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Author: Amory Adrien Martin Publisher: ISBN: Category : Languages : en Pages :
Book Description
Rocking spine systems are innovative earthquake-resistant structural systems that dampen seismic shaking through uplift at the base and confine damage to energy-dissipating fuses, thereby significantly reducing the potential of building downtime. Currently, United States building codes and standards provide very limited design guidelines for such systems. This thesis focuses on developing procedures and algorithms for design and optimization of rocking spine systems under nonlinear earthquake response. A new capacity design procedure, the modified modal superposition (MMS) method, is developed for the seismic design of rocking spine systems. The methodology uses an efficient elastic response spectrum analysis to approximate the nonlinear earthquake response through (1) modified boundary conditions to simulate rocking at maximum considered earthquake (MCE) level and (2) a first mode inelastic reduction factor. The methodology is extended to coupled and stacked rocking braced frames, as well as strongback systems, with various hysteretic and viscous dampers. Using nonlinear dynamic analyses on a set of seven archetype frames ranging from 6 to 18 stories, the MMS procedure is shown to accurately capture higher modes effects and estimate axial brace and column forces. A reliability analysis conducted supports applying a load amplification factor of 1.3 for scaling the MMS seismic forces to design the steel braced frame as force-controlled components. A new dynamic topology optimization methodology, called the sum of modal compliances (SMC), is introduced for seismic loading. Recently developed dynamic topology optimization procedures for linear elastic response in the frequency domain are compared and contrasted. The novel procedure is applied to the design of lateral bracing system of high-rise buildings for various earthquake hazards and yields important considerations of the influence of higher modes on the overall dynamic response of the system. The efficiency of the SMC optimization algorithm is demonstrated on a 3D high-rise building with over one million degrees of freedom. Using the modified modal superposition as inspiration, the dynamic topology optimization procedure is extended to design of the elastic spine in rocking braced frames for nonlinear earthquake response. The extruded optimized bracing pattern is compared to a conventional X-bracing system using nonlinear dynamic analyses. An optimization framework is proposed for selecting the number, location and properties of nonlinear dampers in stacked rocking systems, where the total overturning moment in the spine is minimized, subjected to interstory drift and hinge rotation constraints. A ground motion selection routine is developed to facilitate the optimization by estimating the median dynamic response under earthquakes. Algorithmic procedures are developed to solve the structural optimization problem using both modified sequential linear programming (SLP) method and particle swarm optimization (PSO). On a 20-story dual rocking hinge case study, the SLP algorithm is shown to converge to the optimum with less than 40 nonlinear dynamic analyses compared to over 4,000 for an exhaustive search. For a 20-story stacked rocking system with N arbitrary hinges, the SLP optimization yields three rocking joints, whereby the total overturning moment in the spine is reduced by half compared to the initial design, while maintaining drift limits below 2.5% at MCE level. Overall, this thesis introduces design and optimization procedures for both the rocking spine and nonlinear articulated hinges. This research project demonstrates the advantages of rocking spine systems for improved seismic performance and introduces novel optimization algorithms for structural design under earthquake loading.
