Slip Resistance Research Articles

Test on shear behavior of less-tightened high-strength bolted connections

This paper conducts an experimental study on the mechanical properties of less-tightened high-strength bolted connections composed of 8 bolts under the action of double shear. 63 groups of connections were tested in the experiment, of which 60 groups were tested in different percentage reduction of clamping force and the other three groups were tested with standard clamping force as control groups. The effects of the percentage reduction of clamping force of less-tightened bolts, the number of less-tightened bolts, and the thickness of core plate on the bearing behavior of bolted connections were analyzed. The effects of the three parameters on the failure mode, strain distribution, slip resistance, ultimate bearing capacity, ductility, and initial stiffness of bolted connections are studied. As can be seen from the failure mode, all specimens showed bolt damage, which was cut off on one side and twisted on the other side. The test results revealed that the decrease of clamping force exerts a negative impact on the slip resistance, and the ultimate bearing capacity of less-tightened bolted connections. These capacities of the specimens are reduced significantly with the increase of the percentage reduction of clamping force and the number of less-tightened bolts, while the thickness of the core plate has slight effect on these performances. In addition, with the decrease of the clamping force, the ductility of the specimen increases, while the increase of the thickness of the core plate will decrease the ductility of the specimen. Further, the influence of these factors on the initial stiffness of the specimens can't be ignored. By comparing with specifications, the modified formula of ultimate bearing capacity of bolted connections with reduced clamping force is put forward.

Performance of Porous Slabs Using Recycled Ash.

Permeable concrete is an environmentally friendly material that improves water permeability and slip resistance. The manuscript describes a new study aimed at improving the strength of permeable concrete obtained using local materials for the partial replacement of cement with rice and wheat straw ash due to the high amount of silica and pozzolanic characteristics present in the ash. For this purpose, nine concrete mixes were made (Phase I). The mixes were classified into four groups: Group A, with cement/aggregate ratios of 0.23, 0.34, and 0.44 for Mixes 1, 2, and 3, respectively; Group B, with sand added at 10% and 15% to the coarse aggregate for Mixes 4 and 5; Group C, with rice straw ash replacement ratios of 10% and 15% in the cement for Mixes 6 and 7; and, finally, Group D with wheat straw ash replacement ratios of 10% and 15% in the cement for Mixes 8 and 9. For Groups B to D, the water/binder ratio was 0.238. Fresh and hardened concrete tests were conducted. The results showed that Mixes C and D, which contained rice and wheat straw ash, increased the compaction factor due to their spherical shape and higher surface area compared with traditional pervious concrete. Additionally, permeability and porosity increased slightly for the mixes using rice and wheat straw ash. This could be attributed to increasing the interconnected voids. Optimum porosity was reached with 15% rice straw ash. The optimum mix design from Phase I was used in Phase II. Therefore, six pervious concrete slabs, reinforced with different types of reinforcement, were tested under flexural load. With the help of ANSYS, a finite element model was created to verify the results of experiments. The results of the numerical simulation are consistent with the results of the experiment. This article represents a definite step to new knowledge in the field of research of permeable concrete obtained using the partial replacement of cement with rice and wheat straw ash. Hence, this form of concrete can be used for parking lot paving, sludge beds for sewage plants, swimming pool surfaces, bridge walkways, zoo area floors, and animal barns. This concrete can also be used in applications requiring lightweight concrete.

