Concentrated Load Research Articles

Experimental study and structural analysis of tapered steel beams with cellular openings

As cellular beams are increasingly used in steel construction, different configurations, including tapered cellular beams, are emerging. Steel beams with cellular openings that are tapered have several benefits, as they combine the benefits of an optimally tapered cross-section with practical cellular advantages. To the best of the author's knowledge, the existing literature only contained analytical and numerical studies on tapered cellular beams. Due to the lack of experimental data, an experimental investigation of six tapered specimens with various circular web opening configurations is presented. The geometry of the tested specimens was discussed, and all specimens have narrow web-posts. The tapered cellular I-sections were tested as cantilevers with fixed support and under a vertical concentrated load. Material properties, manufacturing, supports and test-setup were provided. Factors affecting the behavior of the tested specimens, such as taper angles, optimizing the opening diameter and the opening arrangements, were investigated. The results showed that changing the taper angles had an effect on the buckling strength of the investigated beams. In the meantime, optimizing the opening diameter increases the ultimate strength. A structural analysis of a single web-post was presented, and the experimental specimens' web buckling resistance was determined using the simple strut model. The buckling lengths presented in literature were discussed. The results of the analytical methods demonstrated that the change made by Panedpojaman et al. [1] for estimating the buckling strength was visible and more conservative for tapered cellular beams.

Feasibility Study on the Effect of FRP Shear Reinforcements on the Behaviour of FRP-Reinforced Concrete Deep Beams

Unlike steel reinforcements in concrete, Fiber Reinforced Polymer (FRP) materials are light and free from corrosion. Therefore, FRP materials are increasingly being used in structural engineering as a replacement for steel reinforcements. While the use of FRP bars as longitudinal reinforcements in concrete deep beams has been studied somewhat widely, their use and effectiveness as web reinforcements are not well studied. In this study, the effect of the FRP web reinforcements on the behaviour and strength of FRP-reinforced concrete deep beams were investigated in an experimental study. Four glass fiber-reinforced concrete (RC) simply supported deep beam specimens were tested under a concentrated load with different shear span-to-depth ratios and web reinforcement ratios. The behaviour of the deep beams was described in terms of load–deflection behaviour, crack developments, strain in FRP reinforcements, and failure modes. The experimental investigation emphasized the significance of web reinforcements in determining the reinforced concrete deep beam behaviour, such as mid-span deflection, crack breadth, failure modes, and ultimate strengths. Furthermore, to predict the behavior of deep beams, numerical Finite Element models using Abaqus software were created. The present test results were compared to those predicted using the Finite Element models. This investigation shows that web reinforcement is quite important for FRP-RC deep beams to achieve a robust behaviour by enhancing its capacity and deformability.

Time-dependent behaviour of RC beams under eccentric combined loads as a unit of beam-column joint assemblies made from normal strength concrete without/with CFRP wraps

The influence of sustained eccentric loads including torsion on the time-dependent behaviour of monolithically framed RC beams into columns is investigated in this paper. The adopted experimental program entails a number of beam-column assemblies tested under sustained concentric and eccentric combined loads (bending, shear, and torsion). The presence of Fibre Reinforced Polymers (FRP) wraps applied to the beam is considered and the time-dependent performance was thoroughly assessed. The outcomes of the experimental program complemented with finite element (F.E.) results illustrated a significant increase in the time-dependent beam’s twisting and deflection levels. The rise in the beam’s time-dependent deflections was quantified in comparison with those predicted according to Eurocode 2. This rise can be explained by the extent of torsional cracks observed, accompanied by high strain levels, resulting from the interaction between combined loads and the time-dependent deformations of concrete. While the FRP wraps considerably improved the time-dependent torsional stiffness compared to the un-strengthened specimens. The numerical models under different loads ratios (torsion to bending-shear ratio) confirmed the role of the level of combined loads and the developed time-dependent cracks of reducing the members’ stiffness and affecting the twisting levels and hence increased the deflection values. A refined approach of the Eurocode 2 modal has been proposed which considers the interaction of combined forces and hence, the developed stresses on the degrees of the loss of tension stiffening.

