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In the last decades, the demand and use of renewable energies have been increasing. The increase in renewable energies, particularly wind energy, leads to the development and innovation of powerful wind energy converters as well as increased production requirements. Hence, a higher supporting structure is required to achieve higher wind speed with less turbulence. To date, the onshore wind towers with tubular connections are the most used. The maximum diameter of this type of tower is limited by transportation logistics. The purpose of this paper is to propose an alternative wind turbine lattice structure based on half-pipe steel connections.

In this study, a new concept of steel hybrid tower has been proposed. The focus of this work is the development of a lattice structure. Therefore, the geometry of the lattice part of the tower is assessed to decrease the number of joints and bolts. The sections used in the lattice structure are constructed in a polygonal shape. The elements are obtained by cold forming and bolted along the length. The members are connected by gusset plates and preloaded bolts. A numerical investigation of joints is carried out using the finite element (FE) software ABAQUS.

Based on the proposed study, the six “legs” solution with K braces under 45° angle and height/spread ratio of 4/1 and 5/1 provides the most suitable balance between the weight of the supporting structure, number of bolts in joints and reaction forces in the foundations, when compared with four “legs” solution.

In this investigation, the failure modes of elements and joints of an alternative wind turbine lattice structures, as well as the rotation stiffness of the joints, are determined. The FE results show good agreement with the analytical calculation proposed by EC3-1-8 standard.

The purpose of this paper is to present integrated methodologies based on multilevel modelling concepts for finite element analysis (FEA) of reinforced concrete (RC) shell structures, with specific reference to account for the nonlinear behaviour of cracked concrete and the other associated features.

Geometric representation of the shell is enabled through multiple concrete layers. Composite characteristic of concrete is accounted by assigning different material properties to the layers. Steel reinforcement is smeared into selected concrete layers according to its position in the RC shell. The integrated model concurrently accounts for nonlinear effects due to tensile cracking, bond slip and nonlinear stress‐strain relation of concrete in compression. Smeared crack model having crack rotation capability is used to include the influence of tensile cracking of concrete. Propagation and change in direction of crack along thickness of shell with increase in load and deformation are traced using the layered geometry model. Relative movement between reinforcing steel and adjacent concrete is modelled using a compatible bond‐slip model validated earlier by the authors. Nonlinear iterative solution technique with imposed displacement in incremental form is adopted so that structures with local instabilities or strain softening can also be analysed.

Proposed methodologies are validated by evaluating ultimate strength of two RC shell structures. Nonlinear response of McNeice slab is found to compare well with that of experiment available in literature. Then, a RC cooling tower is analysed for factored wind loads to study its behaviour near ultimate load. Numerical validation demonstrates efficacy and usefullness of the proposed methodologies for nonlinear FEA of RC shell structures.

The present paper integrates critical methodologies used for behaviour modelling of concrete and reinforcement with the physical interaction among them. The study is unique by considering interaction of tensile cracking and bond‐slip which are the main contributors to nonlinearity in the nonlinear response of RC shell structures. Further, industrial application of the proposed modelling strategy is demonstrated by analysing a RC cooling tower shell for its nonlinear response. It is observed that the proposed methodologies in the integrated manner are unique and provide stability in nonlinear analysis of RC shell structures.

The paper aims to discuss problems of power and energy losses in a double-circuit overhead transmission line. It was observed from energy meters’ readings, that in such a line, active power losses can be measured as “negative”. The “negative” active power losses appear when the active power injected to the circuit is lower than the active power received at the circuit end. The purpose of this paper is to explain this phenomenon.

Theoretical considerations based on mathematical model of the transmission line of π-type confirming that effect are presented. Power losses related to series impedance of the line and to shunt admittance are calculated. The theoretical considerations are confirmed by measurements done on the real transmission line.

The calculations allow to indicate components of the active power losses, i.e. related to electromagnetic coupling among wires of a given circuit, related to electromagnetic coupling between circuits and related to shunt capacitance asymmetry. The authors indicate the influence of the line/wires geometry on the active power losses in a double-circuit overhead transmission line.

Explanation of the effect of “negative” active power losses’ measurement in a double-circuit overhead transmission line is provided in this paper.

The purpose of this paper is to describe the design and development of “Pylon-Climber”, a pole climbing robot (PCR) for climbing along the corner columns of electricity pylon and assisting the electricians to complete maintenance tasks.

Introduces a PCR that is composed of a simple climbing mechanism and two novel grippers. The gripper consists of two angle-fixed V-blocks, and the size of V-block is variable. The clamping method of the angle bar meets the requirement of the force closure theorem. The whole design adopts symmetrical design ideas.

