Tsung-Yuan Yang

Professor

Relevant Thesis-Based Degree Programs

 
 

Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Three-dimensional vision-based structural damage detection and loss estimation – towards more rapid and comprehensive assessment (2023)

Civil engineering structures such as buildings and bridges inevitably experience damage due to aging effects and natural disasters such as earthquakes. Damage inspection of these structures is of vital importance to maintain their functionalities. Earlier damage identification before natural disasters can greatly alleviate or prevent catastrophic failure in the event of natural disasters. Traditional manual inspection is inefficient and highly reliant on the proper training and experience of inspectors, which may result in false conclusions and erroneous evaluation reports. In recent decades, structural health monitoring (SHM) methods such as vibration-based SHM and non-destructive testing and evaluation (NDTE) methods have been developed to automate the inspection process. These methods generally require relatively complicated and expensive instrumentation to evaluate the conditions of structures. More recently, computer vision-based (or vision-based) SHM has been established as a convenient, economical and efficient complementary approach to the other SHM methods for civil structures. In comparison to contact-type vibration sensors, vision-based methods use low-cost and non-contact sensors, and easy installation and operation. However, most existing vision-based SHM methods are built on 2D computer vision where the evaluation outcomes are sensitive to camera locations and poses. Besides, these 2D vision methods are limited to the evaluation of in-plane damages, while not directly capable of quantifying damages in 3D space. In short, existing 2D vision methods may not provide a reliable and comprehensive damage evaluation outcome. To address these limitations, this dissertation proposes a 3D vision-based SHM and loss estimation framework, which aims to provide a more rapid and comprehensive damage evaluation and loss assessment of civil structures. Within the framework, the dissertation is strongly focused on the development and application of advanced 2D and 3D vision-based SHM methods for civil structures. Experiments of the vision algorithms developed have been conducted on three prevalent structural types including reinforced concrete structures, steel structures and structural bolted components. Results show that the proposed 3D vision-based damage evaluation and loss quantification framework can achieve high accuracy and low cost in damage recognition, localization and quantification, and provide more comprehensive assessment results which can be more easily conveyed to owners and decision-makers.

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Seismic performance evaluation of steel building systems in Canada (2022)

Steel building systems (SBS) are vastly used in North America for low-rise non-residential construction. SBS have many advantages, such as low cost, fast construction, and customizability. The structural components are optimized with usage of tapered steel plates. Despite its popularity, only a few studies have focused on SBS seismic response. In Canada, the seismic design of SBS often adopts equivalent static force procedure with force reduction factors (FRF) which are not developed for SBS. This practice may lead to unexpected seismic performance. In this research, the seismic performance of typical Canadian SBS is investigated through a series of numerical analyses. The complex cyclic behavior of SBS elements is evaluated with a detailed micro model developed in Abaqus and verified with available experimental results. Macro models are then developed with OpenSees to efficiently perform extensive system-level nonlinear time history analyses. A comprehensive seismic performance assessment procedure specially developed for Canadian SBS is proposed. The method accounts for SBS failure mechanisms and for exposure to multiple sources of seismic hazard in Canada. A set of 176 SBS designed with different geometries, types of cladding, force reduction factors (FRF), and locations are assessed with eigen, pushover, and incremental dynamic analyses (IDA). A ? factor is proposed to evaluate the seismic response, where ? is used to estimate the median collapse intensity of a SBS with a given base shear capacity. The variations in ? factor are presented for different geometric configurations. Furthermore, the adjusted collapse margin ratio (ACMR) is compared with acceptance thresholds presented in FEMA P695 document. The present study suggests that FRF = 1.3 can be adopted for designing typical SBS in Canada. The findings herein reduce the gap of knowledge on the seismic performance of SBS while providing crucial data for the development of seismic design guidelines in Canada.

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Development of an innovative earthquake-resilient reinforced concrete core wall system (2021)

This thesis introduces an earthquake-resilient reinforced concrete core wall system, named the controlled rocking outrigger core wall (CROCW). In the CROCW system, along one principal axis is a controlled outriggered rocking wall (CORW), where an outrigger is situated at the roof and the base is designed to rock. Dampers are incorporated within the outrigger and the rocking base to give CORW added energy dissipation. Along the other principal axis is the self-centering coupled wall (SCCW). In the SCCW system, self-centering friction dampers are incorporated within the coupling beams to dissipate the earthquake energy and ensure the wall will self center. In addition, the base is design to rock, to ensure a low damage response. The CROCW, CORW and SCCW were designed using the novel equivalent energy design procedure (EEDP). New factors were developed to modify the original EEDP to account for the dynamic responses and the different hysteretic shapes for the new systems. Using the newly developed design procedure, four prototype buildings (two different building heights and two different building sites) were designed. The uniform hazard spectra at three hazard levels were developed using probabilistic seismic hazard analysis. Detailed nonlinear models were developed and validated using available experimental data. Nonlinear time history analysis showed the CROCW, CORW, and SCCW can meet the design objectives, where the systems have limited damage after strong earthquake shaking. Additional studies were conducted to compare the performance of the newly proposed CROCW with conventional RC core wall system. The result shows that the CROCW has superior performance compare with conventional RC core walls. The newly developed CROCW system will be tested using a shake table to validate the behaviour. Shake table testing will take place at the multi-function shake table array facility in Shanghai China. Due to the COVID-19 pandemic, the experimental test has been temporarily delayed. This thesis presents the specimen design, construction, planned instrumentation, and the testing plan to be implemented at a later date.

