Download or read book Flexural Strength Ductility and Serviceability of Beams that Contain High Strength Steel Reinforcement and High Grade Concrete written by and published by . This book was released on 2018 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes. The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement. The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking. The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone; evaluation of the minimum reinforcement ratio; recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, [lambda], which does not consider the yield strength of reinforcement and the concrete grade.

Download or read book Effects of Confinement and Small Axial Load on Flexural Ductility of High Strength Reinforced Concrete Beams written by Siu-Lee Chau and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Effects of Confinement and Small Axial Load on Flexural Ductility of High-strength Reinforced Concrete Beams" by Siu-lee, Chau, 周小梨, 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 EFFECTS OF CONFINEMENT AND SMALL AXIAL LOAD ON FLEXURAL DUCTILITY OF HIGH-STRENGTH REINFORCED CONCRETE BEAMS Submitted by CHAU Siu Lee for the Degree of Master of Philosophy at The University of Hong Kong in August 2005 Compared with normal-strength concrete, high-strength concrete has higher strength but is generally more brittle. Its use in a reinforced concrete structure could lead to an undesirable reduction in ductility if not properly controlled. In this thesis, the effects of confinement and small axial load on the flexural ductility of reinforced concrete beams cast of both normal- and high-strength concrete have been evaluated by analyzing the complete moment-curvature behaviour of the beam sections. The results reveal that the use of high-strength concrete would at a constant tension steel ratio increase the flexural ductility, while at a constant tension to balanced steel ratio decrease the ductility. On the other hand, provision of confinement enhances the ductility of both normal- and high-strength concrete sections at both a constant tension steel ratio and at a constant tension to balanced steel ratio. It does this in two ways. Firstly, it increases the balanced steel ratio of the section. So, for a constant steel ratio, the section with higher confinement is more under-reinforced. Secondly, it increases the residual strength and ductility of the concrete such that at the same tension to balanced steel ratio, the ductility of the section increases. From the results of the analysis, it can be concluded that providing confinement to a section is an effective way of improving the ductility of reinforced concrete beam sections, especially those cast of high-strength concrete. However, most codes of practice do not specify a suitable design method for reinforced concrete beams that takes into account the effect of confinement. Therefore, design formulas for the flexural strength and ductility design of high-strength concrete beams with the effects of confinement taken into account have been developed. On the other hand, it is proposed to compensate for the reduction in flexural ductility due to the use of high-strength concrete by adding compression and/or confining reinforcement. A simple design method that correlates the amount of addition reinforcement needed to maintain a constant level of minimum ductility and the concrete strength is developed. Conversely, the presence of compressive axial load, even at a low level, has an adverse effect on flexural ductility. As a portion of concrete is used to resist the axial load, the section becomes less under-reinforced. Therefore, the flexural ductility decreases with the level of axial load applied. From the results obtained, it is found that the presence of axial load mainly affects the degree of the section being under- or over-reinforced. Measures should therefore be taken to maintain the ductility level of sections with applied axial load at an acceptable level. The study recommends the provisions of additional compression reinforcement to resist the applied axial load, and proposes a design method for restoring the ductility of a section with applied axial load to a ductility level attained by an identical section without axial load. DOI: 10.5353/th_b3199766 Subjects:

Download or read book Proceedings of the Canadian Society of Civil Engineering Annual Conference 2021 written by Scott Walbridge and published by Springer Nature. This book was released on 2022-05-23 with total page 689 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises the proceedings of the Annual Conference of the Canadian Society of Civil Engineering 2021. The contents of this volume focus on specialty conferences in construction, environmental, hydrotechnical, materials, structures, transportation engineering, etc. This volume will prove a valuable resource for those in academia and industry.

Download or read book Design of Concrete Structures Using High strength Steel Reinforcement written by Bahram M. Shahrooz and published by Transportation Research Board. This book was released on 2011 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Report 679: Design of Concrete Structures Using High-Strength Steel Reinforcement evaluates the existing American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications relevant to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernible yield plateau. The report also includes recommended language to the AASHTO LRFD Bridge Design Specifications that will permit the use of high-strength reinforcing steel with specified yield strengths not greater than 100 ksi. The Appendixes to NCHRP Report 679 were published online.

