A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Cost reduction motivates PE pipe use on bridge crossings
Polyethylene (PE) pipes replacing steel pipes are possible for generating bridge crossings. PE-piping is cheaper because it weighs less, can quickly be fused, is available in continous coils, does not corrode and can easily be repared. Cost savings of installed brigde crossings are 5.4 % to 14.8 %. PE doesn't stand UV-radiation (for less than 2 % carbon black content), has to be protected from Vandalism, dynamic loading (if the cover is less than 18 inch) and seismic loading. Therefore they are usually installed in a casing. Normally the annular space of the casing can be designed sufficient to absorb most of seismic displacement. PE can elongate at least 800 % before failure. The dynamic impact loading imported to the pipe crown by vehicular loading may be calculated by Timoshenko's equation. Spangler's Modified Iowa formula calculates the pipe deflection. With increasing temperatures the allowed maximum operating pressure decreases about 0.15 to 0.75 psi/deg F dependant on the hydrostatic design basis and the wall thickness to diameter ratio. Short time operating above the maximum continous-use temperature is of no problems except with gas pipelines (never over 140 deg F). PE elongate and shrink time-dependant about 1 inch per 100 feet and 10 deg F. The thermal movement is larger than that of steel pipes. Elongation, lateral deflections and the strain are dependant on the pipe length (L), coefficient of thermal expansion (alpha) and temperature difference (delta T). The termal strain depends additional on the pipe-diameter (D) and should be limited to 5 %. The resulting stress (product of elasticity-modulus (E), alpha and delta T) is about 5 % to 10 % of steel-pipe-values. The overall forces (product of stress and area) produced by larger cross sections create stresses in anchors, fittings and transitions. Settlements after construction of the bridge require additional pipe shielding or annular spacing. Also the pipe can be hung under the finished bridge. Bending radii should be larger than 20 times the pipe diameter. Support spacing depends on the fourth root of E-modulus, moment of inertia (I) and pipe-weight. (For equations see the original article).
Cost reduction motivates PE pipe use on bridge crossings
Polyethylene (PE) pipes replacing steel pipes are possible for generating bridge crossings. PE-piping is cheaper because it weighs less, can quickly be fused, is available in continous coils, does not corrode and can easily be repared. Cost savings of installed brigde crossings are 5.4 % to 14.8 %. PE doesn't stand UV-radiation (for less than 2 % carbon black content), has to be protected from Vandalism, dynamic loading (if the cover is less than 18 inch) and seismic loading. Therefore they are usually installed in a casing. Normally the annular space of the casing can be designed sufficient to absorb most of seismic displacement. PE can elongate at least 800 % before failure. The dynamic impact loading imported to the pipe crown by vehicular loading may be calculated by Timoshenko's equation. Spangler's Modified Iowa formula calculates the pipe deflection. With increasing temperatures the allowed maximum operating pressure decreases about 0.15 to 0.75 psi/deg F dependant on the hydrostatic design basis and the wall thickness to diameter ratio. Short time operating above the maximum continous-use temperature is of no problems except with gas pipelines (never over 140 deg F). PE elongate and shrink time-dependant about 1 inch per 100 feet and 10 deg F. The thermal movement is larger than that of steel pipes. Elongation, lateral deflections and the strain are dependant on the pipe length (L), coefficient of thermal expansion (alpha) and temperature difference (delta T). The termal strain depends additional on the pipe-diameter (D) and should be limited to 5 %. The resulting stress (product of elasticity-modulus (E), alpha and delta T) is about 5 % to 10 % of steel-pipe-values. The overall forces (product of stress and area) produced by larger cross sections create stresses in anchors, fittings and transitions. Settlements after construction of the bridge require additional pipe shielding or annular spacing. Also the pipe can be hung under the finished bridge. Bending radii should be larger than 20 times the pipe diameter. Support spacing depends on the fourth root of E-modulus, moment of inertia (I) and pipe-weight. (For equations see the original article).
Cost reduction motivates PE pipe use on bridge crossings
Polyethylenrohre in Brücken - genauso geeignet wie Stahlrohre aber billiger
Brandli, J.W. (author)
Pipe Line and Gas Industry ; 79 ; 43-46
1996
4 Seiten, 8 Bilder, 4 Tabellen, 8 Quellen
Article (Journal)
English
Cost reduction motivates PE pipe use on bridge crossings
| Online Contents | 1996
Online Contents | 1997
Online Contents | 1997
Online Contents | 1997
Online Contents | 1997