Changes In External Load Research Articles

An Investigation into the Impact of Time-Varying Non-Conservative Loads on the Seismic Stability of Concrete-Filled Steel-Tube Arch Bridges

When the arch rib of the mid-bearing through and lower-bearing through arch bridges undergoes out-of-plane deformation, it is usually subject to the resilience force provided by the flexible hanger, which is known as the “non-conservative force effect” of the suspender. In contrast to the static condition, in the dynamic scenario, the time-varying non-conservative force exerted by the flexible suspender becomes more complex due to dynamic changes in external load. Moreover, the difference in fundamental frequency and vibration period between the bridge system and arch rib may influence the stress distribution within the arch rib during ground motion. This paper investigates the impact of time-varying non-conservative forces on the dynamic stability of arch ribs in concrete-filled steel tube (CFST) bridges under seismic loads. Specifically, it examines the influence of different seismic waveforms, frequency disparities between bridge slabs and arch ribs, and suspender stiffness on the non-conservative effect. The results reveal significant disparities in the impact of non-conservative forces exerted by the suspender during seismic events with identical intensity but varying frequency characteristics. The influence of non-conservative forces on the dynamic stability of bridges escalates as deck stiffness increases, while it remains relatively unaffected by changes in suspender stiffness.

Multi-Objective Sensitivity Analysis of a Wind Turbine Equipped with a Pumped Hydro Storage System Using a Reversible Hydraulic Machine

A typical wind system captures wind energy and converts it into electricity, which is then converted to DC for battery storage using an AC/DC converter; an inverter then supplies AC electricity at the grid frequency. However, this solution involves losses in electronic components and incurs costs and environmental impacts associated with battery storage. To address these issues, a different wind system layout configuration is considered, where the energy storage duties are assumed by a hydro storage system employing a reversible hydraulic pump (referred to as a Pump as Turbine). This solution utilises an elevated reservoir connected to the Pump as Turbine to compensate for fluctuations in wind and load; this approach offers lower costs, a longer lifespan, reduced maintenance, and a smaller waste management cost. This study focuses on a comprehensive sensitivity analysis of the new wind system power layout, considering multiple objectives. Specifically, the analysis targets the net change in the mass of water (potential energy) stored in the pumped hydro system, the captured wind energy, and the torque provided in hydraulic turbine mode. On the other hand, the design variables are represented by the Pump as Turbine-specific speed, the hydraulic system gearbox ratio, and the pump head. To assess how solutions are affected by random changes in wind speed and external load, the sensitivity analysis considers the multi-objective optimisation problem showing for both the wind speed and the external load a stochastic contribution.

Robust Structural Health Monitoring of CFRP Structures under Varying Loads using NSFD and Machine Learning with Combined Usage of Acceleration and Strain Data

Structural health monitoring (SHM) of objects in situ often requires a suitable combination of different methods and measurement techniques. In the field of aerospace applications, the previous research project "Combined acoustic and modal structure monitoring" dealt with the development of a robust SHM system for damage detection in carbon-fibre-reinforced polymer (CFRP) structures under varying realistic loads. The methods combined within the project were based on guided waves, acoustic emission, different vibration monitoring techniques and strain measurement. The present paper deals with the application of the nullspace-based fault detection algorithm (NSFD) combined with a machine learning approach based on strain measurements to classify different load conditions of the structure. Due to the high sensitivity to changes in the statistical properties of the measurement data, the NSFD algorithm reacts very sensitively to structural changes, but also to changes in the environmental conditions, such as changes in the external loads and the resulting stress state of the structure. In the paper, the impact of varying external loads on the NSFD damage indicator is analysed and shown. To prevent the NSFD algorithm from causing false alarms due to changes in the load conditions, but still being sensitive to small structural changes due to impact damages, the strain sensor data is used to predict the external loads on the structure. For this, machine learning is used to create clusters of similar stress states. For every cluster, a baseline for the NSFD algorithm must be made. The resulting approach is robust against changes in external loads and sensitive to small changes in the structure due to damages at the same time. The theory and the algorithms are successfully tested with measured data sets from a CFRP-airplane structure.

