16 Sindur p Mangkoesoebroto Paper

PADANG EARTHQUAKE OF SEPTEMBER 30, 2009 WHY IT IS SO DEVASTATING Sindur P. Mangkoesoebroto

1 INTRODUCTION Since the remarkable Mw=9.1 earthquake hit Aceh on December 26, 2004, there have been frequent strong events that struck Indonesia region up to present days. One of the devastating latest latest event event has occurred on September 30, 2009, in the nearby Padang area, West Sumatra. The death tolls were 383 and 48 in the cities cities of Padang and Padang Pariaman, and 666, 11, 81 in the regencies of Padang Pariaman, Pesisir  Selatan, and Agam, respectively; totaling to 1.189 deaths. The total property damage was about US$ 500 millions due to hundred of thousands of damaged houses, thousands of collapsed buildings, roads & bridges, as well well as irrigation system, wide spread landslides mostly in in rural areas, and other[1]; as an illustration illustration Fig. 1 shows picture of a collapsed hotel among others. Had the earthquake accompanied by tsunami the devastation could be much higher; however, unquestionably this was the most devastating earthquake that hit the region after the Aceh’s. The vast destruction had caused some concerns regarding the safety of houses and public buildings, as well as infrastructures such as bridges and embankments. However, it should not be viewed as separate issues in a sense that the seismicity of the area that is quite active especially recently may be an important factor; also peculiar of the last event was its focal depth which could be categorized as deep earthquake differing from almost all the preceding events. This deep earthquake might have generated vertical component which was much higher compared to the horizontal components in case of  normal events. This phenomenon could be more critical for some type of of construction materials than others. These are to add to the fact that the last event is relatively close to the city (only about 50 km) and large in in magnitude (Mw=7.6) (Mw=7.6) with about VII MMI in Padang. Dealing with with the vertical component, especially for near source region, has been stipulated in detail in most international codes; unfortunately, the Indonesia seismic code has not sufficiently addressed the issue.

Figure 1 The collapsed Ambacang Hotel due to September 30, 2009 Padang earthquake. (Courtesy Dr. Sigit Darmawan) Seminar dan Pameran Haki 2010 -

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The construction material commonly used in Padang and the surrounding area for new houses and buildings is red brick confined masonry and reinforced concrete, or  combination of the two; steel structure mostly used as rafters and to less extent can be found in industrial buildings, and in few commercial shops. However, most traditional dwellings used non-engineered wood structures or bamboo materials both on ground or  elevated, with roof of light zinc cladding. Many houses built during Dutch era were made of unconfined red brick masonry with considerable wall thickness (25-30 cm) and height (4-6 meters). There are many building structures that were constructed in compliance with the national building codes, but there are also many others that apparently were not.  Among these types of constructions, the most severe damage was suffered by the unconfined red brick masonry and limitedly to the confined masonry which is normally used in shop-houses or locally known as ruko. In well constructed structures, the frame themselves, especially of the second story and up, usually are in good or fair conditions although the in-fill wall might undergo heavy damage or even collapse due to out-ofplane actions. Many of them suffered first story heavy damage or collapse, especially in poorly constructed buildings, due to soft first story mechanism, or lack of anchorage or  insufficient splices or other poor detailing problems. Prior to the last event, there had been several earthquakes shook the area, with some of  them were relatively of high intensity (V or VI MMI) and had caused light-to-moderate damage to various building structures. The damage, normally in the form of spalls or  cracks in the structural joints or components or non-structural wall panels, usually were left untreated, or only treated superficially. This situation cumulatively has left lower  remaining strength of the structures to resist any up coming earthquakes. Again, albeit this essential issue has been addressed in some countries as programs of rehabilitation, it has not been adequately regulated in Indonesia code up to present time. One among other important aspects to be highlighted is the instrumentation or seismic monitoring. Although Padang is long known to belong to the area of potential high seismicity, it is acknowledged, that frequent earthquakes has been taking place only in the past five years or so, especially after the Aceh’s. It is only very recently that quite a few strong motion recorders have been installed in the area. At least there are two acceleration records available for the last event; however, one of them was not reliable as the recorder was not properly anchored to the foundation. The other machine is installed about 200 meters underground and the data is reported herein.

