Transverse Links Research Articles

Axial and eccentric compressive behavior of partially encased channel–concrete composite columns with bolted connections in modular buildings

This paper introduces a novel partially encased channel–concrete composite (PECC) column for modular buildings, aiming to eliminate the need for cast-in-place concrete and facilitate rapid assembly. The PECC column consists of two prefabricated modules connected by high-strength bolts. To evaluate the column's viability, six slender specimens—one bare steel column and five composite columns—were tested under axial and eccentric compression. Variables considered included the presence of concrete, the type of transverse connections, bolt spacing, and load eccentricity ratio. The compression performance of the PECC columns was analyzed by examining their failure patterns, load–deformation responses, initial stiffness, compressive capacity, and ductility. Test results revealed that the PECC columns failed due to global buckling, concrete spalling, and crushing. The bolted connections effectively prevented module separation, enabling the PECC columns to exhibit favorable compressive behavior. The reinforced concrete encased in the channel delayed the column's buckling failure, increasing its initial stiffness and compressive capacity by 98% and 198%, respectively. Using perforated steel plates instead of transverse links between the concrete and the channel enhanced the column's initial stiffness by 20% but had little effect on its compressive capacity. Reducing the bolt spacing improved the column's initial stiffness and compression resistance by 50% and 5%, respectively. Additionally, a finite element model for the PECC columns was developed and validated against test results. Finally, simplified formulas derived from Eurocode 4 were proposed to estimate the resistance of PECC columns under axial and eccentric compression.

Startup Time Standardization for Thermal Power Plant Generating Equipment with Transverse Links

Startup Time Standardization for Thermal Power Plant Generating Equipment with Transverse Links

Applications of higher‐dimensional Heegaard Floer homology to contact topology

AbstractThe goal of this paper is to set up the general framework of higher‐dimensional Heegaard Floer homology, define the contact class, and use it to give an obstruction to the Liouville fillability of a contact manifold and a sufficient condition for the Weinstein conjecture to hold. We discuss several classes of examples including those coming from analyzing a close cousin of symplectic Khovanov homology and the analog of the Plamenevskaya invariant of transverse links.

Invariants of annular links, cobordisms and transverse links from combinatorial link Floer complex

We define an annular concordance invariant and study its properties. When specialized to braids, this invariant gives bounds on band rank. We introduce a modified chain complex to reformulate the invariant. Then, by focusing on a special case, we give a refinement of the transverse invariant [Formula: see text]. We also study the relationship of this invariant with transverse and braid monodromy properties.

Mechanical Behavior of Cross-shaped Partially Encased Composite Columns under Axial Compression

The mechanical properties of two cross-shaped PEC columns were investigated by an axial compression experiment. The experimental results showed that when the cross-shaped PEC columns were destroyed, the concrete was crushed and the flanges were locally buckled. Based on the experimental parameters, the ABAQUS software was used for finite element simulation, and the results of the finite element analysis agree well with the test results. To prevent concrete cracking and flange local buckling in the cross-shaped PEC column, a transverse link connection method was presented. The finite element simulation demonstrates that this method improves the ultimate carrying capacity and ductility of the columns. The effects of link spacing, link diameter, flange width-to-thickness ratio, and limb width ratio are also investigated.

Effects of the position of confining transverse links on lap strength

AbstractThe article presents the results of an experimental campaign to investigate the effect of the position of transverse links on the strength of lap splices in tension. Lap splices with transverse links either adjacent to the lapped bars or at a distance of 4.5 times the bar diameter from the lap were tested. The stirrups index of confinement was similar in all the specimens. The results show a reduction of the lap strength up to 15% when the transverse links are not close to the lapped bars because of the splitting crack propagation which is not adequately counteracted by the confining action of the links. The test results show that the provisions of MC2010 for lap splices, with links relatively far, may be unconservative. Furthermore, an experimental database on the strength of lap splices with different distances of transverse links to the lapped bars is gathered from studies published in literature. This database enables to assess the accuracy of the efficiency factor km of confining reinforcement in the fib MC2010 formulation. Based on the statistical analysis of the test results concerning the confining reinforcement, a reduction is proposed for the effectiveness factor (km), to be applied whenever the distance of laps to the transverse links exceeds four times the bar diameter.

Links in overtwisted contact manifolds

We prove that Legendrian and transverse links in overtwisted contact structures having overtwisted complements can be classified coarsely by their classical invariants. We further prove that any coarse equivalence class of loose links has support genus zero and construct examples to show that the converse does not hold.

