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We aimed to evaluate the biomechanical contact characteristics of rotating hinge knee (RHK) prostheses with different motion axial systems. We performed finite element (FE) analyses to investigate and compare the peak contact stress and contact location on tibial insert and bushing during a gait cycle. The biaxial (BA) system and spherical center axial (SA) system RHK prostheses were included in this study. The comparisons between experimental tests and FE analyses were performed to verify the validation of FE models. Decreased ISO loadings were then applied to the validated FE models to investigate the peak contact stress and contact location on tibial insert and bushing. The contact areas obtained from experimental tests and FE analyses were in a good agreement. The peak contact stresses on tibial insert and bushing of BA prosthesis were higher than those of SA prosthesis. The contact locations on the superior surface of tibial insert in SA and BA prostheses were at the middle-posterior and posterior side, while those on the rotating axial surface were at the medial and lateral sides, respectively. This study indicate that the tibial insert and bushing of an SA prosthesis have lower peak contact stresses and better contact locations than those of a BA prosthesis during a gait cycle, which may decrease the risk of long-term complications of RHK prostheses. Future studies should be performed to confirm the relationship between the contact characteristics and wear in RHK prostheses.

With the recent advances in miniaturized RADAR and CubeSat technologies, launching multiple copies of a RADAR instrument is now possible. This chapter provides a detailed description of a novel, deployable reflectarray antenna which is currently the largest Ka‐band antenna for 6U‐class CubeSats. The ability of reflectarray to fold in a very constrained volume is very attractive for small satellite platforms. The deployable reflectarray is expected to achieve a gain of 47.4 dBi, which translates into a 32% efficiency. The key drawback of reflectarrays, generally, is the narrow bandwidth that it is driven by its aperture size, focal length, element design, etc. Though the antenna operation is limited to the center frequency of the element, multi‐frequency elements can be used to create multi‐bandwidth antenna systems. Development of new hinges was required to meet the deployment accuracy of the reflectarray panels.

Simplicity and computational efficiency of the lumped plasticity model have made it a popular approach for analyzing structures. However, it has been shown by researchers that the accuracy of the lumped plasticity model for representing the inelastic behavior of reinforced concrete (RC) structures needs further investigations. Two full-scale RC frames with different shear spans were constructed and subjected to the vertical load through their beam. Finite element (FE) models of the tested specimens were established in SAP2000 software, and their results were compared with the experimental tests. The effects of using different plastic hinge lengths, initial effective stiffness, and locations of plastic hinges were investigated. It was observed that regardless of the selected plastic hinge lengths, the established FE models estimated the yield and ultimate loads of the frames accurately. However, they did not estimate accurately the vertical displacements corresponding to the yield and ultimate loads. Results also indicated that the obtained yield and ultimate loads from the established FE models were significantly influenced by the selected locations for plastic hinges. Moreover, at the ultimate load of frames the estimated damage level to the mid-span of beams by FE models was lower than the results of experimental tests.

Coordination-driven self-assembly has been established as an effective strategy for the efficient construction of intricate architectures in both natural and artificial systems, for applications ranging from gene regulation to metal-organic frameworks. Central to these systems is the need for carefully designed organic ligands, generally with rigid components, that can undergo self-assembly with metal ions in a predictable manner. Herein, we report the synthesis and study of three novel organic ligands that feature 3,6-disubstituted acridine as a rigid spacer connected to two 2-(1,2,3-triazol-4-yl)pyridine "click" chelates through hinges of the same length but differing flexibility. The flexibility of these "three-atom" hinges was modulated by i) moving from secondary to tertiary amide functional groups and ii) replacing an sp2 amide carbon with an sp3 methylene carbon. In an effort to understand the role of hinge flexibility in directing self-assembly into mononuclear loops or dinuclear cylinders, the impact of these changes on self-assembly outcomes with zinc(II), iron(II), and copper(II) ions is described.

This report investigates the performance of several viscous damping formulations in the inelastic seismic response of moment-frame buildings. The evaluation employs a detailed model of a 20-story steel building. Damping schemes included in the study are Rayleigh, condensed Rayleigh, Wilson-Penzien, two versions of tangent Rayleigh and one implementation of capped damping. Caughey damping is found not to be computationally viable. Differences among the damping schemes, as quantified by amounts of plastic hinge rotations and story drifts, become noticeable once these quantities reach the 3% level. In order of least to greatest hinge rotations and drifts that occur under lateral response to horizontal ground motion, the damping schemes rank as Rayleigh (most damping action), condensed Rayleigh, Wilson-Penzien, the standard form of tangent Rayleigh and capped damping, which are about the same, and the elastic velocity version of tangent Rayleigh (least damping action). Performance of Rayleigh damping under vertical ground motion is discussed, including the effect of soil-structure interaction. The propensity of Rayleigh damping to generate excessive damping forces and moments during inelastic seismic analysis is explained, and a parameter is introduced that can predict the potential magnitude of the effect. A review of some literature on the role of viscous damping on the inelastic seismic response of moment frames is also presented.

