Abstract:This study explores the potential of back propagation neural networks (BPNN) computingparadigm to predict the ultimate bearing capacity of shallow foundations on cohesionlesssoils. The data from 97 load tests on footings (with sizes corresponding to those of realfootings and smaller sized model footings) were used to train and validate the model. Fiveparameters are considered to have the most significant impact on the magnitude ofultimate bearing capacity of shallow foundations on cohesionless soil and are thus used asthe model inputs. These include the width of the footing, depth of embedment, length towidth ratio, dry or submerge unit weight and angle of internal friction of the soil. Themodel output is the ultimate bearing capacity. Performance of the model wascomprehensively evaluated. The values of the performance evaluation measures such ascoefficient of correlation, root mean square error, mean absolute error reveal that themodel can be effectively used for the bearing capacity prediction. BPNN model iscompared with the values predicted by most commonly used bearing capacity theories.The results indicate that the model perform better than the theoretical methods.KEYWORDS: Ultimate bearing capacity; Shallow foundations; cohesionless soil; backpropagation neural network (BPNN); prediction
The mechanical behaviour of partially saturated soils can be very different from that of fully saturated soils. It has long been established that for such soils, changes in suction do not have the same effect as changes in the applied stresses, and consequently the effective stress principle is not applicable. A procedure was proposed to define the soil water characteristic curve. Then this relation is converted to relation correlating the void ratio and matric suction. The slope of the latter relation can be used to define the H-modulus function. This procedure is utilized in the finite element analysis of a footing on unsaturated coarse grained soil to investigate its bearing capacity. The finite element results demonstrated that there is a significant increase in the bearing capacity of the footing due to the contribution of matric suction in the range 0 to 6 kPa for the tested compacted, coarse-grained soil. The ultimate pressure increases from about 120 kPa when the soil is fully saturated to about 570 kPa when the degree of saturation becomes 90%. This means that an increase in the bearing capacity of about 375% may be obtained when the soil is changed from fully saturated to partially saturated at a degree of saturation of 90%. This development in the bearing capacity may exceed 600% when the degree of saturation decreases to 58%.
Increasing the bearing capacity of shallow foundations is a significant challenge in the urban environment due to increased population growth. This paper presents the bearing capacity of circular foundations encircled by a diaphragm wall. In this study, the effects of diaphragm wall depth (0.5 D, D, 2 D) (D is the foundation diameter) of the foundation on the bearing capacity of the foundation are investigated. Varying relative densities of sand soil (loose, medium, and dense) are utilized. The results of the experimental tests show that the diaphragm wall possesses an influence upon the settlement and the foundation bearing capacity. Where, the capacity of bearing increased as the diaphragm wall depth increased. On the other side, increasing the depth leads to a decrease in the settlement ratio of about 57%. The results of experimental work also demonstrated that the best depth is between D and 2D for all types of relative densities
The difficulty that faces the geotechnical engineers how to find the alternative and effective method to improve bearing capacity and reduce foundation settlement. Therefore, the skirt is considered one of the methods to improving the shallow foundation bearing capacity on different soil. The mechanism of skirt work is confinement soil below the foundation and decrease settlement of the foundation. Soil engineers are worked to devise this method as an alternative to pile foundation for conventional buildings. This paper reviews most of these studies of skirted foundations with different types of soil including laboratory tests, field tests, centrifuge models, numerical method and theoretical analysis; these studies are used in investigation the behaviors skirted foundations.
In this study the behavior of rectangular footing on gypeous soil was studied under inclined and eccentric loading. The experiments were performed using laboratory scale rectangular footing rested on soil taken from Tikrit University site in Salah Al Din province under 3 m depth which has a gypsum content of (50.48 %). The load test was performed on rectangular footing at eccentricity of (e/B= 0, 0.1, 0.2 and 0.3) and an angle of inclination of the load with the vertical ( i= 0°, 5°, 10°, 15°and 20°). The local specifications of the soil are measured (density, moisture, maximum density and optimum moisture content), it is found that that the vertical settlement, horizontal displacement, and base inclination increases with the increasing of eccentricity and inclination of load, the values of bearing capacity that getting in this study was less than of the previous theoretical studies when the load was vertical, and is given a good agreement when load was inclined and field density and moisture of soil. The values of bearing capacity was decreased when the load eccentricity increased because of the effective area became small. It is found that a high settlement occur in footing when a water (unsaturated with gypsum salts) diffuses through the soil, then gypsum become soluble thereby the soil resistance decreases because of rupturing of chemical bond between gypsum and soil.