Application of Waste Plastic Films in Road Infrastructure and Construction

Recycling waste synthetic resins, including rigid and film plastics, is a pressing issue worldwide due to the issues associated with waste treatment. Using products originating only from plastic wastes could be a promising way to improve the waste recycling rate and address plastic consumption. This study presents the applications of waste plastic films (WPFs) in urban infrastructure and construction materials, especially bearing loads. WPF-recycled products (WPF-RPs) were evaluated for mechanical properties, including strength (compressive and tensile), thermal expansion coefficient, accelerated weathering, dynamic stability, and environmental aspects, such as the presence of hazardous substances. Subsequent tests confirmed moderate strength, good weathering stability against solar irradiation, and superior road pavement vehicle load through wheel-tracking tests compared with the standards for asphalt. Additionally, hazardous substances were mostly not detected or were under permissible limits in the composition and leachate contents of WPF-RPs. After using temporary pavement blocks (TPBs) from WPFs at a field site for one month, we conducted slip resistance tests which gave a result of ~33 British pendulum number, indicating the possible application of WPF-RPs in low-speed driving sections, according to the Korean standards of the Ministry of Land, Infrastructure and Transport. Moreover, it was confirmed that fastening structures installed between the TPBs can improve backfilling and compaction defects. This practical research highlights the possible applications of products produced from WPFs for infrastructure development, such as filling materials for burial pipes or tubes; however, these potential aspects should be tested further.

Human Slip Assessment of Candidate Reference Surfaces for Walkway Tribometer Validation: An Update to Standard ASTM F2508

Previous studies have reported on the concept of using human subjects to rank and differentiate walkway surfaces that vary in slipperiness. Surfaces identified as having different levels of slipperiness, based on the outcomes of human subject walking trials, are then used to validate tribometer slip resistance measurements. This concept was adopted in the development of ASTM F2508-11, Standard Practice for Validation and Calibration of Walkway Tribometers Using Reference Surfaces. Because of a depleting supply of the reference surfaces cited by ASTM F2508, new reference surfaces are needed. In this study, our objective was to assess new candidate reference surfaces to update the ASTM F2508-16, Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces. One hundred and forty-eight human subjects walked across four ceramic-based tiles (E, F, G, and H) under contaminated conditions. Our results revealed that, consistent with our prior studies, human subjects were able to rank and differentiate surfaces according to slipperiness. Moreover, the surfaces evaluated in this study demonstrate characteristics that make them suitable replacements for the ASTM F2508 reference surfaces. Based on our findings, we recommend that ASTM F2508 be updated using surfaces E, F, and G and that surface G be considered a candidate to establish a slip resistance threshold for walking.

Affordable 3D-printed tendon prosthetic hands: Expectations and benchmarking questioned

The popularization of 3D-printing has allowed enhancing affordable prostheses for persons with amputations in developing countries, yet manufacturers are not subjected to any control from any medical regulatory authority. Adopted evaluation protocols seem to cherish optimistic expectations. A reduced performance test, derived from the Southampton Hand Assessment Procedure and two bench tests, to evaluate the mechanical advantage in the fingers and the slip resistance, are proposed to assess affordable tendon-driven devices. Ultimately, five models amongst those most commonly found in the scientific literature and the Internet have been evaluated. Three subjects participated with the aid of an able-bodied adaptor. The reduced test of performance provides consistent results but with a more direct interpretation of the failed patterns of prehension. All these models create far more expectations than the results deliver. With the supplementary material provided, an affordable benchmarking can be established with this reduced performance test and the two bench tests. They can lead to improved designs, prescriptions and regulations.

Microstructural evolution in pure copper during accumulative skin pass rolling: experimental and crystal plasticity numerical investigations

Surface mechanical treatments are known to introduce deformation heterogeneity, thus entailing a combination of excellent strength and ductility in metallic metals. Accumulative skin pass rolling (ASPR) was employed to introduce heterogeneous structure in pure copper, which significantly improved yield strength and maintained high ductility. The experimental observations of the ASPR processed copper showed that surface grains possessed a much larger magnitude of misorientations and geometrically necessary dislocations (GNDs) than the centre grains. Crystal plasticity finite element modelling was utilised to provide an in-depth understanding of microstructure evolution during ASPR. It was found that the surface grains accommodated higher shear strain and had higher slip resistance than the centre grains. The multiple active slip systems in the surface grains induce the lattice rotations and then the formation of intragranular misorientations accompanied by a high density of GNDs, while the single active slip system in the centre grains can accommodate the applied material rotation without the lattice rotation.

