Download or read book Bond Behaviour of Steel Reinforcing Bars Embedded in Ultra High Performance Steel Fiber Reinforced Concrete written by Elisabeth Rita Saikali and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra-High-Performance Steel Fiber Reinforced Concrete (UHP-SFRC) is an emerging concrete considered as an optimal, durable material that can substitute conventional concrete owing to its distinct fresh and hardened properties. Thus, it is essential to understand the mechanism of stress transfer between this concrete and conventional reinforcement that permits the composite action of both materials. A four-point bending test program (FPBT) was arranged and conducted on 19 beams designed for the bond development to occur in the constant moment region along a short embedment length in order to achieve a uniform distribution of bond stresses, enabling measurement of bond strength through reverse engineering of beam strength and deformation. Additional material testing was conducted on prisms under 4-point loading in order to extract the mechanical properties for all material mixes considered. The bond-specimens failed either by pullout or by cone formation with minimal deterioration of the concrete cover, illustrating the high confinement provided by the novel concrete surrounding the bar in tension. The bond strength was determined to be directly proportional to the tensile strength capacity of the design mix, where for the strongest material the bond strength was approximately 30 MPa. Moreover, the test results indicated a very ductile flexural beam response accompanied by significant mid-span deflection reaching 27 mm and substantial bar-slip values attaining 19 mm. Different UHP-SFRC mixes, concrete covers, and embedment lengths were considered. A numerical model was developed to simulate the FPBT using a nonlinear finite element analysis platform, VecTor2, with the ability to model this novel concrete. This high bond strength provided by the concrete cover enables a significant reduction in the design development length as compared to what is used today for conventional concrete.

Download or read book High performance Hybrid fibre Concrete written by Ivan Marković and published by IOS Press. This book was released on 2006 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In the research project presented in this PhD-thesis, an innovative type of fibre concrete is developed, with improved both the tensile strength and the ductility: the Hybrid-Fibre Concrete (HFC). The expression "Hybrid" refers to the "hybridisation" of fibres: short and long steel fibres were combined together in one concrete mixture. This is opposite to conventional steel fibre concretes, which contain only one type of fibre. The basic goal of combining short and long fibres is from one side to improve the tensile strength by the action of short fibres, and from the other side to improve the ductility by the action of long fibres." "In this research project, all important aspects needed for the development and application of Hybrid-Fibre Concrete have been considered. In total 15 mixtures, with different types and amounts of steel fibres were developed and tested in the fresh state (workability) as well as in the hardened state (uniaxial tensile tests, flexural tests, pullout tests of single fibres and compressive tests). A new analytical model for bridging of cracks by fibres was developed and successfully implemented for tensile softening response of HFC. At the end, the utilisation of HFC in the engineering practice was discussed, including a case-study on light prestressed long-span beams made of HFC."--BOOK JACKET.

Download or read book Tensile Behaviour of Ultra High Performance Steel Fiber Reinforced Concrete written by Yuechen Yang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reinforcing bars are provided in reinforced concrete structures on account of conventional concretes negligible resistance to tension. However, corrosion of steel reinforcement inevitably occurs due to carbonation and chloride ingress, which significantly reduces the service life of structures. An alternative to this predicament is now feasible with the advent in cementitious material technologies, such as ultra-high-performance, self-consolidating, steel fiber reinforced concrete (UHP-SFRC). The keystone of safe and economically feasible designs with UHP-SFRC is dependant on its characterization in tension. Thus, in the present work, a detailed research study including both experimental and analytical components was conducted to investigate the tensile behaviour of UHP-SFRC: tensile strength was quantified and correlated through direct tension test (DTT), four-point bending test (FPBT), splitting tensile test, nonlinear finite element analysis and a calibrated empirical expression in relation to cylinder compressive strength. In addition, effects of important parameters on flexural strength including casting methodology, volumetric ratio of steel fibers, aspect ratio of bending prism and prism size were assessed. Moreover, the bilinear stress-strain and stress-crack mouth opening relationships of UHP-SFRC were derived according to the inverse analysis procedures proposed by Annex 8.1 of CSA-S6 (2018) and Annex U of CSA-A23.1 (2019). Furthermore, a nonlinear finite element analysis software, VecTor2, was employed to develop numerical models with the ability to match the response curves obtained from FPBT. Analytical results indicated that cracking strength of UHP-SFRC derived from the inverse analysis method was generally greater than those obtained from direct tension test, splitting tensile test, nonlinear finite element models and the calibrated empirical expression. Additionally, inverse analysis and finite element analysis results indicated that the majority of prisms exhibited tension hardening behaviour with a hardening ratio greater than 1.1 and an ultimate tensile strain greater than 0.1%. In addition to tension tests, a host of non-destructive tests were conducted to assess the physical properties and durability performance of UHP-SFRC.

