Thesis (M.S. in civil engineering)--Washington State University, December 2005. / Includes bibliographical references.

Thesis (Ph.D.)--McMaster University, 2004. / Advisor: Ahmed Ghobarah. Includes bibliographical references (p. 341-351). Also available online.

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.E.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

The capacity spectrum method is a very popular tool in the performance based earthquake resistant design of structures. Though it involves nonlinear static analysis, it can be used to predict the dynamic behaviour of the building under earthquake load. Since the analysis is only static and not dynamic, it is very well suited for the design offices and low end computer terminals as opposed to dynamic analysis which is very resource consuming. There are several methods/variations of methods, to perform the nonlinear static analysis, popularly known as pushover analysis and convert it to capacity spectrum. Displacement based pushover analysis, force based pushover analysis, modal pushover analysis, energy based pushover analysis etc. are some of the variations of pushover analysis. There are a few attempts to consider the change in mode shape but all the methods are silent about the change in frequency due to formation of hinges in the structure. The available codes for building design such as ATC-40 provide some guidelines for getting the capacity spectrum but are not yet developed for proper ductility consideration while converting the pushover curve to capacity spectrum. The present study tries to address the above issues while proposing a new energy based approach to draw capacity spectrum. The chapter 1 introduces the concept of pushover analysis and capacity spectrum concepts. Different approaches to get these curves, their theoretical background, variations and limitations are discussed as a quick review. Chapter 2 is about the review of literature present on these topics. It is found that most of the studies have been carried out in the past on the framed buildings regarding the pushover analysis. In the last few years attempts are also made to consider the effect of torsion. Summarising the various contributions till now, it may be concluded that even in the earlier multimode pushover analysis the effect of different modes on the only static force distribution was considered. Further the spectral acceleration is obtained as a ratio of base shear and α times the weight of the building, where α is the modal mass coefficient. Only the first mode frequency could be utilized to convert the maximum displacement at the top to the spectral acceleration and the corresponding maximum potential energy (P.E.) could be used for equivalence of MDOF and SDOF. Therefore in chapter 3 which follows, the above limitation is removed as explained below. In chapter 3, the new methodology based on energy equivalence consideration is proposed step by step. For the given multistorey building, a displacement profile is applied to the building which is proportional to the effective mode shape. The effective mode shape can be the first mode shape or a combination of first few mode shapes. In the present study, two cases are considered. In the first case, the effective mode shape is considered to be the first mode shape itself whereas in the second case the effective mode shape is considered to be a linear combination of first three modes weighted by corresponding participation factors. After this, a nonlinear static analysis is performed on the structure considering the above displacement profile. Due to the above provided displacement profile, there will be yielding in the structure at a few locations. The yielded structure is again analysed for eigenvalues and mode shapes and the first three mode shapes are extracted along with their participation factors. Again the deflected structure is subjected to the deflection proportional to the effective mode shape and the analysis is continued until the collapse. The chapter also describes the details of the model used for simulation. Two kinds of simulation are performed on the model. One is considering only single mode of vibration whereas the other is considering the multiple modes (3 in this case) of vibration of the structure. Chapter 4 discusses the results of the simulations performed on the model. Single mode and multimode cases are treated and discussed separately. The proposed method is in its nascent stage and hence a lot of modification and validation work is needed to consider the method acceptable. The chapter 5 concludes the overall outcome of the present study and provides scope for the further study.

An ultra-lightweight buckling-restrained brace (ULWBRB) is developed using a highly ductile aluminum core and FRP restrainer. Utilization of lightweight materials results in a BRB that is 25% the weight of traditional mortar-filled tube varieties allowing easy installation in small to medium sized buildings requiring seismic retrofit without the need for heavy equipment. Construction utilizes commonly stocked materials able to be customized for required strength, drift, and geometry limitations. Analytical single degree of freedom (SDOF) and Euler buckling models are compared with published equations to determine the required restrainer stiffness (RRS). SDOF models yield RRS values 200% higher than the Euler model. Applied end moments due to frame deformation are incorporated into a modified design method that gives RRS values 50% higher than Euler model without eccentricity. RRS is provided using a bundled and wrapped FRP tube configuration using a developed shear flow method considering composite action. Uniaxial low-cycle fatigue (LCF) testing of a 6061-T6 candidate alloy provides data for a constitutive model using combined kinematic-isotropic hardening. LCF testing of round short gage coupons indicates the candidate alloy is capable of stable cycling to 2%, 3%, and 4% total strain with excellent ductility. Early fracture of specimens at 24, 18, and 11 cycles, respectively, also indicates that other candidate alloys should be examined for improved fatigue life. However, inconsistency is noted between similar tests of 6061-T6 that were able to achieve up to 76 cycles at 2.5% total strain. ULWBRB FEA models loaded monotonically consistently give higher RRS values as compared to the analytical methods. This is due to assignment of initial imperfections, longer more realistic unbraced length, higher axial loads achieved through the post-yield region, and plastic hinging potential. Cyclic simulations of braces with the same RRS values are also able to achieve reliable and stable hysteretic behavior through 21 cycles. If a less stiff restrainer is used, cumulative energy dissipation potential is reduced considerably due to pinched hysteresis loops and strain ratcheting. Applied end moments are found to have a linear effect on the RRS that can be modeled by superposition of the buckling effect plus end moment.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Pierre Hernando Montauban. / M.S.

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Difficulties in characterizing the dynamic behavior of wood structures have hindered investigations into their performance under dynamic loading. Because of this, wood structures are treated unfavorably in seismic design codes, even though past damage assessment surveys after seismic events indicated generally satisfactory performance. To allow investigations into their performance and safety under dynamic loading, the energy dissipation mechanisms of wood joints and structural systems must be known and the hysteretic behavior modeled properly. This thesis presents a general hysteresis model for wood joints and structural systems, based on a modification of the Bouc-Wen-Baber-Noori (BWBN) model. The hysteretic constitutive law, based on the endochronic theory of plasticity and characterized by a single mathematical form, produces a versatile, smoothly varying hysteresis that models previously observed behavior of wood joints and structural systems, namely, (1) nonlinear, inelastic behavior, (2) stiffness degradation, (3) strength degradation, (4) pinching, and (5) memory. The constitutive law takes into account the experimentally observed dependence of wood joints' response to their past history (Le., the input and response at earlier times, or memory). Practical guidelines to estimate the hysteresis parameters of any wood joint or structural system are given. Hysteresis shapes produced by the proposed model are shown to compare reasonably well with experimental hysteresis of wood joints with: (1) yielding plate, (2) yielding nails, and (3) yielding bolts. To demonstrate its use, the proposed model is implemented in a nonlinear dynamic analysis program for single-degree-of-freedom (SDF) systems. System response from arbitrary dynamic loading, such as cyclic or earthquake-type loadings, can be computed. Three SDF wood systems are subjected to the Loma Prieta accelerogram to obtain their response time histories. Advantages of using the proposed model over currently available models in nonlinear dynamic analysis of more complex systems are identified. A multidegree-of-freedom shear building model incorporating the proposed hysteresis model is formulated but not implemented on a computer. / Master of Science

No description available.