Metal Connector Research Articles

Shear tests on stone masonry walls with metal connectors

Many strengthening techniques for masonry structures have been thoroughly investigated in various studies. Nevertheless, there is still a lack of information on the shear effects of metal connectors used in historical masonry structures. This paper presents the investigation of the effectiveness of metal connectors in relation to the shear collapse mechanism of stone masonry walls. A series of 12 stone masonry walls with metal connectors and an unreinforced masonry reference wall were subjected to shear forces. The test parameters were the length and number of clamps (horizontal metal connectors), and number of dowels (vertical metal connectors). The performance of the different metal connector configurations was compared in terms of strength and mechanism of failure. The results clearly show the effectiveness of metal connectors on shear behaviour of stone masonry walls.

Interfacial growth of large-area single-layer metal-organic framework nanosheets

The air/liquid interface is an excellent platform to assemble two-dimensional (2D) sheets of materials by enhancing spontaneous organizational features of the building components and encouraging large length scale in-plane growth. We have grown 2D molecularly-thin crystalline metal-organic-framework (MOF) nanosheets composed of porphyrin building units and metal-ion joints (NAFS-13) under operationally simple ambient conditions at the air/liquid interface. In-situ synchrotron X-ray diffraction studies of the formation process performed directly at the interface were employed to optimize the NAFS-13 growth protocol leading to the development of a post-injection method –post-injection of the metal connectors into the water subphase on whose surface the molecular building blocks are pre-oriented– which allowed us to achieve the formation of large-surface area morphologically-uniform preferentially-oriented single-layer nanosheets. The growth of such large-size high-quality sheets is of interest for the understanding of the fundamental physical/chemical properties associated with ultra-thin sheet-shaped materials and the realization of their use in applications.

Biogenic metal–organic frameworks: 2,5-Furandicarboxylic acid as versatile building block

2,5-Furandicarboxylic acid (FDA) is a promising renewable building block. It can be derived from cellulosic biomass and therefore poses no competition to the food chain. FDA is considered a valuable replacement for terephthalic acid in the industrial production of poly(ethylene terephthalate). Thus, the biogenic linker was investigated in the formation of metal–organic frameworks (MOFs). Novel crystalline compounds and gels have been synthesized and extensively characterized. The bi-functional linker forms Cu-, Al- and Fe-containing framework materials with hierarchical pore systems and high surface areas. Depending on the synthesis conditions crystalline Cu MOFs have been obtained exhibiting dense packings as well as open microporosity. In contrast, Al and Fe resulted in three-dimensional amorphous metal–organic framework gels with hierarchical pore systems ranging from micro- and meso-up to small macropores. By varying the metal connector as well as synthesis conditions the adsorption properties regarding the pore size and specific surface area can thus be tailored utilizing the versatile biogenic linker FDA that can be produced from renewable resources.

Cyclic Behavior of Timber Column Concealed Base Joint

This paper presents experimental and numerical tests on a recently developed timber column concealed base joint. This joint was designed to replace the wood-wood connection found in the post-and-beam structure of Hanok, the traditional Korean timber house. The use of metallic connectors provides an increased ductility and energy dissipation for a better performance under reversed loading, especially seismic. In this study, we investigate the performance of the joint under pseudo-static reversed cyclic moment loading through the study of its ductility and energy dissipation. We first perform experimental tests. Results show that the failure occurs in the metallic connector itself because of stress concentrations, while no brittle fracture of wood occur. Subsequent numerical simulations using a refined finite element model confirm these conclusions. Then, using a practical modification of the joint configuration with limited visual impact, we improve the ductility and energy dissipation of the joint while retaining a same level of rotational strength as the originally designed configuration. We conclude that the joint has a satisfying behavior under reversed moment loading for use in earthquake resistant timber structure in low to moderate seismicity areas like Korea.

