• Structural Engineering and Mechanics
• /
• 제25권1호
• /
• pp.75-89
• /
• 2007

Post-earthquake reconnaissance and experimental research indicate that squat reinforced concrete (RC) columns in existing buildings or bridge piers are vulnerable to non-ductile shear failure. Recently, several experimental studies were conducted to investigate upgrading the shear resistance capacity of such columns in order to modify their failure mode to ductile one. Among these upgrading methods is the use of fibre-reinforced polymer (FRP) jackets. One of the preferred analytical tools to simulate the response of frame structures to earthquake loading is the lumped plasticity macromodels due to their computational efficiency and reasonable accuracy. In these models, the columns' nonlinear response is lumped at its ends. The most important input data for such type of models is the element's lateral force-displacement backbone curve. The objective of this study is to verify an analytical method to predict the lateral force-displacement ductility relationship of axially and laterally loaded rectangular RC squat columns retrofitted with FRP composites. The predicted relationship showed good accuracy when compared with tests available in the literature.

• 한국지진공학회논문집
• /
• 제6권4호
• /
• pp.1-6
• /
• 2002

일반설계에서 요구하는 구조물의 안전성은 탄성영역에서 일정수준의 안전계수를 확보하여 만족된다. 그러나 내진설계에서의 안전성은 소성영역에서 구조물의 형상에 따라 특정한 연성파괴메카니즘을 유도하여 확보하도록 요구하고 있다. 그러므로 이러한 안전성은 구조물의 기본설계단계에서 여러 개의 대안을 가지고 비교, 검토를 수행하여 확보되어야 하며 실시설계단계에서 이를 확인하는 작업이 이루어져야 한다. 이 연구에서는 일반도로교량을 대상으로 하여 기본설계와 실시설계에 사용하는 모델을 설정하였으며 양 모델의 동적거동특성인 주기와 모드형상을 비교하고 다중모드스펙트럼해석을 적용하여 파괴메카니즘을 규명하였다. 기본설계와 실시설계에 사용하는 모델로 각각 확인한 파괴메카니즘을 비교하여 기본설계모델의 타당성을 입증하고 실무에 적용할 수 있는 내진해석모델로 제시하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년 영문 학술대회
• /
• pp.813-822
• /
• 2008

The present work has been developed the interpretation processor including analysis of the failure stress in pyrotechnically releasable mechanical linking device, which has the release characteristic without fragmentation and pyro-shock, using SoildWorks, COSMOS Works and ANSYS programs. The aim of the invention is to propose a pyrotechnically releasable mechanical linking device for two mechanical elements that does not suffer from such drawbacks. The pyrotechnically releasable mechanical linking device according to the invention is simple, compact and inexpensive in structure. It is simple to implement and permit the use of only a reduced quantity of pyrotechnic composition, such composition possibly being devoid of any primary explosive at all. The present work is only focused on the design of structure and the material characteristics. To analyze the fracture morphology resulted from tensile test in the different ball type bolts, the present work has been performed to estimate the failure stress of material and to make the same result from tensile test. The failure stress of SUS 630 in ductile material is approximately 1050 Mpa. The failure stress of SUS 420 in brittle material is about 1790 Mpa. Among the models used the ductile material, the model 6 is suitable a design of structure compared to that of other models. The use of this interpretation processor developed the present work could be extensively helped to estimate the failure stress of material having a complex geometry such as the ball type bolt

• Steel and Composite Structures
• /
• 제47권2호
• /
• pp.289-296
• /
• 2023

The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

• 한국해양공학회지
• /
• 제37권3호
• /
• pp.111-121
• /
• 2023

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

• Geomechanics and Engineering
• /
• 제32권1호
• /
• pp.69-84
• /
• 2023

This paper proposes a novel frame element on Winkler-Pasternak foundation for analysis of a non-ductile reinforced concrete (RC) member resting on foundation. These structural members represent flexural-shear critical members, which are commonly found in existing buildings designed and constructed with the old seismic design standards (inadequately detailed transverse reinforcement). As a result, these structures always experience shear failure or flexure-shear failure under seismic loading. To predict the characteristics of these non-ductile structures, efficient numerical models are required. Therefore, the novel frame element on Winkler-Pasternak foundation with inclusion of the shear-flexure interaction effect is developed in this study. The proposed model is derived within the framework of a displacement-based formulation and fiber section model under Timoshenko beam theory. Uniaxial nonlinear material constitutive models are employed to represent the characteristics of non-ductile RC frame and the underlying foundation. The shear-flexure interaction effect is expressed within the shear constitutive model based on the UCSD shear-strength model as demonstrated in this paper. From several features of the presented model, the proposed model is simple but able to capture several salient characteristics of the non-ductile RC frame resting on foundation, such as failure behavior, soil-structure interaction, and shear-flexure interaction. This confirms through two numerical simulations.

