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原文传递 Pre-Designed Timber Bridges f of Three Types for Arkansas County Roads

题名：	Pre-Designed Timber Bridges f of Three Types for Arkansas County Roads
作者：	Dr. Larry G. Pleimann
关键词：	timber, bridges, county roads
摘要：	According to the annual National Bridge Inventory, the highest percentage of US bridges that are “ structurally deficient ” or “ functionally obsolete ” is in the “ city/county/township ” category. In recent years the major causes of rapid deterioration of bridges with typical steel or concrete superstructures have been deicer chemicals and lack of adequate maintenance monies. Well-designed “ modem ” timber bridges could be a cost-effective alternative for, the replacement of substandard bridges on county and city toads. Three types of simple span timber bridges have been designed with accompanying specifications for ready use; (1) solid sawn stringers with transverse solid sawn deck planks, (2) glulam stringers with transverse glulam decks, and (3) stress-laminated full-span glulam stringers, all constructed of southern pine (SP). This report contains designs for the first type using 6 different SP stringer sections, for the second type using 4 different standard widths of SP glulam stringers, and for the third type using the same 4 separate widths of SP glulam stringers. Designs focused on flexural adequacy. Procedures are included for changing span length or depth of the primary bending sections to fit with any desired allowable deflection limitation or smaller “load duration factor. ”
报告类型：	科技报告