Showing papers on "Portal frame published in 2021"

Relationship between applied force and magnetic field in a pseudo-static test of a portal frame

Abstract: Metal magnetic memory (MMM) testing is a nondestructive approach for evaluating the stress concentration and early damage of ferromagnetic components. However, research on the MMM testing of large steel structures has been limited. Thus, this study investigates the suitability of MMM technology for monitoring the damage in steel structures exposed to complex stresses. The normal components of magnetic signals Hp(y) on the beams and columns of a portal frame are obtained through pseudo-static testing. The signal increment ΔHp(y) and its absolute value |ΔHp(y)| under different loads are analyzed. The relationship between the equivalent stress and magnetic signal is investigated through numerical simulation. The results show that the ΔHp(y) curves are similar during the elastic stage but change abruptly during the plastic phase. Moreover, the differences in the magnetic signal directions caused by the varying detection directions cannot be ignored. In the elastic stage, with the increase in the load, |ΔHp(y)| curves initially increase and then decrease. The formation of the ΔHp(y) curve is similar to the distribution of the equivalent stress. The mutation of ΔHp(y) can determine whether a specimen is entering the plastic phase, and can warn against structural failure. The magnetic signal distribution qualitatively reflects the stress distribution.

Numerical Simulations and Control of Offshore Energy Harvesting Using Piezoelectric Materials in a Portal Frame Structure

Abstract: Buoy systems are an alternative for micropowering small devices in remote locations. Portal frames are very useful to harvest the energy of the waves into usable energy. Thus, using the current models for a portal frame in the literature and the spectrum of available energy in sea waves, a nonlinear mathematical model accounting for the coupling of a nonlinear piezoelectric material is considered. The neighbour of selected variables is analyzed and then optimized by a process utilizing the particle swarm optimization (PSO) algorithm. Furthermore, an optimal control using the linear-quadratic regulator (LQR) controller is applied to control the load resistance of the piezoelectric circuit. The optimization process and the LQR show to be effective. The results show a general gain due to optimization and a relatively small gain using the controller.

Experimental Study and Numerical Simulation of Plane Steel Frame with Rubberized Connecting Technology Subjected to Seismic Effect

Abstract: This paper representsexperimental and numerical study the behavior of the rubberized steel frame connections. One single-bay, one-story without elastic buckling are cyclically tested. The experimental specimens are simulated and analyzed by the ABAQUS program. Four specimens of steel plane portal frame are investigated under horizontal reversed cyclic loads. The specimen connections are developed by using different diameters of composite steel bolts/rubberinstead of conventional steel bolts to connect the beams with columns. The yield and ultimate strength, ductility, envelope curves, and damping ratio of these specimens are analyzed and compared. The finite element method is used to establish and verify the results of the laboratory test. The results of the experimental and numerical tests gave a large load-carrying capacity, reduction in the stresses, excellent ductility and energy dissipation capacity, and remarkably improved damping ratio.

Experimental Study on Lateral-Load-Resisting Capacity of Masonry-Infilled Reinforced Concrete Frames

Abstract: In this study, an experimental program was performed on masonry-infilled frame specimens with varied construction precision and masonry thickness. A total of five portal frame specimens, which consist of four masonry-infilled frames and a bare frame, were tested, and the results were analyzed to investigate the effects of construction precision and interaction between the masonry infill and the frame. The test results indicated that the gap in the masonry infill decreased strength by 75% to 80% and stiffness by 55% to 70%. A comparison between the measured and predicted peak strength using the current code shows that the code equations underestimate the strength by up to 70%. This is due to the fact that the contribution of friction in shear resistance of the masonry wall is actually ignored in the current code since no adequate method for estimating the normal force is provided. In addition, reflecting the observation that the failure mode of the columns changed to shear failure when thick masonry walls were used, a mechanical model that can explain the shear failure and enables the estimation of maximum strength was proposed. The maximum strengths of the specimens calculated using the proposed model were in good agreement with the experimental results.

Study on reinforcement effect of H type assembled anchoring joint in portal frame

Abstract: With the development of society, portal frame has been increasingly used in industrial buildings because of light weight, high degree of industrialization, and high economic efficiency. Some existi...

Dynamics and Control of Energy Harvesting from a Non-ideally Excited Portal Frame System with Fractional Damping

Abstract: This paper analyzes the dynamics of a nonlinear piezoelectric energy harvesting device connected to a portal frame accounting for the influence of the fractional order derivative introduced due to damping. The identification of the behavior of the portal frame is obtained by the analysis of time histories, phase planes, FFT spectrum and 0-1 test. The numerical analyses show that the fractional order sustains the chaotic behaviors of the system. The average harvested power is computed for each value of the chosen fractional derivative, to demonstrate that the system response considerably affects the harvested power. To suppress the chaotic behavior a control technique is proposed associated with two controls: the feedback control by SDRE control and the feedforward control.

