Metal Ties Research Articles

Impacts of plastic-free materials on coral-associated bacterial communities during reef restoration.

Coral propagation and out-planting based restoration approaches are increasingly being applied to assist natural recovery of coral reefs. However, many restoration methods rely on plastic zip-ties to secure coral material which is potentially problematic for the marine environment. Plastic-free biodegradable alternatives may however pose unique risks to coral-associated bacterial communities integral to coral health. Therefore, to identify whether biodegradable materials differentially impact coral-associated bacterial communities we examined Acropora millepora coral-associated bacterial communities during propagation in two experiments on the Great Barrier Reef. Coral fragments were secured to coral nurseries with conventional plastic, metal, or biodegradable (polyester and polycaprolactone) ties. Tie failure and coral-associated bacterial communities were then characterized over six months. Minimal coral mortality was observed (3.6%-8%) and all ties had low failure rates (0%-4.2%) except for biodegradable polyester ties (29.2% failure). No differences were observed between coral-associated bacterial communities of fragments secured with different ties, and no proliferation of putatively pathogenic bacteria was recorded. Overall, our findings suggest that reducing reliance on conventional plastic is feasible through transitions to biodegradable materials, without any notable impacts on coral-associated bacterial communities. However, we caution the need to examine more coral taxa of different morphologies and new plastic-free materials prior to application.

The behaviour of orthodox historic churches built with lime mortar in Romania consolidated with reinforced concrete after the 1977 earthquake

In Romania, historic monuments have suffered significant damage after earthquakes. In the southern part of Romania, in the Oltenia region between the years 1838 and 1977, five strong earthquakes with magnitude exceeding 7 ML occurred, causing severe and repeated damage to Orthodox churches constructed with brick masonry and lime mortar. After the 1940 earthquake, consolidation was carried out with modern materials for that period, such as metal ties and reinforced concrete. Due to the collapse of the central tower made of brick masonry during the 1977 earthquake in the Church of the Holy Archangels Michael and Gabriel in Craiova, it was reconstructed using reinforced concrete columns and beams. Furthermore, the consolidation was carried out using reinforced concrete. Due to the different mechanical properties of historic brick masonry with lime mortar and reinforced concrete, cracks appeared over time on the church walls in the contact zones between these materials. Under the coordination of Bishop Irineu of Oltenia, consolidation works were initiated for 17 historic monument churches in the Gorj region after the earthquakes in 2023, and this Church in Craiova was included in the list. The article presents the modes and areas of damage resulting from the introduction of consolidations with irreversible materials, together with the results of in situ tests conducted by the EXPIN laboratory in Padua, Italy, to determine the mechanical properties of the load-bearing elements comprising the Church and structural analysis of the Church using ETABS software to predict past, present, and future behaviour.

Seismic damage and life cycle cost assessment of unanchored brick masonry veneers

This paper develops the seismic damage models of brick masonry veneer attached to the masonry infill without metal ties and assesses the life cycle cost of veneers subjected to earthquake excitation. Even though anchoring veneers to the backup wall has been prescribed in recent building codes, most of the existing brick veneers in seismic prone areas around the world lack the anchoring details. Besides, the damage and consequence models of masonry façades have not been presented in the FEMA-P58 database restricting detailed performance evaluation of buildings with unanchored masonry veneers. This study develops detailed finite element models to simulate various failure modes of the masonry veneer units and joint interface. The modeling procedure is validated by comparing the capacity curve and the crack pattern of simulation with those of an experiment conducted on a masonry brick wall in the literature. Then, a new procedure based on the endurance time dynamic analysis is proposed to generate fragility models for veneers and the backup masonry infill with lower computational demand than conventional methods. It is found that existing of the opening decreases the median collapse capacity of the façade by 25%. To demonstrate application of the developed fragility models, the life cycle costs of three types of veneer, brick façade, and two types of curtain walls, for a ten-story steel building are estimated using the FEMA-P58 procedure. It is concluded that using masonry veneer induces considerable damage and loss at lower levels of earthquake intensity compared to the curtain wall. Despite the lower initial cost of masonry façade, the total loss associated with these façades is almost 70% greater than the total loss of curtain walls.

