Hinge Concept Research Articles

Parametric design studies of GATOR morphing fairings for folding wingtip joints

Abstract This paper presents the modelling of a morphing fairing designed to cover the joint on hinged commercial airliner wingtips, such as the Semi-Aeroelastic Hinge concept. The fairing is made from Geometrically Anisotropic ThermOplastic Rubber (GATOR) morphing skin panels, which are 3D-printed multi-material thermoplastic polyurethane (TPU) sandwich panels combining flexible facesheets with zero Poisson’s ratio cellular cores to provide large extension capability alongside high out-of-plane stiffness. The morphing fairing is designed to cover the gaps in the hinge with a smooth and continuous surface while minimising added torsional stiffness and distortion of the aerofoil cross-section during wingtip rotation. In order to model the mechanical response of this structure at a reasonable computational cost, a homogenisation approach is proposed, wherein the elastic properties of the panel are homogenised to an equivalent shell stiffness matrix through detailed finite element studies on unit cells. These equivalent shell properties are then applied to the three-dimensional geometry of the wing to predict the global response of the fairing during wingtip rotation. This model is then used to parametrically study the effects of varying panel and fairing design parameters on the two design objectives of minimising torsional stiffness and cross-section distortion. The study indicates that cross-section distortion is best minimised by increasing the skin panel’s core thickness, with the other panel design variables having significantly less impact. In contrast, all design variables significantly affect torsional stiffness, with decreasing facesheet thickness and increasing core chevron wall length and chevron angle being particularly effective at reducing torque. The impact of pre-straining the skin panels is also studied, as is the use of additional internal ribs within the fairing, where both approaches reduce distortion at the cost of modestly higher torque. Together, these results clearly indicate the underlying design trends, useful ranges of design variables, and the strong competition between design objectives.

An Innovative Retrofitting Technique of an Industrial Prefabricated Building Without Evacuation

This paper presents a seismic retrofit of an industrial-type precast reinforced concrete building structure using friction dampers. The project consisted of retrofitting two precast reinforced concrete buildings, one of which will be presented in this paper. Precast concrete is one of the industrial structures' most preferred construction methods due to its low cost, fast construction, and availability in rural areas. Unfortunately, most structures constructed before “Specification for Buildings to be Built in Seismic Zones(TBDY 2018)[5]” are not sufficiently engineered and are expected to perform poorly when exposed to a significant seismic event. The general characteristic of precast reinforced concrete buildings built before TBDY 2018 is their relatively high concrete quality (compared to cast-in-place reinforced concrete buildings) and better reinforcement workmanship. But they have some characteristic weaknesses as well. Weak beam-column connections, high drift ratios due to heavy beams, instability problems, and lack of frame behavior can be considered primary weaknesses. General classical retrofitting techniques include increasing beam/column sections or adding new reinforced concrete or steel members to the system or FRP(fiber-reinforced polymer) wrapping. Mostly classical retrofitting needs additional foundations. All these techniques require a long construction period, causing evacuation and stopping building usage. Because stopping the production cost can be tolerated by the owners, a retrofitting approach that can be assembled during the normal function of the industrial structures is required. As a result of this requirement, friction dampers are selected as the supplemental energy dissipation device. ASCE 41-17 [10] is employed for the building's damper design and performance evaluation. Before the damper study, some instability and weak connection problems are solved by traditional strengthening measures. The most effective damper configuration and capacities are selected after an iterative trial-and-error linear study using the simplified methods developed by PROMER. Nonlinear push-over analyses are conducted after linear prestudies. Finally, a nonlinear time-history analysis is performed for confirmation of the results. , It is shown that the proposed retrofit scheme satisfies the desired performance goals for both DBE and MCE events. Overall, it is considered that the proposed retrofit scheme with dampers provides the optimal solution for the Project stakeholders from a performance, design, constructability, and economic point of view. Some application photos will be presented, and methods will be explained in detail in the paper. The friction damper behavior is based on the rotational friction hinge concept. The dampers increase building damping, causing a decrease in earthquake demand. As a result, dampers provide passive energy dissipation and protect buildings from structural and nonstructural damage during moderate and severe earthquakes.

