CivilEng

Geopolymer materials, alternatives to cement that are synthesized using industrial byproducts, have emerged as some of the leading champion materials due to their environmentally friendly attributes. They can significantly reduce pollution by utilizing a plethora of waste products and conserving natural resources that would otherwise be used in the production of conventional cement. Much work is being carried out to study geopolymers’ characteristics under different conditions. Here, a geopolymer derived from fly ash (FA) was synthesized using a combination of sodium silicate and potassium hydroxide (KOH) (2.5:1 ratio) as an alkali activator (AA) liquid. The FA/AA ratios were optimized, resulting in distinct geopolymer samples with ratios of 1.00, 1.25, 1.50, and 1.75. By adjusting the contribution of alkaline liquid, we investigated the impacts of subtle changes in the FA/AA ratio on the morphology and microstructure using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The FESEM analysis illustrated a mixed matrix and morphology, with the sample with a ratio of 1.00 displaying consistently fused and homogenous morphology. The XRD results revealed the prevalent amorphous nature of geopolymer with a few crystalline phases of quartz, sodalite, hematite, and mullite. An electrical study confirmed the insulating nature of the geopolymer samples. Insulating geopolymers can provide energy-efficient buildings and resistance to fire, hurricanes, and tornadoes. Additionally, using KOH as a part of the alkali activator introduced a less-explored aspect compared to conventional sodium hydroxide-based activators, highlighting the novelty in the synthesis process. Full article

The current investigation delved into the seismic analysis, design intricacies, and assessment of the response of elevated steel containment tanks when supported by concentrically braced frames. The primary focus was placed on comprehending the behavior of the supporting structure, recognizing its heightened vulnerability to damage under horizontal excitation—insights gleaned from reconnaissance teams studying earthquake aftermaths worldwide. A specific case study unfolded featuring a steel concentrically braced frame as the supporting structure, aligning with prevalent industry norms. Throughout the entire process, spanning design phases, seismic vulnerability assessments, and response evaluations, special emphasis was placed on the internal fluid sloshing phenomena. This nuanced consideration plays a pivotal role in sha** the dynamic response of the system. The study introduces two distinct design methods: the first method aligns with relevant international codes, while the second method innovatively incorporates the compressive strength of the braces into its approach. To evaluate the dynamic response of the elevated tank, both linear and nonlinear advanced analyses were employed. The comparative analysis of various strategies underscores the impact of the chosen design methodology on the overall system response. This multifaceted exploration aims to contribute valuable insights to the seismic resilience and design optimization of elevated steel containment tanks, furthering the understanding of their performance under seismic forces. Full article

Monolithic reinforced concrete floor slabs are one of the most common types of building structures, and their optimization is an urgent task. The article presents the methodology for finding the optimal position of point supports under a reinforced concrete floor slab of arbitrary configuration at arbitrary load. The slab is considered thin, elastic and isotropic, with constant over-the-area stiffness, that is, the reinforcement is not taken into account or is constant. The solution is performed using the finite element method in combination with the nonlinear optimization methods. Finite element analysis is implemented by authors in MATLAB (R2024a) environment in such a way that the location of the columns may not coincide with the nodes of the finite element mesh of the slab. This allows to significantly increase the efficiency of solving the optimization problem compared to previously used algorithms, including the Monte Carlo method. Boundary conditions are taken into account using the Lagrange multiplier method. As an optimization criterion, the maximum deflection value is used, as well as the value of the potential strain energy. The effectiveness of six nonlinear optimization methods is compared in the example of a square slab under the action of a uniformly distributed load. For solutions obtained using the pattern search, simulated annealing and internal point methods, the maximum deflections are at least 1.2 times higher than for solutions obtained using the particle swarm method and genetic algorithm. An example of real object optimization is also presented. By changing the position of seven columns, it was possible to reduce the maximum deflection of the floor slab by 1.6 times. Full article

