Maximum Load Capacity Research Articles

Bioactive electrospun zein fibers integrated with ZnO nanoparticles: In vitro investigations

The objective of the current study was the fabrication and characterization of electrospun zein-ZnO fibers containing various concentrations of cumin essential oil (CEO) (0, 1, 2, and 3% (v/v)). The electrospinning solution's apparent viscosity, conductivity, and surface tension were measured. Also, the electrospun's morphological, color, encapsulation efficiency, antioxidant and antimicrobial properties, thermal stability, and release kinetic were investigated. The results represented that following the increase in CEO concentration, the conductivity and surface tension of the electrospinning solution changed from 182.92 μS/cm to 145.22 μS/cm and 19.52 mN/m to 22.35 mN/m, respectively. The scanning electron microscope (SEM) revealed the homogenous and free-bead structure of electrospun fibers. Besides, the diameter of fibers enhanced with a rise in CEO concentration from 217.13 nm to 321.67 nm. The finding estimated the maximum encapsulation efficiency and loading capacity at about 95.09% and 25.65%, respectively in electrospun containing the highest concentration of CEO (3%). CEO inclusion in electrospinning fibers augmented the value of contact angle, color difference, TPC, antioxidant, and antimicrobial properties. The favorable interaction between the CEO ingredients and electrospinning fibers was confirmed through FTIR and XRD analysis. Furthermore, the incorption of CEO enhanced the thermal stability of fibers. Release kinetic in different simulant (aqueous, acidic, alkaline, and fatty) revealed that Fick's diffusion was the main release mechanism. The highest diffusion coefficient was observed in electrospun fibers containing 3% CEO in the fatty media simulant. These findings could present a new horizon into electrospinning fiber's application in various fields of medicine, tissue engineering, food, and pharmaceutical industry.

Investigating the axial compressive behavior of cruciform CFST columns: An experimental study

Concrete-filled steel tube (CFST) columns enhance seismic resistance, enabling lighter-weight structures with improved fire performance. This study investigates the axial performance of cruciform CFST columns using three half-scale experiments. The cruciform sections were internally configured as unstiffened (UnS-CFST), stiffened (S-CFST), and multicell (M-CFST). Failure mode, stress, displacement, ductility, and strength were evaluated to determine the maximum load-bearing capacity. Compared to UnS-CFST columns, S-CFST and M-CFST exhibited improved ductility and axial compressive performance. The study also looks at how the proposed method for cruciform sections compares to existing design standards for square and circular CFST columns, such as AIJ, EC4, GB 50936–2014, CECS 159:2004, ACI 318R-05, and AS3600–2001. A novel method for determining the maximum load capacity of cruciform CFST columns is proposed, achieving an accuracy of approximately 95 % compared to experimental results. This novel method facilitates the design of cruciform CFST columns.

Design and performance evaluation of a stick–slip actuator with Z-shaped beam and two-stage amplification system

Abstract In the domain of piezoelectric driving, actuators that utilize the stick–slip effect at high speeds and low frequency have garnered significant interest. This study presents an innovative linear piezoelectric actuator that integrates a two-stage amplification system with a Z-shaped beam mechanism. The designed actuator has good driving speed at low frequency while overcoming the disadvantage of such actuators requiring two flexible mechanisms to achieve reverse motion and poor reverse performance. The structure and scale of the actuator are explained and designed through theory and simulation. The experimental results demonstrate the prototype’s capability for bidirectional motion. Subjected to a 400 Hz and 140 V excitation, the maximum speed of the actuator is 12.88 mm s−1. The maximum load capacity is tested to be of 0.35 N. This research introduces a new approach for the design of high-speed bidirectional motion stick–slip piezoelectric actuators.

Study on Static Biomechanical Model of Whole Body Based on Virtual Human.

Material handling tasks often lead to skeletal injury of workers. The whole-body static biomechanical modeling method based on virtual humans is the theoretical basis for analyzing the human factor index in the lifting process. This paper focuses on the study of humans' body static biomechanical model for virtual human ergonomics analysis: First, the whole-body static biomechanical model is constructed, which calculates the biomechanical data such as force and moment, average strength, and maximum hand load at human joints. Secondly, the prototype model test system is developed, and the real experiment environment is set up with the inertial motion capture system. Finally, the model reliability verification experiment and application simulation experiment are designed. The comparison results with the industrial ergonomic software show that the model is consistent with the output of the industrial ergonomic software, which proves the reliability of the model. The simulation results show that under the same load, the maximum joint load and the maximum hand load are strongly related to the working posture, and the working posture should be adjusted to adapt to the load. Upright or bent legs have less influence on the maximum load capacity of the hand. Lower hand load capacity is due to forearm extension, and the upper arm extension greatly reduces the load capacity of the hand. Compared with a one-handed load, the two-handed load has a greater load capacity.

