Author: Shuk-Lei Lau
Publisher:
Published: 2017-01-26
Total Pages:
ISBN-13: 9781361234235
DOWNLOAD EBOOK →This dissertation, "Rehabilitation of Reinforced Concrete Beam-column Joints Using Glass Fibre Reinforced Polymer Sheets" by Shuk-lei, Lau, 劉淑妮, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled REHABILITATION OF REINFORCED CONCRETE BEAM-COLUMN JOINTS USING GLASS FIBRE REINFORCED POLYMER SHEETS Submitted by LAU Shuk Lei For the degree of Master of Philosophy At The University of Hong Kong in August 2005 Shear failure of beam-column joints is one of the main causes of collapse of many moment-resisting reinforced concrete (RC) frame buildings in recent earthquakes. Evidence from recent earthquakes indicates that deficient beam-column joints can jeopardize the integrity of the entire structure. The brittle joint shear failure also significantly reduces the overall ductility of structures, resulting in dangerous failure mechanisms. A variety of techniques have been developed to strengthen beam-column joints. These techniques include the use of steel and concrete jacketing. More than a decade ago, a new technique for strengthening structural elements emerged. This involves the use of fibre-reinforced polymer (FRP) as externally bonded reinforcement in critical regions of RC elements. FRP materials have a number of advantages over steel and concrete that make them an ideal material in strengthening deficient beam-column joints. Most of the FRP-strengthening schemes developed for beam-column joints so far have a limited range of applicability and limitations. The aim of this study is to develop a practical rehabilitation system for strengthening and repairing deficient RC beam-column joints. Two rehabilitation schemes aiming at improving the shear strength of beam-column joints were proposed. Glass fibre-reinforced polymer (GFRP) was adopted in the study because it has a higher fracture strain than carbon fibre. A total of seven half-scale RC beam-column joint specimens were investigated, all without transverse reinforcement in the joint region. Five of them were fabricated and tested in this study, while the other two specimens, which served as reference specimens, were fabricated and tested earlier in a separate study. The five specimens produced in this study were rehabilitated with GFRP composite sheets to evaluate the effectiveness of the rehabilitation schemes. Three of the specimens were tested under reversed cyclic quasi-static loading to simulate the seismic effects on structures, and the other two specimens were tested under monotonic loading. Experimental results illustrated that the GFRP-rehabilitated joints exhibited an improved displacement ductility, a lower rate of strength degradation and a higher cumulative energy dissipation than the reference specimens. The strain reduction in steel reinforcement for the rehabilitated specimens exceeded 45%, demonstrating the efficiency of the external GFRP reinforcement. The importance of reliable anchorage methods in preventing premature delamination of FRP was also addressed. DOI: 10.5353/th_b3200163 Subjects: Concrete construction - Joints Reinforced concrete construction - Repairing Fibrous composites Fiber-reinforced concrete
Author: Jenifer Ann Albright
Publisher:
Published: 2022
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOK →Reinforced concrete (RC) moment resisting frames (MRF) have traditionally been one of the most common structural systems used to resist lateral loads induced by seismic activities. Earthquake ground-shaking seismic loads cause displacement of the building, also known as “sway” or “drift”, over multiple displacement cycles. The RC MRF, which consists of beams, columns, and beam-column joints, is designed to achieve a ductile response through optimized detailing and proportioning to resist flexural, axial, and shear forces transferred into the structure during building sway. The current accepted design procedure for seismically active locations is to provide capacity protected members. This theory states that the columns of the beam-column system should be stronger than the beams, such that during ultimate design loads the beams will fail prior to the columns, which is a ductile failure mechanism.There is an abundant desire to improve reliability, safety, economic costs, efficiency, and performance of MRFs. To that end, many innovative MRF solutions have been proposed over the years, including precast or partially precast systems, steel braced RC joints, and concrete-steel composite systems. Among the many novel suggestions, the NPS system represents a recent and promising solution which aims to be unique, advanced, and technologically efficient to attain ductile MRFs capable of high seismic performance. The NPS system is a steel concrete composite system, consisting of a steel HSS square, circular, or rectangular cross sectional column with self-supporting beams made of a flexural steel plate bottom chord with a welded truss (to act as the beam shear reinforcement) and undeformed top rebar steel. The system is completed with concrete cast in-situ. Use of partially prefabricated elements as well as in-place elements represents a delicate challenge of providing adequate moment continuity of the beam-column joint while ensuring the integrity of the joint region. To attempt to solve this challenge and achieve moment continuity, integrative steel elements are inserted through the joint after the beam trusses have been set in position but before the concrete is cast. Prior to this project, no experimental evidence was available to support the dependability of this moment continuity configuration. This thesis presents and discusses the results of an experimental program of nine (five interior and four exterior) full-scale 2D concrete-steel composite NPS beam column joints, and two traditionally Eurocode compliant reinforced concrete beam-column joints (one interior and one exterior). This program was developed to investigate and ultimately assess the seismic performance of the NPS system with specific consideration to the integrative steel elements providing moment continuity. The different moment continuity solutions adopted included the use of integrated truss elements (i.e., continuity trusses) and straight or hooked deformed bars (i.e., continuity bars). Additional variables considered included the level of shear protection of the joint “panel” region and the presence/absence of additional shear reinforcement in the beam end-regions (i.e., the “critical” or “plastic hinge” length). This thesis provides a detailed discussion of the experimental outcomes and a careful analysis of the observed response mechanisms and any subsequent design implications. The results of the experimental investigation were extrapolated to assess the performance of the specimen in terms of shear stress and shear strain in the joint, sub-component contribution to the total drift, energy dissipation, peak and residual strength, initial and residual stiffness, and ductility. The response of the NPS specimens was compared against a tangible target performance from the traditionally Eurocode compliant RC specimens. The experimental results demonstrated that, in at least one configuration, the NPS system can effectively achieve modern proficient seismic performance objectives. This can be seen through equivalent or superior performance criteria comparison to their traditional RC counterparts.