• Structural Engineering and Mechanics
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• v.49 no.1
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• pp.65-80
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• 2014

This paper reports on the development of a minimum cost design model and its application for obtaining economic designs for reinforced High Strength Concrete (HSC) T-sections in bending under ultimate limit state conditions. Cost objective functions, behavior constraint including material nonlinearities of steel and HSC, conditions on strain compatibility in steel and concrete and geometric design variable constraints are derived and implemented within the Conjugate Gradient optimization algorithm. Particular attention is paid to problem formulation, solution behavior and economic considerations. A typical example problem is considered to illustrate the applicability of the minimum cost design model and solution methodology. Results are confronted to design solutions derived from conventional design office methods to evaluate the performance of the cost model and its sensitivity to a wide range of unit cost ratios of construction materials and various classes of HSC described in Eurocode2. It is shown, among others that optimal solutions achieved using the present approach can lead to substantial savings in the amount of construction materials to be used. In addition, the proposed approach is practically simple, reliable and computationally effective compared to standard design procedures used in current engineering practice.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.73-82
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• 2006

Nowadays, the general stripping work of form has brought some problems; increase of total constructing cost resulted from the man-dependent form work procedure and environmental issues by wasting the debonded form. In this study, to effectively reduce unnecessary cost and resolve the environmental problems caused by these kinds of reason, a permanent form method using stainless steel fiber was introduced then its material and structural characteristics were evaluated. In the case of material characteristic, the permanent form had a good ductile behavior in the result of flexural test of the permanent form panel and pull-out test of insert bolt which is installed in the permanent form and perfect bonding capacity with a field concrete. In the case of structural characteristic, compressive and tensile behavior of the permanent form was evaluated. It also showed a good structural behavior in the view of load-deflection relationship, crack patterns and additional strengthening effect.

• Wind and Structures
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• v.21 no.6
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• pp.693-707
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• 2015

The efficiency of wind turbines (WT) is primarily reflected in their ability to generate electricity at any time. Downtimes of WTs due to "conventional" inspections are cost-intensive and undesirable for investors. For this reason, there is a need for structural health monitoring (SHM) systems, to enable service and maintenance on demand and to increase the inspection intervals. In general, monitoring increases the cost effectiveness of WTs. This publication concentrates on the application of two vibration-based SHM algorithms for stability and structural change monitoring of offshore WTs. Only data driven, output-only algorithms based on stochastic subspace identification (SSI) in time domain are considered. The centerpiece of this paper deals with the rough mathematical description of the dynamic behavior of offshore WTs and with the basic presentation of stochastic subspace-based algorithms and their application to these structures. Due to the early stage of the industrial application of SHM on offshore WT on the one side and the required confidentiality to the plant manufacturer and operator on the other side, up to now it is not possible to analyze different isolated structural damages resp. changes in a systematic manner, directly by means of in-situ measurement and to make these "acknowledgements" publicly available. For this reason, the sensitivity of the methods for monitoring purposes are demonstrated through their application on long time measurements from a 1:10 large scale test rig of an offshore WT under different conditions: undamaged, different levels of loosened bolt connections between tower parts, different levels of fouling, scouring and structure inclination. The limitation and further requirements for the approaches and their applicability on real foundations are discussed along the paper.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.359-368
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• 2018

In this paper, a method is presented to identify the physical and modal parameters of multistory shear building based on substructural technique using block pulse generalized operational matrix and genetic algorithm. The substructure approach divides a complete structure into several substructures in order to significantly reduce the number of unknown parameters for each substructure so that identification processes can be independently conducted on each substructure. Block pulse functions are set of orthogonal functions that have been used in recent years as useful tools in signal characterization. Assuming that the input-outputs data of the system are known, their original BP coefficients can be calculated using numerical method. By using generalized BP operational matrices, substructural dynamic vibration equations can be converted into algebraic equations and based on BP coefficient for each story can be estimated. A cost function can be defined for each story based on original and estimated BP coefficients and physical parameters such as mass, stiffness and damping can be obtained by minimizing cost functions with genetic algorithm. Then, the modal parameters can be computed based on physical parameters. This method does not require that all floors are equipped with sensor simultaneously. To prove the validity, numerical simulation of a shear building excited by two different normally distributed random signals is presented. To evaluate the noise effect, measurement random white noise is added to the noise-free structural responses. The results reveal the proposed method can be beneficial in structural identification with less computational expenses and high accuracy.

• Land and Housing Review
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• v.4 no.2
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• pp.193-200
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• 2013

Construction duration in construction project is an important factor which affects project cost. Advanced countries have reduced project cost by time shortening. Even though domestic construction companies have tried to time shortening, they yet failed to find systematic method for time shortening. Typically, duration of structural framework is affected by stripping time of form. Therefore, it need to shorten the stripping time of form for time shortening of structural framework. In this study, specimens of high-early-strength concrete were manufactured with variety conditions and compressive strength was tested. This study proposed stripping time of side and slab forms using test results. The stripping time of form was shortened when using high-early-strength concrete in structural framework by the test results. The result of this study will be useful for time shortening of structural framework.

