Single Connector Research Articles

Seismic performance of precast concrete structures with energy dissipating cladding panel connection systems

The cladding‐structure interaction of precast concrete frame systems under seismic action has not been properly addressed in the past, as shown by several failures occurred under recent earthquakes in Southern Europe, which point out the need of a revision of the current design practice and technology. Dissipative systems of connections are proposed to this purpose within a general framework for seismic design of precast structures with cladding panels. The proposed connection systems consist of friction‐based or plasticity‐based devices interposed in between adjacent cladding panels or between the panels and the resisting frame to control the level of transferred forces and limit the displacements of the structure. Monotonic and cyclic experimental tests are carried out on both single connection devices and structural sub‐assemblies of two panels. Furthermore, cyclic and pseudo‐dynamic tests on a full‐scale prototype of precast structure with cladding panels are performed. The influence on the structural response of silicone sealant is also investigated through experimental testing. The effectiveness of the tested dissipative connections of the cladding panels in enhancing the seismic performance of precast structures is demonstrated by means of nonlinear dynamic analyses considering the influence of the roof diaphragm action. Design guidelines are finally provided for both single connectors and panel structural assemblies based on equilibrium and capacity design criteria.

A Flexible Multiring Concentric Electrode for Non-Invasive Identification of Intestinal Slow Waves.

Developing new types of optimized electrodes for specific biomedical applications can substantially improve the quality of the sensed signals. Concentric ring electrodes have been shown to provide enhanced spatial resolution to that of conventional disc electrodes. A sensor with different electrode sizes and configurations (monopolar, bipolar, etc.) that provides simultaneous records would be very helpful for studying the best signal-sensing arrangement. A 5-pole electrode with an inner disc and four concentric rings of different sizes was developed and tested on surface intestinal myoelectrical recordings from healthy humans. For good adaptation to a curved body surface, the electrode was screen-printed onto a flexible polyester substrate. To facilitate clinical use, it is self-adhesive, incorporates a single connector and can perform dry or wet (with gel) recordings. The results show it to be a versatile electrode that can evaluate the optimal configuration for the identification of the intestinal slow wave and reject undesired interference. A bipolar concentric record with an outer ring diameter of 30 mm, a foam-free adhesive material, and electrolytic gel gave the best results.

De-embedding Unmatched Connectors for Electric Cable Fault Diagnosis

In order to make accurate reflectometry measurements on electric cables for fault diagnosis, connector de-embedding is a procedure for compensating measurement distortions caused by unmatched connectors. The key step in such a procedure is the characterization of the connectors, which is realized through measurements on a pair of connectors linked by a short cable segment. The analysis for deducing the characteristics of a single connector from measurements made on an assembled pair is known as the bisection problem. In this paper, after recalling the underdetermined nature of the bisection problem, a practically effective de-embedding procedure is proposed based on a particular regularization technique. Numerical examples are presented to illustrate the effectiveness of this procedure.

An Innovative Connection System for Cross-Laminated Timber Structures

The paper presents a new connection system for cross-laminated timber (CLT) structures, named X-RAD. This innovative connection system is characterised by the use of a single connector type that is positioned at the corners of the CLT panels. X-RAD is formed by a metal part surrounding a hardwood insert that is fixed to the panels by means of all-threaded screws introduced with double inclination. The peculiar geometry of the connector and the combination of different materials allow the full exploitation of the capacity of the CLT panels while ensuring a ductile response of the connection. Construction modularity, fast assembly/disassembly speed and prefabrication are some of the aspects that can be associated with X-RAD development. The outcomes of an extensive testing campaign on the new connector are also presented in the paper.

Multichannel Dynamic Fourier-Transform IR Spectrometer

A design of a multichannel continuous scan Fourier-transform IR spectrometer for simultaneous recording and analysis of the spectral characteristics of several objects is proposed. For implementing the design, a multi-probe fiber is used, constructed from several optical fibers connected into a single optical connector and attached at the output of the interferometer. The Fourier-transform spectrometer is used as a signal modulator. Each fiber is individually mated with an investigated sample and a dedicated radiation detector. For the developed system, the radiation intensity of the spectrometer is calculated from the condition of the minimum spectral resolution and parameters of the optical fibers. Using the proposed design, emission spectra of a gas-discharge neon lamp have been recorded using a single fiber 1 mm in diameter with a numerical aperture NA = 0.22.

