• Journal of the Korean Institute of Educational Facilities
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• v.20 no.4
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• pp.35-43
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• 2013

Some results of experimental investigation conducted to assess the effect of cement composite strength and ductility on the shear behavior and crack-damage mitigation of stud connections between existing reinforced concrete frame in school buildings and seismic strengthening elements from cyclically direct shear tests are described. The cement composite strengths include 50 for medium strength and 70 MPa for high strength. Two types of cement composites, strain-hardening cement composite (SHCC) and non-shrinkage mortar, are used for stud shear connection specimens. The special SHCCs are reinforced with hybrid 0.2% polyethylene (PE) and 1.3% polyvinyl alcohol (PVA) fibers at the volume fraction and exhibits tensile strain capacity ranging from 0.2 to 0.5%. Test result indicates that SHCC improves the seismic performance and crack-damage mitigation of stud shear connections compared with stud connections with non-shrinkage mortar. However, the performance enhancement in SHCC stud connections with transverse and longitudinal reinforcements is less notable for those without additional reinforcement.

• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.389-399
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• 2020

An infill wall made of high-performance fiber-reinforced cementitious composites (HPFRCC) was utilized in this study to strengthen the reinforced concrete (RC) frame structures that had not been designed for seismic loads. The seismic performance of the RC frame structures strengthened by the HPFRCC infill walls was investigated through the experimental tests, and the test results showed that they have improved strength and deformation capabilities compared to that strengthened by the RC infill wall. A simple numerical modeling method, called the modified longitudinal and diagonal line element model (LDLEM), was introduced to consider the seismic strengthening effect of the infill walls, in which a section aggregator approach was also utilized to reflect the effect of shear in the column members of the RC frames. The proposed model showed accurate estimations on the strength, stiffness, and failure modes of the test specimens strengthened by the infill walls with and without fibers.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.9-12
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• 2001

Composite materials can be used economically and efficiently in broad civil engineering applications when standards and processes for analysis, design, fabrication, construction and quality control are established. Many of the bridge systems, including the girders and cross-beams, and concrete decks behave as the special othotropic plates. Such systems with boundary conditions other than Navier or Levy solution types, or with irregular cross sections, analytical solution is very difficult to obtain. Numerical method for eigenvalue problems are also very much involved in seeking such a solution. A method of calculating the natural frequency corresponding to the first mode of vibration of beam and tower structures with irregular cross-sections was developed and reported by the author in 1974 Recently, this method was extended to two dimensional problems including composite laminates, and has been applied to composite plates with various boundary conditions with/without shear deformation effects and reported at several international conferences including the Eighth Structures Congress of American Society of Civil Engineers in 1990. In this paper, the result of application of this method to the special orthotropic plates with various boundary condition is presented.

• Composites Research
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• v.12 no.4
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• pp.33-41
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• 1999

In this paper, a simple but accurate method of vibration analysis of structural elements with or without attached mass/masses is presented. The method used has been developed by D.H., Kim since 1974. This method is very effective for the plates with arbitrary conditions and irregular sections. This method is applied to the special orthotropic plate with two opposite edges simply supported and the other two opposite edges free. Such plate represents the most of the simply supported bridges/decks, including concrete and girders-cross beam systems. Detailed illustration is given for beams and plates for easy understanding. Some laminate orientation for which the special orthotropic equations can be applied are identified.

• Composites Research
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• v.12 no.4
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• pp.25-32
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• 1999

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates on elastic foundation with free boundaries is presented. Such plates represent the concrete highway slab and hybrid composite pavement on bridges. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation and the aspect ratio of the plate on the natural frequency is thoroughly studied. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is also studied, in deep.

• Computers and Concrete
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• v.26 no.2
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• pp.137-150
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• 2020

In this paper, the bending behavior of single-walled carbon nanotube-reinforced composite (CNTRC) laminated plates is studied using various shear deformation plate theories. Several types of reinforcement material distributions, a uniform distribution (UD) and three functionally graded distributions (FG), are inspected. A generalized higher-order deformation plate theory is utilized to derive the field equations of the CNTRC laminated plates where an analytical technique based on Navier's series is utilized to solve the static problem for simply-supported boundary conditions. A detailed numerical analysis is carried out to examine the influence of carbon nanotube volume fraction, laminated composite structure, side-to-thickness, and aspect ratios on stresses and deflection of the CNTRC laminated plates.

• Computers and Concrete
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• v.7 no.5
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• pp.455-468
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• 2010

This paper presents a prediction and simulation method of tensile stress-strain curves of Engineered Cementitious Composites (ECC). For this purpose, the bridging stress and crack opening relations were obtained by the fiber bridging constitutive law which is quantitatively able to consider the fiber distribution characteristics. And then, a multi-linear model is employed for a simplification of the bridging stress and crack opening relation. In addition, to account the variability of material properties, randomly distributed properties drawn from a normal distribution with 95% confidence are assigned to each element which is determined on the basis of crack spacing. To consider the variation of crack spacing, randomly distributed crack spacing is drawn from the probability density function of fiber inclined angle calculated based on sectional image analysis. An equation for calculation of the crack spacing that takes into quantitative consideration the dimensions and fiber distribution was also derived. Subsequently, a series of simulations of ECC tensile stress-strain curves was performed. The simulation results exhibit obvious strain hardening behavior associated with multiple cracking, which correspond well with test results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.922-927
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• 2006

There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. The advantages of fibre reinforced plastic(FRP) composites over conventional materials motivate their use in highway bridges for replacement of structures. Recently, an FRP deck has been installed on a state highway, located in New York State, as an experimental project. In this paper, a systematic approach for analysis of this FRP deck bridge is presented. Multi-step linear numerical analyses have been performed using the finite element method to study the structural behavior and the possible failure mechanism of the FRP deck-superstructure system Deck's self-weight and ply orientations at the interface between steel girders and FRP deck are considered in this study. From this research, the results of the numerical analyses were corroborated with field test results. Analytical results reveal several potential failure mechanism for the FRP deck and truss bridge system The results presented in this study may be used to propose engineering design guideline for new and replacement FRP bridge deck structure.

• Composites Research
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• v.23 no.1
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• pp.23-30
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• 2010

Most of the bridge systems, including the girders, cross-beams, and concrete decks behave as specially orthotropic plates. In general, the analytical solution for such complex system is very difficult to obtain. In this paper presented, a design method of slab bridge of simple supported made by composite materials. For the design of bridge made by the composite materials, cross-section was used the form-core shape because of this shape is economical and profitable, and for output of the stress value used finite difference method. In this paper, the rate of tensile strength reduction due to increased size was considered. Strength-failure analysis procedure, using the reduced tensile strength, was presented. And also numerical study was made for these cases.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.1
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• pp.23-29
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• 2011

This study investigates the axial behavior of CFRP strengthened circular CFT columns and proposes the design formula of CFRP strengthened circular CFT columns. 10 specimens were prepared and axial loading test were conducted to investigate the retrofitting effects of CFRP composites on CFT columns. The main parameters are the number of FRP sheets and D/t ratio. Test results showed that the CFRP retrofitting enhanced the load bearing capacity of the circular CFT columns. Finally, A ACI 440 code applied ultimate axial strength formula is proposed to predict the ultimate strength of CFRP strengthened circular CFT columns. The proposed formula are good agreement with the test results.