Aeroelastic Scaling of a High-Aspect-Ratio Wing Incorporating a Semi-Aeroelastic Hinge

There has been a growing interest in utilizing flared folding wingtips as an in-flight load alleviation device to enable increased wing spans that meet airport gate limits but with little increase in wing weight. The semi-aeroelastic hinge (SAH) concept is implemented in high-aspect-ratio wings to enable wingtips to be released during severe load cases such as maneuvers and gusts to alleviate the bending moments while maintaining optimum aerodynamic shape for the rest of the flight. In this paper, scaling methods for wings incorporating the SAH are explored, allowing for the development of equivalent scaled unmanned aerial vehicles or wind tunnel models with similar aeroelastic behavior as full-size aircraft. Three scaling approaches are considered in this study, namely, Iso-Froude, Iso-Frequency, and Iso-Strain, where a set of governing nondimensional quantities and scaling factors are determined. Despite the significant nonlinearities resulting from large wingtip fold angles, it is shown that a linear scaling approach can be appropriate for such a wing configuration. Furthermore, the aeroelastic properties of each scaled model are compared to those of the full-scale model, where the best match was obtained from the Iso-Strain model, although it is challenging to meet the required operational conditions.

On the Dynamic Behavior of Wings Incorporating Floating Wingtip Fuel Tanks

Recent studies have shown that semi-aeroelastic hinge devices can enable larger aircraft wingspans. Such a device would be folded on the ground to meet airport width restrictions, locked during cruise for optimal aerodynamic performance, and released during maneuvers to alleviate flight loads. In contrast, this paper uses a wind tunnel experiment to study the aeroelastic behavior of floating wingtip fuel tanks. This device consists of a freely floating wingtip with an additional mass attached in the form of a liquid-filled fuel tank. The static aeroelastic results show that altering the fuel tank’s filling level and position allows the wingtip to float at an optimal angle for aerodynamic efficiency across various angles of attack and fuel masses. Additionally, this paper shows that, with careful selection of the mass distribution of the wingtip, dynamic load alleviation comparable to the semi-aeroelastic hinge concept can be achieved during turbulence and one-minus-cosine encounters. Furthermore, the effect of fluid motion is shown to reduce incremental loads during random turbulence encounters by up to 10%; however, it has a negligible impact on the response to one-minus-cosine encounters. Such results are also confirmed by a numerical model incorporating a simple reduced-order fluid sloshing model.

Study of a Microsatelite Hinge Concept Using 3D Printed Prototypes

AbstractThe CubeSat microsatellites are structures that can be found in many applications of industry and educations, but not only. Based on this, a new concept Card‐Sat structure is used in the present study. For a better understanding of the functionality microstructure Card‐Sat, this paper aims to study the geometry of joints manufactured from plastic materials by using the FFF 3D printing method and assembling to identify the suitable joint for this type of structures.

Retrofitting of a Precast Reinforced Concrete Industrial Building Using Friction Dampers Without Stopping Functionality

This paper presents a seismic retrofit of an industrial-type precast reinforced concrete building structure using friction dampers. This project consisted of retrofitting two precast reinforced concrete buildings, of which one of them will be presented here. Precast concrete is one of the most preferred methods of construction for industrial structures due to its low cost, fast construction and availability in rural areas. Unfortunately, most structures constructed before “Specification for Buildings to be Built in Seismic Zones(TBDY 2018)” are not sufficiently engineered and are expected to have poor performance when exposed to a major seismic event. Because stopping the production cost can be tolerated by the owners, a retrofitting technique that can be assembled during normal function of the industrial structures is required. As a result of this requirement, friction dampers are selected as the supplemental energy dissipation device. ASCE 41-17 [10] is employed for the damper design and performance evaluation of the building. Before the damper study, some instability and weak connection problems are solved by some traditional measures of strengthening. The most effective damper configuration and capacities are selected after an iterative trial-and-error linear study using the simplified methods developed by PROMER. Nonlinear push-over analysis are conducted after linear prestudies. Finally, a nonlinear time-history analyses is performed for confirmation of the results. , It is shown that the proposed retrofit scheme satisfies the desired performance goals for both DBE and MCE events. Overall, it is considered that proposed retrofit scheme with dampers provides the optimal solution for the stakeholders of the project from a performance, design, constructability, and economical point of view. Some application photos will be presented and methods are explained in detail in the paper. The friction damper behavior is based on the rotational friction hinge concept

Seismic Performance of RC Column Using Fiber Hinge Concept with Time Integration Method