Enhancing hydrogen storage efficiency: Computational insights into scandium-decorated 2D polyaramid

This study explores hydrogen storage in 2D polyaramid (2DPA) and its enhancement via scandium decoration for onboard storage in fuel cell vehicles. Sc decoration in 2DPA is accompanied by a net 1.6 e charge transfer from Sc to 2DPA. Hydrogen binding in 2DPA + Sc proceeds with a net charge transfer of 0.32 e from Sc towards H2. 2DPA + Sc demonstrates a maximum hydrogen loading capacity of 8.589 wt% with an average adsorption energy of −0.376 eV/H2. These findings meet the stipulated criteria by the US Department of Energy for solid-state hydrogen storage in light-duty vehicles. Feasibility studies were conducted considering practical limitations in transition metal-modified carbon nanomaterials, including Sc-Sc clustering tendencies, stability, and hydrogen desorption behavior via ab initio molecular dynamics simulations, phonon dispersion, and diffusion studies. The highest barrier height for hydrogen desorption from 2DPA + Sc is 0.48 eV, and desorption is predicted to occur at 412 K (5 bar) indicating possibility of room temperature and reversible hydrogen storage. Our findings indicate that 2DPA + Sc is a promising hydrogen storage substrate material and should be explored in experimental trials.

Numerical simulation and experimental study of the influence of disk groove structure optimization on the air film flow field signature of an air-cushion sandwich belt conveyor

A new type of disk groove mechanism was developed and manufactured. The effects of the structural and operating factors of the disk groove on the air film loading performance were examined using single factor and orthogonal experimental methods. The results of numerical simulation and experimental studies showed that the air film loading performance correlated positively with the orifice diameter and inlet pressure, with the orifice spacing and diameter having the most significant effects, and that the belt speed boosted the air film uniformity. Meanwhile, a comparative analysis of the corresponding level values showed that an air film thickness of 0.8 mm, orifice diameter of 5 mm, orifice spacing of 30 mm, inlet pressure of 8000 Pa, and conveyor speed of 5 m/s were the optimal parameter combinations for the maximum loading capacity. To verify the accuracy of the model, a field experiment was conducted at Jiangmen Southern Conveying Machinery Engineering Co., Ltd. The air film pressure at the experimental position matched the numerical simulation results. In addition, when the number of rows was one and the air volume was 10 m3/h, the smallest value of traction resistance was obtained under minimum power consumption.

Achieving smooth motion in displacement amplification piezoelectric stick-slip actuator.

Traditional piezoelectric stick-slip actuators often suffer from significant backward motion phenomena, which greatly impact their output performance. To overcome this issue, a novel displacement amplification piezoelectric stick-slip actuator was meticulously designed. It integrates an L-shaped displacement amplification mechanism with a parallelogram-compliant mechanism. By dynamically adjusting the compressive force between the stator and the mover, this actuator effectively increases the single-step displacement, resulting in smooth and stable motion output. The design process involved thorough structural feasibility validation and core dimension optimization, utilizing Castigliano's second theorem and finite element simulation analysis. These efforts successfully yielded a substantial increase in the single-step output displacement. Experimental results demonstrate the actuator's capability to achieve smooth and stable motion output, even under challenging conditions, such as symmetric excitation signals and horizontal loading. Under specific operating parameters-preloading force of 3 N, input voltage of 100VP-P, and driving frequency of 625Hz sinusoidal excitation signal, the actuator achieves an impressive maximum driving speed of 25.22 mm/s, with a substantial maximum load capacity of 2.1 N. Compared to previous studies, the designed actuator exhibits superior adaptability to various excitation signals, offering significant potential for enhancing the performance and expanding the applications of piezoelectric stick-slip actuators.

