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A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.

Although it has been established that in-situ soil mixing has improved the bearing capacity of soils, additional research is needed to better understand the effect of soil mixing on lateral resistance of pile caps. To do this, in-situ soil mixing was used to strengthen weak clay adjacent to a pile cap of a driven pile foundation. The mass stabilization method or mass mixing was used to treat an 11 ft wide, 4 ft thick, and 10 ft deep zone consisting of an average 475 psf clay that was adjacent to a 9-pile group in 3x3 pile configuration capped with a 9 ft x 9 ft x 2.5 ft, 5000 psi concrete cap. The mass mixing involved 220 cubic ft of in-situ soil and was mixed with an additional 220 cubic ft of jet grout spoils producing a mixing ratio of 1 to 1. All of the mass mixing took place after construction of the pile caps. Laboratory testing of the mass mix slurry showed an unconfined compressive strength of 20,160 psf or 140 psi. Lateral load testing of the pile foundation was then undertaken. The results of this testing were compared with similar testing performed on the same foundation with native soil conditions. The lateral resistance of the native soil was 282 kips at a pile cap displacement of 1.5 inches, and the total lateral resistance of the pile foundation treated with mass mixing was increased by 62% or 170 kips. Of the 170 kips, 90% to 100% can be attributed to the increased passive force on the face of the mass mixed zone and shear on the sides and bottom denoting that the mass mixed zone behaved as a rigid block.

Traditional seismic load resisting systems in buildings are designed to undergo inelastic deformations in order to dissipate energy, resulting in residual displacements. This work explores an approach to eliminate these residual displacements. The systems investigated have low initial stiffness which increases at a predefined displacement, and are therefore called stiffening elastic systems. This thesis begins with an examination of single-degree-of-freedom stiffening elastic systems. A case study is presented which suggests that the benefits from stiffening elastic behavior may be limited to systems which would have long periods if designed traditionally. A thorough parameter study is also presented which indicates the benefit of stiffening elastic behavior for SDOF systems with periods greater than four seconds. A final case study is presented that compares the response of a twelve-story stiffening elastic system to a ductile system and an elastic system. The stiffening elastic system was able to eliminate the residual displacements inherent in a ductile system while lowering the base shear experienced by the elastic system, but is not clearly better than the ductile system because the base shear force was much higher.

Joel Mondo Kisekini, for the Master of Science degree in Civil Engineering, presented on March 25, 2022, at Southern Illinois University Carbondale.TITLE: EFFECT OF SIMULTANEOUS APPLICATION OF THE TWO HORIZONTAL ORTHOGONAL GROUND MOTION COMPONENTS ON THE SEISMIC BEHAVIOR OF BUILDINGSMAJOR PROFESSOR: Dr. JALE TEZCAN During an earthquake, buildings are simultaneously excited by two horizontal and one vertical ground motion components. Modern seismic codes and guidelines such as ASCE/SEI 41-06 (Seismic rehabilitation of existing buildings, American Society of Civil Engineers), EUROCODE 8 (1998-1) (Design provisions for earthquake resistance of structures, European Committee for Standardization, 2003), FEMA 356 (Prestandard and Commentary for Seismic Rehabilitation of the Buildings) and FEMA P-2082 (NEHRP Recommended Seismic Provisions for new buildings and other structures) require the consideration of the effects of two horizontal orthogonal ground motions in seismic design of buildings. Therefore, the main objective of this study is to evaluate the simultaneous effect of two horizontal orthogonal ground motion components to seismic behavior of buildings. A four-story steel frame is modeled, and it is subjected to a set of twenty ground motion pairs recorded distances between x and y kilometer from epicenter. Three methods for combining peak response to individual component of ground motions is used to estimate the displacement responses. The combination rules used in this present study are 30%, SRSS, and 20%. The response of the four-story steel frame is investigated within the context of linear response history analysis and the results are compared to the peak responses obtained from time history analyses under bidirectional and unidirectional ground motion. The structural response includes the following parameters: nodal displacements and the critical angle of excitation. The output results showed that the maximum response under two components was, on average, 23 % more than the maximum response under a single component, and the two horizontal orthogonal seismic excitations increased the structure displacement response compared to unidirectional excitation.

Highway bridges provide a critical lifeline during extreme seismic events and must maintain serviceability under a large range of earthquake intensities. Consequently, the advent of more computational power has allowed more advanced analysis approaches for predicting performance and vulnerability of highway bridges under these seismic loads. In traditional two-dimensional finite element analyses, it has been demonstrated that the incidence angle of the ground motion can play a significant role in structural response. As three-dimensional nonlinear time history analyses are used more frequently in practice, ground motions are still usually applied along a single bridge axis. It is unknown how three orthogonal components of ground motion excitation should be applied to the structure to best represent the true response. In this study, the fundamental behavior of three-dimensional ground motion was studied using single-degree-of-freedom elastic spectra. Mean spectra computed from various orientation techniques were found indistinguishable when the orthogonal components were combined. The effect of incidence angle on the nonlinear structural response of highway bridges was then investigated through extensive statistical simulation. Three different bridge models were employed for this study implementing a suite of 180 multi-component ground motion records of various magnitude-distance-soil bins. Probabilistic seismic demand models for various response parameters are presented comparing the effects of random incidence angle to that of recorded directions. Although there are instances where the angle of incidence can significantly amplify response, results indicated that incidence angle had negligible effect on average ensemble response. This is consistent with results from the spectral analysis, although existing literature has emphasized incidence angle as a significant parameter of multi-component analysis.