Download or read book Guide for the Design and Construction of Concrete Reinforced with Fiber Reinforced Polymer Bars written by ACI Committee 440 and published by . This book was released on 2003 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bond of Reinforcement in Concrete written by fib Fédération internationale du béton and published by fib Fédération internationale du béton. This book was released on 2000-01-01 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In 1993, the CEB Commission 2 Material and Behavior Modelling established the Task Group 2.5 Bond Models. It's terms of reference were ... to write a state-of-art report concerning bond of reinforcement in concrete and later recommend how the knowledge could be applied in practice (Model Code like text proposal)... {This work} covers the first part ... the state-of-art report."--Pref.

Download or read book fib Model Code for Concrete Structures 2010 written by fib - federation internationale du beton and published by John Wiley & Sons. This book was released on 2013-12-04 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: The International Federation for Structural Concrete (fib) is a pre-normative organization. 'Pre-normative' implies pioneering work in codification. This work has now been realized with the fib Model Code 2010. The objectives of the fib Model Code 2010 are to serve as a basis for future codes for concrete structures, and present new developments with regard to concrete structures, structural materials and new ideas in order to achieve optimum behaviour. The fib Model Code 2010 is now the most comprehensive code on concrete structures, including their complete life cycle: conceptual design, dimensioning, construction, conservation and dismantlement. It is expected to become an important document for both national and international code committees, practitioners and researchers. The fib Model Code 2010 was produced during the last ten years through an exceptional effort by Joost Walraven (Convener; Delft University of Technology, The Netherlands), Agnieszka Bigaj-van Vliet (Technical Secretary; TNO Built Environment and Geosciences, The Netherlands) as well as experts out of 44 countries from five continents.

Download or read book Local Bond Stress slip Behavior of Reinforcing Bars Embedded in Fiber Reinforced Concrete written by Marwan Mohamed Hout and published by . This book was released on 1992 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study summarizes experimental results of the local bond stress-slip relationship of reinforcing bars embedded in fiber reinforced concrete (FRC). More than 70 bond specimens were tested and the effect of several parameters on the local bond stress-slip behavior was investigated. These include, size of reinforcing bar (#6 and #8); type of fibers (hooked steel, polypropylene); volume fraction of fibers Vf (between 0.9% and 1.4ft for the steel fibers, 1.5% for the polypropylene fibers); type of specimen (pullout, beam); and confinement (confined, unconfined). Whereas the primary emphasis was on the monotonic local bond stres3-slip response, some specimens were tested under large slip reversals to study the effect of fibers on the cyclic bond stress-slip behavior. The results showed that the addition of fibers to concrete matrixes improves the bond characteristics of ordinary reinforcing bar3. For specimens in which bond failure was by pull-out, adding steel fibers in 2% by volume fraction increased the maximum local bond resistance by about 15%. However, the intrinsic shape of the local bond stre33-slip behavior does not change in comparison with conventional concrete. Furthermore, the addition of fibers to concrete matrixes does not seem to influence the stiffness degradation characteristics of the local bond stress-slip response under cyclic 1oading compared to conventiona1 confined concrete reported in technical literature.

Download or read book written by 淳一郎·二羽 and published by . This book was released on 2006-10 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bond Behavior of Reinforcing Steel in Ultra high Performance Concrete written by and published by . This book was released on 2014 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document is a technical summary of the Federal Highway Administration (FHWA) report "Bond Behavior of Reinforcing Steel in Ultra-High Performance Concrete" (FHWA-HRT-14-090). Ultra-high performance concrete (UHPC) has garnered interest from the highway infrastructure community for its greatly enhanced mechanical and durability properties. The objective of this research is to extensively evaluate the factors that affect bond strength between deformed reinforcing bar and UHPC, and to facilitate the development of design guidelines for using field-cast UHPC in innovative connection details. The results of the research effort and the design recommendations for reinforcing bar embedded in UHPC are provided in this TechBrief.

