• Steel and Composite Structures
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• v.33 no.5
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• pp.653-661
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• 2019

In this paper aeroelastic behavior of 3-phase nano-composite beam-plate with double delaminations is investigated. It is tried to study the effect of carbon nano-tubes (CNTs) on critical flutter pressure of reinforced damaged nano-composite structures. In this case, the CNTs are appending to the polymer matrix uniformly. The Eshelby-Mori-Tanaka model is used to obtain the effective material properties of 3-phase nano-composite beam-plate. To investigate the aeroelastic behavior of delaminated beam-plate subjected to supersonic flow, it is assumed that the damaged segments are forced to vibrate together. The boundary conditions and auxiliary conditions at edges of delaminated segments are used to predict critical flutter pressure. The influence of CNTs and different delamination parameters such as delamination length, axial position and its position through thickness are investigated on critical flutter pressure.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.217-227
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• 2002

Theoretical and experimental free vibration characteristics of cantilevered laminated composite beams with single or multiple transverse non-propagating open cracks are investigated. The presence of intrinsic cracks in beams modifies the flexibility and in turn free vibration characteristics of the structures, and the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack. Also the experimental results are well coincide with the numerical results in the decrease of natural frequencies and the transformation of mode shapes because of intrinsic cracks in the composite or aluminum beams. It is revealed that non-destructive crack detection(NDT) or vibration based inspection(VBI) is possible by analyzing the free vibration responses of cracked composite beams.

• Coupled systems mechanics
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• v.13 no.2
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• pp.133-151
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• 2024

In this paper, an improved theoretical interfacial stress analysis is presented for simply supported composite aluminum- sandwich honeycomb beam strengthened by imperfect FGM plateusing linear elastic theory. The adherend shear deformations have been included in the present theoretical analyses by assuming a linear shear stress through the thickness of the adherends, while all existing solutions neglect this effect. Remarkable effect of shear deformations of adherends has been noted in the results.It is shown that both the sliding and the shear stress at the interface are influenced by the material and geometry parameters of the composite beam. This new solution is intended for applicationto composite beams made of all kinds of materials bonded with a thin plate. Finally, numerical comparisons between the existing solutions and the present new solution enable a clear appreciation of the effects of various parameters.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.3
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• pp.7-12
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• 2013

The demand for the structural system of reduction of story height increases because buildings are getting higher. The existing structural systems are not efficiency. Thus, it is hard to reduce the story height and existing methods cannot secure economics as expected. This study aims at developing the partially concrete-filled new type composite beam, which can efficiently resist against the end negative moment and central positive moment, also reduce deflection of beams. Through case studies on loading of concentrated load and uniformly distributed load to fixed beam, we could find the most efficient ratio of moment of inertia and the ratio ${\alpha}$(end beam length to span). The gap space between middle and end beam can be used as facilities installation, consequently the suggested Omega beam system is expected to get the effect of reduction in story height as well as reduction of quantity.

• Steel and Composite Structures
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• v.19 no.3
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• pp.735-757
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• 2015

Composite bonding steel plate (CBSP) is a newly developed type of structure strengthened technique applicable to the existing RC beam. This composite structure is applicable to strengthening the existing beam bearing high load. The strengthened beam consists of two layers of epoxy bonding prestressed steel plates and the RC beam sandwiched in between. The bonding enclosed and prestressed U-shaped steel jackets are applied at the beam sides. This technique is adopted in case of structures with high longitudinal reinforcing bar ratio and impracticable unloading. The prestress can be generated on the strengthening steel plates and jackets by using the CBSP technique before loading. The test results of full-scale CBSP strengthened beams show that the strength and stiffness are enhanced without reduction of their ductility. It is demonstrated that the strain hysteresis effect can be effectively overcome after prestressing on the steel plates by using such technique. The applied plates and jackets can jointly behave together with the existing beam under the action of epoxy bonding and the mechanical anchorage of the steel jackets. The simplified formulas are proposed to calculate the prestress and the ultimate capacities of strengthened beams. The accuracy of formulas was verified with the experimental results.

