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Progressive Collapse ODrilled Shaft Bridge
Foundation Under VeImpact
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Content
Abstract
Introduction
Site Description
• Piers and superstructure
• Ground conditions
Failure of the bridge under vessel
impact Drilled shafts and columns
Conclusions
References
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Abstract
On 1 !une "##$% a pier of the 1&$ m long !iu'iang (ridge near Gu
*as impacted b+ a vessel,
-he pier being impacted and t*o ad'acent piers collapsed in a se.ue
appro/imatel+ "## m of the bridge dec0 fell into the river,
ach of the three piers *as supported on a 1,$ m diameter% " / " dril
-he simulation model includes all three drilled shaft groups as an int
connected b+ a bridge dec0,
-he bending moment% displacement and soil reaction along the drillecomputed,
-he pier foundation being impacted collapsed 2rst,
-he failure of this pier *as initiated at the connections bet*een the p
drilled shafts and bet*een the pile cap and the pier columns,
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Introduction
(ridge piers ad'acent to navigation channels are usuall+ at ris0 of
collisions b+ errant ships,
Sometimes ships deviate from the navigation channel and collide
channel piers% *hich can lead to catastrophic conse.uences since t
channel piers are often designed *ith a relativel+ small lateral bea
Different structural s+stems e/hibit different degrees of sensitivit+
failure% *hich is often neglected in conventional design anal+sis,
-raditional design usuall+ pa+s more attention to the safet+ of ind
elements than to the safet+ of the entire structural s+stem,
As a result% failure of one member of a bridge s+stem ma+ cause th
collapse of several members or even the *hole s+stem,
-he purpose of this paper is to investigate the s+stem failure mech
foundations under vessel impact,
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6 Site Description
!iu'iang (ridge is part of 4ational 5igh*a+ G6"% *hich crosses
and connects !iu'iang and !iangmen Cit+ in Guangdong Province%
Fig, 1,
It is 1&$ m long and has 86 spans 9Fig, ":,
-he bridge has been on service since !une 1"% 1;
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Site Description7
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8 Site Description
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Piers and superstructure=
Piers no, "6% "8 and " had the same t+pe of structure,
ach consisted of four drilled shafts% t*o columns% one pile cap% an
as sho*n in Fig, 6, In the 2gure% S1% S"% S6% S8% C1 and C" repres
shafts and t*o columns,
-he piers are connected *ith continuous concrete bo/ girders,
-he cross section of the original bridge dec0 is composed of t*o b
9 Site Description
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Ground conditions=
-he site around the collapsed piers is underlain se.uentiall+ b+ a 2
gravell+ sand la+er and slightl+ or moderatel+ decomposed granite
-he ground conditions near Piers no, "6>" are sho*n in Fig, 8, -of the soil la+ers are summari)ed in -able ",
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13 Failure of the bridge under vessel impact
In the earl+ morning of !une 1% "##$% a vessel named ?4angui'i #
cargo of sand stra+ed from the navigation channel and struc0 on P
bridge pier ad'acent to the non3navigation channel,
ost part of the vessel sun0 into the *ater leaving the buttoc0 abo
9Fig, :,
-he vessel *as 1### tons in self *eight and the sand it carried *e
tons,
-he velocit+ of the vessel before impact *as estimated as appro/im
-he accident caused three piers% Piers no, "6% "8% and "% and appr
m bridge dec0 to fall into the river,
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16 Drilled shafts and columns
ach pier includes four drilled shafts% t*o pier columns% one pile c pier cap 9Fig, 6:,
-he dimensions of the cross sections and the arrangement of the st
reinforcement bars are according to the design in Section ",1 ?Pier
superstructure@ and Fig, 6,
-he properties of the concrete and steel reinforcement bars follo*
values,
-he compressive strength is 1&,$ Pa and the elastic modulus is "
-he stress>strain relationship of the steel reinforcement is assume
elastic% perfectl+ plastic,
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17 Conclusions
-he failure process of !iu'iang (ridge on 1 !une "##$ during a ves
is investigated b+ numerical anal+sis, -he main conclusions are as follo*s=
• -he static bearing capacit+ of the piers under static loading eithe
pile cap or pier cap is much smaller than the e.uivalent static lo
the vessel impact calculated using the AAS5-O method,
• -he failure of the pier sub'ected to vessel impact is initiated at th
connection bet*een the columns and the drilled shafts *here themoments are the largest and e/ceed the bending capacities of th
and drilled shafts,
• -he soil reactions are not full+ mobili)ed *hen the impacted pie
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18 Conclusions
• A failure process is proposed based on the results of detailed d+namic progressive failure *as resulted from the separation of structural elem
centrifugal forces of the falling bridge dec0,
• -he dec0 then rotated about one end of the ad'acent pier% *hich genera
centrifugal forces on the ad'acent pier,
• Subse.uentl+% the ad'acent pier *as pulled to failure b+ the centrifugal
leading to the cutoff of the bridge dec0 above the ad'acent pier,
•
In the same *a+% the nearb+ pier *as pulled to failure b+ the centrifugfrom the rotation of the falling bridge dec0,
• Such a progressive failure process stopped *hen a bridge 'oint *as en
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Than !ou
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