2 EARTHQUAKE ACCELERATION DATA Two strong motion recorders were installed in the nearby area with about the same distance from the epicenter (around 50 km). One was installed at Andalas University (UNAND) by BMKG and the other was at the underground Singkarak Hydro Electric Power Plant (HEPP) controlled by PLN. It is unfortunate that the one at UNAND was not properly anchored to the foundation so that it slipped during the earthquake resulting unreliable acceleration data. The data, however, was further processed and analyzed by USGS[2]. It has given too high dynamic magnification factor for acceleration of about four  for N-S component, while the remaining components were unavailable. The data presented herein was acquired from the recorder installed at the underground Singkarak HEPP. The location of the plant, as well as the epicenter, is shown in Fig. 2. The figure also indicates the contour of the peak surface acceleration reported by USGS. It is indicated that the peak surface acceleration in Padang was about 0.3g, and at the Seminar dan Pameran Haki 2010 -

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HEPP was around 0.26g which corresponds to the underground record of 0.090g (N-S), 0.096g (E-W), and 0.051g (vertical) (see Fig. 3). The distance from the recorder to the epicenter is around 50 km, about the same epicentral distance of Padang. The raw acceleration data acquired was then corrected and consistently integrated to obtain the velocity and displacement records. It is observable from Fig. 3, by comparing the horizontal and vertical components of the acceleration records, the vertical component is appreciable relative to that of the horizontal. This happens for most of the duration and, further, but for the extreme peaks, their magnitude are about the same order. This shows the fact that vertical component was essential in the last event; although when comparing their maximum, the vertical to horizontal ratio is merely about 55%. Table 1 presents the extreme values for  acceleration, velocity and displacement records. Table 1 Extreme values for acceleration, velocity and displacement of Mw=7.6, Sept. 30, 2009 Padang earthquake as recorded at the underground Singkarak HEPP.

Figure 2 The epicenter of Mw=7.6, Sept. 30, 2009. Contour of surface peak acceleration reported by USGS, and the location of the SMA recorder in the underground Singkarak HEPP.

3 Response and Power Spectra  As normally carried out, the response spectra are generated for the recorded ground

motions. Based on the corrected acceleration given in Fig. 3, the 5%-damped response Seminar dan Pameran Haki 2010 -

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spectra are constructed for three components. The results are shown in Fig. 4. The maximum spectral values and their corresponding frequencies are presented in Table 2; and the dynamic magnification factors as defined as the ratio of the maximum spectral with respect to the maximum record values are shown in Table 3. It is worth to note that the vertical dynamic magnification factors are higher than those of the horizontal components. By observing the corner period of around 0.50-0.75 seconds, it can be envisaged that the rock formation around the recording site is not of the compact rock type as normally indicated by Tc=0.4 seconds for rock[3]. Table 2 Maximum spectral values (ζ=5%) and their corresponding f requencies.

Table 3 power.

Dynamic magnification factors for acceleration, velocity, displacement, and

The excitation power is defined as the energy per unit time supplied to the simple oscillator by the ground excitation, which is equal to the product of the inertial force and the ground velocity; and the absorbed power is the energy per unit time absorbed by the simple oscillator through the dashpot and the spring, equals the sum of the damping and the spring forces multiplied by their relative velocity. Mathematically, the excitation and the absorbed power densities (power per unit mass) are expressed as follows[4],

The excitation and the absorbed power density spectra are shown in Fig. 5 for three components; and their magnification factors are indicated in Table 3. It is observable from the figure that the E-W component is the most powerful, and the vertical is the weakest, being only slightly less than that of N-S component. Note that the power density has unit of horse power per ton mass. Seminar dan Pameran Haki 2010 -

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Figure 3 Corrected acceleration records (a’s), and their corresponding velocity and displacement (v and d’s) time series for N -S, E-W, and vertical components. Shown also are their extreme values. Raw acceleration data was recorded at the underground Singkarak HEPP.

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Figure 4 Response spectra of the corrected acceleration records, ζ=5%.

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Figure 5 Power spectra of the corrected acceleration records, ζ=5%, in horse power per  ton mass.

