Calculated Strength Ratios Research Articles

ASSESSMENT OF NOMINAL SHEAR STRENGTH OF REINFORCED CONCRETE COLUMN

: SNI 2847-2019 and ACI 318-19 have regulated the use of materials in the design for shear strength. This study presents an evaluation of nominal shear strength in Reinforced Concrete (RC) column from SNI 2847-2019 and ACI 318-19 by variants of the RC columns experimental database. RC column variants consist of normal strength and high strength RC column with a total of 162 specimens. Furthermore, the database also provides a variety of shear span to depth ratio and axial-load ratio. In this study, the calculation was carried out the mean and the coefficient of variation of measured to calculated strength ratio which is according to SNI, ACI, and other experimental models. Both SNI 2847-2019 and ACI 318-19 have 2 different (concrete nominal shear strength) equations. The calculation results show that the equation is more conservative in both SNI and ACI compared to other nominal shear strength equations. Overall, the combination of both normal strength and high strength RC columns, the calculation using ACI 318-19 with the first nominal shear strength equation can be said to be more conservative than any other calculations models. This study also shows that by using the ACI 318-19 model in the second equation which is used the size effect modification factor , the results do not have a significant effect because the value is close to 1.

Cyclic behavior of beam-column joints with various yielding modes

Abstract This paper discusses the yielding mode of a beam-column joint and proposes a mode classification system. The yielding mode can be classified into six categories, including panel yielding, panel yielding dominated, beam yielding, beam yielding dominated, column yielding, and column yielding dominated. The mode can be determined by the column-to-panel strength ratio and the beam-to-panel strength ratio. Four beam-column joint specimens composed of wide-flange beams and square tube columns were tested. Two specimens were subjected to a high axial force, and the other two were not. The specimens were originally designed with various yielding modes. However, due to the unexpected high yield strength of the steel, the calculated strength ratio indicated that all specimens would exhibit the panel yielding dominated mode. Experimental results showed that the panels of all specimens dissipated the most energy, which is consistent with the characteristics of the panel yielding dominated mode. Despite exhibiting this mode, specimens that were subjected to high axial forces eventually failed by local buckling of the column. Moreover, one of the beam-column joint specimens developed severe column-to-diaphragm weld fractures, although the column had very small rotation. Finite element (FE) analysis was conducted on a series of beam-column joints with various strength ratios and a typical plane steel moment frame, and this approach also verified the concept of yielding mode classification. The FE analysis results indicated that the unexpected column-to-diaphragm weld fracture in one specimen resulted from the out-of-plane deformation of the extended diaphragm.

THE EFFICACY OF ANGLE-MATCHED ISOKINETIC KNEE FLEXOR AND EXTENSOR STRENGTH PARAMETERS IN PREDICTING AGILITY TEST PERFORMANCE.

Agility is a fundamental performance element in many sports, but poses a high risk of injury. Hierarchical modelling has shown that eccentric hamstring strength is the primary determinant of agility performance. The purpose of this study was to investigate the relationship between knee flexor and extensor strength parameters and a battery of agility tests. Controlled laboratory study. Nineteen recreational intermittent games players completed an agility battery and isokinetic testing of the eccentric knee flexors (eccH) and concentric knee extensors (conQ) at 60, 180 and 300°·s-1. Peak torque and the angle at which peak torque occurred were calculated for eccH and conQ at each speed. Dynamic control ratios (eccH:conQ) and fast:slow ratios (300:60) were calculated using peak torque values, and again using angle-matched data, for eccH and conQ. The agility test battery differentiated linear vs directional changes and prescriptive vs reactive tasks. Linear regression showed that eccH parameters were generally a better predictor of agility performance than conQ parameters. Stepwise regression showed that only angle-matched strength ratios contributed to the prediction of each agility test. Trdaitionally calculated strength ratios using peak torque values failed to predict performance. Angle-matched strength parameters were able to account for 80% of the variation in T-test performance, 70% of deceleration distance, 55% of 10m sprint performance, and 44% of reactive change of direction speed. Traditionally calculated strength ratios failed to predict agility performance, whereas angle-matched strength ratios had better predictive ability and featured in a predictive stepwise model for each agility task. 2c.

Concentric and eccentric strength profile of quadriceps and hamstrings in healthy volleyball players

BackgroundLower-extremity strength profile can be used in injury prevention, conditioning and rehabilitation of volleyball players.ObjectivesThe goals were: (1) to describe the concentric and eccentric quadriceps (Q) and hamstrings (H) muscle...

The isokinetic strength profile of quadriceps and hamstrings in elite volleyball players

Knowledge of lower-extremity strength can be used in injury prevention, conditioning and rehabilitation of volleyball players. The goals were: (1) to describe the bilateral concentric and eccentric quadriceps (Q) and hamstrings (H) muscle function in volleyball players, (2) to evaluate the differences in Q and H strength, strength ratios and bilateral strength asymmetry among age groups, playing positions and playing levels, (3) to compare bilateral strength asymmetry in Q and H muscles in two different contraction modes. Ninety five professional male volleyball players were tested on an isokinetic machine at 60 ◦ /s to assess concentric and eccentric Q and H strength. We also calculated strength ratios and bilateral strength asymmetries. MANOVAs indicated significant main effect of playing level on relative PT (p = 0.001) and strength ratios ( p< 0.05). International-level players had significantly ( p< 0.05) higher H strength and dynamic control ratio (DCR) of the right leg compared to the 1st and/or 2nd national division players. There were no signs of bilateral strength asymmetry regardless of muscle group tested and contraction mode. Our results suggest that right H strength and DCR could be important for successful volleyball performance. Descriptive data about Q and H muscle function can be used as guidelines for coaches and therapists during training and rehabilitation of male volleyball players.

Tension development length and lap splice design for reinforced concrete members

AbstractThe key factors that govern development (anchorage) and splice performance of reinforcing bars in tension are described. The bond design provisions of the AASHTO (American Association of State Highway and Transportation Officials) LRFD (Load and Resistance Factor Design) Bridge Design Specifications, the American Concrete Institute Building Code Requirements for Structural Concrete (ACI 318‐05), ACI Committee 408, CEB‐FIP Model Code 1990, and Eurocode 2 are summarized and compared with test results. In terms of the key factors, the bond strength of bars not confined by transverse reinforcement is proportional to the concrete compressive strength to the ¼ power. The contribution of transverse reinforcement to bond strength increases with the area of the transverse reinforcement per bar and the relative rib area and diameter of the bar being developed or spliced and has been found to be proportional to the concrete compressive strength to a power between ¾ and 1.0. For deep members or for high‐slump (conventional and superplasticized) concrete, the effect of bar placement may be greater than accounted for in current design provisions. Of the five design procedures compared in this paper, those developed by ACI Committee 408 provide the best match with test results for both developed and spliced bars. For developed bars, the other four design procedures result in a high percentage of tests for which the test to calculated strength ratios (T/C) are less than 1.0, with the greatest percentage of low T/C values resulting from the AASHTO requirements. The relative safety of the latter four design procedures improves for lap splices. A provision in ACI 318‐05 that allows a 20% reduction in development and lap splice length for bars smaller than 19 mm appears to be unsafe and should be removed or modified.