The developed prototype proved possibility of application of PCRs for inspection and maintenance of pylon. The novel gripper can provide enough adhesion force for climbing robot.

The robot is successfully tested on a test tower composed of different specification steel angles, oblique ledges and overlapping steel struts.

Design and development of a novel climbing assistive robot for pylon maintenance. The robot is able to climb along the column of electricity pylon and pass all obstacles. The gripper can reliably grasp the angle bar with different specification and overlapping steel struts from multiple directions.

A tower crane mainly ensures the success or efficiency of building construction. Fatigue crack analysis is important for tower crane components to prevent any accidents to workers in construction sites caused by component failure and to ease the maintenance or replacement of failed components. This work aimed to characterise the damage of failed components, analyse the relationship between the metal magnetic memory (MMM) result and the damage of failed components, and to validate the relationship between MMM and finite element analysis (FEA).

MMM was used in this work to detect any irregularities or early failure on the basis of the high stress concentration zone of ferromagnetic steel using magnetic flux leakage. Magnetic flux leakage was used on the MMM device to achieve the first objective using the MMM system by detecting the irregularities. The results of MMM analysis were validated through comparison with FEA results by determining their relationship.

MMM results show that the position of defects on the tower crane pulley is within the stress area shown on FEA.

Hence, MMM method is a potential tool in monitoring failure mechanism in construction site.

The purpose of this paper is to discuss two evaluation methods of single pole auto-reclosing process effectiveness in HV transmission lines. Secondary arc current and recovery voltage results obtained by load flow calculation are compared to the results obtained by the time domain simulations. Moreover, a nonlinear secondary arc implementation is presented.

A computer simulation studies were performed using DIgSILENT PowerFactory® software to analyse phenomena during single phase to earth short circuit and during single pole circuit breaker opening. Possibilities of electric arc extinction for different earthing solutions of shunt reactors were examined.

The authors indicate, that precise representation of secondary electric arc in power system studies could lead to different conclusion than analysis carried out on simplified arc models. Recommendations for line construction (i.e. earthing reactor installation) and line operation (i.e. prolongation of dead time during auto-reclosing) based on time domain simulations are less restrictive than resulting from the traditional steady-state calculation approach.

An implementation of mathematical model of nonlinear secondary arc for DIgSILENT PowerFactory® software is presented. The model could be used during the process of design of HV transmission line, to assess its proper operation, to calculate dead time during single pole reclosing or to evaluate the necessity of installing additional earthing reactors.

The purpose of this paper is to propose a numerical method in time domain in order to solve the electric and magnetic fields radiated from lightning in the presence of the tall tower. This paper is very important in calculating lightning electromagnetic field – obtaining directly the solution in time domain with a reduced computation time and reduced space memory.

In this paper, a HYBRID method is proposed for the calculation of the electromagnetic field associated with lightning strikes to tall towers. The proposed method is a combination between a numerical integration method and the finite difference time domain (FDTD) method. The HYBRID method is an alternative approach that takes advantage of this combination to calculate, first, the radiated magnetic field; this field is obtained by the use of the Simpson method, and, second the electric field, based partially on the FDTD method.

The results of lightning electromagnetic field in the presence of a tall tower obtained by this proposed method: HYBRID method are in agreement with experimental results or simulated results (by the use of other methods: method in frequency domain). This method can be applied to solve the lightning electromagnetic field equation for far distances or close distances from lightning stroke.

This paper presents a temporal method to obtain the lightning electromagnetic field in the presence of a tall tower with reduced space memory and reduced time.

The purpose of this paper is to introduce a novel technique for printing with multiple materials using the DLP method. Digital-light-processing (DLP) printing uses a digital projector to selectively cure a full layer of resin using a mask image. One of the challenges with DLP printing is the difficulty of incorporating multiple materials within the same part. As the part is cured within a liquid basin, resin switching introduces issues of cross-contamination and significantly increased print time.

The material handling challenges are investigated and addressed by taking inspiration from automated storage and retrieval systems and using an active cleaning solution. The material tower is a compact design to facilitate the storage and retrieval of different materials during the printing process. A spray mechanism is used for actively cleaning excess resin from the part between material changes.

Challenges encountered within the multi-material DLP technology are addressed and the experimental prototype validates the proposed solution. The system has a cleaning effectiveness of over 90 per cent in 15 s with the build area of 72 inches, in contrast to the previous work of 50 per cent cleaning effectiveness in 2 min with only 6 inches build area. The method can also hold more materials than the previous work.

The techniques from automated storage and retrieval system is applied to develop a storage system so that the time complexity of swapping is reduced from linear to constant. The whole system is sustainable and scalable by using a spraying mechanism. The design of the printer is modular and highly customizable, and the material waste for build materials and cleaning solution is minimized.