Blog Archives

Project Evaluation

Posted by on 12/ 11/ 15

Once projects reach the selected lists, the next phase is project evaluation. This phase

will determine which projects can advance to detail design and which will require a

more detailed evaluation in preliminary development.

Projects that can advance directly to design phase meet the following criteria:

• No additional right-of-way (permanent or temporary) will be required to accomplish the work and there will be no adverse effect on abutting real properties.

• No major changes in the operation of access points, traffic volumes, traffic flows, vehicle mix, or traffic patterns.

• No involvement with a live stream or an intermittent stream having significant year – round pools, upstream or downstream, in the immediate vicinity.

• No involvement with a historic site.

Examples of thes...

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SQUARE

Posted by on 12/ 11/ 15

Foundations and Floors

Floors may seem to be the simplest of the challenges facing a new builder, but the importance of establishing a firm, sound, dependable connection between a house, the foundation, and the earth cannot be overstated. Everything rests, quite literally, on the quality of the foundation and fram­ing work done in the first few days or so after the concrete contractor has left. Our first house, in coastal Oregon, had a concrete foundation made from beach sand. Sixty years of wind and rain had washed much of that sand back toward the beach, leaving us with a shaky, tilted floor that wasn’t even bolted to the foundation.

Know the Foundation Fundamentals

Take a deep breath...

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Random Variables and their Distributions

Posted by on 12/ 11/ 15

In analyzing the statistical features of infrastructural system responses, many events of interest can be defined by the related random variables. A random variable is a real-value function defined on the sample space. In other words, a random variable can be viewed as a mapping from the sample space to the real line, as shown in Fig. 2.4. The standard convention is to denote a random variable by an upper-case letter, whereas a lower-case letter is used to repre­sent the realization of the corresponding random variable. For example, one may use Q to represent flow magnitude, a random variable, whereas q is used to represent the values that Q takes. A random variable can be discrete or con­tinuous...

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AFFORDABLE HOUSING – CHALLENGE AND RESPONSE

Posted by on 12/ 11/ 15

Подпись: IntroductionIn the nearly three decades since the national policy of "a decent home and a suitable living environment" was established in the Housing Act of 1949, millions of families have been able to reach the goal of home ownership. In recent years, however, this goal has proved elusive for others, particularly young families seeking to buy their first home.

Background,

The fundamental problem is that housing prices and mortgage interest rates rose faster than family incomes, particularly in the 1970’s. The median house price rose approximately 115 percent while incomes were increasing only about 105 percent. Even worse, during this period mortgage interest rates more than doubled, from below 9 percent to over 18 percent in many areas.

These figures are not precise, nor need they be to demonstrat...

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BINDER DRAINDOWN TESTING

Posted by on 12/ 11/ 15

Various methods for testing the tendency for binder to draindown in a particular SMA are presented in Chapter 8. The original Schellenberg’s method and other techniques according to AASHTO and EN 12697-18 standards are also described there.

In most countries, Schellenberg’s or a similar method for determining the quantity of stabilizer in a mix has been applied. The maximum allowable mass of drained-off material is essentially the same almost everywhere and is equal to 0.3%. A recom­mended, safer limit is 0.2%.

4.2 SUMMARY

Factors influencing a mixture’s susceptibility to binder draindown are presented in Table 4.1.

TABLE 4.1

Summary of Factors influencing draindown potential in smA

effect on draindown potential

by decreasing

by increasing

Factor

Factor

Factor
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DEALING WITH SUPPLIERS AND SCHEDULING DELIVERIES

Posted by on 12/ 11/ 15

Estimating lumber and materials for a small, affordable house is fairly simple, but it does take some experience to get it right. If you are building a Habitat house, you can call or e-mail affiliates and ask them to share their lists with you (check the Habitat website for the affiliate in your area). You can also take a set of plans to a local supplier. Most building-supply outlets will create a materials list and give you a bid on what everything will cost. Always get bids from more than one supplier. Just make sure every supplier understands the type and grade of each item.

If you don’t make your own list, take the opportunity to in­spect the plans closely. Get acquainted with the house and all its parts before you start...

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MOISTURE CONTENT

Posted by on 12/ 11/ 15

Each day, a mature living tree can pump a ton of water into the atmosphere, so it’s no surprise that logs arrive at the mill with moisture contents of 30 percent to 55 percent. Consequently, a sawmill will rough-cut logs into lumber, air dry or kiln dry it, and then grade the lumber’s moisture con­tent before planing (surfacing) it.

Moisture content of 15 percent to 19 percent is optimal because that approximates the mois­ture content of ambient air in much of North America, except in the dry U. S. Southwest. Most often, lumber will be marked S-DRY or KD (kiln dried), indicating that its moisture content is 19 percent or less. KD-15 or MC-15 indicates a moisture content of 15 percent or less. Of course, even MC-15 lumber may be sopping wet if rained on during storage or transport...

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Materials

Posted by on 12/ 11/ 15

Подпись: Dimension lumber is sawn from logs and then milled to a thickness and width that is slightly less than its nominal end cross sections. For example, the ends of these 2x6s actually measure 1 V> in. by Б1/ in.

This chapter of the

materials needed to frame and sheath a house. Materials include standard lumber; engineered lumber; sheet materials, such as plywood and particleboard; and fasteners, including nails, screws, and construction adhesives.

There’s never been a wider choice of building materials or more readily available information on using them, whether you need to size ceiling joists or find an environmentally safe adhesive that can bond frozen lumber. Just type your requirements into a Web site calculator or ask at your lumber supplier for a recommendation. Many related techniques are covered in Chapter 8.

Standard Lumber

Wood is a superb building material. It is strong, economical, and easily worked...

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Stabilizer Test Results

Posted by on 12/ 11/ 15

Almost every working road laboratory has conducted many series of draindown tests. The results of companion tests on a wide variety of stabilizers are seldom published. However, the following interesting conclusions can be drawn from large – scale research conducted in the United States (Brown and Mallick, 1994):

• SMA binder draindown was seen to be a time-progressive process; the fast­est run-off occurred within the first 30 minutes of hot mix storage, then it continued over 2 hours during testing. Therefore one can conclude that the major part of the draindown process takes place during the 1st hour after SMA production.

• The most effective stabilizers tested were cellulose and mineral fibers.

• Differences between binder-absorbing stabilizers and viscosity-enhancing stablizers we...

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Total probability theorem and Bayes’ theorem

Posted by on 12/ 11/ 15

The probability of the occurrence of an event E, in general, cannot be deter­mined directly or easily. However, the event E may occur along with other attribute events Ak. Referring to Fig. 2.2, event E could occur jointly with K mutually exclusive (Aj П Ak — 0 for j — k) and collectively exhaustive (A1 U A2 U—U AK) — S attributes Ak, k — 1,2,…, K. Then the probability of the occur­rence of an event E, regardless of the attributes, can be computed as

KK

P(E) — P(E, Ak) — P (E | Ak)P(Ak) (2.8)

k—1 k—1

Equation (2.8) is called the total probability theorem.

Example 2.4 Referring to Fig. 2.3, two upstream storm sewer branches (I1 and I2) merge to a sewer main (I3). Assume that the flow-carrying capacities of the two up­stream sewer branches I1 and I2 are equal...

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