• 한국전산구조공학회논문집
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• 제37권1호
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• pp.57-65
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• 2024

내화 구조물에서는 환기 계수, 재료 탄성 계수, 항복 강도, 열팽창 계수, 외력 및 화재 위치에서 불확실성이 관찰된다. 환기 불확실성은 화재 온도에 영향을 미치고, 이는 다시 구조물 온도에 영향을 미친다. 이러한 온도는 재료 특성과 함께 불확실한 구조적 응답으로 이어지고 있다. 화재 시 구조적 비선형 거동으로 인해 몬테카를로 시뮬레이션을 사용하여 화재 취약성을 계산하는데, 이는 시간이 많이 소요된다. 따라서 머신러닝 알고리즘을 활용해 화재 취약성 분석을 예측함으로써 효율성을 높이고 정확성을 확보하려는 연구가 진행되고 있다. 이 연구에서는 화재 크기, 위치, 구조 재료 특성의 불확실성을 고려하여 철골 모멘트 골조 건물의 화재 취약성을 예측했다. 화재 시 비선형 구조 거동 결과를 기반으로 한 취약성 곡선은 로그 정규 분포를 따른다. 마지막으로 제안한 방법이 화재 취약성을 정확하고 효율적으로 예측할 수 있음을 보여주었다.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.73-84
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• 2012

This paper strongly addresses to the problem of the mechanical systems in which parameters are uncertain and bounded. Interval calculation is used to find sharp bounds of the structural parameters for infilled frame system modeled with finite element method. Infill walls are generally treated as non-structural elements considerably to improve the lateral stiffness, strength and ductility of the structure together with the frame elements. Because of their complex nature, they are often neglected in the analytical model of building structures. However, in seismic design, ignoring the effect of infill wall in a numerical model does not accurately simulate the physical behavior. In this context, there are still some uncertainties in mechanical and also geometrical properties in the analysis and design procedure of infill walls. Structural uncertainties can be studied with a finite element formulation to determine sharp bounds of the structural parameters such as wall thickness and Young's modulus. In order to accomplish this sharp solution as much as possible, interval finite element approach can be considered, too. The structural parameters can be considered as interval variables by using the interval number, thus the structural stiffness matrix may be divided into the product of two parts which correspond to the interval values and the deterministic value.

• Earthquakes and Structures
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• 제13권3호
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• pp.323-335
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• 2017

A simplified framework for the probabilistic estimation of economic losses induced by the structural vulnerability in single-story and single-bay precast industrial buildings is presented. The simplifications introduced in the framework are oriented to the definition of an expeditious procedure adoptable by government agencies and insurance companies for preliminary risk assessment. The economic losses are evaluated considering seismic hazard, structural response, damage resulting from the structural vulnerability and only structural-vulnerability-induced e]conomic losses, i.e., structural repair or reconstruction costs (stock and flow costs) and content losses induced by structural collapse. The uncertainties associated with each step are accounted for via Monte Carlo simulations. The estimation results in a probabilistic description of the seismic risk of portal-like industrial buildings, expressed in terms of economic losses for each occurrence (i.e., seismic event) that owners (i.e., insured) and stakeholders can use to make risk management decisions. The outcome may also be useful for the definition of the insurance premiums and the evaluation of the risks and costs for the owner corresponding to the insurance industrial costs. A prototype of a precast concrete industrial building located in Mirandola, Italy, hit by the 2012 Emilia earthquake, is used as an example of the application of the procedure.

• Structural Engineering and Mechanics
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• 제37권5호
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• pp.543-560
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• 2011

In structural engineering there are randomness inherently exist on determination of the loads, strength, geometry, and so on, and the manufacturing of the structural members, workmanship etc. Thus, objective and constraint functions of the optimization problem are functions that depend on those randomly natured components. The constraints being the function of the random variables are evaluated by using reliability index or performance measure approaches in the optimization process. In this study, the minimum weight of a space truss is obtained under the uncertainties on the load, material and cross-section areas with harmony search using reliability index and performance measure approaches. Consequently, optimization algorithm produces the same result when both the approaches converge. Performance measure approach, however, is more efficient compare to reliability index approach in terms of the convergence rate and iterations needed.

• Steel and Composite Structures
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• 제20권2호
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• pp.317-335
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• 2016

Concentrically braced steel frames (CBFs) can be optimised during the seismic design process by using lateral loading distributions derived from the concept of uniform damage distribution. However, it is not known how such structures are affected by uncertainties. This study aims to quantify and manage the effects of structural and ground-motion uncertainty on the seismic performance of optimum and conventionally designed CBFs. Extensive nonlinear dynamic analyses are performed on 5, 10 and 15-storey frames to investigate the effects of storey shear-strength and damping ratio uncertainties by using the Monte Carlo simulation method. For typical uncertainties in conventional steel frames, optimum design frames always exhibit considerably less inter-storey drift and cumulative damage compared to frames designed based on IBC-2012. However, it is noted that optimum structures are in general more sensitive to the random variation of storey shear-strength. It is shown that up to 50% variation in damping ratio does not affect the seismic performance of the optimum design frames compared to their code-based counterparts. Finally, the results indicate that the ground-motion uncertainty can be efficiently managed by optimizing CBFs based on the average of a set of synthetic earthquakes representing a design spectrum. Compared to code-based design structures, CBFs designed with the proposed average patterns exhibit up to 54% less maximum inter-storey drift and 73% less cumulative damage under design earthquakes. It is concluded that the optimisation procedure presented is reliable and should improve the seismic performance of CBFs.

