Concrete is the most utilized material (i.e., average production of 2 billion tons per year) for the construction of buildings, bridges, roads, dams, and several other important infrastructures. The strength and durability of these structures largely depend on the compressive strength of the concrete. The compressive strength of concrete depends on the proportionality of the key constituents (i.e., fine aggregate, coarse aggregate, cement, and water). However, the optimization of the constituent proportions (i.e., matrix design) to achieve high-strength concrete is a challenging task. Furthermore, it is essential to reduce the carbon footprint of the cementitious composites through the optimization of the matrix. In this research, machine learning algorithms including regression models, tree regression models, support vector regression (SVR), ensemble regression (ER), and gaussian process regression (GPR) were utilized to predict the compressive and tensile concrete strength. Also, the… Details

Tube-to-tubesheet joints play a crucial role in providing structural integrity to the shell and tube heat exchangers. This research investigated the combined effect of roller expansion percentages and grooves on the performance of expanded and welded-expanded tube-to-tubesheet joints. The results indicated that the joint strength of welded-expanded (except for 6% tube expansion and 2 grooves) and welded joints exceeded the nominal axial strength of the tube, 404.90 MPa. The highest tube pull-out strength of 290.77 MPa in the expanded only joint (10% tube expansion and 2 grooves), lesser than the axial strength of the tube by 28.25%, suggested avoiding the expansion process alone for 23 mm thick tubesheets. High dilution and inadequate minimum leak path (<1.78 mm) result in the failure of the welded-expanded joint. The highest hardness of 216 HV is formed at the weld zone comprising of a ferrite and widmanstatten ferrite. From 4% to 10% tube expansion percentages, the grains at the inner… Details

Precast concrete sandwich panels (PCSPs) are utilized for the external cladding of structures (i.e., residential, and commercial) due to their high thermal efficiency and adequate composite action that resist applied loads. PCSPs are composed of an insulating layer with high thermal resistance that is mechanically connected to the concrete. In the recent decades, PCSPs have been a viable alternative for the fast deployment of structures due to the low fabrication and maintenance cost. Furthermore, the construction of light and thin concrete wythes that can transfer and resist shear loads has been achieved with the utilization of high-performance cementitious composites. As a result, engineers prefer PCSPs for building construction. PCSP design and use have been examined to guarantee that a building is energy efficient, has structural integrity, is sustainable, is comfortable, and is safe. Hence, this paper reviews the expanding knowledge regarding the current development of the mechanical… Details

This study explores the use of refined analysis methods to potentially increase load ratings of concrete T-beam bridges by obtaining a decrease in live-load distribution factors. The studied T-beam bridges are vulnerable to posting under consideration of the new federal regulations and when using conventional, simplified equations for load distribution factors. Finite-element models for a total of 25 in-service bridges were developed and analyzed under different vehicle loadings, including special hauling vehicles (SHVs). The effect of transverse positioning of the vehicle load on the computation of the distribution factors was also considered. The moment and shear effects in each girder were extracted and the distribution factors for the interior and exterior girders of the selected bridges were computed. These distribution factors were compared with those obtained from the AASHTO code-specified equations. The results were used to develop regression models to predict the percent change… Details

This research investigates the impact of carbon nanotubes (CNTs) on the expansion, mechanical properties, and microstructure of cement mortar subjected to alkali-silica reaction (ASR). A total of eight compositions were cast to investigate the influence of CNT surface condition, concentration and aspect ratio, and ultrasonication energy. Two types of CNTs were used as reinforcement: pristine CNTs with an aspect ratio of 800 (Type I) and COOH-functionalized CNTs with an aspect ratio of 2500 (Type II). CNTs were incorporated at concentrations of 0.1c-wt.% and 0.3c-wt.%. The results indicated that certain combinations of mix proportions could significantly mitigate the ASR-induced damages in the mortar bar test (ASTM C1260). Specimens reinforced with 0.1c-wt.% of Type I CNTs exhibited the highest resistance to alkali-silica reaction. While specimens reinforced with 0.3c-wt.% of Type II CNTs had marginal improvements. More specifically, specimens reinforced with 0.1c-wt.% of Type I CNTs reduced… Details

