A novel stochastic earthquake ground motion model is formulated in association with physically interpretable parameters that are capable of efficiently characterizing the complex evolutionary nature of the phenomenon. A multi-modal, analytical, fully non-stationary spectral version of the Kanai-Tajimi (K-T) model is introduced achieving a realistic description of the evolutionary spectral energy distribution of seismic ground motions. The functional forms describing the temporal evolution of the model parameters can efficiently model highly non-stationary power spectral characteristics. The analysis space, where the analytical forms describing the evolution of the model parameters are established, is the energy domain instead of the typical use of the time domain. This space is used in conjunction with a newly defined energy-associated amplitude modulating function. The Spectral Representation Method supports the simulation of sample ground motions realizations. A predictive stochastic model for simulation of earthquake ground motions is developed, using a user-specified earthquake scenario description as input, and resulting in fully nonstationary ground acceleration time-histories at a site of interest. The previously formed analytical non-stationary K-T ground motion model lies at the core of the developed predictive model. An extensive Californian subset of the NGA-West2 earthquake ground motion database is used to develop and calibrate the predictive stochastic model. Sample observations of the model parameters are obtained by fitting the K-T model to the database records, and their resulting marginal distributions are effectively described by simple probability models. Advanced random-effect regression models are established in the normal probabilistic space, capable of linking the stochastic K-T model parameters with the moment magnitude Mw, closest distance Rrup and average shear-wave velocity VS30 at a Californian site of interest. The included random effects take effectively into account the correlation of ground motions pertaining to the same earthquake event, and the fact that each site is expected to have its own effect on the resulting ground motion. The covariance structure of the normal K-T model parameters is next estimated, allowing finally for the complete mathematical description of the predictive stochastic model for a given earthquake scenario. The entirety of the necessary steps for the simulation of the developed predictive stochastic model is provided, resulting in the generation of any number of fully non-stationary ground acceleration time-series that are statistically consistent with the specified earthquake scenario. In an effort to assess the performance and versatility of the developed predictive stochastic model, a list of simple engineering metrics, associated with the characterization of the earthquake ground motion time-series, is studied, and results from simulated earthquake ground acceleration time-series of the developed predictive model are compared with corresponding predictions of pertinent Ground Motion Prediction Equations (GMPEs) for a variety of earthquake and local-site characteristics. The studied set of ground acceleration time-series features includes the Arias intensity IA, the significant duration T5-95 of the strong ground shaking, and the spectral-based mean period of the earthquake record Tm. The predictive stochastic model is next validated against the state-of-the-art NGA-West2 GMPE models. The statistics of elastic response spectra derived by ensembles of synthetic ground motions are compared with the associated response spectra as predicted by the considered NGA-West2 ground motion prediction equations for a wide spectrum of earthquake scenarios. Finally, earthquake non-linear response-history analyses are conducted for a set of representative single- and multi-degree-of-freedom hysteretic structural systems, comparing the seismically induced inelastic structural demand of the considered systems, when subjected to sets of both real strong ground motion records, and associated simulated ground acceleration time-histories as well. The comparisons are performed in terms of seismic structural demand fragility curves.

Thesis (Ph.D)--City Planning, Georgia Institute of Technology, 2009. / Committee Chair: French, Steven P.; Committee Member: Drummond, William; Committee Member: Goodno, Barry; Committee Member: McCarthy, Patrick; Committee Member: Yang, Jiawen. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This thesis presents the results obtained from a preliminary investigation into the potential application of the friction damping concept to wood structures to improve their seismic response. Sliding friction devices which contain heavy duty brake lining pads have been proposed in order to enhance a wood structure's seismic performance. The devices are mounted onto a structure's shearwalls to dissipate seismic energy input during the wall's deformation in an earthquake. Prototypes of the four friction damping devices were tested to examine their hysteretic behaviour. Conventional full scale, 2.44 x 2.44 m (8 x 8 ft) timber shearwalls, typical of ones used in residential and light-commercial building applications, and ones retrofitted with the friction damping devices were tested on a shake table. Three set of tests were conducted. They involved loading the walls under unidirectional racking, static-cyclic and simulated earthquake loads. Test results from the two types of shearwalls were compared against each other and against the findings from the computer programs SADT and FRICWALL. SADT is a finite elements program which computes the load-deformation behaviour of shearwalls. FRICWALL is an inelastic time-history dynamic model which computes the response time-history of a shearwall under a simulated seismic event. The cyclic tests of the friction damping devices showed that they exhibited very stable and non-deteriorating hysteretic behaviour. The shake table tests of the full scale timber shearwalls showed that the friction damped walls were stiffer, can sustain an average of 23.7 % higher racking load and dissipate an average of 42.9 % more energy than the conventional ones before a ductile failure. Failure in the conventional walls was brittle. These results were in agreement with the SADT findings. Under slow cyclic loads, they dissipated more energy, but because their overall hysteretic behaviour was still pinched, they were just as inefficient as the conventional walls at dissipating energy. On the average, their seismic performance was only marginally better than that of the conventional wall, with an average drop of 9.6 % in peak wall deflection. This is far short of the average of 29.5 % computed by FRICWALL. Detailed analysis of the results show that due to bending in the framing members of the shearwall, the load necessary to cause slippage of the friction devices was not achieved until wall deflections in the order of 25.4 mm (1.0 in) was reached. Since only at the peak or near-peak excitation levels of an earthquake did shearwall deflections surpass this magnitude, the devices were not able to contribute to the energy dissipation of the shearwalls during the majority portion of a seismic event. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Investigations into the behaviour of precast buildings under earthquake loading have shown that the connections are likely to be the weakest link in a pre-cast structure, and the stability of the structure under earthquake loading depends upon the strength & stability of these connections. A 2-dimensional non-linear dynamic analysis of a one storey box-type pre-cast buildings is presented. The shear walls in the buildings are modelled by linear springs, the properties of which depend upon the connections connecting the rigid panels of the shear walls. To check the effectiveness of the NBCC code design, computer studies have been made on a box-type building statically designed for different eccentricities. The strength of the shear walls was calculated assuming that each panel was a cantilever fixed at the base with dowel bars providing the flexural steel. To make the building survive a major earthquake, we need dowel connections that can take 5mm to 6mm elongation which can be easily accommodated. Studies have also shown that under the action of an earthquake, the response of a highly unsymmetrical building will not be very different from that of a symmetric building as long as the building is properly designed using the NBCC code provisions for earthquake loading. It has also been shown that the NBCC code design eccentricity equation is somewhat conservative in calculating the design eccentricity and that a small change in the stiffness of walls perpendicular to the direction of earthquake has little effect on the response of the structures. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 180-184. / by Hooshang Banon. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 140-141. / by Chin Pang Wong. / M.S.

