RELATIONSHIP BETWEEN DAMAGE TO NONSTRUCTURAL BUILDING ELEMENTS AND THE SEISMIC INTENSITIES OF RECENT EARTHQUAKES IN JAPAN

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1 First European Conference on Earthquake Engineering and Seismology (a joint event of the 13 th ECEE & 3 th General Assembly of the ESC) Geneva, Switzerland, 3-8 September 26 Paper Number: 726 RELATONSHP BETWEEN DAMAGE TO NONSTRUCTURAL BULDNG ELEMENTS AND THE SESMC NTENSTES OF RECENT EARTHQUAKES N JAPAN Hiroshi KAMBARA 1, Yasuhiro HAYASH 2 and Kazuo TAMURA 3 SUMMARY n this study, we examined the relationship between the seismic intensities and the percentage of buildings with damaged nonstructural elements based on damage survey data taken after five earthquakes that occurred recently in Japan. The following characteristics are found for damage to nonstructural elements in the areas where the JMA instrumental seismic intensity were under 6. 1) The percentage of buildings in which damage was found at exterior, interior and sanitary accommodations vary according to the type of earthquakes and the characteristics of seismic motions while the percentage of buildings with moved and overturned furniture do not vary. 2) At levels over 5, more than 2 percent of buildings were damaged and needed some amount of money to repair. 3) At levels over 5.5, electric power supply, water supply, lighting and elevator systems stopped in more than 2 percent of buildings although disruption to buildings systems except for water supply and elevator recovered within one day. 1. NTRODUCTON Strong ground motions with level 6 or more in the have been frequently observed in several earthquakes that occurred in Japan recently. These earthquakes gave severe damage to nonstructural elements and equipment of many buildings, though the structural frames of some of those buildings had not serious damage. A long-term cessation of buildings functions caused by damaged equipment and nonstructural elements may affect company activities in some buildings. These disasters indicate that improving seismic performance is very important not only for structural members but also for nonstructural elements of buildings. The probability of earthquake occurrence in the future and the intensity of ground motions due to the future earthquake are being evaluated by the national research organization in Japan[The Headquarters for Earthquake Research Promotion, 25]. Those results indicate that the possibilities of strong motions with more than level 6 in the are highly predicted in some regions of Japan. From such a background the concern about earthquake prevention and mitigation has been increased recently. Buildings with important functions are requested to maintain the functions after large earthquakes. From the viewpoint of disaster prevention and prompt restoration, it is important to predict damage to buildings properly due to earthquakes and to prepare appropriate countermeasures. n order to predict the damage to buildings properly, vulnerable functions [Hayashi et al., 2, Miyakoshi et al., 1997] are often used, which were derived from data based on the during the 1995 Hyogo-ken Nanbu Earthquake. t has been pointed out in the 1995 Hyogo-ken Nanbu Earthquake that the large peak at the period of one second contained in the ground motions gave the severe damage to many buildings[hayashi and Kawase, 1996]. However, it is not clear that the 1 nstitute of Technology, Shimizu Corporation, Tokyo, Japan kambara@shimz.co.jp 2 Kyoto University, Kyoto, Japan hayashi@archi.kyoto-u.ac.jp 3 nstitute of Technology, Shimizu Corporation, Tokyo, Japan tamkaz@shimz.co.jp 1

2 relations between the seismic intensity and damage to buildings by other earthquakes are similar to those by the 1995 Hyogo-ken Nanbu Earthquake. The vulnerable functions based on the data during the 1995 Hyogo-ken Nanbu Earthquake are not necessarily applicable to the prediction of damage to buildings by the various types of earthquakes. Because damage investigations after the 1995 Hyogo-ken Nanbu Earthquake were mainly conducted in the areas where the seismic intensities were large, many of collected data come from severely. Therefore the obtained vulnerable functions cannot be applicable to the prediction of damage in non-structural elements and equipment of buildings. n order to examine the relations between the seismic intensity and the damage degree of RC buildings, we have conducted surveys on damage to buildings caused by several other earthquakes[kambara et al., 24, Kuo et al., 24]. n our previous studies, we derived the relations between the seismic intensity and the percentage of buildings damaged in non-structural elements. The buildings were selected in the areas where the seismic intensities were under 6 during the 2 Tottori-ken Seibu Earthquake and the 2 Geiyo Earthquake[Kambara et al., 24]. n this paper, we present the difference in the percentage of buildings damaged in non-structural elements and equipment by seismic fault types and characteristics of ground motions, based on the damaged building data by the five earthquakes that occurred in Japan recently. We also examine economic and functional losses caused by the damage in non-structural elements and equipment. 