SPECTROSCOPIC STUDY OF BARIUM STARS

We present the abundance results from the high-resolution spectral analysis of fifteen barium stars. The spectral resolution is R ~ 86000 with a wave length coverage of 3900 – 9000˚A. Stellar atmospheric parameters the effective temperature, surface gravity, metallic ties are determined from the local thermodynamic equilibrium analys is using model atmospheres. The effective temperature of the programme stars ranges from 3535 – 7656 K. The surface gravity covers a range from 1.17 – 4.07 cgs and metallicity ranges from -1.41 to - 0.13.We have also obtained temperature from photometric calculations and log g from parallax method. These values are found to match closely with the spectroscopic values within errors. The elemental abundances are determined from the spectrum synthesis calculation of clean and unblended lines due to neutral and ionized elements using iSpec. The abundances of elements such as O, Na, Mg, Ca, Sc, Ti, Mn, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Pr, Sm and Eu are determined. The star HD 22589 shows enhancement in Ba with [Ba/Fe] > 1.33. HD 40430 is found to be Ba normal with [Ba/Fe]0.10.The mass and the age of the programme stars are also determined from their locations in the H-R diagram. The estimated mass of the programmestars ranges from 1.20-4.50M☉ and age from 0.53to3.36Gyr

Effects of inter-cavity corrosion on metallic wall ties in masonry structures

<abstract> <p>An important structural component for cavity brick and masonry-veneer construction are wall ties. Typically, they are galvanized steel, sufficiently strong to provide continuity for transmission of direct and shear forces. However, field observations show they are prone to long-term corrosion and this can have serious structural implications under extreme events such as earthquakes. Opportunistic observations show corrosion occurs largely to the internal masonry interface zone even though conventional Code requirements specify corrosion testing for the whole tie. To throw light on the issue electrochemical test for 2 grades of galvanized ties and 316 stainless steels combined with three different mortar compositions are reported. Most severe corrosion occurred at the masonry interface and sometimes within the masonry itself. Structural capacity tests showed galvanized ties performed better than stainless steel ties in lieu of stainless steel R4 class ties presenting significantly greater relative losses of yield strength, ultimate tensile strength and elongation structural capacity compared to R2 low galvanized and R3 heavy galvanized tie classes.</p> </abstract>

Mechanical modelling of the axial behaviour of traditional masonry wall metal tie connections in cavity walls

The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is a relevant issue in many countries, such as in Central and Northern Europe, Australia, New Zealand, China and several other countries. A cavity wall consists of two separate parallel masonry walls (called leaves) connected by metal ties: an inner loadbearing wall and an outer veneer having mostly aesthetic and insulating functions. Cavity walls are particularly vulnerable structural elements. If the two leaves of the cavity wall are not properly connected, their out-of-plane strength may be significantly smaller than that of an equivalent solid wall with the same thickness.The research presented in this paper focuses on a mechanical model developed to predict the failure mode and the strength capacity of metal tie connections in masonry cavity walls. The model considers six possible failures, namely tie failure, cone break-out failure, pull-out failure, buckling failure, piercing failure and punching failure. Tie failure is a predictable quantity when the possible failure modes can be captured. The mechanical model for the ties has been validated against the outcomes of an experimental campaign conducted earlier by the authors. The mechanical model is able to capture the mean peak force and the failure mode obtained from the tests. The mechanical model can be easily adopted by practising engineers who aim to model the wall ties accurately in order to assess the strength and behaviour of the structures against earthquakes. Furthermore, the proposed mechanical model is used to extrapolate the experimental results to untested configurations, by performing parametric analyses on key parameters including a higher strength mortar of the calcium silicate brick masonry, a different cavity depth, a different tie embedment depth, and solid versus perforated clay bricks.

