Typhoon Engineering Efforts in the Philippines toward Sustainable Structures

DMAPS Looking Forward: Calling for “Typhoon Engineers” Benito M. Pacheco(1), and Ronwaldo Emmanuel R. Aquino(2) (1)

Chairman, PICE Committee on DMAPS and DQRP  Member, PICE Committee on DMAPS and DQRP

(2)

ABSTRACT: The Philippines is considered to be historically one of the most disaster-prone countries in the world. world. Wind storms including including typhoons rank as the worst natural disaster disaster type, with an annual average of 20 tropical cyclones passing the Philippine Area of Responsibility, and with 9 landfalling landfalling or actually crossing the archipelago. This paper advocates advocates more activities in the areas of typhoon disaster engineering, research, and mitigation, or collectively as now referred to here, “typhoon engineering,” similar to attention to the effects of devastating earthquakes. Meanwhile, there are numerous sources of available information for “typhoon engineers,” and some are introduced in this paper. One such information is is typhoon damage information. information. A  photo gallery of damages due to strong winds winds of Typhoon Unding in in November 2004 is presented as an example. The paper suggests how how information such as these may be used in developing developing historical “disaster maps” and current “vulnerability maps” according to the strategies of the PICE DMAPS (Disaster Mitigation Mitigation and Preparedness Strategies). The paper then presents a history of wind speed maps (“hazard maps”) that are used in the NSCP (National Structural Code of the Philippines). Short comments on the NSCP wind load provisions, provisions, intended to inspire inspire more research, are also provided. provided. The paper ends with some ideas for research in other fields of of “typhoon engineering” and a call for “Typhoon Engineers,” as another step in future activities of the PICE Committee on DMAPS & DQRP. KEYWORDS: Philippines, typhoon engineering, disaster maps, vulnerability maps, hazard maps

1 INTRODUCTION: THE PHILIPPINES AND NATURAL DISASTERS

In 2004 the Philippine Institute of Civil Engineers (PICE) launched a national program named Disaster Mitigation and Preparedness Strategies (DMAPS), to complement the earlier Disaster Quick Response Program (DQRP) (DQRP) [Pacheco, 2004a]. In addition to the response phase and recovery/rehabilitation phase, which historically were the first focus of DQRP, the mitigation phase and preparedness phase of disaster management were now being given due attention. In addition to earthquake, which historically was the focus of DQRP, typhoons, typhoons, floods and other natural hazards were now being discussed. Indeed the Philippines tends to be visited by a lot of natural disasters. A database of natural and technological disasters worldwide shows that the Philippines is one of the most disaster prone countries coun tries in the world. (Data source: EM-DAT: The OFDA/CRED International Disaster Database – www.em-dat.net – Universite Catholique de Louvain – Brussels – Belgium; as cited  by [Pacheco, 2004b]) The Asian Disaster Reduction Center (Japan), analyzed trends from the same database, and showed that wind storms (typhoons) rank first as the worst natural disaster type, followed by earthquakes and floods. [ADRC, 2002] [Pacheco, 2004b] (See Table 1.)

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Individual wind storm events also comprise most of the historical top 10 worst natural disasters in the Philippines in terms of number of people killed and affected, and total damages. (Table 2) “Wind storms” include tropical cyclones, tornadoes, and the like, as defined in the EM-DAT database. Their impact could be more intense than that suggested by average annual numbers from the said database, because these disasters would hit in relatively short durations, and that the numbers from the first half of the century were almost surely understated because relatively few major disasters had been adequately recorded prior to 1975 [Pacheco, 2004b]. The Philippines is considered to be in the “Typhoon Alley” or “Typhoon Gateway” of the Pacific northwest. [Rellin, et al, ~2002] An average of 20 tropical cyclones, mostly coming from from the Pacific, pass through the Philippine Area of Responsibility (PAR) each year and about 9 of these are landfalling, or actually crossing the archipelago. In contrast, annual averages for landfalling tropical cyclones in some of our neighbors are around 3 to 5 only. For some years, there were as few as 11 (1998) and as much as 32 (1993) tropical cyclones that entered the PAR, and as few as 4 (1955, 1958, 1997) and as much as 19 (1993) landfalling. (See Figures 1 & 2 .) However, numbers do not indicate the effects on people and property. In 1998, a “dry” year with only 11 cyclones passing through the PAR, damages brought about by Typhoon Iliang (International Name: Zeb) which affected more than 2 million people, and Typhoon Loleng (International Name: Babs) which caused around PHP6.8 million in damages, are comparable to other destructive typhoons. There is much attention to the effects of devastating earthquakes in the Philippines, being in the “Pacific Ring of Fire,” although this is the same case as in other countries, including Japan and the USA. This could perhaps be explained by looking at numbers for individual events. Table 3  shows that the worst individual earthquakes injure and affect more people, as well as cause more damages in terms of monetary costs, than the worst individual wind storms, or floods. However, given the frequency of tropical cyclones, and the total damage by all tropical cyclones combined greater than those by all other disasters combined, there still seems to be a wide range of possible studies in typhoon disaster engineering, research, and mitigation, or collectively referred to here as “typhoon engineering.” The term was probably first first used by Sawada [2002], in the context of disaster prevention, and in parallel to “earthquake-proofing” of infrastructures. A similar term, “hurricane engineering,” was probably first used by the Louisiana State University (USA) as a new academic program in 2000 [Ward, 2000]. Because typhoons cause not only strong winds but also floods, landslides, mudslides, storm surges, and occasionally tornadoes, while strong winds also cause “wind-borne missiles” or are magnified due to the urban environment, it seems that typhoon engineering covers a broad range of various disciplines in the natural and social sciences, and engineering. Thus, typhoon engineering in the context of this paper is similar to earthquake earthquake engineering as a multi-disciplinary field. It is a common ground of wind engineering, structural engineering, geotechnical engineering, meteorology, typhoon prediction, flood control, coastal engineering, disaster management, evacuation planning, public health and sanitation, community development, infrastructure development, architecture, urban planning, wind power generation, and so on. This paper presents some sources of available information that could be used by engineers,  planners, and disaster mitigation experts for typhoon engineering in the Philippines, aligned with objectives of the PICE Committee on DMAPS and DQRP.

