•The welding deformation and residual stress of thin aluminum alloy welded structure are accurately predicted.•Fatigue tests of typical thin-plate aluminum alloy welded joints were carried out.•The ...influence of welding defects on the fatigue strength of thin-plate aluminum alloy welded joints is quantitatively analyzed.
With the transformation and upgrading of shipbuilding industry, aluminum alloy shipbuilding will gradually develop towards energy saving, light weight and environmental protection. As a new generation of trustworthy aluminum alloy structure, 5059 aluminum alloy material has better mechanical properties and corrosion resistance. However, two prominent shortcomings of aluminum alloy welding structure are large welding deformation and low fatigue strength. In order to accurately consider the influence of welding defects, the temperature field simulation program of thin plate welding structure is designed to predict the welding deformation and residual stress. The simulation results of temperature field and welding deformation of typical welded joints are in good agreement with the test results. Moreover, taking welding deformation and residual stress as initial conditions, the fatigue strength class curves of 5059 aluminum alloy welded joints are renewed based on the hot spot stress.
•Substituting SCMs for clinker reduces the strength of blended cements.•SCMs can increase the environmental impact of concrete.•Extra grinding enhances the cement strength and reduces the CO2 ...footprint.
Traditional approaches to reducing the CO2 emissions of cement production are effective yet insufficient, which has driven new research and innovations. A potential alternative that has been poorly explored is optimizing the physical and chemical characteristics of cement to enhance the dosage efficiency for concrete, which can reduce both cement consumption and CO2 emissions. This approach demands an understanding of the potential savings according to the cement strength. In practical terms, increasing the cement strength requires more electric energy to grind cement into finer particles, which ensures that most of the clinker and other reactive particles are hydrated at 28 days; and increasing the reactive phases of the cement, such as the clinker content. Both options improve cement reactivity and can reduce cement consumption to achieve the same mechanical performance of concrete. The objective of this study was to investigate the potential reduction in the CO2 footprint of concrete mixes with cements of different strength classes and discrete clinker substitution ratios. The effect of grinding finer cement on reactivity was also evaluated. The carbon abatement costs were estimated according to the additional CO2 emissions from cement grinding and potential CO2 reduction from a smaller dosage.
Brazil has the world’s second largest forest area, which makes the exploitation and use of varied species in civil construction conducive. One of the traditional uses of wood is to build roofs for ...different purposes. Considering that the most recurrent pathologies in the roof structures are related to the excessive deformations observed in the structural elements, particularly in those subjected to bending. This study verified the effective representativeness of the stiffness value established by the Brazilian Class wood standard, C40. Batches of eight different tropical wood species were considered, whose framing occurred in the referred Class. Results obtained from the confidence intervals for each evaluated species led to the conclusion that the value of 19500 MPa for the modulus of elasticity is not representative for Class C40 because the value observed in this study was 14467 MPa, which is 26% lower than the normative reference. This observation is an initial indication that the adoption of the value of 19500 MPa by the standard is unfavorable to the safety of the structure, justifying the pathologies observed in the service performance of the roof structures.
RESUMO: O Brasil é o segundo maior país em área de florestas no mundo, o que torna propícia a exploração e uso de espécies variadas na construção civil. Um dos usos tradicionais da madeira se dá nos telhados das edificações para as mais diferentes finalidades. Tendo em vista que as patologias mais recorrentes nas estruturas de cobertura estão relacionadas às deformações excessivas verificadas nos elementos estruturais, principalmente nos sujeitos à flexão, o presente trabalho teve como objetivo verificar a efetiva representatividade do valor médio do módulo de elasticidade na compressão paralela estabelecido pela norma brasileira para madeiras da Classe C40. Foram considerados lotes de oito diferentes espécies de madeira tropicais, cujo enquadramento se deu na referida Classe. Os resultados obtidos dos intervalos de confiança para cada espécie avaliada possibilitaram concluir que o valor de 19500 MPa para o módulo de elasticidade não é representativo para a Classe C40, pois o valor encontrado nessa pesquisa foi 14467 MPa, resultado esse 26% inferior à referência normativa. Essa constatação é um indicativo inicial de que a adoção do valor de 19500 MPa pela norma é desfavorável à segurança da estrutura, justificando as patologias observadas no desempenho em serviço das estruturas de cobertura.
•Currently, Populus spp. timber is not included in Spanish visual grading standard.•Qualifying efficiency of UNE-56544:1997 applied in this timber is not appropriate.•ME-1 visual grade does not ...comply to the minimum values established in EN-338.•Supervised Machine Learning algorithms use improves this qualifying process.•Visual defects, sawing systems and non-destructive variables were better predictors than UNE-56544.
The efficiency of visual grading standards applied to structural timber is often inappropriate, and timber properties are either under or over-graded. Although not included in the current UNE 56544 visual grading standard, machine learning algorithms represent a promising alternative to grade structural timber. The general aim of this research was to compare the performance of machine learning algorithms based on visual defects, non-destructive techniques and sawing systems (“cut type”) with UNE 56544:1997 visual grading in order to predict the qualifying efficiency of Populus x euramericana I-214 structural timber. Visual evaluation, ultrasound and vibrational non-destructive testing, and sawing systems register (radial, tangential and mixed) were applied to characterize 945 beams. In addition, in order to retrieve actual physical-mechanical values, density and static bending destructive testing (EN-408:2011 + A1:2012) was also carried out. Several machine learning algorithms were then used to grade the beams, and their predictive accuracy was compared with that of visual grading. To do so, three scenarios were considered: a first scenario in which only visual variables were used; a second scenario in which “cut type” variables were also included; and a third scenario in which additional non-destructive variables were considered. Results showed a poor level of performance of UNE 56544:1997, with an apparent mismatch between the strength values assigned for each visual grade (established by the EN 338 standard) and the actual values. On the opposite, all algorithms performed better than visual grading and may thus be deemed as promising timber strength grading tools.