Experimental characterization of the axial behavior of traditional masonry wall metal tie connections in cavity walls

In recent years, the number of human-induced earthquakes in Groningen, a large gas field in the north of the Netherlands, has increased. The majority of the buildings are built by using unreinforced masonry (URM), most of which consists of cavity (i.e. two-leaf) walls, and were not designed to withstand earthquakes. Efforts to define, test and standardize the metal ties, which do play an important role, are valuable also from the wider construction industry point of view. The presented study exhibits findings on the behavior of the metal tie connections between the masonry leaves often used in Dutch construction practice, but also elsewhere around the world. An experimental campaign has been carried out at Delft University of Technology to provide a complete characterization of the axial behavior of traditional connections in cavity walls. A large number of variations was considered in this research: two embedment lengths, four pre-compression levels, two different tie geometries, and five different testing protocols, including monotonic and cyclic loading. The experimental results showed that the capacity of the connection was strongly influenced by the embedment length and the geometry of the tie, whereas the applied pre-compression and the loading rate did not have a significant influence.

EXPERIMENTAL INVESTIGATION OF PULL OUT STRENGTH OF FLEXIBLE TIES IN THIN BRICK VENEER LAYER

The use of thin brick veneer layers for building facades becomes more popular nowadays. Using thin bricks (50−65 mm thick) instead of normal 100−120 mm thick bricks let us to save expenses up to 50% related to materials. The connection of thin veneer layer with inner construction wall must be assured. Usually, the connection is fulfilled using flexible metal or composite ties. The main issue for this connection is tie pull out strength from thin brick masonry. This strength depends on type and construction of ties and it governs the number of ties need for facades. This article describes experimental research of pull out strength of flexible steel ties in thin brick masonry. Two possible anchoring types were used. Experimental test results and analysis are described in the article.

A service life model of metal ties embedded in the mortar joints of brick veneer walls with applications to reinforced concrete

The issue regarding the corrosion of steel ties connecting brick veneer to a structural backing is well documented. In this paper, the predicted corrosion rate and resulting service life estimates, produced by a time-stepped service life model developed in Visual Basic for EXCEL, for metal ties embedded in mortar, are compared with the empirically determined corrosion rates and service lives of 16 zinc galvanized tie specimens taken from 13 buildings located in 6 different Canadian cities. This tie service life model, coined the “Tie Service Life Predictor”, correlates the external environment of the building to the tie life. As with most corrosion models for steel embedded in concrete (or mortar), the model is broken into two distinct phases: corrosion initiation using Fick’s law of diffusion and corrosion propagation. By considering the mortar surrounding the tie as the tie’s atmosphere, the Tie Service Life Predictor characterizes the microenvironment (atmospheric conditions) surrounding the tie from the macroenvironment conditions. Once the atmospheric conditions were established, the ISOCORRAG atmospheric corrosion model could be used to predict the corrosion rate of zinc galvanized steel ties embedded in the mortar joints of the exterior wythe of brick veneer wall systems. The methods used to create the Tie Service Life Predictor could also be applied to service life estimation of reinforcing steel in concrete structures such as bridge decks and parking structures.

Metal Ties in Genoa, Italy: Manufacture, Trade, and Use from the 15th to the 18th Century

ABSTRACTThe article deals with the use of metal ties in an ancient and stratified urban context, the city of Genoa, starting from the notarial documents preserved in its State Archives. The work has different objectives: to show the results that can be obtained, on an urban scale, thanks to a research path that compares indirect sources of different types with the observation of historical buildings; to highlight the “weight” and the role that the ties, often hidden, had in buildings, and not only the monumental ones; to increase knowledge of the production process of this constructive element. The wide and diversified use of metal ties found in Genoa seems to proceed in parallel, in the 15th century, with the development of a flourishing productive and mercantile business based on the commercial monopoly of the hematite of the island of Elba by the city oligarchy and, between the 16th and 17th centuries, with the huge investments in the construction sector highlighted by the abundant documentary sources.

