Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

PUBLICATION NO. FHWA-HRT-22-110 MARCH 2023 

Performance of Transportation 

Infrastructure During Kumamoto 

Earthquakes of April 14 and 16, 2016—

A Reconnaissance Report
FOREWORD

Determining the engineering performance of the highway infrastructure, especially following 

extreme events, is key to improving design and construction practices, thereby providing 

improved safety to the traveling public. On April 14 and 16, 2016, the Kumamoto Prefecture on 

the Japanese island of Kyushu experienced two very large earthquakes, a magnitude 6.5 followed 

28 h later by a magnitude 7.3. These earthquakes caused extensive damage to the built 

infrastructure, including the transportation infrastructure. At the request of Japan, the Federal 

Highway Administration organized a Transportation Infrastructure Reconnaissance Team to 

assess damage to bridges and other highway structures. This report presents the findings of the 

team during the reconnaissance. It describes the performance of new bridges that had been 

recently designed and older bridges that had been retrofitted for earthquakes. 

This report will be useful to bridge owners, practicing engineers, and researchers. Lessons 

learned will be useful for improving the resilience of bridges so that lives may be saved in future 

extreme events.

Cheryl Allen Richter, P.E., Ph.D. 

Director, Office of Infrastructure Research and 

Development 

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use of 

the information contained in this document. This report does not constitute a standard, 

specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers' names appear in this report only because they are considered essential to the 

objective of the document. 

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement.

.
TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-HRT-22-110

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Performance of Transportation Infrastructure During 

Kumamoto Earthquakes of April 14 and 16, 2016—A 

Reconnaissance Report

5. Report Date

March 2023

6. Performing Organization Code: 

7. Author(s)

Ron Bromenschenkel, Ian G. Buckle, Jim Cuthbertson, 

Sheila Rimal Duwadi, Denis Istrati, and David H. Sanders 

8. Performing Organization Report No.

9. Performing Organization Name and Address

Turner-Fairbank Highway Research Center

Federal Highway Administration

6300 Georgetown Pike, McLean, VA 22101

Department of Civil and Environmental Engineering

University of Nevada Reno

1664 N. Virginia Street

Reno, NV 89557

Geotechnical Office

Washington State Department of Transportation 

310 Maple Park Avenue SE

P.O. Box 47300

Olympia, WA 98504

Office of Earthquake Engineering

California Department of Transportation

P.O. Box 942873

Sacramento, CA 95816

10. Work Unit No.

11. Contract or Grant No.

DTFH61-07-00031

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development

Federal Highway Administration

6300 Georgetown Pike, McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report; July 2016

14. Sponsoring Agency Code

HRDI-30

15. Supplementary Notes

The Contracting Officer’s Representative was Jamie Harris (HRDI-30).

16. Abstract

This report described a reconnaissance effort to document bridge performance during the Kumamoto earthquakes 

in Japan in April 2016. More than 180 bridges were damaged by these earthquakes. Of particular interest is the 

performance of bridges that were relatively new (15–20 yr old) or recently retrofitted. Damage sustained was 

significant and included bearing and shear key failures, distortion and local buckling of the steel superstructures, 

and foundation movement. Most of the damage could be attributed to extensive slope failures and intense shaking 

close to the causative fault. Recommendations for improving bridge performance in future earthquakes are given. 

17. Key Words

Seismic performance, new bridges, retrofitted 

bridges, ground motion, ground failures, 

reconnaissance

18. Distribution Statement: No restrictions. This document 

is available through the National Technical Information 

Service, Springfield, VA 22161.

http://www.ntis.gov

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

131

22. Price

N/A

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized. 
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iii

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION ................................................................................................. 1

Background ............................................................................................................................... 1

Transportation Infrastructure Reconnaissance Team ......................................................... 3

Objective .............................................................................................................................. 3

Team Members ..................................................................................................................... 3

Reconnaissance Schedule ..................................................................................................... 5

Report Organization ................................................................................................................ 6

CHAPTER 2. GEOLOGY, SEISMOLOGY, AND GROUND MOTIONS.............................. 7

Background ............................................................................................................................... 7

Geology and Seismology ........................................................................................................ 10

Tectonic Framework........................................................................................................... 10

Seismic Source Zones ........................................................................................................ 11

Surface Geology ................................................................................................................. 15

Ground Motions ................................................................................................................. 15

CHAPTER 3. SEISMIC DESIGN REQUIREMENTS FOR BRIDGES IN JAPAN ............ 21

Background ............................................................................................................................. 21

1996 JRA Seismic Design Specifications .............................................................................. 22

2002 JRA Seismic Design Specifications .............................................................................. 23

2012 JRA Seismic Design Specifications .............................................................................. 25

CHAPTER 4. STRUCTURAL PERFORMANCE OF HIGHWAY BRIDGES .................... 27

Introduction ............................................................................................................................ 27

Recently Constructed Bridges ............................................................................................... 29

Ookirihata Oh-hashi Bridge ............................................................................................... 29

Ookirihata Dam Bridge ...................................................................................................... 44

Kuwazuru Oh-hashi Bridge ................................................................................................ 48

Susukinohara Bridge .......................................................................................................... 57

Tawarayama Oh-hashi Bridge ............................................................................................ 64

Ooginosaka Bridge ............................................................................................................. 73

Retrofitted Bridges ................................................................................................................. 79

Minami Aso Bridge ............................................................................................................ 79

Kiyama River Bridge.......................................................................................................... 83

Akitsu River Bridge............................................................................................................ 94

Higashibaru Bridge............................................................................................................. 98

Other Bridges ........................................................................................................................ 108

Aso Oh-hashi Bridge ........................................................................................................ 108

CHAPTER 5. LESSONS LEARNED AND RECOMMENDATIONS ................................. 115

Background ........................................................................................................................... 115

Lessons Learned and Recommendations ........................................................................... 116

ACKNOWLEDGMENTS.......................................................................................................... 119

REFERENCES ........................................................................................................................... 121
iv

LIST OF FIGURES

Figure 1. Map. Tectonic map of Japan. ............................................................................................ 1

Figure 2. Map. Epicentral region of Kumamoto earthquakes, Japan. .............................................. 2

Figure 3. Map. Epicentral region of Kumamoto earthquakes, Kyushu............................................ 2

Figure 4. Map. Location of bridges visited by the Reconnaissance Team. ...................................... 6

Figure 5. Map. Epicenter location of the April 14, 2016, Mw 6.2 Kumamoto earthquake 

(USGS n.d.). ........................................................................................................................... 7

Figure 6. Map. Epicenter location of the April 16, 2016, Mw 7.0 Kumamoto earthquake 

(USGS n.d.). ........................................................................................................................... 8

Figure 7. Map. Japan’s plate structure, relative motion (in millimeters), and seismic hazard 

(Rhea et al. 2010). ................................................................................................................. 11

Figure 8. Map. Fault traces in the Kumamoto Prefecture. ............................................................. 12

Figure 9. Map. JMA seismic intensity for April 14 Mw 6.2 foreshock. ........................................ 14

Figure 10. Map. JMA seismic intensity for April 16 Mw 7.0 main shock..................................... 14

Figure 11. Graphs. Acceleration response spectra at Mashiki Town for April 16 Mw 7.0 

main shock. ........................................................................................................................... 18

Figure 12. Graphs. Acceleration response spectra for Nishihara Village for April 16 Mw 7.0 

main shock. ........................................................................................................................... 19

Figure 13. Map. Location of damaged bridges described in this chapter and proximity to the 

Futagawa fault. ..................................................................................................................... 29

Figure 14. Photo. Aerial view of Ookirihata Oh-hashi bridge and nearby area. ............................ 30

Figure 15. Drawing. Elevation of Ookirihata Oh-hashi bridge. ..................................................... 30

Figure 16. Photo. Slope on the south side of the bridge before the earthquake. ............................ 31

Figure 17. Photo. Slope on the south side of the bridge after the earthquake. ............................... 31

Figure 18. Photo. Walls and remnants of the old road on the south side of the bridge.................. 32

Figure 19. Photos. Offset of the superstructure at abutment A1. ................................................... 33

Figure 20. Photos. Offset of the superstructure at abutment A2. ................................................... 34

Figure 21. Photos. Bearing failure below each girder starting from the outside girder G1 to 

the inside girder G5 at abutment A1. .................................................................................... 37

Figure 22. Photos. Rupture of longitudinal restrainers at abutment A1. ........................................ 38

Figure 23. Photo. Abrasion on the back wall of abutment A1. ...................................................... 38

Figure 24. Photo. Damage in girder-to-diaphragm connection at abutment A1. ........................... 39

Figure 25. Photo. Offset of superstructure at piers P3 and P4. ...................................................... 39

Figure 26. Photos. Elastomeric bearing at pier P4. ........................................................................ 40

Figure 27. Photo. Elastomeric bearing at pier P1. .......................................................................... 41

Figure 28. Photo. Cracks at the base of pier P2. ............................................................................ 41

Figure 29. Photos. Damaged expansion joint at abutment A2. ...................................................... 42

Figure 30. Photo. Failed bearing below girder G1 at abutment A2. .............................................. 43

Figure 31. Photos. Damage to elastomeric bearing and stiffener at girder G5 at 

abutment A2.......................................................................................................................... 44

Figure 32. Drawing. Elevation of Ookirihata Dam bridge. ............................................................ 45

Figure 33. Drawing. Soil profile at the site of Ookirihata Dam bridge.......................................... 45

Figure 34. Photos. Approach fill movement at the abutment. ........................................................ 46

Figure 35. Photos. Approach fill movement at the abutment. ........................................................ 47

Figure 36. Drawing. Elevation and plan of Kuwazuru Oh-hashi bridge........................................ 48
v 

Figure 37. Photo. Kuwazuru Oh-hashi bridge looking NE. ........................................................... 49

Figure 38. Photos. Damage to steel bearings at abutment A1. ....................................................... 50

Figure 39. Photo. Damaged restrainers at abutment A1. ................................................................ 51

Figure 40. Photo. Expansion joint at abutment A1. ....................................................................... 51

Figure 41. Photo. Damage to steel bearings at abutment A2. ........................................................ 52

Figure 42. Photo. Center pier of Kuwazuru Oh-hashi bridge. ....................................................... 53

Figure 43. Photo. Distance from the bridge rail to the east tower leg. ........................................... 53

Figure 44. Photo. Distance from the bridge rail to the west tower leg. .......................................... 54

Figure 45. Photos. Damage to the east side and west side support blocks at the center pier. ........ 55

Figure 46. Photo. Cable damage. ................................................................................................... 56

Figure 47. Photo. Cable extension.................................................................................................. 56

Figure 48. Map. Location of Susukinohara bridge. ........................................................................ 57

Figure 49. Drawing. Elevation, plan, and cross sections of Susukinohara bridge. ........................ 58

Figure 50. Photo. Susukinohara bridge showing concrete T-girder superstructure with 

diaphragms............................................................................................................................ 59

Figure 51. Photo. Distant view of damaged approach at the west abutment. ................................ 60

Figure 52. Photo. Close-up view of damaged approach at the west abutment............................... 61

Figure 53. Photo. Longitudinal and lateral movement at the east abutment. ................................. 61

Figure 54. Photo. Rotation of an elastomeric bearing. ................................................................... 62

Figure 55. Photo. Timber blocks being used for additional support of girders at abutment 

seats....................................................................................................................................... 62

Figure 56. Photo. Damaged end diaphragm at the east abutment and dislodged timber block 

from under the second girder from the left. .......................................................................... 63

Figure 57. Photo. Crushing of the end diaphragm at the east abutment......................................... 63

Figure 58. Map. Location of Tawarayama Oh-hashi bridge. ......................................................... 64

Figure 59. Drawing. Elevation of Tawarayama Oh-hashi bridge. ................................................. 65

Figure 60. Photo. Tawarayama Oh-hashi bridge looking east. ...................................................... 65

Figure 61. Photo. Failure of the west approach.............................................................................. 66

Figure 62. Photo. Rotation of the west abutment. .......................................................................... 66

Figure 63. Photo. Pounding at the west abutment and permanent bearing deformation. ............... 67

Figure 64. Photo. Buckled girder flange and web. ......................................................................... 67

Figure 65. Photo. Vertical offset at the east abutment between the bridge and approach 

pavement. .............................................................................................................................. 68

Figure 66. Photo. Lateral movement of a girder and bearing at the east abutment. ....................... 68

Figure 67. Photo. Failure of a bearing stopper at the east abutment. ............................................. 69

Figure 68. Photo. Out-of-plane buckling of the lower chord brace. .............................................. 69

Figure 69. Photo. In-plane buckling of lower chord braces. .......................................................... 70

Figure 70. Photo. Longitudinal restrainer unable to prevent girder unseating transversely, as 

might be expected. ................................................................................................................ 70

Figure 71. Photo. Elastomeric bearing and transverse stopper at the east abutment showing 

rotation of the bearing and implied bolt fractures in anchor plates. ..................................... 71

Figure 72. Photo. Permanent deformation in the elastomeric bearing on pier P1. ......................... 72

Figure 73. Photo. Permanent lateral movement of the superstructure and girder unseating on 

pier P2. .................................................................................................................................. 72

Figure 74. Photo. Undamaged connection detail for lower chord bracing..................................... 73
vi 

