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Seismic Fragility Assessment of a SCED Brace System Through Hybrid Simulation
Seismic fragility assessment requires a large number of data points and reliable numerical models which can predict the responses of structures under a wide range of excitation intensities. Nonlinear time history analysis methods have been traditionally used to develop seismic fragility curves in which the reliability of the fragility curves largely depends on the accuracy of the numerical models. In this project, the seismic fragility of Self-Centering Energy Dissipative (SCED) Bracing Systems is assessed through hybrid simulations using UI-SimCor. The SCED Bracing System which has been actively developed by Prof. Christopoulos' group can sustain large inter-story drifts, has the ability to dissipate energy, and does not develop any permanent deformations or damage under multiple seismic excitations. Since numerical models have inherent limitations due to simplification of complicated force-deformation relationships, over thirty hybrid simulations of a six-storey steel structure were carried out to experimentally derive seismic fragility curves. The SCED Brace in the first floor of the structure was experimentally tested in full scale while the rest of the building was numerically represented. The simulation results showed that the SCED Brace system could resist MCE level ground motions without developing noticeable damage while meeting drift requirements. The experiments also demonstrated that the hybrid simulation is a reliable experimental method for seismic fragility assessment of structures.
Reference: Kammula et al. (2014)
Reference: Kammula et al. (2014)
Hybrid Simulation of a Five-Story BRBF
Two hybrid simulation were conducted on a 5-story steel frames equipped with buckling-restrained braced frames (BRBs) using UT10 Hybrid Simulator. In the first simulation, a single physical specimen was used to represent the first floor BRB and in the second simulation, three independent physical specimens were used to represent the BRBs in floors 1 to 3. The rest of the frames were numerically modelled with OpenSees. The main purpose of these simulations verified the performance of the UT10 Hybrid Simulator under an actual ground motion and also when testing multiple specimens. In addition, the simulation results can also be used to identify the accuracy improvements in the response predictions when more BRB elements are physically tested.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: OpenSees
- Substructure Module: UT10 simulation platform @ UofT
- Contributors: Dr. Saeid Mojiri, University of Toronto; Pedram Mortazavi, University of Toronto; Prof. Oh-Sung Kwon, University of Toronto; Prof. Constantin Christopoulos, University of Toronto
- Reference: Mojiri et al. (2019)
Four-Element Hybrid Simulation of a Five-Story SCBF
A hybrid simulation were performed on a five-story special concentrically braced frame (SCBF) with four physical specimens representing the buckling braces in the first two floors. In an SCBF, the seismic energy is mainly dissipated through yielding of the braces in tension and nonlinear buckling of the braces in compression. Therefore, the hysteretic response of the braces in an SCBF not only involves isotropic and kinematic hardening but also it involves a sharp drop of compressive force and negative stiffness during and after buckling of the braces. The complex hysteretic response of the conventional braces in an SCBF makes this system an interesting choice for hybrid simulations and performance verification of the UT10.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: OpenSees
- Substructure Module: UT10 simulation platform @ UofT
- Contributors: Dr. Saeid Mojiri, University of Toronto; Pedram Mortazavi, University of Toronto; Prof. Oh-Sung Kwon, University of Toronto; Prof. Constantin Christopoulos, University of Toronto
- Reference: Mojiri et al. (2019)
Hybrid Fire Simulation of a Steel Frame
A hybrid fire simulation was performed on a steel frame structure in which a critical element (i.e. column) was experimentally tested in the furnace and heated with the ISO834 fire curve up to 740°C while the remaining structural system was numerically modelled in ABAQUS. The proposed method is different from previous approaches in that it is fully validated with full-scale specimen subjected to high temperature and that it is an automated displacement controlled test with deformation error compensation. The proposed hybrid simulation method can be applied to more challenging structural systems such as the structural behavior under fire load, which is computationally difficult using numerical models. The method was recently improved with a continuous real-time algorithm with error compensation to compensate the deformation of the loading frame during large-scale tests.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: ABAQUS
- Substructure Module: Fire testing facility at Korea Institute of Civil Engineering and Building Technology
- Contributors: Xuguang Wang, University of Toronto; Prof. Oh-Sung Kwon, University of Toronto; Dr. Robin E. Kim, Korea Institute of Civil Engineering and Building Technology; Dr. Inhwan Yeo, Korea Institute of Civil Engineering and Building Technology.