2. DATA ON DAMAGE TO BULDNGS N EARTHQUAKES This study used questionnaire surveys to investigate damage levels of nonstructural elements of buildings in selected areas[kambara et al., 24]. The surveys were conducted on selected RC buildings located near earthquake observation points where JMA instruments recorded seismic intensities over 4. for any of the past five earthquakes in Japan. The five earthquakes are the 2 Tottori-ken Seibu Earthquake, the 21 Geiyo Earthquake, the May off Miyagi Prefecture Earthquake, the July Northern Miyagi Prefecture Earthquake and the 23 Tokachi-oki Earthquake. The questionnaires consisted of questions about damage to various nonstructural elements and to various kinds of building equipment due to earthquake shaking. We asked users of buildings whether they experienced any of the states of damage and/or collateral damage as shown in table 2 in the questionnaires. The study used data on damage of 686 RC buildings. The number of the examined buildings in selected areas is shown in Table 2 according to construction year, usage, number of stories and seismic intensity. More than half of the buildings were constructed before 198 when the regulations for seismic design in Japan were revised. Many of the buildings are schools, public offices, or private company offices. Many of the buildings are under 5 stories tall. More than half of the buildings were located at an area where seismic intensity was in the range of 4.5 to 5.5. The percentage of buildings with direct or collateral damage to all buildings was about 4 percent. The states of damage to buildings and states of collateral damage that occurred inside the buildings shown in Table 1 are classified into categories shown in Table 2 by degree of direct damage or collateral damage. The percentage of buildings with any states of direct damage or collateral damage in each category are calculated at the same level of seismic intensity. Figure1 shows the percentage of buildings with damage of each category shown in Table 1. The percentage of buildings with damaged nonstructural (a) before Exterior() Exterior() nterior() nterior() nterior() Window/door() Window/door() Window/door() Ceiling() Ceiling() Fire Protection Elevated Equipment() Elevated Equipment() Furniture() Furniture() Building Systems (Except for elevator) (b) after 1981 Exterior() Exterior() nterior() nterior() nterior() Window/door() Window/door() Window/door() Ceiling() Ceiling() Fire Protection Elevated Equipment() Elevated Equipment() Furniture() Furniture() Building Systems (Except for elevator) Figure 1: at the same level of in the areas 2

3 elements increases with the age of the buildings. Among buildings constructed before 198, slight damage such as exterior (), interior () and window/door () were detected at seismic intensity levels over 4.. At seismic intensity levels over 5, more sever damage such as exterior (), interior (), ceiling and lighting (), sanitary accommodations and furniture (,,) were detected and the percentage of occurrence are more than 1 percent. At seismic intensity levels over 5.5, the percentage of buildings with slight damage and damage to furniture reached over 4 percent. As for equipment, the percentage of buildings with damage to lighting and sanitary accommodations increase with seismic intensity, while damage to air conditioning systems, fire protection systems and elevated equipment was found less frequently. On the other hand, among buildings constructed after 1981, slight damage such as exterior (), interior () and opening () and damage to furniture(,,) were detected at seismic intensity levels over 5. Damage to ceilings, sanitary accommodations and cessation of basic building functions were detected at seismic intensity levels over 5.5 and more than 1 percent of the buildings surveyed had these levels of damage. Table 1: States of direct damage and collateral damage due to earthquake shaking Nonstructural Elements Exterior nterior Equipment Column, Wall