Figure 75. Photo. Ooginosaka bridge from the south approach showing left lateral offset at 

the abutment. ......................................................................................................................... 74

Figure 76. Photo. Finger joint relocking. ....................................................................................... 74

Figure 77. Photo. North abutment with easterly superstructure shift. ............................................ 75

Figure 78. Illustration. Potential rotation of superstructure creating observed abutment 

offsets. ................................................................................................................................... 75

Figure 79. Photos. Offset at the pier cap for piers P2 and P3. ....................................................... 76

Figure 80. Illustration. Directions of substructure movement necessary to explain observed 

bearing displacements at each location. ................................................................................ 77

Figure 81. Photo. Gap at the top of superposed column profiles, looking south. .......................... 78

Figure 82. Photo. Gap at the bottom of superposed column profiles, looking north. .................... 78

Figure 83. Photo. South abutment shear key damage. ................................................................... 79

Figure 84. Photo. West side of Minami Aso bridge viewed from the south abutment wing 

wall. ...................................................................................................................................... 80

Figure 85. Photo. Damage to the anchorage of longitudinal damper and shear key on the 

west side of the south abutment. ........................................................................................... 81

Figure 86. Photo. Damage to the anchorage of the longitudinal damper and shear key on the 

east side of the south abutment. ............................................................................................ 81

Figure 87. Photo. Longitudinal damper on the east side of the north abutment. ........................... 82

Figure 88. Photo. Damage to the shear key block on the east side of the north abutment. ............ 82

Figure 89. Photo. Damage to the shear key block on the west side of the north abutment. ........... 83

Figure 90. Drawing. Elevation and plan of Kiyama River bridge from pier P7 to pier P12 

(NILIM 2017). ...................................................................................................................... 84

Figure 91. Drawing. Cross section through the east and west bridges from pier P7 to pier 

P12 (NILIM 2017). ............................................................................................................... 85

Figure 92. Photo. Opening of the expansion joint at pier P12 of the east bridge. .......................... 86

Figure 93. Photo. Misalignment of consecutive spans at pier P12 of the east bridge. ................... 86

Figure 94. Photos. Temporary support systems at pier P12 of the east bridge. ............................. 88

Figure 95. Photo. Side view of tilted pier P11. .............................................................................. 89

Figure 96. Photos. Exposed column-to-pile cap connection at pier P11 of the east bridge. .......... 90

Figure 97. Photos. Gap opening between the bottom of both columns and the top of the pile 

cap at pier P11 of the east bridge. ......................................................................................... 91

Figure 98. Photo. View into the gap at the column-pile cap connection at pier P11 of the 

east bridge. ............................................................................................................................ 91

Figure 99. Photo. Failed bearing connection under the west girder at pier P10 of the east 

bridge. ................................................................................................................................... 92

Figure 100. Photo. Failed bearing connections under interior girders at pier P10 of the east 

bridge. ................................................................................................................................... 93

Figure 101. Photo. Failed bearing connection under the east exterior girder at pier P10 of 

the east bridge. ...................................................................................................................... 93

Figure 102. Drawing. Elevation and plan of Akitsu River bridge. ................................................ 94

Figure 103. Photo. General view of abutment A1. ......................................................................... 95

Figure 104. Photo. Side view of abutment A1. .............................................................................. 95

Figure 105. Photo. Vertical cracks in the seat of abutment A1. ..................................................... 96

Figure 106. Photo. Damaged expansion bearing and girder at abutment A1................................. 97

Figure 107. Photo. Bridge approach replacement. ......................................................................... 98
vii 

Figure 108. Map. Location of Higashibaru bridge. ........................................................................ 99

Figure 109. Drawing. Elevation and plan of Higashibaru bridge. ............................................... 100

Figure 110. Photos. Higashibaru bridge before the earthquake. .................................................. 101

Figure 111. Photos. Another bridge with pin-pin columns near Higashibaru bridge. ................. 102

Figure 112. Photos. Inclination of pinned columns after the earthquake. .................................... 104

Figure 113. Photos. Shear key damage at abutment A2. .............................................................. 105

Figure 114. Photos. Side view shear key damage at abutment A2. ............................................. 106

Figure 115. Photo. Repaired piers. ............................................................................................... 107

Figure 116. Photos. Repaired abutment A2. ................................................................................ 108

Figure 117. Map. Location of Aso Oh-hashi bridge. ................................................................... 109

Figure 118. Drawing. Elevation of Aso Oh-hashi bridge. ............................................................ 109

Figure 119. Photo. Side view before the earthquake. ................................................................... 110

Figure 120. Photo. Remainder of the approach slab at the east abutment. .................................. 111

Figure 121. Photo. Remainder of the east abutment and unseated first span. .............................. 111

Figure 122. Photo. Unseated first span below the east abutment. ................................................ 112

Figure 123. Photo. Seat and back wall of the east abutment and remainder of the expansion 

joint. .................................................................................................................................... 112

Figure 124. Photo. Landslide upstream of the west abutment across the gorge causing 

bridge collapse. ................................................................................................................... 113
viii

LIST OF TABLES

Table 1. U.S. and Japan Reconnaissance Team for the Kumamoto earthquake bridge 

damage investigation. ............................................................................................................. 4

Table 2. Schedule. ............................................................................................................................ 5

Table 3. JMA Shindo scale of earthquake intensity (JMA n.d.). ..................................................... 9

Table 4. Earthquakes exceeding JMA seismic intensity level 6 since April 14, 2016 

(JMA 2016). .......................................................................................................................... 13

Table 5. NIED seismic stations in Kumamoto Prefecture and their locations. .............................. 16

Table 6. Seismic performance matrix (Kawashima and Unjoh 2004). .......................................... 24

Table 7. Seismic performance criteria (Kawashima and Unjoh 2004). ......................................... 24

Table 8. List of bridges visited and damage sustained. .................................................................. 28
ix

LIST OF ABBREVIATIONS

EW east-west

FHWA Federal Highway Administration

JMA Japan Meteorological Agency

JRA Japan Road Association 

JST Japan Standard Time 

KiK-net Kiban Kyoshin 

K-NET Kyoshin 

M magnitude 

MLIT Ministry of Land, Infrastructure and Transport, and Tourism 

Mw moment magnitude 

NE northeast 

NIED National Research Institute for Earth Science and Disaster Resilience

NILIM National Institute for Land and Infrastructure Management

NS north-south 

NW northwest 

PSP Philippine Sea 

PWRI Public Works Research Institute 

SE southeast 

SPL seismic performance levels

SW southwest 

USGS U.S. Geological Survey 

UTC Coordinated Universal Time 

yBP years before present

1 

CHAPTER 1. INTRODUCTION

BACKGROUND 

Japan is situated near the intersection of the Eurasia, Philippine Sea (PSP), Pacific, and North 

American Plates (figure 1). Japan is, therefore, susceptible to earthquakes. On April 14 and 16, 

2016, the Kumamoto Prefecture on the island of Kyushu experienced two very large earthquakes, 

a magnitude (M) of 6.5 followed 28 h later by a M7.3. These earthquakes occurred several 

hundred kilometers northwest (NW) of the Ryukyu Trench, where the PSP begins its 

northwestward subduction beneath Japan and the Eurasia Plate (figure 2 and figure 3). Movement 

occurred on two mapped fault zones, Futagawa and Hinagu, as discussed in detail in chapter 2. 

The faults in the region generally trend east-west (EW) or northeast (NE)-southwest (SW). The 

strongest shaking was reported in the EW direction for the two earthquakes, with significant 

vertical, in addition to horizontal, acceleration. Peak motions exceeded design acceleration 

response spectra over a certain range of the natural period. The result was permanent horizontal 

and vertical ground displacement of 1–2 yd (1–2 m). 

Source: U.S. Geological Survey (USGS). 

Figure 1. Map. Tectonic map of Japan. 
2 

Source: USGS. 

Figure 2. Map. Epicentral region of Kumamoto earthquakes, Japan. 

Source: USGS. 

Figure 3. Map. Epicentral region of Kumamoto earthquakes, Kyushu. 
3 

In terms of lives impacted, the April 14 foreshock resulted in at least 9 fatalities and 1,108 

injuries, and the April 16 main shock resulted in 40 fatalities and 2,021 injuries. Many homes in 

the Kumamoto Prefecture were damaged or destroyed. In addition, reports from Japan described 

significant damage to highway infrastructure. Immediate investigation by the National Institute 

for Land and Infrastructure Management (NILIM) and the Public Works Research Institute 

(PWRI) revealed strong ground motions equivalent to or greater than the ground motions 

recorded during the January 1995 earthquake near the city of Kobe (population 1.5 million) that 

killed over 5,000 people. Japan invested heavily in research and development after the Kobe 

earthquake, resulting in significant changes to seismic design specifications and retrofit 

procedures. The performance of structures during the Kumamoto earthquakes is particularly 

significant in that many of the damaged structures had been designed and/or retrofitted to these 

new standards. Approximately 180 bridges out of 15,000 in the Kumamoto Prefecture were 

damaged during the earthquakes. This number is relatively low (less than 1.5 percent), given the 

intensity of the ground motions, and speaks to the validity of the new standards. 

Immediate posthazard assessment by NILIM and PWRI reported damage to new bridges even 

though several had been designed in accordance with the Design Specifications of Highway 

Bridges (Japan Road Association (JRA) 1996). They observed damage to rubber bearings 

supporting curved steel bridges, hydraulic dampers in an arch bridge, and shear keys; substructure 

tilting and settlement; and extensive slope failures. U.S. and Japanese researchers and 

practitioners have a history of collaboration following significant hazard events. The purpose of 

this collaboration is to learn from the hazards and share knowledge and skills that have benefited 

both countries as they seek to improve their highway infrastructure. More recently, after the 2011 

Great East Japan earthquake and tsunami, information sharing and discussions led to ongoing 

collaborative research on the tsunami effects on bridges. This collaboration is producing design 

guidelines vital to the regions of the U.S. Pacific Northwest as well as Japan.

TRANSPORTATION INFRASTRUCTURE RECONNAISSANCE TEAM 

Objective

Taking advantage of the opportunity to study the design, retrofit practices, and specifications 

developed since the 1995 Kobe earthquake, and at the request of the Japanese government, the 

Federal Highway Administration (FHWA) deployed a Transportation Infrastructure

Reconnaissance Team to Japan 3 mo after the earthquakes. Its mission was to conduct 

post-earthquake assessment on highway bridges in the area affected by the earthquake, examining 

bridges that performed well and those that failed. A comparative study of the affected 

infrastructure and the lessons learned could lead to further improvements in design specifications 

and retrofit procedures to prevent similar damage, increase resilience, and maintain sustainability.

Team Members

FHWA assembled a team of individuals with backgrounds in structural and geotechnical 

earthquake engineering to form the Transportation Infrastructure Reconnaissance Team. Members 

were asked to assess bridge performance and compile a report of their findings. The names and 

affiliations of U.S. and Japanese team members are listed in table 1. 
4 

Table 1. U.S. and Japan Reconnaissance Team for the Kumamoto earthquake bridge 

damage investigation. 

Team Member Affiliation

U.S. side: 

Sheila Rimal Duwadi, P.E.

Principal Research Engineer, Infrastructure 

Safety and Security 

sheila.duwadi@dot.gov

FHWA 

Turner-Fairbank Highway Research Center

6300 Georgetown Pike 

McLean, VA 22101 

Ian G. Buckle 

Professor Civil and Environmental Engineering 

igbuckle@unr.edu

University of Nevada, Reno 

1664 N. Virginia Street, Mail Stop 258 

Reno, NV 89557-0258 

David H. Sanders, P.E. 

Professor Civil, Construction and Environmental 

Engineering

sandersd@iastate.edu

Iowa State University

813 Bissell Rd 

Ames, IA 50014 

Ron Bromenschenkel 

Senior Bridge Engineer, Earthquake Engineering 

Group 

ron.bromenschenkel@dot.ca.gov

California Department of Transportation 

P.O. Box 168041, MS 9 2/7J 

Sacramento, California 95816-8041 

Jim Cuthbertson 

Chief Foundations Engineer, Geotechnical Office 

CuthbeJ@wsdot.wa.gov

Washington State Department of 

Transportation 

P.O. Box 47365 

Olympia, WA 98504 

Denis Istrati

Graduate Research Assistant, Civil Engineering 

denis.istrati@gmail.com

University of Nevada, Reno 

1664 N. Virginia Street, Mail Stop 258 

Reno, NV 89557-0258 

Japan side: 

Masahiro Shirato 

Senior Researcher, Bridge Division

shirato-m92ta@nilim.go.jp

NILIM

MLIT, Japan 

Jun-ichi Hoshikuma 

Head, Bridge Division 

hoshikuma-j92ta@nilim.go.jp

NILIM 

MLIT, Japan 

Shigeki Unjoh 

Research Coordinator for Earthquake Disaster 

Prevention 

unjoh@pwri.go.jp

PWRI

Tsukuba, Japan 

Nobuhiro Imachou

Senior Researcher

Earthquake Disaster Management Division

NILIM

MLIT, Japan

Yasumoto Aoki 

Researcher, Center for Advanced Engineering 

Structural Assessment and Research

PWRI

Tsukuba, Japan 

MLIT = Ministry of Land, Infrastructure, Transport and Tourism. 
5 

Reconnaissance Schedule

The Reconnaissance Team had a full, 3-d schedule in the field. U.S. team members left for Japan 

on July 10, arrived on July 11, completed their assessment, and returned to the United States on 

July 14. Visits to the damaged bridge sites were organized by Japanese colleagues at 

NILIM/PWRI, who provided access to closed areas and greatly facilitated the schedule. The team 

visited 11 damaged bridge sites with a half-day reserved to discuss of initial findings. The 

schedule is shown in table 2. A map of the bridge sites visited is shown in figure 4. 