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4 GROUND MOTION ANALYSIS OF PADANG AND ITS VICINITY  As mentioned earlier, reliable acceleration ground surface record for Padang earthquake of September 30, 2009, is unavailable; therefore, some combination of  information obtained from several sources will be carried out to perform further analysis. USGS has developed a contour map for the peak surface acceleration and is presented in Fig. 2. City of Padang is located around 50 km from the epicenter, about the same epicentral distance of the recording machine at Singkarak HEPP. The peak acceleration estimate for Padang is 0.3g and that for Singkarak HEPP is 0.26g at surface. This peak surface acceleration is closely dependent on the soil condition of the region in question. The geological information for Padang is alluvium deposit[5], in general, and can be classified as medium soil. Based on this information the required peak ground acceleration specified by Indonesia seismic code for Padang area[3] is 0.33g. More precisely, for the area the code specifies the peak ground acceleration of 0.25g for  bedrock, 0.29g for hard, 0.33g for medium, and 0.36g for soft soils.  As described earlier the acceleration data recorded at Singkarak HEPP was obtained at elevation of about 200 meters below the ground surface. The characteristic of the recorded acceleration may differ from that at the surface, however, it will be maintained and the maximum acceleration is scaled to that of the USGS value for Padang, i.e., 0.3g. More over the ratio of the vertical to horizontal peak ground acceleration is taken to be 70% as suggested by the code. A modified acceleration spectra are then generated according to the previously mentioned procedure and compared to that of the code. The curves are shown in Fig. 6 for horizontal (top) and vertical (bottom) components. Similarly, vertical code acceleration spectrum is taken as 70% that of the horizontal. Fig. 6 (top) shows that the horizontal acceleration spectra are lower than that of the code except for periods of about 1.4-1.6 seconds where the E-W spectral values are almost the same as that of the code. This, however, is not the case for vertical component (bottom). In general, the spectral values of the vertical components are very close to that of the code for wide range of periods. The reason for this is that because the acceleration dynamic amplification factor is higher for vertical component (2.75) as compared to that of the horizontal (2.2 on average). This has raised the concern of  coping with vertical component in seismic resistant structural design, especially the issue is about the sufficiency of taking the vertical component as 70% to that of the horizontal for some seismically critical regions. The excitation and absorbed power density spectra as shown in Fig. 7 for three components can better illustrate the significance of the vertical component. In general, the absorbed power is appreciably higher than the excitation at period range of 0.5-2 seconds for all three components. The highest absorbed power demand is for the E-W component of 2.65 hp/ton, followed by the vertical of 2.2 hp/ton, and the least in N-S direction of 1.9 hp/ton. It can be seen that on average the absorbed power demand in horizontal direction is of the same magnitude of that of the vertical. Further more, a closer observation reveals that the absorbed power consistently higher than that of the excitation in the period of interest for vertical component; it is in contrary to that of the horizontal. This might explain the critical role of vertical component in case of Padang, September 30, 2009 earthquake.

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Figure 6 Modified response spectra of Padang earthquake, September 30, 2009, compared to that of the code. Top for horizontal; bottom for vertical components. ζ=5%.

Figure 7 Modified power spectra of Padang earthquake, September  30, 2009, for three components, in horse power per ton mass. ζ=5%. Seminar dan Pameran Haki 2010 -

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5 SOME EXPERIMENTAL RESULTS Experimental investigations have been carried out for some structural specimens and materials[6,7,8,9]. Full-scale beam-column sub-assemblage models of steel as well as concrete have been tested under cyclic displacement history. Another experiment was performed on full-scale confined masonry panel also in cyclic manner. Some of  the results which is relevant to be discussed herein, i.e., the hysteretic energy capacity per cycle versus the drift ratio, is presented. The typical model of the confined masonry investigated is shown in Fig. 8 (left). There were totally six specimens which were divided into two groups. Two types of material involved are red brick and lower-quality concrete block or locally known as conblock. Group 1 investigates one red brick panel and two conblock specimens. One conblock specimen is an ordinary panel, while the other has horizontal reinforcement at every mortar joint running from the end-to-end confining non-structural columns. The over all dimensions of all specimens in Group 1 are 1,070 x 1,330 mm2 (including two endconfining non-structural columns of 100 x 100 x 1,330 mm3 reinforced by 4 D-10 rebar); panel thickness is 100 mm. Group 2 performed similar experiment for three specimens all made of red brick with different configuration of the intermediate confining non- structural columns or beam. The specimen dimensions are 2,200 x 2,100 mm (including two end-confining non-structural columns of 100 x 100 x 2,100 mm3 with 4 D10 rebar); panel thickness is 100 mm. Unlike the first, the second specimen has vertical non- structural column inserted in the middle between the end non-structural columns; and the third has non-structural beam inserted in the mid-height of the second one. Vertical load resulting 0.4 MPa compressive stress was applied during the experiment to all six specimens. The typical resulting hysteretic loops are shown in Fig. 8 (right). Based on the hysteretic loop, a relationship between hysteretic energy capacities per cycle versus drift ratio can be constructed. By looking at the hysteretic loops it can be observed the phenomena of stiffness decrement and pinching, which become more appreciable at higher cycles. Physically it corresponds to crack formation and the widening of the crack gaps. Therefore it can be reasoned that the reduction of the hysteretic energy capacity is related to the number  and to the width of cracks in the energy dissipating sections.