Window, door Column, Wall Door Ceiling Floor Electric installation accommodations Air conditioning system Fire protection system Elevator Elevated equipment nside of building Building system States of direct damage and collateral damage Crack, Peeling off, Exposure of reinforcement bar Crack of window glass, Deformation of window frame Difficult to open or shut window and door mpossible to open or shut window and door Crack, Peeling off, Exposure of reinfored Difficult to open or shut door mpossible to open or shut door Gap of ceiling board, fall of ceiling board Crack, Peeling off Movement of lighting, Break of lighting Fall of lighting Break of sanitary accommodations Peeling of tile, Break of water pipe Break of air conditioning equipment Break of air outlet equipment Break of pipe Overturnning of air conditioning equipment Break of sprinkler Break of fire protection equipment breakdown Movement of air conditioning equipment Overturning of air conditioning equipment Break of elevated water tank Overturning of elevated water tank Break of pipe Overturning of things on the desk Movement of desk Overturning of TV Movement of Large-scale furnitur Overturning of Large-scale furniture Cessation of electric power supply Cessation of lighting system Cessation of water supply Cessation of air conditioning system Cessation of function of elevator 3

4 Table 2: The number of buildings examined for this study Earthquake Tottori-ken Seibu Geiyo Off Miyagi Prefecture Northern Miyagi Prefecture Tokachi-oki Total Construction year Number of buildings school Usage public office Number of floors office Number of damaged buildings (ratio) before (.55) after (6) before (8) after (.36) before (1) after (.3) before (.52) after (.62) before (.51) after (7) before (8) after () All year (5) Table 3: Classifications of states of direct damage and collateral damage Category Exterior nterior Window/door Ceiling Air conditioning Fire protection Elevated equipment Furniture Building system States of direct damage and collateral damage Crack of wall, Crack of column Peeling of wall, Peeling of column, Crack of glass Difficult to open or shut window and door Exposure of reinforcment bar mpossible to open or shut window and door Crack of wall, Crack of column Peeling of wall, Peeling of column, Crack of glass Deformation of window frame, Difficult to open or shut door Exposure of reinforcment bar, mpossible to open or shut door Crack of glass Break of glass, Difficult to open or shut door and window mpossible to open and shut door and window Gap of ceiling board, movement of lighting Fall of ceiling board, Fall of lighting Break of accommodations, Peeling of tile, Break of pipe Break of air conditioning equipment, Break of air outlet equipment Break of pipe, Overturning of air condtioning equipment Break of splinker, Break of fire protection equipment Movement of equipment, Break of elevated water tank Overturning of air condtioning equipment Overturning of elevated water tank, Break of pipe Overturning of things on the desk Movement of desk or large-scale furniture Mverturning of TV or large-scale furniture Cessation of electric power supply, Cessation of lighting system Cessation of water supply, Cessation of air conditioning system Cessation of function of elevator 4

5 3. RELATON BETWEEN SESMC NTENSTY AND DAMAGE TO NONSTRUCTURAL ELEMENTS 3.1 DFFERENCE N THE PERCENTAGE OF DAMAGED BULDNGS BY THE TYPE OF EARTHQUAKE The five earthquakes, the damage of which are surveyed are classified into three categories by the type of seismic faults where they occurred. The 2 Tottori-ken Seibu Earthquake and the July 26, 23 Northern Miyagi Prefecture Earthquake are crustal earthquakes. The 21 Geiyo Earthquake and the May off Miyagi Prefecture Earthquake were intra-plate Earthquakes. The 23 Tokachi-oki Earthquake was an interplate earthquake. Figure 2 shows the percentage of buildings with damage to exterior, ceiling and lighting, sanitary accommodations, and furniture calculated at the same level of seismic intensity according to the type of seismic faults where they occurred. The percentage of corresponding to JMA seismic intensity is calculated among buildings in the area where JMA seismic intensities were in the range of -5 to +5. The percentage of is not calculated if the number of buildings surveyed at the same level of seismic intensity was less than 1. At levels under 5.5, the percentage of buildings with damage to their exterior in inter-plate earthquakes is about half of the percentage in the other types of earthquakes. The difference in the percentage of by the types of earthquakes