Table 2. Schedule. 

Date Destination

July 10–11, 2016 

Sunday–Monday 

Travel to Japan—United States to Narita then to Fukuoka. 

Lodging in Fukuoka. 

July 12, 2016 

Tuesday

Visits to the following sites by car and on foot: 

• Tawarayama Oh-hashi bridge 

• Susukinohara Oh-hashi bridge 

• Ooginosaka bridge 

• Kuwazuru Oh-hashi bridge 

• Ookirihata Dam bridge

• Ookirihata Oh-hashi bridge 

• Minami Aso bridge 

• Aso Oh-hashi bridge 

Lodging in Aso area, Kumamoto. 

July 13, 2016 

Wednesday

Visits to the following sites by car and on foot: 

• Kiyama River bridge 

• Akitsugawa bridge 

• Mashiki Town (epicenter) 

• Higashibaru bridge 

Fly from Fukuoka to Haneda and then drive to Tsukuba. Lodging in 

Tsukuba. 

July14, 2016 

Thursday 

FHWA-NILIM meeting in Tsukuba. 

Departure from Narita to the United States.
6 

Source: FHWA.

Figure 4. Map. Location of bridges visited by the Reconnaissance Team. 

REPORT ORGANIZATION 

This report presents reconnaissance findings of earthquake performance of transportation 

infrastructure based on available information and visual observations. The report is organized to 

provide, first, an understanding of the geology and seismology of the region and of this 

earthquake; second, information on the design standards used; and third, observations, lessons 

learned, and conclusions by the team. Specifically, chapter 2 describes the geology, seismology, 

and ground motions in and around the Kumamoto area. Chapter 3 reviews the development of 

seismic design requirements for bridges in Japan. Chapter 4 reports the findings of the 

Reconnaissance Team related to the performance of new bridges designed to the 1996 

specifications and the performance of retrofitted bridges. Chapter 5 summarizes bridge 

performance and lists lessons learned from the reconnaissance and recommendations. 
7 

CHAPTER 2. GEOLOGY, SEISMOLOGY, AND GROUND MOTIONS

BACKGROUND 

As noted in chapter 1, the southern Japanese island of Kyushu experienced two significant 

earthquakes in April 2016. On Thursday, April 14, 2016, a moment magnitude (Mw) 6.2 

earthquake occurred NW of the city of Kumamoto in Kumamoto Prefecture at 21:26 JST (Japan 

Standard Time) (12:26 UTC [Coordinated Universal Time]). Approximately 28 h later, a second 

larger (Mw 7.0) earthquake occurred beneath Kumamoto early Saturday morning, April 16, 2016, 

at 01:25 JST (16:25 UTC). Because of the short duration between events, seismologists believe 

the first event was a foreshock. Having two major earthquakes in the same area resulted in 

significant structural and property damage, especially in nearby Mashiki Town. The foreshock 

reportedly caused 9 fatalities and 1,108 injuries in the region, and the main shock caused another 

40 fatalities and 2,021 injuries. 

The epicenters of the two earthquakes are shown in figure 5 and figure 6. 

Source: USGS. 

Figure 5. Map. Epicenter location of the April 14, 2016, Mw 6.2 Kumamoto earthquake

(USGS n.d.). 
8 

 Source: USGS.

Figure 6. Map. Epicenter location of the April 16, 2016, Mw 7.0 Kumamoto earthquake

(USGS n.d.). 

Several magnitudes have been reported for the two earthquakes. The U.S. Geological Survey 

(USGS) reports the two earthquakes were Mw 6.2 and Mw 7.0. The NILIM in Japan and the 

Japan Meteorological Agency (JMA) both reported M6.5 and M7.3. In addition to the magnitude, 

Japan also uses a seismic scale associated with the level of shaking (shindo) experienced at the 

ground surface and is similar to the Modified Mercalli scale. The JMA Shindo scale is given in

table 3. 
9 

Table 3. JMA Shindo scale of earthquake intensity (JMA n.d.). 

Seismic 

Intensity

Human Perception and 

Reaction Indoor Situation Outdoor Situation 

0 Imperceptible to people 

but recorded by 

seismometers.

— — 

1 Felt slightly by some 

people keeping quiet in 

buildings. 

— — 

2 Felt by many people 

keeping quiet in 

buildings. Some people 

may be awoken.

Hanging objects such as 

lamps swing slightly.

— 

3 Felt by most people in 

buildings. Felt by some 

people walking. Many 

people are awoken.

Dishes in cupboards may 

rattle.

Power lines swing 

slightly.

4 Most people are startled. 

Felt by most people 

walking. Most people are 

awoken. 

Hanging objects swing 

significantly, and dishes 

in cupboards rattle. 

Unstable ornaments may 

fall.

Power lines swing 

significantly. Those 

driving vehicles may 

notice the tremor.

5 Lower Many people are 

frightened and feel the 

need to hold onto 

something stable. 

Hanging objects swing 

violently. Dishes in 

cupboards and items on 

bookshelves fall. 

Unsecured furniture may 

move, and unstable 

furniture may topple 

over. 

In some cases, windows 

may break and fall. 

People notice electricity 

poles moving. Roads may 

sustain damage.

5 Upper Many people find it hard 

to move; walking is 

difficult without holding 

onto something stable. 

Dishes in cupboards and 

items on bookshelves are 

more likely to fall. 

Televisions may fall from 

their stands, and 

unsecured furniture may 

topple over. 

Windows may break and 

fall, unreinforced 

concrete block walls may 

collapse, poorly installed 

vending machines may 

topple over, and 

automobiles and trucks 

may stop due to difficulty 

maintaining control. 
10 

Seismic 

Intensity

Human Perception and 

Reaction Indoor Situation Outdoor Situation 

6 Lower It is difficult to remain 

standing. 

Some unsecured furniture 

moves and may topple 

over. Doors may become 

wedged shut. 

Wall tiles and windows 

may sustain damage and 

fall.

6 Upper It is impossible to remain 

standing or move without 

crawling. People may be 

thrown into the air. 

Most unsecured furniture 

moves and is more likely 

to topple over. 

Wall tiles and windows 

are more likely to break 

and fall. Most 

unreinforced concrete 

block walls collapse.

7 It is impossible to remain 

standing or move without 

crawling. People may be 

thrown into the air. 

Most unsecured furniture 

moves and topples over 

or may even be thrown 

into the air.

Wall tiles and windows 

break and fall. 

Unreinforced concrete 

block walls collapse.

All Rights Reserved, Copyright © n.d. Japan Meteorological Agency.

—No data.

GEOLOGY AND SEISMOLOGY 

Tectonic Framework

Japan is on the western Pacific Rim, where the Pacific Plate, PSP, Okhotsk Plate, and Eurasia 

Plate meet (figure 7). 

According to Rhea et al. (2010), in northern Japan, the Pacific Plate is subducting under the 

Okhotsk Plate into the mantle beneath Hokkaido and northern Honshu. In southeast (SE) Japan, 

the Pacific Plate is subducting under the PSP and forms the deep offshore Ogasawara and Japan 

trenches. Along the southern half of Japan and under the island of Kyushu, the PSP is moving 

NW at a rate of about 2 inches/yr (5 cm/yr), where it subducts under the Eurasia Plate (Wei and 

Seno 1998). 
11 

Source: USGS. 

Figure 7. Map. Japan’s plate structure, relative motion (in millimeters), and seismic hazard

(Rhea et al. 2010). 

Seismic Source Zones

The subducting PSP under Kyushu highly influences the seismicity and the geology of Kyushu.1

It causes EW compression and deforms the overriding Eurasia Plate, resulting in faulting, shallow 

crustal earthquakes, and orogeny. Movement along the subducting plate boundaries causes 

interplate earthquakes at depths of 25–40 mi (40–60 km). The subducting plate is responsible for 

volcanism on the island and offshore subduction zone earthquakes with Mw 8.0 and greater. The

subducting PSP under Kyushu creates similar conditions to those found along the western coast of 

the United States. Northern California, Oregon, and Washington have similar plate mechanics, 

seismic source zones, and volcanism, although Japan is more seismically active than the United 

States. 

Shallow crustal faulting in the Eurasia Plate was the source for the April earthquakes on Kyushu 

in Kumamoto City and Mashiki Town. Movement occurred on two mapped fault zones: Futagawa 

and Hinagu (figure 8). 

1

Materials presented by Earthquake Disaster Management Division, 20th FHWA-MLIT Meeting, Tsukuba, July 14, 

2016. 
12 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management. 

Figure 8. Map. Fault traces in the Kumamoto Prefecture.

2

Movement along the Hinagu fault was responsible for the Mw 6.2 April 14 earthquake, whereas

movement along the Futagawa fault zone was responsible for the Mw 7.0 April 16 earthquake. 

Both faults are high-angle, right-lateral, strike-slip faults dipping 60–80 degrees. 

The Hinagu fault strikes N30°E. During the Mw 6.2 earthquake, the Hinagu fault ruptured along 

10 mi (15 km) of its 35-mi (55-km) length, but surface ruptures associated with the April 14 

earthquake were not reported (Okumura 2016). Before April, the last reported activity based on 

paleoseismic study of the Hinagu fault was 2,000–7,400 14C years before present (yBP), and its 

vertical displacement amounted to about 10 ft (3 m) (Shimokawa 1999).

Movement on the Futagawa fault was the source of the April 16 Mw 7.0 main shock. This fault is 

12 mi (20 km) long and strikes N60°E. Surface ruptures were observed and consisted of a 6-ft 

(2-m) right lateral permanent offset with about a 3-ft (1-m) vertical subsidence. The last rupture 

on the Futagawa fault, based on paleoseismic study, occurred earlier than 6,000 14C yBP

(Shimokawa 1999). The April 14 and April 16 earthquakes were not the only earthquakes that 

occurred between April 14 and 16, 2016. Approximately 140 earthquakes were recorded during 

this period, and several had JMA seismic intensities greater than 6 (table 4) (JMA 2016). 

2

Ibid.
13 

Table 4. Earthquakes exceeding JMA seismic intensity level 6 since April 14, 2016 

(JMA 2016). 

Date and Time Hypocenter

JMA 

Magnitude

JMA 

Seismic 

Intensity

April 14, 2016 

21:26 JST (12:26 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

6.5a 7 

April 14, 2016 

22:07 JST (13:07 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

5.8 6−

April 15, 2016 

00:03 JST (April 14, 2016 

15:03 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

6.4 6+ 

April 16, 2016 

01:25 JST (April 15, 2016 

16:25 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

7.3b 7 

April 16, 2016 

01:45 JST (April 15, 2016 

16:45 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

5.9 6−

April 16, 2016 

03:55 JST (April 15, 2016 

18:55 UTC) 

Aso Chiho of Kumamoto 

Prefecture

5.8 6+ 

April 16, 2016 

09:48 JST (00:48 UTC) 

Kumamoto Chiho of Kumamoto 

Prefecture

5.4 6−

All Rights Reserved, Copyright © 2016 Japan Meteorological Agency.

a Mw 6.2 USGS. b Mw 7.0 USGS. 

Both seismic events produced significant shaking in the Kumamoto area. JMA seismic intensities 

of 4 were felt throughout the Kumamoto Prefecture. JMA level 4 is characterized by shaking 

enough to startle people, hanging objects swinging significantly, and dishes rattling in cupboards. 

Those closest to the epicenters experienced upper level 6 and 7 shaking. These intensities are

characterized as follows: it is impossible to remain standing or move without crawling, people 

may be thrown into the air, most unsecured furniture moves and topples over or may even be 

thrown into the air, wall tiles and windows are likely to break and fall, and unreinforced concrete

block walls may collapse. Figure 9 and figure 10 show the JMA seismic intensities in and around 

the Kumamoto Prefecture during the foreshock and main shock earthquakes. 
14 

All Rights Reserved, Copyright © 2016 National Institute 

for Land and Infrastructure Management.

Figure 9. Map. JMA seismic intensity for April 14 Mw 6.2 foreshock.3

All Rights Reserved, Copyright © 2016 National Institute 

for Land and Infrastructure Management.

Figure 10. Map. JMA seismic intensity for April 16 Mw 7.0 main shock.

4

3

Ibid.

4

Ibid.
15 

Surface Geology

Some of the oldest basement rock in Japan is Cambrian and Ordovician ophiolites. Younger 

Jurassic rocks have been accreted onto the Eurasia Plate to form current Japan (Taira 2001). Since 

the middle Miocene, the predominant geological processes that form modern Japan have been 

volcanism and weathering. In the area most severely affected by the recent earthquakes, 

Kumamoto and Mashiki, Holocene alluvium fills the valleys with Pleistocene fluvial terraces and 

late Pleistocene pyroclastic flows (Okumura 2016). Fine-grained soils of varying plasticity are 

common in the valleys, as well as deposits of loose, cohesionless sands that are liquefiable. 

