Ugur Ersoy

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.

IN SERVICE SEISMIC STRENGTHENING OF RC FRAMED BUILDINGS

An innovative non-evacuation retrofitting technique has been developed for RC buildings, which form the major portion of the existing stock in Turkey. The introduction of cast-in-place RC infill walls, connected to existing frame members, is known to be very effective in improving the overall seismic performance. However, this technique is not suitable since it involves messy construction work and requires evacuation. The idea behind the proposed method is to transform existing hollow masonry infill walls into strong and rigid infill walls by reinforcing them with relatively high strength precast concrete panels epoxy-glued to the wall and dowel connected to the frame members to enhance the lateral stiffness of the frame. The panels to be assembled are small enough to be handled by two workers. All specimens were tested to failure under reversed cyclic quasi-static lateral loading and constant vertical load. All strengthened specimens exhibited superior performance compared to the reference specimens designed to represent the present state of ordinary RC frames with hollow brick infill walls plastered on both sides.

LESSONS FROM RECENT EARTHQUAKES IN TURKEY AND SEISMIC REHABILITATION OF BUILDINGS

This paper discusses recent earthquakes in Turkey. Large-scale seismic rehabilitation projects carried out by the Middle East Technical University (METU) faculty and staff on moderately damaged reinforced concrete structures are summarized. Research at METU related to seismic rehabilitation is presented, emphasizing infilled frames, a system used extensively in Turkey.

Occupant Friendly Seismic Retrofit (OFR) of RC Framed Buildings

An innovative non-evacuation retrofitting technique is being developed for Re buildings. The introduction of cast-in-place Re infill walls is very effective, but involves messy construction work and requires evacuation. The proposed method transforms existing hollow masonry infill walls by reinforcing them with precast concrete panels epoxy glued to the wall and frame members. Three tests have so far been performed under reversed cyclic loading. The first specimen was an ordinary Re frame with hollow brick infill walls, to serve as a reference specimen. The infills of the other two specimens were strengthened with epoxy glued precast concrete panels. Both strengthened specimens exhibited superior behaviour and capacity, indicating the potential of the retrofitting technique.

A Comparative Study on the Strengthening of RC Frames

In order to improve the behavior of buildings and in order to prevent total collapse, necessary amount of strengthening must be provided. The frame of the test specimen (1/3 scaled, 2-story, 3-bay) is detailed such that it has the common deficiencies of existing buildings in Turkey. Two types of strengthening techniques, namely introducing an infill RC wall, and CFRP strengthened hollow clay tile wall, are investigated. The test specimens are subjected to reversed cyclic quasi-static loading. By means of special transducers, axial force, shear force and bending moment at the base of the exterior columns are measured. Strength, stiffness, and story drifts of the test specimen are determined.

THE SEISMIC WELL-BEING OF BUILDINGS: DIAGNOSTICS AND REMEDIES

An overview of old as well as emerging problems and solutions in earthquake engineering with particular emphasis on the assessment and rehabilitation of seismically vulnerable buildings is presented. Earthquakes continue to result in vast loss of life and damage to property especially in populated urban areas. As a result, with an increase in both awareness and experience, traditional repair and strengthening techniques are giving way to more efficient methods applicable on a larger scale and with greater speed, in order to ensure that as many existing buildings as possible are retrofitted in advance of future earthquakes.

Seismic Rehabilitation of Reinforced Concrete Buildings

Turkey is located on one of the major earthquake belts of earth. In the past fifteen years five major earthquakes caused significant damages and loss of lives. Turkish government sponsored comprehensive repair and strengthening projects after each of these earthquakes.

Uniaxially Loaded High-Strength Concrete Spiral Columns

Three series of tests were carried out to investigate the behavior and strength of high and normal strength concrete spiral columns under uniaxial compressive loading. Five columns with normal strength and fourteen high strength spiral columns were tested. Normal strength and high strength steel were used as spiral reinforcement. The main variables investigated were: 91) volumetric ratio (varied from 0.008 to 0.038) and spacing of spiral reinforcement; (b) ratio of gross to core area (varied between 1.05 and 1.45); and (c) strength of spiral reinforcement. Strength increase and ductility due to the presence of spiral reinforcement were investigated. When high strength concrete is used, the minimum spiral reinforcement required by ACI 318-02 results in extremely small spacing as the ratio of the gross to core area increases. Spacing of the spiral reinforcement can be increased to reasonable values if higher strength steel is used. During the tests it was observed that the columns having high strength spiral reinforcement behaved well, and had adequate ductility.

Bringing to Buildings the Healing Touch

Civilization and civil engineering are intimately connected, and few animate — inanimate relationships are more enduring than those between human beings and their built environment. This interactive relationship goes back thousands of years. The assessment of how a building will react to a natural disaster like an earthquake requires a detailed examination of the architectural features and engineering design. Structural damage can always be investigated after it has occurred, but the challenge is to pre-empt such damage by suitably equipping a building in advance to resist the onslaught of disaster.