Iranian Journal of Science and Technology, Transactions of Civil Engineering最新文献

Wrap-faced Sand Reinforced Retaining Wall (WSRW) Model is a worthwhile method that has been used worldwide for studying the seismic performance and successful implementation to fix the erosion problems in low-lying areas for earthquake resiliency purposes. In this research, a holistic WSRW model was built to compute its response under three different earthquake loading conditions namely˗ Kobe, Loma and Koaecli. The model was implemented using a shake table at the laboratory of Bangladesh University of Engineering and Technology (BUET). Several parameters were utilized. Such as, base acceleration (0.1 g, 0.15 g, 0.2 g), relative density (For Sylhet sand relative density of 48%, 64% and 80%, and for local sand relative density of 26%, 45% and 57%), surcharge (0.7 kPa, 1.12 kPa and 1.72 kPa). It was observed that, strain, face displacement and acceleration amplifications were decreased at higher relative density and surcharge pressure but were increased with high base accelerations. For instance, for a Sylhet sand sample with 48% relative density under the Kobe earthquake testing, acceleration amplifications for base accelerations of 0.1 g and 0.15 g are, respectively, 6.5% and 2.7% less than base accelerations of 0.2 g at normalized elevation 0.5 using a surcharge pressure of 0.7 kPa. However, at normalized elevation 0.5 for the Local sand sample with 26% relative density under Kobe earthquake testing employing the same surcharge pressure, acceleration amplification of 0.1 g and base acceleration of 0.15 g are respectively 10.6% and 7.7% less than base acceleration test for 0.2 g. Another result from the experiment of the Loma earthquake with a surcharge load of 0.7 kPa and 0.1 g base acceleration of Sylhet sand reveals that sample with 80% face displacements as well as relative density of 64% are respectively 12.9% and 8.2% less than the sample with relative density of 48% at normalized elevation 0.625. For similar base acceleration and similar surcharge load Local sand model experiments, samples with face displacements of 57% and relative density of 45% are respectively 14.2% and 8.5% less than the samples with relative density of 26% which is observed at normalized elevation 0.625. In the case of the local sand model, at normalized elevation 0.5, samples having the similar base acceleration and surcharge load, strains of a relative density of 57% and 45% are respectively 10% and 5.1% less than the sample having a relative density of 26%. Seismic characteristics observed from this research are beneficial for not only the design but also construction of WSRW.

Concrete is a significant construction material, with a 25% increase in production by 2030. However, rapid industrialization and urbanization have made it non-sustainable due to the use of ordinary Portland cement (OPC). OPC production requires extensive energy and resources and causes greenhouse gas emissions. To promote sustainable development, the construction industry is now seeking alternative raw materials, like reusing waste from infrastructure and buildings. The use of recycled cement as a substitute for OPC has been the subject of recent research. Considering this, the main goal of this study was to determine how using ground recycled concrete cement (GRC) as a partial cement substitution affects the fresh, mechanical, microstructure, and durability properties of mortar. To achieve this goal, several tests were performed after a thorough preliminary analysis. GRC particles lack smoothness and have irregular edges, affecting mortar workability. Nonetheless, the 10% replacement improves mechanical and durability performance and has comparable structural compactness to reference mortar, particularly for the latter ages.

Among various alternative approaches, Tuned Mass Dampers (TMDs) represent an established technology for controlling earthquake-induced vibrations. However, traditional TMD systems need a substantial amount of additional damping mass and a sizable installation area at the top floors of the building. Due to these difficulties, besides developing a new type of modular facade system along the height of buildings, the method of Peripheral Mass Dampers (PMDs) is introduced. This technique employs several layouts of the panelized facade system as the mass dampers. However, if the facade mass changes along the height of the building, the variable PMD (V-PMD) method can be used. To show the reliability and efficiency of the proposed method, the passive/active PMD model is investigated and compared with the results of the controlled and uncontrolled models. The presented models are assumed and verified under FEMA P695 seismic records for reference structure models with 12 and 20 stories. Single- and multi-objective optimization is performed on variable mass along the height of the building and damper parameters to minimize structural responses. Meanwhile, compared with a typical non-controlled and controlled system, the results of passive models have shown a sensible reduction in all seismic responses of the building, and active strategy gives further improvements.