• Advances in nano research
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• v.14 no.2
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• pp.141-154
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• 2023

Effects of viscoelastic foundation on vibration of curved-beam structure with clamped and simply-supported boundary conditions is investigated in this study. In doing so, a micro-scale laminate composite beam with two piezoelectric face layer with a carbon nanotube reinforces composite core is considered. The whole beam structure is laid on a viscoelastic substrate which normally occurred in actual conditions. Due to small scale of the structure non-classical elasticity theory provided more accurate results. Therefore, nonlocal strain gradient theory is employed here to capture both nano-scale effects on carbon nanotubes and microscale effects because of overall scale of the structure. Equivalent homogenous properties of the composite core is obtained using Halpin-Tsai equation. The equations of motion is derived considering energy terms of the beam and variational principle in minimizing total energy. The boundary condition is assumed to be clamped at one end and simply supported at the other end. Due to nonlinear terms in the equations of motion, semi-analytical method of general differential quadrature method is engaged to solve the equations. In addition, due to complexity in developing and solving equations of motion of arches, an artificial neural network is design and implemented to capture effects of different parameters on the inplane vibration of sandwich arches. At the end, effects of several parameters including nonlocal and gradient parameters, geometrical aspect ratios and substrate constants of the structure on the natural frequency and amplitude is derived. It is observed that increasing nonlocal and gradient parameters have contradictory effects of the amplitude and frequency of vibration of the laminate beam.

• Steel and Composite Structures
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• v.21 no.4
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• pp.829-847
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• 2016

This paper investigates the flexural capacity of simply supported steel-concrete composite I beam and box beam under positive bending moment through combined experimental and finite element (FE) modeling. 24 composite beams are included into the experiments and parameters including shear connection degree, transverse reinforcement ratio, section form of girder, diameter of stud and loading way are also considered and investigated. ABAQUS is employed to establish FE models to simulate the behavior of composite beams. The influences of a few key parameters, such as the shear connection degree, stud arrangement, stud diameter, beam length and loading way, on flexural capacity are discussed. In addition, three methods including GB standard, Eurocode 4, and Nie method are also used to estimate the flexural capacity of composite beams and also for comparison with experimental and numerical results. The results indicate that Nie method may provide a better estimation in comparison to other two standards.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.3
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• pp.145-152
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• 2000

In simply supported composite beams, the neutral axis of the composite cross section is usually located near the top flange of the steel H-shape, so that the top flange does not impart much strength to the member. This suggests that omitting the top flange entirely could be a means to lower the cost of the beam without greatly reducing the strength. However, It is not easy for inverted T-shaped composite beam to construct and to apply continuous beam which has negative bending moment. As a result, it would get more workability and decrease capability of lateral buckling and local buckling, if the bottom flange of inverted T-shaped steel used as a form. Therefore. the objectives of this study are to investigate strength and behaviors of inverted T-shaped composite beam which web is encased by concrete and to grasp bending capacity and efficiency of composite by comparing and analyzing in test piece.

• Computers and Concrete
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• v.28 no.5
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• pp.497-506
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• 2021

Steel-concrete composite structures and precast concrete elements have a common prefabrication process and allow fast construction. The use of hollow-core slabs associated with composite floors can be advantageous. However, there are few studies on the subject, impeding the application of such systems. In this paper, a numerical model representing the considered system using the FE (finite element)-based software DIANA is developed. The results of an experimental test were also presented in Souza (2016) and were used to validate the model. Comparisons between the numerical and test results were performed in terms of the load versus displacement, load versus slip, and load versus strain curves, showing satisfactory agreement. In addition, a wide parametric study was performed, evaluating the influence of several parameters on the behaviour of the composite system: The strength of the steel beam, thickness of the web, thickness and width of the bottom flange of the steel beam and concrete cover thickness on top of the beam. The results indicated a great influence of the steel strength and the thickness of the bottom flange of the steel beam on the capacity of the composite floor. The remaining parameters had limited influences on the results.

• Steel and Composite Structures
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• v.51 no.5
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• pp.563-573
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• 2024

This research experimentally evaluated the local stress distribution along the cross-section of composite beams under both positive and negative moments. The experiment utilized a large-scale, two-story, two-by-three bay steel gravity frame with a concrete on metal deck floor system. The composite shear connections, which are nominally assumed to be pinned under gravity loading, can develop non-negligible moment-resisting capacity when subjected to lateral loads. This paper discusses the local stress distribution, orshear lag effects, observed near the beam-to-column connections when subjected to combined gravity and lateral loading. Strain gauges were used for measurements along the beam depth at varying distances from the connection. The experimental data showed amplified shear lag effects near the unconnected region of the beam web and bottom flange under the applied loading conditions. These results indicate that strain does not vary linearly across the beam cross-section adjacent to the connection components. This insight has implications for the use of experimental strain gauge data in estimating beam demands near the connections. These findings can be beneficial in informing instrumentation plans for future experimental studies on composite beams.