00473164

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http://onlinepubs.trb.org...1987/1106v2/1106v2-038.pdf

https://scholar.google.co...ieta&publication_year=1987

In Ecuador, as in many Third World countries, low-volume rural roads can only be economically justified when very low-cost bridges and simple water crossings (fords) are used. Traffic analyses indicate that in most cases the trucks that travel these roads carry loads that weigh less than 6 to 10 metric tons. Therefore, most of the drainage structures are designed to carry only 10 tons on two-axle light vehicles. Roads are designed according to AASHTO HS-15 standard loading in those locations where heavy traffic is generated from timber production or banana plantations. The standard AASHTO HS-20 live load cannot be economically justified for these low-volume roads. The traffic volume in rural regions is very low, which enables such economical structures as graveled fords to be used, and when economically feasible, one-lane bridges with either complete or split decks. The relationships between the type of material, the span or length of the superstructure, and the cost are analyzed. It is primarily concluded that simple timber bridges made of stringers and transverse laminated decks are the most economical solutions for simple spans up to 17, 14, and 10 m for 6-, 10-, and 24.5-ton truckloads, respectively. Simple-span, split-deck, reinforced-concrete superstructures are feasible for spans of up to 30 m. Spans can be as long as 45 m if prestressed girders are used. Suspension bridges with timber decks and timber-stiffening trusses were built to carry 6-ton trucks or cattle wagons and were more cost-effective than timber or concrete structures. It was concluded that with the judicious reduction of the design standards of live loads, cross-sections, geometry, material specifications, and hydrologic and hydraulic considerations, construction costs could be reduced by 50 percent or more. These savings make it possible to justify the construction of many low-volume rural roads that would otherwise be impossible to finance.

This paper appeared in Transportation Research Record N1106, Fourth International Conference on Low-Volume Roads, Volume 2. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

00490258

pp 318-327

1987-8

Transportation Research Record

International Conference on Low Volume Roads, 4th, 1987, Ithaca, New York, USA

0309044545

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Figures (7) ; Photos (12) ; References (9) ; Tables (2)

Bridges; Causeways; Construction; Costs; Design; Guidelines; Low volume roads; Reduction (Chemistry); Suspension bridges; Timber; Wooden bridges

Construction costs; Low cost roads

Bridges and other structures; Construction; Design; Finance; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I24: Design of Bridges and Retaining Walls

TRIS, TRB

Sep 30 1987 12:00AM