Experimental study of slip‐resistant connections under cyclic load

AbstractThe slip‐resistant shear connections with preload bolts have traditionally use in the steel structures exposed to cyclic / fatigue loading or in the cases when the bolt slipping or connection deformations should be restricted. Hence, the shear load is transferred through the friction surfaces rather than the contact between bolt surface and hole. The main influencing parameters determine the connection slip resistance are the friction between the contact surfaces and the level of preload in the bolts. This paper presents an experimental study of preloaded bolted connections under cyclic load. Experiment was performed on double lap shear connections using high strength bolts and lock bolts, both M20 of grade 10.9. The steel plates used in experiment are grade S355JRG2. Sandblasting was performed using quartz sand as the abrasive after which the zinc‐silicate coating was applied on plate surfaces. To address the required pretension force in the bolts, the strain gauge method was employed. All strain gauges were calibrated. Six specimens were exposed to cyclic loading after monitoring initial and short‐term losses of pretension forces in the bolts. The main objective of the presented study is to investigate the influence of the cyclic load on the losses of pretension force in high strength bolts and lock bolts. The results of comparative experimental analysis are presented and discussed.

Variability of Friction Measurements Using Three Common Walkway Tribometers

Abstract Walkway tribometers are used to assess the slip resistance of flooring surfaces. To yield valid measurements, the ASTM F2508-16e1, Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces, standard practice requires an annual calibration to show a tribometer’s test results fall within the 95th percentile confidence intervals (CI) of its supplier’s validation test results on 4 reference surfaces. Many users, however, report difficulty meeting this requirement. Here we examine the variability within and between multiple calibrations to evaluate the current calibration procedure and assess whether field measurements of a surface can be directly compared to calibration test results. We performed multiple calibrations with three common walkway tribometers on one set of reference surfaces. We then simulated field tests on each reference surface and compared these results to the calibration test results. Overall, all three tribometers ranked and differentiated the reference surfaces in all calibrations; however, none of the calibrations fell within the supplier’s CIs for all four surfaces. The between-calibrations variance ranged from 15 % to 90 % of the total variance in the data set, and only 25 % of the “field” test results fell within the 95th percentile CI of our calibration values. Our findings show that the current ASTM F2508 calibration requirement does not adequately account for measurement variability. Moreover, our findings indicate that field measurements should not be compared directly to calibration measurements without factoring in measurement uncertainty. Overall, our results show the need for an improved calibration procedure and more research to establish a valid method for estimating slip risk on field surfaces.

The impact of heterogeneous microstructural features on crystal plasticity modeling of plastic anisotropy

Crystal plasticity finite element models typically assume each grain starts with a spatially uniform dislocation distribution, meaning each grain is initialized with a single lattice orientation and all grains share the same slip resistance. This study assessed that assumption by comparing crystal plasticity simulations of tensile tests against experiments on an extruded aluminum 7079 alloy. The simulations utilized computational microstructures with ‘pancaked’ grains and a significant degree of crystallographic texture, consistent with experimental measurements. In one case, the computational microstructures were assigned a single slip resistance and a single lattice orientation for each grain prior to the tension tests. In another case, the extrusion process prior to the tension tests was simulated to cause nonuniform slip resistances, nonuniform crystal orientations within each grain, and nonuniform slip resistances at each material point. Both approaches produced reasonably accurate predictions of the measured yield stress and lateral strain ratio anisotropy, but the predictions considering the initial nonuniformity exhibited less prediction error. Other factors, such as latent vs self hardening of slip systems and fine vs coarse grains, did not have as large an impact. These results suggest that dislocation heterogeneity should be experimentally characterized and fed into future crystal plasticity simulations.