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TYPHOON DAMAGE INFORMATION: TOWARDS DEVELOPING HISTORICAL “DISASTER MAPS” AND CURRENT “VULNERABILITY MAPS”

2.1 Sources of Typhoon Damage Information The OCD-NDCC is an umbrella organization headed by the Secretary of National Defense and composed of about 17 branches of the government including the Armed Forces of the Philippines, the Philippine National Red Cross, the DPWH, the DOJ, the DOH, the DSWD,  NEDA, the DepEd, and many others, as disaster management surely necessitates a multidisciplinary and multi-sectoral effort. The OCD-NDCC covers a broad scope that includes  preparedness, mitigation, response, and rehabilitation. In preparing for typhoons, it ties up with PAGASA, as it does with PHIVOLCS for earthquake-related disasters. One of the activities of the OCD-NDCC is the documentation of property damages and affected populations. In line with this, they prepare two sets of publicly accessible documents. PAGASA likewise prepares “Tropical Cyclone Summaries.” (See Table 5.) Mr. David Michael Padua of Naga City collected some interesting “Top 10” lists of typhoon effects at his website (http://www.typhoon2000.ph/info.htm). One of the notable compilations of damages by Mr. Padua is the summary of documented “worst” typhoons in the Spanish Period, shown in Table 6, showing that typhoon news is not so new in the Philippines. Philippine media (newspapers, TV and radio, and news websites) are also sources of typhoon damage information. 2.2 PAGASA Storm Warning Signals PAGASA issues Storm Warning Signals as well as Severe Weather Bulletins when a tropical cyclone enters the PAR. A tropical cyclone is classified according to its maximum sustained (1hour average) wind speeds: a tropical depression (45 to 63 kph), a tropical storm (64 to 117 kph), a typhoon (118 to 239 kph), or a super typhoon (240 kph or faster). PAGASA’s storm signals likewise correspond to forecasted or recorded maximum sustained winds, and corresponding expected damages. Note that these “expected damages,” with the appropriate mitigation and  preparedness, could be reduced. 2.3 A Photo-Gallery of Damages due to Strong Winds of Typhoon Unding (Muifa) Typhoon Unding (International Name: Muifa) came from the Pacific (Figure 3) and was the first of four consecutive destructive tropical cyclones that struck the Philippines between  November and December 2004. The four cyclones accounted for a total of about 1,000 deaths, 1,100 injuries, 500 missing persons, around 57,000 totally damaged houses, around 167,000  partially damaged houses, and about PHP 1.6 Billion (US$ 29 Million) in total cost of damages in a span of one month, and also brought about floods and landslides. A report on the aftereffects of these four cyclones was also prepared by OCD-NDCC. Mr. Padua has his own eyewitness accounts of some damages within the vicinity of his residence in Naga City, including a detailed “Full Passage Report” on Unding (http://typhoon2000.ph/stormarchives/2004/unding_report). It is important to note here that Unding was within 5 to 10 km of Naga City. A photo gallery of damages due to strong winds of Typhoon Unding is shown in Figure 4, which were also taken from Mr. Padua’s Typhoon2000.ph website. 2.4 Towards Developing “Typhoon Disaster Maps” and “Typhoon Vulnerability Maps” Typhoon-related damage information documenting the occurrence of disasters is publicly available from the OCD-NDCC and PAGASA, although presented in a general, nationwide Pacheco, BM, and Aquino, RER, DMAPS Looking Forward: Calling for “Typhoon Engineers” , Page 3 of 24

sense. Still, this information could be used in initial attempts in preparing historical “typhoon disaster maps,” under Strategy #1 of the PICE-DMAPS program [Pacheco, 2004a]. The tropical cyclone tracks and corresponding wind speeds provided by PAGASA is also particularly useful. Likewise, the effects of disasters also shown in the available damage information could  provide a starting point in preparing current “vulnerability maps,” under Strategy #3 of the PICE-DMAPS program [Pacheco, 2004a]. The documentation of damages due to typhoons, ideally with accompanying photographs, notes, and sketches, could provide us information as to typhoon vulnerabilities of our structure types and other properties. Any individual could take  photos or notes of damages within his locality right after a disaster strikes, such as shown in the example photos of damages due to Typhoon Unding in Naga City. These reports from individuals could be collected and then used in the preparation of current “typhoon vulnerability maps.”

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A HISTORY OF WIND SPEED MAPS: TOWARDS DEVELOPING “HAZARD MAPS”

3.1 Data from PAGASA The development of wind speed maps in the Philippines starts with the gathering of meteorological data from PAGASA, a member of the World Meteorological Organization. PAGASA presently has around 56 synoptic stations. Details about the stations are contained in a report entitled “Station Profile,” documenting PAGASA’s initiatives in maintaining a nationwide  basic synoptic network and other observational network of stations for international, regional, and national exchange of data. However, as Rosaria & Pacheco [2002a] have noted, the actual terrain exposure, elevation, and calibration of instruments, as well as topographic features at the stations have not been surveyed. Also available from the PAGASA Climate Data Section (PAGASA-CDS) are two types of raw data files: the “Monthly Maximum Wind Speed and Direction” (MMWS) data file, and the “Daily and Monthly Climatic Data” (DMCD) data file. The MMWS for a station tabulates the monthly maximum gust speed and corresponding direction for specified years. Rosaria [2001] validated the data in the MMWS against the data in the (more detailed) DMCD and used MMWS data in his statistical analysis. The DMCD for a station is a tabulation of the daily recorded values of various climate indicators including (daily maximum) “10-minute average” wind speed and corresponding direction, and (daily maximum) gust speed and corresponding time and direction. [Rosaria & Pacheco, 1999] DMCD files have also been used in developing extreme wind speed maps. [Garciano et al, 2005a] PAGASA’s Climatology and Agrometeorology Branch (PAGASA-CAB) also generates wind-rose diagrams for specified stations using 10 or 30 years of data, showing the percentage of the time that the wind occurs in a given direction. However, the format of the wind-rose analysis report may not be directly useful for engineering purposes. PAGASA-CAB also prepares reports called “Climatological Extremes” and “Climatological  Normals” as of a certain year, which simply present recorded extreme and average climate conditions such as maximum wind gusts for a given month, for each station. “Climatological  Normals” publications also include prevailing wind velocity maps which show that wind generally comes from the northeast for months from December to March, and from the southwest from June to September.

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3.2 Early Study by Simiu (1973/1974) Dr. Emil Simiu conducted a study on estimation of extreme wind speeds in the Philippines, which was presented at a joint US-Philippines workshop in 1973 on improving the design of low-rise buildings against strong wind effects, organized by the then-National Bureau of Standards (USA). The study used annual maximum “one-minute” average wind speed data from 16 stations with varying number of years of records, with correction to account for anemometer elevation, and actual terrain exposure. The study estimated extreme wind speeds for each station at different return periods, and grouped the stations according to three wind zones with Zone I as the highest wind zone. A plot is shown in Figure 5. st

