Introduction/Objective Civil engineering structures face major challenges, particularly earthquakes, which are random phenomena in their intensity and frequency content. The seismic response of structures depends largely on the intensity of an earthquake and especially on its frequency content. The assessment of the dynamic behavior of structures subjected to seismic excitations is therefore essential for understanding their performance. The main objective of this study is the experimental identification of the vibration signature of a single-degree-of-freedom SDOF steel system. Methods Based on the laws of similarity, a 1:6 reduced-scale steel model is developed. In this context, dynamic experiments using the shaking table of the RISAM laboratory (Risk Assessment and Management: University of Tlemcen) are carried out to determine the structural dynamic parameters of this steel system. This is achieved through experimental determination of natural frequency and damping. Acceleration and displacement measurements are also established. The experimental estimation of damping is established using the logarithmic decrement method. Several dynamic analyses are carried out based on the finite element model of the reduced-scale steel system. Results The experimental investigations allowed the identification of the natural frequency, damping ratio, acceleration, and displacement response of the reduced-scale SDOF steel model. In addition, the numerical analyses showed a close agreement with the experimental measurements. Discussion The comparison between numerical and experimental investigations confirms the effectiveness of the adopted methodology in accurately reproducing the dynamic behavior of the steel system. The proposed experimental and numerical framework can therefore be considered a reliable approach for evaluating the seismic response of steel structures. Conclusion This study successfully identified the vibration signature and dynamic characteristics of an SDOF steel system through combined experimental and numerical analyses. The excellent correlation between the finite element results and shaking table experiments validates the proposed methodology and highlights its applicability for future seismic assessment studies of steel structures.
Introduction Pipelines are among the main systems for conveying fluids over long distances and are typically installed below ground level along most of their alignment. These systems are widely employed for transporting water, petroleum, natural gas, and other fluids, as well as for serving as utility corridors. During seismic events, buried pipelines may experience both transient and permanent ground deformations. Methods In this study, the influence of key parameters-including pipe wall thickness, burial depth, and soil type-on the behavior of underground pipelines subjected to surface loading and earthquake waves was investigated using PLAXIS 2D. Three pipe diameters and various burial depths were analyzed in both homogeneous and composite soil layers to evaluate pipeline crown displacement. Results The results show that pipe displacement tends to increase with larger pipe diameters and greater burial depths under various soil conditions and wall thicknesses. Pipelines installed in loose sand demonstrated higher seismic sensitivity compared to those embedded in clay soils, where lower displacement values were observed. Increasing the pipe wall thickness, and consequently its stiffness, resulted in a noticeable reduction in displacement. Additionally, the crown displacement was found to rise with increasing surface loads and pipe diameters, especially at shallow embedment depths. Furthermore, pipelines placed in composite soil exhibited improved performance, with reduced displacements compared to those in uniform soil layers. Discussion The observed behavior indicates that both geometric properties, such as diameter and thickness, and geotechnical conditions, such as soil type and layering, play critical roles in controlling pipeline response under seismic and surface loading. The improved performance in composite soils suggests that soil stratification can enhance system stability, while loose sand conditions amplify seismic effects due to lower stiffness. Conclusion The findings of this study provide quantitative relationships that can help explain how burial depth, pipe geometry, and soil conditions influence pipeline displacement under different loading scenarios.
