https://ceej.aut.ac.ir/ Amirkabir Journal of Civil Engineering en daily 1 Thu, 23 Jul 2026 00:00:00 +0330 Thu, 23 Jul 2026 00:00:00 +0330 https://ceej.aut.ac.ir/article_6158.html ABSTRACT Safety culture is a set of beliefs, perceptions, and values that employees share regarding risks within an organization, such as the workplace or society. The present study was conducted with the aim of evaluating safety culture in Shazand Petrochemical Company. The present study was conducted in two qualitative and quantitative parts. In the qualitative part, 51 components for employee safety culture were first identified by the research literature. The statistical population in the qualitative part is university professors and managers and engineers of Shazand Petrochemical Company, of which 10 people were selected as a sample through purposive and snowball sampling. Then, the components were screened using the Delphi method and finally, in three stages, 40 components for employee safety culture were obtained. These components were categorized into 7 dimensions: individual, psychological, behavioral, situational (organizational), management commitment, workplace, and participation. In the quantitative part, a questionnaire was designed with 40 questions for safety culture components, two questions for improving company performance, and two questions for reducing employee error. This part was conducted by structural equation modeling. The statistical population to answer the questions of the quantitative part questionnaire is the employees of Shazand Petrochemical Company. The sample size was obtained by random sampling and Cochran formula equal to 348 people. The results of structural equation modeling analysis showed that safety culture has a positive and significant effect on improving company performance and reducing employee error by 0.528 and 0.542, respectively. https://ceej.aut.ac.ir/article_6159.html Improving difficult and soft soils by means of stone columns is a favored technique to strengthen their ability to support loads. Yet, when loads are high or the subsoil is extremely soft, stone columns by themselves may not perform as they should. However, piles support heavy loads well, but they do not allow for drainage and are easily liquefied. We hope to understand how a compound system of stone and piles performs better than each part on its own, by using PLAXIS 3D software to model the system. The results of a raft at 10×10 meters on soft clay were compared against a system with no reinforcement, ground treated only with stone columns and ground treated only with piles. The way changes in diameter, length and the spacing of several stone columns impact their ability to support loads was also looked into parametrically. The data revealed that together, the reinforcements and raft material cause a big rise in bearing capacity and improved safety by decreasing settlement. It was found that a higher number of stone columns were the best solution for the raft foundation. The parametric study revealed that the bearing capacity of the stone column is mainly affected by its diameter. https://ceej.aut.ac.ir/article_6160.html Fracture toughness is one of the key parameters in evaluating the mechanical behavior of cementitious, rock, and quasi‑rock materials, particularly when these materials are subjected to temperature variations. Given that many engineering structures, such as tunnels and underground facilities, operate across a wide range of temperatures, the simultaneous investigation of temperature effects and specimen geometry on fracture behavior is of particular importance. In this study, the effects of temperature and specimen geometry on the mode‑II fracture toughness of cement mortar were experimentally examined. To this end, tests were conducted on three different specimen geometries, including the centrally notched Brazilian disc, the modified semi‑Brazilian disc with an initial notch, and the Brazilian disc with double diagonal cracks, under four temperature levels of −10, 25, 50, and 100 °C. In addition to fracture toughness, uniaxial compressive strength and the velocities of compressional and shear waves were measured to evaluate changes in internal material quality under thermal effects. The results indicate that decreasing the temperature relative to the reference level improves the internal quality of the specimens and increases fracture toughness, whereas increasing the temperature leads to quality degradation, reduced ultrasonic wave velocities, and ultimately a lower resistance to crack propagation. Moreover, comparison of the geometries revealed that the sensitivity of fracture toughness to temperature variations is governed by the stress distribution and crack‑tip conditions specific to each geometry. https://ceej.aut.ac.ir/article_6165.html In this study, the structural behavior of the LCF system with convergent bracing under near- and far-fault earthquakes has been investigated. For this purpose, 3-, 6-, and 12-story structures have been designed and modeled. The results showed that in the 3-story structure under near-fault earthquakes, the highest drift percentage is for the Imperial Valley earthquake and the lowest drift percentage is for the Hillers Super Station earthquake. In the case of the 3-story structure under far-fault earthquakes, the highest drift percentage is for the Landers earthquake and the lowest drift percentage is for the Hillers Super Station