Evaluation the behavior of Ring Footing on Gypseous Soil Subjected to Eccentric and Inclined Loads

An extensive program of laboratory testing was conducted on ring footing rested on gypseous soil brought from the north of Iraq (Salah El-Deen governorate) with a gypsum content of 59%. There are limited researches available, and even fewer have been done experimentally to understand how to ring footings behave; almost all the previous works only concern the behavior of ring footing under vertical loads, Moreover, relatively few studies have examined the impact of eccentric load and inclined load on such footing. In this study, a series of tests, including dry and wet tests, were carried out using a steel container (600×600×600) mm, metal ring footing (100 mm outer diameter and 40 mm inner diameter) was placed in the middle of the container top surface that filled with the gypseous soil. Subject to (vertical and inclined) (concentric and eccentric) loads was carried out for dry and soaking soil to discover the differences in bearing capacity as well as ring behaviors. According to the results when the load eccentricity increases on the ring footing from the rate (e = 0B, e = 0.04B e = 0.08B, e = 0.16B) and the inclination load increases as (0°, 5°, 10°, 15°) respectively the ring footing ultimate loads will be reduced.

Behavior study of the steel plate girder with a cellular honeycomb web

Based on the experimental test results of the authors, this investigation is concerned with the finite element analysis to examine and compare the load values and failure modes of the authors’ results. This research was conducted using the Abaqus software. The experimental work included the fabrication of twelve plate girders with honeycomb and flat web plate corrugation patterns, which were then tested under a single concentrated load at the midspan. According to the corrugation dimension or outer honeycomb web thickness, the honeycomb steel plate web girder is divided into three groups (60 mm, 80 mm and 100 mm). The specimens also involved plate girders with a flat web. The specimens were created with three lengths (600 mm, 1,200 mm and 1,800 mm). The Abaqus software was used in finite element models to simulate the concentrated load. The numerical results demonstrated that the 60 mm thick honeycomb web provides a greater load-bearing capacity and shear strength than other girders. The 20 mm honeycomb corrugation on the steel plate girder indicates the increased and improved shear resistance. The conclusion was that as the width of the corrugation increased, so did the steel web’s ultimate load and shear strength, resulting in a positive relationship between the critical shear buckling load of the web and the moment of inertia at the strong axis. When the dimension of the corrugation increases, the moment of inertia of the Y axis (Iy) decreases; thus, the plate girder will fail with a less critical buckling load (Pcr). Also, it can be concluded that as the steel plate thickness of the honeycomb web increases, the shear resistance increases as well. However, the spacing between the intermediate stiffener or the horizontal spacing of the web panel can enhance the shear resistance of honeycomb web girder if it was decreased due to increasing the action of tension field force that resists the diagonal tension developed at the web panel by the applied midspan concentrated force.

A computer vision-assisted method for identifying wheel loads of moving vehicles from dynamic bridge responses

Bridge weigh-in-motion (BWIM) technology, which identifies traffic information such as the axle weights, wheelbases, and velocities of vehicles passing over a bridge from bridge responses, can be beneficial for bridge design, management, and maintenance. However, conventional BWIM methods simplified the coaxial wheel loads of a vehicle using one concentrated force, commonly known as the axle load. Such simplification would lead to two problems. Firstly, it fails to calculate the wheel weights of moving vehicles, which are essential for evaluating the service status of roads and is required to be measured by national weigh-in-motion specifications, such as ASTM E1318-09. Secondly, the transverse distance between the coaxial wheels (track width), and unequal load distributions between left and right coaxial wheels (unbalance) were ignored in the conventional BWIM methods. However, these two factors represented the actual characteristics of the vehicle load applied on the bridge. Hence, ignoring these two factors could lead to significant errors in estimating the vehicle weight when the track width or the unbalance ratio of the test vehicle was different from that of the calibration vehicle. To address the above two problems, this study proposed a new BWIM method, where two concentrated loads with fixed transverse distance were used to represent the coaxial wheel loads of the truck in analyzing the interactions between the truck and the bridge. By doing so, the wheel weights of moving vehicles can be calculated, and both the effects of the unbalance and the track width can be considered in estimating the axle weights of the vehicle. Both experiment results and simulation results demonstrated that the proposed method can effectively identify the wheel weights of moving vehicles, and provide more accurate axle weights than conventional BWIM methods under complex traffic scenarios.