Reeb orbits that force topological entropy

Abstract We develop a forcing theory of topological entropy for Reeb flows in dimension three. A transverse link L in a closed contact $3$ -manifold $(Y,\xi )$ is said to force topological entropy if $(Y,\xi )$ admits a Reeb flow with vanishing topological entropy, and every Reeb flow on $(Y,\xi )$ realizing L as a set of periodic Reeb orbits has positive topological entropy. Our main results establish topological conditions on a transverse link L, which imply that L forces topological entropy. These conditions are formulated in terms of two Floer theoretical invariants: the cylindrical contact homology on the complement of transverse links introduced by Momin [A. Momin. J. Mod. Dyn.5 (2011), 409–472], and the strip Legendrian contact homology on the complement of transverse links, introduced by Alves [M. R. R. Alves. PhD Thesis, Université Libre de Bruxelles, 2014] and further developed here. We then use these results to show that on every closed contact $3$ -manifold that admits a Reeb flow with vanishing topological entropy, there exist transverse knots that force topological entropy.

A biomechanical comparison of crossed and parallel rod configurations in atlantoaxial internal fixation.

Posterior atlantoaxial fixation with screw rod forms an approximate "II" shape or "H" increasing transverse link for better stability. In order to improve stability and in consideration of difficult placement of transverse connecting rod, possibility of inadequate bone graft, some scholars have preliminarily researched biomechanics of a novel crossed rod as an approximate "X" configuration of screw rod. The aim of this study was to evaluate and compare the biomechanics of the crossed and parallel rod configurations in the screw rod system for posterior atlantoaxial fixation on a cadaveric model. Six fresh cervical specimens were used to complete the range of motion (ROM) testing by applying pure moments of ± 2.0nm. Following intactstate and under destabilization testing, screws were implanted. The specimens were then tested in the following sequence: Group BLS + PR (C2 bilateral laminar screws + parallel rod), Group BLS + CR (C2 bilateral laminar screws + crossed rod), LPRLS + PR (C2 left pedicle screw and right laminar screw + parallel rod), LPRLS + CR (C2 left pedicle screw and right laminar screw + crossed rod), BPS + PR (C2 bilateral pedicle screws + parallel rod) and BPS + CR (C2 bilateral pedicle screws + crossed rod). The ROM of the C1-2 segments was measured in flexion-extension, lateral bending and axial rotation. Six surgical constructs were compared between the groupsand with intact condition, respectively. The six fixed modes significantly increased stability compared with both the intact and destabilization group in flexion-extension, lateral bending and axial rotation (p < .05). In extension, BPS + CR and BLS + CR showed greater stability than BLS + PR (p < .05). During flexion, the six fixation methods showed no statistical significance (p > .05). In left lateral bending, stability of the other five screw rod fixation techniques significantly increased when compared with BLS + PR (p < .05). In the right lateral bending direction, the stability of BLS + PR was worse than that of BPS + CR and BPS + PR (p < .05). In the left axial rotation, stability of BLS + CR, LPRLS + CR and BPS + CR was greater than that of BLS + PR, LPRLS + PR and BPS + PR (p < .05). In the right axial rotation, the stability of BPS + CR and BLS + CR was greater than that of BLS + PR (p < .05). The six investigated fixation methods provide sufficient biomechanical stability. The crossed rod configuration can further enhance the axial rotation stability of the screw rod system, which consists of C1 bilateral pedicle and C2 pedicle, or C2 lamina screws. The crossed rod can also improve the stability of the screw rod system made up of C1 bilateral pedicle and C2 lamina screws in lateral bending and extension. The crossed rod configuration is reliable and provides superior stability for clinical application.

Transverse link invariants from the deformations of Khovanov 𝔰𝔩3–homology

In this paper we will make use of the Mackaay-Vaz approach to the universal $\mathfrak{sl}_3$-homology to define a family of cycles (called $\beta_3$-invariants) which are transverse braid invariants. This family includes Wu's $\psi_{3}$-invariant. Furthermore, we analyse the vanishing of the homology classes of the $\beta_3$-invariants and relate it to the vanishing of Plamenevskaya's and Wu's invariants. Finally, we use the $\beta_3$-invariants to produce some Bennequin-type inequalities.

On Bennequin-type inequalities for links in tight contact 3-manifolds

We prove that a version of the Thurston–Bennequin inequality holds for Legendrian and transverse links in a rational homology contact 3-sphere [Formula: see text], whenever [Formula: see text] is tight. More specifically, we show that the self-linking number of a transverse link [Formula: see text] in [Formula: see text], such that the boundary of its tubular neighborhood consists of incompressible tori, is bounded by the Thurston norm [Formula: see text] of [Formula: see text]. A similar inequality is given for Legendrian links by using the notions of positive and negative transverse push-off. We apply this bound to compute the tau-invariant for every strongly quasi-positive link in [Formula: see text]. This is done by proving that our inequality is sharp for this family of smooth links. Moreover, we use a stronger Bennequin inequality, for links in the tight 3-sphere, to generalize this result to quasi-positive links and determine their maximal self-linking number.

