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PREFACE:

 This Article reinforces the traditional method of selecting load combinations to obtain realistic extreme effects and is intended to clarify the issue of the variability of permanent loads and their effects. 

As has always been the case, the Owner or Designer may determine that not all of the loads in a given load combination apply to the situation under investigation. It is recognized herein that the actual magnitude of permanent loads may also be less than the nominal value. 

This becomes important where the permanent load reduces the effects of transient loads. The factors shall be selected to produce the total extreme factored force effect. For each load combination, both positive and negative extremes shall be investigated.

 In load combinations where one force effect decreases another effect, the minimum value shall be applied to the load reducing the force effect. For permanent force effects, the load factor that produces the more critical combination shall be selected from Table 3.4.1-2. Where the permanent load increases the stability or load-carrying capacity of a component or bridge, the minimum value of the load factor for that permanent load shall also be investigated.

 It has been observed that permanent loads are more  likely to be greater than the nominal value than to be less than this value. In the application of permanent loads, force effects for each of the specified six load types should be computed separately.

 It is unnecessary to assume that one type of load varies by span, length, or component within a bridge. For example, when investigating uplift at a bearing in a continuous beam, it would not be appropriate to use the maximum load factor for permanent loads in spans that produce a negative reaction and the minimum load factor in spans that produce a positive reaction. Consider the