Overload Permit Procedures (1266-4F)

This document defines criteria for issuing permits for overweight vehicles passing over H15, H20, and HS20 highway bridges in the state of Texas. The resulting formulae have been developed to ensure that the maximum stress does not exceed the operational stress level.|Criteria is first developed for simple span bridges. The approach used analyzes the discrete point on the bridge where overstress is most likely to occur. This is done in the manner prescribed by the American Association of State Highway and Transportation Officials (AASHTO) in the Standard Specifications for Highway Bridges and the Maintenance Manual for the Inspection of Bridges. Two formulae for each bridge type, a general formula and a bridge specific formula, have been developed to limit the group axle weight on simple span bridges.|The general formula is a function of only the vehicle dimensions and is similar to the current Texas permit rules. The current Texas Department of Transportation (TxDOT) permit rules for mobile cranes and oil well equipment vehicles only formula developed is significantly more restrictive than that currently used by TxDOT. A second formula has been developed based on the vehicle dimensions and the span length of any bridge along the permitted vehicle route. With this bridge-specific formula, higher permit weights can be safely authorized without additional engineering analysis.|In addition, several critical reinforced concrete continuous span slab bridges have been investigated to ensure that the formulae calculated for simple span bridges do not exceed the allowable stresses. The greatest concern on the continuous span bridges is at the supports where negative moments can become great. The results indicate that the capacities of the reinforced concrete continuous span slab bridges are well above those allowed by the proposed simple span formulae.