Effects of torsion factors on simple non-linear systems using fully-bidirectional analyses

De-la-Colina, Jaime

doi:10.1002/(sici)1096-9845(199907)28:7<691::aid-eqe834>3.0.co;2-u

Cited by 17 publications

(9 citation statements)

References 9 publications

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“…All codes [IAEE, 1996;Eurocode 8, 1994] and with few exceptions most researchers [Rutenberg, 1992;Rutenberg et al, 1995;De-La-Conia, 1999] conducting parametric studies, consider stiffness eccentricities, e r , only. This is understandable because current approaches to torsional phenomena were primarily based on elastic response.…”

Section: Types Of Eccentricitiesmentioning

confidence: 99%

“…While the traditional allocation to elements of strength is satisfactory because equilibrium criteria are met, it should be noted that in the customary process [IAEE, 1996] of deriving element strength, widely used in relevant publications [Rutenberg, 1992;Rutenberg et al, 1995;De-La-Conia, 1999;Paulay, 1998c], stiffness were assumed to remain unchanged. One of the major shortcomings of these traditional approaches is the erroneous estimation of displacements associated with nominal strength, i.e.…”

Section: Notesmentioning

confidence: 99%

“…In the absence of type (3) transverse elements, the system may be shown torsionally very flexible. In most studies [De-La-Conia, 1999;Porus and Fajfar, 1999] the use of such systems is discouraged. With some eccentricity, not shown in Fig.…”

Section: Geometric Sensitivity To Element Displacement Demandsmentioning

confidence: 99%

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PAULAY¹

2001

J. Earth. Eng.

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Recent studies provided opportunities to review some of the principles, which have been used in the formulations of internationally accepted code-recommendations relevant to the seismic design of ductile buildings also subjected to torsional phenomena. With the progress of this study, features emerged which are considered to have contributed to a better understanding of structural behaviour. Moreover, the identification of deeply embedded fallacies, relevant to ductile response, suggested the introduction of some changes in seismic design strategies, yet not widely known or appreciated. Reasons for necessary re-interpretations of traditional structural properties, together with illustrative examples, demonstrating applications, rather than set code-type rules, are offered. Keywords: Component behaviour, displacements, ductility, seismic response of buildings, seismic torsion, walls. 273 J. Earth. Eng. 2001.05:273-308. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 06/01/15. For personal use only. J. Earth. Eng. 2001.05:273-308. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 06/01/15. For personal use only. J. Earth. Eng. 2001.05:273-308. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 06/01/15. For personal use only.where E c is the modulus of elasticity of the concrete and I g is the second moment of the gross concrete area. J. Earth. Eng. 2001.05:273-308. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 06/01/15. For personal use only.

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Section: Types Of Eccentricitiesmentioning

confidence: 99%

Section: Notesmentioning

confidence: 99%

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PAULAY¹

2001

J. Earth. Eng.

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“…However, it seems that additional work is needed to support other results, which can be incorporated in building codes. For instance, some one-storey model studies [4,5] observed that the amplification factor related with the estimation of design eccentricity benefits more large-eccentricity systems than small-eccentricity ones.The results presented here are part of a broad set of experimental tests on models and actual buildings to gather additional information on the measured response of TU systems which can support (or refute) the results obtained from analytical studies. The experiments reported here were initially intended to study the effect of the natural eccentricity e s on the response of simple physical twisting systems.…”

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Laboratory tests of steel simple torsionally unbalanced models

De-la-Colina

Acuña

Hernández

et al. 2006

Earthq Engng Struct Dyn

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The objective of this work is to obtain estimations of the amplification factors and used for torsion design of buildings, from experiments. For this study, simple one-storey torsionally unbalanced (TU) steel models were considered. Models consisted of a deck supported on four columns with a selected arrangement of hinges at column ends. Two theoretical structural eccentricities (e = 0.05 and 0.15) were considered. Models were excited with a simple long-period pendulum consisting of a hanging platform with a forced-vibration generator on it. Eight models were tested at several excitation levels (frequencies and force magnitudes) in both ranges of behaviour: elastic and inelastic. Experiments were conducted at three frequency ratios of excitation. Registered accelerations of the pendulum platform indicate that the experimental set-up leads to excitations that resemble narrow-band seismic ground motions. Frame shear force estimations, based on accelerations recorded at both deck sides, indicate that torsion design factors ( and ) depend on eccentricity. Estimations of frame shears based on measurements indicate that for normalized eccentricities e 0.025, the amplification can be between 2 and 3; while factor resulted between 0.0 and 1.6. systems can provide a good global understanding of the structural behaviour of buildings, more recent analytical studies turned to linear and nonlinear multi-storey systems, most of them modelled as shear beams.In addition to these analytical studies, understanding of the torsion structural behaviour has also been gathered from experiments and from instrumented buildings when they are either subjected to earthquakes or excited with forced-vibration generators. For instance Maheri et al.[1] tested a series of structural models. Their experimental work was limited to the study of frequencies and mode shapes within the linear response.As for measurements in buildings, Foutch [2] used two forced-vibration generators to study the vibration characteristics of a 12-storey steel frame building. These generators were placed at the building top. Frequencies and mode shapes obtained from experiments were compared with those computed with finite-element models. His results confirmed that displacement amplifications can arise in some structural frames when the building is susceptible to twist. Important observations on building torsion were also obtained by Lu and Hall [3] who monitored two instrumented buildings during the 1987 Whittier Narrows Earthquake. They concluded that symmetric buildings are particularly sensitive to accidental torsion.The previous findings obtained from measurements of either models or buildings are also important because they support some of the results obtained from analytical studies. However, it seems that additional work is needed to support other results, which can be incorporated in building codes. For instance, some one-storey model studies [4,5] observed that the amplification factor related with the estimation of design eccentricity benefits more large-eccen...

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Inelastic earthquake response of single‐story asymmetric buildings: an assessment of simplified shear‐beam models

Stathopoulos

Anagnostopoulos

2003

Earthq Engng Struct Dyn

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SUMMARYThe inelastic seismic torsional response of simple structures is examined by means of shear-beam type models as well as with plastic hinge idealization of one-story buildings. Using mean values of ductility factors, obtained for groups of ten earthquake motions, as the basic index of post-elastic response, the following topics are examined with the shear-beam type model: mass eccentric versus sti ness eccentric systems, e ects of di erent types of motions and e ects of double eccentricities. Subsequently, comparisons are made with results obtained using a more realistic, plastic hinge type model of singlestory reinforced concrete frame buildings designed according to a modern Code. The consequences of designing for di erent levels of accidental eccentricity are also examined for the aforementioned frame buildings.

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Effects of torsion factors on simple non-linear systems using fully-bidirectional analyses

Cited by 17 publications

References 9 publications

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Laboratory tests of steel simple torsionally unbalanced models

Inelastic earthquake response of single‐story asymmetric buildings: an assessment of simplified shear‐beam models

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