• 한국구조물진단유지관리공학회 논문집
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• 제15권1호
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• pp.235-242
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• 2011

지진동에 대처하기 위한 구조물의 능동제어기를 설계할 때, 모델링의 오차 및 외란의 불확실성을 무시하고 진행하면 제어성능이 크게 퇴화될 수 있다. 심지어 시스템 전체가 불안정하게 되어 제진이 불가능하게 될 가능성도 배제할 수 없다. 본 연구의 목적은 슬라이딩 모드제어기(SMC)라 불리는 비선형제어기의 제어성능을 TMD가 장착된 구조물에 설계하여 그 적용 가능성을 검토하는 것이다. 이때 가진 외란은 FFT 해석으로 탁월주파수를 분석한 3개의 지진동이다. SMC로 제어한 결과, 구조물의 질량과 강성이 ${\pm}30%$ 섭동되어도 강인성을 유지하고 있음을 확인할 수 있었다. 다만, 오버슈트가 증대되고 정정시간이 증가하는 등 과도응답성능은 다소 퇴화되는 것을 확인할 수 있었다. 전반적으로 SMC는 모델링 및 외란의 불확실성에 대해 강인함을 유지하고 지진동을 효과적으로 제어하는 능동제어법으로 TMD 구조물과 결합시켜 지진동제어에 적용해 볼 수 있는 유용한 기법이라 판단된다.

• Earthquakes and Structures
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• 제10권1호
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• pp.141-161
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• 2016

In seismic fragility and risk analysis, the definition of structural limit state (LS) capacities is of crucial importance. Traditionally, LS capacities are defined according to design code provisions or using deterministic pushover analysis without considering the inherent randomness of structural parameters. To assess the effects of structural randomness on LS capacities, ten structural parameters that include material strengths and gravity loads are considered as random variables, and a probabilistic pushover method based on a correlation-controlled Latin hypercube sampling technique is used to estimate the uncertainties in LS capacities for four typical reinforced concrete frame buildings. A series of ten LSs are identified from the pushover curves based on the design-code-given thresholds and the available damage-controlled criteria. The obtained LS capacities are further represented by a lognormal model with the median $m_C$ and the dispersion ${\beta}_C$. The results show that structural uncertainties have limited influence on $m_C$ for the LSs other than that near collapse. The commonly used assumption of ${\beta}_C$ between 0.25 and 0.30 overestimates the uncertainties in LS capacities for each individual building, but they are suitable for a building group with moderate damages. A low uncertainty as ${\beta}_C=0.1{\sim}0.15$ is adequate for the LSs associated with slight damages of structures, while a large uncertainty as ${\beta}_C=0.40{\sim}0.45$ is suggested for the LSs near collapse.

• 대한기계학회논문집A
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• 제24권1호
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• pp.259-268
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• 2000

Because of their superior mechanical properties to isotropic materials, composite laminated plates are used for many structural applications that require high stiffness-to-weight and strength-to-weight ratios. Composite materials are always subject to a certain amount of scatter in their elastic moduli, but most analyses and designs with the materials are usually conducted by assuming that the material properties are fixed and have no uncertainties. In this paper, a convex modeling approach is introduced to take account of such uncertainties in elastic moduli. It is used with the finite element method to predict the onset of failures in composite laminated plates subject to in-plane loading. Numerical results show that failures begin at the smaller load when the uncertainties of elastic moduli considered and therefore, such uncertainties should be considered at the design stage for the safety and reliability of the structures.

• 콘크리트학회논문집
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• 제17권6호
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• pp.1045-1051
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• 2005

For critical structures and application, where a given reliability must be met, it is necessary to account for uncertainties and variability in material properties, structural parameters affecting the corrosion process, in addition to the statistical and decision uncertainties. This paper presents an approach to the fuzzy arithmetic based modeling of the chloride-induced corrosion of reinforcement in concrete structures that takes into account the uncertainties in the physical models of chloride penetration into concrete and corrosion of steel reinforcement, as well as the uncertainties in the governing parameters, including concrete diffusivity, concrete cover depth, surface chloride concentration and critical chloride level for corrosion initiation. The parameters of the models are regarded as fuzzy numbers with proper membership function adapted to statistical data of the governing parameters and the fuzziness of the corrosion time is determined by the fuzzy arithmetic of interval arithmetic and extension principle

• Smart Structures and Systems
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• 제5권3호
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• pp.223-240
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• 2009

As in any engineering application, the problem of structural assessment should face the different uncertainties present in real world. The main source of uncertainty in Health Monitoring System (HMS) applications are those related to the sensor accuracy, the theoretical models and the variability in structural parameters and applied loads. In present work, two methodologies have been developed to deal with these uncertainties in order to adopt reliable decisions related to the presence of damage. A simple example, a steel beam analysis, is considered in order to establish a liable comparison between them. Also, such methodologies are used with a developed structural assessment algorithm that consists in a direct and consistent comparison between sensor data and numerical model results, both affected by uncertainty. Such algorithm is applied to a simple concrete laboratory beam, tested till rupture, to show it feasibility and operational process. From these applications several conclusions are derived with a high value, regarding the final objective of the work, which is the implementation of this algorithm within a HMS, developed and applied into a prototype structure.