Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete Beams

Bernardo, Luís; Nepomuceno, Miguel; Pinto, Hugo Alexandre Silva

doi:10.3390/ma12213479

Cited by 7 publications

(4 citation statements)

References 8 publications

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“…Since the neutral axis depth and rebar strain are key parameters describing flexural ductility [33], it is important to understand their behavior well. The movement of the neutral axis, after it rises to the midspan section's bottom fiber, with the moment for the beams with different types of rebars (ρ r = 1.19%) is illustrated in Figure 9a.…”

Section: Neutral Axis Depth and Rebar Strainmentioning

confidence: 99%

Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons

Pang

Lou

2020

Polymers

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This study aimed at examining the feasibility of using fiber-reinforced polymer (FRP) rebars instead of steel ones in prestressed concrete beams (PCBs) with external FRP tendons. By applying an experimentally validated program, numerical tests were performed on simply supported PCBs, with investigated variables including rebars’ type and area. Three types of rebars were considered, i.e., carbon, glass FRPs (CFRP, GFRP), and reinforcing steel. The ratio of tensile rebars ranged from 0.22% to 2.16%. The results indicated that the beams with CFRP rebars exhibited better crack mode and higher ultimate load than the beams with GFRP or steel rebars. GFRP rebars led to considerably higher ultimate deflection and tendon stress increment than steel rebars. In addition, several models for calculating the ultimate stress in unbonded tendons were assessed. An analytical model was also proposed to predict the tendon stress at ultimate and flexural strength in externally PCBs with steel and FRP rebars. The model predictions agreed well with the numerical results.

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Section: Neutral Axis Depth and Rebar Strainmentioning

confidence: 99%

Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons

Pang

Lou

2020

Polymers

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“…The ductility of a structural system is a measure of its plasticity-to-elasticity deformations and can be used to describe a system's toughness. This structural parameter is generally measured by the deflection ductility index (𝜇) [1,8,36,48]. The amount of the apparent mid-span deflection is, therefore, required for the evaluation of 𝜇.…”

Section: Ductility Analysismentioning

confidence: 99%

Behavior of Non-Shear-Strengthened UHPC Beams under Flexural Loading: Influence of Reinforcement Depth

2021

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This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high-performance concrete (UHPC) containing hybrid microsteel straight fibers and natural fine aggregates under four-point flexural loading. The experimental results revealed that the fiber pullout mechanism had a progressive pullout (collapse) mode. A highly flexural crack developed when the fiber pulling mechanism was explicitly triggered, leading to the failure of most beams. The maximum load in beams reinforced by 1.2, 1.6, and 2.0% exceeded that in beams without longitudinal reinforcement by 56, 73, and 94%, respectively. Further, bar reinforcements at 125, 115, 95, 85, and 75 mm depths led to increases of 56, 55, 73, 96, and 94% in beam load capacity, respectively. In addition, bar reinforcement at 115, 95, 85, and 75 mm depths reduced the beams’ ductility by 40, 23, 35, and 39% compared to those with 125 mm depth. All studied UHPC beams had an uncracked phase that extended to a curvature of about 7.5 × 10−6 rad, which occurred at about 10 kNm. The use of the design of experiments was exploited in this investigation to develop a prediction model for the ultimate moment capacity of UHPC beams. This prediction model took into account the sectional and material properties of UHPC beams. To carry out this analysis, a database of 25 beams, developed by other investigators, as well as the present authors, was utilized. With a mean prediction-to-test ratio of 0.92, this prediction model had a reasonable performance capacity. In turn, this model was used to generate isoresponsive surface contours that could be used for UHPC beam design.

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“…Nonetheless it is difficult to state unambiguously the role of neutral axis and how it will be observed in an unloaded closed structure with a large margin of strength. However, based on the observations that with increasing load, the neutral axis shifts into the depth of bending material ( Bernardo and Lopes, 2004 ; Shim et al, 2009 ; Anastasopoulos et al, 2019 ; Bernardo et al, 2019 ; Vrijdaghs et al, 2021 ), it can be assumed that the higher the neutral axis, the greater the margin of strength in the analyzed structure. After all, the magnitude of its possible displacement is limited by the shell thickness.…”

Section: Introductionmentioning

confidence: 99%

Egg-inspired engineering in the design of thin-walled shelled vessels: a theoretical approach for shell strength

Narushin¹,

Romanov

Griffin

2022

Front. Bioeng. Biotechnol.

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A novel subdiscipline of bionics is emerging in the form of ‘egg-inspired engineering’ through the use of egg-shaped ovoids as thin-walled tanks and building structures. Hügelschäffer’s and Narushin’s models of egg geometry are highly applicable within this proposed subdiscipline. Here we conducted a comparative analysis between the two models with respect to some of the most important egg parameters. These included contents volume, shell volume, and the location of the neutral axis along the shell thickness. As a first step, theoretical studies using the Narushin’s model were carried out due to the lack (or limited amount) of data on the geometric relationships of parameters and available calculation formulae. Considering experimental data accumulated in the engineering and construction industries, we postulate a hypothesis that there is a correlation between location of the neutral axis and the strength of the walls in the egg-shaped structure. We suggest that the use of Narushin’s model is preferable to Hügelschäffer’s model for designing thin-walled shelled vessels and egg-shaped building structures. This is due to its relative simplicity (because of the requirement for only two initial parameters in the basic equation), optimal geometry in terms of material costs per unit of internal capacity, and effective prerequisites for shell strength characteristics.

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Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete Beams

Cited by 7 publications

References 8 publications

Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons

Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons

Behavior of Non-Shear-Strengthened UHPC Beams under Flexural Loading: Influence of Reinforcement Depth

Egg-inspired engineering in the design of thin-walled shelled vessels: a theoretical approach for shell strength

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