Developing bistable metamaterials has recently offered a new design paradigm for deployable structures and reusable dampers. While most bistable mechanisms possess inclined/curved struts, a new 3D multistable shellular metamaterial is developed by introducing delicate perforations on the surface of Schwarz's Primitive shellular, integrating the unique properties of shellular materials such as high surface area, stiffness, and energy absorption with the multistability concept. Denoting the fundamental snapping part by motif, certain shellular motifs with elliptical perforations exhibit mechanical bistability. To bring the concept of multistability to a single motif, multistable shellular motifs are developed by introducing multilayer staggered perforations that form hinges and facilitate local instability. Adopting an n-layer staggered perforation (n hinges) design leads to a maximum 2n-1 stable states within one shellular motif during loading and unloading. Three-directional multistable shellulars are attained by extending the perforation design in three orthogonal directions. Harnessing snap-through and snap-back behaviors and self-contact, the introduced multistable perforated shellulars exhibit strong rigidity both in loading and unloading, and enhanced energy dissipation. The introduced design strategy opens up new horizons for creating multidirectional multistable metamaterials with load bearing capabilities for applications in soft robotics, shape-morphing architectures, and reusable and deployable energy absorbers/dampers.

The paper discusses nonlinear pushover curves for multistory moment-frame buildings. Attention is brought to the steepening effect that elastic unloading has on the slope of the descending branch of the pushover curve, with the possibility of snapback. Displacement control is shown to be effective for the entire range of pushover analysis, including the descending branch. The method is enhanced by controlling the difference in displacement of 2 floors in the vicinity of the collapse mechanism rather than, say, controlling the roof displacement. An automated drift control version is described and tested. Analysis of a 20-story building demonstrates that variable strength of plastic hinges and inclusion of the strength and stiffness of the gravity frames in the model affect the pushover curve significantly, especially the descending branch. The concept of dynamic pushover is described, and results are compared with the static version.

Precast piers incorporated with high-strength bars (≥500 MPa) have great potential to accelerate bridge construction and enhance seismic performance. Four large-scale pier column specimens using high-strength bars by cast-in-place (CIP) and precast construction were experimentally studied. The distinctions of damage pattern between CIP and precast piers were characterized by plastic hinge and toed hinge, which expounded the smaller damage in precast piers. In contrast with CIP piers, the energy dissipation of precast pier was reduced by approximately 50–60% after pier yielding. An appropriate reinforcement ratio was essential for CIP piers to maintain enough displacement ductility and prevent premature fracture of energy dissipation bars. In terms of displacement components, the plastic term of precast pier was much smaller than that of CIP pier, and the gap opening-induced displacement predominates after pier yielding. The toed hinge was elaborated to disclose the displacement mechanism in precast piers. The experimental findings in this paper can provide additional input for seismic design of precast piers with high-strength bars.

Summary Unstiffened steel plate shear walls (SPSWs) are used as lateral load-resisting systems in building structures. The energy dissipation mechanism of SPSWs consists of the tension yielding of web plates and the formation of plastic hinges at the ends of horizontal boundary elements. However, vertical boundary elements (VBEs) of high-rise SPSWs may experience high axial forces under lateral loading. This study explores the effectiveness of staggering of web plates on the reduction of VBE forces and drift response of SPSWs during an earthquake event. An analytical study has been conducted to determine the base shear reduction factor so as to match the overstrength of staggered systems with conventional SPSWs. A design methodology has been proposed for staggered SPSWs. Six-, 9-, and 20-storey staggered and conventional SPSWs with varying aspect ratios are considered in this study to compare their seismic response. These study frames are modelled and analysed in OpenSEES platform. Nonlinear static and dynamic analyses are performed to compare the drift response, hinge mechanisms, and steel tonnage. Staggered SPSWs showed uniform drift distribution and reduction in interstorey drift and axial force demand on the VBEs.