Comments on the Influence of Fractional Damping on the Nonlinear Dynamics of a Portal FrameEnergy Harvester Using Wavelet Spectrum and 0–1 Test for Chaos

Abstract: This note analyzes the vibrations of a non-linear piezoelectric energy harvesting device connected to a portal frame, considering the influence of fractional-order derivative damping. The identification of the behavior of the portal frame was obtained by analysis of various dynamic responses, using time histories, phase portraits, the continuous wavelet transform (CWT) using Morlet wavelet, FFT spectrum and 0–1 test for chaos. The numerical analysis shows that the fractional-order damping sustains chaotic behaviors of the system. The average harvested power was computed for each value of fractional derivative order chosen, to demonstrate that the system response considerably affects the power harvested.

Sliding wheel type steel wire rope dragging and lifting portal system of electric forklift

Abstract: The invention discloses a sliding wheel type steel wire rope dragging and lifting portal frame system of an electric forklift, and belongs to the technical field of forklifts. The system comprises a bottom sliding double-movable-wheel mechanism, a main power transmission system, a top sliding double-fixed-wheel mechanism, a steel wire rope, an inner portal frame, an outer portal frame, a pallet fork, a position control system and the like. According to the system, on the basis of a conventional forklift assembly, the steel wire rope, the top sliding double-fixed-wheel mechanism, a double-shaftmotor, a double-domain variable-torque roller, the bottom sliding double-movable-wheel mechanism and the like drag and pull a portal frame of the electric forklift to lift so as to achieve lifting motion of the pallet fork; and the problems that an existing hydraulic drive forklift lifting system is large in weight, high in energy consumption, large in number of parts and high in production and maintenance cost are solved, and the purposes of stable portal frame lifting, light weight, low energy consumption, simple structure, convenient control and easy maintenance are achieved.

Hoisting frame convenient to fold

Abstract: The invention belongs to the technical field of hoisting equipment, and particularly relates to a hoisting frame convenient to fold. The hoisting frame comprises a portal frame and a winch connected to the portal frame, wherein the portal frame comprises a portal support and two folding bases connected to vertical supports of the portal support; each folding base comprises a storage box and two supporting arms connected to the storage box; each storage box comprises two U-shaped wall plates; the vertical supports penetrate into U-shaped openings of the wall plates to be connected with the storage boxes; the two wall plates are arranged in a spaced manner to form a cavity used for storing the supporting arms. U-shaped sliding grooves are formed in the wall plates; sliding blocks matched with the two U-shaped sliding grooves are arranged on the supporting arms; and stop blocks are arranged on the supporting arms. The hoisting frame is used for solving the technical problem that an existing hoisting frame structure is fixed and not convenient to fold.

Application of improved gradient projection method to parametric optimization of steel lattice portal frame

Abstract: The paper has proposed a mathematical model for parametric optimization problem of the steel lattice portal frame. The design variable vector includes geometrical parameters of the structure (node coordinates), as well as cross-sectional dimensions of the structural members. The system of constraints covers load-carrying capacities constraints formulated for all design sections of structural members of the steel structure subjected to all ultimate load case combinations. The displacements constraints formulated for the specified nodes of the steel structure subjected to all serviceability load case combinations have been also included into the system of constraints. Additional requirements in the form of constraints on lower and upper values of the design variables, constraints on permissible minimal thicknesses, constraints on permissible maximum diameter-to-thickness ratio for the structural members with circle hollow sections, as well as the conditions for designing gusset-less welded joints between structural members with circle hollow sections have been also considered in the scope of the mathematical model. The method of the objective function gradient projection onto the active constraints surface with simultaneous correction of the constraints violations has been used to solve the formulated parametric optimization problem. New optimal layouts of the steel lattice portal frame by the criterion of the minimum weight, as well as minimum costs on manufacturing and erection have been presented.

The Influence on Portal Frame Buckling of Different Cladding Systems – A Comparative Numerical Study Considering Stressed Skin Effect

Abstract: In 2016 the authors investigated the stressed skin effect of trapezoidal steel sheeting and of deep deck sheeting as roof cladding on the pitched roof portal frame structure, in terms of buckling modes and the load multiplication factor, by comparing the results of a traditional design model with the result of a numerical model including the diaphragm stiffness of the considered claddings. Later, in 2018 the influence of the purlin-to-beam connection stiffness on the stress skin action of trapezoidal steel sheeting was investigated. The study of stressed skin action was further extended by the authors to the effects given by sandwich panels in 2019, where a methodology was presented to including the stressed skin effect of sandwich panels in a simple and time effective way into the day-to-day design methodologies of common engineers. In 2021 the procedures were improved to present a comparison between different cladding types in terms of sway displacement of the frame structure with semi-rigid joints and load transfer by applying the developed methodology to a reference building. The purpose of the current paper is to compare and to estimate in a numerical manner the influence of the cladding type on the sway stability indicators of the structure, such as buckling modes and critical load multiplication factors cr. The paper presents comparative results obtained in terms of stabilization effects given by trapezoidal sheeting and mineral wool core sandwich panels supported by Z purlins applied on the reference cold-formed steel structure.