Properties and benefits of rebar cages

In drilled shaft construction, rebar cages are generally utilized to reinforce the shaft throughout excavation. To retain the strength of this cage as well as complete the entire construction project successfully, the design of the cage should be perfect.

Normally, a rebar cage for a drilled shaft comprises of longitudinal bars which are allocated with uniform spacing along the boundary of a cylinder.

In order to reinforce these bars, steel is arranged transverse to the bars and connected with ties, clamps or welds. Other elements of rebar cages may contain hoops for sizes, guides for centering the cages in the borehole and the premie inside of the cage, and stiffeners and pickup devices applied to facilitate lifting the cages.

Larger cages should contain temporary or permanent strengthening components to get rid of permanent distortion due to the stresses of lifting and placing.

As rebar cages are vital drilled shaft construction, it is essential that these cages should be properly constructed on the basis of a calculation of the stresses that it will endure.

The amount of reinforcing steel in a rebar cage should adhere to the structural requirements, taking into account combined stresses of axial load, lateral load and moment.

Properties of Steel Used for Rebar Cages

The American Society for Testing and Materials (ASTM) defines various steels which are employed for reinforcing drilling shafts.

The American Association of State Highway and Transportation Officials (AASHTO) approves most of these ASTM steels for being applied in building rebar cages for drilled shaft construction.

Normally, the steel accessible for these cages is AASHTO M 31 (ASTM A 615) in Grade 40 or Grade 60. If welding is required, then weldable steel, like ASTM A 706, should be utilized.

In case, there is risk for corrosion, galvanized or epoxy-coated steel are useful for longitudinal and transverse reinforcement. This is often stated for marine environments where the chloride content of ground or surface water is extreme.

As nicks and blemishes in the coating may happen at the time of the lifting and disposition of the rebar cases, rapid corrosion may occur. Under this situation, rebar without epoxy should be utilized and the drilled shaft should be filled with a low-permeability concrete to enhance the resistance strength against corrosion.

In unusual situations, high strength reinforcement is suitable. It may comprise of threaded couplers for splice connections and higher-strength rebar.

Contractors should compute the structural requirements of a drilled shaft cautiously while deciding the requirements of a rebar cage.

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Published By
Rajib Dey
www.constructioncost.co
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The 7 Major Highway Cross Sectional Elements of a Road

Given below, the details of cross sectional components of a road

1) Right of way: Right of way or permanent land stands for the area of land obtained and conserved for construction and formation of a road along its alignment. The width of right of way is termed as permanent land width or road land width.

2) Road way / Formation width: The top width of a highway embankment or bottom width of highway cutting exclusive of the side drain is known as roadway width or formation width. It belongs to the sum of width of carriageway and the shoulders.

3) Carriageway: Carriageway or pavement or crust is defined as the segment of roadway developed for movement of vehicular traffic

4) Shoulder: The segments of roadway among the exterior edges of the pavement and edges of the top surface of the embankment or inside edges of the side drains in cutting are termed as shoulders.

The objective of shoulders

i) They offer lateral strength to the carriageway.
ii) They function as parking place for vehicle for emergency purpose.
iii) They arrange space for constructing road signals.
iv) They arrange space for animal drawn vehicles, cyclists, pedestrians.

5) Berm: The segments of land width kept among the toe of road embankment and the inner edges of borrow pits or the segments amid the top edges of road in cutting and the adjacent edges of spoil banks on either side are described as berm.

6) Building Line: It refers to the line, on either side of the road, among which and the road; no building activity can be done at all.

7) Control Line: It refers to the line which shows the nearby restraint of future unrestrained building activity concerning a road. It implies that though building activity is not entirely combined among the building line and control line, the nature of building allowable here is restricted.



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Published By
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www.constructioncost.co
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The detailed method of highway construction

By making extensive surveys and subgrade groundwork, highway construction is normally conducted. The methods and technology for constructing highways are upgraded in due course of time and turns to be more advanced.

The improvement in technology has increased the grade of skill sets essential for dealing with highway construction projects.

This skill differs from project to project, on the basis of different factors like the project’s complications and type, the contrasts among new construction and reconstruction, and variations among urban region and rural region projects.

There exist various components of highway construction which are segregated into technical and commercial components of the system. Given below, some illustrations of them:

Technical Components -

a. Materials
b. Material quality
c. Installation systems
d. Traffic

Commercial Components -

a. Contract understanding
b. Ecological characteristics
c. Political characteristics
d. Legal characteristics
e. Public interests

Generally, construction starts at the lowermost elevation of the site, in spite of the project type, and moves upward. After evaluation of the geotechnical specifications of the project, the following information is provided:

Present ground conditions -

a. Necessary apparatus for excavation, grading, and material transportation to and from the site
b. Characteristics of materials to be excavated
c. Necessity of dewatering for below-grade work
d. Necessity of shoring for excavation protection
e. The quantities of water for compaction and dust control



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Published By
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www.constructioncost.co
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