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3.3 Wind Zone Maps in NSCP 1  to 4  editions (1972/1977, 1982, 1987, 1992) The NSCP is probably the most important, first-line-of-defense document in typhoon disaster mitigation and preparedness in the Philippines, providing minimum requirements for design of various structures. The NSCP 1992 provided a wind zone map of fastest-kilometer wind speeds with a 50-year return period (Figure 5) for use in wind design of buildings and other vertical structures. The  problem with this wind zone map is that there are no direct measurements made of fastestkilometer speeds in the Philippines. There is also no known documentation as to how this wind zone map was developed, but this has practically been the same wind zone map that appeared starting from the NSCB 1 st  edition 2nd  printing (1977; no map given in the 1972 1st  printing).  Note that Simiu’s zoning of the 16 considered stations is compatible with NSCP 1992 and pre NSCP 1992 wind zoning, showing that Simiu’s work has partially been the basis of the  NSCB/NSCP wind zone map. 3.4 Study by Rosaria [2001] In 2001, Rosaria subjected 35 years (1961 to 1995) of monthly maximum wind data from 50 stations to extreme value statistical analysis. The study notes that for some months, there was no data, and that some wind speeds exceeding the maximum recordable speed were discarded from the analysis. Corrections were not applied to account for actual conditions at the stations. The study generated the wind contour map (3-second gust speeds at a 50-year return period) shown in Figure 6. To maintain some similarity with the NSCP 1992 wind map which delineated different areas of the Philippines into three wind zones, Rosaria employed the concept of “superstations” to form three wind zones as shown in Figure 7. The proposed map is actually a hybrid zone/contour map, with zone numbering similar to that for seismic loading, wherein a higher number corresponds to a higher design load. Rosaria also illustrated the conversion of  basic wind speeds to return periods other than the 50-year return period. 3.5 Wind Zone Map of NSCP 2001 The NSCP 2001 wind zone map (Figure 8), based almost entirely on Rosaria’s study, tried to maintain a close similarity with the NSCP 1992 wind zone map in terms of the zone boundary lines and in zone numbering, and in strictly being a zone map rather than a contour map to be fully compatible with the ASCE7-95 Standard on which the NSCP 2001 was based. 3.6 An Australian Handbook with Design Wind Speeds in the Philippines (2002) A handbook (HB 212-2002) published in 2002 by Standards Australia International, presents wind zone maps for various countries in the Asia-Pacific region, including the Philippines Pacheco, BM, and Aquino, RER, DMAPS Looking Forward: Calling for “Typhoon Engineers” , Page 5 of 24

(Figure 9), that is intended to be compatible with provisions of the Australian/New Zealand wind loading standard. In effect, the handbook together with the AS/NZS standard could be considered as a recommendation for wind loads in the Philippines. Additionally, wind loads in the Philippines could thus be “directly compared” with wind loads in Australia, New Zealand, and in other countries in the Asia-Pacific. [Holmes & Weller, 2002] The handbook’s wind zone map recognizes, and shows some similarity to the NSCP 1992 wind zone map, with a slight variation based on a “recent re-analysis,” perhaps referring to the  NSCP 2001. The handbook divides the Philippines into four wind zones, according to the handbook’s own zoning system. Table 7  shows a comparison of the handbook’s wind zones with the NSCP. However, the handbook assumes that NSCP 1992 fastest-kilometer wind speeds are “1minute average” wind speeds, and proceeds to say that the basic wind speed given by the NSCP (1992) for Western Mindanao and Palawan, maybe conservative. This is true, as Rosaria & Pacheco [2002b] have shown that in the NSCP Zone III, the design wind speed could be much lower than is suggested in NSCP 1992. However, the handbook also shows that the design wind speed for Eastern Mindanao may also be conservative. While the handbook may be updated to reflect updated design wind speeds from NSCP 2001, the next edition of the NSCP wind zone map may be updated to consider that portions of Eastern Mindanao could have lower design wind speeds. This is shown by the fact that the NSCP 1992 and pre-NSCP 1992 wind zone maps are most likely based on Simiu’s work, which did not have data from any Eastern Mindanao station. Meanwhile, the Zone II and Zone III boundary line of  NSCP 2001 were patterned after NSCP 1992, although Rosaria’s study suggests that Zone III may well include some parts of Eastern Mindano. 3.7 A Recent Study by Garciano, et al [2005a] A group from the Musashi Institute of Technology (Japan) also recently developed an extreme wind map, which were also presented at the recent 11th  ASEP International Convention [Garciano et al, 2005b]. The study employed a slightly different procedure from that by Rosaria, using 35 years (1961 to 1995) of monthly maximum wind speeds from 5 stations, and 40 years (1961 to 2000) of daily maximum wind speeds from 45 stations. Additional procedures were applied in the wind speed contour mapping, to generate smoother contours. However, corrections were also not applied to the wind speeds. [Garciano et al, 2005a] The group has proposed a new wind zone/contour map (Figure 10 ) with 6 zones and using an additional 5 years of data from at least 45 stations over the NSCP 2001 map. A significant highlight of the study includes a generally significant decrease in basic wind speeds (3-second gust speeds at 50-year return period), especially for parts of Zones II and III. Additionally, regional boundaries were added for ease in using the map. The group also prepared maps for 30year and 40-year return periods, owing to the fact that the data used was less than 50 years. 3.8 An Extreme Wind Hazard Map from PAGASA-NDRB Among one of the activities of the PAGASA-NDRB (Natural Disaster Reduction Branch) is the preparation of technical reports, covering a variety of topics from hazard mitigation to social sciences, for a variety of usually typhoon-related natural disasters. (See next chapter.) In ca. 2002, a group from PAGASA-NDRB prepared “extreme wind hazard maps.” The study used as much as 49 years of data (between 1948-1996) from 56 stations, although seemingly subjected only to a simple statistical analysis of obtaining maximum wind gusts. The Pacheco, BM, and Aquino, RER, DMAPS Looking Forward: Calling for “Typhoon Engineers” , Page 6 of 24

