Fragility curves for the buildings related to The 2015 Gorkha Earthquake.
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Presentation by Dr. Tsuneo OHSUMI Principal Research Fellow, Disaster Risk Unit, National Research Institute for Earth Science and Disaster Resilience (NIED), Japan at 1st JICA ERAKV Project Seminar
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Fragility curves for the buildings related to The 2015 Gorkha Earthquake.
- 1. Fragility curves for the buildings related to The 2015 Gorkha Earthquake. Tsuneo OHSUMI Principal Research Fellow, Disaster Risk Unit, National Research Institute for Earth Science and Disaster Resilience (NIED), Japan1 Motivation • The motivation behind the survey was to obtain ground truth data for the calibration. • A survey of the degree of damage was conducted for every house in Sankhu, Khokana and Bhaktapur by the European Macroseismic Scale (EMS) -98. • Hazards and damage were analyzed in a study on earthquake disaster mitigation in the Kathmandu Valley (JICA, 2002, 2016). • JICA (2016) study defining fragility curves for estimating damage to buildings was to determine the relationship between damage ratio and ground acceleration for each building type. Building type classification in Kathmandu Valley 3JICA2002 Hazards and damage were analyzed in a study on earthquake disaster mitigation in the Kathmandu Valley (JICA, 2002) . Building structure types were grouped into the classes based on the inventory Why did old core areas have concentrated casualties? 4 First, the dominant old core areas’ housing style in the area consists mainly of brick masonry with mud mortar. The damage to houses in this region was typically concentrated in non-engineered structures. In old core areas, unreinforced masonry walls the main construction material.
- 2. Comparison of the SMGA’s contour peak points (a) and the strong waveform were bifurcated areas (b). a b This damage survey was conducted for every house in Sankhu, Khokana and Bhaktapur, using European Macroseismic Scale (EMS)‐98. Sankhu Survey of damage extent for every house in Sankhu. Survey of building type for every house in Sankhu. Sankhu 2015 Gorkha Eq. for Verification 8 Damage Building Survey Area The PGA estimation was the result by the seismic hazard assessment of the JICA Project, 2016. This estimation was the result of the one dimensional earthquake response analysis using the ground model for each 250m grid above bed rock and the input motion for the 2015 Gorkha Earthquake.
- 3. 9 10 Sankhu: 150-180gal Khokana Survey of damage extent for every house in Khokana. Survey of building type for every house in Khokana. Khokana 2015 Gorkha Eq. for Verification 12 Damage Building Survey Area
- 4. 13 14 Khokhna: 130-180gal p.112 Bhaktapur Survey of damage extent for every house in Bhaktapur . Survey of building type for every house in Bhaktapur. Bhaktapur 2015 Gorkha Eq. for Verification 16 Damage Building Survey Area
- 5. Bhaktapur 2015 Gorkha Eq. for Verification 17 18 Bhaktapur: 150-180gal EMS‐Level EMS‐Level EMS‐Level EMS‐Level 1 2‐3 4 5 RC 237 0 2 1 % 99% 0% 1% 0% BC 207 0 10 7 % 92% 0% 4% 3% BM Well 156 0 11 2 % 92% 0% 7% 1% BM 442 0 83 54 % 76% 0% 14% 9% EMS‐Level EMS‐Level EMS‐Level EMS‐Level 1 2‐3 4 5 RC 67 0 4 0 % 94% 0% 6% 0% BC 54 0 17 2 % 74% 0% 23% 3% BM Well 7 0 4 0 % 64% 0% 36% 0% BM 39 3 75 28 % 27% 2% 52% 19% EMS‐Level EMS‐Level EMS‐Level EMS‐Level 1 2‐3 4 5 RC 144 1 9 0 % 94% 0% 6% 0% BC 76 5 23 15 % 64% 4% 19% 13% BM Well 9 3 2 0 % 64% 22% 14% 0% BM 50 13 71 90 % 22% 6% 32% 40% Khokana Sankhu Bhaktapur EMS level for each ratio and building type 20 0% 20% 40% 60% 80% 100% 0 200 400 600 800 Masonry 1p Masonry 2p Masonry 3p Masonry 4p RC 1p RC 2p Peak ground acceleration (PGA: cm/sec2, gal) DamageGrade4+5 Sankhu: 150-180gal RC: 6% BM: 70% BC: 26% JICA (2016) study defining fragility curves for estimating damage to buildings was to determine the relationship between damage ratio and ground acceleration for each building type. These curves refer to the graph showing this relationship.