earthquake. In the case of the 6-story structure under near-fault earthquakes, the highest drift percentage is for the Imperial Valley earthquake and the lowest drift percentage is for the Hillers Super Station earthquake. In the case of the 6-story structure under far-fault earthquakes, the highest drift percentage is for the Landers earthquake and the lowest drift percentage is for the Hillers Super Station earthquake. In the case of a 12-story structure under near-field earthquakes, the highest percent drift is for the Imperial Valley earthquake and the lowest percent drift is for the Loma Prieta earthquake, which is 94.76 percent less than the lowest value. In the case of a 12-story structure under far-field earthquakes, the highest percent drift is for the Landers earthquake and the lowest percent drift is for the Northridge earthquake, which is 83 percent less than the lowest value. https://ceej.aut.ac.ir/article_6173.html Air pollution, as one of the serious environmental challenges, has significant negative impacts on public health and quality of life. This study investigates and models air pollution using the traffic density index and wind speed. The main objective of this research is to analyze the impact of various factors on air pollution and provide reliable predictions for pollutants including carbon monoxide, particulate matter, and sulfur dioxide. Modeling was performed using the traffic density index and wind speed. In the data preparation stage, to investigate short-term and cumulative effects, data were organized and analyzed in the form of hourly intervals, as well as two-hour and three-hour averages and sums. The results of this section indicated that using hourly data provides better performance in predicting air pollution compared to cumulative states. By analyzing density data collected on an hourly basis and utilizing neural network and machine learning models, accurate predictions for pollutants were provided. The results showed that air pollution can be effectively modeled using the traffic density index, and the XGBoost model demonstrated the best performance in this regard. This research highlights the importance of using traffic data and meteorological variations in air pollution analysis and the high potential of machine learning models in predicting pollutant concentrations. https://ceej.aut.ac.ir/article_6198.html The aim of this study is to evaluate the seismic performance and calculate the fragility of self-centering structures under mainshock and mainshock–aftershock sequences. For this purpose, two three- and nine-story structures were designed based on available references in the field of self-centering structures and then modeled nonlinearly in Perform software. Twenty mainshock records along with aftershocks were selected and applied to the structures through nonlinear dynamic analysis. Finally, various performance evaluation parameters of the structures, such as roof horizontal displacement, distribution of dissipated strain energy in the structure due to the mainshock and aftershock, and rocking displacement under both cases were investigated. Subsequently, incremental dynamic analysis (IDA) curves and fragility curves were calculated and presented. The fragility results indicate that, firstly, the fragility of shorter structures (three-story) is greater than that of taller ones (nine-story). Secondly, the fragility values for aftershock and mainshock at different performance levels are close to each other with only slight differences. For example, in the three-story structure at the LS performance level and maximum PGA = 1.8g, the probability of exceedance in the mainshock-only case was calculated as 0.87, while in the mainshock–aftershock case it was 0.93. In the nine-story structure at the LS performance level under the same maximum acceleration, the probability of exceedance in the mainshock-only case was 0.78, and in the mainshock–aftershock case it was 0.88. https://ceej.aut.ac.ir/article_6199.html In this study, the simultaneous effect of recycled aggregates (recycled fine and coarse aggregates obtained from crushed waste concrete) and the potential improvement induced by acrylic polymer were investigated. First, concrete specimens containing different replacement levels of recycled fine and coarse aggregates (12.5%, 25%, 50%, and 100%) were examined separately. Subsequently, concrete mixes containing both fine and coarse recycled aggregates were tested. In the next stage, different contents of acrylic polymer (0.25%, 0.5%, 1%, 2%, 4%, and 8%) were incorporated to evaluate its influence on concrete performance. Finally, the synergistic effect of polymer and recycled aggregates on the mechanical behavior of concrete was assessed. For all mixtures, compressive strength was measured at curing ages of 7, 14, and 28 days. The results indicated that the use of recycled fine and coarse aggregates led to reductions in compressive strength by approximately 37% and 28%, respectively. The combined use of both recycled fine and coarse aggregates resulted in an even greater reduction in strength. However, the incorporation of polymer at its optimum content of 4% significantly enhanced the compressive strength across all mix designs. At this optimum level, a remarkable increase of 114% was observed compared to the control concrete. At a low dosage of 0.25%, the polymer effectively mitigated the detrimental effects of recycled aggregates. Furthermore, at 