Increase In Load-bearing Capacity Research Articles

A 3D bi-material lattice concept for tailoring compressive properties

The current article explores 3D bi-material lattice concepts for tailoring compressive stress-strain response. The unit cells of the lattices consist of six stiff inclined struts that together form the edges of two stacked tetrahedra. The central plane (between the two tetrahedra) contains elastomeric elements that stretch when the lattice is compressed. The geometric configurations of the elastomers examined here include: (i) straight struts between each node pair within the central plane, (ii) multiple struts between each node pair, including one straight strut and one or more curved struts, and (iii) flat sheets, either uniform or graded in thickness, connected at the mid-plane nodes. Assessments of the concepts are made using analytical models, finite element simulations, and experiments on lattices fabricated by 3D printing. The experimental results affirm the understanding of mechanical response gleaned from the models and highlight the importance of joint design in attaining large straining capacity and strain reversibility. They also demonstrate a nearly twofold increase in load bearing capacity when straight struts are replaced by graded sheets. The work also raises the prospects for computational design optimization for maximum efficiency in material use.

Load-Bearing Capacities and Pseudo-Ductility of Carbon Fiber-Reinforced New Zealand Pine Timber Beams

Building construction contributes a significant portion to the global consumption of energy and greenhouse gas (GHG) emissions, and decarbonization has become one of the main targets. This has turned much attention to renewable materials, particularly timber construction. Wood is a natural composite, and it causes challenges in its natural state due to its mechanical properties and functionality, which has constrained its use in construction. Laminating wood sections into glue-laminated (glulam) and cross-laminated timber (CLT) components overcomes limitations in dimensions and inconsistencies in its properties. We went beyond these technologies and explored the potential of combining timber of the radiata pine species with synthetic fibers, aiming for hybrid natural–synthetic composite beams. This research illustrated various reinforcement mechanisms and analyzed their structural properties. The results from the experiments showed that carbon fiber-reinforced timber composites have up to 49% additional increase in load-bearing capacity compared to unreinforced beams. An identical amount of strain required less stress, and the composite portrayed a metal-like ductility property, a characteristic referred to as pseudo-ductility. It reduces the material consumption in beams through a more efficient use of materials, particularly around compression areas before tensile rupture. The resulting composites are sustainable yet structurally capable, contributing to the reduction in CO2 emissions in timber construction systems.

Experimental and Computational Study of Mechanical and Thermal Characteristics of h-BN and GNP Infused Polymer Composites for Elevated Temperature Applications

Polymer-based nanocomposites are being considered as replacements for conventional materials in medium to high-temperature applications. This article aims to discover the synergistic effects of reinforcements on the developed polymer-based nanocomposite. An epoxy-based polymer composite was manufactured by reinforcing graphene nanoplatelets (GNP) and h-boron nitride (h-BN) nanofillers. The composites were prepared by varying the reinforcements with the step of 0.1 from 0.1 to 0.6%. Ultrasonication was carried out to ensure the homogenous dispersion of reinforcements. Mechanical, thermal, functional, and scanning electron microscopy (SEM) analysis was carried out on the novel manufactured composites. The evaluation revealed that the polymer composite with GNP 0.2 by wt % has shown an increase in load-bearing capacity by 265% and flexural strength by 165% compared with the pristine form, and the polymer composite with GNP and h-BN 0.6 by wt % showed an increase in load-bearing capacity by 219% and flexural strength by 114% when compared with the pristine form. Furthermore, the evaluation showed that the novel prepared nanocomposite reinforced with GNP and h-BN withstands a higher temperature, around 340 °C, which is validated by thermogravimetric analysis (TGA) trials. The numerical simulation model is implemented to gather the synthesised nanocomposite’s best composition and mechanical properties. The minor error between the simulation and experimental data endorses the model’s validity. To demonstrate the industrial applicability of the presented material, a case study is proposed to predict the temperature range for compressor blades of gas turbine engines containing nanocomposite material as the substrate and graphene/h-BN as reinforcement particles.

Failure Modes of Masonry Pillars Strengthened with PBO Fibres

The paper presents compression tests of stocky and slender masonry pillars strengthened in bed joints with PBO fibres and an inorganic matrix. Five stocky pillars and four slender pillars were tested under static loading. Physical models were prepared using lime mortar similar to that used in historical structures. Fibres were applied in the grooves that were made after the mortar setting period in order to recreate real-world conditions. One of the models was subjected to preloading before the strengthening was applied. The failure modes, load-bearing capacity, cracking stresses, stiffness and deformations (longitudinal and transverse) were all determined through experimental testing. Strengthening effectiveness in terms of the increase in load-bearing capacity and stiffness, as well as anti-cracking was determined on the basis of the experimental results. The results obtained for the stocky and slender pillars were also compared, indicating the influence of slenderness on strengthening effectiveness. Special attention was also paid to failure modes and the interaction of the PBO fibres with the bed joint. Methods that strengthen pillars in their bed joints using PBO fibres increase their load-bearing capacity, stiffness and cracking resistance, while maintaining a satisfactory visual appearance which is especially important in heritage structures.