Waste ceramic is produced from different sources and, if not reused, is often disposed of in landfills, contributing to the pressure on landfill capacity and potentially releasing toxins into the surrounding environment as ceramics break down over time. The waste can easily be crushed to the required sizes, which has interested many researchers. It has been used as a replacement for concrete constituents, including cement and aggregates. This offers a promising avenue for reducing the environmental impact and promoting sustainable construction practices by reducing the amount of energy consumed and resources required for concrete production, as well as the amount of waste being sent to landfills. This paper aims to provide a review of the use of waste ceramic in concrete. In essence, the paper is divided into several sections. The first section highlights the current environmental issues associated with concrete production and waste disposal. The second section deals with ceramics, its raw materials, production steps, and the different types of waste ceramic used in concrete. A literature review of the use of waste ceramic in concrete was included in the third section. The study reports different research on the use of waste ceramic and its impacts on the mechanical and durability properties of concrete. Full article

This research investigates the potential of utilizing recycled concrete aggregate (RCA) and recycled sand (RS), derived from crushed concrete cubes, as sustainable alternatives in construction materials. The study comprehensively evaluates the properties of RCA and RS, focusing on workability, impact resistance, abrasion resistance, and compressive strength to determine their viability as substitute construction materials. A notable finding is RS’s enhanced fire and heat resistance when used as a fine aggregate in mortar blends, mixed with cement and Sinicon PP in a 3:1 ratio. The experimental analysis included thorough assessments of uniformity, durability, and curing time, alongside Scanning Electron Microscopy (SEM) for structural examination. Results show that RCA has an Aggregate Impact Value (AIV) of 5.76% and a Los Angeles Abrasion Value (LAA) of 21.78%, demonstrating excellent strength of the recycled aggregates. The mortar mix was also prepared using recycled sand, cement, and Sinicon PP, and its stability was confirmed through soundness tests, which resulted in a 0.53 mm expansion and a satisfactory consistency level of 44%. Ultrasonic pulse velocity (UPV) tests also indicated high-quality concrete formation using RCA and RS. SEM imaging corroborated this by revealing a bond between the cement paste and the aggregates. Incorporating RS and RCA in concrete mixtures impressively yielded a compressive strength of 26.22 N/mm² in M20-grade concrete. The study concludes that using RCA and RS waste materials in the construction sector underlines that sustainable practices can be integrated without compromising material quality. This approach aligns with sustainable development goals and fosters a more environmentally friendly construction industry. Full article

South Africa is endowed with a wealth of coal-fired power stations that can produce extremely high volumes of fly ash per year exceeding 34 million tonnes. The use of high-volume fly ash (HVFA) binders in the construction sector has the capacity to significantly reduce greenhouse gas emissions associated with traditional cement production and offset the carbon footprint of Eskom. The excessive production of fly ash by Eskom warrants the need for develo** ultra-high-volume fly ash binders (UHVFA, fly ash/binder > 60 wt%). Nonetheless, fly ash (FA) replacement of cement is still largely limited to 35% regardless of more ambitious research indicating the potential to surpass 60%. In view of the urgent need for South Africa to offset and reduce its carbon footprint, this work reviews and summarises the literature on the performance of HVFA binders with a focus on two specific areas: (i) strength and (ii) durability. On HVFA binder strength, the focus is drawn on work that analysed the compressive strength, flexural strength, and split tensile strength. This review focuses on the extant literature analysing the durability of HVFA binders using various tests, including sorptivity, resistivity, permeability, tortuosity, rapid chloride penetration tests, resistance to sulphate attack, and microstructural analysis. As the FA content increases towards optima, i.e., 50–80%, the most indicative composite characteristics of the strength and durability properties are UCS (30–90 MPa) and permeability (low). This review reveals the leading methodologies, instrumentation, findings, challenges, and contradictions. Full article

The stick–slip phenomenon is a jerking motion that can occur while two objects slide over each other with friction. There are several situations in which this phenomenon can be observed: between the slabs of the friction dampers used to mitigate vibrations in buildings, as well as between the components of the base isolation systems used for seismic protection. The systems of this kind are usually designed to work in a smooth and flawless manner, but under particular conditions undesired jerking motions may develop, yielding complex dynamic behavior even when only a few degrees of freedom are involved. A simplified approach to the problems of this kind leads to the mechanical model of a rigid block connected elastically to a rigid support and at the same time with friction to a second rigid support, both the supports having a prescribed motion. Despite the apparent simplicity of this model, it is very useful for studying important features of the non-linear dynamics of many physical systems. In this work, after a suitable formulation of the problem, the equations of motion are solved analytically in the sticking and sliding phases, and the influence of the main parameters of the system on its dynamics and limit cycles is investigated and discussed. Full article

