Blog Archives

WARRANTS FOR ROADSIDE BARRIERS

Posted by on 19/ 11/ 15

Longitudinal roadside barriers are used to shield motorists from natural or human – made obstacles located along either side of the traveled way, and sometimes to protect pedestrians and bicyclists. Median barriers and barrier end treatments are discussed separately in Arts. 6.9 and 6.12.

Barriers must contain and redirect vehicles. Because of the complicated dynamic behavior involved, the most effective way to ensure performance of new designs is through full-scale crash testing. Standard crash tests are presented in NCHRP Report 350, “Recommended Procedures for the Safety Performance Evaluation of Highway Features.” To match barrier performance to service needs, a series of six test levels are recommended to evaluate occupant risk, structural integrity, and postimpact vehicle behavior...

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CONNECTING TO FIXTURES

Posted by on 19/ 11/ 15

Electrical connections to light or fan fixtures are simple: ground wire pigtail to green screw (if any), hot pigtail to black lead wire or gold screw, and neutral pigtail to white lead wire or silver screw. If fixture lead lines are stranded, cut them a little longer than solid-copper pigtails so that both will seat correctly when they’re spliced with wire nuts. Push-in Wago Wall-Nuts are a good alternative (see "A New Kind of Nut,” on p. 248). Physical connections, such as mounting fixtures

WIRING A RECEPTACLE

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After finish walls are installed and painted, attach the wires to the devices. Start by stripping the wire ends.

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Some wire strippers have a small hole near the handle...

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Repair rate and its relationship with repair density and repair probability

Posted by on 19/ 11/ 15

The repair rate r (t), similar to the failure rate, is the conditional probability that the system is repaired per unit time given that the system failed at time zero and is still not repaired at time t. The quantity r (t) dt is the probability that the system is repaired during the time interval (t, t + dt] given that the system fails at time t. Similar to Eq. (5.3), the relationship among repair density function, repair rate, and repair probability is

r (t 1=t—GW,5-22’

Given a repair rate r (t), the repair density function and the maintainability can be determined, respectively, as

г c t -|

Подпись: I r(T) dr 0 Подпись:

Repair rate and its relationship with repair density and repair probability Подпись: (5.24)

gt(t) = r (t) X exp

5.1.2 Mean time to repair, mean time between failures, and mean time between repairs

The mean time to repair (MTTR) is the expected value of time to repair of a fa...

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Shingling across a valley

Posted by on 19/ 11/ 15

When a porch roof intersects the main roof at a right angle, a valley is formed. Shingles can be laid across a vallev in different wavs.

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A woven valley is formed by weaving shingles across the valley, alternately overlapping from the main roof onto the porch roof, then vice versa. When properly done, a woven valley is watertight. Let each course of shingles overlap the valley by at least 12 in. and keep nails 8 in. or more from the centerline of the vallev.

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An alternative to a woven valley is a closed, or cut, valley. To create a cut valley, let all shingle courses from the main roof lap across the porch valley by at least 12 in. Don’t alter­nate back and forth from the main roof to the porch roof. After the shingles are laid on the main roof, lay the shingles on the porch roof

Shingling across a valley

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Supports for Utility Poles

Posted by on 19/ 11/ 15

Utility supports represent a serious hazard that accounts for about 10 percent of all fixed-object fatal crashes. Elimination, relocation, and burying the lines are preferred options. Increased spacings or multiple use may reduce the number of poles. A breakaway device has been tested and may be considered for vulnerable locations. A breakaway device for utility pole guy wires has also been developed. As with other obstacles, shielding is also an option.

6.3.1 Trees

Collisions of single vehicles with trees account for nearly 25 percent of fixed-object fatal crashes and result in about 3000 deaths each year. Most of these are along county and township roads, which tend to have narrow recovery zones...

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Repair density and repair probability

Posted by on 19/ 11/ 15

Like the time to failure, the random time to repair (TTR) has the repair density function gt (t) describing the random characteristics of the time required to re­pair a failed system when the failure occurs at time zero. The repair probability Gt(t) is the probability that the failed system can be restored within a given time period (0, t]:

Gt(t) = P(TTR < t) = f gt(t) dr (5.19)

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The repair probability Gt (t) is also called the maintainability function (Knezevic, 1993), which is one of the measures for maintainability (Kapur, 1988b). Main­tainability is a design characteristic to achieve fast, easy maintenance at the lowest life-cycle cost...

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Operating Rollers

Posted by on 19/ 11/ 15

The following sections outline some considerations regarding the operation of rollers once the roller combination for a specific job has been determined.

10.4.2.1 General Rules

In standard conditions, rollers should follow as closely as possible behind the paver. If it is not possible for the rollers to keep up with the paver, the speed of the paver should be reduced or the number of rollers increased. The method of rolling and positions of the different rollers are thoroughly discussed in the USACE Handbook 2000, Dynapac Handbook, and German DAV Handbook (Milster et al., 2004), where detailed directives can be found.

Rolling thin SMA layers should be executed with great caution, with vibra­tion only rarely applied. The use of slightly lighter rollers instead of heavy ones is recommended.

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Assembling the walls

Posted by on 19/ 11/ 15

Once the door and window frames are assembled, you can start nailing walls together. Start by scattering enough 921/4-in. studs to frame one of the exte­rior through walls, which I always build and raise first. Later you’ll frame and raise the butt walls, which are generally shorter and rise up between the through walls. Scatter the studs on the floor per­pendicular to the plates, one stud per layout mark and three studs for each corner and channel.

As a beginning carpenter, one of my jobs was to set up and nail together all the corners and channels needed for an entire building. Some builders still do this, but I’ve found that it works better to build everything flat on the deck as you nail the wall together...

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Layout Methods

Posted by on 19/ 11/ 15

Use the Correct Order

When you perform the layout, follow a prioritized order. For example, trimmer and king studs for doors and windows take priority over studs. That is because if a stud falls on the location of a trimmer or king stud, then the stud is eliminated. Using a certain order for layout also helps you keep track of where you were if you are pulled off layout and have to come back later to pick up where you left off. The order should be doors and windows first, then bearing posts, backers and corners, then hold- downs—followed by special studs like medicine cabinet studs, then regular studs, and finally miscellaneous framing, such as blocks.

Align Framing Members

It is good practice when laying out studs to align the roof trusses, floor joists, and studs...

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Sill Plates and Sill Beams

Posted by on 19/ 11/ 15

Very often, a two-inch thick sill plate is fastened to the foundation, and the wooden frame is attached to that. This sill plate is usually bolted to the foundation all around its perimeter. Yet another neighbor, Chris Ryan — we live in a community of owner-builders — did this at his new garage. First, he laid a course of ordinary eight-inch concrete blocks around the perimeter of his slab, except where his doors would be, because he wanted to keep his posts (and his cordwood masonry) about eight inches (20 centimeters) off the slab. (Fig. 4.3 is actually a detail from the Ryan garage.) Then, at appropriate locations, he filled block cores with concrete and placed anchor bolts into the fresh mix. (Use any bagged dry concrete mix for this, such as Sakrete® or equivalent...

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