Download or read book Flexural Behavior of Steel Fiber Reinforced Prestressed Concrete Beams and Double Punch Test for Fiber Reinforced Concrete written by Netra Bahadur Karki and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Steel fibers have widely been used in the past to reinforce brittle materials in many nonstructural applications such as pavement, tunneling lining, etc. On the basis of numerous previous studies, ACI 318-11 [2011] has recently accepted steel fiber as a minimum shear reinforcement replacement with minimum 0.75% volume fraction for both reinforced concrete and prestressed concrete members. However, not much previous research has talked about the flexural behavior of fiber reinforced concrete (FRC). As per ACI 318-11 for tension-controlled sections, the net tensile strains in the outermost layer of steel, et, should be greater than or equal to 0.005 and for the moment redistribution in continuous beam the section should sufficiently ductile (et [greater or equal to] 0.0075). For this, the sections should have small longitudinal reinforcement ratio which ultimately leads to an inefficient beam section with a large cross-sectional area. In contrast, the use of smaller concrete cross sections can lead to a diminished ductile flexural behavior as well as premature shear failure. In this context, the use of steel fiber reinforced concrete could be a potential solution since fiber can increase both the concrete shear strength and it's usable compressive strains. However limited previous researches on the flexural behavior on SFRC beams are available and most of them are of small scales and concentrated only basically for shear behavior. To the best of our knowledge, the large-scale prestressed fiber reinforced concrete beam specimens have yet to be studied for flexure behavior. In this project, six large scale prestressed concrete beams with or without steel fiber along with some material test were tested. Our experimental investigations indicated that even with inclusion of small percentage volume of fraction of steel fiber (Vf =0.75%) could not only increase the ductility and shear strength of the SFRPC beam but also change the failure pattern by increasing usable strain in concrete and steel. A modification on the limit for c/dt ratio and [phi] factor for design of flexural member given in current ACI could be proposed which could imply the smaller sections with higher longitudinal reinforcement ratio and less shear reinforcement. could be used. Any standard material test results have to ensure that FRC has, at least, been batched properly and it can give indications of probable performance when used in structures. In the current material testing method suggested by ACI, the third point bending test (ASTM C1609) has an inherent problem in that the coefficients of variations for post cracking strength and residual strength are generally very high on the order of 20%. The direct tensile test can be a more appropriate material. However, it is currently not recommended as standard method in the U.S. Because of it's difficultly in gripping arrangement which will lead to cracking of the specimen at the grips. Both the test methods also require close loop servo controlled machine. The round panel test method (ASTM C1550) requires large size specimen and heavy steel supports prevents performing test in small laboratories. Split cylinder test (ASTM C496), do not necessarily reflect the true properties of the material as the specimen is forced to fail in the line of the application of the load and the test method is also not recommended by ACI for SFRC. In order to improve the material assessment procedure, the double Punch Test (DPT) introduced by Chen in 1970 [Chen, 1970] was extensively evaluated to develop a simple, quick and reliable testing method for SFRC. Various tests were carried out in order to evaluate peak and residual strength, stiffness, strain hardening and softening, toughness and other post crack properties. Our test results indicated that the DPT method could be immersed as reliable, easier and economical material test method. It could be used to distinguish the peak strength, residual strength, toughness stiffness and crack resistance, of different SFRC mixtures with less scatter results compared to other material test methods.

