| PaperNO | Paper / Abstract |
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SE2-001
10:50
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11:10
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AXIAL COLLAPSE MODELS FOR RC STRUCTURAL WALLS AND WALL PIERS
A large number of reinforced concrete buildings constructed prior to the mid-1970s in earthquake prone regions rely on lightly reinforced or perforated, perimeter structural walls to resist earthquake-induced lateral forces. In general, these walls are susceptible to diagonal tension failures (or distress) when subjected to moderate-to-strong shaking. A significant number of walls with this type of damage were observed in the region affected by the 1999 Chi Chi Earthquake. Despite typically being classified as a brittle failure mode (e.g., by ASCE 41), local or global building collapse was generally not observed, either in the Chi-Chi Earthquake or in the Kocaeli Earthquake impacting Turkey in August 1999. Based on these observations and the lack of studies reported in the literature, research efforts were initiated to study mechanisms and propose models that could be used to predict under what conditions walls or wall piers might lose the ability to support tributary gravity loads. Initial work was conducted between 2005 and 2008 to extend models developed to predict axial failures in columns to walls. However, at the time, relatively little data existed to calibrate and validate the model, in part because most laboratory testing conducted prior to this time frame did not address this issue. However, over the last ten years, a large number of laboratory studies examining the behavior of RC structural walls have been reported in the literature. Based on this new information, a comprehensive wall database has been developed at University of California, Los Angeles (UCLA) that includes detailed information on more than 1000 tests reported in the literature. To study axial failure of RC structural walls, the database is filtered to identify and analyze datasets of 32 and 80 wall tests on shear- and flexure-controlled walls, respectively, where information on behavior following lateral strength loss was available. Based on the newly available data and the prior study, new relationships were derived to predict the lateral drift capacity at axial collapse and derive new modeling parameters for ASCE 41.
John Wallace, Saman Abdullah
ASCE 41, axial failure, database, deformation capacity, flexure critical, shear critical, structural wall
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SE2-021
11:10
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11:25
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Seismic Assessment Methodology for Corroded Reinforced Concrete Buildings
The durability of older reinforced concrete (RC) structures is significantly affected by corrosion of the reinforcement and is a critical issue for New Zealand RC buildings because of the close proximity of most urban centres to a marine environment. Currently, the seismic assessment of such buildings is a challenging task because there is limited and dispersed guidance for how to assess the residual seismic capacity of corroded RC members and determine the likely overall seismic behaviour of an RC building exhibiting corrosion. An assessment procedure was developed to account for the effect of corrosion on the residual strength and deformation capacity of corroded RC members. Analytical models to predict material and member properties were considered and modified to account for pitting corrosion. These predictions were verified against a large database of experimental results from the available literature. A case study of a severely corroded RC building in New Zealand constructed in the year 1928 was assessed using the proposed methodology to investigate the reduction in seismic capacity due to corrosion. While no change in failure mechanism was found, the overall displacement capacity of the building was reduced by 25% compared to the assessed uncorroded condition. Finally, to estimate the changes in capacity and failure mode with respect to exposure time in a corrosive environment, the long-term corrosion effect was studied for the case study building assuming no remediation of corroded reinforcement. As a result, the displacement capacity was significantly reduced forming storey collapse at less than 1% drift, if no remediation was made after 30 years of continued corrosion deterioration.
Sunil Nataraj, Allan Scott, Jason Ingham, Lucas Hogan
buildings, corrosion, reinforced concrete, residual capacity, seismic assessment
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SE2-022
11:25
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11:40
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SEISMIC EVALUATION AND FRAGILITY CURVES OF A TYPICAL SCHOOL BUILDING IN TAIWAN
At present, pushover analysis based on the capacity spectrum method is often used for the detailed seismic evaluation of existing typical school buildings in Taiwan. The performance-target ground acceleration is compared with the site’s peak ground acceleration (PGA) for a design earthquake with a 475-year return period in order to evaluate whether the seismic capacity is sufficient. However, as stated in FEMA 440, the results of the evaluation are too conservative for relatively short-period structures. In this paper, incremental dynamic analysis (IDA) of a typical school building is used to study its seismic capacity and how conservative is the capacity spectrum method. Additionally, from the results of IDA, a seismic fragility curve of a sample school building can be built in order to evaluate the probability of collapse of this building under an earthquake with the evaluated performance-target PGA. From the analysis results, under the performance-target earthquake for seismic evaluation, this structure has a 5.3% probability of collapse, which is acceptable, and the specified performance target is a reasonable and conservative choice.
