This paper investigates the development, design and modeling of a human spine-inspired seismic lateral force resisting system. The overall goal is to create a design for a lateral force resisting system that reflects human spine behavior that is both practical and effective. The first phase of this project involved a literature review of the human spine and rocking structural systems. The goal of this phase was to identify concepts from the spine that could be transferred to a lateral force resisting system. The second phase involved creating a 3-dimensional model of the lumbar region of the spine in SAP2000 and using it to examine concepts that could be transferred to a lateral force resisting system. The third phase consisted of creating possible system designs using concepts and principles identified through phases one and two and identifying a final system design. The last phase involved modeling the final lateral force resisting system design in SAP2000, validating the model and testing the design's effectiveness. This paper shows that this system is a viable option to prevent permanent structural damage in buildings during a seismic event. / Master of Science

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / Dual Lateral Force Resisting Systems are currently required by code to include a Moment Resisting Frame capable of resisting at least 25% of the lateral loads. This thesis evaluates the seismic performance of a specific type of dual system: a Special Moment Resisting Frame-Special Concentric Brace Frame System (SMRF-SCBF) under three different force distributions. The three distributions were 80% - 20%, 75% - 25%, and 70% - 30% with the lesser force being allotted to the Special Moment Resisting Frame (SMRF) portion of the system. In order to evaluate the system, a parametric study was performed. The parametric study consisted of three SMRF-SCBF systems designed with different seismic force distributions. The aim of this study was to determine accuracy of the three different seismic force distributions. The accuracy was measured by comparing individual system models’ data and combined system models’ data. The data used for comparison included joint deflections (both horizontal and vertical), induced moments at moment connections, brace axial loads, column shears, and column base reactions. Two-dimensional models using the structural software RISA 3D were used to assist in designing the independent Seismic Force Resisting Systems. The designs of the frames were not finely tuned (smallest member size for strength), but were designed for drift (horizontal deflection) requirements and constructability issues. Connection designs were outside the scope of the study, except for constructability considerations – the SMRF and the SCBF did not have a common column; the frames were a bay apart connected with a link beam. The results indicated that a seismic force distribution of 75% to the SCBF and 25% to the SMRF most accurately predicts that frame’s behavior. A force distribution of 80% to the SCBF and 20% to the SMRF resulted in moderately accurate results as well. A vast opportunity for further research into this area of study exists. Alterations to the design process, consideration of wind loads, or additional force distributions are all recommended changes for further research into this topic.

Master of Science / Department of Architectural Engineering / Kimberly Waggle Kramer / Braced frames are a common seismic lateral force resisting system used in steel structure. Eccentrically braced frames (EBFs) are a relatively new lateral force resisting system developed to resist seismic events in a predictable manner. Properly designed and detailed EBFs behave in a ductile manner through shear or flexural yielding of a link element. The link is created through brace eccentricity with either the column centerlines or the beam midpoint. The ductile yielding produces wide, balanced hysteresis loops, indicating excellent energy dissipation, which is required for high seismic events. This report explains the underlying research of the behavior of EBFs and details the seismic specification used in design. The design process of an EBF is described in detail with design calculations for a 2- and 5-story structure. The design process is from the AISC 341-10 Seismic Provisions for Structural Steel Buildings with the gravity and lateral loads calculated according to ASCE 7-10 Minimum Design Loads for Buildings and Other Structures. Seismic loads are calculated using the Equivalent Lateral Force Procedure. The final member sizes of the 2-story EBF are compared to the results of a study by Eric Grusenmeyer (2012). The results of the parametric study are discussed in detail.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / Of seismic steel lateral force resisting systems in practice today, the Moment Frame has most diverse connection types. Special Moment frames resist lateral loads through energy dissipation of the inelastic deformation of the beam members. The 1994 Northridge earthquake proved that the standard for welded beam-column connections were not sufficient to prevent damage to the connection or failure of the connection. Through numerous studies, new methods and standards for Special Moment Frame connections are presented in the Seismic Design Manual 2nd Edition to promote energy dissipation away from the beam-column connection. A common type of SMF is the Reduce Beams Section (RBS). To encourage inelastic deformation away from the beam-column connection, the beam flange’s dimensions are reduced a distance away from the beam-column connection; making the member “weaker” at that specific location dictating where the plastic hinging will occur during a seismic event. The reduction is usually taken in a semi-circular pattern. Another type of SMF connection is the Kaiser Bolted Bracket® (KBB) which consists of brackets that stiffen the beam-column connection. KBB connections are similar to RBS connections as the stiffness is higher near the connection and lower away from the connection. Instead of reducing the beam’s sectional properties, KBB uses a bracket to stiffen the connection. The building used in this parametric study is a 4-story office building. This thesis reports the results of the parametric study by comparing two SMF connections: Reduced Beam Section and Kaiser Bolted Brackets. This parametric study includes results from three Seismic Design Categories; B, C, and D, and the use of two different foundation connections; fixed and pinned. The purpose of this parametric study is to compare member sizes, member forces, and story drift. The results of Seismic Design Category D are discussed in depth in this thesis, while the results of Seismic Design Category B and C are provided in the Appendices.

