• Structural Engineering and Mechanics
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• 제85권5호
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• pp.679-691
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• 2023

Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (𝛽_u) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on 𝛽_u in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence 𝛽_u to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (𝜌_s1/𝜌_s2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the 𝛽_u. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on 𝛽_u. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on 𝛽_u have been further proved by theoretical derivation. Finally, due to 𝜀_t is found to have a better linear correlation with 𝛽_u than x_u/d, equations as a function of 𝜀_t for predicting the 𝛽_u of continuous beams under the two loads are proposed, respectively.

• 대한토목학회논문집
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• 제14권1호
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• pp.105-117
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• 1994

평면(平面)뼈대 구조물(構造物)에 대해 기하학적(幾何學的)인 비선형성(非線形性)과 소성(塑性)힌지의 개념(槪念)을 이용한 재료(材料)의 비선형성(非線形性)이 동시에 고려될 수 있도록 한 유한요소이론(有限要素理論) 및 해석방법(解析方法)을 제시한다. 단면(斷面)은 길이방향으로 일정하고, 구형(矩形) 및 I형(形) 단면(斷面)을 갖는 것으로 가정한다. 휨모멘트와 축방향력(軸方向力)의 결합된 효과를 고려한 한계함수(限界凾數) 사용하여 평면(平面)뼈대부재(部材)의 탄소성(彈塑性) 강도(剛度)매트릭스를 유도(誘導)한다. 변위증분법(變位增分法)을 적용하여 탄소성해석(彈塑性解析)에 의한 뼈대 구조물(構造物)의 극한거동(極限擧動)을 추적한다. 예제(例題)들을 통하여 다른 문헌(文獻)의 결과(結果)와 본(本) 연구(硏究)에 의한 결과(結果)를 비교(比較) 분석(分析)함으로써 제시된 이론(理論)의 정당성(正當性) 입증(立證)한다.

• 한국구조물진단유지관리공학회 논문집
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• 제13권1호통권53호
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• pp.115-124
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• 2009

본 연구에서는 구조물에 발생하는 변상 진전 특성을 수치 해석적으로 평가할 수 있는 기법을 새롭게 개발하기 위한 연구를 수행한 것이다. 이를 위해서, 변상발생 메커니즘을 토대로 하여, 인장균열 발생 후, 휨압축에 의한 압축손상까지를 해석에 반영하였다. 특히 인장균열이 발생하고나서 압축손상이 발생하기까지의 해석 단계를 위해서는, 등가소성힌지길이 개념을 새롭게 도입하여, 균열의 진전을 해석하게 된다. 등가소성힌지 길이개념을 도입함으로써, 균열발생단면에 대한 단면력, 즉, 축력과 모멘트를 균열폭과 관계지어 균열폭의 확장을 추적해 나가게 된다.

• Steel and Composite Structures
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• 제3권6호
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• pp.421-438
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• 2003

Aging and deterioration of existing steel structures necessitate the development of simple and efficient rehabilitation techniques. The current study investigates a methodology to enhance the flexural capacity of steel beams by bonding Glass Fibre Reinforced Plastic (GFRP) sheets to their flanges. A heavy duty adhesive, tested in a previous study is used to bond the steel and the GFRP sheet. In addition to its ease of application, the GFRP sheet provides a protective layer that prevents future corrosion of the steel section. The study reports the results of bending tests conducted on a W-shaped steel beam before and after rehabilitation using GFRP sheets. Enhancement in the moment capacity of the beam due to bonding GFRP sheet is determined from the test results. A closed form analytical model that can predict the yield moment as well as the stresses induced in the adhesive and the GFRP sheets of rehabilitated steel beam is developed. A detailed finite element analysis for the tested specimens is also conducted in this paper. The steel web and flanges as well as the GFRP sheets are simulated using three-dimensional brick elements. The shear and peel stiffness of the adhesive are modeled as equivalent linear spring systems. The analytical and experimental results indicate that a significant enhancement in the ultimate capacity of the steel beam is achieved using the proposed technique. The finite element analysis is employed to describe in detail the profile of stresses and strains that develop in the rehabilitated steel beam.