An analytical formulation for seismic analysis of multiply supported secondary systems is developed. The formulation is based on the random vibration theory of structural systems subjected to correlated inputs at several points. The response of the secondary systems is expressed as a combination of the dynamic, pseudo-static and cross response components. The dynamic part is associated with the inertial effect induced by the support accelerations. The pseudo-static part is due to the relative displacement between supports, and the cross part takes into account the correlation between these two parts of the response. The seismic input in this approach is defined in terms of the auto and cross pseudo-acceleration and relative velocity floor spectra. The information about floor displacements and velocities as well as their correlations is required for calculating the pseudo-static and cross response components. These inputs can be directly obtained from the ground response spectra. The interaction effect between the primary and secondary systems is studied. This effect is specially significant when the modes of the secondary system are tuned or nearly tuned to the modes of the primary system. The floor spectral inputs are appropriately modified to take into account this interaction effect. The design response of the secondary system when computed with these modified floor inputs will incorporate the interaction effect. The applicability of the proposed methods is demonstrated by several numerical examples. / Ph. D. / incomplete_metadata

The available earthquake records are classified into five groups according to their site stiffness and epicentral distance as the grouping parameters. For the groups thus defined, normalized response spectra are obtained for single-degree-of-freedom and massless oscillators. The effectiveness of the grouping scheme is examined by studying the variance of response quantities within each group. The implicit parameters of average frequency and significant duration are obtained for each group and their effect on the response spectra is studied. Correlation analyses between various ground motion characteristics such as peak displacement, velocity, acceleration and root mean square acceleration are carried out for each group. Smoothed design spectra for relative and pseudo velocities and relative acceleration responses of single degree of freedom oscillators and the velocity and acceleration responses of massless oscillators are proposed for each group. Methods to predict relative velocity and relative acceleration spectra directly from the pseudo velocity spectra are presented. It is shown that the relative spectra can be reliably estimated from the pseudo spectra. The site dependent design spectra are defined for a wide range of oscillator periods and damping ratios. / Master of Science

Structures built next to each other in congested cities are likely to pound on each other during strong ground shaking caused by earthquakes. The main objective of this study is to examine the problem of mutual structural pounding to identify its effect on structures and then propose solutions to mitigate its effects. Mutual pounding of structural systems with varying mass, stiffness, and seismic joint gaps, subjected to several different input motions are examined. To evaluate the effects of pounding, the numerical results with and without pounding have been considered. The resilience between two impacting masses is represented by linear springs and also nonlinear Hertz model contact stiffness. Pounding causes a large increase in the shear force in the stories higher than the top pounding story, a large increase in the accelerations of the pounding floors and also large overturning effects on both structures. The parametric study of pounding of structures in series showed that in most cases the corner structures are penalized more than the interior structures. The study of the effect of foundation flexibility on the structural pounding response showed that a proper consideration of this parameter must be included in the analysis. To alleviate the pounding effects to avoid damage to structural elements and supported secondary equipment, it was found necessary to join the structures by rigid links and brace all the stories of at least the taller structure. Joining of the floors is required to reduce the excessive floor accelerations caused by impact, whereas the story bracings are required to reduce the excessive story shears or bending moments in the higher stories caused by pounding of the lower floors. It is observed that except for very soft soils, the proposed pounding mitigation scheme will increase the shear force transmitted to the foundation, thus requiring a strengthening of the foundation as well. Since the forces in the rigid links connecting the two structures were observed to be reasonable, the joining of the two structures does not pose any special problem; it can be easily accomplished by using large-size steel rods hooked properly with both structures. In the case of column pounding where the floors of one structure pound on the columns of the other structure, the pounding mitigation strategy is to provide K-bracings on all pounding columns and diagonal bracing in the other stories to reduce high bending moment in the column, and to rigidly join them to avoid high pounding acceleration. / Ph. D.

published_or_final_version / Civil Engineering / Master / Master of Philosophy