Composite Tower Research Articles

Wind-Induced Response Analysis and Fatigue Reliability Study of a Steel–Concrete Composite Wind Turbine Tower

Taking an actual 3MW steel–concrete composite wind turbine tower as an example, a finite element model of the tower structure was established, and static bearing capacity and dynamic time history response analyses were performed to identify the locations where the structure is prone to failure. On this basis, the fatigue lives of the turbine tower at the most unfavorable locations were predicted using linear cumulative damage theory, and the fatigue reliability at the corresponding locations of the structure was calculated using the kriging–subset simulation method. The most dangerous locations of the tower that are most prone to failure are as follows: the bottom of the leeward side of the upper steel tube, the flange of the steel tube, the bolt-hole imprinting surface of the flange, the leeward side of the transition tube, and the top of the leeward side of the concrete tube. The failure risk of the flange and bolt-hole imprinting surface of the upper steel tube is relatively high, followed by that of the transition tube. This indicates that special attention should be given to the design and daily maintenance of this part. The fatigue resistance of the tower can be enhanced by improving the strength of the flange plate or increasing the number of bolts and strengthening the transition tube.

Harnessing the joint effect of approach bridges in arch bridge construction: an analytical study on thrust stiffness and elevation error mitigation

Achieving full equilibrium for the horizontal component force of the backstay in cable-stayed arch bridges is challenging, and the stiffness of the buckle tower has a notable influence on the overall shape of the main arch structure. Increased stiffness in the buckle tower leads to reduced construction complexity. Therefore, this study proposed a method of enhancing the longitudinal thrust stiffness of the buckle tower using the joint effect of approach bridges. A sensitivity analysis was conducted on the approach bridge–composite buckle tower structure to determine the optimal combination method, resulting in the formulation of an analytical expression for the thrust stiffness of this structure. In this study, numerical analysis was performed to explore the composition mechanism of the thrust stiffness influenced by the pier–girder connection, and we discussed the applicability of the joint effect of approach bridges during the cantilever assembly process of arch ribs. The following conclusions were obtained: 1) prior to installing the main girder of the approach bridge, when the steel buckle tower and the junction pier have already been secured, the most effective approach is to form a “T” rigid structure by firmly connecting the main girder of the approach bridge with the composite buckle tower. This configuration provides self-weight deflection and pier–girder rotation restriction effects. 2) The study presents analytical formulas for the completely rigid pier–girder connection of the approach bridge–composite buckle tower structure, partially rigid pier–girder connection, and pre-deviation. Combined with the calculation program, this can guide structural design. 3) When a large downward elevation error of the arch ribs occurs in the middle and later stages, the cable force needed to install new arch segments becomes overly large. Therefore, the joint effect of approach bridges can be utilized to substitute for a portion of the cable force, effectively reducing potential elevation errors that might arise in subsequent arch ribs in the absence of this joint effect.

Internal force and damage analysis of foundation of steel–concrete wind turbine tower

The internal cavity of the foundation of a steel–concrete composite wind turbine tower (WTT) is designed to facilitate prestressed construction. The load-bearing mechanisms of this type of foundation are different from those of ring-type and anchor-type foundations commonly used in steel WTTs. Based on a real project, an integrated model of a prestressed tower–foundation–ground was built using the finite-element software Abaqus. The internal force and damage in the foundation of a steel–concrete WTT under extreme load conditions were studied using the static loading method. Under extreme load conditions, prestressed reinforcements were found to have little impact on the local pressure at the anchor end of the foundation. Prestressing the reinforcement effectively prevented concrete cracking and tower deformation. For areas experiencing extreme loads on both sides, simplified calculations for stress and reinforcement can be performed using calculation formulae for the bracket.

