Tensegrity Footbridge with Prestressed Deck
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Tensegrity
A tensegrity structure is a type of self-balancing tensile structure, which consists of tension cables surrounding compression struts. Based on the geometry and topology of the classic half-octahedron tensegrity, this article presents a form-finding analysis of semi-regular tensegrity units using singular value decomposition of the equilibrium matrix. We propose the design formulas for the unit geometric transformation, obtain its internal self-stress modes and inextensional mechanism modes, and verify its geometric stability. Then, we devise a design method and compute the overall feasible self-stress of a tensegrity torus. A novel cable–strut tensile structural system is generated through combining a tensegrity torus and a Levy-type cable dome. Finally, a physical model is constructed to verify the feasibility of this structural system. This work enriches existing forms of tensegrity structures and contributes to further practical applications of tensegrity systems.
Tensegrity
Tension (geology)
Representation
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There are a large number of welded fatigue weak points in steel deck which are prone to fatigue damage under cyclic loads.The second structural system effect has been mainly considered in domestic and international study of the mechanical properties and details fatigue of steel deck.The first structural system effect of fatigue stresses by replacing the corresponding position of fish bone beams with whole shell element through hybrid finite element method,and choosing the fatigue curve of Eurocode to calculate the cumulative damage of fatigue details.The results show that compression beam segment is no need for fatigue checking,while the effect of whole structural system can be ignored in fatigue assessment of tesion beam segment of steel deck.
Eurocode
Fatigue limit
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For the demolishing construction of a 3-span continuous box girder bridge with span arrangement(18+26.4+18) m,a demolishing scheme was proposed and designed,i.e.,the main girder of the bridge was stabilized by the bailey truss and suspenders,the girder was cut into 3 sections by the diamond steel wire cutting method,the section of the girder over the central span was lifted away by the overhead launching gantry and shifted to an open ground where it was then broken into pieces.The side spans flanking the central span and the 2-m remaining sections of the central span were broken in situ on staging.To ensure the construction safety,the internal force and deformation of the structure in the construction process were analyzed by the finite element software.The results of the analysis indicated that the deflection of the bailey truss was greater than that of the main girder,which caused great tensile force in the suspenders at both sides of the truss and little tensile force in the suspenders in the middle.In that case,the suspenders were pre-tensioned before lifting and in the lifting process,the axial forces of the suspenders were adjusted.Presently,the demolishing of the bridge has been completed and the whole process of the demolishing is safe and controllable.
Box girder
Internal forces
Bridge (graph theory)
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Based on an orthotropic steel deck of a long-span cable-stayed bridge,a full-scale fatigue test was carried out for researching the fatigue behavior of critical details in steel bridge decks.The load cycle had reached 10.2 million when the fatigue test was completed.The results show that fatigue cracks are found at the rib-to-deck details and also at weld toe of rib-to-diaphragm which expand along rib web;due to the welding residual stress,cracks are found in the compressive zone of rib-to-diaphragm;however,none is found in the cutout of diaphragm;based on the stress change criterion,the fatigue detail of rib-to-diaphragm satisfies the category D of AASHTO Specification and the category 63 of Eurocode while the fatigue detail of rib-to-deck is more than the category D of AASHTO Specification and the category 71 of Eurocode;if fatigue crack observation rule is adopted,the fatigue detail of rib-to-diaphragm is higher than the category D of AASHTO Specification and the category 80 of Eurocode.
Orthotropic material
Eurocode
Diaphragm (acoustics)
Fatigue limit
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For this study,the installation process of the steel box girder of the main bridge of Xiazhang Sea-Crossing Bridge was taken as the background.The lifting points for installation were optimized through the finite element calculation of the steel box girder sections.Originally,there was a small number of lifting points and the problem of stress concentration also existed,after the optimization,a sound installation condition of multiple lifting points and good stress distribution were created.The natural vibration property of the sections of the steel box girder was studied to guide the application of the equipments which showed vibration during the construction process.The maximum stress near the derrick crane under the transient working condition was analyzed and calculated,so as to control the most unfavorable working stress during the construction process and ensure the safety of the construction.
Bridge (graph theory)
Box girder
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Abstract Various fatigue failure modes (i.e., cracking position and orientation with respect to a weld) can develop in welded rib to deck connections in orthotropic bridge deck structures. After demonstrating its effectiveness in correlating fatigue test data covering different failure modes, the master S‐N curve method was then adopted in this study for determining the critical failure mode in welded U‐rib to deck connections. These include considerations of additional failure modes potentially present in double‐sided welds between U‐rib and deck versus the traditional single‐sided weld design. The effects of weld penetrations and test loading conditions on failure mode development have been quantitatively established by means of the master S‐N curve method.
Orthotropic material
Bridge deck
Bridge (graph theory)
Mode (computer interface)
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This paper presents a new numerical method to analyse tensegrity structures by using singular value decomposition and force method. The tensegrity system consisting of compressive and tensle elements are pin-jointed system. Tensegrity structures, unlike the general structure should be preceded by form-finding. Tensegrity structures form-finding of the self-equilibrium stress stability, seeking to have the process. In this study, tensegrity structures when subjected to external loads, find the optimal pre-stress values was studied.
Tensegrity
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Box girder
Bracing
Slab
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Tensegrity
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Citations (70)
Tensegrity frameworks form remarkable structures: they frequently do not have enough members to satisfy Maxwell's 1864 rule for the rigidity of frameworks, and yet form stable structures. Commonly, tensegrity frameworks are both statically and kinematically indeterminate, and rely on prestress to achieve stiffness. Here, I will describe the stability of tensegrity structures using the remarkably simple 'stress' matrix, which captures the effect of prestress on the stiffness of pin-jointed structures. The stiffness of tensegrity structures comes from two sources: the change of force carried by members as their length is changed, and the reorientation of forces as already stressed members are rotated. For any particular tensegrity, both sources of stiffness may have a critical role to play. This paper will explore how the stiffness of two example tensegrity structures changes as the level of prestress in a member varies. It is shown that, for high levels of prestress, an originally stable tensegrity can be made to have zero stiffness, or indeed be made unstable.
Tensegrity
Rigidity (electromagnetism)
Direct stiffness method
Statically indeterminate
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