Author: Amory Adrien Martin Publisher: ISBN: Category : Languages : en Pages :
Book Description
Rocking spine systems are innovative earthquake-resistant structural systems that dampen seismic shaking through uplift at the base and confine damage to energy-dissipating fuses, thereby significantly reducing the potential of building downtime. Currently, United States building codes and standards provide very limited design guidelines for such systems. This thesis focuses on developing procedures and algorithms for design and optimization of rocking spine systems under nonlinear earthquake response. A new capacity design procedure, the modified modal superposition (MMS) method, is developed for the seismic design of rocking spine systems. The methodology uses an efficient elastic response spectrum analysis to approximate the nonlinear earthquake response through (1) modified boundary conditions to simulate rocking at maximum considered earthquake (MCE) level and (2) a first mode inelastic reduction factor. The methodology is extended to coupled and stacked rocking braced frames, as well as strongback systems, with various hysteretic and viscous dampers. Using nonlinear dynamic analyses on a set of seven archetype frames ranging from 6 to 18 stories, the MMS procedure is shown to accurately capture higher modes effects and estimate axial brace and column forces. A reliability analysis conducted supports applying a load amplification factor of 1.3 for scaling the MMS seismic forces to design the steel braced frame as force-controlled components. A new dynamic topology optimization methodology, called the sum of modal compliances (SMC), is introduced for seismic loading. Recently developed dynamic topology optimization procedures for linear elastic response in the frequency domain are compared and contrasted. The novel procedure is applied to the design of lateral bracing system of high-rise buildings for various earthquake hazards and yields important considerations of the influence of higher modes on the overall dynamic response of the system. The efficiency of the SMC optimization algorithm is demonstrated on a 3D high-rise building with over one million degrees of freedom. Using the modified modal superposition as inspiration, the dynamic topology optimization procedure is extended to design of the elastic spine in rocking braced frames for nonlinear earthquake response. The extruded optimized bracing pattern is compared to a conventional X-bracing system using nonlinear dynamic analyses. An optimization framework is proposed for selecting the number, location and properties of nonlinear dampers in stacked rocking systems, where the total overturning moment in the spine is minimized, subjected to interstory drift and hinge rotation constraints. A ground motion selection routine is developed to facilitate the optimization by estimating the median dynamic response under earthquakes. Algorithmic procedures are developed to solve the structural optimization problem using both modified sequential linear programming (SLP) method and particle swarm optimization (PSO). On a 20-story dual rocking hinge case study, the SLP algorithm is shown to converge to the optimum with less than 40 nonlinear dynamic analyses compared to over 4,000 for an exhaustive search. For a 20-story stacked rocking system with N arbitrary hinges, the SLP optimization yields three rocking joints, whereby the total overturning moment in the spine is reduced by half compared to the initial design, while maintaining drift limits below 2.5% at MCE level. Overall, this thesis introduces design and optimization procedures for both the rocking spine and nonlinear articulated hinges. This research project demonstrates the advantages of rocking spine systems for improved seismic performance and introduces novel optimization algorithms for structural design under earthquake loading.
Author: Cornelius T. Leondes Publisher: Elsevier ISBN: 9789056996567 Category : Computers Languages : en Pages : 262
Book Description
Conventional seismic design has been based on structural strength in the initial design of structures, resulting in lateral force resisting systems with sufficient strength to be able to absorb and dissipate the seismic. For important structures such as urban high speed road systems, high rise buildings, hospitals, airports and other essential structures which must be quite functional after an earthquake, modern seismic structural design techniques have been developed with a view toward eliminating or significantly reducing seismic damage to such structures. This volume is a comprehensive treatment of the issues involved in modern seismic design techniques for structure with a view to significantly enhancing their capability of surviving earthquakes to an adequate degree, i.e., enhancing the ability of structural systems to withstand high level earthquakes.
Author: Plevris, Vagelis Publisher: IGI Global ISBN: 1466616415 Category : Technology & Engineering Languages : en Pages : 456
Book Description
Throughout the past few years, there has been extensive research done on structural design in terms of optimization methods or problem formulation. But, much of this attention has been on the linear elastic structural behavior, under static loading condition. Such a focus has left researchers scratching their heads as it has led to vulnerable structural configurations. What researchers have left out of the equation is the element of seismic loading. It is essential for researchers to take this into account in order to develop earthquake resistant real-world structures. Structural Seismic Design Optimization and Earthquake Engineering: Formulations and Applications focuses on the research around earthquake engineering, in particular, the field of implementation of optimization algorithms in earthquake engineering problems. Topics discussed within this book include, but are not limited to, simulation issues for the accurate prediction of the seismic response of structures, design optimization procedures, soft computing applications, and other important advancements in seismic analysis and design where optimization algorithms can be implemented. Readers will discover that this book provides relevant theoretical frameworks in order to enhance their learning on earthquake engineering as it deals with the latest research findings and their practical implementations, as well as new formulations and solutions.