- Reference: Wang et al. (2018)
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Small-Scale Multi-Axial Hybrid Simulation of a Shear-Critical RC Frame
The integration module Cyrus, which was developed for VecTor programs specialized in analyzing reinforced concrete structures based on the Modified Compression Field Theory (MCFT), has been further extended to combine numerical models with experimental components to accommodate hybrid testing. A small-scale shear-critical reinforced concrete frame was tested using a multi-axial hydraulic testing equipment under a reversed cyclic loading condition to verify the proposed hybrid simulation method. The physical model was a 1/3.23-scale representation of the shear-critical beam in the first story. The reminder of the frame was analyzed by integrating two programs: VecTor5 (columns) and VecTor2 (the shear-critical beam in the second story). The hybrid test results demonstrated that, if precautions are taken in preparing the model materials and constructing the scale specimen, small-scale hybrid simulation can represent the behaviour of the prototype reinforced concrete structure reasonably well.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: Cyrus
- Substructure Module: 6-DOF testing machine @ UofT
- Contributors: Prof. Vahid Sadeghian, Carleton University; Prof. Oh-Sung Kwon, University of Toronto; Prof. Frank Vecchio, University of Toronto.
- Reference: Sadeghian et al. (2017)
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Seismic Performance Assessment of a Three-Story RC Structure
To numerically evaluate the seismic performance of a RC structure significant efforts are required to capture the nonlinear response of the critical elements. A hybrid simulation framework has been developed to test RC columns as part of a three storey RC frame structure. To implement hybrid simulations in a testing facility, it is necessary to properly control the boundary conditions of physically tested specimens. This requirement poses a important limitation to the facilities that are capable to perform hybrid simulations as a significant number of actuators is required. In this framework a methodology is developed to perform hybrid simulations when a limited number of actuators are available and the full control of the boundary conditions is not possible. As part of this framework, the seismic assessment is performed for the cases of an intact, repaired and retrofitted structure, where externally applied Carbon Fiber Reinforced Polymer (CFRP) fabric is used for repairing and retrofitting.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: OpenSees
- Substructure Module: Column Testing Frame @ UofT
- Contributors: Georgios Giotis, Arup; Prof. Oh-Sung Kwon, University of Toronto; Prof. Shamim Sheikh, University of Toronto.
- Reference: Giotis et al. (2017)
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Prototype Demo-Scale Equipment in Support of Distributed Hybrid Simulation
Within the framework of the EXCHANGE-RISK project (Experimental & Computational Hybrid Assessment of Natural Gas pipelines Exposed to Seismic Risk), it is envisaged to implement the combined experimental-analytical method of distributed hybrid simulation for the identification of the principal failure modes of soil-pipeline systems. Given that the objective was to involve several of the partner academic institutions in the hybrid simulation endeavor, it was deemed useful to develop a demonstration size low-power actuator.
The concept was that of a relatively simple and low-cost device that could be easily replicated at the labs of each project partner, able to interface with the UT-SIM hybrid simulation platform developed at the University of Toronto (UofT) and to perform small-scale experimentation on simplified physical specimens. The purpose of the device (Figure 1) is to provide a testbed for the software implementation of the simulation before moving into the lab and connecting the controllers to hydraulic actuators and, importantly, to facilitate coordinated development of the control and network communication code among the partner institutions. So far, incarnations of this demo-scale scale setup have been assembled at the UofT, the University of Naples Federico II and the University of Bristol.
Details:
The concept was that of a relatively simple and low-cost device that could be easily replicated at the labs of each project partner, able to interface with the UT-SIM hybrid simulation platform developed at the University of Toronto (UofT) and to perform small-scale experimentation on simplified physical specimens. The purpose of the device (Figure 1) is to provide a testbed for the software implementation of the simulation before moving into the lab and connecting the controllers to hydraulic actuators and, importantly, to facilitate coordinated development of the control and network communication code among the partner institutions. So far, incarnations of this demo-scale scale setup have been assembled at the UofT, the University of Naples Federico II and the University of Bristol.
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: Any Integration Module in UT-SIM
- Substructure Module: Demo-Scale Equipment
- Contributors: George Baltzopoulos, University of Naples Federico II; Prof. Oh-Sung Kwon, University of Toronto; Ziliang Zhang, University of Bristol; Prof. Anastasios Sextos, University of Bristol.
