Design Of Large-scale Applications Research Articles

Including global stability in truss layout optimization for the conceptual design of large-scale applications

Including stability in truss topology optimization is critical to avoid unstable optimized designs in practical applications. While prior research addresses this challenge by implementing local buckling and linear prebuckling, numerical difficulties remain due to the global stability singularity phenomenon. Therefore, the goal of this paper is to develop an optimization formulation for truss topology optimization including global stability without numerical singularities, within the framework of the preliminary design of large-scale structures. This task is performed by considering an appropriate simultaneous analysis and design formulation, in which the use of a disaggregated form for the equilibrium equations alleviates the singularities inherent to global stability. By implementing a local buckling criterion for hollow truss elements, the resulting formulation is well-suited for the preliminary design of large-scale trusses in civil engineering applications. Three applications illustrate the efficiency of the proposed approach, including a benchmark truss structure and the preliminary design of a footbridge and a dome. The results demonstrate that including local buckling and global stability can considerably affect the optimized design, while offering a systematic means of avoiding unstable solutions. It is also shown that the proposed approach is in a good agreement with linear prebuckling assumptions.

Two-axis Magnetic Field Orientation Dependence of Critical Current in Full-Width REBCO Coated Conductors

Abstract Considerable progress has been made with the development of YBa2Cu3O7-δ and related rare-earth (REBCO) coated conductors in recent years. The introduction of BaZrO3 (BZO) nanoparticles has resulted in enhanced critical current density ( Jc ) for magnetic field orientations away from the intrinsic ab peak, with the absolute Jc and the degree of anisotropy depending on the geometry and orientation distribution of the nanoparticles; and REBCO coated conductors with a variety of substitutions and additions (Gd, Sm, Ba, Zr, Sn) are becoming commercially available in kilometre lengths. It is therefore increasingly important to characterise the magnetic field orientation dependence of critical current ( Ic ) in full-width coated conductors without destructive sample preparation, both for fundamental pinning studies and the design of large-scale applications. A two-axis goniometer has been developed, allowing the critical current to be measured as a function of both the magnitude and orientation of the applied magnetic field, Ic(B,θ,ϕ) , on full-width samples. Measurements of Ic(B,θ,ϕ) at 77 K are reported for four REBCO tapes made by metal organic chemical vapour deposition (MOCVD) with different rare earth content and the results interpreted in relation to rare earth substitution and pinning centre populations. The implications of the field orientation dependence for low and intermediate field applications are discussed.