Figure 8 Crack pattern and typical confined masonry specimen (left), the resulting hysteretic loops (right).  Another experiment was performed on two concrete beam-column sub-assemblies; Seminar dan Pameran Haki 2010 -

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see Fig. 9 (left). One assembly was conventionally detailed as required by code for fully ductile section especially for its beam segment close to the column, and also satisfying the strong column weak beam criteria. A beam stub on the other side of the column was facilitated to ensure no-rebar-slip on the critical column face of the beam. The other  specimen was similar to the first, however, pairs of diagonal web rebar was added to improve its shear strength and to control the crack distribution in hoping of enhancement of the energy dissipating capacity. The detailed is shown in Fig. 9 (left) with dimensions in mm, and the resulting hysteretic loops are in the right. It turns out that the additional diagonal web rebar has increased the energy dissipating capacity, and reducing the pinching phenomenon that is commonly associated with conventionally shear-reinforced concrete section. The observation of the hysteretic loops reveals that minor pinching phenomenon has been noted, however, the stiffness decrement remains noticeable. Visual observation during the experimental run shows cracks with thin gaps but well distributed in relatively wide area. The other specimen without diagonal rebar (not shown) present higher  pinching but with the same stiffness decrement, and this corresponds to more concentrated cracks in narrower area with larger gaps.

Figure 9 Typical concrete beam column sub-assembly (left, dimensions are in mm), and the resulting hysteretic loops (right) for the energy dissipating beam section. Experiment was also performed on a steel beam-column sub-assembly. The specimen was of compact section so as to satisfy requirements of fully ductile section and strong column weak beam. The specimen is shown in Fig. 10 (left) with dimensions in mm, and the resulting hysteretic loops are in the right. The pinching is not observable in this experiment, but the stiffness decrement due to local buckling, especially in the web, was noticeable.

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Figure 10 Steel beam column sub-assembly (left, dimensions are in mm), and the resulting hysteretic loops (right) for the dissipating beam section. Based on the experiments, relations of hysteretic energy capacity per cycle versus drift ratio is constructed and shown in Fig. 11. From the figure it can be learned about the robustness of steel structure and the inferiority of confined masonry, while concrete structure is in between them. The steel specimen can undergo a drift ratio as high as 3.5%, or ductility value of almost 5, with the energy capacity about twice that of the concrete at approximately the same drift ratio. Concrete can achieve drift ratio as far as 4.5%, or ductility value close to 5, with higher energy capacity for one with diagonal rebar  than that with none. Confined masonry can sway for as high as 1.5% inter-story drift ratio with very low energy capacity. The achievable drift ratio should be compared with the limiting values from the codes[10, 11], e.g., 0.7-1.3% for masonry buildings, and 2-2.5% for any other structures. The drift limitation of 2-2.5% for concrete and steel structure implies the ductility value of about 2.5-3 for steel and 2-2.5 for concrete which are much lower than the maximum experimental values of 4 and 5 for steel and concrete, respectively. This means there is ample safety margin for the typical steel and reinforced concrete components to be used in seismic regions as long as proper detailing is provided. When used as infill wall or panel, the confined or unconfined masonry is limited to much less drift ratio of 0.7-1.3% than that of the framing concrete or steel structures. This emphasizes the need of seismic gap between the panel and the enclosing frame, which is, unfortunately, commonly disregarded by builders in Indonesia, even in moderate to high seismic zones. Considering these common practices and also its low energy capacity, the failure of confined masonry has occurred rather early during the earthquake, and frequently fall down due to out-of-plane forces.

