This thesis investigates the performance of concentrically braced zipper frames through complementary experimental and numerical simulation approaches and proposes a design methodology for an innovative bracing scheme labeled as the suspended zipper frame. The suspended zipper frame intends to ensure that the top-story hat truss remains elastic, resulting in very ductile behavior of the structure. In the first part of the work, a three-story prototype frame was designed based on a preliminary design method. Three tests were conducted on one-third scale models of this prototype to verify the design procedure and assess the system performance under very different load histories. Comparisons of the results between analyses and experiments validated the partial-height zipper mechanism envisioned, and led to refinements of the design procedure and establishment of appropriate design details for these frames. The design and performance of this structural system are illustrated with three-, nine-, and twenty-story buildings designed for the same masses as those used in the SAC studies for the Los Angeles area. The proposed design strategy results in suspended zipper frames having more ductile behavior and higher strength than typical zipper frames. In addition, the suspended zipper frames also appear to reduce the tendency of chevron-braced frames to form soft stories and to improve seismic performance without having to use overly stiff beams. Finally, an explanation of the design philosophy as well as code language format of the design procedure is given.

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.

Multidisciplinary design optimization (MDO) requires many designs to be evaluated while searching for an optimum. As a result, the calculations done to evaluate the designs must be quick and simple to have a reasonable turn-around time. This makes aerodynamic calculations in the transonic regime difficult. Running computational fluid dynamics (CFD) calculations within the MDO code would be too computationally expensive. Instead, CFD is used outside the MDO to find two-dimensional aerodynamic properties of a chosen airfoil shape, BACJ, at a number of points over a range of thickness-to-chord ratios, free-stream Mach numbers, and lift coefficients. These points are used to generate surrogate models which can be used for the two-dimensional aerodynamic calculations required by the MDO computational design environment. Strip theory is used to relate these two-dimensional results to the three-dimensional wing. Models are developed for the center of pressure location, the lift curve slope, the wave drag, and the maximum allowable lift coefficient before buffet. These models have good agreement with the original CFD results for the airfoil. The models are integrated into the aerodynamic and aeroelastic sections of the MDO code. / Master of Science

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / In 2006, a research project was being carried out by architects at architecture/engineering firm Cannon Design involving an optimum bay size for a hospital. RISA computer modeling was used to explore a set of lateral force resisting system (LFRS) options for a building based on this optimum bay size and importance category. The structural material was first narrowed down to steel, and then moment frames and braced frames are examined. The LFRS was narrowed down to braced frames, discarding moment frames due to their inordinate story drift. Of the different types of braced frames, the study further narrowed the LFRS system to chevron braced frames. Then the precise arrangement of braces for a particular building size using this bay system was examined. The steel material cost of the final system was compared to a system that only included members sized for gravity loads to demonstrate the rough amount of cost that a lateral system can add to a building.

Techniques for preliminary analysis of various tall building systems subjected to lateral loads have been studied herein. Three computer programs written in Matlab® graphical user interface language for use on any personal computer are presented. Two of these programs incorporate interactive graphics. A program called Wall_Frame_2D is introduced for two-dimensional analysis of shear wall-frame interactive structures, using the shear-flexural cantilever analogy. The rigid outrigger approach was utilized to develop a program called Outrigger Program to analyze multi-outrigger braced tall buildings. In addition, a program called Frame Tube was developed which allows analysis of single and quad-bundled framed tube structures. The tube grids are replaced with an equivalent orthotropic plate, and the governing differential equations are solved in closed form. Results for lateral deflections, rotations, and moment, shear, and torque distributions within the various resisting elements are compared against other preliminary and "exact" matrix analysis methods for several examples. SAP2000 was used to obtain "exact" results. The approximate analyses are found to give reasonable results and a fairly good indication of the behavior of the actual structure. These programs are proposed for inclusion in a knowledge-based approach to preliminary tall building design. The tall building design process is outlined and criteria are given for the incorporation of these "Resource Level Knowledge Modules" into an integrated tall building design system.

One of the most common retaining systems for deep excavations is by supporting a wall with multiple levels of anchors. In densely built urban areas, preventing soil movement with such a system can be very costly. Additionally, anchored walls are assumed and forced to act independently during design calculations, thus fail to take the advantage of the rigidity of the whole system at the corners of the excavation area. An alternative support system that uses the entire system is bracing of the walls with struts. But such a system greatly hinders construction space. In this research, a new type of supporting system has been investigated by performing a parametric study in finite element analyses program. New system is a single ring at each support level, supporting the system at several locations. A comparative study has been undertaken between the conventional systems and the new system in both 2D and 3D. PLAXIS finite element analysis software was used for the analyses. The primary aim was to investigate the structural and geotechnical performance of the arch supported system. The study revealed that the new system provides improvement for specific cases and can be considered as an alternatve support system for such cases.

