( LONGITUDINAL REINFORCEMENT IN SIMPLE BEAMS Simple beams (also simple slabs,joisis, and girders) supponing loads usumc the dellceled shape as shown in Fig. 6-7. loads Longitud inal Steel loaded Member Deflected Sl\ope Fig. 5.. 7 Simplo Beam The top of the beam is in compression (pushing tog<:lber action) and the bot­ tom ill in tem,ion (pulling apart action). so lo11gitudinn1 reinforcing 5teel is located near the bottom to prevent failure of tbe concrete in tension. STIRRUPS IN BEAMS When a beam deflects under a loac\ shear stre SSes are al~o presen L es1~'t the d1agpnal tecsion, small U-sbaped ot closed-shape reinforcing baxs called stirrups a. re used and arc placed venienlly across the beom. Waft Load. son Bam Stirrups Possible shear cracks at ab OUt 4S0 angle Fig. 6-8 Stirrups in a Beam ti wan Because shear is usually at a max..imum near the support and decreases toward mid-i;pon, the stirrups llt C mor,, closely spaced near lhc support and spaced increasingly tiuther aparl towanl mid-span, as shown in Fig. 6-8. Concrete is able to rcsisl some shear thus stirrups arc occasionally omiacd near mid-span. Welded wire reinforcement cages can also be used instead of reinfordng bar stirrups to resist shear stresses. 6-4 Concre<e Re;nforang Steel lnoti Me Section 609 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 6-9