generated contour shapes for their “annual” wind hazard map (Figure 11) show some difference from the contour map by Rosaria [2001] or from the zone/contour map by Garciano et al [2005]. It is also noticeable that wind speed values in the wind hazard map are generally lower than those in the maps by Rosaria or by Garciano et al, as this study did not involve any extreme value statistical analysis, nor did it apply any correction factors. The study grouped locations according to maximum wind speed: moderately extreme winds (60– 100 kph), extreme winds (101–184 kph), and severely extreme winds (>185 kph), corresponding to typhoon warning signals of PAGASA. The study also generated “monthly” wind hazard maps which could be useful in describing seasonal trends. The report could be considered only as a historical account of maximum recorded gust speeds. It nonetheless provides an insight into the wind climate in the country. In its conclusion, it gives quite a good list of recommendations including one concern on non-engineered structures such as a majority of residential dwellings, and one recommendation on imposing a study of basic meteorology for architects and engineers. The study also cites that the DSWD has a recommended “Typhoon Resistant Housing” design for low-income families. 3.9 Wind Map used by Wind Power Companies Also cited by Rellin et al [2005], wind speed maps for the Philippines was prepared by the US Department of Energy–National Renewable Energy Laboratory (NREL) in collaboration with our DOE in 1999, in a publication called “Wind Energy Resource Atlas of the Philippines.” A sample page is shown in Figure 12. It should be noted that the wind speed map shows average wind speed at 30 meters height as opposed to the 10 meters meteorological standard height. The map also shows corresponding wind power density, which is more for use by wind power companies. As Rellin et al [2002] states, the study does not include information on extreme wind speeds but nonetheless provides a good insight on the wind climatology in the region. 3.10 Wind Speed Data from Other Sources Wind power companies also conduct wind speed measurements for one to two straight years, usually at an ideal location for a wind farm. The measurements are usually conducted at heights of 20 meters or higher. The NREL publication however also used data from PAGASA (recorded at 10 meters height) as well as from the National Power Corporation (NPC). Among the freely available information at the Typhoon2000.ph website is a recording of wind speeds in Naga City during the passing of Typhoon Unding in November 2004. Weather and other wind- and typhoon-related information in the Philippines may also be taken from the Kochi University website, which compiles different satellite images from various sources. The JTWC and NOAA websites also provide valuable information. 3.11 Towards Developing “Typhoon Hazard Maps” This chapter has shown available data from PAGASA and other sources, and that these have  been used in a number of studies by different groups in estimating extreme wind speeds in the Philippines. These “wind hazard maps,” together with “flood hazard maps” and so on, could be collectively called “typhoon hazard maps,” in line with Strategy #2 of the PICE-DMAPS  program [Pacheco, 2004a]. It has been shown that existing “wind hazard maps” such as the wind zone map in the NSCP could still use some improvement. Some of these possible improvements are discussed in the next chapter. Perhaps one single group could coordinate activities of all groups involved in developing these hazard maps. Pacheco, BM, and Aquino, RER, DMAPS Looking Forward: Calling for “Typhoon Engineers” , Page 7 of 24

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SUMMARY OF RECENT TYPHOON-RELATED RESEARCH: TOWARDS DISASTER MITIGATION AND PREPAREDNESS

4.1 Comparisons of NSCP 1992 and NSCP 2001 The NSCP 2001 has significant improvements over NSCP 1992 in general, and in its wind loading provisions in particular: (a) use of 3-second gust speeds instead of fastest-kilometer wind speeds; (b) consideration of dynamic effects; and (c) consideration of topographic effects. Considering that Rosaria’s work (and consequentially the NSCP 2001 wind zone map) has  been based on extreme value statistical analysis of a more consistent set of data, the actual fastest-kilometer wind speeds for each of the three zones could be calculated after some conversion. Results (Table 8) show that NSCP 1992 basic wind speeds may be 10% less in Zone I, and 30% more in Zone III, similar to conclusions by Rosaria & Pacheco [2002a, 2002b]. Caution should thus be exercised when using the NSCP 1992 wind zone map. The NSCP 2001 specifies the use of an independent gust effect factor (GEF) that is meant to account for dynamic amplification due to resonance with wind gusts, among others. For “flexible structures” that are susceptible to the dynamic effects of wind, the GEF must be obtained by rational analysis. Resonant response is most likely ignored in NSCP 1992, similar to codes released at around the same time as NSCP 1992, as the gust factor is combined with height and exposure under one coefficient. An example by Mehta [1998] shows that for one flexible structure, the gust effect factor is around 1.0, thus there is possibly an under-design of about 15% if 0.85 were assumed as gust effect factor. Possibly the most significant new feature of NSCP 2001 is the consideration of topographic effects, particularly for structures that are on top of hills, ridges, or escarpments. As Rosaria & Pacheco [2002b] have noted, in some cases, the design wind loads computed using the NSCP 1992 and NSCP 2001 are just about equal before the calculation of any topographic multiplier. However, for the said structures on one of the mentioned topographic features, the topographic multiplier could increase the design wind loads by more than 200%. 4.2 Recent Developments in International Codes There have been significant recent developments in international codes, such as those from the USA (ASCE7-05), Japan (AIJ-RLB-2004), and Australia/New Zealand (AS/NZS1170.2: 2002). These new features (listed in Table 9) are not yet present in the NSCP 2001. 4.3 Additional Comments on NSCP 2001 Wind Load Provisions There are certainly some more studies that could be conducted to further improve the NSCP. Some suggestions are listed in Table 10. 4.4 PAGASA Research Studies Related to Tropical Cyclone Winds Almost unknown to the civil engineering community, PAGASA conducts research in different fields of the natural and social sciences related to mitigating the effects of typhoons. Table 11  lists some of these research studies by the PAGASA Atmospheric Geophysical & Space Sciences Branch (PAGASA-AGSSB) and by the PAGASA-NDRB. 4.5 Other Possible Research Activities There are many more possibilities for research in the many sub-fields of typhoon engineering. Some suggested research ideas are listed in Table 12.

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4.6 Towards Disaster Mitigation and Preparedness While in recent years, there have been a number of research studies related to typhoon engineering in the Philippines, as well as to typhoon disaster mitigation, there are still more  possible activities and research studies that may be conducted in the Philippines, given the amount of available information. All groups with a common goal in terms of typhoon disaster mitigation, could very well do some collaboration, and integration and harmonization of data. For example, this paper cited some documents prepared by PAGASA, which are not previously known or not immediately useful for engineering purposes. Collaboration and close coordination between PAGASA and PICE/ASEP engineers in research on typhoon disaster mitigation would benefit both parties and the general public as well. PAGASA has its own quick response team, the STRIDE (short for Special Tropical Cyclone Reconnaissance, Information Dissemination and Damage Evaluation), which could very well coordinate with the PICE/ASEP DQRP teams for an engineering reconnaissance of typhooninduced damages. A manual for such could be drafted and then used by the PICE/ASEP engineers together with PAGASA researchers and volunteers. The NSCP does not limit the structural designer in using its provisions, particularly when any “rational” method is available that could justify the use of lower design loads. Certainly, firmlygrounded, peer-reviewed, and published research towards the improvement of the NSCP wind loading provisions, or typhoon disaster mitigation in general, although not immediately part of the NSCP, could be used to justify lower design values, or to evaluate existing structures. It should be emphasized here however that “codes are just guidelines and have not yet been tested in a worse case scenario.” [Thickett, 2001] Focus should also be more on typhoon-resistant communities, which comprise individual typhoon-resistant buildings and other structures.