Behavior and design of multi-sided composite sections

ABSTRACT Composite construction is advantageous due to the combination of steel and concrete materials in structural members. Composite column’s cross-section types such as hexagonal, octagonal, and decagonal and high diameter-to-thickness (D/t) ratios are highly desirable in transmission towers, yet not covered in the applicable codes. Therefore, the objective of this study is to investigate the behavior of composite columns with various characteristics including cross-section types, and height and propose a design procedure based on Force – Moment (P-M) Interaction diagrams and related equations. Three-dimensional non-linear finite element models were developed using a nonlinear finite element software to simulate and verify the behavior of the composite towers against prior experimental work. Concrete Damage Plasticity and Steel Bilinear Elasto-Plastic Model were calibrated and used in capturing the realistic nonlinear behavior of the materials and their interaction. Based on the computational models, a concrete reduction factor, needed for the development of design equations, was derived. Conclusively, typical normalized P-M Interaction diagrams were constructed for various polygonal shapes with high D/t ratios beyond code limitations. The corresponding derived design equations play a significant role in the applicability of the composite columns in transmission towers.

Seismic Reduction Analysis of Super-Long Span Suspension Bridge with Lattice Composite Tower and Damping System: A Case of Study for Qiongzhou Strait Bridge

In this paper, we proposed a lattice composite tower damping system to reduce the seismic response of super-long-span suspension bridges. Taking the QiongZhou strait bridge as a case study, we evaluated seismic performances through a finite element analysis (FEA) and shaking-table tests. First, the seismic responses of a super-long-span suspension bridge with or without a lattice composite tower to far-fault and near-fault earthquakes were analyzed and compared. The influence of the lattice composite tower on the dynamic characteristics and seismic performance was then investigated using shaking-table tests. Finally, the influences of different damping systems on the seismic response were evaluated, considering factors such as the damper type, damper arrangement scheme and design parameters. The results indicated that lattice composite tower could significantly increase the seismic performance of super-long span suspension bridge, while the optimal damping system could markedly improve the energy dissipation ability of whole system. Subsequently, this could provide references to enhance the seismic safety of the super-long span suspension bridge under strong earthquakes.

The Bearing Capacity of Composite Insulated Cross Arm Tower under Typhoon Load

Typhoon meteorological disasters occur frequently, which seriously threaten the safe and stable operation of old transmission lines. The old transmission towers can be retrofitted with composite insulated cross arms to solve the problems of low capacity of wind protection design and insufficient distance between conductor and ground. The paper analyzes the wind load and bearing capacity of composite insulated cross-arm towers under the action of a typhoon through theoretical calculation and finite element analysis and puts forward the calculation method of wind load under the action of a typhoon, and it is revealed that typhoon has less influence on the force of composite cross arm and greater influence on the deformation of the composite cross-arm. Finally, the bearing capacity of a composite insulated cross-arm tower under typhoon load is proposed.

Suppression Measures of Partial Discharge at Rod–Plate Connection in Composite Tower

Rods and plates at the connections in composite insulating material towers are commonly fixed to each other by metal bolts, which may cause electrical field distortion at the connections. So, the rod–plate connections are prone to partial discharge under polluted and wet conditions, and the resulting electric field and temperature changes can affect the mechanical and electrical performance of the whole tower. In this paper, an artificial pollution test synchronous observation platform with an infrared and visible light imager, leakage current, and voltage measurement was built to observe the dry band formation and partial discharge at the simplified rod–plate connections in the composite towers. Then, the electric field simulation of the rod–plate connection specimen showed the current density distribution. When combining the test and the simulation, it was concluded that the cause of the partial discharge was the distortion of the current density and, thus, measures to suppress the partial discharge at the rod–plate connections were proposed. Finally, it was verified that the measures can improve the current density distortion phenomenon, delay dry band formation, and effectively suppress the partial discharge at the rod–plate connections under the same test conditions.

