• Title/Summary/Keyword: Tubular Joint

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Thermal Characteristic of the Tubular Single tap Adhesively Bonded Joint bonded with filler containing epoxy adhesive (충전재가 함유된 단일겹치기 접착 조인트의 열적 특성에 관한 연구)

  • Kim, Jin-Kook;Lee, Dai-Gil
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.370-376
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    • 2001
  • When an adhesive joint is exposed to high environmental temperature, the tensile load capability of the adhesive joint decreases because the elastic modulus and failure strength of structural adhesive decrease. The thermo-mechanical properties of structural adhesive can be improved by addition of fillers to the adhesive. In this paper, the elastic modulus and failure strength of adhesives as well as the tensile load capability of tubular single lap adhesive joints were experimentally and theoretically investigated with respect to the volume fraction of filler (alumina) and the environmental temperature. Also the tensile modulus of the fille containing epoxy adhesive was predicted using a new equation which considers filler shape, filler content and environmental temperature. The tensile load capability of the adhesive joint was predicted by using the effective strain obtained from the finite element analysis and a new failure model, from which the relation between the bonding length and the crack length was developed with respect to the volume fraction of filler.

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Effect of FRP parameters in strengthening the tubular joint for offshore structures

  • Prashob, P.S.;Shashikala, A.P.;Somasundaran, T.P.
    • Ocean Systems Engineering
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    • v.8 no.4
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    • pp.409-426
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    • 2018
  • This paper presents the strengthening of tubular joint by wrapping Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). In this study, total number of layers, stacking sequence and length of wrapping are the different parameters involved when fiber reinforced polymers (FRP) composites are used for strengthening. For this, parameters where varied and results were compared with the reference joint. The best stacking sequence was identified which has the highest value in ultimate load with lesser deflections. For determining the best stacking sequence, numerical investigation was performed on CFRP composites; length of wrapping and number of layers were fixed. Later, the studies were focused on CFRP and GFRP strengthened joint by varying the total number of layers and length of wrapping. An attempt was done to propose a parametric equation from multiple regression analysis, which can be used for CFRP strengthened joints. Hashin failure criteria was used to check the failure of composites. Results revealed that FRP was having a greater influence in the load bearing capacity of joints, and in reducing the deflections and stresses of joint under axial compressive loads. It was also seen that, CFRP was far better than GFRP in reducing the stresses and deflection.

Experimental and numerical analysis of fatigue behaviour for tubular K-joints

  • Shao, Yong-Bo;Cao, Zhen-Bin
    • Structural Engineering and Mechanics
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    • v.19 no.6
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    • pp.639-652
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    • 2005
  • In this paper, a full-scale K-joint specimen was tested to failure under cyclic combined axial and in-plane bending loads. In the fatigue test, the crack developments were monitored step by step using the alternating current potential drop (ACPD) technique. Using Paris' law, stress intensity factor, which is a fracture parameter to be frequently used by many designers to predict the integrity and residual life of tubular joints, can be obtained from experimental test results of the crack growth rate. Furthermore, a scheme of automatic mesh generation for a cracked K-joint is introduced, and numerical analysis of stress intensity factor for the K-joint specimen has then been carried out. In the finite element analysis, J-integral method is used to estimate the stress intensity factors along the crack front. The numerical stress intensity factor results have been validated through comparing them with the experimental results. The comparison shows that the proposed numerical model can produce reasonably accurate stress intensity factor values. The effects of different crack shapes on the stress intensity factors have also been investigated, and it has been found that semi-ellipse is suitable and accurate to be adopted in numerical analysis for the stress intensity factor. Therefore, the proposed model in this paper is reliable to be used for estimating the stress intensity factor values of cracked tubular K-joints for design purposes.

FATIGUE DESIGN OF BUTT-WELDED TUBULAR JOINTS

  • Kim, D. S.;S. Nho;F. Kopp
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.127-132
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    • 2002
  • Recent deepwater offshore structures in Gulf of Mexico utilize butt welded tubular joints. Application of welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical because the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimating the fatigue behavior of these tubular members in the design stage is generally conducted by using S-N curves specified in the codes and standards. Applying the stress concentration factor of the welded structure to S-N approach often results in very conservative assessment because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fracture mechanics and fitness for service (FFS) technology have been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves to be used and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. An attempt was made to develop set of S-N curves based on fracture mechanics approach by considering non-uniform stress distribution and a threshold stress intensity factor. Series of S-N curves generated from this approach were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02"). Similar comparison with API X′ was made for tubular joint.. These initial crack depths are larger than the limits of inspection by current Non-destructive examination (NDE) means, such as Automatic Ultrasonic Inspection (AUT). Thus a safe approach can be taken by specifying acceptance criteria that are close to limits of sizing capability of the selected NDE method. The comparison illustrates conservatism built into the S-N design curve.

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Fatigue Behavior of K-Joint Structure for API 2W Gr.60 Steel (API 2W Gr.60 강재적용 K-Joint 구조의 피로성능평가)

  • Im, Sung-Woo;Chang, In-Hwa;Jo, Chul-Hee;Park, Kwan-Kyu
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.217-222
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    • 2006
  • Large-scale model tests of welded tubular K-joints were carried out to observe the fatigue behavior of API 2W Gr.60 steel produced by POSCO. The fatigue crack behaviors for various loading conditions were measured and investigated around the critical joint sections. The experimental results have been verified with numerical approaches and also compared with the IIW, DnV RP-C203 and API RP 2A-WSD design curves. The hot spot stress method was applied in the study. The SCF factor for tubular K-joint was also obtained.

