Strength Design Research Articles

Behaviour of sewage sludge based lightweight aggregate in geopolymer concrete

The global challenge of sewage sludge disposal has encouraged innovative solutions aimed at reducing environmental impact while simultaneously addressing the growing demand for sustainable construction materials. This study aimed to develop treated raw sewage sludge-based lightweight aggregates with strength comparable to commercially available aggregates. Two methods, namely cold bonding and sintering, were employed for the formation of aggregates. The sintering method produced well-formed and hard aggregates, while the cold bonded aggregates exhibited weakness and disintegrated under the slightest pressure. The optimal mix for quality aggregates was found to be 10%–20% sewage sludge, 70%–80% fly ash, and 10% lime using the sintering method. In the sintering method, an increase in sewage sludge content resulted in the reduction of bulk density and specific gravity by 13% and 4% respectively due to the high organic content in sewage sludge, volatile gas release, and porous structure formation. When 10% to 20% sewage sludge content was added, water absorption of the aggregates also increased by approximately 2%. Physical properties such as individual pellet strength. aggregate crushing value reduced by 18%, 20% respectively and the aggregate impact value increased by about 9%. These aggregates were then used to produce lightweight geopolymer concrete, which exceeded the design strength by 7% for the aggregate containing 20% sewage sludge and demonstrated excellent physical properties. The use of waste-based aggregates offers advantages including savings in cost, sustainability, resource conservation, waste reduction, and reduced environmental impact, making them a valuable alternative to natural crushed stone aggregates in specific applications.

Evolution law and mechanism analysis of strength for backfill under different stress and drainage conditions

In recent years, with the improvement of construction safety requirements in deep well mining, the backfill mining method has been widely used. However, the strength of paste filling acquired in quarry often surpasses the design strength determined in laboratory settings. In view of the problems that indoor conditions cannot restore deep mining environment, and the mechanism of coupling effect under multiple fields is unclear. This paper has carried out relevant research work through theoretical analysis and indoor experiments. First of all, after completing the preparatory experiments, this paper analyzed the strength difference of backfill under different curing stress and drainage conditions, and studies the influence of different curing conditions on the strength. Secondly, MPS-6 and 5TE sensors were used to monitor the electrical conductivity, pore water pressure, porosity and other parameters of backfill during the stress-drainage curing process, and changes of parameters during curing process were analyzed. Finally, the relationship among relevant parameters and strength properties of paste backfill was analyzed, as to clarify the influence mechanism of stress-drainage curing conditions on the strength formation for paste backfill. Research shows that both stress-undrained and stress-drained conditions can effectively increase the strength of backfill. Under stress-drainage conditions, the internal porosity of backfill will decrease, and the pore water pressure of backfill will first increase slightly and then continue to decrease. Under this condition, the electrical conductivity of backfill will first increase and then continue to decrease. The entire research has important positive significance for reducing mining costs, optimizing mining processes, and developing mining technology.

XGBoost algorithm based estimation of near surface mounted FRP rod-to-concrete bond strength and failure mode

Using fiber-reinforced polymer (FRP) in reinforced concrete (RC) structures can mitigate the colossal repair costs due to reinforcing steel corrosion. Hence, FRP rod/bar is gaining wider applications in diverse RC structures as a partial or full replacement for steel rebar. The FRP rod-to-concrete interfacial bond is pivotal in transferring stresses from concrete to FRP rods. This study develops a novel prediction model to estimate the near surface mounted FRP rod-to-concrete bond strength as well as the failure type using five machine learning (ML) algorithms, namely, linear regression, decision tree, gradient boosting tree, random forest, and extreme gradient boosting (XGB). The performance of the developed models was compared with that of four bond strength design guidelines and one analytical model. A database comprising 416 experimental datasets was constructed and used for model training and validation. Based on statistical performance metrics, the precision of the XGB algorithm was superior to that of the other ML models, design guidelines, and analytical model. Feature importance analysis based on the SHapley Additive exPlanations theory and partial dependence plot was performed. The results show that the bond length had the most significant influence on the bond strength, followed by the tensile strength of the FRP composite, diameter of the FRP rod, compressive strength of concrete, and elastic modulus of the FRP composite. A graphical user interface was developed and offers a user friendly, free access, and simple tool for estimating the bond strength and failure type of FRP rods in concrete.

