Flat-slab buildings designed and detailed for gravity loads only typically do not have the ability to resist moderate earthquakes without experiencing severe damage. The damage potential of such seismically deficient buildings therefore needs to be assessed and strategies developed to improve their seismic resistance. Punching failure at slab-column connections in non-ductile flat-slab buildings during earthquakes can trigger progressive collapse of floor slabs. Based on the test results of a large number of interior and exterior connections, a methodology is developed to predict shear and unbalanced moment-transfer capacities of connections under combined gravity and lateral loads. Furthermore, a frame analysis procedure is developed based on the equivalent frame concept which targets both the moment-transfer capacity as well as stiffness of the interior and exterior slab-column connections. The approach employs a parametric hysteretic model and is based on the effective slab-width concept. The proposed procedure for evaluating the seismic capacity of flat-slab connections and frames is verified by comparing the calculated and measured responses of two-bay flat-slab subassemblies tested under earthquake-type loading. Seismic reliability against punching failure of slab-column connections in flat-slab buildings designed for gravity loads was investigated using the proposed equivalent frame approach. The reliability analysis indicated that the flat-slab buildings constructed prior to the 1960's could experience significant damage during moderate intensity earthquakes. By limiting the gravity load on floor slabs and by controlling the lateral drift, the potential for punching failure in flat-slab buildings can be minimized. The seismic resistance of older flat-slab buildings can be improved by retrofitting interior connections to protect against progressive collapse and by utilizing infill walls to control lateral drift. An economical connection retrofit scheme is proposed and verified experimentally. The equivalent strut concept is used to model masonry infills whose effectiveness in controlling the lateral drift is demonstrated through theoretical analysis of typical flat-slab frames.

The dynamic interaction between the soil and the structure resting on it during earthquakes can alter the response characteristics both of the structure and the soil. Despite significant efforts over the past decades, the interaction effect is not yet fully understood and is sometimes misunderstood. In the context of performance based design, there remain a number of uncertainties to be addressed seriously. Current practice of seismic soil-structure response analysis has tended to focus on the effect of horizontal motion although actual ground motions are comprised of both horizontal and vertical components. In several recent earthquakes, very strong vertical ground motions have been recorded, raising great concern over the potential effect of vertical motion on engineering structures. To address this emerging problem, seismic response considering the soil-structure interaction effect to both vertical and horizontal earthquake motions needs to be investigated. This thesis presents a simple and practical framework for the analysis of site response and soil-structure interaction to both horizontal and vertical earthquake motions, which can take into account the soil nonlinearity and material damping effect. The analysis procedure involves the use of the dynamic stiffness matrix method and equivalent-linear approach and is built in the modern MATLAB environment to take the full advantages of the matrix operations in MATLAB. The input motions can be specified at the soil–bedrock interface or a rock outcropping. A detailed assessment of the procedure is provided to illustrate that the procedure is able to produce acceptable predictions of both vertical and horizontal response of soil-structure systems. It is shown that soil nonlinearity plays an important role in altering the response of the structure and soil, and the methods of analysis for soil-structure interaction adopted in current engineering practice may not be able to adequately account for soil nonlinearity. Furthermore, effects of a number of influencing factors, such as material damping ratio, Poisson’s ratio of soil, intensity and location of input motion and the embedment ratio of the foundation are examined, leading to several useful implications for seismic engineering practice. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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Thesis (M. Env. Sc.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1999? / Includes bibliographical references (leaves 94-99).

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on March 11, 2009. "January 2009." "In partial fulfillment of the requirements for the degree [of] Master of Science in Architecture with a Specialization in Architectural Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Brent Nuttall, M.S. Includes bibliographical references (p. 82-84). Also available on microfiche.

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on Sept. 16, 2009. "August 2009." "In partial fulfillment of the requirements for the degree [of] Master of Science in Civil and Environmental Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Charles B. Chadwell, Ph.D. Includes bibliographical references (p. 67-71).

