Damage due to Earthquakes and Improvement of Seismic Performance of Reinforced Concrete Buildings in Japan

Damage due to Earthquakes and Improvement of Seismic Performance of Reinforced Concrete Buildings in Japan Prof. Maeda Masaki Tohoku University 2017/06/16 6NCEE & 2NCEES Romania 1

Summary History of Damaging EQ and Revision of Seismic Codes in Japan Damage to RC Buildings and Lessons from 1995 Kobe EQ Basic Concept of Seismic Capacity Evaluation Damage to RC Buildings due to recent EQs 2011 East Japan EQ 2016 Kumamoto EQ 2017/06/16 6NCEE & 2NCEES Romania 2

Damaging EQ and Code Revision (1) 1891 Nohbi EQ M8.0 1923 Great Kantoh EQ M7.9 death:140000 1924 Introduction of Seismic design to building code Allowable stress design 1944 Nankai EQ M8? 1945 Toh-Nankai EQ M8? 1948 Fukui EQ M7.3 death:3895 1950 Building Standard Law 1964 Niigata EQ M7.5 death:26 1968 Tokachi-oki EQ M7.9 death:52 Damage to RC buildings (shear failure) 1971 Revision (requirement for mimimum hoop spacing changed from 30cm to 10cm) 2017/06/16 6NCEE & 2NCEES Romania 3

Damage to RC Buildings (1968 Tokachi oki EQ) Hakodate Univ. 2017/06/16 6NCEE & 2NCEES Romania 4

Damage to RC Buildings (1978 Miyagiken-oki EQ) Obisan building 2017/06/16 6NCEE & 2NCEES Romania 5

Damage to RC Buildings (1978 Miyagike-oki EQ) 2017/06/16 6NCEE & 2NCEES Romania 6

Collapse of RC Building with soft (1978 Miyagike-oki EQ) 2017/06/16 6NCEE & 2NCEES Romania 7

Damaging EQ and Code Revision (2) 1977 Guideline of Seismic Evaluation and Retrofit of Existing Buildings 1978 Miyagi-ken-oki EQ M7.4 Death:28 1981 Revision (Ultimate State Design) CB = Co x Ds (not less than 0.3 for RC) CB : Design Base Shear Coefficient Co : Design Spectrum (not less than 1.0 g for peak acc. ) Ds : Reduction Factor by Ductility ( not less than 0.3 for RC) 2017/06/16 6NCEE & 2NCEES Romania 8

Damaging EQ and Code Revision (3) 1983 Nihonkai-chubu EQ M7.7 death:104 (Tsunami) 1993 Kushiro-oki EQ M7.8 death:2 1993 Hokkaido-nansei-oki EQ M7.8 death:230 (Tsunami) 1994 Hokkaido-tohou-oki EQ M8.1 no death 1994 Sanriku-harukaoki EQ M7.5 death:3 1995 Hyogoken-Nambu(Kobe) EQ M7.2 death:6430 Severer damage to existing buildings 1995 Law for Promotion of Seismic Evaluation and Retrofit 2017/06/16 6NCEE & 2NCEES Romania 9

Damage to RC buildings and lessons from 1995 Kobe Earthquake 2017/06/16 6NCEE & 2NCEES Romania 10

神戸 Kobe 東京 Tokyo Kobe Osaka Kyoto Red line : Nojima Fault Caused 1995 Hyogo-ken Nanbu 2017/06/16 6NCEE & 2NCEES Romania 11

Collapse of RC Building with soft first story (1995 Kobe EQ) 2017/06/16 6NCEE & 2NCEES Romania 12

Total collapse of RC Buildings Total collapse (1995 Kobe EQ) 2017/06/16 6NCEE & 2NCEES Romania 13

Damage in old and new Buildings Few hoops (pre-1971) Hoop spacing is 10cm (Post-1971) 2017/06/16 6NCEE & 2NCEES Romania 14

Damage Statistics for RC school buildings 631 RC school buildings Total post-1982 1972-1981 pre-1971 0% 20% 40% 60% 80% 100% Collapse Severe Moderate Minor Slight/None 2017/06/16 6NCEE & 2NCEES Romania 15

New Law to Promote Seismic Retrofit 1995 Oct. New Law to promote Seismic Evaluation and Retrofit of Pre-code Revision School, Hospital, Theater, Department Store, Hotel, Market etc. ( 3 stories and 1,000m 2 total floor area) Equivalent capacity required in the current code Japanese Guideline for Seismic Evaluation and Retrofit are applied. 2017/06/16 6NCEE & 2NCEES Romania 16

