Many forms of shells are available for use as foundations. Then frustum of a cone in the upright position can serve as footing for columns or raft for structure such as chimneys. Reactive Powder Concrete (RPC) is an ultra-high strength, low porosity material with high cement and silica fume contents and steel fibers. RPC uses low water-binder ratios and new generation superplasticizers with eliminating the coarse aggregates, all optimized particle size less than 600 micrometers. RPC can be readily used in a wide variety of structural applications, including situations where the concrete is required to carry substantial tensile stresses due to shear and bursting forces. The present study is devoted to study the behavior of RPC shell foundations. A complete load-frame assembly was designed and fabricated for experimental work. Five values of steel fiber volume fractions of 0, 0.5%, 1.0%, 1.5%, and 2.0% were used in casting the shells in order to study the effect of steel fiber content on the shear strength. Three percentages of silica fume were used to obtain different grades of concrete to study the effect of concrete compressive strength on the shear strength. The percentages of silica fume are 5%, 10% and 15% by mass of cementations materials. Results of loading tests conducted on wire – reinforced small – concrete models of conical foundations under loads established substantially high values of load factors involved in the traditional design of the conical foundations by membrane theory. The inclusion of steel fibers in RPC footings results in enhanced stiffness, reduced crack width and reduced rate of crack propagation. At failure, the RPC footings behave in a ductile manner as compared with the nonfibrous footing and most of the steel fibers pulled out of the cement matrix. The inclusion of steel fibers in RPC footings results in a significant enhanced ductility and absorbed energy. For RPC footings with the same steel fiber content, the footings with ring beam have stiffness greater than footings without ring beam. The failure of the conical shell footing is found to start with tension to extend upwards along the generator with its width decreasing with edge. As the applied load increases, the value of circumferential tension increases bending in the radial vertical plane increase near the pedestal base at top where there is complete fixity.
Strengthening and upgrading the performance reinforced concrete curved structures for functional purpose as well as for conversation of architectural aesthetic aspect is the main concern for engineers. In the present study, four full-scale experimental Curved Reinforced Concrete (CRC) beams conducted. The cross-section of all CRC beams was T-section. The parametric studies are carried out to investigate the effect of time of casting segmental layers (web and flange) and the compressive strength of concrete on the structural behavior of such structures. Three values of compressive strength of concrete used in this study, these are (25, 50, 75 MPa). The control specimen casting as one unit with the compressive strength of concrete was 25 MPa. The present outcomes showed that the increase in the compressive strength of concrete up to 75 MPa of the flange zone plays a significant role in raising the ultimate capacity by 22.86% and reducing the deflection by 61.43% in the quarter span as compared with control specimen. Additionally, the trend and distribution of cracks, mode of failure, and strain response of CRC specimens are briefly discussed in this study.
This study is intended to deal with twelve reinforced concrete beams cast into three categories of Concrete type with Normal, Self Compacted and High Strength Concrete. Two beams of each category have steel fibers and the other used as reference one. Test results are presented in graphs also listed in Tables. Test results indicated that, category of High Strength Concrete beams is the strongest category depending onto the ultimate load capacity and the highest stiffness, followed by the Self Compacted Concrete beams category then the Normal Strength Concrete beams category comes later, with an increase of about (3.6-5.3%). Increasing steel fibers contained in concrete beam section will rise the ultimate load capacity of fiberious concrete beam, an increase of about 36% has been obtained. Increasing steel fiber contained with increasing concrete compressive strength of the fiberious concrete section will help increasing the ultimate load capacity of beam, an increase of about 166% has been noted. Due to continuing in rising the steel fibers contained in fiberious concrete section, the rate of development of ultimate load capacity of the fiberious concrete beam will decrease.
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