Summary The reinforced concrete (RC) shear wall serves as one of the most important components sustaining lateral seismic forces. Although they allow advanced seismic performance to be achieved, RC shear walls are rather difficult to repair once the physical plastic hinge at the bottom part has been formed. To overcome this, a damage-controllable plastic hinge with a large energy dissipation capacity is developed herein, in which the sectional forces are decoupled and sustained separately by different components. The components sustaining the axial and the shear forces all remain elastic even under a rarely occurred earthquake, while the bending components yield and dissipate seismic energy during a design-level earthquake. This design makes the behavior of the system more predictable and thus more easily customizable to different performance demands. Moreover, the energy dissipation components can be conveniently replaced to fully restore the occupancy function of a building. To examine the seismic behavior of the newly developed component, 3 one third-scale specimens were tested quasi-statically, including 1 RC wall complying with the current design codes of China and 2 installed with the damage-controllable plastic hinges. Each wall was designed to have the same strength. The experimental results demonstrated that the plastic-hinge-supported walls had a better energy dissipation capacity and damage controllability than the RC specimen. Both achieved drift ratios greater than 3% under a steadily increasing lateral force.

Two bladed wind turbines are discussed as a possible turbine alternative for offshore use as they show a potential to save cost of energy. But compared to three-bladed turbines, their dynamic behavior is much more challenging. A possible solution to handle these larger dynamic loads is the use of a teeter hinge, which can significantly reduce fatigue loads. In contrast to that, extreme loads, coming from teeter end impacts, are often described as a problem for teetered turbines. There are different design parameters of the teeter system of a turbine, which have an influence on extreme loads during teeter end impacts. Despite numerous studies on teeter movement and load reduction potentials of operational loads, scientific literature does not give information about suitable load-reducing combinations of teeter design parameters and their influence on extreme loads. This paper, which is a summary of a PhD thesis,[1] analyses which combination of teeter parameters has the largest load-reducing influence on extreme loads. Aeroelastic load simulations of the teetered turbine CART2 from the NREL test site and one of today's commercial two-bladed turbines, the SCD3MW from aerodyn (both pitch controlled upwind turbines), will be used.

Although steel moment resisting frame (MRF) systems had long been recognized as effective seismic resistant structures, recent earthquake events and seismic loss estimations indicated that uniform damages of structural members and significant residual deformations would be expected after even a moderate earthquake event for steel MRF systems designed following the conventional ductility-based design philosophy, and this incompleteness produced the impetus for overhaul of design methodologies and developing innovative systems. With the goal of enhancing the seismic performance of steel MRF structures in low-to-moderate seismic regions, this research explored the seismic behavior of high-strength-steel (HSS) frame with energy dissipation bays (EDBs) equipped with buckling hinge beams, denoted as the HSSF-BHEDB system. In particular, the HSS frame is composed of steel with the nominal yield strength higher than 460 MPa, and the buckling hinge beams in the EDBs are constructed with cross-sections classified as Class 3 or Class 4 by Eurocode 3. The motive of the novel design concept was to improve the structural nonlinearity of steel MRF systems with encouraging damage evolution mode and controllable residual deformations under earthquakes, and the limited energy dissipation of both the buckling hinge beams composed of slender cross-sections and HSS members can provide a solution for structures in low-to-moderate seismic regions. In this work, the design concept and the rationale of the HSSF-BHEDB were explored in detail. Then, a large-scale quasi-static test of a structure was conducted to provide experimental evidence and assess the feasibility of the design concept, and the behavior of the specimen from inception of yielding to failure was completely investigated. The test results showed that the system was characterized by the damage-control behavior that diverted inelastic damages in the buckling hinge beams of the energy dissipation bay (EDB) in a wide deformation range. In the stage where the HSS frame initiated inelasticity and the energy dissipation of buckling hinge beams deteriorated, a ductile manner was still achieved. In addition, the controllable residual deformations of the specimen highlighted the satisfactory recentering behavior of the HSSF-BHEDB structure. Lastly, the applicability of the bilinear hysteretic model of significant post-yielding stiffness ratio and trilinear hysteretic model for featuring the hysteretic behavior of the HSSF-BHEDB system in different yielding stages were validated by the test results.

Steel framework is one of the most commonly used structural systems in modern construction and beam-to-column connections play a significant role in overall performance of the structure. Semi-rigid behaviour of steel connections was investigated both experimentally and numerically over the last few decades. Stainless steel alloys are now increasingly used in construction industry owing to their superior material properties such as corrosion resistance, higher strength, enhanced ductility, significantly lower maintenance cost and attractive appearance. In this study, the performance of stainless steel top-seat with or without double web angle (DWA) bolted connections are analytically investigated using a proposed four parameter power model assuming plastic hinges are formed in the connected angles. The proposed analytical model can predict the moment-rotation behaviour using four key connection parameters such as initial stiffness, strain hardening stiffness, reference plastic rotation and shape parameter. These key parameters were expressed as functions of easily obtainable geometric and material properties. This model allows to predict complete moment-rotation curves for stainless steel connections using the knowledge of easily available properties and configurations of the connecting elements. Analytically predicted moment-rotation curves were compared with those obtained using 3D finite element models, and showed good agreement with actual connection behaviour.

