Rapid assessment of the public buildings after the February 25 th , 2022 West Pasaman Earthquake

. The earthquake that occurred on February 25th, 2022 (6.2 M) and the aftershock in the West Pasaman Regency, West Sumatra Province has caused damages to infrastructure and community settlements. One of those affected by the Pasaman Earthquake 2022 are public buildings. To determine the level of public building damage, an assessment should be carried out before reoccupying the buildings. In this study, a rapid assessment of damaged public buildings was conducted after the Pasaman Earthquake by the Disaster Study Center of Andalas University team. The assessed buildings include the buildings of Balerong Hall, Ibnu Sina Hospital, Grand Mosque, Population and Civil Registration Agency (Disdukcapil) office, Regional Public Hospital, and Elementary School (SDN) 22 of Talamau. The results of the assessment show that in general, these public buildings have non-structural damages, such as cracks in the walls and ceiling crashes from their positions. Meanwhile, in the buildings of Elementary School (SDN) 22 Talamau, Grand Mosque, and Disdukcapil, it is found that there are some structural damages observed, such as cracks on the columns. The main factor causing the damage is the low quality of the concrete in the columns. Recommendations for repairing the damaged building are also discussed in this study.


Introduction
Indonesia is a seismically active area where 4,486 earthquakes with a magnitude of more than 6.0 M occurred during 1976-2006.The results of research by the Meteorology, Climatology, and Geophysical Agency (BMKG) from 1991-2009 have documented that there were 27 destructive earthquakes and 13 earthquakes causing tsunamis.Indonesia is estimated to have an earthquake twice a year and the earthquakes followed by a tsunami once a year.A series of earthquakes had struck several areas in Indonesia, such as Aceh in 2004 and 2016 [1], West Sumatra in 2009 [2,3], Lombok and Central Sulawesi in 2018 [4].
West Sumatra Province is located between the confluence of two large continental plates (the Eurasian plate and the Indo-Australian plate) and the Semangko fault.Adjacent to the plate meeting points, there is the Mentawai fault.Therefore, West Sumatra is classified as an area prone to large earthquake intensity, as stated in the Indonesian Seismic Standard (SNI-1726-2019) [5].
On Friday, February 25, 2022, an earthquake centered at the bottom of Mount Talamau, West Pasaman hit the region with the epicentres, as shown in Fig. 1.The early earthquake occurred at 8:35:51 a.m., with the epicenter on the ground at the coordinates of 0.14°LU and 99.99°BT, with a magnitude (5.2 M) at a depth of 10 km, 18 km northeast of The West Pasaman.Later, the main shock of the Pasaman Earthquake 2022 occurred on Friday, February 25, 2022 at 8:39:29 a.m. with the epicenter on the ground at 99.98° BT and 0.15° LU approximately 17 km northeast of the West Pasaman, with a magnitude of (6.2 M) at a depth of 10 km.Other aftershocks occurred at 11:02:20 a.m. and 11:06:38 a.m. with the magnitude of M=5.0 and M=5.1, respectively 10 km.
The earthquake caused damage to infrastructure and community settlements, one of which are the public buildings.A public building is defined as a building that is more than 50% of its floor used for public activities.Generally, the public building has the following characteristics: a. High economic value.b.Public and service area.c. High rate of occupancy d.Standard facility to guarantee the business or trading activities can be done properly.e. Good architecture.f.Particular vertical building structure.g.Good protection for any disaster is based on standard and valid regulations.
To determine the level of damage, an assessment should be carried out before reoccupying the buildings.In this study, a rapid assessment of damaged public buildings was conducted after the Pasaman Earthquake by the team from the Disaster Study Center of Andalas University.The assessed buildings include the Balerong Hall, Ibnu Sina Hospital, Grand Mosque, Population and Civil Registration Agency Office, Regional Public Hospital, and Elementary School (SDN) 22 of Talamau.

Method
The method of assessing buildings that are at risk of postearthquake damage must consider long-term aspects and the possibility of disasters in the future.Risks, vulnerabilities and approaches based on disaster risk management are also considered in conducting the assessment.Various methods can be used to conduct rapid visual screening after an earthquake occurs.However, some of the building assessment methods applied are the method published by the Directorate General of Human Settlements PUPR "Quick Assessment for Non-Engineered Structures" [6] and the method of Quick Inspection Manual for Damaged Concrete Buildings due to Earthquakes, NILIM, 2002 [7].In this study, a rapid visual assessment of the public buildings post-West Pasaman earthquake was carried out by the Disaster Study Center of Andalas University team.These public buildings were surveyed due to their relatively close distance to the epicenter and the damage, as shown in Fig. 2. The building assessment form used in this survey is based on Minister of Public Works Regulation number 16/PRT/M/2010 concerning technical guidelines for periodic inspection of buildings form [8]. The form contains the identity of the objects under review, potential hazards around the objects, the criticality checking of the building, estimated damage percentage of each building structural element, and assessment of nonstructural elements in general.After filling out the form, the results of the evaluation of building damage can be determined.

