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“...numerical modeling, the primary causes of the damage are discussed. [DOI: 10.1193/121616FQS241M]
INTRODUCTION
Cultural heritage structures are major assets in a society and, therefore need proper maintenance, repair, and rehabilitation. Failure to provide these can render them vulnerable to natural catastrophes like earthquakes. The recent Gorkha earthquake of Mw7.8 (USGS 2015) severely damaged cultural heritage structures in Nepal. According to a survey report by the Department of .Archaeology in Nepal, 745 monuments in and around the Kathmandu Valley were damaged by the earthquake (DoA 2015). The report notes that 133 monuments were in a totally collapsed state, 97 were partially collapsed, and 515 suffered partial damage. In Kathmandu Valley, 447 monuments were affected by the earthquake, out of which 83 totally collapsed to the base (DoA 2015). In particular, the seven UNESCO world heritage sites of the Kathmandu Valley suffered extensive damage, and Kathmandu Durbar Square was the most...”
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“...outer layers of masonry walls, and failure of timber connections. Such damage can trigger the sudden or brittle collapse of a masonry structure with very little warning. For effective restoration and conservation of any historic building, a detailed assessment of the structure and of the physical damage to its masonry is required, for which a deep knowledge of actual internal construction, geometries, materials, morphologies, and mechanical properties is necessary.
Table 1. Damage states in the seven Kathmandu Valley World Heritage Property monument zones
Monument zone Number of classified monuments Number of totally collapsed monuments Number of partially damaged monuments
Hanuman Dhoka Durbar Square 97 11 39
Bhaktapur Durbar Square 39 5 14
Patan Durbar Square 44 6 21
Changunarayan 67 3 2
Pashupati 44 6 21
Swayambhu 82 4 9
Bauddhanath Partial damage in stupa...”
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“...timber nail is shown in Figure 2b. Timber nails used for the connection, in single or double pairs, act as pin joints, allowing movement in case of an earthquake. This gives some amount of flexibility to the structure along with a capacity to absorb energy. These framing arrangements make the Nepalese tiered temples safer from seismic disturbances compared with other unreinforced masonry structures (Jaisi 2003). Experimental work also provides evidence that timber-framed masonry walls exhibit a large capacity to deform in the nonlinear regime with remarkable lateral drifts and controlled damages under in-plane cyclic loading (Vasconcelos 2013). The roofs are supported by timber struts, and the connections between wall and frame are made using timber nails.
Typical damage patterns observed in the tiered temples after the Gorkha earthquake are presented in Figure 3. The most common failure type observed was the failure of the comer walls in the lower level as shown Figure 3a. This failure...”
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“...(Figure 2c) (Beckh 2006). In addition to partial damages, some of the monuments (mostly in Kathmandu Durbar Square) were totally collapsed (Figure 3d).
The Shikhara temples of Kathmandu Valley have tall slender masonry walls, constructed with or without timber framing. A typical cross section of a Shikhara Temple is shown in Figure 4a. Because of the greater slenderness and the height of the unsupported mud-mortar masonry walls, these structures are vulnerable to seismic events, as the Gorkha earthquake revealed. In general, wood frames (if provided) exist only in the inner core and...”
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“...totally collapsed during the Gorkha earthquake, revealed that one of the four saddle stones that supported the central vertical timber posts was missing, causing the post to rest on the ground without any connection (Coningham 2015). There was a strong possibility that the missing saddle stone was removed during the flooring work in the previous restoration. In Bhaktapur Durbar Square, the stone-clad Vatshala Temple totally collapsed. Past partial restoration work in the cladding at the top of the structure had been carried out with replacement of the original mud mortar with lime mortar. These partial changes in the mortar, only in the top of the structure, might have triggered the incompatibility between the old and new materials, perhaps resulting in in the structure’s incompatible local responses and ultimately leading to its sudden failure in the Gorkha earthquake (Figure 6) while other similar structures nearby suffered only partial damage.
Damage to structures resulting from similar...”
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“...S368
SHRESTHA ET AL.
