Continuous Reinforced Concrete Beams Strengthened with Fabric-Reinforced Cementitious Matrix: Experimental Investigation and Numerical Simulation

This paper aims to examine the nonlinear flexural behavior of continuous RC beam specimens strengthened with fabric-reinforced cementitious matrix (FRCM) composites through experimental testing and numerical modeling. A total of nine two-span RC beam specimens were constructed and tested. Test parameters included the type of FRCM (carbon (C-FRCM) and polyparaphenylene benzobisoxazole (PBO-FRCM), location of strengthening (sagging and hogging regions) and number of FRCM layers (two and four layers). Test results indicated that sagging strengthening resulted in a strength gain in the range of 17 to 29%, whereas hogging strengthening increased the load capacity by 9 to 17%. The use of C-FRCM resulted in a higher strength gain than that provided by PBO-FRCM composites. Specimens strengthened with PBO-FRCM exhibited, however, higher ductility and deformational capacity than those of their counterparts strengthened with C-FRCM. Doubling the number of FRCM layers resulted in no or insignificant increase in the load capacity but reduced the beam ductility. Specimens strengthened in the sagging regions exhibited moment redistribution ratios of 13 to 26% between the hogging and sagging regions. Insignificant moment redistribution was recorded for the specimens strengthened in the hogging region. Three-dimensional (3D) numerical simulation models, with and without an interfacial bond-slip law at the fabric–matrix interface, were developed. The inclusion of the bond-slip law in the modeling had an insignificant effect on predicted response. Although the models tended to underestimate the deflection, the predicted load capacities were within a 12% error band. Numerical findings were in agreement with those obtained from laboratory testing.

Moment Redistribution of Shear-Critical GFRP Reinforced Continuously Supported Slender Beams

Fiber-Reinforced Concrete (FRC) is a competitive solution for the durability of reinforced structures. This paper aims to observe moment redistribution behavior occurring due to flexural and shear loading in GFRP reinforced continuous concrete beams. A rectangular cross-section was adopted in this study with dimensions of 200 mm in width and 300 mm in depth with a constant shear span-to-depth ratio of 3. The reinforcement ratio for the top and bottom were equal at sagging and hogging moment regions. A finite element model was created using ANSYS and validated with the existing experimental results in the literature review. Based on the literature review, the parametric study was conducted on twelve beam specimens to evaluate the influence of concrete compressive strength, transversal GFRP stirrups ratio, and longitudinal reinforcement ratio on the redistribution of the moment in beams. Several codes and guidelines adopted different analytical models. The CSA S806 adopted the modified compression field theory in predicting the shear capacity of the simply supported beams. Recently, various researchers encountered several factors and modifications to account for concrete contribution, longitudinal and transverse reinforcement. A comparison between the predicting shear capacity of the generated finite element model and the analytical model and the existing data from literature was held. The generated finite element model showed a good agreement with experimental results while the beam specimens failed in shear after undergoing significant moment redistribution from hogging to sagging moment region. Doi: 10.28991/CEJ-SP2021-07-02 Full Text: PDF

Flexural Behaviour and Internal Forces Redistribution in LWAC Double-Span Beams

This research study aimed to investigate the effect of the lightweight aggregate concrete and steel reinforcement interaction on the behaviour of continuous beams compared to the normal concrete of the same strength. This paper presents six full-scale, double-span beams with a rectangular cross-section made of both lightweight and normal concrete. The study confirmed that beams made of lightweight aggregate concrete achieve comparable flexural capacities to those made of NWC but their deformability and ductility are lower. Although the redistribution of internal forces depends mainly on the longitudinal reinforcement ratio, the influence of ultimate compressive strains of concrete is also noticeable. The ultimate compressive strains in LWAC are generally lower than in NWC. The lower rotational capacity of LWAC results in smaller degrees of moment redistribution in beams made of this concrete compared to normal concrete beams.

Numerical investigation on moment redistribution of continuous reinforced concrete beams under local fire conditions

This article presents a numerical investigation on the mechanical behaviours, such as the fire resistance, the moment redistribution and the failure mode, of continuous reinforced concrete beams with two spans and three spans under the standard fire of ISO-834. Firstly, a 3D finite element model was established and validated against the fire test beam. Secondly, the three stages associated with the fire time of fire behaviour for the continuous reinforced concrete beams were divided and explained. An index of the moment redistribution amplitude was modified and used to evaluate the fire performance of continuous reinforced concrete beams. A series of parametric analyses for continuous reinforced concrete beams with two spans were conducted in order to investigate the influence of some parameters such as the load ratio, the load position, the support condition and the sectional size. Finally, the distributions of the vertical deflection and the plastic hinge within beam spans and the failure modes for continuous reinforced concrete beams with three spans under local fire conditions were discussed emphatically.