Modeling cyclic plasticity of additively manufactured alloy Mar-M-509 using a high-performance spectral-based micromechanical model

A high-performance full-field spectral crystal plasticity model referred to as MPI-ACC-EVPCUFFT is adapted to study the deformation behavior of additively manufactured Mar-M-509® cobalt-based superalloy. The model features a dislocation density-based hardening law for the evolution of slip resistance, a barrier effect induced by grain morphology to influence the slip resistance, and a slip system-level back-stress law for adjusting the driving force to slip. The model is used to interpret and predict strength of the alloy in tension, compression, load reversal, and low-cycle fatigue as a function of initial microstructure. The initial microstructure varied from sample-to-sample to represent the effects of build orientation and heat treatment. Results show that the model successfully reproduces phenomena pertaining to monotonic and cyclic deformation including the non-linear unloading, Bauschinger effect, and cyclic hardening/softening using a single set of model parameters. Moreover, the model offers insights into fluctuations of mechanical fields and strain partitioning.

Lithology, physical and mechanical characterization of Chinese Porphyry

A thorough characterisation of porphyry from China (Province of Fujian) was made, regarding three chromatic variants: red, brown and grey. The properties object of study are: petrographic, chemical and mineralogical analysis, real and apparent density as well as open and total porosity, water absorption at atmospheric pressure, resistance to salt crystallization, rupture energy, compressive strength, flexural strength, abrasion resistance and slip resistance. The achieved results remain into the expected ones for this kind of stone. Nevertheless, small differences were found according to the colour of the sample. Finally, those properties which are covered in the CE marking were compared with the representative values of commercial samples from countries as Italy, Argentina and Mexico.

Safety Comes First: Novel Styrene Butadiene Rubber (SBR) and Ethylene Propylene Diene Monomer (EPDM) Surfaces as a Response to Sport Injuries

An athlete’s performance depends not only on the shoes they wear but also on the surface used in sports facilities. In addition, it can significantly contribute to reducing injuries, which are easy to get during sports competitions. In the present study, we wanted to investigate whether recycled styrene butadiene rubber (SBR) and ethylene propylene diene monomer (EPDM) could be used in the production of sports surfaces. For this purpose, we designed three different sports surfaces: (1) SBR covered with a thin EPDM spray layer on the top, (2) clean EPDM, and (3) bottom SBR layer with the top layer of EPDM. The test program of these surfaces included in its scope: shock absorption, vertical deformation, tensile strength, abrasion resistance, and slip resistance tests. Our research also involved the influence of the substrate under surface, temperature, and surface conditions. Presented results show that both materials, in the right proportions, can be used in the production of sports surfaces.

Dynamic mechanical analysis as a predictor for slip resistance and traction in footwear

Adequate friction between footwear and surface is essential to reduce the risk of slipping (Chang et al., 2001) and maximise athletic performance (Luo & Stefanyshyn, 2011). Footwear outsole materia...

Utilization of Waste Plastic for Construction of Flexible Pavement

The major threat to the environment is the disposal of waste plastic and on the other side; the road traffic intensity is increasing. The load bearing capacity of roads are increasing. This study discusses the suitability of plastic waste for construction of roads. A material that contain more organic polymer of large molecular weight, solid in its finished state, can be shaped by its flow is called as “plastic”. Generally plastic is used in various domestic and industrial applications. In the Current Period Use of plastic bags and bottles is very common. Use of plastics in road construction can reduce the cost of road construction and pollution index of environment to an appreciable extent. Use of this mix for road construction it helps to reduce or use plastic waste effectively. Use of waste plastic in construction material is becoming more and more acceptable due to the improved properties. Due to use of waste plastic the Cost of construction materials also decreases. When we use the waste plastic in flexible pavement it improves the abrasion & slip resistance of asphalt pavement. It is economical and eco-friendly.

