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Plastic Rotations (plastic + rotation)
Selected AbstractsFailure Mechanism of Deformed Concrete Tunnels Subject to Diagonally Concentrated LoadsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2009Wei He Based on the experimental findings, an extended discussion is carried out to select a rational compressive model for concrete that represents the dominant failure modes of deformed concrete tunnels. Three main dominant final failure modes are described: structural failure due to the plastic rotation of softening hinges, tensile failure caused by localized cracks, and material failure due to concrete deterioration. A parametric analysis of the material properties of concrete shows that the compressive strength of concrete has a dominant effect on the load-carrying capacity, although the compressive fracture energy of concrete remarkably influences the post-peak deformation behavior of the tunnel. Moreover, the soil pressure, which is regarded as a distributed external load, plays an important role in controlling the final failure modes and the deformation behavior of concrete tunnels. The size effect on the load-carrying capacities of different-sized concrete tunnels is also discussed based on the numerical simulations. [source] Microcellular model evaluation for the deformation of dynamically vulcanized EPDM/iPP blendsPOLYMER ENGINEERING & SCIENCE, Issue 3 2003Kathryn J. Wright The origins of elasticity in thermoplastic vulcanizates have been debated for the past decade. Previous modeling attempts provide numerical solutions that make assessment of constituent concentration and interaction unclear. A microcellular modeling approach is proposed and evaluated herein to describe the steady-state behavior of dynamically vulcanized blends of ethylene-propylene-diene monomer (EPDM) and isotactic polypropylene (iPP). This approach provides an analytic result including terms for composition and cure state. Three types of deformation are accounted for: elastic and plastic deformation of iPP, elastic deformation of EPDM, and localized elastic and plastic rotation about iPP junction points. The viability of the constitutive model is evaluated in terms of iPP concentration and EPDM cure state. [source] Probabilistic evaluation of seismic performance of 3-story 3D one- and two-way steel moment-frame structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2008Hiroyuki Tagawa Abstract This paper presents the results of a probabilistic evaluation of the seismic performance of 3D steel moment-frame structures. Two types of framing system are considered: one-way frames typical of construction in the United States and two-way frames typical of construction in Japan. For each framing system, four types of beam,column connections are considered: pre-Northridge welded-flange bolted-web, post-Northridge welded-flange welded-web, reduced-beam-section, and bolted-flange-plate connections. A suite of earthquake ground motions is used to compute the annual probability of exceedence (APE) for a series of drift demand levels and for member plastic-rotation capacity. Results are compared for the different framing systems and connection details. It is found that the two-way frames, which have a larger initial stiffness and strength than the one-way frames for the same beam and column volumes, have a smaller APE for small drift demands for which members exhibit no or minimal yielding, but have a larger APE for large drift demands for which members exhibit large plastic rotations. However, the one-way frames, which typically comprise a few seismic frames with large-sized members that have relatively small rotation capacities, may have a larger APE for member failure. The probabilistic approach presented in this study may be used to determine the most appropriate frame configuration to meet an owner's performance objectives. Copyright © 2008 John Wiley & Sons, Ltd. [source] Case studies of damage to 19-storey irregular steel moment-frame buildings under near-source ground motionEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2007Swaminathan Krishnan Abstract This paper describes the three-dimensional nonlinear analysis of six 19-storey steel moment-frame buildings, designed per the 1997 Uniform Building Code, under strong ground motion records from near-source earthquakes with magnitudes in the range of 6.7,7.3. Three of these buildings possess a reentrant corner irregularity, while the remaining three possess a torsional plan irregularity. The records create drift demands of the order of 0.05 and plastic rotation demands of the order of 4,5% of a radian in the buildings with reentrant corners. These values point to performance at or near ,Collapse Prevention'. Twisting in the torsionally sensitive buildings causes the plastic rotations on the moment frame on one face of the building (4,5% of a radian) to be as high as twice of that on the opposite face (2,3% of a radian). The asymmetric yield pattern implies a lower redundancy in the lateral force-resisting system as the failure of the heavily loaded frame could result in a total loss of resistance to torsion. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effects of column axial force , bending moment interaction on inelastic seismic response of steel framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2003Marina Como Abstract It is well known that axial force , bending moment interaction (N,M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium,high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N,M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N,M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Zur Momentenumlagerung in Elementdecken mit GitterträgernBETON- UND STAHLBETONBAU, Issue 12 2006Rüdiger Beutel Dr.-Ing. Elementdecken aus vorgefertigten Stahlbetonplatten mit Gitterträgern und aufbetonierter Ortbetonschicht werden bei einem zusätzlichen Nachweis der Verbundfuge wie Ortbetondecken bemessen. Während nichtlineare und plastische Bemessungsverfahren in bauaufsichtlichen Zulassungen für Gitterträger derzeit aufgrund mangelnder Erfahrung ausgeschlossen sind, ist eine lineare Schnittgrößenermittlung mit nachträglicher begrenzter Momentenumlagerung wie bei Ortbetondecken möglich. Für Momentenumlagerungen von 30% muß nach DIN 1045-1 hochduktiler Betonstahl für die Biegezugbewehrung verwendet werden. Wenngleich DIN 1045-1 hierbei normalduktilen Betonstahl für Gitterträger nicht ausschließt, ist die notwendige Rotationsfähigkeit sicherzustellen. Vier Versuche am Institut für Massivbau der RWTH Aachen haben gezeigt, daß auch mit Gitterträgern aus normalduktilem Betonstahl große plastische Rotationen möglich sind, ohne daß eine Reduktion der Querkrafttragfähigkeit festzustellen war. Moment Redistribution in Precast Plates with Lattice Girders Semi precast slabs consist of precast plates with lattice girders and an in-situ concrete topping. The structural behaviour is nearly equivalent to monolithic slabs. However, the shear capacity at the interface between precast element and concrete topping has to design thoroughly. Although technical approvals of lattice girders do not allow non-linear analysis due to insufficient experience, a linear elastic analysis with limited moment redistribution is permitted. For a moment redistribution of 30% the use of class B (high ductility) reinforcement is required according to DIN 1045-1. Hereby, a sufficient rotation capacity has to be ensured for both bending reinforcement and lattice girder, too. Beam tests with lattice girders of class A (normal ductility) reinforcing steel have performed at the institute of structural concrete at RWTH Aachen University revealed high plastic rotations without reducing the shear capacity. [source] | ||||||||||