Investigating the Fracture Process and Tensile Mechanical Behaviours of Brittle Materials under Concentrated and Distributed Boundary Conditions

In this study, concrete was selected to investigate the real-time splitting tensile mechanical and fracture behaviours of brittle materials using the Brazilian test under concentrated and distributed boundary conditions. The digital image correlation (DIC) method was adopted to evaluate the tensile strength and failure process in Brazilian tests using a high-resolution camera. The DIC results showed that the position of the crack initiation randomly occurred at the centre of a disc and at the boundary in Brazilian tests with concentrated loads (BTC). Comparatively, the crack initiated at the centre of discs in most Brazilian tests with distributed loads (BTD), as validated by the DIC results. Our results indicated that the average nominal tensile strength of specimens cracking at the boundary was larger than that of specimens cracking at the centre in the BTC, suggesting that the nominal tensile strength measured by the Brazilian test was related to the failure process of the discs. Moreover, this study demonstrated that the tensile strength measured by the Brazilian test was dependent on the boundary conditions. The equation recommended by the ISRM (International Society for Rock Mechanics) might slightly overestimate the tensile strength of brittle materials based on the pure elastic theory and hyperbolic-distributed loading conditions at the boundaries.

Energy-based strut stress analysis of 3D lattice cores in sandwich panels

3D strut-based lattices consisting of periodic representative volume elements (RVE) have gained more importance over the last few years since they provide outstanding mechanical performance and an efficient design in lightweight engineering. In sandwich panels, strut-based lattices may replace the established honeycomb cores. In this study, an analytical model is introduced to investigate 3D strut-based lattice cores of sandwich panels. Body-centered cubic and face-centered cubic RVEs reinforced by vertical struts (BCCZ and F2CCZ) are considered as sandwich cores. Since the core stiffness is generally low in comparison with the face sheet stiffness, the derived model considers through the thickness stresses in the core caused by transverse concentrated loads, which are not obtained by the common sandwich theories. Furthermore, stress concentrations near the support points are sufficiently captured thanks to higher-order displacement representations. The analysis of the core behavior is based on the homogenization and dehomogenization of the lattice core methods. Compared with the finite element analysis, the stresses in the lattice struts are determined by the proposed model with ten times less computational effort and adequate accuracy, particularly in the highly loaded vertical struts.

Effect of load application method on thermal contact resistance and uniformity of temperature distribution

Traditionally, the research on thermal contact resistance based on real rough surfaces is often limited to the uniform load. This study investigated the effects of the material, surface roughness, pressure load, and temperature on the thermal contact resistance and contact interface temperature distribution non-uniformity under a concentrated load. First, rough surfaces with different surface roughness degrees were generated by using a random generation method, and microscopic contact numerical models of three different materials were established. Then, the real contact area of different pressure loads under uniform and concentrated loads were calculated. Finally, heat transfer analysis was performed at different temperatures based on the microcontact state, the thermal contact resistance and the contact interface temperature distribution non-uniformity were calculated. Compared with the uniform load, the thermal contact resistance and the non-uniformity of the temperature distribution were improved under the concentrated load, and the effect was more obvious under the conditions of a large pressure load and small surface roughness degree. In addition, it was found that the uniformity of the temperature distribution on the contact surface was proportional to the real contact area and temperature instead of the thermal contact resistance except when the real contact area was very small.

Experimental study of steel plate girder with innovative shape of web under concentrated load

Experimental study of steel plate girder with innovative shape of web under concentrated load

Research on stability of deepwater drilling riser system in freestanding mode

If a floating drilling platform encounters sudden bad sea conditions during deepwater operation, it is necessary to disconnect the drilling riser and the floating platform in an emergency. A buoyancy can structure is required to be installed at the top of the riser to ensure that the disconnected drilling riser can stand alone without instability accidents. According to the main structural characteristics and environmental conditions of the freestanding riser and the buoyancy can at the top of the riser, the compressive buckling stability of deepwater drilling riser in freestanding mode under the condition of insufficient top tension is studied in this paper, and the main problem is simplified to the buckling problem of an equal section beam under uniformly distributed axial load and top concentrated force. Firstly, the elastic stability control equation of the riser is established according to the mechanical balance, geometry and constitutive relationship of the riser's micro-element, and the equation as well as the corresponding top and bottom boundary conditions are made dimensionless. Secondly, the elastic stability equation of the micro-bending riser is linearized, the power series solution is obtained according to the perturbation theory, and the influence of different parameters on linear buckling is analyzed. Finally, we convert the elastic stability equation with large deflection into a two-point boundary value problem of the first-order differential equation system under the boundary conditions and two other given conditions. The shooting method program of the two-point boundary value problem including the changes of the top concentrated load and the distributed axial load parameters is developed by using MATLAB, and the calculation analysis is carried out, which reveals the rules of the buckling load and buckling shape after the buckling. The research results of this paper can provide scientific basis and technical guidance for the structure and size design of drilling riser and buoyancy can.

