• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.2
• /
• pp.173-182
• /
• 2003

In equivalent static nonlinear analysis and in energy-based design, the structures are generally transformed into an equivalent SDOF system. In this study the seismic energy demands in multi story structures, such as three-, eight-, and twenty-story steel moment-resisting frames(MRF), buckling restrained braced frames(BRBF) and a damage tolerant braced frame(DTBF), are compared with those of equivalent single degree of freedom(ESDOF) systems. Sixty earthquake ground motions recorded In different soil conditions, which are soft rock, soft soil, and neat fault, were used to compute the input and hysteretic energy demands in model structures. In case the modal mass coefficient is less than 0.8, the effects of higher modes are considered in the process of converting into ESDOF According to the analysis results, the hysteretic and input energies obtained from 3 story and 8 story MRF and DTBF agreed well with the results from analysis of equivalent SDOF systems. However in the 20 story BRBF the results from ESDOF underestimated those obtained from the original structures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.1
• /
• pp.755-761
• /
• 2015

Temporary fencing is a mandatory installation in construction sites because of environmental regulations and pedestrian safety. Contractors are responsible for the structural integrity of frames. The fence frame composed of a ledger and post is very weak in the out-of-plane direction, which is normally reinforced by diagonal bracing with a sub post. In this study, the location of lateral bracing for the main post was investigated analytically. Three types of frame were suggested and their performance was compared in terms of the maximum moment and deflection. A construction site may be located at city centers or crowed areas, and a contingent accident should be considered. The EOD type was found to be most efficient among the three frames suggested.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.3
• /
• pp.139-150
• /
• 2005

Finite element method is applied to the determinations of the two eigenvalues(the elastic critical load and the natural frequence of lateral vibrations) of single story-3 equal bay rectangular frame. The analysis parameters are taper parameter ${\alpha}$ for column, and beam span to column height ratio, ${\beta}$ and second moment area ratio of beam to column, ${\Upsilon}$. Support condition at the column base and sway condition at the column top are also considered in the stability analysis of frame. The changes in the coefficient of eigenvalue are represented by algebraic function of analysis parameter. The coefficients estimated by the proposed algebraic function show good agreement with those determined by finite element method, which suggest the design aid role of the proposed function. By increasing the column axial forces step by step, the corresponding frequencies are also determined, which makes one examine or confirm the relationship suggested by other studies.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.7
• /
• pp.4611-4617
• /
• 2014

This paper proposes an approximate method to estimate member forces of columns in a rigid frame. One of the conventional methods, Cantilever Method assumes the midpoint of a column as a hinge and linear distribution of axial stresses regarding the centroid of the column areas. As a result, it shows erroneous results compared to those of matrix analysis of two frames. In this study, a new method is proposed to estimate the member forces in columns and location of hinges in columns, which can be adopted easily by a practicing engineer, and numerical examples showed improved results compared to conventional methods.

• Journal of Navigation and Port Research
• /
• v.36 no.3
• /
• pp.225-232
• /
• 2012

In this research, the influence of additional vertical deformation of floating pontoon when dead load of each story is loaded during construction was investigated. The analysis procedure is presented for considering the influence of the additional deformation to calculate the additional moment of super-frame. Following the procedure, an example building with 3 storied steel frame was analyzed. Analysis method that taking no account for deformation of pontoon to the modeling was underestimated by ignoring design load following deformation of vertical load. By operating the load at the same time, design load under the influence of large deflection of model which whole modeling of floating structure was overestimated. So analysis method of floating structure considering the construction sequences demonstrated the suitable method.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.4 no.3
• /
• pp.23-34
• /
• 2000

반복하중을 지지하는 4개의 2/3 크리 접합부 실험을 통하여 콘크리트 기둥 및 강재 보로 구성된 골조에 대한 외부 모멘트 접합부의 이력거동을 조사하였다. 주요 실험 변수는 접합부에 배치된 후프근의 수, 콘크리트만의 전단강도 발현응ㄹ 유도한 접합부 상세, 강재 보 플랜지 상, 하부에 스터드 형태의 전단키를 사용한 상세 등이다. 실험 시 관측된 균열양상, 파괴형상 및 다양한 계측결과에 근거하여 접합부 상세에 따른 각 시험체의 거동이 자세히 기술되었으며, 항복 후 보유강도, 강성저하 정도 및 에너지 소산능력 등이 분석되었다. 실험결과에 의하면, 이들 중 패널 및 인접 기둥 영역에 각각 2개의 후프근을 갖는 시험체 (CF3) 가 가장 우수한 이력응답을 나타냈으며, 이러한 형태의 접합부 상헤는 우리나와 같은 약진 지역에 적합할 것으로 판단되었다.

• Journal of the Korea Concrete Institute
• /
• v.17 no.3 s.87
• /
• pp.419-426
• /
• 2005

This study is to propose a modified equivalent frame model for flat plate slabs under lateral loads. ACI 318 (2002) allows equivalent frame methods to conduct two-way slab system analysis subjected to gravity loads as well as lateral loads. Since the equivalent frame method in the ACI 318 (2002) has been developed base on the behavior of two-way system for gravity loads, and nay not predict the behavior of flat plate slabs under lateral loads with good precision. This study develops a modified equivalent frame model which can give more precise answer for flat plate slabs under lateral loads. This model reflects the actual force transfer mechanism among the components of flat plate slab system, which are slabs, columns and torsional members, more accurately under lateral loads than existing equivalent frame models. The accuracy of this model is verified by comparing the analysis results using the proposed model with the results of finite element analysis. The analysis results of other existing models are included in the comparison. For this purpose, 2 story building having 3 spans in both directions is considered. Analytical results show that the modified equivalent frame model produces comparable drift and slab internal moments with those obtained from finite element analysis.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.1
• /
• pp.85-93
• /
• 2016

In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.6
• /
• pp.33-39
• /
• 2002

Response Modification Factor(R-factor) approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. However R factors were set empirically and simply based on the professional committee consensus on observed performance of building structures during past earthquakes. Consequently some major shortcomings linked to the current R factor approach have been pointed out. Using reinforced concrete intermediate moment-resisting frames(RC IMRFs), an analytical procedure is presented in this paper to establish R factor rationally. To this end, analytical R values were evaluated based on N2 Method and compared with the values recommended by IBC 2000. Overall, the analytical results correlated well with the code values. However the results also revealed that R factor might strongly depend on the system fundamental period. As evidenced by the interstory drift index(IDI) analysis results of this study, current R-factor based(or, Life Safety based) design tends to fail in fulfilling other implicit and hopeful performance objectives such as immediate Occupancy and Collapse Prevention. Performance based design(PBD) appears to be a promising approach to meet the multi level seismic performance objectives assigned to the building structures of nowadays.

• Journal of the Korea Concrete Institute
• /
• v.21 no.5
• /
• pp.661-668
• /
• 2009

Effective beam width model(EBWM) has been used for analysis of post-tensioned(PT) flat plate slab frames under lateral loads. The accuracy of this model in predicting lateral drifts and unbalanced moments strongly depends on the estimated effective stiffness of PT flat plate slabs. As moments on the slab due to lateral loads increases, cracks occur which leads to stiffness reduction in slabs. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for EBWM. For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis using the stiffness ratio of the reduced width of slab to the effective width of EBWM with respect to the level of slab moments, an equation for calculating stiffness reduction factor for slab is proposed. For verifying the accuracy of the proposed equation, this study compared with the test result of the PT flat plate frame. It is shown that the EBWM with the proposed equation predicts the actual stiffness of the PT specimen which varied according to the level of applied moment.