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Figure 11 Hysteretic energy capacity per cycle versus drift ratio for confined masonry panel, concrete, and steel beam-column sub-assemblies.

6 CUMULATIVE DAMAGE The important effect of earthquake duration has been discussed in some research reports and can be found elsewhere[4]. In Ref. [4] the duration is categorized as short, moderate, and long. The effect of duration enters into the picture through the hysteretic energy spectra of the models being investigated. For the kinematic hardening model, for  instance, the mean hysteretic energy demand for long duration is about 1.4 that of  moderate, and about twice that of the short durations. In experimental run the hysteretic energy is associated with deterioration in the form of cracks, yielding, plastic hinge formation or local buckling, during the post-elastic regime. More deterioration will occur  when more post-elastic displacement cycles is imposed, whether continuously or  intermittently. This phenomenon should be closely observed in case of Padang’s last earthquake, because prior to this last event there were several strong earthquakes struck the region. Table 4 lists some major earthquakes that shook the region during 2005-2009. There are at least five earthquakes occurrences before the most devastating one in September  30, 2009. The earthquake intensity ranges from IV-VII MMI, and the depth varies from shallow to normal except the last one that belongs to deep earthquake. Considering the ratio between the depth to epicentral distance, it can be expected that the vertical component is the most significant in the last event. The largest magnitude occurred in 2007 with VI MMI and its epicenter was about 185 km from Padang. The event had caused light to moderate damage to so many building structures, mostly concrete, as well as infrastructures; similar situation was also the case of the April 2005 event although with lower scale. Despite the structural damage incurred, most structures that survive those events were left untreated for cracks or  spallings in their critical sections, unless for some n on-structural or cosmetic repair.

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Table 4 List of Some Major Earthquakes Occurred Around Padang between 2005 2009 (USGS)

The cracks formed in concrete or masonry structures during the earthquake have reduced the hysteretic energy capacity of the structural components. On the other hand, it is not very easy to fill the gap by injecting epoxy or cement-based material into structural building joints. Even if this injection were performed, it was hard to inspect and to test to verify the results. Moreover it is unclear how the structure would behave in the next earthquake event, and therefore doubting the benefit over cost of the treatment. Certainly, the structures that left untreated for the cracks will have lower energy capacity than they were before the event. Due to some major earthquakes prior to the last one, much cumulative damage has occurred and further reducing the energy capacity of the relevant seismic resisting components. This condition has, presumably among other  important factors, caused the extensive destruction in case of September 30, 2009 Padang earthquake. Despite this important issue, the Indonesia code has not regulated on how to deal with it.

7 DISCUSSIONS AND CONCLUSIONS Several aspects have been presented and highlighted regarding the presumably key issues in relation to the September 10, 2009 Padang earthquake; especially considering its vast destruction. These include common local construction practices, the property of  the construction materials used, the regional seismicity, the characteristic of the earthquake, and the national building structure regulations. Other important issues, but untouched in the paper, that should be dealt with is raising the public awareness as well as mitigation in case of natural disaster, especially earthquake, for the area or region with high risk. The discussion of the latter can be found in Ref. [2]. Observing at the local culture and in the vicinity of Padang as well as the geological formation of the region, it must be clear that local people are aware of their condition as being prone to earth movement. Traditional dwellings and all kind of buildings that are constructed from wooden structures with light roof can be found almost every where in the region. However, due to seismic ‘silen t’ for long period that has the effect of lowering awareness, and better economic growth, authorities and public in general start constructing relatively modern structures for offices, houses, and other buildings. Some of them well comply with the national building code and some otherwise, while the local enforcements of the regulations were not ready for the boom and tend to be weak. Seminar dan Pameran Haki 2010 -

