b'FEATURESTEEL COLUMN BASES Under Combined Axial Load and Bi-Axial BendingBy Dr. Muntasir Billah,P.Eng. Assistant Professor, Department of Civil Engineering, Lakehead UniversityCOLUMNBASEPLATE connec- 250tions,typicallyconsistingofasteelmember welded to a steel base plate connected to the Anchor Rod Force (kN)concrete base via anchor rods and grout, are200commonly found in building and non-building structures. This base connection is one of the150most important structural components, which acts as a transfer medium for all the forces and100moments from the entire building into the foun-dation. Failure of these base plate connectionsExperimentcan result in the collapse of the entire frame as50 FEMit affects the ductility demand and force distri-bution in the structure (Grauvilardell et al., 2005).0After the 1994 Northridge Earthquake, design0.00 2.00 4.00 6.00 8.00 10.00 12.00ofsteelconnectionshasbeensignificantlyColumn Drift (%)revampedacrossNorthAmerica.However, a significant amount of effort has been dedi- Fig. 1: Comparison of experimental and numerical results cated to the steel beam-column connectionsFIG. 1:Comparison of experimental and numerical resultsunder seismic loading. In comparison, limited experimental and numerical investigations were devoted to study the behaviour of column baseto the base plate connection, only the axialbehaviour of exposed column base plates and connections. As a result, the design of a columnload and major axis bending are considered.(iv) developing interaction equations, design base connection presents several issues, whichPractisingengineersoftenadoptcomplexmethodsandsimplifiedtoolsforpractising arenotlimitedtocharacterizationofforcefinite element methods or design them in theengineers.anddeformationdemands,characterizationtwo directions separately, which often results in ofdeformationcapacitiesoftheconnectionoverly conservative design. PRE-TEST ANALYTICAL STUDYcomponents and failure mechanisms and devel- Currently, there exists a gap in the research toAND FINITE ELEMENT ANALYSISopment of desirable hierarchies of failure modesdevelop a design guideline for exposed columnThis pre-test analytical study is conducted to (Gomez et al., 2010). base plate connection under combined axialinvestigate the performance of column base Mostofthepreviousstudiesanddesignloadandbi-axialbending.Theoverarchingconnectionsunderaxialloadanduniaxial guidelines are focused on base plate designobjectiveofthisresearchistodevelopabending. The purpose of this analytical study under axial load and uniaxial bending momentsimplifieddesignguidelineforexposedis to select and validate a suitable modelling (typically major axis). However, very often thesecolumn base plates under combined axial loadstrategythatcanmimictheexperimental baseplatesaresubjectedtobidirectionalandbi-axialbending.Thiswillbeachievedresponse of column base connections with bendingmomentfromlateralloadssuchasthrough the pursuit of the following objectives:reasonable accuracy. For pre-test analytical wind and earthquake. Current design codes and(i) finite element simulation of base plates understudy,a3Dfiniteelement(FE)modelis guidelines do not address the design of thesecombined axial load and bi-axial bending, (ii)developedusingABAQUSsimulation exposedbaseplateconnectionsunderaxialexperimentalinvestigationofcolumnbaseplatform.Inordertovalidatetheaccuracy load and bi-axial bending. Although the columnsplates under combined axial load and bi-axialoftheadoptedmodellingtechniquesand aredesignedandcheckedundercombinedbending, (iii) comprehensive parametric studymaterialmodels,theresultsfromtheFE axial load and bi-axial bending, when it comesto identify the parameters that influence themodeliscomparedwiththeexperimental 24|SUMMER 2020 ADVANTAGE STEEL'