This study aims to investigate the axial stress-strain behavior of macro-synthetic fiber reinforced recycled aggregate concrete. Concrete cylinders reinforced with macro-synthetic fibers were tested under axial compression, with the variation of three different replacement ratios of recycled aggregates (i.e., 0, 50 and 100%) and three different dosages of macro polypropylene fibers (i.e., 0, 0.5 and 1% of volume of recycled aggregate concrete). A comparative study of the existing stress-strain models for steel fiber reinforced normal and recycled aggregate concrete with the test results indicates that the stress-strain behavior of steel fiber reinforced normal and recycled aggregate concrete can be well predicted by these existing models. No stress-strain model for macro-synthetic fiber reinforced normal and recycled aggregate concrete has been developed. Based on the test results, a stress-strain model is developed in this work by modifying the parameters of best performing stress-strain model for steel fiber reinforced normal aggregate concrete. The proposed model can effectively predict the stress-strain behavior of both steel and macro-synthetic fiber reinforced normal and recycled aggregate concrete. Test results show that the peak stress, peak strain and ultimate strain of concrete specimens increase with the increase in fiber dosage and the addition of fibers has a better effect on recycled aggregate concrete and as compared to normal aggregate concrete.

Axial stress-strain behavior of macro-synthetic fiber reinforced recycled aggregate concrete

Geopolymers vs. alkali-activated materials (AAMs): A comparative study on durability, microstructure, and resistance to elevated temperatures of lightweight mortars

Investigation of the macro performance, mechanism, and durability of multiscale steel fiber reinforced low-carbon ecological UHPC

Experimental investigation of concrete fracture behavior with different loading rates based on acoustic emission

Mechanical properties and permeability of fiber-reinforced concrete with recycled aggregate made from waste clay brick

Effects of fiber type, volume fraction and aspect ratio on the flexural and acoustic emission behaviors of steel fiber reinforced concrete

The use of a self-compacting lower expansion concrete in a concrete-filled steel tube (CFST) structure not only promotes the quality of concrete pouring but also improves the bond behaviour between the steel and the concrete. In combination with the actual stress state of the columns in the engineering structure, it is necessary to study the eccentric compression behaviour of the column. In this study, experimental studies involving both uniaxial and biaxial bending tests of rectangular self-compacting lower expansion CFST columns were carried out. The variation laws of the load–displacement curves, the lateral deflection curves and the stress–strain curves during the loading phase were analysed. Furthermore, the failure modes and the mechanical properties of the specimens under eccentric compression loads were investigated. Subsequently, the numerical models of CFST columns with self-compacting lower expansion concrete were considered and established. In order to verify the rationality of the finite element modelling, the numerical calculation results were compared with test results. Then, a parametric analysis of the compression and the bending bearing capacities of each column was carried out by changing the eccentricity of the load, and the N–M curves or N-Mx-My surfaces describing the ultimate bearing capacity of the column were obtained. Finally, by the parametric finite element analysis of the rectangular CFST columns regarding to the bearing capacity under the same eccentricity, a conclusion was obtained: when the expansion agent content γ of a specimen increased from 0% to 10%, the bearing capacity of the columns increases significantly, but when continue increasing the expansive agent content, the expansion agent content has little effect on the compression–bending bearing capacity.

Eccentric compression behaviour of rectangular concrete-filled steel tube columns with self-compacting lower expansion concrete

Abstract Earthquake-induced poundings have been identified as a critical factor influencing bridge seismic behavior. However, most previous studies on this topic did not consider link-slabs in the continuous deck, which would influence the pounding occurrence and thus the subsequent seismic response. This paper uses a probabilistic method to evaluate the seismic vulnerability of a simply-supported bridge considering pounding and link-slabs. The damage states of girder ends due to poundings are proposed according to the cumulative damage. To analyze the seismic vulnerability of the whole bridge, both the joint probabilistic seismic demand model considering multiple engineering demand parameters and the joint damage state model considering the capability of each bridge component are established. Based on these models, the fragility curve of the whole bridge is obtained using the Monte Carlo method. The effects of gap sizes between pounding components and pier heights on the bridge seismic vulnerability are also investigated. The result reveals that the fragility of the whole bridge system is higher than that of any individual component. Ignoring the contribution of damage to each component to the whole system will lead to an overestimation of the seismic resistance of the overall bridge, which is detrimental to structural safety.

Seismic vulnerability of simply-supported bridges considering link-slabs in the continuous deck and pounding

To develop feasible carbon fiber reinforced polymer (CFRP) retrofit schemes for the shear strengthening of real three-dimensional reinforced concrete (RC) beam-column joints, a series of parameters in relation to the contributions of the CFRP sheets externally bonded to joint panels was numerically investigated in this study. The parameters include CFRP reinforcement ratio, CFRP layout, transverse beam-to-joint panel width ratio, transverse beam-to-joint panel height ratio, location of transverse beam, and number of transverse beams. Strengthening efficiency, a new dimensionless index, was introduced to evaluate the residual effect of a CFRP-strengthening system weakened by the presence of transverse beams in comparison with the increase in joint shear capacity in relation to the one-way counterpart. The results obtained from 44 nonlinear finite element models, which were calibrated against experimental observations, confirmed the effectiveness of the CFRP strengthening technique with regard to the relatively wide ranges of the parameters. The significant differences among the roles of the parameters were revealed, and the reasons behind the differences were analyzed. Furthermore, the shear mechanism of the CFRP-retrofitted joint panels was discussed with the proposed strut-and-tie model.

https://www.mdpi.com/2073-4360/14/7/1347/pdf

Effectiveness and Efficiency of Externally Bonded CFRP Sheets for Shear Strengthening of RC Beam-Column Joints

The damage of asphalt concrete pavement (AC pavement) structure caused by reflection crack is an urgent problem in many areas of China, especially in cold regions of China, so it is necessary to study how to reduce the reflective cracking and prevent the AC pavement structures cracking. The acoustic emission (AE) information is fetched in this paper to study the AE characteristics of pavement structures and the crack propagation law inside the system. On the above basis, cracks with crack spacing/layer thickness values of 1.25, 2.5, 3.75, and 5 were prefabricated in the foundation course by the numerical simulation method. The models with different foundation course crack spacing were calculated by Realistic Failure Process Analysis finite element software. The influence of varying crack spacing on the propagation mechanism of reflective cracks in the foundation course structure was studied. The results show that the AC pavement structure has prominent AE characteristics. The faster the cooling rate is, the more serious the damage to the AC pavement surface is. In addition, with the increase of crack spacing/layer thickness value, the stress level between cracks increases continuously. Most of the stress will make the cracks expand toward the foundation course structure, and only a tiny part of stress is used to form reflective cracks. In practical engineering, it is suggested to increase the crack resistance of foundation course materials and preset some small spacing cracks in the large spacing cracks in the foundation course.

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Qi Liu

Papers

Effects of fiber type, volume fraction and aspect ratio on the flexural and acoustic emission behaviors of steel fiber reinforced concrete

Eccentric compression behaviour of rectangular concrete-filled steel tube columns with self-compacting lower expansion concrete

Seismic vulnerability of simply-supported bridges considering link-slabs in the continuous deck and pounding

Effectiveness and Efficiency of Externally Bonded CFRP Sheets for Shear Strengthening of RC Beam-Column Joints

Influence of Crack Spacing/Layer Thickness Value on Reflection Crack Propagation Mechanism Under Low Temperatures