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Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / The hazards of seismic activity on building structures require that engineers continually look for new and better methods of resisting seismic forces. Buckling restrained braced frames (BRBF) are a relatively new lateral force resisting system developed to resist highly unpredictable seismic forces in a very predictable way. Generally, structures with a more ductile lateral force resisting system perform better in resisting high seismic forces than systems with more rigid, brittle elements. The BRBF is a more ductile frame choice than special concentrically braced frames (SCBF). The ductility is gained through brace yielding in both compression and tension. The balanced hysteretic curve this produces provides consistent brace behavior under extreme seismic loads. However regular use of the BRB is largely limited to Japan where the brace type was first designed. The wide acceptance of buckling restrained braced frames requires the system to become easily designable, perform predictably, and common to engineers. This report explains the design process to help increase knowledge of the design and background. This report also details a comparison of a BRBF to a SCBF to give familiarity and promote confidence in the system. The design process of the BRBF is described in detail with design calculations of an example frame. The design process is from the AISC Seismic Provisions with the seismic loads calculated according to ASCE 7 equivalent lateral force procedure. The final members sizes of the BRBF and SCBF are compared based on forces and members selected. The results of the parametric study are discussed in detail.

<p> A moment resisting frame is one of the most commonly used lateral load resisting system in modem structures because it is suitable for low and medium rise buildings and industrial structures. It can be designed to behave in a ductile manner under seismic loads. </p> <p> Masonry infills have traditionally been used in buildings as partitions and for architectural or aesthetic reasons. They are normally considered as non-structural elements, and their effect on the structural system has been ignored in the design. However, even though they are considered non-structural elements, there is mounting evidence that they interact with the frame when the structures are subjected to lateral loads Infill walls have been identified as a contributing factor to catastrophic structural failures during earthquakes. Frame-infill interaction can induce brittle shear failures of reinforced concrete columns by creating a short column. Furthermore, infills can over-strengthen the upper stories of a structure and when they fail a soft first storey is created, which is highly undesirable from the earthquake resistance standpoint. </p> <p> There is a need for an efficient and accurate computational model to simulate the nonlinear hysteretic force-deformation behaviour of masonry infills, which is also suitable for implementation in time-history analysis of large structures. The aim is to develop a simplified advanced and cost-effective model for nonlinear time history analysis and seismic design of masonry infill frame structures. </p> <p> The objective of this research was to develop a practical and economical technique applicable for global analysis of general three-dimensional reinforced concrete infilled frames under lateral loads. Novel finite element model for the infill and the surrounding frame was developed using a special finite element configuration to represent the masonry panel. Some prescribed failure planes in different directions were defined depending on the common failure mode of masonry panels. Moreover, some of contact elements were used on the failure planes to connect among the panel elements, and between the panel elements and the boundary reinforced concrete frame. Different material models were used to represent the behaviour of concrete, reinforcing steel, mortar joints and inclined saw-tooth cracks in the infill panel. Different material models were used to describe the behaviour through and perpendicular to the prescribed failure planes. The proposed model and the used material models were described in details in the first part of this research. </p> <p> The proposed finite element model was verified against experimental and analytical results previously published by others. Different frames configurations, reinforcing details, boundary conditions and material properties were consider in that section to verify the capability of the proposed model to simulate the behaviour of different frames. The overall behaviour "Load-deflection relationship", failure point and failure mode were compared with the experimental and analytical results. Satisfactory agreement with the previously published results was obtained. </p> <p> The study investigates the capability of the proposed model to simulate the behaviour of infilled frames subjected to cyclic loads. Hysteretic loops obtained by using the new model were verified against experimental and analytical results and good correlation were obtained. The failure modes and crack patterns were compared with the experimental results and good agreements were obtained. The proposed model failed to capture some shear cracks in the RC frames as per the experimental results. </p> / Thesis / Doctor of Philosophy (PhD)

