• International Journal of Concrete Structures and Materials
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• 제7권2호
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• pp.135-153
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• 2013

This study investigates the direct displacement based design (DDBD) approach for different types of reinforced concrete structural systems including single moment-resisting, dual wall-frame and dual steel-braced systems. In this methodology, the displacement profile is calculated and the equivalent single degree of freedom system is then modeled considering the damping characteristics of each member. Having calculated the effective period and secant stiffness of the structure, the base shear is obtained, based on which the design process can be carried out. For each system three frames are designed using DDBD approach. The frames are then analyzed using nonlinear time-history analysis with 7 earthquake accelerograms and the damage index is investigated through lateral drift profile of the models. Results of the analyses and comparison of the nonlinear time-history analysis results indicate efficiency of the DDBD approach for different reinforced concrete structural systems.

• Earthquakes and Structures
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• 제9권3호
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• pp.455-480
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• 2015

In the last decade, displacement-based (DB) methods have become established design procedures for reinforced concrete (RC) structures. They use strain and displacement measures as seismic performance control parameters. As for other simplified seismic design methods, it is of great interest to prove if they are usually conservative in respect to more refined, nonlinear, time history analyses, and can estimate design parameters with acceptable accuracy. In this paper, the current Direct Displacement-Based Design (DDBD) procedure is evaluated for designing simple single degree of freedom (SDOF) systems with specific reference to simply supported RC bridge piers. Using different formulations proposed in literature for the equivalent viscous damping and spectrum reduction factor, a parametric study is carried out on a comprehensive set of SDOF systems, and an average error chart of the method is derived allowing prediction of the expected error for an ample range of design cases. Following the chart, it can be observed that, for the design of actual RC bridge piers, underestimation errors of the DDBD method are very low, while the overestimation range of the simplified displacement-based procedure is strongly dependent on design ductility.

• 한국지진공학회논문집
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• 제22권5호
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• pp.299-309
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• 2018

Now that problems with force-based seismic design have been clearly identified, design is inclined toward displacement-based methods. One such widely used method is Direct-Displacement-Based Design (DDBD). Yet, one of the shortcomings of DDBD is considering higher-mode amplification of story shear, moments, and displacements using equations obtained from limited parametric studies of regular planar frames. In this paper, a different approach to account for higher-mode effects is proposed. This approach determines the lateral secant stiffness of the building frames that fulfill the allowable inter-story drift without exceeding the desired story displacements. Using the stiffness, an elastic response spectrum analysis is carried out to determine elastic higher-mode force effects. These force effects are then combined with DDBD-obtained first-mode force effects using the appropriate modal superposition method so that design can be performed. The proposed design procedure is verified using Nonlinear Time History Analysis (NTHA) of twelve planar frames in four categories accounting for mass and stiffness irregularity along the height. In general, the NTHA response outputs compared well with the allowable limits of the performance objective. Thus, it fulfills the aim of minimizing the use of NTHA for planar frame buildings, thereby saving computational resources and effort.

• Computers and Concrete
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• 제11권6호
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• pp.493-513
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• 2013

Direct displacement-based design (DDBD) represents an innovative philosophy for seismic design of structures. When structural considerations are more critical, DDBD design should be carried on the basis of limiting material strains since structural damage is always strain related. In this case, the outcome of DDBD is strongly influenced by the displacement demand of the structural element for the target limit strains. Experimental studies have shown that anchorage slip may contribute significantly to the total displacement capacity of R/C column elements. However, in the previous studies, anchorage slip effect is either ignored or lumped into flexural deformations by applying the equivalent strain penetration length. In the light of the above, an attempt is made in this paper to include explicitly anchorage slip effect in DDBD of R/C column elements. For this purpose, a new computer program named RCCOLA-DBD is developed for the DDBD of single R/C elements for limiting material strains. By applying this program, more than 300 parametric designs are conducted to investigate the influence of anchorage slip effect as well as of numerous other parameters on the seismic design of R/C members according to this methodology.

• 한국공간구조학회논문집
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• 제12권3호
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• pp.63-70
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• 2012

본 연구에서는 변위기반 성능설계 개념에 의해 기존 철근콘크리트 기둥과 콘크리트에 강재를 매입한 SRC 합성기둥에 대하여 최대 설계지진 가속도에 대한 내진성능개선의 성능설계을 비교하였다. SRC 합성기둥은 구조물의 강도를 증가시킬 뿐 아니라 연성도를 증가시키는 효과가 있다. SRC 합성기둥의 단면은 H형 강재와 원형의 중공 강관을 매입한 형태로 구성되어 있다. SRC 합성기둥에 대한 P-M상관도와 단면 공칭휨모멘트를 분석하고 이를 바탕으로 SRC 합성기둥에 대한 설계 변위 추정을 위해 변위기반 내진 설계 알고리즘을 제시하였다. 성능기반설계에 의한 성능개선설계를 위하여 목표성능변위 및 설계지진가속도 조건에 대해 직접변위 기반 설계방법 및 변위계수법에 의한 내진성능개선 설계 방법을 제시하였다. SRC 합성기둥은 기존 RC 기둥과 비교하여 성능개선 설계 결과 변위 연성비 및 변위성능에서 크게 개선된 성능설계 결과를 나타내었다.