Ground Motions

Japan has a national seismic network, which has been operated by the National Research Institute 

for Earth Science and Disaster Resilience (NIED) since June 1996. Japan has two main types of 

stations: Kyoshin (K-NET) and Kiban Kyoshin (KiK-net). K-NET stations are ground surface 

seismograph monitoring stations, whereas KiK-net stations are both ground stations and pairs of 

seismographs installed in boreholes. Table 5 lists the Kumamoto Prefecture stations and their 

locations. Earthquake motions from these stations can be downloaded from the NIED Strong 

Motion Seismograph Network website (NIED n.d.). 

The accelerograms recorded in Mashiki Town for the foreshock and main shock events can be 

found in Iwata and Asano (2016). The unit of acceleration used in Japan is the “gal,” which is 

defined as 1 centimeter per second squared (1 cm/s2). The conversion from gal to gravity is a 

convenient one: 1 gal = 1 cm/s2

 = 0.001020 g = 0.001 g (approximately). Accordingly, the peak 

acceleration for the EW component of Mashiki Town foreshock accelerogram was 732 gal or 

0.73 g (approximately). The peak acceleration for the EW component of Mashiki Town main 

shock accelerogram was 825 gal or 0.82 g (approximately). Both accelerations are the highest

Japan has experienced since the offshore Miyagi earthquake of April 7, 2011. 

The subducting PSP causes EW compression in Kyushu. The Futagawa and Hinagu faults strike 

NE. Therefore, it is not surprising that the strongest shaking was in the EW direction for the two 

events. Because of the NE strike, the north-south (NS) accelerations were also significant at 

0.63 g and 0.78 g for the foreshock and main shock, respectively. Significant vertical acceleration

was also recorded: 0.34 g for the foreshock and 0.67 g for the main shock. The severity of the 

shaking has been attributed to the shallow epicentral depths of about 6.2 mi (10 km) for the two 

events.

The main shock caused the most damage and propagated fault rupture to the ground surface. Two 

seismic stations were closest to the heaviest damage. One was located in Mashiki Town, and the 

other was in Nishihara Village. Velocity, displacement, and particle displacement histories were 

determined from the main shock accelerograms by integration for both stations. 
16 

Table 5. NIED seismic stations in Kumamoto Prefecture and their locations. 

Network Site Code Site Name Latitude Longitude Altitude (ft [m]) Depth (ft [m]) Seismograph 

K-NET KMM001 Oguni 33.1208 131.0687 1,417 (432) — K-NET02

K-NET KMM002 Yamaga 33.0185 130.6846 98 (30) — K-NET02

K-NET KMM003 Tamana 32.9336 130.5477 46 (14) — K-NET02

K-NET KMM004 Ichinomiya 32.9320 131.1214 1,824 (556) — K-NET11A

K-NET KMM005 Ohdu 32.8761 130.8774 407 (124) — K-NET02

K-NET KMM006 Kumamoto 32.7934 130.7772 112 (34) — K-NET02

K-NET KMM007 Takamori 32.8267 131.1226 1,798 (548) — K-NET02

K-NET KMM008 Uto 32.6878 130.6582 13 (4) — K-NET02

K-NET KMM009 Yabe 32.6858 130.9856 1,453 (443) — K-NET02

K-NET KMM010 Misumi 32.6136 130.4874 7 (2) — K-NET02

K-NET KMM011 Tomochi 32.6167 130.8652 466 (142) — K-NET02

K-NET KMM012 Yatsushiro 32.5078 130.6024 10 (3) — K-NET02

K-NET KMM013 Tanoura 32.3650 130.5099 10 (3) — K-NET02

K-NET KMM014 Itsuki 32.3961 130.8268 984 (300) — K-NET02

K-NET KMM015 Minamata 32.2161 130.4046 16 (5) — K-NET02

K-NET KMM016 Hitoyoshi 32.1966 130.7757 489 (149) — K-NET02

K-NET KMM017 Taragi 32.2561 130.9257 509 (155) — K-NET02

K-NET KMM018 Ryuhgatake 32.3942 130.3885 10 (3) — K-NET02

K-NET KMM019 Hondo 32.4548 130.1807 23 (7) — K-NET02

K-NET KMM020 Shinwa 32.3636 130.1807 33 (10) — K-NET02

K-NET KMM021 Amakusa 32.3793 129.9997 33 (10) — K-NET02

K-NET KMM022 Ushibuka 32.1945 130.0265 13 (4) — K-NET02

KiK-net KMMH01 Kahoku 33.1089 130.6949 246 (75) 328 (100) KiK-net06 

KiK-net KMMH02 Oguni 33.1220 131.0629 1,411 (430) 407 (124) KiK-net06 

KiK-net KMMH03 Kikuchi 32.9984 130.8301 584 (178) 656 (200) KiK-net06 

KiK-net KMMH04 Aso 32.9514 131.0199 1,558 (475) 417 (127) KiK-net06 

KiK-net KMMH05 Namino 32.9553 131.2207 2,274 (693) 328 (100) KiK-net06 

KiK-net KMMH06 Hakusui 32.8114 131.1010 1,614 (492) 364 (111) KiK-net06 

KiK-net KMMH07 Mitsumi 32.6234 130.5584 72 (22) 984 (300) KiK-net06 

KiK-net KMMH08 Yabe 32.6501 131.0251 1,476 (450) 338 (103) KiK-net06 
17 

Network Site Code Site Name Latitude Longitude Altitude (ft [m]) Depth (ft [m]) Seismograph 

KiK-net KMMH09 Izumi 32.4901 130.9046 1,706 (520) 328 (100) KiK-net06 

KiK-net KMMH10 Shinwa 32.3151 130.1811 518 (158) 984 (300) KiK-net06 

KiK-net KMMH11 Ashikita 32.2918 130.5777 328 (100) 984 (300) KiK-net06 

KiK-net KMMH12 Hitoyoshi 32.2054 130.7371 344 (105) 404 (123) KiK-net06 

KiK-net KMMH13 Ue 32.2209 130.9096 574 (175) 581 (177) KiK-net06 

KiK-net KMMH14 Toyono 32.6345 130.7521 230 (70) 361 (110) KiK-net06 

KiK-net KMMH15 Minamata 32.1704 130.3647 49 (15) 361 (110) KiK-net06 

KiK-net KMMH16 Mashiki 32.7967 130.8199 180 (55) 827 (252) KiK-net06 

KiK-net KMMH17 Tamana 32.9873 130.5608 180 (55) 328 (100) KiK-net06 

—No data.
18 

The permanent displacement is quite large at both sites. For Mashiki Town, the integral shows 

about 4.9 ft (1.5 m) of displacement to the east and about 2.5 ft (0.75 m) of subsidence. For 

Nishihara Village, the integral shows about 6.6 ft (2 m) of displacement to the east and about 

6.6 ft (2 m) of vertical subsidence. The accelerations were also large. The foreshock was 

essentially equivalent to the current design acceleration response spectra (figure 11 and 

figure 12). The main shock exceeded the current design spectra in a certain range of structural 

periods. 

All Rights Reserved, Copyright © 2016 National 

Institute for Land and Infrastructure Management.

A. EW components. 

All Rights Reserved, Copyright © 2016 National 

Institute for Land and Infrastructure Management.

B. NS components. 

Figure 11. Graphs. Acceleration response spectra at Mashiki Town for April 16 Mw 7.0 

main shock.5

5

Ibid. 
19 

All Rights Reserved, Copyright © 2016 National 

Institute for Land and Infrastructure Management.

A. EW components. 

All Rights Reserved, Copyright © 2016 National 

Institute for Land and Infrastructure Management.

B. NS components. 

Figure 12. Graphs. Acceleration response spectra for Nishihara Village for April 16 Mw 7.0 

main shock.

6

6

Ibid.

21 

CHAPTER 3. SEISMIC DESIGN REQUIREMENTS FOR BRIDGES IN 

JAPAN

BACKGROUND 

Seismic design methods for highway bridges in Japan have evolved from lessons learned in past 

earthquakes, going back to the Kanto earthquake (M7.9) of 1923. By introducing various 

provisions for preventing serious damage, including restrainers to help prevent girder unseating 

and remediation measures to mitigate soil liquefaction, the number of highway bridges that have 

suffered complete collapse has been few up until the mid-1990s. 

However, the Hyogo-ken-Nanbu (Kobe) earthquake of January 17, 1995, caused destructive 

damage to many bridges. Collapse or near-collapse of superstructures occurred at 9 locations, and 

other kinds of major damage occurred at 16 locations (Ministry of Construction 1995; Kawashima 

1995). The earthquake revealed a number of critical issues that needed immediate attention in the 

design and strengthening of bridges for earthquakes. 

Immediately after the earthquake, the Committee for Investigation on the Damage of Highway 

Bridges Caused by the Hyogo-ken-Nanbu Earthquake was established by the Ministry of 

Construction to survey the damages and investigate their causes. The committee released an 

intermediate investigative report in March 1995 and a final report in December 1995 (Ministry of 

Construction 1995). In addition to the investigation of damage, the Committee approved “Guide 

Specifications for Reconstruction and Repair of Highway Bridges Which Suffered Damage Due 

to the Hyogo-ken-Nanbu Earthquake” on February 27, 1995, which was immediately adopted by 

the Ministry of Construction (Kawashima et al. 1996b). Then, on May 25, 1995, the Ministry of 

Construction announced these guide specifications should be tentatively used throughout Japan as 

emergency measures for the seismic design of new highway bridges and strengthening of existing 

bridges, until the Design Specifications for Highway Bridges could be revised. This major 

revision was completed in 1996 (JRA 1996; Kawashima et al. 1996a).

Since then, these design specifications have been continuously improved. A major step was taken 

in 2002, when performance-based design was introduced to enhance the durability of bridge 

structures for long-term use, as well as the inclusion of new knowledge about bridge design and 

performance that had been gained since the 1996 specifications. The 2002 design specifications 

were issued by the Ministry of Land, Infrastructure and Transport (MLIT) on December 27, 2001 

(JRA 2002; Unjoh, Terayama, and JRA 2002). 

Following the Great East Japan earthquake of March 2011, another major revision was issued by 

MLIT on February 16, 2012. The revised specifications and commentary were published in 

March 2012 (JRA 2012; Kuwabara et al. 2013). These modifications were based on recent 

research findings in safety, serviceability, and durability of bridges. Examples include the 

introduction of integral abutment bridges; use of higher strength rebar compared with

conventional reinforcement; consideration of age and deterioration on performance; revision of 

design ground motions for subduction-type earthquakes; and inclusion of requirements to 

facilitate maintenance, inspection and repair work for bridges. Tsunamis were first mentioned in 
22 

the JRA Specification in the 2012 edition (JRA 2012). More information about each revision is 

given in Kawashima and Unjoh (2004) and Kuwabara et al. (2013). 

1996 JRA SEISMIC DESIGN SPECIFICATIONS 

Of the damaged bridges that the team visited, five were designed and constructed for the same 

road realignment in 1998, and their seismic design was based on the same set of provisions, the 

1996 JRA specifications (JRA 1996). Accordingly, the changes made in these specifications as a 

consequence of the Hyogo-ken-Nanbu (Kobe) earthquake of 1995 are of particular interest. These 

changes are summarized in this section.

Although the damage sustained in the Kobe earthquake was concentrated in bridges designed to 

older design specifications, making comprehensive revisions to the then current specifications

was considered necessary, based on lessons learned, to reduce the extent of bridge damage in 

future large earthquakes.

Major updates included the following changes (JRA 1996): 

• The ground motion of the 1995 Kobe earthquake, which had the largest ground motion to 

date in terms of its influence on structures, was to be considered for inland, 

direct-strike-type earthquakes. The Kobe earthquake ground motion was specified as a 

new design seismic force, in addition to the conventional design seismic forces. 

• A ductility design method was introduced, especially for key structural elements such as 

bridge piers, foundations, bearing supports, and unseating prevention systems, while the 

traditional seismic coefficient method was retained for conventional design. 

• Clarification was added that, to accurately predict the behavior of a bridge during an 

earthquake, including nonlinear effects in structural members, dynamic analysis was 

necessary. For this purpose, input earthquake motions were specified, and the provisions 

concerning analytical models, analytical methods, and safety checks by dynamic analysis 

were revised.

• Soil layers to be examined and ground motions to be used to evaluate liquefaction 

potential were specified. A design procedure for the treatment of liquefaction was 

specified in cases where it would be probable. 

• A design procedure was introduced for the treatment of lateral spreading caused by 

liquefaction under or near a bridge. 

• The seismic isolation design method was modified to consider the distribution of seismic 

force from superstructure to substructures and the increase of damping capacity. 

• The stress-strain relationship of concrete in reinforced concrete piers, considering the 

confining effect of ties and hoops, was introduced. The method of calculating the 

horizontal force-displacement relationship was revised. Furthermore, a method for 

evaluating the shear strength of piers considering scale effects, detailed arrangements of 
23 

reinforcement to improve the ductility capacity, and a design method for reinforced 

concrete rigid frame piers based on the ductility design method were also introduced. 

• Methods were introduced for calculating the horizontal capacity and ductility of concretefilled steel piers, as well as seismic design details for hollow steel piers.

• Methods were specified for checking the horizontal capacity and ductility of various types 

of foundations, including the effects of nonlinearity. A seismic design method for 

foundations based on the ductility design method was introduced. 