• Steel and Composite Structures
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• 제22권1호
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• pp.141-159
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• 2016

Commonly in steel frames, steel beam and concrete slab are connected together by shear keys to work as a unit member which is called composite beam. When a composite beam is subjected to positive bending, flexural strength and stiffness of the beam can be increased due to "composite action". At the same time despite these advantages, composite action increases the strain at the beam bottom flange and it might affect beam plastic rotation capacity. This paper presents results of study on the rotation capacity of composite beam connected to Rectangular Hollow Section (RHS) column in the steel moment resisting frame buildings. Due to out-of-plane deformation of column flange, moment transfer efficiency of web connection is reduced and this results in reduction of beam plastic rotation capacity. In order to investigate the effects of width-to-thickness ratio (B/t) of RHS column on the rotation capacity of composite beam, cyclic loading tests were conducted on three full scale beam-to-column subassemblies. Detailed study on the different steel beam damages and concrete slab damages are presented. Experimental data showed the importance of this parameter of RHS column on the seismic behavior of composite beams. It is found that occurrence of severe concrete bearing crush at the face of RHS column of specimen with smaller width-to-thickness ratio resulted in considerable reduction on the rate of strain increase in the bottom flange. This behavior resulted in considerable improvement of rotation capacity of this specimen compared with composite and even bare steel beam connected to the RHS column with larger width-to-thickness ratio.

• Structural Engineering and Mechanics
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• 제51권6호
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• pp.1017-1036
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• 2014

Steel tubes have an efficient shape with large second moment of inertia relative to their light weight. One of the main problems of these members is their low buckling resistance caused from having thin walls. In this study, steel foams with high strength over weight ratio is used to fill the steel tube to beneficially modify the response of steel tubes. The linear eigenvalue and plastic collapse FE analysis is done on steel foam filled tube under pure compression and three point bending simulation. It is shown that steel foam improves the maximum strength and the ability of energy absorption of the steel tubes significantly. Different configurations with different volume of steel foam and composite behavior is investigated. It is demonstrated that there are some optimum configurations with more efficient behavior. If composite action between steel foam and steel increases, the strength of the element will improve, in a way that, the failure mode change from local buckling to yielding.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.907-910
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• 2010

This study has developed a numerical analysis technique newly which can evaluate the damage propagation characteristics of civil infrastructures. To do this, numerical techniques are incorporated for the concrete members up to the compressive damage due to the bending compressive forces after the tensile crack based on the deformation mechanism. Especially, for the compressive damage stage after the tensile crack, the crack propagation process will be analyzed numerically using the concept of an equivalent plastic hinged length. Using this concept, we investigate the reasonability of the developed module by comparing commercial program for the tunnel structure. It can be established from this study that section forces, such as axial forces and the moment cracks takes place, can be related to the width of the crack making it possible to analyze the crack extension.

• Structural Engineering and Mechanics
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• 제38권2호
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• pp.231-247
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• 2011

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.

• Earthquakes and Structures
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• 제16권4호
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• pp.455-468
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• 2019

The behavior of pile-deck connections of pile-supported marginal wharfs subjected to earthquake loading is of key importance to ensure a good performance of this type of structures. Two precast-pretensioned pile-deck connections used in the construction of pile-supported marginal wharfs were tested under cyclic loading. The first is a connection with simple reinforcement details and light steel ratio developed for use where moderate pile-deck rotation demands are expected in the wharf. The second is specifically developed to sustain the large rotation, shear force and bending moment demands, as required for the shortest piles in a marginal wharf. Data obtained from the test program is used in the paper to calibrate an equivalent plastic hinge length that can be incorporated into nonlinear analysis models of these structures when prestressed pile-deck connections with duct embedded dowels are used.

• 한국강구조학회 논문집
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• 제29권1호
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• pp.1-12
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• 2017

본 연구에는 HSB600 고강도 강재의 변형-경화를 고려한 조밀 강합성 I-거더의 정모멘트부 공칭휨강도를 제안한다. HSB600은 일반강재와는 다르게 명확한 항복 고원을 보이지 않고 항복 직후 변형-경화가 진행된다. 하지만 현 국내외 설계기준에 있는 공칭휨강도 식은 일반강재에 대하여 개발된 설계식이기 때문에 HSB600의 변형-경화 특성을 제대로 반영하지 못하고 있다. 따라서 HSB600의 변형-경화 특성이 휨강도에 미치는 영향을 고려하기 위해, 강합성 거더의 변형-경화를 고려한 소성모멘트를 제안한 후 다수의 해석단면을 대상으로 모멘트-곡률 수치해석을 수행하였다. 해석 결과를 토대로 HSB600 고강도 강재의 변형-경화가 강합성 거더 휨강도에 미치는 영향을 나타내는 매개변수를 제안하였다. 또한 이 매개변수를 이용하여 HSB600 강합성 거더의 변형-경화를 고려한 정모멘트부 공칭휨강도를 제안하였고 현 AASHTO LRFD 교량설계기준의 공칭휨강도와 비교 검토하였다.