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

Mechanical properties of concrete containing recycle concrete aggregates and multi-walled carbon nanotubes under static and dynamic stresses

The growing demand for natural aggregates in the construction industry has motivated researchers to utilize recycled concrete aggregates (RCA) to preserve the natural resources and provide sustainable structure. However, the use of RCA in concrete applications has revealed defects in performance with low strength and rapid collapse under static and dynamic loads, respectively. Thus, the objective of present research is to improve these properties by using multi-walled carbon nanotubes (MWCNT). This study involves evaluating the fresh and hardened properties of recycled aggregate concrete (RAC) modified with different levels of MWCNT. The study involves RCA (i.e., 0 %, 25 %, 50 %, 75 % and 100 %) as replacement for natural aggregates, and MWCNT (i.e., 0.05 %, 0.1 % and 0.25 %) as weight of cement. The experimental testing consists of 240 specimens prepared from different mixtures. Workability is assessed using slump tests. Mechanical properties including static compressive strength and dynamic impact resistance are evaluated at 7 and 28 days. Experimental results show that incorporating MWCNT at all levels significantly reduces the slump values for all specimens. On the other hand, the compressive strength is increased by adding MWCNT to the concrete samples. The compressive strength of the RAC increased by as much as 70 % when modified with MWCNT. Furthermore, the inclusion of MWCNT is found to significantly increase the impact resistance of RAC specimens with percentage developments reaching approximately 11–508 % and 110–679 % at 7 and 28 days, respectively, at both first crack and failure stages. The dosage of 0.1 % MWCNT is shown to exhibit the highest percentage enhancement in impact resistance among the other nano levels. The failure patterns and cracks propagation are presented as well

Relationship between outrigger position and external columns size in minimizing building response to wind

This research presents the relationship between the position of outrigger and the size of the external columns in minimizing the building responses to wind. Outrigger system has been one of the many structural systems in tall buildings used to reduce the building responses to wind load. The study on the usage of this system has been given little or no attention to the effect of the size of the external columns to the optimum position of outrigger. This research involves the position of the outrigger being varied and the responses: displacement and acceleration being computed. The procedure is repeated for each different size of the external columns. This analysis is carried out with the use of structural analysis computer software to determine the natural frequency of the building and Excel spreadsheet to determine the responses. The observations from the analysis will provide the conclusion on the relationship between the size of the external columns and the outrigger location with respect to the building response to wind

Experimental damage assessment of support condition for plate structures using wavelet transform

Wavelet transforms (WTs) have gained popularity due to their ability to identify singularities by decomposing mode shapes of structures. In VBDD, the support condition of a structure influences structural responses and modal properties. In fact, the structural responses and modal properties are a lot more sensitive to changing boundary conditions than to crack and fatigue damage, resulting in inaccurate damage detection results. Therefore, in this study, sensitivity tests to estimate a suitable distance range which allows damage detection by imposing single support damage are carried out. The estimated appropriate distance is then applied to detect damage at multiple supports. This involved the applicability of response acceleration of plate structures to support assessment by applying continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The damage cases have been introduced by releasing bolts at specified fixed supports of the plate to simulate the damage. The response accelerations of the rectangular plate at points close to the supports were measured and decomposed using CWT and DWT to assess the structural integrity of each support. The results showed that an appropriate distance range was necessary for accurate damage detection, and both, CWT and DWT could provide reliable outputs. However, the first- and fourth-level detail coefficients of DWT failed to indicate damage in some cases. A more detailed investigation of the effect of different wavelet scale ranges on damage detection using CWT demonstrated that the accuracy of damage detection increased as the scale decreased

Application of two-dimensional wavelet transform to detect damage in steel plate structures

Wavelet Transforms (WT) have been receiving an increasing attention for the detection of damage in structures based on vibration response. The existence of the problem of boundary distortion in WT may lead to unreliable results at and around the boundaries of the structure. Previous studies have applied methods such as signal extension, zero padding and windowing to avoid border distortion. However, these methods try to avoid border distortion by distorting/reducing the original signal to prevent the distortion at the boundaries of the signal from occurring, thus altering the original signal and leading to unreliable damage identification. In this study, a WT-based method is proposed to solve boundary distortion problem. To achieve this, the mode shape difference of a structure is applied for WT decomposition. By using mode shape difference, the problem of border distortion is solved by reducing the effect of sudden change in stiffness that occurs at boundaries. A two-dimensional Continuous Wavelet Transform (CWT) is applied to decompose the difference between the damaged and the undamaged first mode shape signal. The damaged mode shape is subtracted from the undamaged mode shape to obtain the difference, and the difference is decomposed to detect and locate the damage. This method is demonstrated via numerical and experimental examples of a square steel plate. The reliability of the method is demonstrated through different damage intensities and locations. The numerical study involves applying a square plate model with two boundaries formats: all four sides fixed, and two opposite sides fixed and free. The mode shape and mode shape difference are decomposed and the coefficients of the two are compared to show the advantage of this method. The experimental example was applied to a square steel plate with all four sides fixed to verify the efficiency of the method. The numerical results showed that the problem of boundary distortion is resolved by using the mode shape difference and damage at all locations are detected, while applying mode shape provided unreliable results for both numerical models even at 25% severity. The sensitivity of the proposed method to noise is investigated by introducing various levels of signal to noise ratios and showed the detection of damage with 5% severity when mode shape difference was applied in presence of noise

Undergraduate student experience in development of ZVS power converter for voltage control with low cost microcontroller

