Underground geotechnical structures, such as deep and shallow foundations, diaphragm walls, tunnel linings and anchors are being increasingly employed as energy geostructures to exchange heat with ...the ground by installing absorber pipes into the structural elements. This paper focuses on the application of this technology to reinforced concrete diaphragm walls used for construction of underground car parks, basements and metro stations, with the purpose of heating and cooling the adjacent buildings. Preliminary numerical modelling allowed optimising the geothermal plant design of the diaphragm wall. Then its energy efficiency is investigated through finite element thermo-hydro coupled analyses together with the effects of the thermal activation on the surrounding soil. Finally, finite difference thermo-mechanical analyses are used to study the mechanical effects induced by the thermal activation.
•Thermal and mechanical aspects of energy walls are discussed.•The horizontal configuration of pipes geometry allows maximising the heat exchange.•Heat exchange between 20 and 25 W/m2 with static ground water.•Heat exchange between 40 and 50 W/m2 with favourable groundwater flow.•Bending moment increase up to 16% due to thermal activation.
This study presents a comprehensive exploration of Peridynamic (PD) theory, with a specific focus on its theoretical foundations and practical implementations, including various PD formulations and ...PD operators. The objective is to highlight the unique attributes of each PD formulation and assess their suitability in the framework of material failure simulations by providing an extensive literature review. The research focuses on the bond-based (BB), ordinary state-based (OSB), and non-ordinary state-based (NOSB) PD formulations, offering a thorough understanding of their distinctive characteristics. Moreover, this study presents the importance of the PD operators on the solution of the differential equations. Numerical implementation is a central aspect of this research, providing a detailed flow chart of the computer codes for PD and PD operator models. In order to demonstrate the robustness of the PD formulations, this study presents numerical results, showcasing predictions generated by computer codes that can be accessed online.
•Comprehensive review of current state-of-the-art peridynamics (PD).•Comprehensive review of novel methods based on PD- and nonlocal operators.•Extensive comparison of different methods.•Links to source codes and implementations.
•A water-heat-salt coupled model under evaporation for saline soil is developed.•Comparison of the water-heat-salt transport characteristics at varying salt content.•Salt content crucially affects ...liquid water and salt transport under evaporation.
Soil salinization is aggravated by evaporation, resulting in salt crystallizing on the soil surface. Soil salinization is harmful to agriculture and has significant implications for the engineering and construction industry. Therefore, this paper investigates water and salt transport in saline soils through comparison of numerical simulations with indoor evaporation tests. Based on Darcy's law, ideal gas law, mass conservation law, and energy conservation law, a one-dimensional transient mathematical model of coupled water-heat-salt transport is derived. The bottom of the model represents a recharge boundary condition, the sides of the soil column are insulated and impermeable, and the top serves as a heat source. The results show that the greater the salinity of the soil, the more drastic the temperature change, and at the same time, the greater the water retention of the soil. The temperature gradient along the height of the soil column provides a tremendous driving force for water-salt transport, and although the volumetric water content of the soil column at 3 ∼ 4 cm dissipates quickly, there is a gradient of increasing salt concentration towards the ends and decreasing towards the middle. The modeled results agree with the experimental data, indicating that the model can effectively simulate the water-heat-salt transport process for different saline sites under evaporation conditions. The model is essential for the improvement of saline soils and for finding new methods to prevent further soil salinization.
This study presents a comparative dynamic analysis of hybrid composites, which are suitable for new technological vehicles and possess greater advantages over non-hybrid fiber-reinforced composites. ...In this context, non-hybrid (NH), interply hybrid (IN) and intraply hybrid (IR) composites are manufactured. In the manufacturing process, NH and IN composites are utilized by using Carbon (C), Aramid (A), and Glass (G) while IR composites are manufactured with Aramid-Carbon (AC), Carbon-Glass (CG), Glass-Aramid (GA). In the manufacturing stage, a variety of layer numbers and fiber orientation angles is taken into consideration to determine the most advantageous structures for vibration characteristics. As there are a great number of productions required because of the parameters of interest, Taguchi production design is used. These composites are manufactured using Vacuum Assisted Resin Transfer Molding (VARTM). In accordance with the relevant standards, density, tensile, and dynamic properties are determined experimentally. Further, numerical models are developed using the ANSYS® software, and modal analysis is conducted. The results of the numerical analysis are compared with the experimental results. Taguchi analyses are performed to determine the most effective manufacturing configurations for the purpose. Consequently, IN and IR composites with similar content are compared to each other and the previous literature. According to the experimental and numerical results, the factors most effective in determining the natural frequency and damping ratio are layer numbers, orientation angles, and fabric types, respectively. The effectiveness of each parameter in the ranking is determined by using Taguchi levels.
Underground structures must be able to support both static overburden and seismic loads. Previous work has found that the dynamic amplification of stress waves impinging on a tunnel is negligible ...when the wave length (λ) of peak velocities is at least eight times larger than the width (B) or diameter (D) of the opening. This condition is applicable to tunnels located far from the seismic source, where the predominant frequencies range between 0.1 and 10 Hz. While such statement has been used and verified for underground structures placed in linear-elastic ground under dry or drained conditions, the effect of input frequency (f) on the seismic response of tunnels placed in nonlinear ground has not been well investigated, especially when undrained conditions apply. Two-dimensional dynamic numerical analyses are conducted, using FLAC 7.0, to evaluate the effect of frequency on the seismic response of deep circular tunnels placed in nonlinear ground under drained and undrained loading. It is assumed that the liner remains elastic, and that plane strain conditions apply. For the ground, an elastoplastic constitutive model is implemented in FLAC. It is found that the effect of input frequency is negligible for λ/D ratios larger than eight to ten, which, given the geometry of the tunnels investigated, correspond to frequencies f≤ 5 Hz. Pseudo-static numerical analyses are also conducted for a much smaller and less expensive model, and the results are compared with those of the dynamic analyses. Differences smaller than 2% are found, which suggests that pseudo-static analyses may be sufficient to evaluate the drained or undrained seismic response of deep tunnels placed in nonlinear ground far from the seismic source.
