• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.219-229
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• 2003

The extended tangent stiffness matrices and force-deformation relations of the elastic catenary element were initially derived through the addition of the unstrained length of cables to unknown nodal 'displacements. A beam-column element was then introduced to model the deck and pylon of cable-stayed bridges. The conventional geometric nonlinear analysis, initial force method, and TCUD method were summarized, with an effective method combining two methods presented to determine the initial shapes of cable-stayed bridges with dead loads. In this combined method, TCUD method was applied to eliminate vertical and horizontal displacements at cable-supported points of decks and on top of pylons, respectively. The initial force method was also adopted to eliminate horizontal and vertical displacements of decks and pylons. Finally, the accuracy and validity of the proposed combined method were demonstrated through numerical examples.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.13-21
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• 2005

Advanced analysis and optimal design of steel arch bridges is presented. In the design method using an advanced analysis, separate member capacity checks after analysis are not required because the stability and strength of the structural system and its component members can be rigorously treated in the analysis. The geometric nonlinearity is considered by using the stability function. The Column Research Council tangent modulus is used to account for gradual yielding due to residual stresses. A parabolic function is used to represent the transition from elastic to zero stiffness associated with a developing hinge. An optimization technique used is a modified section increment method. The member with the largest unit value evaluated by AASHTO-LRFD interaction equation is replaced one by one with an adjacent larger member selected in the database. The objective function is taken as the weight of the steel arch bridge and the constraint functions account for load-carrying capacities and deflection requirements. Member sizes determined by the proposed method are compared with those given by other approaches.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.661-670
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• 2000

To investigate the characteristics of the dynamic response of long-span cable-stayed bridges due to various dynamic loadings likes moving traffic loads, two different 3-D cable-stayed bridge models are considered in this study. Two models are exactly the same in structural configurations but different in finite element discretization. Modal analysis is conducted using the deformed dead-load tangent stiffness matrix. A new concept was presented by using divided a cable into several elements in order to study the effect of the cable vibration (both in-plane and swinging) on the overall bridge dynamics. Futhermore case of asymmetric traffic loading clustered in one direction are also considered to study the torsional response of the bridge. The result of this study demonstrates the importance of cable vibration on the overall bridge dynamics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.17-26
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• 1990

A solution strategy for geometric non-linear analysis for the plane frame structures subjected to conservative and non-conservative forces is presented. By making efficient combination of the load incremental method and the displacement incremental method, this strategy can find postbuckling configuration such as snap-through and turning-back phenomena which cannot be easily found by the conventional load and displacement incrementation scheme. In the case of the analysis of the framed structure subjected to circulatory non-conservative forces, the total tangent stiffness matrix becomes unsymmetric and when calculating the incremental load and unbalanced load vector components, the direction change of the non-conservative forces is considered. Several example problems to demonstrate the feasibility of the present strategy, over ranges of deformation that are well beyond those likly to occur in practical framed structures, are given and discussed.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.75-82
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• 2004

Many researcher's efforts have made a significant advancement of space frame structure with various portion, and it becomes the most outsanding one of space structures. However, with the characteristics of thin and long term of spacing, the unstable behavior of space structure is shown by initial imperfection, erection procedure or joint, especially space frame structure represents more. This kind of unstable problem could not be set up clearly and there is a huge difference between theory and experiment. Moreover, the discrete structure such as space frame has more complex solution, this it is not easy to derive the formulation of design about space structure. In this space frame structure, the character of rise-span ratio or load mode is represented by the instability of space frame structure with initial imperfection, and snap-through or bifurcation might be the main phenomenon. Therefore, in this study, space frame structure which has a lot of aesthetic effect and profitable for large space covering single layer is dealt. And because that the unstable behavior due to variation of inner force resistance in the elastic range is very important collapse mechanism, I would like to investigate unstable character as a nonlinear behavior with a geometric nonlinear. In order to study the instability. I derive tangent stiffness matrix using finite element method and with displacement incremental method perform nonlinear analysis of unit space structure, star dome and 3-ring star dome considering rise-span $ratio(\mu}$ and load $ratio(R_L)$ for analyzing unstable phenomenon.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.159-168
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• 2005

An improved stability design method for beam-columns of plane frames is proposed based on system buckling analysis and second-order elastic analysis. For this, the tangent stiffness matrix of beam-column elements is first derived using stability functions and a procedure for evaluating effective buckling lengths is reviewed using elastic system buckling analysis. And then the second-order analysis procedure is presented considering $P-\Delta$ effects and is compared with the closed-form solution through numerical examples. Design examples showing the validity of the proposed method we presented and their numerical results are compared with those obtained from the conventional stability design methods. Finally some useful conclusions are drawn.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.395-404
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• 2005

This paper presents a reliable numerical procedure for nonlinear time-history analysis of space steel frames subjected to dynamic loads. Geometric nonlinearities of member (P-$\delta$) and frame (P-$\Delta$) are taken into account by the use of stability functions in framed stiffness matrix formulation. The gradual yielding along the member length and over the cross section is included by using a tangent modulus concept and a softening plastic hinge model based on the New-Orbison yield surface. A computer program utilizing the average acceleration method for the integration scheme is developed to numerically solve the equation of motion of framed structure formulated in an incremental form. The results of several numerical examples are compared with those derived from using beam element model of ABAQUS program to illustrate the accuracy and the computational efficiency of the proposed procedure.

• Journal of the Society of Disaster Information
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• v.13 no.2
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• pp.249-257
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• 2017

Recently, a cable disconnection accident occurred due to a lightning strike at the Seohae Bridge located in Dangjin-Pyeongtaek City. This is a natural occurrence, but it is a recall that it is very important to review the safety issues due to the disconnection of cable bridges. In other words, the role of cables in cable bridges has a profound effect on the safety of the structure, and it has become necessary to grasp the effect on the entire structural system. The cable bridge is an economic bridge that builds the main tower and supports the bottom plate by cable. The influence of the cable is the main member, which is a big influence on the safety of the whole bridge system. In the cable-stayed bridge, the cables exhibit nonlinear behavior because of the change in sag, due to the dead weight of the cable, which occurs with changing tension in the cable resulting from the movement of the end points of the cable as the bridge is loaded. Modal analysis is conducted using the deformed dead-load tangent stiffness matrix. A new concept was presented by using divided a cable into several elements in order to study the effect of the cable vibration (both in-plane and swinging) on the overall bridge dynamics. The result of this study demonstrates the importance of cable vibration on the overall bridge dynamics.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.132-139
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• 1992

This paper presents geometrically nonlinear formulation of shell problems using the three-dimensional curved shell element, which includs large displacements and large rotations. Formulations of the geometrically nonlinear problems can be derived in a variety of ways, but most of them have been obtained by assuming that nodal rotations are small. Hence, the tangent stiffness matrix is derived under the assumptions that rotational increments are infinitesimal and the effect of finite rotational increments have to be considered during the equilibrium iterations. To study the large displacement and large rotation problems, the restrictions are removed and the formulations of the curved shell element including the effect of large rotational increments are developed in this paper. The displacement based finite element method using this improved formulation are applied to the analyses of the geometrically nonlinear behaviors of the single and double curved shells, which are compared with the results by others.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.153-165
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• 1999

In order to trace the lateral-torsional post-bucking behaviors of thin-walled space frames with non-symmetric cross sections, a geometrically non-linear finite element formulation is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for non-symmetric thin-walled cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, tangent stiffness matrices of thin-walled space frame element are derived by using the Hermition polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines and incremental member forces.