Observation of the damaged public buildings
The building, located in Nagari Kajai, Talamau District, West Pasaman Regency, is one of the school buildings affected by the 2022 West Pasaman earthquake.This building is made of reinforced concrete frames with brick walls (Fig. 3(a)).Based on the assessment, it was found that there are structural damages in the building, such as the column and non-structural, as shown in Fig. 3(b).Damage to the building structure is observed in the form of local destruction of the columns caused by the lowquality of the concrete (Fig. 3(c)).Meanwhile, for nonstructural damage, it was found that 80% of the walls cracks, ranging from hairline cracks in plastering (<0.2 mm) to partial or total falling of the walls, as shown in Fig. 3(d, e, f).
This damage is due to the relatively low quality concrete and there are no anchorages between the column and the wall.In addition, damage occurred to the ceiling, causing almost all segments separated from their position, as shown in Fig. 3(e).This is due to the lack of supervision during the installation of the ceiling and the materials with low quality.The assessment result of the building shows that the damage to the building is categorized as moderate because, in general, the structural elements are still sturdy, and the damages mainly occurred on the non-structural elements such as walls, ceilings, and floors.For structural damage, it is recommended that repair the column by rebuilding the column using the correct steel reinforcement detailing must be done, while for nonstructural damages on the wall, it can be repaired and retrofitted using ferrocement layers [9].

Ibnu Sina Hospital building
Ibnu Sina Hospital of West Pasaman Regency is located in Simpang Empat, the capital city of West Pasaman Regency, West Sumatera Province, Indonesia.It is a four-story building made of reinforced concrete with the special moment resisting frame structure, shown in Fig. 4(a).From the assessment, it was found that the damage to the buildings occurred on the non-structural components, such as the flexible cracks and sliding on the walls, as shown in Fig. 4(b, c, d, e, f).This is caused by the response of the building structure in carrying the earthquake load due to the pounding that occurred between the main and the annex buildings.The damage level of the building is categorized as lightly damaged, therefore, it is recommended that the building walls must be repaired and strengthened using ferrocement layers with bandage system.

The West Pasaman Grand Mosque building
Grand Mosque of West Pasaman is the main mosque with beautiful architecture and has four towers, as shown in Fig. 5(a).It is located near the Regency Office of West Pasaman, around 18 km from the earthquake epicenter.The structural damages were found in the column in which the cracks were evident in the column's concrete surface (approximately 0.2-1.0mm) (Fig. 5(b, c, d)).Meanwhile, the non-structural damages were observed on the minarets by the presence of sliding cracks on the top of the minarets (Fig. s 5(e)) and walls of the mosque (Fig. 5(f)).These cracks are mainly due to the bad quality concrete and low-density bricks.This building is safe to be used after immediate repairs on the minarets and walls of the mosque.

Population and Civil Registration Agency Office building
The next building assessed by the team is the Office of Population and Civil Registration Agency in West Pasaman Regency, which is located near Ibnu Sina Hospital.This office is built of reinforced concrete with brick walls.It was found that damages occurred in the structural and non-structural building components (Fig. 6(a)).Cracks were evident on the concrete surface of the practical column and chill blocks (the width of a crack is approximately 0.2-1.0mm), making it structural damage, as shown in Fig. 6(b, c, d).The non-structural damages occurred because there are no anchors that connect the wall to the window, as shown in Fig. 6(e).In addition, damage also occurred in the office ceiling because the ceiling did not fit properly according to the standard installation (Fig. 6(f)).The building is categorized as a safe building that can be occupied while repairing the damaged components.The wall cracks can be repaired and strengthened using ferrocement layers method.

The West Pasaman Regional Public Hospital building
West Pasaman Regional Public Hospital is the biggest hospital located in Jambak, West Pasaman Regency, around 20 km from the epicenter of the earthquake.This three-story building is built using a reinforced concrete structure, as shown in Fig. 7(a, b).The damages were observed occurring on non-structural parts of buildings.Fig. 7(c) shows a crack along the wall's junction with the column.This might be due to the absence of anchors to connect the wall and column.Damages in the form of hairline cracks occur on stucco (< 0.2 mm) of the front facade (Fig. 7(d)), walls (Fig. 7(e)), and floor (Fig. 7(f)) of the building.These cracks were caused by the low quality of the stucco.Considering the light damage of the building, the Hospital can be used as usual, and it is suggested that repair must be done immediately and can be carried out during the operational hours of the hospital.

