Thesis (Ph. D.)--Texas A&M University, 2005. / Vita. Includes bibliographical references (p. 150-156). Also available online via the Texas A&M Digital Repository website (https://txspace.tamu.edu/).

The use of base isolation to help mitigate and reduce the effects of earthquake excitations has become common place on many important structures. There is also a larger amount of heavier machinery and equipment being stored in some of these important structures; this means that there is a possibility that there are mass irregularities with in a structure. While the response of structures that have been base isolated has been studied they are typically design with floors having a uniform mass. This thesis investigates how mass irregularities affect the response of the floor accelerations and interstorey drifts within a flexural structure with and without a base isolation unit. The ductility demand of the isolator unit is also investigated at during the course of the analysis. The reason for observing the response of the structure is because often in building design there is a need to have floors that have larger masses then the rest of the structure, and understanding how these mass irregularities affect the response of the structure, then the designing of such structures will be simpler during the initial concept stage.

Base isolated buildings are well known to provide enhanced performance due to minimized accelerations and decreased interstory drifts. However, the reduced demands are obtained at the expense of large displacements at the isolation layer. This study investigates an innovative system, termed ‘dual isolation’, which applies two layers of isolation, one at the base and one mid-story to resolve this issue. An analytical solution for the equation of motion of the proposed system is developed based on linear isolation theory. This creates a foundation to assess the behavior of various types of seismic protection systems and to select the damping, mass and frequency ratio that leads to an optimal dual isolation design. Time history responses of the dual isolation system with viscous damping are compared to those of a conventional isolation counterpart to examine the effectiveness of the system. The system reduces first floor displacements by 40% on average, while the roof displacement is increased by roughly 15%. This results in reduced design forces for the structure. In addition, accelerations, especially above the second isolation layer, are significantly decreased. By reducing story shears and accelerations, the dual isolation system limits damage to both structural and nonstructural systems and components, thereby increasing global system performance. / Thesis / Master of Applied Science (MASc)

A continuous formulation to calculate the dynamic stiffness matrix of structural members with distributed masses is presented in detail and verified with some simple examples. The dynamic model of a specific bridge (the Marga-Marga bridge in Chile) was developed using this formulation, and the model was then used to obtain the transfer functions of the motions at different points of the bridge due to seismic excitation. The model included rubber pads, used for base isolation, as additional members. The transfer functions were obtained with and without rubber pads to investigate their effect. The dynamic stiffness of complete pile foundations was calculated by a semi-analytical solution with Poulos?? assumption. General observations on group effects under various conditions were obtained from the result of these studies. The dynamic stiffness of the pile foundations for the Marga-Marga bridge was then obtained and used to study the soil structure interaction effects on the seismic response of the bridge. Records obtained during a real earthquake were examined and interpreted in light of the results from all these analyses. Finally, conclusions and recommendations on future studies are presented.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Seismic hazards are a primary concern in some of the most populous regions in the United States. Performance-based seismic design has brought about new technology advances and introduced an innovative approach towards constructing seismic resistant buildings. Base isolation and structural damping systems are becoming increasingly utilized methods of advanced seismic resistance. This relatively new design approach presents various issues that must be addressed throughout the design and construction processes. A brief background on the origin, dynamics, and hazards of earthquakes and a discussion on designs of traditional, fixedbased structures is presented in this report. A description for selected types of new advanced seismic restraint systems, with an emphasis on base isolation, is also provided. Examples of current applications of buildings equipped with base isolation are presented. This report concludes with a review of the fundamental design methodology for structural base isolation along with additional requirements not addressed by the current building codes.

No description available.

The 7th German-Japanese Bridge Symposium, July 30-August 1, 2007 Osaka, JAPAN (GJBS07), full paper + extended abstract (p.84-85)

Ground-borne vibration has existed ever since the development of urban road and rail networks. Vibration generated by the moving traffic propagates through the ground and into buildings, resulting in unacceptable levels of internal noise and vibration. A common solution to this increasingly significant problem is the base-isolation of buildings by incorporating vibration isolation bearings between the buildings and their foundations. This technique has been employed for over forty years but the exact performance of base isolation remains uncertain. This dissertation is concerned with the development of a generic computational model; generic in that it accounts for the essential dynamic behaviour of a typical base-isolated building in order to make predictions of isolation performance. The model is a linear one, formulated in the frequency domain, and consists of a two-dimensional portal-frame model of a building coupled to a three-dimensional boundary-element model of a piled-foundation. Both components of the model achieve computational efficiency by assuming they are infinitely long and using periodic structure theory. The development of the model is described systematically, from the modelling of a building and its isolation bearings to that of its foundation. The majority of the work is concerned with the piled-foundation model, which is comprehensive in that it accounts for the vertical, horizontal and rotational motion of the pile heads due to both direct pile-head loading and interaction through wave propagation in the surrounding soil. It is shown that this level of detail is important in the prediction of base isolation efficiency. A key question facing designers is not only how but on what basis base isolation should be assessed, since fundamental problems exist with the existing measures of isolation performance. Power flow analysis is explored and the concept of power flow insertion gain, based on the total mean vibrational power flow entering a building, is introduced as a useful measure of isolation performance. This is shown to offer clear benefits by providing a single measure of performance that is suitable for design purposes. Finally, the development of a prototype force-sensitive vibration isolation bearing is described as a contribution to verifying base-isolation theory with experiments.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / his paper proposes a Lean Green model for increasing profitability in small and medium-sized businesses operating within the plastics sector. This model will use the 5S methodology, KanBan for inventory control and TPM to standardize new corrective and preventive maintenance processes. As an added contribution, a Circular Economy process will be included to reuse products, thus reducing consumption and generating less solid waste. In this way, companies will not only prevent damaging the environment but will also guarantee their compliance with regulatory standards. As a result, an 11% reduction was observed in the acquisition of supplies and spare parts for machine maintenance along with a 4% reduction in the number of machine breakdowns.

We extend the application of the substructure synthesis method to more complex structures, and establish a design methodology for base isolation and active control in a distributed model of a building under seismic excitation. Our objective is to show that passive and active control complement each other in such an advantageous manner for the case at hand, that simple devices for both types of control are sufficient to achieve excellent response characteristics with very low control forces. The Rayleigh-Ritz based substructure synthesis method proved to be highly successful in analyzing a structure more complex than the ones previously analyzed with it. Comparing the responses of the hybridly controlled building and the conventional fixed building under El Centro excitation, we conclude that the stresses are reduced by 99.6 %, the base displacement is reduced by 91.7 % and the required control force to achieve this is 1.1 % of the building weight. / Ph. D.