Basic Concept of Japanese Seismic Evaluation Guideline 2017/06/16 6NCEE & 2NCEES Romania 17

Seismic Capacity Evaluation Is-Index defined in the Japanese Seismic Evaluation Guideline (1977, revisided in2001) Is = E 0 S D T E 0 : Basic structural seismic capacity index S D : Shape index ( 0.4-1.0 ) T : Age index ( 0.5-1.0 ) 2017/06/16 6NCEE & 2NCEES Romania 18

Basic Structural Index E 0 E 0 =f C F f:mode Shape Factor (1.0 for 1 st story) C:Strength Index (Story Shear Coefficient ) = lateral strength / building weight F:Ductility Index (0.8, 1.0-3.2) C C1 E0 = C1 F1 C2 E0 = C2 F2 2017/06/16 6NCEE & 2NCEES Romania 19 F1 F2 F

Basic Structural Index E 0 -(2) C-Index Extremely brittle column Shear column & Shear wall 1 2 Flexural column (F=1.27~3.2) C1 C2 Flexural wall (F=1.0~2.0) 3 C3 0.8 1.0 1.27 3.2 F-Index (1/500) (1/250) (1/150) (1/30) Story drift angle 2017/06/16 6NCEE & 2NCEES Romania 22

Shape Index S D A factor to modify E0-index due to structural irregularity Irregular shaped plan Unbalanced distribution of stiffness (strength) Torsion Soft story mechanism Shear wall 2017/06/16 6NCEE & 2NCEES Romania 23

Age Index T A factor to allow for the deterioration of original performance Structural Cracking and deflection Crack by uneven settlement, shear crack Deflection of a slab and/or beam Deterioration and aging Rust of reinforcing bar Crack by concrete expansion Crack by a fire disaster 2017/06/16 6NCEE & 2NCEES Romania 24

Is 2 2.5 2 1.5 1 Seismic Capacity Is index vs. Construction Age No severe damage when Is>0.6 Seismic retrofit of buildings before 1981 Classification by Investigators Collapse Severe Moderate Minor Slight or None 0.5 Judging criteria Is=0.6 0 1950 1960 1970 1980 1990 2000 Construction Age 2017/06/16 6NCEE & 2NCEES Romania 27

90 80 70 60 50 40 30 20 10 0 Damage Indices, D 100 Damage Level vs. Seismic Capacity Is Severe Moderate Minor Ductile structure 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Seismic Performance Indices, Is 2 Classification by Investigators Collapse Severe Moderate Minor Slight or None 2017/06/16 6NCEE & 2NCEES Romania 28

Damaging EQ and Code Revision (4) 2000 Performance-based Design 2000 Geiyo EQ M6.7 death:2 2004 Niigata-ken-chuetsu M6.8 death:68 2007 Miyagi-ken-oki EQ M6.8 death:15 2011 Great East Japan EQ M9.0 death:15894, missing: 2561 (Tsunami) 2016 Kumamoto EQ M7.3 death: 88 2017/06/16 6NCEE & 2NCEES Romania 29

Damage to RC buildings due to 2011 East Japan Earthquake 2017/06/16 6NCEE & 2NCEES Romania 30

Summary of 2011 East Japan EQ Date: March 11, 2011 at 14:46 pm Location: 38.06 N Depth: 24km Magnitude: 9.0 142.51 E 2017/06/16 6NCEE & 2NCEES Romania 31

2011 East Japan Earthquake 2011/03/11 14:46(JST) Some old RC building was Damagedee 2017/06/16 6NCEE & 2NCEES Romania 32

Seismic record in Miyagi pref. Station PGA (gal) PGV (kine) MYG004 (Tsukidate) MYG013 (Sendai) THU (Sendai) JMA 4B9 (Furukawa) NS 2699 118 EW 1269 51 NS 1517 84 EW 982 43 NS 332 49 EW 330 61 NS 550 78 EW 456 87 K-net JMA Building Research Institute 2017/06/16 6NCEE & 2NCEES Romania 33

5% damped Response Spectrum Accellaration(cm/sec 2 ) Acceleration spectrum 3000 2500 2000 2011 East Japan MYG004 1994 Northridge 2011 East Japan MYG013 2011 4B9 1995Kobe 1500 1000 2011 Chiristcurch 500 0 2011 East Japan THU 1978 Miyagi-Oki 0 1 2 3 Period T(sec) 2017/06/16 6NCEE & 2NCEES Romania 34