The effect of the load type on the behavior of a large piled raft foundation (PRF) with an intermediate flexible raft in stiff clay soil has been investigated. For this purpose, three-dimensional numerical analyses have been carried out for the piled raft with varying pile configurations subjected to either uniformly distributed load (UDL) or equivalent point loads (PL). The average and differential settlements, raft bending moment, and pile axial load distribution are evaluated and discussed in detail. Results show that for piles covering the maximum area of the raft, the average settlement for the PL case is always marginally higher compared to the UDL case, whereas the differential settlement is substantially greater. The raft bending moments for PL are always significantly higher than for UDL. For UDL, the pile axial load distribution is predominantly affected by the pile positions, and for the PL, it is mainly affected by the column point load locations in addition to pile positions. Based on the loading intensity and serviceability limit considerations, the optimum pile configuration has been determined for the PRF under column point loads.

Holes are often retained in concrete for holding cables and other industrial components. To ensure the safe application of high-performance concrete (HPC) members in a state of three-dimensional compression, research on the effects of holes on the mechanical properties of HPC members under triaxial compression is important. However, the triaxial compressive mechanical properties of HPC members with holes have not been studied. In this work, HPC specimens containing holes were experimentally studied under triaxial compression. The stress‒strain curves, strength, and failure mechanisms of HPC were obtained. The experimental results showed that both the confining pressure and the hole size influenced the mechanical properties of HPC. Moreover, the power-law failure criterion was modified to elucidate the relationship between the triaxial compressive strength of HPC and the hole size. In addition, the stress averaging method was first introduced to predict sidewall failure of a hole in concrete, and the experimental results were considered to modify the stress averaging method. The results indicated that the modified method can be used to accurately predict sidewall failure of holes and that both a decrease in the confining pressure and an increase in the hole size are conducive to hole failure. This study bridges the gap in research on HPC members with holes under triaxial compression, and provides an effective method to predict hole failure.

Nanocomposite fabrics have been extensively employed as moisture harvesting media. In this study, flower-like zinc oxide nanostructures were coated on cotton fabrics by precipitation technique at different operational conditions of precursor concentration, temperature, and residence time. Then, the impact of aforementioned parameters on wettability of coated fabrics and morphology of nanostructures were investigated through water contact angle (WCA) measurements and SEM/EDX analyses, respectively. Optimal conditions of the coating procedure was experimentally determined and later validated using Minitab software. Afterwards, the fabrics prepared at optimal conditions were utilized in moisture harvesting experiments which were planned to scrutinize the effects of 3 parameters; humid airflow rate, temperature, and humidity on the final amount of harvested moisture. Experimental results in terms of WCA measurements led to an optimal value of 156°. Moreover, Minitab confirmation of the obtained results revealed that the optimization of coating process occurred at a precursor concentration of 3.1 mM, a temperature of 85 °C, and a residence time of 50 min. Furthermore, SEM/EDX analyses ascertain the flower-like zinc oxide nanostructure coating as well as its uniform distribution on the fabric surface. The abrasion resistance of the coated nanostructure was evaluated via performing a standard abrasion test proving the coating mechanical stability, as evidenced by a negligible reduction in the WCA. Finally, optimal moisture harvesting results led to 64.8 mg/cm².h of water, showing the dominancy of air humidity effect on the amount of harvested moisture as compared to factors such as temperature and air flowrate.

Reinforced concrete structures, which generally resist high temperatures well and usually do not suffer destruction, therefore require an assessment of the concrete’s condition after a fire. This review explores various techniques for assessing Fire Exposed Concrete (FEC) and provides comprehensive insights into their application by examining the principles, advantages, drawbacks, and feasibility of these methods. This comprehensive analysis aims to enhance assessment effectiveness and improve outcomes in restoring the integrity and safety of fire-damaged concrete structures. Overall, this review contributes to the literature by systematically outlining assessment techniques and providing valuable insights for researchers, engineers, and practitioners in selecting suitable methods and aiding informed decision-making on repair strategies. Samples extracted utilizing core procedures may be subjected to laboratory studies, especially non-linear approaches. The bibliometric analysis concludes significant linkages and trends in study areas including fire resistance and Non-Destructive Testing (NDT) of FEC are presented by analyzing keyword networks during the last 20 years. With more than 40 citations to back up their findings, highlighted the importance of and relationships between important subjects in this discipline. Techniques such as crack density measurement, indirect UPV, impact echo, Ground-Penetrating Radar (GPR), petrography, Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) may be performed to determine the damage depth of concrete subjected to fire; however, caution is advised as each approach has its limitations.