Author: Henry Verjil Burton Publisher: ISBN: Category : Languages : en Pages :
Book Description
Reinforced concrete frames with infill panels is a commonly used building system in many moderate and high seismic regions around the world, particularly in developing countries. In some cases, the frames are designed to resist earthquake loads but the infill panels are rarely ever incorporated in the structural design. Moreover, the layout of the infill can have severe negative effects on seismic performance, which is also seldom considered. This research utilizes state-of-the-art performance-based earthquake engineering and computational modeling methods to develop a novel technique envisioned as a cost-effective approach to improving the seismic collapse safety in infill frame buildings. The proposed technique uses strong, stiff structural spines that resist earthquake effects through rocking action. The rocking spine system is applicable to both retrofit and new design; however, this work is primarily focused on the latter. The primary sources of overturning resistance are the gravity loads acting directly on the spine and the restoring forces transferred to the spine through outrigger action of adjacent structural members. These include beams framing into the spine and the infill panels constructed in the adjacent bays parallel and orthogonal to the spine. The use of rocking as the primary yielding mechanism reduces the required level of detailing that would otherwise be required in ductile concrete frames, which make the spine infill frame more practical and economical to construct. Additional material and labor cost savings can be realized for taller buildings since deep foundations are not required for the spine system. The project is executed in three phases that focused on the component, building and community scales.
Author: Gary Satwika Djojo Publisher: ISBN: Category : Building, Iron and steel Languages : en Pages : 390
Book Description
Conventional ductile structures rely on system ductility involving inelastic action in selected components in their lateral load resisting systems to dissipate earthquake energy. When subjected to severe earthquakes, the lateral load resisting systems are expected to undergo large deformations without losing their strength and structural integrity. However, the extent of damage caused by these severe earthquakes can be considerable, requiring extensive structural repairs or demolitions and causing significant ongoing social and economic disruption. In order to minimise the disruption, a low damage design philosophy is adopted. Low damage structures are expected to withstand severe earthquakes without requiring extensive structural repairs, using either or both isolating systems or sacrificial systems which either do not need repair or are readily replaceable. In order to respond the performance targets for low damage design, an innovative Centralised Rocking Concentrically Braced Frame (CRCBF) system has been developed in this thesis. The CRCBF system utilises a free-base V-braced Concentrically Braced Frame and a centralised rocking system with Ringfeder® - Friction ring springs as its energy dissipation devices. The CRCBF system does not rock under gravity loading, Ultimate Limit State (ULS) wind loading, and Serviceability Limit State (SLS) earthquake loading, remains essentially elastic under ULS earthquake loading by undergoing controlled rocking, and dependably returns to its initial position following the ULS earthquake. As the CRCBF system rocks back-and-forth about the central base of the CRCBF, the ring springs are arranged to work as a double acting system to accommodate cyclic vertical movements of the CRCBF columns and to dissipate earthquake energy during rocking. Additionally, the ring springs are partially prestressed to provide a high initial stiffness for the CRCBF system in order to prevent rocking at the SLS earthquake level. Two designs of double acting ring springs systems have been developed for the CRCBF system. The first design (Type I) of the double acting ring springs system generates a parallelogram-shaped hysteresis response, whereas the second design (Type II) of the double acting ring springs system generates a flag-shaped hysteresis response. Upon the lock-up of the ring springs in the MCE event, structural fuses, such as machined-down threaded rods and - ii - column baseplates, are designed to yield. The yielding of the machined-down threaded rods and the column baseplates prevents yielding of the other CRCBF components, which have less dependable inelastic behaviour. Then, after the MCE event, the yielded machined-down threaded rods can be replaced and the deformed column baseplates are repaired if necessary, allowing a structure designed with the CRCBF system to be fully operational. To maintain the lateral stiffness of the CRCBF and to transfer internal forces between those components at all time, all joint connections for the CRCBF system are designed as rigid connections, especially for the beam-brace-column joint connections. Therefore, two advanced pass-through beam-brace-column connections are developed