Damage ratio of RC school buildings due to 1995 Kobe Earthquake 1971 1981 1 st generation 2 nd genaration 3 rd generation 1995 2011 Seismic code revision Code revision Kobe EQ East Japan EQ 1971 年以前未補強 1 st generation:73 第一年代 2 nd generation:34 第二年代 3 rd generation:50 第三年代 1971 年以前補強済 or 不要 1972-1981 未補強 1972-1981 補強済 or 不要 1982 年以降全体 50% 60% 70% 80% 90% 100% 1972-1972- 1971 年以 1971 年以 1982 年以 1981 補全体 1981 前未補強前未補降強済 or 不補強済 or 不要強要軽微 40% 50% 60% 70% 513 80% 232 200 13 90% 55 6100% 小破 22 3 17 0 1 1 中破 8 3 4 0 1 0 Less damage for new buildings owing 大破 to 3seismic 0 0 1 code 0 2 revision 基礎 7 2 3 2 0 0 軽微 Slight 小破 Minor 中破 Moderate 大破 Severe 基礎 Basement 2017/06/16 6NCEE & 2NCEES Romania 35

Damage ratio of RC school buildings due to 2011 East Japan Earthquake 1 st generation 第一年代 (w/o ( retrofit):9 未補強 ) 1 st generation (retrofitted) :57 第一年代 ( 補強済 / 補強不要 ) 2 nd generation 第二年代 (w/o retrofit) ( 未補強 :16 ) 2 nd 第二年代 generation ( 補強済 (retrofitted) / 補強不要 :224 ) 3 rd generation:240 第三年代 1971 年以前未補強 1971 年以前補強済 or 不要 1972-1981 未補強 1972-1981 補強済 or 不要 1982 年以降全体 50% 60% 70% 80% 90% 100% 1972-1972- 1971 年以 1971 年以 1982 年以 1981 補全体 1981 前未補強前未補降強済 or 不補強済 or 不要強要軽微 513 232 200 13 55 6 40% 50% 60% 70% 80% 90% 100% 小破 22 3 17 0 1 1 中破 8 3 4 0 1 0 Less damage to new buildings 大破 3 0 0 1 0 2 基礎 7 2 3 2 0 0 Slight 軽微 Minor 小破 Moderate 中破 Severe 大破 Basement 基礎 2017/06/16 6NCEE & 2NCEES Romania 36

Damage ratio of RC school buildings due to 2011 East Japan Earthquake 1 st generation 第一年代 (w/o ( retrofit):9 未補強 ) 1 st generation (retrofitted):57 第一年代 ( 補強済 / 補強不要 ) 2 nd generation 第二年代 (w/o retrofit) ( 未補強 :16 ) 2 nd 第二年代 generation ( 補強済 (retrofitted) / 補強不要 :224 ) 3 rd generation :240 第三年代 1971 年以前未補強 1971 年以前補強済 or 不要 1972-1981 未補強 1972-1981 補強済 or 不要 1982 年以降全体 50% 60% 70% 80% 90% 100% 1972-1972- 1971 年以 1971 年以 1982 年以 1981 補全体 1981 前未補強前未補降強済 or 不補強済 or 不要強要軽微 513 232 200 13 55 6 40% 50% 60% 70% 80% 90% 100% 小破 22 3 17 0 1 1 中破 8 3 4 0 1 0 Less damage for retrofitted buildings 大破 3 0 0 1 0 2 基礎 7 2 3 2 0 0 Slight 軽微 Minor 小破 Moderate 中破 Severe 大破 Basement 基礎 2017/06/16 6NCEE & 2NCEES Romania 37

Is-Index 0.9 0.8 0.7 0.6 0.5 Seismic Capacity Is index vs. Construction Age 2011 East Japan 0.4 Slight or Non 0.3 Minor 0.2 Moderate 0.1 Severe 0 1960 1965 1970 1975 1980 1985 Construction Age Criteria for school bldgs. 2017/06/16 6NCEE & 2NCEES Romania 38

Residual seismic capacity ratio, R[%] 100 90 80 70 60 50 40 30 20 10 0 Slight Minor Moderate Severe 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Is-Index Criteria for school bldgs. 2017/06/16 6NCEE & 2NCEES Romania 39

Summary of damage Seismic capacity of existing RC school buildings in Miyagi prefecture were much improved owing to seismic evaluation & retrofit. Good correlation between Is-index and damage level is observed. however, Some of retrofitted and evaluated-safe buildings suffered from damage, even though they escaped collapse. Those buildings were un-functional and some were demolished. 2017/6/19 2011 East Japan EQ 40