Research on the Calculation Method of Propeller 1P Loads Based on the Blade Element Momentum Theory

Aircraft propellers produce relatively large in-plane loads, called propeller 1P loads, during maneuvers such as turning, diving, and lifting, and these loads can negatively affect the flight and control of the aircraft. In order to study the change rule of 1P aerodynamic loads, in this paper, a mathematical model of the propeller 1P aerodynamic loads has been developed based on the blade element momentum theory. This mathematical model was then corrected using the Pitt–Peters incoming flow correction method, the Prandtl tip correction method, and the propeller root flow correction method. Based on this mathematical model, a calculation procedure for the propeller 1P aerodynamic loads was developed using MATLAB software, and the accuracy of the procedure was verified by comparing the results with CFD simulation results. Numerical simulations show that the results calculated based on the proposed mathematical model for the coefficients of thrust, power, bending moment, and the tangential force of the propeller have an error of less than ±6.00% compared to the CFD simulation results. For a small inflow angle, the coefficients of bending moment and tangential force of the whole propeller fluctuate in a small range. But, as the inflow angle increases, the fluctuation range of the aerodynamic characteristic parameters of the propeller increases and the fluctuation becomes more complicated. Through numerical calculations, it has been shown that the mathematical model presented herein is reliable and accurate. In addition, it greatly shortens the calculation time and improves the calculation efficiency. It is expected that the proposed model can provide a certain help for the strength design of the propeller structure and the study of the aerodynamic performance of the whole aircraft.

Damage and reliability analysis of double-arch tunnel without a middle pilot tunnel under blast load

In this study, a new type of multi-arch tunnel construction method is proposed. This effort is undertaken due to the many disadvantages of the traditional multi-arch tunnel construction method. Furthermore, this method omits the construction of a middle pilot tunnel, and it has the advantages of safety, high efficiency, and being economical. When using the method of continuous arch tunneling without a middle pilot tunnel, the blasting of the first tunnel and the following tunnel has a greater impact on the surrounding rock damage, as well as on the supporting structure of the same cross-section. Therefore, this study uses LS-DYNA finite element software to construct a three-dimensional numerical model. In addition, the perimeter rock damage law and mechanical response characteristics of the supporting structure in the same cross-section of the first tunnel, as well as the following tunnel after blasting without a middle pilot tunnel, are analyzed. At the same time, the results of the study are based on optimizing the blasting program, and these are then applied to the field. Through the results, it is found that, after blasting a continuous arch tunnel without a medial pilot tunnel, the surrounding rock damage in the arch cross-region of the double-arch tunnel (where the arch top and the arch shoulder are more significant) and the effective stress of the supporting structure exceed the strength design value. In addition, the maximum adequate pressure is distributed in the medial diaphragm wall. With the optimized blasting scheme, the range of the peripheral rock damage is reduced by a maximum of 67%, and the effective stress in the supporting structure is reduced by 25.9–64.8%. The research results are of great significance in terms of improving construction safety, economic efficiency, and project quality, as well as in promoting the research and development of new work methods for double-arch tunnels.

Study of Fatigue Performance of Ultra-Short Stud Connectors in Ultra-High Performance Concrete

Steel–UHPC composite bridge decking made of ultra-high performance concrete (UHPC) has been progressively employed to reinforce historic steel bridges. The coordinated force and deformation between the steel deck and UHPC are therefore greatly influenced by the shear stud connectors at the shear interface. Four fatigue push-out specimens of ultra-short studs with an aspect ratio of 1.84 in UHPC were examined to investigate the fatigue properties of ultra-short studs with an aspect ratio below 2.0 utilized in UHPC reinforcing aged steel bridges. The test results indicated that three failure modes—fracture surface at stud shank, fracture surface at steel flange, and fracture surface at stud cap—were noted for ultra-short studs in UHPC under various load ranges. The fatigue life decreased from 1287.3 × 104 to 24.4 × 104 as the shear stress range of the stud increased from 88.2 MPa to 158.8 MPa. The UHPC can ensure that the failure mode of the specimens was stud shank failure. Based on the test and literature results, a fatigue strength design S–N curve for short studs in UHPC was proposed, and calculation models for stiffness degradation and plastic slip accumulation of short studs in UHPC were established. The employment of ultra-short studs in the field of UHPC reinforcing aging steel bridges can be supported by the research findings.