Te-Kuang Chow, Yeong-Kae Yeh
capacity spectrum method, detailed seismic evaluation, incremental dynamic analysi, nonlinear pushover analysis
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SE2-026
11:40
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11:55
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Study on seismic retrofitting for existing buildings with exterior reinforced concrete frames
This research is for existing reinforced concrete structures and uses the external reinforced concrete frames method to retrofit. Study on traditional reinforced concrete retrofit methods (Column-Jacketing, shear walls and etc.). Those that traditional methods usually affect existing building. Take some cases for example-internal structures interior spaces are changed, people can’t stay in buildings, and existing walls, windows and doors may need to reinstalled. Those reasons mentioned above restrict promotion of retrofits on buildings.The research on RC existing structures with RC external retrofit frames is taken at NCREE. The research includes experiments and structural analysis. Three specimen are tested with reversed cyclic loading to compare the behaviors between an existing and and two retrofitted frames. The results show that external retrofit frames are effective to increase the lateral strength. Anchors of the interfaces between and there is no separation between existing and external frames. The method provided by this study is suitable to use in real buildings because it was proven to be effective in improving the seismic resistance. In addition, compared with other traditional methods, this retrofitting method can be applied in general buildings without affecting the space and usability of the building during the retrofitting work.
Fu-Pei Hsiao, Pu-Wen Weng, Yi-An Li, Wei-Li Yen, Yi-Ching Lin, KAWAMOTO Takanori, Chao-Hsun Huang
Cyclic Loading Tests, Existing Building, Retrofitted By External Frames, seismic retrofit
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SE2-014
11:55
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12:10
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Automatic Hinge Property Generation System for Nonlinear Analysis Considering P-M Interaction of Columns
Nonlinear Static Pushover Analysis (NSPA) has been widely used for seismic performance evaluation in Taiwan for years. The analysis requires prediction of nonlinear behavior of each structural element in the buildings. Modeling of the above-mentioned nonlinear behavior is often achieved by concentrated plastic hinges in commercial software for structural analysis and design. According to the relevant state-of-the-art and -practice in Taiwan, the hinge properties are different from the built-in default properties. In order to reduce the complexity of defining plenty of non-default hinges, an automatic user-defined hinge property generation system designed for structural analysis software, SAP2000, are presented in this paper. The nonlinear hinge properties of this system are based on Taiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA) with additional consideration of P-M interaction behavior. The system is composed of three modules: SecGen, FrameInfo, and HingeProp. These modules can generate section properties, extract frame information and compute hinge properties, respectively. By utilizing the system, engineers can perform nonlinear analysis with the most state-of-the-art P-M hinge properties in Taiwan with the least effort. The system has been used in case studies. The result shows that the P-M interaction behavior of vertical elements definitely impacts the seismic performance of buildings with large height to depth ratio.
Chi-Hang Li, Jian-Hwang Weng, Chien-Chun Liu, Guan-Hao Hung, Qiang Xue
hinge, nonlinear, P-M interaction, pushover, seismic assessment
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SE2-016
12:10
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12:25
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DATA SYSTEM AND DATA ANALYSIS OF SCHOOL BUILDING RETROFITTING IN TAIWAN
A series of projects has been carried out to organize and manage the procedures of safety evaluation, retrofitting design, and engineering of existing school house buildings in Taiwan since year 2008. More than twenty thousands of school house buildings were evaluated by professional licensed structural engineers, and thousands of them have either on the progress actively or have completed their retrofitting engineering, leveraging the overall seismic safety of possibly up to millions of students. The process of every school house building being evaluated or retrofitted involves many persons and rules, yielding to a complicated interactions and networking of documentation exchanges, organization, progress monitoring, and management. None of these achievements could be realized without a stable and well organized database system of the school house retrofitting. With thousands of user accounts, tens of thousands of records, possibly millions of files of documentations, tens of records of buildings being updated every day, the school house retrofitting database system has been providing many types of services, as well as being progressively modified, updated, and debugged continuously during it service. This paper introduces the basic framework and functionalities of this framework. In addition, some of the preliminary data analysis is also presented. The experiences of development of this database system aims to facilitate the construction of future projects of structural retrofitting or similar projects.
Yuan-Sen Yang, Jia-Xing Liao, Ting-Wei Chang, Lap-Loi Chung, Shyh-Jiann Hwang
database management system, School house building retrofitting, school house retrofitting data analysis
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