assessed and strengthened. Performance evaluation of deficient buildings has become a major concern due to devastating earthquakes in the past. In order to justify new provisions in design and assessment codes, experiments and analyses are inherently necessary. In this thesis study, investigations into the behaviour of two deficient reinforced concrete frames built at Middle East Technical University&rsquo / s Structural and Earthquake Laboratory and tested via pseudo-dynamic tests were made. These frames were modelled on the OpenSees platform by following methods of analyses outlined in the Turkish Earthquake Code of 2007 (TEC 2007) and ASCE/SEI-41-06. Both deficient frames were essentially the same, with the only difference being the presence of insufficient lap splices, which was the focus of the study. Time history performance assessments were conducted in accordance to TEC 2007&rsquo / s damage state limits and ASCE/SEI 41-06&rsquo / s performance limits. The damages observed matched the performance levels estimated through the procedure outlined in TEC 2007 rather well. Specific to the specimen with lap splice deficiencies, ASCE/SEI 41-06 was overly conservative in its assessments. TEC 2007&rsquo / s requirements for lap splice lengths were found to be conservative in the laboratory and are able to tolerate deficiencies up to 25% of the required length. With respect to mathematical models, accounting for materials in deficient systems by using nominal but reduced strength properties is not very efficient and unless joint deformations are explicitly accounted for, local deformations cannot be captured.

Hybrid testing is an emerging technique for system emulation that uses a transfer system composed of actuators and sensors to couple physical tests of a critical component or substructure to a numerical simulation of the remainder of a system and its complete operating environment. The realisation of modern real-time hybrid tests for multi-body contact-impact problems often proves infeasible due to (i) hardware with bandwidth limitations and (ii) the unavailability of control schemes that provide satisfactory force and position tracking in the presence of sharp non-linearities or discontinuities. Where this is the case, the possibility of employing a pseudo-dynamic technique remains, enabling tests to be conducted on an enlarged time scale thus relaxing bothbandwidth and response time constraints and providing inherent loop stability. Exploiting the pseudo-dynamic technique, this thesis presents the development of Robotic Pseudo-Dynamic Testing (RPsDT), a dedicated method that specifically targets the realisation of hybrid tests for multi-body contact-impact problems using commercial off- the shelve (COTS) industrial robotic manipulators. The RPsDT method is evaluated in on-ground studies of air-to-air refuelling (AAR) maneuvers with probe-hose-drogue systems where the critical contact and coupling phase is tested pseudo-dynamicallywith full-scale refuelling hardware while the flight regime is emulated in simulation. It is shown that the RPsDT method can faithfully reproduce the dominant contact impact phenomena between probe and drogue while minor discrepancies result from the absence of rate-dependant damping in the force feedback measurements. In combination with full-speed robot controlled contact tests, reliable estimates for impact forces, strain distributions and drogue responses to off-centre hits are obtained providing extensive improvements over current predictive capabilities for the in-flight behaviour of refuelling hardware and it is concluded that the technique shows great promise for industrial applications.

Considering the deficiencies frequently observed in the existing reinforced concrete buildings, detailed assessment and rehabilitation must be conducted to avoid significant life and value loss in seismic zones. In this sense, performance based evaluation methods suggested in the regulations and codes must be examined and revised through experimental and analytical research to provide safe and economical rehabilitation solutions. In this study, seismic behavior of three reinforced concrete frames built and tested in Middle East Technical University Structural Mechanics Laboratory is examined. The specimens are extracted from a typical interior frame of 3-story 3-bay reinforced concrete structure. One of the specimens has compliant design according to Turkish Earthquake Code (2007) and each of the other two specimens represents different types of deficiencies in terms of material strength and detailing. The test specimens were modeled using different modeling approaches and nonlinear dynamic analyses were conducted on the numerical models. Results of continuous pseudo-dynamic testing of three ground motions are presented and compared with the numerical simulations on models. Calibrated finite element models were used for evaluation of performance assessment procedure of Turkish Earthquake Code (2007) and further investigation on local deformation components in light of experimental findings and observations. Deformation sources of columns and joints were studied in terms of their interaction and contributions to the total drift. Estimated plastic hinge lengths of columns were compared with the experimental observations and the proposed expressions in the literature.

No description available.