The biomechanical efficacy of a hybrid support surface in protecting supine patients from sacral pressure ulcers.

Support surfaces are the most important pressure ulcer/injury prevention technology available to clinicians for protecting their at-risk patients. A hybrid support surface marries the benefits of reactive and active support surfaces, by using high-quality foam material inside inflatable air cells. When used in its "static mode", it is a constant low air pressure mattress which delivers pressure redistribution in response to patient bodyweight and movements, by maximising the immersion and envelopment performance of the support surface. When used in its powered "dynamic mode", this system further delivers alternating pressure care via the connected foam and air cells. Modes of action of hybrid support surfaces were never studied quantitatively before, excluding through the limited scope of interface pressure mapping. In this work, we developed a novel computational modelling framework and simulations to visualise and quantify the state of soft tissue loading at the buttocks of a supine patient positioned on a hybrid support surface, in both the static and dynamic modes. We found that the dynamic mode effectively shifts deep concentrated soft tissue loading from under the sacral bone (towards the sacral promontory) to the tip of the sacrum (coccyx) and vice versa, and thereby, generates a deep tissue offloading effect.

Nonlinear Modeling of Contact Stress Distribution in Thin Plate Substrates Subjected to Aspect Ratio.

The foundation substrate's basal contact stresses are typically thought to have a linear distribution, although the actual form is nonlinear. Basal contact stress in thin plates is experimentally measured using a thin film pressure distribution system. This study examines the nonlinear distribution law of basal contact stresses in thin plates with various aspect ratios under concentrated loading, and it establishes a model for the distribution of contact stresses in thin plates using an exponential function that accounts for aspect ratio coefficients. The outcomes demonstrate that the thin plate's aspect ratio significantly affects how the substrate contact stress is distributed during concentrated loading. The contact stresses in the thin plate's base exhibit significant nonlinearity when the aspect ratio of the test thin plate is greater than 6~8. The aspect ratio coefficient-added exponential function model can better optimize the strength and stiffness calculations of the base substrate and more accurately describe the actual distribution of contact stresses in the base of the thin plate compared to linear and parabolic functions. The correctness of the exponential function model is confirmed by the film pressure distribution measurement system that directly measures the contact stress at the base of the thin plate, providing a more accurate nonlinear load input for the calculation of the internal force of the base thin plate.

Mechanical model for the shear-punching strength of steel fiber reinforced concrete slabs under concentric loading

Experimental studies have shown that the use of steel fiber reinforced concrete increases the punching strength of concrete slabs, due to the capacity of steel fibers to bridge residual tensile stresses across the shear crack. Despite this, there is a lack of simple and accurate design formulations capable of providing substantiated explanations for the experimentally observed behavior of steel fiber reinforced concrete slabs subjected to concentrated loads. In this paper, a previously developed model for the shear and punching strength of conventional reinforced concrete, namely “Multi-Action Shear Model”, has been extended to shear punching of steel fiber reinforced concrete slabs without shear reinforcement. The contribution of fibers to the punching strength is accounted for by including the vertical component of the residual stresses transferred along the critical shear crack. Such residual stress accounts for the volume, geometry and resistant characteristics of the fibers, and for the tensile strength provided by the concrete matrix. In addition, the residual stress is affected by a size factor to account for the effects of the slab depth on the efficiency of the steel fibers. The results of the model have been compared with the experimental results of 94 tests available in the literature, obtaining a mean value and a coefficient of variation of 1.10 and 0.12, respectively. Moreover, the robustness of the model has been demonstrated through a study of sensitivity in front of the dimensions of the slab and the support, the amount of longitudinal reinforcement, the strength of the concrete, the volume and the residual tensile stress of the fibers, having detected little influence of these parameters on the mean value and scatter of the results.

