Summary 2) Human Casualty Human casualties are estimated based on the estimated building damages, and the relations between the building damage and casualties are due to the study by DANE on the number of deaths and the number of heavily damaged buildings in the 1999 Quindio earthquake. The number of human casualties are estimated and shown in the following table: Table 33 Number of Human Casualties and Injuries Location Case-1 Case-2 Case-3 La Cajita Guayuriba Subduction Deaths Injuries Deaths Injujries Deaths Injuries Bogotá City 37,627 261,005 38,667 268,792 3,026 21,959 Eight Municipalities 1,621 11,621 1,771 12,768 239 1,790 Total 39,249 272,626 40,438 281,560 3,265 23,749 3) Lifeline Facilities The following four types of lifelines area considered for damage estimation: 1. Water supply pipelines, 2. Gas pipelines, 3. Electric power supply cables, 4. Telecommunications cables. Lifeline facilities are composed of nodes and links. The nodes include facilities such as purification plants, gas tanks, power generators and substations, and the links include facilities such as distribution pipes or lines. In the damage estimation of lifeline facilities, nodes are not included, yet individual diagnostic study for node facilities should be conducted to evaluate their seismic safety. (1) Water supply pipeline A. Damage function Damage due to the direct result of ground motion is estimated, such as breakage or disjoint of pipelines. Secondary damage such as effect of landslide or building collapse is not included. The damage estimation should be based on past experiences of seismic damages, but in cases when necessary data are not available, assumptions are made. An analysis method for the damage estimation of water and gas pipelines proposed by Japan Waterworks Association, and which is widely used in Japan, was applied to the study taking into account the experience of the 1999 Quindio earthquake. In Japan, standard damage ratio R (a) for water pipeline proposed by Kubo and Katayama (1975) is commonly used to evaluate seismic risks of water pipelines. 45 The Study on Disaster Prevention in the Bogotá Metropolitan Area in the Republic of Colombia The damage ratio for pipeline Rm (α) is defined as follows: Rm (α) = Cp Cd Cg Cl R (α) Where, R (α): standard damage ratio (damaged points/km), Cp: correction factor for pipe material Cd: correction factor for pipe diameter Cg : correction factor for topography and ground Cl: correction factor for liquefaction α: peak ground acceleration (gal) Japan Waterworks Association compiled in 1966 the relationship between damage ratios of pipelines and PGA values based upon the actual observed damages in the 1995 Kobe earthquake. They applied an average damage ratio especially case for larger PGA. There is a significant difference in damage ratio between the above two procedures, especially for the case of acceleration range from 300 gal to 800 gal. Kawakami’s study (1996) shows that 1) service interruption rate after two days from the main shock is about 60% for 0.6 damaged points/km, 2) service interruption rate is 87% in case for 2.0 damaged points/km. According to the damage study on the 1999 Quindío earthquake, the following are noted. - In Armenia, recorded PGA was 589 gal, and almost no service was available after two days from the main shock. - In Pereira, recorded PGA was 291 gal. Almost all service was available after two days from main shock. Standard Damage Ratio Proposed for this Study If PGA of 589 gal in Armenia earthquake is applied to the damage curve of Japan Waterworks Association, damage ratio is about 0.6 points/km. However, the fact that there was almost no service available after two days is an indication of a higher damage ratio than 0.6 points/km considering Kawakami’s study. Therefore, a higher damage ratio than the damage curve of Japan Waterworks Association is proposed as shown in the following figure: 46 Summary Pipeline Damage Function R(a) 2.5 2.0 Kubo & Katayama(1975) 1.5 Japan Waterworks Association ATC-13 1.0 Proposed Damage ratio (points/km) ratio Damage 0.5 0.0 0 200 400 600 800 PGA (gal) Figure 10 Standard Damage Ratio for Pipelines B. Result of estimation The results are as follows: Case-1: La Cajita The estimated damages are concentrated in the southern part of the Study Area, due to the high ground acceleration and the liquefaction phenomena. In Cundinamarca, Soacha suffers major damage. In Bogotá, damage ratio in Usme and Ciudad Bolivar exceeds 2.0 points per km. The damage ratio in San Cristobal and Soacha is also