• 대한토목학회논문집
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• 제26권3A호
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• pp.473-484
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• 2006

역량스펙트럼 방법은 비선형 거동을 하는 구조물의 최대 변위응답을 간편하게 산정하는데 사용된다. 역량스펙트럼 방법을 사용하여 다경간 교량의 내진성능을 평가하기 위해서는 구조계를 대표하는 하나의 응답을 등가단자유도계 방법을 이용하여 다자유도 응답들로부터 유도하여야 한다. 등가단자유도 방법은 비탄성 정적해석에 의해 산정된 힘-변위 곡선들로부터 역량곡선을 계산하는데 사용된다. 역량스펙트럼 방법에 사용되는 등가단자유도 방법의 정확성을 평가하기 위하여, 몇 개의 등가단 자유도방법과 결합된 역량스펙트럼 방법에 의해 산정된 최대변위응답을 설계지진스펙트럼에 대응되는 인공지진을 사용한 비탄성 시간이력해석의 변위응답과 비교하였다.

• 대한토목학회논문집
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• 제26권4A호
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• pp.659-675
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• 2006

근래에 비선형 정적해석법에 기초를 둔 성능-기반 방법이 각광을 받으면서 개선되고 있다. 역량스펙트럼 방법과 변위계수법이 비선형 정적해석법 중에서 대표적이라고 할 수 있다. 새로 건설되거나 기존의 구조물에 대하여 내진설계와 내진성능 평가에 대한 비선형 정적해석법의 적용성을 평가하기 위해서는 우선적으로 역량스펙트럼 방법과 변위계수법의 정확성이 평가되어야 한다. 비선형 정적해석법의 정확성은 근거리 및 원거리 지진하중에 대한 철근 콘크리트 벽체 구조물의 진동대 실험결과와 비교하여 평가하였다. 또한, 단자유도계, 등가단자유도계와 다자유도계에 대한 비선형 동적해석기법에 의해 평가된 지진응답도 진동대 실험결과와 비교하여 평가하였다.

• Earthquakes and Structures
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• 제23권2호
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• pp.129-138
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• 2022

One of the objectives to prevent building pounding between two adjacentstructures is to considerseparation distance or decrease relative displacement during seismic excitation. Although the majority of building codes around the world have basically suggested some equations or approximately recommended various distances between structuresto avoid pounding hazard, but a lot of reportsin zone of pounding have obviously shown thatsafety situation or economic consideration are not always provided due to the collisions between buildings and the cost of land, respectively. For this purpose, a dynamic MDOF model by having base isolation system is numerically considered and using various earthquake records, relative displacements are mathematically investigated. Different equations to determine the value of damping ratio are collected and the results of evaluations are listed for comparison among them to present a new equation for determination of impact damping ratio. Presented equation is depends significantly on impact velocity before and after impact based on artificial neural network, which the accuracy of them is investigated and also confirmed. In order to select the optimum equation, hysteresisloop of impact between base of building and rubber bumper is considered and compared with the hysteresis loop of each impact, calculated by different equations. Finally, using representative equation, the effect of thickness, number and stiffness of rubber bumpers are numerically investigated. The results of analysis indicate that stiffness and number of bumpers have significantly affected in zone of impact force while the thickness of bumpers have not shown significant influence to calculate impact force during earthquake. For instance, increasing the number of bumpers, gap size between structures and also the value of stiffness is caused to decrease impact force between models. The final evaluation demonstrates that bumpers are able to decrease peak lateral displacement of top story during impact.

• Structural Engineering and Mechanics
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• 제90권3호
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• pp.313-323
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• 2024

Most of existing buildings in Mexico City are made of reinforced concrete (RC), however, it has been shown that they are very susceptible to narrow-band long duration ground motions. In recent years, the use of dual systems composed by Buckling Restrained Braces (BRB) has increased due to its high energy dissipation capacity under reversible cyclical loads. Therefore, in this work the behavior of RC buildings with BRB is studied in order to know their performance, specifically, the energy distribution through height and response transformation factors between the RC and simplified systems are estimated. For this propose, seven RC buildings with different heights were designed according to the Mexico City Seismic Design Provisions (MCSDP), in addition, equivalent single degree of freedom (SDOF) systems were obtained. Incremental dynamic analyses on the buildings under 30 narrow-band ground motions in order to compute the relationship between normalized hysteretic energy, maximum inter-story drift and roof displacement demands were performed. The results shown that the entire structural frames participate in energy dissipation and their distribution is independent of the global ductility. The results let propose energy distribution equations through height. Finally, response transformation factors between the SDOF and multi degree of freedom (MDOF) systems were developed aimed to propose a new energy-based approach of BRB reinforced concrete buildings.

• Smart Structures and Systems
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• 제20권1호
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• pp.61-74
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• 2017

One of the most reliable and simplest tools for structural vibration control in civil engineering is Tuned Mass Damper, TMD. Provided that the frequency and damping parameters of these dampers are tuned appropriately, they can reduce the vibrations of the structure through their generated inertia forces, as they vibrate continuously. To achieve the optimal parameters of TMD, many different methods have been provided so far. In old approaches, some formulas have been offered based on simplifying models and their applied loadings while novel procedures need to model structures completely in order to obtain TMD parameters. In this paper, with regard to the nonlinear decision-making of fuzzy systems and their enough ability to cope with different unreliability, a method is proposed. Furthermore, by taking advantage of both old and new methods a fuzzy system is designed to be operational and reduce uncertainties related to models and applied loads. To design fuzzy system, it is required to gain data on structures and optimum parameters of TMDs corresponding to these structures. This information is obtained through modeling MDOF systems with various numbers of stories subjected to far and near field earthquakes. The design of the fuzzy systems is performed by three methods: look-up table, the data space grid-partitioning, and clustering. After that, rule weights of Mamdani fuzzy system using the look-up table are optimized through genetic algorithm and rule weights of Sugeno fuzzy system designed based on grid-partitioning methods and clustering data are optimized through ANFIS (Adaptive Neuro-Fuzzy Inference System). By comparing these methods, it is observed that the fuzzy system technique based on data clustering has an efficient function to predict the optimal parameters of TMDs. In this method, average of errors in estimating frequency and damping ratio is close to zero. Also, standard deviation of frequency errors and damping ratio errors decrease by 78% and 4.1% respectively in comparison with the look-up table method. While, this reductions compared to the grid partitioning method are 2.2% and 1.8% respectively. In this research, TMD parameters are estimated for a 15-degree of freedom structure based on designed fuzzy system and are compared to parameters obtained from the genetic algorithm and empirical relations. The progress up to 1.9% and 2% under far-field earthquakes and 0.4% and 2.2% under near-field earthquakes is obtained in decreasing respectively roof maximum displacement and its RMS ratio through fuzzy system method compared to those obtained by empirical relations.