4% polymer content, the mechanical properties of concrete containing recycled fine, coarse, and combined aggregates increased by approximately 109%, 107%, and 100%, respectively, relative to the control specimen. https://ceej.aut.ac.ir/article_6200.html This study separates the regional shoreline-change tendency from local positional uncertainty along Mal-Khalifeh–Chahak. Four shorelines derived from TM, ETM Plus, and OLI imagery acquired in 1993, 2002, 2013, and 2023 were analysed along 300 transects spaced at 50 m using NSM, EPR, LRR, and SCE. Erosion dominance was tested with an exact binomial test and moving-block bootstrap, while NSM–LRR concordance, transect-spacing sensitivity, and uncertainty propagation were assessed. Mean NSM, EPR, LRR, and SCE were −26.01 m, −0.87 m yr−1, −0.48 m yr−1, and 48.62 m, respectively. Under the NSM<−5 m threshold, 238 transects (79.3%) were erosional, with a spatial-dependence-aware 95% block-bootstrap interval of 67.7–89.0%. NSM and LRR were strongly correlated (Pearson r=0.958) and agreed in direction at 237 transects (79.0%); however, 60 transects (20.0%) had opposite directions. Twenty transects combined high SCE with |LRR|≤0.25 m yr−1, indicating substantial mobility without a persistent linear tendency. A nominal 15.85 m uncertainty per shoreline propagated to 22.42 m for NSM and 0.75 m yr−1 for EPR. Independent validation of the 2023 Landsat shoreline against a Google Earth shoreline dated 23 June 2023 produced a bias of +11.80 m, MAE of 14.68 m, and RMSE of 17.32 m across 280 transects; 95% of absolute offsets were below 30 m. The regional erosional tendency is therefore robust, whereas local interpretation requires tide-matched imagery and field data. https://ceej.aut.ac.ir/article_6201.html Connections are recognized as the most critical components in structural systems for transferring loads and maintaining overall integrity under various static and dynamic loading conditions. Replaceable energy-dissipating structural fuses provide an effective means of protecting structures against earthquake forces. However, previous studies have identified two major challenges: the dependence of the cyclic performance of yielding fuses on beam-section dimensions and the risk of damage to primary load-bearing members. To overcome these limitations, this study proposes an innovative pin-jointed connection that converts beam rotation into yielding of a replaceable damper, thereby concentrating damage exclusively in a designated region. This mechanism protects the beam and column while simultaneously making the cyclic response of the connection independent of beam-section dimensions. First, the seismic behavior of three yielding mechanisms—flexural, shear, and ADAS dampers—was experimentally compared under cyclic loading. Owing to the superior performance of the ADAS damper, the numerical model of the connection was then validated, and a parametric study was conducted on 12 models by varying the damper’s minimum width and thickness to systematically evaluate their effects on the seismic response. The results showed that the ADAS damper reached a final rotation of 0.08 rad and provided notably greater ductility and energy-dissipation capacity than the other specimens. Increasing the damper width and thickness enhanced the connection stiffness, maximum moment, and absorbed energy. Finally, the evaluation of beam-section dimensions showed that, when the force-transfer arm remained constant, changing the beam size had no significant effect on the cyclic response of the connection. https://ceej.aut.ac.ir/article_6202.html Reinforced concrete–steel composite structures supporting air-cooled condenser (ACC) systems in power plants are critical components of power generation infrastructure. Since many of these facilities are located in seismic-prone regions, a comprehensive evaluation of their nonlinear seismic behavior is essential to ensure reliable performance under extreme loading conditions. This study investigates the nonlinear response of these specialized industrial structures to determine key seismic performance parameters, including the response modification factor (R), ductility factor (μ), and overstrength factor (Ω), while identifying their governing failure mechanisms. For this purpose, eleven structural configurations representing common geometric and constructional characteristics of power plant projects were designed, numerically modeled, and evaluated. To characterize the nonlinear behavior of the structures, nonlinear static (pushover) analyses were performed in two orthogonal directions. Subsequently, one representative configuration was selected and assessed through nonlinear time-history analysis to investigate its response under biaxial seismic excitation. The results indicate that the average response modification factor (R) of the investigated structures is 7.49, with more than 90% of the calculated values falling within the range of 6.0 to 9.0. Furthermore, the average overstrength and ductility factors were obtained as 1.77 and 4.50, respectively. Evaluation of plastic hinge formation patterns revealed that nonlinear behavior primarily initiates at the bases of the reinforced concrete columns; however, the most critical hinges, in terms of approaching failure limits, develop in the upper brace-to-column connection regions. These regions play a decisive role in controlling the overall structural stability and progression of damage.