A 3D-finite element analysis within the numerical program ABAQUS is adopted in order to simulate the seismic behavior of reinforced concrete beam-column joints and beam-column joints strengthened with CFRP ropes. The suitability of the adopted approach is investigated herein. For this purpose, experimental and numerical cyclic tests were performed. The experiments include four reinforced concrete (RC) joints with the same ratio of shear closed-stirrup reinforcement and two different volumetric ratios of longitudinal steel reinforcing bars. Two joints were tested as-built, and the other two were strengthened with CFRP ropes. The ropes were applied as Near Surface Mounted (NSM) reinforcement, forming an X-shape around the joint body and further as flexural reinforcement at the top and bottom of the beam. The purpose of the externally mounted CFRP ropes is to allow the development of higher values of concrete principal stresses inside the joint core, compared with the specimens without ropes, and also to reduce the develo** shear deformation in the joint. From the results, it is concluded that X-shaped ropes reduced the shear deformation in the joint body remarkably, especially in high drifts. Further, as a result of the comparisons between the yielded outcome from the attempted nonlinear analysis and the observed response from the tests, it is deduced that the adopted method sufficiently describes the whole behavior of the RC beam-column connections. In particular, comparisons between experimental and numerical results of principal stresses develo** in the joint body of all examined specimens, along with similar comparisons of force displacement envelopes and shear deformations of the joint body, confirmed the adequacy of the applied finite element approach for the investigation of the use of CFRP-ropes as an efficient and easy-to-apply strengthening technique. The findings also reveal that the connections that have been strengthened with the FRP ropes demonstrated improved performance, and the crack system preserved its load capacity during the reversal loading tests. Full article

Regular monitoring and inspection of military railroad tracks are necessary to ensure the safe transportation of military freight. Manual railroad inspection has drawbacks and limitations that can impact accuracy and efficiency. This study introduces a novel tool designed to automate Ground Penetrating Radar (GPR) imaging interpretation for railroad ballast condition assessment, aiming to reduce human intervention in inspections. The tool uses advanced signal processing techniques, such as the Short-Time Fourier Transform (STFT) and Wavelet Transform (WT), to quantify ballast fouling levels accurately, enhancing maintenance and safety protocols for railroad tracks. Validation through comprehensive testing, including two case studies, demonstrates the tool’s superior efficacy over traditional manual inspection methods. This research represents a pivotal step towards more efficient and reliable infrastructure management, ensuring critical railroad systems’ safety and operational integrity. Full article

This paper describes the development of a dual hazard spectrum for use in the dynamic analysis of steel frames subject to the combined effects of earthquakes and wind. The proposed spectrum is obtained by combining the power spectra of earthquakes and wind using the square root of the sum of squares (SRSS) combination method. An equivalent time excitation function is then computed using an inverse fast Fourier transform (IFFT) and serves as input for the dynamic analysis. Using time-history analysis on the OpenSees platform, the dynamic responses expressed in terms of peak and residual inter-story and roof drifts for two multistory steel frames located in two US cities (Los Angeles and Charleston) are obtained to demonstrate that designing these buildings based on just one hazard may not be adequate. For frames that are considered under-designed, an energy-based design procedure that uses buckling-restrained braces (BRBs) to dissipate the excess energy imparted to these frames is proposed so they will satisfy the FEMA 356 recommended drift limits for the performance levels of immediate occupancy and life safety. Full article

The intriguing rocking behavior of foundations has attracted the attention of both researchers and professionals, owing to its beneficial characteristics such as energy absorption and self-adjusting capability. This paper offers a thorough examination of various modeling techniques, seismic performance evaluation methods, and the practical application of innovative rocking shallow foundations. While conventional fixed-base designs can absorb seismic energy, they often suffer from lasting damage due to residual deformation. In contrast, rocking foundation structures facilitate controlled rocking movements by loosening the connection between the structure and the foundation, thereby enhancing overall stability. Historical studies dating back to the 19th century demonstrate the effectiveness of rocking foundations in reducing seismic impact and ductility demands, leading to cost savings. Furthermore, this paper extends its focus to contemporary considerations, exploring modern modeling techniques, seismic performance assessments, and practical applications for rocking shallow foundations. By highlighting their role in improving structural resilience, this study investigates seismic hazard analysis, geological factors, and site-specific conditions influencing foundation behavior. It covers essential aspects such as dynamic responses and modeling methodologies, drawing insights from real-world case studies. Through a comprehensive review of both numerical and experimental investigations, the article provides a synthesis of current knowledge and identifies avenues for future research. Full article

