Citation: Lasmal, J., K. Kusunoki, and M. Seki (2019), Seismic retrofit of existing residential building in
Nepal to functionalize as hospital using ferrocement, Synopsis of IISEE-GRIPS master report.

SEISMIC RETROFIT OF EXISTING RESIDENTIAL
BUILDING IN NEPAL TO FUNCTIONALIZE AS
HOSPITAL USING FERROCEMENT
Jyoti LAMSAL1,2

Supervisor:

Koichi KUSUNOKI3
Matsutaro SEKI4

ABSTRACT
Because of urbanization, the land price becomes high, and the space in the core cities of Nepal are notavailable for constructing new facilities. Therefore, the trend of converting residential buildings topublic buildings is increasing. Here in this study, the existing non-engineered building that survived the2015 Nepal Gorkha earthquake that intended to shift its occupancy from residential to the hospital wasevaluated. The building was assessed considering the infilled and bare frame and reevaluated theferrocement retrofitted building using JBDPA, 2001 and Nonlinear Pushover Analysis. Three different
techniques of the retrofit were considered (1-partial retrofit, 2-whole wall retrofit, and 3-partial retrofit
with some non-retrofitted additional walls). The structural performance of the third types of retrofitting
techniques was found to be best. To elaborate on the necessity of retrofit for changing the functionality.
Three different cases for the same target building were considered, using Nonlinear Pushover Analysis.
Case A as a residential building without retrofit, Case B as a hospital building without retrofit (thatdepicts the current scenario of Nepal), and Case C as a hospital building with a retrofit. The recent 2015
earthquake and NBC 105 demand curves used for this study. Case A found to be safe in the 2015 Gorkha
earthquake and satisfied code provision, whereas case B could not satisfy any of the demand, and caseC satisfied both. The result of analysis could capture the real field scenario of Gorkha earthquakes. Manybuildings of case B types collapsed during the earthquake. However, Case C type building remain safer
after the earthquake. The result of the case study implies that many existing non-engineered buildings
by the recent earthquake are in a vulnerable state and needs a retrofit. In the same way, this thesis
identifies the retrofitting is urgent need before switching the occupancy of the buildings.
Keywords: FC-Retrofit, Functionality change, Non-engineered Buildings.

1. INTRODUCTION
The topographic structure, frequent tectonic movement make Nepal as seismically prone. Damage
caused by past earthquakes was massive. The recent great earthquake on April 25, 2015, claimed livesof 8970 people in Nepal. More than 498,852 residential buildings and 2,656 governmental buildings
were collapsed, and 256,697 private houses and 3,622 government buildings were partially damaged.

1

Bharatpur Metropolitancity, Bharatpur, Chitwan, Nepal.
IISEE-GRIPS master course student
3Professor, Earthquake Research Institute, Univ. of Tokyo.
4
Visiting Research Fellow, International Institute of Seismology and Earthquake Engineering, BRI.
2

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The maximum public buildings which were damaged by the earthquake were non-complying to current
building codes as well as those which changes its occupancy from residential to public.
It was found that the collapse of buildings is 95% cause of human death and economic
losses from earthquakes. Failures of the buildings are the result of poor construction practice, noncomplying building codes, lack of frequent revision of seismic codes, lack of awareness, lack ofpreparedness and old un-repaired/retrofitted buildings. Therefore, such structures with the low seismic
performance required a retrofit. The retrofitting of buildings is feasible if the cost of retrofit is less orequal to 30% for reinforced concrete (RC) structure. So for developing countries like Nepal suitable andeconomical ways of retrofitting is also another issues. Therefore, ferrocement (FC) lamination
retrofitting techniques, which is found to be appropriate techniques for developing countries like Nepal(Debashish et al. (2018)) are presented in this study.

2. DATAThe selected target building “Chiranjibi Model Hospital” that survived the recent Gorkha EQ is threestory with attic floor RC framed structure. It has a brick masonry infill. The target building constructed
before the building code implemented in this area, as a usual trend of construction in Nepal, this building
was also built without consulting to engineers and architects. As a result, construction materials,construction methods, design and detailing are not as requirements of the existing code.

Table 1. Outline of the target building.

