AISC LRFD 1.pdf

Comm. N4.] EVALUATION BY LOAD TESTS 263R = 0.95 for tests taken from web specimensR = 1.00 for tests taken from flange specimensThe R factor in Equation C-N2-1 accounts for the effect of the coupon location onthe reported yield stress. Prior to 1997, certified mill test reports for structuralshapes were based on specimens removed from the web, in accordance with ASTMA6/A6M. Subsequently the specified coupon location was changed to the flange.During 1997-1998, there was a transition from web specimens to flange specimensas the new provisions of ASTM A6/A6M were adopted.4. Base Metal Notch ToughnessThe Engineer of Record shall specify the location of samples. Samples shall becored, flame cut, or saw cut. The Engineer of Record will determine if remedialactions are required, such as the possible use of bolted splice plates.5. Weld MetalBecause connections typically have a greater reliability index than structural members,strength testing of weld metal is not usually necessary. However, field investigationshave sometimes indicated that complete-joint-penetration welds, such as atbeam-to-column connections, were not made in accordance with AWS D1.1 (AWS,1998). The specified provisions in Section N2.4 provide a means for judging thequality of such a weld. Where feasible, any samples removed should be obtainedfrom compression splices rather than tension splices, because the effects of repairsto restore the sampled area are less critical.6. Bolts and RivetsBecause connections typically have a greater reliability index than structural members,removal and strength testing of fasteners is not usually necessary. However,strength testing of bolts is required where they can not be properly identified otherwise.Because removal and testing of rivets is difficult, assuming the lowest rivetstrength grade simplifies the investigation.N3. EVALUATION BY STRUCTURAL ANALYSIS2. Strength EvaluationResistance factors reflect variations in determining strength of members and connections,such as uncertainty in theory and variations in material properties anddimensions. If an investigation of an existing structure indicates that there are variationsin material properties or dimensions significantly greater than those anticipatedin new construction, the Engineer of Record should consider the use of moreconservative values.N4. EVALUATION BY LOAD TESTS1. Determination of Live Load Rating by TestingGenerally, structures that can be designed according to the provisions of this Specificationneed no confirmation of calculated results by test. However, special situationsmay arise when it is desirable to confirm by tests the results of calculations.Minimal test procedures are provided to determine the live load rating of a structure.However, in no case is the live load rating determined by test to exceed thatLRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION