Nonlinear analysis of steel frameworks through direct modification of member stiffness properties

Xu, Lei; Liu, Y.; Grierson, Donald E.

doi:10.1016/j.advengsoft.2004.10.010

Cited by 17 publications

(21 citation statements)

References 6 publications

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“…The variations of stiffnesses predicted by Eqs. (6) for EEP and FEP connections are plotted in Fig. 9 versus applied moment M. The corresponding values of the stiffness of these two connections are listed in Tables 2 and 3.…”

Section: Full-strength Connections: M N ≥ M Pmentioning

confidence: 99%

“…where the factor r p is interpreted as the ratio of the elastic rotation ML/3EI to the total elastic and inelastic rotation ML/3EI + M/R p due to bending moment M applied at the end connected to the compound element, where the far end of the elastic member is simply supported [6].…”

Section: Stiffness Degradation Factorsmentioning

confidence: 99%

“…To that end, member plasticity stiffness R p is directly given by Refs. [5,6], and semi-rigid connection stiffness R c alone needs to be established in the following.…”

Section: Determining Connection Stiffness R Cmentioning

confidence: 99%

“…As given in the authors' studies [5,6], the post-elastic rotation of the connecting member is taken by this study to be,…”

Section: Determining Connection Stiffness R Cmentioning

confidence: 99%

“…of the stiffness of semi-rigid connections is discussed in detail, while that for member-end plasticity is adopted directly from previous research [5,6].…”

Section: Introductionmentioning

confidence: 99%

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Compound-element modeling accounting for semi-rigid connections and member plasticity

Liu

Grierson

2008

Engineering Structures

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Section: Full-strength Connections: M N ≥ M Pmentioning

confidence: 99%

Section: Stiffness Degradation Factorsmentioning

confidence: 99%

“…To that end, member plasticity stiffness R p is directly given by Refs. [5,6], and semi-rigid connection stiffness R c alone needs to be established in the following.…”

Section: Determining Connection Stiffness R Cmentioning

confidence: 99%

“…As given in the authors' studies [5,6], the post-elastic rotation of the connecting member is taken by this study to be,…”

Section: Determining Connection Stiffness R Cmentioning

confidence: 99%

“…of the stiffness of semi-rigid connections is discussed in detail, while that for member-end plasticity is adopted directly from previous research [5,6].…”

Section: Introductionmentioning

confidence: 99%

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Compound-element modeling accounting for semi-rigid connections and member plasticity

Liu

Grierson

2008

Engineering Structures

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Nonlinear dynamic analysis of frames with plastic hinges at arbitrary locations

Yan¹,

Au²

2009

Structural Design Tall Build

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This paper presents a method for nonlinear dynamic analysis of frames subjected to distributed loads, which is based on the semi-rigid technique and moving node strategy. The plastic hinge is modelled as a pseudo-semi-rigid connection with nonlinear hysteretic moment-curvature characteristics at element ends. The stiffness matrix with material and geometric nonlinearities is expressed as a sum of products of the standard and geometric stiffness matrices with their corresponding correction matrices based on the plasticity-factors developed from the section fl exural stiffness at the plastic hinge locations. Each beam member is modelled by two elements. The moving node strategy is applied to the intermediate node to track the exact location of any intermediate plastic hinge that may be formed. Equilibrium iterations and geometry updating are carried out in every time step. Stiffness degradation is adopted to describe the deterioration of plastic hinges, and the effects of various parameters in the degradation model are evaluated. Examples are used to illustrate the applicability and excellent performance of the proposed method. practical design, nonlinear dynamic analysis is still essential, especially to those structures that are irregular and those of which the higher mode effects cannot be ignored. Besides, the strong-motion peculiarity is also a problem that the pushover analysis needs to overcome (Elnashai, 2002). Therefore, dynamic analysis is still important to frames with nonlinearities.Under lateral loading, the frame members subjected to distributed load may have plastic hinges formed at intermediate locations besides the member ends. To capture the behaviour of the intermediate plastic hinges, an effi cient method for elasto-plastic large defl ection analysis of steel frames using an element with plastic hinges at mid-span and two ends was proposed (Chen and Chan, 1995). As the intermediate plastic hinges can only be formed at mid-span, the results obtained are subject to certain errors. Later, the moving node strategy was presented for the elasto-plastic analysis of frames subjected to loads including linearly varying distributed load (Wong, 1996). In addition, certain applications of the moving node method in the second-order inelastic analysis of two-and three-dimensional steel frames were reported (Kim et al., 2004;Kim and Choi, 2005). However, the above research on the intermediate plastic hinge was only for the static analysis of frames. Such plastic hinges are often formed when the frame is subjected to strong seismic excitations, and therefore, the corresponding dynamic problem warrants further study.The material and geometric nonlinearities in beam-column elements may be simulated by either the plastic hinge element or the fi bre element. Although the fi bre element model can handle the residual stresses and better simulate the yielding process, it is rather computation intensive. On the other hand, the plastic hinge element model can simulate nonlinearities well and it is computationally effi c...

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Spread of Plasticity: An Adaptive Gradual Plastic-hinge Approach for Steel Frames

Gong

Advances in Engineering Structures, Mechanics &Amp; Construction

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IntroductionConsiderable studies have been undertaken on the inelastic analysis of steel frames in recent years (Chen and Toma 1994, Xu et al. 2005). The inelastic analysis methods are generally classified into two types: the distributed plasticity method and the plastic-hinge method. The distributed plasticity method discretizes frame members both along their length and through their cross section into many elements. The spread of plasticity is traced by the sequential yielding of the elements. This method is usually adopted to create benchmark solutions, as it is too computationally intensive and not suitable for practical design purposes. On the contrary, the plastic-hinge method usually involves using single or multiple elements to model a frame member, thus making it more efficient and the preferred method in engineering practice. The plastic-hinge method assumes that inelastic deformations are concentrated at plastic hinges at the end of elastic elements. The early studies used an elastic-plastichinge model, where the relationship between moment and curvature is linear up to the full plasticmoment of a section, after which the section becomes a perfect hinge. Though this approach is easy to implement, it often overestimates the ultimate strength of structural systems. More recently, refinedand quasi-plastic-hinge approaches (Liew et al. 1993, Attalla et al. 1994) with two-surface yielding criteria were proposed to account for the gradual plastification within steel members. Often, a model was constructed to simulate the gradual softening of plastic-hinges whose force point falls within the two yielding surfaces (Chen and Chan 1995, Hasan et al. 2002.This study proposes a new gradual plastic-hinge model for the inelastic analysis of planar steel frames. The analysis approach belongs to the domain of matrix displacement method. The plastichinge model is capable of mimicking the spread of plasticity both through the depth of a section and along the length of an element. The moment gradient of a frame member is directly taken into account in the plastic-hinge model. The model is unique and applicable to a general steel beam-column.In this study, it is assumed that the cross sections are doubly symmetric and the stress-strain relation for steel material is elastic-perfectly-plastic. Only moment yielding is considered, while shear and axial yielding are ignored. Local plate, torsional, and lateral-torsional buckling are not considered. Inelastic Beam-Column ModelA hybrid element (see Fig.1) is employed to model planar inelastic beam-columns. The element consists of two potential plastic-hinges at the ends of an elastic beam-column. Each plastic-hinge is modeled by a nonlinear zero-length rotational spring (which is called a hinge-spring or spring hereafter). For the elastic beam-column, E, I, and A correspond to Young's modulus, moment of Department of Civil Engineering, Lakehead University, Thunder Bay, Ontario, Abstract This paper presents a new plastic-hinge method for inelastic analysis of steel frames. The p...

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Nonlinear analysis of steel frameworks through direct modification of member stiffness properties

Cited by 17 publications

References 6 publications

Compound-element modeling accounting for semi-rigid connections and member plasticity

Compound-element modeling accounting for semi-rigid connections and member plasticity

Nonlinear dynamic analysis of frames with plastic hinges at arbitrary locations

Spread of Plasticity: An Adaptive Gradual Plastic-hinge Approach for Steel Frames

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