Figure 1. Typical first-floor plan.

1.
Geological Information
Soil Class: Type II: Medium
Seismic Zonation Value (Z) NBC:105 =1
2.
Structural Information
All floor 2.87m
Columns: All 9” x 12” Main Bar: (4-12mmØ+2-10mmØ)
Lateral ties: 8 mmØ @ 150 mm c/c
Beams: All (230 X 355 mm) with 2-12 Ø (th)+2-12 Ø (ext.)
mm top +4-12 Ø mm bottom bars. Hoop 8mm Ø @ 150 mmc/c
Slab: 125mm thick (with 8mm Ø @ 150 mm c/c)
Concrete Grade: M20 (Compressive Strength 20MPa)
Steel Grade: Fe415 (Tensile yield strength 415MPa)
Locally made brick masonry infill having a wall thickness of230mm and 110 mm.
Load Considered: 14.75 KN/m2 for first and second floor 8.4& 7.97 KN/m2 for third and staircase cover floor.
Seismic Demand Index (Is0) as per NBC 105: 0.48

Initially, the building was a residential building, and later the ownership was transferred to the hospital.
The design loads and performance objectives for the hospital buildings and residential buildings aredifferent. Thus, the building requires retrofitting for changing the functionality. The typical floor planof the building is given below in the figure1. The brief information and data related to the building areprovided below in Table1.

3. THEORY AND METHODOLOGY
The selected building evaluated as a bare frame, by using the Japanese Building Disaster Prevention
Association (JBDPA), 2001 Standard for first level and second level screening. Then, the building wasreevaluated considering existing infill of the structures using the second level procedure of the JBDPA2Standard. Based on the deficiency of the structure obtained after considering the infill, the lagging
strength to the seismic demand index needed to supply from the retrofitting. As the retrofitting,ferrocement lamination technique introduced. The number of walls required to retrofit by ferrocement(FC) lamination calculated and applied to the structure. The retrofitted building again reevaluated as per
JBDPA second level screening. Three different methods of wall retrofitting were selected and evaluatedby manual calculation using JBDPA, 2001.
In addition to this, the same building evaluated using Nonlinear Static Pushover Analysis(NSPA) method, using ETABS 2016 software, considering both bare and infill. Finally, the retrofitted
building with ferrocement for all three different cases was reevaluated using NSPA. Based on theseismic performance of the various retrofitting plans of the building, the appropriate one was selected.
In addition to this, the target building was evaluated its performance based on threedifferent types of occupancy. Case A: As a residential building (no change in its occupancy) without
retrofitting, Case B: a residential building, however it changes its occupancy as hospital building without
retrofitting and Case C: a residential building used as hospital building but with retrofitting (as perhospital requirements). The building was evaluated using NSPA using ETABS, and their performanceagainst the recent Gorkha earthquake was studied.

4. RESULTS AND DISCUSSION
4.1. Results of JBDPA seismic evaluation of existing buildings
From the bare frame analysis of the building except for the fourth floor, none of the stories meets thestandard seismic demand index (0.48, as per NBC 105). However, when infilled of the existing building
strength was considered, then the third and fourth story found to be safe. However, the first and second
story still could not meet the standard criteria. Therefore, the lagging strength needs to supply by theretrofitting by ferrocements. Figure 2 illustrates the results of the bare and infilled frame as case 1 andcase 2.
4.2. Results of Retrofitting using ferrocement (FC) lamination.
The steps involved in retrofitting using ferrocements given below.
1. The value of Isi,bare-mod. (corresponding to ductility index F=1) from the JBDPA analysis istaken from the second level procedure for longitudinal strips and compared to Is0.
2. The value obtained (Is0-Isi, bare-mod)/Ø *Wi is the required strength to satisfy by the existing
infill and ferrocements. The ductility index F=1 was assumed for infill and ferrocement.
3. The value of shear strength by existing infills (Qinfill) considering reduction factor for openings
are obtained respectively to observed directions.
4. Now total strength that needs to be satisfied by the ferrocement is obtained as ∆Qfc= (Is0-Isi,baremod) *Wi/Ø- Qinfill.
5. Various combination of walls is added considering the opening to get the required strength.
The mortar with the strength of 20MPa and steel wire mesh 0.9mm @ 5.45 mm c/c having
415MPa used for ferro lamination. The figure below shows the results of the evaluation of the existingbuilding (case 1 and 2) and retrofitted buildings (case 3 to 5). Here, case 1 and case 2 are an existing
bare frame (BF) and existing building considering infill masonry (BM) respectively. By the same way,for the retrofitted cases; case 3 has the retrofit only in the first floor and second floor without disturbing
initial plan (FC2-NW), case 4 is same as case 3 but with additional four masonry wall replacing shutterof grid C and D (FC2-AW) and case 5 is same as case 3, but whole walls of third and fourth floors also
retrofitted (FC4-NW). The result of retrofitting shows that the Is value in case of case 5 for the thirdand fourth floor found to be increased in comparison to that of other it is because of retrofitting in thosefloors was done only in case 5. The Is value for case 4 in bottom floor found to increase slightly becauseof strength due to new masonry walls on the bottom floor. Because of having the same strength to that3