The Balerong Hall building
Balerong Pusako Anak Nagari Hall is a multipurpose building used for government meetings and ceremonies.This building is located behind the regency office in Simpang Empat, West Pasaman Regency, around 18 km from the epicenter of the earthquake.This building is made of a reinforced concrete frame with a brick wall, as shown in Fig. 8(a).In this building, non-structural damages were observed as almost all of the ceiling segments were unstuck from their position due to improper installation of the ceiling, which is not in accordance with the standard (Fig. 8(b, c)).Hairline crack that is < 0.2 mm also appears on some walls, and this is due to the poor quality of the plaster, as shown in Fig. 8(d).The damages in this building can be repaired instantly by installing a new ceiling and re-plastering the wall crack.The Hospital can be used as usual and it is suggested to repair the damages immediately during the operational hours of the hospital.

Balerong Hall -
The fall of a part of a ceiling and the crack in the wall The damages to the building can be repaired instantly by installing new ceilings and replastering the wall cracks.Based on the observation of the damages in public buildings in West Pasaman Regency, Indonesia, there are some recommendations, as shown in Table 1.
From Table 1, it can be seen that the damage to the public building due to the Pasaman earthquake mainly occurred on non-structural components, especially the cracks in the wall.The repair and retrofit of the wall can be done by using ferrocement layers method by adding plaster or mortar and woven wire to the cracked part of the wall with the procedure as shown in Fig. 9.The repair and equalizing method using this ferrocement layers is simple (no professionals needed).It is also quick and inexpensive.
Damages to public buildings assessed are generally classified as light damage.However, to anticipate future earthquakes, it is recommended to carry out the assessment of other public buildings even though the buildings show no damage after the West Pasaman Earthquake as most of the buildings were built using the old Indonesian Seismic Standard.

Conclusion
Based on the results of the study, the following are conclusions that can be drawn: 1.Many public buildings were damaged by the West Pasaman Earthquake, in which most of the buildings are light-damaged.From the six public buildings assessed, one building has moderate damage, namely SDN 22 of Talamau building, while the other public buildings have light or minor damage.2. Public buildings with minor damage generally experienced non-structural damages such as cracks in the walls and fallen ceiling from its position, while public buildings with moderate damages (SDN 22 Talamau Building) experienced structural damages, such as local destruction of the concrete column, cracks on the column surface, cracks in the walls, falling of the ceiling from its position, and partial collapse of the walls of the building.Due to the relatively close distance to the epicenter of the earthquake, the intensity of the earthquake in the SDN 22 of Talamau building is greater than other buildings.3. Structural damages in the public buildings were mainly caused by the low-quality concrete and plaster on the column and the distance between the stirrup reinforcement on the column was not up to standard.Meanwhile, the buildings with non-structural damages were caused by the low quality of concrete and bricks, the low quality of plaster, the unavailability of anchors at the wall-column connection, and the improper installation of the ceiling that does not follow the standard.4. The building that suffered minor damage, especially the cracks on the building wall, can be repaired and strengthened using ferrocement layer method by adding plaster or mortar and woven wire to the cracked part of the wall.Meanwhile, buildings with moderate damage to columns can be repaired by rebuilding the column using the correct steel reinforcement detailing.5.For anticipating future earthquakes, it is recommended to carry out the assessment of other public buildings even though the buildings show no visible damage after the West Pasaman Earthquake because most of the buildings were built using the old Indonesian Seismic Standard.

Fig. 2 .
Fig. 2. The locations of the building assessment.

Fig. 3 .
Fig. 3. (a) Front view of the building, (b) Building damage survey, (c) Column damage, (d) Wall damage, (e) Wall and ceiling damage, and (f) Visible cracks on the wall.

Fig. 4 .
Fig. 4. (a) Front view of the building, (b) Survey damage, (c) Damage to the rear left of the building, (d) Damage to the rear right of the building, (e) Damage to the operating room, and (f) Damage to the inside of the building.

Fig. 5 .
Fig. 5. (a) Front view of the mosque, (b) Survey damage to the mosque, (c) Damage to the exterior, (d) Damage to the column, (e) Damage to the minaret tower, and (f) The damage to the inner part of the mosque.

Fig. 6 .
Fig. 6.(a) Damage survey, (b) Damage to the columns, (c) Damage to the chilled beam, (d) Cracks in the chilled beam, (e) Damage to window and wall connections, and (f) Damage to ceilings.

Fig. 7 .
Fig. 7. (a) Front view of the hospital building, (b) Survey damage, (c) Damage to column and wall connections, (d) Damage to the front of the building, (e) Wall West Pasaman Regional Public Hospital damage, and (f) Damage to the floor.

Fig. 8 .
Fig. 8. (a) Front view of the building, (b) Survey damage, (c) Damage to the plafond, and (d) Damage to the wall.

Table 1 .
Results of public buildings observation and the repair recommendation.