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LOOKING FORWARD: A CALL FOR “TYPHOON ENGINEERS”

Wind storms such as typhoons affect the Philippines more than any other disaster: around 32 thousand people killed, 8 billion made homeless, and around 7 billion U.S. dollars in total cost of damage for all wind-related disasters in the 20th  century. The number goes up obviously when considering the effects of other typhoon-related disasters such as floods, landslides, mudslides, storm surges, and tornadoes. As Pacheco [2004b] states, civil and structural engineers could contribute to disaster  preparedness in terms of contingency evacuation plans, public information campaigns, and risk evaluation of structures and facilities. A study by PAGASA-NDRB illustrates that out of 687 survey respondents, around 70% claim full comprehension of PAGASA’s storm warning signals,  but only 4% fully comprehend the warnings. Certainly, there is more to be done in terms of  public information campaigns, and engineers could provide significant contributions. With the involvement of more civil engineers in conducting research towards typhoon disaster mitigation, and then consequentially in the preparation of “disaster maps,” “hazard maps,” and “vulnerability maps,” the next logical step would be to integrate all these data at the national level, under Strategy #4 of the PICE-DMAPS Program [Pacheco, 2004a]. Strategy #5 [Pacheco, 2004a], related to training, hopefully starts with the presentation of this paper, with regard to typhoon disaster mitigation.

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Together as a developing nation, possibly this statement by Sawada [2000] could inspire us civil engineers, and all of us Filipinos in general, to strive to contribute in whatever capacity towards disaster mitigation and preparedness, whether for typhoons or other disasters: “It is generally believed that infrastructure development has (both) direct and indirect effects on reducing chronic poverty (such as in the case of the Philippines in general). …provision of disaster prevention, electricity and water services, …the development of roads, railways, ports, and communication systems, are also important in the reduction of transient poverty.” REFERENCES

American Society of Civil Engineers (2005). Standard 7: Minimum Design Loads for Buildings and Other Structures (ASCE7-05). ASCE Press, USA. Aquino, R.E.R. (2005). Philippine Wind Information for Engineering, Research, and Mitigation. Country report submitted to the Tokyo Polytechnic University. http://www.wind.arch.tkougei. ac.jp/ info_center/APECwind/philippine.pdf  Architectural Institute of Japan (2004). Recommendations for Loads on Buildings (in Japanese) . Asian Disaster Reduction Center (2003). ADRC 20th Century Asian Natural Disasters Data Book . http:// www.adrc.or.jp/publications/databook/databook_20th/top_e.htm ASEP (1992). National Structural Code of the Philippines 1992, Volume 1 – Buildings, Towers, and Other Vertical Structures. 4th ed. ASEP (2001). National Structural Code of the Philippines 2001, Volume 1 – Buildings, Towers, and Other Vertical Structures (NSCP C101-01). 5th ed. Campbell, Shawn. (2005). Detailed information on meteorology and wind damage in Hongkong, China. Country report submitted to the Tokyo Polytechnic University. http://www.wind.arch.tkougei.ac.jp/info_center/APECwind/hongkong1.pdf  Elliott, D., M. Schwartz, R. George, S. Haymes, D. Heimiller, and G. Scott (2001). Wind Energy Resource Atlas of the Philippines.  US Department of Energy – Natural Renewable Energy Laboratory. EM-DAT: The OFDA/CRED International Disaster Database – www.em-dat.net  – Universite Catholique de Louvain – Brussels – Belgium. Garciano, L.E., Hoshiya, M., and Maruyama, O. (2005a). Development of a Regional Map of Extreme Wind Speeds in the Philippines. Structural Eng./Earthquake Eng., JSCE, Vol. 22, No. 1, 15s 26s, 2005 April. (J. Struct. Mech. Earthquake Eng., JSCE, No. 787/ I - 71.) Garciano, L.E., et al (2005b). A Proposed Wind Zone Map of the Philippines and its use for Performance-Based Design. Proc. 11th ASEP International Convention. Holmes, J.D., and Weller, R. (2002). Design Wind Speeds for the Asia-Pacific Region (HB 2122002). Standards Australia. Joint Typhoon Warning Center website. http://www.npmoc.navy.mil/jtwc.html Kochi University (Japan). Weather Home website. http://weather.is.kochi-u.ac.jp/ Le, Giang Truong. (2005). Damages Caused by Strong Wind and Wind Loading Standard in Vietnam. Country report submitted to the Tokyo Polytechnic University. http://www.wind.arch.tkougei.ac.jp/info_center/APECwind/vietnam.pdf  Mehta, K.C., and Marshall, R.D. (1998). Guide to the use of the Wind Load Provisions of ASCE7-95. ASCE Press.  National Renewable Energy Laboratory. Wind Resource Atlas of the Philippines . http://www.nrel. gov/international/rr_assessment.html#wind_atlases Pacheco, B.M. (2004a). Introduction to Disaster Mitigation and Preparedness Strategies: the DMAPS Program of the PICE . Proc. PICE 2004 National Midyear Convention, Davao, July 2004.

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Pacheco, B.M. (2004b). 100 Years of Natural Disasters in the Philippines. Proc. PICE Seminar on DMAPS. Padua, Michael. Typhoon2000.ph website. http://typhoon2000.ph/ PAGASA. PAGASA website. http://www.pagasa.dost.gov.ph/ PAGASA (2004). The PAGASA Annual Report 2004. http://www.pagasa.dost.gov.ph/ annualreport/annual_report.html PAGASA Climatology and Agrometeorology Branch (____). Climatological Normal of Surface Winds in the Philippines. PAGASA – Climatology and Agrometeorology Branch (2004). Station Profile. Pardo, R.R. (1990). “A Primer on Terms Used By PAGASA,” Philippine Almanac: Book of Facts 1990, Aurora Publications, pp. 968-969. Rellin, M.F., Jesuitas, A.T., Sulapat, L.R., and Valeroso, I.I. (2002). NDRB Technical Report No. 111: Extreme Wind Hazard Mapping in the Philippines. Philippine Atmospheric, Geophysical and Astronomical Services Administration – Natural Disaster Reduction Branch. Rosaria, N.E., and Pacheco, B.M. (1999). Maximum Wind Speed Data from PAGASA in the Past 30 Years: Statistical Analysis for Engineering Use . Proc. ASEP 8th International Convention, Manila, Philippines. Rosaria, N.E. (2001). Estimation of Extreme Wind Speeds for the Development of Wind Zone Map for the Philippines. MS Thesis. University of the Philippines, Diliman, Quezon City. Rosaria, N.E., and Pacheco, B.M. (2002a). Overview of the Wind Load Provisions of Section 207 of NSCP 2001. Proc. ASEP Seminar on the NSCP 2001, Philippines. Rosaria, N.E., and Pacheco, B.M. (2002b). Comprehensive Guide on the Use of the Wind Load Provisions of NSCP 2001 . Proc. 2002 Conference on the Safety & Reliability of Built Structures, ASEP, Manila, Philippines. Sawada, Y. (2000). Dynamic Poverty Problem and the Role of Infrastructure . JBIC Review, No. 3, pp. 20-40. Japan Bank for International Cooperation. Simiu, E. (1973). “Estimation of Extreme Wind Speeds—Application to the Philippines,” Development of improved design criteria for low-rise buildings in developing countries to better resist the effects of extreme winds: proceedings of a workshop held at the Dr. Paulino J. Garcia Memorial Hall,  National Science Development Board, Manila, Philippines, November 14-17, 1973. Noel J. Raufaste Jr and Richard D. Marshall (eds). Building Science Series No. 100, vol 2. National Insitute of Standards and Technology. Simiu, E., and Scanlan, R. (1996). Wind effects on structures: fundamentals and applications to design. 3rd ed. John Wiley & Sons, Inc. Standards Australia/Standards New Zealand (2002). Australian/New Zealand Standard: Structural Design Actions Part 2: Wind Actions (AS/NZS 1170.2:2002). Tamura, Y., Kawai, H., Uematsu, Y., Okada, H., and Ohkuma, T. (2004) Documents for wind resistant design of buildings in Japan . Proc. Workshop on Regional Harmonization of Wind Loading and Wind Environmental Specifications in Asia-Pacific Economies, Nov. 19-20, 2004. Tanzo, W.T., and Pacheco, B.M. (2004). Philippine Structural Code. Proc. Workshop on Regional Harmonization of Wind Loading and Wind Environmental Specifications in Asia-Pacific Economies (APEC-WW), November 19 & 20, 2004, Wind Engineering Research Center, Tokyo Polytechnic University, Atsugi, Japan. Thickett, W. (2001) Hurricane Engineering: New Technology. http://www.civil.port.ac.uk/ comp_prog/hurricane/newpage2.htm Ward, C. (2000) LSU Wins Grant to Develop First 'Hurricane Engineering' Program. http:// www.hurricane.lsu.edu/_in_the_news/aug08_disaster.htm