• For bearing supports, for which no clear design method has been specified, design seismic 

forces and design methods were introduced for various types of bearings, including 

structural design methods for bearing anchorages. 

• To reduce the likelihood of span collapse due to girder unseating, the function of 

restrainers was clarified, and an unseating prevention system was introduced. Design loads 

and design methods were also specified. 

2002 JRA SEISMIC DESIGN SPECIFICATIONS 

As noted in 1996 JRA Seismic Design Specifications above, a major step was taken in 2002 when 

performance-based design was introduced into the design specifications. At the same time, 

improvements were made based on new knowledge in seismic design.

Major updates included the following changes (JRA 2002): 

• Seismic performance criteria for highway bridges were specified to implement the 

performance-based design concept, along with the determination of design earthquake 

ground motions and the verification of seismic performance. 

• Two-level design criteria were introduced for design earthquake ground motion of 

moderate intensity with high probability of occurrence, and design earthquake ground 

motion of high intensity and low probability of occurrence. These criteria in the 1996 JRA 

specifications were called type 1 and type 2 motions (JRA 1996). In the 2002 update, 

these motions were renamed level 1 earthquake and level 2 earthquake, respectively. 

Level 2 earthquakes were further subdivided into interplate, subduction events (type I), 

and inland shallow events (type II). 

• Three seismic performance levels (SPL) were defined and assigned to bridges based on 

their importance (type A and type B), and earthquake level (level 1 and level 2), as shown 

in table 6. Expectations with regard to safety, functionality, and reparability for each SPL 

are shown in table 7. 

• Verification methods of seismic performance were reformatted as static analysis and 

dynamic analysis. The selection of two design methods was clarified. The applicability of 

the dynamic analysis was greatly expanded, and a detailed verification method based on 

dynamic analysis was specified.
24 

• Evaluation method for dynamic earth pressure for the level 2 earthquake design was 

introduced, based on the modified Mononobe-Okabe earth pressure theory. An evaluation 

method for dynamic water pressure for the level 2 earthquake design was also introduced. 

• Verification method for the seismic performance of abutment foundations on liquefiable 

ground was introduced. 

• Evaluation method for the force-displacement models for steel columns with or without 

infilled concrete was improved.

• Verification method for the seismic performance of steel and concrete superstructures was

introduced. 

• Evaluation methods for the strength of bearing supports were improved. 

• References giving more detail on the design methods and related information were added 

at the end of the specifications. 

Table 6. Seismic performance matrix (Kawashima and Unjoh 2004). 

Type of Design Ground Motions 

Standard Bridges

(Type A)

Important Bridges

(Type B)

Level 1 earthquake: ground motions 

with high probability to occur. 

SPL 1: prevent damage. SPL 1: prevent damage. 

Level 2 earthquake: ground motions 

with low probability to occur. 

Interplate earthquakes (type I).

Inland earthquakes (type II). 

SPL 3: prevent critical

damage. 

SPL 2: limited damage for

function recovery. 

Table 7. Seismic performance criteria (Kawashima and Unjoh 2004). 

SPL Safety Functionality 

Reparability

Short Term Long Term

SPL 1: 

prevent damage

Safety against

unseating of 

superstructure 

Same 

functionality as 

before 

earthquake

Repair not 

required to 

recover 

functionality

Repair 

nonstructural 

damage not 

affecting 

functionality

SPL 2: 

limited damage

for function 

recovery

Safety against

unseating of 

superstructure 

Some 

functionality lost 

but quickly 

recovered

Functionality 

recovered using 

temporary repairs

Relatively easy to 

make permanent

repairs

SPL 3: 

prevent critical

damage

Safety against

unseating of 

superstructure 

- - -

—No data.
25 

2012 JRA SEISMIC DESIGN SPECIFICATIONS 

As noted in 2002 JRA Seismic Design Specifications section above, another major revision to the 

design specifications was made following the Great East Japan earthquake of March 2011. These 

revised specifications were based on lessons learned during this M9 earthquake and tsunami, as 

well as recent research findings in the safety, serviceability, and durability of bridges. Examples 

of the revised specifications are as follows: 

• Using revised zone factors based on deterministic hazard maps that consider M9 

earthquakes and saturation of ground motion intensity. Acceleration spectra were also 

revised based on new ground motion predictive equations. In addition, a new set of input 

acceleration response histories for use in response history dynamic analysis was 

introduced. This set includes nine motions—one for each of three soil classes at each of 

the three earthquake levels.

• Planning for tsunami inundation and large-scale landslides, introduced for the first time. 

For example, for the prevention of collapse of important bridges due to extreme tsunami, 

giving sufficient clearance is recommended to allow the wave to pass under the 

superstructure. 

• Improving the ductility design method to better quantify the ductility capacity of 

reinforced concrete bridges. In particular, a new equation for plastic hinge length and 

allowable tensile strain of longitudinal reinforcement that considers the buckling behavior 

of this reinforcement was introduced. 

• Improving requirements for hollow piers to reflect the trend toward thinner walls, higher 

axial stresses, and rebar congestion. Examples include the requirement that pier sections 

must be solid in the plastic hinge regions, and haunches must be used at the four internal 

corners inside the hollow section of the pier. 

• Developing seismic design methods for integral abutment and portal frame bridges to take 

advantage of lower maintenance costs in these types of bridges. Because the abutment 

backfill is used for earthquake resistance in these bridges, specifications were also 

developed for soil compaction in the approach embankments, which are more rigorous 

than those for conventional bridges. 

• Using higher strength rebar to reduce congestion in reinforced concrete piers and improve 

quality of construction. Based on cyclic loading tests of piers, increasing the yield strength 

from 345 MPa (50 ksi) to 490 MPa (71 ksi) had no adverse effect on minimum bending 

radius or ductility. 

• Including requirements to facilitate inspection, not just for routine maintenance but also 

for damage surveys following major earthquakes. In addition, consideration is given to 

facilitate maintenance and repair work, such as: 
26 

o Avoidance of designs that will be difficult to inspect and maintain/repair. 

o Consideration of maintenance/repair methods and provision of maintenance/repair 

equipment, such as inspection ladders and walkways. 

o Strengthening of girders over abutment and pier seats to facilitate installation of 

temporary supports and replacement of damaged bearings. 

o Preservation of a comprehensive set of bridge records about the investigation, design, 

construction, quality control, retrofit, maintenance, and repair of every bridge in the 

inventory. 
27 

CHAPTER 4. STRUCTURAL PERFORMANCE OF HIGHWAY BRIDGES

INTRODUCTION 

Approximately 180 bridges out of 15,000 in the Kumamoto Prefecture were damaged during the 

Kumamoto earthquake. This number is relatively low (less than 1.5 percent), given the intensity 

of the ground motion. The performance of 12 of these bridges is described in this chapter 

(table 8), including 5 relatively new structures and 5 retrofitted structures. Their approximate 

locations are given in figure 13, which shows that all but one lie within 1 km of the Futagawa 

fault. 

As shown in table 8, bridge descriptions are grouped in this chapter according to age, as follows: 

• Relatively new bridges designed to the 1996 JRA specifications and built in 1999–2000 

(JRA 1996). 

• Older but retrofitted bridges. 

• Other bridges. 
28 

Table 8. List of bridges visited and damage sustained.

Bridge Category Name Type

Bearings/ConnectionsDamage SuperstructureDamage AbutmentDamage Column/Footing Damage GroundFailure

A. Recently constructed 

bridges, i.e., design 

based on 1996 JRA 

specifications, as 

revised after Great 

Hanshin earthquake 

(1995), except if noted 

otherwise (JRA 1996) 

Ookirihata Oh-hashi bridge Curved steel plate 

girders with concrete 

columns 

● ● — ● ●

Ookirihata Dam bridge Prestressed concrete

girders and slab — ● — — ●

Kuwazuru Oh-hashi bridge 

(designed to 1994 JRA 

specifications, but retrofitted) 

(Japanese Road Association 

1994) 

Cable-stayed steel tub 

girders

● ● — — — 

Susukinohara bridge Concrete girders and 

slab — — — — ●

Tawarayama Oh-hashi bridge Steel plate girders ● ● — — ●

Ooginosaka bridge Steel plate girders ● ● — — — 

B. Retrofitted bridges Minami Aso bridge Steel arch — — ● — ●

Kiyama River bridge Steel plate girders on 

concrete columns 

● ● — ● — 

Akitsu River bridge Steel plate girders on 

concrete columns 

● ● ● — — 

Higashibaru bridge Pin-pin columns with 

external shear keys at 

abutments 

— — ● — — 

C. Other bridges Ookirihata Dam bridge (on old 

road) 

Single-span skew — ● — — — 

Aso Oh-hashi bridge Steel arch ● ● ● ● ●

● Visited.

—Not visited. 
29 

Original Map: © 2022 Google®. Modified by FHWA (see Acknowledgments section).

Figure 13. Map. Location of damaged bridges described in this chapter and proximity to the 

Futagawa fault. 

RECENTLY CONSTRUCTED BRIDGES 

In the late 1990s and early 2000s, Route 28 from Mashiki to Takamori in the Kumamoto 

Prefecture was realigned. This road runs through predominantly hilly country, crossing 

fast-flowing streams on more than a half-dozen major bridges and through two tunnels. With one 

exception, all bridges were designed to the 1996 JRA specifications and share many similar 

details, such as steel plate girder superstructures, concrete deck slabs, and reinforced concrete 

single-column piers on piled foundations (JRA 1996). All lie within 1 km of the Futagawa fault. 

The performance of six of these bridges is described in this section. 

Ookirihata Oh-hashi Bridge

The Ookirihata Oh-hashi bridge was built in 2001 and is a horizontally curved continuous I-girder 

steel bridge with five spans and a total length of 871 ft (265.4 m). A pedestrian walkway is 

located along the north side of the bridge. The bridge is oriented NW-SE.

Abutment A1, which is straight, is in NW, and A2, which is skewed, is in SE, as shown in 

figure 14 and figure 15. Interestingly, piers P2 and P3 are square (with 11.5 ft (3.5 m) and 13.1 ft 

(4 m) sides), whereas P1 and P4 are circular. Piers P1 and P4 are supported on deep foundations 

(shafts) of 14.8 ft (4.5 m) in diameter and 49.2 ft (15.0 m) in length, and 19.7 ft (6.0 m) diameter 

and 98.4 ft (30 m) length, respectively. Piers P2 and P3 are supported on multiple cast-in-place 
30 

piles of 4.9 ft (1.5 m) in diameter with lengths of 45.9 ft (14.0 m) and 42.7 ft (13.0 m), 

respectively.

Original Map: © 2016 Google®. Modified by NILIM (see Acknowledgments section). 

Figure 14. Photo. Aerial view of Ookirihata Oh-hashi bridge and nearby area.

1

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 15. Drawing. Elevation of Ookirihata Oh-hashi bridge.

2

1

Materials presented by Earthquake Disaster Management Division, 20th FHWA-MLIT Meeting, Tsukuba, July 14, 

2016. 2

Ibid.
31 

The surrounding area sustained a significant number of slope failures, which damaged a number 

of retaining walls. A landslide occurred at the location of the bridge, which totally destroyed the 

adjacent old road (figure 14, figure 16, and figure 17). Only a few retaining walls survived, as 

shown in figure 18. 

© 2013 Google® EarthTM.

Figure 16. Photo. Slope on the south side of the bridge before the earthquake. 

Source: FHWA.

Figure 17. Photo. Slope on the south side of the bridge after the earthquake. 
32 

Source: FHWA. 

Figure 18. Photo. Walls and remnants of the old road on the south side of the bridge.

In addition to the damage in the surrounding area, the earthquake had significant effects on the 

bridge superstructure and substructure. As shown in figure 19 and figure 20, the superstructure 

had a large offset toward the north at both abutments, which was approximately 40 inches

(1.0 m). This offset was accompanied by extensive failure of the elastomeric bearings. At 

abutment A1, the bearings below all five girders were ruptured close to either the top plate or the 

bottom, as shown in figure 21. At the same abutment, some of the longitudinal restrainers failed 

due to excessive movements of the superstructure (figure 22) from south to north, or due to the 

combination of lateral and longitudinal displacements that characterize the complex response of a 

curved bridge. The complexity of the curved bridge response is expected to have been increased 

by the fact that abutment A2 is skewed. Abrasion on the back wall indicates that pounding of the 

superstructure on the abutment occurred during shaking (figure 23), which may have led to 

buckling in the web stiffener under a partial height diaphragm at this abutment (figure 24).
33 

Source: FHWA.

A. North. 

Source: FHWA.

B. Measurement of the offset.

Figure 19. Photos. Offset of the superstructure at abutment A1.
34 

 Source: FHWA.

A. North. 

Source: FHWA.

B. Measurement of the offset. 

Figure 20. Photos. Offset of the superstructure at abutment A2. 
35 

Source: FHWA.

A. Outside girder G1. 

Source: FHWA.

B. Girder G2. 
36 

Source: FHWA.

C. Girder G3.

Source: FHWA.

D. Girder G4.
37 

Source: FHWA.

E. Inside girder G5.

Figure 21. Photos. Bearing failure below each girder starting from the outside girder G1 to 

the inside girder G5 at abutment A1. 

Source: FHWA.

A. South. 
38 

 Source: FHWA.

B. North. 

Figure 22. Photos. Rupture of longitudinal restrainers at abutment A1.

Source: FHWA. 

