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Three damage zones can be identified. In Zone 1, ice contacts the pipeline and the unprotected pipe is damaged heavily. In Zone 2, the soil is severely deformed and the pipeline is carried with it. Questions about the extent of Zone 2, deformations at different levels, and soil-state influence remain unanswered. In Zone 3, the soil deforms only elastically and a pipeline normally can resist applied forces without special strengthening.

Limit-State Design.

Limit-state design concepts have become widely applied to pipelines and are beginning to be reflected in design codes. Limit-state design focuses on states that directly threaten safe operations such as rupture and blockage rather than on indirect conditions such as yield and overstress.

The limit state that most concerns Arctic pipeline operations is pipe-wall rupture that allows liquid hydrocarbons to escape and pollute the environment. While limit states such as blockage by wax and hydrates are economically damaging to the operator, design should concentrate on gouging events that lead to rupture.

Most concern has been focused on extreme bending events. A marine pipeline loaded by a concentrated load is bent severely and kinked at the impact point. This is the deformation that would occur to a pipeline in Zone 1 when hit by ice. In Zone 2, the loading is less concentrated and distributed over a greater length. Full-scale tests and field experience have demonstrated that pipelines can be bent to very high curvatures before a leak limit state is reached. Implication is that design against the rupture limit state can be based safely on rupture bending strain.

For a pipeline under a gouging ice mass in Zone 2, the soil moves farther than the pipeline and drags the pipeline with it. An idealized thin-walled cylinder pipeline will have an effective axial force that is compressive when in operation. After the gouge, the effective axial force becomes tensile and in the extreme case, the longitudinal stress reaches a level where the von Mises equivalent stress reaches yield stress. An analysis detailed in the full-length paper indicates that longitudinal tension is the factor that determines rupture limit state and that bending may be less important.

Seabed Shakedown. The seabed in Zone 2 is loaded many times so that when a gouging ice mass passes over a pipeline, the soil conditions around the pipe are a result of previous gouges. If the soil had been a dilatant soil when it was first deposited, by the time the extreme gouge occurs, the soil will have repeatedly dilated, returned to pore-pressure equilibrium with the sea, and dilated again. This process brings the seabed to the critical state and keeps it there where further remolding does not induce any dilatation or pore-pressure change. This is parallel to the process structural engineers call "shakedown," in

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which the first loading of a structure leads to plastic deformation but repeated application of the same loads produces only an elastic response. One useful consequence of shakedown is that geotechnical measurements can be used to delimit the extent of Zone 2 more directly and perhaps more reliably than extrapolations from extreme scour-depth observations. Another consequence is that gouging experiments based on first-time loading may exaggerate dilatancy effects.

Construction

Because there has been so little construction of Arctic marine pipelines, there is very little experience in their construction. An attractive possibility is to construct the pipeline in winter using the sea ice as a stable work platform and cut holes and slots where necessary. A pipeline construction project in the Canadian Arctic islands constructed a moon pool in an ice island at the well site and cut holes for the pull cables, a hole to launch the plough, and a continuous slot from the shore to the edge of the ice island.

Whether in winter or summer, Arctic offshore-construction plans have to work within limited weather windows when ice conditions are favorable. Delays from storms, blizzards, and interruptions in transportation can cause delays and cost overruns that can be controlled best by robust schemes that include generous contingency margins.

New Technology

The record horizontal distance for extended-reach drilling is 10.728 km. Horizontal drilling of pipeline shore crossings has become an accepted part of pipeline technology and the method of choice for many crossings. In the Arctic, extended-reach and horizontal drilling are particularly attractive because of their minimal environmental impact, absence of weather and seasonal sensitivity, and possibility of drilling sufficiently deep to eliminate subgouge deformation effects. Extended-reach and horizontal drilling can be expected to have an enormous effect on Arctic offshore development.

Conclusions

Ice gouging and construction remain difficult questions for Arctic pipeline construction. The other issues are either unlikely to be significant or can be solved in a routine way. By adopting a very conservative design strategy and incorporating large safety margins, the effects of uncertainties can be minimized.