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Experimental and numerical investigation of a novel sandwich panel under free air blast loads (2020)

For a long time, Humanity has been suffering from explosive attacks. These attacks mainly focused on essential infrastructure, which cost much money to rebuild. However, these structures can be effectively fortified using protective systems. Sandwich panels are commonly used as protective layers for underground structures. The front panel and interlayer are designed to mitigate the blast energy from reaching the back panel (the main structure). Traditionally, a sand layer has been used as a protective layer to absorb the blast energy. However, the sand layer has several shortcomings, including (1) rapid plastic compaction after a blast shot, (2) a heavyweight layer and, (3) difficult to control the density and water contents. In this research, a newly lightweight sandwich panel, named reinforced concrete (RC) panel - Helical springs- RC panel (RHR) sandwich panel, is proposed. RHR consists of RC panel attached to a number of helical springs and connected to RC panel (main structure). Numerical and experimental studies of the RHR under free air blast load are conducted. The performance of the RHR is compared to the Sand – RC panel (SR) and the RC panel – Sand – RC panel (RSR) protective systems against free air blast loads. SR consists of a sand layer on the top of the RC panel. The sand layer has the same depth as the front RC panel and helical springs interlayer of the RHR. Whereas, RSR uses the same configuration as RHR, except the helical springs are replaced with a sand layer. To effectively compare the performance of the three systems, an advanced Riedel-Hiermaier-Thoma (RHT) concrete model is calibrated to accurately simulate the post failure behavior of concrete panel under blast loads. The results show that the proposed RHT model can accurately model the damage level of the concrete panel under blast loads when compared with the experimental results. The result shows that RHR has superior performance in storing the applied energy elastically when compared with the other protective systems. Lastly, a parametric study is conducted to optimize the performance of RHR. The results emphasized that RHR is an effective and efficient protective system for the roof of shallow underground structures.

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Experimental and numerical investigations of ductile slender reinforced masonry shear walls subjected to in-plane seismic loads (2020)

Ductile slender reinforced masonry shear walls (DSRMSWs), defined here as ductile walls with height-to-thickness (hu/tw) ratios greater than 20 and height-to-length (hu/Lw) ratios greater than 1.5, that are designed and detailed with modern seismic design provisions are often used as the seismic-force-resisting system (SFRS) for contemporary buildings. The in-plane seismic performance of these walls is however relatively poorly understood compared to other types of SFRS shear walls, particularly with regards to their lateral stability during in-plane seismic loading. This is partially because the majority of recent experimental testing on reinforced masonry shear walls (RMSWs) has been conducted using wall specimens that are either non-slender, with design parameters that do not reflect walls typically used in current Canadian masonry construction practice, or that do not experience any form of lateral instability. Moreover, as the Canadian Standards Association standards transition to performance-based design provisions, there becomes a need for practical and reliable numerical models that have been developed and validated using experimental results, which are limited at this time. This dissertation presents experimental and analytical studies examining the in-plane performance of DSRMSWs undergoing simulated seismic effects. The experimental phase involved the testing of eight full-scale DSRMSWs (two of which were tested during the author’s M.A.Sc. thesis work) composed of fully-grouted concrete block masonry units with varying hu/Lw and hu/tw ratios, amount and distribution of reinforcement, cross-sectional shape, axial stress level, and type of cyclic loading protocol. The analytical phase first analyzed the results of the experimental phase to classify and improve the understanding of the failure modes affecting DSRMSWs, as well as to compare current design provisions of several international masonry design codes. The analytical phase also employed a nonlinear multiple-vertical-line-element (MVLE) model that was calibrated using the numerical results of the specimens tested in the experimental phase. It was demonstrated that the model was able to reproduce the observed in-plane lateral load-displacement responses of both the experimental phase specimens as well as those of another study by others, with reasonable accuracy. The proposed MVLE model may be used as a useful tool for practicing engineers following performance-based design provisions for DSRMSWs.

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Design and validation of innovative earthquake resilient fused structures (2017)

Recent earthquakes worldwide have shown that even countries with modern building codes suffer significant structural damages after a strong earthquake shaking. The issue lies in the design philosophy that earthquake energy is absorbed through inelastic deformation of structural components. This creates unrecoverable structural damages and prolonged recovery time. These deficiencies can be minimized using earthquake resilient structures where earthquake energy is dissipated by specially designed structural fuses. The structural fuses are decoupled from the gravity system, and hence, they can be replaced efficiently without affecting the functionality of a structure after an earthquake. This dissertation aims to provide a consistent approach for researchers to develop and validate earthquake resilient fused structures and for engineers to design and implement such structures. It encompasses two major constituents: alternative design approach and advanced experimental technique. An equivalent energy design procedure (EEDP) is developed for fused structures. EEDP allows designers to select different performance objectives at different levels of earthquake shaking intensities. EEDP also allows engineers to select structural members to achieve the desired structural period, strength, and deformation without iterations. In addition to the design procedure, this dissertation also develops an innovative hybrid simulation testing technique where a switch-based hybrid simulation (SHS) method is proposed to validate the seismic performance of fused structures. SHS combines analytical and experimental sub-assemblies to examine the dynamic responses of a fused structure during an earthquake shaking. SHS switches between the displacement-based and force-based algorithms to control hydraulic servo actuators in displacement or force. It improves experimental accuracy and safety to test structural fuses that undergo drastic changes in stiffness. An innovative fused seismic force resisting system named fused truss moment frame (FTMF) is presented in this dissertation. The FTMF is designed using EEDP and validated using SHS. The SHS result shows that the FTMF can be easily designed using EEDP to achieve various target performance objectives under different earthquake shaking intensities. This dissertation has demonstrated that EEDP and SHS are efficient and effective procedures to design and validate innovative earthquake resilient fused structures.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Development of a bond-based peridynamic model for masonry structures (2023)

Masonry is a popular construction material that has many desirable properties including ease of construction, durability, and fire resistance. However, numerical modeling of masonry prisms and structures with hollow masonry units, such as hollow concrete blocks, remains a challenge due to a discontinuous interface between masonry units and grout. This thesis proposed a new bond-based peridynamic (BPD) model to simulate the nonlinear response of masonry structures. The proposed BPD model was verified using an experimental study. The result demonstrated that the proposed BPD model can effectively simulate the behaviour of masonry prisms.The verified BPD model was implemented using a parallel version of an open-source finite element analysis platform, OpenSeesMP. A parametric study, including the prism height-to-thickness ratio, inclusion of grout, grout strength, and block configuration, was conducted to simulate the ultimate strength and failure mode of masonry prism under compression load. The result shows that the masonry compression strength increases with decreasing height-to-thickness ratio, inclusion of grout, higher grout strength, and block configuration without central web.