Dynamic biaxial loading of vascular smooth muscle cell seeded tissue equivalents

An intricate reciprocal relationship exists between adherent synthetic cells and their extracellular matrix (ECM). These cells deposit, organize, and degrade the ECM, which in turn influences cell phenotype via responses that include sensitivity to changes in the mechanical state that arises from changes in external loading. Collagen-based tissue equivalents are commonly used as simple but revealing model systems to study cell–matrix interactions. Nevertheless, few quantitative studies report changes in the forces that the cells establish and maintain in such gels under dynamic loading. Moreover, most prior studies have been limited to uniaxial experiments despite many soft tissues, including arteries, experiencing multiaxial loading in vivo. To begin to close this gap, we use a custom biaxial bioreactor to subject collagen gels seeded with primary aortic smooth muscle cells to different biaxial loading conditions. These conditions include cyclic loading with different amplitudes as well as different mechanical constraints at the boundaries of a cruciform sample. Irrespective of loading amplitude and boundary condition, similar mean steady-state biaxial forces emerged across all tests. Additionally, stiffness-force relationships assessed via intermittent equibiaxial force–extension tests showed remarkable similarity for ranges of forces to which the cells adapted during periods of cyclic loading. Taken together, these findings are consistent with a load-mediated homeostatic response by vascular smooth muscle cells.

Connection strength analysis and prediction of external swaging based on tube deformation measurement

Fittings have extensive use in the aerospace, automotive, and other industries as they serve as sealing and connecting components for tube systems. External Swaging (ES) forming creates a permanent joint through plastic deformation of the metal. This technique is not dependent on the tube's wall thickness and offers benefits such as high-pressure resistance and effective sealing. Using the forming process of a 10 mm Ti-3Al-2.5 V tube with an adapted 21-6-9 fitting as an illustration, a three-dimensional finite element model for the entire assembly was developed. The model consists of the tube, fitting, elastic clamp, and crimping tool. The formation mechanism and joint strength of external swaging are analyzed by numerical simulation and experimental testing. The results show that during the extrusion process, the tangential contact between the extrusion tool and the elastic clamps converts external radial loads into circumferential loads, resulting in circumferential strains in the tube. Circumferential strain creates an arched sealing area between the tube and fitting contact surfaces, providing sealing and joint strength. The joint strength of 10.60 kN was determined through finite element simulation. The load required for forming is determined by analysis to be 80.13 kN. and the relationship between squeeze load, crimp volume and joint strength is clarified. The study revealed that the height of the arch area aligns with the connection strength's change rule concerning extrusion load, fitting the two found that when the external extrusion load changes, the two are linear rule of changing. Based on this, a method is suggested for forecasting the strength of a joint by measuring the height of the arch in the tube after forming.

Sliding-mode Active Disturbance Rejection Permanent Magnet Synchronous Motor Control System

Aiming at the permanent magnet synchronous motor with external perturbations and internal uncertainties such as external load, rotational inertia and armature resistance changes, a servo control system based on sliding mode self-immunity controller is designed. By constructing a mathematical model of the servo system of the permanent magnet synchronous motor, considering the internal uncertainty caused by the change of the system parameters and the external random disturbance as the "total disturbance", and designing the transition process and the linear expansion state observer to observe and compensate for it, the system response can track the input signal quickly and without overshooting, and the sliding-mode state feedback makes the closed-loop servo system achieve fast and stable control, and the sliding-mode Active Disturbance Rejection control controller can be used to control the system. The sliding mode state feedback enables the closed-loop servo system to realize fast and stable control, and its consistent stability is proved by the Lyapunov method. Simulations show that this sliding- mode Active Disturbance Rejection control control strategy improves the system response speed and load carrying capability compared with the traditional sliding-mode control.

An optimization method of acceleration and deceleration time of feed system based on load inertia

The acceleration and deceleration time is usually a constant value in the process of computer numerical control (CNC) machine tool processing, which cannot adapt to the change of external load and greatly affects processing efficiency. This paper proposes an optimization method for the acceleration and deceleration time of the feed system based on load inertia, which provides the basis for the adaptive adjustment of the acceleration and deceleration time of the feed system. Firstly, by establishing the dynamic model of the servo system, the acceleration and deceleration method is used to identify the external load inertia under different working conditions. The prediction model of the current variance based on load inertia and acceleration and deceleration time parameters is established by using the response surface method, and then the multi-objective particle swarm optimization algorithm is used to build the acceleration and deceleration time optimization model based on the load inertia. At the same time, the inertia identification part is compared with the model reference adaptive system method and the empirical formula estimation method based on current and velocity, the simulation and cutting experiment results show that the inertia identification method based on acceleration and deceleration optimizes the other method. Finally, the machining experiments are carried out on three-axis and five-axis machine tools with the same machine tool type, and by adding different counterweight blocks to change the external load. The test proves that the acceleration and deceleration adaptive adjustment strategy based on load inertia can effectively improve processing efficiency and reduce the fluctuation of the processing load.