Introduction The increasing environmental impact of conventional concrete production and the seismic vulnerability of reinforced concrete structures in Morocco have encouraged the development of sustainable alternative construction materials. This study evaluates the seismic and thermal performance of reinforced concrete frames incorporating shale powder from the Settat-Khouribga region as a partial replacement for natural sand. Methods Four concrete formulations containing 0%, 5%, 15%, and 25% shale substitution were evaluated using calibrated finite element modeling. Linear elastic analyses were done in SAP2000 as per the Moroccan seismic code RPS 2011. Pushover and Incremental Dynamic Analysis (IDA) analyses were carried out in OpenSees software with 12 spectrum-consistent ground motions. Thermal behavior was determined using steady-state analysis in ANSYS Mechanical. Results The F15 mixture, which consisted of 15% shale substitution, demonstrated the best behavior in terms of structure and thermal stability. Compressive strength was achieved at 22.3 MPa, and the ductility index rose to 3.97. Median capacity for collapse was measured at 1.19 g, and the probability of surpassing the design level of earthquake protection is 9.8%, while in the case of the reference concrete, the same indicator is 12.1%. Discussion The mixture F15, which was made up of 15% shale replacement, showed the best performance in respect of structural properties and thermal stability. Compressive strength was observed to be equal to 22.3 MPa, while the ductility factor increased to 3.97. The median collapse capacity reached 1.19 g, and the possibility of exceeding earthquake protection design levels was calculated to be 9.8%, as compared to 12.1% for reference concrete. Conclusion The addition of 15% shale powder is considered to achieve an optimum combination of seismoprotection, structural flexibility, and energy savings. The obtained results confirm the possibility of using the shale powder as a sustainable construction material for reinforced concrete structures in seismically active areas of Morocco.
Introduction Environmental problems are becoming increasingly prevalent in the construction industry, mainly due to the significant carbon emissions associated with Ordinary Portland Cement (OPC) production and the growing accumulation of non-biodegradable plastic waste. In this context, the present study focuses on the use of discarded Low-Density Polyethylene (LDPE) as a partial replacement for fine aggregate in geopolymer mortars. Methods Three distinct binder systems were considered: fly ash-based Geopolymer Mortar (GPM), blended Fly ash–GGBS Geopolymer Mortar (FG), and traditional OPC mortar, with LDPE replacement levels ranging from 0% to 50%. The experimental investigation was carried out to evaluate compressive strength, thermal properties including thermal conductivity and specific heat capacity, and dynamic thermal parameters such as time lag (φ) and decrement factor (f). Results The results showed that as the LDPE content increased, the thermal performance of all mixtures consistently improved, while the compressive strength gradually decreased. The fly ash–GGBS blended geopolymer mortar with 50% LDPE showed better thermal performance among all the mixtures, with a low thermal conductivity of 0.29 W/m·K, a decrement factor of 0.029, and a time lag of approximately 4.10 hours. Discussion The inclusion of LDPE improved internal porosity, which reduced thermal conductivity and enhanced dynamic thermal performance. This demonstrates the ability of fly ash–GGBS geopolymer mortar to maintain a balance between mechanical strength and thermal insulation. Conclusion These findings suggest that LDPE-incorporated geopolymer mortars, especially fly ash–GGBS-based systems, can serve as energy-efficient and sustainable alternatives for non-structural building envelope applications.
Introduction/Objective The depletion of natural aggregates and accumulation of steel slag waste pose environmental challenges. However, there is limited research on the combined effect of steel fiber and slag aggregate in concrete. This study evaluates the fresh, mechanical, durability, and microstructural properties of Steel Fiber-Reinforced Slag Aggregate Concrete (SFRSAC) to identify the optimum fiber content and slag replacement level for durable, sustainable concrete. Methods Twenty concrete mixes were prepared with varying amounts of steel fiber and slag aggregate replacing coarse aggregate. Fresh properties were assessed via the slump test, and hardened properties via compressive, flexural, and split tensile strength, ultrasonic pulse velocity, abrasion resistance, apparent density, permeable voids, water permeability, acid attack, and chloride penetration. The microstructure was investigated using detailed SEM analysis. Results Steel fiber improved mechanical performance, with the optimum mix achieving a compressive strength of 59 MPa, approximately 27% higher than conventional concrete. Slag aggregate enhanced acid and chloride resistance, and SEM confirmed a denser microstructure with improved interfacial bonding and reduced microcracking. Slag utilization reduced natural resource consumption and material cost. Discussion The interaction between steel fiber and slag aggregate improved mechanical properties, durability, and microstructural integrity, confirming that combining fiber reinforcement with industrial waste aggregate is an effective route to durable, high-performance, sustainable concrete. Conclusion Combined utilization of steel fiber and slag aggregate produces sustainable, high-performance concrete, with 3% steel fiber and 50% slag aggregate replacement giving the optimum overall performance. This mixture is recommended for structural and infrastructure applications requiring enhanced strength, durability, and sustainability.