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In-plane shear capacity of 3-panel BEHLEN frameless wall system under axial compression load (2023)

BEHLEN frameless building is a novel structural system for low-rise, large-span building applications. The BEHLEN frameless building is made of specially corrugated cold-form steel wall, footing channels, boundary columns, ceiling plates, arched roof, and optional convex. The pre-manufactured steel components are then assembled using bolts on site. BFWS is the prime structural component to resist both vertical and lateral loads in the BEHLEN frameless building. To date, BFWS has been tested under axial compression, lateral shear, and out-of-plane bending moment. However, the capacity of BFWS subjected to combined compression and shear loads has not been examined. This thesis presents a study to evaluate the in-plane shear capacity of 3-panel BEHLEN frameless wall system (BFWS).Four full-scaled BFWS with different wall thicknesses were tested in the laboratory. Specimens were subjected to monotonic and cyclic shear displacement under constant compression loads. Damage patterns of the 3-panel BFWS were observed. The observed shear resistance – lateral displacement curves were recorded. The damage patterns were sudden interactive buckling, deformation of footing channels, and the slotting of bolt holes along panel seamlines.A detailed finite element model (FEM) was developed in Abaqus. The FEM was validated using the experimental results. The results show that the FEM was able to simulate the failure patterns and capacities of the 3-panel BFWS.Further parametric study including variation of wall thickness, wall height, and axial compression was investigated using the validated FEM. The maximum in-plane shear resistance Vₘ, and the damage patterns of the specimens were reported. The experimental and simulation results are used to estimate the maximum shear capacity of 3-panel BFWS under different levels of compression loads. The results can be used to optimize the design of the 3-panel BFWS under combined axial and shear loads.

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Development of a novel self-centering balloon-type CLT shear wall system for tall buildings (2022)

The use of mass timber structures has considerably grown in recent years. This has increased the demand for sustainable, resilient, and high-performance mass timber structural systems. In this thesis, a novel self-centering balloon-type cross-laminated timber (CLT) shear wall system named the dual-pinned self-centering coupled CLT shear wall (DSCW) is proposed for tall buildings. The DSCW consists of two sets of CLT panels that are pinned at their base and coupled to one another using self-centering friction dampers. Optional V-shaped truss assemblies can also be used at the base of the panels. This thesis also presents a procedure that can be used to design the DSCW. This procedure is a modified version of the equivalent energy design procedure (EEDP). It ensures that the DSCW meets different roof displacements targets and performance objectives at various shaking intensities. The procedure was used to design the DSCWs of a 12-story prototype building located in the high-seismicity region of Vancouver (Canada). The DSCWs of the prototype building were numerically modeled and subjected to nonlinear time history analyses as well as to an incremental dynamic analysis. The results of these various analyses demonstrate that the DSCWs of the prototype building achieve the target roof displacements and performance objectives. The results also show that the DSCWs meet the seismic performance requirements of FEMA P695.

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Earthquake and deterioration inclusive probabilistic life cycle assessment (EDP-LCA) framework for buildings (2022)

With increasing demand to reduce the carbon emission of buildings, it is crucial to quantify the life cycle environmental impact of new buildings, including the environmental impact due to natural hazards, such as earthquakes. In this thesis, a novel and comprehensive probabilistic framework has been developed to quantify the environmental impact of buildings, including uncertainties in the extraction and production, transportation, construction, seismic exposure and aging (including deterioration) and end-of-life stages. The developed framework is used to quantify the environmental impact of a 3-storey residential building located in Vancouver, Canada. The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment stages. If the prototype building is hit by the design level earthquake, it is expected that the median environmental impact for the prototype will be further increased by 43%. In addition, by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building, the earthquake related damage will result in an additional 5% of the initial carbon emission of the building. This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.

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Experimental and numerical investigations of Frameless cold form steel corrugated wall panels subjected to in-plane monotonic and cyclic loads (2022)

Cold-formed steel corrugated wall panels (CFSCWs) have recently gained traction as structural elements in buildings. A novel application of CFSCWs, named as Frameless system, has been developed by BEHLEN Industries LP. The Frameless systems have been used as load bearing elements. However, no investigation has been conducted to assess the seismic performance of Frameless panels under axial and shear loads. Within this context, a series of experimental and numerical studies are being conducted at the University of British Columbia to assess the seismic performance of Frameless panels. First, a robust experimental test setup is designed to simulate the effect of gravity and seismic loads on the Frameless panels simultaneously. A total of 10 specimens with different corrugation patterns and varying axial loads were tested. Subsequently, a finite element model is developed to simulate the monotonic behavior of the Frameless panels and is validated by the experiments. A comprehensive evaluation of the influence of different corrugations and axial loads on the initial stiffness, the buckling-failure mode, the peak force capacity, the post-buckling stiffness, and the residual force capacity are presented. The results of the experimental and numerical investigations show the lateral force-deformation response of Frameless panel is highly influenced by the corrugation patterns and the axial loads. A linearized backbone curve was proposed for the Frameless panels with axial loads as the design parameter. Key design parameters such as overstrength and ductility ratios of the Frameless panels have been identified. The findings from this research allow the users to design one-span Frameless panels as seismic force resisting system under different axial loads. This research is the first of a series of investigations performed to quantify the seismic safety of Frameless systems