Confinement-based design and behaviour of concrete-filled stiffened steel tubular square slender columns

This paper presents the details, analysis and results of an investigation into the compressive behaviour of concrete-filled stiffened steel tubular (CFSST) slender columns. These are members comprising an outer steel section with longitudinal stiffeners welded to the interior surface. A finite element (FE) model was developed and validated. An improvement in ultimate strength compared to conventional concrete-filled steel tubular column has been found due to the presence of stiffeners that reduce the width-to-thickness ratio of the steel tube, which in turn increases the effective cross-sectional area of the steel tube. Moreover, it was found that stiffeners increase the lateral confining pressure on the concrete. FE modelling was then employed to conduct a thorough parametric study to investigate the influence of a wide range of parameters. These included the slenderness ratio, concrete compressive strength, as well as the geometry and details of the stiffeners. Both medium-length and long CFSST columns, classified on the basis of slenderness ratio, were carefully studied and discussed, as well as their inherent differences. The strengths predicted from the FE simulations were compared with the design strengths obtained from various international design codes, and it was shown that the design expressions provide very conservative capacity predictions. Accordingly, a new three-stage confinement-based design model was proposed, which takes into account different confining mechanisms of columns based on their slenderness ratio. It is illustrated that this model provides a very accurate prediction of the square CFSST slender columns, and captures the key behavioural characteristics.

The microstructural evolution and mechanical response of laser direct energy deposition Inconel 718 alloy based on simulation and experimental methods

During laser directed energy deposition (LDED), the complex microstructure created by multiple rapid heating and cooling cycles results in the uneven performance of the parts. This work investigates the microstructure evolution and mechanical properties of LDED Inconel 718 samples with different deposit shapes of single-track and thin-wall. The crystal plasticity constitutive and statistical microstructure modeling combined with experiments were performed to explore the influence of microstructure on tensile property. Compared to the thin-wall samples, the single-track sample has smaller sub-grains because of the higher cooling rate, resulting in higher hardness. Furthermore, the anisotropy of the mechanical properties is not changed by the scanning strategy, although the grain size and the yield strength with the Hall-Petch relation are affected by the scanning strategy. The slip system with maximum and secondary Schmid factors is more easily activated during deformation. The rotational behavior of the grains suggests that the anisotropy of mechanical properties is closely linked to the dominant texture of the 〈001〉 orientation crystals, including the dominant direction of the grain long axis and the ratio of the long and short axis. The results can provide guidance for understanding the deformation mechanism of LDED parts and optimizing the strength design.

ESTABLISHING THE RELIABILITY LEVEL OF MASONRY BEARING STRUCTURES BASED ON ITS COMPONENT STRENGTH ANALYSIS

The article discusses aspects related to assessing the reliability of masonry structures. The authors present methods for determining the compressive strength of masonry in existing structures, taking into account reliability theory. We also consider practical solutions for calculating the design strength of masonry, which may help to assess the safety of massive brick walls and pillars that act as core structural elements of existing buildings. Thus, walls and pillars operating in compression are vital elements of stone buildings and require special attention when analysing and assessing their strength. They carry enormous loads and are critical to the stability of the entire structure. There are cases when it may be hard to obtain safe samples for testing masonry mechanical performance, making the analysis of existing masonry structures difficult. However, building codes and methods provide specific methods for determining the strength of existing structures based on reliability theory. These methods assume uniformity of masonry with regularly spaced brick layers. Although such assumptions may simplify the analysis, they can still provide sufficiently accurate results for making decisions about the safety and reliability of the building. It is essential to consider all possible factors and limitations when using these methods to ensure a reliable assessment of the condition of masonry structures. Stone materials are among the most traditional in various areas of construction production. Buildings with brick load-bearing walls represent the lion’s share of the existing housing development in Ukraine. Ensuring its high-quality operation and the safety of residents during the life cycle of such buildings are priority areas. However, changes occurring in the external environment and the state of regulatory support for construction production require a periodic return to the issues of assessing the load-bearing capacity of both previously erected building structures and those under design. Thus, lately, the territories with previously unusual force impacts on building structures, such as horizontal displacements of the base of the building, have significantly expanded. The reasons for this include seismic activity in certain regions of the country and the results of anthropogenic factors, particularly the areas with unstable soils. We should note that many buildings and structures are subject to external influence due to military operations on a large territory of Ukraine. So, in the event of a hit by warheads or the action of a blast wave, they generate new, non-typical, but dangerous effects on the load-bearing structures of the entire building. Keywords: reliability theory, reliability assessment, structural safety, stone structures, masonry strength.

Analysis of equivalent substitution of rectangular stress block for nonlinear stress diagram

This article deals with the analysis of equivalency of the substitution of rectangular stress block for nonlinear stress diagram with descending branch for the calculation of flexural, eccentrically compressed and eccentrically tensioned reinforced concrete members of rectangular cross-section. The method for equivalent substitution of these diagrams is proposed. Analytical relationships of area and its centre for the nonlinear diagram with descending branch are presented. Coefficients for equivalent  substitution of the said diagrams for the standard concrete strength classes are determined and given. It gives the opportunity to design reinforced concrete members  using rectangular stress block model. Substitution of the diagrams applied in EC2 and in STR 2.05.05:2005 is compared with the equivalent substitution of rectangular stress diagram for nonlinear stress diagram with descending branch. It is shown that in STR 2.05.05:2005 description of the ratio between the depth of the rectangular diagram and that of the equivalent nonlinear one with descending branch is very poor. An explicit analytical relationship for this ratio and its linear approximation in respect to the concrete characteristic and design strengths are presented in this article as well.

Comparative Analysis of Gradient-Boosting Ensembles for Estimation of Compressive Strength of Quaternary Blend Concrete

Concrete compressive strength is usually determined 28 days after casting via crushing of samples. However, the design strength may not be achieved after this time-consuming and tedious process. While the use of machine learning (ML) and other computational intelligence methods have become increasingly common in recent years, findings from pertinent literatures show that the gradient-boosting ensemble models mostly outperform comparative methods while also allowing interpretable model. Contrary to comparison with other model types that has dominated existing studies, this study centres on a comprehensive comparative analysis of the performance of four widely used gradient-boosting ensemble implementations [namely, gradient-boosting regressor, light gradient-boosting model (LightGBM), extreme gradient boosting (XGBoost), and CatBoost] for estimation of the compressive strength of quaternary blend concrete. Given components of cement, Blast Furnace Slag (GGBS), Fly Ash, water, superplasticizer, coarse aggregate, and fine aggregate in addition to the age of each concrete mixture as input features, the performance of each model based on R2, RMSE, MAPE and MAE across varying training–test ratios generally show a decreasing trend in model performance as test partition increases. Overall, the test results showed that CatBoost outperformed the other models with R2, RMSE, MAE and MAPE values of 0.9838, 2.0709, 1.5966 and 0.0629, respectively, with further statistical analysis showing the significance of these results. Although the age of each concrete mixture was found to be the most important input feature for all four boosting models, sensitivity analysis of each model shows that the compressive strength of the mixtures does increase significantly after 100 days. Finally, a comparison of the performance with results from different ML-based methods in pertinent literature further shows the superiority of CatBoost over reported the methods.

Experimentally Induced Reductions in Alcohol Consumption and Brain, Cognitive, and Clinical Outcomes in Older Persons With and Those Without HIV Infection (30-Day Challenge Study): Protocol for a Nonrandomized Clinical Trial.