for the CRCBF system. A Square Hollow Section (SHS) column has been designed with pass-through beam and brace slots, allowing a collector beam and a brace to pass through the SHS column. The collector beam and the brace are then welded to the SHS column faces. Finally, the SHS column is filled with concrete. These joint connections are not only cost-effective, when compared to bolted connections, but also easy to fabricate with modern equipment. The behaviour of the CRCBFs has been validated by numerical analyses and a series of experimental tests. Two CRCBF models were developed with the Type II double acting ring springs system and two different types of pass-through beam-brace-column connections where each CRCBF model represented each type of pass-through beam-brace-column connections. The numerical analyses were conducted using SAP2000 and Abaqus/CAE. Linear static analysis, non-linear pushover analysis, and non-linear time history analyses were undertaken using SAP2000, while finite element analyses (FEA) for investigating the complex behaviour of the two pass-through beam-brace-columns were undertaken using Abaqus. Then, a series of experimental tests were undertaken, comprising component testing, energy dissipation device testing, and centralised rocking frame testing. Lastly, the test results were compared with the analysis results derived from SAP2000 and Abaqus. The numerical analyses and experimental testing of the CRCBF systems showed that the CRCBF systems exhibit stable and repeatable flag-shaped hysteresis responses. A good agreement in axial forces is achieved between the SAP2000 analysis results and the test results. Also, a good agreement in Von Mises stresses in the beam-brace-column panel zones is achieved between the Abaqus FEA results and the test results. Lastly, the Abaqus FEA results showed that column baseplates, which were optimised with mild steel square supports, - iii - perform well as structural fuses for the CRCBF systems. The column baseplates developed a yieldline when the CRCBF columns are in compression. The results derived from the experimental testing and the numerical analyses have determined the behaviour of the CRCBF systems and have shown that the CRCBF systems meet the performance criteria required for a low damage system.
Author: Ali H Al Ateah Publisher: ISBN: Category : Earthquake engineering Languages : en Pages : 0
Book Description
Buildings designed with conventional lateral force resisting systems aim to ensure the safety of their occupants during seismic activities (earthquakes). Earthquake-induced damages to buildings' structural members are anticipated and allowed (FEMA 450), but the building should not collapse. Examples of conventional lateral force resisting systems are steel moment resisting frame, steel concentrically braced frame and concrete shear wall. With conventional lateral force resisting system, designing a structure to withstand a design basis earthquake (DBE) without sustaining any structural damage is unpractical and economically unrealistic. These systems dissipate seismic energy through inelastic behavior of structural elements. Those anticipated structural damages are expected to be repairable, but that might not be feasible economically. In general, conventional seismic lateral force resisting systems are inherently inefficient in limiting structural damage or residual drifts. The need for designing a lateral resisting system with high drift capacity (e.g., roof, soft-story and residual drifts) while maintaining the advantages of conventional systems has led to the development of self-centering (SC) systems, such as the self-centering concentrically-braced frame (SC-CBF) developed by (Roke et al. 2010) and the self-centering rocking core with buckling restrained columns (SC-RC-BRC) developed by Blebo (2010). SC systems are designed with special connections that decompress at a particular level of earthquake lateral loading, which softens the lateral force-drift response and increases their lateral drifty capacity prior to causing structure damage to essential structural elements. Both systems use vertically-oriented post-tensioning (PT) bars that help to return the building to a plumb condition after an earthquake. Friction elements or replaceable yielding energy dissipation elements are also installed in the systems to dissipate seismic energy. The proposed design procedures for both the SC-CBF and SC-RC-BRC systems underestimate the force demand of the structural members, which might lead to unconservative member design and possible yielding or failure of these members during a seismic event. Moreover, these two systems were only tested on 4-story buildings.This dissertation describes the development of the SC-RC-BRC system for mid-rise structures. The concept of using multiple rocking sections in SC-RC-BRC system for mid-rise structures is examined and developed in this PhD dissertation, in addition to introducing a new design methodology to accurately estimate structural member force demands. This research established that the SC-RC-BRC-MR is as a viable seismic-resistant system for mid-rise structures.