Hybrid force-assisted 3-D assembly of helical nanobelts

. • We present a new manipulation system for hybrid force assisted assembly. • We propose a hybrid force assisted assembly process for 3-D helical nanobelts. • Helical nanobelt tweezer and sensing probe have been assembled using the proposed method. Freestanding flexible thin-film nanostructures are promising candidates for many potential applications, such as in the fields of electromechanical sensing, optical detection, tweezer, controlled release, and drug delivery. In this paper three-dimensional (3-D) suspended helical nanobelts (HNBs) with ultra-high flexibility are assembled by the external field guidance. Electromagnetic (EM) and electrostatic (ES) force by external potential are characterized quantitatively to guide the assembly of HNBs to create tweezer and sensing probe. Both ends of HNBs and target electrodes are attached with ferromagnetic metal connector. By the help of this hybrid assembly approach, we could successfully realize tweezer function and create sensing probe by parallel aligning and closing HNBs and soldering to interconnect HNBs onto electrodes. Adhesive force between HNBs and electrodes are characterized to show its assembly performance can be improved quantitatively. The demonstrated approach shows that the hybrid force assisted assembly is an effective and non-clean room way for assisting serial 3-D robotic assembly of ultra-flexible nanostructures, interconnection soldering which may potentially reduce the production cost and time for future manufacturing realization.

1D, 2D and 3D coordination polymers of 5,5′-methylenebis(oxy)dinicotinic acid with Co(ii), Mn(ii), Cu(ii) and Cd(ii) ions

A series of new coordination polymers of the 5,5′-methylenebis(oxy)dinicotinic acid ligand with various metal ions, have been synthesized under hydro(solvo)thermal conditions and characterized by X-ray crystallography: [Co(L)(H2O)4]n (1), [Cu(L)(H2O)2]n (2), two polymorphs of [Cd(L)(H2O)]n·(DMA)n (3 and 4), [Co4(L)4(H2O)3]n·(acetonitrile)n (5), [Mn2(L)2(H2O)]n·(acetonitrile)n (6) and [Cd2(L)2(H2O)]n·(DMA)n·1½(H2O)n (7) (H2L = 5,5′-methylenebis(oxy)dinicotinic acid; DMA = dimethyl acetamide) The hybrid metal–organic polymeric assemblies reveal diverse connectivity and topological features in one-, two- and three-dimensions, depending on the number of ligation sites available on the metal centers for binding the organic ligands and the nuclearity of connecting nodes. Compounds 1–4 involve mono-nuclear metal connectors and represent 1D and 2D coordination polymers. The three-dimensional single-framework polymers in compounds 5–7 are tessellated via dinuclear coordination nodes. Solid-state variable temperature magnetic susceptibility data of 5 and 6 involving the paramagnetic Co(II) and Mn(II) ions are reported as well. They reveal week anti-ferromagnetic coupling between the proxime metal centers observed in these two complexes.

Comparison Study on Thermal Performance of the RC Sandwich Panels with Different Connectors

To explore the thermal performance of RC Sandwich Panel with different connectors, three experiments were carried out to develop a study. In the experiments, three RC Sandwich Panels were manufactured using three kinds of connectors, the thermal performance of them was separately tested by corresponding device, and the thermal calculation of every panel was done according to the current thermal code. It is found that thermal performance of the three RC Sandwich Panels will be changed with connector’s variation. The results show that the thermal performance of RC Sandwich Panel using nonmetal connector is better than using metal connector, and the thermal performance of the RC Sandwich Panel using little section connector is better than using bigger section.

Structural Performance of Typical Beam-Column Joints in Yingxian Wood Pagoda - An Experimental Study