Figure 23. Photo. Abrasion on the back wall of abutment A1. 
39 

Source: FHWA. 

Figure 24. Photo. Damage in girder-to-diaphragm connection at abutment A1.

Apart from the offset of the superstructure at the abutments, significant offsets were also observed 

at interior piers (figure 25). These offsets were associated with the failure of the connections of 

the deck to the piers. However, as shown in figure 26 and figure 27, the elastomeric bearings at 

these locations did not rupture as did those at abutment A1 but, instead, the bolts connecting the 

top plates to the bearings failed. Pier P2 also had cracking close to the base of the column just 

above the foundation, indicating the existence of large moments during the shaking (figure 28).

Source: FHWA. 

Figure 25. Photo. Offset of superstructure at piers P3 and P4. 
40 

Source: FHWA.

A. Side view. 

Source: FHWA.

B. Top view. 

Figure 26. Photos. Elastomeric bearing at pier P4. 
41 

Source: FHWA.

Figure 27. Photo. Elastomeric bearing at pier P1. 

Source: FHWA.

Figure 28. Photo. Cracks at the base of pier P2. 

Visible damage also occurred at abutment A2 and was primarily at the joints and the bearings, as 

shown in figure 29, figure 30, and figure 31. At girders G1 and G5, the connections of the 

elastomeric bearings to their anchor plates seem to have failed. At this same girder, buckling of 

the stiffener was also observed (figure 31).
42 

Source: FHWA.

A. Overview. 

Source: FHWA.

B. Details of the damage. 

Figure 29. Photos. Damaged expansion joint at abutment A2. 
43 

Source: FHWA.

Figure 30. Photo. Failed bearing below girder G1 at abutment A2. 

Source: FHWA.

A. Damaged elastomeric bearing. 
44 

Source: FHWA.

B. Damaged stiffener. 

Figure 31. Photos. Damage to elastomeric bearing and stiffener at girder G5 at 

abutment A2.

Ookirihata Dam Bridge 

The Ookirihata Dam bridge is a single-span bridge constructed in 1998 with a span of 114.8 ft 

(35 m). It is a prestressed concrete T-girder bridge on a deep pile foundation with pile diameter of 

8.2 ft (2.5 m) and length of 44.3 ft (13.5 m) (figure 32 and figure 33). The ground around the 

bridge experienced substantial movement, which led to permanent bridge displacement (figure 34

and figure 35). 
45 

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Figure 32. Drawing. Elevation of Ookirihata Dam bridge.

3

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 33. Drawing. Soil profile at the site of Ookirihata Dam bridge.

4

3

Ibid.

4

Ibid.
46 

Source: FHWA.

A. Overview. 

Source: FHWA.

B. Measurement of the settlement. 

Figure 34. Photos. Approach fill movement at the abutment.
47 

Source: FHWA. 

A. Overview. 

Source: FHWA. 

B. Deformed railing indicating the amount of ground deformation. 

Figure 35. Photos. Approach fill movement at the abutment.
48 

Kuwazuru Oh-hashi Bridge

The Kuwazuru Oh-hashi bridge was designed in 1994 and constructed in 1997 following the 

then-current JRA specifications (figure 36 and figure 37). It was retrofitted based on the 

specification revisions that occurred following the 1995 Great Hanshin earthquake (Kobe) 

earthquake. The bridge is oriented south to north, with abutment A1 south and A2 north. It is a 

cable-stayed bridge with a single central pier consisting of two steel towers that form an “X” in 

the plane perpendicular to the bridge. The two spans of the bridge are unequal in length. The long 

span off abutment A1 is 325 ft (99 m), and the short span off abutment A2 is 194 ft (59 m). The 

short span is 60 percent of the longer span’s length. The total structure length is 525 ft (160 m). 

The superstructure deck has two main steel tub-shaped girders, for the full length, connected by 

transverse diaphragms. The deck has a 4.8 percent grade, resulting in abutment A2 being 25.3 ft 

(7.7 m) higher in elevation than abutment A1. The deck has two undivided traffic lanes, one for

each direction, with modest shoulders and a multiuse path on one side. 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 36. Drawing. Elevation and plan of Kuwazuru Oh-hashi bridge.

5

5

Ibid.
49 

Source: FHWA. 

Figure 37. Photo. Kuwazuru Oh-hashi bridge looking NE. 

There was substantial damage at the abutments. The damage observed at abutment A1 was mainly 

to the steel bearings and unseating prevention devices (figure 38 and figure 39). The expansion 

joint at this abutment showed little displacement (figure 40). Abutment A2, which supports the 

short north span, experienced more damage than abutment A1. The short north span required 

vertical tension restrainers to maintain its position. These restrainers failed, allowing the 

superstructure to move upward and lift off the abutment seat. At the same time, the superstructure 

moved to the right when looking at abutment A2 under the structure. A large arcuate gouge was 

present in the abutment wall that was lower in elevation than the current girder position, 

suggesting the gouge occurred on restrainer failure. The steel girder also impacted the stop block 

and crushed it (figure 41).
50 

Source: FHWA.

A. East bearing. 

Source: FHWA.

B. West bearing. 

Figure 38. Photos. Damage to steel bearings at abutment A1. 
51 

Source: FHWA.

Figure 39. Photo. Damaged restrainers at abutment A1. 

Source: FHWA.

Figure 40. Photo. Expansion joint at abutment A1. 
52 

Source: FHWA.

Figure 41. Photo. Damage to steel bearings at abutment A2. 

At the center pier, the bridge deck was displaced to the west by about 2 ft (0.6 m). Figure 42

shows the superstructure displaced to the west (right side of photo). On the east side of the bridge, 

the distance to the tower leg is 7.2 ft (2.2 m) at the railing elevation (figure 43). On the west side 

of the bridge, the distance to the tower leg is 9 inches (23 cm) at the railing elevation (figure 44). 

The deck was not centered between the tower legs before the earthquake, but the offset is now 

more severe. Figure 45 shows the damage and permanent displacement of the center pier.
53 

Source: FHWA.

Figure 42. Photo. Center pier of Kuwazuru Oh-hashi bridge. 

Source: FHWA.

Figure 43. Photo. Distance from the bridge rail to the east tower leg. 
54 

Source: FHWA.

Figure 44. Photo. Distance from the bridge rail to the west tower leg.

Source: FHWA.

A. East side.
55 

Source: FHWA.

B. West side.

Figure 45. Photos. Damage to the east side and west side support blocks at the center pier.

Damage to the cables also occurred (figure 46 and figure 47). On the west side of the long span, a 

gouge occurred in the high-density polyethylene sheathing on a cable where it appeared to have 

made contact with a luminaire. The current separation between the luminaire arm and cable 

appeared to be 3 ft (0.9 m). At least two cables failed, both on the west side of the bridge, one in

each span. The failure does not appear to be a complete rupture of the cable and is likely 

associated with movement of the wedges and anchor plate. This opinion is based on the observed 

extension in the corrosion protection shielding. 
56 

Source: FHWA.

Figure 46. Photo. Cable damage. 

Source: FHWA.

Figure 47. Photo. Cable extension. 
57 

Susukinohara Bridge

The Susukinohara bridge is oriented EW on Route 28 (figure 48). It was constructed in 1999 and 

is a 141 ft (43 m), single-span, concrete T-beam bridge. The substructure sits on deep pile 

foundations bearing on bedrock that is 25–31 ft (7.5–9.5 m) in length. Plan layout and elevation 

views are shown in figure 49 and figure 50. Although damaged, the bridge survived the 

earthquake but was closed to traffic.

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Management.

Figure 48. Map. Location of Susukinohara bridge.

6

6

Ibid.
58 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 49. Drawing. Elevation, plan, and cross sections of Susukinohara bridge.

7

7

Ibid.
59 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

Figure 50. Photo. Susukinohara bridge showing concrete T-girder superstructure with 

diaphragms.

8

The damage observed is shown in figure 51, which includes settlement of the bridge relative to 

the roadway and damage to the end diaphragm at the east abutment due to lateral movement and 

possible pounding of the girders. No visible cracks were observed on the girders, and, for the 

most part, there was little damage to the bridge girders or the deck. 

8

Ibid.
60 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

Figure 51. Photo. Distant view of damaged approach at the west abutment.

9

Figure 51 and figure 52 show damage to the approach slab, which had folded up. This damage

was at the west abutment. At the east abutment, a large gap appeared between the end of the 

bridge and the approach (figure 53). This damage indicates the bridge had moved longitudinally 

toward the west. The amount of permanent lateral movement can be judged from the 

misalignment of the roadway stripe. 

9

Ibid.
61 

Source: FHWA.

Figure 52. Photo. Close-up view of damaged approach at the west abutment. 

Source: FHWA.

Figure 53. Photo. Longitudinal and lateral movement at the east abutment. 

Figure 54 shows the rotation of the elastomeric bearing about a vertical axis. However, none of 

the girders had fallen off the bearings or the abutments. Figure 55 shows timber blocking that is 

currently being used for additional support. 
62 

All Rights Reserved, Copyright © 2016 National Institute for Land 

and Infrastructure Management.

Figure 54. Photo. Rotation of an elastomeric bearing.10

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 55. Photo. Timber blocks being used for additional support of girders at abutment 

seats.

11

10Ibid.

11Ibid.
63 

The most severe damage observed in this bridge was the failure of the end diaphragm at the east 

abutment (figure 56 and figure 57). The longitudinal and lateral movements of the bridge toward 

the abutment resulted in the failure of the diaphragm.

Source: FHWA.

Figure 56. Photo. Damaged end diaphragm at the east abutment and dislodged timber block 

from under the second girder from the left.

Source: FHWA.

Figure 57. Photo. Crushing of the end diaphragm at the east abutment. 

In summary, the bridge had been displaced both laterally and longitudinally, but there was little 

damage to the girders or the deck and the riding surface. The damage was mostly to the end 
64 

diaphragm and the approaches. The bridge, however, moved permanently out of its original 

alignment. 

Tawarayama Oh-hashi Bridge

The Tawarayama Oh-hashi bridge is oriented EW on Route 28 (figure 58). This three-span, 

continuous steel, I-girder bridge was constructed in 2001 and has a total span length of 459.3 ft 

(140.0 m). The cross section consists of three girders with steel cross frames. Finger joints are 

used for the expansion joints. The bridge is supported on deep pile foundations that are 23–87 ft 

(7–26.5 m) in length, with soil profile and bridge elevation as given in figure 59. Figure 60 shows 

the bridge as it sits after the earthquake. It was designed with lateral stoppers on each side of the 

girders, along with cables to prevent the bridge from lateral and longitudinal movement during 

earthquakes. It was closed to traffic due to damage.

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

Figure 58. Map. Location of Tawarayama Oh-hashi bridge.

12

12Ibid.
65 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 59. Drawing. Elevation of Tawarayama Oh-hashi bridge.

13

Source: FHWA.

Figure 60. Photo. Tawarayama Oh-hashi bridge looking east. 

The observed damage included girder and cross-frame buckling, bearing distortion, lateral and 

longitudinal movement of the girders, ground and abutment movement, lateral and vertical 

movement of finger joints, settlement of approaches, span unseating, shear key failures, and cable 

restrainer failure. At the road level, settlement of the superstructure and deformation of the 

railings could be observed. Elastomeric bearings were damaged at several supports. 

13Ibid.
66 

At the west end, damage was predominantly due to ground movement, leading to failure of the 

approach roadway, abutment rotation, pounding of girders, and bearing distortion (figure 61, 

figure 62, and figure 63). 

Source: FHWA.

Figure 61. Photo. Failure of the west approach. 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 62. Photo. Rotation of the west abutment.

14

14Ibid.
67 

Source: FHWA.

Figure 63. Photo. Pounding at the west abutment and permanent bearing deformation. 

Abutment rotation can be visualized in figure 62 from the greater separation distance between the 

top of the girder and abutment back wall compared with that at the bottom of the girder. 

Additionally, figure 62 and figure 63 show substantial residual displacement in the bearing. Large 

permanent displacements in elastomeric bearings were observed on a number of bridges due to 

residual displacements in their superstructures and/or substructures. Rupture of the drain pipe can 

also be seen. Furthermore, the back wall was crushed during pounding by the girders, and there 

was slight distortion of the girders at this location.

In addition to girder distortion at the abutment, buckling was observed in the web and lower 

flange of the outside girder in the same span (figure 64). This type of buckling failure was not 

seen in other girders. 

Source: FHWA. 

Figure 64. Photo. Buckled girder flange and web. 
68 

Figure 65 and figure 66 show the condition at the east abutment. As seen in figure 65, the bridge 

separated from the finger joint and settled about 12 inches (30 cm). Directly below the deck level, 

figure 66 shows the condition of the elastomeric bearings and the girder. The bearing and the 

girder moved laterally and longitudinally together and buckled the flange and web as the bridge 

hit the back wall. This movement resulted in failure of the steel stopper, which was designed to 

prevent the girder from moving laterally (figure 67). 

Source: FHWA.

Figure 65. Photo. Vertical offset at the east abutment between the bridge and approach 

pavement. 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 66. Photo. Lateral movement of a girder and bearing at the east abutment.

15

15Ibid.
69 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 67. Photo. Failure of a bearing stopper at the east abutment.

16

Additionally, buckling occurred in the lower chord braces (figure 68 and figure 69). 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 68. Photo. Out-of-plane buckling of the lower chord brace.