08.02: Experimental research of multiple perfobond connectors for composite girders

ABSTRACTExtensive research has been carried out in recent years focusing on the behaviour of innovative connectors for steel and concrete composite girders. Those elements exhibit large resistance and adequate behaviour under different load types, and at the same time are easy to fabricate and to erect on site. Among these types, the Perfobond connector or Perfobond rib, consisting of a perforated steel plate welded to the steel beam flange, has been extensively studied by numerous authors, due to its particularly convenient efficiency, behaviour and ductility characteristics.Although many connector types have been studied in the past, few studies focused on the behaviour of groups of special connectors, a typical arrangement used in conventional headed stud connectors.This paper focuses on the behaviour of multiple Perfobond connectors placed side‐by‐side on a steel girder and immersed in the reinforced concrete slab. This quite innovative arrangement enhances the resistance from a single connector classic layout, but the proximity to other connectors may significantly change the behaviour of individual connectors that interact with each other.Fourteen push‐out tests on groups of Perfobond connectors were carried out at the Civil Engineering Department of the University of Coimbra, Portugal, while this paper reports and discuss the results.The investigated variables were: the number of connectors, ranging from one (the basic arrangement) to three; the spacing between connectors; the transverse reinforcement within the connector's holes; and the concrete strength. The results are presented and discussed concentrating on the connector's structural response for shear transfer capacity, ductility and collapse modes. A comparative assessment of these properties focusing on the number of connectors and its spacing is presented and discussed, aiming at establishing preliminary conclusions about the behaviour of Perfobond groups. In addition, a brief comparison of the experimental results with existing analytical models for Perfobond connectors is also presented to establish the most convenient model for this particular geometry. Finally, some adapted models referred in the literature to cope with Perfobond groups are applied to the tested geometries and the analytical and experimental tests are compared and discussed.

Friction-based dissipative devices for precast concrete panels

Abstract The stability of precast concrete wall panels under seismic action can be ensured by means of dissipative systems of panel-to-panel connections that allow to control the level of forces and limit the displacements. This paper deals with a connection system consisting of friction-based devices inserted into appropriate recesses within the joints between vertical or horizontal panels. The results of experimental tests carried out on single connectors, as well as on structural sub-assemblies consisting of two full scale panels, are presented. The technological choices of materials and components that ensure a stable hysteretic behaviour of the devices are discussed. The effectiveness of the devices in improving the seismic performance of precast buildings under seismic action is also shown based on the results of cyclic and pseudo-dynamic tests on full-scale structural prototypes.

Behaviour of Corroded Single Stud Shear Connectors.

In this study, the effect of corrosion on the static behavior of stud shear connectors was investigated. An innovative test setup for single stud shear connectors was designed and established. Two series of specimens having different stud diameters were fabricated and tested. The test specimens were firstly corroded to different corrosion rates by the electronic accelerating method. Static loading tests were then performed to obtain the load-slip curves and ultimate strengths of the corroded test specimens. The actual corrosion rates were measured from the studs obtained from the tested specimens. The test results were compared with the push out test specimens having similar corrosion rates. It is shown that the test results obtained from the single stud shear connectors are conservative compared with the corroded push test specimens, which prove the validation of the single stud shear connector test method. The effect of corrosion on the behavior of stud shear connectors was also presented.

Serviceability performance of steel–concrete composite beams

The use of steel–concrete composite beams in which wide-flanged steel beams act compositely with a concrete or steel–concrete composite slab above is well established in building construction. However, for composite beams with low degrees of shear connection between the beam and slab, significant additional deflections can occur due to slip in the shear connectors. A design formula is presented for the effective stiffness of composite beams taking account of the stiffness of the shear connectors, which is compared to measured deflections of six symmetric composite beams and an 11 m span composite beam of asymmetric profile. It is shown that the comparison is good when using a shear connector stiffness of 70 kN/mm for single shear connectors and 100 kN/mm for pairs of shear connectors per slab rib. The results of push tests on a range of slab profiles confirmed these initial elastic stiffnesses. To ensure that the slip at the serviceability limit state does not lead to permanent deformations of the composite beam, it is proposed that the minimum degree of shear connection should not fall below 30% for unpropped beams and 40% for propped beams of symmetric cross-section.

