AISC LRFD 1.pdf

274 WELDS [Comm. J2.and Kennedy (1990). Conversion of the SI equation to foot-pound units results inthe following weld strength equation for R n :15Rn = 085210 . ( . + 050 . sin . θ) FEXX AwBecause the maximum strength is limited to 0.60F EXX for longitudinally loadedwelds ( = 0º), the LRFD Specification provision provides, in the reduced equationcoefficient, a reasonable margin for any variation in welding techniques and procedures.To eliminate possible computational difficulties, the maximum deformationin the weld elements is limited to 0.17w. For design convenience, a simple ellipticalformula is used for f(p) to closely approximate the empirically derived polynomialin Lesik and Kennedy (1990).The total resistance of all the weld elements combine to resist the eccentric ultimateload, and when the correct location of the instantaneous center has been selected,the three in-plane equations of statics (F x , F y , M) will be satisfied. Numericaltechniques, such as those given by Brandt (1982), have been developed to locate theinstantaneous center of rotation subject to convergent tolerances. Earlier editions ofthe AISC Manual of Steel Construction (AISC, 1980, 1986a, 1989) took advantageof the inelastic redistribution of stresses that is inherent in the Appendix J2.4 procedure.However, in each of the utilized computational techniques the resulting coefficientswere factored down so that the maximum stress, at any point in the weldgroup, did not exceed the limiting value specified by either the Allowable StressDesign or LRFD Specifications, 0.3F u or 0.6F u , respectively. As a result, the tabulatedweld-capacity data shown in the appropriate referenced manual tables will beFig. C-A-J2.2. Load deformation relationship.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION