Profile beams with adaptive bending–twist coupling by adjustable shear centre location

2012 ◽  
Vol 24 (3) ◽  
pp. 334-346 ◽  
Author(s):  
Wolfram Raither ◽  
Andrea Bergamini ◽  
Paolo Ermanni
Keyword(s):  
Flexural Rigidity ◽  
Variable Stiffness ◽  
Structural Elements ◽  
Lightweight Structures ◽  
Load Carrying ◽  
Structural Concept ◽  
Simulation And Experiment ◽  
Coupling Stiffness ◽  
Shear Centre

Semi-active structural elements based on variable stiffness represent a promising approach to the solution of the conflict of requirements between load-carrying capability and shape adaptivity in morphing lightweight structures. In the present work, a structural concept with adaptive bending–twist coupling aiming at a broad adjustment range of coupling stiffness while maintaining high flexural rigidity is investigated by analysis, simulation and experiment.

DESIGN AND ANALYSIS OF AN INTEGRATED THREE- BAY THERMOPLASTIC COMPOSITE WINGBOX

2021 ◽  
Author(s):  
VINCENZO OLIVERI ◽  
GIOVANNI ZUCCO ◽  
MOHAMMAD ROUHI ◽  
ENZO COSENTINO ◽  
RONAN O’HIGGINS ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Thermoplastic Composite ◽  
High Fidelity ◽  
Material System ◽  
Load Carrying Capacity ◽  
Element Analysis ◽  
Single Piece ◽  
Load Carrying ◽  
Post Buckling ◽  
Composite Material System

The design of a multi-part aerospace structural component, such as a wingbox, is a challenging process because of the complexity arising from assembly and integration, and their associated limitations and considerations. In this study, a design process of a stiffeners-integrated variable stiffness three-bay wingbox is presented. The wingbox has been designed for a prescribed buckling and post-buckling performance (a prescribed real testing scenario) and made from thermoplastic composite material system (Carbon-PEEK) with the total length of three meters. The stiffeners and spars are integrated into the top and bottom panels of the wingbox resulting a single-piece blended structure with no fasteners or joints. The bottom skin also has an elliptical cut-out for access purposes. The composite tows are steered around this cutout for strain concentration reduction purposes. The fiber/tow steering in the top skin bays (compression side) has also been considered for improved compression-induced buckling load carrying capacity. The proposed design has been virtually verified via high fidelity finite element analysis.

scholarly journals Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

Actuators ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 269
Author(s):  
Tingchen Liao ◽  
Manivannan Sivaperuman Kalairaj ◽  
Catherine Jiayi Cai ◽  
Zion Tsz Ho Tse ◽  
Hongliang Ren
Keyword(s):  
Transition Period ◽  
Shape Memory Polymer ◽  
Variable Stiffness ◽  
Pressure Variation ◽  
Soft Actuator ◽  
Output Force ◽  
Load Carrying ◽  
Force Variation ◽  
Stiffness Variation ◽  
Short Transition

Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20 ∘C and 45 mN/mm at 50 ∘C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30 ∘C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50 ∘C compared to the output force variation (0.16 N) at 20 ∘C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20 ∘C displayed no bending in the actuator. In contrast, the same variation of pressure at 50 ∘C displayed a bending angle of 80∘. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) shows the ability to bend 80∘. At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160∘. We demonstrated a soft robotic gripper varying its stiffness to carry objects (≈100 g) using two individual actuators.

Load-Carrying Capacities of Fully Clamped RC Slab Accompanying Compressive-Tensile Membrane Actions: A Theoretical Approach

2020 ◽  
Vol 20 (08) ◽  
pp. 2050094
Author(s):  
Wanxiang Chen ◽  
Lisheng Luo ◽  
Zhikun Guo ◽  
Yingjie Wang
Keyword(s):  
Bearing Capacity ◽  
Carrying Capacity ◽  
Flexural Rigidity ◽  
Load Carrying Capacity ◽  
Membrane Action ◽  
Yield Line ◽  
Load Carrying ◽  
Membrane Effects ◽  
Rc Slab ◽  
Rc Slabs

Fully clamped reinforced concrete (RC) slab is a common structural component possessing better load-carrying capacity over simply supported slab. Currently, typical yield line theory is a popular approach to estimate the bearing capacity of fully clamped RC slab, although it would greatly underestimate the actual ultimate resistance. This paper is devoted to enriching the knowledge of membrane action and its contribution to the load-carrying capacity of the clamped slab. The resistance trajectory of fully clamped RC slab from loading to failure undergoes three phases: the ascending branch raised by outward movement prevention, the descending branch due to crushed concrete and the re-ascending branch caused by reinforcement strain. Applied load–deflection curves of RC slab accompanying compressive-membrane actions are achieved according to the bending theory of normal cross-section. The reserve capacities accompanying tensile-membrane actions in the condition of large deformations are further derived. The whole load–deflection curves that considered compressive-tensile membrane effects are finally presented, where the mid-span displacements are revised by the deflection equations and the softening coefficient of flexural rigidity. It is indicated that the load–deflection relationships of fully clamped RC slabs can be reasonably depicted by taking compressive-tensile membrane effects into account, which are fairly different from yield line approaches. Comparative analysis shows that analytical results are in good agreement with experimental data reported by Park et al. and illustrates that the proposed model is capable of predicting the bearing capacity of fully clamped RC slab with very good accuracy.