Strong motion Observe Accelerometer 9F Building of civil eng. and architecture, Tohoku Univ. 1968 年 Constructed 1978 年 Miyagi Oki earthquake Moderate damage 2001 年 Seismically Retrofitted 2011 年 Great East Japan earthquake Severe damage Accelerometer 1F Strong motion was observed experience large earthquake retrofitted severe damage over 40years 2017/06/16 6NCEE & 2NCEES Romania 41

Damage (crack) pattern 1978 EQ 2011 EQ 2017/06/16 6NCEE & 2NCEES Romania 42

Damage to Building of civil eng. 3 rd story was most severely damaged. Large displacement occurred in shear wall. Spalling and crush of concrete, fracture and buckling of rebars are observed in corner columns. 2017/06/16 6NCEE & 2NCEES Romania 43

3 rd floor plan and seismic retrofit Damage levels are classified by residual seismic capacity ratio R. Correlation between damage level and Is-index are observed. 2017/06/16 6NCEE & 2NCEES Romania 44

Damage to columns in 3 rd story Severe damage to corner columns Shear wall 2017/06/16 6NCEE & 2NCEES Romania 45

Damage to shear wall and columns in 3 rd story Cracks at the bottom of shear wall due to pull-out reinforcement with poor anchorage High axial load in column due to oveturnning moment 2017/06/16 6NCEE & 2NCEES Romania 46

Damage to corner columns in 3 rd story Fracture of steel Crush of concrete Buckling 2017/06/16 6NCEE & 2NCEES Romania 47

Primary School Buildings 3 stories RC building, Const. in 1974 West side structure Is=0.8 > Iso(required) No Retrofit was needed moderate damage East side structure Seismically retrofitted slight damage East West N Ѳ 45 o 2017/06/16 6NCEE & 2NCEES Romania 51

Seismic Capacity East Building before retrofit East Building after retrofit C F SD T Is 0.66 1 0.88 0.98 0.57 C F SD T Is 0.88 1 0.88 0.98 0.75 Slight damage West Building C F SD T Is 0.5 1.75 0.93 0.98 0.8 Ductility = Damage Moderate 2017/06/16 6NCEE & 2NCEES Romania 52

Shear failure of column and wall observed in un-retrofitted west building Short column failed in shear 2017/06/16 6NCEE & 2NCEES Romania 53

Damage classification of Post-earthquake Damage Evaluation Standard used in Japan Ⅱ Ⅲ Ⅳ Ⅴ 2017/06/16 6NCEE & 2NCEES Romania 54

Damage distribution in west building Building (B) 1 st floor 2017/06/16 6NCEE & 2NCEES Romania 55 55

85000 Damage distribution 4500 4500 4500 4500 4000 4500 4500 4500 4500 4500 4500 4500 4500 4500 4500 4500 4500 4500 4500 Ⅰf Ⅴs Ⅳs Ⅰf Ⅰf Ⅳs Ⅲs Ⅲs Ⅲs Ⅲs Ⅰf Ⅰf Ⅳs Ⅲs Ⅳs Ⅳs Ⅰf Ⅰf Ⅴs Ⅱs Ⅱs Ⅱs Ⅱs Ⅱs Ⅰs Ⅰs Ⅱs Ⅱs Ⅱs Ⅰf Ⅱs Ⅰs Ⅰs Ⅰf Ⅰf Ⅰs ⅠfⅤ Ⅰs Ⅰf Ⅱs Ⅱs Ⅱs Ⅱs ⅠsⅣ Ⅰf Ⅰs Ⅱs Ⅱs Ⅰf Ⅰf Ⅱf Ⅱs Ⅰs Ⅰf Ⅰf Ⅰs Ⅰs Ⅱf Ⅰf Ⅱs Ⅱs Ⅱs Ⅱf Ⅱs Ⅰf Ⅰf Ⅰs Ⅰs Ⅰf Ⅰf Ⅰf Damage was concentrated to short columns in North side corridor. Is= strength index X ductility=c X F = 0.5 1.75 =0.8 by ignoring brittle short column. The damage pattern agree with seismic evaluation results. C index 0.8 1.0 F index 1.75 2017/06/16 6NCEE & 2NCEES Romania 56 0.5

Less damage to retrofitted building Seismically retrofitted by steel bracing Effect of seismic retrofit was observed 2017/06/16 6NCEE & 2NCEES Romania 57

Damage to non-structural concrete walls in apartment Const. in 1979 11 story, SRC Enough is-index, but 2017/06/16 6NCEE & 2NCEES Romania 58

Damage to non-structural elements RC non-structural walls failed in shear RC moment frame structure escaped from major damage. However,. Demolished. 2017/06/16 6NCEE & 2NCEES Romania 59