Download or read book Response of Ultra High Performance Fiber Reinforced Concrete Beams Under Flexure and Shear written by Roya Solhmirzaei and published by . This book was released on 2021 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra high performance concrete (UHPC) is an advanced cementitious material made with low water to binder ratio and high fineness admixtures, and possesses a unique combination of superior strength, durability, corrosion resistance, and impact resistance. However, increased strength of UHPC results in a brittle behavior. To overcome this brittle behavior of UHPC and improve post cracking response of UHPC, steel fibers are often added to UHPC and this concrete type is designated as Ultra High Performance Fiber Reinforced Concrete (UHPFRC). Being a relatively new construction material, there are limited guidelines and specifications in standards and codes for the design of structural members fabricated using UHPFRC. To develop a deeper understanding on the behavior of UHPFRC flexural members, seven beams made of UHPFRC are tested under different loading conditions. The test variables include level of longitudinal reinforcement, type of loading (shear and flexure), and presence of shear reinforcement. Further, a finite element based numerical model for tracing structural behavior of UHPFRC beams is developed in ABAQUS. The developed model can account for the nonlinear material response of UHPFRC and steel reinforcement in both tension and compression, as well as bond between concrete and reinforcing steel, and can trace the detailed response of the beams in the entire range of loading. This model is validated by comparing predicted response parameters including load-deflection, load-strain, and crack propagation against experimental data obtained from tests on UHPFRC beams with different material characteristics and under different loading configurations. The validated model is applied to conduct a set of parametric studies to quantify the effect of different parameters on structural response of UHPFRC beams, including the contribution of stirrups and concrete to shear capacity of beams, to explore feasibility of removing the need for shear reinforcement in UHPFRC beams. Results from experiments and numerical model reveal that UHPFRC beams exhibit distinct cracking pattern characterized by the propagation of multiple micro cracks followed by widening of a single crack leading to failure. Also, UHPFRC beams exhibit high flexural and shear capacity, as well as ductility due to high compressive and tensile strength of UHPFRC and fiber bridging developing at the crack surfaces that leads to strain hardening in UHPFRC after cracking. Thus, absence of shear reinforcement in UHPFRC beams does not result in brittle failure, even under dominant shear loading. Data from the conducted experiments as well as those reported in literature is utilized to develop a machine learning (ML) framework for predicting structural response of UHPFRC beams. On this basis, a comprehensive database on reported tests on UHPFRC beams with different geometric, fiber properties, loading and material characteristics is collected. This database is then analyzed utilizing different ML algorithms, including support vector machine, artificial neural networks, k-nearest neighbor, support vector machine regression, and genetic programing, to develop a data-driven computational framework for predicting failure mode and flexural and shear capacity of UHPFRC beams. Predictions obtained from the proposed framework are compared against the values obtained from design equations in codes, and also results from full-scale tests to demonstrate the reliability of the proposed approach. The results clearly indicate that the proposed ML framework can effectively predict failure mode and flexural and shear capacity of UHPFRC beams with varying reinforcement detailing and configurations. The research presented in this dissertation contributes to the development of preliminary guidance on evaluating capacity of UHPFRC beams under different configurations.

Download or read book Advanced Composites written by Viktor Gribniak and published by MDPI. This book was released on 2021-06-02 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Engineering practice has revealed that innovative technologies’ structural applications require new design concepts related to developing materials with mechanical properties tailored for construction purposes. This would allow the efficient use of engineering materials. The efficiency can be understood in a simplified and heuristic manner as the optimization of performance and the proper combination of structural components, leading to the consumption of the least amount of natural resources. The solution to the eco-optimization problem, based on the adequate characterization of the materials, will enable implementing environmentally friendly engineering principles when the efficient use of advanced materials guarantees the required structural safety. Identifying fundamental relationships between the structure of advanced composites and their physical properties is the focus of this book. The collected articles explore the development of sustainable composites with valorized manufacturability corresponding to Industrial Revolution 4.0 ideology. The publications, amongst others, reveal that the application of nano-particles improves the mechanical performance of composite materials; heat-resistant aluminium composites ensure the safety of overhead power transmission lines; chemical additives can detect the impact of temperature on concrete structures. This book demonstrates that construction materials’ choice has considerable room for improvement from a scientific viewpoint, following heuristic approaches.

Download or read book SHEAR CAPACITY FLEXURAL DUCT written by Md Shahidul Islam and published by Open Dissertation Press. This book was released on 2017-01-27 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Shear Capacity and Flexural Ductility of Reinforced High- and Normal-strength Concrete Beams" by Md Shahidul, Islam, 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. DOI: 10.5353/th_b3121444 Subjects: Concrete beams - Testing High strength concrete - Testing Shear (Mechanics)

