Vietnam Journal of Mechanics

Comparing with reinforced concrete structure, member rigidity of steel structure is less, and displacement of steel structure is larger than that of reinforced concrete structure, so the secondary moment due to axial force has to be considered, i e., the problem of P-Delta effect. For most building structures, especially tall steel buildings, the P-Delta effect of most concern occurs in the columns due to gravity load, including dead and live load. The column axial forces are compressive, making the structure more flexible against lateral loads. If compressive P-forces are present and are large enough, the structure may buckle. Local buckling of individual members or global buckling of the whole structure is possible. This paper presents the method to analysis stability of steel frames with semi-rigid connections and rigid zones by using P-Delta effect.

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This paper is a study of the vibroacoustic behavior of orthotropic laminated composite rectangular plate under a sound wave excitation in thermal environments. An improved analytical procedure has been developed that allows for an efficient solution of the finite composite plate sound transmission problem. A symmetrically orthotropic laminated composite plate is considered. The plate is modeled with classic thin-plate theory and is assumed to be clamped on all four sides. The incident acoustic pressure is modeled as a harmonic plane wave impinging on the plate at an arbitrary angle. The sound transmission loss is calculated from the ratio of incident to transmitted acoustic powers.

The spectral approach is employed for spectral analysis of a beam subjected to an arbitrary force traveling along the beam with constant speed. First, an expression for exact frequency response of a beam subjected to moving arbitrary force and general boundary conditions has been constructed. The obtained frequency domain response allows straightforwardly exhibiting response vibration components governed by different frequencies such as the natural, loading and driving ones and their interaction. This provides also alternative insight to the cancellation of response at natural frequency. The theoretical development is illustrated and validated by numerical examination on a simply supported beam under moving harmonic forces.

This report presents an analytical approach to the natural frequency analysis of a porous beam consisting of a host porous layer reinforced with graphene platelets (GPLs), namely GPL-reinforced porous core, and two piezoelectric outer layers. In the modelling, symmetric distributions of both porosity and GPLs in the core are supposed. The effective mechanical properties of the GPL-reinforced porous core are estimated by Halpin–Tsai model and the rule of mixture. The electric potential in each piezoelectric layer is assumed to vary linearly across its thickness. Two types of electrical boundary conditions, which are open- and closed-circuits, are considered for the free surfaces of the piezoelectric layers. Parabolic shear deformation beam theory associated with Hamilton’s principle is adopted to derive the governing equations of the free vibration. Afterwards these equations are solved analytically by Navier’s solution. Comparative and comprehensive studies are carried out to examine the accuracy and effects of parameters and conditions, such as GPL weight fraction, porosity coefficient, and electrical boundary conditions on the natural frequencies of the beam.

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Các cấu trúc hàn giữa thép carbon và thép không gỉ hiện đang được ứng dụng rộng rãi trong nhiều lĩnh vực như cầu đi bộ, công nghiệp thực phẩm, công nghiệp hóa chất, ngành dầu khí và nhà máy nhiệt điện,... Các cấu trúc composite này tận dụng những ưu điểm của từng loại vật liệu cho các bộ phận khác nhau của cấu trúc. Trong các cấu trúc hàn giữa thép carbon và thép không gỉ, cấu trúc được tạo thành bởi mối hàn T, đây là loại mối hàn phổ biến nhất. Việc tính toán ứng suất dư và biến dạng hàn của mối hàn T giữa thép carbon thấp và thép không gỉ là cơ sở để đánh giá khả năng làm việc của cấu trúc này. Trong nghiên cứu này, ứng suất dư và biến dạng hàn của mối hàn T được xác định bằng phương pháp lực tưởng tượng. Mối hàn hai mặt của mối hàn T giữa thép carbon thấp và thép không gỉ được hàn đồng thời bằng quy trình hàn MIG. Kết quả thu được về ứng suất dư và biến dạng hàn trong trường hợp này được so sánh với trường hợp hàn một mặt để xác định sự khác biệt về ứng suất dư và biến dạng hàn trong hai trường hợp.

Let \(\Omega \) be a bounded domain in the plane, representing an elastic body. Let \(\Gamma_0 \) be a portion of the boundary \(\Gamma\) of \(\Omega \), \(\Gamma_0 \) being assumed to be paralled to the \(x\)-axis. It is proposed to determine the stress field in \(\Omega \) from the displacements and surface stresses given on \(\Gamma_0 \). Under the assumption of plane stress, it is shown that \(u_x + u_y\) is a harmonic function. An Airy stress function is introduced, from which the stress field is computed.