was small at levels over 5.5. As for sanitary accommodations, damage was not detected in inter-plate earthquakes while damage was detected in other types of earthquakes at levels under 5.5. The difference in the percentage of buildings with damage to interior and window/door between inter-plate earthquakes and the other types of earthquakes are also found. On the other hand, the percentage of buildings with damage to ceiling and lighting does not vary with the type of earthquakes at JMA seismic intensity levels under 5.5. Moreover, at levels over 5.5, the percentage of buildings with damage to ceiling or lighting in inter-plate earthquakes was bigger than those in the other types of earthquakes. As for furniture damage, the percentage of buildings with damage to furniture increased greatly at JMA seismic intensity levels over 5.5. The difference in percentage of among the three types of earthquakes is relatively small though levels of seismic intensities at which the percentage of begins to increase vary according to the types of earthquakes..8.6 All ntra-plate Crustal nter-plate.8.6 All ntra-plate Crustal nter-plate Ceiling() JMA seicmic intensity JMA seicmic intensity JMA seicmic intensity.8.6 All ntra-plate Crustal nter-plate.8.6 All ntra-plate Crustal nter-plate JMA seicmic intensity Figure 2: Difference in percentage of between three types of earthquakes at the same level of in the areas (constructed before 198) 3.2 DFFERENCE N PERCENTAGE OF DAMAGED BULDNGS BY CHARACTERSTCS OF SESMC MOTONS Figure 3 shows peak acceleration (A), peak velocity (V) and of seismic motions observed in the areas where the damage surveys were conducted. These figures indicate the following: The ratios A/V vary according to the type of earthquakes. The ratios A/V of seismic motions observed in crustal and intra-plate earthquakes are mainly over 1 while the seismic motions observed in inter-plate earthquakes are mainly under 2. At the same level of, the peak acceleration of seismic motions observed in inter-plate earthquakes is relatively small while the peak velocity of seismic motions observed in inter-plate earthquakes is relatively large. Therefore, the characteristics of seismic motions vary according to the type of earthquakes. According to the ratios A/V, seismic motions observed in crustal and intra-plate earthquakes have a large peak in a short period. Seismic motions observed in inter-plate earthquakes have a large peak in a long period. Here, observed seismic motions are classified into three categories by the ratios A/V to examine how the percentage of at the same level of seismic intensity varies according to characteristics of seismic motions. 5

6 Crustal ntra-plate nter-plate Crustal ntra-plate nter-plate Crustal ntra-plate nter-plate Peak ground acceleration (cm/s 2 ) A/V= Peak ground velocity (cm/s) Peak ground acceleration (cm/s 2 ) Peak ground velosity (cm/s) Figure 3: ntensities of seismic motions observed in the investigation area.8.6 All A/V=1-2 A/V<1 2<A/V.8.6 All A/V=1-2 A/V<1 2<A/V Ceiling().8.6 All A/V=1-2 A/V<1 2<A/V JMA seicmic intensity JMA seicmic intensity JMA seicmic intensity JMA seicmic intensity.8.6 All A/V=1-2 A/V<1 2<A/V Figure 4: Difference in percentage of by the ratios A/V at the same level of seismic intensity in the areas (constructed before 198).8.6 All A/V=1-2 A/V<1 2<A/V Peak ground acceleration (cm/s 2 ) Peak ground acceleration (cm/s 2 ).8.6 All A/V=1-2 A/V<1 2<A/V.6 All A/V=1-2 A/V<1 2<A/V Pead ground velocity (cm/s).6 All A/V=1-2 A/V<1 2<A/V Pead ground velocity (cm/s) (a) Peak ground acceleration (b) Peak ground velocity Figure 5: Difference in percentage of by the ratios A/V at the same level of peak acceleration and peak ground velocity in the areas (constructed before 198) Figure 4 shows the percentage of at the same level of seismic intensity which is calculated in the areas where the ratios A/V of observed seismic motions are under 1, 1-2, over 2. Except for furniture, the percentage of for the ratios A/V under 1 was obviously different from those of damaged buildings for the ratios A/V over 1. There is not much difference in the percentage of buildings with damage to furniture calculated by the ratios of A/V. This result indicates that the percentage of buildings with damage to furniture can be predicted accurately by the level of. t should be noted that the percentage of increases with peak acceleration when the percentage of at the same level of seismic intensity increases with the ratios A/V. Therefore, the percentage of damaged buildings at the same level of the other indices for seismic intensity is calculated to examine which indices of seismic intensity can be applicable to explain the damage levels of buildings. Figure 5 shows the percentage of buildings with damage to exterior and furniture at the same level of peak acceleration and peak velocity. The percentage of is not calculated where peak acceleration or peak velocity is over 5 cm/s2 or 6