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Mechanism and experimental validation of innovative self-centering conical friction damper (2020)

Past earthquakes have shown that traditional structural design relies on the component ductility to dissipate the earthquake energy. This has led to significant damage for the structure. Innovative energy dissipation devices have been developed in the past to dissipate the earthquake energy. However, the big disadvantage of energy dissipation devices is the lack of self-centering feature. Significant residual deformation can have effects on the building resilience. Failing to eliminate the residual deformation can lead to prolong downtime and significant financial losses. In this thesis, a novel damper named self-centering conical friction damper (SCFD) is proposed. SCFD utilizes conical, flat surfaces and post-tensioning tendons to resist the earthquake loads in all directions. The conical surfaces force the SCFD to self-center, making the SCFD highly desired for earthquake applications. In this thesis, detailed mechanical behavior for the SCFD was derived using theoretical equations in this thesis. The hysteresis behavior was verified through the experimental tests. The behavior observed from the test matches well with the theoretical solution Using the derived equations, detailed parameter study including the influences of pretension forces, effective stiffness of post tension tendons, slope angle and friction coefficients have been investigated. Results show the hysteresis behavior can be achieved using different combinations of the slope angle, PT tendons and friction coefficients. Overall, high slope and friction coefficients will lead to highly efficient SCFD with lower demands on the PT tendons. Detailed design approaches have been presented which allows the engineers to design SCDF for different applications. Overall, this thesis shows the SCFD can be used efficiently for application in earthquake engineering with stable energy dissipation and self-centering capabilities.

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Mechanism and experimental validation of self-centering nonlinear friction damper (2020)

Current earthquake design philosophy in North America focuses on providing minimum “life safety” requirement, where main structural components are designed to dissipate the earthquake energy through inelastic yielding during strong earthquake shaking. This could result in significant financial losses and downtime. The next-generation seismic design focuses on the use of energy dissipation devices which forces the earthquake energy dissipation in specially designed devices, while majority of the structures are capacity protected to be damage free. Hence, structure can be inspected or repaired efficiently after earthquake. To make the structure even more resilient, newer high-performance structures are designed to have low residual drift after the earthquake, hence the structures can be used shortly or immediately after strong earthquake. In this thesis, a novel self-centering energy dissipation device, named self-centering nonlinear friction damper (SCNFD), is proposed. SCNFD utilizes pivot hinge, specially designed grove plates and pre-compressed springs to create self-centering nonlinear elastic force-deformation response. In addition, friction pads are added to create the energy dissipation needed. Detailed theoretical equations were derived to describe the mechanical behavior of the SCNFD. The behavior of the SCNFD was validated using nine experimental tests. The results show the behavior of SCNFD can be well modeled using the theoretical equations presented in this thesis. Finally, a detailed parameter study on the stiffness of springs, pre-compressed force, friction and pivot plate ratio have been calculated to evaluate their effects on the hysteretic response of the SCNFD. Results demonstrate different flag-shaped hysteresis responses can be achieved using different SCNFD configurations, which make SCNFD a versatile, reliable and efficient damper for seismic applications.

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Quantification of energy demand for buckling-restrained braces (2020)

Buckling Restrained Brace (BRB) is a novel energy dissipation device that was developed in the 1980s. Past experimental investigations were performed by using deformation-related parameters such as drift and ductility-based loading history to evaluate the performance of the BRBs. The outcome of the performance evaluation of the BRBs was based on either the ability of the BRBs against the fracture or its ability to sustain axial deformation, as opposed to evaluating the energy demand of the BRBs during earthquake excitation. A novel approach was proposed to explicitly quantify the energy demand of the BRBs during earthquakes. First, an equation was proposed to determine energy demand from the site-specific design spectrum. After that, floor-wise energy distribution was proposed based on empirical equations. Finally, equations to obtain rise time for the energy demand for the BRB were proposed. Engineers can use the equations to quantify the energy demand for BRBs at different floors at different site locations. The empirical equations were obtained by studying a range of single-degree-of-freedom systems and a series of prototype buildings with 3, 6 and 8 storeys. The proposed equations were used to quantify the seismic demand of the BRBs in a 5-storey configuration. The results show that the energy demand obtained by applying the proposed method is similar to the median demand obtained from the time history analysis. The results show that the proposed procedure is effective and efficient for quantifying the energy demand for buildings with BRBs.

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Seismic design and performance evaluation of innovative controlled rocking dual-fused bridge system (2020)

It is crucial for highway bridges to remain operational after strong earthquakes as they are critical infrastructures to transport resources. In this study, an innovative seismic-resilient bridge structural system, named controlled rocking dual fused bridge (CRDFB) system is proposed. The CRDFB system is designed to improve the seismic performance of bridges through the use of replaceable lead extrusion dampers at the base of the rocking piers. The CRDFB system is strategically designed to achieve three tiers of performance objectives at different shaking intensities. For this purpose, the state-of-the-art Equivalent Energy Design Procedure (EEDP) is adopted. The proposed step-by-step EEDP allows engineers to design the CRDFB system to achieve the desired performance objectives with simple hand calculations and without iterations. Examples of seismic design using the proposed EEDP are presented for one 2-span and one 3-span CRDFB prototypes located in Vancouver, Canada. To validate the performance of the proposed CRDFB system, advanced three-dimensional analytical models of designed prototypes are developed in finite element software OpenSees and subjected to a broad array of two-dimensional and three-dimensional nonlinear time history analyses. Simulation results show that CRDFB prototypes can successfully achieve the targeted performance, as specified by EEDP design, at different shaking intensities. Hence, the proposed CRDFB system can be designed efficiently using the EEDP design procedure outlined in this paper, and be used as an efficient, reliable, and resilient seismic force-resisting bridge system for high seismic zones.

