Abstract

Due to the problem of lacking enough fresh air for passengers in underground metro stations, increasing attention has been paid to improving ventilation in underground metro stations. In this paper, the distribution characteristics of airflow fields, geometry of the station, and the influence of airflow rate changes on passengers’ ventilation conditions have been investigated and simulated according to computational fluid dynamics (CFD) theory. In addition, the volume of the stations was treated with a central air conditioning system, including several air handling units (AHU) connected to chilled water. Air flow for trains and stations has been calculated and compared with the actual data of the National Authority for Tunnels (NAT). It has been found that the highest air flow rate Q for Attaba station is 24.97 m³/s at ticket hall level, and the lowest air flow rate is 5.23 m³/s at platform level. Also, the required air flow rate is 111.02 m³/s for trains has been calculated. This value is acceptable and suitable in comparison to the actual results from the NAT. This is to reduce the necessary heat and improve the air quality inside underground metro stations. It is concluded that, in cases where an air flow rate is required in stations, the efficiency of the fans must be superior to 70%. The rotation speed of the fans will range from 750 to 1480 revolutions per minute (r.p.m).

Abstract

One of the problems of tunnels is lacking enough fresh air for passengers inside the subway. Also, because of the friction of the train with the railways inside the tunnel, high heat is generated. So, the design and calculation of an efficient ventilation system are critical for the tunnels. There are several methods used to determine the most effective tunnel ventilation systems while reducing fan energy costs, including their operating performance. The main task of an optimal tunnel ventilation system is to determine the quantity, location, and function of fans to distribute the required fresh air flow at the lowest possible cost. The main parameters for selecting a suitable fan that meet the optimal design of the tunnel ventilation system are the ventilation rate (Q) and the static head pressure (H). Both Q and H of Cairo Metro Line 3 were studied and calculated under different conditions of ventilation design from the obtained data. The amount of the ventilation rate by the fan was taken 80 m3/s which is the actual air flow rate taken from data of the National authority of Cairo Metro No.3. In addition, a comparison is made between various methods to determine the most effective tunnel ventilation system. The static head pressure (H) was calculated. According to the American Brattice Cloth (ABC) rigid duct method, the static head equals to 1171.5Pa, which is the most economical value that is giving the lower power consumption and rate of ventilation.

The main purpose of mine workings is the exploitation of ores and minerals that are used in different aspects of life. The most common underground method all over the world is the longwall mining method. The increasing demand for minerals and ores and the difficult mining conditions at greater depths make the longwall mining system a good candidate in mining. The equilibrium condition is disrupted when the longwall face advances, and as a result, the surrounding rocks eventually fracture and cave. Moreover, the induced pressure due to caving or fractures of the immediate roof rocks and the tilting of the main roof exerts an excessive load on the hydraulic supports in the longwall faces. Induced disturbances of the overburden rocks must be thoroughly investigated since this will enhance our understanding of rock pressure and ground control. The main objectives of this paper are to review the importance of the longwall mining system as an exploitation method and its applications around the world. as well as the main factors affecting the stability of supports in longwall faces, especially hydraulic supports. From this study, it can be seen that the most important technical factor that affects face stability is the rate of face advance. In addition, the significant natural factors affecting the stability of workings are roof conditions and the geometry of the panel.

Underground mining of ores affects in-situ rock conditions, resulting in a sequence of strata motions. Roof rock pressure, which is the basis of all ground control issues, is caused by these instabilities. The hydraulic supports are subjected to excessive stress due to the roof rock pressure. The correct forecast of Rock Roof Loading (RRL) provides longwall face stability during ore exploitation, allowing the hydraulic supports to move more freely.This paper presents some of the current theories, approaches, and concepts for the determination of roof loading on longwall faces, with emphasis on the current gaps. This could improve the ability to manage the roof during mining workings, and govern the roof loading conditions and the supporting system. From this study, it can be seen that the periodic weighting of the main roof is an important aspect in the determination of loading requirements. Moreover, many loading calculation methods failed to take into consideration the swelling pressure of immediate roof rocks, and the tilting of the main roof blocks, which exert excessive loads on the supporting system

Hybrid resistance systems employing steel and fiber-reinforced polymers (FRP) can be an optimum solution for more ductile structures with high energy dissipation ability and reasonable seismic force reduction factor. Since the available experimental data on the seismic behavior of hybrid (steel/FRP) reinforced concrete circular bridge piers remains limited; this article presents a comprehensive numerical study to investigate the effect of different parameters on their behavior. A 3D finite element model (FEM) that takes into account the material and geometric nonlinearity and the bond behavior of steel and glass FRP (GFRP) reinforcement was performed and calibrated against the available experimental data. The calibrated FEM was then used to perform a parametric study to evaluate different GFRP replacement ratios and configurations from the perspective of different seismic design performance levels. The analysis included strength, deformation capacity, energy dissipation, residual damage, ductility, and the equivalent viscous damping. The results indicate that the hybrid RC columns demonstrate significant displacements while maintaining controlled residual deformations. Furthermore, the simulated hybrid RC columns exhibited acceptable ductile flexural behavior. Based on the findings of the parametric study, the optimum mixing ratios between steel/GFRP bars are proposed.

This study investigates the effectiveness of tuned mass damper (TMD) systems in mitigating torsional irregularities impact on seismic response of L-shaped reinforced concrete (RC) buildings, with a particular emphasis on soil–structure interaction (SSI) effects. Nonlinear time history analyses were conducted on a nine-story RC building constructed on both ZC (moderate) and ZD (soft) soil types, under three different conditions: fixed-base, SSI without control, and SSI with TMD control. The SSI effects were modeled using a substructure approach, and 15 bidirectional ground motion records were used for input excitation for each case. This paper presents a novel configuration of TMDs on building roof; the effectiveness of TMD in mitigating seismic responses of L-Shaped RC Structures subjected to a range of earthquake ground motions is assessed. This study investigates how torsional behavior is affected by soil–structure interaction (SSI) and how this behavior can be mitigated through the implementation of TMDs. The outcome results show that SSI notably amplifies torsional responses, especially in soft soils, leading to higher exceedance probabilities of the torsional irregularity index η_bi. The introduction of the TMD control system significantly reduced torsional irregularities impact on seismic demands, with a reduction exceeding 12 % in upper stories for ZD soils. Fragility curves further confirmed the TMD’s effectiveness in reducing the probability of torsional irregularity impact exceedance. These findings highlight the necessity of incorporating SSI effects on seismic demands assessment and the effectiveness of TMD control devices for seismic mitigation as a seismic design approach for irregular RC buildings.

The architectural design process is complex, involving diverse objectives that may be contradictory, and on which orientation exerts significant influence. The artificial intelligence application, Generative Design facilitates solving multi-objective design dilemmas through the creation and evaluation of numerous design alternatives. However, its exploration in educational buildings in hot arid climates remains limited. Given the impact of spaces’ function distribution, this study aims to optimize it in the typical plans of educational buildings. Employing a multi-objective design approach to enhance environmental performance. The study is conducted and evaluated in national universities in Egypt as a case study, specifically in Assiut City.