STUDY OF A DISTRICT HEATING SYSTEM WATER BOILER AS A OBJECT OF CONTROL


 
 The analysis of the operating conditions of a typical district heating system, in particular, a hot water gas boiler, was carried out. It is shown that the boiler, as the main control object, operates under conditions of constant change in external heat load, which, due to their random nature, leads to a number of uncertainties. The expediency of the mathematical description of uncertainties using the stochastic method as the most tested in practical conditions is substantiated. According to the results of the passive experiment on the hot water gas boiler KVG6.5-150 of the district heating system of one of the districts of Kharkov, an array of hourly experimental data was obtained, reflecting the main performance indicators of the hot water boiler. As a result of data processing by the least squares method, a mathematical model of the boiler was obtained in the form of a linear regression equation, reflecting the relationship between the temperature of the coolant at the boiler outlet and the ambient air temperature, the temperature of the coolant at the inlet to the boiler and with the flow rates of natural gas and coolant to the boiler. The obtained regression equation was verified by Student's t-test, which confirmed the significance of all coefficients of the regression model. The practical significance of the multiple regression equation was assessed using the coefficient of determination. The quality of the multiple regression equation as a whole was assessed using Fisher's F-test. Since parallel surveys were not conducted, instead of checking the adequacy, the quality of the approximation of the experimental points by the accepted regression equation was assessed, that is, it was checked whether this equation makes sense. Such a test was carried out by comparing the residual variance and the variance relative to the mean. The calculation results showed that the value of the coefficient of determination significantly exceeds the allowable value, and the actual value of the Fisher criterion significantly exceeds the table value. The obtained indicators led to the conclusion that the relationship between the variables in the regression model is significant, and the proposed stochastic method and the multiple linear regression equation can be used to make decisions in the process of synthesizing the technical structure of a computer-integrated control system for objects of a district heating system.
 
 
 
 
 

Adaptive shift strategy of a novel power-cycling variable transmission for construction vehicles

A new power-cycling variable transmission (PCVT) is proposed and applied to construction vehicles to improve transmission efficiency. To adapt to changes in external loads, construction vehicles need to shift gears continuously. However, the shift points obtained by traditional method cannot change with working conditions. This study aims to identify construction vehicles’ mass and gradient changes, and to develop a shift correction strategy. The double-forgetting factors least squares method is designed to identify slope gradient and load. A PCVT dynamic shift strategy is developed based on speed ratio adjustment characteristics. Next, a modified shift strategy under different loading mass and slope gradient conditions is proposed based on the construction vehicles’ mass change ratio, the gradient change ratio and balanced velocity. Simulation results show the proposed method can correct shift points, improve operation efficiency, avoid shift cycles and ensure a safer operation process.

High-Quality Positioning Strategy for Biaxial Contour Machining System With Nonlinear Model Predictive Control

The trajectory tracking ability is an important index to measure the computer numerical control (CNC) machining tools. In this paper, the nonlinear model predictive control strategy (NMPC) is proposed to improve the trajectory tracking ability of the biaxial contour machining system (BCMS). The position-, velocity-, and current-loop of the permanent magnet synchronous motors (PMSMs) of the BCMS are considered as the complete control object to construct a single-loop nonlinear model predictive controller. Meanwhile, the matching non-linear disturbance observer (NL-DOB) is designed to estimate the uncertainty disturbances caused by the parameters mismatch, external load changes and harmonic disturbances in real-time. And the estimated disturbance values are used as feed-forward compensations, which can improve the steady-state performance of the system. At last, the positioning performance comparison between the proposed strategy and the conventional ones are carried on the testbench. The experimental results indicate that the positioning errros can be reduced by up to 40% with the proposed algorithm.