Performance analyses of conventional hot mix asphalt with waste additives

The continuous increase in traffic volume demands performance enhancement of pavements. Common techniques for this performance improvement utilize modifications in the conventional hot mixture asphalt (HMA) through additives. Utilization of urban waste materials as additives for HMA provides opportunity for effective utilization and disposal of these unwanted materials. In this research, two waste materials, low-density polyethylene (LDPE) and crumb rubber (CR), are tested as additives to HMA for performance enhancement, optimization, and cost effectiveness. Performance evaluations are made through comparing stiffness modulus. Stiffness moduli of conventional and waste-material-modified HMA mixtures are evaluated through creep testing. Further, the effect of asphalt binder content, additive content, and mixing methodologies (1 and 2) were also investigated in this research. The experimental results showed a 22.4% increase in stiffness modulus with increases in asphalt binder content. Modified HMAs showed better (5–15%) results than conventional HMAs. Between the two modified mixtures, LDPE modified mixtures displayed better strength (about 1.5 times higher) than CR modified mixtures. Mixing methodology-1 resulted in 9.35% lower stiffness modulus values than the methodology-2. The results also showed that the excessive use of asphalt binder as well as waste material additive reduced the stiffness modulus up-to 21.9% and 15% respectively. Further, it was observed that the addition of waste material additives to conventional HMA mixtures increased the viscosity of mixtures which resulted in an increase of load-bearing capacity in terms of stiffness modulus.

Compression deformation and fracture behavior of additively manufactured Ti–6Al–4V cellular structures

Corresponding research was carried out to assess if the porous structures with modified diamond-shaped lattice cells can provide better integrity of the constructions in the case of overloading. The aim of the study is designing the structures with high porosity for the biomedical applications (implants) having good load bearing capacity. Studied lattice structures are based on the modified tetrahedral beam-based cells with spherical reinforcements at the beam joints and variable beam diameter. Samples with a porosity of 50–80% were studied in present research. Structures were additively manufactured from a titanium alloy Ti–6Al–4V using SLM. Sample compression tests were carried out according to the ISO 13314 standard. Loading experiments were carried out and critical parameters extracted from the stress-strain curves. Finite element modeling was carried out for the analysis of the stress and assessment of the potential failure mechanisms. Corresponding hypothesis explaining the appearance of shear bands in porous structures under compression is formulated. Obtained results show that when the sample porosity rises from 50% to 80%, corresponding plateau stress decreases by 13 times, first maximum compressive strength decreases by 12 times, and compression offset stress decreases by 12 times, while the plateau end does not change significantly. The experiments revealed the barrel distortion of the samples geometry, which corresponds to the general knowledge how the friction between the solid compressing surfaces (anvils of the compression testing machine) and the lattice affects the sample deformation. Compression experiments also revealed the formation of shear bands during sample deformation. The stochastic nature of their development suggests that the main reason of shear bands appearing is the initial inhomogeneity of the boundary conditions of the experiment.Suggested modifications of the basic cells show a good potential for achieving regular beam-based lattice structures with high porosity and increased load bearing capacity. More experiments are needed for statistical analysis, and improvements of the loading experiments methodology for better failure mode analysis are planned for the future.

Investigation on Lateral Loading on Masonry Walls

5) Though a traditional material used for construction for ages, masonry is a complex composite material, and its mechanical behavior is influenced by a large number of factors, is not generally well understood. This research aims to study the methodology available in the literature to evaluate the increase in performance of masonry by applying different reinforcement options under in-plane lateral loading. Nonlinear static analysis has been carried out as part of this research to achieve the above objectives. Different unreinforced masonry wall panels were analyzed at various load conditions. Material properties for the masonry wall were taken from the experimental test results of previous literature. The walls were first checked for two failure mechanisms. The stress distributions of walls were checked in each step of analysis and shear failure, and rocking failure was found. Each wall was then analyzed for six different reinforcement options. The comparison of results obtained from the reinforced wall analysis with that of the unreinforced wall indicated significant increase in lateral load-bearing capacity and decreased wall displacement with reinforcement. The maximum increase in load-bearing capacity was achieved by adding chicken wire mesh or CFRP bands throughout the wall while the maximum decrease in displacement was achieved by adding 12 mm diameter bars at the spacing of one meter.