Download or read book Investigation of the Bond Behavior of Steel Reinforcement Bars Embedded in Ultra High Performance Concrete Under Static Loads Using Finite Element Modeling written by Manish Roy and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The bond properties of reinforcement bars (rebar) embedded in concrete depends on the tensile behavior of the surrounding material and its capability of resisting micro cracks. Since the tensile behavior of Ultra High Performance Concrete (UHPC) is dominated by the amount and the orientation of fibers as well as the type of fibers, an effort has been made in this study to investigate the influence of the fiber volume fraction () and the fiber orientation on the bond behavior of steel rebar embedded in UHPC under a static loading condition using finite element simulation. Owing to the inclusion of discrete fibers, the characteristic of UHPC is highly anisotropic even at a macro level and it is important that the material model of UHPC captures that anisotropy properly. While modeling fibers discretely is time consuming and involves a lot of computational power, the present study proposes a computationally efficient way of modeling UHPC. In this approach, UHPC is considered as a composite material with the matrix modeled as a homogeneous material and the fibers modeled as smeared reinforcement. The directional vector of the smeared reinforcement represents the orientation of the fibers inside the matrix. ATENA, a finite element program, is used for this purpose. The material properties of the fibers are calibrated using the stress-stain data obtained from uniaxial direct tensile tests of UHPC. The calibrated fiber properties are then used to model pullout tests of a rebar embedded in UHPC. The bond stress versus slip properties of the rebar are validated with the experimental pullout test results. The calibrated rebar properties along with the fiber properties are then used to model uniaxial direct tensile tests of UHPC with embedded rebar. Once the tensile test model of the composite is validated using the experimental data, parametric studies are conducted to determine the effect of and fiber orientation on the uniaxial tensile behavior of rebar-reinforced UHPC. Based on the parametric studies, the dependence of the structural ductility on is discussed and a recommendation for the minimum strain to attain ductility is made.

Download or read book Bond Behavior of High Performance Reinforcing Bars for Concrete Structures written by Amr Ihab-Ahmed Hosny and published by . This book was released on 2007 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: Reinforced Concrete, High Strength Steel, High Performance Steel, Bond.