of case 5 for the first and second floor, and some strength to that of third and fourth floor for case 4, theline overlapped and could not be visible.
4.3. Results of Analytical Modelling4

In the analysis, frame elements (beams,columns, and struts) were modeled as lineIs Value for different Cases X-Direction Push
elements by assigning respective crossCase 1
sectional properties of frame and masonry2
Case 2struts. The rigid diaphragm applied to theCase 3
shell elements (slab). The default hinges
Case 41properties in ETABS 2016 (P-M2-M3) for
Case-5the column as per Table 10-8, of ASCE 41Is013, and flexural hinge properties (as perIs-Value
0Table 10-7, of ASCE 41-13, was used) for
0.000 0.400 0.800 1.200 1.600 2.000 2.400 2.800 3.200 3.600 4.000
beam was applied. The hinge length for
Figure 2. Is values for various cases of evaluation andbeam and columns applied at the10% fromretrofitting cases.
each end. The hinge properties of theequivalent compressive strut for masonry and retrofitted walls referred as per FEMA 356, table 7-9. It
was applied at the mid-section of the struts. The gravity load applied on the model are given above inTable 1, whereas the lateral loads applied on the model are as per NBC 105 distribution pattern.
Storey3Inter-Story Drift of Various Cases at Performance Points
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Case 3 (FC2-NW)

StoreyCase 4 (FC2-AW)
Case 5 (FC4-NW)

21Story Drift, unitless

000.0005

0.001

0.00150.002

0.0025Figure 4. An inter-story drift of various cases atperformance point.

Figure 3. Performance points for various cases.

The figure above shows that at the ultimate state, case 4 has higher strength than that of theother cases. The probable reason is that the addition of walls in the bottom story of case 4 significantly
increased the performance of the buildings. Although the story drift for all the cases is within the drift
limit of 0.4% (which is considered as Immediate Occupancy (IO) for important building in Nepal).
However, in the case of case 4, the inter-story drifts (ID) was found to be evenly distributed and least
ID values in comparison to other cases. The values of ID for case 3 and case 4 are almost the same forthe third and fourth floor because both have no retrofitting in the upper two floors. However, the ID inupper floors in case 5 seems to be lesser because for this case we have retrofitted the upper two floors,that increased the stiffness of the building. As a result, lesser deformation occurred on those floors. Inoverall, this study found that just by adding four masonry walls could significantly change the structural
performance of the building rather than investing a huge amount of money in the name of retrofitting
such as case 5. Figure 5 to 7 the hinge results at the performance point for various cases which was
found to be at immediate occupancy state.

4Figure 5. Hinge Results for Figure 6. Hinge Results for Case Figure 7. Hinge Results forCase 3 at performance points.
4 at performance points.
Case 5 at performance points.

