• Coupled systems mechanics
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• v.10 no.2
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• pp.161-184
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• 2021

Strengthening of reinforced concrete beams with externally bonded fiber reinforced polymer plates/sheets technique has become widespread in the last two decades. Although a great deal of research has been conducted on simply supported RC beams, a few studies have been carried out on continuous beams strengthened with FRP composites. This paper presents a simple uniaxial nonlinear analytical model that is able to accurately estimate the load carrying capacity and the behaviour of damaged RC continuous beams flexural strengthened with externally bonded prestressed composite plates on both of the upper and lower fibers, taking into account the thermal load. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the damaged concrete beam, the FRP plate and the adhesive layer. The flexural analysis results and analytical predictions for the prestressed composite strengthened damaged RC continuous beams were compared and showed very good agreement in terms of the debonding load, yield load, and ultimate load. The use of composite materials increased the ultimate load capacity compared with the non strengthened beams. The major objective of the current model is to help engineers' model FRP strengthened RC continuous beams in a simple manner. Finally, this research is helpful for the understanding on mechanical behaviour of the interface and design of the FRP-damaged RC hybrid structures.

• Computers and Concrete
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• v.16 no.3
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• pp.357-380
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• 2015

In this study, a simple indeterminate strut-tie model which reflects complicated characteristics of the ultimate structural behavior of continuous reinforced concrete deep beams was proposed. In addition, the load distribution ratio, defined as the fraction of applied load transferred by a vertical tie of truss load transfer mechanism, was proposed to help structural designers perform the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie was introduced to ensure the ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete were reflected upon. To verify the appropriateness of the present study, the ultimate strength of 58 continuous reinforced concrete deep beams tested to shear failure was evaluated by the ACI 318M-11's strut-tie model approach associated with the presented indeterminate strut-tie model and load distribution ratio. The ultimate strength of the continuous deep beams was also estimated by the experimental shear equations, conventional design codes that were based on experimental and theoretical shear strength models, and current strut-tie model design codes. The validity of the proposed strut-tie model and load distribution ratio was examined through the comparison of the strength analysis results classified according to the primary design variables. The present study associated with the indeterminate strut-tie model and load distribution ratio evaluated the ultimate strength of the continuous deep beams fairly well compared with those by other approaches. In addition, the present approach reflected the effects of the primary design variables on the ultimate strength of the continuous deep beams consistently and reasonably. The present study may provide an opportunity to help structural designers conduct the rational and practical strut-tie model design of continuous deep beams.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.167-174
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• 2003

It is absolutely natural to be interested in durability and safety of the structure under shear behavior. To fulfill this desire, a comparison on the shear behavior between steel fiber reinforced concrete both simple and continuous beams is done to use in the field working. Several operations are conducted : First of all, plan for optimal combination is standardized. Second, resistance for shear has been generalized in that it is decided by combination of individual elements. Third, as the fracture of tensile bar leads to destruction of specimen, shear behavior of whole specimen is decided by stress working on tensile bar. It should be generalized for other specimens also. Forth, evidence of the softness of steel fiber reinforced concrete beam by experiment lead to application in the fields. Finally, numeral values of the steel fiber reinforced concrete are analyzed and the result is compared to those of experiments. With these consequences, this study was done for the application to dynamic structures such as bridges and the repair and rehabilitation.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.6
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• pp.47-58
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• 2004

As concrete structures are getting larger, higher, longer and more specialized, it is more required to develop steel fiber concrete and apply to the real world. In this research, it is aimed to have fatigue strength examined, varying the steel fiber content of 0%, 0.75%, 1.00%, 1.25% by experimental study of fatigue behavior of the steel fiber reinforced concrete continuous beams under cyclic loading. The ultimate load and initial load of flexural cracking were measured by static test. In addition, the load versus strain relation, load versus deflection relation, crack pattern and fracture mode by increasing weight were observed. On the other hand, the crack propagation and the modes of fracture according to cycle number and the relation of cyclic loading to deflection relation and strain relation were investigated by fatigue test. As the result of fatigue test, continuous beam without steel fiber was failed at 60 ~ 70% of The static ultimate strength and it could be concluded that fatigue strength to two million cyclic loading was arround 67.2% by S-N curve. On the other hand, that with steel fiber was failed at 65 ~ 85% of the static ultimate strength and it could be concluded fatigue strength to two million cyclic loading around 71.7%.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.291-305
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• 2013

