Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanREPAIR AND RETROFIT OF BRIDGESDAMAGED BYTHE 2010 CHILE MAULE EARTHQUAKE
Shigeki UNJOH11Research Coordinator for Earthquake Disaster Prevention, National Institute for Land andInfrastructure Management, MLIT, Tsukuba, Japan, unjoh-s92ta@nilim.go.jp

ABSTRACT: The Chile Maule earthquake with magnitude 8.8 occurred off the coast ofthe Maule Region of Chile on February 27, 2010. Several bridges were heavily damagedby the strong shaking. Typical and important damage was the rotation and the unseatingof superstructures found at skewed bridges supported by rubber pad bearings. Based onsuch damage experiences, the Chilean Seismic Standards for the Design of Bridges wererevised in June 2010. This paper presents the repair and retrofit of bridges damaged by
the 2010 Chile Maule earthquake with application of the New Seismic Standards.
Key Words: Chile Maule Earthquake, Bridge Damage, Skewed Bridge, SeismicStandard, Repair, Retrofit

INTRODUCTION
The Chile Maule earthquake with magnitude 8.8 occurred off the coast of the Maule Region of Chileon February 27, 2010. Several bridges were heavily damaged including complete collapse by thestrong shaking. Japan Society of Civil Engineers (JSCE) dispatched the reconnaissance team to Chileand the damage investigation was made at 31 sites along Highway Route 5 as well as in cities ofSantiago, Constitucion, Concepcion, and Arauco from March 28 to April 4, 2010, jointly with theChilean Ministry of Public Works (MOP) (Kawashima et. al., 2010a, b).
Typical and important damage was the in-plane rotation and the unseating of superstructures
found at skewed bridges supported by rubber pad bearings. Large rotation displacement wasdeveloped under the strong ground motion. Based on such damage experiences to the skewed bridges,
the “Chilean Seismic Standard for the Design of Bridges” were revised in June 2010, and theunseating prevention concept was employed by reference to the Japanese Seismic Design
Specifications for Bridges (JRA, 2002).
The author visited Santiago and Concepcion, Chile, in February, 2011, just 1 year after theearthquake, as a mission of the JICA short term expert program on “The Project on Capacity Building
to Seismic Events and Tsunamis.” During this occasion, the author visited the bridges which suffereddamage during the 2010 Chile Maule earthquake and were repaired and/or retrofitted after theearthquake.
This paper presents the repair and retrofit of bridges damaged by the 2010 Chile Maule
earthquake with application of the New Chilean Seismic Standards.

1788

LESSONS LEARNED AND REVISION OF CHILEAN SEISMIC STANDARDS
Based on the damage investigation by the JSCE Reconnaissance team (Kawashima, et. al., 2010), thetypical damage was caused by the in-plane rotation of a whole bridge system due to the strong groundmotion. Prestressed concrete girder bridges have been commonly constructed in recent years in Chile.
In particular, as for the bridges constructed in concessions after the mid-1990s, the diaphragms toincrease the integrity of superstructures and the effective stopper mechanism have been eliminated forthe structural simplicity. Therefore, there was no effective structure to resist large lateral displacementof superstructures and the resulting unseating from substructures against the strong shaking. It should
be noted here that the girders have been supported by rubber pad bearings without any stiff connection
including anchors between superstructures and substructures. The girders were relatively easy to moveat bearing supports against the strong shaking.
Such damage caused by the in-plane rotation was particularly extensive in skewed bridges. Thelarge rotation motion was developed due to the unbalanced restraint effect by the interaction between
superstructure and abutment. The bridges suffered unseating of superstructures from substructures
and/or the significant damage at the end of concrete girders. Photo 1 shows a typical collapse ofsuperstructure and damage of concrete girder.
On the other hand, the bridges designed based on the original Chilean design practice including
the placement of end diaphragms and lateral stoppers behaved very well even against the strong
shaking as shown in Photo 2. It should be noted here that some bridges were damaged in coastal
region where soil instability including soil liquefaction and lateral spreading was observed.