- 6. 21 0% 20% 40% 60% 80% 100% 0 200 400 600 800 Masonry 1p Masonry 2p Masonry 3p Masonry 4p RC 1p RC 2p Peak ground acceleration (PGA: cm/sec2, gal) DamageGrade4+5 Khokhna: 130-180gal RC: 6% BM: 71% BC: 32% 22 0% 20% 40% 60% 80% 100% 0 200 400 600 800 Masonry 1p Masonry 2p Masonry 3p Masonry 4p RC 1p RC 2p Peak ground acceleration (PGA: cm/sec2, gal) DamageGrade4+5 Bhaktapur: 150-180gal RC: 1% BM: 23% BC: 7% Findings • BM buildings survived in old core areas. Damage extent and building type classification were surveyed for every house in Sankhu, Khokana and Bhaktapur. There was no damage to 99-94% of surveyed RC buildings. • For RC, the actual damage rate and damage function rate were in good agreement. The damage curve of BM exceeded that of Masonry-1 in Sankhu and Khokhna. 23 Beyond the 2015 Gorkha Earthquake • The recovery and reconstruction processes following the 2015 Gorkha Earthquake are ongoing. • Damage to reinforced concrete (RC) structures was generally minor.
- 7. Buildings damaged form the difference appeared in the remarkable The damage to RC structures was generally minor. These structures were mainly five to six story buildings. Many of the non‐engineered masonry structures that experienced complete collapse or partial damage were two to four story buildings in Sankhu. Structure having no RC column to the corner part, a crack was generated from the corner. Outer wall structure of the received building damage, the inside with mud mortar joints of the brick outer burned withstand rain, structure of adobe bricks. A crack was generated from the corner. Adobe / Charikot Primarily, adobe houses collapsed as a result of cracks in the gables and corner foundations as a result of ground motion. Many adobe style houses were broken at their gables. Stone / Charikot
- 8. • The Government of Nepal’s Post Disaster Needs Assessment presented, after the 2015 Gorkha Earthquake, principles for recovering human settlements and rebuilding homes. • The house prototypes and flexible designs offered in the government’s Design Catalogue for Reconstruction of Earthquake Resistant Houses provided various options for house price, size, layout, and type. • The design concepts therein are intended to help formulate a strong model to reinforce security against future earthquakes. The Prototype Designs were developed to full fill NBC by DUDBC with support from related organizations. Band installed between the first and second floors in a house. Roof CGI Sheets Timber Frame. Gable: Wooden Board. What Can We Learn from the past earthquakes? These PGA level of the seismic hazard analysis are controversial issue, and should be developed so as not to change the feasible level. These reconstruction PGA level hint is behind the damage level from the 1934 earthquake. Considering it is the maximum earthquake damage to Kathmandu Valley in the past records, which were rather than that by the 1833 and the 1866 earthquakes. Nepal and Japan have a long history of cooperation in earthquake engineering. Many joint research projects have been carried out in the academic field for earthquake disaster mitigation. 2016 is the 60th anniversary of the establishment of diplomatic relations between Nepal and Japan. All of the members of NIED and JICA team wish to strengthen the partnership in earthquake engineering that has been developed between Nepal and Japan through ongoing cooperation in investigations of this earthquake disaster and through future joint research projects.
Editor's Notes
- JICA2002 犠牲者の多くがKathmandu北東のSindhupal Chok地区に集中するのは、一つは、都市部と建物構造が大きく異なることにある。郊外・農村部は石造りの家が多く存在し、倒壊により多くの被害が生じ、重い石書構造の倒壊は多くの人命を奪った。旧市街の被害は甚大で、特にRC枠組の存在しないレンガ＋セメント・モルタルの住宅が多くの被害を受けていた。Kathmanduのリングロード内は、RC枠組を有する住宅が多く存在し、傾いた建物は川沿いの 特に川が分岐する地点の軟弱地盤領域に被害が点在する。 Hazards and damage were analyzed in a study on earthquake disaster mitigation in the Kathmandu Valley (JICA, 2002) . To estimate damage to buildings from the earthquake, a building inventory, especially one with the distribution of buildings by structural type, is necessary. Building structure types were grouped into the following seven classes based on the inventory - ST: Stone - AD: Adobe - BM: Brick with mud mortar, poorly built - BMW: Brick with mud mortar, well built - BC: Brick with cement or lime mortar - RC5: Reinforced concrete (RC) frame with masonry of four stories or more - RC3: RC frame with masonry of three stories or less According to the inventory, this study determined building types and their distribution in the settlement types of Kathmandu Valley. The main types are ST, AD, BM, BC and RC. Newer types (BC and RC) are predominant in the central and rapidly developing areas, and other types (ST, AD and BM) are predominant in rural or older core areas with dense population. Results of a building age survey revealed the current trend of building construction; there was an increase in newer structure types and a decrease of older types. The introduction of cement and sand some 30/40 years ago significantly changed building construction methods.
