• Wind and Structures
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• v.38 no.4
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• pp.325-339
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• 2024

The longitudinal force resulting from tornado loads on transmission line is considered a crucial factor contributing to the failure of transmission line structures during tornado events. Accurate estimation of this longitudinal force poses a challenge for structural designers. Therefore, the objective of this paper is to provide a set of charts that can be easily used to estimate the peak longitudinal forces transferred from the conductors to a tower. The critical wind field and corresponding configuration considered in this paper are previously studied and determined. The charts should account for all the conductor parameters that can affect the value of the longitudinal force. In order to achieve that, a parametric study is first conducted to assess the variation of the longitudinal forces with different conductor parameters, based on the critical tornado configuration. Results of this parametric study are used to develop the charts that can be used to calculate longitudinal forces by adopting a multi-variable line regression. The forces calculated from charts are validated by finite element analysis. An example for the usage of the charts is provided at the end of this paper.

• Journal of the Korean Professional Engineers Association
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• v.15 no.4
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• pp.12-24
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• 1982

East Parts of Bangladesh have been benifited by low cost energy generated by domestic natural gas but West parts where energy generated by imported fuel. Bangladesh Government authority has very much concerned to transmit the low cost electricity to the West from the East for past several years. To solve such concerns, cross-country 230kv double circuits Power transmission line was proposed, however there was a big obstacle for the realization of this line to cross the Jamuna river which has 12 km long width with a deep muddy river bed. A consultant engineering firm named Merz-Mclellan anyway finalized this plan and a world-wide bid was announced on June 31, 1979. Due to the expected difficulty to construct the towers on sea like area, only three construction groups have participated. including a Korean joint venture organization of Samsung-Korean Developement corporation-Kolon Electric Machinery company. After 3 months bid evaluation, contract was awarded to Korean Consosium and KEM Co was in charge of designing steel towers with anchor bolts and base plates beside to electrical engineering field. Then KEM Co have faced and over-comed many unenpected technical difficulties such as forced eccentricity joint on base plate, distorsion issue of 60mm thick plates welding, threading anchor bolts, tad heat treatment of some anchor bolts, disagreement from Consultant Engineer on multiplying factor of leg stresses for 45$^{\circ}$ wind and on reducing O.L.F for wind loads on cables for such 1220km long spans. After spending two years long period for designing and engineering towers, base plates, and anchor bolts, first shipment of tower was finally realized on Nov. 8, 1981 and on the other hand KDD has proceeded concrete caisson work on schedule at Jamuna river site and expected to complete tower erection and stringing of cables within this year of 1982 which was original completion target.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.99-106
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• 2014

This paper presents the determination of the structural system of the Changsha IFC T1 tower with 452 m in architectural height and 440.45 m in structural height. Sensitivity analyses are carried out by varying the location of belt trusses and outriggers. The enhancement of seismic capacity of the outer frame by reasonably adjusting the column size is confirmed based on parametric studies. The results from construction simulation including the non-load effect of structures demonstrate that the deformation of vertical members has little effect on the load-bearing capacity of belt trusses and outriggers. The elastoplastic time-history analysis shows that the overall structure under rare earthquake load remains in an elastic state. The influence of the frame shear ratio and frame overturning moment ratio on the proposed model and equivalent mega column model is investigated. It is found that the frame overturning moment ratio is more applicable for judging the resistance of the outer frame against lateral loads. Comparison is made on the variation of these two effects between a classical frame-core tube-outrigger structure and a structure with diagonal braces between super columns under rare earthquakes. The results indicate that plasticity development of the top core cube of the braced structure may be significantly improved.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.191-199
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• 2007

This paper presents a closing method for a cable-stayed bridge erected by the free cantilever method to produce the initial equilibrium configuration at the final construction stage. To realize the initial equilibrium condition in cable-stayed bridge by the cantilever method, compatibility conditions for vertical displacements, rotational angles, and axial displacements at the closing section of both side girders should be satisfied. In this paper, it was shown that it can be accomplished by using some applicable loads during construction such as the pull-up force of the derrick crane, some cable tension forces, and jacking force at the pylon. The proposed method was applied to a construction stage analysis of a sample bridge to demonstrate its validity, and it was acknowledged that the tower was considerably affected by the compatibility condition for axial displacement in the closing step.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.214-221
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• 2019

A series of model tests was performed to evaluate the survivability of an articulated tower-type buoy structure under harsh environmental conditions. The buoy structure consisted of three long pipes, a buoyancy module, and top equipment. The scale model was made of acrylic pipe and plastic with a scale ratio of 1/22. The experiments were carried out at the ocean engineering basin of KRISO. The performance of the buoy structure was investigated under waves only and under combined environmental conditions from sea state (SS) 5 to 7. A nonlinear time-domain numerical simulation was conducted using the mooring analysis program OrcaFlex. The survivability of the buoy was analyzed based on three factors: the pitch motion, submergence of the top structure, and anchor reaction force. The model test results were directly compared to the results of numerical simulations. The effects of the sea state and combined environment on the performance of the buoy structure were investigated.