Finite element analysis of stress field and fatigue life prediction of notched specimens under multiaxial load

PurposeThe stress state near the notch affects fatigue damage directly, but quantifying the stress field is difficult. The purpose of this study is to provide a mathematical description method of the stress field near the notch to achieve a reliable assessment of the fatigue life of notched specimens.Design/methodology/approachFirstly, the stress distribution of notched specimens of different materials and shapes under different stress levels is investigated, and a method for calculating the stress gradient impact factor is presented. Then, the newly defined stress gradient impact factor is used to describe the stress field near the notch, and an expression for the stress at any point along a specified path is developed. Furthermore, by combining the mathematical expressions for the stress field near the notch, a multiaxial fatigue life prediction model for notched shaft specimens is established based on the damage mechanics theory and closed solution method.FindingsThe stress gradient factor for notched specimens with higher stress concentration factors (V60-notch, V90-notch) varies to a certain extent when the external load and material change, but for notched specimens with relatively lower stress concentration factors (C-notch, U-notch, stepped shaft), the stress gradient factor hardly varies with the change in load and material, indicating that the shape of the notch has a greater influence on the stress gradient. It is also found that the effect of size on the stress gradient factor is not obvious for notched specimens with different shapes, there is an obvious positive correlation between the normal stress gradient factor and the normal stress concentration factor compared with the relationship between the shear stress gradient factor and the stress concentration factor. Moreover, the predicted results of the proposed model are in better agreement with the experimental results of five kinds of materials compared with the FS model, the SWT model, and the Manson–Coffin equation.Originality/valueIn this paper, a new stress gradient factor is defined based on the stress distribution of a smooth specimen. Then, a mathematical description of the stress field near the notch is provided, which contains the nominal stress, notch size, and stress concentration factor which is calculated by the finite element method (FEM). In addition, a multiaxial fatigue life prediction model for shaft specimens with different notch shapes is established with the newly established expressions based on the theory of damage mechanics and the closed solution method.

Shape perception of soft hand based on dual-signal comparison contact detection

PurposeThe structural adaptive ability of the soft robot is fully demonstrated in the grasping task of the soft hand. A soft hand can easily realize the envelope operation of the object without planning. With the continuous development of robot applications, researchers are no longer satisfied with the ability of the soft hand to grasp. The purpose of this paper is to perceive the object’s shape while grasping to provide a decision-making basis for more intelligent robot applications.Design/methodology/approachThis paper proposes a dual-signal comparison method to obtain the fingertip position. The dual signal includes the displacement calculated by the static model without considering the external load change and the displacement calculated by the bending sensor. The dual-signal comparison method can use the obvious change trend difference between the above two signals in the hover and contact states to identify the touch position. The authors make the soft hand scan around the object through touch operation to detect the object’s shape, and the tracks of every touch fingertip position can envelop the object’s shape.FindingsThe experimental results show that the dual-signal comparison method can accurately identify the contact moment of soft fingers. This detection method makes the soft hand develop the shape detection ability. The soft hand in the experiment can perceive squares, circles and a few other complex shapes.Originality/valueThe dual-signal comparison method proposed in this paper can detect a touch action by using the signal change trend when the working condition suddenly changes with the rough robotic model and sensing, thus improving the utilization value of the measured signal. The problems of large model errors and inaccurate sensors also negatively impact the use of other soft robots. It is generally difficult to achieve good results by directly using these models and sensors with the thinking of rigid robot analysis. The dual-signal comparison method in this paper can provide some reference for this aspect.

Dynamic modelling and control system design of micro-high-temperature gas-cooled reactor with helium brayton cycle

It is possible to use the micro-high-temperature gas-cooled reactor with helium Brayton cycle (Mi-HTR) as a mobile micro-nuclear power source to provide a stable power supply. Because the Mi-HTR is a highly integrated system, the devices involved are highly coupled and mutually constrained. Therefore, the dynamic model of 5 MW Mi-HTR was established through theoretical derivation. Compared with the design value, the maximum error of steady-state calculation results is less than 2%, and the temperature error is less than 1 K. The transient behaviour is consistent with the experimental trend. The maximum relative error of flow is less than 1.5%, and the maximum relative error of pressure is less than 2.8%. On this basis, the characteristics of Mi-HTR such as large time delay, nonlinear, strong coupling and parameter time-varying are obtained by analysing the dynamic characteristics. The steady-state operation scheme of Mi-HTR is proposed. The reactor outlet helium temperature control, the electric power/rotor speed control, and the precooler/intercooler outlet helium temperature control are designed. A dynamic control model for Mi-HTR is established. The designed control system can cope with the 33% step change of external load.