Theoretical Efficiency Study of Output Lubricant Flow Rate Regulating Principle on the Example of a Two-Row Aerostatic Journal Bearing with Longitudinal Microgrooves and a System of External Combined Throttling

Due to their vanishingly low air friction, high wear resistance, and environmental friendliness, aerostatic bearings are used in machines, machine tools, and devices that require high accuracy of micro-movement and positioning. The characteristic disadvantages of aerostatic bearings are low load capacity, high compliance and an increased tendency for instability. In radial bearings, it is possible to use longitudinal microgrooves, which practically exclude circumferential air leakage, and contributes to a significant increase in load-bearing capacity. To reduce compliance to zero and negative values, inlet diaphragm and elastic airflow regulators are used. Active flow compensation is inextricably linked to the problem of ensuring the stability of bearings due to the presence of relatively large volumes of gas in the regulator, which have a destabilizing effect. This problem was solved by using an external combined throttling system. Bearings with input flow regulators have a number of disadvantages-they are very energy-intensive and have an insufficiently stable load capacity. A more promising way to reduce compliance is the use of displacement compensators for the movable element. Such bearings also allow for a decrease in compliance to zero and negative values, which makes it possible to use them not only as supports, but also as active deformation compensators of the technological system of machine tools in order to reduce the time and increase the accuracy of metalworking. The new idea of using active flow compensators is to regulate the flow rate not at the inlet, but at the outlet of the air flow. This design has the energy efficiency that is inherent to a conventional bearing, but the regulation of the lubricant output flow allows the compliance to be reduced to zero and negative values. This article discusses the results of a theoretical study of the static and dynamic characteristics of a two-row radial aerostatic bearing with longitudinal microgrooves and an output flow regulator. Mathematical modeling and theoretical study of stationary modes have been carried out. Formulas for determining static compliance and load capacity are obtained. Iterative finite-difference methods for determining the dynamic characteristics of a structure are proposed. The calculation of dynamic quality criteria was carried out on the basis of the method of rational interpolation of the bearing transfer function, as a system with distributed parameters, developed by the authors. It was found that the volumes of the microgrooves do not have a noticeable effect on the bearing dynamics. It is shown that, in this design, the external combined throttling system is an effective means of maintaining stability and high dynamic quality of the design operating in the modes of low, zero and negative compliance.

Influence of soil density on performance of geocell-reinforced vertical anchor in sand

Influence of soil density on the performance of geocell-reinforced vertical plate anchors was studied through a series of model tests and numerical analyses. It is observed that the geocell-induced performance improvement is present over a wide range of relative density, varying from 30% (loose) to 95% (very dense). However, increase in load bearing capacity and stiffness of the anchor bed continues to increase with increase in density of the soil mass. Moreover, compared to the unreinforced case, the increase in anchor capacity due to increase in soil density tends to be greater with geocell reinforcement. This is attributed to the dilation-induced volume expansion that tends to mobilise enhanced resistance from the geocell reinforcement. In addition, the size of the rupture surface was found to increase with the increase in density of the fill soil, which indicates that, at higher density, a larger volume of soil mass has participated in sharing the anchor load, leading to the enhanced performance of the system. Numerical analysis using the computer program Fast Lagrangian Analysis of Continua was carried out. The computed results were found to be in good agreement with the observed ones.