Using Granular Waste Tire as a Factor to Increase Shear Strength of Cohesionless Soils

Soils are called problematic soils when they do not have sufficient bearing strength to provide a founda-tion for the structures to be built on them and these types of soils need to be improved with appropriate methods depending on their properties. Improvement methods applied to strengthen soils often cause financial burden. Recently, there are studies about the use of waste rubber tires, which pose an environ-mental risk during storage, as a reinforcement material for soils. The main purpose of this study is to examine the effect of poorly graded sand (SP) mixed with granular waste tires in different proportions (10%, 20%, 30%, 40% and 50%) on the shear strength of the sand. For this purpose, the physical (water content, specific weight, unit weight) and mechanical (shear strength) parameters of the mixtures were determined. According to the results of the research, the material with 100% sand content contributes to the shear strength by a certain proportion when compared to the mixed materials containing granular-sized waste rubber. According to the results of this research, the highest slip resistance value was observed in material with 20% tire content in waste rubber sand mixtures, while higher rates of tire addition provided lower results than 100% sand material. In addition, considering the issue in terms of environmental im-pact, a column test was carried out on the mixture containing 20% rubber-80% sand and no adverse ef-fects of the pollutants were observed.

Emerging safety risks from public facilities: a field study for ablution spaces in mosques

PurposeMuslims require an exclusive ablution space for preparing for daily prayers in mosques. Ablution floors seem to entail design challenges since they are often encountered in lubricated conditions from worshippers’ body cleaning manoeuvers. Accordingly, fall risks on saturated surfaces of ablution floors would be a major issue to Muslim worshippers. Thus, the purpose of this study is to investigate the safety status of mosque ablution floors in terms of slip resistance properties and surface texture.Design/methodology/approachFifteen mosques in Dubai and Sharjah cities of the UAE were randomly chosen to investigate the safety conditions of ablution spaces. In-situ slip-resistance properties and surface finishes of each ablution floor were measured under clean, wet, and soapy conditions at two different volumes of traffic areas: heavy- and non-traffic. Surface finishes of ablution floors were also measured and analysed.FindingsOutcomes from this study evidently showed that the inspected ablution floors were not currently protected against falls, especially under wet and soapy environments. Surface analyses identified that the present ablution floors have extremely flat surfaces (? 2 µm in the Ra parameter) so they require significant improvements against fall risks.Originality/valueRegardless of the magnitude of this issue, it is scarce to attain any published study on ablution floors’ fall incidence and avoidance plans in the scientific and technical literature. There are also no officially and publicly available data on fall incidents from ablution places in mosques. Findings from this study would be a great step forward to establish safer ablution floors for Muslim prayers.

ЗАЛЕЖНІСТЬ ОПОРУ ПЕРЕМІЩЕННЯ ГНУЧКОЇ СМУГИ ПО ПОВЕРХНІ ВІД КРИВИНИ ЇЇ ОСІ

During considering the movement of the body on the surface, it is usually replaced by a material particle. It greatly simplifies the analytical description of the movement, which makes it possible with some probability to predict the impact of certain factors on the process. The particles can create a continuous environment, one of which may be a flexible strip. It is deformed during moving on the surface, acquiring its shape. This movement can occur during plowing the soil, permeated with roots. In this case, the slice can be taken as a strip of the rectilinear cross-section, the length of which does not change during deformation, i.e. it is incompressible. The article considers the movement of such a strip on a cylindrical surface with a horizontal arrangement of rectilinear generatrices. The strip can enter the surface perpendicularly to the generatrices and moves farther in this direction. In this case, the trajectory will be a flat curve – in fact, a cross-section of the cylinder. The article considers the variant when the strip enters the surface of the cylinder at a certain angle to the generatrices. In this case, the trajectory of the strip movement will be a spatial curve. Some effort is required to overcome the slip resistance of the strip. It is the sum of certain components: the effort to lift the strip, to overcome the friction, to its deformation in the case of an elastic strip. The article considers the forces, the magnitude of which is influenced by the curvature of the trajectory of the strip, for which its axis is taken. The force is determined by the summation of the elementary forces acting on the elements of the strip along its axis. It is considered that at the deformation of a strip the profile of its cross-section does not change and remains rectangular. On the basis of this rectangle, an elementary parallelepiped of a strip is formed, one of the dimensions of which is the differential of the arc of its axis. Thus, the definition of the force is reduced to the integration of the forces applied to the elementary parallelepiped along the length of the arc of the axis of the strip. One of such forces is the centrifugal force, which depends on the curvature of the trajectory along which the strip moves on the surface. The component of this force causes the pressure of the strip element on the surface, which causes the appearance of friction. If the strip is elastic, then there are deformation forces, which also depend on the curvature of the axis of the strip. Keywords: flexible strip, cylindrical surface, axis curvature, centrifugal force, friction force.

