Measuring Seismic Risk in the Kyrgyz Republic – Development of fragility functions – November 2017 Measuring Seismic Risk in the Kyrgyz Republic Development of Fragility Functions – November 2017 About the Project The Kyrgyz Republic is located in a region of high Component 2. Developing a database of buildings and seismic hazard with earthquakes of magnitude Mw≥5 infrastructure across the entire country. occurring about once per month, and potentially Component 3. Undertaking seismic risk calculations to devastating earthquakes of magnitude Mw≥7 occurring estimate the amount of damage to buildings and with return periods of several decades. The Government infrastructure and potential casualties that could occur in of the Kyrgyz Republic is aware of this issue and has the future as a result of earthquakes. been making efforts to understand the seismic hazard that affects the country. In order to better understand the Component 4. Developing seismic risk management hazard and the risk from earthquakes, the Government strategies that allow cost-effective risk reduction and of the Kyrgyz Republic, with support from the World prioritization. Bank and the Global Facility for Disaster Risk Component 5. Communicating the methodology and Reduction, is funding the project “Measuring Seismic outcomes of the project to end-users in the Government Risk in the Kyrgyz Republic”. The project consists of and other sectors of society in the Kyrgyz Republic. five components: This brochure presents a summary of the key input Component 1. Undertaking a seismic hazard information compiled within Component 2 of the project assessment which identifies where earthquakes occur to develop fragility functions for buildings and and how strong is the ground shaking and other infrastructure in the Kyrgyz Republic. hazards. Definition and Use of Fragility Functions In seismic risk assessment, expected losses and damage concrete building subjected to ground shaking of 0.2g to buildings are described by fragility functions. Fragility PGA is approximately 4% likely to collapse or be very functions describe the probability of exceeding different heavily damaged, 40% likely to sustain heavy damage, damage or injury levels with increasing levels of ground 47% likely to sustain moderate damage and 9% likely to shaking. These functions represent the resilience of sustain no or negligible damage. building typologies that share common features such as Damage levels provide a relationship between damage construction material. Figure 1 shows example fragility and the financial or human losses that an asset may incur. functions for reinforced concrete buildings in the Kyrgyz Different damage scales are used for buildings, roads and Republic. On the horizontal axis of the fragility function bridges. Damage states for masonry buildings are is a measure of the intensity of the ground shaking, which illustrated and described in Figure 2, according to EMS. is typically defined in terms of: • Macroseismic intensity: based on post-earthquake data, Fragility Function Development felt intensity of ground shaking and effects on buildings. Methods for developing fragility functions include: • Instrumental intensity: based on seismic shaking 1. Empirical: Damage observations from previous measured by recording instruments. Peak ground earthquakes are plotted against seismic intensity, and acceleration (PGA) and permanent ground displacement regression is used to fit a function form to the data. (PGD) are commonly used for buildings and transport infrastructure, respectively. 2. Analytical: Building response to different levels of ground shaking is simulated through numerical The vertical axis represents the probability that a modelling of buildings of each typology; building of a given typology would be damaged to a particular degree. Degrees of damage are measured in 3. Expert judgement: Experts with experience in terms of discrete thresholds, referred to as “damage assessing building damage data provide estimates of states”. The adopted damage scale (as per European the probabilities of damage for different building Macroseismic Scale, EMS) is based on five damage typologies as a function of ground motion intensity. states, ranging from 1 (for negligible to slight damage) 4. Hybrid methods: A combination of the above to 5 (destruction or collapse). methods (e.g. using observational data to calibrate A specific fragility function provides the probability