• Structural Engineering and Mechanics
• /
• 제60권1호
• /
• pp.51-69
• /
• 2016

A large number of welded steel moment-resisting framed (SMRF) structures failed due to brittle fracture induced by ductile fracture at beam-to-column connections during 1994 Northridge earthquake and 1995 Kobe (Hyogoken-Nanbu) earthquake. Extensive research efforts have been devoted to clarifying the mechanism of the observed failures and corresponding countermeasures to ensure more ductile design of welded SMRF structures, while limited research on the failure analysis of the ductile cracking was conducted due to lack of computational capacity and proper theoretical models. As the first step to solve this complicated problem, this paper aims to establish a straightforward procedure to simulate ductile cracking of welded joints under monotonic tension. There are two difficulties in achieving the aim of this study, including measurement of true stress-true strain data and ductile fracture parameters of different subzones in a welded joint, such as weld deposit, heat affected zone and the boundary between the two. Butt joints are employed in this study for their simple configuration. Both experimental and numerical studies on two types of butt joints are conducted. The validity of the proposed procedure is proved by comparison between the experimental and numerical results.

• 한국전산구조공학회논문집
• /
• 제28권2호
• /
• pp.207-212
• /
• 2015

사회기반시설물인 교량은 인적/물적 자원의 신속하고 원활한 이동을 위해 지장물을 극복하도록 설계/시공되는 구조물이다. 그러므로 교량의 교축방향으로 배열되는 교각의 형상과 규모는 지형의 제약을 받을 수밖에 없다. 이러한 교각의 형상과 규모는 지진하중의 전달경로를 결정하는 연결부분 배열과 함께 연결부분과 교각에 발생하는 작용력을 좌우하게 된다. 이 연구에서는 강재받침과 철근콘크리트 기둥을 연결부분과 교각으로 하는 일반교량을 대상으로 교각 및 강재받침 배열이 다른 해석모델을 설정하여 지진해석을 수행하였다. 해석결과로 구한 교각기둥과 강재받침의 강도/작용력 비로부터 각 해석모델의 연성파괴메카니즘을 구성하고 연결부분 및 교각 배열이 일반교량의 내진성능에 미치는 영향을 연성파괴메카니즘 구성 측면에서 제시하였다.

• Steel and Composite Structures
• /
• 제22권2호
• /
• pp.323-352
• /
• 2016

The results of a series of finite element (FE) simulations and experimental studies are used to develop strength and stiffness models that predict the failure capacity and response characteristics of unstiffened extended endplate connections with circular and rectangular bolt configurations associated with deep girders. The proposed stiffness models are composed of multi-linear springs which model the overall extended endplate/column flange system deformation and strength of key-components. Comparison of model predictions with FE and experimental results available in the literature show that the proposed models accurately predict the strength and the response of extended endplate/column system with circular and rectangular bolt configurations. The effect of the bolt configuration (circular and rectangular) on the prying phenomenon encountered in the unstiffened extended endplate/column system was investigated. Based on FE results, extended endplate with circular bolt configuration has a more ductile behavior and exhibits higher total prying forces. The proposed models can be used to design connections that cover all possible failure modes for extended endplate with circular bolt configuration. This study provides guidelines for engineers to account for the additional forces induced in the tension bolts and for the maximum rotational capacity demand in the connection which are required for seismic analysis and design.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2003년도 추계 학술발표회논문집
• /
• pp.255-262
• /
• 2003

In present Korea Highway Bridge Standards the lap splice of longitudinal bars in a potential plastic hinge region is allowed so that large amount of transverse rebar specified in high seismicity regions Is required to prevent brittle bond failure If the brittle failure effects can be completely removed from the conventional designed piers, the amount of transverse rebar will be reduced drastically. In this study scaled models with solid and hollow rectangular sections were tested to investigate the seismic behavior of RC piers with 50％ of lap-spliced longitudinal bars in plastic hinge regions. In the tests the typical flexural failure conducting a ductile behavior were observed in both models. It is shown that the 50％ of lap-spliced bars can be considered as a good alternative of seismic detailing for longitudinal bars.