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Seismic performance of controlled outrigger rocking wall system with different types of energy dissipation devices (2020)

Controlled Outrigger Rocking Wall (CORW) system is a novel earthquake resilient system which combines reinforced concrete wall with controlled rocking base hinge and outrigger system. At the end of the rocking base and the outrigger, different dampers are used to provide the supplemental energy dissipation needed, to control seismic response, and to reduce damage on structural walls. In this study, a 100-meter-tall prototype CORW building was designed using Equivalent Energy Design Procedure (EEDP). EEDP allows designers to design the CORW system to achieve different performance objectives under different levels of earthquake hazard. Based on the prototype design, five types of alternative dampers were selected to meet the design requirements. The seismic performance of the prototype CORW system with different dampers was systematically compared. First, hysteretic behaviors of the dampers were obtained from experimental tests. Second, constitutive models of the dampers were calibrated, and detailed finite element models of the CORW were developed. Third, nonlinear time history analyses were done for 25 combinations of dampers, with 39 input ground motions records under three hazard levels. To further validate the analyses, hybrid simulation was conducted, where two dampers were experimentally tested in laboratory, and the remainder of CORW system was simulated in a finite element program. The result shows that EEDP is efficient in designing CORW system with different types of dampers, and the performance of the CORW system is not significantly affected by different types of dampers. Hence, CORW can be used as an efficient alternative seismic force resisting system for high-rise buildings in high seismic zones.

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Experimental testing and numerical modelling of honeycomb structural fuse (2019)

This thesis presents a novel metallic damper, called Honeycomb Structural Fuse (HSF), for seismic applications. HSF utilizes commonly available welded wide flange sections with honeycomb-shape perforations on web. It is designed to dissipate earthquake energy through plastic deformation of the web in shear, while the flanges remain elastic. The HSF can be fabricated into different shapes to fit different structural demands. To investigate the seismic behavior of the HSF, a total of 12 specimens with different honeycomb cell wall aspect ratios (wall thickness to central length) and honeycomb cell combinations (rows and columns) were manufactured and tested under displacement-based static cyclic loads. The influence of the different geometry parameters on the initial stiffness, yield force, yield drift, force-drift relationship, buckling, and failure modes are summarized in this thesis. Finally, a robust finite element model was built to simulate the hysteretic behavior of the HSF. The effectiveness of the proposed model was validated using experimental results. The study shows that the newly proposed HSF has stable energy dissipation, which can be used as an efficient metallic damper for seismic applications.

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Development of an innovative modular steel truss system (2018)

This thesis proposes an innovative and economical modular steel truss system (MSTS), using modular steel floor system (MSFS) and modular buckling restrained braced truss moment frame (MBRBTMF). The proposed MSTS can be fabricated offsite and then shipped and assembled on site, saving construction time and fabrication expense. This specially designed floor system, MSFS, consists of space trusses and precast concrete slab toppings, and to fully utilize the spaces within the floors, the mechanical, electrical and plumbing (MEP) systems are pre-installed within. The proposed floor system was optimized for both gravity and lateral loads, using a robust structural optimization method conducted in conjunction with the Matlab and OpenSees. Space trusses are utilized to provide sufficient stiffness to support gravity, eliminate vertical deflection and transfer lateral force without significantly increasing floor depth. The buckling restrained braces (BRBs) in MBRBTMF are employed as energy dissipation components, allowing the structures to be repaired efficiently after earthquakes. The seismic performances of a MSTS structure and conventional structures with MSFS were systematically analyzed with OpenSees. The nonlinear dynamic responses of these structures show that the proposed modular system is highly efficient in resisting gravity and lateral loads, and can be used efficiently for modular constructions worldwide.

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Experimental and numerical studies on the nonlinear responses of welded wide flange fuses (2018)

Metallic yielding damper is an example of commonly used as a sacrificial structural element to dissipate earthquake energy. In this thesis, a novel structural fuse, called Welded Wide Flange Fuse (WWFF), which utilizes commonly available welded wide flange sections to dissipate earthquake energy is proposed. WWFF is versatile, economic, and easy to fabricate. To dissipate earthquake energy, the WWFF is subjected to shear load in the longitudinal direction of the web. The inelastic behavior of the WWFF is expected to be concentrated in the web part of WWFF, where the earthquake energy is dissipated, while the flanges remain elastic. Experiment was conducted to study different parameters such as aspect ratios, slenderness ratios, and size ratios. These parametric studies provide detailed understanding in predicting the important engineering characteristics, such as yielding force, elastic stiffness, energy absorption, over-strength factor, and ductility of the WWFF. Nineteen specimens were tested under two type of loading protocols. Two analytical equations were derived to predict the yielding force and stiffness of the WWFF with different geometry parameters. Finite element models were developed using finite element software ABAQUS/CAE. The developed numerical models were verified using the experimental data. The verified numerical models were used to conduct detailed parametric studies on the WWFF with large array of aspect ratios and slenderness ratios. Beside the FE modelling approach, parametric studies on aspect ratio, slenderness ratio, and size ratio are conducted. Using this model, the effect of these parameters on key engineering characteristics is studied.