МОДЕЛИ АРХИТЕКТУРНОГО ФОРМИРОВАНИЯ ОБЩЕСТВЕННЫХ ПРОСТРАНСТВ В СТРУКТУРЕ ГОРОДСКИХ АКВАТОРИЙ

An approach to the architectural and landscape formation of public spaces on water, based on a model representation of the contact zone "river-city", is proposed. The functional loads of public spaces that are transferred to the structure of urban water areas are systematized. Several promising methods in the formation of public spaces on water are presented as meaningful levels of interaction between water area and coastal urban structure: 1) a scenario-functional approach to the formation of linear spaces of public pedestrian environment, 2) the addition and development of ecological complex of the waters, 3) the aesthetic harmonization of environment of coastal areas; 4) strengthening the transverse links of the city and the water area through the placement of public spaces on water. The first method based on scenario-functional approach proposes eight functional planning models for organizing public spaces on water: linear-translational model, complex-dissected model, transverse (scenario-functional) model, closed (ring) model, radial (arched) model, fan (beam) model of public spaces in the structure of the water area, reciprocating (combined) model and discrete model. A number of theoretical models of the organization of public spaces in the structure of urban water areas are proposed. They reflect the principles of aesthetic harmonization of riverside landscape, complement and rehabilitate lost qualities of their ecological complex and organize transverse links of urban environment with water area. The presented models expand the range of possible conceptual approaches and methods of riverside and water areas reconstruction, modernization and adaptation to public functions. In addition, they form new methodological tools for pre-project analysis, architectural concept search and modeling of the building-water zone.

Stability and triviality of the transverse invariant from Khovanov homology

We explore properties of braids such as their fractional Dehn twist coefficients, right-veeringness, and quasipositivity, in relation to the transverse invariant from Khovanov homology defined by Plamenevskaya for their closures, which are naturally transverse links in the standard contact 3-sphere. For any 3-braid β, we show that the transverse invariant of its closure does not vanish whenever the fractional Dehn twist coefficient of β is strictly greater than one. We show that Plamenevskaya's transverse invariant is stable under adding full twists on n or fewer strands to any n-braid, and use this to detect families of braids that are not quasipositive. Motivated by the question of understanding the relationship between the smooth isotopy class of a knot and its transverse isotopy class, we also exhibit an infinite family of pretzel knots for which the transverse invariant vanishes for every transverse representative, and conclude that these knots are not quasipositive.

Simplified relations for confinement factors of partially and highly confined areas of concrete in partially encased composite columns

In this paper, the new analytical expressions of confinement factors for partially and highly confined areas of partially encased composite (PEC) columns fabricated by thin-walled cross- and H-shaped structural steel sections are proposed. A three-dimensional (3D) nonlinear finite element analysis based on the dynamic explicit method was performed to predict the load-displacement relationship of the PEC columns using the proposed confinement factors. The model was verified against experimental results from the literature, which indicated that load bearing capacity and load-displacement behavior of PEC columns can be estimated accurately. A parametric study was performed based on numerical model to investigate the influence of the compressive strength of concrete, transverse link spacing, and structural steel shape on axial behavior of the PEC columns. The findings demonstrate that the partially and highly confined area is greatly influenced by the shape of steel section. As consequence of improvement in behavior, the usage of cross-shaped section possesses greater highly confined area which the maximum coefficients of partially and highly confined areas are 1.55 and 2.01, respectively. The comparison of proposed model and squash load against test results shows that analytical generated expressions are advisable to be used for design purposes.

Experimental Study on Mechanical Behavior of Prefabricated PEC Composite Beams Under Cyclic Loading

In this paper, a new type prefabricated partially encased composite beam (PEC beam) using screw arbors instead of stirrups or welded transverse links in ordinary PEC structures to connect the upper and lower steel flange has been proposed. It not only retains the performance advantages of PEC structures, but also greatly enhances the prefabricated degree of structure and simplifies construction process. Twelve beams with and without screw arbors were tested under cyclic loading to study the mechanical behavior of this new type of PEC beams. The major factors considered were shear span ratio (λ = 1.0, 2.0, 3.0 and 4.0), with or without screw arbors and concrete thickness. Test results including failure mode, load–deflection curves (P − Δ curves), characteristic points, ductility and stiffness were introduced and discussed in detail. The test results showed that the failure mode of PEC beams changed from shear failure to bending failure with the increase of shear span ratio, and the asymmetric damage of specimens can be improved by screw arbors. In addition, PEC beams with screw arbors have better ductility and slower stiffness degeneration than those without screw arbors. Potential application value can be seen from this new type of prefabricated PEC beams.