• Advances in aircraft and spacecraft science
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• v.10 no.3
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• pp.223-243
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• 2023

There is a burgeoning demand for minimizing the mass of satellites because of its direct impact on reducing launch-to-orbit cost. This must be done without compromising the structure's efficiency. The present paper introduces a relatively low-cost and easily implementable approach for optimizing structural mass to a maximum natural frequency. The natural frequencies of the satellite are of utmost pertinence to the application requirements, as the sensitive electronic instrumentation and onboard computers should not be affected by the vibrations of the satellite structure. This methodology is applied to a realistic model of Al-Azhar University micro-satellite in partnership with the Egyptian Space Agency. The procedure used in structural design can be summarized in two steps. The first step is to select the most favorable primary structural configuration among several different candidate variants. The nominated variant is selected as the one scoring maximum relative dynamic stiffness. The second step is to use perforation patterns reduce the overall mass of structural elements in the selected variant without changing the weight. The results of the presented procedure demonstrate that the mass reduction percentage was found to be 39% when compared to the unperforated configuration that had the same plate thickness. The findings of this study challenge the commonly accepted notion that isogrid perforations are the most effective means of achieving the goal of reducing mass while maintaining stiffness. Rather, the study highlights the potential benefits of exploring a wider range of perforation unit cells during the design process. The study revealed that rectangular perforation patterns had the lowest efficiency in terms of modal stiffness, while triangular patterns resulted in the highest efficiency. These results suggest that there may be significant gains to be made by considering a broader range of perforation shapes and configurations in the design of lightweight structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.130-137
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• 2017

To maintain traffic safety during the target lifetime of bridges, it is essential to secure an appropriate maintenance budget and allocate that budget appropriately. This paper proposes a reasonable budget allocation system that considers various impact factors to improve the conventional budget allocation method simply considering the bridge scale. The maintenance action rate model and the unit cost model based on the prior maintenance history were developed to allocate appropriately the bridge maintenance budget for the total bridges of the management organization with the target management level. A method to determine the optimal budget allocation ratio for each management subject was proposed and case analysis was conducted using the proposed model. Proper budget allocation was made considering the bridge types, current safety level, and service life as well as the bridge size as an impact factor of the budget allocation of the bridge. The developed method can prevent budget waste and provide a rational basis for budget allocation by implementing the rational budget distribution.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.113-123
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• 2011

LCC analysis is a method that coordinates with function evaluation for value improvement, rather than a separate one for cost evaluation. Although its accuracy is rising, materials and structural types developed or applied relatively recently have yet to obtain a sufficient maintenance profile DB, inducing reliability to reduce from difficulties in estimating maintenance records. Based on the above mentioned background, this paper presents the LCC methodology of coordinating functional intensification matters with cost for analysis on alternatives with difficulties in setting maintenance profile. Recently, steel plate bridge deck pavements are faced with problems such as plastic deformation due to the increase in heavy vehicles and traffic, promoting the development of a new compound pavement. This paper execute LCC analysis by mentioning case studies of SMA, Guss and PSMA pavements to include performance scale compared between alternatives as relative evaluation coefficients into the maintenance profile.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.564-568
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• 2006

Smooth picture module is operated by vibration to tilt the light from the DMD (digital micro mirror device) of DLP projection TV, which makes the screen of the TV smoother and DMD chip cost lower. To satisfy the vibration characteristics of smooth picture module, it is designed by optimizing moment of inertia, spring constant and damping coefficient, using structural and fluid dynamic simulation that showed a good agreement with experimental data. To reduce the material cost and moment of inertia, engineering plastic is used and the reliability is estimated. A VCM (voice coil motor) type actuator for smooth picture has to satisfy performance requirements such as higher driving force, lower power consumption, and lower cost. The initial design and optimization for VCM was performed using FE analysis. It allowed us to optimize the design of magnetic circuit of the proposed actuator to obtain higher force while maintaining a lower cost.

• Structural Engineering and Mechanics
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• v.45 no.5
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• pp.643-654
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• 2013

Optimum cost design of columns subjected to axial force and uniaxial bending moment is presented in this paper. In the formulation of the optimum design problem, the height and width of the column, diameter and number of reinforcement bars are treated as design variables. The design constraints are implemented according to ACI 318-08 and studies in the literature. The objective function is taken as the cost of unit length of the column consisting the cost of concrete, steel, and shuttering. The solution of the design problem is obtained using the artificial bee colony algorithm which is one of the recent additions to metaheuristic techniques. The Artificial Bee Colony Algorithm is imitated the foraging behaviors of bee swarms. In application of this algorithm to the constraint problem, Deb's constraint handling method is used. Obtained results showed that the optimum value of numerical example is nearly same with the existing values in the literature.