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

With the increasing number of construction projects in modern times, there is a pressing need to effectively manage the three key aspects of a project: time, cost, and quality. Among these 3 aspects, time and cost aspects play a very important role in different stages of the project life cycle, because they can influence each other. Delays in the project can lead to increased costs, especially in countries suffering from inflation. Conversely, attempts to complete the project on time despite delays can result in a decrease in quality. Therefore, the aim of this research is to provide a risk assessment method based on Bayesian Belief network (BBN) to predict the delay and cost increase as well as the time and cost of the project and also to provide a decision support system (DSS) to determine the most suitable delay reduction strategy in terms of cost it was in construction project. The developed proposed framework was implemented in a 17-story tower and its results were compared with real data from the project. The findings show that the developed BBN has a high degree of accuracy in predicting project delays and cost overruns, and the proposed DDS can effectively determine the most suitable delay reduction strategy while keeping costs under control.

The present study aims to investigate a trend of long-term changes in drought proneness in Iran. For this purpose, we first evaluate the reliability, resilience, and vulnerability (RRV) based on the gridded data of soil moisture of the Climate Prediction Center (CPC), NOAA, for 64 years (1955–2018) within the Iranian political boundaries. The mutual relations of reliability, resilience, and vulnerability were analyzed through the Kendall-Tau correlation coefficient. It was shown that the combination of reliability and vulnerability could be the best combination for developing the Drought Management Index (DMI) on Normal copula. In addition, the long-term trends of change in drought proneness were evaluated through various fuzzy regression models in the framework of DMI. The results of trend analysis indicated that disregarding the northern and western halves of the country, which lack any trend, the long-term trends of change in drought proneness have been increasing in the eastern, southeastern, and central parts, in a way that the highest increasing trend gradient in these regions was 0.0038 for 5-year periods (or 0.228 for the whole 64 years). This increasing trend indicates the higher drought proneness for these areas.

The emerging trend in civil engineering involves incorporating geopolymer into soil amendments. This experimental investigation involved the preparation of composite samples by blending soil, ground granulated blast furnace slag (GGBS), red mud (RM), and phosphogypsum, activated using a sodium-based alkali solution. A series of mechanical and durability tests were conducted to identify the optimal sample for further evaluation. Utilizing a statistical approach, analysis of variance was applied to ascertain the optimal mix design and evaluate the sensitivity of RM, GGBS, and chemicals to strength characteristics. The maximum unconfined compressive strength obtained was 12.08 MPa after 28 days of curing, representing a significant increase of 140 times compared to the original soil, with a 55% soil replacement by weight. As GGBS increased and soil content decreased in the matrix, the composite exhibited brittle behaviour during failure. Weathering resistance was evaluated through wet-dry cycles and submergence in a sulphuric acid solution. It was noticed that structural integrity was achieved by using both sodium silicate and sodium hydroxide. The findings highlighted the crucial role of GGBS among the by-products in enhancing strength and preserving structural integrity. Statistical analysis, with a p-value significantly below 0.05, confirmed the model’s alignment with laboratory results. To gain a comprehensive understanding of the material, the surface morphology and diffractogram of the composite were analysed using scanning electron microscopy and X-ray diffractogram, revealing structural and morphological changes in the geopolymer-bonded soil.

Graphical Abstract

The investigation conducted in this work aims to analyse the stability response of functionally graded restrained nanobeams with four different porosity distributions and embedded in an elastic matrix. To take into concern the size effects, Eringen’s nonlocal elasticity is employed as a higher-order continuum theory. The material properties of the functionally graded porous nano-sized beams with deformable boundaries are changed gradually in spatial coordinates through the power-law model which covers four kinds of porosity distributions. A system of linear equations consists of infinite power series for an embedded functionally graded porous nanobeam under axial point loads obtained from Fourier trigonometric series and Stokes’ transformation is solved by an eigenvalue problem which satisfies rigid or deformable supporting conditions including classical boundary conditions such as simply supported, clamped–clamped and clamped-simply supported. In this study, Stokes' transform based solutions that can calculate the buckling loads of elastically restrained functionally graded nonlocal beams on Winkler foundation for four different pore types are presented for the first time. Analytical results are obtained for various porosity distributions and boundary conditions to reveal the effects of nonlocality, Winkler foundation and power-law index on the lateral buckling behavior of functionally graded nanoscale nanobeams.

Despite its widespread use and status as a groundbreaking construction material, concrete presents challenges due to its susceptibility to degradation. Due to this reason, concrete structures require regular maintenance, and traditional concrete crack repair methods are resource-intensive and expensive, while also having limitations in their applicability to different crack types. Microbially induced calcite precipitation (MICP) is a promising technique for the maintenance of concrete structures due to its novel approach in concrete technology for healing. The concept of MICP holds promise for sustainable infrastructure development by reducing the need for maintenance and repairs. This paper aims to provide a thorough review of published knowledge on MICP for concrete maintenance to assess and identify effective techniques and methods for MICP in concrete crack healing; this helps practitioners and designers in their decision-making processes. The study focuses on (1) MICP healing efficacy, (2) bacterial species, (3) nutrient supply methods, (4) crack remediation strategies and material compatibility, and (5) environmental conditions. This paper discusses and summarizes effective techniques and methods for MICP healing of concrete. Finally, potential future research directions for further optimizing and implementing MICP in practical applications are discussed. The significance of this work is to provide a concise review summary of the effective strategies and methods of applying MICP to the healing of concrete cracks for researchers and professionals.