Photo 1 Typical Collapse and Damage of Concrete Girders during 2010 Chile Maule Earthquake(Courtesy of Chilean Ministry of Public Works)(Left: Collapse of Superstructures due to Rotation, Right: Damage at End of Concrete Girder)

Photo 2 Bridges designed by Original Chilean Practice with End Diaphragms
and Lateral Stopper Mechanism

1789Based on such critical damage experiences, the Road Administration of the Chilean Ministry ofPublic Works (MOP) revised “the Chilean Seismic Design Standards for the Design of Bridges” inJune 2010, about 3 months after the earthquake. The new aspects learned from the damage have been
incorporated into the revision as immediate and medium term measures to improve the seismic
performance of bridges.
Fig. 1 shows the copies of the seismic provisions on the unseating prevention measures
including minimum seat width and lateral stopper specified in the new seismic standards. The newly
specified provisions were based on the “Japanese Specifications for Highway Bridges, Part V. SeismicDesign, 2002.” The formula to calculate the minimum seat width and the stopper structures were fromthe Japanese Standard.
The repair and the reconstruction of the damaged bridges were made according to the newseismic design standard.

Fig. 1 Specified Unseating Prevention Mechanismin the New Seismic Standards for the Design of Bridges in Chile which revised in June, 2010

1790

BRIDGE DAMAGE AND THE REPAIR/RETROFIT
Fig. 2 shows the locations of bridges damaged during 2010 Chile Maule earthquake investigated by
the JSCE reconnaissance team (Kawashima et. al., 2010a, b). The author investigated the repair andreconstruction works for some of the damaged bridges in February, 2011. The investigation was madefor the bridges with red-colored underlines in cities of Santiago and Concepcion as shown in Fig. 2. In
total, the repair and reconstruction of 12 bridges were investigated, in which 2 bridges were notinvestigated by the JSCE reconnaissance team in 2010.
In this paper, the typical damage and the employed repair methods are presented for someselected bridges.

Fig. 2 Locations of Bridges damaged during 2010 Chile Maule Earthquake (Kawashima et. al.,2010a, b) (Repair/Retrofit was investigated for bridges with red-colored underlines in February, 2011)

Overpass in Santiago
Mira Flores and Lo Echeveres Overpasses
There is the Metropolitan freeway network in Santiago city. The network consists of a ring highway
and trunk highways in a radial pattern. The critical damage including collapse of superstructures
occurred on the network. The typical damage was found at Mira Flores and Lo Echeveres overpasses.
The outer and inner ring bridges of Mira Flores overpass collapsed. They were 22.5m+28m+22.5m
long 3-span simply-supported PC girder bridges with a skew angle of 68 degrees. Similarly, the innerring bridge of Lo Echeveres overpass collapsed as well. It was a 92m long 3-span simply-supported

1791

PC girder bridge with a skew angle of 60 degrees. Two overpasses had almost similar structuralcharacteristics.
During the earthquake, the acute corner of the superstructures was offset nearly 1.5-2.0m in thetransverse direction and unseated from the abutments. There was almost no significant damage toabutment walls and piers.
To repair the bridges, the collapsed superstructures were replaced by new PC girders. Based on
the new seismic standards, the lateral beams to connect adjacent girders were placed at the girder ends
and the concrete block type stoppers were installed between the girders at the cap beam. Photos 3 and4 show the repaired abutments and piers of Mira Flores overpass and Lo Echeveres overpass,
respectively. It should be noted hear that the widening of the seat width as well as the installation of
the stoppers was also made at the abutment of Lo Echeveres overpass.

Photo 3 Repair and Retrofit for Mira Flores Overpass(Left: Lateral Stopper at Abutment, Right: Lateral Beam and Lateral Stopper at Pier)

Photo 4 Repair and Retrofit for Lo Echeveres Overpass(Left: Lateral Stopper at Abutment, Right: Lateral Beam and Lateral Stopper at Pier)

Antonio Matta Bridge
Photo 5 shows the collapse of Antonio Matta Bridge. The bridge is on the Manuel Antonio Matta Street
which overpasses the Linea de Ferroccarril Railroad. Superstructure consisted of 3-span simply-supportedsteel girders and the continuous slab at joints. The skewed angle was about 50 degrees. The piers werereinforced concrete multi-column bent. The steel girders were supported by rubber pad bearings.
During the earthquake, a whole bridge was rotated and the large transverse displacement wasdeveloped at both ends, then the superstructures were unseated from their abutments. The displacement in1792

the transverse direction at the abutment was about 90cm. In contrast, there was almost no damage to thereinforced concrete columns. The collapse mechanism is similar to that found at Mira Flores and Lo
Echeveres overpasses.
Photo 6 shows the completion of repair for Antonio Matta Bridge. The existing steel girders
were reused. At the abutments and piers, the stopper structures using concrete blocks were provided
and the seat width was widened at the abutments as well.