The applications of carbon fiber reinforced polymers (CFRPs) to strengthen aging steel structures and bridges have recently gained a wide interest due to their ease of use, corrosion resistance, and high tensile strength. In this research, the effects of aggressive corrosion environment on the mechanical and fatigue properties of CFRP strand sheet/steel double strap joints with various bond length were investigated. The CFRPs consisted of small-diameter strands stitched together to form a sheet. Initially, the stiffness, ultimate tensile and bond strength of the specimens were evaluated using a quasi-static tensile protocol. Then, specimens were exposed to an accelerated corrosive environments for 24, 48 and 72 h and their quasi-static properties were analyzed. Furthermore, the specimens were subjected to fatigue loading with a frequency of 10 Hz and a stress ratio of 0.1. Finally, a fatigue model was developed based on the observed results. The experimental results revealed that the use… Details

During the past decade, researchers investigated the incorporation of carbon nanotubes (CNTs) as a reinforcement for cementitious materials to achieve multifunctional properties. Nevertheless, the mechanisms by which CNTs affect various properties of the cementitious composites including the fresh and hardened states remain elusive. Furthermore, conflicting experimental results have been reported. The discrepancy is attributed to the variability in dispersion, bonding states, and the inconsistencies in the fabrication process (e.g., matrix composition and material characteristics) of the various research conducted. To overcome these challenges, few researchers have investigated the development of analytical equations that could capture the complex interactions between CNTs and the cementitious matrix in order to predict the final properties. This review presents a comprehensive discussion on the research that has been conducted to this date, and provides a detailed insight into the various… Details

Welding is a vital component of several industries such as automotive, aerospace, robotics, and construction. Without welding, these industries utilize aluminum alloys for the manufacturing of many components or systems. However, fusion welding of aluminum alloys is challenging due to several factors, including the presence of non-heat-treatable alloys, porosity, solidification, and liquation of cracks. Many manufacturers adopt conventional in-air friction stir welding (FSW) to weld metallic alloys and dissimilar materials. Many researchers reported the drawbacks of this traditional in-air FSW technique in welding metallic and polymeric materials in general and aluminum alloys and aluminum matrix composites in specific. A number of FSW techniques were developed recently, such as underwater friction stir welding (UFSW), vibrational friction-stir welding (VFSW), and others, for welding of aluminum alloy joints to overcome the issues of welding using conventional FSW. Therefore, the main … Details

Palm oil clinker (POC) aggregates is a viable alternative to the naturally occurring sand and gravel in the manufacturing of concrete. The usage of POC aggregates assists in the reduction of solid waste and preserves the consumption of natural resources. Although researchers investigated the mechanical response of POC-containing concrete, limited research is available for its torsional behavior. In general, the torsional strength depends on the tensile strength of concrete. This research investigates the compressive, tensile, and torsional response of concrete with various ratios of POC-aggregates. Five batches of concrete were casted with POC-aggregate replacing granite at ratios of 0, 20, 40, 60, and 100%. The selection for the mixture proportions for the various batches was based on the design of experiments (DOE) methodology. The hard density, compressive strength, splitting tensile strength, and flexural strength of concrete with a 100% replacement of granite with POC-aggregates reduced… Details

In recent years, researchers have investigated the development of artificial neural networks (ANN) and finite element models (FEM) for predicting crack propagation in reinforced concrete (RC) members. However, most of the developed prediction models have been limited to focus on individual isolated RC members without considering the interaction of members in a structure subjected to hazard loads, due to earthquake and wind. This research develops models to predict the evolution of the cracks in the RC beam-column joint (BCJ) region. The RC beam-column joint is subjected to lateral cyclic loading. Four machine learning models are developed using Rapidminer to predict the crack width experienced by seven RC beam-column joints. The design parameters associated with RC beam-column joints and lateral cyclic loadings in terms of drift ratio are used as inputs. Several prediction models are developed, and the highest performing neural networks are selected, refined, and optimized using the various… Details