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Study on seismic performance of base-isolated and base-fixed Ancient timber buildings in hanging-wall/footwall Earthquakes
Study on seismic performance of base-isolated and base-fixed Ancient timber buildings in...
Ou, Tong; Wang, Dayang
JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING https://doi.org/10.1080/13467581.2022.2045999 Study on seismic performance of base-isolated and base-fixed Ancient timber buildings in hanging-wall/footwall Earthquakes a,b b,c Tong Ou and Dayang Wang a b GuangDong Architectural Design & Research Institute Co., Ltd, GuangZhou, GuangDong, P.R. China; Guangdong Engineering Research Centre for Metal Cladding and Roofing System (GDERC-MCRS), GuangZhou, GuangDong, P.R. China; School of Civil Engineering, Guangzhou University, Guangzhou, GuangDong, P.R. China ABSTRACT ARTICLE HISTORY Received 6 April 2021 This study aims to quantify effects of hanging-wall/footwall fault parameters on dynamic Accepted 18 February 2022 responses of base-isolated and base-fixed ancient timber buildings. Finite element models of a real timber building with and without isolation technology are first built and verified by KEYWORDS comparison with existing studies. Fitting analysis of three typical models, Abrahamson-Silva- Fault parameters; hanging- Kamai, Campbell-Bozorgnia and Chiou-Youngs models, as well as 622 recorded ground wall/footwall effect; ancient motions, is then conducted to determine the optimal model to generate earthquake waves. timber structure; isolation Finally, effects of hanging-wall/footwall fault parameters on seismic performance of the based- isolated and base-fixed buildings are investigated. The results show that the Abrahamson-Silva -Kamai model achieves the best fitting results with the lowest computational errors. Isolation technology can improve seismic performance for ancient timber buildings with different ages. Isolation effectiveness of the base-isolated models decreases with increasing building ages in different fault parameters. The isolation effectiveness remains unchanged with different fault dip angles in footwall earthquakes, whereas it decreases with the increase of fault dip angles in hanging-wall earthquakes at the same site distance. The structural isolation effectiveness in hanging-wall earthquakes is better than that in footwall earthquakes. 1. Introduction including good earthquake resistance due to the excel- lent strength-to-density ratio and the ductility of joints Dynamic responses of near-fault ground motions have with metal fasteners, providing limited inertia forces received much attention in recent years due to the and good energy dissipation, respectively (Oudjene obvious impulsive effects on structures (Sun et al. and Khelifa 2009). But, as time goes by, it is inevitable 2020; Bilgin and Hysenlliu 2020; Güllü and that the ancient timber structure will be damaged to Karabekmez 2017; Todorov and Muntasir 2021). The a certain extent under baptism of time and various significant hanging-wall/footwall effect may aggravate natural and man-made disasters. As a result, the mate- the damage of structures (Sapkota et al. 2013). The rial and structural properties will deteriorate and the hanging-wall ground motion has large acceleration risk of damage under the earthquake will increase. For peaks and high input energy, which amplifies the example, the Yunyan Temple with a timber structure is ground motion during propagation (Abrahamson damaged with roof failure and overhanging wooden 1996). Many studies can be found focusing on the beams broken in Wenchuan earthquake (Jia, Liu, and effects of near-fault ground motions on civil structures, Ye 2014), and the timber Changu Temple is collapsed such as buildings, tunnels and bridges (Aghamolaei in Yushu earthquake (Huang 2017). et al. 2021; Xie and Sun 2021; Abd-Elhamed and Obviously, although existing studies highlight the Mahmoud 2019; Faherty et al. 2022; Bedon, Rinaldin, importance of near-fault ground motion effects on the and Frgiacomo 2015; Bedon et al. 2019; Shehata, above-mentioned structural responses, investigations Mohamed, and Tarek 2014; Hadianfard and Sedaghat of the hanging-wall/ footwall effect on ancient timber 2013). In ancient China, most architectures are timber structures are very limited, especially for those base- buildings of towers, temples, palaces and other forms, isolated ancient timbers. Many works should be done accounting for more than 50% of the total ancient to enrich the research results of this field so as to architectures (Hu, Han, and Yu 2011a). Timber, as provide effective control strategies for the safety of a construction material, is worth studying for its ancient wooden buildings under earthquakes. mechanical properties in earthquakes (Humbert et al. Therefore, it is meaningful to explore the specific seis- 2014). Timber structures present many qualities, mic responses and control effectiveness of ancient CONTACT Dayang Wang firstname.lastname@example.org School of Civil Engineering, , Guangzhou University, GuangDong, GuangZhou, 510006, P.R. China © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of the Architectural Institute of Japan, Architectural Institute of Korea and Architectural Society of China. