Current Issue : January-March Volume : 2025 Issue Number : 1 Articles : 5 Articles
The use of industrial residues in civil construction is an exciting alternative to mitigate environmental impacts and promote the circular economy. This work developed new compositions of geopolymer mortars activated by NaOH from fine kaolin residue (RCF), coarse kaolin residue (RCG) and granite (RG). All residues were benefited and characterized by chemical analysis (Xray fluorescence), mineralogical phases (X-ray diffraction) and granulometry (laser granulometry). Additionally, the RCF was calcined at 650 ◦C for 2 h (RCFC) to produce metakaolin, which is the starting point for the geopolymer reaction. A mixture of experimental designs was accomplished to evaluate the water/binder factor (Wexp (%)) necessary for new geopolymer mortar compositions to reach the consistency index (260 mm, ASTM C1437-15) and the effect of different curing conditions on the simple compressive strength (SCS). The geopolymeric compositions with RCFCs, pre-cured at room temperature, exhibited the highestWexp% values (>40%) and significant SCS, with curing conditions A and B reaching 6 MPa and 7 MPa, respectively. Such behavior can be explained by the fact that the pre-curing step at room temperature keeps the system humidity relatively high, favoring the dissolution of Si4+ and Al3+ ions and, therefore, increasing the Si/Al ratio, which positively influences the geopolymerization kinetics reaction....
The simulation of the soil–structure interface (SSI) under cyclic loading is critically important in geotechnical engineering. Numerous studies have been conducted to explore the cyclic behaviors exhibited at the SSI. However, existing model evaluations primarily rely on direct comparisons between experiments and simulations, with limited analysis focused on specific behaviors like accumulated normal displacement and stress degradation under cyclic loading. This study proposes and adapts six SSI models, including three nonlinear incremental models and three elastoplastic models. These models incorporate nonlinear shear modulus, critical state theory, and particle breakage effects to enhance their capability to capture SSI behaviors. Utilizing optimizationbased calibration for a fair comparison, the model parameters are fine-tuned based on the experimental data. Comprehensive assessments including global comparisons and specific behaviors like accumulated normal displacement and stress degradation are carried out to evaluate the models’ performance. The results indicate that all models effectively replicate the typical behaviors of SSI systems. By incorporating the particle breakage effect, the models can represent both the reversible and irreversible normal displacements under cyclic loading with better performance. The irreversible normal displacement remains stable and is solely influenced by the soil properties rather than the stress level. Moreover, the models successfully capture the stress degradation under constant normal stiffness caused by the irreversible normal displacement....
Tensile perpendicular to grain is an important mechanical property in the design of joints in timber structures. However, according to the standards, this strength can be determined using at least two different methods: uniaxial tensile and three-point static bending. In this context, the present paper aims to investigate the influence of these test methods on the determination of tensile strength perpendicular to grain of wood used in civil construction timber. Three wood species from Brazilian planted forests (Pinus spp., Eucalyptus saligna, and Corymbia citriodora) were used in this investigation. Twelve specimens of each species were used for each test method investigated. Moreover, a statistical analysis was performed to propose an adjustment to the equation of the Code of International Organization for Standardization 13910:2014 for the three-point bending test. Tensile strength values perpendicular to grain obtained from the uniaxial tensile test were significantly higher than those determined by the three-point bending test. It is proposed that the tensile strength perpendicular to grain can be determined more precisely with adoption of coefficient 5.233 in the term [(3.75·Fult)/b·Lh] of the equation specified by the Code of International Organization for Standardization 13910:2014 for the three-point bending test....
Freezing weather can introduce challenges in long-term structural health monitoring of civil structures, particularly bridges. A noticeable impact of freezing temperature is the emergence of sudden and sharp increases in structural modal frequencies, causing false alarm and mis-detection errors in change detection of civil structures. This paper proposes an innovative unsupervised data normalization method to mitigate freezing effects. The proposed method integrates locally robust principal component analysis (LRPCA) with Gaussian density distance (GDD) clustering, called GDD-LRPCA, which automatically determines the number of clusters. Initially, a training set of original modal frequencies is partitioned via the GDD clustering. Subsequently, an individual LRPCA model is fitted to each partition to extract new normalized modal frequencies insensitive to freezing effects. The groundbreaking nature of this research relies on developing an integrated unsupervised data normalizer by leveraging advanced machine learning algorithms such as local learning, robust learning, and hybrid unsupervised learning. The major advantage of the proposed method is its non-parametric nature obviating any supplementary technique for hyperparameter optimization. The validity of this method is benchmarked by real-world bridge structures along with several comparative analyses. Results demonstrate that GDDLRPCA effectively removes the freezing effects from structural modal frequencies and outperforms its counterparts in unsupervised data normalization....
The slope protection structure of the prefabricated lattice beam is one of the most widely used and studied systems in slope structure, with the connection between the lattice beam joint and the longitudinal and transverse beams being critical for structural performance and stability in engineering applications. Because the prefabricated structure is weak in its structural integrity, it is necessary to study the influence of prefabricated lattice beam joints and the longitudinal and transverse beams on the overall mechanical properties of the structure. In this paper, one ordinary cast-in-place concrete beam and six prefabricated beams with different joint-connection modes are designed, and the influence of different connection modes on the bending capacity of the beams is accordingly explored. Moreover, the flexural capacity, bending stiffness change, ductility, and energy absorption capacity of the beams are analyzed through three-point bending test. The test results show that the connection mode at the joints could significantly affect the overall mechanical properties of the structure. By embedding holes in steel sleeves, filling cement mortar in the middle, and using steel plates with a thickness of 16 mm for anchoring treatment joints of end plates, the specimen beams are thus obtained with the same flexural capacity, ductility, and energy absorption capacity as ordinary cast-in-place concrete beams. This study provides valuable insights into optimizing connection methods for prefabricated beams, which can lead to improved structural performance and wider adoption of prefabricated structures in the construction industry....
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