Download or read book Flexural Behaviour of High Strength Steel Fibre Normal and Lightweight Concrete Beams written by Mohamed Abdulhakim Zurgani and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was conducted to investigate the flexural behaviour of high strength normal and lightweight reinforced concrete beams with steel fibres. Three different mixtures were developed for each type of concrete with three different steel fibre volume ratios. The target compressive strength was 85 MPa. Material and structural experimental programs were performed. In the material investigation, twenty four prisms with dimensions of 100 mm × 100 mm × 400 mm and one hundred and twenty cylinders with dimensions of 100 mm × 200 mm were cast, cured and tested to determine the mechanical properties for all different mixtures. The investigated mechanical properties included the compressive strength, splitting tensile strength, modulus of rupture and flexural toughness. In the structural investigation, a series of six high strength lightweight aggregate (LWAC) concrete reinforced beams and six high strength normal weight (NWC) reinforced concrete beams were cast and tested. The beams were 200 mm × 400 mm × 3200 mm and were simply supported on a clear span of 2900 mm. The main variables in this study were the concrete type (normal weight concrete and light weight aggregate concrete), steel fibre volume ratio, (0 %, 0.375%, 0.75%), and the longitudinal reinforcement ratio, (0.85%, 1.50%). The structural behaviour of the test beams was examined in terms of load-deflection behaviour, steel reinforcement strain, concrete strain, crack pattern, crack width, crack spacing, mode of failure and ultimate moment capacity. The test results revealed that the addition of steel fibres to high strength lightweight or normal weight concrete improved the mechanical properties. The compressive strength, splitting tensile strength and the modulus of rupture of fibrous LWAC and NWC concrete increased compared to the plain concrete. Adding steel fibre to both high strength normal and lightweight concrete increased both cracked and un-cracked stiffness in addition to increasing the ultimate flexural capacity. The steel fibres also enhanced the cracking behaviour for both NWC and LWAC beams, reduced the crack widths and increased the number of the cracks for both type of concrete. The LWAC beams developed more cracks but less cracks width compared to their identical NWC beams. The ductility indexes of fibrous and non-fibrous NWC beams were higher than the ductility indexes measured for the corresponding LWAC beams. For all fibre reinforced NWC and LWAC beams, CSA A23.3-14, ACI 318-08, EC2-04, and EC2-91 codes overestimated the maximum crack width due to the fact that these models do not consider the presence of steel fibres. The Rilem TC162-TDF was found to accurately predict the maximum crack width of fibrous NWC beams. However, the model was seen to be conservative when predicting the maximum crack width for fibrous LWAC beams.

Download or read book Behavior of High Performance Steel as Shear Reinforcement for Concrete Beams written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research is to study the feasibility of using high performance steel as shear reinforcement for concrete beams. High performance steel is characterized by enhanced corrosion resistance and higher strength in comparison to conventional Grade 60 steel reinforcement. Advantages of using higher strength steel include the ability to design for longer span lengths and/or reducing the amount of material needed for design. This could greatly reduce the overall costs of construction for future structures. Nine reinforced concrete beams were constructed using No. 9 longitudinal bars and No. 3 bars for the stirrups. The main variables considered in the study are the stirrup spacing and the type of reinforcing steel material. Testing was performed using a single concentrated load positioned closer to one end of the beam, which allowed for two tests per beam. Research findings indicate that using MMFX stirrups increases the overall shear strength and enhances serviceability by distributing cracks and reducing crack width. Pairing high performance longitudinal and transverse reinforcement shows an optimum design in terms of strength gain and reduction in crack width. Enhanced serviceability behavior can be attributed to the better bond characteristics of MMFX steel in comparison to conventional Grade 60 steel. Test results suggest that combining high performance steel with high strength concrete could lead to a better utilization of the materials. Analysis shows that the ACI 318-05, CSA, and AASHTO LRFD design codes can conservatively be used for the design of high performance steel up to a yield strength of 80 ksi. Detailed analysis using the Modified Compression Field Theory can be used to accurately predict the behavior of the beams.

Download or read book Evaluation of the Flexural Performance of Small scale Ultra high Performance Concrete Beams Reinforced with Fibers and Mild Steel written by Turki S. Alahmari and published by . This book was released on 2017 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra-high performance concrete (UHPC) is an advanced material that provides exceptional durability and mechanical properties. UHPC exhibits high compressive strengths, improved environmental resistance, and increased tensile strengths. Additionally, the post-cracking capacity is improved through the contribution of fiber reinforcement. UHPC materials can provide advantages to structure applications, such as decreased member size, lighter weights, and an increased design life with a reduction in the required maintenance. However, standard design procedures have not been developed, thus implementation of UHPC is still slow. Therefore, there is a need for more research efforts to provide the knowledge necessary for implementing UHPC in structural applications. At New Mexico State University (NMSU) non-proprietary UHPC mixture proportions have been developed. This mixtures uses locally available materials typically used in concrete production in New Mexico. This provides a more economic material compared to commercially available products, while providing the enhanced mechanical and durability properties. An experimental program and evaluation continues to be conducted on this material to provide an evidence for use in structural design, particularly bridge applications within the state of New Mexico. This research focused on the evaluation of the flexural performance of small-scale beams that had previously been tested at NMSU. The first evaluation was conducted on specimens based on the ASTM C1609 standard. This focuses on the flexural performance of fiber reinforced concrete tested under three-point loading. After the analysis of experimental test results, the relation between load and deformation was used to evaluate the behavior specimens. The second evaluation investigated the ductility behavior of specimens reinforced with fibers and mild steel reinforcement. The experimental results were used to study the behavior. The load and deformation behavior was used to calculate the ductility index. The moment and curvature behavior was used to calculate the performance factor of ductility and the curvature ductility. The UHPC specimens were compared to high performance concrete (HPC) and conventional concrete. The results and discussions are provided in this thesis.