This paper presents the continuous hoop reinforcement method as a means to overcome the difficulty of rebar construction due to the seismic detail of lateral reinforcement. Because the continuous hoop has no seismic hook, and there is less interference during the rebar work, rebar quantities and construction time can be reduced. Since the details of column and beam continuous hoops are different from those of conventional lateral reinforcements, the construction method should be developed through mock-up tests. The length of the beam mock-up is 8m and the section size is $500mm{\times}700mm$, the height of the column mock-up is 2.8m and 4m, and the section size is $800{\times}800mm$. The length and the size are determined based on the elements that are generally used in reinforced concrete basement parking lots and office buildings. The results of the mock-up test showed that the quantities of rebar could be reduced by 20% and the time could be reduced by up to 40% compared with conventional lateral reinforcements.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.3-12
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• 2011

The structural behavior of continuous reinforced concrete deep beams is mainly controlled by the mechanical relationships associated with the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, a simple indeterminate strut-tie model which reflects characteristics of the complicated structural behavior of the continuous deep beams is presented. In addition, the reaction and load distribution ratios defined as the fraction of load carried by an exterior support of continuous deep beam and the fraction of load transferred by a vertical truss mechanism, respectively, are proposed to help structural designers for the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie is introduced to ensure a ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and concrete compressive strength are implemented after thorough parametric numerical analyses. In the companion paper, the validity of the presented model and load distribution ratio was examined by applying them in the evaluation of the ultimate strength of multiple continuous reinforced concrete deep beams, which were tested to failure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.171-172
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• 2012

In this study the continuous rectangular spiral hoop is used for saving cost and time, solving manpower shortage, and the quality of structures. Generally the use of continuous spiral reinforcement in reinforced concrete elements improve the strength and the ductility of the concrete. Savings in cost and time is demonstrated with the continuous rectangular spiral hoop through the mock up test of beam and column elements. In case of a 4m column element the time of rebar work decreases up to 40% compared with traditional hoop, and in case of a 8m beam the time also decreases 40%. This study present the construction method and details.

• Computers and Concrete
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• v.24 no.4
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• pp.313-327
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• 2019

The purpose of the present study is to present a new approach to designing and selecting the details of multidimensional continuous RC beam by applying all strength, serviceability, ductility and other constraints based on ACI318-14 using Teaching Learning Based Optimization (TLBO) algorithm. The optimum reinforcement detailing of longitudinal bars is done in two steps. in the first stage, only the dimensions of the beam in each span are considered as the variables of the optimization algorithm. in the second stage, the optimal design of the longitudinal bars of the beam is made according to the first step inputs. In the optimum shear reinforcement, using gradient-based methods, the most optimal possible mode is selected based on the existing assumptions. The objective function in this study is a cost function that includes the cost of concrete, formwork and reinforcing steel bars. The steel used in the objective function is the sum of longitudinal and shear bars. The use of a catalog list consisting of all existing patterns of longitudinal bars based on the minimum rules of the regulation in the second stage, leads to a sharp reduction in the volume of calculations and the achievement of the best solution. Three example with varying degrees of complexity, have been selected in order to investigate the optimal design of the longitudinal and shear reinforcement of continuous beam.

• Steel and Composite Structures
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• v.16 no.2
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• pp.187-201
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• 2014

A new through-beam connection system for a concrete filled steel tube column to RC beam is proposed. In this connection, there are openings on the steel tube while the reinforced concrete beams are continuous in the joint zone. The moment and shear force at the beam ends can be transferred to column by continuous rebar and concrete. The weakening of the axial load and shear bearing capacity due to the opening of the steel tube can be compensated by strengthening steel tube at joint zone. Using this connection, construction of the joint can be made more convenient since welding and hole drilling in situ can be avoided. Axial compression and reversed cyclic loading tests on specimens were carried out to evaluate performance of the new beam-column connection. Load-deflection performance, typical failure modes, stress and strain distributions, and the energy dissipation capacity were obtained. The experimental results showed that the new connection have good bearing capacity, superior ductility and energy dissipation capacity by effectively strengthen the steel tube at joint zone. According to the test and analysis results, some suggestions were proposed to design method of this new connection.

• Structural Engineering and Mechanics
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• v.43 no.5
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• pp.623-636
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• 2012

The aim of the current work is to describe the flexural behaviour of simply supported concrete beams with tension reinforcement spliced at mid-span. The parameters included in the study were the type of the concrete, the splice length and the configuration of the hooked splice. Fifteen beams were cast using an ordinary concrete mix and two fiber reinforced concrete mixes incorporating steel and polypropylene fibers. Each concrete mix was used to cast five beams with continuous, spliced and hooked spliced tension steel bars. A test beam was reinforced on the tension side with two 12 mm bars and the splice length was 20 and 40 times the bar diameter. The hooked bars were spliced along 20 times the bar diameter and provided with 45-degree and 90-degree hooks. The test results in terms of cracking and ultimate loads, cracking patterns, ductility, and failure modes are reported. The results demonstrated the consequences due to short splices and the improvement in the structural behaviour due to the use of hooks and the confinement provided by the steel and polypropylene fibers.