7 35 cm/s and the ratios A/V are under 2 or over 1 respectively because the number of examined buildings is less than 1. At the same level of peak acceleration, the percentage of buildings with damaged exteriors does not vary according to the ratios A/V while the percentage of buildings with damaged furniture does vary according to the ratios A/V. On the other hand, at the same level of peak velocity, the percentage of buildings with damaged exteriors vary according to the ratio A/V while the percentage of buildings with damaged furniture does not vary. These results indicate that the level of peak acceleration is an appropriate parameter to predict the percentage of buildings with exterior damage while the level of peak velocity is a suitable parameter to express the percentage of buildings with damaged furniture. 4. ECONOMC LOSS AND FUNCTONAL DAMAGE 4.1 ECONOMC LOSS AND FUNCTONAL DAMAGE RELATED TO SESMC NTENSTY We surveyed the amount of economic loss due to earthquake shaking and a period of functional cessation in the May off Miyagi Prefecture Earthquake, the July Northern Miyagi Prefecture Earthquake and the 23 Tokachi-oki Earthquake. Figure 6(a) shows the relationship between the level of and the percentage of buildings that suffered economic loss. The difference in construction year between buildings is not considered here. The amount of economic loss is necessarily correspondent to a degree of damage to structural and nonstructural elements because the amount of economic loss depends on the scale of a building, the material used in construction and finishing, the amount of equipment the building contained, the actual use of the building, degree of occupancy, etc. According to the percentage of buildings with losses of more than 1, yen, at levels over 5, more than 2 percent of buildings were damaged and needed some amount of money to repair. The percentage of buildings with losses of more than one million yen is about half of those of buildings with losses of more than 1, yen. This indicates that repair costs are more than one million yen for half of which needed repairs. Losses of more than 1 million yen which may be expensive for some owners of buildings were detected in about 1 percent of buildings at level 6. Figure 6(b) and Figure 6(c) show the percentage of buildings with cessation of electric power supply, lighting, water supply and air conditioning systems at the same level of JMA seismic intensity. The solid line in figures shows the percentage of buildings where any of the buildings systems stopped. At seismic intensity levels over 5.5, electric power supply, lighting and water supply systems ceased to function in more than 2 percent of buildings. Most of these functions were restored within one day except for water supply. According to figure 1, the percentage of buildings with damage to sanitary accommodations at levels over 5.5 were about 2 percent. This value corresponds to the percentage of buildings with disruption of water supply. Damage to sanitary accommodations caused disruption of water supply and it took one day or longer to repair them. Figure 6(d) shows the percentage of buildings with cessation of function of elevators at the same level of seismic intensity. n more than 2 percent of elevators stopped at levels over 5. At levels over 5.5, the percentage of buildings where elevators stopped for one day or longer increased. buildings.8.6 over 1, yen over 1 million yen over 5 million yen over 1 million yen Amount of losses.8.6 Electric power supply Water supply Lighting Air conditioning Cessation of building system.8.6 Electric power supply Water supply Lighting Air conditioning Cessation of building system (for one day or longer) JMA seicmic intensity JMA seicmic intensity JMA seicmic intensity JMA seicmic intensity.8.6 Stoppage for 1 day or longer for 3 days or longer Cessation of function of elevator Figure 6: Relationship between seismic intensities and the percentage of buildings with economic loss and functional damage 4.2 RELATON BETWEEN ECONOMC LOSS AND DAMAGE TO NONSTRUCTURAL ELEMENTS To examine contents of losses, the percentage of buildings with damaged nonstructural elements and equipment is calculated among buildings with losses of less than 1, yen, more than 1, yen, more than 1 million 7