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Seismic design and performance evaluation of dual-fused h-frame system (2018)

A Dual-Fused H-Frame (DFHF) is an efficient structural system that combines Damped H-Frame (DHF) modules with Welded Wide Flange Fuses (WWFFs) to create a structural solution which is efficient in construction and more seismic resilient. Each DHF module consists of two columns pin connected to a beam with two buckling restrained knee braces (BRKBs). Each DHF module can be prefabricated in the factory, shipped to the site and connected vertically using simple bolt connections. The connections between the DHF modules have relatively small moment demand which makes the design, fabrication and construction of the DHF modules very efficient. Once the DHF modules have been assembled vertically, the bays of the DHF can be connected using WWFFs. WWFFs are simple shear connectors which can dissipate stable earthquake energy. In this paper, two prototype DFHF buildings of varying heights (3- and 9- story) are designed using the Equivalent Energy Design Procedure (EEDP). EEDP is a novel design method which is developed to design innovative systems, where the structural system can achieve different performance objectives under different earthquake shaking intensities. To verify the performance of the DFHF, advanced finite element models are developed using OpenSees and subjected to an extensive array of time history analyses. The results show that the proposed EEDP designed DFHF can achieve the targeted performance objectives under different seismic shaking intensities. In addition, DFHF has sufficient margin of safety against collapse. Hence the proposed DFHF can be used as an efficient structural system in high seismic zone.

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Seismic safety assessment of base isolated buildings using lead-rubber bearings (2018)

Base isolation using lead-rubber bearing (LRB) has been well-developed and widely-implemented in high seismic zones worldwide. During strong earthquake shaking, LRB is designed to move horizontally and meanwhile carry large axial load. One of the main design challenges is to prevent the LRB from buckling. Although detailed component behavior of LRB under combined axial and shear loads has been well investigated, the seismic performance of base isolated building with LRB has not been systematically examined. In this study, the seismic performances of two prototype buildings, each with different LRB geometric properties, structural periods, and axial loads, were systematically examined. To properly account for the buckling response of the LRB under combined axial and shear loads, robust finite element models of the prototype buildings were developed using the state-of-the-art LRB buckling model implemented in OpenSees. Nonlinear time history analyses were conducted using ground motions selected and scaled based on the 2015 National Building Code of Canada. As shown by the result, when the LRB is designed without accounting the axial and shear interaction, this leads to high probability of failure of the LRB, which can be difficult and expansive to fix. In some situations, this might lead to the collapse of the base isolated building. To mitigate the failed probability of the LRB during strong earthquake shaking, a simple amplification factor of 2.5 is proposed to amplify the design axial load calculated from the combined gravity and earthquake loads when the coupled axial and shear interaction of LRB is not explicitly modeled.

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Development of advanced control strategies for high performance shake table tests (2017)

Shake table test provides a feasible solution for evaluating structural performances in earthquake engineering. It can test structural system in real time. However, high fidelity shake table control remains a challenging issue due to several difficulties, such as hydraulic actuator nonlinearity and the control-structure interaction (CSI) effect. Conventional shake table control employs linear controllers such as proportional-integral-derivative (PID) or loop-shaping controller to regulate the actuator’s movement. However, it is difficult to tune a linear controller to accurately regulate the shake table when the payload and the hydraulic system are nonlinear. These challenges become more problematic when the payload mass is large relative to that of the table. Moreover, it is difficult to track a high frequency reference signal using a linear controller. The main objectives of this study are to illustrate the implementation of hierarchical control and to improve the performance and robustness of shake table test. This thesis consists of three parts. First, the system identification procedure was used to investigate the dynamic characteristics of a hydraulic shake table at the University of British Columbia. The results of the system identification were used to build a reliable simulation model of the hydraulic shake table system. Second, the developed system identification model was used to develop different low-level controllers to regulate the actuator’s movement. Third, advanced high-level control algorithms were implemented to increase tracking performance and control robustness. One nonlinear control algorithm named sliding mode control (SMC) and another optimal control algorithm named model predictive control (MPC) were presented in this thesis. The performance of the newly developed controllers was compared to that of the state-of-the-art linear controllers. The results show that the newly proposed hierarchical control architecture and the advanced high-level controller developed in this thesis can improve the tracking performance and robustness of shake table test.

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Development of dual replaceable link eccentrically braced frames using equivalent energy based design procedure (2017)

Conventional seismic force resisting systems (SFRSs) rely on the use of ductile design philosophy, where structural components are designed to undergo large inelastic deformations to dissipate the sudden surge of the earthquake energy. This design philosophy has shown to be very effective in preventing structural collapse. However, the extensive inelastic deformation usually leads to significant damage to the structural and non-structural components. Many earthquake reconnaissance reports show that this design philosophy typically leads to hefty financial losses. Eccentrically Braced Frames (EBFs) have been proven through testing and earthquakes to exhibit a high level of ductile behaviour. However, the damage of the link leads to hefty repair costs, which lead to the Replaceable-Link Eccentrically Braced Frame (REBF). A well-tuned link can control the response of the REBF, which provides the advantage for the REBF over an EBF. While the link is designed to yield, and deform, the rest of the REBF and gravity system are designed to remain elastic. This mechanism makes the link act as a fuse in the REBF system, which allows the structure to be more resilient towards earthquakes.In this study, a novel seismic design methodology named the Equivalent Energy-Based Design Procedure (EEDP) was implemented for the seismic design of two REBFs operating in parallel, which is referred to as the Dual REBF (DREBF) system. The conventional Equivalent Static Force Procedure (ESFP) was also used to achieve an alternate, comparative model. The designs and the design procedures themselves were compared to highlight potential benefits of designing from an energy based perspective. EEDP allows the designers to select different performance objectives at different shaking intensities, where the structure can be designed to achieve these objectives using simple hand calculations. More importantly, the design can be achieved without iteration. This study demonstrated that the design procedure of one simple prototype building utilizing both the ESFP and EEDP philosophies. Their seismic responses have been analyzed using detailed numerical models developed using OpenSees. The results of the nonlinear dynamic analysis showed that the EEDP designed DREBF can achieve the target performance defined by the designer at different shaking intensities.

