A Study on the development of vehicular loding for design of highway bridges in Saudi Arabia

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Saudi Digital Library
The current MOC 600 kN truck loading for design of bridges in Saudi Arabia was adopted arbitrarily following the configuration of AASHTO HS20 truck loading, ensuing a transition from earlier lighter truck load models. However, it was not developed on a rational basis from data analysis of the local traffic. The primary objective of this work is to develop a load model for design of short span bridges and to examine the adequacy of the current MOC 600 kN truck loading under the context of the prevailing truck loadings. A rigorous load survey of the heavy trucks is carried out to obtain informative data on truck configurations and axle loads. Based on the survey data a proposed bridge loading formula is adopted using the concept of 'equivalent base length', and from this formula a 650kN Model truck load is developed for design of short span bridges. A modified uniformly distributed lane load is also presented as a substitute for the design load. The adequacy of the current MOC 600 kN model is compared with the proposed 650 kN Truck Model by rigorous analysis of slab and girder-slab type bridge decks, simple and two span continuous, having different geometric configurations. An overweight truck of 790 kN found in the truck survey is also included in the comparative study to give an insight into the extent of the possible over stressing of members and draw attention to the need of development of appropriate load factors for Load Resistance Factor Design (LRFD).