- Reference: Baltzopoulos et al. (2019)
Soil-Structure Interaction Analysis of Daikai Subway Tunnel
The multi-platform simulation of the well-known Daikai Station tunnel was carried out to replicate the collapse mechanism and failure of the center column of the tunnel during the 1995 Kobe earthquake. The actual tunnel collapsed due to the high lateral forces during the ground shaking, and due to the insufficient shear reinforcement and ductility of the center column. The UT-SIM framework is considered for the multi-platform simulation by dividing the complex soil-tunnel model into two modules namely, the integration module (soil model), and the substructure module (tunnel lining model). The open-source finite element analysis program, OpenSees, is used to model the soil domain subjected to the ground motion excitation, while the state-of-the-art reinforced concrete analysis software package, VecTor2, is used to model the nonlinear behavior of the tunnel. The multi-platform simulation through UT-SIM framework allowed us to adequately capture the unique shear failure mechanism observed in the Daikai tunnel, and hence replicate the collapse of the tunnel, as the center column started to develop wide diagonal shear cracks that indicated the insufficient shear reinforcement of the center column.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: OpenSees
- Substructure Module: VecTor2
- Contributors: Mohamed Sayed, University of Toronto; Prof. Oh-Sung Kwon, University of Toronto; Prof. Duhee Park, Hanyang University; Dr. Quang V. Nguyen, Hanyang University.
- Reference: Sayed et al. (2019)
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Performance Assessment of a High-Rise RC Building
In the current engineering practice, the performance assessment of structures is carried out through a two-stage process. First, a system-level analysis is performed mostly based on equivalent linear elements. Then, the critical components identified from the system-level assessment are examined in more detail using either sophisticated nonlinear analysis tools or laboratory testing. Such two-stage process does not accurately capture the interaction of the critical elements with the rest of the structural system, particularly in highly nonlinear stages of structural response. In this paper, the application of the proposed method is illustrated through an integration of a commercial structural analysis and design software, S-FRAME, with a state-of-the-art analysis tool, VecTor2, for the performance assessment of a reinforced concrete high-rise building. Based on the analysis results, the procedure is found to provide a more realistic behaviour of the critical elements and also considered the influence of the force redistribution due to the failure of critical elements on the performance of the structural system.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: S-Frame
- Substructure Module: VecTor2
- Contributors: Dr. Xu Huang, University of Toronto; Prof. Vahid Sadeghian, Carleton University; Prof. Oh-Sung Kwon, University of Toronto; Prof. Frank Vecchio, University of Toronto
- Reference: Huang et al. (2017)
Integrated Simulation of a Reinforced Concrete Frame with Shear-Critical Elements
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The substructuring concept has been used in different forms such as in hybrid simulation and parallel computing methods, all contributing significantly to experimental testing and numerical analysis research programs. In this study, unlike previous studies, the main goal is to use the substructuring technique to develop a framework which expands the capabilities of current nonlinear programs, enabling detailed analysis of mixed-type reinforced concrete (RC) systems in an integrated fashion, to a degree of accuracy unattained before. To achieve this goal, the primary objective of the proposed framework is to combine different VecTor programs which are among the most advanced nonlinear analysis tools for RC structures, while fully considering the interaction between substructures. This can greatly extend the application of conventional standalone nonlinear analysis. For instance, integrating VecTor2 (membrane software) and VecTor5 (frame software) provides a unique and effective solution technique for detailed analysis of disturbed regions in RC frames which is not available in any other stand-alone frame type analysis program. The flexible and object-oriented architecture of the framework facilitates inclusion of new analysis software.
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Details:
- Decomposition Method: Component-level decomposition
- Integration Module: Cyrus
- Substructure Module: VecTor2 and VecTor5
- Contributors: Prof. Vahid Sadeghian, Carleton University; Prof. Oh-Sung Kwon, University of Toronto; Prof. Frank Vecchio, University of Toronto.
- Reference: Sadeghian et al. (2015)
Response of a Structure Subjected to Fire Following an Earthquake Event
In this study, the fire performance of a steel structure with different level of residual deformation from an earthquake event was investigated. Abaqus numerical models are used to determine the residual deformations on a column on the first floor. To realistically simulate the structural behavior subjected to the elevated temperatures, the ramp-hold fire simulation method is adopted where a column is modeled physically with temperature and mechanical loads while the rest of the system is modeled numerically. The residual deformation from the numerical earthquake analysis in the horizontal direction was applied when setting up the physical specimen. Although the test was done with a small scale structure, it provides valuable information for assessing the potential effects of the earthquake to fire performance.
Details:
Details:
- Decomposition Method: Component-level decomposition
- Integration Module: Abaqus
- Substructure Module: Radiative Thermal Heaters @ Colorado State University
- Contributors: Dr. Mehrdad Memari, Colorado State University; Xuguang Wang, University of Toronto; Prof. Hussam Mohamoud, Colorado State University; Prof. Oh-Sung Kwon, University of Toronto
- Reference: Memari et al. (2019)
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