Soil concrete is a material produced by mixing the soil at the site with a hydraulic binder. This paper aims to study the influence of the nature of binder on the physical and mechanical properties of soil concrete. For the mixtures, three types of soil were chosen and studied: sandy clay with a granular class of 0/5 (SA5), laterite with a granular class of 0/5 (LA5), and laterite with a granular class of 0/10 (LA10). Three different cements were used: CEM I 52.5, CEM II 42.5, and CEM III 32.5, with cement contents of 150 and 250 kg/m³. The soil concretes were designed for a constant spread of 32–33 cm measured on a mini-slump. The results showed that LA5-based soil concrete has a higher water content of about 8.8% more than SA5 and LA10-based soil concretes. For all the mixtures, the lowest porosity values were obtained with CEM III 32.5, followed by CEM I 52.5, and finally CEM II 42.5. For the three types of cement and the same soil granular size, the compressive strength, static, and dynamic modulus of SA5-based soil concretes are higher than LA5. It was noted that the mechanical properties of soil concretes made with CEM III 32.5 are higher than those made with CEM I 52.5 and CEM II 42.5. Regardless of the type of cement used, the mechanical properties obtained on LA10-based soil concrete are higher than those on LA5-based soil concrete. Full article

Orthotropic steel bridge decks (OSDs) are very popular all over the world because of the low dead load, high stiffness in the longitudinal direction, high strength ratio to weight, and can be used in various types of bridges. The life of these bridges is affected by fatigue cracks in different portions. One of major areas where the fatigue cracks appear in these bridges is rib-to-deck connection. In this research finite element analysis is carried out by using ABAQUS/CAE 2022 software to determine the ways to increase the fatigue life at rib to deck connection in OSDs. In the first part, smaller models are simulated; stress concentration is analyzed and hot spot stress (HSS) is calculated according to International Institute of Welding (IIW) and Det Norske Veritas (DNV) recommendations. In the second part, a parametric analysis is carried out to analyze the effect of weld penetration, thickness of deck, thickness of rib and rib to deck connection type. In the third part, simulation of models similar to the real field is carried out to determine whether the double welded connections are better than single welded connections. Different models are analyzed for different load cases like single wheel load, double wheel load and also the position of the wheels is changed. The boundary conditions are changed to analyze whether the boundary condition has any significant effect on the result obtained. It is found that thicker decks, thinner ribs, and low penetrated welded connections reduce the stress concentrations at rib to deck connections which ultimately increase fatigue life. Among the parameters examined, deck thickness is the most important parameter. It is found that the percentage of stress increase with percentage decrease in deck thickness follows a power relation. The overall fatigue life of double welded connection is excepted to be lower since the stress concentration is maximum at the weld toe at deck on the outer side of the closed stiffener; however, if the cracks initiate on the inner side of closed stiffener, the cracks at the weld root of single welded connection can propagate much rapidly than the cracks initiating on the inner side of the closed stiffener at the weld toe, thereby reducing the fatigue life of the single-welded specimen significantly. Full article

Despite the subjective and error-prone nature of manual visual inspection procedures, this type of inspection is still a common process in most construction projects. However, Automated Construction Inspection and Progress Monitoring (ACIPM) has the potential to improve inspection processes. The objective of this paper is to examine the applications, challenges, and future directions of ACIPM in a systematic review. It explores various application areas of ACIPM in two domains of (a) transportation construction inspection, and (b) building construction inspection. The review identifies key ACIPM tools and techniques including Laser Scanning (LS), Uncrewed Aerial Systems (UAS), Robots, Radio Frequency Identification (RFID), Augmented Reality (AR), Virtual Reality (VR), Computer Vision (CV), Deep Learning, and Building Information Modeling (BIM). It also explores the challenges in implementing ACIPM, including limited generalization, data quality and validity, data integration, and real-time considerations. Studying legal implications and ethical and social impacts are among the future directions in ACIPM that are pinpointed in this paper. As the main contribution, this paper provides a comprehensive understanding of ACIPM for academic researchers and industry professionals. Full article