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ACKNOWLEDGEMENTS

The authors would like to acknowledge contributions from: Mr. Nicetos Rosaria, former structural engineer, PNOC-EDC; Mr. Michael Padua from Naga City for use of the damage photos and other information from his website, Typhoon2000.ph; Dr. William T. Tanzo of Vibrametrics, Inc.; Mr. Lessandro Garciano, of Musashi Institute of Technology; Dr. John D. Holmes of JDH Consulting (Australia); Dr. Emil Simiu of the National Institute of Standards and Technology (USA); Prof. Yukio Tamura, Tokyo Polytechnic University (Japan); Mrs. Emilia Tadeo of the National Disaster Coordinating Council for generously providing information; and, Staff at the PAGASA-CDS, PAGASA-PIIAS, PAGASA-NDRB, and at the PAGASA Library. ABOUT THE AUTHORS

Benito M. Pacheco, PhD, PE, F.ASEP, F.PICE, is co-founder of Vibrametrics, Inc. Vibrametrics  provides vibration testing and other non-destructive tests for full-scale existing structures. The group  performs: testing & monitoring; site & structure assessment; mitigation design; earthquake risk management solutions; training; and specialized studies. (Email:[email protected]) Dr. Pacheco is former ASEP president, former PICE national PRO, and current chairman of the PICE Committee on DMAPS and DQRP. He is a licensed civil engineer in the Philippines, registered professional engineer in the USA, certified ASEAN engineer, and certified APEC engineer. He is a professorial lecturer in structural engineering at UP Diliman, special lecturer at PUP for the program in master of earthquake engineering, and former associate professor of civil engineering at the University of Tokyo in Japan. Ronwaldo “Ronjie” Aquino, M.PICE, A.ASEP, currently a member of the PICE Committee on DMAPS and DQRP, is finishing his thesis in the field of wind engineering for his M.S. in Civil Engineering degree (Major in Structural Engineering) at the University of the Philippines, Diliman, where he also graduated B.S. in Civil Engineering. He was recently a short-term researcher at the Tokyo Polytechnic University (Japan), awarded as the Center of Excellence for Wind Effects on Buildings and Urban Environment, where he prepared a report that forms the basis of a bulk of this paper. (Email: [email protected])

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Table 1. Total Damages by Recorded Natural Disasters* in the Philippines (1901-2000)

Disaster Count

Disaster Type

Thousand Thousand People People Killed Injured

Million People Affected

Thousand Million Million People Total People US$ in Homeless Affected Damage

Wind Storms 214 32 28 76 8,000 84 7,000 Earthquakes 21 10 11 2 135 2 517 Floods 54 3 1 77 >1 227 * Data source: EM-DAT: The OFDA/CRED International Disaster Database - www.em-dat.net - Université Catholique de Louvain - Brussels – Belgium. Numbers are rounded off. Numbers are not significantly different when the years 2001-2004 are included.

Table 2. Top 10 Natural Disasters in the Philippines  by Number of People Killed, by Number of People Affected, and by Total Cost of Damages Disaster Type Earthquake Wind Storm Earthquake Wind Storm Wind Storm Wind Storm Volcano Wind Storm Wind Storm Wind Storm

Year 1976 1991 1990 2004 1970 1984 1911 1984 1949 1952

Killed 6,000 5,956* 2,412 1,619 1,551 1,399 1,335 1,079 1,000 995

Disaster Type Wind Storm Wind Storm Wind Storm Flood Wind Storm Drought Wind Storm Flood Wind Storm Wind Storm

Year 1991 1990 1973 1972 1976 1998 1984 1999 1998 1994

Affected 6.5 M 6.2 M 3.4 M 2.8 M 2.7 M 2.6 M 2.3 M 2.1 M 2.1 M 2.0 M

Disaster Type Earthquake Wind Storm Wind Storm Wind Storm Wind Storm Wind Storm Wind Storm Wind Storm Flood Wind Storm

Year 1990 1995 1991 1990 1998 1991 1995 1988 1972 1984

Damages $ 920 M $ 709 M $ 435 M $ 388 M $ 319 M $ 311 M $ 244 M $ 240 M $ 220 M $ 216 M

As of April 22, 2005; Source: “EM-DAT: The OFDA/CRED International Disaster Database, www.em-dat.net – Université Catholique de Louvain – Brussels – Belgium”

Table 3. Damages by Worst Individual Natural Disasters* in the Philippines (1901-2000) Thousand Thousand Million Thousand Million Million People People People People Total People US$ in Disaster Type Killed Injured Affected Homeless Affected Damage Worst Wind Storms 3 709 6 6 1,171 7 Worst Earthquakes 2 135 2 6 7 920 Worst Floods 1 0 3 371 3 220 Worst Volcanic Eruptions 2 1 1 57 1 211 * Data source: EM-DAT: The OFDA/CRED International Disaster Database - www.em-dat.net - Université Catholique de Louvain - Brussels – Belgium. Numbers are rounded off and approximate. Note that the wind storm that caused the most number of people injured may not be the same wind storm that caused the most number of  people killed, and so on.