LIFE CYCLE ASSESSMENT OF TOXICITY POTENTIAL OF METALLIC ELEMENTS AND PROCESS STAGES IN ELECTRONICS: A CASE STUDY OF ELECTRONIC CONNECTOR LEADS

The electronic waste (e-waste) is increasingly flooding Asia, especially in developing countries. E-waste could precipitate a growing volume of toxic input to the local environment if it was not handled properly. This brings the evaluation of environmental impact from electronics an essentially important task for the life cycle assessment (LCA) and the end-of-life management of electronic products. This case study presented a quantitative investigation on the environmental impact analysis on electronics connector lead via LCA. A single connector lead can have a considerable toxicity to the environment as referred to hazardous metallic elements. LCA using SimaPro7 software showed that carcinogenic effect is the serious impact of electronic part on human health (57.33%). However, the metallic constituents in the electronic connector leads and its process stages indirectly become major contributor to the environmental impact. This suggests a major concern for the environmental impact of the total e-waste with such a large mass since most electronics are similar in composition, but the other electronic products and processes are much far and multiple times heavier than this small electronics part. LCA tool is good benchmarking to impact assessment even though several supporting tools complement each other to solve e-waste issue.

Structural performance of FCS wall subjected to axial load

The primary purpose of this paper is to present the structural behavior of precast foamed concrete sandwich walls (FCS) strengthened with double steel shear connectors (DSC) subjected to axial load. The discussion of results addresses the effect of slenderness ratio (H/t) on the behavior of the walls. It also addresses the significant effects of using double shear connectors on these behaviors compared to single steel shear connector (SSC). The FCS wall was modeled using ABAQUS and validated by the results from experiment and previous research. Parametric finite element study (FEA) was conducted by simulating these walls with various H/t under axial load. The structural behavior recorded from FEA includes its ultimate load, failure mode, load-deflection profiles, strain distribution across the wall’s thickness, and ultimate shear load. It was found that as H/t increased, the ultimate load decreased but the maximum horizontal deflection increased. FCS with H/t ⩽25 failed from crushes and cracks within the top and bottom area while FCS with H/t ⩾25 failed from buckling at its mid-height. It was also noticed that FCS with lower H/t experienced more uniform strain distribution across its thickness. FCS with DSC was able to sustain higher load but it deflected less compared to walls with SSC, caused by higher stiffness due to larger steel areas. It is interesting to find that FCS walls with DSC behaved in a more composite manner and was able to sustain higher ultimate shear force under push of loading test compared to FCS walls with SSC. These findings show that the FCS wall with DSC is suitable to be used as a load-bearing wall.

Theoretical and Experimental Studies of the Internal Force Transfer Mechanism of Perfobond Rib Shear Connector Group

Abstract Perfobond rib shear connector (PBL) is capable of transferring large internal force between steel and concrete components. It has been widely used in composite bridges as a key load-transferring component. In this paper, the load-transfer mechanism of the PBL shear connector group is investigated theoretically and experimentally. An analytical model was developed based on load-slip characteristics of a single shear connector and load-deformation compatibility of a perforated steel plate and concrete component. The model was validated through full-scale connection loading experiments. Test results indicate that the applied load is unevenly distributed to multiple layers of PBL shear connectors in a connector group in the elastic stage, and the load becomes more evenly distributed as plastic deformation of the connectors takes place. The presented analytical model provides an efficient way for analyzing and designing a PBL shear connector group. The analytical results indicate that increasing the n...

Absorb Bioresorbable Vascular Scaffold in Complex Coronary Bifurcation Interventions: Insights From an In Vivo Multimodality Imaging Study.

