Browsing by Issue Date, starting with "2019-09-03"
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- Flow-3D Modelling of the Debris Effect on Maximum Scour Hole Depth at Bridge PiersPublication . Mendonça, Inês Sofia Pereira; Canilho, Hugo Daniel Leitão; Fael, Cristina Maria SenaBridge foundations are frequently inserted in riverbeds constituted by alluvial material, being, therefore, subjected to scouring processes. Such phenomenon is aggravated during flood events due to the increase of water flow or due to the increase of the debris carried by the flow that can pile up along the bridge structural elements. The debris can partially obstruct bridge spans and accumulate near bridge piers and abutments, which will have consequences in terms of reduction of flow capacity and an increment of the maximum scour depth. The dimensions, shape and its location are characteristics that must be considered when predicting the scour depth. The present study aims at analyzing the effect of the debris on the maximum clear-water scour depth at cylindrical piers inserted in uniform sand, non-ripple forming sand, fully-developed turbulent flows in wide rectangular channel, using computational fluid dynamics software, Flow-3D. For this purpose, debris with a triangular and rectangular shape, floating and on the sand bed, were tested, using the k-ε RNG turbulence model and the numerical results were compared with those obtained experimentally. It was possible to verify that the floating debris gives greater scour hole depth and the debris on sand bed behave as scour countermeasure reducing the scour hole depth. Also, rectangular shaped debris seems to cause more scour near the structures than the triangular shaped ones, which also seemed beneficial to the scour hole, by reducing it. However, the results obtained computationally are significantly lower than those obtained experimentally.
- Coach decision-making in Futsal: from preparation to competitionPublication . Almeida, João; Sarmento, Hugo; Kelly, Seamus; Travassos, BrunoThe purpose of this paper was to analyse expert futsal coaches process of decision-making from preparation to competitive moments. Ten expert and professional coaches’ (M = 46,9 ± 7,93 years old andM= 15,4 ± 7,22 years of coaching experience) from different countries were interviewed using asemi-structured interview (quantitative and qualitative) with two different goals: (1) evaluate the preparation for decision-making moment during the game; (2) classifying the importance of different game related points for decision-making during match moment. The data analysis was processed through combination of deductive and inductive methods through software QSR NVivo 11. The results revealed that coaches’ share similar ideas when preparing their teams. Coaches focus first their attention on their own team identity and frame andsecond on opposition team behaviour and frame. It was also possible to identify clear coaching behavioural signs possible to be structured as cues and guiding lines for their decision-making process and actions before and during competitive moments. Such information can be important for the development of most appropriated coaching education curriculums according to game demands specificities.
- How Does the Adjustment of Training Task Difficulty Level Influence Tactical Behavior in Soccer?Publication . Machado, João Cláudio; Barreira, Daniel; Teoldo, Israel; Travassos, Bruno; Júnior, João Bosco; Santos, João Otacílio Libardoni dos; Scaglia, Alcides JoséPurpose: This study aimed to investigate if player tactical skill level and age category influence team performance and player exploratory behavior in tasks with different difficulty levels. Method: In total, 48 youth male soccer players participated in the study (U15, n = 24, mean age = 13.06 ± 1.53 years; U17, n = 24, mean age = 16.89 ± 0.11 years). Player tactical skills were evaluated through the System of Tactical Assessment in Soccer (FUT-SAT), allowing them to be organized into three groups according to tactical efficiency: Higher tactical skill level (Group 01), Intermediate tactical skill level (Group 02), and Lower tactical skill level (Group 03). Next, Group 01 and Group 03 of both categories performed six Small-Sided and Conditioned Games (SSCG) each, namely three High difficulty SSCGs and three Low difficulty SSCGs. Team performance and players' exploratory behavior were analyzed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. Results: We found that team performance and players' exploratory behavior were influenced both by the age and tactical skill level of the players, as well as by task difficulty level. Conclusion: Therefore, in an attempt to improve player performance, practitioners must carefully manipulate key task constraints to adapt training task difficulty levels to player age and tactical skill level.
- Different marks in the pitch constraint youth players’ performances during football small-sided gamesPublication . Coutinho, Diogo; Gonçalves, Bruno; Travassos, Bruno; Folgado, Hugo; Figueira, Bruno; Sampaio, JaimePurpose: This study aimed to compare players' performances when manipulating the external markings of the pitch during football small-sided games. Methods: Ten under-15 players performed a 5-a-side (plus goalkeepers) under three conditions: (i) Lines, the game was played in a pitch in which the external boundaries were painted with full lines; (ii) Dashed, the game was played in a pitch in which the external boundaries were painted with dashed lines; (iii) Corners, the game was played in a pitch were the external boundaries were delimited by one marker at each pitch corner. Players' positional data was used to compute tactical and time-motion variables. Also, technical analysis was comprised using video footage. Results: Results showed similar tactical, physical and technical performances between the Lines and Dashed conditions. In contrast, the Lines condition showed small higher effects than Corners scenario in the time spent synchronized in longitudinal and lateral displacements, game pace, total distance covered, distance covered while jogging, number successful dribbles and shots on target. The Lines scenario has also revealed a lower effective playing space, distance covered at walking and running and a lower number of passes (small effects) compared to Corners. Conclusions: These results highlight that these changes in informational perception constraints modify players movement behavior. Accordingly, pitches with more visible boundaries were likely to decrease team dispersion, which may optimize team synchrony and technical performances, while decreasing the distance covered at higher speeds. Coaches may use this information to modify the types of pitch external boundaries markings, exposing the players to different environmental information.