Blog Archives

Multilane Exit Ramps and Diverging Roadways

Posted by on 13/ 11/ 15

Figure 2.47 shows recommended designs for multilane exit ramps and diverging roadways. A diverging roadway is defined as a single roadway that branches or forks into two separate roadways without the use of a speed change lane.

Class I and II diverging roadways should be used when either or both the diverging roadways are mainline roadways of an expressway or a freeway. Class III diverging road­ways should be used at the divergence of directional ramps within an interchange or at the divergence of ramps with non-limited-access roads or streets. In general, class III is applicable at all locations other than those requiring class I or class II.

Lane Balance and Continuity...

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MULTILANE RAMP AND ROADWAY TERMINALS AND TRANSITIONS

Posted by on 13/ 11/ 15

When two roadways converge or diverge, the less significant roadway should exit or enter on the right. Left-hand exits or entrances are contrary to driver expectancy and should be avoided wherever possible.

2.7.1 Multilane Entrance Ramps and Converging Roadways

Figure 2.46 shows recommended designs to be used for multilane entrance ramps and converging roadways. Converging roadways are defined as separate and nearly parallel roadways or ramps that combine into a single continuous roadway or ramp having a greater number of lanes beyond the nose than the number of lanes on either approach roadway. High-speed and low-speed entrance terminals should be used in lieu of converg­ing roadway drawings when applicable...

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Skewness coefficient and kurtosis

Posted by on 13/ 11/ 15

The asymmetry of the PDF of a random variable is measured by the skewness coefficient Yx, defined as

Skewness coefficient and kurtosis

E [(X – ,x)3]

 

_ _M3_ Yx = ,,1.5 ^2

 

(2.40)

 

a

 

Skewness coefficient and kurtosis
The skewness coefficient is dimensionless and is related to the third-order central moment. The sign of the skewness coefficient indicates the degree of symmetry of the probability distribution function. If yx = 0, the distribution is symmetric about its mean. When yx > 0, the distribution has a long tail to the right, whereas yx < 0 indicates that the distribution has a long tail to the left. Shapes of distribution functions with different values of skewness coeffi­cients and the relative positions of the mean, median, and mode are shown in Fig. 2.13.

Similarly, the degree of asymmetry can...

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About the drawings

Posted by on 13/ 11/ 15

The sizes of building elements indicated in the draw­ings in this section are for the purposes of illustrating principles and reminding the designer and the builder to consider their use carefully. These drawings should therefore be used only for reference.

Подпись: w

Подпись: ■ * t
About the drawings

Footings are the part of a foundation that transfers the building’s loads—its weight in materials, contents, occupants, and snow, and possibly wind and earthquake loads—directly to the ground. Consequently, the size and type of footing should be matched carefully to the ground upon which it bears.

Soil type—Concrete footings should be placed on firm, undisturbed soil that is free from organic mate­rial. Soil types are tested and rated as to their ability to support loads (bearing capacity).

Compaction of soil ma...

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According to the European Standard EN 13108-5

Posted by on 13/ 11/ 15

The requirements for gradation of SMA mixtures have been provided in the European standard PN-EN 13108-5 (see Chapter 14). This standard does not set out the crite­ria and conditions for selecting the particular gradation of a mixture. Establishing these criteria remains the responsibility of each CEN-member state. In Figures 14.2 through 14.5, examples of gradation limits are presented.

6.1 GENERAL RULES

6.2.1 Original Zichner’s Proportions

In his publications (Zichner, 1971; Zichner, 1972) Dr. Zichner described a recom­mended composition of an SMA mixture as follows:

• The stone content should be about 65-80% (m/m), preferably 70-75%, using only crushed stones.

• The main rule governing gradations is that the mixture is composed “so that the percentage of the coarser size is greater ...

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Plumb bob

Posted by on 13/ 11/ 15

As its name implies, a plumb bob is used to check a vertical surface—-such as a door, wall, or window—-for plumb, or to find a spot directly below any given point. It is a simple but very accurate tool consisting of a tapered weight attached to a string. It’s really easy to use, too. To find plumb below a spot on a ceiling joist, for example, hold the string to a point on a joist and extend the string so that the weight is close to the floor (see the photo on the facing page). Plumb is directly below the point of the weight.

Plumb bob

A plumb bob is a very accurate tool for finding the location of a point that is directly above or below another point.

 
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The Material Safety Data Sheet (MSDS)

Posted by on 13/ 11/ 15

The Material Safety Data Sheet (MSDS) pro­vides information about the chemical sub­stances in a product, its handling precautions,

and its known health effects. The responsi­bility for preparing the MSDS lies with the chemical manufacturer. All manufacturers are required to create an MSDS for every chemi­cal compound they offer. The following infor­mation must be included:

• with the exception of trade secrets, the spe­cific chemical name and common names for hazardous ingredients

• physical and chemical characteristics

• physical hazards

• health hazards

• primary routes of entry to the body

• OSHA permissible exposure limit (PEL) and any other recommended exposure limit

• whether the chemical is a confirmed or potential carcinogen

• precautions for safe handling and ...

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Traffic Loading and Location

Posted by on 13/ 11/ 15

Coarse-graded mixtures make stronger skeletons. That is why the majority of requirements for SMA contain a noticeable tendency toward increasing the maxi­mum particle size in a mixture in conjunction with an increase in the traffic loading. When selecting a mixture, both the strengths and weaknesses of an accepted solution
should be considered; mixtures with larger maximum particle size (let us suppose greater than 10 mm) are characterized by higher rut resistance but lower noise reduc­tion ability and poorer skid resistance. Therefore, when at all possible, SMA 0/11 is being gradually abandoned for SMA 0/8.

In Germany, SMA 0/8S and 0/11S have been used on the most heavily trafficked roads while on lesser trafficked roads mixtures without an S marking are used...

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COLLECTOR-DISTRIBUTOR ROADS

Posted by on 13/ 11/ 15

Collector-distributor (C-D) roads are used to minimize weaving problems and reduce the number of conflict points (merging and diverging) on the mainline. C-D roads may be used within a single interchange, through two adjacent interchanges, or continuously through several interchanges.

2.6.1 Design of C-D Roads

When a C-D road is provided between interchanges, a minimum of two lanes should be used. Either one or two lanes may be used on C-D roads within a single interchange. The cross-section elements for one – and two-lane C-D roads should be in accordance with the criteria for one-lane and two-lane directional roadways provided in Fig. 2.27. The separation between the mainline and C-D road pavements should be designed to prevent, or at least discourage, indiscriminate crossovers...

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Foundation wall insulation

Posted by on 13/ 11/ 15

Foundation insulation isn’t used in mild cli­mates. But in areas with frigid winter months, il uni improve interior comfort and save on heating costs. Even though it’s not required by code in many areas, it’s definitely worth installing wherever prolonged freezing tem­peratures are expected. You can install insula­tion on the inside or outside of a crawl space or basement wall. Exterior insulation, in the form of rigid foam boards, is glued to the foundation walls before backfilling. Where they’re exposed above the finished grade on the exterior, insulation boards must be pro­tected with siding material or stucco. It’s important to remember that ary type of foun­dation insulation can provide a hidden pas­sageway for termites and other insects to enter the house...

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