5. Case Study: Functionality ChangeThis is the case study, carried out to capture a real scenario (occupancy shifting without taking any
strengthening measures for buildings) of Nepal, during the 2015 Gorkha earthquake. Here, as a casestudy, three different scenarios of a given target building were considered. Case A: If a building is used
as a residential building, Case B: If a building of case A is used as a hospital building without retrofitting.
(this is the case 2 of the previous section) Case C: If a building of case A is used as a hospital building
with retrofitting. (this is the case 4 of the previous section). The LL for residential and hospital building
considered as 2.5 and 4 KN/m2 respectively whereas for the first and second floor the DL for residential
and the hospital are 9 and 10.75KN/m2 respectively. The load for the third and fourth floor considered
as same being roof floor for both cases. Nonlinear Pushover Analysis was carried out for different cases.
The capacity curve of three cases of the building plotted over the demand curve of NBC 105 for hospitaland residential buildings as well as the N-S component of the 2015 Gorkha earthquake given in Figure
8. The demand curve for the 2015 Gorkha earthquake was plotted by using View Wave software.

Figure 8. Capacity curve versus NBC & Gorkha
earthquake 2015 demand curve for case A, B, and C.

Figure 9. ID for residential building (caseA) corresponding to performance Point.

The Figure 8 shows that the building which was occupied as a residential building without
being retrofit, had a performance point of (Sd, Sg); (16.5, 0.34g) values and corresponding story drift isgiven in above Figure 9. The corresponding base shear and displacement for this point is 1603.03 KN
corresponding to performance point. The maximum drift corresponding to this point is 0.38%, which isa bit smaller than ID limit 0.4% and this implies that building remains safe during the 2015 Gorkha
earthquake. The building seems just satisfying the NBC provision for residential buildings. However,there are many other existing buildings which have poor construction detailing in comparison to this5building. It implies that although the buildings that remain safe during the 2015 Gorkha earthquake are
required to retrofit for satisfying the present NBC demand. However, if the building was used without
retrofitting as a hospital building, then, in that case, the importance factor of the building is considered
as 1.5 because the demand index must be increased by 1.5 times. Because of the increase in building
seismic weight due to the change in occupancy load, the capacity of (Sa,g) decreased. Because of this,the building could neither satisfy the 2015 Gorkha earthquake demand nor requirements of hospitalbuildings as per NBC 105. This building will collapse if the same scale earthquake as the 2015 Gorkha
earthquake occurs.
However, if we can do a retrofit for the buildings as per the intended occupancy to satisfy
the NBC provision, the building could be safer. The retrofitted building was found to fulfill the 2015
Gorkha earthquake demand almost linearly within the elastic region without any damage. The building
also found to satisfy the hospital demand as per codal provision. Therefore, a retrofit is an urgent needfor changing the occupancy of the buildings.

6. CONCLUSION
The presence of infill could not ignore. It plays a significant role in strengths and stiffness; therefore, toidentify the actual behaviors of the building, it is most to consider the infill. The strength and stiffness
found to be increased significantly, from bare to infill and infill to ferro laminated structures. From theanalytical results, it was found that the performance of the buildings in case 4 was better. It was becauseof the additional four masonry walls on the first floor. These walls increased the performance of thebuilding significantly. From this, we can conclude that the performance of the building will not increase
only by retrofitting in uneconomic ways as in the case of 5. Thus, the judgment of the retrofitting planis significant, so that cost-effective work could be achieved. The vulnerability (seismic demand) of thebuilding increases as the occupancy converted from residential to the public. Therefore, the building
which is intending to shift their functionality must be retrofitted. The ferrocement techniques found tobe suitable techniques in developing countries like Nepal.

ACKNOWLEDGEMENTS
This research was conducted during the individual study period of the training course “Seismology,Earthquake Engineering and Tsunami Disaster Mitigation” by the Building Research Institute, JICA,and GRIPS.I want to express my sincere gratitude to Professor Koichi Kusunoki Dr. Matsutaro Seki, Dr.
Toshihide Kashima, course coordinator Dr. Tatsuya Azuhata and Dr. Trevor Yeow (University ofTokyo) for their continuous support, valuable suggestion and instruction during my study. At last, I wantto thanks all the supportive hands that make my study success.

REFERENCES
ATC-40 (1996), vol. I, Applied Technology Council, Redwood City, CA, USA.
FEMA 356 (2000), Federal Emergency Management Agency, Washington, DC, USA.
Government of Nepal Ministry of Home Affairs Nepal Disaster Report 2017.
Viewwave software.

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