•The response is frequency-independent for f ≤ 5 Hz, for drained or undrained loading.•The seismic response is frequency-independent for ratios λ/D ≥ 8–10.•λ/D ratios change during seismic analyses, as the ground stiffness changes.•The relative flexibility, F, of underground structures decreases during earthquakes.•Pseudo-static analyses may be sufficient to evaluate the seismic response of tunnels.
•A new type of device using a combination of titanium steel and recycled tires was proposed.•The proposed device has larger ultimate capacity compared to the device using regular steel material.•The ...increase of the thickness and number of interior diaphragms can enhance ultimate capacity of the structures.
Anti-collision devices can reduce the damage of bridge columns under ship collision, and a new type of device is proposed in the paper using a combination of titanium steel and recycled tires. The use of titanium steel is to improve the corrosion resistance, and the use of recycled tires is to improve self-floating capacity as well as save the cost. Three test specimens were designed and tested to investigate the behavior of the device under impact load and reveal the failure mechanism; finite element models were conducted to analyze and compare with the experimental results. Also, parametric study was conducted to reveal the effect of parameters on the ultimate capacity of the device. The performances of different types of the anti-collision device are compared, and the failure mechanism is studied. The results show that the proposed device effectively improves the performance of buffering energy dissipation and durability under impact load.
Waves, a constant presence in the ocean, significantly influence the stability of a vehicle's water entry. In the present work, the effects of waves on the water entry of a vehicle equipped with a ...cavitator, utilizing the Computational Fluid Dynamics (CFD) method. The Stokes V wave theory serves as the basis for wave simulations, while the moving computational domain method is used to realize the motion of the vehicle. The water entry process is most influenced by waves at the peak point of wave inclination. This research delves into the impacts and underlying mechanisms of wave height, entry angle, and speed on the water-entry process, particularly focusing on the range of wave influence. Re-entry may occur when the entry angle is smaller than the maximum wave inclination. Under such circumstances, the vehicle's motion could become more erratic, potentially leading to re-entry failure. Consequently, two critical angles are defined: one where re-entry is likely to occur, and another where re-entry is inevitable. The influences of wave parameters and entry angle on the possibility of re-entry are investigated. The proposed critical angles and their calculation method lay the groundwork for future research aimed at ensuring safe water entry for vehicles amid waves.
•The fluid-structure coupling between waves and vehicles is realized using moving computational domain method.•Two critical angles are defined as the water-entry angles where re-entry is likely to occur and bound to occur.•A theoretical method for calculating the probability of re-entry is established.•The law of influence of the entry and wave parameters on the range of wave influence on the water entry is obtained.
•Snow loads may cause catastrophic damages at prefabricated industrial buildings.•Brittle damages may occur at the thinned ends of the purlin.•Different prefabricated RC purlin tests have been ...conducted.•The proposed Z type reinforcement enhanced shear capacity of the purlin.•The results were compared with TS-9967 standards and field tests.•The numerical analysis was performed using ABAQUS to determine optimum Z type reinforcement.
In prefabricated industrial buildings, damages and collapses may occur under snow loads. If the necessary precautions are not taken, the damage can spread to the whole structure which leads to total collapse. Therefore, it is very crucial for manufacturers to comprehend the nature of the damage and to take necessary precautions to prevent this damage. In this present study, the damages occurred at dapped-end region of prefabricated purlins due to snow load accumulated at the roof and the reasons for these damages were investigated in detail. Pursuant to this goal, comprehensive experimental and numerical studies have been undertaken. 10 specimens with 5 different configurations were tested under four point loading. A novel reinforcement detail and the usage of practical methods used by the manufacturers are selected as main parameters. In all purlins, damages occurred at the dapped-end in shear formation. The experimentally obtained results were compared with field tests and TS9967 design code. It was observed that the specimen with “Z” type of the proposed novel reinforcement exhibited approximately 30% higher load capacity than that of other specimens. Moreover, the numerical analyses were performed in order to determine optimum “Z” type reinforcement for dapped-end purlin beams using finite element methods.
The "U-shaped ferrule joint bars connections" have a stable mechanical property, requiring a low level of construction accuracy and a relatively simple connection process, which significantly ...increase the construction speed. Based on the "U-shaped ferrule joint bars connections" technology, a new type of prefabricated concrete underground utility tunnel was proposed. This prefabricated technology realizes a formwork-free construction and vertical support-free assembly of the top plate on site. Through the full-scale model static test and numerical analyses, the mechanical properties, i.e., the crack development law and bearing capacity, were systematically investigated to validate the effectiveness of the "U-shaped ferrule joint bars connections". The test results indicated that the performance of the "U-shaped ferrule joint bars connections" is reliable. During the loading process, the prefabricated utility tunnel experienced three stages, i.e., cracking, stiffness degradation, and ultimate failure. The numerical analysis results correlated with the test results well. The simulation results showed that the bearing capacities of the prefabricated underground utility tunnel and the cast-in-place utility tunnel were similar. The longitudinal joint connections of the prefabricated utility tunnel allow the structure as an integration to maintain favourable mechanical properties.
