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TO: The Honorable Members of DATE: November 13 1985410F-G-�`9�S <br />the Board of County Commissioners <br />�Lo <br />CO�r <br />THROUGH: <br />Michael Wright, C"/ <br />County Administrator " �.: ^� r7 4 �.• <br />SUBJECT: Bi -Annual Inspection of'Coun <br />Bridges and Weight Posting <br />Recommendations <br />w <br />FROM:'�114� REFERENCE81 George L. 'Marton, PE, <br />James W. Davis, P.E., FDOT District IV <br />Public Works Director Structures Engineer to James <br />W. eawis da --4 as y 3, 1985 <br />2) George E. MacDonald, PE, <br />Wilbur Smith and Assoc. Inc. <br />to Jim Davis dated Oct. 18, <br />1985 <br />The Florida DOT's Bridge Inspection Consultant, Wilbur Smith and <br />Assoc., Inc., has completed the inspections of 40 of the County's 85 <br />bridges. The structural load carrying capacity of each bridge was <br />determined using two types of rating analysis as follows: <br />INVENTORY RATING - a load level which can safely utilize a bridge for <br />an indefinite period of time. For this rating, there exists a <br />conservative level of safety above and beyond the Ultimate Strength of <br />the bridge. In Florida, cities and counties should use the Inventory <br />Rating to post bridges for weight restrictions. If the County <br />maintains a level of inspection which exceeds the minimum required <br />(once every 2 years) and closely monitors the bridge, the County may, <br />in its judgement, utilize for posting purposes load levels higher than <br />those used for inventory rating. This is allowed in order to obtain <br />the very maximum safe utilization of the highway facility. On the <br />"Load Rating Summary" form attached, the "Inventory Rating" for each <br />type vehicle has been calculated by Wilbur Smith and Assoc. Inc. <br />OPERATING RATING - The absolute maximum permissible load level to <br />which the structure may be subjected. Special permits for heavier <br />than normal vehicles can be issued only if such loads are distributed <br />so as not to exceed the ultimate structural capacity determined by the <br />Operating Rating. Usually, Operating Ratings are 5/3 those of <br />inventory levels. On the "Load Rating Summary" form attached the <br />"Operating Rating" for each type vehicle has been calculated by Wilbur <br />Smith and Assoc., Inc. <br />ALTERNATIVES AND ANALYSIS <br />The County has 3 options in posting those bridges that require weight <br />restrictions: <br />Option 1 - Post bridge at the "Inventory Rating". For .Florida <br />Counties, this posting is recommended and is a conservative approach. <br />This posting will not require more frequent monitoring and inspection <br />than the 2 -year interval now required. The County's potential <br />liability is minimal. <br />Option 2 - Post. bridge at the "Operating Rating" if the maximum legal <br />loads under State Law exceed the Operating Rating of the Structure. <br />This is a very liberal approach. This posting will require more <br />frequent inspection of the structure. The. County's potential <br />liability is greater than posting the Inventory Rating. <br />Option 3 - Post Bridge at sane level between the Inventory and . <br />Operating Rating. This is a practical approach based on good <br />engineering judgement, increased monitoring, and local conditions. <br />Staff has reviewed each of the 40 bridge reports with Andy vaillen- <br />court, AOT Structures Engineer, and has prepared tke--following data chart: <br />43 <br />NOV 2 0 1985 BOOK 62 FAFjE 8v9SQ <br />