Shear Connectors

Shear ConnectorsLoad bearing mechanism of shear connectorsWhile resisting the shear load,Connectors deform & transfer load to concrete thro bearing.Load causes tensile cracks in concrete (ripping, shear & splitting action)Frictional force between dowel & concrete is to be considered.Ripping of concrete

Strength of shear connectorsDowel strength depends uponCSA of dowelTensile strength of steelFckModular ratio

Design resistance based on steel & concrete:Prd=0.8 fu(3.14d2/4)/1.25Prd=0.29d2(fckE)1/2/1.25Fu=ultimate tensile strength of steel1.25=partial safety factor for stud connectorl

Ultimate load behavior of composite beamThe design procedure of composite beam depends onClass of the compression flange & webClassification is based on buckling tendency of steel flange & web4 classes-plastic, compact, semi compact, slenderFor class 1 & 2-plastic analysis is recommendedSs composite beams-plastic neutral axis is within the slab or steel flange for full interaction.Assumptions made for the analysis of the section(Pg:40)The tensile strength of concrete is ignored.Plane sections of both steel & concrete remain plane after bending.

3. The effective area of concrete resists a constant stress=0.85fck/partial safety factor for concrete.4. The effective area of steel is stressed to its design yield strength fy/safety factor.Note: Composite beams are generally designed as SS beam with shear connections with columns. As plastic moment capacity depends on the geometry of the section, no account of prop or unprop is considered.Composite beamRolled steel sections are used.Built up girders are unnecessary.Profiled steel sheetingTrapezoidal profileRe entrant profile

Shape of profile provides interlocking between concrete & steel.Tests on shear connectorsPush testStandard push test-steel section & rftSpecific push test-slab & rftPreparation of specimen2 concrete slab is cast in horizontal position.Bond at interface between flanges of beam and slab is greased.Air cured4 cubes & cylinders are also cast in accordance to push specimen.Compressive strength is determined.The tensile strength of steel specimen is determined.Sheeting-tensile & yield strength of steel sheet is also determinedTesting procedureLoad is applied in increments upto 40%.Then cycled 25 times between 5% and 40%

Failure should not happen in 15 minutes.

The slip is then measured for every increment of load.Advantages of composite beamApplicability in bridges, ms buildings, car parks with reduced construction time.

Saving in high strength steel can be upto 40% in composite construction.

Method is cost effective for larger spans and taller buildings.