Yingxian Wood Pagoda, built in 1056, is located in the town of Yingxian County, Shanxi Province, China. It is the oldest and highest standing ancient wood structure in China. The pagoda is octagon-shaped in plan, with a total height of 67.31m and a base diameter of 30.27m. It appears as a five-storeyed structure, but actually consists of nine storeys, with four shorter but stiffer storeys hidden between the five apparent storeys. Yingxian Wood Pagoda was built without any metal connectors like nail, screw, or bolt. Instead, Tenon-Mortise connections and Dou-Gong brackets were used to connect all posts and beams. Tenon-Mortise connections and Dou-Gong brackets have been playing a vital role for the pagoda to resist severe winds, earthquakes and some human-induced disasters for nearly a thousand years. To evaluate the safety of the pagoda, it is, therefore, useful to investigate the structural performance of the beam-column joints, most important for Yingxian Wood Pagoda to resist lateral load. In this study, two models of typical beam-column joints of the pagoda, MBCJ-I and MBCJ-II, were manufactured following a ratio of 3.4 to the prototype of the joints. Non-destructive cyclic loading test of the models under different vertical load and destructive cyclic test of the models under vertical load of 20kN were conducted. The hysteretic stiffness of MBCJ-I was lager than MBCJ-II, and increased linearly with vertical load N. The relationship between and N was obtained by regression of the test results using the least square method. The stiffness of model joint under vertical load was 70.6kN/mm. The failure modes, energy-dissipation performance, moment resistance and bending stiffness of both model joints were derived and discussed.

Design optimization of bonded steel-concrete composite beams

Bonded steel-concrete is one new type composite structure in civil engineering domain. Generally, for steel-concrete composite structures, the steel beam and the concrete are connected by means of shear connectors. This work consists in analyzing the design optimization of the steel-concrete composite beam connected by adhesives instead of metal connectors. The principal parameters, including elastic modulus of adhesive, the adhesive layer thickness, the bonding strength and the bonding area, which influence the mechanical behaviours of the bonded steel-concrete composite structures, have been investigated. Finally, an example of design optimization of a single span adhesive bonded steel-concrete composite beam is proposed.

Multi-axis treatment of typical light-frame wood roof-to-wall metal connectors in design

Proper selection of metal roof-to-wall connectors is needed to provide a cost-effective load path to transfer uplift loads on a roof system down to the supporting walls and transfer lateral loads into and out of the roof diaphragm of light frame wood structures. Structural engineers, architects and builders rely upon published design values in catalogs, software, and websites provided by individual manufacturers to aid in the appropriate selection of connectors once the determination has been made for the required capacities of the connector. To date, the state-of-the-practice for dealing with multi-axis loads in these connectors is to use a linear unity equation based on uni-axis design values. However, no significant validation of this practice is to be found in the literature. This study experimentally examines three very common connector types under both bi-axis and tri-axis loads and helps to understand the behavior of such connectors under multi-axis loads. After testing over 350 connections and performing detailed analyses, the currently used design equation is found to be inefficient (has the least usable design space compared to other considered design equations) and overly conservative. Based on the criteria of efficiency, performance and safety, a design space using either the linear unity equation or by simply taking a 25% reduction on all allowable loads is proposed. The proposed design space for the three types of connectors is shown to have a high level of safety and adequate performance while providing up to 2.5 times the usable design space as compared with the current practice.

Triaxial Load Testing of Metal and FRP Roof-to-Wall Connectors

The allowable capacity of conventional roof-to-wall metal connectors is based on results of unidirectional component tests that do not simulate triaxial aerodynamic loading effects induced by high-wind events. The results of wind and wind-driven rain tests conducted at a full-scale facility were used to create a database on aerodynamic and aerohydrodynamic load effects on roof-to-wall connectors. Based on these results, three axial mean force components (triaxial mean loads) were combined into a series of resultant mean force vectors. A new test protocol was then developed for roof-to-wall connectors under simulated triaxial loading as opposed to simple uniaxial loading. The findings confirm that current testing methods tend to overestimate the actual load capacities of metal connectors. The performance of a nonintrusive roof-to-wall connector system using fiber-reinforced polymer (FRP) ties was also tested and compared with that of a traditional metal connector under simulated aerodynamic loads. The test...

From molecules to materials: Molecular paddle-wheel synthons of macromolecules, cage compounds and metal–organic frameworks

Metal-organic frameworks (MOF) are becoming a more and more important class of functional materials. Yet, very often, the synthesis of MOFs is not easy to control and requires a profound knowledge and experience in solid state chemistry. One of the most frequently used metal connectors is the so-called 'paddle-wheel' (PW) unit, which is a well-known molecular compound type in inorganic coordination chemistry. Depending on the ligands, the geometry of PWs strictly directs the assembly of ordered networks. This review focuses on the question, to what extent ordered network structures can be accessed by typical molecular syntheses in solution, starting from molecular PW complexes to ordered macromolecules, finite cage compounds and finally, three-dimensional superstructures.

