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RISS 인기검색어
- 검색키워드
- 저자 : David L.N.F. Amorim (검색결과 3 건)
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A new formulation of cracking in concrete structures based on lumped damage mechanics
Daniel V.C. Teles,Rafael N. Cunha,Ricardo A. Picón,David L.N.F. Amorim,Yongtao Bai,Sergio P.B. Proença,Julio Flórez-López 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.5
Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.
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Energy equivalent lumped damage model for reinforced concrete structures
Renério Pereira Neto,Daniel V.C. Teles,Camila S. Vieira,David L.N.F. Amorim 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.2
Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.
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Leonardo A. B. Silva,Higor S. D. Argôlo,David L. N. F. Amorim 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1
The search to reduce engineering costs leads to the development of new materials and design concepts to obtain lighter and slender structures. Consequently, when using structural parts with cross-sections composed by slender plates, the phenomenon of local instability becomes more evident and is usually treated as a form of collapse. Generally, the behaviour of the structure in terms of local buckling requires refi ned solutions. Then, it is usual to employ fi nite element modelling using meshes with several shell or three-dimensional elements, leading to high computational costs. Therefore, this study proposes a numerical model based on Lumped Damage Mechanics (LDM) applied to local buckling in steel rectangular hollow sections subjected to compressive axial force with bending moment. In the LDM, it is assumed that all the nonlinear eff ects of a fi nite element are concentrated in plastic hinges, where it signifi cantly reduces the computational cost of the computational analysis. For the proposed formulation, equations based on experiments of other authors were introduced to analytically calculate the model parameters. To evaluate the accuracy of the proposed model, the numerical results were compared to other experiments. Thus, it was concluded that the numerical results were satisfactory, since the numerical curves showed similar behaviour when compared to the experimental ones.
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