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5) Строительные материалы и изделия

Clay street pavers

Brick Pavers

Reclaimed antique brick pavers for your unique brick-paving project. Our beautiful brick pavers are shipped nationwide direct to your job site. These one of a kind brick pavers materials are perfect for driveways, patios and walkways.

Our antique brick pavers have been salvaged from streets in the MidWestUSA. These pavers are approx. 9" x 4" x 3.5" and weigh 91bs each. These bricks are 100+ years old and are in amazing shape. These bricks do not fade like the concrete pavers of today.

Brick pavers gain their strength through verification, a process that makes brick impervious to water. The term vitrified when applied to brick means that a chemical action has coalesced the clay particles and fused them with heat to form a near-liquid substance, which then slowly hardens over a sevento tenday period. A thoroughly vitrified brick has no visible pores and breaks with a smooth fracture. The crushing strength of good quality paving brick is eight to ten thousand pounds per square inch. In comparison, concrete has a strength of thirty-five hundred pounds per square inch.

Below are some commonly asked questions regarding installation of brick pavers.

What type of base should I use for brick paving?

A flexible base consists of compacted crushed stone, gravel or coarse sand. Only mortar-less brick paving is suitable for this type of base. A semirigid base consists of asphalt concrete, commonly referred to as asphalt. Once again, only mortar-less brick paving is suitable over this type of base. A rigid base is defined as a reinforced or un-reinforced concrete slab on grade. Mortarless or mortared brick paving may be placed over this type of base.

Flexible bases include crushed stone, gravel or coarse sand. Applications for flexible bases range from residential patios to city streets. Flexible paving systems are typically the most economical to install since less labor and fewer materials are involved. A flexible paving system allows easier repairs to utilities located beneath the pavement. Flexible pavements also allow for water to percolate down through the system instead of running off on the surface. The thickness of each layer in a flexible pavement depends upon the imposed loads and the properties of each layer. A pavement subjected to heavy vehicular traffic requires a thicker base than a pavement subjected to pedestrian traffic.

Mortared brick paving can be used for any type of pedestrian or vehicular

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traffic in both interior and exterior applications. This type of assembly is especially well-suited for heavy vehicular areas such as streets or parking lots and where surface drainage is necessary.

Can brick pavers be installed over an existing concrete or asphalt driveway, patio or walk?

Brick paving can be installed over existing concrete or asphalt as long as it is in reasonably good shape. To ensure an adequate foundation for the brick, the existing concrete slab or asphalt should be inspected and repaired as necessary. Any cracks, chips, holes, ruts or spalls should be repaired in order to achieve a flat surface.

The brick can be installed either with or without mortar. If no mortar is used, a half-inch setting bed of coarse sand should be laid and compacted. An edging of metal or heavy-duty plastic should be placed around the perimeter of the brickwork and set to just below the height of the finished brick surface. Pavers can then be placed in the desired pattern on top of the sand. The bricks should be placed as close to each other as possible.

It may be necessary to cut some of the brick near the edging. Once the brick are all in place, install mason's sand between the brick and over the surface. Sweep away excess surface sand and the brick pavement is ready for traffic.

If mortar is used, the concrete slab should be prepared in the same manner as above. A half-inch mortar setting bed should then be applied upon which the bricks are set with mortar placed between the pavers. Only a small area should receive the setting bed at a time in order to ensure that it does not set prior to laying the brick. Mortared brickwork should not be laid on asphalt.

Can a do-it-yourselfer construct a new brick driveway, patio or walk?

A new brick pavement can be constructed on asphalt, concrete, or compacted gravel as a base. For asphalt and concrete bases, the base material should be installed according to standard construction procedure and then the brick can be constructed on top. (See previous question.)

For a compacted aggregate base, the earth below should be well compacted. All brick pavements should have the earth graded to a minimum slope of a quarterinch per foot for drainage. Then four-inches of crushed stone, followed by a layer of geotextile material, if desired, and one inch sand setting bed of coarse concrete sand is laid. An edging of heavy plastic or metal should be installed at the perimeter of the brick. The brick should then be laid on top of the sand and cut as needed at the edging. Mason's sand should then be spread on the top and in between the brick and consolidated with a plate

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compactor if necessary. Mason's sand should be added until all the joints are filled and any excess sand should be removed.