Photo 5 Collapse of Antonio Matta Bridge(Left: Side View, Right: Skewed Seat at Abutment)

Photo 6 Repair and Retrofit for Antonio Matta Bridge(Left: Abutment with Lateral Stopper, Right: Pier Cap with Lateral Stopper)
Overpass on Highway Route 5Las Mercedes Bridge
The rotation of a whole bridge occurred not only in skewed bridges but also in straight bridges. Las
Mercedes bridge which crossed over Highway Route 5 was also heavily damaged due to the rotation.
Las Mercedes Bridge was a 54m long 2-span simply-supported PC girder bridge with connecting deckslab at center pier joint. The length and the structural properties were typical for the overpasses on
Highway Route 5. The skew angle was 79 degrees, it was an almost straight bridge. PC girders weresupported by rubber pad bearings without any stiff connection between superstructures andsubstructures.
During the earthquake, Las Mercedes bridge rotated around the center pier resulting intransverse displacement around 1.0-1.4m at both ends. Photo 7 shows the unseated PC girders at theabutment. There was evidence of the collision between the end of a deck slab and the abutment
parapet wall at both ends.

1793

Photos 8 and 9 show the repair and retrofit of Les Mercedes bridge. Both the end sections ofconcrete girders were repaired and strengthened by adding reinforced concrete to increase the lateralshear strength of the web and flange. Also, lateral beams to connect adjacent girders were placed at thegirder ends. The seat width was widened by adding the reinforced concrete at the abutments, and thelateral stoppers made of concrete block were installed at both abutments and pier cap.
The similar repair and/or retrofit methods were employed for several overpasses on Highway
Route 5. Photo 10 shows Los Pinos overpass. The lateral beams and lateral stopper were installed at
the abutments and piers. It should be noted here that Chilean MOP also employed the strengthening
method for the abutments which were constructed on soft soil ground condition. Photo 11 shows
Azufradero bridges as an example of the strengthening method for the abutment. Removing thebackfill soils, and vertical walls were added to increase the stiffness and stability of abutment wallsand foundations.

Photo 7 Damage of Les Mercedes Bridge(Left: Side View, Right: Lateral Offset at Abutment)

Photo 8 Repair and Retrofit for Les Mercedes Bridge (1)(Left: Strengthening of PC Web, Right: Widening of Seat Width at Abutment)

Photo 9 Repair and Retrofit for Les Mercedes Bridge (2)(Left: Lateral Stopper at Abutment, Right: Lateral Beams and Lateral Stoppers at Pier)

1794

Photo 10 Repair and Retrofit for Los Pinos Bridge(Left: Side View, Right: Lateral Beams and Lateral Stoppers at Pier Cap)

Photo 11 Repair and Retrofit for Azufradero Bridge(Left: Damage to Girders and Abutment, Right: Stiffening Wall at Backside of Abutment)

Hospital Overpass
One of the typical examples of collapse due to the rotation of skewed bridges was Hospital overpass
on Highway Route 5 at the crossing over railways and a local road. It was a 2-span simply-supported
PC girder bridge with deck slab which connected two spans. There were two overpasses to thenorth-bound and to the south-bound. The north-bound overpass collapsed as shown in Photo 12,
whereas the south-bound overpass suffered almost no damage. The south-bound overpass was
relatively old and designed based on the original Chilean design practice, in contrast, the north-boundoverpass was recently designed bridge. It should be noted here the skewed angle of the collapsed
north-bound overpass was 45 degrees, on the other hand, the south-bound overpass was a straightbridge. Both abutments did not suffer damage and pier suffered only minor flexural cracks at thecolumns.
Photo 13 shows the reconstruction of Hospital overpass. The collapsed concrete girders werereplaced by new steel girders. The end lateral beams were provided to connect adjacent girders and thelateral stoppers were provided at the abutments and piers.

1795

Photo 12 Collapse of Spans at Hospital Overpass

Photo 13 Reconstruction and Retrofit of Hospital Overpass(Left: Side View, Right: Lateral Stopper at Cap Beam of Pier)

Bridges in Concepcion
Juan Pablo II Bridge
Juan Pablo II bridge is a 2,310m long 70-span simply-supported bridge which crosses over Biobio
river in Concepcion city. The concrete superstructures were supported by reinforced concrete piers.
Extensive settlement as large as 0.5m occurred at pier foundations and 3 reinforced concrete columns
and a lateral cap beam failed in shear as shown in Photo 14. The settlement of pier foundations wasestimated to be developed due to the insufficient bearing capacity as well as the effect of soilliquefaction.
Photo 15 shows the repair and retrofit of Juan Pablo II bridge. Additional piles were placed at
the both sides of settled piers to support the superstructures. The failed reinforced columns in shear
were reconstructed. The lateral stoppers were also provided at the pier cap.
Llacolen Bridge
Similar to Juan Pablo II bridge, Llacolen bridge is a critically important bridge crossing Biobio river inConcepcion city. Main spans in the river section did not collapse, but an approach span consisting ofPC girders collapsed as shown in Photo 16. Short seat support width resulted in unseating of theapproaching span against large longitudinal displacement caused by the strong shaking. Photos 17 and18 show the replaced span of Llacolen bridge and the retrofit. Collapsed concrete girders werereplaced by the steel girders which were connected by lateral beams at both ends.