Free vibration analysis of two parallel beams connected together through variable stiffness elastic layer with elastically restrained ends

2016 ◽  
Vol 20 (3) ◽  
pp. 275-287 ◽  
Author(s):  
Alborz Mirzabeigy ◽  
Reza Madoliat ◽  
Mehdi Vahabi
Keyword(s):  
Differential Equations ◽  
Elastic Layer ◽  
Flexural Rigidity ◽  
Free Vibration Analysis ◽  
Variable Stiffness ◽  
Differential Transform Method ◽  
Mode Shapes ◽  
Algebraic Equations ◽  
Transform Method ◽  
Differential Transform

In this study, free transverse vibration of two parallel beams connected together through variable stiffness Winkler-type elastic layer is investigated. Euler–Bernoulli beam hypothesis has been applied and the support is considered to be translational and rotational elastic springs in each ends. Linear and parabolic variation has been considered for connecting layer. The equations of motion have been derived in the form of coupled differential equations with variable coefficients. The differential transform method has been applied to obtain natural frequencies and normalized mode shapes of system. Differential transform method is a semi-analytical approach based on Taylor expansion series which converts differential equations to recursive algebraic equations and does not need domain discretization. The results obtained from differential transform method have been validated with the results reported by well-known references in the case of two parallel beams connected through uniform elastic layer. The effects of variation type and total stiffness of connecting layer, flexural rigidity ratio of beams, and boundary conditions on behavior of system are investigated and discussed in detail.

Effect of Tow Sheet Composite Wrap Architecture on Strengthening of Concrete Due to Confinement: I—Experimental Studies

1995 ◽  
Vol 14 (9) ◽  
pp. 1008-1030 ◽  
Author(s):  
Ian Howie ◽  
Vistasp M. Karbhari
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Load Carrying Capacity ◽  
Structural Elements ◽  
New Techniques ◽  
Column Type ◽  
Load Carrying ◽  
Concrete Shell ◽  
Original Construction ◽  
Stub Columns

Worldwide there is a need for the renewal of infrastructure because of age, deterioration, misuse, lack of timely repair and maintenance, use of improper materials and/or techniques in the original construction, and even changing needs. Notwithstanding the need for retrofit and repair methods for column-type structural elements, there is also a need for new techniques that would increase the confining action of concrete, as well as enhance the load-carrying capacity and ductility of such structures from a strengthening, rather than a seismic, viewpoint. This study investigates the use of carbon-fiber-reinforced jackets applied to concrete stub columns through the use of tow-sheet-type fabric forms. The primary emphasis is on the investigation of orientation and thickness effects of the composite wraps on the load-carrying efficiency and enhanced ductility of the new structural elements. It was seen that the predominant use of hoop reinforcement provides significant enhancement in concrete strength through confining action and also offers the potential for fabrication of concrete shell-type elements that would enable reinforcing action without the use of steel and the attending problems of corrosion.

scholarly journals Unidirectional variable stiffness hydraulic actuator for load-carrying knee exoskeleton

2017 ◽  
Vol 14 (1) ◽  
pp. 172988141668695 ◽  
Author(s):  
Jun Zhu ◽  
Yu Wang ◽  
Jinlin Jiang ◽  
Bo Sun ◽  
Heng Cao
Keyword(s):  
High Efficiency ◽  
Experimental Testing ◽  
Variable Stiffness ◽  
Torque Control ◽  
Joint Torque ◽  
Hydraulic Actuator ◽  
Passive Behavior ◽  
Compliance Behavior ◽  
Load Carrying ◽  
Passive Compliance

This article presents the design and experimental testing of a unidirectional variable stiffness hydraulic actuator for load-carrying knee exoskeleton. The proposed actuator is designed for mimicking the high-efficiency passive behavior of biological knee and providing actively assistance in locomotion. The adjustable passive compliance of exoskeletal knee is achieved through a variable ratio lever mechanism with linear elastic element. A compact customized electrohydraulic system is also designed to accommodate application demands. Preliminary experimental results show the prototype has good performances in terms of stiffness regulation and joint torque control. The actuator is also implemented in an exoskeleton knee joint, resulting in anticipant human-like passive compliance behavior.

