This paper investigates the resultant strength and ductility behavior when randomly distributed palm fibers are used to reinforce silty-sand soils. The composite soils were tested under laboratory conditions and examined for unconfined compression strength (UCS), California Bearing Ratio (CBR) and compaction test. The results indicated that; the maximum and residual strengths, orientation of surface failures, ductility and the stress-strain relationship of the specimens were substantially affected by the inclusion of palm fibers. A significant result was the determination that the sliding failure strength controlled the failure of the specimens rather than the rupture failure strength. Overall it was found that reinforced soil using palm fibers as the primary reinforcement are beneficial engineering materials and could potentially be used more often, though additional field use and testing should be carried out. Given the current concern over the environment and greenhouse gas emissions, strengthening soil through the use of natural materials (in this case palm fibers) and the promotion of the cultivation of palm groves is one way that engineers and designers can contribute to a greener earth. Add to this the fact that the date palm is one of the most cultivated tree crops in the world with a worldwide distribution of around 100 million palms distributed in 30 countries including the Middle East, Asia, Africa, North America, Mediterranean countries and Australia in a bountiful resource that is available in many places where high technology engineering practices are either not available or too expensive. The use of the date palm for soil reinforcement means that in many areas of the world there is a readily available, effective local source of material for road foundation construction.
In this paper a mathematical model for the combined system of framed tube, shear core and belt truss is developed with the objective of determining the optimum location of belt truss along the height of the building. The effect of belt truss and shear core on a framed tube is considered as a concentrated moment at the belt truss location. This concentrated moment acts in a direction opposite to rotation due to lateral loads. The axial deformation functions for web and fl ange of the frames are considered to be quadratic and cubic functions, respectively; developing their stress relations and minimizing the total potential energy of the structure with respect to the lateral defl ection (u), rotation of the plane section (f) and unknown coeffi cients of shear lag (a 1 , a 2 , b 1 and b 2 ), the mathematical model is developed. This model yields the displacement, axial stress distribution and bending stiffness as a function of the height of the combined system. The range application and validity of the proposed model is demonstrated by several numerical examples (30-, 40-and 50-storey buildings). The effects of belt truss position on lateral displacement and stress distribution are investigated and the optimum location for belt truss is obtained. basic form, the system consists of closely spaced exterior columns along the periphery interconnected by deep spandrel beams at each fl oor. This produces a system of rigidly connected jointed orthogonal frame panels forming a rectangular tube, which acts as a cantilevered hollow box according to classical beam theory.A relatively new concept that has evolved within the past two decades is the technique of using a belt truss on a braced core combined with exterior columns. In this system, columns are tied to the belt trusses. Therefore, in addition to the traditional function of supporting gravity loads, the columns restrain the lateral movement of the building. When the building is subjected to lateral forces, tie-down action of the belt truss restrains bending of the shear core by introducing a point of infl ection in its defl ection curve. This reversal in curvature reduces the lateral movement at the top. The belt trusses function as horizontal fascia stiffeners and engage the exterior columns, which are not directly connected to the outrigger belt truss. If a building is to have one or more fl oors devoted to mechanical equipment, rather than lease space, large belt or outrigger trusses can be placed in the perimeter, one storey in height (
In this paper, on the basis of the D'Alembert's principle, approximate formulas for dynamic response of tubular tall building structures are presented. Using D'Alembert's principle and applying the compatibility conditions on deformation of the tubes, the governing dynamic equation of the tubular structure's motion is derived. Then, natural boundary conditions of the parallel cantilevered flexural-shear beams are derived, and by using Rayleigh-Ritz method, value problem is solved, and trivial and nontrivial solutions are derived, which can be used for calculating natural frequencies and mode shapes of tubular structures. By solving numerically the frequency equation, a design chart and graph are given for the first five nondimensional natural frequencies of tubular tall buildings. The proposed mathematical model gives dynamic characteristics and provides a simple, efficient and reasonably accurate algorithm for free vibration studies that are needed to be quick at the preliminary design stages of tall buildings with tubular systems.
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