Download or read book Structural Performance of Reinforced Concrete Beams Subjected to Service Loads Coupled with Corrosion of Flexural Reinforcement written by Abdullah Al-Bayti and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Corrosion of steel reinforcement has been identified as one of the major problems facing many existing reinforced concrete structures including bridges. The exposure to aggressive environmental conditions such as those with high concentrations of chloride ions due to the use of de-icing salt in cold regions or high concentrations of carbon dioxide due to increased greenhouse gas emissions, accelerate the initiation process of corrosion. As corrosion initiates, the structural performance in terms of load-carrying capacity, ductility, and service life deteriorate over time. Coupling the effect of reinforcement corrosion with service loads may further weaken the structural performance of reinforced concrete bridges due to the presence of transverse load-induced cracks. Accordingly, a research program was conducted to evaluate the structural performance of reinforced concrete beams subjected to coupled effects of service loads and reinforcement corrosion. The research project consisted of combined experimental and numerical investigations. The experimental phase consisted of tests of nine small-scale beams and six large-scale beams. The beams were designed, constructed, instrumented, and loaded under a four-point load test. The primary test variables were the applied corrosion current density, level of corrosion, and level of sustained loading as percentage of beam ultimate capacity (0% Pu, 40% Pu, and 60% Pu). The corrosion level of steel reinforcement was quantitatively assessed using gravimetric weight measurements and three-dimensional laser scanner technique. Test results indicated that failure of corroded RC beams was brittle due to premature rupture of corroded steel bars, which was attributed to the development of localized corrosion at the sections with flexural cracks in beams. Furthermore, it was found that beams subjected to higher levels of service loads, experienced further reductions in ultimate load capacity and ductility. In addition, tensile tests were used to evaluate the effect of corrosion on the mechanical performance of steel bars retrieved from the corroded beams. It was found that the tensile strength of corroded steel bars, based on nominal sectional area, was reduced with the increase of corrosion levels. In contrast, the tensile strength, based on minimum sectional area, was not influenced by the non-uniform distribution and localization of corrosion. In fact, there was a slight increase in strength with the increase of corrosion levels. The numerical phase consisted of finite element analyses of beams using DIANA FE analysis software. A simplified approach was implemented to introduce the damage induced by corrosion into two-dimensional nonlinear FE models, based on the experimental testing of corroded beams and corroded steel bars. The analyses were reasonably accurate in predicting cracking patterns, residual load capacity, residual ductility, and failure modes of corroded beams. Subsequently, the validated model was used to conduct a parametric study on the level of service loads, level of corrosion, strength of concrete, and tensile reinforcement ratio. It was found that the FE model of corroded beams was strongly influenced by the level of service loads, level of corrosion, and tensile reinforcement ratio.

Download or read book Reinforced Concrete Design with FRP Composites written by Hota V.S. GangaRao and published by CRC Press. This book was released on 2006-11-20 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the use of composites has increased in many industrial, commercial, medical, and defense applications, there is a lack of technical literature that examines composites in conjunction with concrete construction. Fulfilling the need for a comprehensive, explicit guide, Reinforced Concrete Design with FRP Composites presents specific informat