Numerical Simulations on the Flexural Behaviours of Reinforced Concrete Girders Strengthened with Bolts

Precast reinforced concrete (RC) girders with dapped ends are used in order to reduce the overall depths of concrete floors and bridge decking and meet architectural requirements. The structural requirements by reducing the depths of these girders result in stress concentrations within the recessed zones. Thus, girders with dapped ends require special details for the strengthening systems. The use of open transverse holes in RC sections is for the passage of various service lines such as telecommunication cables, gas lines, water pipes, electricity cables, etc. The behaviours of RC girders with dapped ends and openings strengthened by bolts subjected to two vertical concentrated loads were numerically simulated by utilising commercial finite element software ANSYS. The numerical results from the simulated models were identical and compatible with those experimental results stated in literature. The validation of the numerical results with those experimental ones was based on the statistical analysis by including the calculations of the correlation coefficients, arithmetic means, and standard deviations for all the simulated girder models in terms of loads and deflections. The obtained numerical results showed that an increase in the compressive strength of concrete by 20% would cause an increase in the loading resistance of the models by 13% and a decrease in the deflection by 21%, respectively. Also, it was indicated that the type of section, i.e., the change of the section from solid to open (with transverse openings), would decrease the resistance of the section by 8–16% and increase the deflections by 15–20%. Similarly, an increase in the number of holes would result in the decreases in the load resistance by up to 6% and the increases in the deflections by up to 24% under the same applied loads. Strengthening openings using vertical bolts has an important role in enhancing the resistance of the models by 8–20% and decreasing the deflections by 20–30%. The failure patterns were hybrid, e.g., flexure and shear, and identical with the experimental ones. Finally, the effect of using the cylindrical compressive strength of concrete as a mechanical parameter on the structural behaviours of the simulated models was investigated, which could improve the resistance loading and decrease the deflections of the models.

Flexural Strength of Reinforced - Bamboo Concrete Infill Structural Beam Subjected to Concentrated Load at Midspan

Bamboo is still considered a material for poor people in rural areas. Still, it also has the potential to be fully developed engineering material reinforced structural beams with concrete infill to increase the structural strength of the structures, which is natural aesthetic, and more durable than bamboo alone as structural parts of buildings. This study aims to determine the flexural strength of bamboo with concrete infill as a structural beam subjected to a concentrated load at midspan. The materials used were whole bamboo culms, specifically Dendrocalamus Asper Schultes, Dendrocalamus Merrillianos Elmer, Bambusa Vulgaris Schrad, and Bambusa Blumeana Schultes cut into 600 mm lengths and treated with seawater and seawater with mango polyphenol infilled with concrete. The concrete was cured for 7, 14, 28, and 56 days, respectively. The results showed that the whole bamboo culm treated with seawater and treated with seawater plus a 10 percent solution of mango polyphenol extract remarkably increased its flexural strength. The concrete infill to the whole bamboo culm as the beam is effective, increasing flexural strength when treated with mango polyphenol. The curing age of concrete and treatment of bamboo culm with seawater and mango polyphenol affects the flexural strength of reinforced bamboo with concrete infill subjected to a concentrated load at midspan. Reinforced bamboo concrete infill-based construction materials can reduce pressure on resources and the environment. These materials have environmental and mechanical advantages over conventional construction materials.

Axial compressive strength of slender UHPFRC-filled steel tubes

Ultra-high performance fiber-reinforced concrete (UHPFRC)-filled steel tube (UHPFRC-FST) slender columns have not been studied to date, although ample research exists on this system as short columns. Furthermore, current code provisions (e.g. CAN/CSA S16) were developed for normal strength concrete and are thus potentially inadequate for UHPFRC-FSTs. In this study, a robust three-dimensional nonlinear finite element model was developed and validated using LS-DYNA software to simulate behaviour of slender UHPFRC-FSTs of circular cross-section under concentric axial compressive loads. An extensive parametric study was then performed, varying slenderness ratio (kL/r) based on column length (L) where r is the radius of gyration, diameter-to-thickness ratio (D/t) of the steel tube, effective length factor (k), and tube’s yield strength (Fy). The study showed that axial load-carrying capacity reduced by 78% when slenderness ratio increased from 12 to 157. The column transitions from material failure by diagonal shear plane in concrete, to global buckling at a slenderness ratio of about 80. Axial load-carrying capacity also reduces rapidly with D/t until a ratio of about 45 and then reduces at a much lower rate thereafter. CAN/CSA S16 code provisions grossly underestimate the load-carrying capacity of slender UHPFRC-FSTs by 13 to 46% as slenderness ratio increased from 12 to 157. The underestimation also increased dramatically with diameter-to-thickness ratio, from 8% atD/t = 10 to 40% atD/t = 80, and with effective length factor k, by 15% at k=0.5 to 48% at k=2. 0. A modification to CAN/CSA S16:19 equation is proposed based on multiple regression analysis of the results of the parametric study.