Model Predictive Current Control for IPMSM Drives With Extended-State-Observer-Based Sliding Mode Speed Controller

Aiming at the characteristics that the classical proportional-integral (PI) controllers and the model predictive current control (MPCC) is extremely dependent on the motor parameters, and PI controllers are sensitive to the changes of the load torque, a novel extended-state-observer-based sliding mode speed control (ESO-SMSC) scheme and an extended-state-observer-based MPCC (ESO-MPCC) scheme are proposed to improve the speed and current tracking performance of the interior permanent magnet synchronous motor (IPMSM) under the disturbances of the internal parameter mismatch and the external load change. Firstly, the reaching law of the SMSC will be redesigned, and an ESO is designed to estimate the total disturbance to update the control law of the SMSC in real-time. Secondly, the stability of the closed-loop IPMSM drive system with the ESO-SMSC is proved by the Lyapunov theory. Thirdly, in the prediction part of the MPCC, another ESO real-time estimation of total disturbance is designed to compensate for the disturbance, which improves the strong robustness of the MPCC to the disturbance caused by parameter mismatch. Finally, experimental comparisons of the ESO-SMSC scheme, the ESO-MPCC scheme, and the ESO-SMSC+ESO-MPCC scheme are compared experimentally. The analysis and results show that the ESO-SMSC+ESO-MPCC scheme has good speed response and current characteristics, which proves the superiority of the proposed scheme for disturbance rejection.

The Influence of Configuration Parameters of the Planetary Drive of Crank Presses on its Dynamic and Energy-Consumption Characteristics

Introduction. The planetary drive has been widely found in the activation systems of crank presses as it improves working conditions of friction units and reduces press metal consumption and energy consumption.Problem Statement. For studying the planetary motion of its main parts, it is advisable to consider its operation as four periods characterized by different patterns of changes in external loads and, consequently, different patterns of motion of core parts. The periods between switching the brakes when one link has not stopped, while other one starts moving is of the greatest interest. The problem of dynamic and energy-consumption parameters of the drive in transient conditions still remain a little open.Purpose. The purpose of this research is to qualitatively assess the influence of configuration parameters on the dynamics of the processes of switching and stopping the planetary drive.Material and Methods. The parameters of the experimental pilot plant, a model planetary drive with a nominal load of 400 kN, have been calculated. The minimum speed of the central gear has been estimated depending on the moments of inertia of the leading mass and the outer gear. The obtained dependences have been processed with the use of a standard mathematical apparatus.Results. It has been found that the energy-consumption and dynamic parameters of the drive are significantly influenced by such characteristics as moments of inertia and braking moments, while decreasing angular velocity of the drive flywheel does not depend on the moments of inertia of the stopped links. The rate of braking processes is determined by the elastic properties of the friction materials and the parameters of the brake springs, not by the parameters of compressed air outflow.Conclusions. The obtained analytical and graphical dependences have allowed not only qualitative, but also quantitative assessment of the influence of the parameters on the dynamics of processes. These recommendations can be used at the design stage, to select the optimal parameters of the drive with the predicted properties.

Wear Calculation for a Radial Plain Bearing under Randomly Changing Temperature and Load

A stochastic model of the wear process of a thin coating in a radial plain bearing that takes into account random changes in the bearing temperature and external load is described. The results of a numerical analysis of the process of bearing wear in relation to the conditions of operation in open space at near-Earth orbital stations are presented. The importance of taking into account random changes in temperature and external load for predicting bearing wear and, in particular, its durability is evaluated.

Water quality modeling of a eutrophic drinking water source: Impact of future climate on Cyanobacterial blooms

Cyanobacterial blooms are becoming more frequent in freshwater sources, causing concern throughout the world. Cyanobacterial blooms affect human health and the entire environment. Numerical modeling is an effective tool for investigating aquatic systems. In this study, a 3D hydrodynamic and water quality (ecological) model was used to simulate eutrophication of a drinking water source, Lake Vomb, in Sweden under present and future scenarios. The hydrodynamic model was set-up in MIKE 3 FM software based on meteorological, hydrological, and water quality data. The hydrodynamic model performance was satisfactory in terms of the water temperature simulation, with root-mean-square-error (RMSE) ranging from 0.38 to 1.2 °C. In the ecological model, Chlorophyll-a (Chl-a) was used as a proxy for Cyanobacteria, and the model proved acceptable in simulating the Chl-a concentrations, with a Nash-Sutcliffe efficiency (NSE) of 0.93 and 0.87 for calibration and validation respectively. The findings revealed that external nitrogen loading and internal phosphorus loading had significant impact on the nutrient concentrations in Lake Vomb. The findings also showed a correlation between Chl-a levels and total phosphorus levels in the lake. To simulate future water quality in the lake, two Representative Concentration Pathways (RCP) for the year 2050 were used to make projections for changes in air temperature and precipitation. Under the projected future climate, the simulations showed a considerable rise in Cyanobacteria biomass independent of the changes in external nutrient loading. The model findings can assist water managers in planning mitigation strategies by identifying major nutrient sources.