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Table 4. Philippine Public Storm Warning Signals (PSWS) issued by PAGASA PSWS #

Expected Wind Speeds

Time expected to arrive

1

30 to 60 kph

Within 36 hours

2

60 to 100 kph

Within 24 hours

Expected Level of General Damages Very light or no damage Light to moderate damage

Other Expected Damages

• • • • • • •

3

4

100 to 185 kph

Over 185 kph

Within 18 hours

Within 12 hours

Moderate to heavy damage Very heavy damage

•

•

• • •

Damage to small trees and rice crops, Banana plants tilted or downed, Houses with roofs made of light material may be partially unroofed Damage to corn and rice, few big trees and banana plants, Coconut trees tilted or downed,  Nipa and cogon houses partially or totally unroofed, Steel roofs partially unroofed Damage to coconut trees, all banana plants, and to rice and corn crops, Considerable damage to houses of light and medium construction, Disruption to power and communication Severe damage to plants, trees, and agricultural crops, Most buildings of mixed construction severely damaged, Power and communication down

Table 5. Contents of Available Documents Showing Damage Information (as of April 2005) Source OCD NDCC

Title “Destructive Tropical Cyclones from 1970 to 2003”, and “2004 Summary of Destructive Tropical Cyclones and their Effects”

Information For each tropical cyclone:  Name, Dates inside PAR Cost of damages to agricultural  properties, infrastructure, and to Regions affected  private properties  Number of killed, injured, or Totals of damages per year; missing persons Totals specifically for the  Number of affected families destructive last 4 tropical and persons cyclones in 2004  Number of totally or partially damaged houses Same as above for other types of disasters: Strong winds (non-typhoon Storm surges related) Tornado and minor tornado Floods incidents Landslides Other natural disasters Mudslides Man-made disasters For each tropical cyclone: Classification, Name, Dates Brief summary of tropical inside PAR cyclone Highest recorded maximum Areas affected wind speeds + corresponding Issued storm warning signals  place and time observed Tropical cyclone tracks Lowest recorded mean sea level For later years, summary of  pressure + corresponding place affected persons and costs of and time observed damages (from OCD-NDCC) •

•

• •

•

•

•

•

OCD NDCC

PAGASA

“Other Disaster Incidents from 1980 to 2003”, and ”Summary of Disaster Incidents Monitored from January to December 2004” “Tropical Cyclone Summary” (per year for the years 1978-2003)

•

• •

• •

•

•

•

•

•

•

• • •

•

•

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Table 6. Worst “Ancient” Documented Typhoons of the Philippines (1617-1876) Date OCT 10-15, 1617 APR 28-MAY 5, 1866

MAY 4-5, 1870

JUN 24, 1871

OCT 12, 1872

MAR 4-5, 1874

DEC 25, 1874

JAN 1, 1875  NOV 25-27, 1876

Damage 6 large ships off Marinduque  were sunk due to high sea waves generated by a typhoon. A rampaging whirlwind smashed the provinces of the Bicol Region, Southern Luzon, Masbate, Panay and Mindoro. In Manila, the barometer plummeted to a record low of 746.62 mm. 400 houses and 15 bridges destroyed by one typhoon, while another one destroyed 247 houses in Negros, and sinking 13 fishing boats and 5 other boats. A very strong cyclone hit Southern Luzon, Central Luzon and Samar. Big buildings were destroyed and several boats sunk or slammed against the shores. A strong cyclone hit Samar for eight whole hours, crushing houses and drowning agricultural crops  with its floodwaters before toppling tall trees and leveling down whole towns  in southern Luzon This first cyclone of 1874 hit areas in Samar as it passed Panay Island; in one  place, Laoang, only two houses remained standing , and as it hit Capiz  province, even strong buildings and churches were severely damaged A violent tornado came howling over Misamis, Northern Mindanao and Cebu; "uprooting" a stone church and mortar buildings ; running a large naval ship destroyer aground; dislodging massive stone docks  of Cebu A strong tropical cyclone destroyed bridges and roads  in Samar, as well as destroying towns on the far northern suburb of Manila Surging tidal waves rampaging rivers destroyed agricultural crops and livestock , swept away 2,500 houses in the then still sparsely populated areas of Mindanao and the Visayas.

Source: PAGASA, "Everything You've Always Wanted to Know About Typhoons". FILIPINO HERITAGE: The Making of a  Nation by Lahing Pilipino Publishing Inc.,1977. Compiled for Typhoon2000.ph by Dominic Alojado, 2005.

Table 7. Comparison of NSCP and HB 212-2002 wind zones  NSCP 1992 I

Wind Zone HB  NSCP212-2002 2001 V I

Philippine Region/Area

 NSCP1992*

3-second gust speed, mps (kph)  NSCPHB 212 NSCP1992** 2002 2001** 61 (220) 60 (215) 70 (250)

56 (200) Eastern Luzon & Eastern Visayas II IV II Rest of the Philippines 54 (195) 52 (185) 55 (200) 49 (175) II III II Eastern Mindanao 54 (195) 49 (175) 44 (165) 55 (200) 42 (150) 46 (165) 39 (140) III II III Western Mindanao & 35 (125) Palawan * NSCP 1992 values in the column are fastest-kilometer wind speeds in mps (kph). ** After [Rosaria, 2001].

Table 8. Conversion of NSCP 2001 3-sec Gust Speeds to Fastest-Kilometer Wind Speeds Zone

I II III

NSCP 2001 3-sec gust (kph) 250 200 125

 NSCP 2001 equiv. fastest-km (kph) 230 180 110

 NSCP 1992 fastest-km (kph) 200 175 150

% diff

-13% -3% 36%

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Table 9. Recent Developments in International Codes Code(s) ASCE7, AIJ-RLB ASCE7 ASCE7 ASCE7, AIJ-RLB AIJ-RLB, AS/NZS ASCE7, AIJ-RLB ASCE7, AIJ-RLB, AS/NZS

New feature Wind speed contour map or hybrid zone/contour wind map Flood hazard map, and flood loads Simplified procedure for regular, low-rise buildings Modified gust effect factor formulation Across-wind and/or torsional response of buildings and similar structures Monte-carlo simulation of typhoons/hurricanes Wind directionality factor

Table 10. Some Possible Research Studies to Further Improve the NSCP 2001 Topic Correction of wind speed measurements Calibration of mass density of air constant (47.3x10-6) in NSCP Eq. 207-1 Simplified procedure for simple structures Applicability for antenna tower design Which governs, wind loads or earthquake loads? Performance-based design

Possible Requirements Engineering survey of PAGASA synoptic stations Procedures for adjusting mass density of air according to altitude, latitude, temperature. Defining scope of applicability (e.g. design of new, and evaluation of existing small residential buildings and similar structures, units of mass housing  projects, indigenous structures) Procedures and assumptions in using NSCP provisions for antenna towers; Information from antenna tower owners for serviceability criteria. Understanding the wind loading distribution versus seismic load distribution; Roofing systems, components and cladding directly affected by wind; Serviceability requirements could govern. Different wind speed maps of different return periods corresponding to specified performance level (serviceability, life safety, continuous use, etc.).