Although bioresorbable scaffolds offer potential advantages compared with metallic drug-eluting stents in the treatment of complex coronary bifurcation lesions, there are concerns that the polymeric scaffold integrity may be compromised. This in vivo study sought to provide insights about the feasibility of performing complex bifurcation stenting with Absorb bioresorbable vascular scaffolds (Abbott Vascular, Santa Clara, CA). Twenty New Zealand white rabbits underwent stenting of the nondiseased aortoiliac bifurcation with bioresorbable vascular scaffolds using provisional (PS, n=5), culotte (n=5), modified-T (n=5), or T-and protrusion (n=5) stenting techniques. Angiography, optical coherence tomography, and microcomputed tomography were performed. Angiographic results were excellent without evidence of dissection or side branch (SB) compromise. PS optimally opened the SB ostium without deforming the main vessel (MV) bioresorbable vascular scaffolds, avoiding malapposition, and revealing a single connector fracture in 1 of 5 cases on microcomputed tomography. Culotte stenting resulted in complete bifurcation coverage with extensive segments of double-layered struts and inappropriately apposed struts at the bifurcation level in 3 of 5 cases. On microcomputed tomography, there was MV and SB scaffold distortion at the bifurcation with single strut fractures in 4 of 5 and double fractures in 1 of 5. Modified-T and T-and protrusion resulted in complete bifurcation coverage and in minimal double-strut layers at the neocarina. On microcomputed tomography, no strut fractures were present after modified-T, whereas in 3 of 5 T-and protrusion procedures single strut fractures were noted. Bifurcation stenting using bioresorbable vascular scaffolds is feasible with excellent angiographic results. PS with additional T-and protrusion whenever needed seems a reasonable approach. Whenever a 2-stent technique is planned, modified T-stenting appears the most promising.

Experimental study on demountable shear connectors in composite slabs with profiled decking

This paper presents an experimental study on shear strength, stiffness and ductility of demountable shear connectors in metal decking composite slabs through push-off tests. Twelve full-scale push-off tests were carried out using different concrete strength, number of connectors and different connector diameter. The experimental results showed that the demountable shear connectors in metal decking composite slabs have similar shear capacity and behaviour as welded shear studs and fulfilled the minimum ductility requirement of 6mm required by Eurocode 4. The shear capacity was compared against the prediction methods used for the welded shear connections given in Eurocode 4, AISC 360-10, ACI 318-08 and method used for bolted connection in Eurocode 3. It was found that the AISC 360-10 method overestimated the shear capacity while the ACI 318-08 method underestimated the shear capacity of specimens with single shear connector per trough. The Eurocodes method was found to provide a safe prediction for specimens with single and pair demountable connectors per trough. In addition, prediction methods given in both AISC 360-10 and ACI 318-08 for welded shear studs overestimated the shear capacity of specimens with 22mm diameter demountable connectors that failed in concrete crushing.

Behavior of stud connections between concrete slabs and steel girders under transverse bending moment

The effect of transverse bending moment on stud connections is usually ignored in the design of steel–concrete composite bridges due to beam web flexibility. However, large transverse moment may arise near transverse stiffeners and diaphragms, because they constrain and stiffen the webs and cause tensile forces in stud connectors. Large web spacing and wide cantilevers increase these effects. This study experimentally and numerically investigates this behavior. Four groups of pull-out tests of a single stud connector under tension force are performed, and they provide insight into the behavior of stud connectors under direct tensile loading. Then four stud connections at interfaces near transverse stiffeners are tested to investigate their behavior under transverse bending moment. Numerical models of the stud connections are established to explore local behavior. The pull-out tests show that stud height greatly influences failure mode, tension strength and ultimate separation between the steel flange and the concrete slab. A tension–separation relationship is developed from the test results and used in subsequent numerical simulations. The stud connection tests suggest that longer studs can increase the bending moment and deformation capacities. Reduced longitudinal stud spacing significantly increases the stiffness, but may result in brittle failure of the concrete slab. Stud connectors should not be welded immediately over transverse stiffeners. Numerical simulations and test data compare well, and numerical results predict tensile forces in studs located near the steel web and in the region near stiffeners and other web restraint. The stud connectors in the two innermost rows on either side of a transverse stiffener provide the restraint to develop the tensile force in the studs caused by transverse bending moments. The force in a stud increases as its distance from the steel web increases and its distance from the transverse stiffener decreases. Shear–tension interaction should be checked for these connectors. Details of transverse stud arrangements with various stud heights are provided.

