Guney Ozcebe

RESPONSE OF REINFORCED CONCRETE COLUMNS TO SIMULATED SEISMIC LOADING

Response of reinforced concrete columns to seismic loading was investigated experimentally. Full-scale columns were tested under slowly applied lateral reversals. Both unidirectional and bidirectional loadings were included. Columns with and without axial loads, including variable axial tension and compression, were tested. The test parameters included: axial load, shear/confinement reinforcement, and deformation path. Test results indicate that axial loads have a significant influence on hysteretic response of columns. Column capacity changes with the concurrent level of axial load, axial compression reduces column response, and bidirectional load cycles can produce severe strength and stiffness degradation.

Seismic assessment and rehabilitation of existing buildings

Bringing to Buildings the Healing Touch.- The Velocity of Displacement.- Preliminary Seismic Vulnerability Assessment of Existing Reinforced Concrete Buildings In Turkey.- Parameters Affecting Damageability of Reinforced Concrete Members.- Parameters Affecting Damageability of Reinforced Concrete Members.- Peak Ground Velocity Sensitive Deformation Demands and a Rapid Damage Assessment Approach.- Simple Survey Procedures for Seismic Risk Assessment in Urban Building Stocks.- The Use of Microtremors for Soil and Site Characterisation and Microzonation Applications.- Estimation of Earthquake Damage Probabilities for Reinforced Concrete Buildings.- Just How Prescient are our Building Damage Predictions?.- Condition Assessment Techniques Used for Non-Building Structures.- Seismic Assessment of Existing RC Buildings.- Experimental Research on Vulnerability and Retrofitting of Old-Type RC Columns under Cyclic Loading.- Earthquake Engineering, Seismic Vulnerability Assessment and Seismic Rehabilitation in Colombia.- Strengthening of Infilled Walls with CFRP Sheets.- Structural Behaviour of Ordinary RC Bare and Brittle Partitioned Frames with and Without Lap Splice Deficiency.- Seismic Retrofit of R/C Frames with CFRP Overlays.- Experimental Response of a Precast Infill Wall System.- A Comparative Study on The Strengthening of RC Frames.- Occupant Friendly Seismic Retrofit (OFR) of RC Framed Buildings.- Seismic Retrofit of Reinforced Concrete Structures.- Experimental and Analytical Investigation of 1/3-Model R/C Frame-Wall Building Structures PART I (Model Design and Analytical Evaluation of Dynamic Characteristics of the Model).- II (Nonlinear Analytical Prediction of Structural Behavior).- A Building Code is of Value only if it is Enforced.- Educational Aspects of SfP977231 - Spreading the Insight.- Acknowledgments.

