Creep Behaviour of Reinforced Concrete Beam under Long-Term Bending

Concrete structure after casting will be subjected to external load, peripheral components and other constraints, the overall performance of the structure under a long-term loading state will change continuously. In practical engineering, reinforcement is usually calculated and configured based on external load, but the role of reinforcement in the continuous loading process of concrete structure is not fully considered. Based on the elastic creep theory, this paper deduces the concrete creep calculation formula considering the influence of reinforcement, and analyses the law of the influence of reinforcement ratio and loading age on the strain and stress of concrete. The results show that the reinforcement can effectively restrain the deformation of concrete and reduce the load level of concrete.

he Relationship between External and Internal Load during Elite Pre-season Friendly Basketball Games.

The aim of this study was to analyse the relationship between External Load (EL) and internal load (IL). Thirteen male basketball players competing at professional level in First Spanish Division (ACB) during six friendly games throughout the 2020/2021 preseason were monitored. The EL variables collected were movement load (ML), movement intensity (MI), box score time (BST), and total duration (TD)] while IL variables monitored were heart rate (HR), respiratory rate (RR), training impulse (TRIMP) and time invested in five HR zones. Very large to almost perfect correlation (r= 0.77-0.91) exists between EL variables except TD. In addition, HR, TRIMP and RR present large to very large correlation (r= 0.55-0.79) with all EL variables except TD. Monitoring HR-based variables would present general information and an estimated prediction of players EL which could allow basketball practitioners to prioritize time invested players internal/external load.

Bending-torsional-axial-pendular nonlinear dynamic modeling and frequency response analysis of a marine double-helical gear drive system considering backlash

The double-helical gear system was widely used in ship transmission. In order to study the influence of backlash on the nonlinear frequency response characteristics of marine double-helical gear system, according to the structural characteristics of double-helical gear transmission, considering the time-varying meshing stiffness, backlash, damping, comprehensive transmission error, external load excitation, and other factors, a three-dimensional bending-torsional-axial-pendular coupling nonlinear dynamic modeling and dynamic differential equation of 24-DOF double-helical gear transmission system were established. The Runge–Kutta numerical method was used to analyze the influence of backlash, time-varying meshing stiffness, damping, error and external load excitation on the amplitude frequency characteristics. The results show that the backlash can cause the runout of the double-helical gear system, and the system has first harmonic and second harmonic response. With the increase of backlash, the amplitude of the system increases and the jumping phenomenon remains unchanged. The amplitude frequency response of the system is stimulated by time-varying meshing stiffness and comprehensive transmission error, and restrained by damping and external load excitation. The vibration displacement amplitude of the system increases with the increase of vibration displacement and has little effect on the state change of the system. The vibration test of double-helical gear is carried out. The frequency response components obtained by numerical simulation are basically consistent with the experimental results, which proves the correctness of the theoretical calculation. It provides a technical basis for the study of vibration and noise reduction performance of double-helical gear.

Theoretical and Experimental Investigation on Air Film Pressure Field Characteristics of Aerostatic Thrust Bearing

This paper studied the air film pressure field (AFPF) characteristics of aerostatic thrust bearing, in which we proposed the measurement equipment for the 2D AFPF and successfully verified the theoretical simulation results. The experimental results agreed well with the theoretical results. However, in the area between the distribution circle of orifice to the air film outlet boundary, the experimental air film pressure (AFP) was slightly higher than the theoretical one. While for the area between the distribution circle of orifice and the center of the bearing, it showed the opposite law. Besides, the increase ratio of the AFP was close to that of the external load with its increase.

Analysis of the External and Internal Load in 5vs5 Large Sided Games: Differences Between Different Sized Fields

The study purpose. The purpose of the study is to analyze and understand the internal and external load in Large Sided Games (LSG) exercises carried out on fields of different sizes, defined as Small – Large Sided Games (SLSG) and Big – Large Sided Games (BLSG), according to the different square meters assigned to each player. Materials and methods. 22 professional soccer players (average age: 23.59 ± 4.87 years, weight: 77.8 ± 7.6 kg, height: 183.5 ± 7.5 cm, age training: 13.1 ± 1.7). The LSG exercises were carried out on a 60 x 54 m field (270 m2/player), defined as "small" (SLSG) and on a 65 x 60 m field (325 m2/player) defined as "big" (BLSG). During the two LSG exercises, the internal load and the external load were analyzed. LSG exercises were performed with 4 sets of 5 minutes each, with 2 minutes of passive recovery between each set. Results. The results of the internal load analysis show how the LSG carried out on a SLSG field provides higher and more significant HR values (p < 0.0005) than those emerged during the exercise carried out on a BLSG field. The RPE value is also higher during the SLSG, although statistically no significant difference appears. The analysis of the external load in relation with the observed parameters shows higher values in the BLSG, except for the number of accelerations. Conclusions. In terms of external and internal load, the results of this study showed how the difference of 55 m2/player can radically change the configuration of the two exercises. These differences allow to use both dimensions within a micro-cycle, but in sessions with different goals. The most appropriate sessions for LSGs are the first post-match session in which the rest day is not gone and the fourth session 3 days before the match.