The resistance of a typical shear connection with headed shear studs in a composite beam is analysed for the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking to the ultimate loadbearing capacity is considered with empirically derived reduction factors and equations that were developed between the late 1970s and early 1980s. The RFCS research project ”DISCCO“ [1] investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance predicted by EN 1994-1-1 [2] was not reached in tests. In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the loadbearing capacity of the shear stud, which formed one or two plastic hinges in the shaft depending on the actual geometry. Based on these observations, new equations have been developed to predict the shear connection's resistance with more accuracy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen [3], was extended by the aforementioned loadbearing component ”concrete cone“. The formulae consider the geometry of the stud and the steel decking and the material strength of the stud and the concrete. The statistical evaluation of the equations developed demonstrates good agreement with test results.

Summary This paper presents the results of 12 full-scale tests on buckling-restrained brace (BRB) specimens. A simple-to-fabricate all-steel encasing joined by high-strength bolts was used as the buckling-restrainer mechanism. Steel BRBs offer significant energy dissipation capability through nondeteriorating inelastic response of an internal ductile core. However, seismic performance of BRBs is characterized by interaction between several factors. In this experimental study, the effects of core-restrainer interfacial condition, gap size, loading history, bolt spacing, and restraining capacity are evaluated. A simple hinge detail is introduced at the brace ends to reduce the flexural demand on the framing components. Tested specimens with bare steel contact surfaces exhibited satisfactory performance under the American Institute of Steel Construction qualification test protocol. The BRBs with friction-control self-adhesive polymer liners and a graphite-based dry lubricant displayed larger cumulative inelastic ductility under large-amplitude cyclic loading, exceeding current code minimum requirements. The BRB system is also examined under repeated fast-rate seismic deformation history. This system showed significant ductility capacity and remarkable endurance under dynamic loading. Furthermore, performance is qualified under long-duration loading history from subduction zone's megathrust type of earthquake. Predictable and stable performance of the proposed hinge detail was confirmed by the test results. Internally imposed normal thrust on the restrainer is measured using series of instrumented bolts. Weak- and strong-axis buckling responses of the core are examined. Higher post-yield stiffness was achieved when the latter governed, which could be advantageous to the overall seismic response of braced frames incorporating BRBs.

The thermo-mechanical response of heat activated shape memory polymers (SMPs) has been investigated using a thermo-viscoelastic finite element analysis that accounts for external and internal heat sources. SMPs can be thermally stimulated by external heat sources, such as temperature and surface heat flux, or from internal viscous heating. Viscous heating can significantly affect the response of SMP sheets by increasing the temperature during pre-strain, which accelerates stress relaxation. This stress relaxation results in a slower shrinking rate when the SMP is reheated. Viscous heating also causes an increase in temperatures during unconstrained recovery. The predicted results elucidate how the coupled thermo-mechanical loading conditions affect folding and unfolding of SMP sheets in response to localized heating in a hinged region. A parametric study of sheet thickness, hinge width, degree of pre-strain, and hinge surface temperature is also conducted. The validated results can provide guidelines for the design of functional, self-folding structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

The eccentricity charts presented in this paper have been developed on the basis of experimental investigations in order to enable a realistic calculation method of the ultimate load of flat brickwork vaulted floors with standard structural software. The vault is modelled as a three-hinged arch with eccentric hinges in order to thus represent the non-linear behaviour of the load-bearing structure. Furthermore the hinge configuration, which is adapted with the eccentricity charts, takes into account the degree of plastification of historic masonry, existing load-induced damage, any displacement of the abutments and the location of the thrust line. Two examples are described to explain the applicability of this method, and the results are compared with results from other modelling approaches. This makes clear that the eccentricity charts enable realistic structural analysis of flat brickwork vaults with various geometries and with highly efficient use of time.

Rotation capacity of reinforced concrete (RC) beams is a vital property for its relationships with moment redistribution, energy absorbability, and so on. Evaluation of the rotation capacity has been one of the classic and intractable problems in structural engineering over the past decades. The precise prediction about rotational behavior of a RC beam is the primary basis of quantifying its rotation capacity. In this paper a displacement-based finite layer element method considering the factors of flexural cracks, concrete crushing, and pre-and postyield behavior of bond is presented to predict the rotational behavior. In conclusion, it shows good agreement between simulation results, implemented by the proposed method, and the test results in the literature.