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 T. OU AND D. WANG timbers with and without base-isolated technology in integral stiffness and mass of the foundation base are hanging-wall/footwall earthquakes. An optimal model far higher than those of the upper tower body and the of generating hanging-wall/footwall earthquake waves roof, which therefore can be ignored in the computa- is provided based on fitting analysis results of 622 tional model. recorded ground motions. The main aim of this study Commercial analysis software SAP2000 (version 16) is to explore whether base-isolated technology can (SAP2000 Version 16, 2013) is used to establish the improve structural seismic performance in near fault finite element model of the tower body and the roof. earthquakes and to clear the corresponding parameter The wooden beam and column are modeled by frame influence laws. Based on the research results, better beam elements. Mortise-tenon joints are adopted to seismic methods and isolation measures can be sug- connect structural members of beams, columns and gested to protect ancient timber buildings in future trusses, which are actually a kind of semi-rigid and unpredictable hanging-wall/footwall earthquakes. semi-articulated joint. The simulation of semi-rigid node in SAP2000 can be realized by end release of line element. The end release includes 3 translational 2. Finite element model and verification degrees of freedom (axial load, principal axis shear and sub-axis shear) and 3 rotational degrees of freedom 2.1. Numerical modeling (torque, principal axis bending moment and sub-axis Xi’an Bell Tower, a representative ancient timber build- bending moment). When the end part is released, the ing, is adopted as an object of investigation of this spring stiffness values of the starting point and the end study. This two-storey tower of the Bell tower is built point are defined to partially constrain the node, so as in 1384 and has a total height of 36 m and an area of to achieve the effect of simulating semi-rigid node 1377.4 m , as shown in Figure 1(a). The tower has (Yokoyama et al. 2009). Material elastic modulus and a square plane with the dimension of 35.5 m. The the connection stiffness of mortise-tenon joints tower is considered as the largest and most complete between the beam and the column can be calculated ancient timber structure in China (Wang and Meng based on the literature (Wang and Meng 2017), as 2017). Three main components compose the Bell shown in Table 2. Therefore, the three-dimensional tower, namely, the foundation base, the tower body finite element model of the Bell tower can be estab- and the roof, in which the tower body is the wood lished, as shown in Figure 1(c), in which the column frame structural system. Specific parameters of the bottom of the wooden frame is fixedly connected. cross-sections of the beams and columns are shown Besides, it is worth mentioning that the density of in Table 1. The corresponding section numbers of the wood material, 410 kg/m3, is assumed to be constant beams and columns are shown in Figure 1(b). The for all the investigated models since the wood density tower body and the roof are primary concerns of this is found to be increased by only 2.05% for 600 years study, as the foundation base is a huge masonry struc- (Jia, Liu, and Ye 2014). The wall and roof loads are tural platform with passageways through it, on which modeled as masses and uniformly loaded on the the tower body and the roof are supported. Obviously, beam-column joints. The total mass of one beam- L-3 L-3 L-2 L-3 L-3 L-1 L-1 Z-2 Z-1 Z-1 Z-2 L-2 L-1 L-1 Z-1 Z-2 Z-2 Z-1 4320 7940 4320 (a) Xi’an Bell Tower (b) Structurl geometry (b) Three-dimensional model Figure 1. Xi’an Bell Tower and the corresponding numerical model. (a) Xi’an Bell Tower, (b) structural geometry and (b) three- dimensional model Table 1. Member cross-section of the ancient timber building. Type L-1 (mm) L-2 (mm) L-3 (mm) Z-1 (mm) Z-2 (mm) Shape Rectangle Rectangle Rectangle Circle Circle Dimension 300 × 700 300 × 800 200 × 300 500 (diameter) 700 (dDiameter) 8500 6300 2200 1976 18976 JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 3 Table 2. Spring stiffness of mortise-tenon joint and wooden material properties. Parameters Symbol M640 M500 M300 M100 Adjustment coefficients – 68% 75% 85% 95% 7 7 7 7 Spring stiffness K (N/m) 1.55 × 10 1.71 × 10 1.94 × 10 2.17 × 10 8 8 8 8 of mortise-tenon joint K (N/m) 1.88 × 10 2.08 × 10 2.36 × 10 2.63 × 10 7 7 7 7 K (N/m) 1.55 × 10 1.71 × 10 1.94 × 10 2.17 × 10 8 8 8 8 K (N·m/rad) 5.66 × 10 6.24 × 10 7.08 × 10 7.91 × 10 9 9 10 10 Elastic