A highway culvert is a drainage facility that allows water to flow under the road without causing any traffic disruption. Corrugated and spiral steel pipe are popular for culverts because they can be installed quickly, have long life, are low in cost, and require little maintenance. With corrugated steel pipe, the seam strength must be adequate to withstand the ring-compression thrust from the total load supported by the pipe. This thrust C, lb/ft (N/m), of structure is

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While taking a turn,the centifugal forces develop so a vehicle and its contents are immediately subjected to centrifugal forces. More is the speed of vehicle sharper is the curvature and thus the greater the influence on vehicles and drivers of the change from tangent to curve. When transition curves are not provided, drivers tend to create their own transition curves by moving laterally within their travel lane and sometimes the adjoining lane,which is risky not only for them but also for other road users.
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The figure below shows how the highway turning lanes can be classified: Read the rest of this entry »

STRUCTURAL NUMBERS FOR FLEXIBLE PAVEMENTS

The design of a flexible pavement or surface treatment expected to carry more than 50,000 repetitions of equiva- lent single 18-kip axle load (SAI) requires identification of a structural number SN that is used as a measure of the ability of the pavement to withstand anticipated axle loads. In the AASHTO design method, the structural number is defined by

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The Geometric design of a highway consist of horizontal alignment, vertical alignment and cross-sectional elements.
Horizontal alignment of a highway defines its location and orientation in plan view. Vertical alignment of a highway deals with its shape in profile.

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