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Effect of Axial Load on the Seismic Performance of Steel Reinforced Concrete Beam-Column Joint
Get PDFSteel-reinforced concrete (SRC) provides numerous advantages, such as enhanced energy dissipation, ductility, stiffness, and strength, particularly in seismic performance. Several studies on the effect of axial loads on columns found that axial loads have an insignificant influence on column capacity, though they influence long-term performance. Beam-column joint elements are among the critical components that determine the seismic behavior of a structure. Inaccurate design of these joints can lead to fatal structural damage, potentially causing structural collapse. This study aimed to perform a numerical analysis of various joint configurations under cyclic and axial loads to identify models with the best seismic performance that consisted of four models using different SRC length parameters. The research used nonlinear finite element methods with the ABAQUS software, which enables detailed simulations of joint behavior, including predictions of failure mechanisms that are difficult to observe in experimental testing. The results of the analysis showed that the CS-02 model demonstrated the best seismic performance. Axial load increased the capacity in all models, improved energy dissipation in the RC model, slightly reduced dissipation in CS models, and caused different rotational behavior across models
Advanced Geogrid Reinforcement Strategies for Superior Bearing Capacity and Settlement Control in Square Shallow Foundations
No full textRecently, many research studies on square-shaped soil foundations have failed to achieve acceptable results due to their low resistance, in addition to the expected settlement of these foundations when constructed on weak granular soil. This study aims to overcome the low resistance and excessive settlement of square shallow foundations on weak granular soils by developing advanced geogrid reinforcement strategies to enhance load-bearing capacity and control settlement. A series of scaled laboratory experiments were conducted on simulated weak soil profiles, varying three key parameters—the depth of geogrid reinforcement layers, the width of each geogrid layer, and the number of layers—while quantifying performance through the Bearing Capacity Ratio (BCR) and Settlement Reduction Ratio (SRR); these empirical results were complemented by theoretical derivations of novel mathematical models to predict reinforced foundation behavior under diverse difficulty conditions. Experimental outcomes reveal that multilayer geogrid systems substantially elevate BCR and diminish settlement, with optimal configurations achieving up to a 60% improvement in bearing capacity and a 50% reduction in settlement compared to unreinforced foundations, and that deeper placement and additional layers yield significant yet progressively smaller gains. The proposed approach uniquely employs insulating geogrid layers to prevent water ingress and moisture infiltration—preserving structural integrity and imparting anti-settlement properties—and introduces high-precision predictive models; furthermore, the multilayer arrangement creates a barrier against moisture migration, reducing long-term settlement risks under fluctuating groundwater conditions, and cost analysis indicates that the optimal configurations deliver superior performance with minimal additional material investment, offering a cost-effective and geotechnically sound solution for foundation engineering
Nonlinear Inelastic Local Buckling Behavior of Steel Columns Subjected to Axial Compression
Get PDFThis study develops a displacement-based finite element approach using one-element modeling to analyze the second-order inelastic local buckling of steel columns under axial compression. To account for local buckling, two new stress-strain relationships are proposed for steel using an energy method and assumptions from previous studies for both compact and slender cross-sections. Stress-strain curves of post-buckling regimes are modeled as nonlinear curves. Both geometric and material nonlinearity are considered in the buckling analysis. The effects of geometric nonlinearity are traced through stability functions. The tangent stiffness of steel members is continuously updated during the nonlinear analysis by updating the fiber behavior at monitoring cross-sections using the Gauss-Lobatto integration rule. The proposed stress-strain relationships accurately predict the ultimate strength, elastic, and inelastic local buckling behaviors of steel columns under axial compression, compared with ABAQUS and previous studies. The model accurately predicts elastic, inelastic, and ultimate strength behaviors, with post-buckling responses closely matching ABAQUS results (e.g. 0.881 (proposed with residual stress), 1.008 (proposed without residual stress) vs. 0.948 (ABAQUS) load ratio for HB3 specimen). This approach offers significant computational efficiency (~1.0 sec vs. 20–30 min for ABAQUS) and introduces adjustable constitutive models, enhancing practical design applications for steel structures. This study proves that the effects of residual stress on the local buckling cannot be ignored in the case of slender sections, since the differences of the ultimate load (with and without the initial residual stress) are equal to 63.3% for the HI4 specimen and 43.2% for the HS40-SH(B) specimen
Shear Strength of One-Way Slabs Subjected to Concentrated Loads
