Multi-layered composite beams, which consist of multiple layers with different material are commonly used in various engineering fields to obtain enhanced structural property. However, complete shear connec-tion between the layers can hardly be achieved in practice and it gives rise to partial interaction between the layers. The partial interaction in the multi-layered composite beam induces interlayer slips between the layers and it results in a decrease in strength and an increase in deflection. Thus, the partial interaction effect be-tween the layers and the resulting interlayer slips should be taken into account for optimal design and accu-rate analysis of the actual behavior of the multi-layered structures.
In spite of many analysis of two-layer and three-layer composite beams with deformable shear connec-tions, the researches about general multi-layered structures have been very rarely discussed and most of the researches are limited to only two-dimensional loading condition. In order to fulfill the needs for more accu-rate evaluation of the actual structure behavior, the further study about the three-dimensional model for gen-eral multi-layered beam structure is necessary.
In the present research, the beam finite element which is applicable to the three-dimensional analysis of the multi-layered composite beam structures was introduced. Instead of modeling the each layer of the beam, the beam structure was regarded as an association of the sub-beams including slip modes. Conse-quently, the displacement field of the multi-layered composite beam was decomposed into the displacements of the associated sub-beams represented by a single beam element and the slip displacements modeled by slip modulus and slip modes that composed of the bending slip modes and axial slip modes. Load-slip rela-tion is assumed to be linear elastic behavior with the constant slip modulus. Since the total slip displacements are represented by slip modes with the slip modulus, only two additional DOFs are required for the two-dimensional analysis and it can be easily extended to the three-dimensional problems by inserting another slip DOF corresponding to the extended dimension.
The main advantage of the present beam model is that any multi-layered beam can be modeled by a single beam and slip modes. Therefore, the present beam element enables straightforward modeling of the multi-layered composite beam with relatively small number of DOFs. Also, three-dimensional analysis can be easily performed without complicated modeling procedure by applying additional slip mode with correspond-ing slip DOF.
In order to verify the present beam model, several numerical studies are performed. Firstly, the present beam model is compared to the conventional one to demonstrate the influence of the slip modulus on the partial interaction effect. Secondly, the numerical examples discussed by other authors are examined. Lastly, extension to the three-dimensional problem is introduced
본 논문에서는 적층빔에서의 불완전한 전단 연결로 인한 휨강성의 저하와 경계면에서의 슬립을 모델링할 수 있는 빔 유한요소를 제시한다. 적층빔의 각 구성요소를 개별적으로 해석하는 방법이 아닌, 하나의 빔과 빔 절점에서의 슬립모드를 통해서 전체 적층빔을 모델링한다. 슬립모드는 빔의 단면에서 정의되는 슬립함수와 빔 절점에서의 슬립 자유도를 통해서 모델링되며, 슬립 모듈러스와 함께 경계면에서의 불완전한 전단 연결을 나타낸다. 이를 통해서 적층빔에서의 경계면의 수와 관계없이 상대적으로 적은 자유도만으로도 전체 적층빔의 모델링이 가능하다. 또한 슬립 자유도를 추가함으로써 간단히 3D 모델로의 확장이 가능하다.