Freeform trajectory generation for fiber reinforced polymer composites additive manufacturing with variable-deposition-width

Continuous carbon fiber-reinforced polymers (CCFRPs) printing is a unique additive manufacturing (AM) technique that enhances design flexibility and enables on-demand production of lightweight, high-strength composite parts. However, current trajectory generation methods for CCFRPs-AM have limited control over fiber placement and flexible matrix path infill, particularly in complex regions, often using constant deposition widths that restrict path coverage and mechanical properties. To address these limitations, this paper presents a variable-deposition-width (VDW) trajectory generation method for CCFRPs-AM. The approach integrates a streamline-based technique for fiber paths with a Voronoi diagram-based method for matrix path generation, optimizing path placement based on 2D stress fields while accommodating user-defined fiber paths. Mechanical tests by us on fabricated open-hole composite components demonstrate that the proposed approach enhances the interfacial bonding and increases the maximal loading capacity under tensile stress.

Preparation and Evaluation of Stability and Acute Oral Toxicity of a Drug Delivery System Combining MIL‐100(Fe) with Chloroquine Phosphate

AbstractMetal‐organic framework materials (MOFs) are highly porous and are the subject of growing interest among scientists globally for their utilization in drug delivery. In this work, iron‐based metal‐organic frameworks (MOFs) MIL‐100(Fe) were synthesized by ultrasonic method and studied for the loading of the chloroquine phosphate (CQP). The CQP‐release behavior of the material was investigated in water media with various pH solutions of 1.2, 2, 4.5, and phosphate‐buffered saline (PBS) at temperatures of 25 °C to 45 °C. MIL‐100(Fe) material had a high surface area of up to 1080 m2/g and could completely release the CQP at a pH of 1.2 after 25 hours. At other pH conditions, the drug exhibited an initial rapid release, followed by a gradual slowdown, ultimately achieving complete release after 96 hours. The maximal loading capacity for the CQP by the MIL‐100(Fe) was determined to be approximately 30 % at the pH solution of 2 (stomach environment). The findings from the activity assessment against the K1 malaria parasite strain (P. falciparum) indicated that the concentration at which the active ingredient, when carried by the material, exhibited inhibition was 193 nM/L. The evaluation outcomes for acute toxicity of the drug carrier material revealed an LD50 value exceeding 5000 mg/kg (equivalent to 1500 mg of CQP base). In contrast, when using the active substance alone, acute toxicity resulted in an LD50 value of 675 mg/kg.

The Structural Behavior of Lightweight Self-Compacting Concrete Slabs Using Different Types of Reinforcement

The purpose of this study is to examine how the type of reinforcement used in self-compacting concrete (SCC) and lightweight self-compacting concrete (LWSCC) affects their structural behavior. There were three forms of reinforcement used: wire mesh, glass fiber-reinforced rebars, and regular steel rebars. To evaluate the mechanical characteristics of reinforced concrete slabs with various types of reinforcement, extensive experiments were carried out. The tensile strength, stiffness, and crack resistance of the concrete were studied in each case. The finite element program Abaqus was utilized in addition to the experimental investigations to create the numerical simulation of the test. The experimental results revealed that the reinforcement type significantly affects the structural behavior of SCC and LWSCC slabs. Conventional steel rebars provided high tensile strength and excellent crack resistance, while glass fiber-reinforced rebars contributed to enhanced flexibility and reduced overall weight of the concrete. On the other hand, the wire mesh exhibited average mechanical and structural properties. These findings emphasize the importance of selecting the appropriate reinforcement type based on specific applications and desired performance requirements. This research provides valuable guidance for architects and civil engineers in choosing optimal reinforcement for SCC and LWSCC. Furthermore, it can contribute to the advancement of techniques and potential improvements in these materials to achieve better performance and enhance sustainability in infrastructure and building construction. From the practical results, it was found that in the case of using lightweight self-compacting concrete and self-compacting concrete, it is preferable to reinforce it with ordinary reinforcement steel, as it gives the best results in terms of maximum load capacity at failure. Although the use of steel reinforcement in self-compacting concrete also gives the best results, but from the laboratory results it is possible to improve the performance of self-compacting concrete by reinforcing it with GFRP or welded wire mesh.