Recent seismic events showed the importance of understanding the structural performance of RC column that can be predicted numerically. The accuracy of column performance depends on type of the analysis and representation of seismic effect. Therefore, in this paper a nonlinear time history analysis has been performed to assess the seismic performance of bridge column using fiber hinge concept with time integration method using sap2000 software. A long bridge RC column is utilized and subjected to seismic excitation. The column has been divided into different size and numbers of fiber to assess the accuracy of the analysis and time consuming to analyze each case of fiber hinges. In addition, this paper used three-time integration methods, Newmark, Hilber-Hughes-Taylor, and Chung & Hulbert to predict the most suitable method to be used in column seismic analysis. The time history displacement and base shear in addition to moment rotation of the column are the most important factors to evaluate the column seismic performance. The analysis results demonstrated that the most suitable time integration method is Hilber-Hughes-Taylor for such type of the analysis since it gives more stable base shear result than other two methods. Furthermore, the results indicated that the accuracy of seismic performance increased by number of fibers incremental. Moreover, the number of steel fibers should be equal to the number of bars with same area and location. The unconfined and confined concrete should be divided into small areas to get accurate prediction of column seismic performance.

Efficient Storage and Deployment of Tubular Composite Boom Using Spring Root Hinges

This paper proposes a metallic spring root hinge to effectively stow and deploy a collapsible and rollable tubular carbon fiber reinforced polymer (CFRP) boom. The proposed hinge consists of two half-cylindrical parts with narrowed regions and a hole. One of the ends of the hinge is fixed to a hub with the circular cross section, and the other end that is connected to the boom is flattened with the boom to roll the boom around the hub with a small diameter. First, the hinge concept was designed, and a numerical analysis of the stowing of the hinge was conducted. Subsequently, the tests of compression, expansion, bending, stowage, and vibration of the hinge and the boom were conducted to show the effectiveness of the hinge, especially in the stowage radius and the bending stiffness. Finite element simulations of the compression test and vibration mode analysis were also conducted. Finally, deployment tests of the boom with and without the hinge were performed to compare the deployment behaviors. The tubular CFRP booms with the hinges are expected to be used for developing an efficient lightweight large membrane structure.

Parametric studies on punching shear behavior of RC flat slabs without shear reinforcement

This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

A niche perspective on the range expansion of symbionts.

Range expansion results from complex eco-evolutionary processes where range dynamics and niche shifts interact in a novel physical space and/or environment, with scale playing a major role. Obligate symbionts (i.e. organisms permanently living on hosts) differ from free-living organisms in that they depend on strong biotic interactions with their hosts which alter their niche and spatial dynamics. A symbiotic lifestyle modifies organism-environment relationships across levels of organisation, from individuals to geographical ranges. These changes influence how symbionts experience colonisation and, by extension, range expansion. Here, we investigate the potential implications of a symbiotic lifestyle on range expansion capacity. We present a unified conceptual overview on range expansion of symbionts that integrates concepts grounded in niche and metapopulation theories. Overall, we explain how niche-driven and dispersal-driven processes govern symbiont range dynamics through their interaction across scales, from host switching to geographical range shifts. First, we describe a background framework for range dynamics based on metapopulation concepts applied to symbiont organisation levels. Then, we integrate metapopulation processes operating in the physical space with niche dynamics grounded in the environmental arena. For this purpose, we provide a definition of the biotope (i.e. living place) specific to symbionts as a hinge concept to link the physical and environmental spaces, wherein the biotope unit is a metapopulation patch (either a host individual or a land fragment). Further, we highlight the dual nature of the symbionts' niche, which is characterised by both host traits and the external environment, and define proper conceptual variants to provide a meaningful unification of niche, biotope and symbiont organisation levels. We also explore variation across systems in the relative relevance of both external environment and host traits to the symbiont's niche and their potential implications on range expansion. We describe in detail the potential mechanisms by which hosts, through their function as biotopes, could influence how some symbionts expand their range - depending on the life history and traits of both associates. From the spatial point of view, hosts can extend symbiont dispersal range via host-mediated dispersal, although the requirement for among-host dispersal can challenge symbiont range expansion. From the niche point of view, homeostatic properties of host bodies may allow symbiont populations to become insensitive to off-host environmental gradients during host-mediated dispersal. These two potential benefits of the symbiont-host interaction can enhance symbiont range expansion capacity. On the other hand, the central role of hosts governing the symbiont niche makes symbionts strongly dependent on the availability of suitable hosts. Thus, environmental, dispersal and biotic barriers faced by suitable hosts apply also to the symbiont, unless eventual opportunities for host switching allow the symbiont to expand its repertoire of suitable hosts (thus expanding its fundamental niche). Finally, symbionts can also improve their range expansion capacity through their impacts on hosts, via protecting their affiliated hosts from environmental harshness through biotic facilitation.