Download or read book Journal of the American Concrete Institute written by American Concrete Institute and published by . This book was released on 1986 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structural Performance of High Strength Reinforced Concrete Beams Built with Synthetic Fibers written by Roukaya Bastami and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of a research program examining the effects of macro-synthetic fibers on the shear and flexural behaviour of high-strength concrete (HSC) beams subjected to static and blast loads. As part of the study, a series of seventeen fiber-reinforced HSC beams are built and tested under either quasi-static four-point bending or simulated blast loads using a shock-tube. The investigated test parameters include the effects of: macro-synthetic fibers, fiber hybridization, combined use of fibers and stirrups and longitudinal steel ratio and type. The results show that under slowly applied loads, the provision of synthetic fibers improves the shear capacity of the beams by allowing for the development of yield stresses in the longitudinal reinforcement, while the combined use of synthetic fibers and stirrups is found to improve flexural ductility and cracking behaviour. The results also show that the provision of synthetic fibers delays shear failure in beams tested under blast pressures, with improved control of blast-induced displacements and increased damage tolerance in beams designed with combined fibers and stirrups. The study also shows that the use of hybrid fibers was capable of effectively replacing transverse reinforcement under both loading types, allowing for ductile flexural failure. Moreover, the use of synthetic fibers was effective in better controlling crushing and spalling in beams designed with Grade 690 MPa high-strength reinforcement. Furthermore, the results demonstrate that synthetic fibers can possibly be used to relax the stringent detailing required by modern blast codes by increasing the transverse reinforcement hoop spacing without compromising performance. As part of the analytical study, the load-deflection responses (resistance functions) of the beams are predicted using sectional (moment-curvature) analysis, as well as more advanced 2D finite element modelling. Dynamic resistance functions developed using both approaches, and incorporating material strain-rate effects, are then used to conduct non-linear single-degree-of-freedom (SDOF) analyses of the blast-tested beams. In general, the results show that both methods resulted in reasonably accurate predictions of the static and dynamic experimental results.

Download or read book Flexural Behavior of Reinforced Concrete Beams Strengthened with Externally Bonded Hybrid Systems written by Abubakr Ahmed Abdelall Mohammed and published by . This book was released on 2017 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The demand for strengthening of aging reinforced concrete (RC) structures are continuously rising. Carbon fiber reinforced polymers (CFRP) are the most widely used externally bonded-reinforcing (EBR) materials for strengthening and retrofitting of RC structural members. The use of high strength galvanized steel mesh (GSM) strengthening material has recently gained some acceptance. However, Both CFRP and GSM have high strength but have low ductility. Recently developed aluminum alloys (AA) have high ductility and some desirable characteristics that may overcome some of the shortcomings of CFRP and GSM. Combining AA with CFRP and GSM will result in a hybrid material with balanced strength and ductility. Therefore, the major aim of this research is to develop a hybrid ductile and strong retrofitting system by combining AA plates with GSM and CFRP laminates to strengthen RC beams in flexure. A comprehensive experimental program was carried out to determine the tensile strength and the bond strength of the hybrid system. Fifteen-coupon specimens were tested for tensile strength, six specimens of concrete prisms for bond strength and 25 T-beam specimens for flexural strength under a four-point loading. Results showed an increase in the flexural capacity of the strengthened specimen ranging from 10% to 77% compared to the control beam and a decline in ductility of 13% to 59% compared to the un-strengthened specimen. Furthermore, analytical models based on ACI 440.2R-08 guidelines were employed to capture the flexural behavior of the tested specimens. Experimental results correlated well with the analytical predictions in a range of 30% of the experimental values. The study concluded that the newly proposed hybrid systems are promising systems for the improvement of the flexural behavior (strength and ductility) of RC beams."--Abstract.

Download or read book Introduction of Low Ductility 500MPa Reinforcing Steel in Reinforced Concrete Beams written by Aaron Charles Holmes and published by . This book was released on 2000 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The current Reinforced Concrete Design Code AS3600 specifies that the standard yield strength of reinforcing steel for concrete beams to be 400 MPa. Soon a higher strength 500 MPa steel will be introduced which will replace the 400 MPa steel in reinforced concrete structures. This shift from 400 MPa to 500 MPa steel will affect the design of the reinforced concrete beam in that yield strain will change from 0.002 (for 400 MPa steel) to 0.0025 (for 500 MPa steel). This change will affect all basic definitions of neutral axis depth and subsequently alter all design charts currently used by professional engineers. The introduction of the new grade of steel bar will result in more efficient and cost effective reinforced concete beam designs. This report looks at the introduction of the low ductility 500 MPa reinforcing steel into rectangular sectioned singly and doubly reinforced concrete beams. Flexural design charts for rectangular cross-sectioned beams were constructed using a spread-sheeting program for the 500 MPa reinforcing steel which were then compared to current design charts for 400 MPa reinforcing steel. Ductility and curvature were also investigated using a curvature analysis program to observe what effect the higher strength reinforcing steel would have on singly reinforced beams with relationships obtained for moment-curvature and neutral axis parameter-ductility coefficients. From these relationships characteristics the ultimate strength and ductility of each section were able to be established. Comparisons were also made on how concrete and steel strengths and dimensions of the beam section effected these characteristics in reinforced concrete beam sections. Flexural design charts and curvature relationships charts were established for the rectangular cross sectioned beams which have been included within this report fulfilling the objectives of this thesis." -- Abstract.