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A Study on Welding Distortion and Residual Stress for Tubular Welded Joint (튜브 용접부의 용접변형 및 잔류응력에 관한 연구)

  • Jin, Hyung-Kook;Shin, Sang-Beom;Lee, Dong-Ju;Park, Dong-Hwan
    • Journal of Welding and Joining
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    • v.30 no.5
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    • pp.51-56
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    • 2012
  • The purpose of this study is to evaluate the distortion and the residual stress of GTA tubular welds between tube and head. In order to do it, the heat input model for GTA welding process was first developed by experiment and FE analyses. The welding distortion and the residual stress distribution of the tubular welds according to welding pass and various restraint degrees were evaluated by using FEA with the heat input model. From FEA results, it was found that the residual stress and the radial distortion at the weld toe of tube part decrease with a decrease in the number of welding pass. However, the maximum residual stresses in each direction of tubular welds are almost constant regardless of the external restraint degree. It was mainly due to the high internal restraint of the welds.

A Study on the Stress Concentration Factor and Fatigue Strength for T-Tubular Joints by FEM (유한요소법에 의한 튜블라 이음부의 응력집중계수 및 피로강도 해석)

  • 엄동석;강성원;하우일
    • Journal of Ocean Engineering and Technology
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    • v.8 no.2
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    • pp.141-150
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    • 1994
  • In designing, the strength of tubular joint has been an important problem for integrity of steel structures in which many tubular members are used. This paper presents the results of FEM analysis on stress concentration and fatigue crack initiation life for two types of tubular joints. One is circular and rectangular T type joints which consist of circular brace and rectangular chord. Another is circular and circular T type joints which consist of circular brace and circular chord. FEM analyses were performed under the axial load and in-plane bending moment. The fatigue crack initiation life can be estimated by using $\varepsilon$-N curve and by applying the Palmgren-Miner linear damage rule. According to the results, the stress concentration factor(SCF) of circular and rectangular joints is higher than that of circular and circular joints. The fatigue crack initiation lives of circular-circular joints and circular-rectangular joints were calculated.

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Ultimate Strength Interaction of Steel Tubular T-Joint Subjected to Concurrent Action of Compression and Bending (압축과 휨을 동시에 받는 강관 T조인트 극한강도 상호작용)

  • Kim, Kyung-Sik
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.1
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    • pp.298-303
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    • 2016
  • Owing to the advantages of reduced weight and wind effect, the space-framed towers that consist of vertical and horizontal members of circular hollow tubular sections have been adopted widely for various purposes. It is critical to guarantee the strengths of tubular joints where vertical and horizontal members are connected structurally to make the entire space-framed system behave as a single tower structure. In this study, a strength evaluation was conducted for T-type tubular joints subjected to the concurrent action of compression and bending. Three of the available design codes, i.e., AISC, Eurocode 3, ISO 19902 were investigated and a design equation was suggested for an ultimate strength interaction between the axial force and bending moment based on nonlinear finite element analyses by selecting the slenderness ratios at the joints as major parameters.

Strength Evaluation Formulae for Ring-Stiffened Tubular X-Joints (내부 환보강 X형 관이음부의 강도산정식)

  • 조현만;류연선
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.04a
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    • pp.61-68
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    • 2002
  • Tubular members have been applied in a wide range of frame structures including offshore structures. For the efficient load flow in tubular-member structures, the joints of tubular members are usually reinforced using internal ring stiffener for the steel tubular joint having a large diameter. The objective of this paper is to numerically assess the behavior of X-joints with an internal ring stiffener, and to evaluate the reinforcement effect of a ring stiffener, and to establish the strength formulae. Nonlinear finite element analysis is used to compute the static strength of axially loaded tubular joints. From the numerical results, internal ring stiffener is found to be efficient in improving static strength of tubular X-joints. Maximum strength ratios are calculated as 1.5~3.5, and the effective dimensions of ring stiffener are found. Regression analyses are performed considering practical size of ring stiffener and strength estimation formulae are proposed.

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Exposed Reinforced Concrete-Filled Steel Tubular (RCFST) column-base joint with high-strength

  • Mou, Ben;Wang, Zian;Qiao, Qiyun;Zhou, Wanqiu
    • Steel and Composite Structures
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    • v.44 no.1
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    • pp.1-15
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    • 2022
  • The weld quality has always been an important factor affecting the development of exposed CFT column-base joint. In this paper, a new type of exposed RCFST column-base joint is proposed, in which the high strength steel bars (USD 685) are set through the column and reinforced concrete foundation without any base plate and anchor bolts. Three specimens, the varying axial force ratio (0, 0.25 and 0.5), were tested under cyclic loadings. In addition, the bending moment capacity, energy dissipation capacity and deformation capacity of column-base joints were clarified. The experimental results indicated that the axial force ratio increases the stiffness and the bending moment and improves the energy dissipation capacity of column-base joints. This is because a large axial force can limit the slip between steel tubular and infilled concrete effectively. The specimens show stable hysteresis behavior.