The PapC usher and MpAFP ice-adhesin feature Ig-like domains, which are similar in shape and sequence but are engaged in very different functions. We explore how evolution reshaped the surfaces of these two domains to fit to their respective functions. In PapC, the Ig-like domain forms a rigid plug that seals the translocation channel in the inactive state. Upon activation, it undergoes a hinge motion, as an intact domain, to allow passage and assembly of the pili that goes through the pore. In accordance with this function, our calculations show that its surface is, in essence, electrostatically neutral, to facilitate the interaction with the PapC pore, and that this feature is evolutionarily conserved among its close homologues. On the other hand, within the context of MpAFP, the Ig-like domain is the main repeating unit, and our calculations show that its surface features a negative electrostatic potential of unusually high magnitude. The potential is balanced by bound Ca2+ ions. This is consistent with Ca2+-dependent secretion of unfolded MpAFP across the double membrane of the bacterium, and folding outside, where Ca2+ concentration is high.

Summary Special concentrically braced frames (SCBFs) are considered as one of the most economical and effective lateral force-resisting systems in structures located in the regions of high seismicity. Steel braces in a braced frame undergo large axial deformations in tension and compression to dissipate the seismic energy. However, past studies have shown that SCBFs exhibit the soft-story hinge mechanisms and unpredictable failure patterns under earthquake loading conditions. These inelastic responses along with the use of continuous structural sections as columns over consecutive floors induce flexural demand that is not considered in the current design practice. In this study, the evaluation of seismic performance of nine SCBFs designed as per the current practice has been carried out for three different story heights (i.e., three-story, six-story, and nine-story) and three types of brace configurations (namely, chevron, split X, and single X). Three additional design techniques are also explored based on (i) the inclusion of column moments in the design; (ii) the theory of formation of plastic hinges; and (iii) the design of braces considering the forces computed at their post-buckled stages. Nonlinear dynamic analyses of these study frames have been evaluated numerically using a computer software Perform-3D for a suite of 40 ground motions representing the design basis earthquake and maximum considered earthquake hazard levels. Analyses results showed that the SCBFs designed as per the modified procedures achieved the desired performance objectives without the formation of soft-story mechanism. Copyright © 2017 John Wiley & Sons, Ltd.

The research into a specific type of unstiffened extended end-plate joint used to connect I-shaped beams to concrete-filled rectangular hollow section columns is presented in this paper. The main idea is to use long bolts passing through the column to connect the beam end-plates in order to… avoid intermediate connecting elements (e.g. a reversed channel) or special bolts (e.g. blind bolts), which are sometimes used in practice, and improve the resistance and stiffness of the joint when used in seismic-resistant frames. Firstly, a test programme was performed within an RFCS European project entitled HSS-SERF ”High-Strength Steel in Seismic-resistant Building Frames“, 2009–2013. The test programme included defining specimens subjected to significant bending moments (and shear) or shear only. Analytical models based on the component approach and aimed at predicting the joint response were then proposed; their validity is demonstrated through comparisons with the test results. Finally, the requirements of EN 1998-1-1 related to full-strength resistance for the proposed joint configuration are discussed, accounting for the actual positions of plastic hinges and the possible individual over-strength factors for each component.

This article focuses on the hinge party both as a concept and a strategy. It seeks to ‘liberate’ the hinge party from the clutches of such close conceptual relatives as the ‘pivot party’, the ‘genuine pivot party’, the ‘pivotal centre party’, the ‘pivotal middle party’ and the ‘pivotal median party’. This is a taxonomical jungle and while some use the terms ‘hinge party’ and ‘pivot party’ interchangeably, this study urges a ‘velvet divorce’. The main theoretical question is in two parts: (1) What are the distinguishing features of the hinge party and how does it differ from the pivot party?; and (2) What set of legislative party system circumstances would seem most likely to favour a hinge party strategy of keeping options open to both left and right? Self-styled centrist parties would seem most likely to favour a hinge party strategy and the empirical question is: To what extent have the Nordic Centre-label [former agrarian] parties sought and been able to do so?

Multistable shape-reconfigurable architected materials encompassing living hinges and enabling combinations of high strength, high volumetric change, and complex shape-morphing patterns are introduced. Analytical and numerical investigations, validated by experiments, are performed to characterize the mechanical behavior of the proposed materials. The proposed architected materials can be constructed from virtually any base material, at any length scale and dimensionality.