• Smart Structures and Systems
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• 제30권6호
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• pp.627-637
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• 2022

Recent years, direct displacement-based design (DDBD) procedure is proposed for the design of un-bonded posttensioned (UPT) concrete wall systems. In the DDBD procedure, the determination of the equivalent viscous damping (EVD) ratio is critical since it would influence the strength demand of the UPT wall systems. Nevertheless, the influence of EVD ratio determination of the UPT wall systems were not thoroughly evaluated. This study was aimed to investigate the influence of different EVD ratio determinations on the DDBD procedure of UPT wall systems. Case study structures with four, twelve and twenty storeys have been designed with DDBD procedure considering different EVD ratio determinations. Nonlinear time history analysis was performed to validate the design results of those UPT wall systems. And the simulation results showed that the global responses of the case study structures were influenced by the EVD ratio determination.

• 한국공간구조학회논문집
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• 제10권4호
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• pp.49-57
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• 2010

본 연구는 기존 철근콘크리트 구조물에 대하여 대표적인 변위-기반 설계법인 Chopra&Goel 이 제안한 직접변위-기반 설계법의 기본개념을 적용하여 최대 설계지반 가속도에 대한 보강 Steel Jacket의 두께를 결장하고, 결정된 보강 두께를 적용하여 보강전 후 성능설계기법에 의한 비선형 해석 및 보강설계법에 의한 보다 개선된 알고리즘 및 프로그램을 제시하였다. Steel Jacket 보강된 철근콘크리트 기둥에 대한 설계 변위 추정을 위해 Steel Jacket 보강된 철근콘크리트 부재의 비선형 층상화 세그멘트 해석 모델을 제시하고, 성능기반설계에 의한 성능개선설계를 위하여 목표성능변위 및 설계자전가속도 조건에 대해 직접 변위-기반 설계 방법 및 변위계 수법에 의한 내진성능개선 설계 방법을 제시하였다. 적용 예에서 본 방법은 기존 철근콘크리트 기둥과 비교하여 성능개선설계 결과 보강 전에 비해 변위 연성비 및 변위성능에서 크게 개선된 성능설계 결과를 제공해 주었다.

• Computers and Concrete
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• 제6권2호
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• pp.95-108
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• 2009

In the current research, a displacement-based seismic design scheme to retrofit reinforced concrete columns using FRP composite materials has been proposed. An accurate prediction for the nonlinear flexural analysis of FRP jacketed concrete members has been presented under multiaxial constitutive laws of concrete and composite materials. Through modification of the displacement coefficient method (DCM) and the direct displacement-based design method (DDM) of reinforced concrete structures, two algorithms for a performance-based seismic retrofit design of reinforced concrete columns with a FRP jacket have been newly introduced. From applications to retrofit design it is known that two methods are easy to apply in retrofit design and the DCM procedure underestimates the target displacement to compare with the DDM procedure.

• Steel and Composite Structures
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• 제28권6호
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• pp.691-708
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• 2018

An innovative Hybrid Passive Resistive configuration for Truss Girder Frames (HPR-TGFs) is introduced in the present study. The proposed system is principally consisting of Fluid Viscous Dampers (FVDs) and Buckling Restrained Braces (BRBs) as its seismic resistive components. Concurrent utilization of these devices will develop an efficient energy dissipating mechanism which is able to mitigate lateral displacements as well as the base shear, simultaneously. However, under certain circumstances which the presence of FVDs might not be essential, the proposed configuration has the potential to incorporate double BRBs in order to achieve the redundancy of alternative load bearing paths. This study is extending the modern Direct Displacement Based Design (DDBD) procedure as the design methodology for HPR-TGF systems. Based on a series of nonlinear time history analysis, it is demonstrated that the design outcomes are almost identical to the pre-assumed design criteria. This implies that the ultimate characteristics of HPR-TGFs such as lateral stiffness and inter-story drifts are well-proportioned through the proposed design procedure.

• 한국지진공학회논문집
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• 제11권2호
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• pp.105-113
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• 2007

본 연구에서는, 기존 철근 콘크리트 구조물에 적용된 직접 변위-기반 설계법을 적용 FRP 피복 보강된 성능개선 콘크리트 부재에 대한 정밀 비선형 휨 해석 및 내진성능설계의 구체적 알고리즘을 제시하였다. 비선형 휨 해석의 정밀 예측을 위하여 콘크리트 및 FRP 복합재료의 다축 구성관계를 고려하였으며, Chopra 등 (1999)이 제안한 직접 변위-기반 설계법(DDM)을 개선하여 철근콘크리트 기둥에 대한 성능개선을 위한 FRP 피복 보강을 위한 성능설계 알고리즘을 제시하였다. 제시된 직접 변위-기반 설계법은, 변위계수법과 비교하여, 비선형 거동이 큰 경우에도 목표 변위 성능 값에 대한 정확한 추정을 해준다. 이는 변위계수법이 항복 이전의 유효탄성계수를 사용하는 반면, 직접 변위-기반 설계법은 유효탄할선탄성계수를 고려하고 있어, 목표 변위에 따른 성능설계 평가에 있어서 보다 높은 연성비의 거동을 반영하고 있기 때문인 것으로 평가된다.