An efficient model for solar radiation induced top displacement of steel-concrete composite bridge towers

The temperature effect caused by solar radiation significantly influences the stress state of bridges. Especially for ultra-high bridge towers, considerable deformation induced by solar radiation affects the safety of the structures. This research is conducted to evaluate the temperature deformation of a steel–concrete composite bridge tower where a sliding saddle is adopted. First, the temperature distribution pattern of the structure is analyzed. Second, based on the temperature distribution, an efficient model which can be applied to the long-term calculation is established, aiming at directly calculating the deformation results. Then, an outdoor experiment study is carried out to verify the temperature distribution and the results of sectional curvature. Finally, the efficient model is applied to calculate the annual bidirectional deformation. This method realizes the long-term temperature effect evaluation of the structure before construction, and the results can be referred to as guidance for the analysis of related types of structures.

Predicting the Climatic Resistance of the Material and the Durability of the Structural Elements of the Composite Tower of the Power Line

Comparative analysis of two models for predicting residual resource of polymer composite, one proposed by specialists from RS Technologies Inc and the other proposed by Institute of Oil and Gas Problems SB RAS (Russia), was carried out to obtain service life of composite poles for power transmission lines manufactured by RS Technologies Inc (Canada) for cold climate of Republic of Sakha (Yakutia). Models are based on experimental studies of strength of materials during accelerated and full-scale climatic tests. The difference lies in the presence of parameters of climatic zone and test methods in the first model, while the second model considers changes in physical and mechanical properties and structure of materials during aging under conditions of full-scale exposure and accelerated climatic tests. Comparison of results of predicting the durability of fiberglass products in cold climate of Yakutsk (Russia) according to Institute of Oil and Gas Problems SB RAS model and similar products in Calgary (Canada) climate (the closest in terms of climate conditions) according to RS Technologies Inc model showed the same results. Service life of composite support material was approximately 120 years with specified level of permissible decrease in characteristic property index of 75% of the original.

Experiment study on temperature field and effect on steel-concrete composite bridge towers

Due to the significant difference in thermal parameters between steel and concrete, complex temperature-related problems exist in steel–concrete composite bridge towers. Especially for the bridge tower with a particular type of Steel-Box-CFST section, the temperature distribution shows unique characteristics. To ensure the safety and regular use of the structure, it is necessary to analyse the temperature distribution mode of the composite bridge tower under solar radiation and to provide a method of temperature simulation at different conditions. In this paper, an indoor experiment in which the loading mode can be manually controlled has been carried out to study the temperature time-history and distribution in different loading conditions. The interface void between steel and concrete in CFST has also been detected. The results show that the outer steel box can protect the inner CFST from the temperature effect caused by solar radiation. A finite element model has also been established and verified by the experiment, providing a feasible way to simulate the temperature field under solar radiation.

Experimental and analytical study on compressive bearing capacity of steel shell-concrete composite bridge tower

To improve the mechanical performance and construction convenience of the bridge towers, a steel shell-concrete composite tower (SSC structures) was proposed. The steel shell consists of outer and inner steel plates, diaphragms, and stud connectors inside the cells. Then the high fluidity concrete is poured into the steel shell to form the composite tower. Through the uniaxial compressive tests of the specimens with different concrete strength and the nonlinear finite element parametric analyses, the force transfer mechanism of the steel shell, the infilled concrete, and the stud connectors at the steel–concrete interface were revealed. The results show that the proposed steel shell-concrete composite tower has a higher bearing capacity than the conventional concrete-filled steel tube tower, in which the bearing capacity of concrete was increased by about 20% from the test results due to the composite effect between steel and concrete. Diagonal breakage bands were formed when the specimens finally failed, on which the concrete was crushed, and the steel plates had large out-of-plane deformation and weld cracking. Through finite element calculation, it was found that the increase of stud forces mainly occurred after the yield of the steel wall plates, and the maximum values of the shear forces and tension forces were 3.6 kN and 4.7 kN, respectively. The results also show that the multiple-cell section has better mechanical performance than the double steel section, which is suitable for the section form of the composite bridge tower.