This article analyzes the effect of the rehydration method on the physical–mechanical properties of accelerated carbonation-cured magnesium-based fiber cement boards. The rehydration process of the boards was analyzed in conjunction with the analysis of the pre-curing time before accelerated carbonation (24, 48, and 72 h before carbonation), resulting in eight different curing parameters used in this investigation. The physical–mechanical performance and microstructural characteristics of magnesium oxysulfate boards before and after carbonation were investigated by water absorption, apparent porosity, and bulk density using the four-point bending test, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. According to the results, the accelerated carbonation process improved the mechanical properties of the boards. The samples that carbonated after 48 h showed a higher modulus of rupture. The rehydration process of the composites before carbonation led to enhancements in the pre-cured boards for 48 and 72 h, demonstrating that carbonation occurred more effectively after water rehydration. The mechanical improvements were associated with the formation of hydration products, which preferentially formed in the pores and voids of the fiber cement matrix. These carbonation products altered the physical properties of the composites, increasing the density of the boards and reducing the void volume. The decomposition of the formed carbonates was confirmed by thermogravimetric analysis, which indicated that the rehydration process favored the carbonation of the composites. Full article

In the case of solid slabs made of reinforced concrete that are usually subjected to bending, large areas of the structure are stressed well below their load-bearing capacity. Contrary to this are shell structures, which can bridge large spans with little material if designed according to the force flow. To improve the efficiency of ceiling slabs, we want to utilize the shell load-bearing behavior on a smaller scale by resolving the solid interior accordingly. In order to study a wide range of such constructions virtually, a parametric multi-objective simulation environment is being developed in an ongoing research project. The basic analysis approaches that were implemented are presented in this paper. The basic workflow, the used programs and material models, and their calibration on the tests on textile-reinforced concrete (TRC) samples are described. Full article

The demand for lightweight aggregates in concrete compositions for diverse structural and non-structural applications in contemporary building construction has increased. This is to achieve a controllable low-density lightweight concrete, which reduces the overall structural weight. However, the challenge lies in achieving an appropriate strength in lightweight concrete while maintaining a lower unit weight. This research aims to evaluate the performance of lightweight concrete by integrating expanded polystyrene (EPS) as a partial replacement for coarse aggregate. Test specimens were cast by blending EPS with coarse aggregate at varying proportions of 0%, 15%, 30%, and 45%, while maintaining a constant water-to-binder ratio of 0.60. To enhance the bonding and structural capabilities of the proposed lightweight concrete mixes, reinforcement with 2% and 4% steel fibers by volume of the total concrete mix was incorporated. Silica fume was introduced into the mix to counteract the water hydrophobicity of EPS material and enhance the durability of lightweight concrete, added at a rate of 10% by weight of cement in all specimens. A total of 60 samples, including cylinders and beams, were prepared and cured over 28 days. The physical and mechanical properties of the lightweight EPS-based concrete were systematically examined through experimental testing and compared against a standard concrete mix. The analysis of the results indicates that EPS-based concrete exhibits a controllable low density. It also reveals that incorporating reinforcement materials, such as steel fibers, enhances the overall strength of lightweight concrete. Full article

Vertical shortening, a phenomenon inherent to concrete structures, plays a key role in the quality and safety of construction, particularly in tall reinforced concrete buildings. This behavior is intrinsically linked to the time-dependent properties of concrete, encompassing both creep and shrinkage. Neglecting these aspects, especially when non-uniformly distributed, can give rise to various structural issues, including partition distress, overloading, and potential cracking in horizontal elements. This paper delves into the principal factors influencing vertical shortening and presents a rigorous approach to their evaluation, treating creep and shrinkage as critical parameters. The investigation employs two illustrative case studies: the first revolves around a 15-story reinforced concrete building with single columns supporting tributary areas at various levels, acting as a calibration case; the second encompasses a 30-story reinforced concrete structure employing a dual system, providing a broader perspective applicable to three-dimensional structures. A diverse array of analyses is conducted, incorporating considerations for concrete’s linear and nonlinear behavior as well as the impact of construction stages. Our findings reveal that vertical shortening is directly proportional to the building’s height and inversely related to concrete strength, longitudinal reinforcement ratios, member dimensions, volume-to-surface ratios, age of the structure upon load application, and relative humidity. Consequently, precise assessments of differential shortening effects are paramount. The utilization of staged construction analysis and time-dependent effects is recommended as the most suitable approach for evaluating vertical shortening effects. Full article