Buckling of Perforated Plates Repaired with Composite Patches

2008 ◽  
Vol 385-387 ◽  
pp. 377-380 ◽  
Author(s):  
Jalil Rezaeepazhand ◽  
H. Sabori
Keyword(s):  
Laminated Composite ◽  
Quantitative Measure ◽  
Structural Elements ◽  
Structural Element ◽  
Perforated Plates ◽  
Advanced Composite ◽  
Numerical Studies ◽  
Load Carrying ◽  
Circular Cutout ◽  
Relative Change

Performance level and life span of existing structural elements can be increased by repair and strengthening of these structural elements using advanced composite materials.The performance of damaged metallic plates reinforced with fiber-reinforced polymer composite materials (composite patch) are presented in this study. A square aluminum plate with a central circular cutout is considered as a damaged structural element. Numerical studies using commercial finite element code were conducted to investigate the effects of variation in patch geometries and lamination parameters on buckling responses of repaired plates. The varying laminate parameters such as, fiber angles and stacking sequences are considered in this study. A quantitative measure for the effectiveness of the composite patches is taken to be the relative change in buckling loads of the reinforced plates compare to those of the perfect one. The results presented herein indicated that, for buckling response of a repaired metallic plate with central cutout, a set of laminated composite patches with different shape and stacking sequences can be found which improve load carrying capacity of damaged plates.

scholarly journals The Influence of Dowel-Pin Connections on the Seismic Fragility Assessment of RC Precast Industrial Buildings

2017 ◽  
Vol 11 (1) ◽  
pp. 1138-1157 ◽  
Author(s):  
Pardo Antonio Mezzapelle ◽  
Agnese Scalbi ◽  
Francesco Clementi ◽  
Stefano Lenci
Keyword(s):  
Seismic Vulnerability ◽  
Structural Safety ◽  
Seismic Fragility ◽  
Load Carrying Capacity ◽  
Structural Elements ◽  
The Past ◽  
Industrial Buildings ◽  
Load Carrying ◽  
Annual Frequency ◽  
The Mean

Background:Recent major earthquakes in the centre of the Italy, between August and October 2016, have reaffirmed the seismic vulnerability of precast industrial buildings with a lot of collapse recorded. This is typical due to the past Italian building practices, where structural deficiencies are mainly related to the capacity to transfer horizontal forces between primary structural elements.Objectives and Methods:In these types of structures, a key role is played by the dowel pin connections which allow to transfer lateral horizontal forces from the beam to the column, without losing load carrying capacity. For this reason, in this work, the assessment of the seismic fragility of single-story reinforced concrete precast building located not far from the epicentres of the two aforementioned earthquakes was done.Results and Conclusion:The seismic risk was evaluated in terms of annual frequency of exceedance for three performance levels provided by the European and Italian seismic codes, considering the mean hazard curves for the site. The comparison between the fragility of different structural models shows the importance in the choice of the column-beam connection modelling to obtain reliable results on the structural safety assessment.

scholarly journals FLEXURAL LOAD AND DEFLECTION BEHAVIOR OF STRUCTURAL BAMBOO FILLED WITH CEMENT MORTAR

2021 ◽  
Vol 83 (4) ◽  
pp. 31-39
Author(s):  
Gathot Heri Sudibyo ◽  
Nor Intang Setyo Hermanto ◽  
Hsuan-Teh Hu ◽  
Yanuar Haryanto ◽  
Laurencius Nugroho ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Carrying Capacity ◽  
Cement Mortar ◽  
Natural Material ◽  
Load Carrying Capacity ◽  
Structural Elements ◽  
Load Bearing ◽  
Four Point Bending ◽  
Bamboo Nodes ◽  
Load Carrying

Bamboo has been significantly and rapidly used to build temporal and permanent structures since time immemorial. However, this renewable natural material has a low bearing capacity, limiting its application to structures under light loads. Therefore, this research was carried out to determine an innovative scheme capable of enhancing bamboo's load-bearing by filling the cavity with cement mortar. Furthermore, a study was carried out to experiment flexural load carrying capacity and the deflection of mortar-filled structural bamboo by considering the diameter and node parameters. A total of 12 specimens were examined using a four-point bending protocol. The result showed the ultimate flexural load carrying capacity of mortar-filled bamboo specimens are higher than those of the conventional bamboo specimens. Specifically, mortar filled bamboo specimen with a diameter of 70 mm was significantly better, 41.10 and 47.06%, as compared than the conventional bamboo in terms of its flexural load carrying capacity for specimen without and with nodes, respectively. Increases in flexural load carrying capacity were also observed for the mortar-filled bamboo specimens having 80 and 90 mm diameter and these observed increases were recorded as 104.55 and 112.00%, and 48.72 and 60.74%, respectively for specimen without and with nodes. Furthermore, the deflection of mortar-filled bamboo elements are substantially greater than those of conventional. Finally, the advantages of the bamboo diameter and bamboo nodes on the flexural load carrying capacity indicated that these essential findings need to be carefully considered in designing structural elements for both mortar-filled and conventional bamboos.

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