Structural behavior of GFRP reinforced recycled aggregate concrete columns with polyvinyl alcohol and polypropylene fibers

The objective of this research study is to demonstrate the axial compressive behavior of GRFC columns by fabricating five circular columns (1150 mm high and 250 mm in cross-section) and testing them under axial concentric loading. Two different kinds of fibers, that is, polyvinyl alcoholfibers (PVA) and polypropylene fibers (PPF) were incorporated into the concrete. Two types of transverse confinement (GFRP hoops and GFRP spirals) were provided. The efficiency of GFRP hoops was explored by providing them at the spacing of 75 mm, 150 mm, and 250 mm, respectively. The efficiency of GFRP spirals was examined by keeping the spacing of 38 mm and 75 mm, respectively. The GRFC columns confined with GFRP spirals portrayed higher axial strength and higher ductility indices. Furthermore, an extensive finite element modeling (FEM) was performed by considering the effect of hybrid fibers using a modified concrete damaged plastic (CDP) model. The proposed FEM captured the axial response and cracking behavior of GRFC columns with high accuracy. This study also proposed a new empirical model for capturing the axial strength of GRFC columns by considering the influence of GFRP bars and lateral confinement of GFRP hoops/spirals.

Accentuated Eccentric Loading in the Bench Press: Considerations for Eccentric and Concentric Loading

This study examined the effects of accentuated eccentric loading (AEL) on bench press velocities across a spectrum of concentric and eccentric loads. Ten strength trained men (bench press one-repetition maximum (1-RM): 124.3 ± 19.4 kg; relative strength ratio: 1.5 ± 0.2 kg∙body mass−1) participated. Subjects completed bench press repetitions using concentric loads from 30% to 80% 1-RM in 10% increments in each experimental session. The AEL protocols were implemented using 100% (AEL100) and 110% 1-RM (AEL110) loads during the eccentric action, while the eccentric load remained the same as the concentric for traditional loading (TRAD). Multilevel models analyzed the effects of each AEL protocol on concentric velocities across concentric loads (p < 0.05). Faster concentric velocities were observed at 30% 1-RM and 80% 1-RM with AEL100 compared to TRAD (p ≤ 0.05) but this effect was reduced for individuals moving the barbell through a greater displacement. Additionally, AEL110 presented a greater change in velocity from 30% to 80% 1-RM than TRAD (p ≤ 0.05). The AEL100 protocol resulted in faster concentric velocities throughout concentric loads of 30–80% 1-RM, but AEL110 may have been too great to elicit consistent performance enhancements. Thus, the efficacy of AEL at various concentric loads is dependent on the eccentric loading and barbell displacement.