This paper presents an integration of a low cost microcontroller with a power converter for controlling the output voltage. Here, it will benefit the UTHM final year student in order to apply what have been taught during Power Electronics subject in Year 3. The power converter that has been developed is the zero voltage switching (ZVS) with inverter voltage control mechanism. As for the microcontroller application, the Raspberry Pi has been used. A test on open loop and closed loop conditions have been applied using Proportional Integral (PI) control for controlling the Pulse Width Modulation (PWM) signal pattern for inverter output in hardware experiment test. The PI controller is developed and simulated using the MATLAB/Simulink software and then downloaded to the Arduino and Raspberry Pi microcontroller boards for testing purposes. At the end of the project, the students are able to understand more especially on integrating the control mechanism to the microcontroller device using a power converter in order to achieve the control target output

Application of Automobile Used Engine Oils and Silica Fume to Improve Concrete Properties for Eco-Friendly Construction

Proper disposal of industrial waste can be very burdensome and expensive. On the other hand, improper disposal leads to environmental denigration. A brilliant, safe and cheap means of industrial waste disposal is its addition to concrete. These wastes are added to concrete to modify or improve the properties of the concrete in its fresh and/or hardened state. Used engine oil (UEO) and Silica fume (SF) are industrial wastes that can cause serious environmental pollution. A gallon of UEO is sufficient to pollute a million gallons of water. In this study, two types of UEOs (petrol and diesel engines) and SF are incorporated into concrete to improve the latter’s properties. The two UEOs are applied since they differ in chemical composition and undergo different operations. This study involves obtaining the optimum amounts of UEOs by considering workability and 28-day compressive strengths. Thereafter, SF of 10 % and 15 % replacement of cement was added to concrete with optimum UEOs and the properties were evaluated. The results showed that the UEOs and SF can be disposed of by adding to concrete to modify or improve properties. The results showed that the optimum DUEO and PUEO are 0.8 % and 0.6 % with 32 N/mm2 and 31 N/mm2 compressive strengths. The addition of the SF decreased workability by as much as 17.6 %, while having no significant influence on the compacting factor. In addition, the 10 % and 15 % of SF showed increase in the compressive strength of concrete with optimum UEOs by as much as 37 %

Nanomaterials in recycled aggregates concrete applications: mechanical properties and durability. A review

The use of recycled aggregates concrete (RAC) contributes effectively to reduce CO2 emissions from concrete manufacturing process while also protecting natural resources by utilizing existing available concrete as an aggregates source for a new one. Studies on the behaviour of RAC have revealed negative effects on concrete strength and microstructure development, resulting in deterioration of mechanical and durability properties. As a result, numerous practical studies have been implemented to enhance the RAC properties using various treatment techniques such as chemical, physical and heating treatments. However, most of these techniques are ineffective compared to conventional concrete applications due to poor mechanical performance of RAC, insufficient environmental requirements, and prolonged treatment times. Recently, the use of nanomaterials has been given significant concern in RAC research. Their nano-sized particles can help to reduce micropores formation by acting as a filling agent to produce a high-density microstructure, thereby enhancing the mechanical properties and durability of RAC. This had led to a wide range of studies being published on improving RAC properties by using nanomaterials. However, relatively few literatures had been conducted on the effects of different types of nanomaterials on the performance of RAC exposed to various types of loads and various external environmental impacts. Besides, the conditions used by authors in these literatures limit comparisons, and in some cases contradictory findings are observed. Thus, this paper aims to bridge the knowledge gap between researchers. This would allow the potential of nanotechnology in innovations to be applied in appropriate areas of RAC applications to benefit the general public good. This paper aims to provide a critical review and comprehensive conclusions on the performance of nano-modified RAC under external loads, environmental impacts and other various conditions. The effects of nanomaterials on the compressive, tensile, and flexural strength of RAC are discussed. The nanomaterials considered are nano-SiO2, nano-CaCO3, nano-TiO2, nano-Clay, nano-Al2O3, and nano-Carbon. Durability characteristics including water absorption, chloride penetration, fire exposure, abrasion resistance, acid and carbonation diffusions are extensively discussed. Microstructure characteristics using SEM, XRD, EDS, and micro-hardness of nano-modified RAC are addressed as well

Biogenic approach for concrete durability and sustainability using effective microorganisms: a review

Over the past few years, concrete durability has attracted much attention from researchers. The demand for durable and sustainable concrete is on the rise due to the daily increase in global greenhouse gas (GHG) emissions and global warming. This has necessitated the use of chemical admixtures as ingredients to improve the fresh and hardened properties of concrete. However, these admixtures are associated with drawbacks, like high cost, coloration, GHG, and rapid shrinkage, among others, all of which are limitations to its sustained use. Biogenic methods in concrete production are now being harnessed due to their relatively low cost, high sustainability, and greenness. One such method is the use of effective microorganisms (EM). The coexistence of these microorganisms propels modifications through the biosynthesis of metabolites, which prolongs their existence. However, their mechanism of interaction in concrete is still unclear. Some reviews have been presented on EM concrete; however, these reviews have focused specifically on the hydration characteristics and mechanical properties of concrete. This paper presents a comprehensive review and up-to-date findings of the use of EM in concrete. The EM types, constituents, and preparation procedures are discussed in-depth, as are the influences of EM on the mechanical properties, durability properties, and microstructure of concrete. In addition, recommendations for further research are highlighted. This review shows that EM can be utilized to improve the strength and durability of concrete