Non-linear simulation of shaking-table tests on 3- and 7-storey X-Lam timber buildings

This paper presents an advanced FE modelling of cross-laminated (X-Lam) timber buildings for non-linear dynamic analyses. The model has been used to reproduce the experimental results of the shaking table tests carried out in Japan within the SOFIE project on the 3- and 7-storey full-scale timber buildings. The X-Lam timber panels have been schematized with linear-elastic shell elements, whereas all metal connectors (hold-downs, angle brackets, screws) have been described with 3-DOFs non-linear hysteretic springs. The hysteretic law has a trilinear backbone curve, and is characterised by pinching, post-peak softening, strength and stiffness degradation. The approximating hysteretic laws of the springs have been calibrated on the experimental cyclic tests carried out on each single metal connector. Additional features of the model are the possibilities to account for friction at the interface between upper and lower X-Lam panels, and for a strength domain between shear and tensile force in the metal connectors. Due to the lack of experimental results, these variables have been identified via parametric study so as to reduce the difference between the numerical prediction and the experimental result of X-Lam single walls loaded with cyclic horizontal load. The experimental–numerical comparisons of the shaking table tests demonstrate the capacity of the model to capture the seismic responses of both buildings with errors within 20% in relative acceleration and 7% in roof displacement. Friction has been found to significantly affect the seismic response as it reduces the peak top displacement up to 31%.

The mesh is a network of microtubule connectors that stabilizes individual kinetochore fibers of the mitotic spindle.

Kinetochore fibers (K-fibers) of the mitotic spindle are force-generating units that power chromosome movement during mitosis. K-fibers are composed of many microtubules that are held together throughout their length. Here, we show, using 3D electron microscopy, that K-fiber microtubules (MTs) are connected by a network of MT connectors. We term this network 'the mesh'. The K-fiber mesh is made of linked multipolar connectors. Each connector has up to four struts, so that a single connector can link up to four MTs. Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs. Optimal stabilization of K-fibers by the mesh is required for normal progression through mitosis. We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber. Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.

Behavior of Double Fish Plate Connector between Steel Plate Shear Wall Structure and Steel Frame

This paper mainly researched the behavior of double fish plate connector between steel plate shear wall structure and steel frame. Four single fish plate connectors and four double fish plate connectors were tested under monotonic and cyclic loading. The hysteretic curves, skeleton curves, stiffness degradation curve and ductility coefficient were considered to study the behavior of two connections. Results showed that the behavior of double fish plate connector between steel plate shear walls and steel frame was better than single fish plate connector. Double fish plate connectors had higher bearing capacity, slower stiffness degradation, better ductility and better energy dissipation capacity. Constraint effect of steel plate shear walls became stronger, and the out-of-plane buckling failure of steel plate shear walls was delayed. Therefore, the double fish plate connectors could improve the behavior of connection between steel plate shear walls and steel frame, and provide a reference for engineering application

Macroscopic strength and failure properties of flow-drill screw connections

Force–displacement responses and failure behaviour of connections using flow-drill screws to join aluminium sheets were investigated under various quasi-static loading conditions. This included single connector tests under tensile, shear and combined tensile and shear loadings, using cross test coupons in a new test set-up, and peeling and single lap-joint tests. The strength of the connection increased with the amount of shear loading, while the ductility decreased. No effect of the anisotropy of the sheets on the behaviour in the single connector tests was found. Axial crushing tests of aluminium single-hat sections joined with flow-drill screws were also performed. Two connection failure modes not observed during the single connector test were found in these tests. For comparison, equivalent single connector and component tests were carried out for self-piercing rivet connections. Similar trends with respect to the ductility, maximum force and shape of force–displacement curves were observed for the two connections, but the local failure modes were different.

Static behaviour of multi-row stud shear connectors in high- strength concrete

In regions of high shear forces in composite bridges, headed stud shear connectors need to be arranged with a small spacing in order to satisfy the design requirement of resisting the high interface shear force present at this location. Despite this, studies related to groups of headed studs are somewhat rare. This paper presents an investigation of the static behaviour of grouped stud shear connectors in high-strength concrete. Descriptions are given of five push-out test specimens with different arrangements of the studs that were fabricated and tested, and the failure modes, load-slip response, ultimate load capacities and related slip values that were obtained are reported. It is found that the load-slip equation given by some researchers based on a single stud shear connector in normal strength concrete do not apply to grouped stud shear connectors in high-strength concrete, and an algebraic load-slip expression is proposed based on the test results. Comparisons between the test results and the formulae provided by some national codes show that the equations for the ultimate capacity provided in these codes are conservative when used for connectors in high-strength concrete. A reduction coefficient is proposed to take into account the effect of the studs being in a group.