Blog Archives

Terminals on Crest Vertical Curves

Posted by on 13/ 11/ 15

Mainline crest vertical curves in the vicinity of ramp terminals should be designed using stopping sight distance values 25 percent higher than the design speed value from Table 2.18. Where a crest vertical curve occurs on an exit ramp at or near the nose, the crest vertical curve should be designed using the “upper-range” design speeds of Table 2.28.

2.5.2 Ramp At-Grade Intersections

Ramp at-grade intersections are designed using many of the same criteria as outlined in Art. 2.4.1. However, one of the basic differences is the one-way nature of ramps and the fact that most traffic at ramp intersections is turning. Figure 2.44 shows the design of a typical uncurbed ramp intersection. Curbed returns are normally used in urban areas where space is more restricted.

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Superelevation at Terminals

Posted by on 13/ 11/ 15

Superelevation at ramp terminals should be developed using the following guidelines. The rate of superelevation at the entrance and exit nose should be selected on the basis of the design speed of the ramp at the nose. All transverse changes or breaks in superelevation should be made at joint lines in concrete pavement. In the case of bituminous pavement, the superelevation breaks should occur in the same locations as they would in concrete pavement. For high-speed terminals, the transverse breaks in superelevation cross slope should not exceed a differential of 0.032 ft/ft (0.032 m/m) at the mainline pavement edge or 0.050 ft/ft (0.050 m/m) at other locations. When a double break occurs on longitudinal joints less than 6 ft (1.83 m) apart, it should not exceed a total differential of 0...

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STRIPPING AN OLD ROOF

Posted by on 13/ 11/ 15

Roof stripping is one of the nastiest, dirtiest, most dangerous jobs in renovation. If you can afford it, hire an insured contractor for this. Most roofing contractors know of tear-off crews that will obtain permits, rip off the old roof, and cart away the debris, or you might be able to sub­contract the job through a roofer. Professional stripping takes at most a couple of days, and it’s money well spent to allow the start of new work.

If you must strip the roof yourself, remove all drain gutters and then minimize the mess by buying a heavy 6-mil plastic tarp to catch shin­gles and old roofing nails. So you won’t be pick­ing shingle shards and nails from the lawn for years to come, lay tarps from the house to the Dumpster as well...

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Basic Timber Frame Structure

Posted by on 13/ 11/ 15

M

y father was a mechanical engineer. When we kids had difficulty learning how to coordinate the clutch with changing gears, he would explain to us the mechanics of what was actually taking place inside the transmission, and that seemed to make learning to shift a whole lot easier. We could visualize the nasty things that would happen if the clutch were not engaged before changing gears. You don’t need to know anything about clutches to build a timber frame, but in a similar way, knowledge about a few basic principles of structure will help you to prevent nasty things from happening to your building.

Load and Line of Thrust

Any structure has to support itself and anything that is added to it, such as furniture, people, earth, snow, even wind...

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Product Substitution Procedure

Posted by on 13/ 11/ 15

Contractors will often ask if they can substi­tute a product that is different from the one you have specified. The specified product may be unavailable, too expensive, or too difficult to apply, or contractors may have one that they have used before and prefer. New and health­ier products continue to be developed; it may be worth your while to consider certain sub­stitutions. The first step in researching alter­natives is to examine the Material Safety Data Sheet (MSDS). (Refer to the section on MSDS that follows.) You may also request a physi­cal sample. To ensure that no substitutions are made without your consent or that of your architect, you may wish to add the following language to your agreement:

• No products may be substituted for the specified product unless agreed upon in ...

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In the Mesopotamian north: the kingdum of Urartu. The oldest dams still in use

Posted by on 13/ 11/ 15

The kingdom of Urartu, in the south of Armenia, was a powerful rival of Assyria during the period from about 850 BC to 600 BC. Its capital was Tushpa, on the shores of the lake Van, whose water is too salty to be potable. Therefore this capital city’s thirst led to the development of a vast water management program in this mountainous region, developed in successive stages (Figure 2.18).

In about 800 BC, the king Menua brought water to the capital from a perennial and abundant spring located some thirty kilometers to the southeast. The 56-km canal – aqueduct built for this purpose carried at least 1.5 m3/sec, and was destined to be used

In the Mesopotamian north: the kingdum of Urartu. The oldest dams still in use

Figure 2.18 Water supply for the two successive capitals of Urartu (Tushpa and Toprak Kale) in the 8th century BC – after Garbrecht (1980, 1988).
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Development of Assyria. The waters of Nineveh

Posted by on 13/ 11/ 15

The sovereigns of Assyria begin development of their land on the upper course of

Development of Assyria. The waters of Nineveh

Подпись: Figure 2.16 Fluvial transport of wood beams. Bas-relief from the palace of Sargon II at Khorsabad, on display at the Louvre museum (photo by the author).

Figure 2.15 Irrigation and water supply works in Assyria in the 9th and 8th centuries BC (after Jacobsen and Lloyd, 1935; Roaf, 1990; Schnitter, 1994; Bagg, 2000)

the Tigris in about 900 BC. This date marks the flowering of an Assyrian Empire des­tined to reign over all of Mesopotamia, and even as far as Egypt, for about three cen­turies. In 860 BC, Ashurnasirpal builds a new capital Kahlu (today Nimrud) on the left bank of the Tigris near its confluence with the upper Zab. A canal called babilat nuhshi (“bringer of abundance”) is dug to irrigate the plain with waters of the Zab diverted into the canal by a dam or weir.

It is interesting to note also that a ventilation system comprising chimneys...

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Single-Lane Ramp Terminals

Posted by on 13/ 11/ 15

A ramp terminal is the portion of a ramp adjacent to the through lane on the mainline. It includes both the taper and the speed-change lane. Ohio has recently revised its ter­minal criteria and uses two basic terminal classifications:

High-speed terminals are intended for use on all facilities with a design speed of 50 mi/h (80 km/h) or higher. They are used in both rural and urban locales. Figure 2.41 shows the details for high-speed single-lane entrance terminals. This terminal is a taper-type design for the last 1250 ft (381 m), tapering from a 25-ft (7.6-m) offset from the mainline to zero. Tables A and B in Fig. 2...

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INTERCHANGE RAMP DESIGN

Posted by on 13/ 11/ 15

An interchange ramp is a roadway that connects two legs of an interchange. Ramp cross­section elements are discussed in Art. 2.3, Cross-Section Design. Elements contributing to horizontal and vertical alignments are designed similar to any roadway once the ramp design speed has been determined.

2.5.1 Ramp Design Speed

To design horizontal and vertical alignment features, a design speed must be determined for each ramp. Since the driver expects a speed adjustment on a ramp, the design speed may vary within the ramp limits. Table 2.28 includes three ranges of ramp design speeds that vary with the design speed of the mainline roadway. The ramp design speed range is determined by judgment based on several conditions:

• The types of roadways at each end of the ramp and their design speeds

• ...

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SPREADING OFFSETS EQUALLY

Posted by on 13/ 11/ 15

If you take a lot of pride in your work or are working to detailed piping dia­grams, you may find that the spacing of your offsets must be equal. Equally – spaced offsets are not only more attractive and more professional looking, they might required. You can guess and eyeball measurements to get them close, but you will need a formula to work with if you want the offsets to be accurate. Fortunately, I can provide you with such a formula, and I will.

Again, we will concentrate on 45°, 60°, and 22V2° bends, since these are the three most often used in plumbing and pipefitting. We will start with the 45° turns. In our example, you should envision two pipes rising vertically. Each pipe will be offset to the left and then the pipes will continue to rise ver­tically...

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