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The lesson learned from the last event is that the public and authorities should reconsider all procedures to build safe constructions, to increase the public awareness of  the natural threats that always in wait, to exercise the mitigation plans, to perform the post-earthquake assessment and rehabilitations, to review and up date the building codes, and to critically asses the deficiency of the systems or regulations in place. The latter emphasizes that strong earthquake such as the last one may not necessarily mean that the required level of horizontal design earthquake should be increased as there is no supporting evidence based on the earthquakes that occurred thus far. However, there is need to observe the proper selection of construction materials, to deal with the vertical component of earthquake, and to account for the cumulative damage, besides improvement of the commonly technical procedure such as seismic resistant design and sectional detailing. These aspects should be formally specified in the national building code and strictly adopted and enforced during the designs and constructions. In conclusion, based on the presentation outlined earlier the key issues that should be highlighted are as follows: a) The vertical component of the last earthquake plays significant role as were not clearly observed in almost all former events. Therefore, the code should better  regulate the vertical component of earthquake both in design procedures and to revise its present fractions. b) The low remaining strength of the critical structural components due to the previous earthquakes, which were left untreated, has caused inadequate energy dissipating capacity of structures in coping with the last event. In the future, there shall be effective regulations for post-earthquake assessments and rehabilitations of  structures and shall be required in the code. c) The severe damage that suffered by most masonry brick wall constructions, notable for their relatively low strength compared to concrete or steel materials, shows its unsuitability for region of moderate to high seismicity. Consequently, there should be stringent rules regarding the selection of construction materials used, and more on design procedures such as the determination of structur e’s ductility level and sectional detailing, especially, for the first story of multi-story building structures. d) Based on the earthquakes that have occurred thus far, there is yet no evidence to increase the required level of horizontal design earthquake in Padang and its vicinity, as the problem more related to the vertical component of the ground motions, or  others. e) Due to the limited reliable earthquake data, more monitoring instruments, e.g., strong motion recorders, should be installed in the region so that better earthquake analysis can be performed in the future.

8 ACKNOWLEDGMENT The author acknowledges Mrs. Netto Mulyanto, Riza N. Gustam and Andrianto, of PT PLN (Persero) for the earthquake data provided and reported in the paper.

REFERENCES Pikiran Rakyat, Kerugian Gempa Sumbar Rp. 4,8 Trilyun , Kamis, 29 Oktober, 2009. --------, Learning from Earthquakes: The Mw 7.6 Western Sumatra Earthquake of 

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EERI Special 2009. [http://www.eeri.org/site/images.PDF] September 30, 2009,

Earthquake

Report,

December,

SNI 03-1726-2003, Provision for Seismic Resistant Structural Building Design, Indonesia National Standard, 2003. (Document in Bahasa.) Mangkoesoebroto, S.P., Seismic Performance Chart for Simple Structures, Indonesia Centre for Earthquake Engineering, Research Report Series Number 1/2007 (ISBN 978-979-16472-0-5),  August, 2007. [http://www.icfee.info] Kastowo, D. and Gerhard, W.L., Geology Map of the Padang Quadrangle, Sumatra, Geological Survey of Indonesia, Geology Quadrangle Map , Sumatra, Padang 4/VIII, 1973. Mangkoesoebroto, S.P., Tambunan, S., and Goto, T., Experimental and Numerical Study  of Confined Masonry Wall Under Cyclic Loading, Journal Indonesian Society  of Civil and Structural Engineers (HAKI) , Vol. 4 No. 1, May 2003. Mangkoesoebroto, S.P., Goto, T., and Khadavi, Investigation of Full-Scale Confined Masonry in Reversed Cyclic, The Ninth East Asia-Pacific Conference on Structural Engineering and Construction, Bali-Indonesia, Dec. 2003. Mangkoesoebroto, S.P., Surahman, A., Batubara, S., and Irawan, P., Investigation of  Full-Scale Concrete Beam-Column Sub-Assemblies, The Ninth East AsiaPacific Conference on Structural Engineering and Construction, Bali-Indonesia, Dec. 2003. Mangkoesoebroto, S.P. and Sofyan, Non-Conventional Performance-Based  Seismic Engineering Applied To Strong Column-Fully Ductile Weak Beam Steel  Framed Structures: Energy Perspective, Indonesian Society of Civil and Structural Engineers (HAKI) Conference on the Excellence in Construction, Jakarta, August, 2004. FEMA 368, NEHRP Recommended Provisions for Seismic Regulations for New  Buildings and Other Structures, Part 1: Provisions, 2001. --------, International Building Code , 2000.

M a k a la h i n i d i s a m p a i k a n d a l a m r a n g k a d i s e m i n a s i i n f o r m a s i m e l a l u i S e m i n a r H A K I . I s i m a k a la h s e p e n u h n y a m e r u p a k a n t a n g g u n g j a w a b p e n u l i s , d a n t i d a k m e w a k i l i p e n d a p a t HA K I .

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