Synthesis and evaluation of iron oxide nanoparticles from banana peel (Musa spp.) extract for the delivery of ciprofloxacin against resistant Escherichia coli

Background and objectiveResistance to antimicrobials is one of our most significant worldwide challenges. In Africa, around 31 % of the infections of urinary tract (UTIs) initiated by Escherichia coli (E. coli) have been observed to develop ciprofloxacin (CIP) resistance. As a result, significant efforts have been made to investigate novel and improved antibiotics. This study aimed at synthesizing iron oxide nanoparticles (IONPs) using banana peels (Musa Spp.) extract for delivery of CIP against resistant E. coli. MethodsA green synthesis method was used for the synthesis of IONPs using FeCl3.6H2O as a precursor and banana peel extract as a reducing and stabilizing agent. The physicochemical characteristics of the formed nanoparticles (NPs) were characterized using different methods. ResultsThe formation of hematite (α-Fe2O3) was confirmed with its FTIR characteristic peak at 461 cm−1, 542 cm−1, and 1131 cm−1. The size of synthesized IONPs was found to be 10.4 nm ± 1.98, 48 nm ± 0.9, and 67.3 nm ± 0.9 under XRD, SEM, and DLS measurements respectively. CIP-IONPs had almost the maximum drug loading capacity (33.3 % ± 0.67) with fast and slow drug release patterns at gastric and intestinal or blood pH respectively, and it had a promising resistant reversal with a zone of inhibition (ZOI) 22 mm ± 0.15 against resistance E. coli. ConclusionThe green synthesis of IONP using banana peel extract represents a novel and eco-friendly approach for the delivery of ciprofloxacin, with potential applications in addressing antimicrobial resistance.

Development of reinforced concrete column with replaceable plastic hinge based on metabolism concept

To update seismic performance and rapidly restore the transportation capacity of a bridge following an earthquake, this study introduces a new reinforced concrete (RC) column, termed “Metabolic RC column,” which incorporates the Design for Disassembly and Metabolism Movement concepts. The proposed column features a plastic hinge comprising a permanent hinge and replaceable plastic zones. A Mesnager hinge is employed as the permanent hinge to resist the axial loads within the column cross section. In addition, cast-in-place RC members are used in replaceable plastic zones to dissipate the seismic energy. By replacing the plastic zone with an equivalent or superior alternative while the permanent hinge continues to carry the axial forces, the updating (i.e., metabolization) of the column seismic performance can be achieved without interrupting the daily operations of the structure. The feasibility of replacing plastic hinges while maintaining the resistance to axial loads was demonstrated through plastic zone replacement tests. Cyclic loading tests indicated that the maximum lateral load of the proposed Metabolic RC Column remained unchanged before and after the plastic zone replacement. The energy dissipated also remained nearly consistent before and after the plastic zone replacement. The largest reduction in dissipated energy at each displacement amplitude was approximately 6.7 % before and after replacement. Additionally, the cyclic loading tests emphasized the importance of minimizing damage to the permanent hinge and preventing the axial stiffness reduction to ensure maximum load capacity of the column after plastic zone replacement. Further, a numerical model was developed to replicate the load-displacement relationship of the specimens. The proposed model accurately calculated the maximum load of the specimen with an average error of approximately 3 % for each displacement amplitude and the dissipated energy with an error of approximately 6 %. The numerical analysis effectively captured the changes in the secondary stiffness of the columns before and after plastic zone replacement, attributing the differences in secondary stiffness to the reduced tensile forces exerted by the permanent hinge rebar.

A Self-Assembling γPFD-SpyCatcher Hydrogel Scaffold for the Coimmobilization of SpyTag-Enzymes to Facilitate the Catalysis of Regulated Enzymes.

In this study, a γPFD-SpyCatcher hydrogel scaffold with the capacity for spontaneous assembly was established. With a maximum loading capacity of a 1:1 molar ratio with SpyTag-enzymes, the immobilized proteins can not only rapidly provide pure enzymes but also exhibit improved thermal and pH stability. The results of the transmission electron microscopic analysis and the traits they present indicated that SpyCatcher promotes the aggregation of γPFD and the formation of hydrogels. In the cell-free pyruvate synthesis system, the γPFD-SpyCatcher coimmobilized SpyTag-hexokinase (HK), SpyTag-phosphofructokinase (PFK) and SpyTag-pyruvate kinase (PK) were employed, and the production of pyruvate increased by 43, 78 and 47% respectively. In in vitro experiments, the oxidative deamination activity of glutamate dehydrogenase (GDH) coimmobilized with γPFD-SpyCatcher was 38% higher than that of purified enzymes. These findings indicate that the γPFD-SpyCatcher-based hydrogels play an important role in breaking the barrier of regulatory enzymes and will provide more strategies for the development of synthetic biology.