Quasi-right-veering braids and nonloose links

We introduce a notion of "quasi-right-veering" for closed braids, which plays an analogous role to "right-veering" for open books. We show that a transverse link $K$ in a contact 3-manifold $(M,\xi)$ is non-loose if and only if every braid representative of $K$ with respect to every open book decomposition that supports $(M,\xi)$ is quasi-right-veering. We also show that several definitions of "right-veering" closed braids are equivalent.

Structural behavior of steel-concrete partially encased composite columns containing demolished concrete lumps under axial compression

Steel-concrete composite members incorporating demolished concrete lumps (DCLs) have been devised to provide an innovative alternative means of recycling old concrete. Field applications have demonstrated those members’ potential. In this study the aforementioned recycling method is applied to steel-concrete partially encased composite (PEC) columns. To evaluate the viability of this new solution, a comparative experimental campaign was implemented to investigate the behavior of eleven large-scale PEC columns containing different content of DCLs under axial compression. The key parameters considered were replacement ratio of DCLs, steel flange thickness, spacing of transverse links, the source of DCLs.Overall, the initial stiffness and axial load-carrying capacity of the PEC columns containing up to 33% DCLs were found to be comparable to those of the columns cast with new concrete alone. Nevertheless, a more rapid load drop right after the peak was observed for the columns containing DCLs when the link spacing equaled or exceeded half the column section depth. To remedy this, a maximum link spacing limit of 0.3d (d = the column section depth) is recommended for the columns containing DCLs. An analytical model is then developed to reproduce the full-range axial response of the PEC columns. The model accounts for the gain in strength due to concrete encasement and the loss due to flange buckling. It also attempts to capture the columns’ descending branch with recourse to the concept of compression fracture energy. Applicable to both types of PEC columns (i.e. containing DCLs or not), the proposed model exhibits a good accuracy, evidenced by comparing the prediction results against a set of test data compiled in this study.

Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls.

The purpose of this study is to improve the performance of walls under out-of-plane loads especially when subjected to the hammering action of the floors. The idea behind the paper is to provide the masonry walls with a device that behaves like a buttress, without having to build a traditional buttress. The solution presented in this paper consists of a mechanical coupling between the three-dimensional net of steel ribbons of the CAM (Active Confinement of Masonry) system and the CFRP (Carbon Fiber Reinforced Polymer) strips. Since the steel ribbons of the CAM system have a pre-tension, the mechanical coupling allows the steel ribbons to establish a semi-rigid transverse link between the CFRP strips bonded on the two opposite sides of a wall. Therefore, two vertical CFRP strips tied by the steel ribbons behave like the flanges of an I-beam and the flexural strength of the ideal I-beam counteracts the out-of-plane displacements of the wall. The experimental results showed that the combined technique inherits the strong points of both constituent techniques. In fact, the delamination load is comparable to that of the specimens reinforced with the CFRP strips and the overall behavior is as ductile as for the specimens reinforced with the CAM system. They also inspired a more performing combined technique.

Cosmetic contact surgeries along transverse knots and the knot complement problem

We study cosmetic contact surgeries along transverse knots in the standard contact 3-sphere, i.e. contact surgeries that yield again the standard contact 3-sphere. The main result is that we can exclude non-trivial cosmetic contact surgeries along all transverse knots not isotopic to the transverse unknot with self-linking number −1.As a corollary it follows that every transverse knot in the standard contact 3-sphere is determined by the contactomorphism type of its exteriors. Moreover, we give counterexamples to this for transverse links in the standard contact 3-sphere.

The defect of Bennequin-Eliashberg inequality and Bennequin surfaces

For a null-homologous transverse link $\mathcal T$ in a general contact manifold with an open book, we explore strongly quasipositive braids and Bennequin surfaces. We define the defect $\delta(\mathcal T)$ of the Bennequin-Eliashberg inequality. We study relations between $\delta(\mathcal T)$ and minimal genus Bennequin surfaces of $\mathcal T$. In particular, in the disk open book case, under some large fractional Dehn twist coefficient assumption, we show that $\delta(\mathcal T)=N$ if and only if $\mathcal T$ is the boundary of a Bennequin surface with exactly $N$ negatively twisted bands. That is, the Bennequin inequality is sharp if and only if it is the closure of a strongly quasipositive braid.