Made available in DSpace on 2014-06-11T19:25:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-02-12Bitstream added on 2014-06-13T19:53:03Z : No. of bitstreams: 1 molina_jc_me_ilha.pdf: 1032005 bytes, checksum: ca5a19c94abacf21752f94991dff250b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Fundação de Ensino Pesquisa e Extensão de Ilha Solteira (FEPISA) / Este trabalho de pesquisa tem a finalidade de analisar o comportamento de edificações de aço. Essas edificações são constituídas de pórticos, espaçados igualmente no sentido longitudinal, considerando o conjunto telha - terça na sua contenção transversal e principalmente longitudinal. As telhas são fixadas nas terças e este conjunto é fixado ao pórtico, de maneira a garantir a sua funcionalidade como um painel rígido, ação diafragma. A análise estrutural é efetuada através do processamento numérico, e são analisadas edificações de aço com dimensões transversais de 10.0, 15.0 e 20.0 metros de vão, tendo o espaçamento longitudinal entre pórticos de 4.0, 5.0, 6.0 e 7.0 metros. Primeiramente são analisados os painéis laterais das edificações, e na seqüência a edificação como um todo com relação ao seu comportamento global. Para finalizar, uma vez definidas todas as características da estrutura, é avaliado o comportamento da edificação quanto ao seu estado limite de utilização, ou seja, a rigidez proporcionada pelo sistema convencional e a ação diafragma formada pelo conjunto telha - terça. / This research work has the purpose to analyze the behavior of buildings in steel. Those buildings have been made by frames, with the same distance in the longitudinal direction, and used the purlin-sheeting system it your transverse restrain and mainly longitudinal. The sheetings are fastened on purlins and this system conected in the frame, in way to guarantee the functionality as a rigid panel, diaphragm action. The structural analysis is made through the numeric processing, and the steel buildings are analyzed with traverse dimensions of 10.0, 15.0 and 20.0 meters, and longitudinal dimension to the each other with 4.0, 5.0, 6.0 and 7.0 meters. Initially the lateral panels purlinsheeting system, are analyzed isolated, and in the sequence this system is connected to the building and analyzed with relationship the global behavior. Finally, once defined all the characteristics of the structure, the building behavior is evaluated with the limit state used, in other words, the proportionate rigidity for the braced system and the action diaphragm formed by the purlin-sheeting system.

Orientador : Renato Bertolino Júnior / Banca: Maximiliano Malite / Banca: José Antônio Matthiesen / Resumo: Este trabalho de pesquisa tem a finalidade de analisar o comportamento de edificações de aço. Essas edificações são constituídas de pórticos, espaçados igualmente no sentido longitudinal, considerando o conjunto telha - terça na sua contenção transversal e principalmente longitudinal. As telhas são fixadas nas terças e este conjunto é fixado ao pórtico, de maneira a garantir a sua funcionalidade como um painel rígido, ação diafragma. A análise estrutural é efetuada através do processamento numérico, e são analisadas edificações de aço com dimensões transversais de 10.0, 15.0 e 20.0 metros de vão, tendo o espaçamento longitudinal entre pórticos de 4.0, 5.0, 6.0 e 7.0 metros. Primeiramente são analisados os painéis laterais das edificações, e na seqüência a edificação como um todo com relação ao seu comportamento global. Para finalizar, uma vez definidas todas as características da estrutura, é avaliado o comportamento da edificação quanto ao seu estado limite de utilização, ou seja, a rigidez proporcionada pelo sistema convencional e a ação diafragma formada pelo conjunto telha - terça. / Abstract: This research work has the purpose to analyze the behavior of buildings in steel. Those buildings have been made by frames, with the same distance in the longitudinal direction, and used the purlin-sheeting system it your transverse restrain and mainly longitudinal. The sheetings are fastened on purlins and this system conected in the frame, in way to guarantee the functionality as a rigid panel, diaphragm action. The structural analysis is made through the numeric processing, and the steel buildings are analyzed with traverse dimensions of 10.0, 15.0 and 20.0 meters, and longitudinal dimension to the each other with 4.0, 5.0, 6.0 and 7.0 meters. Initially the lateral panels purlinsheeting system, are analyzed isolated, and in the sequence this system is connected to the building and analyzed with relationship the global behavior. Finally, once defined all the characteristics of the structure, the building behavior is evaluated with the limit state used, in other words, the proportionate rigidity for the braced system and the action diaphragm formed by the purlin-sheeting system. / Mestre

Strength Reduction Factor (R-Factor), often referred to as Response Modification Factor, is commonly used in the design of lateral force resisting systems under seismic loading. R-Factors allow for a reduction in design base shear demands, leading to more economical designs. The reduction of strength is remedied with ductile behavior in members of proper detailing. Modern seismic codes and provisions recommend R-Factors for many types of lateral force resisting systems. However these factors are independent of the system fundamental frequency and many other important system properties, resulting in factors that may result in an unfavorable seismic response. To evaluate the validity of prescribed R-Factors an extensive analytical parameter study was conducted using a FEM single degree-of-freedom Concentrically Braced Frame (CBF) under incremental dynamic analysis over a suite of ground motions. Parameters of the study include brace slenderness, fundamental frequency, increment resolution, FEM mesh refinement, effects of leaning columns, and effects of low-cycle fatigue. Results suggest that R-Factor can vary drastically for CBF systems with differing properties.

This thesis presents the development of a design procedure for buckling-restrained braced frames (BRBF's). This procedure uses nonlinear time history analysis and a formal optimization algorithm. The time history analysis includes an elasto-plastic model for the braces. The optimization algorithm is a genetic algorithm. This procedure is referred to throughout the thesis as the "Nonlinear Time History Analysis Procedure with Optimization" (NTHO). Current design specifications for BRBF's are based on inelastic design spectra and approximate formulas for the determination of natural period. These spectra are used to obtain seismic base shear, and the distribution of equivalent lateral forces. Yielding and drift criteria are then used to determine brace areas. This design procedure is referred to throughout the thesis as the "Equivalent Lateral Force Procedure" (ELF). The thesis compares results from the NTHO and ELF procedures for a variety of BRBF's and levels of seismicity. The ELF procedure is judged against the more accurate NTHO procedure, and BRBF's are identified where the ELF procedure produces unconservative and excessively conservative designs. Since the NTHO procedure is more computationally expensive than the ELF procedure, design charts are developed for quickly sizing brace areas for a variety of BRBF's based on the NTHO procedure. Among the conclusions at the end of the thesis is the surprising result that the design charts show a near linear variation of brace area from story to story.