Blog Archives

AESTHETIC CONSIDERATIONS

Posted by on 15/ 11/ 15

While highway bridges are utilitarian structures, they are visible to the public and therefore should be pleasing to the eye. At the outset of design, one should be conscious of the aesthetic qualities of the structure, lest one end the project saying (after Shelley), “Look on my works, ye Mighty, and despair!”

Some basic guidelines that were adopted by the Ohio Department of Transportation (DOT), Bureau of Bridges and Structural Design, and are included in its Bridge Design Manual illustrate the commonsense approach that can be taken to apply this consciousness:

Aesthetics. Each structure should be evaluated for aesthetics...

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Czech method

Posted by on 15/ 11/ 15

2.3.1 General Principles

The Czech method has been employed in the Czech Republic based on the Czech guidelines TP 109.

The distinctive feature of this method is the consideration of the influence of the coarse aggregate content on asphalt mixture properties. Some knowledge of the impact of coarse particle quantity in creating an SMA aggregate structure has been adopted during design. In the Czech method, particles bigger than 4 mm (called

HDK here as designated in Czech method) are regarded as coarse aggregate, making an active part of the aggregate mix.

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The Mechanical Processes Contributing to Water-Induced Damage

Posted by on 15/ 11/ 15

Because water-induced damage influences the dry response of the material, the effects of the physical processes must be coupled with a three dimensional elasto- visco-plastic constitutive model for mastic response (Scarpas et al., 2005). Mastic in asphaltic mixtures is known to be a material whose behaviour, depending on strain rate and/or temperature, exhibits response characteristics varying anywhere between the elasto-plastic and the visco-elastic limits. Constitutive models for such types of materials can be developed by combining the features of purely elasto-plastic and purely visco-elastic materials to create a more general category of constitutive models termed elasto-visco-plastic...

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Stage 7: Selecting an Optimum Content of Binder

Posted by on 15/ 11/ 15

After the selection of an optimum aggregate mix, the amount of binder should be selected in such a manner that the desired content of air voids in a compacted SMA

TABLE 7.1

Requirements for a Laboratory-Compacted SMA Binder Mixture Using a Marshall Hammer or superpave Gyratory compactora

property

requirement

Notes

Minimum content of binder,

>6.0

Before adjustment of aggregate density

% (m/m)

Content of air voids in a

>4.0

Usually 3.5-4.0

compacted sample, % (v/v)

Voids in a mineral aggregate VMA, % (v/v)

>17.0

Quantity required at production in an asphalt plant; in fact it should be slightly higher in a laboratory, min. 17.5%-18.0%

VCAMIX

<vcadrc

Appropriate filling volume among coarse particles and stone-to-stone contact are guaranteed
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Types of Geophysical Data Series

Posted by on 15/ 11/ 15

The first step in the frequency-analysis process is to identify the set of data or sample to be studied. The sample is called a data series because many events of interest occur in a time sequence, and time is a useful frame of reference. The events are continuous, and thus their complete description as a function of time would constitute an infinite number of data points. To overcome this, it is customary to divide the events into a series of finite time increments and con­sider the average magnitude or instantaneous values of the largest or smallest within each interval. In frequency analysis, geophysical events that make up the data series generally are assumed to be statistically independent in time...

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NAILING TOGETHER THE WINDOW FRAME ASSEMBLIES

Posted by on 15/ 11/ 15

NAILING TOGETHER THE WINDOW FRAME ASSEMBLIES

Dull tips are IIP useful! When you need to drive a nail near the end of a board, first blunt the tip of the nail. This helps prevent splitting the wood.

 

NAILING TOGETHER THE WINDOW FRAME ASSEMBLIES

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When you come to a door or window open­ing, just continue the stud layout, marking cripple locations on the headers and the rough sills. Lay out all exterior walls and then begin on the interior walls. The layout of interior walls is not as critical as that of exterior walls, because most drywall hangers use long sheets of drywall, which often run from corner to corner. Just put the stick in a corner against a through wall and start marking. Make sure you put the stud mark­ings on the same side of the plates as the header markings. When you encounter rough plumbing, don’t put a stud next to a pipe...

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WATER TABLE

Posted by on 15/ 11/ 15

The water table is horizontal trim running around the base of a building below the siding, and not all houses have it. Depending mostly on regional preferences, the water table takes sever­al forms. In the West, it typically looks like win­dowsill ears (the parts that stick out) and is often used to separate different types of siding materi­als, such as shiplap siding from wood shingles above. This strip-like water table usually runs continuously around the building and is mitered at the corners. It often has a rabbeted heel, which fits over the top of the wood siding below, and a

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Water-table trim often finishes off the bottom of a wall and provides a level base for the first course of siding.

To forestall rot, cap the water table with metal or vinyl flashing before installing the s...

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Densities Too Low

Posted by on 15/ 11/ 15

Myths about high-density housing abound. It is widely believed, for example, that higher population densities necessarily increase congestion and strain infrastructures. This just simply is not the case. The congestion myth and the fear it inspires stem largely from some very real conditions that exist in our everyday world. Wherever a design does not accommodate for the number of people and the type of activities that occupy it, there will be overcrowding. But, just as with a house, the solution is not necessarily more space; it is usu­ally better design.

The goal of design is the same for neighborhoods as it is for houses. Good community design has to meet our needs without far exceeding them. The suburbs fail on both these counts...

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Stage 6: Selecting an Aggregate Mix

Posted by on 15/ 11/ 15

An optimum variant should be selected out of the three defined trial design grada­tion curves. The selection criteria of the optimal gradation curve should consist of the smallest amount of coarse aggregate combined with the following two conditions at the same time:

• VCAMIX is lower than VCAdrc or the VCA ratio (VCAmix/VCAdrc) is less than 1.0.

• VMA is higher than 17.0% (v/v) (usually minimum values of 17.5-18.0%).

If the VCAMIX is higher than the VCAdrc, the creation of a skeleton is not guaran­teed. It can be changed by increasing the amount of particles bigger than the BP sieve—that is, increasing the amount of aggregates retained on the BP sieve should increase the VCAdrc. So sometimes additional trial gradations must be analyzed before finding an optimal solution.

Using thi...

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CLIENT-CONSULTANT RELATIONSHIP

Posted by on 15/ 11/ 15

State departments of transportation, bridge and turnpike authorities, and other agencies often require the services of a consulting engineering firm. This may be because the agency chooses not to maintain an engineering staff of its own, because its workload is greater than its staff can handle, or because expertise in special kinds of bridges is needed. Consultants can fill these needs.

Where only routine types of bridges are involved and the agency has an engineer­ing staff, the best that a consultant can be expected to do, usually, is only as good a job as the agency’s engineers can do...

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