Blog Archives

Tangible costs in risk-based design

Posted by on 25/ 11/ 15

Design of a hydrosystem infrastructure, by nature, is an optimization prob­lem consisting of an analysis of the hydraulic performance of the structure to convey flow across or through the structure and a determination of the most economical design alternative. The objective function is to minimize the sum of capital investment cost, the expected flood damage costs, and operation and maintenance costs. The relevant variables and parameters associated with the investment cost and the expected damage costs of a hydraulic structure, i. e., a highway drainage structure, are listed in Tables 8.1 and 8.2, respectively. The maintenance costs over the service life of the structure generally are treated as a yearly constants. Based on Tables 8.1 and 8...

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NOISE BARRIERS

Posted by on 25/ 11/ 15

James J. Hill, P. E.

Structural Engineer
Consultant
Anoka, Minnesota

Roger L. Brockenbrough, P. E.

President

R. L. Brockenbrough & Associates, Inc.
Pittsburgh, Pennsylvania

During recent years, there has been increasing concern over noise generated by highway traffic in urban areas. Noise abatement programs have been implemented by many agencies. Source control methods have included the development of quieter pave­ments, quieter tire tread patterns, and speed restrictions. In some regions, noise levels have been reduced by depressing roadways or building tunnels, or by special designs of adjacent buildings. In many cases, however, noise reduction has been achieved through controlling the noise path by the design and construction of noise barriers...

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THE EUROPEAN STANDARD EN 13108-5

Posted by on 25/ 11/ 15

EN 13108-5 defines the requirements for SMA mixtures for use on roads, airfields, and other trafficked areas. This standard should be read along with other standards as follows:

• EN 13108-20:2006, Bituminous Mixtures—Material Specifications— Part 20: Type Testing

• EN 13108-21:2006, Bituminous Mixtures— Material Specifications—Part 21: Factory Production Control

• EN 12697-x, Bituminous Mixtures. Test Methods

The mutual relationships among those standards are displayed in Figure 14.1.

Sets of properties of asphalt mixtures (Figure 14.1) are listed in the standard EN 13108-x (any from 1 to 7). Each of these properties corresponds to an appropriate test method described in a standard from the series EN 12697-x...

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PREFABRICATED MODULAR WALLS

Posted by on 25/ 11/ 15

There are also a number of prefabricated modular wall systems in use. Such systems are generally composed of modules or bins filled with soil, and function much like gravity retaining walls. The bins may be of concrete or steel, and can be used in most cases where conventional gravity, cantilever, or other wall systems are considered. AASHTO indicates that such walls should not be used on curves less than 800 ft in radius, unless a series of chords can be substituted; or where the calculated longitudinal differential set­tlement along the face of the wall is excessive. Also, durability considerations must be addressed, particularly where acidic water or deicing spray is anticipated.

8.9 MSE BRIDGE ABUTMENT WALLS

The abutment wall is an earth-retaining wall supporting traffic surcharge loa...

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PREPPING PAINTED SURFACES

Posted by on 25/ 11/ 15

Before you wallpaper painted surfaces, figure out what kind of paint you’ve got and what shape it’s in. In general, oil-based paints are stable surfaces for wallcovering because they aren’t water solu­ble. Yet some primer-sealers can stabilize even latex paint. You could scrape off a small patch of paint and have a paint store analyze it, but two simple tests should suffice.

Hot towel test. Soak a hand towel in hot water, wring it well, and then rub the paint vigorously for 20 seconds to 30 seconds. If paint comes off on the towel, you’ve probably got latex. Alterna­tively, you can use duct tape to hold a moist sponge next to a painted surface for 15 minutes before removing the sponge. If you see paint on the sponge, it’s latex.

LOOKING Sharp

This clever magnetic bracelet keeps a single­...

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The Grand Canal of the Yuan and the Ming Dynasties

Posted by on 25/ 11/ 15

In 1126 the Song were forced to abandon the north of China, pushed out by barbarians who had partially adopted Chinese culture (the Jurchen, or Jin). During their retreat the Song destroy the south-bank dike of the Yellow River in the Kaifeng region, and this causes considerable damage to the Tongji canal and destabilizes the river. For more than three centuries after this the Yellow River will tend to form multiple and unstable branches. Pushed to the south, the Song further destroy hydraulic infrastructure and set up their capital at Hangzhou, at the southern extremity of the Grand Canal. During the period of wars that follows, in about 1190,[432] the river starts to migrate toward the south (Figure 8.2)...

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Global Stability

Posted by on 25/ 11/ 15

Evaluation of a global safety factor that includes the nailed soil and the surrounding ground requires determination of the critical sliding surface. This surface may be located totally inside, totally outside, or part inside and part outside the nailed zone. Limit equilibrium methods are usually used, and the Davis method is recommended because of its simplicity and availability in the public domain (C. K. Shen et al., “Field Measurements of an Earth Support System,” Journal of the Geotechnical Division, American Society of Civil Engineers, vol. 107, no. 12, 1981). The Davis method has been modified (V. Elias and I...

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Types Of Tanks

Posted by on 25/ 11/ 15

There are many types of septic tanks in use today. Pre-cast concrete tanks are, by far, the most common. However, they are not the only type of sep­tic tank available. For this reason, let’s discuss some of the material options that are available.

Pre-cast concrete is the most popular type of septic tank. When this type of tank is installed properly and is not abused, it can last almost indefinitely. However, heavy vehicular traffic running over the tank can damage it, so this situation should be avoided.

Metal septic tanks were once prolific. There are still a great number of them in use, but new installations rarely involve a metal tank. The reason is simple, metal tends to rust out, and that’s not good for a septic tank...

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Historical development of hydrosystem design methods

Posted by on 25/ 11/ 15

The evolution of hydrosystem design methods can be roughly classified into four stages: (1) historical event-based design, (2) return-period design, (3) conven­tional risk-based design, and (4) optimal risk-based design with consideration given to a variety of uncertainties.

Historical event-based design. In the design of hydrosystem infrastructures and the establishment of land-use management practices to prevent and/or reduce damages resulting from natural disasters, the risk (damage) assessment typ­ically has been implicit. The earliest structures and land-use management approaches for flood protection were designed or established on the basis of their ability to withstand previous disastrous floods...

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Basic concept

Posted by on 25/ 11/ 15

The basic concept of risk-based design is shown schematically in Fig. 8.9. The risk function accounting for the uncertainties of various factors can be obtained using the reliability computation procedures described in earlier chapters. Al­ternatively, the risk function can account for the potential undesirable conse­quences associated with the failure of hydrosystem infrastructures. For sim­plicity, only the tangible damage cost is presented herein.

Risk costs associated with the failure of a hydrosystem infrastructure cannot be predicted accurately from year to year. A practical way is to quantify risk cost using an expected value on an annual basis...

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