modulus E (Pa) 7.51 × 10 8.30 × 10 9.41 × 10 1.05 × 10 9 10 8 9 of wood material E (Pa) 7.51 × 10 8.30 × 10 9.41 × 10 1.05 × 10 8 8 8 9 E (Pa) 3.76 × 10 4.15 × 10 4.70 × 10 5.26 × 10 Note: M640, M500, M300 and M100 represent models with ages of 640, 500, 300 and 100 years. column joint is 6850 kg, which is the same as the ancient timber buildings with different construction reference (Meng 2009). More details of introducing times and the connection stiffness of mortise-tenon the establishment of the finite element model, such joints between beam and column are calculated, as as element selection, constitutive model and para- also shown in Table 2, in which the spring stiffness of meter design, can be found in previous research stu- the mortise-tenon joints can be calculated based the dies of the author’s team (Huang 2017). equations of Hu, Han, and Yu (2011b). It is known that there are many ancient timber buildings in China and also around the world. 2.2. Model verification A common knowledge on ancient timber buildings is that their mechanical properties are affected by time, The dynamic characteristics of the Bell tower are com- indicating that considering the influence of aging on pared with the results of existing literature mechanical properties is necessary. To investigate the studies (Meng 2009; Han 2011; Wen 2015) of the Bell influence of construction time on structural responses tower. The comparison results are shown in Table 3. of ancient timber buildings in near-fault ground Figure 2 shows the first three mode shapes. It can be motions, four computational models that are 100, seen that the first-order and second-order frequencies 300, 500 and 640 years old, respectively, are consid- of the Bell tower are around 0.95 Hz, and the third- ered, in which the age of 640 years represents the real order frequencies are between 1.0 Hz and 1.2 Hz. The building time of the Bell tower. The timber perfor- maximum error in comparison to the three literature mance adjustment factor provided by Technical code studies is 2.16% for the first-order, 1.90% for for maintenance and strengthening of ancient timber the second-order and 15.56% for the third-order. buildings (GB/50165-1993) is used to consider the However, the first two models are the main control aging influence, namely, the adjustment factors of models with great modal participation coefficients, 95%, 85%, 75% and 68% for the corresponding ages namely, 86% for the first modal with X-direction trans- of 100, 300, 500 and 640 years. According to the position and 99% for the second modal with adjustment factors, material elastic modulus of the Y-direction transposition as shown in Table 3. It can Table 3. Verification the model of Bell Tower computer results (Unit: Hz). Literature (Meng 2009) Literature (GB/50165-1993) Literature (Wen 2015) This study Modal Frequency Error Frequency Error Frequency Error Frequency UX UY First-order 0.9628 2.16% 0.9604 1.91% 0.9501 0.82% 0.9424 0.86 0.00 Second-order 0.9628 0.54% 0.9864 1.90% 0.9781 1.04% 0.9680 0.00 0.99 Third-order 1.2251 15.56% 1.0008 5.59% 1.2000 13.20% 1.0601 0.14 0.00 Note: Error = (This study – Literature)/This study × 100%. UX/UY are modal participation coefficients. st nd rd Figure 2. The first three mode shapes. (a) 1 mode (X-Translation), (b) 2 mode (Y-Translation) and (b) 3 mode (Torsion) 4 T. OU AND D. WANG then be found that the finite element model of the Bell proposed with a magnitude range of [3.0, 8.5] and tower established in this study is reasonable and can a fault distance of [0, 300 km] and expressed as be used for the following discussion. ln PGAðY< pga; t< 0:25Þ ln Y ¼ f þ f þ f þ f þ f þ f þ f (2) mag dis fit hng site sed hyp þf þ f ðotherwiseÞ dip atn 3. Fitting of hanging-wall/footwall ground where Y is the acceleration peak or acceleration motion response spectrum value, f is the magnitude term, mag 3.1. Optimization of fitting models f is the distance term, f is the style of the faulting dis fit term, f is the hanging wall term, f is the shallow hng site The NGA (Next-Generation Attenuation) program, site response term, f is the vasin response term, f sed hyp published by the Pacific Earthquake Engineering is the hypocentral depth term, f is the fault dip term dip Research Center (PEER) in conjunction with the U.S. and f is the anelastic attenuation term. atn Geological Survey (USGS) and the Southern California Considering the same synthesized influence with Earthquake Center (SECE), represents the frontier the CB model, the CY model (Chiou et al. 2010) is research on the ground motion attenuation relation- proposed with a magnitude range of [3.0, 8.5] and ship. Based on the NGA program, three typical mod- a fault distance of [0, 300 km] and expressed as els of fitting hang-wall-footwall ground motions, Abrahamson-Silva-Kamai (ASK) model (Abrahamson S30j lnðy Þ ¼ lnðy Þþ F þϕ ðmin lnð Þ; 0Þ ij refij HW et al., 2014), Campbell-Bozorgnia (CB) model ϕ ðminðV ;1130Þ