LABORATORY TESTING OF STEEL FIBER CONCRETE PRISM FOR TENSION IN BENDING

Abstract. Laboratory bending tests of concrete and steel-fiber-concrete prisms were carried out. The concrete matrix for all prisms is made of a concrete mixture of the same composition with a coarse aggregate size up to 10 mm and a water-cement ratio that allows correct mixing of the ready mixture with fiber, so that the latter is evenly distributed over the sample volume. Fiber reinforcement is 1% for all three types of fiber, a fiber made of the same steel with an ultimate strength of 1335 MPa, fiber length 50 mm, diameter 1 mm is used. Fibers differ only in shape, which makes it possible to compare test results across series without correction factors. Concrete samples without fiber are considered as control samples. As a result of laboratory tests, data sets were obtained and analyzed, which are presented in the form of diagrams. Different types of steel fiber show different increases in the load at the beginning of cracking and load-bearing capacity. The most profitable from this point of view is the addition of anchor fiber to concrete, the least – wave fiber. However, the presence of any of the considered steel fibers in the mixture significantly increases the load-bearing capacity of the sample. In addition, the type of destruction of such a sample changes from brittle to viscous. We also studied the deformability of samples with different fiber reinforcement and plotted the dependence of the relative longitudinal strain on the load. Before the crack formation begins, there is a direct proportionality between the load and the strain with the appearance of cracks, the slope of the graphs changes sharply. When the load-bearing capacity is lost, steel fiber-reinforced concrete samples are restrained from final destruction. The use of steel fiber in concrete on average increases the crack resistance by 40%, and the load-bearing capacity by 64%. Compared with samples without fiber reinforcement, samples with anchor fiber show an increase in load-bearing capacity by 89%, and crack resistance by 61%. When using flattened fiber, these values are 56% and 32%, and for wave fiber – 47% and 25%, respectively. The use of steel fiber in the manufacture of concrete mix avoids the brittle nature of destruction.

Load-deformation of piled embankments considering geosynthetic membrane effect and interface friction

The use of high-strength geosynthetics to enhance the load transfer mechanism onto columns is an established and increasingly popular technique in geosynthetic-reinforced and column-supported embankments. The main focus of this paper is to extend the existing models that describe the membrane action and soil arching with skin friction along the geosynthetic. This extension was undertaken to identify the parameters that affect the tension in the geosynthetic and assess the effect of geosynthetics on the load transfer. A general expression for the increase in load-bearing capacity due to the membrane action based on strict equilibrium conditions is also shown. The geosynthetic deformation is described assuming both circular and parabolic deformation shapes. These two deformation shapes do not result in a significantly different membrane effect. Therefore, the choice of deformation parameter is more important than the choice of deformation shape. The new method using both deformation models was combined with the Concentric Arches model of Van Eekelen and co-workers, and compared with the measurements and numerical results. A reasonable consistency is found. For the considered cases, the skin friction along the geosynthetic reduces the maximum geosynthetic deflection to 2.5 to 5.3%. This reduction becomes more important when the embankment is higher.

Increased load bearing capacity of mechanically joined FRP/metal joints using a pin structured auxiliary joining element

Abstract Due to their excellent mechanical properties, fiber-reinforced plastics are increasingly being used in technical lightweight products. The multi-material design of fiber-reinforced plastic and metal leads to great lightweight constructions because the potential of the materials can be efficiently used for the specific field of application. This restricts conventional thermal joining technologies and shows the demand for cost-effective and efficient mechanical and adhesive joining technologies. This paper depicts the development of a new type of auxiliary joining element with integrated pin structures whose purpose is to increase the load-bearing capacity of mechanically joined fiber-reinforced plastic/metal combinations. In addition, the hole area of the fiber-reinforced plastic can be relieved in this way by transferring the operating loads into the laminate via the pin structures. In addition to experimental studies of the application methodology, the quasi-static and dynamic load-bearing capacity will be investigated. This paper presents detailed information about the development of the new auxiliary joining element and the characteristics of the joints, including corrosion effects generated by a corrosion camber.

Numerical and Experimental Study on Deficient Short Steel Tubes Strengthened with CFRP Under Compression

In view of development and repair costs, support of structures is imperative. Several factors, for example, design and calculation errors, absence of appropriate installation, change of structures application, exhaustion, seismic tremor, fire and natural conditions diminish their strength. In such cases, structures have need of rehabilitation and restoration to achieve their original performance. One of the most up to date materials for retrofitting is carbon fiber reinforced polymer (CFRP) that can provide an amount of restriction to postpone buckling of thin steel walls. This paper provides a numerical and experimental investigation on CFRP strengthened short steel tubes with initial horizontal and vertical deficiency under compression. Ten square and circular specimens were tested to study effects of the following parameters: (1) position of deficiency, horizontal or vertical; (2) tube shape, square or circular; (3) CFRP strengthening. In the experiments, axial static loading was gradually applied and for the numerical study three-dimensional (3D) static nonlinear analysis method using ABAQUS software was performed. The results show that deficiency reduces load-bearing capacity of steel columns and the impact of horizontal deficiency is higher than the impact of vertical deficiency, in both square and circular tubes. Use of CFRP materials for strengthening of short steel columns with initial deficiency indicates that fibers play a considerable role on increasing load bearing capacity, reducing stress at the damage location, preventing deformation caused by deficiency and delaying local buckling. Both numerical and experimental outcomes are in good agreement, which underlines the accuracy of the models adopted.