A Distributed Plasticity Approach for Steel Frames Analysis Including Strain Hardening Effects

This paper focuses on the creation and numerical application of physically nonlinear plane steel frames analysis problems. The frames are analysed using finite elements with axial and bending deformations taken into account. Two nonlinear physical models are used and compared – linear hardening and ideal elastic-plastic. In the first model, distributions of plastic deformations along the elements and across the sections are taken into account. The proposed method allows for an exact determination of the stress-strain state of a rectangular section subjected to an arbitrary combination of bending moment and axial force. Development of plastic deformations in time and distribution along the length of elements are determined by dividing the structure (and loading) into the parts (increments) and determining the reduced modulus of elasticity for every part. The plastic hinge concept is used for the analysis based on the ideal elastic-plastic model. The created calculation algorithms have been fully implemented in a computer program. The numerical results of the two problems are presented in detail. Besides the stress-strain analysis, the described examples demonstrate how the accuracy of the results depends on the number of finite elements, on the number of load increments and on the physical material model. COMSOL finite element analysis software was used to compare the presented 1D FEM methodology to the 3D FEM mesh model analysis.

Fiber hinge approach for nonlinear analysis of structural members accounting for local buckling under large deformation

In order to improve the use of efficiency and economy in steel structures, we always try to make the steel plate with larger width–thickness ratio. Existing analysis methods including plastic hinge method and plastic zone method, but they have their own limitation. In this paper, we proposed an approach based on fiber hinge concept and effective width method which could take local buckling into consideration. Significant parameters of the proposed approach are discussed, including fiber hinge length, effective cross-section width and fiber failure criterion. We verify the accuracy and validity of the proposed approach according to comparison of analysis results and the test data from published literature. By comparing with the plastic zone method, the error of the ultimate bearing capacity is about 4%, at the same time, the calculation speed of this method is 64 times faster than that of the plastic zone method.

A controlled destruction and progressive collapse of 2D reinforced concrete frames

A successful methodology for modelling controlled destruction and progressive collapse of 2D reinforced concrete frames is presented in this paper. The strategy is subdivided into several aspects including the failure mechanism creation, and dynamic motion in failure represented with multibody system (MBS) simulation that are used to jointly capture controlled demolition. First phase employs linear elasto-plastic analysis with isotropic hardening along with softening plastic hinge concept to investigate the complete failure of structure, leading to creation of final failure mechanism that behaves like MBS. Second phase deals with simulation and control of the progressive collapse of the structure up to total demolition, using the nonlinear dynamic analysis, with conserving/decaying energy scheme which is performed on MBS. The contact between structure and ground is also considered in simulation of collapse process. The efficiency of the proposed methodology is proved with several numerical examples including six story reinforced concrete frame structures.

Closed form solutions of a multi-cracked circular arch under static loads

Generalised functions have been widely adopted in structural mechanics to treat singularities of beam-like structures. However due to the curved geometry, that couples axial and transversal displacements, their use has never been explored for curved beams. In this paper the capability of distributions of leading to closed form exact solutions for multi-cracked circular arch is shown. The exact closed-form solution of a circular Euler arch in presence of any number of discontinuities due to concentrated damage and subjected to an arbitrary distribution of static loads is obtained. Damage, under the form of concentrated cracks, has been modeled through the widely adopted and validated equivalent elastic hinge concept and has been introduced in the governing differential equations by making use of Dirac's delta functions. The resulting nontrivial generalised six order differential equations have been derived and solved in closed form. Independently of the number of along arch concentrated cracks, the solution is expressed as a function of six integration constants only in which the damage positions and intensities are given data appearing explicitly in the solution expression. This latter aspect constitutes a fundamental aid towards the resolution of the static damage inverse identification problem. The results have been validated through some comparisons with finite element numerical simulations: examples referred to multi-cracked Euler arches with different boundary conditions, damage and load scenarios are presented.