Recent geologic research has shown that earthquakes more destructive than formerly expected are likely to occur in the Pacific Northwest. To mitigate catastrophic loss, planners are gathering information to make decision on implementing regional seismic retrofit programs. This research develops a model to estimate regional earthquake losses for existing buildings, and determine optimal retrofit priorities and budgets. Fragility curves are developed to provide earthquake damage estimates for a range of seismic intensities. The published earthquake damage estimates of a large group of prominent earthquake engineering experts are extended to include the combined effect of structure type, earthquake-sensitive variations in building design, site-specific soil conditions, and local seismic design practice. Building inventory data from a rapid visual screening survey of individual buildings form the basis for modeling structural variations. Earthquake Hazard Maps are the basis of modeling the effect on building damage of ground motion amplification, soil liquefaction, and slope instability. Published retrofit effectiveness estimates and retrofit cost data are used to estimate post-retrofit damage avoided, lives saved, and retrofit cost. A Building Classification System is formulated to aggregate buildings with similar retrofit benefit magnitudes. A cost-benefit analysis is used as the basis for a retrofit prioritization and efficiency analysis, to establish the cut-off point for an optimal retrofit program. Results from an Expected Value and a Scenario Earthquake Event are compared. Regional Earthquake Loss and Retrofit Analysis Program (REAL-RAP) software was developed, and used to make a loss estimate for more than 7,500 buildings inventoried in the 1993 Portland Seismic Hazards Survey. One hundred percent of the loss of life is attributed to only 10-percent of the buildings. A retrofit analysis is made for a Design Basis Earthquake. Twelve-percent of the building inventory was identified for the optimal retrofit program, wherein 98-percent of the loss of life is avoided at less than one-quarter the cost of retrofitting all the buildings. An alternate optimal retrofit program was determined using an Expected Value Analysis. Most of the buildings in the Design Basis Earthquake optimal retrofit program are also contained in the alternate program.

While site effects are accounted for in most modern U.S. seismic design codes for building structures, there exist no standardized procedures for the computationally efficient integration of nonlinear ground response analyses in broadband ground motion simulations. In turn, the lack of a unified methodology affects the prediction accuracy of site-specific ground motion intensity measures, the evaluation of site amplification factors when broadband simulations are used for the development of hybrid attenuation relations and the estimation of inelastic structural performance when strong motion records are used as input in aseismic structural design procedures. In this study, a set of criteria is established, which quantifies how strong nonlinear effects are anticipated to manifest at a site by investigating the empirical relation between nonlinear soil response, soil properties, and ground motion characteristics. More specifically, the modeling variability and parametric uncertainty of nonlinear soil response predictions are studied, along with the uncertainty propagation of site response analyses to the estimation of inelastic structural performance. Due to the scarcity of design level ground motion recording, the geotechnical information at 24 downhole arrays is used and the profiles are subjected to broadband ground motion synthetics. For the modeling variability study, the site response models are validated against available downhole array observations. The site and ground motion parameters that govern the intensity of nonlinear effects are next identified, and an empirical relationship is established, which may be used to estimate to a first approximation the error introduced in ground motion predictions if nonlinear effects are not accounted for. The soil parameter uncertainty in site response predictions is next evaluated as a function of the same measures of soil properties and ground motion characteristics. It is shown that the effects of nonlinear soil property uncertainties on the ground-motion variability strongly depend on the seismic motion intensity, and this dependency is more pronounced for soft soil profiles. By contrast, the effects of velocity profile uncertainties are less intensity dependent and more sensitive to the velocity impedance in the near surface that governs the maximum site amplification. Finally, a series of bilinear single degree of freedom oscillators are subjected to the synthetic ground motions computed using the alternative soil models, and evaluate the consequent variability in structural response. Results show high bias and uncertainty of the inelastic structural displacement ratio predicted using the linear site response model for periods close to the fundamental period of the soil profile. The amount of bias and the period range where the structural performance uncertainty manifests are shown to be a function of both input motion and site parameters.

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