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Seismic design of outrigger systems for tall buildings (2017)

Outrigger systems are an effective structural scheme that is commonly used in high-rise construction to increase stiffness and distribute the moment demand within the core to the exterior columns. Despite the on-going use of outrigger structural systems around the world, a formal seismic design procedure for outrigger system is missing. This thesis presents an equivalent energy-based design procedure (EEDP) to design outrigger systems for seismic applications. Using the concept of an energy balance, elastic single-degree of freedom systems are equated to equivalent nonlinear systems, and plastic mechanisms are used to derive design forces for the outrigger systems. EEDP allows engineers to design the outrigger-wall buildings to achieve different performance objectives at different seismic hazard levels, which is desirable for creating earthquake-resilient buildings. Three prototype outrigger-wall buildings of various heights were designed using the proposed procedure for a hypothetical site in Vancouver, Canada. Detailed finite element models were developed using OpenSees to assess the seismic performance of the prototype buildings. The results of the nonlinear time history analyses show that the prototypes can meet the performance objectives specified during the design procedure. Lastly, incremental dynamic analyses were conducted using the FEMA P695 methodology to quantify the seismic safety of outrigger systems designed using EEDP. The results show that the proposed EEDP is an effective method to design outrigger systems, where the structure can achieve sufficient margin of safety against collapse and satisfy multiple performance objectives at different hazard levels without iteration.

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The development of a detailed seismic performance assessment: a framework for China's HSR MSSS bridge system (2017)

The Multi Span Simply Supported (MSSS) bridge system is the most commonly used structural system for High Speed Railway (HSR) networks in China. With China Railway rapidly expanding to the southwestern region of China, an area of high seismic activity, significant concerns have been raised to confirm whether the conventional HSR MSSS bridge, designed for low seismic zones, can be used in areas of high earthquake shaking intensities. In this thesis, the performance-based earthquake engineering (PBEE) methodology, originally developed for the seismic performance assessment of buildings, has been modified and applied to quantify the direct seismic loss of the China’s HSR MSSS bridge system. This study is the first of its kind to systematically define and quantify the damage states, and associated repair actions, repair costs and travel delay losses for the China’s HSR MSSS bridge system. The developed loss assessment model can be employed to assess the seismic performance of the HSR MSSS bridge system in diverse regions of China. In this study, a detailed parameter study using a framework developed in this thesis was utilized to study the influence of the shear capacity of fixed bearings on the seismic performance of a typical four-span HSR MSSS bridge system located in the Sichuan-Yunnan region in China. The results reveal that the financial loss of the HSR MSSS bridge system is highly dependent on the shear strength of the fixed bearing. Overall, the travel delay costs outweigh those for structural repair, where most of the financial loss was attributed to loss of functionality and repairs of the track-slab system and the bearings of the HSR MSSS bridge system. In addition, the developed fragility data and PBEE framework were used to optimize the design of the HSR MSSS bridge system using friction pendulum devices. The results show that the most optimal seismic loss of the isolated HSR MSSS bridge system can be reduced by 90% when compared to the that in the absence of seismic isolation.

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Equivalent Energy Based Design Procedure for Controlled Rocking-Concentrically Braced Frames (2016)

Conventional seismic force resisting systems (SFRSs) such as moment frames, braced frames and shear wall systems rely on the use of ductile design philosophy, where structural components are designed to undergo large inelastic deformations to dissipate the sudden surge of the earthquake energy. This design philosophy has shown to be very effective in preventing structural collapse. However, the extensive inelastic deformation usually leads to significant damage to the structural and non-structural components. Many earthquake reconnaissance reports show that this design philosophy typically leads to residual deformations which result in hefty financial losses. In recent years, novel structural systems, which are targeted to achieve higher performance, have been developed. These structural systems are targeted to resist strong earthquake shaking with minimal structural/non-structural damages. This allows the structure to remain functional immediately after the earthquake. Controlled rocking-concentrically braced frame (CR-CBF) is one such novel system developed to achieve higher performance. CR-CBF relies on the use of post-tensioning (PT) tendons and supplemental damping devices (ED), to create a controlled-rocking mechanism at the base of the structure. Since gravity loads alone cannot eliminate the residual deformations, the PT are introduced in the system to allow self-centering. In addition, ED are installed in the system to dissipate the sudden surge of seismic energy and control the peak displacement response of the structure. Both the PT and ED components are designed to be easily replaceable without affecting the functionality of the structure after a strong earthquake shaking. A novel seismic design methodology named Equivalent-Energy Design Procedure (EEDP) is adopted in this study to design the CR-CBF. This design procedure allows the designers to select different performance objectives at different shaking intensities. Two prototype buildings with varying heights are designed using EEDP. Detailed numerical models of these prototypes are developed in OpenSees (2010) to evaluate the seismic performance of CR-CBF. Detailed performance assessment of the CR-CBFs, in terms of adjusted collapse margin ratio, are evaluated using the FEMA P695 (2009) methodology. The results presented in this thesis demonstrate that the proposed CR-CBFs have adequate earthquake safety and they can be designed efficiently using the proposed EEDP approach.