Investigation on the impact resistance of reinforced geopolymer concrete slab

Geopolymer concrete (GPC) as a green construction material has the potential to substitute traditional concrete, but there is a lack of understanding of the performances of geopolymer concrete structures subjected to dynamic loadings. This study investigates the dynamic responses of reinforced concrete slabs made of ambient cured alkali-activated GPC under static and dynamic concentrated load. Laboratory tests are performed which revealed that GPC slabs exhibited typical punching shear failure model under both static and impact load. Current design codes including ACI, Eurocode 2 and CSCT model can well predict the static punching resistance capacity of GPC slab, but fail to predict the dynamic punching resistance. Numerical modelling is carried out to investigate the dynamic punching shear mechanism. The results indicate that the impact response of GPC slab is highly influenced by inertial effect. In the initial response stage the impact force is mainly resisted by the slab inertial resistance. The GPC dynamic material properties and structural dynamic amplification effect affect the dynamic response and damage of GPC slabs. Intensive numerical simulations are performed to quantify the influences of slab thickness, reinforcement ratio, impactor weight and impact velocity on impact responses of GPC slabs. Empirical formula is derived based on the test and numerical results to predict the dynamic punching resistance of reinforced GPC slabs.

Behavior of confined concrete with recycled glass fiber-reinforced polymer needles as coarse aggregates under axial compression

Cutting waste GFRP into needles as part of coarse aggregates in concrete shows to be a promising approach for recycling the waste GFRP composites. However, the resulting concrete has its compressive strength lower than that of normal concrete, and is therefore limited for use in nonstructural elements. The present study proposes a method to improve the robustness of such concrete in structural elements by utilizing the confined concrete concept, in which the concrete with GFRP needles is confined with carbon fiber-reinforced polymer wraps. A series of compression tests under concentric loading were conducted with the ratio of GFRP needles to the total coarse aggregates (i.e., replacement ratio) and the confining jacket stiffness as the two test parameters. The test results indicate that the compressive strength of unconfined concrete decreased by approximately 10% due to replacing 15% coarse aggregates with GFRP needles, while the confining jackets of the same stiffness applied resulted the compressive performance of the confined concrete with needles comparable to or even slightly higher than that of its counterpart without needles. Two widely-used theoretical models were used to predict the compressive performance of the confined concrete, finding that both of them overestimated the axial stress but underestimated the axial strain of the confined concrete with GFRP needles. Therefore, a refined model is required to predict the behavior of confined concrete with GFRP needles under axial compression.

Acute adaptation of central and peripheral motor unit features to exercise-induced fatigue differs with concentric and eccentric loading.

What is the central question of this study? Conflicting evidence exists on motor unit (MU) firing rate in response to exercise-induced fatigue, possibly due to the contraction modality used: Do MU properties adapt similarly following concentric and eccentric loading? What is the main finding and its importance? MU firing rate increased following eccentric loading only despite a decline in absolute force. Force steadiness deteriorated following both loading methods. Central and peripheral MU features are altered in a contraction type-dependant manner, which is an important consideration for training interventions. Force output of muscle is partly mediated by the adjustment of motor unit (MU) firing rate (FR). Disparities in MU features in response to fatigue may be influenced by contraction type, as concentric (CON) and eccentric (ECC) contractions demand variable amounts of neural input, which alters the response to fatigue. This study aimed to determine the effects of fatigue following CON and ECC loading on MU features of the vastus lateralis (VL). High-density surface (HD-sEMG) and intramuscular (iEMG) electromyography were used to record MU potentials (MUPs) from bilateral VLs of 12 young volunteers (six females) during sustained isometric contractions at 25% and 40% of the maximum voluntary contraction (MVC), before and after completing CON and ECC weighted stepping exercise. Multi-level mixed effects linear regression models were performed with significance assumed as P<0.05. MVC decreased in both CON and ECC legs post-exercise (P<0.0001), as did force steadiness at both 25% and 40% MVC (P<0.004). MU FR increased in ECC at both contraction levels (P<0.001) but did not change in CON. FR variability increased in both legs at 25% and 40% MVC following fatigue (P<0.01). From iEMG measures at 25% MVC, MUP shape did not change (P>0.1) but neuromuscular junction transmission instability increased in both legs (P<0.04), and markers of fibre membrane excitability increased following CON only (P=0.018). These data demonstrate that central and peripheral MU features are altered following exercise-induced fatigue and differ according to exercise modality. This is important when considering interventional strategies targeting MU function.