Advances in earthquake engineering for urban risk reduction

Contributing Authors.Preface. Foreword. From Duzce to the City.- M. Sozen.- Recent Advances in the Seismic Rehabilitation of Reinforced Concrete Buildings in Japan S. Sugano.- Concrete or FRP Jacketing of Concrete Columns for Seismic Retrofitting S.N. Bousias et al.- In Service Seismic Strenghtening of RC Framed Buildings T. Tankut et al.- An Equivalent Linearization Procedure for Displacement-Based Seismic Assessment of Vulnerable RC Buildings M. S. Gunay, H. Sucuoglu.- A Displacement-Based Adaptive Pushover for Assessment of Buildings and Bridges R. Pinho et al.- In Defence of Zeytinburnu G. Ozceb et al.- Automated Post-Earthquake Damage Assessment of Instrumented Buildings F. Naeim et al.- A Detailed Seismic Performance Assessment Procedure for RC Frame Buildings A. Yakut, E. Erduran.- Assessment of Seismic Fragility Curves for low-and-mid-rise Reinforced Concrete Frame Buildings using Dusce Field Database M. A. Erberik, S. Cullu.- Seismic Rehabilitation of low-rise Precast Industrial Buildings in Turkey S.L. Wood.- Seismic Risk Mitigation through Retrofitting Non-Ductile Concrete Frame Systems M. Saatcioglu.- Hyde-systems for Earthquake Protection of Residential Buildings U.E. Dorka, S. Gleim.- Learning from Earthquakes to improve Rehabilitaion Guidelines for Reinforced Concrete Buildings J.0. Jirsa.- Seismic Risk Scenarios for an Efficient Seismic Risk Management: The Case of Thessaloniki (Greece) K.Pitilakis et al.-The Multi-Axial Full-Scale Sub-Structured Testing and Simulation (Must-Sim) Facility at the University of Illinois at Urbana-Champaign A. S. Elnashai et al.- Recent Experimental Evidence on the Seismic Performance of Rehabilitation Techniques in Mexico S.M. Alcoce et al.- CFRP Overlays in strengthening of Frames with Column Rebar Lap Splice Problem S.t Ozden, U. Akguzel.- Seismic Retrofit of Infilles Reinforced Concrete Frames with CFRP Composites E. Yukse et al.-Axial Behavior of RC Columns Retrofitted with FRP Composites A.Ilkiet al.- Collapse of Lightly Confined Reinforced Concrete Frames during Earthquakes J.P. Moehie et al.- Evaluation of Approximate Nonlinear Procedures for Observed Response of a Shear Wall Structure P. Gulkan et al.-Assessment and Retrofit of Full-scale Models of Existing RC Frames A. V. Pinto, F. Taucer.- Development of Internet Based Seismic Vulnerability Assessment Tools A. Turer, B.Yalim.-A Comparative Study of Displecement, Force and Pushover Approaches for Design of Continuous Span Bridges M.Calvi et al.- Seismic Rehabilitation using Infill Wall Systems R.J. Frosch.- Shake Table Experiment on One-Story RC Structure with and without Masonry Infill A.Hashemi, K.M. Mosalam.- Opportunities and Challenges of Modern Concrete Technology in Earthquake Hazard Mitigation C. Meyer.- Shaking Table Tests of Scaled RC Frame Models for Investigation of Validity and Applicability of Different Retrofitting Techniques M.Garevsk et al.-Analysis of Infilled Reinforced concrete Frames Strengthened with FRPS B.Binici et al.- Tensile Capacities of CFRP Anchors G.Ozdemir, U.Akyuz.- Using a Displacement-Based Approach for Earthquake Loss Estimation J.J. Bommer et al.-Nonlinear Drift Demands on Moment-Resisting Stiff Frames A.Mettin, S. Akkar.- The Seismic Well-being of Buildings: Diagnostics and Remedies S.Tanvir Wasti, U.Ersoy.- Envoi.- Acknowledgements.

Numerical Study on CFRP Strengthening of Reinforced Concrete Frames with Masonry Infill Walls

AbstractIn the last decade, a new strengthening methodology has been developed for reinforced concrete (RC) frames with hollow clay tile (HCT) infill walls by means of diagonally applied carbon fiber–reinforced polymer (CFRP) fabrics. In the experimental part of a study conducted by the authors, this user-friendly methodology was experimentally investigated considering different aspect (height/width) ratios of the infill walls. In this study, first a numerical model of the FRP strengthened infill walls strengthened with the proposed methodology is developed. Afterwards, the numerical simulation results are validated by use of experimental response curves and finally, a parametric study, which further investigates the effect of aspect ratio of HCT infill walls is presented.

Evaluation of the Predictive Models for Stiffness, Strength, and Deformation Capacity of RC Frames with Masonry Infill Walls

AbstractBuildings with masonry infill walls (MIWs) in reinforced concrete (RC) frames are commonly used all around the world. It is well known that infill walls may affect the strength, stiffness, and displacement ductility of the structural system. Different approaches have been adopted in different codes and guidelines to consider the stiffness and strength contribution of MIWs on RC frame behavior. This study compares the ability of the existing guidelines to estimate stiffness, strength, and deformability of RC frames with MIWs by using a compiled experimental database composed of 51 experiments from 24 different studies. Alternative expressions are proposed in this study to provide improved estimates of stiffness and deformability of infilled RC frames.

Preliminary Seismic Vulnerability Assessment of Existing Reinforced Concrete Buildings in Turkey

The vulnerability assessment method, described in the companion paper [1], relies on a damage score, which is compared with an appropriate cutoff value to identify the buildings as “safe”, “unsafe” or “intermediate”. The cutoff values are considered to be valid for damaging earthquakes and regions similar to DUzce, where the data was gathered. To generalize the procedure, the variability of ground motion with respect to soil properties and the distance to source needs to be incorporated. This was done by modifying the cutoff values based on the above factors. Sites are classified according to the Turkish Seismic Code’s [2] definitions based on the shear wave velocity. Various attenuation relations are used to account for the variation of the ground motion with distance and the soil type.