of a analytical models). building exceeding the associated damage state for each value of intensity. Figure 1 shows that a reinforced 1 Measuring Seismic Risk in the Kyrgyz Republic – Development of fragility functions – November 2017 Figure 1 Fragility functions for reinforced concrete buildings in the Kyrgyz Figure 2 Definition of damage states according to the European Republic and illustration of damage states. Macroseismic Scale damage scale for masonry buildings Fragility Functions for Kyrgyz Buildings The vulnerability index approach was used to develop average, adobe buildings are significantly more fragility functions in this project. This is a hybrid vulnerable than steel buildings. approach combining empirical data with expert Vulnerability indices were converted to fragility judgement. The empirical component is based on the functions through equivalent normal distribution performance of buildings in previous earthquakes. functions in terms of EMS-98 macroseismic intensity, Expert judgement is then used to adjust the baseline and equivalent lognormal distribution functions in terms values based on specific characteristics of the buildings of peak ground acceleration. Fragility functions for the (e.g. the level of earthquake resistant design). The most common building typologies in the Kyrgyz benefits of this approach are the following: Republic are shown in Figure 3 to Figure 10.  It offers a consistent approach that can be applied Table 1: Vulnerability indices assigned to Kyrgyz building across all building typologies. typologies (higher Vi means higher vulnerability).  It allows characteristics of the building construction to Type EMCA EMCA Description Vi be considered without significant analytical effort. Class Unreinforced masonry with wooden  It allows all typologies to be considered, not just those c1.1 floors 0.93 which have experienced earthquake damage in the past. Masonry Unreinforced masonry with concrete buildings c1.2 0.84 floors The method works by assigning a vulnerability index (Vi) c1.3/c1.4 Reinforced or confined masonry 0.56 to each building typology. Values for the vulnerability c2.1 Monolithic concrete frames 0.60 indices range typically between 0 and 1, although higher Cast-in- c2.2 Dual frame and wall system 0.55 situ values, which correspond to more fragile structures, are concrete c2.3 Monolithic frames with brick infill walls 0.71 also possible. Fragility functions for each damage state c2.4 Monolithic concrete walls with flat slabs 0.50 are then developed on the basis of this index. c3.1 Large panel walls with monolithic joints 0.47 Large panel walls with welded plate Precast c3.2 0.41 Average vulnerability indices assigned to the building concrete connections typologies commonly encountered in the Kyrgyz c3.3 Flat slab 0.80 Republic are shown in Table 1. The most vulnerable c3.4 Frame with cruciform and linear-beams 0.56 Adobe c4 Adobe structures 1.06 building typology (Vi = 1.06) was considered to be the Timber c5.1 Wooden structures 0.72 adobe buildings. The least vulnerable building typology Steel c6 Steel structures 0.28 (Vi = 0.28) was considered to be steel buildings. It is possible that a given steel building may be more vulnerable than a given adobe building, but on the 2 Measuring Seismic Risk in the Kyrgyz Republic – Development of Fragility Functions – November 2017 1 1 1: Negligible to Probability of damage exceeding 1: Negligible to Probability of damage exceeding slight damage slight damage 0.8 0.8 each damage state 2: Moderate each damage state 2: Moderate damage damage 0.6 0.6 3: Substantial to 3: Substantial to 0.4 heavy damage 0.4 heavy damage 4: Very heavy 4: Very heavy 0.2 damage 0.2 damage 0 5: Collapse 0 5: Collapse 5 6 7 8 9 10 5 6 7 8 9 10 Macroseismic Intensity (EMS-98) Macroseismic Intensity (EMS-98) 98 macroseismic intensity. Figure 3: Fragility functions for unreinforced masonry buildings with wooden floors (c1.1) in EMS-98 macroseismic intensity. Figure 7: Fragility functions for unreinforced masonry buildings with wooden floors (c1.1) in peak ground acceleration 1 1: Negligible to Probability of damage exceeding slight damage 1 Probability of damage exceeding 0.8 1: Negligible to slight damage each damage state 2: Moderate 0.8 each damage state damage 2: Moderate 0.6 0.6 damage 3: Substantial to 0.4 heavy damage 3: Substantial to 0.4 heavy damage 4: Very heavy 0.2 damage 4: Very heavy 0.2 damage 0 5: Collapse 5: Collapse 0 5 6 7 8 9 10 0 0.1 0.2 0.3 0.4 Macroseismic Intensity (EMS-98) Peak Ground Acceleration (g) Figure 4: Fragility functions for in-situ monolithic concrete frame buildings (c2.1) in EMS-98 macroseismic intensity. Figure 8: Fragility functions for in-situ monolithic concrete frame buildings (c2.1) in peak ground acceleration. 