Purification of Na+-Driven MotPS Stator Complexes and Single-Molecule Imaging by High-Speed Atomic Force Microscopy.

The stator unit of the bacterial flagellar motor coordinates the number of active stators in the motor by sensing changes in external load and ion motive force across the cytoplasmic membrane. The structural dynamics of the stator unit at the single-molecule level is key to understanding the sensing mechanism and motor assembly. High-speed atomic force microscopy (HS-AFM) is a powerful tool for directly observing dynamically acting biological molecules with high spatiotemporal resolution without interfering with their function. Here, we describe protocols for single-molecule imaging of the Na+-driven MotPS stator complex by HS-AFM.

Intra-unit reliability and movement variability of submission grappling external load as measured by torso mounted accelerometery.

Submission grappling consists of skills and movements used in combat sports to physically control opponents whilst trying to apply choke holds and joint locks. There is currently no accepted method of monitoring external load in grappling-based sports due to the absence of key variables such as distance, velocity or time. The primary aim of this study was to determine whether PlayerLoad is a reliable variable for measuring external load of submission grappling movements, with a secondary aim of determining the between repetition variance of submission grappling movements. 7 experienced submission grapplers were recruited. Each wore a torso mounted Catapult® Optimeye S5 microelectromechanical systems (MEMS) device and completed 5 repetitions of each of the following: 4 submission techniques; 5 transition techniques; 2 guard pass techniques; 2 takedown techniques. Accumulated PlayerLoad (PLdACC) was recorded as a marker of absolute load, with accumulated PlayerLoad per minute (PLdACC∙min-1) representing relative load. Reliability of each was assessed using intraclass correlation coefficient (ICC(3,1)) (≥ 0.70). Between repetition movement variation was assessed via coefficient of variation with 95% confidence intervals (CV, 95%CI) (acceptable ≤ 15%, good ≤ 10%). PLdACC ICC(3,1) range = 0.78-0.98, with CV range = 9-22%. PLdACC∙min-1 ICC(3,1) range = 0.83-0.98, with CV range = 11-19%. Though several variables displayed CV > 15%, all had 95%CI lower boundaries ≤ 15%. Whilst PlayerLoad was found to be a reliable measure for submission grappling, relatively high CVs across most techniques examined suggest PlayerLoad may not be appropriate for measuring changes in external load for individual movements in submission grappling. However, it may prove a useful tool for monitoring the external load of full, grappling-based, training sessions within an individual.

Relationships between weekly changes in salivary hormonal responses and load measures during the pre-season phase in professional male basketball players.

The aim of this study was to assess the relationships between weekly changes in external and internal load considered separately and jointly and salivary hormonal responses during the pre-season phase in professional male basketball players. Twenty-one professional male basketball players (mean ± standard deviation, age: 26.2 ± 4.9 years; height: 198.7 ± 6.7 cm; body mass: 93.2 ± 10.0 kg) were assessed during 5 weeks of the pre-season phase. External load was measured using microsensors and reported as PlayerLoad (PL) and PL/ min. Internal load was calculated using the session rating of perceived exertion scale (sRPE-load), summated heart rate zones (SHRZ) and percentage of maximal heart rate (%HRmax). Salivary hormone responses were monitored weekly by measuring testosterone (T), cortisol (C), and their ratio (T:C). The relationships between weekly changes in load measures considered separately and jointly and hormonal responses were assessed using linear mixed model analysis. No significant (p > 0.05) relationships were evident between weekly changes in T, C or T:C with external and internal load measures considered separately (R2-conditional = < 0.001-0.027) or jointly (R2-conditional = 0.028-0.075). Factors other than measured loads might be responsible for weekly changes in hormonal responses and therefore external and internal load measures cannot be used to anticipate weekly hormonal responses during the pre-season phase in professional basketball players.