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ENCE 717 BRIDGE ENGINEERING
ABUTMENT/PIER DESIGN(Ref: FHWA PSC Girder Design)
C. C. Fu, Ph.D., P.E.The BEST Center
University of MarylandDecember 2008
Integral Abutment Design (1)Pile Cap (7.1.2)
Stage I (noncomposite)PSI = 1.25 x (girder + slab + haunch)
Final Stage (composite)PFNL = 1.25(DC) + 1.50 (DW) + 1.75(LL + IM) (Nlanes)/Ngirders
Pile (7.1.3)Case A – Capacity of the pileCase B – Transfer load to the groundCase C – Ground to support the load(assume rock, only Case A needs to be investigated.)
Integral Abutment Design (2)
Backwall (7.1.4) (80% of simple beam moment)Case A -Pu = 1.5 x (girder + slab)wu = 1.5 x (pile cap + diaphragm)
Case B -PStr-I = factored girder reactionwStr-I = 1.25(pile cap + end diaph. + approach slab) + 1.50 (approach FWS) + 1.75(approach slab lane load) (Nlanes)/Ngirders
Integral Abutment Design (3)
Backwall (7.1.4)Passive pressure -wp = 1/2 x γz2kp
wu = 1.5 x wp
Integral Abutment Design (4)
Wingwall (7.1.5)Passive pressure (kp=3) -wu at bottom of slab=0.2k/ft2; at bottom of wall=3.24 k/ft2
Mp = (Rect. Volume x ½ base length) + (pyramid volume x ¼ base length)
Active pressure (ka = 0.333) –Ma = (ka/kp)*Mp +Mcollision
½ base length
1/4 base length
Integral Abutment Design (5)
Approach Slab (7.1.6)Single lane loadedE = 10 + 5 √(L1W1)
Multiple lane loadedE = 84 + 1.44 √(L1W) ≤ 12W/NL
Mu = wl2/8 + 1.75 (LL+IM Moment)
Intermediate Pier Design (1)
Intermediate Pier Design (2)
Intermediate Pier Design (3)
Longitudinal –Braking force (BR)
Wind load along axes of superstructure
Wind load on sub = Wcap + Wcol
Transverse –Wind load transverse to the
superstructure
Wind load on sub
Wind on live load
Intermediate Pier Design (4)
Moment –σ1, σ2 = P/LW ±
Ml(L/2)(L3W/12)
σ5, σ6 = P/LW ±Mt(L/2)(W3L/12)
Shear –Vux = σ4L2 + 0.5(σ1 – σ4)L2
Vuy = σ8L4 + 0.5(σ5 – σ8)L4
Two-way (punching shear)
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