(a) Typical section (b) Overturning of walls (c) Failure of the tip
(d) The collapse of the walls (e) Total Collapse
(a) Improper connection
Figure 5. Wooden elements in traditional structures.
Figure 4. Damage to Shikhara temples.
(b) Decayed floor joists and wall plates...”
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“...DAMAGE ASSESSMENT OF CULTURAL HERITAGE STRUCTURES: JAGANNATH TEMPLE
S3 69
Figure 6. Vatshala Temple, Bhaktapur Durbar Square before and after earthquake.
(a) Crushing of old brick work in (b) Timber/clay tile roof of structure replaced with
Pratappur temple concrete roof
Figure 7. Damages due to variations in material integrity during restoration work.
portion of the old and new construction, resulting in the crushing of old brick work around the circumference. In contrast, the Anantapur Temple, with almost the same configuration in the same locality and which had never before been restored, experienced partial collapse at the top and shear cracks in the ground wall. It is worth noting that, in the first case, the compatibility of materials in restoration work was at issue whereas at .Anantapur lack of proper monitoring and maintenance, along with the age of the structure led to the damage. In some cases, timber and clay tile roofs were replaced with concrete, adding substantially to the...”
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“...S370
SHRESTHA ET AL.
(a) Before Gorkha EQ
(b) After 1934 EQ
Figure 8. Jagarmath Temple before and after earthquake.
(c) After Gorkha 2015 EQ
wooden planks and rafters, and a wooden floor system. The temple was heavily damaged during the Mw 8 Great Nepal-Bihar Earthquake of 1934 (Figure 8b) and was reconstructed from the plinth level in 1935. In 2000, both roofs of the temple were restored completely, and some repair work in the wood-crafted elements was carried out (KVPT 2000).
After the 2015 Gorkha earthquake, a comprehensive visual damage assessment of the temple was prepared, as shown in Figure 9a. It was found that two types of mortar (lime and mud) had been used during reconstruction in 1935. Most of the ground floor brick walls were built up with lime mortar (Figure 9b), whereas the first-floor brick walls and top-floor walls were constructed with mud mortar. The top-floor masonry wall was heavily damaged, with significant diagonal tension shear cracks through the brick and mortar...”
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“...DAMAGE ASSESSMENT OF CULTURAL HERITAGE STRUCTURES: JAGANNATH TEMPLE
S37I
Undamaged Partially damaged Heavily damaged
(a) Damage grade of structural wall
□ Limo Surkhi Mortar
Ground Floor Plan MudMonar Jagannath Temple
Second Floor Wan Inclination Jag&nnath Temple
(c) Inclination measurement of top floor wall
(b) Different composition of masonry wall
(d) Damage in upper wall
Figure 9. Condition assessment of Jagannath Temple.
NUMERICAL MODELING
To evaluate the response of the temple during the Gorkha earthquake, finite-element analysis was performed in SAP 2000 (v. 16.0.0). Given the limited knowledge of the temple’s material characteristics, nonlinear analysis of the masonry was out of the scope of analysis. In this study, the structural component materials were assumed to be homogeneous, isotropic, and linearly elastic. The masonry wall was modeled using solid elements, and timber elements were modeled using frame elements. In total, 1,890 solid elements and 784 frame elements were used...”
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“...Compressive strength (fcm) MPa Mortar quality (Class)
Lime 36 8 3.7 Normal (C)
Table 4. Mechanical properties used in numerical model (Parajuli 2012)
Type Density (kg/m3) Compressive strength (N/mm2) Shear strength (N/mm2) E (N/mm2) V G (N/mm2) ys (m/s)
Wall 1,768 1.82 0.15 509 0.25 204 336
Timber 800 - - 12,500 0.12 1,500 -
objective of this analysis was to understand the behavior of the structure and to validate the model by comparing stress concentrations with an actual crack created by the earthquake. The mechanical properties used in the model are presented in Table 4 (Thapa 2011, Parajuli 2012, Jaishi 2003). Permissible stresses for the masonry wall (Jaishi 2003) are shown in Table 5. Results obtained from linear static analysis are presented and discussed.