Preparation and Characterization of Iron Matrix Syntactic Foams with Glass Microspheres via Powder Metallurgy

Iron matrix syntactic foams with four different glass microsphere fractions were prepared via powder metallurgy. Effects of compaction pressure and lubricant addition on the microstructure and the mechanical properties were investigated. It was observed that matrix densification and fracture, softening, shrinkage, and bonding of the microspheres tended to increase with the compaction pressures. The compaction pressure incurring microsphere fractures was in inverse ratio to the microsphere fraction. The fracture and softened microspheres degraded onset of plateau stress values proportionally to the microsphere fractions at low compaction pressure, while enhanced and stabilized them at about 240 MPa at higher pressures regardless of the microsphere fraction, owing to increased load bearing capacity by a formation of solid particle-like microspheres. The lubricant formed pores in the matrix or accelerated densification and microsphere fractures depending on the microsphere fractions, while it had no significant effect on mechanical characteristics except brittleness.

Development of the multiple tenon timber connection based on experimental studies and FE simulation

This paper describes the development of the multiple tenon connection from the basic idea to an optimised timber connection. Based on the promising results of a first series of experimental testing, a finite element model considering different failure modes was developed to simulate the load-bearing behaviour of a four-tenon connection. The shape of the multiple tenons and the geometrical position was studied to compare the varying ultimate loads depending on different geometrical parameters. Based on these relations, a second experimental series was developed with an improved design. The results show significantly higher load capacities compared to the results of the first test series. Different possibilities of additional reinforcement have been studied. In comparison to existing form-fitting connections, multiple tenons exhibit a remarkable increase of load-bearing capacity together with reduced scattering of test results. Two-dimensional finite element simulations supported the design optimisation of wood-to-wood connections in a very efficient way.

Soil reinforcement with geosynthetics

The proportionality of existence of land with good bearing to erect any building or building is very small, to remedy this deficiency it is necessary to resort to techniques of reinforcement of the soils which can constitute a very important development. Among these methods of remediation, there is reinforcement by the geosynthetics which constitute an effective solution to these constraints. This process tends to stabilize the soil in question with increased load bearing capacity in civil engineering and geotechnical works such as embankments, slopes, embankments and hydraulic structures, with an inestimable gain in time, economy and durability while preserving the natural and environmental aspect.

Design, Development and Testing of an Omnidirectional ISI Device

In present scenario, all available omni directional mobile devices use more than two drives to accomplish omnidirectionality except synchro drive. Synchro drives employ chain sprocket mechanism to drive and steer three wheels at vertex of triangular chassis. The concept of uni-wheeled device discussed in this paper also uses two drives but utilizes reliable gear systems, compact symmetric chassis with a mid support wheel; these imparts omnidirectional, pivot rotation characteristics, increased load bearing capacity, better tracking accuracy etc. This paper highlights the design, simulation, development and testing of a uni-wheeled drive and its steer based omnidirectional mobile In-service inspection (ISI).

Evolution of the reinforced I-beam strain state

The paper presents experimental results of the strain state evolution of the steel I-beam reinforced with composite material under four-point bending loading. Digital image correlation technique was used to trace the evolution of plastic strain zones distribution. The images of longitudinal relative strain on the lateral surface of the reinforced I-beam web were obtained and analyzed. It was found that the increase of load-bearing capacity of the reinforced beams can exceed 26 %.

Evolution of the reinforced I-beam strain state

The paper presents experimental results of the strain state evolution of the steel I-beam reinforced with composite material under four-point bending loading. Digital image correlation technique was used to trace the evolution of plastic strain zones distribution. The images of longitudinal relative strain on the lateral surface of the reinforced I-beam web were obtained and analyzed. It was found that the increase of load-bearing capacity of the reinforced beams can exceed 26 %.

Experimental and Numerical Research of Stress-Strain State of Homogeneous Soil Massif at Interaction with Single Barrette

Deep foundations are used for the design of high-rise buildings due to a large pressure transfer on the soil base. The foundations of buildings sometimes use barrettes which are able to perceive significant vertical and horizontal loads due to improved lateral surface. Barrettes have increased load bearing capacity as compared with large diameter piles. In modern practice the interaction between barrettes and soil is investigated by analytical and numerical methods and has no sufficient experimental confirmation. The review of experimental methods for the research of the intense stress-strain state of the uniform soil massif at interaction with elements of a deep foundation is provided in this article. Experimental research are planned with the use of laboratory stand for the purpose of qualitative data obtaining on the interaction barrettes with an assessment of a settlement model adequacy and also at the research of the intense stress-strain state by numerical methods.