Résumé : Ce projet de maîtrise s’intéresse au comportement ultime d’une structure en acier, contrôlée sismiquement par des amortisseurs élastomères et des contreventements en chevron. Les séismes peuvent causer des dommages considérables quand les infrastructures et les bâtiments ne sont pas construits selon les normes et les techniques appropriées. Par conséquent, réduire l’impact des séismes revient particulièrement à construire des ouvrages sécuritaires en tenant compte bien entendu du paramètre économique. Ainsi Gauron, Girard, Paultre et Proulx ont étudié en 2009, un système de reprise de forces latérales, constitué uniquement de treventements en chevron montés en série avec des amortisseurs en caoutchouc naturel fibré ayant de nombreux avantages. Premièrement, le système reste élastique sous le séisme de design en réduisant les efforts sismiques linéaires par un facteur supérieur à R[indice inférieur d] = 3 par rapport à un cadre conventionnel. Deuxièmement, il est capable de contrôler les déplacements sous la limite du CNBC 2010 (Code National du Bâtiment du Canada 2010), et même de réduire ces derniers dans certains cas. Par conséquent, il permet de réduire les sections des poutres et des poteaux des cadres par rapport à une structure conventionnelle ainsi que les coûts de réparation après un séisme. Toutefois, le comportement à l’état limite ultime d’un tel système, ses limites et ses réserves de sécurité restaient à déterminer. Ainsi, l’objectif global de ce projet de recherche est de déterminer les différents mécanismes de ruine possibles de ce système, d’établir des limites et réserves de sécurité, et de préciser, après avoir formulé certaines recommandations, à quelles conditions il peut être utilisé dans le dimensionnement de nouvelles structures. Pour atteindre les objectifs fixés, deux essais quasi statiques ont été réalisés sur deux cadres en acier dimensionnés avec le système. Des essais dynamiques ont aussi été réalisés afin d’avoir les propriétés viscoélastiques des amortisseurs. Le premier essai a mis en évidence un mécanisme de ruine inattendu et prématuré qui a souligné un défaut majeur dans les connexions des diagonales avec l’amortisseur. Le second essai a révélé un des mécanismes de ruine envisagés initialement où le caoutchouc se déchire après l’initiation du flambement dans la diagonale comprimée. Les résultats expérimentaux ont montré que l’amortisseur constitue le maillon faible du système, et que des efforts parasites peuvent réduire significativement la capacité portante des structures dimensionnées avec un tel système. Dans les deux cas, les résultats ont montré que la méthode de dimensionnement du système tel qu’elle est définie actuellement mérite d’être améliorée. En ce sens, des recommandations relatives au dimensionnement des différents éléments des structures dimensionnées avec le système ont été élaborées, particulièrement en ce qui concerne le caoutchouc et les connexions. // Abstract : This thesis focuses on the ultimate behavior of steel structures, controlled seismically by elastomeric dampers and chevron bracings. Earthquakes can cause considerable damages when infrastructures and buildings are not built considering appropriate standards and technics. Therefore, mitigating the impact of earthquakes means essentially building safe structures by taking account of economic parameters too. Thus Gauron, Girard, Paultre and Proulx studied in 2009 a seismic force resisting system consisting only of chevron braces connected in series with fiber-reinforced natural rubber dampers that offers many benefits. First, the system remains elastic under the design earthquake by reducing linear seismic efforts by a factor of R[subscript d] = 3 compared to a conventional frame. Secondly, it allows to control the displacements under the limits of NBCC 2010 (National Building Code of Canada 2010), and even to reduce them in some cases. Therefore, it allows a reduction of sections of beams and columns of conventional frames and it prevents repairing costs of the structure after an earthquake. However, the ultimate limit state behavior of this system, its limitations and safety reserves have not been determined yet. Thus, the overall objective of this project is to determine the different possible failure mechanisms of the system, to set its limits and safety reserves, and to state after some recommendations, how it can be used in the design of new structures. To achieve these objectives, two quasi static tests were performed on two steel frames designed with the new system. Dynamic tests were also conducted to get the viscoelastic properties of the damping material. The first quasi static test revealed an unexpected and premature failure mechanism that pointed out a major flaw in the connections of the braces with the damper. The second test revealed one of the failure mechanisms originally expected where the rubber tears after buckling of the compression brace. The experimental results have shown that the damper is the weak element in the system, and that additional forces can significantly reduce the structural capacity of structures designed with the system. In both cases, the results have shown that the actual design method of the system should be improved. Thus, recommendations for the design of elements of structures designed with this system have been developed, particularly with regard to the rubber and brace connections.