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Theory and Simulation of Electromagnetic Dampers for Earthquake Engineering Applications (2016)

The present study develops applications of electromagnetic devices in Civil Engineering. Three different types of electromagnetic system are investigated through mathematical and numerical models.Chapter 3 deals with Coil-Based Electromagnetic Damper (CBED). CBEDs can operate as passive, semi-active and active systems. They can also be considered as energy harvesting systems. However, results show that CBEDs cannot simultaneously perform as an energy harvesting and vibration control system. In order to assess the maximum capacity of CBEDs, an optimization is conducted. Results show that CBEDs can produce high damping density only when they are considered as a passive vibration control system. Chapter 4 deals with the development of a novel Eddy Current Damper (ECD). The eddy current damper uses permanent magnets arranged in a circular manner to create a strong magnetic field, where specially shaped conductive plates are placed between the permanent magnets to cut through the magnetic fields. Detailed analytical equations are derived and verified using the finite element analysis program Flux. The verified analytical models are used to optimize the damper design to reach the maximum damping capacity. The analytical simulation shows that the proposed eddy current damper can provide a high damping density up to 2,733 kN-s/m⁴.The Hybrid Electromagnetic Damper (HEMD) are developed and designed in Chapter 5. The idea is to couple the CBED and ECD with the aim of designing a semi-active, active and energy harvesting electromagnetic damper. The simulation results show that it is feasible to manufacture hybrid electromagnetic dampers for industrial applications.

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Seismic Behaviour and Nonlinear Modeling of Reinforced Concrete Flat Slab-Column Connections (2015)

The contemporary structural design practice of tall buildings typically incorporates a lateral force resisting system, along with a gravity system that often includes reinforced concrete flat slabs. A major challenge with the design of this system is ensuring adequate strength and deformation capacities of the flat slab-column connections, especially when the structure is prone to strong seismic excitations. When a flat slab-column connection is subjected to a combination of gravity and lateral loads, failure may occur in multiple modes. Comprehensive literature reviews of the experimental studies and the analytical models related to reinforced concrete flat slabs, and flat slab-column connections are presented in Chapters 2 and 3, respectively.The existing nonlinear models that are currently available in literature were developed as assessment tools for old flat-plate structures. Thus, they are not capable of capturing the hysteretic behaviour of ductile flat slab-column connections with shear reinforcement. In Chapter 4, a new nonlinear model for flat slab-column connections is proposed. Utilizing the proposed model allows detecting potential failures due to all the possible modes of failure. The model was verified and calibrated using data from actual experimental studies.Chapter 5 investigates the effects of flat slabs on the global seismic response of typical high-rise concrete shear wall buildings. Two analytical case studies were conducted using a prototype building designed in Vancouver, Canada. The results from nonlinear dynamic analyses confirmed that including flat slabs in the analysis models of tall buildings is important to obtain accurate estimates of the structural responses and seismic demands. A concise summary of the research outcomes is presented in Chapter 6.

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Performance-based design and evaluation of innovative steel knee braced truss moment frames (2014)

Steel truss girders are very economical and practical to span large distances, when used efficiently this can create large interior opening which cannot be economically accomplished by any other structural systems. However, due to lack of ductility in connections and poor element energy dissipation capacity, conventional steel trusses are not suitable for seismic applications. To retain the advantages of steel trusses, a novel and innovative steel structural system, named buckling restrained knee braced truss moment frame (BRKBTMF) system has been introduced and extensively studied in this thesis. The BRKBTMF system utilizes buckling restrained braces (BRBs) as the designated structural elements to dissipate earthquake energy. This allows BRKBTMF to span long distances, while having efficient and robust energy dissipation capacity to resist earthquake loads. More importantly, by using the BRBs as structural fuses, the structural damages can be controlled. This allows the structure to be repaired more efficiently and effectively after the earthquake, which reduces the repair time and repair costs, making the BRKBTMF more resilient towards future earthquakes. This thesis consisted of three parts. First, the performance-based plastic design procedure (PBPD) was applied to design a prototype office building located in Berkeley, California. Nonlinear dynamic analysis was conducted to examine the performance of the BRKBTMF under ranges of earthquakes. The result showed that the PBPD was a viable and efficient deign procedure for the BRKBTMF, where both the drift and strength limits were satisfied without design iterations. Second, new material model and element removal techniques were implemented to model the behavior of BRBs and BRKBTMF, where detailed failure modes could be explicitly modeled. Third, detailed parameter studies, including influence of the BRB hysteresis, BRB configuration, and truss span, were conducted. The parameter studies showed that these parameters can significantly affect the seismic structural performance of the BRKBTMF system.

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Numerical modeling for the seismic response of concrete tilt-up buildings (2013)

Concrete tilt-up building is a prevalent construction technique used for industrial andcommercial applications in North America. This construction technique offers manysignificant advantages over conventional cast-in-place construction. This includes thereduction in construction time and the amount of formworks. Despite the large array ofbuildings that has been constructed using such technique, the nonlinear behaviour of theconcrete tilt-up buildings is still not well understood.The nonlinear behaviour of the concrete tilt-up building has been studied in this thesis. Thenonlinear response of the concrete tilt-up building is largely affected by the nonlinearbehaviour of the connectors between the panels and the slab, and between the panels. Pastresearches have been conducted to experimentally examine the nonlinear behaviour ofthe tilt-up panel connectors. The experimental results were used in this thesis todevelop an empirical numerical model capable of reproducing the force-deformationresponse of the tilt-up connectors under combined axial and shear deformation. Thenumerical model takes the shear strength and stiffness degradation into account afteraxial cycles of inelastic deformation.A finite-element software was developed specifically to study the nonlinear static anddynamic behaviour of concrete tilt-up buildings. A typical tilt-up building designed in thestudy of Olund (2009) was modeled. Incremental dynamic analysis was performed usingthe developed finite element software to assess the seismic performance of the prototypetilt-up building. The results of the incremental dynamic analysis provided valuableinformation to understand the nonlinear behaviour of the concrete tilt-up buildings underseismic load. Detailed parametric studies were carried out to examine the nonlinearbehaviour of tilt-up buildings. Parameters such as connector configurations; variation ofthe roof stiffness and strength; and coefficient of friction between the panels and slab werestudied.

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