Testing and analysis of infilled reinforced concrete frames strengthened with CFRP reinforcement

There is an excessive demand for the rehabilitation of frame-type RC buildings which do not satisfy current seismic code provisions. Therefore, it is imperative to develop user-friendly strengthening methodologies which do not necessitate the evacuation of the building during rehabilitation period. The aim of this study was to strengthen the masonry infill walls by means of diagonal carbon fiber-reinforced polymer fabrics and to integrate them with the existing structural frame in order to form a new lateral load resisting system. This study investigated the possible effects of height-to-width ratio of the infills on the overall behavior attained by the previously developed rehabilitation methodology. In the first part of the study, eight 1/3 scaled, one-bay, two-story RC frames with two different aspect ratios were tested. The experimental results in terms of lateral stiffness, strength, drift, and energy dissipation characteristics of the specimens were discussed. In the second part, a numerical study of the frames was conducted to estimate the non-linear behavior of the specimens.

Repair and strengthening of reinforced concrete columns with CFRPs

In this study, seismic retrofitting of undamaged and moderately damaged RC columns with CFRP was investigated. The experimental program was conducted on five RC columns with inadequate tie spacing, 90-degree hooks at tie ends, and plain (undeformed) reinforcing bars. Columns were tested under a constant axial load of 27% of axial capacity and under reversed lateral cyclic loading. The primary objective of this study was to investigate the influence of sustained axial load during repairing, damage, and corner-rounding radius of CFRP wraps on the seismic performance of RC columns. Improved performance in terms of ductility, dissipated energy, and secant-stiffness degradation was observed for the CFRP strengthened columns. Reducing the corner-rounding radius deteriorated the seismic behavior of the columns, while the stiffness degradation response remained unaffected. The sustained axial load during repairing had only minor effect on column behavior. After CFRP repairing, the increase in yield drift ratio and curvature was observed to be in proportion with the corresponding consumed ductility values during damage cycles. A drift-based design equation for FRP repaired columns was proposed that considers the damage amount and axial load level as the major parameters as consistent with the experimental results.

STATISTICAL SEISMIC VULNERABILITY ASSESSMENT OF EXISTING REINFORCED CONCRETE BUILDINGS IN TURKEY ON A REGIONAL SCALE

A statistical procedure, called discriminant analysis, is used to develop a model for the preliminary assessment of the seismic vulnerability of low- to medium-rise (2-7 storey) reinforced concrete buildings. The earthquake damage data compiled in Düzce province after the 12 November 1999 Düzce earthquake formed the damage database. Number of storeys, minimum normalised lateral stiffness index, minimum normalised lateral strength index, normalised redundancy score, soft storey index and overhang ratio are selected as the basic damage inducing variables. Two discriminant functions are derived in terms of these variables considering immediate occupancy and life safety performance levels. In the proposed preliminary seismic vulnerability assessment model, the discri-minant scores obtained from these two discriminant functions are combined in an optimal way and axe used to classify existing buildings as “safe”, “unsafe” and “requires further evaluation”. The optimality criterion imposed into the model is the minimisation of the misclassification rate of damage states causing collapse. The validity of the proposed model is checked by using the seismic damage data associated with recent earthquakes that occurred in Turkey. The consistency between the observed damage distribution and the predictions of the proposed model supports the effectiveness of the proposed model.

Strengthening of Brick Infilled Reinforced Concrete (RC) Frames with Carbon Fiber Reinforced Polymers (CFRP) Sheets

In Turkey, experimental research on seismic rehabilitation started at Middle East Technical University (METU) in 1969. Since then several research projects in this field leading to developing rehabilitation technologies have been carried out. Majority of these researches inquired the introduction of reinforced concrete infills to the selected bays of the frames. This method developed at METU was applied to a significant number of seismically deficient RC buildings and it was proven to be effective in the past earthquakes. Application of this method, however, necessitates evacuation of the building during construction. Urgent developments of new strengthening methodologies which do not require the evacuation of the building, therefore, become imperative. Subsequently, a research project was initiated at METU Structural Mechanics Laboratory in 2001, which aimed to strengthen the existing masonry infill walls by means of CFRP sheets, to convert these walls into structural elements forming a new lateral load resisting system. As a continuation of the former project, in this study eight 1/3 scaled 2-story 1-bay RC frames, having the common deficiencies of the structures in Turkey, were tested. In this chapter, the test results are revealed in terms of lateral strength, stiffness and energy dissipation characteristics of the specimens.