Shear repairing of reinforced concrete beams exposed to high temperature using basalt fiber reinforcing bars and CFRP ropes and strips

In this research, the shear behavior of reinforced concrete (RC) beams subjected to high temperatures and then repaired using Basalt Fiber Reinforcing (BFRP) bars and Carbon Fiber Reinforced Polymer (CFRP) ropes and strips was investigated experimentally. Eleven reinforced concrete beams with shear deficiency were cast with dimensions 200mmx300mmx1800mm in width, depth, and span length, respectively. Then, after 28 days, ten beams were heated in an electric furnace for three hours at a temperature of 650 °C. Later, nine of the heated beams were repaired using near surface mounted technique (NSM) with different configurations of BFRP bars and CFRP ropes and strips, and one beam was left unrepaired to serve as a control heated sample. The behavior of the beams was evaluated under two-point loading. The experimental results showed that using NSM CFRP or BFRP efficiently enhances the shear capacity of heat damaged beams. Using NSM rope increased the ultimate loads by 40 % to 95 % compared to control heat beams. The highest improvement in maximum load capacity was achieved by using an inclined rope positioned at 150 mm. While, using BFRP bar increased the maximum load by 37 % to 63 % compared to control heat beams depending on the configuration and spacing between bars. Also, it has been found that the overall effectiveness of CFRP rope in increasing the shear capacity is 32 % higher than that of the BFRP bars.

An enhancing flexibility piezoelectric stick-slip actuator by introducing perforation of flexible hinge

Piezoelectric stick-slip actuators (PSSAs) utilize sliding friction between the mover and stator to convert and transmit motion. However, the phenomenon of backward displacement often hinders the output performance of PSSAs. This paper proposes a method to mitigate backward displacement and enhance output performance by modifying the overall flexibility of the actuator. The key idea of this approach is to propose a novel flexible hinge structure and apply it to PSSA. Numerical calculations and finite element analysis confirm that the flexibility and output performance of the PSSA are significantly improved. The method's feasibility is supported by comparing experiments. The experimental results show that under the same locking force, the optimal excitation frequency of perforated Elliptical Flexure Hinge (EFH) is significantly lower than the non-perforated EFH and the speed is increased over 53 %. Furthermore, the PSSA has a maximum load capacity of 190 g, which is 31.7 times its own weight (6 g). The proposed PSSA can provide valuable insights for its application in precision motion control systems in the foreseeable future.

Experimental and numerical analysis of the flexural behavior of slab beam in a 30-year-old reinforced concrete bridge

This paper presents experimental results analyzing the flexural behavior of a 30-year-old reinforced concrete bridge that was dismantled for replacement. The results revealed that the beam underwent three main phases: elastic, cracking, and failure, with a maximum load capacity of 226 kN. The primary failure mode was flexural, characterized by concrete crushing in the compression zone, yielding of the tensile reinforcement, and crack widening up to 1.2 mm. Simultaneously, a numerical model using ATENA software was developed to specifically analyze the flexural behavior of the beam and compare it with experimental results. These results provide important quantitative data for assessing load-bearing capacity and proposing effective repair and strengthening solutions.

Sorption experiments as efficient as possible: Mini-column experiments (MCE) using HPLC-ICP-MS coupling with a new data analysis approach to determine sorption parameters

To quantify retention and sorption parameters, diffusion-, batch- or column experiments are common practice. However, these are either not close to nature, extremely time-consuming or material intensive. A promising approach to eliminate these problems is the performance of mini-column experiments (MCE). Due to dynamic retention and realistic solid–liquid ratios, these are close to nature and resource-efficient. The aim of this work is to perform highly controllable MCE using a HPLC (high-performance liquid chromatography) system and HPLC-ICP-MS (inductively coupled plasma mass spectrometry) coupling. With this approach, ultra-fast sorption experiments are possible only using 100–150 mg adsorbent and 160 mL eluent. That means, sorption experiments are even more time- and cost-efficient and also more controllable than with conventional methods. The presented method is based on a newly developed MCE-HPLC-ICP-MS coupling, which was applied to investigate the sorption of Eu(III) on kaolinite and sand in 10 mM NaCl. With that it was possible to carry out dynamic sorption experiments in just 5–15 h and thus determine e.g. maximum loading capacity (qmax) in a very short amount of time. Furthermore, a quantification method for eluates of high ionic strength is presented. Here, the sorption of Cs(I) on calcium silicate hydrate (C-S-H) phases in 10 mM and 100 mM NaCl was investigated. For validation, the sorption distribution ratios (Rd) obtained were compared with those from batch experiments. These agreed very well with each other and with those from the literature. Overall, with MCE more sorption parameters can be determined much faster, more accurately and more efficient than with the conventional methods.