8 yen, and more than 5 million yen. These results are shown in figure 7. Among the buildings with losses more than 1, yen, the percentage of buildings with damage to exterior, interior and furniture are high. Among the buildings with losses of more than 1 million yen, damage to sanitary accommodations and outage of electric power supply, water supply and lighting were detected. Among the buildings with losses of more than 5 million yen, damage was detected at the same nonstructural elements of buildings and the percentage of were high. There were no buildings where any of building systems ceased functioning for one entire day or longer. This shows that long-term outages caused by damage to nonstructural elements and equipment were not found in areas where levels under 6 in the areas surveyed. Amount of losses Under 1, yen Over 1, yen Over million yen Over 5 million yen Exterior() Exterior() nterior() nterior() nterior() Window/door() Window/door() Window/door() Ceiling() Ceiling() Fire Protection Elevated Equipment() Elevated Equipment() Furniture() Furniture() (a) Direct damage buildings Amount of losses Under 1, yen Over 1, yen Cessation of building systems Electric Power Supply Lighting System Water Supply Elevator Over million yen Over 5 million yen Cessation of building systems (for one day or longer) Electric Power Supply Lighting System Water Supply Elevator (b) Collateral damage Figure 7: Relationship between percentage of and economic loss 5. CONCLUSONS Based on damage survey data taken after five earthquakes that occurred recently in Japan, we examined how the difference in the percentage of buildings damaged in non-structural elements varies according to the seismic fault types and the characteristics of ground motions. We also examined the relations between the seismic intensity and economic loss and functional damage caused by earthquakes. As a result, we can draw our conclusions as follows. 1) The percentage of buildings with damaged nonstructural elements and equipment may vary according to the type of seismic faults and characteristics of ground motions. 2) The percentage of at exterior and interior parts and sanitary accommodations in the crustal and intra-plate earthquakes was larger than that in the inter-plate earthquakes. The percentage of damaged buildings in the same parts shows also larger values in accordance with the increase of the A/V ratios of ground motions. This result indicates that the percentage of in exterior and interior parts and sanitary accommodations has relationship to the peak acceleration of ground motions. 3) The percentage of buildings in which furniture is moved and/or overturned does not vary according to the type of earthquakes and the A/V ratios. 4) As for economic losses, in the areas where the seismic intensity was over 5, more than 2 percent of buildings were damaged and needed some amount of money to repair. At level 6, losses of more than 1 million yen, which may be expensive for some owners, may be found in about 1 percent of buildings. 5) As for functional damage, at levels over 5.5, more than 2 percent of buildings experienced disruptions in electric power supply, water supply and lighting systems. At level 6, periods of outage of elevators and water supplies were one or more days, although disruption to building systems except for elevators and water supplies recovered within one day. 8

9 6. REFERENCES Hayashi, Y. and H. Kawase (1996), Strong Motion Evaluation in Chuo Ward Kobe During the Hyogo-ken Nambu Earthquake of 1995, Journal of Structural and Construction Engineering, Architectural nstitute of Japan, No.481, (in Japanese). Hayashi, Y., J. Miyakoshi, and M. Watanabe (2), Seismic Risk Evaluation of RC Buildings Based on Kobe Earthquake of 1995, Japan, Proc. of 6th nternational Conference on Seismic Zonation, Kambara H., Y. Hayashi and K. Tamura (24), Relationship between Non-structural Elements Damage and Seismic ntensity based on Questionnaire Survey, Journal of Structural and Construction Engineering, Architectural nstitute of Japan, No.578, (in Japanese). Kuo K., Y. Hayashi and H. Kambara (24), Relationship between Damages of Hospital Buildings and Seismic ntensity based on Questionnaire Survey, Journal of Structural and Construction Engineering, Architectural nstitute of Japan, No.586, (in Japanese). Miyakoshi, J., Y. Hayashi and K. Tamura (1997), Damage Ratio Functions of Buildings Using Damage Data of the 1995 Hyogo-Ken Nanbu Earthquake, Proc. of COSSAR'97, , The Headquarters for Earthquake Research Promotion (25), National Seismic Hazrad Maps for Japan (25), 9