Multiple plastic hinge concept for high-rise reinforced-concrete core wall buildings

High-rise reinforced-concrete core wall buildings are a very popular choice in areas of high seismic activity. Conventionally, a single plastic hinge is allowed at the base of the wall to control responses in these buildings. Recent studies, however, show that these core walls will be subjected to large inelastic seismic demands in a seismic event. It is not economical and sometimes difficult to design these walls for large shear and moment demands. To reduce these demands, a multiple plastic hinges concept is proposed in this study. Locations of the multiple plastic hinges are identified using elastic modal decomposition analysis. A 40-storey case study building is investigated in detail to check the effectiveness of the proposed approach. The seismic demands are found using non-linear response history analysis at maximum considered earthquake level. A comparison of the multiple plastic hinges approach with the single plastic hinge approach shows that seismic shear demand reduces 17% at the base of the wall, whereas moment demand reduces 33 and 60% at the base and mid-height of the wall, respectively.

Research on the normality of the plastic strain vector to the yield surface in RC sections

In this study, the normality condition of the plastic strain vector to the yield surface utilized for elastic-perfectly plastic materials is investigated for reinforced concrete (RC) sections. If the plastic strain vector can be assumed outward normal to the yield surface in RC sections under combined biaxial bending and axial load, the components of the vector can be expressed by a single parameter. Thus, the material nonlinearity can be simplified through the extended plastic hinge concept based on the normality condition. In this study the normality of the plastic strain vector is verified via numerical examples in symmetrically reinforced rectangular and circular RC sections subjected to biaxial bending and axial load for various configurations of longitudinal reinforcement.

Seismic failure mode interaction for the equivalent frame modeling of unreinforced masonry structures

The paper presents a relatively simple and computationally less demanding technique for the modeling and analysis of regular unreinforced masonry (URM) structures. This technique is based on the equivalent frame approach, and incorporates linear beam elements and the plastic hinge concept. The complex seismic failure mechanism of masonry piers is expressed by a single failure mode interaction surface (an “FMI surface”), taking into account the influence of variation in the pier’s vertical loading, and its bending moment distribution. The effect of the governing mechanical and geometrical parameters which determine the shape of the FMI surface is presented and discussed. For modeling purposes, the ultimate lateral strength of a masonry element is expressed as a section which cuts through the FMI surface. A single failure mode interaction plastic hinge (an “FMI hinge”) for each masonry frame element is introduced by combining specific failure modes, taking into account their minimum envelope. Calculations were carried out using the commercially available computer program SAP2000 Ultimate, and the validity of the proposed modeling procedure was confirmed by means of a comparative analysis of an URM wall assemblage which has already been studied by other researchers, using different modeling techniques and analysis software. The effect of the vertical loading acting on piers was studied, as well as the formation of typical failure mechanisms throughout the structure. The final part of the paper broadens the research to a fictitious 3D URM structure, where the out-of-plane behavior of piers has been considered alongside the standard in-plane failure mechanisms. Results obtained using the incremental N2 method were compared, for a range of ground-motion intensities, with selected results obtained using incremental nonlinear dynamic analysis.

Concept development for the ITER equatorial port visible/infrared wide angle viewing system

The ITER equatorial port visible∕infrared wide angle viewing system concept is developed from the measurement requirements. The proposed solution situates 4 viewing systems in the equatorial ports 3, 9, 12, and 17 with 4 views each (looking at the upper target, the inner divertor, and tangentially left and right). This gives sufficient coverage. The spatial resolution of the divertor system is 2 times higher than the other views. For compensation of vacuum-vessel movements, an optical hinge concept is proposed. Compactness and low neutron streaming is achieved by orienting port plug doglegs horizontally. Calibration methods, risks, and R&D topics are outlined.

Second-order elastoplastic analysis of semirigid steel frames under cyclic loading

The evolutive second-order geometry elastoplastic analysis of flexibly connected planar structures is performed to investigate their cyclic behavior under quasistatic loading conditions. The formulation is cast as a mathematical programming problem, involving so-called “complementarity” constraints. A “fictitious force” concept, that preserves static-kinematic duality, is used to describe geometric nonlinearity. A second-order approximation, deemed sufficiently accurate for practical structures, is adopted. A semirigid connection is idealized as a zero-length elastoplastic element attached to either or both ends of a beam element. Inelasticity is captured through the familiar generalized plastic hinge concept, and a piecewise linear approximation of the nonlinear plastic capacity domain is used to represent the yield condition. A number of examples concerning realistic structures and benchmark cases is provided to check the validity and applicability of the proposed method and to study the cyclic behavior of flexibly connected planar frames.

A load increment method for ductile reinforced concrete (RC) frame structures considering strain hardening effects

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.