Damage to Non structural element Gym constructed about 10 years ago Rehabilitated after Iwate-Miyagi EQ in 2008 Again damaged by 2011 earthquake 特別教室棟 2017/06/16 6NCEE & 2NCEES Romania 60

Non structural element damage (Junior high school gym in Kurihara city) Large parts of the ceiling fell down (3/11, and also in 4/7) The fixed parts after 2008 EQ escaped damage 2017/06/16 6NCEE & 2NCEES Romania 61

Damage by tsunami Onagawa town Minami Sanriku town 2017/06/16 6NCEE & 2NCEES Romania 62

Damage by tsunami Most of students and teachers were killed by tsunami. 2017/06/16 6NCEE & 2NCEES Romania 63

Damage by tsunami Passage collapsed due to tsunami. Bottom of column of passage. 2017/06/16 6NCEE & 2NCEES Romania 64

Damage to buildings due to 2016 Kumamoto Earthquake 2017/06/16 6NCEE & 2NCEES Romania 65

Affected area & Epicenter From Google Map Minamiaso Mashikimachi Kumamoto Airport 九州 Nishihara Kumamoto Uto City Main shock (4/16, Mj=7.3) Fore-shorck (4/14, Mj=6.5) 67 2017/06/16 2016/9/7 6NCEE & 2NCEES Romania 67

Damage in Mashiki town Local destructive damage Some of current code timber houses suffered collapse or sever damage 2017/06/16 6NCEE & 2NCEES Romania 69

Madage in Mashiki town Damage to steel and RC strucutures 2017/06/16 6NCEE & 2NCEES Romania 70

Damage in Minami Aso village Land slides around Aso Mt. 2017/06/16 6NCEE & 2NCEES Romania 71

Results of Quick Inspection in Kumamoto inspected number Green yellow Red Kumamoto city 30,487 14,126 10,514 5,847 Ratio[%] 100 46 35 19 Mashiki town 9,769 3,006 2,957 3,806 Ratio[%] 100 31 30 39 Uto city 1,265 506 531 228 Ratio[%] 100 40 42 18 2017/06/16 6NCEE & 2NCEES Romania 72

Damage to RC buildings Un-retrofitted buildings designed by old seismic code. Soft first story collapse. Non-structural elements (nonstructural wall, ceiling etc.). Most of the damage was similar to those observed in the past earthquakes Important point is to speed up retrofit schemes to existing vulnerable buildings 2017/06/16 6NCEE & 2NCEES Romania 73

Building designed by old seismic code Buildings of high school C without retrofitting 4-story RC building constructed in 1960 Shear failure of columns 4-story RC building constructed in 1964 Shear failure of wall 2017/06/16 6NCEE & 2NCEES Romania 74

Building designed by old seismic code City hall (5-story, RC) without retrofitting Story collapse occurred at the 4 th story There was future plans to rebuild because of its low seismic capacity index, Is. 2017/06/16 6NCEE & 2NCEES Romania 75

Building with soft first story Apartment K 7-story, RC, designed by old seismic code, without retrofitting L shape plan, core wall for EV and staircase located on one side. 2017/06/16 6NCEE & 2NCEES Romania 76

Collapse in soft first story 2017/06/16 6NCEE & 2NCEES Romania 77

Apartment G Damage to non-structural concrete walls Damage to structure elements is slight, nonstructural wall failed in shear. 2017/06/16 6NCEE & 2NCEES Romania 78

School gym Damage to non-structural elements Falling of ceiling, exterior wall (window sash and glass) Damage of the steel frame-rc column joint 2017/06/16 6NCEE & 2NCEES Romania 79

Damage Statistics of Public School Buildings in Kumamoto City Public school buildings for damage assessment RC buildings + corridors connecting buildings (121 in total) were assessed. Note 1: Total number of buildings and passages is 911. Note 2: Ratio of buildings satisfying the current design code is 100%. 2017/06/16 6NCEE & 2NCEES Romania 80

Concluding remarks - preparedness for coming earthquakes - Seismic upgrading Progressive for Public buildings. Almost completed for school bldgs. Private buildings are the problem. Damage to disaster management facilities may be a big obstacle to recovery of damaged community. Soft first story collapse was repeated. Collapse of old timber housed induced casualty. Non-structural elements Non-structural damage does not affect safety but function. Fall of ceiling boards may cause casualty. Structural engineer should be responsible seismic design of whole building structure including non-structural elements. 2017/06/16 6NCEE & 2NCEES Romania 82