Composite beams, made up of a concrete slab and steel in the IPE steel section, are commonly used in bridges and buildings. Their main function is to enhance structural efficiency by merging the compressive strength of concrete with the tensile resistance of steel, thereby improving overall stiffness, ductility, and load-bearing capacity. This study offers an extensive review of the flexural behavior of steel-concrete composite beams, focusing on the interplay of concrete strength, shear connector types, and interaction levels in determining structural performance. It integrates experimental and numerical research to analyze critical parameters, including load-deflection behavior, shear transfer efficiency, and crack propagation at the steel-concrete interface. The study emphasizes the effect of concrete compressive strength, particularly in ultra-high-performance concrete (UHPC) and lightweight concrete, on stiffness, ductility, and load-bearing capacity while reducing self-weight and enhancing sustainability. The study revealed that fully bonded shear connectors, using CFRP sheets and welded plates, enhance flexural capacity and stiffness. In contrast, partial bonding or pre-debonding reduces performance due to crack propagation. Indented and hot-rolled U-section connectors enhance interaction and minimize slip, while uniform distribution of shear connectors optimizes load capacity and stiffness. Lightweight concrete decreases slab weight without compromising performance, and high-performance materials such as ECC, SFRC, and UHPFRC improve strength and ductility. Numerical modeling, particularly finite element methods, and higher-order beam theories validate experimental results, providing accurate tools for predicting structural behavior under various loading and environmental conditions.
Today waste plastic bottles are spread widely throughout our world especially in Kurdistan, an autonomous region in Iraq. These waste products cause many environmental problems and at the same time some soils are weak and need reinforcement using cheap materials such as Polyethylene terephthalate (PET) waste plastic bottle. Use of waste plastic bottles as a reinforcement of soil is highly recommended to reduce the amounts of plastic waste, which creates a disposal problem. In this study an attempt was made to use plastic fibres produced from waste bottles to reinforce sandy soil. This can solve both environmental and geotechnical problems. In the research, the effect of plastic fibres content as well as fibre length on shear strength parameters (cohesion and internal friction) were experimentally predicted using the direct shear test method so as to improve bearing capacity of weak soils. The results showed that under low normal stress the inclusion of plastic fibres increased both angle of internal friction and cohesion; however, under high normal stress (greater than 100 kPa) the cohesion increased and the internal friction was roughly unchanged. Also, it was concluded in this study that the suitable amount of fibers that can be added to weak soils is 1% of dry weight of sand.
A study examined the ductility and toughness properties of beams made of reinforced concrete, including foamed, normal, and hybrid beams. Nine reinforced concrete beams were produced: three foamed concrete beams, three normal concrete beams, and three hybrid concrete beams. Each beam possessed identical rectangular cross-sectional dimensions of 1500 mm × 250 mm × 150 mm. The flexural parameters (ultimate load, ductility, deflection, and durability) were assessed for each type of concrete utilized. The study's results showed that the load-bearing capacity of hybrid concrete beams was comparable to that of normal concrete beams, whereas foamed concrete beams exhibited slight improvement in their ability to carry loads. The ductility of reinforced foamed concrete beams was lesser than that of normal concrete. For over-reinforced beams, the ductility of hybrid concrete beams showed a significant improvement of 61% compared to foamed beams and an even more significant increase of 91.7% compared to normal beams. Furthermore, the hybrid concrete beam with over-reinforcement had a flexural toughness of 18.7% greater than the normal concrete beam. Suggested that a hybrid section comprising conventional and foamed concrete be utilized to decrease ductility and improve stiffness.
ABSTRACTStudies in geotechnical engineering have the nonlinear behavior of soils. An experimental study was carried out on models of piled rafts, and four piles with a diameter of 25 mm and a length of (300, 400, and 500) mm were taken, with a raft of (180x180) mm, and compared with the piled-raft system of 180 × 180 raft and nine piles of 19 mm and 500 mm in diameter and length respectively. They were tested for raft resistance, number of piles, length, and diameter while maintaining the spacing between piles. Test results showed the raft performance improved by 76% when adding piles. The increase in the (L/D) ratio for variable (L) length leads to an increase in pile share of 87% for the groups (2×2). Also, pile share was increased by 10% with a decrease in the diameter of piles and an increase in the number of piles in the group. Therefore, the increment in each pile’s skin friction results in an increase in the bearing capacity of each pile.