Quantifying Training and Game Demands of a National Basketball Association Season

Purpose: There are currently no data describing combined practice and game load demands throughout a National Basketball Association (NBA) season. The primary objective of this study was to integrate external load data garnered from all on-court activity throughout an NBA season, according to different activity and player characteristics.Methods: Data from 14 professional male basketball players (mean ± SD; age, 27.3 ± 4.8 years; height, 201.0 ± 7.2 cm; body mass, 104.9 ± 10.6 kg) playing for the same club during the 2017–2018 NBA season were retrospectively analyzed. Game and training data were integrated to create a consolidated external load measure, which was termed integrated load. Players were categorized by years of NBA experience (1-2y, 3-5y, 6-9y, and 10 + y), position (frontcourt and backcourt), and playing rotation status (starter, rotation, and bench).Results: Total weekly duration was significantly different (p &lt; 0.001) between years of NBA playing experience, with duration highest in 3–5 year players, compared with 6–9 (d = 0.46) and 10+ (d = 0.78) year players. Starters experienced the highest integrated load, compared with bench (d = 0.77) players. There were no significant differences in integrated load or duration between positions.Conclusion: This is the first study to describe the seasonal training loads of NBA players for an entire season and shows that a most training load is accumulated in non-game activities. This study highlights the need for integrated and unobtrusive training load monitoring, with engagement of all stakeholders to develop well-informed individualized training prescription to optimize preparation of NBA players.

Carga interna y externa en el tenis de competición: comparación de tres tipos de entrenamiento (Internal and external load in competitive tennis: comparison of three types of training)

El objetivo principal de esta investigación es cuantificar la carga externa y la carga interna en tres tipos de entrenamiento (cubos con la mano, cubos con raqueta y peloteos) más utilizados en el ámbito del tenis de competición y compararlos entre sí. Participaron 6 jugadores de tenis (cuatro jugadores masculinos y 2 jugadoras) con una media de edad de 16.67 (± 2.73) años. Para cuantificar las cargas, se han utilizado pulsómetros POLAR +M400 para recoger los datos relacionados con la frecuencia cardíaca, distancia recorrida, velocidad media y máxima, y sensores ZEPP TENNIS, con los que se han recogido los datos relativos a tipo de golpe, número de golpeos y velocidad de raqueta en cada uno de los golpes realizados. Además, para registrar la percepción subjetiva de esfuerzo, en cada tarea realizada y al final de cada entrenamiento, se ha utilizado la Escala de Borg CR-10 (Borg, 1982). Se realizaron 9 sesiones de entrenamiento por parejas: tres para el entrenamiento del drive, tres para el entrenamiento del revés y tres para el entrenamiento del drive y el revés de forma conjunta, una para cada tipo de entrenamiento. Los resultados obtenidos muestran que el entrenamiento de cubos con la mano tiene mayor carga interna en cuanto a número de golpeos y velocidad media de raqueta, siendo el entrenamiento de peloteos el que mayor carga externa refleja en relación a velocidades y distancias recorridas. Abstract. The main objective of this research is to quantify the external load and the internal load in three types of training (buckets with the hand, buckets with racket and rallies) most used in the field of tennis and compare them to each other. Six tennis players participated (four male and two female players) with an average age of 16.67 (± 2.73) years. To quantify the loads, POLAR +M400 heart rate monitors were used to collect the data related to heart rate, distance covered, average and maximum speed, and ZEPP TENNIS sensors were used to collect the data related to type of stroke, number of strokes and racket speed for each of the strokes made. In addition, the Borg CR-10 Scale (Borg, 1982) has been used to record the rate of perceived exertion, in each task performed and at the end of each training session. Nine training sessions were carried out in pairs: three for drive training, three for backhand training and three for drive and backhand training together, one for each type of training. The results obtained show that bucket training with the hand has a greater internal load in terms of the number of strokes and average racket speed, with racket training having the greatest external load in relation to speed and distance travelled.

The comparison of triboelectric power generated by electron-donating polymers KAPTON and PDMS in contact with PET polymer

The Triboelectric nanogenerators (TENGs) are Fabricated by contact between two surfaces of different materials and convert of electric loads between them. In such structures, the two contacting layers should be radically different in terms of their electric property so that one of the layers could induce positive electrical charge while the other induces a negative charge. The application of force on and friction between the two layers induce positive and negative charges. Through the electrodes in external load, the electrical charges flow as electric current. In the present study, TEGN structures fabricated of polyethylene terephthalate polymers (PET) act as electron acceptor while Polyamide (KAPTON) and polydimethylsiloxane (PDMS) act as electron donator. The resulting outputs are compared consequently. Considering the fact that the two materials are relatively identical in terms of electron donation as they are in contact with PET, the generators fabricated of KAPTON could generate 400% more power under identical conditions. Therefore, one may conclude that KAPTON could be more suitable for development of self-power system as they are more available and more environmentally compatible.