•Andesite rock have pozzolanicity due to high SiO2 content.•Andesite waste powder was used as mineral additive in concrete.•Pozzolanic activity of andesite powder was compared with other ...pozzolans.•The optimum replacement rate of andesite powder was determined as 10%.
Andesite stone is widely used in civil engineering and architectural applications in Turkey. Mining, cutting and polishing of andesite stone leads to the generation of significant amounts of waste material. Andesite contains SiO2 as the main component. Therefore, andesite may have pozzolanicity and thus may be used as mineral additive in concrete. In this study, the efficiency factor of andesite waste powder as a mineral additive was investigated and compared with F type fly ashes. The efficiency factors of mineral additives were also analyzed according to the curing ages of concrete specimens. Concrete specimens were prepared at various cement dosages to determine the efficiency factors of mineral additives at different replacement levels. The compressive strengths of concrete specimens were tested at 28th and 90th days. The efficiency factors were calculated by determining the variable Feret coefficient for each specimen series. For C40 strength class, the optimum replacement rate of andesite waste powder was determined as 10% at curing ages of 28 and 90 days.
Recommendations
to assign steel grades most commonly used in industry and energy of the Republic of Belarus to a specific group and subgroup of the international standard ISO/TR 15608 are presented. ...These recommendations were made on the basis of a comparative analysis of the base metal chemical composition and its mechanical properties, given in the national and foreign standards for sheet and pipe metal rolling. Analysis of mechanical properties have been included conditions of thermal and thermomechanical treatment of the base metal. The information presented in the article can be useful for a wide range of welding specialists in documentation development for welding processes (WPS, WPQR), issuing welders attestation certificates (qualification test certificate) and other technological documentation.
The
possibility of using zirconium in the steel composition of the Arx-Zr brand in the cold-deformed reinforcement of a threesided periodic profile of strength class 500 MPa manufacture in order to ...increase the finished reinforcement strength characteristics is determined. There is test results information of a wire rod /blank with an 8.8 mm diameter, which is intended for the manufacture of cold-deformed fittings with an 8.0 mm diameter, are presented. A comparative analysis of the physical and mechanical finished cold-deformed fittings properties with an 8.0 mm diameter made of steel grade Arch-Zr and fittings of a three-sided periodic profile made of wire rod of ordinary quality was done. Analyzed the obtained properties and the cold-deformed fittings evaluation for meeting the standards’ requirements. Identified that the addition of zirconium to steel in an amount of 0.019 % does not affect the final strength characteristics of the produced cold-deformed reinforcement of a three-sided periodic profile of strength class 500 MPa. The values of the physical and mechanical parameters of the produced cold-deformed reinforcement are similar to the cold-formed reinforcement parameters made of wire rod of ordinary quality without the use of alloying.
The structural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) is mainly affected by the fiber volume fraction, the fiber distribution, and the fiber orientation. Fiber ...orientation especially may vary (locally) in structural members depending on their geometry, the consistency of the fresh concrete, and the way of placing and compacting the concrete. As a result, UHPFRC may behave anisotropically in both tension and compression. To quantify the effect of fiber orientation on the behavior of UHPFRC in compression, tests on cylinders and differently fabricated cubes made of fine-and coarse-grained UHPFRC mixtures were performed. Especially for high fiber volume fraction, specimens with predominantly unidirectional fiber orientation perpendicular to the loading direction showed significantly higher compressive strengths than specimens with predominantly unidirectional alignment of the fibers parallel to the loading direction. Unlike for ultra-high-performance concrete without fibers, a noticeable difference between cylinder and cube compressive strength could be observed in case of UHPFRC. Keywords: anisotropy; compressive strength; failure; induction; orientation; specimen; strength class for concrete; strength test; ultra-high-performance concrete (UHPC).
So far, there has been a lack of generally applicable factors to convert between compressive strengths obtained in tests on ultra-high-performance concrete (UHPC) specimens of different shapes and ...sizes. Thus, a test program covering compression tests on 150 and 100 mm (6 and 4 in.) cylinders and cubes was initiated. For comparison reasons, ordinary-performance concrete (OPC), high-performance concrete (HPC), and UHPC mixtures without fibers were examined. The maximum aggregate size of the UHPC mixtures was 0.5, 3, 5, and 8 mm (0.020, 0.12, 0.20, and 0.31 in.), which covers the scope of application. The mean cylinder compressive strengths ranged between 30 and 200 MP a (4.35 and 29.0 ksi). Very small coefficients of variation of test results document high accuracy and validity obtained by standardized procedures throughout fabrication and testing. Compared with OPC and HPC, the effect of specimen's geometry on the compressive strength is very small for UHPC. Keywords: compressive strength; conversion factor; cube; cylinder; guideline; strength class for concrete; strength test; ultra-high-performance concrete (UHPC).
The construction industry has a notably negative impact on the environment; thus, the promotion of the use of timber structures is an alternative to mitigate its effects. This research develops an ...artificial intelligence-based decision approach in the calculation of timber structures focused on the enhancement of the sustainability of roof structures. Based on the optimization carried out through genetic algorithms and the framework established in Eurocode 5, a general set of equations has been proposed for a laminated timber roof structure. The tool, which determines the most suitable roof structure for each strength class of laminated timber, allows for the determination of the dimensions of beams and purlins and their respective separations in order to minimize wood consumption. The ultimate goal is to offer multiple solutions regarding strength classes and structural designs in order to foster sustainability-informed choices that promote efficient use of resources in construction.
PDF