Role of wall-fluid interaction and rough morphology in heat and momentum exchange in nanochannel

As an efficient cooling method, the convective heat transfer in nanochannel has been widely utilized in thermal management of various energy systems. However, the effects of surface roughness on velocity slip and flow resistance in nanochannel are still unclear. The effects of rough morphology and wall-fluid interaction on the flow and thermal characteristics in rectangular nanochannel are probed with molecular dynamics method. The results show that nanostructure morphology and wall-fluid interaction induce distinct variations in temperature jump and velocity slip, which further determine the heat and momentum exchange between the channel wall and fluid. Specifically, rough morphology is responsible for the augments of heat transfer and flow resistance, which is derived from limitation on the motion of fluid atoms by the nanostructure grooves in channel. In comparison, the strong wall-fluid interaction brings about the improvement of heat transfer and the increase of flow resistance, which owes to the adsorption enhancement. As the nanostructure free shear ratio increases from 0.1875 to 0.75, the flow resistance increases and heat transfer performance weakens. Yet, the combination of rough morphology and wall-fluid interaction is significant for overall heat transfer performance. The overall heat transfer performance in rough channel with the weak wall-fluid interaction is superior. The Nusselt number in rough channel only decreases by 1.78% while the resistance coefficient reduces by 27.1%. The optimal overall performance is achieved in rough channel with the nanostructure free shear ratio of 0.1875.

Heat damage and bond-slip performance of steel arch frame-concrete in high-geothermal tunnels

According to the real construction environment in high-geothermal tunnel, push-out test on fifty-four I-shaped steel and concrete samples subjected to different relative humidity and variable temperature curing conditions were carried out to evaluate the bond slip performance at the interface. The study results indicated that there are three models of crack evolution in failure process under different curing conditions. Compared with the samples cured under standard condition, higher curing temperature contributes to the early development of bond strength, but the long-term bond strength decreased significantly. Relative humidity is beneficial for increasing the intensity and shearing stiffness, enhancing bonding properties and reducing the loss of long-term bond strength of samples cured under VTC condition. More initial defects lead to the weak slip resistance of the interface under hot and dry environment. According to the regression analysis of experiment data, the formula of characteristic strength and segmental constitutive equation of the bond-slip under coupling effect of temperature and humidity are obtained. The parametric finite element model (FEM) of the new constitutive relation proposed in this paper was established using parametric design language. The final results may contribute to provide a reference for related support design and construction in high geothermal tunnel.

Eksperimentalno istraživanje gubitaka prednapinjanja u visokovrijednim vijcima pod cikličkim opterećenjem

Slip-resistant shear connections with preloaded bolts have traditionally been used in steel structures exposed to cyclic / fatigue loading or in cases when bolt slipping or connection deformations should be restricted. Hence, shear load is transferred through friction surfaces rather than through contact between the bolt surface and the hole. The main influencing parameters determining slip resistance of the connection are the friction between contact surfaces and the bolt preload level. This paper presents an experimental study of preloaded bolted connections under cyclic load, the main objective being to investigate the influence of cyclic load on the losses of preload force in high strength bolts and lock bolts.