Two-way bending out-of-plane collapse of a full-scale URM building tested on a shake table

This paper describes a shake table test on a one-storey full-scale unreinforced masonry structure, which complements an earlier testing of a two-storey structure with similar characteristics. The building specimen was meant to represent the upper floors of the end-unit of a terraced house, built with cavity walls and without any particular seismic design or detailing. In these specimens, the masonry walls were composed of two leaves: a load-bearing inner one made of calcium silicate bricks sustaining a reinforced concrete floor and an external leaf made of clay-bricks connected to the inner leaf by means of metallic ties. A pitched timber roof was supported by two triangular gable walls. Floor acceleration response histories of the previously tested two-storey specimen were used as input motions. An incremental dynamic test, with vertical and horizontal inputs, was carried out up to the explicit collapse of some bearing elements of the structure. In particular, a two-way bending out-of-plane collapse of a load-bearing wall was observed and described.

Shaking table test on a full scale URM cavity wall building

A shaking table test on a two-storey full scale unreinforced masonry (URM) building was performed at the EUCENTRE laboratory within a comprehensive research programme on the seismic vulnerability of the existing Dutch URM structures. The building specimen was meant to represent the end-unit of a terraced house, built with cavity walls and without any particular seismic design or detailing. Cavity walls are usually composed of an inner loadbearing leaf and an outer leaf having aesthetic and weather-protection functions. In the tested specimen, the loadbearing masonry was composed of calcium silicate bricks, sustaining two reinforced concrete floors. A pitched timber roof was supported by two gable walls. The veneer was made of clay bricks connected to the inner masonry by means of metallic ties, as seen in common construction practice. An incremental dynamic test was carried out up to the near-collapse limit state of the specimen. The input motions were selected to be consistent with the characteristics of induced seismicity ground motions. The article describes the characteristics of the building and presents the results obtained during the material characterization and the shaking table tests, illustrating the response of the structure, the damage mechanism and its evolution during the experimental phases. All the processed data are freely available upon request (see http://www.eucentre.it/nam-project ).

Influence of ligation method on friction resistance of lingual brackets with different second-order angulations: an in vitro study.

ABSTRACTObjective: To evaluate stainless steel archwire static friction in active and passive self-ligating lingual and conventional brackets with second-order angulations. Methods: Two conventional lingual brackets for canines (STb light/Ormco; PSWb/Tecnident), and two self-ligating brackets, one active (In-Ovation L/GAC) and the other passive (3D/ Forestadent), were evaluated. A stainless steel archwire was used at 0°, 3° and 5° angulations. Metal ligatures, conventional elastic ligatures, and low friction elastic ligatures were also tested. A universal testing machine applied friction between brackets and wires, simulating sliding mechanics, to produce 2-mm sliding at 3 mm/minute speed. Results: Two-way analysis of variance demonstrated a significant effect of the interaction between brackets and angulations (p < 0.001). Tukey test indicated that the highest frictional resistance values were observed at 5° angulation for In-Ovation L, PSWb bracket with non conventional ligature, and STb bracket with metal ligature. As for 3D, PSWb with conventional or metal ligatures, and STb brackets with non conventional ligature, showed significantly lower static frictional resistance with 0° angulation. At 0° angulation, STb brackets with metal ties, In-Ovation L brackets and 3D brackets had the lowest frictional resistance. Conclusions: As the angulation increased from 0° to 3°, static friction resistance increased. When angulation increased from 3° to 5°, static friction resistance increased or remained the same. Self-ligating 3D and In-Ovation L brackets, as well as conventional STb brackets, seem to be the best option when sliding mechanics is used to perform lingual orthodontic treatment.