Development of a novel type of steel‐shell concrete composite tower

Development of a novel type of steel‐shell concrete composite tower

Optimization of the Seismic Performance of a Steel-Concrete Wind Turbine Tower with the Tuned Mass Damper

To optimize the seismic performance of a new type of steel-concrete tower, a 120 m steel-concrete composite tower model with a tuned mass damper (TMD) was constructed in ABAQUS for simulation analysis. Firstly, a time history analysis was conducted to study the towers with and without a TMD to determine the difference in their accelerations, velocities, and displacements. Then, a frequency spectrum analysis was performed to determine the tower vibration reduction effect of TMDs with different mass ratios. Five different cases were considered to explore the impact of different layouts on the dynamic performance of the tower. The results showed that the TMD had a significant vibration reduction effect on the tower accelerations, velocities, and displacements. The acceleration was reduced the most, while the vibration reduction effect in the middle of the tower was more significant than that at the top of the tower. For the steel-concrete tower studied in this paper, the optimal mass ratio of TMD was found to be 0.01. Placing one TMD at the top and another in the middle of the tower was found to be the optimal TMD arrangement for tower vibration reduction.

Modelling of overhead transmission lines with composite towers for 35-330 kV electric power networks

Based on the analysis of the technical condition of the equipment of the electric power networks of the UES of Ukraine, current challenges in the development of the energy sector and existing technologies for the transmission of electric energy, the expediency of using towers made of composite materials in the development, reconstruction and design of new overhead transmission lines for electric networks of different voltage classes is substantiated. The peculiarities of operation of towers made of composite materials in electric networks of many countries of the world are investigated, on the basis of which the prospects of using such towers for overhead transmission lines in Ukraine in the conditions of the introduced liberalised electricity market, as well as the requirements for the performance of electric power networks with the investigated towers made of composite materials are formulated. The article analyses the main characteristics and properties of composite materials that are most commonly used for the manufacture of towers in modern energy systems, as well as compares the physical and mechanical properties of towers made of different materials. The analysis of the obtained results confirms certain advantages of towers made of composite materials, which contribute to the widespread introduction of such towers in the Ukrainian energy system. To investigate the influence of the type of composite material and the design of the towers on the performance of electrical networks, a mechanical calculation of the towers was performed using the method of limit states. Using the obtained results, mathematical models of overhead transmission lines with composite towers for electric power networks with a voltage of 35-330 kV were developed, which take into account the technical characteristics of overhead transmission line elements and the operating conditions of electric power networks, and also allow forecasting quantitative indicators of further operation of the investigated electric power networks.

Reliability-based design optimization of 3D orthogonal woven composite automobile shock tower

Three-dimensional orthogonal woven composites are noted for their excellent mechanical properties and delamination resistance, so they are expected to have promising prospects in lightweight applications in the automobile industry. The multi-scale characteristics and inherent uncertainty of design variables pose great challenges to the optimization procedure for 3D orthogonal woven composite structures. This paper aims to propose a reliability-based design optimization method for guidance on the lightweight design of 3D orthogonal woven composite automobile shock tower, which includes design variables from material and structure. An analytical model was firstly set up to accurately predict the elastic and strength properties of composites. After that, a novel optimization procedure was established for the multi-scale reliability optimization design of composite shock tower, based on the combination of Monte Carlo reliability analysis method, Kriging surrogate model, and particle swarm optimization algorithm. According to the results, the optimized shock tower meets the requirements of structural performance and reliability, with a weight reduction of 37.83%.