Immunoglobulin G (IgG) is a Y-shaped globular protein consisting of two Fab segments connecting to an Fc segment with a flexible hinge region, in which the Fab segments show secondary flexibility at an "elbow" region. In the present work, the hinge-bending and elbow-bending motions of aqueous solutions of IgG by microwave dielectric measurements below the freezing point of bulk water was observed. The presence of unfreezable water around the macromolecules reduced the effects of steric hindrance normally generated by ice and enabled the intramolecular motions of IgG. At the same time, the overall IgG molecule rotation was restricted by ice. Papain digestion and reduction of the disulfide linkage at the hinge region was used to generate Fab and Fc fragments. In solutions of these fragments, the dielectric relaxation process of the hinge-bending motion was absent, although the elbow-bending motion remained. Three relaxation processes were observed for papain-digested IgG. The high, middle, and low frequency processes were attributed to unfrozen water, local peptide motions cooperating with bound water, and the elbow-bending motion, respectively. In the case of the intact IgG, an additional relaxation process due to the hinge-bending motion was observed at frequencies lower than that of the elbow-bending motion. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 626-632, 2016.

Summary Frame pin-supported wall structure is a kind of rocking structure, which releases constraints at the bottom of the wall. The wall is affiliated to the frame and can rotate around the hinge. Previous studies have investigated seismic performance (such as deformation pattern and plastic hinge distribution) of frame pin-supported wall structure. Strength demand of this system was investigated through static pushover analysis. However, dynamic characteristics, especially higher mode effects, remain to be quantified. As demonstrated in several researches, higher mode effects have non-negligible effects on seismic response. For this purpose, a distributed model for analyzing higher mode effects in frame pin-supported wall structure was proposed, where the pin-supported wall and the frame were simplified as a bending beam and a shear beam, respectively. The model was solved by differential equations derived from equilibrium and compatibility. Displacement and inner force distribution of frame pin-supported wall structure in higher modes were quantified according to the model. Influence of critical parameters, such as wall stiffness and structure period, was assessed on higher mode effects. It was demonstrated that response in higher modes cannot be neglected in the design of frame pin-supported wall structure. Capacity design based on the fundamental mode is not conservative, especially in the wall. Furthermore, pin-supported walls tend to force the frame to vibrate in the rocking mode and suppress higher mode effects in the frame. Copyright © 2016 John Wiley & Sons, Ltd.

This discussion deals with recommendations in the paper on appropriate damping formulations for use in nonlinear response history analysis of buildings. Concern over potentially excessive damping forces and moments should extend beyond the damping moments produced by the stiffness proportional part of Rayleigh damping that corresponds to rotational springs used to explicitly model plastic hinges. The key to an appropriate damping formulation for nonlinear analysis is a realistic mechanism that allows all damping forces and moments to be meaningfully assessed. Then features can be added to keep these forces and moments within reasonable bounds.

Summary This paper presents three-dimensional nonlinear dynamic analyses of a full-scale four-story steel building tested to collapse in 2007 at the E-Defense shake-table facility in Japan, using strong ground motion. Local buckling and consequent strength deterioration of all six columns at the first-story level were observed as the main reason for the building collapse. Fiber hinge element that consists of fibers discretizing the column cross section is used model each end of the column. It has zero length but considers finite yield-zone length for the fiber to simulate elastoplastic behavior and local buckling. Other parts of the building are modeled by standard column, beam, truss, and spring elements. Despite the unavoidable limitation of the parameters defining the fiber hinge element's properties that are empirically determined from the behavior of the cantilever column tested using an identical steel member, the analysis using the element appears to simulate well the column behavior because of the axial load and biaxial bending moment whose relative magnitudes differ considerably because of the locations. The analysis results indicate different deterioration patterns of the columns and effects of complex loading such as compression and tensile axial load applied alternately, additional high frequency axial load caused by vertical accelerations, and shifting of the principal directions of the bending moments cycle by cycle. Responses such as story drift, accelerations, base shear, and energy dissipation are also simulated well, and progress of local deterioration in the first-story columns and global soft-story mechanism is clarified by the analysis. Copyright © 2016 John Wiley & Sons, Ltd.

SUMMARY In this study, different energy components in the tall reinforced concrete core-wall buildings with numerous plastic hinges over the height are investigated using nonlinear time history analysis. The effect of near-fault and far-fault earthquakes is compared. The idea of one-plastic, two-plastic, three-plastic and whole-plastic hinge approaches along the core wall is examined. The input energy, inelastic, damping, kinetic and elastic strain energy during the earthquakes are studied. The results show that a large energy quantity transfers to the structure at the arrival time of the near-fault motion pulse. Inelastic energy distribution over the height shows a considerable amount of inelastic energy dissipation occurring at the base and above the mid-height of the walls. Copyright © 2016 John Wiley & Sons, Ltd.