Despite advancements in energy efficiency, the construction and operation of our built environment remains responsible for 34% of global energy demand and 37% of CO₂ emissions, exacerbating environmental challenges. Climate indicators are worsening; carbon dioxide levels continue to rise, putting the world on a trajectory for a 2% annual increase. Every country, city, organization, and company need to adopt net-zero plans to combat this crisis. The construction industry requires innovative and sustainable solutions, including the exploration of eco-friendly construction materials, to achieve carbon neutrality by 2050. The use of supplementary cementitious materials (SCMs) to partially replace cement in concrete production is a significant stride towards sustainable construction practices, effectively addressing waste generation and environmental concerns associated with traditional cement usage. SCMs help in recycling industrial by-products and agricultural wastes, significantly reducing landfill waste and promoting resource efficiency. Additionally, partial replacement of cement with SCMs can lower CO₂ emissions from cement production, contributing to the construction sector’s net-zero goals. Moreover, SCMs can improve the durability and lifespan of concrete structures, reducing the need for frequent repairs and maintenance, thus saving costs and resources over time. This study summarizes diverse SCMs for partial cement replacement, explores their compositions, and emphasizes their crucial role in achieving carbon neutrality by 2050. It evaluates key characteristics such as compressive strength, durability, workability, and environmental impact to assess the performance, advantages, and challenges associated with these materials. This analysis guides practitioners in making informed decisions about their implementation in construction projects. Our review guides the construction industry towards more eco-friendly practices, contributing to the long-term sustainability and resilience of concrete structures. By mitigating the environmental footprint of cement production, we promote the creation of more sustainable and high-performance concrete structures.

Determining the factor of safety against sliding of slopes in engineering projects is a major challenges for civil engineers. A method that can provide an accurate estimation of sliding likelihood can be a significant aid to designers. In the first part of this study, formulae based on classical regression methods such as multiple linear regression (MLR), multiple non-linear regression (MNLR), and multivariate adaptive regression splines (MARS) to calculate the factor of safety ((overline{{F }_{s}}) _LEM) of finite slopes are developed. In the second part, in order to develop soft computing methods for estimating (overline{{F }_{s}}) _LEM, from soft computing methods (boosted trees (BT) and gene expression programming (GEP)) and two regression methods (MLR and MNLR) data-driven based methods are used. Values of (overline{{F }_{s}}) _LEM for development of classical regression and soft computing models are generated using the limit equilibrium methods (LEMs). To assess the performance of the proposed models, different statistical metrics such as R², RMSE, RE%, MAE and NSE, and graphical diagrams such as scatter plots, box plots, RE% plots and Taylor plots are used. Classical regression methods indicate that the results obtained from the MARS model is closer to the extracted results of the MNLR model. Moreover, the results showed that the performance of the GEP model with R² = 0.994, RMSE = 0.0381, RE% = 1.66%, MAE = 0.027 and NSE = 0.992 is better than the other soft computing models for estimating (overline{{F }_{s}}) _LEM. Designers of simple slopes with homogenous and dry soils could consider using the proposed approaches as an alternative to traditional stability charts and limit equilibrium methods (LEM).

An experiment was conducted to investigate the influence of the shear span-to-depth ratio (a/d) on the shear capacity and behavior of high-strength concrete (HSC) beams reinforced with basalt fiber-reinforced polymer (BFRP) bars. Six BFRP reinforced HSC beams, concrete compressive strength({(f}_{c}^{prime})) equal to 90.67 MPa, were cast and tested in a four-point bending arrangement. The shear span-to-depth ratios ranged from 1.5 to 4. The results indicated that the shear span-to-depth ratio, remarkably, affects the shear capacity and behavior of HSC deep beams reinforced with BFRP bars. Due to the increase in the shear span-to-depth ratio from 1.5 to 2.5, the shear capacity of BFRP-reinforced HSC deep beams decreased by 51.78%; however, an insignificant effect was observed in HSC slender beams reinforced with BFRP bars. Additionally, the applicability of models from different design codes to predict the shear strength of FRP-reinforced concrete beams was investigated. The strut coefficients from ACI 318-19 were modified to predict more accurate results from strut and tie models. The ratio of the experimental to predicted ultimate shear strength of the beams with the modified strut-and-tie model from ACI 318-19 (({V}_{u,exp}/{V}_{propse } )) had a mean value of 1.02 and a coefficient of variation (CV) of 15.03%.