• Wind and Structures
• /
• v.15 no.4
• /
• pp.285-299
• /
• 2012

This paper describes the development and calibration of a structural monitoring system installed in a 80 meters high steel wind tower supporting a 2.1 MW turbine Wind Class III IEC2a erected in the central part of Portugal. The several signals are measured at four different levels and include accelerations, strains on the tower wall and inside the connection bolts, inclinations and temperature. In order to correlate measurements with the wind velocity and direction and with the turbine operational parameters the corresponding signals are obtained directly from the turbine own monitoring system and are incorporated in the developed system. Results from the system calibration, the structural identification and the initial period of data acquisition are presented in this paper.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.30 no.2
• /
• pp.67-81
• /
• 1988

The purpose of the present study is to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir and to establish a solid foundation for the automatic optimum structural design combined with finite element analysis. The major design variables are the dimensions and steel areas of each member of the structures. The construction cost which is composed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of the working stress design method. The corresponding design guides including the standard specification for concrete structures have been also employed in deraving the constraint conditions. The present nonlinear optimization problem is solved by SUMT method. The reinforced concrete intake-tower is decomposed into three major substructures. The optimization is then conducted for both the whole structure and the substructures. The following conclusions can be drawn from the present study. 1. The basis of automatic optimum design of reinforced concrete cylindrical shell structures which is combined with finite element analysis was established. 2. The efficient optimization algorithms which can execute the automatic optimum desigh of reinforced concrete intake-tower based on the working stress design method were developed. 3. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optImization algorithms developed in this study seem to be efficient and stable. 4. The difference in construction cost between the optimum designs with the substructures and with the entire structure was found to be small and thus the optimum design with the substructures,rnay conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the tensile stress insteel for salb, the minimum lonitudinal steel ratio constraints for tower body and the shearing stress in concrete, tensile stress in steel and maximum eccentricityconstraints for footing, respectively. 6. The computer program develope in the present study can be effectively used even by an unexperienced designer for the optimum design of reinforced concrete intake-tower.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.337-340
• /
• 2008

There were two transmission tower collapses due to Typhoon 'Maemi' in 2003. The reason that a collapse was happened was excessive wind load. One was buckled in the leg part and the other was buckled in the middle bracing part. To investigate a steel transmission tower failure mechanism, 2nd order nonlinear analysis should be performed. Considering the effect of initial imperfection and theresidual stress of angle section during nonlinear analysis, this study can estimate the ultimate strength and the ultimate behavior of the transmission tower.

• International Journal of High-Rise Buildings
• /
• v.5 no.3
• /
• pp.213-220
• /
• 2016

The "China Zun" tower in Beijing will rise to 528 meters in height and will be the tallest building in Beijing once built. Inspired by an ancient Chinese vessel, the "Zun", the plan dimensions reduce gradually from the bottom of the tower to the waist and then expand again as it rises to form an aesthetically beautiful and unique geometry. To satisfy the structural requirement for seismic and wind resistance, the structure is a dual system composed of a perimeter mega structure made of composite mega columns, mega braces, and belt trusses, and a reinforced-concrete core with steel plate-embedded walls. Advanced parametric design technology is applied to find the most efficient outer-perimeter structure system. The seismic design basically follows a mixed empirical and performance-based methodology that was verified by a shaking table test and other specimen lab tests. The tower is now half-way through its construction.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.283-286
• /
• 2008

There were two transmission tower collapses due to Typhoon 'Maemi' in 2003. The reason that a collapse was happened was excessive wind load. One was buckled in the leg part and the other was buckled in the middle bracing part. To investigate a steel transmission tower failure mechanism, 2nd order nonlinear analysis should be performed. Considering the effect of initial imperfection and theresidual stress of angle section during nonlinear analysis, this study can estimate the ultimate strength and the ultimate behavior of the transmission tower.

• Wind and Structures
• /
• v.12 no.4
• /
• pp.333-347
• /
• 2009

Many tower-supported steel stacks have been constructed in Japan, primarily for economic reasons. However the dynamic behavior of these stacks under a strong wind is not well known and the wind load design standard for this type of a stack has not yet been formulated. In light of this situation, we carried out wind response observation of an operating tower-supported steel stack with and without a tuned-mass damper. The observation revealed the performance of the tuned-mass damper installed on the stack in order to control the wind-induced vibration. Based on the observed data, we performed a wind tunnel test of a specimen of the stack. In this paper we report the results of the wind tunnel test and some comparisons with the results of observation. Our findings are as follows: 1) the tuned-mass damper installed on the specimen in the wind tunnel test worked as well as the one on the observed stack, 2) the amplitude of the vortex-induced vibration of the specimen corresponded approximately to that of the observed stack, and 3) correlation between Scruton number and reduced amplitude, y/d, (y is amplitude, d is diameter) was confirmed by both the wind tunnel test and the observed results.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.107-108
• /
• 2007

