Resumo em Inglês:

Abstract The laminated beam with uniformly vertical displacement can be divided into contact region and separation region when bending deformation occurs. Friction between the interfaces will cause the stiffness inconsistency between the separation region and contact region. In this paper, calculation formula of section stiffness considering interface friction effect is derived. Assuming that the beam vibrates freely in equal wavelength and equal stiffness forms respectively, the calculating formulas of natural vibration frequencies of simply supported and cantilever beams are derived. Finally, based on a steel-concrete laminated test beam with uniform vertical displacement, the natural vibration frequencies of the beam are calculated. The conclusions are as follows: The derived formulas can calculate the natural vibration frequencies of laminated beams under different interface states effectively; The influence of friction effect on the vibration frequency of laminated beams becomes more and more obvious with the increase of the order.

Resumo em Inglês:

Abstract In this paper, a finite element (FE)-based model that efficiently evaluates the dynamic behavior of dam-reservoir-foundation interaction (DRFI) problem was proposed including the radiation of waves to the unbounded rock and reservoir domains. Lagrangian fluid elements were used to discretize the near-field reservoir domain, while the presented infinite fluid elements were used to discretize the far-field reservoir domain. The fully coupled equation of motion for DRFI problem was solved by direct method. A two-dimensional (2D) plane-strain FE formulation of the problem is written in FORTRAN 90 programming language. Investigations were conducted on the effect of near-field domain size (length and depth) on the dynamic behavior of DRFI, dam-foundation interaction (DFI), and dam-reservoir interaction (DRI) problems. The results of this study demonstrate that the proposed model outperforms many other models that have been evolved in the literature in terms of accuracy and speed. The reflected hydrodynamic pressures at the far-field reservoir domain were efficiently absorbed by the suggested infinite fluid elements. The near-field domains size has a noticeable impact on the dynamic behavior of the dam. Making an exact choice about the size is more challenging. However, it was observed that the size of 1.5H is the physically appropriate response.

Resumo em Inglês:

Abstract This paper investigates the effect of KFRP composite sheets as a strengthening material in improving the load-carrying resistance of lightweight foam concrete beams using a FEA modelling framework. The study employed three parametric strengthening schemes (i.e., KFRP length, woven architecture types and KFRP thickness). Twenty-seven beam specimens were tested, and respective failure modes and ultimate load at failure were discussed. All the strengthened beam specimens failed mostly in shear mode and, to a lesser extent, in FRP fracture. Despite the absence of de-bonding failure, improvement of strengthening using KFRP sheet technique was exhibited. Later, Extended Finite Element Method (XFEM) Modelling was incorporated following failure mode exhibited. Strength predictions incorporating the traction-separation relationship using XFEM techniques. Validation work with experimental datasets showed good agreements with average discrepancies of less than 10%. The numerical approach can be used as a strength prediction tool in concrete beams with externally bonded FRPs.

Resumo em Inglês:

Abstract A reinforced concrete (RC) column improved with central large-diameter butted steel rods (CLBSR column) has been proposed to increase the limit value of the axial compression ratio. This paper presents the seismic behavior analysis of CLBSR columns subjected to low-cycle reciprocating loading. The CLBSR columns were also compared with the RC column improved with central large-diameter steel rods (CLSR column) and the RC column improved with central reinforcement bars (CRB column) under the same experimental conditions. The typical failure modes, hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation capacity were all investigated. The improved PARK damage model obtained the corresponding relationships between the damage indices and the damage state of each column. The test results indicated that the CLBSR columns and CLSR columns had similar seismic behavior, but were slightly inferior to the CRB columns. Overall, the butt joint of large-diameter steel rods had little effect on the seismic behavior.

Resumo em Inglês:

Abstract In this paper, a semi-analytical method for solving circular curved beams is proposed to study the free vibration of in-plane circular curved beams in both undamaged and damaged configurations. The crack damage of the structure is represented by the cross-sectional reduction of the damaged element. Based on the discrete circular curved beam model, the coupling stiffness matrices of shear, compression and bending are derived. Combined with the lumped mass matrix and the dynamic characteristic equation of the multi-degree-of-freedom system, the frequencies and modes of the damaged and undamaged structures are calculated. The results are compared with the finite element method, and the good consistency between them is verified.