1 1: Negligible to Probability of damage exceeding 1 slight damage Probability of damage exceeding 1: Negligible to 0.8 slight damage each damage state 2: Moderate 0.8 each damage state damage 2: Moderate 0.6 damage 0.6 3: Substantial to 3: Substantial to 0.4 heavy damage heavy damage 0.4 4: Very heavy 4: Very heavy 0.2 damage 0.2 damage 5: Collapse 0 5: Collapse 0 5 6 7 8 9 10 0 0.1 0.2 0.3 0.4 Peak Ground Acceleration (g) Macroseismic Intensity (EMS-98) Figure 5: Fragility functions for large precast panel wall Figure 9: Fragility functions for large precast panel wall buildings buildings with monolithic panel joints (c3.1) in EMS-98 with monolithic panel joints (c3.1) in peak ground acceleration macroseismic intensity. 1 Probability of damage exceeding 1: Negligible to slight damage 1 0.8 Probability of damage exceeding 1: Negligible to each damage state 2: Moderate slight damage damage 0.8 0.6 each damage state 2: Moderate 3: Substantial to 0.6 damage 0.4 heavy damage 3: Substantial to 4: Very heavy 0.2 damage 0.4 heavy damage 0 5: Collapse 4: Very heavy 0.2 damage 0 0.1 0.2 0.3 0.4 Peak Ground Acceleration (g) 0 5: Collapse 0 0.1 0.2 0.3 0.4 Peak Ground Acceleration (g) Figure 10: Fragility functions for adobe buildings (c4) in peak Figure 6: Fragility functions for adobe buildings (c4) in EMS- ground acceleration. 3 Measuring Seismic Risk in the Kyrgyz Republic – Development of Fragility Functions – November 2017 Fragility Functions for Transport Infrastructure In the case of transport infrastructure (roads and bridges), Bridge vulnerability is dependent on material type, available and validated fragility functions were compiled complexity of the structure, the interaction with the bridge and further corrected through a regional modification abutments, and the local ground conditions. In this project, factor. In the event of an earthquake, ground shaking has fragility functions for road bridges were defined for two a direct impact on bridges and the corresponding fragility bridge types: concrete and steel. Damage state descriptions functions are given in terms of peak ground acceleration. were given using two states: (i) minor damage (or Damage to roads, however, is mainly caused by lateral yielding) and (ii) extensive/complete damage ground movement induced by earthquake action (e.g. In this project, fragility functions were determined as a through liquefaction), and as a result, fragility functions weighted combination of curves proposed for various for roads are given in terms of permanent ground bridge configurations in Europe. In the case of concrete deformation (PGD). brides, these include the combination of two sets of The damage state description for roads includes attributes: isolated / non-isolated, and regular / irregular “minor”, “moderate” and “extensive/collapse” limit (Figure 12). Fragility functions for steel road bridges were states. These are associated with serviceability obtained through a similar approach, whereby curves constraints identified as “reduced speed or partially proposed for multi-span simply-supported (MSSS), multi- closed” to “completely closed for weeks”. Fragility span continuous (MSC), and continuous steel (CS) bridges functions are defined according to the type of road in Europe were combined. (Figure 11), which is assumed as either “major” or “urban”, depending on the number of traffic lanes (equal or greater than four lanes in the case of “major” roads; and urban otherwise). Figure 11: Fragility functions for urban roads. Figure 12: Fragility functions for concrete bridges. Project Office The reports and digital datasets produced as part of this project are available on the Kyrgyz Geonode Central Asian Institute of Applied Geoscience, Timur (http://geonode.mes.kg/). Frunze Str. 73/2, 720027, Bishkek, Kyrgyz Republic Key Contacts For further information, please contact: Dr Bolot Moldobekov, Director of the Central Asian Institute of Applied Geoscience, Bishkek, at b.moldobekov@caiag.kg; Dr Matthew Free and Dr Yannis Fourniadis (Arup) at Matthew.Free@arup.com and Yannis.Fourniadis@arup.com; and Dr Stefano Parolai (GFZ) at parolai@gfz-potsdam.de. 4