Implementing Fiber-reinforced, Self-consolidating Concrete as a Repair Material for AASHTO Prestressed Concrete Girders PDF Download
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Author: Jacob G. Choate
Publisher:
ISBN:
Category : Concrete bridges
Languages : en
Pages : 278
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Book Description
Author: Jacob G. Choate
Publisher:
ISBN:
Category : Concrete bridges
Languages : en
Pages : 278
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Book Description
Author: Paul Zia
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 98
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Book Description
Author: Maher K. Tadros
Publisher: Transportation Research Board
ISBN: 0309118352
Category : Technology & Engineering
Languages : en
Pages : 76
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Book Description
This report establishes a user's manual for the acceptance, repair, or rejection of precast/prestressed concrete girders with longitudinal web cracking. The report also proposes revisions to the AASHTO LRFD Bridge Design Specifications and provides recommendations to develop improved crack control reinforcement details for use in new girders. The material in this report will be of immediate interest to bridge engineers.
Author: Kamal H. Khayat
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 181
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Book Description
The proposed research investigates the combined use of self-consolidating concrete (SCC) and fibers reinforcements to develop a novel repair material, fiber-reinforced self-consolidating concrete (FR-SCC) that can be used for the rehabilitation and strengthening of existing structures. Furthermore, the feasibility of using super workable concrete (SWC) reinforced with different types of fibers for new structural cast-in-place applications is investigated. The use of SCC matrix can greatly enhance the workability of fibrous mixtures along with incorporation of greater volume of fibers. SWC is a new type of flowable concrete with lower workability than SCC. Containing lower binder content can be more cost effective than SCC. SWC requires some mechanical consolidation energy to ensure proper filling of the formwork. Eight types of fibers, including a propylene synthetic fiber, five steel fibers and a hybrid steel and polypropylene synthetic fiber were investigated. Fibers were incorporated at a volume of 0.5% in FR-SCC and at 0.5% and 0.75% in FR-SWC. Two types of expansive agents (EA), Type G and Type K, were added to both concrete types to reduce shrinkage and enhance resistance to restrained shrinkage cracking. The optimized mixtures exhibited high workability, mechanical properties, and freeze/thaw durability. The incorporation of fibers with 4% Type-G EA in FR-SCC increased the 56-day flexural strength by up to 32%, and flexural toughness up to 23 times. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers (ST1) in FR-SCC made with 4% Type-G EA increased the elapsed time to cracking determined from restrained shrinkage ring test from 16 to 20 days compared to FR-SCC made with 0.5% ST1 fibers without EA. The use of ST1 steel fibers and 4% Type-G EA decreased the 1-year drying shrinkage by 48% compared to the reference SCC mixture without any fibers and expansive agent. In case of FR-SWC, the decrease in shrinkage was 37% compared to SWC. In addition, 20 monolithic full-scale beams were cast using different types of concrete, including conventional vibrated concrete (CVC), fiber-reinforced conventional vibrated concrete (FR-CVC), SCC, FR-SCC, SWC and FR-SWC. Twelve reinforced concrete beams were cast using CVC to fill two thirds of the beam height. They were then filled with five different types of FR-SCC and SCC to simulate beam repair in the tension zone. Findings indicated that macro fibers can be used with FR-SCC designated for repair with fiber length ≤ 2 in. (50 mm) up to 0.5% fiber volume. Macro fibers can be used with FR-SWC designated for construction with fiber length ≤ 2.6 in. (65 mm) up to 0.75% fiber volume. Fibers had great impact on structural performance of the full-scale monolithic beams. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers combined with 0.5 in. (13-mm) straight steel fibers at ratio 4 to1 (STST) with 4% Type-G EA increased toughness of FR-SWC beams by 95% compared to SWC beams and by 86% in case of 0.75% 5D fibers. Repair using FR-SCC increased the flexural capacity of the beam by 6% and the toughness by 110% in case of using 0.5% ST1 fibers with 4% Type-G EA.