Get PDFReinforced concrete (RC) one-way slabs without transverse reinforcement are found extensively in bridge constructions. In the presence of concentrated loads (CLs) close to the supports, the shear strength (SS) of such slabs is usually determined using design expressions provided by the codes of practice that were derived originally from tests performed on beams or one-way slabs that were loaded along their entire width, which are inconsistent with the actual shear failure mechanism of one-way slabs under CLs. This paper presents an empirical SS model developed using the gene expression programming method (GEP), where the SS is related to six influencing parameters. The proposed model is derived employing the test results of 238 RC one-way slabs that experienced shear failure from the literature. The accuracy of the proposed model is measured using several statistical indices and compared with the existing shear design methods. The GEP model agreed favorably with the test results. The GEP model was also employed to conduct a parametric study for further validation and sensitivity analysis to define the contribution of input parameters to the SS. The parametric study demonstrated the efficiency of the GEP model in replicating the physical behavior, and the sensitivity analysis revealed that the SS is sensitive to the concrete strength and the shear span-effective depth ratio
Performance Characterization for Polymer Modified Bitumen Contained Newly Used Terpolymer
Get PDFPolymer-modified bitumen (PMB) plays a vital role in extending the service life of hot mix asphalt (HMA) used in flexible pavement construction. Several types of polymers have been used to produce PMB, among which styrene–butadiene–styrene (SBS) is the most widely used. However, the use of SBS in PMB production presents several limitations, including storage stability issues, high mixing temperatures, and the requirement for a relatively high modifier content. The present research investigated the use of a new terpolymer, EVA-GMA (LOTADER® AX8670T), for PMB production and compared the resulting PMB with PMB produced using 4% SBS polymer. Rheological, performance, and chemical composition tests were conducted on neat bitumen as well as PMB modified with EVA-GMA and SBS. The results indicated that the optimal LOTADER® AX8670T content required to produce PMB was 2.5%. In addition, storage stability increased by 11% compared to 4% SBS-modified PMB. The viscosity was found to be 50% higher than that of asphalt modified with 4% SBS-PMB and 100% higher than that of unmodified asphalt. The performance grade (PG) was determined to be PG 82-10 for both PMB types, while unmodified bitumen exhibited a PG of 76-10. Based on these results, it can be concluded that PMB produced with LOTADER® AX8670T can perform comparably to SBS-modified PMB while requiring a lower modifier content, lower mixing temperatures, and offering improved storage stability, thereby enhancing economic, production, and environmental aspects
Predicting Soil Electrical Resistivity Using Geotechnical Properties and Artificial Neural Networks
No full textThis study investigates the influence of key geotechnical parameters—water content, dry density, and plasticity index—on soil electrical resistivity, with the goal of improving prediction accuracy for substation grounding system design. A dataset comprising 150 laboratory test results was compiled from soil samples collected at three substations in Thailand, representing diverse moisture conditions to reflect field variability. Two modeling approaches were applied: multiple regression (MR) and artificial neural networks (ANN), evaluated using the coefficient of determination (R²) and root mean square error (RMSE). The MR models achieved relatively strong correlations, with R² values up to 0.8281; however, their higher RMSE values indicated limited precision under variable conditions. In contrast, the ANN models, particularly those incorporating the plasticity index, demonstrated superior performance, achieving lower RMSE values—down to 0.057—highlighting their ability to capture complex nonlinear relationships. In comparison to prior studies that often relied on single-variable models or uniform soil datasets, this research adopts a more integrative and generalizable framework. By incorporating multiple soil parameters into the ANN model and validating against a diverse dataset, the study offers practical insights for engineering applications. The findings are particularly valuable in tropical regions where soil moisture variation significantly impacts resistivity and grounding system performance
Performance of Sustainable Underwater Concrete Containing GGBS and Micro Silica with Anti-Washout
No full textAnti-washout concrete (AWC) is engineered for underwater constructions, with resistance to dispersion achieved through the use of anti-washout admixtures (AWAs). This study experimentally investigated the design of sustainable anti-washout concrete mixtures containing a high content of by-product waste materials. The study aims to evaluate sustainable underwater concrete mixtures with high supplementary cementitious materials content, analyze the influence of AWA on compressive strength, and assess the compatibility of anti-washout admixture with both SCMs and superplasticizers. However, the interaction of AWA with a high content of ground granulated blast furnace slag (GGBS) and microsilica in underwater concrete has not been previously investigated. Two groups of concrete mixtures were developed: the first group consisted of two sustainable mixtures, with and without AWA, containing 52.15% ordinary Portland cement (OPC), 43.5% GGBS, and 4.35% micro silica. The second group consisted of two conventional mixtures: one with 100% OPC and the other with 100% OPC plus AWA. Fresh properties, such as slump flow, viscosity (measured by the V-funnel), and air content, were evaluated. Compressive strength was measured to assess mechanical performance. Durability was investigated using four tests: rapid chloride penetration tests (RCPT), water penetration, water absorption, and initial surface absorption tests (ISAT). An anti-washout test was conducted to determine the effectiveness of AWC in minimizing the washout of cement particles. The mixture design introduces an innovative approach to utilizing high levels of SCMs for producing high-strength, durable, and sustainable AWC. The durability results showed that the ISAT test was ineffective for evaluating concrete performance underwater. This research contributes to understanding the effects of AWAs and their compatibility with superplasticizers and SCMs. AWA forms a thixotropic gel that protects cement particles from washout and is highly compatible with superplasticizers