Summary Near-fault (NF) ground motion having forward directivity and far-fault (FF) earthquakes can generate different responses on tall reinforced concrete cantilever walls. In this paper, the behavior of the core wall buildings were examined by performing nonlinear time history analyses on 20-story, 30-story and 40-story fiber element models. The concept of one, two, three and extended plastic hinge in the core walls subjected to the NF motions having forward directivity (pulse-like) and FF motion was studied by carrying out inelastic dynamic analysis. At the upper levels of the walls, NF pulse-like ground motions can produce considerably larger curvature ductility, inter-story drift and displacement demands as compared with the FF motions. A new approach was proposed to obtain the moment demand and reinforcement required to balance the curvature ductility demand along the height of a core wall. Copyright © 2015 John Wiley & Sons, Ltd.

The seismic design of optimal damped outrigger structures relies on the assumption that most of the input energy will be absorbed by the dampers, whilst the rest of the structure remains elastic. When subjected to strong earthquakes, nevertheless, the building structure may exhibit plastic hinges before the dampers begin to work. In order to determine to which extent the use of viscously damped outriggers would avoid damage, both the host structure's hysteretic behaviour and the dampers' performance need to be evaluated in parallel. This article provides a parametric study on the factors that influence the distribution of seismic energy in tall buildings equipped with damped outriggers: First, the influence of outrigger's location, damping coefficients, and rigidity ratios core-to-outrigger and core-to-column in the seismic performance of a 60-story building with conventional and with damped outriggers is studied. In parallel, nonlinear behaviour of the outrigger with and without viscous dampers is examined under small, moderate, strong, and severe long-period earthquakes to assess the hysteretic energy distribution through the core and outriggers. The results show that, as the ground motion becomes stronger, viscous dampers effectively reduce the potential of damage in the structure if compared to conventional outriggers. However, the use of dampers cannot entirely prevent damage under critical excitations., Comision Nacional de Investigacion Cientifica y Tecnologica (72100284)

To alleviate the mass-scaling issues associated with conventional upwind rotors of extreme-scale wind turbines (>/=10 MW), a morphing downwind-aligned rotor (MoDaR) concept is proposed herein. The concept employs a downwind rotor with blades whose elements are stiff (no intentional flexibility) but with hub-joints that can be unlocked to allow for moment-free downwind alignment. Aligning the combination of gravitational, centrifugal and thrust forces along the blade path reduces downwind cantilever loads, resulting in primarily tensile loading. For control simplicity, the blade curvature can be fixed with a single morphing degree of freedom using a near-hub joint for coning angle: 22 degrees at rated conditions. The conventional baseline was set as the 13.2-MW Sandia 100-m all glass blade in a three-bladed upwind configuration. To quantify potential mass savings, a downwind load-aligning, two-bladed rotor was designed. Because of the reduced number of blades, the MoDaR concept had a favorable 33% mass reduction. The blade reduction and coning led to a reduction in rated power, but morphing increased energy capture at lower speeds such that both the MoDaR and conventional rotors have the same average power: 5.4 MW. A finite element analysis showed that quasi-steady structural stresses could be reduced, over a range ofmore » operating wind speeds and azimuthal angles, despite the increases in loading per blade. However, the concept feasibility requires additional investigation of the mass, cost and complexity of the morphing hinge, the impact of unsteady aeroelastic influence because of turbulence and off-design conditions, along with system-level Levelized Cost of Energy analysis.« less

Many proteins undergo large-scale motions where relatively rigid domains move against each other. The identification of rigid domains, as well as the hinge residues important for their relative movements, is important for various applications including flexible docking simulations. In this work, we develop a method for protein rigid domain identification based on an exhaustive enumeration of maximal rigid domains, the rigid domains not fully contained within other domains. The computation is performed by mapping the problem to that of finding maximal cliques in a graph. A minimal set of rigid domains are then selected, which cover most of the protein with minimal overlap. In contrast to the results of existing methods that partition a protein into non-overlapping domains using approximate algorithms, the rigid domains obtained from exact enumeration naturally contain overlapping regions, which correspond to the hinges of the inter-domain bending motion. The performance of the algorithm is demonstrated on several proteins. Proteins 2015; 83:1054–1067. © 2015 Wiley Periodicals, Inc.