Overhead transmission lines are completely exposed to the environment. This causes faults in transmission lines due to natural environmental conditions. In some cases, transmission towers are damaged by typhoons and snow, as well as sleet on the transmission lines. It takes a lot of time to repair the damaged towers. For emergency restoration purposes, steel poles are installed to temporarily supply power. Before 2003, emergency restoration steel poles were made of angled steel, which required a large number of beams, bolts, etc. In addition, the foundation of the steel pole and ground wire was constructed using excavation and burial methods, therefore it required a lot of manpower and time to construct temporary transmission lines. In September 2003, typhoon Maemi, whose maximum wind speed was 60m/s, hit Korea. 'Maemi' destroyed transmission lines in the Busan and Geojea area, causing long blackouts. To reduce the recovery time to the damaged transmission lines, self-build based emergency towers were developed. self-build based emergency towers reduced recovery time from 24 hours to 4 hours or less. However, the self-build based emergency tower had no arms, so the temporary transmission lines could only be constructed without curves in line routes. In this paper, solving these self-build based emergency tower limitations, using insulated arms(designed for use with the self-build based emergency tower), shall be explained.

• Structural Engineering and Mechanics
• /
• v.73 no.6
• /
• pp.641-649
• /
• 2020

The determination of midtower longitudinal stiffness has become an essential component in the preliminary design of multi-tower suspension bridges. For a specific multi-tower suspension bridge, the midtower longitudinal stiffness must be controlled within a certain range to meet the requirements of sliding resistance coefficient and deflection-to-span ratio. This study presents a numerical method to divide different types of midtower and determine rational range of longitudinal stiffness for rigid midtower. In this method, influence curves of midtower longitudinal stiffness on sliding resistance coefficient and maximum vertical deflection-to-span ratio are first obtained from the finite element analysis. Then, different types of midtower are divided based on the regression analysis of influence curves. Finally, rational range for longitudinal stiffness of rigid midtower is derived. The Oujiang River North Estuary Bridge which is a three-tower four-span suspension bridge with two main spans of 800m under construction in China is selected as the subject of this study. This will be the first three-tower four-span suspension bridge with steel truss girders and concrete midtower in the world. The proposed method provides an effective and feasible tool for engineers to design midtower of multi-tower suspension bridges.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1115-1144
• /
• 2015

Current climate conditions along with advances in technology make further design and verification methods for structural strength and reliability of wind turbine towers imperative. Along with the growing interest for "green" energy, the wind energy sector has been developed tremendously the past decades. To this end, the improvement of wind turbine towers in terms of structural detailing and performance result in more efficient, durable and robust structures that facilitate their wider application, thus leading to energy harvesting increase. The wind tower industry is set to expand to greater heights than before and tapered steel towers with a circular cross-section are widely used as more capable of carrying heavier loads. The present study focuses on the improvement of the structural response of steel wind turbine towers, by means of internal stiffening. A thorough investigation of the contribution of stiffening rings to the overall structural behavior of the tower is being carried out. These stiffening rings are placed along the tower height to reduce local buckling phenomena, thus increasing the buckling strength of steel wind energy towers and leading the structure to a behavior closer to the one provided by the beam theory. Additionally to ring stiffeners, vertical stiffening schemes are studied to eliminate the presence of short wavelength buckles due to bending. For the purposes of this research, finite element analysis is applied in order to describe and predict in an accurate way the structural response of a model tower stiffened by internal stiffeners. Moreover, a parametric study is being performed in order to investigate the effect of the stiffeners' number to the functionality of the aforementioned stiffening systems and the improved structural behavior of the overall wind converter.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.2
• /
• pp.1516-1523
• /
• 2015

This study investigates the stress concentration factor of a door opening of an offshore tubular steel tower. The tubular steel tower is subjected to eight (8) different load combinations which are deemed to be normal and abnormal operating cases for the ultimate limit state and serviceability limit state. Analytical method using parametric equations and numerical method of finite element are used to analyze the stress components as well as any translations or rotations where the flow of stress is interfered with. A finite element program, ABAQUS, is used for the numerical method analysis. Trends of the stress concentration in the localized area near the opening are studied, and points of interest are defined for comparison among three different cases of tubular steel tower: without door and without reinforcement; without door opening and with reinforcement; and with door opening and with reinforcement. Findings are tabulated and shown in illustrative charts, and conclusions are made.