Author: AmirHossein Gandomi Publisher: ISBN: Category : Earthquake engineering Languages : en Pages : 115
Book Description
One of the commonly used earthquake-resistant structural systems is the conventional concentrically braced frame (CBF) system, which is widely used in the US. However, CBFs have limited drift capacity prior to a brace buckling occurrence. Self-centering concentrically braced frame (SC-CBF) systems have been recently developed to increase drift capacity prior to initiation of damage and to minimize residual drift. SC-CBF systems have more complex behaviors than conventional CBFs: the seismic response of SC-CBF systems depends on many new parameters such as rocking behavior, post-tensioning bars, and energy dissipation elements. Additionally, uncertainty of earthquake properties affects the system response. An accurate prediction of roof drift is essential to the design of SC-CBF systems. In this study, a robust modeling tool, genetic programming, is used to predict the peak roof drift response under seismic loading. At first, the design and analysis procedure of the SC-CBF is automated in this study, as is not available in current design software. Three levels of complexity are considered for the numerical models: i.Linear materials and geometry ii.Nonlinear materials and linear geometry iii.Nonlinear materials and nonlinear geometry where nonlinear materials capture yielding of the structural members and nonlinear geometry is considered by modeling buckling in the braces. Using these three levels of nonlinearity, the effect of nonlinearity on SC-CBF response is also investigated in this study.Several SC-CBF systems are designed based on the design basis earthquake using a variety of mechanical and geometrical parameters. Then, the peak roof drift is predicted and formulated in two ways. First, the statistical parameters of peak roof drift (mean and standard deviation) are formulated based on the design variables (mechanical and geometrical parameters) in three different nonlinearity levels. Second, the peak roof drift response of each earthquake is formulated based on the design variables and selected ground motion intensity measures. To select the prediction parameters, particularly the ground motion intensity measures, evolutionary correlation coefficients are introduced in this study. There are many parameters involved in the formulation of the peak roof drift response of an individual earthquake. Therefore, a multi-objective strategy is also used in this study to maximize the accuracy and minimize the complexity of the model. The results of this study can then be used in future designs to implement more efficient SC-CBF systems with a more accurate roof drift prediction.
Author: Robert Park Publisher: John Wiley & Sons ISBN: 9780471659174 Category : Technology & Engineering Languages : en Pages : 794
Book Description
Sets out basic theory for the behavior of reinforced concrete structural elements and structures in considerable depth. Emphasizes behavior at the ultimate load, and, in particular, aspects of the seismic design of reinforced concrete structures. Based on American practice, but also examines European practice.
Author: Alphose Zingoni Publisher: CRC Press ISBN: 1315850788 Category : Science Languages : en Pages : 960
Book Description
Research and Applications in Structural Engineering, Mechanics and Computation contains the Proceedings of the Fifth International Conference on Structural Engineering, Mechanics and Computation (SEMC 2013, Cape Town, South Africa, 2-4 September 2013). Over 420 papers are featured. Many topics are covered, but the contributions may be seen to fall
Author: Amory Adrien Martin
Author: Amory Adrien Martin
Author: Cornelius T. Leondes
Author: Plevris, Vagelis
Author: Henry Verjil Burton
Author: Gary Satwika Djojo
Author: Ali H Al Ateah
Author: AmirHossein Gandomi
Author: Keith D. Hjelmstad
Author: Robert Park
Author: Alphose Zingoni