Behavior of Light-Framed Wood Roof-to-Wall Connectors Using Aged Lumber and Multiple Connection Mechanisms

Ensuring a complete load path in light-framed wood structures is critical in providing proper load transfer during wind and seismic events. Roof-to-wall metal-connectors are often used to accomplish this goal. Currently, the design and construction community utilizes published metal connector capacities found in manufacturer documentation or other design aids to properly size connectors for a given demand. However, with the ever-increasing trend of using recycled dimensioned lumber and in situ retrofits of older buildings, the limited supply of research in this area is becoming more apparent. At present, the state-of-the-practice does not provide guidance to account for changes in material properties in structurally sound reclaimed or aged lumber. This study uses dimensioned lumber that was extracted from decommissioned buildings, originally built in the 1960s, to examine the effect of reclaimed dimensioned lumber on the design strength of connections by using metal-connectors. Through the use of testing ...

Nanoscale Ln(III)-Carboxylate Coordination Polymers (Ln = Gd, Eu, Yb): Temperature-Controlled Guest Encapsulation and Light Harvesting

We report the self-assembly of stable nanoscale coordination polymers (NCPs), which exhibit temperature-controlled guest encapsulation and release, as well as an efficient light-harvesting property. NCPs are obtained by coordination-directed organization of pi-conjugated dicarboxylate (L1) and lanthanide metal ions Gd(III), Eu(III), and Yb(III) in a DMF system. Guest molecules trans-4-styryl-1-methylpyridiniumiodide (D1) and methylene blue (D2) can be encapsulated into NCPs, and the loading amounts can be controlled by changing reaction temperatures. Small angle X-ray diffraction (SAXRD) results reveal that the self-assembled discus-like NCPs exhibit long-range ordered structures, which remain unchanged after guest encapsulations. Experimental results reveal that the negatively charged local environment around the metal connector is the driving force for the encapsulation of cationic guests. The D1 molecules encapsulated in NCPs at 140 degrees C can be released gradually at room temperature in DMF. Guest-loaded NCPs exhibit efficient light harvesting with energy transfer from the framework to the guest D1 molecule, which is studied by photoluminescence and fluorescence lifetime decays. This coordination-directed encapsulation approach is general and should be extended to the fabrication of a wide range of multifunctional nanomaterials.

Mismatched Connections

Historically, anaesthetic equipment manufacturers used a number of differently-sized connectors in anaesthetic breathing systems. This gave rise to the potentially dangerous possibility of mismatched taper connections and a failure to create a gas-tight breathing system capable of ventilating a patient. The British Standard 3849 of 1965 attempted to correct this problem but manufacturers' designs, in some cases, still caused problems. The problem was aggravated by a move to adopt a slightly different International Standards Organisation design. By the time that universally-interchangeable connectors were widespread twenty years later disposable breathing systems had replaced the old, heavy metal connectors.

Development of wooden block shear wall – Improvement of stiffness by utilizing elements of densified wood

Abstract The objective of this research was to study the performance of a wooden block shear wall which utilizes compressed wood as a connecting element in place of the traditional metal connectors. The compressed wood was made by compressing Japanese cedar (Cryptomeria japonica) to a compression ratio of 63% without fixation treatment. The connecting elements, namely diamond keys (DKs), recover their radial compressed dimension when absorbing moisture. The expansion of the wood causes a tighter fit of the wood blocks, thereby improving the system stiffness. DKs work as fuses by absorbing most of the stress and damage. This allows the structure to be readjusted and reused after earthquakes. The wooden blocks are made of glued-laminated timber based on European red pine (Pinus sylvestris). The behavior of the wall was studied by means of a finite element method (FEM) and full-scale shear tests. The material properties were found by performing mechanical tests, using digital image analysis, and strain gauges to measure the strain. The stiffness of the wall and how it is affected by the DKs are described. The FEM provided predictions which are in agreement with experimental results of wood block wall systems. The addition of DKs increased the stiffness by up to 2.5-fold. Future improvement of FEM will include accounting for the contribution of vertical connectors and out-of-plane forces.