Out-of-plane shaking table tests on URM single leaf and cavity walls

Damage observations from recent seismic events have confirmed that the activation of out-of-plane local mechanisms is one of the major causes of structural collapse in unreinforced masonry buildings. Particularly vulnerable are cavity walls commonly used in residential building in regions such as Central and Northern Europe, Australia, New Zealand, China and several other countries. Usually, the inner leaf has a load-bearing function, carrying vertical loads transmitted by floors and roof while the outer leaf, having only aesthetic and insulation functions, is lightly loaded. The two leaves are typically connected by means of metallic ties. The high out-of-plane vulnerability, which may prevent the exploitation of the global capacity associated with the in-plane capacity of the structural walls, is mainly due to the high slenderness of the masonry leaves and the lack, or ineffectiveness, of ties between leaves. Often ties are too widely spaced and/or heavily degraded. Despite the complexity of the composite behaviour of such a construction typology, no dynamic tests on cavity walls are reported in current literature. For this reason, four out-of-plane shaking table tests were conducted on full-scale unreinforced masonry assemblies of three cavity wall panels with different tie distributions (inner calcium silicate brick wall and outer clay brick wall) and one single-leaf wall constructed using calcium silicate brick masonry. The experimental arrangement allowed the specimens to be tested under different input signals and loading conditions, inducing an out-of-plane one-way bending action in the walls. The research is aimed at understanding the seismic behaviour of cavity walls, their failure mechanisms and how they are affected by boundary conditions and degree of connection between the two leaves. The paper describes the main experimental results, including deformed shapes, damage patterns, force-displacement relationships, and the capacities in term of acceleration sustained by the specimens. Additionally, the energy dissipation involved in the mechanism has been investigated in terms of coefficient of restitution and damping ratio. All the processed data are freely available upon request (see http://www.eucentre.it/nam-project).

On the damage of frescoes and stuccoes on the lower surface of historical flat suspended light vaults

Abstract In many historical and monumental Italian buildings, frescoes or stuccoes of artistic and historical value are present on the lower surface of flat light vaults, made by wooden arches, reeds and plaster. These vaults are often suspended by wooden or metallic ties to the upper bearing structures. When differential settlements of the wooden arches happen (i.e.: due to a bad working of their hangings) cracks appear on these precious surfaces. This paper experimentally and numerically investigates on this issue, pointing out which constructive parameters mainly influence the cracking behaviour of the frescoed or stuccoed lower surface, and thus providing guide lines for designing compatible conservation and retrofitting interventions.

Changes in oral trace gas concentrations following orthognathic surgery and intermaxillary fixation: a case study using selected ion flow tube mass spectrometry

Orthognathic surgery is frequently accompanied by intermaxillary fixation. Intermaxillary fixation impedes the maintenance of effective oral hygiene and prolonged fixation can result in periodontal disease. A potential shorter term effect is the generation of oral malodour. It is unclear, however, as to how the production of malodorous compounds in the oral cavity is altered post-surgery. Oral air concentration of sulphur containing compounds, short chain organic acids, ammonia, isoprene and acetone were measured using selected ion flow tube-mass spectrometry in a patient who had undergone orthognathic surgery with subsequent intermaxillary fixation. Total sulphide levels rose approximately 5-fold during fixation with metal ties, with smaller increases recorded for the other compounds measured with the exception of isoprene which remained close to baseline levels. Organic acid levels declined markedly once elastic ties had replaced metal ties, with a lesser reduction being observed in sulphide levels, with both declining further after the commencement of a chlorhexidine-containing mouthwash. These data suggest that bacterial generation of a variety of malodorous compounds increases markedly following intermaxillary fixation. This single case also suggests that the use of elastic ties and effective oral hygiene techniques, including the use of chlorhexidine mouthwash, may help ameliorate such post-surgical effects.

Shear Behavior of Corrugated Tie Connections in Anchored Brick Veneer–Wood Frame Wall Systems

An experimental study was carried out to investigate the shear behavior of corrugated metal ties anchoring brick veneer walls to light wood frame backing. Connection subassemblies were tested under monotonic and cyclic shear, simulating in-plane loading of veneer wall systems, and statistical analyses were conducted to identify and quantify the parameters influencing their behavior. Force-displacement curves obtained under monotonic loading can be considered an upper bound for the hysteresis loop envelopes. Fastener slippage during cyclic loading enabled by the localized damage of the surrounding wood fibers diminished the energy dissipation capacity of the connection and caused pronounced pinching in the hystereses. When corrugated ties with minimum thickness permitted by the Masonry Standards Joint Committee (MSJC) Code were considered under in-plane loading, tie design and bend eccentricity were found to be the most important factors, while tie location in the bed joint, fastener type, and fastener qua...

