If the gauge shows no pressure loss over a given period, the inspector signs off.

Roughing-In Supply Pipes

Water-supply pipes are easier to run than DWVs because they’re smaller and don’t need to slope. Metal supply pipes should be bonded to the house’s electrical grounding system (see p. 231).

Run supply pipes to fixtures once hot and cold trunk lines are connected. Run 24-in. trunk lines, using 12-in. pipe for branch lines serving two fix­tures or fewer. Individual supply risers for toilets and lavatories are often 28 in. You save some money by using smaller-diameter pipes, but the main reason to reduce pipe diameter is to ensure adequate water pressure when several fixtures are used simultaneously. Reducing tees, such as the 22 by 12 shown in the bottom photo on p. 270, provide a 12-in. branch takeoff from a 22-in. trunk line.

Support horizontal runs of copper supply pipe at least every 6 ft., but if pipes run perpendicular to joists, plumbers usually secure the pipe every second or third joist. Support vertical runs of copper at every floor or every 10 ft., whichever is

Adhesives for Wood Flooring

Posted by on 20/ 11/ 15

Use only solvent-free adhesives or 100 percent silicone. Refer to the section on wood adhe­sives in Division 6.

Finishes for Wood Flooring When finishing or refinishing a wood floor on­site, it is advisable to specify “dustless” sand­ing, as explained above. This technique will help lower the amount of dust generated, but a thorough vacuuming with a true HEPA (high efficiency particulate air) vacuum will still be required.

A wide variety of floor-finishing prod­ucts are available, some with very toxic in­gredients. Because the floor is usually one of the last things to be finished, these emissions can be readily absorbed into other porous fin­ishes and may continue to outgas for weeks or months before the finish is fully cured. It is therefore important to apply a product that is free of harsh, solvent-based chemicals.

Water-Based Sealers for Wood Flooring

• AFM Safecoat Hard Seal over AFM Safe – coat Lock-In New Wood Sealer for me­dium gloss

• AFM Safecoat Polyureseal BP over AFM Safecoat Lock-In New Wood Sealer

• Bonakemi Mega Polyurethane: An ox­ygen crosslinking, waterborne polyure­thane wood finish

• Zip-Guard Environmental Wood Finish:

A clear finish

Natural Sealers, Waxes, and Oils for Wood Flooring A naturally finished wood floor often will require more maintenance than one that is sealed with a synthetic finish, but it will have a nicer feel underfoot. It will not have the elec­trostatic buildup associated with synthetics and will maintain its “breathability.” From a Building Biology standpoint, natural options are preferred. Most naturally derived prod­ucts have a scent associated with them that many people find to be pleasant but that may be intolerable to sensitive individuals. It is im­portant to test the following natural finishes prior to application:

• AFM Naturals Oil Wax Finish: Plant – based hardener and sealer for unfinished wood

• Auro Floor and Furniture Wax Finish No. 171: Dirt-repellent, solvent-free wax paste for wooden floors

• Auro European Furniture Wax No. 173:

High-coverage, dirt-repellent wax paste for wooden floors

• BioShield Penetrating Sealer #5: Use by

itself, as an undercoat with BioShield Hard Oil #9, or as an undercoat with a topcoat of BioShield Resin Floor Finish #4

• Livos Ardvos Wood Oil or Livos Meldos Hard Oil: Medium to high gloss

• Livos Bilo Floor Wax or Livos Glievo Liquid Wax: Plant chemistry or beeswax products

• OS Color Hard Wax/Oil: A satin matt oil or wax finish

• Trip Trap oils: A range of wood surface flooring treatment oils imported from Denmark and designed to maintain and clean hardwood or engineered wood floor­ing

Bamboo Flooring

Bamboo flooring has now become a cost com­petitive and aesthetic rival to wood flooring. The bamboo used for flooring can grow to a height of 40 feet in five years and a bamboo forest will continually renew itself. The bam­boo is split into strips and then kiln dried. Bamboo is more dimensionally stable than wood flooring and is 12 percent harder than rock maple. Bamboo flooring is available through the following sources:

• Bamboo Flooring Directory: Internet di­rectory of bamboo flooring manufacturers.

• Bamboo Hardwoods: Engineered pre­finished bamboo floors, sustainably har­vested, with a 50-year warranty on finish.

• Duro Design: Bamboo flooring supplier.

• EcoTimber: Supplier of bamboo flooring, floating floor padding, and sustainably harvested wood flooring.

• Plyboo: Hand harvested and grown in managed forests in Asia. Planks are 3-inch­wide tongue-and-groove and come in natural or amber color. Accessories, pan­eling, and veneer are also available. Plyboo comes unfinished or with an acrylic poly­urethane finish. Processing occurs in Asia and an MSDS is not available.