Both alcohol consumption and HIV infection are associated with worse brain, cognitive, and clinical outcomes in older adults. However, the extent to which brain and cognitive dysfunction is reversible with reduction or cessation of drinking is unknown. The 30-Day Challenge study was designed to determine whether reduction or cessation of drinking would be associated with improvements in cognition, reduction of systemic and brain inflammation, and improvement in HIV-related outcomes in adults with heavy drinking. The study design was a mechanistic experimental trial, in which all participants received an alcohol reduction intervention followed by repeated assessments of behavioral and clinical outcomes. Persons were eligible if they were 45 years of age or older, had weekly alcohol consumption of 21 or more drinks (men) or 14 or more drinks (women), and were not at high risk of alcohol withdrawal. After a baseline assessment, participants received an intervention consisting of contingency management (money for nondrinking days) for at least 30 days followed by a brief motivational interview. After this, participants could either resume drinking or not. Study questionnaires, neurocognitive assessments, neuroimaging, and blood, urine, and stool samples were collected at baseline, 30 days, 90 days, and 1 year after enrollment. We enrolled 57 persons with heavy drinking who initiated the contingency management protocol (mean age 56 years, SD 4.6 years; 63%, n=36 male, 77%, n=44 Black, and 58%, n=33 people with HIV) of whom 50 completed 30-day follow-up and 43 the 90-day follow-up. The planned study procedures were interrupted and modified due to the COVID-19 pandemic of 2020-2021. This was the first study seeking to assess changes in brain (neuroimaging) and cognition after alcohol intervention in nontreatment-seeking people with HIV together with people without HIV as controls. Study design strengths, limitations, and lessons for future study design considerations are discussed. Planned analyses are in progress, after which deidentified study data will be available for sharing. ClinicalTrials.gov NCT03353701; https://clinicaltrials.gov/study/NCT03353701. DERR1-10.2196/53684.

Axial compressive stability design of longitudinal asymmetrical shuttle-shaped columns

Longitudinal asymmetrical shuttle-shaped column (LA-SSC) has found its wide application when subjected to combined axial compression and horizontal point load in practical engineering. This paper focuses on elastic and elasto-plastic buckling behaviors of the LA-SSC only under axial compression and the resulting outcome could provide an indispensable basis for further establishing buckling strength prediction of LA-SSC under axial compression and horizontal point load. At first, the elastic buckling behavior of tapered columns (TC) and longitudinal symmetrical shuttle-shaped columns (LS-SSC) are derived in theory and verified by finite element numerical results, and corresponding elastic buckling modes are discussed. Subsequently the elastic buckling load prediction of LA-SSCs is established first and the corresponding normalized slender ratio, as a key design parameter, is generalized. Finally, the stability capacity of LA-SSCs is involved in theoretical analysis and finite element (FE) numerical calculation under axial pressure. Through investigating the axial load-lateral displacement curves and axial stress distributions the buckled LA-SSCs, the effects of different parameters (such as overall length, plate thickness, and steel strength) on the axial compression stability capacity of LS-SSCs are explored. As a result, the complete design formulas for axial compression stability capacity of LA-SSCs are presented first and compared with current major design codes in various countries. It is observed that the proposed strength design formulas are in good correspondence with the FE numerical results. The proposed formulas could provide references and guidance for the axial compression buckling strength of LA-SSCs under axial compression and they further supply fundamentals for establishing the strength design recommendation of LA-SSCs under axial compression and bending moments.

Member Capacity of Cold-rolled Aluminium Alloy Channel Columns - Part II: Numerical Investigation and Design

The paper first presents the development of detailed finite element (FE) models for investigating the member capacity of cold-rolled aluminium alloy 5052-36 channel columns. The numerical non-linear FE models are developed using the commercial FE software package ABAQUS to simulate laboratory experiments and calibrated against the test results. The experimental program was performed by the authors at the University of Sydney and the detailed test results are fully described in a companion paper. The calibrated numerical FE models with actual mechanical properties and measured geometric imperfections in analyses accurately predict the experimental results and behaviours, including flexural and flexural-torsional buckling as well as local-global interaction buckling failure modes. A parametric study is subsequently performed to extend the data range by varying cross-section dimensions and member lengths. The effects of loading eccentricity positions and initial geometric imperfections are also considered in the parametric study. The experimental and numerical results are compared with design strength predictions from current Australian/New Zealand, American and European specifications for aluminium structures in the companion paper. In this paper, the Direct Strength Method (DSM) for the design of compression members as per the Australian/New Zealand standard AS/NZS 4600 for cold-formed steel structures is adopted for comparison. The DSM design rules for cold-formed steel compression members are found to provide more accurate predictions than those of current specifications for aluminium structures and therefore used to propose improved design equations for cold-rolled aluminium alloy columns. Finally, a reliability analysis is performed to evaluate the safety level of current design specifications and the proposed design rules.