Modified Asphalt Mixtures Incorporating Pulverized Recycled Rubber and Recycled Asphalt Pavement
Get PDFIn the search to achieve eco-friendly techniques that ensure significant improvements in the properties of hot mix asphalt (HMA), recycled materials are being considered with greater application, coming from the pavement itself and also from artificial elements such as rubber. In this sense, the objective was to study the behavior of the mechanical and microstructural properties of HMA by adding pulverized recycled rubber (PRR) and recycled asphalt pavement (RAP), taking into account a control group without any addition and an experimental group with PRR and RAP. The research involved the production of briquettes with the modification of asphalt cement (AC) using doses of 3%, 5%, and 7% of PRR as a replacement by weight of AC. Then, the optimal percentage of PRR was combined with 10%, 20%, and 30% RAP as a partial substitute for the coarse aggregate. It should be noted that in both aspects, the thermogravimetric and microstructural performance of the asphalt mixture was evaluated. Subsequently, the results obtained indicate that the HMA is MAC-1 type, and it was established that the combinations of PRR and RAP significantly influence the physical-mechanical properties of the HMA with 3%PRR+10%RAP. On the other hand, the findings of the PRR thermogravimetric analysis show that the degradation of HMA occurs at 350°C, causing the loss of both mechanical and microstructural properties. However, infrared spectroscopy and scanning electron microscopy revealed that the PRR adheres correctly with the aggregate, improving the morphology and texture of the HMA. Doi: 10.28991/CEJ-2025-011-02-02 Full Text: PD
On the Use of a Confined Sand Cell to Dampen Induced Machine Vibration in a Stabilized Clay Numerical Study
Get PDFEnvironmental vibrations produced often by industrial and construction processes can affect adjacent soils and structures, sometimes resulting in foundation failure and structural damage. The application of confined cells under foundations as a mitigation technique against dynamic sources, such as generators, is investigated in this study. Numerical models were developed using Plaxis 3D software to simulate the effect of a vibrating source on a circular footing, both with and without confined cells filled with sand soil at varying depths and diameters. In these cells, the soil modeling considered compaction loads typical in actual construction conditions. Results indicate that placing a minimum-diameter cell closer to the foundation with adequate penetration depth can significantly enhance dynamic response and reduce subgrade deformation. The effectiveness of confined soil in minimizing displacement amplitude in the foundation is evaluated, revealing an impressive 86% reduction with specific cell dimensions (Hc/D = 0.50 and Dc/D = 1.15). Moreover, peak particle velocity and excess pore water pressure at monitored points in the surrounding environment experience reductions of 62% and 87%, respectively, demonstrating substantial vibration attenuation. The study does effectively highlight the novelty of the confined sand cell approach, positioning it as a more targeted, efficient, and cost-effective alternative to existing methods, especially for conditions where large-scale, deep vibrations are a concern. Doi: 10.28991/CEJ-2025-011-01-018 Full Text: PD
Flexural Behaviour of Precast Lightweight Concrete Sandwich Slabs With Demountable Bolted Steel Shear Connectors
Get PDFA concrete slab is a fundamental element and contributes the highest weight in structural buildings. In this paper, a new type of sandwich slab consisting of two layers of lightweight concrete and demountable steel connectors is proposed in a new attempt to reduce the weight of the floors within the structure and apply a simpler and faster approach to connecting the layers of sandwich panels. The structural effects of the proposed connectors on Precast Lightweight Concrete Sandwich Slab (PLCSS) are evaluated experimentally and theoretically in terms of strength, stiffness, degree of composite action, and usability for floor construction. The behaviors of six PLCSS specimens subjected to four-point loads were investigated, studying the effects of varied parameters such as different numbers, arrangements, and shapes of demountable steel connectors (I, V, and X connector shapes) fastened with steel bolts, in addition to one solid concrete slab as a reference specimen. The panels' performance in this structural system was evaluated by measuring the degree of composite action using load, displacement, stress, and neutral axis methods. Based on the experimental results, the slab panels exhibited composite panel behavior until the point of failure. Under flexural loads, the panel behaved similarly to that of a solid one-way slab; crack patterns appeared in one direction. The specimens with IC, VC, and XC showed different load capacity values, ranging from 22.74 kN to 50.55 kN; these values depend on the types of shear connectors and their numbers in the sandwich panels. Using V and X connectors enhances the composite action between layers, increasing the shear demand and making the shear failure more likely. It can be concluded that demountable shear connectors can transfer shear between the two concrete wythes, resulting in a composite panel with structural integrity, a lighter weight, and satisfying ACI specifications for floor applications. Doi: 10.28991/CEJ-2025-011-02-06 Full Text: PD