• Hanlite Bamboo, available through Sus­tainable Flooring: Claims to have the lowest formaldehyde in the industry. Sus­tainably harvested six-year-old bamboo with horizontal, vertical, or strand grain (the newest and most stable bamboo con­struction), unfinished or finished, 4У2 inches wide, 20-year nondelamination warranty. Also extensive line of bamboo millwork.

• Teragren: Available unfinished in vertical or flat grain in 12-inch-wide panels or 4-inch-wide tongue-and-groove planks for flooring. A variety of milled trim acces­sories are also available. Sustainably har­vested and grown without the use of pes­ticides, fertilizers, or irrigation. Available with a very durable German-made UV – catalyzed factory-applied urethane finish.

Learn More about the Principles of Siting a House

Posted by on 20/ 11/ 15

For more information on siting principles, additional detailing, and solar-design strate­gies for houses, as well as the mathematical formulas required to analyze these strate­gies for their potential energy savings, check out the second edition of Sun, Wind & Light: Architectural Design Strategies by G. Z. Brown and Mark DeKay (John Wiley & Sons Inc., 2000).

Although out of print, another good resource available at used-book stores and libraries is Climatic Building Design: Energy – Efficient Building Principles and Practice by Donald Watson and Kenneth Labs (McGraw – Hill, 1993). Both books contain a wealth of helpful charts, meteorological data, and ex­amples of solar siting and building design.

M. Joe Numbers is an architect with Gile-Buck & Associates in Boise, Idaho.

Подпись:Guidelines for Shaping an Energy-Efficient House

A house with a high ratio of interior space to exterior surface costs less to heat and cool. In very cold or very hot areas, then, houses should be more square than rectangular. In temperate areas, shape is not critical, but in humid areas, a long, narrow house allows for cross ventilation.

Подпись:Подпись:Learn More about the Principles of Siting a HouseIn hot, arid climates, a house whose long side is 1.3 to 1.6 times the length of its short side offers the best ratio of cool indoor space to exterior wall area.

Mediterranean ports in the Roman period

Posted by on 20/ 11/ 15

Under the Republic, the Roman provinces were resources to be exploited for the sole benefit of Italy. Later on, the emperors came to understand that the cohesion of the Empire depended on the prosperity of the provinces. As the 2nd and 3rd centuries of our

era unfolded, the economic situation of the provinces flourished; a number of them offi-

79

cially declared their wish that “the Roman domination should last eternally.” Maritime navigation is the most effective link among these provinces, and also the most economical. Transport ships plow the Mediterranean Sea, the mare nostrum of the Romans, at least during the warm season – from September to May navigation is offi­cially forbidden on the mare closum. In reality, the navigation period is between March and November. The largest merchant ships are those that transport wheat, routinely dis­placing 200 of our modern tons and measuring 25 m in length – some attain 60 m.

Merchandise circulates widely – from the granaries of Numedia (present-day [283]

Mediterranean ports in the Roman period

Figure 6.35 Harbor scene on a Roman sarcophagus (photo by the author)

Tunisia), Sicily, and Egypt[284] [285] toward the large Italian cities to be fed; from the regions of oil production, such as Tripolitania, the south of Spain, the north of Syria; from Greece whose wine is highly valued, and also from the regions of Bordeaux (Burdigala), Tarragona (Tarraco), and the south of Gaul, already renowned for their wine. Some of the goods come from far away, like silk from China, spices from southeast Asia, and incense from Arabia. Under the Empire, merchants based at Alexandria or Antioch forge the first direct relations with China of the Han Dynasty.

All of this merchandise attracts pirates, the restive adventurers of the pax romana, often spawned by the upheavals that accompany the progressive annexation of the Orient. Piracy in the Mediterranean is reduced somewhat after the naval victory of Pompeii, and it is eradicated at the beginning of the Christian era, an achievement of Augustus and his son-in-law Agrippa. The Roman military fleet had its beginnings in the Punic wars (3rd century BC). Subsequently, the Empire maintains a military fleet whose squadrons are based at Miseno (near Pouzzuoli, in the Gulf of Naples); at Ravenna, on the Adriatic in the northwest of Italy; and at Alexandria.

Make the Wind Work for You

Posted by on 20/ 11/ 15

Generally, summer and winter winds come from different directions. It’s usually pos­sible to divert winter winds and to channel
summer breezes by carefully locating the house in relation to its surroundings. Check with your local airport, meteorological sta­tion, or state energy office to determine the prevailing summer – and winter-wind direc­tions for your area. Also, this data can be obtained from the U. S. Department of Com­merce National Climatic Center in Asheville, N. C. (www. ncdc. noaa. gov/oa/climate/ climatedata. html).