Torsional strength design method and cost analysis of FRP bars reinforced ECC beams without stirrups

Fiber reinforced plastic (FRP) bars reinforced engineered cementitious composites (ECC) beams without stirrups own excellent torsional performance and good application prospect. However, the corresponding torsional strength design method is not available. In order to predict the torsional strength of the ECC beams, a theoretical design method is established in this research. The proposed design method is based on the variable-angle space truss (VAST) model, and the tensile resistance supplied by fibers is carefully considered. The established design method is verified through the experimental results. It can be found that the predicted values agree well with the experimental values. A parametric analysis is carried out. Ultimate torque (i.e., torsional strength) increases significantly with the increment of ECC strength grade or longitudinal reinforcement ratio. However, at the same cross-section area, ultimate torque decreases slightly with the increment of height/width ratio. In addition, the cost effectiveness of the ECC beams without stirrups is discussed. Compared with mortar beam with a stirrup reinforcement ratio of 0.7%, FRP bars reinforced ECC beams without stirrups have small cost/ultimate torque ratio (a reduction ratio of 39.14%–60.86%), indicating that the ECC beams without stirrups own satisfactory cost effectiveness. This study will provide a torsional strength design guideline for FRP bars reinforced ECC beams without stirrups.

Structure Design and Strength Analysis of the Glass Reinforcement Plastic (GRP) Malay Traditional “Perahu Bedar”

The Perahu Bedar, a traditional fishing boat in the Terengganu region of Malaysia, has been historically crafted from Cengal wood. In response to challenges posed by wood scarcity and limitations in skilled craftsmen, this study pioneers the exploration of Glass Reinforced Plastic (GRP) as a novel alternative material for constructing the traditional Perahu Bedar, measuring 4.32 meters in length. Through a rigorous analysis, the research delves into the structural design intricacies and strength attributes of the GRP Perahu Bedar, marking a significant departure from conventional wood-based construction methods. The study conducts a comprehensive analysis of the structure design and strength characteristics of the GRP Perahu Bedar. The weight, buoyancy force, and load distribution along the boat are analyzed. The data shows varying weight and buoyancy forces along the stations, with positive load values indicating upward forces contributing to buoyancy and negative load values representing downward forces. This analysis provides insights into the boat’s stability and distribution of forces. The sheer force and bending moment along the Perahu Bedar are evaluated. The sheer force values gradually increase or decrease along the boat, while the bending moment is highest at the midsection and decreases towards the ends. These results indicate the distribution of forces and stress on the boat’s structure, aiding in understanding its integrity and stability. The Factor of Safety (FoS) analysis demonstrates a FoS value of 2.2368, indicating a safety margin greater than 1. This suggests that the GRP Perahu Bedar design meets safety requirements and can withstand applied 
 
 stresses without exceeding yield strength. The FoS value provides assurance of structural integrity and safety during normal operating conditions. In summary, this study underscores the groundbreaking potential of Glass Reinforced Plastic (GRP) as a viable alternative to traditional wooden Perahu Bedar due to very high cost of Cengal Wood (wood that been used to build Peahu Bedar). By meticulously analyzing critical factors such as weight, buoyancy, load, shear force, bending moment, and Factor of Safety (FoS), the research offers invaluable insights into the structural integrity and safety aspects of GRP Perahu Bedar. These revelations not only herald a new era of sustainable and cost-effective boatbuilding practices but also serve as a crucial step towards safeguarding and perpetuating the rich maritime heritage of the region.

Design and Development of Marigold Flower Petal Separating Machine

Abstract: A marigold flower petal separating machine has been fabricated. The machine is fabricated for separating flower in two different parts, upper part consist of petals and lower part consisting of seeds. This project focuses in design fabrication of mechanical part of machine and the system of petal and seed separating machine. To achieve this project objective, the machine body structure and the mechanical system need to analyses some other criteria such as performance, strength, safety, and ergonomic design. Design of Model (Mechanism). Fabrication of Model setup as per CAD or CREO design. Conducting Experiment on the Model setup. Results and discussions. Conclusion as per results. After testing and obtaining results the conclusion of project will be done and put to use.