17

16Ibid.

17Ibid.
70 

Source: FHWA.

Figure 69. Photo. In-plane buckling of lower chord braces. 

Figure 70 shows a typical restraining cable system used to prevent girders from unseating 

longitudinally. However, as seen in this figure, these cables were not able to prevent lateral 

movement, as might be expected. Although this restrainer was still attached, the girder moved 

laterally off the bearing but remained vertical.

Source: FHWA.

Figure 70. Photo. Longitudinal restrainer unable to prevent girder unseating transversely, 

as might be expected. 
71 

Figure 71 shows a close-up view of an elastomeric bearing and the connection details used on the 

Tawarayama bridge. Four bolts, one at each corner, were used to anchor the bearing to the 

masonry plate on the abutment seat. Also seen are two transverse stoppers to guide the bearing in 

the longitudinal direction. All four bolts were sheared off, and the bearing rotated about 

90 degrees at this location.

Source: FHWA.

Figure 71. Photo. Elastomeric bearing and transverse stopper at the east abutment showing 

rotation of the bearing and implied bolt fractures in anchor plates. 

Figure 72 and figure 73 show damage at the pier locations. The superstructure as a system moved 

laterally, distorting the bearing pads on the pier closest to the west abutment (figure 72). On the 

second pier, shown in figure 73, the superstructure moved off the bearing pads altogether and is 

sitting directly on the pier. This movement is about 3 ft (about 1 m). Spalling of the concrete is 

also present on the pier cap, possibly due to the impact of girders falling from the bearings onto 

the cap. 
72 

Source: FHWA.

Figure 72. Photo. Permanent deformation in the elastomeric bearing on pier P1. 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 73. Photo. Permanent lateral movement of the superstructure and girder unseating

on pier P2.

18

18Ibid.
73 

Figure 74 shows a bracing detail in the plane of the lower flange that was not damaged. This lack 

of damage was also noted in other bridges on Route 28. Despite strong ground shaking and 

pervasive ground failures, many superstructure details performed very well. 

All Rights Reserved, Copyright © 2016 National Institute for Land 

and Infrastructure Management.

Figure 74. Photo. Undamaged connection detail for lower chord bracing.19

In summary, although the Tawarayama Oh-hashi bridge was out of alignment after the 

earthquake, and many bearings were damaged as a result, no span collapsed, thus satisfying the 

life-safety performance criterion. 

Ooginosaka Bridge

One of the larger bridges in this group on Route 28, the Ooginosaka bridge is a five plate-girder 

bridge consisting of two equal 127.6-ft (38.9-m) end spans and a 160.1-ft (48.8-m) center span. 

The superstructure is supported by tall reinforced concrete columns on large shaft foundations. 

Constructed in 2000, it is built on a slight horizontal curve and is oriented primarily in the NS

direction. A pedestrian walkway/bike path is located along the west side of the bridge. Visible 

damage was primarily to the bearings, shear keys, and joints. A subsurface investigation to 

discover possible foundation damage was underway at the time of the reconnaissance. 

The nature of superstructure and substructure movement was of most interest. Figure 75 shows a 

seemingly westerly shift of the superstructure relative to its abutment. Figure 76 shows the 

relocking of finger joints, indicating the bridge moved longitudinally enough to open the joint, 

shifted, and closed again in a new offset position. The south end shift was approximately 

12 inches (0.30 m). Examining the north abutment (figure 77) revealed a 10-inch (0.25-m) 

easterly shift. This shift suggests a clockwise rotation of the superstructure (figure 78. However, 

the at-rest position of the intermediate bearings indicates another possibility. Instead of having 

slightly less displacement of the same direction as the nearest abutment (with rotation about the 

19Ibid.
74 

center of the structure), the intermediate bearings were set in opposite directions. Figure 79 shows 

the easterly offset of the superstructure at the second support and the westerly offset at the third. 

Source: FHWA.

Figure 75. Photo. Ooginosaka bridge from the south approach showing left lateral offset at 

the abutment.

Source: FHWA.

Figure 76. Photo. Finger joint relocking. 
75 

Source: FHWA.

Figure 77. Photo. North abutment with easterly superstructure shift. 

Source: FHWA.

Figure 78. Illustration. Potential rotation of superstructure creating observed abutment 

offsets.
76 

Source: FHWA.

A. Pier P2.

Source: FHWA.

B. Pier P3.

Figure 79. Photos. Offset at the pier cap for piers P2 and P3.

If these movements are entirely caused by superstructure movement, there must be significant 

in-plane deformation for the deck, which would produce significant cracking. That was not the 

case. The deck condition indicated that the deck remained a rigid diaphragm. Figure 80 shows the 
77 

direction of movement of each substructure that would have produced the bearing offsets. This 

result means the ground supporting each foundation through the canyon moved in the opposite 

direction relative to the next foundation. Given the amount of slope instability in the region, this 

is a conceivable conclusion. One way to check this concept is to view the center supports from 

each abutment and check for column drift. Aside from construction tolerances, columns that are 

out of plumb may indicate seismic shifts in local supporting soil and foundations. When one looks 

south along the column edges from under the north abutment, the column drifts become evident 

as a gap can be seen between the tops of the columns in figure 81. A corresponding lower gap can 

also be seen when one looks north from the southerly abutment (figure 82). Other damage at the 

bridge included failed shear keys. Figure 83 shows the south abutment shear key after being hit by 

its steel bumper. Keys were located only in the outside direction of transverse travel, as 

movement to the east would be less due to the geometry of the inside of the curve. 

Source: FHWA.

Figure 80. Illustration. Directions of substructure movement necessary to explain observed 

bearing displacements at each location. 
78 

Source: FHWA.

Figure 81. Photo. Gap at the top of superposed column profiles, looking south. 

Source: FHWA.

Figure 82. Photo. Gap at the bottom of superposed column profiles, looking north.
79 

Source: FHWA.

Figure 83. Photo. South abutment shear key damage. 

Retrofitted Bridges 

Japan has an active seismic retrofit program, and practically all bridges on the national 

expressways and major highways have been retrofitted. The performance of five of these 

structures is described in this section. 

Minami Aso Bridge

This structure comprises a steel arch for the main span and two short back spans for a total length 

of 364 ft (110.8 m). Built in 1971, the bridge is located on national Route 325. It had been 

retrofitted using longitudinal dampers at both abutments and buckling-restrained braces in the 

transverse frames directly above the springing blocks. Figure 84 shows the west side of the 

structure looking north. 
80 

Source: FHWA.

Figure 84. Photo. West side of Minami Aso bridge viewed from the south abutment wing 

wall. 

Damage was primarily sustained by the shear keys and back walls at both abutments. Figure 85

and figure 86 show close-ups of shear key failures at both sides of the south abutment. Dampers 

were secured to the abutments in the upper shear key area. Transverse displacements at the south 

abutment appear to have broken the keys, rendering the dampers ineffective. Another possible 

failure scenario is that longitudinal forces in the dampers pulled the keys free and damaged the 

back wall, but there was no evidence of longitudinal movement in the road joints at either end of 

the bridge or of damage to the dampers (no oil leakage, mounting bolt yielding, or pin distortion). 

A more likely scenario is first the transverse failure of shear keys and then anchorage failures in

the dampers due to the weakened back wall. This hypothesis is consistent with the angle of the 

failure plane in the keys as seen in figure 88 and figure 89. 
81 

Source: FHWA.

Figure 85. Photo. Damage to the anchorage of longitudinal damper and shear key on the

west side of the south abutment. 

Source: FHWA.

Figure 86. Photo. Damage to the anchorage of the longitudinal damper and shear key on the 

east side of the south abutment. 

Dampers were still secured at the north abutments. However, shear cracks at both keys were 

visible (figure 87, figure 88, and figure 89), indicating a high level of transverse demand. 
82 

Source: FHWA.

Figure 87. Photo. Longitudinal damper on the east side of the north abutment.

Source: FHWA.

Figure 88. Photo. Damage to the shear key block on the east side of the north abutment. 
83 

Source: FHWA.

Figure 89. Photo. Damage to the shear key block on the west side of the north abutment. 

Note the longitudinal bumpers mounted below the bottom girder flanges in figure 87 and

figure 89. It is likely these bumpers were designed to prevent dampers from bottoming out in a 

compression cycle, further supporting the failure sequence in which the keys failed first. All chain 

restrainers appeared undamaged. 

Kiyama River Bridge 

The Kiyama River bridge is located in Kumamoto Prefecture and is part of the Kyushu 

Expressway (figure 13). It is a composite bridge with four steel girders and cross frames. This 

structure was built in 1976 and has 32 spans, including a number of two-span and three-span 

continuous segments. It has a total length of 2,844 ft (867.0 m). The bridge runs NS and has a 

small in-plane curvature. The piers are supported on pipe piles 95–130 ft (29–40 m) long, which 

are either vertical or battered, as shown in figure 90. There are actually two parallel bridges, one 

for each direction of traffic, as shown in figure 91. Between 2005 and 2007, the bridge was 

retrofitted using concrete jackets for the columns and unseating prevention devices at certain 

supports. However, the girders, bearings, pier-to-pile cap connections, and foundations were not 

retrofitted at that time.
84 

 All Rights Reserved, Copyright © 2017 National Institute for Land and Infrastructure Management.

Figure 90. Drawing. Elevation and plan of Kiyama River bridge from pier P7 to pier P12

(NILIM 2017). 
85 

All Rights Reserved, Copyright © 2017 National Institute for Land and Infrastructure 

Management.

Figure 91. Drawing. Cross section through the east and west bridges from pier P7 to pier 

P12 (NILIM 2017). 

During the Kumamoto earthquake, the eastern bridge moved to the north and east. This 

movement resulted in the opening of a gap at pier 12 (figure 92) and the misalignment of 

consecutive spans (figure 93) in the eastern bridge. According to NEXCO West Japan—the 

company that manages the bridge—the western bridge shifted during the foreshock but then 

shifted back in the main shock. The heavy damage to the eastern bridge rendered it 

nonoperational, and it was closed to traffic, but the western bridge remained open. 
86 

Source: FHWA.

Figure 92. Photo. Opening of the expansion joint at pier P12 of the east bridge. 

Source: FHWA.

Figure 93. Photo. Misalignment of consecutive spans at pier P12 of the east bridge. 
87 

As shown in figure 90, the three piers, P10, P11, and P12, supported a two-span continuous 

segment with expansion joints at each end. This segment is the one that shifted east by 

approximately 3 ft (1 m), and the misalignment is observed at the joints of P10 and P12. At the 

time of the visit of the Reconnaissance Team, falsework and temporary supports had been 

installed below the segment in order to lift the deck and move it back to its initial position 

(figure 94).

Source: FHWA.

A. Span-end support. 
88 

Source: FHWA.

B. In-span support. 

Figure 94. Photos. Temporary support systems at pier P12 of the east bridge. 

Pier 11 of the east bridge was the only pier reported to have extensive damage. It was also the 

only pier on which the anchorages of the pinned bearings on the cap beam had not failed, thus, 

subjecting the pier to significant longitudinal load from the superstructure. The rotation can be 

seen in figure 95. It opened a vertical gap of about 2.5 inches (6.35 cm) between the column 

jacket and pile cap, which seemed to run the entire length of the cap. It was observed under both 

columns of pier P11 of the eastern bridge, indicating the reinforcement connecting the column to 

the pile cap had been either yielded, pulled out, or sheared. It was not possible to be more 

definitive without demolishing the column. This damage is shown in figure 96, figure 97, and 

figure 98. 
89 

Source: FHWA.

Figure 95. Photo. Side view of tilted pier P11. 

 Source: FHWA.

A. Overview of the pier. 
90 

Source: FHWA.

B. Close-up for the column-pile cap connection. 

Figure 96. Photos. Exposed column-to-pile cap connection at pier P11 of the east bridge. 

 Source: FHWA.

A. Size of the opening. 
91 

 Source: FHWA.

B. Damaged concrete. 

Figure 97. Photos. Gap opening between the bottom of both columns and the top of the pile 

cap at pier P11 of the east bridge. 

Source: FHWA.

Figure 98. Photo. View into the gap at the column-pile cap connection at pier P11 of the east 

bridge. 
92 

Apart from the damage to the column-to-pile cap connection at pier P11, significant damage also 

occurred at the bearing connections on the other piers. The superstructure appeared to have 

“jumped” longitudinally in both directions. There were indentations on both sides of the stiffener. 

As shown in figure 99, the large longitudinal movement of the bridge deck damaged the bolted 

connections of the steel bearings to the bottom flanges of the girders. Another consequence of this 

movement was that the web stiffeners were no longer aligned with the bearings, causing damage 

to the girder webs and flanges in the vicinity of the bearings. This type of damage was observed 

in both interior and exterior girders (figure 99 and figure 100). In addition, some bearings were 

also torn apart (figure 101). However, it appears that the failure of the bearings and/or their 

connections acted as a fuse, protecting the columns below from damage. As noted in the 

preceding paragraph, in the only case (pier 11) where the bearings and/or their connections did 

not fail, the pier below rotated and the pier-to-pile cap connection failed.

Source: FHWA.

Figure 99. Photo. Failed bearing connection under the west girder at pier P10 of the east 

bridge. 
93 

Source: FHWA.

Figure 100. Photo. Failed bearing connections under interior girders at pier P10 of the east 

bridge. 