For pavements such as driveways, a six to eight-inch gravel base should be installed and compacted with a plate compactor. Then a geotextile material should be installed and a one-inch setting bed of coarse sand laid. Placing edging, brick and mason's sand between the joints should then proceed as outlined above. Heavier duty pavements can be laid in the same manner, but the base is thicker.

Adequate preparation of the earth before installation and compaction of the entire assembly after installation with a plate compactor are essential to a well-constructed brick pavement.

Flawless Walls

Skim-coat plaster is a cure for drywall's shortcomings by Sam Singer

The days of applying horsehair plaster onto wood lathe are long gone, yet plaster is still a viable option for interior wall construction. Modern systems consist of thick coats of high-strength gypsum plaster over expanded wire lath. This creates surfaces far superior to drywall in quality, durability, and the ability to straighten the most crooked framing. The downside to this system is that it is extremely labor intensive and very expensive.

Skim-coat plaster provides the same high-quality finish at a fraction of the cost. Both systems use a thin topcoat of lime putty plaster, which gets troweled to a hard polished surface. Compared to standard drywall and joint compound, skim-coat plaster has greater impact and abrasion resistance, improved sound isolation, and can be brought to a truer flat plane resulting in a virtually flawless surface.

The dry plaster is polished to a mirror finish. With a sheen this high, it would be easy to spot any imperfections in the wall.

Set up and preparation

The most common plaster systems used today are called veneer or skimcoat plasters. Falling under the general category of drywall systems, they consist of one or two coats of thin plaster over sheets of special gypsum board. This gypsum board, also known as blueboard, is basically the same as standard gypsum board except it has a different paper surface designed for greater moisture absorption and bonding with plaster. The blueboard is available in 1/2- in. and fire-code 5/8-in. thicknesses and comes in standard drywall dimensions.

Our crew doesn't install the blueboard, so prior to starting any plaster work; we check the installation to ensure that all the panels are tightly fastened.

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Protruding or loose screws that missed the framing are corrected. The panels should be tight to each other, and electrical boxes should be inset. We then cover the subflooring with tarps and protect all of the windows and the doors with painter's plastic and masking tape. If plaster were to get on any wood, glass or metal surface, it would clean off easily, but it's better to keep it off in the first place.

Blueboard that has been faded by ultraviolet light should be treated with either an alum solution or plaster bonding agent only if a lime putty plaster is applied directly to the board. With a two-coat system this is not a concern because the base coat is gypsum, which will adhere just fine.

Installing corner bead and taping joints

For two-coat work, a #900 mesh mini bead is recommended for outside corners. In many cases we opt to use a much heavier 1-A type of corner bead, which is designed for heavy three-coat plasterwork. Though this deviates from specification and requires us to put on a much thicker base coat, it significantly increases our ability to straighten and plumb walls, and it is much sturdier and less susceptible to damage. The beads are set straight and plumb with a level and attached with an electric powered stapler.

The 1-A type of corner bead (top) lets the plasterers build out the depth of the plaster to correct any bows or dips in a wall. The #900 mesh is appropriate for a single skim coat over blueboard.

Unlike drywall, the seams get a coat of setting type compound. Then the tape is embedded, and that's it. It's important to feather this joint so it won't interfere with plastering later.

We tape the blueboard seams with a high-strength setting type joint compound (hot mud) and paper tape. Nothing resists seam cracks, as well and this is recommended under rapid drying conditions or when the framing is of steel construction. Self-sticking fiberglass tape is an acceptable method of treating the seams. All-purpose joint compounds should never be used for joints under plaster. It offers less strength and will soften again when the wet plaster is applied.

The critical task of mixing plaster

There are many ways to ruin a plaster mix. If the water is too cold, the plaster will set prematurely. Too hot, and the plaster will take too long to set. Dirty water will cause a rapid, premature set. We will not use plaster that is older than six months because it is no longer reliable and may not set properly.