Disputes and confrontational rhetoric have characterized Greek-Turkish relations in recent years. In February 2023 a high magnitude earthquake hit Türkiye  with devastating consequences. Greece’s response was immediate and substantial despite the political enmity between the two countries, which revealed a willingness to cooperate in times of crisis. This cooperation was in fact expedited by the disaster which is why it accounts for a disaster diplomacy case.   This paper aims to test the theoretical proposition that disaster-related activities “have the possibility of catalyzing diplomatic action” (Kelman, 2012:14). This case study examines the dynamics of the two countries on three different levels before the earthquake and the ways in which disaster diplomacy has catalyzed their relations. By building on Kenneth Waltz’s well-established, three-images framework of analysis (1959), both countries have been investigated concerning their decision makers, the internal structure of the two states, as well as their international presence.   By analyzing the three images of Greece and Türkiye  it is evident that the earthquake has in fact stimulated the relations of the two countries in all three levels. The sense of urgency generated by the earthquake has created a window of opportunity for dialogue. The confrontational so far situation was abruptly disturbed by the disaster and an immediate shift in sentiment can be observed. While the findings of this research confirm the theoretical proposition that disaster diplomacy can indeed act as a catalyst for cooperation between the two countries, it also acknowledges the need for further exploration to assess the long-term potential of disaster diplomacy as a conflict resolution tool.

Assessment of post-liquefaction residual strength is needed for the development of empirically-based, predictive correlations for earthquake engineering design. Previous practice commonly assigned negligible strengths to liquefied materials for engineering analysis, producing overly-conservative designs. Increasingly available case history data, and improved analytical tools have allowed for more accurate and less overly-conservative estimation of soil residual strength, improving empirical predictive models. This study provides a new case history to the limited suite of (approximately 30) liquefaction failure case histories available for post-liquefaction in-situ strength predictive correlations. This case history documents the Las Palmas gold mine tailings dam failure, resulting from seismic-induced liquefaction during the moment magnitude 8.8 February 27, 2010 Maule, Chile earthquake; the sixth largest since 1900. Forensic analysis provides reasonably well-constrained values of 1) back-calculated representative post-liquefaction residual strength, 2) representative penetration resistance, and 3) representative vertical effective stress along the suspected liquefied failure surface. This study employs the incremental momentum method to incorporate momentum effects of a moving soil mass. The incremental momentum method requires a series of cross sections animating the geometry of failure progression from initiation to termination, converging on the observed final geometry. Using interpreted soil strength characteristics, an iterative procedure approximates the back-calculated value of post-liquefaction residual strength. Findings of this case history plot well with existing empirical deterministic regression charts and are in general agreement with previous, related efforts. Results yield representative, well-constrained values of: 1) post-liquefaction residual strength ≈ 173 psf, 2) penetration resistance of N1,60,CS ≈ 5 and N1,60 ≈ 2.5, and 3) vertical effective stress ≈ 4,300 lb/ft2, or ≈ 2.0 atm.

This thesis evaluates the application of a simplified analysis procedure as implemented in version 16 of CSiBridgeTM for design of bridges crossing earthquake fault ruptures. The fault-rupture response spectrum analysis (FR-RSA) approximation method has been proved adequate for both straight and curved ordinary bridges, but lacked a comfortable interface to accommodate the method users. Computers and Structure, Inc. has implemented the FR-RSA procedure into CSiBridgeTM, a user-friendly integrated 3-D bridge design software, as an added seismic design feature. By combining the response of the bridge due to the quasi-static displacement from the fault strike-slip rupture and the pseudo-dynamic displacement from the earthquake response spectrum analysis, a combined seismic demand is approximated using the software. The CSiBridgeTM bridge model creation process and application of FR-RSA as the Caltrans Fault Crossing Seismic Design Request is explained and evaluated in this thesis. In order to validate the implementation of FR-RSA in CSiBridgeTM v.16, the bridge demands for a three span and a four span curved bridge crossing earthquake fault rupture zones from the analytical models developed in Open System for Earthquake Engineering Simulation (OpenSees) and CSiBridgeTM v.16 are compared and discussed. It was found that the displacement demands from the abutments and bents were comparable from the two programs, supporting the correct application of the approximation method. This thesis also presents recommendations for improving the analysis function of CSiBridgeTM v.16 for bridges crossing fault ruptures.