Biomimetic 3D printing: Cocoon-like silk reinforcements from discarded cocoons for hemispherical composite components

Silkworm cocoons serve as the primary raw material for silk fabric production. However, due to stringent quality requirements for silk products, only high-quality cocoons are selected, while defective ones such as spotted cocoons are relegated to low-value textile fillers or direct landfilling. To enhance the value of discarded cocoons, this study combines continuous fiber 3D printing technology with traditional molding techniques, using discarded cocoons as raw materials to create high-performance hemispherical composite materials that mimic the natural structure of silkworm cocoons, thereby achieving efficient resource reuse. Additionally, a novel random path algorithm for 3D printing was developed to address the issue of uneven fiber orientation in the manufacturing of curved composite materials. The vacuum bag molding method was utilized to combine silk-like hemispherical fiber-reinforced bodies with resin, producing hemispherical composites with a high fiber content. Extensive tensile testing on longitudinally and laterally cut cocoon fiber samples was conducted to explore the mechanical behavior in various directions, revealing unique anisotropic properties. Further tensile testing on homemade silk yarn confirmed the material's high strength and excellent toughness. Scanning Electron Microscopy (SEM) analysis demonstrated good interfacial bonding between the silk and bio-based epoxy resin within the composites. Compression tests indicated a maximum load capacity of 6717 N, showcasing exceptional impact resistance and superior energy absorption in projectile impact tests. Even under extreme loads, the hemispherical composites maintained a substantial intact area, highlighting their structural integrity advantages. This study not only breathes new life into industrial waste but also provides a new direction for the manufacturing sector to achieve a greener and more sustainable development path.

Prestressed CFRP Plates and Tendon Strengthening of Steel–Concrete Composite Beams

This study aims to enhance the ultimate capacity and stiffness of steel–concrete composite beams through external strengthening with prestressed carbon fiber-reinforced polymer (CFRP) plates and post-tensioned CFRP tendons. A 3D finite element model was developed using ANSYS and validated using experiments. The impact of various parameters on the capacity of the beam was investigated, including the level of post-tensioning in the CFRP tendons, tendon profile, degree of shear connection, and beam load level when adding strengthening CFRP tendons. Results indicate that reinforcing composite beams with bonded CFRP plates using post-tensioning tendons with trapezoidal and parabolic profiles can increase maximum load capacity by 37% and 60%, respectively, while maintaining high stiffness. This study also indicates that the optimal strengthening conditions for the composite beam are when the beam is loaded up to 70% of its capacity and has a composite action degree of 100%.

A New Approach to Prevent Injuries Related to Manual Handling of Carts: Correcting Resistive Forces between Floors and Wheels to Evaluate the Maximal Load Capacity

Test methods that use pushing forces to evaluate the maximal load capacities of carts in design standards require a flat, smooth and horizontal steel plate and thus do not take into account the real conditions of work. Resistive forces of a single wheel of a cart in a uniform rectilinear motion were measured using a unique test bench with five loads. Forty-four wheels were tested (varying diameters, treads and bearings) with one steel plate and four resilient floor coverings. Based on a linear mixed model, all the following results were significant (p < 0.05). Resistive forces were increased linearly with the load and depended on the characteristics of both the wheel and floor. These forces decreased as the diameter increased. They were important for wheels with sleeve bearings but decreased for cone ball bearings and precision ball bearings. Resistive forces depended on the material of the tread and were higher for solid rubber treads. In contrast, the hardness of the tread had little effect. Resistive forces strongly depended on the hardness of the base foam of resilient floor coverings: the softer the base foam, the higher the resistive forces. Test methods in design standards should be reviewed, using corrective forces based on these present results, to prevent musculoskeletal disorders.