The main purpose of this research is to investigate the effectiveness and feasibility of semi-active control systems for structural protection during severe earthquake loading. However, the research reported herein also involves analytical studies on the effect of adding viscous damping to the second and fourth quadrants of the force-displacement curve, and laboratory and field testing of a fibre-optic gyroscope (FOG) for measuring rotations in civil engineering structures. The concept of the 2-4 viscous damping is introduced to reduce the response of single-degree-of-freedom (SDOF) systems subjected to harmonic and earthquake excitations. This concept involves the addition of structural viscous damping to the second and fourth quadrants of the force-displacement graph. Time-history analyses and response spectra for various SDOF systems are carried out to assess the effect of adding 2-4 viscous damping. The analytical results indicate that the addition of 2-4 viscous damping is beneficial for reducing the harmonic and seismic response of a wide range of SDOF systems. A newly developed semi-active resettable device is proposed to reduce the seismic response of a one-fifth scale structure. The device is investigated as part of a resettable tendon system installed in the structure. Nonlinear dynamic analyses are performed to determine the optimal configuration of the resettable tendon in the structure. Several shake table tests are performed on the structure equipped with two resettable devices. The dynamic characteristics of the structure and the devices are described. Various earthquake records at different levels of intensity are used during the seismic testing. Different control laws are employed to manipulate the hysteretic behaviour of the devices. The results of the shake table tests validate the effectiveness of the resettable devices to reduce the seismic response of structures. Analytical studies are performed to determine the optimal utilization of the resettable devices in a twelve-storey reinforced concrete building. The seismic performance of the structure is discussed in relation to the number and distribution of the devices. Inelastic time-history analyses are carried out to assess the effectiveness of the devices to reduce the seismic response of the building. The impact of various tendon arrangements and different control laws on the earthquake response is investigated. Relevant issues for the implementation of the resettable devices in actual building systems are identified. Finally, a new measurement concept based on the use of the fibre-optic gyroscope is proposed to measure rotation rates, rotations, displacements and inter-storey drifts of civil engineering structures. FOGs are compact, easy to install and, unlike conventional linear potentiometers, do not require a fixed reference frame to operate. Measurements recorded during the seismic testing of the one-fifth scale structure and displacement measurements at the Sky Tower in Auckland validate the suitability of the FOGs for applications in civil engineering.

This dissertation describes the analytical research as part of a comprehensive research program to develop a new floor anchorage system for seismic resistant design, termed the Inertial Force-limiting Floor Anchorage System (IFAS). The IFAS intends to reduce damage in seismic resistant building structures by limiting the inertial force that develops in the building during earthquakes. The development of the IFAS is being conducted through a large research project involving both experimental and analytical research. This dissertation work focuses on analytical component of this research, which involves stand-alone computational simulation as well as analytical simulation in support of the experimental research (structural and shake table testing). The analytical research covered in this dissertation includes four major parts: (1) Examination of the fundamental dynamic behavior of structures possessing the IFAS (termed herein IFAS structures) by evaluation of simple two-degree of freedom systems (2DOF). The 2DOF system is based on a prototype structure, and simplified to represent only its fundamental mode response. Equations of motions are derived for the 2DOF system and used to find the optimum design space of the 2DOF system. The optimum design space is validated by transient analysis using earthquakes. (2) Evaluation of the effectiveness of IFAS designs for different design parameters through earthquake simulations of two-dimensional (2D) nonlinear numerical models of an evaluation structure. The models are based on a IFAS prototype developed by a fellow researcher on the project at Lehigh University. (3) Development and calibration of three-dimensional nonlinear numerical models of the shake table test specimen used in the experimental research. This model was used for predicting and designing the shake table testing program. (4) Analytical parameter studies of the calibrated shake table test model. These studies include: relating the shake table test performance to the previous evaluation structure analytical response, performing extended parametric analyses, and investigating and explaining certain unexpected shake table test responses. This dissertation describes the concept and scope of the analytical research, the analytical results, the conclusions, and suggests future work. The conclusions include analytical results that verify the IFAS effectiveness, show the potential of the IFAS in reducing building seismic demands, and provide an optimum design space of the IFAS.