The ever-increasing material performance requirements in modern engineering structures have thrust engineered cementitious composites (ECCs) into the limelight of civil engineering research. The exceptional tensile, bending, and crack-control abilities of ECCs have sparked significant interest. However, the current research on the mechanical behavior of ECCs primarily focuses on uniaxial tensile and compressive constitutive relationships, leaving a gap in the form of a comprehensive multidimensional constitutive model that can fully describe its complex behavior at large strains. This study rigorously addresses this gap by initially investigating the uniaxial tensile and compressive behavior of ECCs through experiments and establishing a one-dimensional constitutive relationship of ECCs. It then introduces the concepts of damage energy release rate and energy equivalent strain, and constructs a three-dimensional constitutive model of ECCs by introducing the damage variable function. We write the numerical algorithm of our theoretical model in terms of the VUMAT subroutine and implement it into ABAQUS 2019 finite element software. We validate the accuracy and practicality of the multidimensional constitutive model by comparing the experimental data of uniaxial tension/compression and four-point bending. This paper enriches the theoretical system of ECCs and provides rigorous guidance for the performance optimization and practical application of such advanced engineering materials.
This study aimed to investigate the feasibility and effectiveness of spray-on polyurethane coating as a seismic strengthening method for rural masonry buildings. Three masonry wall specimens were tested under cyclic lateral loading, including a control specimen, a single-side strengthened specimen, and a double-side strengthened specimen. Digital image correlation (DIC) techniques were used to evaluate full-field strain, crack width, and failure progression in a non-contact manner. The seismic performances were compared in terms of failure mode, hysteretic behavior, skeleton curve, deformation performance, energy dissipation capacity, and stiffness degradation. Results indicated that a spray-on polyurethane coating effectively delayed the onset and progression of cracks, postponing the peak load and slowing strength and stiffness degradation. Compared to the unstrengthened specimen, the bearing capacity, ultimate displacement, and cumulative energy dissipation of the single-side strengthened specimen increased by 20%, 60%, and 514%, respectively. Compared to the single-side strengthened specimen, the double-side strengthened specimen BW-D exhibited improved integrity, deformation capacity, and energy dissipation capacity. Its ultimate displacement and cumulative energy dissipation increased by 28% and 10%, respectively.
It is a new technique to embed near-surface mounted(NSM) CFRP rods in a stone beam to improve the flexural performance of the beam,and it can be used for retrofitting existing stone structures.26 pull-out specimens were tested to investigate the bond behavior between CFRP rods and the stone.The main experimental parameters were the diameter of CFRP rod,the bonded length and the thickness of epoxy cover.Test results indicate that there are three typical failure modes,namely tensile rupture of CFRP rod,CFRP rod-epoxy interface-interfacial failure and fracture in the stone along the groove corner.The failure mechanism is influenced by the bonded length,the thickness of adhesive cover and the diameter of CFRP rod.An epoxy cover thicker than 0.5Db has no significant influence on the ultimate load of pull-out specimen.The ultimate load of pull-out specimen increases with the increase of bonded length,whereas the average bond strength decreases with the increase of bonded length.The basic anchorage length is related to the diameter of CFRP rod,which is 30Db and 35Db respectively for bars with diameter of 5mm and 7mm.
The mechanical properties and durability of concrete with or without ultrafine fly ash were studied by measuring the compressive strength and determining the chloride ion penetration and open porosity of concrete.The results show that the addition of ultrafine fly ash reduces the compressive strength at 1 day and can significantly improve the compressive strength of concrete at later ages.The durability of concrete can be enhanced by the using of ultrafine fly ash and lowering the W/B.
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