high, 1.3 points per km and 1.4 points per km respectively. - The liquefaction will cause an extensive damage to the susceptible locality such as Kennedy, Puente Aranda, Rafael Uribe and Ciudad Bolivar. - Regarding the pipe material, asbestos cement suffers major damages. This is partly because it is a relatively fragile material, and partly because majority (70%) of pipeline material in the whole area is asbestos cement . Case 2 Guayuriba The estimated damages spread wider in Bogotá City, though total amount of damage is smaller than that in Case 1. Damage will extend in the liquefied area. The area with maximum damage ratio is Tunjuelito whose value is 0.5 points per km. 47 The Study on Disaster Prevention in the Bogotá Metropolitan Area in the Republic of Colombia Case 3 Subduction The results show almost no damage. Table 34 Water Supply Pipeline: Damage Points and Damage Ratios Case-1 Case-2 Case-3 La Cajita Guayuriba Subduction Location Length (m) (m) Length Points Damage Ratio Damage (Points/Km) Points Damage Ratio Damage (Points/Km) Points Damage Ratio Damage (Points/Km) Bogotá City 6,253,444 3,504 0.6 1,488 0.2 15 0.0 Eight 536,048 249 0.5 57 0.1 1 0.0 Municipalities Total 6,789,491 3,7530.6 1,545 0.2 16 0.0 C. Damage estimation of other lifeline facilities a) Gas Pipeline: Total Length and Damage Points and Damage Ratios Location Length (m) Damage points Damage Ratio (points/km) Case-1 Case-2 Case-3 Case-1 Case-2 Case-3 Bogotá 8,023,800 388 132 1 0.05 0.02 0.00 Eight Municipalities 767, 657 39 7 0 0.05 0.01 0.00 Total 8,790,457 428 139 1 0.05 0.02 0.00 b) Electric Power Supply: Cable Length and Damage/Damage Ratios Location Length (m) Damage (m) Damage Ratio (%) Case-1 Case-2 Case-3 Case-1 Case-2 Case-3 Bogotá 4,921,217 2,319 950 0 0.05 0.02 0.00 Eight Municipalities 843,730 90 51 0 0.01 0.01 0.00 Total 5,764,947 2,409 1,001 0 0.04 0.02 0.00 c) Telecommunication: Cable length and Damage/Damage Ratio Location Length (m) Damage (m) Damage Ratio (%) Case-1 Case-2 Case-3 Case-1 Case-2 Case-3 Bogotá 10,503,245 5,088 2,083 0 0.05 0.02 0.00 Eight Municipalities 1,196,524 495 105 0 0.05 0.02 0.00 Total 11,699,770 5,583 2,189 0 0.05 0.02 0.00 4) Damage Estimation of Vehicular Bridges (1) Methods and procedures Methods The seismic damage of bridges is estimated based on Tsuneo Katayama's method, which has been adopted in the Disaster Prevention Council of Tokyo Metropolitan Area (1978) and is widely used in Japan. The method does not evaluate collapsing of beams, breaking of piers or foundations etc. The following factors are taken into account for evaluation: 48 Summary - Ground type, liquefaction, girder type, number of individual girders, - Bearing type (shoe type), minimum bridge seat width, - Maximum height of abutment and pier, earthquake intensity scale - Foundation type, material of abutment and pier Estimated seismic risk is expressed as a total score. Stability judgment of bridges is defined as follows: - Total score of 31 and above: High Seismic Risk - Total score from 26 to 30: Medium Seismic Risk - Total score of 25 and below: Low Seismic Risk Pedestrian Bridge In this Study, pedestrian bridges are evaluated only with respect to liquefaction potential area. This is partly because collapsed pedestrian bridges will not be major obstructions after an earthquake, since it is relatively easy to clear the wreckage afterwards. No information on collapse of pedestrian bridges during earthquakes in Colombia was available. (2) Results of damage estimation The estimated damages by Case 1 and Case 2 are almost the same and about one-third of the bridges is estimated to be “high risk,” but no damage is expected in Case 3. All the bridges in the municipalities of Cundinamarca are evaluated “low risk” for the three Cases. Regarding liquefaction effects, more than 70% of high-risk bridges are estimated to be affected by liquefaction. Results of damage estimation are summarized in the following table: Table 35 Summary of Estimated Seismic Risk Seismic Case 1: La Cajita Case 2:Guayuriba Case 3: Subduction Risk Nom. % Nom. % Nom. % High 53 27.3 58 29.9 0 0.0 Medium 1 0.5 0 0.0 0 0.0 Low 140 72.2 136 70.1 194 100.0 Total 194 100.0 194 100.0 194 100.0 (3) Pedestrian bridges in liquefaction potential area Liquefaction during earthquake would cause serious damage to bridges. In this Study, location of pedestrian bridges is examined from the viewpoint of potentially liquefiable area for two scenario earthquakes. As a result, almost 20% of pedestrian bridges are located in liquefaction potential area.