Download or read book Multi scale Pull out Behaviors of Fiber and Steel Reinforcing Bar in Hybrid Fiber Reinforced Concrete written by Alexander Lin and published by . This book was released on 2017 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a reinforced concrete structural member, sufficient bond between steel reinforcing bar and concrete guarantees a steel/concrete composite behavior, which is essential for a good overall member performance. Under severe loading, high slippage between rebar and concrete leads to matrix cracking and crushing in the bond region followed by degradation of the rebar/matrix bond. Fiber reinforcement provides a fiber bridging mechanism to resist such cracking behavior by modifying the tensile properties of the matrix. This thesis investigated a deflection hardening hybrid fiber reinforced concrete (HyFRC) with micro/macro fiber hybridization and recommends it as a matrix to enhance the rebar/matrix bond by utilizing its superior crack resisting ability. In the experimental phase, the rebar bond behaviors in ordinary concrete (OC), HyFRC without/with high volume fly ash and Engineered Cementitious Composites (ECC), another type of fiber reinforced cement-based composite (FRCC) with hardening behavior, were studied. The experimental program consists of monotonic and cyclic rebar pull-out test series and was supported by digital image correlation (DIC) and vibration test techniques. Different specimens were made by varying some conditions such as rebar size (no. 4 and no. 8) and absence/presence of transverse reinforcement (spiral) so the effect of such conditions in regards to bond between rebar and different matrices can also be studied. In addition to experiments, Finite element models were developed to further investigate the mechanical behavior of the HyFRC matrix during rebar pull-out and to examine how a transverse steel reinforcement affects such behavior. The experimental results showed that HyFRC can improve the rebar pull-out behavior by changing the failure mode from brittle splitting failure to a more ductile frictional pull-out failure compared to the OC material. The HyFRC material without fly ash provided better rebar bond performance compared to OC with spiral reinforcement and other type of FRCC under investigation. Compared to the monotonic rebar pull-out behavior, only minimal amount of additional damage was induced in such HyFRC material by repeated loading and unloading process from cyclic loading protocol. DIC measurement indicated that the width of the splitting cracks that form in HyFRC matrices due to rebar pull-out could be further reduced when such specimens were confined by spirals. The finer the splitting cracks, the higher the rebar gripping stress and hence the higher the rebar pull-out resistance. The DIC measurement was consistent with the results from finite element analysis because both of them showed that confining the HyFRC matrix with transverse steel reinforcement led to a more uniform distribution of the splitting crack width during rebar pull-out. The vibration test showed that rebar pull-out induced similar degree of damage in the bond regions of HyFRC with and without transverse reinforcement. If severe macrofiber pull-out occurs within the cracks induced by rebar pull-out, the macrofibers become less effective in resisting such cracks. Therefore, good macrofiber pull-out resistance in HyFRC is essential for an improved rebar pull-out performance. To investigate the macrofiber pull-out behavior and how it is affected by the presence of PVA microfibers in HyFRC, single fiber pull-out tests were conducted for various mortar mixtures. In some of these mortars, the cement was replaced by industrial by-products, such as fly ash and slag. In addition, macrofiber pull-out behavior in an ultra-high strength concrete with and without steel microfiber reinforcement was also studied. The results of the single fiber pull-out tests revealed that the presence of PVA microfibers in a mortar mixture designed based on the HyFRC mixture enhances the steel macrofiber pull-out resistance. This synergy between micro and macrofibers provided a more effective control of the splitting cracks and was responsible for the superior rebar bond performance. Hence, the research revealed a multi-scale bond enhancement in a HyFRC member reinforced by steel rebar. The macrofiber pull-out behaviors from mortars in which 45% and 15% of cement were replaced by slag and fly ash, respectively, showed that slag densified the steel macrofiber/matrix interface and hence, improved the pull-out resistance for the macrofiber. On the other hand, test results of fiber pull-out specimens in which 55% of cement was replaced by fly ash showed that increasing curing age made the PVA microfiber reinforcement less effective in resisting steel macrofiber pull-out. Such characteristic showed how high-volume fly ash weakened the PVA fiber/matrix bond. This mechanism induced by fly ash made PVA fibers in HyFRC less effective in improving steel macrofiber pull-out resistance and hence, reduced the micro/macro fiber synergy, which is beneficial for the rebar bond behavior. Therefore, using high volume fly ash decreased the rebar pull-out resistance in HyFRC. When steel macrofibers were pulled out from extremely strong matrices, almost no microcracks formed around macrofibers and the steel microfiber reinforcement didn’t affect the macrofiber pull-out behavior because such microfibers function by bridging the microcracks.

Download or read book Tensile Behavior of Ultra high Performance Fiber Reinforced Concrete and Reinforcement Bar written by Corey P. Hollmann and published by . This book was released on 2014 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book BOND STRENGTH CHARACTERISTICS OF DEFORMED REINFORCING STEEL BARS EMBEDDED IN SIFCON STEEL BARS CONCRETE written by ALI MORSI HAMZA and published by . This book was released on 1992 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: monitored and the modes of bond failure were determined.

Download or read book Studies of Bond Between Concrete and Steel written by Duff Andrew Abrams and published by . This book was released on 1925 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bond Behavior of High Performance Reinforcing Bars for Concrete Structures written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bond between the concrete and the reinforcing steel is a major factor affecting the performance of reinforced concrete structures. Advances in material science led to the production of High Performance Steel that has enhanced corrosion resistance and higher strength compared to conventional Grade 60 steel. Such material can lead to more economical design reducing the material requirements for a particular project and expanding its life span. The objective of this research is to study the bond behavior of High Performance reinforcing bars for concrete structures and to evaluate the effect of different parameters believed to affect the bond characteristics. Twenty-two large scale reinforced concrete splice beams were constructed using No. 8 and No. 11 reinforcing bars, having different cross-sections with varying concrete compressive strengths and development lengths. The beams were tested using four point bending setup to provide a constant moment region over the splice zone. Test results indicate that stresses up 90 ksi can be achieved in the No. 8 bars and up to 70 ksi in the No. 11 bars without confinement; however, it is recommended to use transverse reinforcement to confine the High Performance bars in order to ensure ductility. These stresses can be evaluated at failure using a simple proposed equation. Test results were used to extend the current ACI Committee 408 equations to better predict the stresses in the High Performance Steel.