For small batches (less than a bag) we mix it in 5-gallon buckets. We also

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have 15-gallon plastic buckets for one or two bag mixes. For three to five bag mixes, we use heavy-duty plastic trashcans. To mix the plaster, we use the prescribed cage style mixers and heavy-duty 1/2-in. drills that spin at 900 RPM, which delivers the necessary shearing action to make the plaster fully workable within the twoto five-minute mixing period. Overmixing will significantly shorten the workable time span. Paddles should not be used to mix plaster. They have a folding action, which is inadequate for achieving proper workability. With the exception of a plaster finish called Keenes Cement, plaster should never be re-tempered, so once mixed, that is it, and we never remix. Doing so would significantly weaken the plaster.

Applying the first coat

The base coat of plaster is applied in two applications from the same mix. The first application is commonly called the scratch coat. The term is a carryover from the first coat in conventional systems, where the plaster is raked with a scarifier. The second application we call the double, sometimes referred to as greasing or sweetening. These two applications together make one coat. The double should leave the surface without voids (cat's eyes) or trowel marks. A browning rod is brought to the surface to ensure straightness. Once all corrections are made, a cement brush is dragged across the surface to roughen it for the finish coat.

The pressure on the upward stroke is kept to the bottom inside edge of the trowel. The next motion is a downward arc to fill any voids that may have occurred. By shifting your wrist you'll apply pressure to the outer top edge of the trowel.

The plaster is setting, and a brush is used to scratch the surface so that the final coat can form a strong bond to the base coat. After the plaster sets, the loose plaster burls are scraped off with a putty knife.

This base coat will set within an hour of mixing, after which the lime putty finish coat can be applied. Most of the time, we prefer to wait a day to put on the finish coat to allow the base coat to give up most of its moisture, especially on damp days. However, in the winter, when the air is heated and dry, the base coat that has set, but is still wet (green) is best finish coated the same day. Lime putty over a dry base coat will be difficult to spread evenly and could dry out and check. If the base coat is too wet, blisters are likely to appear and polishing will be more difficult.

Applying the finish coat

Like the base coat, the finish coat is applied using a two-coat application method. The finish coat should be pressed up tight as it is applied. The main

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objective when putting on the scratch coat is to get an even thickness with as few trowel lines and cat's eyes as possible. I always use three strokes to put it on. The first stroke spreads it on, a backstroke presses it in the opposite direction and the third stroke comes back again erasing the trowel line. All three strokes happen in one continuous motion, without the trowel leaving the surface.

The plaster is troweled on in arcs. The reason is that trowels have a slight bow to them. The front edge of the trowel is pressed as the trowel is arced. On the back stroke, the same applies except the back edge gets pressed. Executed correctly true flat surfaces are achievable without trowel lines.

The finish coat is applied in the same arcing motion over the brushed plaster. The emphasis is on creating a smooth, trowel free finish. This coat takes a little more elbow grease as well.

The double is a lighter coat that is applied with just two strokes. I like to leave the surface near perfectly smooth at this point. The fewer times the trowel is run over the surface the better. Over trowelling will only make things worse. When the plaster begins to set, it can be water troweled to a smooth finish. The key is to be patient, because if the plaster is troweled too soon, it will pull and drag, causing lumps, ridges, and blisters. I use water sparingly, because too much water can also cause blisters and weaker the plaster. When the plaster begins to turn brown in color (brown out), it begins to harden. At this point we begin hard polishing the surface.

Before calling it a day, we ensure that plaster has been removed from all electrical boxes, that door and window jambs are clean and bottoms are left neat and clean so the baseboard and trim can be installed without the carpenters having to scrape or chip away my plaster. The plaster is now ready for primer and paint. Though the surfaces are left very smooth and polished, the painters should never sand the surface. Sanding is not necessary for the primer to adhere. Sanding will only mar and weaken the hard-packed and polished surface.