- Regardless of the masonry material used, serious damage occurred with houses as a result of masonry cemented with mud mortar. This housing construction method also exists in urban areas, primarily for constructions undertaken more than 30 years ago. In the rural areas, this type of housing is still the most popular method of housing construction. Thus, the retrofitting of low-cost earthquake-damaged housing without the consideration of engineering standards is a key issue.
- The rupture process extended to the east side of Kathmandu City. Figure shows snapshots of the rupture propagation at 10 time steps. The strong waveform was bifurcated, with two SMGAs. Contour peaks on Figure mark the two SMGAs. The first point corresponds to a location on Lachyang - Urleni Road, and the second point corresponds to a location on Unnamed Road (Figure). Comparison of the SMGA’s contour peak points (Figure a) and the strong waveform were bifurcated areas (Figure b). I'm sorry, but I do not understand this part of the discussion. On Figure 19, there are 10 separate illustrations. None of these illustrations has latitude-longitude markers, and the peaks are located differently in each time step. I think you mean to refer to Figure 18, final-slip distribution, for these two points? I have edited as if this is the case. Unless you mark the locations of the roads you mention on the illustration, it would be better to refer to the locations as something directional, like "60 km east-southeast of the epicenter, and 90 km east-southeast of the epicenter". Please check carefully to be sure I have not changed your intended meaning, and either mark the roads on the illustration or give directional locations.
- This damage survey was conducted for every house in Sankhu and Khokana, using European Macroseismic Scale (EMS)-98. According to this, Grades 1–5 are defined below. Grade 5: Very heavy structural damage Grade 4: Very heavy structural and non-structural damage. Grade 3: Moderate structural damage and heavy non-structural damage Grade 2: Slight structural damage and non-structural damage Grade 1: No structural damage and slight non-structural damage
- The PGA estimation was the result by the seismic hazard assessment of the JICA Project, 2016. This estimation was the result of the one dimensional earthquake response analysis using the ground model for each 250m grid above bed rock and the input motion for each scenario earthquake. According to the results, seismic ground motion in Sankhu showed similar level of 150 to 180 gals. Also this level at the regions was not larger than that of the surroundings. Even though there may be some possibilities of effect, but situation of geomorphology and soils are not so specific in the regions. Therefore, the building damage was caused due to the PGA level of course, but mainly due to the weakness of the buildings such as structural type, height, age, construction manner, repair opportunity, maintenance etc.
- Survey of damage extent for every house in Bhaktapur . Survey of building type for every house in Bhaktapur.
- The total number of buildings for each area are shown in the upper stage, and the percentages of each item are shown in the lower stage. There was no damage to 94% of the surveyed RC buildings. From the comparison of BM and BC, the collapse ratio was improved by 27% in Sankhu, which EMS-Level 40% (BM) was improved 13% (BC), and 16% in Khokana, which EMS-Level 19% (BM) was improved 3% (BC). There was 0% BM Well with very heavy structural damage in both areas. There was no damage to 99% of the surveyed RC buildings. From the comparison of BM and BC, the collapse ratio was improved by 6% for BC houses, which EMS-Level 9% (BM) was improved 3% (BC). There was 0% BM Well with very heavy structural damage.
- JICA (20016) study defining fragility curves for estimating damage to buildings was to determine the relationship between damage ratio and ground acceleration for each building type. These curves refer to the graph showing this relationship. In this study, the curves for buildings in the Kathmandu Valley were determined as shown in Figure 14a and b.
- RCの建物は健全で構造形態の違いが顕著の現れた。 RC buildings were no damaged form the difference appeared in the remarkable. Sankuの被害は甚大で、特にRC柱の存在しないレンガ＋セメント・モルタルの住宅が多くの被害を受けていた。 Damage in Sanku is enormous, the brick and cement-mortar houses without no RC column had a lot of damages. The difference in damage as a result of building type was remarkable. Damage in Sankhu was extensive. Brick and cement mortar houses without RC columns experienced a lot of damage. In contrast, the damage to RC structures – particularly those erected in recent years – was generally minor. These structures were mainly five to six story buildings. In contrast, many of the non-engineered masonry structures that experienced complete collapse or partial damage were two to four story buildings in Sankhu (Fig.: left). Damage in non-engineered masonry structures was initiated by vertical cracks in the corners of the buildings (Fig.: a), which contained no RC columns (Fig.: b). The outer wall structures of such buildings were generally burned brick with cement mortar joints to withstand rain. In several cases, the inner walls of buildings are adobe bricks with mud mortar.
- The damage to RC structures was generally minor.These structures were mainly five to six story buildings. Many of the non-engineered masonry structures that experienced complete collapse or partial damage were two to four story buildings in Sankhu (left). Damage in non-engineered masonry structures was initiated by vertical cracks in the corners of the buildings (a), which contained no RC columns (b). .
- Roof CGI Sheets Timber Frame Gable: Wooden Board