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Foundations, ground slabs, retaining walls, culverts and subways
Published in Charles E. Reynolds, James C. Steedman, Anthony J. Threlfall, Reynolds's Reinforced Concrete Designer's Handbook, 2007
Charles E. Reynolds, James C. Steedman, Anthony J. Threlfall
Where basements are in water-bearing soils, the effect of hydrostatic pressure must be taken into account. The upward water pressure is uniform below the whole area of the floor, which must be capable of resisting the total pressure less the weight of the floor. The walls must be designed to resist the horizontal pressures due to the waterlogged ground, and the basement must be prevented from floating. Two conditions need to be considered. Upon completion, the total weight of the basement and superimposed dead load must exceed the worst credible upward force due to the water by a substantial margin. During construction, there must always be an excess of downward load. If these conditions cannot be satisfied, one of the following steps should be taken:The level of the groundwater near the basement should be controlled by pumping or other means.Temporary vents should be formed in the basement floor, or at the base of the walls, to enable water to freely enter the basement, thereby equalising the external and internal pressures. The vents should be sealed when sufficient dead load from the superstructure has been obtained.The basement should be temporarily flooded to a depth such that the weight of water in the basement, together with the dead load, exceeds the total upward force on the structure.
Fluid and Thermal Systems
Published in Ramin S. Esfandiari, Bei Lu, Modeling and Analysis of Dynamic Systems, 2018
The dynamic behavior of a liquid-level system can be described using volume flow rate q, pressure p, and liquid height h. Note that the hydrostatic pressure, rather than the dynamic pressure, will be used in the modeling of liquid-level systems. The hydrostatic pressure is defined as the pressure that exists in a fluid at rest. It is caused by the weight of the fluid. For a liquid of density ρ, the absolute pressure p and the liquid height h are related by () p=pa+ρgh
Bioclimatic Design Overview
Published in Kyoung Hee Kim, Microalgae Building Enclosures, 2022
When it comes to selecting a fabrication technique, one of the primary requirements is low cost, quality control, and scalability of microalgae panel production. A rotocasting technique was utilized to fabricate modular units in a cost-effective and time-efficient manner. The full-scale mock-up consists of four different modular parts (Figure 9.6). Each unit was made of a quarter-inch-thick polyurethane-based resin, and structural analysis was carried out to secure a safety factor of 10 to account for long-term performance under gravity load and hydrostatic pressure. Hydrostatic pressure in a liquid is determined by P = ρgh where, P = hydrostatic pressure, ρ is liquid density, g is gravity, and h is the height of the liquid. 20 CFM (cubic foot per minute) of room air was circulated to supply CO2 for biomass productivity. The environmental factors affecting algae growth include light, nutrients, and CO2 levels. Bubbling air into the system is important for not only supplying CO2 but also simultaneously providing uniform temperature, light exposure, and nutrients. Because CO2 is essential for microalgae growth, the larger interfacial area (i.e.., higher surface area-to-volume ratio) of a bubble, with slow bubble velocity, results in a high CO2 residency time in the growth media. Computational fluid dynamics (CFD) analysis can be used to verify aerodynamic behaviors of bubbles in the media and their velocities to minimize hydrodynamic stress that causes reduced growth (Figure 9.7). Full-scale prototype installation consists of interlocking the modular photobioreactor facing the western orientation. The microalgae mock-up provides view-out and daylighting for better occupant satisfaction. Figure 9.8 shows the installation and operation of the microalgae mock-up for performance monitoring and verification. Table 9.2 summarizes microalgae building research found in scientific publications.
Effectiveness of different conditioning procedures for moisture susceptibility evaluation of foamed bitumen stabilised mixes
Published in International Journal of Pavement Engineering, 2023
Purbayan Ghosh Mondal, Kranthi K. Kuna
Figure 3 shows the developed laboratory-based moisture conditioning system that simulates the ASTM D7870 conditioning method. In the developed conditioning system, the bituminous mixes can be conditioned under stress, water, and high temperature inside an enclosed chamber. The system consists of a temperature-controlled specimen chamber capable of testing upto four specimens of 100 mm diameter and three specimens of 150 mm diameter. The specimen chamber is capable to withstand pressure up to 690 kPa (100 psi). To apply hydrostatic pore pressure to the compacted specimens, a diaphragm was used. The pressure inside the chamber can be increased and decreased by inflating and deflating the diaphragm. A pneumatic valve was used in the diaphragm to control or modulate the amount of airflow and pressure inside it. During the pressurisation phase, the pneumatic valve remains open and the diaphragm receives compressed air from an external air source. The compressed air creates pressure on the wall of the diaphragm and it increases in volume. This inflation of the diaphragm can produce hydrostatic pressure up to 100 psi inside the enclosed chamber. A pressure transmitter was used inside the specimen chamber to measure the hydrostatic pressure. When the hydrostatic pressure reaches the operating pressure level, the pneumatic valve automatically closes causing a reduction of applied air pressure inside the diaphragm. As a result, the diaphragm deflates back to its original position, and the hydrostatic pressure inside the chamber is released. A pressure gauge was installed on the top of the specimen chamber so that the user can monitor the hydrostatic pressure level inside the chamber during testing. The hydrostatic pressure can be controlled (increase/decrease) by using the ‘applied pressure controller’ attached to the pressure gauge. During the pressurisation phase, water is pushed into the specimens which causes some part of the entrapped air to displace. This air can cause fluctuation of hydrostatic pressure levels inside the chamber. Therefore, a de-airing valve was used for de-airing the specimen chamber and allow the replacement of the accessible air void spaces with water periodically. The user can select the number of cycles after which de-airing of the specimen chamber happens periodically.