Articles in This Issue
Abstract
ABSTRACT: In this study an attempt is made to develop a method of analysis dealing with a multi-layer composite beam, for linear material and shear connector behavior in which the slip (horizontal displacement) and uplift force (vertical displacement) are taken into consideration. The analysis is based on a approach presented by Roberts[1], which takes into consideration horizontal and vertical displacement in interfaces. The analysis led to a set of eight differential equations contains derivatives of the fourth and third order. A program based on the present analysis is built. Series of three push-out tests were carried out to investigate the capacity of shear stiffness for connectors. From these tests, load-slip curves were obtained. Also, series of multi-layer composite simply supported beams were tested. Each one consists of three layers in different material properties and dimensions. A comparison between the experimental values and numerical analysis is carried out. Close agreement is obtained with experimental values for different materials, layers thickness and shear stiffness.
Abstract
This research includes a study of the behavior of beams made from No-fine concrete using 10 maximum size of aggregate and improved by SBR polymer. From test results, the effect of addition of polymer to concrete leads to improved compressive and flexural strengths, The beams improved by polymer failed under loads more than the beams which were made from reference concrete. The percentage increases in compressive strength for No-fines polymer concrete compared with reference concrete were (41%, 58, 38%) for ages (3,7,28) days respectively
Abstract
Concrete is by far the most widely used construction material now today. Foamed concrete is light building material with good strength as well as low thermal conductivity and easy workability; it is produced by either Mix Foam Method or Preformed Foam Method. Ultrasonic Pulse Velocity(UPV) is a non destructive technique involve measuring the speed of sound through concrete in order to predict concrete strength and to detect the presence of cracking, voids, decay and other damages. This research includes three main experimental stages:- The first stage includes the production of foamed concrete and it was divided into two parts, the first part, mixing design(determination the proportions of the raw materials) was presented in the second part, the mixing procedure has been illustrated. The second stage includes preparation of samples,(i.e. molding, finishing surface, removal from molds, and curing). The third stage includes several teste to estimate properties the final product and factors influencing them, these properties include density, compressive strength, and the ultrasonic pulse velocity. From the experimental work and at the same test's age, the compressive strength and the ultrasonic pulse velocity for foamed concrete with 800 kg/m3 density were respectively (2.38 MPa,1.56 km/s)and the compressive strength and the ultrasonic pulse velocity for foamed concrete with 1200 kg/m3 density were respectively (3.7 MPa,1.96 km/s) while it were (7.8 MPa and 2.12 km/s) for foamed concrete with 1600 kg/m3 density
Abstract
ABSTRACT: Many of researchers study the uses of chopped worn-out tires as a replacement material to production special types of concrete. In presented work, the worn-out tires were used as fibers which have dimensions of 1×1×3 cm. The fibers used as a partial replacement from volume of coarse aggregate. Two mixes of fiber worn-out tires (F.W.T.) concrete in addition to reference mix were selected, using Partial Replacement Ratio (PRR) of 20% and 30%. The tests which were used in this study were: compressive strength, splitting tensile strength and flexural strength. It was found that incorporating of F.W.T. in concrete effected negatively on most properties of concrete, for example the percentage decreases in compressive strength relative to reference mix at 28 day were 20% and 27.3% for concrete with 20% and 30% F.W.T. by volume of coarse aggregate respectively. However, it gave good indicator to be utilized as a new construction material in many applications.
Abstract
ABSTRACT:The resistance of concrete to sulfate attack is considered as one of the important factors for concrete durability.The effect of SBR polymer on sulfate resistance of concrete is investigated. Both internal and external sulfate attack are considered.Internal sulfate attack was made by adding gypsum to raise the sulfate content of sand to that of Ramadi city soil (2.17%), while the external sulfate attack was made by adding chemical materials (MgSO4.7H2O, Na2SO4, CaCl2.2H2O, NaCl) to tap water to convert it into water similar to groundwater of Ramadi city.The laboratory tests were compressive and flexural strength, modulus of elasticity, slump, ultra-sound velocity and total percentage of sulfate after exposing to attack for different ages. It was found that the compressive strength of reinforced normal concrete (RNC) for ages (7,28,90,180) days respectively were (20,28,11.166,7) MPa, the compressive strength of polymer Portland cement concrete( PPCC) with polymer/cement ratio( P/C)=5% (PPCC5) were (21.83,32.666,12.766,8.733) MPa and for PPCC with (P/C)=10% were (24.166,35.866,15.533,11.366)MPa.While the flexural strength of RNC for different ages (7,28,90,180) respectively were (3.953,3.7,1.68,11.305) MPa, the flexural strength of PPCC5 were (4.05,5.025,2.13,1.605) MPa and for PPCC10 were (4.43,6.375,2.43,1.92) MPa.The static modulus of elasticity at age (28) days for (RNC) was (37.4) GPa , for PPCC5 was (9.7) GPa and for PPCC10 was (13.63) GPa.Slump for (RNC) was (155) mm, for PPCC5 was (142) mm and for PPCC10 was (75) mm.T he ultra-sound velocity of RNC for ages (7,28,90,180) respectively were (4.2,4.445,4.203,4.53) Km/sec , for PPCC5 were (4.36,4.646,4.53,4.176) Km/sec and for PPCC10 were (4.437,4.837,4.656,4.52) Km/sec.It was found that (PPCC10) has higher resistance to sulfate attack than (PPCC5) and (NRC). The thesis refers to necessity of polymer to improve the resistance of concrete to sulfate attack although if the sulfate percentage raise to more than (0.5) % which represents the maximum limit of sulfate percentage in I.O.S No. 45-1970.
Abstract
ABSTRACT:The gypseous soils are distributed in many regions in Iraq and other countries. Therefore, it is necessary to study the behavior of such soils due to the large damages that affects the structures founded and constructed in or on it.This research is concerned with studying the effect of leaching soil process on the stability of an embankment erected on foundation gypseous soil. The finite element method is adopted in this research. The analyses carried out using a nonlinear, increment, and stress-dependent finite element computer program. The hyperbolic stress-strain parameters used in the finite element analyses are estimated by the data collected from triaxial compression tests of some researchers. The analysis of the embankment problem carried out, shows that the leaching process for foundation gypseous soil increases the displacements and deformations of the embankment and its foundation. Finally, this research necessitate the success using of the finite element method in design and analyses of the important structures and buildings erected on gypseous soils that may expose to the effect of leaching process. This means that there is possibility to predicate the behavior of structure by a powerful means to establish the suitable solutions for any problems that may be occurred as a result of the present gypseous soil.
Abstract
A BSTRACT: Leaching effects on permeability and compressibility characteristics of undisturbed sandy gypseous soil were investigated in this study. Time, stress level, strain, leachate condition and flow velocity were considered. The loading, leaching and permeability measurements were carried out utilizing the constant head pereameter with special modifications. Test results show that salt leaching and thereby leaching strain is a time dependent process. Also as leaching strain continued coefficient of permeability decreases.
Abstract
ABSTRACT The rapid development in computer Technology and in the instruments used in field measurements helped to overcome the problem of accuracy improvement and accuracy assessment of high precision networks. This paper deals with solution of the use of mixed observation systems, it is an essential requirement to improve the accuracy. The study of the magnitude of the correlation of error is of great importance in the efficient performance of planning, measuring and adjusting operation of survey. This paper concludes that the use of weights for mixed observation constitutes an important part in the improvement of the accuracy of a micronetwork. Weights which are determined for mixed observation after the assessment of the standard error of unit weight for each kind of observation .