In today’s world, terrorist bomb attacks and sudden explosion accidents bring serious challenges to underground engineering. Improving the dynamic protection capability of underground engineering is an important social and scientific problem that remains to be solved. Rubber concrete (RC) has an outstanding application prospect in the field of dynamic protection in underground engineering due to its excellent buffering and energy absorption characteristics. Functionally gradient material is a kind of material that can be designed according to the actual situation. This paper combines the concept of functionally gradient material (FGM) with traditional rubber concrete, proposing a new material: layered gradient rubber concrete, and explores the impact compression resistance and anti-explosion performance of specimens with different gradient modes based on Hopkinson pressure bar testing and LS-DYNA (a finite element software). The results show that there is a strain rate effect in layered gradient rubber concrete, and its failure starts at the weakest strength layer. Considering the stress–strain curve, DIF value and toughness index of the specimens, the concave gradient mode can effectively improve the impact compression performance of traditional rubber concrete. Through numerical simulation, the anti-explosion ability of layered gradient rubber concrete was tested. The concave gradient rubber concrete has the best attenuation effect in the face of explosion stress waves. Compared with the homogeneous rubber concrete, the stress attenuation effects on the structure surface X0, X1.5 and X3 of the concave gradient mode were improved by about 15, 25 and 43%, respectively.

This study addresses the challenges associated with urban tunnel construction in China’s rapidly expanding cities, emphasizing the EPB-TBM method. While the EPB-TBM offers high efficiency and minimal disruption, concerns arise when implementing it in densely populated urban spaces with pre-existing structures. The study aims to provide a numerical simulation of EPB-TBM using an advanced constitutive model to closely align with real monitoring data, highlighting the need for effective geotechnical protective measures. Without proper safeguards, the risk of damage remains significant, especially for aging tunnels. This study presents a scenario wherein twin tunnels in close proximity are excavated above pre-existing tunnels within a soft soil stratum. The research method includes numerical simulations and in situ monitoring to analyze deformation characteristics. Key findings reveal uplift in the first overcrossing and a shift in symmetry centers in the second, offering valuable insights for optimal protection and prompt assessment methods for existing tunnels during urban tunnel expansion.

The Halabja Water Supply Project (HWSP) in northern Iraq, relies predominantly on the Sirwan River for its water supply. However, the new dam constructions upstream on the Sirwan River within Iranian territory have led to a marked decline in water availability, thereby jeopardizing the sustainability of HWSP operations. This research focuses on pinpointing the most strategic location for erecting a new dam to secure a reliable and consistent water supply for the HWSP, mitigating the adverse effects of upstream water management practices. In the initial phase of this study, ArcGIS was employed in conjunction with the Fuzzy gamma overlay method and weights derived from the Fuzzy Analytic Hierarchy Process (FAHP). Several critical factors were evaluated, including rainfall, slope, land use/land cover, drainage density, geology, and proximity to the intake point. Through this comprehensive analysis, it was determined that only 3% of the study area was highly suitable for dam construction. In the second phase, three highly suitable locations—Gryana, Zmkan A, and Zmkan B—were assessed within the identified areas using the Adaptive Neuro-fuzzy Inference System (ANFIS) approach. The evaluation considered reservoir volume, watershed area, peak discharge, dam length, sedimentation, and cost factors. The analysis ultimately identified Zmkan B as the most suitable site for dam construction. The study's novelty is the integrated and multi-faceted approach to dam site selection. This approach addresses the complexities of site selection, integrating additional assessments to ensure the site’s suitability. This methodology offers a robust dam site selection framework which is highly recommended.

This paper presents a hybrid approach for assessing the durability of self-compacting concrete (SCC) in Algeria using Fuzzy-logic and Bayesian network (BN) methods. The methodology comprises three principal steps: Constructing a database based on expert opinions, learning the Bayesian Network (BN) structure, and using the BN for durability assessment. Focusing on the influence of uncertainties for eighty-six (86) basic events, probabilistic inference techniques combined with fuzzy set theories are used to predict SCC durability. The study classifies and evaluates the impact of critical events on SCC durability, conducting a comparative analysis between coastal and desert regions. Results indicate a significant SCC durability rate of 84.73%, highlighting influences from material defects, bad design, corrosion, poor construction sites, external forces, and cracks. These insights aid decision-makers in improving SCC structures.

This paper introduces a computer-aided, program-based algorithm to assess the potential floor-wise column size for direct displacement-based design of base-isolated reinforced concrete frame buildings. Lead rubber bearings are considered as base isolator for the base-isolated systems. The design storey drifts are kept low as base-isolated buildings are mostly intended to achieve a low storey drift fully operational performance level under spectrum-compatible ground motions. The frame deformation components considered in the algorithm are column tip displacement due to flexure, average column displacement due to shear, and joint rotation due to flexure and shear. To account for the dynamic amplification due to the inter-storey drift ratio, a regression line equation is evaluated from the developed relationship between design and target drifts. An approximate transformation relationship of effective toward the fundamental period for isolated buildings is also introduced to control and account for the dynamic amplification of column moment and shear. Results of time history analyses show that the proposed method effectively determines the storey-wise column size for various building plans, heights up to 12 stories, and design base displacements up to 350 mm for target storey drifts up to 0.25%.