Tools for the trade

A plasterer's trowel is the single most important tool. It should be a flat stainless steel finishing trowel. We use trowels made by Curry Tool, because they are rigid, yet have just the right amount of flex. The 41/2x11-in. trowel is very popular with many plasterers because it is easy to control. I use a larger 5 x 14-in. trowel because it covers a lot more area and with a little practice is relatively easy to control. I'll use the smaller sized trowel for heavy base-coat mixes. For tight spots, I use a midget 3x5 or margin trowel. Contrary to convention we prefer to use new trowels to scratch and double the plaster. Though it is very difficult to plaster with a rigid new trowel, once you get used

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to it you can achieve flatter surfaces. An old well-worn trowel is best fro smoothing and polishing. A light coat of WD-40 on the tools makes it easy to keep them clean.

A long-handled brush with a five-gallon bucket, one quarter filled with water, is kept handy to clean off the trowels while working. It is important to keep all the tools clean. Dried or set plaster on tools will draw moisture from the fresh wet mix, making it hard to spread smoothly.

FRAMES

Premier Building Systems offers several types of steel building framing options. All framing members are shop fabricated and ready for field bolt assembly.

-Classic Frame

-Clear Span, also referred to as gable-symmetrical. (A ridged double slope building where the ridge of the roof is in the center of the building) and gableunsymmetrical (A ridged double slope building where the ridge of the roof is off-center).

-Modular span

-Single slope

-Lean-to

Main Framing

The main frame (rigid frame) is the primary structural member of the steel building system, consisting of columns and rafters. Columns transfer loads from main roof beams, trusses, or rafters to the foundations. Rafters are the main beams supporting the roof system. Main frames are normally connected to the foundation using anchor bolts in a configuration described as a pinned condition.

Endwall frames consist of endwall columns and rake rafters. Typically, end-frames only support half as much load as a main frame, so their components are often manufactured using the less expensive process of "cold forming" coils of steel in a roll former. Customers expecting to add to their building car order an expandable endwall. These are designed with the loadbearing capability of main frames so they can serve as interior frames when the building is expanded.

Secondary Framing

Secondary framing members join the primary-framing members together to form building bays and provide the means of supporting and attaching the walls and roof. Secondary framing members consist of eave struts, purlins, girts

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and bracing. Eave Struts provide attachment and bearing points for the enc of the roof sheets and wall sheets. Purlins support roof panels and transfer the roof loads to the rafters Girts are horizontal structural members attached to sidewall or endwall columns that support paneling. They run horizontally, between main frame columns and between endwall columns. Bracing Steel buildings employ one or more forms of bracing to counteract the constant pressure from forces like torsion, shear, compression, and lift. Flange bracing is standard on all metal buildings, consisting of structural angles connected between rafters and purlins to prevent the rafters form rolling side to side under a load. Diaphragm bracing is created by wall and roof sheeting. 'X' bracing uses steel rods or cables to tightly connect various parts of the frame together and strengthen the diaphragm effect. It is useful for extra stresses on a building, such as high winds, heavy snow loads, or even a large number of openings.

Connecting Clips

Steel plates called clips provide the connection points for attaching the secondary frame components to the main frames and to each other. They are welded on at the factory and have bolt patterns prepunched.

Bays and Framed Openings

Bays are the spaces between columns. A framed opening is an opening within a bay framed by jams; I can be anything from doors and windows to drive-through vehicle openings.

Surroundings or centrality: Prague developments show consumer preference

by Pavel Velebil of Tide Realty and David Friday of Estates News

PRAGUE - When in October 1994 two Czech developers announced construction of the Hvezda condominium complex with more than 300 apartments, they rocked the local residential market.

Before that, from 1990-94, the only alternative to living in substandard housing built during the communist era was to build a family home or to convert an attic space in the centre of the city. But Hvezda offered Czech citizens something new; it represented the first chance to buy an apartment built to a European standard. In concept and design, it clearly expressed that it had nothing in common with the housing of the past era.

Investors located their unique project in the highly demanded Prague 6 district and hired Czech architect Vlado Milunic who had already proved his