From the numerical analysis, it was determined that the fundamental mode of the structure had a frequency of 4.55 Hz (Figure 10a). However, microtremor investigation revealed the fundamental frequency of the structure to be 2.6 Hz...”
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“...DAMAGE ASSESSMENT OF CULTURAL HERITAGE STRUCTURES: JAGANNATH TEMPLE
S3 73
(a) First mode (bending along X-axis), T=0.219sec; f= 4.55Hz
X S33 Contour! (IQX)
__________________________________» } ■» jolOB-l -[[H.mm.C u|
(c) Direct normal stress S33 in +EQX loading
(b) First mode (modified) (bending along X-axis), T=0.337sec; f= 2.96 Hz
-. M3 Contour! IKJX)
_______________________________________» I ■» |aioe»i jJ|kn,«,c xl
(d) Direct shear stress S23 in +EQX loading
JSC S33 Contour! (IQX)
$= | 4 iGLOE-L <•; c, C
(e) Schematic diagram of timber confinement (f) Direct normal stress S33 in +EQX loading
in inner wall (with additional timber element)
Figure 10. Numerical analysis results....”
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“...thus that timber bands in the masonry inner wall of the temple (Figure 1 Of) is a possible approach to minimizing damage in a future earthquake.
CONCLUSION
This paper presented details of the damage to various heritage structures observed after the 2015 Gorkha earthquake. Vulnerabilities of the heritage structures to strong ground shaking were noted, and it was observed that the damage patterns were difficult to generalize because they could be quite different in heritage buildings with similar architectural features. Moreover, damage to some of the buildings was exacerbated by inappropriate interventions, insufficient details regarding timber elements in rebuilt structures, and lack of maintenance.
A case study using the Jagannath Temple was presented. To assess the condition of the temple’s masonry walls, limited field tests were conducted. A three-dimensional numerical model of the temple was developed in SAP 2000, and linear static analysis was carried out. The numerical evaluation revealed...”
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“...R., 2008. Seismic performance of masonry buildings during recent earthquake in Turkey, Proceedings of the 14th World Conference on Earthquake Engineering, 12-17 October, Beijing.
Gentile, C., and Saisi, A., 2007. Ambient vibration testing of historic masonry towers for structural identification and damage assessment, Construction and Building Materials 21, 1311-1321.
Gulkan, P., and Langenbaeh, R., 2004. The earthquake resistance of traditional timber and masonry dwellings in Turkey, Proceedings of the 13th World Conference on Earthquake Engineering, 1-6 August, Vancouver, BC.
Jaishi, B., Ren, W. X., Zong, Z. H., and Maskey, P. N., 2003. Dynamic and seismic performance of old multi-tiered temples in Nepal, Engineering Structures 25, 1827-1839.
Karantoni, F. V, Papadopoulos, M. L, and Pantazopoulou, S. I,2016. Simple seismic assessment of traditional unreinforeed masonry buildings, International Journal of Architectural Heritage 10, 1055-1077.
Kathmandu Valley Preservation Trust (KVPT), 2000...”
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“... P. N., 2013. Lesson learned from the performance of buildings during the September 18,2011, earthquake in Nepal, Asian Journal of Civil Engineering 14, 719-733.
Shakya, M., 2010. Modal analysis using ambient vibration measurement and damage identification of three-tiered Radha Krishna temple, Master’s thesis, Purbanehal University, Nepal. Shakya, M., Varum, H., Vicente, R., and Costa, A., 2012. Structural vulnerability of Nepalese
pagoda temples, Proceedings of the 15th World Conference on Earthquake Engineering, 24-28 September, Lisbon.
Shakya, M., Varum, H., Vicente, R., and Costa, A., 2014. Seismic sensitivity analysis of the common structural components of Nepalese pagoda temples, Bulletin of Earthquake Engineering 12, 1679-1703.
Sorrentino, L., Liberatore, L., Liberatore, D., and Masiani, R., 2014. The behavior of vernacular buildings in the 2012 Emilia earthquakes, Bulletin of Earthquake Engineering 12, 2367-2382.
Tiwari, S. R., 2009. Temples of the Nepal Valley, Himal Books, Kathmandu...”
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