SMATool: Strength of Materials Analysis Toolkit

The study of the strength of materials is a cornerstone in material science and engineering, playing a critical role in shaping the progress and application of materials in diverse industrial sectors. The strength of a material is meticulously examined to understand the behavior of the material under different stress conditions and environments, thereby guiding material selection and structural design. Herein, we introduce the SMATool, a computational toolkit for the efficient calculation and analysis of material strength at both zero and finite temperatures for 3D, 2D, 1D, and tubular 2D-based nanostructures and nanotubes, as well as 1D nanoribbons. The toolkit is capable of calculating tensile, shear, ultimate, yield, and indentation (Vickers' hardness) strengths in various dimensions, as well as the energy storage capacity. We conducted several calculations both at zero and finite temperatures to validate the accuracy and reliability of the developed software. The results show that the SMATool package provides accurate predictions that align with existing data on material strength. SMATool integrates seamlessly with widely used electronic structure codes like VASP and Quantum Espresso, providing a user-friendly interface catering to academic researchers and industry professionals. SMATool is useful for either the exploration of the strength of materials or high-throughput new material design. SMATool is open-source and available on GitHub at SMATool@github. Program summaryProgram Title: SMAToolCPC Library link to program files:https://doi.org/10.17632/fnkzfsg7t7.1Licensing provisions: GNU General Public License, version 3Programming language: Python 3Nature of problem: Developing a comprehensive framework to accurately determine the strength of materials is crucial in various engineering and scientific disciplines. This involves developing a robust and efficient computational toolkit to predict the strength of a material under different loading conditions, including tension, compression, shear, and indentation.Solution method:SMATool effectively addresses the challenge of accurately simulating the mechanical properties of materials by leveraging advances in ab initio methods, including density functional theory and molecular dynamics within the atomic simulation environment. The SMATool toolkit can efficiently compute various material strengths, such as tensile, shear, ultimate, yield, and indentation (Vickers' hardness) strengths as well as the corresponding energy storage capacity of the material. It is adept at handling a variety of material dimensions, ranging from 1D nanotubes and nanoribbons to 2D and 3D structures, at both zero and finite temperatures. SMATool currently integrates VASP and Quantum Espresso as the stress calculator and is easily adaptable to use other electronic structure codes.Additional comments including restrictions and unusual features:SMATool offers serial and parallel execution. Depending on the system size, the nature of the calculations (zero or finite temperature), and the computing architecture, the computing time can vary from ∼5 minutes to as high as 18 hours.

Out-of-Plane Design Equations for Confined Masonry Walls

Nowadays there is still a lack of requirements for the out-of-plane design of confined masonry walls. Current code requirements are mainly based on the in-plane behavior of those walls. This research is divided into two parts. In the first part, two confined walls subjected to out-of-plane uniform loads were tested in the laboratory. Confining elements with minimum cross-section dimensions and wall aspect ratios smaller than one were considered. The variable studied was the wall length. Out-of-plane load—displacement curves of walls were obtained. In the second part, two design equations were developed to determine the out-of-plane strength of confined walls. A design equation was developed to determine the corresponding in-plane forces transferred to the confining elements. The out-of-plane strength of 6912 walls was determined using a computer program based on the bidirectional strut method. A parametric analysis was carried out for the out-of-plane strength considering different variables. Multiple linear regression analyses were carried out to propose out-of-plane strength design equations. It was concluded that the experimental out-of-plane strength increased, and the wall failure type changed as the wall length decreased. In addition, the experimental out-of-plane strength of walls was well predicted with both out-of-plane design equations.

Probabilistic effect of non-potable mixing water on characteristic strength of concrete

Across the world, the acceptance criterion for concrete made with non-potable water (SA) is stipulated for mean strength with reference to similar concrete made with potable water (SP). The basis for the strength design of concrete is the characteristic strength. The effect of the acceptance criteria on the characteristic strength of SA and SP was examined using statistical simulations, for the first time. It was found that, compared with a two-sample set, using a three-sample set would improve the characteristic strength of SA. A higher allowable ratio between the means of SA and SP and a lower deviation of individual samples from the mean would improve the characteristic strength of SA. The effect of the coefficient of variation (CoV) of the original population on the characteristic strength of SA varied. On the one hand, a higher CoV reduced the characteristic strength of SP, thereby increasing the probability of SA strength being higher than SP strength. On the other, a higher CoV of SP meant a wider spread of the samples and that could increase the CoV of SA, thereby reducing the characteristic strength of SA. Probabilistic charts were developed for the characteristic strengths of SA and SP for different combinations of the aforementioned variables, with guidance for practical application.