Download or read book Advances on bond in concrete written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2022-12-01 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well the crack development and crack width. At Ultimate Limit State, bond governs anchorage and lap splices behavior as well as structural ductility. When plain (smooth) bars were used, the steel-to-concrete bond was mainly associated with “chemical adhesion/friction” that is related to the surface roughness of the rebar. As steel strengths increased the need to enhance interaction between steel and the surrounding concrete was recognized, and square twisted rebars, indented rebars or, later on, ribbed rebars came into the market, the latter being the type of deformed bar most commonly adopted since the 1960/70s. When ribbed rebars became widely used, several research studies started worldwide for better understanding the interaction between ribs and the surrounding concrete. Researchers evidenced the development of micro-cracks (due to the wedge action of the ribs) towards the external face of the structural element. If confinement is provided by the concrete cover, by transverse reinforcement or by an external transverse pressure, the full-anchorage capacity is guaranteed and a pull-out failure occurs, with crushing of concrete between the ribs. On the contrary, with lesser confining action, a splitting failure of bond occurs; the latter may provoke a brittle failure of the lap splice or, in some cases, of anchorages. However, after many years of research studies on bond-related topics, there are still several open issues. In fact, new materials entered into the market, as concrete with recycled aggregates or fibre reinforced concrete; the latter, having a kind of distributed reinforcement into the matrix (the fibres), provides a better confinement to the wedge action of the ribs. In addition, concrete and steel strength continuously increased over the years, causing changes in the bond behavior due to differences in mechanical properties of materials but also to the different concrete composition at the interface with the steel rebar causing a different bond behavior. Moreover, the lower water/cement ratio of these high-strength concrete makes the bleeding phenomena less evident, changing the concrete porosity in the upper layers of the structural element and thus making the current casting position parameters no-longer reliable. Finally, concrete with recycled aggregates are becoming more important in a market that is looking forward to a circular economy. As such, all the experimental results and database that allowed the calibration of bond rules now present in building codes for conventional concrete, may be not be representative of these new types of materials nowadays adopted in practice. Furthermore, after more than 50 years of service life, structural elements may not satisfy the current safety requirements for several reasons, including material degradation (with particular reference to steel corrosion) or increased loads, by also considering the seismic actions that were non considered by building codes at the time of the original design. The structural assessment of existing structures requires proper conceptual models and new approaches for evaluating the reliability of existing structures by also considering the remaining expected service life. In addition, specific rules for older materials, as plain smooth bars, should be revised for a better assessment of old structures. Last, but not least, interventions in existing structures may require new technologies now available such as post-installed rebars. While many advances have been achieved, there remain areas where a better understanding of bond and its mechanisms are required, and where further work is required to incorporate this understanding into safe and economic rules to guide construction and maintenance of existing infrastructures. These aspects were widely discussed within the technical community, particularly in the fib Task Group 2.5 and in the ACI 408 Committee dealing with bond and anchorage issues. Furthermore, special opportunities for discussing bond developments were represented by the International Conferences on ‘Bond in Concrete’ held each decade since 1982 as well as by joint workshops organized by fib TG2.5 and ACI 408. Within this technical collaboration, this Bulletin was conceived, and, thus, it collects selected papers presented at the joint fib-ACI Convention Session on Bond in Concrete held in Detroit (USA) in 2017. The bulletin is based on four main Sections concerning: - General aspects of bond - Anchorages and laps of bars and prestressing tendons - Bond under severe conditions - Degradation of bond for corrosion - Bond in new types of concrete The main aim of the Bulletin is to shed some new lights on the advances in understanding and application of bond related issues achieved over the last few years, and identify the challenges and priorities to be addressed in the next years. Another important aspect of the bulletin is to provide practical information from research findings.