Out-of-Plane Seismic Performance and Detailing of Brick Veneer Walls

The out-of-plane seismic performance of residential brick veneer walls built over wood-frame backup was evaluated as a function of construction detailing. Shake table tests were conducted on a full-scale brick veneer wall panel, with a window opening, representing the gable-end wall of a typical home structure; the structural performance of corrugated sheet metal veneer-to-wood tie connections was also characterized by separate laboratory testing. The wall panel test specimen was prepared following typical construction practice for brick veneer wall systems, in general conformance with current specified prescriptive design and construction requirements. The shake table tests captured the performance of the brick veneer wall system, including interaction and load-sharing between the brick veneer, corrugated sheet metal ties, and wood-frame backup. Detailed three-dimensional finite-element (FE) models were also developed representing the full-scale brick veneer wall panel specimen, including nonlinear inelastic properties for the tie connections. After calibration based on test results, the FE wall panel model effectively captured static and dynamic experimental brick veneer wall behavior at different response levels, up to and including tie damage and even instability/collapse of the wall panel. Parametric studies were then carried out using FE wall panel models to evaluate the effects of certain types and layouts of tie connections, as well as geometric variations in brick veneer wall construction. Overall seismic performance of brick veneer walls was closely related to the individual tie connection deformation limits, especially for damage in tension. The grid spacing of tie connections, as well as tie installation along the edges and in upper regions of the walls, controlled the ultimate behavior of the brick veneer wall panels. Design guides, codes, and current construction practices have been evaluated in light of the overall findings from these experimental and analytical studies.

Use of waste tyre bales to construct a flood embankment

A case study in the use of tyre bales in the design of a UK flood embankment is presented and the legal, technical and environmental issues are briefly discussed. A few major risks in the use of tyre bales in a flood prevention embankment—such as possible buoyancy of the tyre bale under water, possible piping of underlying soil and overlying capping soils due to their extremely high permeability, possible rebound of the bales upon release or deterioration of metal ties, release of unacceptable leachate to the controlled water from old tyres—were taken into consideration in the design stage and necessary steps and precautions were adopted. The use of tyre bales on the project provided a cost-effective and environmentally sustainable solution and has potentially paved the way for other applications. The pilot project scheme, which is now complete, has used around 1 million tyres, which is approximately 10% of the total number of tyres that would normally go to landfill in any one year in the UK.

Bipolar pulse coagulation for resection of the cirrhotic liver

Background: The major technical challenge of liver surgery is controlling bleeding during transection of the parenchyma. The aim of this study was to compare the effectiveness of the traditional “clamp crush” technique (CCT) with that of a vessel sealing system that uses the Gyrus hand piece (GHP) in controlling bleeding during liver resection. The GHP is a bipolar cautery pulsation instrument that is similar in design to a large hemostat clamp that divides tissue while the clamp remains closed. The advantage of the GHP is that it can be used in the traditional “clamp crush” manner, but, unlike traditional CCT, does not require metal clips or ties. Methods: We retrospectively analyzed the peri-operative data from 10 patients with early cirrhosis (grade 1-2 fibrosis) who underwent liver resection for hepatocellular cancer between February 2004 and July 2005. Five resections were performed using CCT and five were performed using the GHP. Data are presented as means ± standard error (SE). This was a retrospective study of a nonrandom sample of patients, thus we present the descriptive data. Results: Eight patients underwent minor hepatectomy (< 3 segments) and two underwent major hepatectomy (> 3 segments). When the CCT was used, the average Pringle time was 13 ± 3 min, mean blood loss was 630 ± 67 ml, and mean operative time was 312 ± 29 min. When the GHP was used, the mean Pringle time was 13 ± 5 min, mean blood loss was 520 ml ± 118, and mean operative time was 252 ± 15 min. There were 3 major complications in the CCT group and 2 in the GHP group. Major complications included transient hepatic failure (i.e.ascites / encephalopathy) and biloma. One patient from each group suffered a minor wound complication. The average hospital stay was 8 days (range 7-10) for the CCT group, and 8 days (range 6-9) for GHP group. The operative mortality was 0%. Conclusion: The GHP appears to provide an excellent and safe alternative to CCT for dividing the liver parenchyma in cirrhotic patients.