Comparison of Backflashover performance between a novel composite pylon and metallic towers

A design of a fully composite pylon with external grounding down-leads has been proposed for new-generation 400 kV transmission towers, able to save lines corridors and to reduce visual impact. This paper investigates and compares the backflashover performance of a composite pylon and two conventional metallic towers, which have been widely installed in Denmark. The transient models of overhead lines and all three towers were established respectively and the transient analysis was carried out in PSCAD. Monte Carlo method was used to estimate backflashover rate. The backflashover rate of composite pylon is 0.4526 cases per 100 km per year, which is in the same range, but slightly higher than that of metallic towers. The separated grounding down-leads of double circuits on composite pylon eliminates the danger of simultaneous backflashover of double circuits, which exists in transmission lines supported by metallic towers. After comparing the overvoltages to three phases of the three towers from backflashover, it is worthy considering that the installation of surge arresters at all three phases of composite pylon has a strong impact on the backflashover rather, but for the two metallic towers only the surge arresters at the upper phase has an impact.

КОМПОЗИТНІ ОПОРИ ПОВІТРЯНИХ ЛІНІЙ ЕЛЕКТРОПЕРЕДАЧІ

The article considers the feasibility of using composite supports during the replacement of overhead power lines, analyzes the relevance of these technologies. The advantages of composite overhead power line towers for construction, modernization and restoration work over traditional wooden and metal towers are substantiated.

Effects of a Crossarm Brace Application on a 275 kV Fiberglass-Reinforced Polymer Crossarm Subjected to a Lightning Impulse

The crossarm is an important component of transmission towers, providing insulation for transmission lines at different voltage ratings. Recently, composite crossarms were widely used as a composite tower component and were found to be the most favorable choice for replacing old wooden crossarms. Owing to the satisfactory pilot operation and multiple sets of testing, fiberglass-reinforced polymer (FRP) composite crossarms have been used in Malaysia in both 132 and 275 kV transmission lines since the late 1990′s. Since then, some modifications have been proposed to improve the mechanical performance of the crossarm, in order to ensure the reliability of its performance. In this investigation, the effect of a proposed improvement, achieved by installing a brace for the crossarm, was investigated numerically. A simulation study was conducted, with a consideration of the lightning impulse voltage (LIV) and swing angle exhibited by the crossarm. The potential and electric field (E-Field) distribution were analyzed and are presented in this paper. It was found that the potential distribution and E-Field strength for the crossarm and the surrounding air were greatly affected by the installation of the brace.

The “Frankentower:” A clinician-driven approach to enhancing endoscopic data technology

ObjectiveTo develop a more efficient endoscopy tower and evaluate its capability to improve retrieval and storage of videos across 6 clinical sites. MethodsDescriptive study that took place at tertiary care Pediatric Otolaryngology Department over a 2 year period. In collaboration with our Information Services Department and Otolaryngology endoscopy vendors, we assembled our “Frankentower” endoscopy cart using components from 3 medical device manufacturers. ResultsIt is feasible to create a functional composite endoscopic tower. Implementation of “Frankentower” improved overall management and retrieval of endoscopy video and images in our department which lead to better patient care and facilitated education for medical students, residents and faculty. ConclusionsThe “Frankentower” is a feasible, cost-effective solution to streamline the capture, access and storage of patient endoscopy exams across our operating rooms, inpatient consult service, Emergency Department and outpatient clinics.

Influence of CaCO3 in pultruded glass fiber/unsaturated polyester resin composite on flexural creep behavior using conventional and time-temperature superposition principle methods

The effect of calcium carbonate on the creep phenomenon of glass fiber/unsaturated polyester resin composites (GFRP) (obtained by pultrusion) was investigated due to failure that happened during installation of one of the composite transmission tower. To assess long-term creep and predict the life of composites, a conventional bending method with 45-day creep and time-temperature superposition principle (TTSP) were used. In the conventional method, the composites (with and without calcium carbonate) underwent only slight deformation. It was found that their lifetime could be 25 years. However, based on the standard curve obtained by the TTSP method, significant differences were shown in the stability of calcium carbonate composite samples at 95°C (111 days) and 160°C (11 days). It was found that the addition of calcium carbonate extends the service life of the tested composites. Thus, the results obtained by the conventional method do not reflect the real behavior of the samples over time. On the other hand, the TTSP method allows better estimation of the long-term durability of composites.