Make the Wind Work for YouStudy the adjacent topography, trees, and buildings during your initial site inspection. Look for those existing conditions that can block or divert cold winter winds around the building site. Locate the house in these lee – side areas (see the top drawing on p. 134).

In warm or humid climates, place the house in a part of the site that maximizes summer ventilation. For example, the pro­
cess of evaporation cools summer breezes as they pass over water bodies. These water bodies don’t have to be big to have an effect. Locate the house to catch prevailing sum­mertime breezes coming off lakes, ponds, rivers, and even streams.

Conversely, in cool and temperate cli­mates, avoid locations near bodies of water on the lee side of prevailing winter winds. In other words, if winter winds generally blow from the north, avoid sites at the south end of a water body.

Water isn’t the only medium that induces cold winter winds. Landforms, vegetation, and buildings all can increase wind veloci­ties because of a phenomenon called the Venturi effect.

Make the Wind Work for You Make the Wind Work for You

The Venturi effect occurs when any mov­ing medium—in this case air—squeezes

through a constricted opening. To maintain a constant volume of air passing through the opening, the wind velocity increases accordingly. That’s why it’s so windy at the base of tall buildings.

Keep away from topography, adjacent buildings, or vegetation that funnels cold winter winds at increased velocities. If you do have a problem because of the Venturi ef­fect, you can position adjacent outbuildings and evergreen trees and shrubs where they will block winter winds.

Conversely, locate the house (and any new vegetation, fences, or outbuildings) to take advantage of increased wind velocities created by the Venturi effect during summer months (see the bottom drawing on p. 134). Use buildings and vegetation to channel summertime breezes into the house. As a rule, try to orient the house within 30 de­grees of perpendicular to prevailing summer winds to maximize their cooling effects.

If solar orientation and siting for wind are at cross-purposes (that is, if optimum solar orientation is perpendicular to optimum sit­ing for wind), then solar orientation should take precedence because it has a greater cu­mulative effect on the heating and cooling of a house.

House Shape Should Fit the Climate

Are you familiar with the aluminum heat – radiating fins that can be slipped over hot – water pipes in a basement? They’re supposed to turn hot-water pipes into heating ele­ments to heat the basement space. The prin­ciple behind the fins is that they increase the heated surface area so that more heat es­capes from the pipe with the fins than from the bare pipe.

The same principle applies to a house’s shape, or configuration. As a house’s surface area increases, so does the amount of heat it loses. To hold on to the heat, configure the house so that it is relatively compact. Com­pact shapes, such as cubes, lose less heat through the building skin than narrow or elongated shapes.

As a general rule for siting a house in cold regions, the long dimension of the house should be approximately 1.1 to 1.3 times the length of the short side. This proportion yields a high ratio of heated interior space to exterior skin. Remember that the longer side of the house is oriented along the east – west axis.

For temperate climates, the configura­tion is not as important. There is less envi­ronmental stress on the building skin, so the designer has more freedom in terms of building configuration. For this region, a ratio between 1.6:1 and 2.4:1 provides good energy performance.

In hot, arid climates, the environmental stresses are greater, so buildings should be shaped similarly to cold-climate configura­tions. A ratio somewhere between 1.3:1 and 1.6:1 is the most energy-conserving for hot, arid climates.

In warm or humid climates, elongated shapes with openings on the long sides al­low for cross ventilation. Generally, ratios in the range of 1.7:1 to 3.0:1 are preferred. When these elongated plans are oriented with the long side on the east-west axis, summer overheating at the short east and west elevations is avoided.

Try to keep corners on the house to a minimum. Unnecessary corners mean more exterior-wall surface is exposed to wind, which increases heating loads on the house.

Regardless of wind direction and particu­larly in areas where wind direction changes frequently, a good overall strategy is to use a compact, low-profile house design. Avoid tall facades and roof designs that block or trap wind. For example, a tall, broad gable is less aerodynamic than a hip roof, which allows for smoother airflow around and over the house. Orient the narrowest dimension of the house into prevailing winter winds to minimize wind exposure.

Make the Wind Work for YouControl Exposure to the Wind

Make the Wind Work for YouUse plants and outbuildings to direct prevailing summer breezes into the house and to divert prevailing winter winds away from the house. Once you know the direction of prevailing winter winds, choose a site where topography, vegetation, and other buildings offer protection.

Garage

 

Evergreen trees and a garage shelter the house from prevailing winter winds.

 

House

 

Prevailing summer breezes are funneled by deciduous trees into the house at increased velocity due to the Venturi effect.

Configure the house and its surround­ings to funnel or channel cooling summer breezes into windows and screened-door openings. For example, you can orient breezeways and window openings to accept these summer winds. Use roof overhangs to
trap incoming breezes and channel them into window openings. On the other hand, locate and configure the house to avoid channeling any cold winter winds into doors and windows.