Intermittent obstructive apnea in conscious rats

We developed a new method to intermittently obstruct the airway in conscious rats to replicate the hypercapnea and respiratory effort characteristic of sleep apnea. A teflon tube (6 mm long, o.d. 2.5 mm, i.d. 2.1 mm) was inserted in the trachea of adult male rats. This tube contained the tip of an inflatable balloon catheter made from polyurethane tubing (10 cm long, o.d. 1.0 mm, i.d. 0.6 mm, Scientific Commodities, USA). The open end of the balloon catheter left the trachea through the incision, and was led subcutaneously to a metal connector that was externalized between the shoulder blades. Thus inflation of the balloon catheter closed the trachea without causing pain. Rats rapidly regained body weight after surgery and appeared healthy, although breathing occasionally was audible during the subsequent 1 – 2 months. Inflation of the balloon for 10 sec with 15 μL water caused forceful breathing movements. Heart rate became irregular and fell by up to 200 beats/min, and these effects were blocked by pretreatment with 3 mg atropine. Balloon inflation increased blood pressure by up to 40 mm Hg, and caused caused alertness, locomotion and rearing. These effects disappeared almost instantly after disinflation. Inflations repeated every 3 min gave reproducible cardiovascular changes. This method seems suitable for the analysis of the effects of chronic intermittent apnea. Financial support: FAPESP, CNPq.

STRENGTH PERFORMANCE OF JOINT WITH BAMBOO CONNECTOR FOR TIMBER STRUCTURES

In timber structures, the easy dismantling method and easy segregating method are required for reuse and recycling of wood, as the environmental disruption is the problem to solve. We designed the new connecting system using adhesive and bamboo connector. The joint part composed of bamboo connectors and adhesive can be cut easily by a saw or chain-saw. In addition, the separation of metal connector from wood at joint is not necessary for reuse and recycle of the connected wood in timber structure. In this study, the some tests were carried out to confirm the strength of joints using the new connecting system with the bamboo connector. High strength performance can be obtained from the test results by laminated bamboo connectors.

External Force Assisted Nanorobotic Assembly of 3-D Helical Nanobelts

In this paper three-dimensional (3-D) suspended helical nanobelts (HNBs) with ultra-high flexibility are assembled by the external field guidance. Electromagnetic (EM) and electrostatic (ES) force by external potential are characterized quantitatively to guide the assembly of HNBs to create force sensing probe. Both ends of HNBs and target electrodes are attached with ferromagnetic metal connector. By the help of this hybrid nanorobotic assembly approach, we could successfully create force sensing probe by aligning and closing HNBs in vertical way and soldering to interconnect HNBs onto electrodes. Adhesive force between HNBs and electrodes are characterized to show its assembly performance quantitatively. The demonstrated approach shows that external force assisted assembly is an effective way for assisting serial nanorobotic assembly, interconnection soldering which may potentially reduce the production cost and time for future manufacturing realization.

In-depth temperature measurements in wood exposed to intense radiant energy

Modern timber construction techniques rely on metallic connectors. Their failure during fires is related to shear failure, which can happen at lower temperatures than those leading to pyrolysis. Based on this information, a series of tests were carried out exposing wood specimens to various heat fluxes in a Cone Calorimeter on a vertical configuration with no pilot ignition and a normal air atmosphere. The aim of this investigation was to develop a dependable temperature measurement methodology in wood samples exposed to high heat fluxes and to build a data-base in order to assess different wood pyrolysis models. The experiments yielded highly repeatable results that are hard to achieve with wood, although at lower heat fluxes the repeatability was poorer. The data were then normalized using a simple, inert, heat transfer model. It will be used as a tool to assess the importance of different terms that are incorporated in models that predict in-depth temperature profiles for wood. The samples behaved almost like an inert solid when subjected to low heat fluxes. Poorer repeatability at the lower levels of heat flux is justified by the beginning of pyrolytic reactions in wood at about 10 kW m −2.