In this article, an actively formed dual anchor structure was newly designed and applied to improve the tuning range and mechanical reliability of an RF micro electromechanical system (MEMS) tunable capacitor. To construct the dual anchor structure, metal dimples, which are formed on the centers of hinges, are placed in contact with metal posts before pull-in occurs, resulting in the formation of second anchors. The measured tuning ranges of the fabricated MEMS tunable capacitors with and without dual anchors were 59.2% and 28.3% at the applied voltage ranging from 0 V until pull-in voltages of 17 and 9 V, respectively. The fabricated tunable capacitor also exhibited high quality factors of 80.63 and 61.19 at 5 GHz and the applied voltages of 0 and 16 V, respectively. Its size/volume is 1.032 × 1.628 × 0.0089 (H) mm3. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1451–1454, 2015

The Δ-distance maps can detect local remodeling that is difficult to accurately determine using superimpositions. Transmembrane segments (TMSs) 11 in both LacY and XylE of the major facilitator superfamily uniquely contribute the greatest amount of mobile surface area in the outward-occluded state and undergo analogous movements. The intracellular part of TMS11 moves away from the C-terminal domain and into the substrate cavity during the conformational change from the outward-occluded to the inward-occluded state. A difference was noted between LacY and XylE when they assumed the inward open state after releasing a substrate to the inside in which TMS11 of LacY moved further into the substrate release space, whereas in XylE, TMS11 slightly retracted into the C-terminal domain. Independent movement of the N-terminal half of TMS11 suggests that it is flexible in the middle. Repeat-swapped homology modeling was used to discover that a loop connecting TMSs 10 and 11 in LacY probably moves during the transition between the unavailable outward-open state and the outward-occluded state. TMSs 11 and the other elements displaying a notable domain-independent movement colocalize with the interdomain linker, suggesting that these elements could drive the alternating access movement between the domain halves. Preliminary evidence indicates that analogous movements occur in other members of the major facilitator superfamily.

Two-bladed wind turbines are recently being discussed more often as the question arises for the most suitable offshore turbine concept. Regarding this turbine concept, a solution is required for the more challenging dynamics. A teetered hub has often been a load reduction concept of two-bladed turbines. During normal operation, a teetered hub eliminates the hub bending moment coming from unequal blade loading. But looking at extreme load cases, the teeter end impact is a major problem. The teeter end impact is quite often described as the occasion that destroys the load-reducing advantage of the teeter mechanism. The turbine must be designed to withstand the loads from the teeter impacts leading to additional weight, which is actually supposed to be reduced by using the teeter hinge. Although the teeter end impact is often described as a kind of ‘killer aspect’, a more detailed analysis and quantification of its nature is not given in open literature. This paper will do an analysis and quantification of the loads coming from teeter end impacts using an existing teetered turbine, the Controls Advanced Research Turbine 2 (CART2). First, there will be a look at analytical teeter equations to get an overview of the basic parameters leading to teeter movement. Then, teeter end impact behaviour will be analysed using aeroelastic load simulations of the CART2 according to International Electrotechnical Commission (IEC) 61400-1 edition 3. For each design load case, the most significant teeter response will be examined. A classification of teeter end impacts will be extracted from the simulation data. Results will be compared with a rigid turbine in order to get an evaluation of how severe teeter end impacts are, compared with extreme loads of a rigid turbine. Additionally, these results will be compared with modified teeter parameters of the CART2. These are the introduction of pitch–teeter coupling, a reduced free teeter angle and a different Lock number. It will be shown to what extent these parameters may reduce the intensity of teeter end impacts. Results show that it is worth discussing teetered turbines as an alternative to today's three-bladed turbines. According to this study, teeter end impacts need not be regarded as completely intolerable, and there are several turbine parameters that have a significant influence on them. Copyright © 2015 John Wiley & Sons, Ltd.

Summary Although modern seismic codes have undoubtedly led to safer structures, the seismic vulnerability of metropolitan areas is unavoidably governed by that of older buildings, which constitute the vast majority of the current building stock. Quite alarmingly, even relatively moderate intensity earthquakes have been proven capable of challenging their structural integrity, leading to severe damage or collapse. Therefore, there is an urgent need to assess the vulnerability of existing structures and to evaluate the efficiency of novel retrofit techniques. This paper studies experimentally the seismic performance of an existing three-storey building, retrofitted through addition of shear walls. Emphasis is placed on the foundation of the shear walls, and two design alternatives are comparatively assessed: (a) conventional design according to current seismic codes and (b) ‘rocking isolation’ by reducing the size of the foundation. A series of reduced-scale shaking table tests are conducted at the Laboratory of Soil Mechanics of the National Technical University of Athens. The physical model encompasses the structural system, along with the foundations, and the soil. The nonlinearity of structural members is simulated through specially designed and carefully calibrated artificial plastic hinges. The vulnerability of the original structure is confirmed, as it is found to collapse with a soft-storey mechanism when subjected to moderate intensity shaking. The conventionally retrofitted structure is proven capable of sustaining larger intensity shaking, and the rocking-isolated structure is shown to offer increased safety margins. Thanks to its inherent self-centering mechanism, the rocking system is characterized by reduced permanent drifts. Copyright © 2014 John Wiley & Sons, Ltd.