Table 11. Some Research Studies Related to Tropical Cyclones in the Philippines Title of Research Study by PAGASA-AGSSB http://www.pagasa.dost.gov.ph/researchAGSSB.html Tropical Cyclone Variations 2003 A Study Of Tropical Cyclone Activity Over Northwest Pacific Before, During And After The 1997-1998 El Niño Episode 1990 Variations Of Tropical Cyclones In The Western North Pacific 1989 Long Period Variations Of Tropical Cyclones In The Western North Pacific  Air Pollution 1976 Air Pollution Model For Metropolitan Manila Area Using The Gaussian Distribution  Miscellaneous Research Related to Wind 2004 Simulation Of Sea And Mountain Breezes Over Metro Manila 1970 An Analysis Of The Relationship Between The Position Of The Major Wind Discontinuity And The Position Of Areas Of Rainfall Over The Philippines Storm Surges 2000 Analysis Of Storm Surge Potential Of Various Landfalling Tropical Cyclones 1999 Storm Surge Prediction For Leyte Gulf Area 1994 Numerical Model For Storm Surge Prediction Incorporating Overland Flooding 1985 Storm Surge Numerical Model For Manila Bay 1984 One Dimensional Numerical Model For Storm Surge Prediction 1978 Storm Surge Potentials Of Selected Philippine Coastal Basins Year

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Table 11. Some Research Studies Related to Tropical Cyclones in the Philippines (cont’d) Title of Technical Report by PAGASA-NDRB (Tech. Rep. No.) http://www.pagasa.dost.gov.ph/researchNDRB.html  Extreme Wind Speeds ~2002 Extreme Wind Hazard Mapping in the Philippines (111)* Tropical Cyclone Variations ~2002 A Study of Tropical Cyclones Originating from the South China Sea (110) 1997 Southwest Monsoon Surge Associated with Tropical Cyclone (93) 1996 Tropical Cyclone Wind Profiles (87) Tropical Cyclone Forecasting ~2000 A Verification of 1994-1998 Tropical Cyclone Movement Forecasts of PAGASA (106) 1999 Analyses Of Vorticity, Omega And 850 HPa Wind of the FLM 12 in Relation to Tropical Cyclones Forecasting (104) 1999 The Revised Analog Method of Forecasting Tropical Cyclone Movement (101) 1998 The Development And Application Of The Direct Model Output Statistics (DMOS) to Improve Forecasting Of Tropical Cyclone Tracks (97)  Miscellaneous Research Related to Tropical Cyclone Hazard Mitigation 1996 Tropical Cyclone Winds, Warnings and Damages (92) 2000 Socio-Economic Influence on Human Response to Tropical Cyclone Warning (107) Discussed in this report; see previous chapter. Year

Table 12. Other Possible Research Studies • •

•

•

Wind-response monitoring Feasibility of setting up a wind tunnel for extensive wind engineering research Low-cost typhoon-resistant construction materials Typhoon-resistant construction manual in Filipino

• •

•

• •

Feasibility of special “typhoon shelters” Introduction to natural disasters and their effects on  property and the population for college students Separately published, continuously updated wind zone map, or Dynamic/digital wind hazard map Typhoon Design Manual ISO-compatible version of NSCP 2001

Typhoons before June or after September generally recurve at lower latitudes.

Typhoons causing strong winds

Typhoons in November or December

(a)

(b)

Figure 1. (a) Annual Average of Typhoon Occurrences in the Pacific Northwest from 1972-2002 [Campbell, 2005, after Joint Typhoon Warning Center], and (b) Typical Tracks of Typhoons Affecting the Philippines [Campbell, 2005, after Hong Kong Observatory]

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(a)

(b)

Figure 2. (a) Annual Frequency of Tropical Cyclone in the PAR, and (b) Landfalling Tropical Cyclones in the Philippines (1948-2004) (from PAGASA: http://www.pagasa.dost.gov.ph/cab/statfram.htm)

Figure 3. Track of Tropical Cyclone Unding. from http://typhoon2000.ph/stormarchives/2004/trax/unding04_21tx.gif 

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(a) Trees uprooted or permanently deformed

(b) Signs and billboards damaged

Figure 4. Damages in Naga City due to Typhoon Unding (from: http://www.typhoon2000.ph/stormarchives/2004/galleries/photos/unding/index.htm)

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(c) external wall collapsed

(d) car and building windows shattered due most likely to extreme wind pressures, or possibly due to “wind-borne missiles”

(e) internal walls of school building damaged

Figure 4. Damages in Naga City due to Typhoon Unding (cont’d)

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(f) roof structures overturned, blown away, or with partial damage to roof tiles

(g) structures under construction damaged

Figure 4. Damages in Naga City due to Typhoon Unding (cont’d)

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(h) electrical transmission line supporting poles and trussed towers overturned or permanently deformed

Figure 4. Damages in Naga City due to Typhoon Unding (cont’d)

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Zone I II III

ZONE II

Simiu [1974] 213 to 242 kph 103 to 209 kph 75 to 88 kph NSCP-92 and pre-NSCP-92 wind zone boundary lines

V = 175kph (NSCP-92) V = 175kph (Pre-NSCP-92)

II

Sierra Madre Mountain Range

II II

ZONE I V = 200kph (NSCP-92) V = 200kph (Pre-NSCP-92)

I

II II II

I II

I

II II II

ZONE III V = 150kph III

(NSCP-92) V = 153kph (Pre-NSCP-92)

III

III

Figure 5. Simiu Station Zoning (1974), and NSCP 1992 and Pre-NSCP 1992 Wind Zone Map

Figure 6. Wind Speed Contour Map  by Rosaria [2001]

(courtesy of Nicetos Rosaria) 118°

6     0      (     2     1     5      )   

120°

122°

124°

126°E

N 20°

18°

16°

ZONE II V = 55m/s (200kph)

ZONE I V = 70m/s (250kph)

14° 8     0      (     2     9    0      )   

 4 0 (1 45 )

12°

6 0  (   2 1  5    ) 

10°

ZONE III

40 (145)

8°

V = 35m/s (125kph)

6°

Figure 7. Wind Zone/Contour Map proposed by Rosaria [2001] for NSCP 2001

Figure 8. NSCP 2001 Wind Zone Map

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Figure 9. Philippine Wind Zone Map intended to be compatible with AS/NZS 1170.2:2002 [Holmes and Weller, 2001]

Figure 10. Regional Map of Extreme Wind Speeds in the Philippines proposed by Garciano, et al (2005)

200 185

250 250

250

250

200 185 100 100 80 60

100

80 60

Figure 11. Annual Extreme Wind Hazard Map  by PAGASA-NDRB (Rellen et al, ~2002); colored lines by the authors

Figure 12. Sample page of Wind Speed/Wind Power Density Map prepared by the US DOE-NREL [2001]

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