Author: Fodhil Kassimi
Publisher:
ISBN:
Category :
Languages : en
Pages : 377
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Book Description
The use of self-consolidating concrete (SCC) in the concrete industry in cast-in-place applications, including repair applications, is growing given the various advantages offered in both fresh and hardened states. The present study deals with the design and performance of fiber-reinforced self-consolidating concrete (FR-SCC) as a repair material of concrete infrastructure. The study also considers the use of various steel and synthetic fibers (five fibers in total) that were used to produce FR-SCC and fiber-reinforced self-consolidating mortar (FR-SCM) that can be employed for structural and non-structural repair applications. The study evaluates the effect of material properties and mixture composition of the fibrous concrete and mortar on workability, mechanical, visco-elastic, durability, and structural behavior. The investigation that is presented in this thesis included the testing of 28 full-scale beams under four-point flexural loading. The majority of these beams were repaired by casting concrete to fill a relatively thin section along the tension zone of the beams. The repair technique was based on the FR-SCC characteristics including the maximum fiber volume and length. This technique required mixtures of high range of fluidity. The optimized FR-SCC and FR-SCM mixtures exhibited excellent flow characteristics along the 3.2-m long beams without blockage, segregation, nor debonding at the interface of repair-substrate concrete. Based on the structural characteristics of the composite beams, the overall performance of the beams repaired using the FR-SCC and FR-SCM was similar or higher (up to 2.6 times) than that of monolithic beams made with conventional vibrated concrete (CVC). The use of optimized FRSCC mixtures enabled the replacement of 50% of the tension steel reinforcement in repair sections; i.e., the number of bars in the tension zone decreased from three bars to two bars with the addition of fibers in the SCC without mitigating structural performance. The degree of prediction of crack width, cracking load/moment, ultimate loads, and deflection of various FR-SCC and FR-SCM mixture was evaluated using several design and code models. The results indicate that these code models can provide safe predictions for crack and ultimate loads, as well as crack width of FR-SCC. The deflection of FR-SCC is unsafe but predictable by these code models. In total, 18 large-scale beams were tested in four-point for flexural creep. FR-SCC incorporating steel fibers combined with expansive agent provided overall performance up to 10 times of that obtained with CVC with the same fiber type and volume. The cracking under constant load was reduced by 60% to 80% using self-consolidating fibrous mixtures made with or without expansion agents, compared to SCC without fibers. The best combination to reduce the cracking potential when the restrained shrinkage ring test was employed was obtained with SCC mixtures made with steel fibers and expansive agent. Models were elaborated to predict the time-to-cracking for FR-SCC and FR-SCM mixtures based on mixture modulus of elasticity and drying and autogenous shrinkages. The project involved extensive testing of highly flowable fibrous materials to determine drying shrinkage (nearly 260 prisms), modulus of rupture (nearly 180 prisms), as well as compressive and splitting tensile strengths and elastic modulus (nearly 2100 cylinders). Based on the results, models were proposed to predict these key material properties that affect the performance of FR-SCC and FR-SCM used in repair applications. In addition to FR-SCC, the investigation also was set to evaluate the feasibility of using fiber-reinforced superworkable concrete (FR-SWC) in construction and repair applications. Such highly flowable concrete that requires limited vibration consolidation can represent some advantages over FR-SCC (lower admixtures demand, lower risk of segregation, greater robustness, lower formwork pressure, etc.). The energy needed to ensure proper consolidation, using either vibration or rodding, applied on samples made with FR-SWC was determined. The energy requirement took into consideration the development of mechanical properties, the resistance to segregation, and the development of proper surface quality. The study also demonstrated the higher overall structural performance of optimized FR-SWC compared to the corresponding FR-SCC mixtures. The findings of the thesis on the design and performance of highly workable fiber-reinforced cementitious materials should facilitate the acceptance of such novel high-performance material in infrastructure construction and repair applications.
Author: Dennis R. Mertz
Publisher: Transportation Research Board
ISBN: 0309087694
Category : Political Science
Languages : en
Pages : 88
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Book Description
Rising awareness of and increased attention to sexual harassment has resulted in momentum to implement sexual harassment prevention efforts in higher education institutions. Work on preventing sexual harassment is an area that has recently garnered a lot of attention, especially around education and programs that go beyond the standard anti-sexual harassment trainings often used to comply with legal requirements. On April 20-21, 2021, the National Academies of Sciences, Engineering, and Medicine hosted the workshop Developing Evaluation Metrics for Sexual Harassment Prevention Efforts. The workshop explored approaches and strategies for evaluating and measuring the effectiveness of sexual harassment interventions being implemented at higher education institutions and research and training sites, in order to assist institutions in transforming promising ideas into evidence-based best practices. Workshop participants also addressed methods, metrics, and measures that could be used to evaluate sexual harassment prevention efforts that lead to change in the organizational climate and culture and/or a change in behavior among community members. This publication summarizes the presentations and discussion of the workshop.
Author: Bassem O. Andrawes
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 56
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Author: רבקה משולח
Publisher:
ISBN:
Category : Theater programs
Languages : en
Pages : 28
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Book Description
Author: Anthony David Miller
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
Keywords: impact damage, flexure modeling, shear modeling, CFRP repair, prestressed concrete, bridge girder.
Author: Perumalsamy Balaguru
Publisher: CRC Press
ISBN: 0203926889
Category : Technology & Engineering
Languages : en
Pages : 348
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Book Description
High strength fibre composites (FRPs) have been used with civil structures since the 1980s, mostly in the repair, strengthening and retrofitting of concrete structures. This has attracted considerable research, and the industry has expanded exponentially in the last decade. Design guidelines have been developed by professional organizations in a number of countries including USA, Japan, Europe and China, but until now designers have had no publication which provides practical guidance or accessible coverage of the fundamentals. This book fills this void. It deals with the fundamentals of composites, and basic design principles, and provides step-by-step guidelines for design. Its main theme is the repair and retrofit of un-reinforced, reinforced and prestressed concrete structures using carbon, glass and other high strength fibre composites. In the case of beams, the focus is on their strengthening for flexure and shear or their stiffening. The main interest with columns is the improvement of their ductility; and both strengthening and ductility improvement of un-reinforced structures are covered. Methods for evaluating the strengthened structures are presented. Step by step procedures are set out, including flow charts, for the various structural components, and design examples and practice problems are used to illustrate. As infrastructure ages worldwide, and its demolition and replacement becomes less of an option, the need for repair and retrofit of existing facilities will increase. Besides its audience of design professionals, this book suits graduate and advanced undergraduate students.