• Structural Engineering and Mechanics
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• v.90 no.2
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• pp.159-175
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• 2024

In order to solve the problem of calculating the reasonable completed bridge state of a self-anchored hybrid cable-stayed suspension bridge (SA-HCSB), this paper proposes an analytical method. This method simplifies the main beam into a continuous beam with multi-point rigid supports and solves the support reaction forces. According to the segmented catenary theory, it simultaneously solves the horizontal forces of the main span main cables and the stay cables and iteratively calculates the equilibrium force system on the main beam in the collaborative system bridge state while completing the shape finding of the main span main cable and stay cables. Then, the horizontal forces of the side span main cables and stay cables are obtained based on the balance of horizontal forces on the bridge towers, and the shape finding of the side spans are completed according to the segmented catenary theory. Next, the difference between the support reaction forces of the continuous beam with multiple rigid supports obtained from the initial and final iterations is used to calculate the load of ballast on the side span main beam. Finally, the axial forces and strains of each segment of the main beam and bridge tower are obtained based on the loads applied by the main cable and stay cables on the main beam and bridge tower, thereby obtaining analytical data for the bridge in the reasonable completed state. In this paper, the rationality and effectiveness of this analytical method are verified through a case study of a SA-HCSB with a main span of 720m in finite element analysis. At the same time, it is also verified that the equilibrium force of the main beam under the reasonably completed bridge state can be obtained through iterative calculation. The analytical algorithm in this paper has clear physical significance, strong applicability, and high accuracy of calculation results, enriching the shape-finding method of this bridge type.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.19-26
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• 2024

In this study, the compressive behavior of a 1/12.5 scale model of a wind tower support structure connection was experimentally analyzed. A high-performance cementitious grout with a compressive strength of 140 MPa was used to fill the connection, and experiments were conducted with shear key spacing, the shape, and connection length as variables. When the number of shear keys in the connection is the same, the smaller the spacing of the shear keys than the length of the connection, the higher the shear strength, and for the same spacing and connection length, the higher the height of the shear keys, the higher the strength. In addition, it was found that the strength showed a linear behaviour until the connection slip reached 1.0 mm, and it reached the maximum strength at 7.0 mm connection slip showing a non-linear behaviour as the load increased. It was found that the failure mode changed from interfacial shear failure to grout failure as the strength increased according to the shape and spacing of the shear key, and brittle failure did not occur due to steel fibers.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.239-247
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• 2013

Recently renewable energy such as offshore wind energy takes a higher interest due to the depletion of fossil fuel and the environmental pollution. This paper deals with multi-body dynamics (MBD) analysis technique for offshore wind turbine system considering aerodynamic loads and Thevenin equation used for determination of electric generator torque. Dynamic responses of 5MW offshore wind turbine system are evaluated via the MBD analysis, and the system is the horizontal axis wind turbine (HAWT) which generates electricity from the three blades horizontally installed at upwind direction. The aerodynamic loads acting on the blades are computed by AeroDyn code, which is capable of accommodating a generalized dynamic wake using blade element momentum (BEM) theory. In order that the characteristics of dynamic loads and torques on the main joint parts of offshore wind turbine system are simulated similarly such an actual system, flexible body modeling including the actual structural properties are applied for both blade and tower in the multi-body dynamics model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.407-414
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• 2016

As wind turbines are getting larger in size with multi-MW capacity, the blades are getting longer, over 40 m, and hence the asymmetric loads produced during the rotation of the rotor blades are increasing. Some factors such as wind shear, tower shadow, and turbulence have an effect on the asymmetric loads on the blades. This paper focuses on a method of modeling the dynamic load acting on a blade because of thrust variation under wind shear. A method that uses thrust coefficient is presented. For this purpose, "wind shear coefficient of thrust variation" is defined and introduced. Further, we calculate the values of the "wind shear coefficient of thrust variation" for a 2 MW on-shore wind turbine, and analyze them for speeds below the rated wind speed. Then, we implement a dynamic model that represents the thrust variation under wind shear on a blade, using MATLAB/Simulink. It is shown that it is possible to express thrust variations on three blades under wind shear by using both thrust coefficient and "wind shear coefficient of thrust variation."

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.33-40
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• 2014

Reliability analysis of jacket type offshore wind turbine (OWT) support structure under extreme ocean environmental loads was performed. Limit state function (LSF) of OWF support structure is defined by using structural dynamic response at mud-line. Then, the dynamic response is expressed as the static response multiplied by dynamic response factor (DRF). Probabilistic distribution of DRF is found from response time history under design significant wave load. Band limited beta distribution is used for internal friction angle of ground soil. Wind load is obtained in the form of thrust force from commercial code called GH_Bladed and then, applied to tower hub as random load. In a numerical example, the response surface method (RSM) is used to express LSF of jacket type support structure for 5MW OWF. Reliability index is found using first order reliability method (FORM).