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)