1796

Photo 14 Damage of Juan Pablo II Bridge(Left: Settlement of Pier Foundation, Right: Shear Failure of Pier Columns)

Photo 15 Repair and Retrofit of Juan Pablo II Bridge(Left: Additional Piles at settled Piers, Right: Replaced Pier Columns and Lateral Stopper Structures)

The lateral stoppers were provided at the pier caps. The seat supports was also widened byadding reinforced concrete. Some of the reinforced concrete columns were jacketed by fiber sheets torepair the flexural cracks and to enhance the shear and ductility capacity. It should be noted that a newbridge was also under construction to cross Biobio river in Concepcion city as shown in Photo 19.

Photo 16 Collapse of Llacolen Bridge

Photo 17 Replaced Collapsed Span of Llacolen Bridge

1797

Photo 18 Repair and Retrofit for Llacolen Bridge(Left: Placement of Lateral Beams and Lateral Stoppers, Right: Widening of Pier Cap and Retrofitted
Column by Fiber-Sheet Jacketing)

Photo 19 New Bridge Construction (Chacabuco Bridge) to cross BioBio River
La Mochita Bridge
La Mochita bridge is a 4-span simply-supported PC girder bridge which crosses a waterway along theBioBio river. The piers were two column bents. During the earthquake, the large lateral displacement of thesuperstructures as large as 85 cm was developed as shown in Photo 20. Several cracks were found on theground surface around the foundations. The foundations were estimated to move laterally because of thelateral spreading of the surrounding soils. Since sand boiling was found at several locations on thesurrounding ground, the lateral spreading was estimated to be caused by the effect of soil liquefaction.

Photo 20 Lateral Displacement of Superstructure and Foundations at La Mochita Bridge

1798

Photo 21 shows the repair and retrofit for La Mochita bridge. The displaced deck was moved
back to the original position and the lateral stoppers were installed at the top of abutments and piers.
The two column bents were strengthened to wall type columns and new piles to increase stability wereplaced and connected the existing columns.

Photo 21 Repair and Retrofit for La Mochita Bridge(Left: Pier Cap with Lateral Stopper, Right: Strengthening of Foundations by Placing New Piles)

CONCLUSIONSThis paper presented the repair and retrofit of bridges damaged by the 2010 Chile Maule earthquakewith application of the New Chilean Seismic Standards for the Design of Bridges. Basic concept of therepair and retrofit measures were to increase the integrity of girders by adding the end lateral beams
and to restrain the lateral displacement by providing with the unseating structures. Strengthening
measures by constructing new piles and walls to the foundations were also employed for the bridges
on the soft soil ground conditions to increase the stability of foundations against the effect of soilliquefaction.

ACKNOWLEDGMENTS
The damage investigation in February 2011 was supported by the Chilean Ministry of Public Works,
Embassy of Japan, and Japan International Cooperation Agency (JICA). Special appreciations areextended to Mr. R. Gonzalez and Ing. M. Guzman of Chilean Ministry of Public Works for their kindarrangement to the damaged and repaired/retrofitted bridge sites. The photos of damaged bridges
shown in this paper were taken by the Structure Group of the JSCE Reconnaissance Team. Prof. K.
Kawashima of Tokyo Institute of Technology, Prof. K. Kosa of Kyusyu Institute of Technology andDr. J. Hoshikuma of Public Works Research Institute are greatly appreciated

REFERENCES
Japan Road Association (JRA). (2002). “Design specifications of bridges, Part V. Seismic design.”
Kawashima, K., Unjoh, S., Hoshikuma, J and Kosa, K. (2010a). “Damage of bridges due to the 2010
Maule, Chile, Earthquake.” Report of Japan Society of Civil Engineers.
Kawashima, K., Unjoh, S., Hoshikuma, J and Kosa, K. (2010b). “Damage of bridges due to the 2010
Maule, Chile, Earthquake.” Journal of Earthquake Engineering, 15:7, 1036-1068.
Chilean Ministry of Public Works (MOP) (2010). “New seismic standards for the design of bridges inChile.”

1799