This implies that the beam-column baseplate from the supporting concrete. That is, a rigid frame with a All three methods summarized by AISC5 assume a lin-fixed base plate will usually attract enough bending mo- ear triangular distribution of the resultant compressivement to require anchor rods to prevent uplift of the base bearing stress. This is a common situation for fixed base platesin structural office practice. Assume independent strain distribution.crete. Assume a linear strain distribution such that the an- chor rod strain is dependent on the bearing area Case D evolves from Case C by the addition of suffi- strain.cient bending moment to require anchor rods to preventseparation between the base plate and the supporting con- 3. Assume that the resultant compressive bearing stresscorresponds to the common elastic limit where any addi- is directly under the column flange.tional moment would initiate separation between the baseplate and the supporting concrete. Case C evolves from Case B by the addition of a spe- cific bending moment such that the uniform pressure dis- tribution is the smallest possible length without separation ENGINEERING JOURNAL / FIRST QUARTER / 1999 29īetween the base plate and the supporting concrete. #Lrfd beam design full#The moment changes the full length uniform pressure distribution to a partial length uniform pressure distribution, but is not large enough to cause sepa- ration between the base plate and the supporting concrete. Case B evolves from Case A by the addition of a small bending moment. This case is summarized in the LRFD Manual4 beginning on page 11-54 and is summa- rized herein for completeness. This case results in a full length uniform pressure distribution between the base plate and the supporting concrete. Case A is a load case with axial compression and shear, without bending moment. The progression of beam-column loadings, in order of in- creasing moments, is presented in four load cases. Elkin is Structural Engineer, Fluor Daniel, Irvine,CA. Drake is Principal Structural Engineer, Fluor x סf Ϫ d םtf (3)Daniel, Irvine, CA. Base Plate Design Variables moment direction, in.Richard M. A typical beam-column base plate geometry is shown n סB Ϫ 0.80b f (2)in Figure 1, which is consistent with that shown on page 211-61 of the LRFD Manual.4 x סbase plate tension interface cantilever parallel to Fig. f סanchor rod distance from column and base plate Typically, these beam-column base plates have beendesigned and/or analyzed by using service loads1 or by centerline parallel to moment direction, in.approximating the stress relationship assuming the com- m סbase plate bearing interface cantilever directionpression bearing location.2 The authors present anotherapproach, using factored loads directly in a method consis- parallel to moment direction, in.tent with the equations of static equilibrium and the LRFDSpecification.3 m סN Ϫ 0.95d (1) 2 The moment-resisting base plate must have designstrengths in excess of the required strengths, flexural (Mu), n סbase plate bearing interface cantilever perpendic-axial (Pu), and shear (Vu) for all load combinations. ELKIN INTRODUCTION where:It is common design practice to design a building or struc- B סbase plate width perpendicular to moment direc- tion, in.ture beam-column with a moment-resisting or fixed base.Therefore the base plate and anchor rods must be capable N סbase plate length parallel to moment direction, in.of transferring shear loads, axial loads, and bending mo- b f סcolumn flange width, in.ments to the supporting foundation. #Lrfd beam design verification#Other code verification is also carried out at these locations, the results of which can be printed out in "calculation style" to be included in a user report.Beam-Column Base Plate Design-LRFD MethodRICHARD M.Capacity Resistance checks are carried out at default and user defined locations along the span and displayed graphically. Load effects for a variety of load cases can be entered manually or obtained automatically from the Structural Analysis.Reinforcement can be placed within the sections and curtailed at positions along the span.Features such as transverse web stiffeners, lateral restraints, shear studs etc.Each beam is defined by one or more sections which can vary along the span.The above beams can also be defined to AASHTO 17th Edition but there no code checking to this standard. Multiple spans may be defined and each analyzed in turn. Post-tensioned, prestressed bridge beams to AASHTO LRFD 7.Reinforced concrete beams to AASHTO LRFD 7.Pre-tensioned, prestressed bridge beams to AASHTO LRFD 7.Steel/Concrete Composite bridge beams to AASHTO LRFD 7.There are four design beam types for which analysis and code checking is carried out:
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