This study presents the nonlinear design of a state space controller to control hydraulic actuators under displacement control, specifically for real-time pseudo-dynamic testing applications. The proposed control design process uses the nonlinear state space model of the dynamics of the system to be controlled; and utilizes state feedback linearization through a transformation of the state variables. Comparisons of numerical simulation results for linear state-space and nonlinear state-space controllers are given. Also robustness of the control design with respect to identified parameters is investigated. It is shown that a controller with improved performance can be designed using nonlinear state space control design techniques, provided that a representative model of the system is available. / Structural Engineering

Pseudo-dynamic testing was employed to observe the seismic performance of three different retrofit methods on two story three bay reinforced concrete frame structures. The three test frames have hollow clay tile (HCT) infills in the central bay. All of the test frames represent the seismic deficiencies of the Turkish construction practice such as use of plain reinforcing bars, low strength concrete and insufficient confining steel. Two non-invasive and occupant friendly retrofit schemes suggested in the Turkish Earthquake Code, namely use of Fiber Reinforced Polymers and precast concrete panels integrated on the HCT infills and traditional approach of adding concrete infill wall were employed. Specimens were subjected to three different scale levels of North-South component of Duzce ground motion. Reference specimen experienced severe damage at 100% scale level and reached collapse stage due to the loss of integrity of the infill wall and significant damage on the boundary columns. The retrofitted test structures were able to survive the highest level 140% Duzce ground motion. Test results confirmed the success of the retrofit methods for simulated earthquake loads.

Design of retaining structures depends upon the load which is transferred from backfill soil as well as external loads and also the resisting capacity of the structure. The traditional safety factor approach of the design of retaining structures does not address the variability of soils and loads. The properties of backfill soil are inherently variable and influence the design decisions considerably. A rational procedure for the design of retaining structures needs to explicitly consider variability, as they may cause significant changes in the performance and stability assessment. Reliability based design enables identification and separation of different variabilities in loading and resistance and recommends reliability indices to ensure the margin of safety based on probability theory. Detailed studies in this area are limited and the work presented in the dissertation on the Optimum design of retaining structures under static and seismic conditions: A reliability based approach is an attempt in this direction. This thesis contains ten chapters including Chapter 1 which provides a general introduction regarding the contents of the thesis and Chapter 2 presents a detailed review of literature regarding static and seismic design of retaining structures and highlights the importance of consideration of variability in the optimum design and leads to scope of the investigation. Targeted stability is formulated as optimization problem in the framework of target reliability based design optimization (TRBDO) and presented in Chapter 3. In Chapter 4, TRBDO approach for cantilever sheet pile walls and anchored cantilever sheet pile walls penetrating sandy and clayey soils is developed. Design penetration depth and section modulus for the various anchor pulls are obtained considering the failure criteria (rotational, sliding, and flexural failure modes) as well as variability in the back fill soil properties, soil-steel pile interface friction angle, depth of the water table, total depth of embedment, yield strength of steel, section modulus of sheet pile and anchor pull. The stability of reinforced concrete gravity, cantilever and L-shaped retaining walls in static conditions is examined in the context of reliability based design optimization and results are presented in Chapter 5 considering failure modes viz. overturning, sliding, eccentricity, bearing, shear and moment failures in the base slab and stem of wall. Optimum wall proportions are proposed for different coefficients of variation of friction angle of the backfill soil and cohesion of the foundation soil corresponding to different values of component as well as lower bounds of system reliability indices. Chapter 6 presents an approach to obtain seismic passive resistance behind gravity walls using composite curved rupture surface considering limit equilibrium method of analysis with the pseudo-dynamic approach. The study is extended to obtain the rotational and sliding displacements of gravity retaining walls under passive condition when subjected to sinusoidal nature of earthquake loading. Chapter 7 focuses on the reliability based design of gravity retaining wall when subjected to passive condition during earthquakes. Reliability analysis is performed for two modes of failure namely rotation of the wall about its heel and sliding of the wall on its base are considering variabilities associated with characteristics of earthquake ground motions, geometric proportions of wall, backfill soil and foundation soil properties. The studies reported in Chapter 8 and Chapter 9 present a method to evaluate reliability for external as well as internal stability of reinforced soil structures (RSS) using reliability based design optimization in the framework of pseudo static and pseudo dynamic methods respectively. The optimum length of reinforcement needed to maintain the stability against four modes of failure (sliding, overturning, eccentricity and bearing) by taking into account the variabilities associated with the properties of reinforced backfill, retained backfill, foundation soil, tensile strength and length of the geosynthetic reinforcement by targeting various component and system reliability indices is computed. Finally, Chapter 10 contains the important conclusions, along with scope for further work in the area. It is hoped that the methodology and conclusions presented in this study will be beneficial to the geotechnical engineering community in particular and society as a whole.