Source: FHWA.

Figure 101. Photo. Failed bearing connection under the east exterior girder at pier P10 of 

the east bridge. 
94 

Akitsu River Bridge

The Akitsu River bridge was constructed in 1976 and retrofitted between 2005 and 2007. The 

retrofit consisted of column jacketing, strengthening and widening pier cap beams, and adding 

additional seat width at the abutments and unseating prevention devices. 

The bridge is on the Kyushu Expressway on the western side of Mashiki Town. It is oriented NS, 

with abutment A1 north and A2 south. The bridge has a steel plate girder superstructure that is 

397 ft (121 m) in length with four spans (figure 102). The team only visited the northern 

abutment A1 (figure 103, figure 104, and figure 105). Abutment A1 is supported on steel pipe 

piles 31.5 inches (80 cm) in diameter. There are five rows of piles. The two rows at the back of 

the abutment are plumb. The three rows in the front of the abutment are slightly battered. Pile 

batter information is not available. Pile lengths are 69–130 ft (21–39.5 m). 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 102. Drawing. Elevation and plan of Akitsu River bridge.

20

20Ibid.
95 

Source: FHWA.

Figure 103. Photo. General view of abutment A1. 

Source: FHWA.

Figure 104. Photo. Side view of abutment A1. 
96 

Source: FHWA.

Figure 105. Photo. Vertical cracks in the seat of abutment A1. 

There were obvious signs of liquefaction and lateral spread at abutment A1 approach. There is a 

wall-lined canal in front of the abutment. The canal passes under the structure then turns north 

and parallels the east side of the approach. The canal wall closest to the abutment and approach 

was severely damaged. Lateral spreading moved the northern canal wall away from the abutment. 

Abutment A1 has some vertical shear cracks that are shown in figure 105. One crack looks fresh, 

but adjacent to it is a similar crack with staining that has obviously been there a long time.

The entire superstructure was reported to have been displaced to the north. Coincident with 

superstructure displacement northward, abutment A1 may have displaced southward. As a result, 

the back wall of the abutment was damaged, the bearings suffered damage, and the girder 

stiffening plates were no longer aligned over the bearings, which resulted in damage to the bottom 

flange and web of the girder (figure 106). 
97 

Source: FHWA.

Figure 106. Photo. Damaged expansion bearing and girder at abutment A1. 

The approach fill was excavated to gain access to the abutment wall for demolition and 

reconstruction. Figure 107 shows the back of the abutment with the end wall removed. In the left 

of the figure, the curtain wall is shown still standing with shoring supporting the adjacent 

roadway. 
98 

Source: FHWA.

Figure 107. Photo. Bridge approach replacement. 

Higashibaru Bridge 

The Higashibaru bridge was constructed in 1971 and is located on the Kyushu Expressway 

(figure 108). It has three equal spans, as shown in figure 109 and figure 110. It was designed 

according to the S39 Design Specifications of Reinforced Concrete Highway Bridges (JRA 1964). 

It is a reinforced concrete hollow slab bridge with pin-pin columns, as well as external shear keys 

at the abutments. 
99 

Original Map: © 2022 Google®. Modified by FHWA (see Acknowledgments section).

Figure 108. Map. Location of Higashibaru bridge.
100 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 109. Drawing. Elevation and plan of Higashibaru bridge.

21

21Ibid.
101 

© 2022 Google® EarthTM.

A. Pier before the earthquake. 

 

© 2022 Google® EarthTM.

B. Abutment before the earthquake. 

Figure 110. Photos. Higashibaru bridge before the earthquake.
102 

The team noted that several bridges crossing the Kyushu Expressway were of this type and no 

doubt were designed and constructed at about the same time (figure 111). 

Source: FHWA.

A. Close-up of similar columns of a nearby bridge. 

Source: FHWA.

B. Similar columns of a nearby bridge. 

Figure 111. Photos. Another bridge with pin-pin columns near Higashibaru bridge. 

Earthquake damage to the bridge consisted of permanent lateral deformations and damage to 

abutment A2 (figure 112, figure 113, and figure 114). Damage to the shear keys led to permanent 

lateral deformation of the bridge. There was no damage to abutment A1. 
103 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

A. Inclined columns after the earthquake. 
104 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

B. Inclined columns after the earthquake. 

Figure 112. Photos. Inclination of pinned columns after the earthquake. 22

22Ibid.
105 

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

A. Close-up. 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

B. Overview. 

Figure 113. Photos. Shear key damage at abutment A2.23

23Ibid.
106 

All Rights Reserved, Copyright © 2016 National Institute for 

Land and Infrastructure Management.

A. Close-up. 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

B. Overview. 

Figure 114. Photos. Side view shear key damage at abutment A2.24

24Ibid.
107 

At the time the team visited the bridge, repairs had already occurred: the columns had been 

completely encapsulated in concrete (figure 115), and the abutment had also been repaired 

(figure 116). In effect, the bridge had been converted from a system with pin-pin columns to a 

pier-wall system with shear keys to constrain lateral movement.

Source: FHWA.

Figure 115. Photo. Repaired piers. 

Source: FHWA.

A. Overview. 
108 

Source: FHWA.

B. Close-up. 

Figure 116. Photos. Repaired abutment A2. 

OTHER BRIDGES

Aso Oh-hashi Bridge

The Aso Oh-hashi bridge was a steel deck-truss bridge built in 1971 on Route 325 (figure 117). It 

consisted of five spans, including one arch span of 406.82 ft (124 m), and had a total length of 

675.85 ft (206.0 m). Figure 118 and figure 119 are a rendering and a photograph of the bridge 

before the earthquake, respectively. 
109 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 117. Map. Location of Aso Oh-hashi bridge.

25

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 118. Drawing. Elevation of Aso Oh-hashi bridge.

26

25Ibid.

26Ibid.
110 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 119. Photo. Side view before the earthquake. 27

During the earthquake, a massive landslide occurred immediately upstream and above the west

abutment. The arch springing just below this abutment was totally undermined, and it collapsed 

into the river gorge below, taking with it the remainder of the bridge. At the time of the 

reconnaissance, the east approach remained, and the views from this abutment are shown in 

figure 120 through figure 124. 

27Ibid.
111 

Source: FHWA.

Figure 120. Photo. Remainder of the approach slab at the east abutment. 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure 

Management.

Figure 121. Photo. Remainder of the east abutment and unseated first span.28

28Ibid.
112 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 122. Photo. Unseated first span below the east abutment.29

All Rights Reserved, Copyright © 2016 National Institute for Land and 

Infrastructure Management.

Figure 123. Photo. Seat and back wall of the east abutment and remainder of the expansion 

joint.

30

29Ibid.

30Ibid.
113 

All Rights Reserved, Copyright © 2016 National Institute for Land and Infrastructure Management.

Figure 124. Photo. Landslide upstream of the west abutment across the gorge causing 

bridge collapse.31

31Ibid.

115 

CHAPTER 5. LESSONS LEARNED AND RECOMMENDATIONS

BACKGROUND 

Roughly 180 bridges were damaged by the Kumamoto earthquakes, and a number of them were 

either recently constructed (15–20 yr old) or recently retrofitted. 

Many of the new bridges that were damaged were located on a highway that had been realigned to 

improve access to a resort area. They were thus designed to the same specification and 

constructed about the same time (JRA 1996). Many of these bridges shared the same details, such 

as steel superstructures, elastomeric bearings, and reinforced concrete piers. This realigned road 

ran through steep, hilly country and was almost parallel to the Futagawa fault. Although no span 

collapsed on this road, damage sustained was significant, including bearing and shear key 

failures, steel superstructure distortion and local buckling, and foundation movement. The most 

likely cause was ground movement due to nearby slope failures and intense shaking in the near 

field of the causative fault.

Many of the retrofitted bridges that were damaged had only been partially retrofitted. For 

example, the piers of a multispan viaduct had been retrofitted with concrete jackets, but the steel 

pin bearings above the piers had not been strengthened or replaced. Many of these bearings failed. 

In another case, longitudinal dampers and transverse shear keys had been used to retrofit an arch 

bridge, but the abutment wall to which they were attached had not been adequately strengthened 

for shear, leading to a total loss of anchorage for the dampers. In this case, the weak link of the 

bridge system shifted from one component to another. 

As far as can be determined, only 2 of the 180 damaged bridges had collapsed spans due to 

ground shaking. One collapse was due to a massive landslide immediately upstream of the bridge, 

leading to extreme debris loading on its foundation for which it had not been designed, leading to 

its total collapse. The other was a bridge with pin-pin columns, which suffered uncontrolled 

lateral displacements when the transverse stoppers at the abutments failed.

Bridge damage can be summarized as follows: 

• Damage to bridges occurred due to intense shaking and/or extensive ground deformation 

associated with landslides. 

• Observed damage patterns include:

o Damage to bearings and bearing connections due to significant longitudinal and/or 

lateral displacement of either superstructure, substructure, or both. 

o Damage to bearings and bearing connections due to uplift and shear in curved steel 

girder bridges and a cable-stayed bridge. 

o Damage to shear keys and longitudinal restrainers. 
116 

o Buckling of steel girders (stiffeners, flanges), most likely due to uplift followed by 

horizontal impact of the girders on the abutment seats, and longitudinal impact of the 

girders on the abutment back walls. 

o Significant lateral displacement of expansion joints and back walls of abutments due 

to ground deformation or impact of the girders on the abutments. 

o Cracks at the base of reinforced concrete columns, but no spalling. 

o Rotation of a jacketed pier and failure of the pier-to-pile cap connection.

• Total collapse occurred in only two cases and under extraordinary circumstances. 

• Minimal column damage was observed due, in many cases, to one or more connection 

failures between the super- and substructures. These failures acted as fuses and protected 

the substructures from high inertial loads generated in the superstructure. 

• Bridge performance overall was excellent, given the intense nature of the ground motions 

and unstable soil conditions at many bridge sites. 

LESSONS LEARNED AND RECOMMENDATIONS 

Seven lessons learned and associated recommendations are listed as follows: 

1. Extensive landslides occurred throughout the Kumamoto Prefecture with detrimental 

effects on highway bridges. This widespread damage indicates the need for: 

a) Better understanding of landslides/slope failures. 

b) Probabilistic assessment of slope instability. 

c) Development of mitigation measures to stabilize vulnerable slopes. 

d) Investigation of landslide effects on structures and measures to minimize these effects, 

such as “flow-through” abutments. 

2. Bearings and their connections should be designed for uplift, or combined uplift and 

lateral displacement, for certain types of bridges,. 

3. Longitudinal restrainers and energy dissipation devices should be designed and installed to 

accommodate simultaneous imposition of large, relative displacements in both the 

longitudinal and transverse directions. 

4. Partial retrofitting of a bridge is better than not retrofitting at all, but it should be followed 

by a full retrofit as soon as possible. All components in the load path should be 

strengthened accordingly (e.g., girders, cross frames, bearings, columns, footings, and 

piles), including connections (e.g., bearings-to-pier cap and pier-to-pile cap).

5. Inadvertent fusing of a bridge superstructure can protect a bridge substructure. This 

phenomenon has been observed in other earthquakes (such as the Maule 2010 earthquake 

in Chile) and confirms the validity of one of the Seismic Design Strategies in the AASHTO 
117 

Guide Specifications for LRFD Seismic Bridge Design, in which deliberate fusing is 

acceptable. Such a strategy deserves further exploration (AASHTO 2012). 

6. Bridges with pin-pin columns can suffer from large, transverse displacements and 

potential instability if the shear keys at the abutments fail. Such bridges should be avoided 

unless a restoring mechanism can be devised, such as a posttensioned column. 

7. Cable-stayed bridges with uneven spans and horizontal curvature have a complex dynamic 

behavior. They can become unbalanced if uplift occurs during shaking and cable tension is 

lost. This unbalance results in overstressing of certain cables and damage to different 

components of the bridge. 

119 

ACKNOWLEDGMENTS 

The authors gratefully acknowledge the assistance of the following organizations and personnel 

with the successful completion of this reconnaissance exercise:

• NILIM and PWRI for technical and logistical support under the U.S.-Japan Cooperative 

Programs of FHWA, MLIT, and the U.S./Japan Natural Resources Panel on Wind and 

Seismic Effects.

• Drs. Junichi Hoshikuma, Masahiro Shirato, and Shigeki Unjoh (NILIM, PWRI) for 

generous assistance in the field and free exchange of expertise. 

• Earthquake Engineering Research Institute and Department of Civil and Environmental 

Engineering, University of Nevada, Reno, NV, for additional financial support. 

The map in figure 13 was modified by NILIM to show the Futagawa fault orientation and bridge 

sites.

The map in figure 14 was modified by NILIM to show to show abutment labels and orientation. 

The original map is the copyright property of Google® EarthTM and can be accessed from 

https://www.google.com/maps (Google 2016). 

The map in figure 108 was modified by NILIM to show the location of the bridge. 

Any opinions, findings, conclusions, or recommendations expressed in this report are those of the 

authors and do not necessarily reflect the views of the sponsors. 

121 

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HRDI-30/03-23(WEB)E Recycled

Recyclable

Recommended citation: Federal Highway Administration,

Performance of Transportation Infrastructure During Kumamoto 

Earthquakes of April 14 and 16, 2016—A Reconnaissance Report

(Washington, DC: 2023) https://doi.org/10.21949/1521940