Digital Repository for faculty of Engineering

Abstract

Steel joints are the main part a steel structure. The steel members come together in a joint, to where the load action will be transferred between them.These members are with different section properties, may be joined with different type of connections welds, bolts or rivets. The level of fixity is also important which varies from flexible, semi-rigid to fixed. There is also an important factor of joint behavior, the type of loading (tension, shear, bending and torsion). For these the mentioned different factors that affects the behavior of a joint very complicated to demonstrate exactly.The design procedure according to the well known specification is generally based on experimental studies.The present study tries to throw light on some factors affecting the strength consideration for designing beam to columnconnection because of its importance in steel structures from point of view of uses.
علي عبدالله الجعط (2008)

Abstract

Pouring of concrete underwater is necessary in the implementation of most in-shore, and off-shore structures. The pouring of underwater concrete is considered as a challenge for engineers, even during the design stage or during implementation and supervision. This is due to the fact that many precautions must be taken for the success of casting process. The most important precaution is to protect the fresh concrete during the casting process from the water to avoid the risk of washout of cement past and segregation of aggregates. Concrete can be placed underwater successfully though good design of concrete mix, and through choosing the most suitable method for placing of concrete. There are new techniques for underwater concreting such as grouted aggregate which is known as two-stage concrete (TSC) method which, as the name implies, consists of filling a form work with the coarse aggregate and then injecting the grout to fill the voids through pumping tubes extended to the bottom of the form. The main objective of the thesis is to present the capability of pouring the concrete underwater by using (TSC) method. A laboratory model was prepared and visually investigated and tested by extracting core samples, performing compressive test, tensile test and using ultrasonic pulse velocity test. From the obtained results it has been observed that, it is possible to pour concrete underwater by using two stage concrete in successful way, and it is recommended to develop this research by using different water cement ratios and cement sand ratios to get the optimum mix design and also, different types of aggregates which are available in local quarries.
منال فاروق النجار (2010)

Abstract

Behavior of constant thickness circular plates under axisymmetric uniform loading and for different edge boundary conditions may be obtained analytically, but for the case of variable thickness and transverse shear effect is usually difficult to follow analytically. Since the numerical analysis has become an essential tool in engineering mechanics, where the use of numerical methods enables the engineer to expand his or her ability to solve practical design problems, where the engineer may now treat real shapes as distinct from the somewhat limited variety of shapes amenable to simple analytic solution. That is why developing an appropriate numerical analysis becomes a more suited procedure to solve such problems. The standard stiffness procedure of finite element method may encounter some difficulty in formulation when dealing with both cases of variable thickness and transverse shear effect. The usually followed procedure is to utilize ring elements of constant thickness and increase the number of elements to reach an accurate solution. Mixed finite element formulation utilizing curved ring element with linearly varying thickness as well as considering the shear effect has proved to be successful to obtain accurate results for shells of revolution with small number of elements, due to the fact that the mixed formulation allows for nodal values in the form of global displacement components (ur, uz) and bending moment (Mr, M) as field variables, where second order polynomials may be used allowing for shear deformation effect to be considered as a function of moments and does not require higher order polynomials.
ايناس عبدالمولي المصراتي (2009)

Abstract

An atomic bomb or any normal bomb may be exploded in the air or at or near the surface of the earth. The medium in which the bomb is burst determines to a large extent the relative magnitudes of the various damaging effects. The detonation of an atomic weapon releases a largeamount of energy in a fraction of a second. During this time the bombcomponents are volatilized into a sphere of hot compressed gas at a temperature of millions of degrees and a pressure of the order of hundredsof thousands of atmospheres. This phenomenon is characterized by an instantaneous and very rapid rise to a maximum pressure followed by a decline to sub-atmospheric pressure and then a gradual return to normal pressure. In this thesis the definitions and types of explosives and explosions are studied, effects of the different types of explosions are explained, transition of atomic air blast pressure from center of explosion to buildings are presented, determination of atomic air blast loading on buildings is studied as well.
أحمد عبدالرحيم سليمان (2008)

Abstract

Applications of cooperative multicast communication techniques for emerging broadband multimedia services, such as Internet Protocol TV (IPTV), over WiMAX air interface have an important and attractive feature of reducing the network resource consumption, by broadcasting the data once to multiple users (e.g., TV channel group members) simultaneously independently of their number, using a common shared downlink channel. But users distributed around the cell face different channel conditions due to fading, user location, mobility, and other related characteristics. Several schemes were reported in the literature that attempt to introduce cooperative multicasting reliably and efficiently, some of which utilize subscribers with good-channel as relay agents (RA) to provide coverage for subscribers with bad-channel but fail to consider the huge amount of energy consumed in the process. In this thesis, we propose energy-efficient cooperative multicasting schemes by properly selecting RAs based on their location, channel condition and coverage. By exploiting the channel state information (CSI) and the location based service (LBS) techniques, protocol based on nearest neighbor, transmission distance and subscriber-subscriber interlink instantaneous CSI were proposed and implemented in order to achieve much improvement in the system performance. The number of RAs was varied in accordance to channel conditions and treated on a frame-per-frame basis. This approach considerably reduces the amount of energy consumed as proven by analysis and simulation models, providing a lower cost coverage solution with no dereliction in achieving high throughput for all group members.
سارة مفتاح الربيعي (2010)

Abstract

As user applications continue to drive network growth and evolution, demand to support different types of traffic is also increasing. Different types of applications with differing network requirements create a need for administrative policies mandating how individual applications are to be treated by the network. Network traffic from business-critical applications must be protected from other types of traffic. Requests from business-critical and delay-sensitive applications must be serviced with priority. The employment and enforcement of quality of service (QoS) policies within a network play an essential role in enabling network administrators and architects to meet networked application demands. QoS is a crucial element of any administrative policy that mandates how to handle application traffic on a network. Networks must provide secure, predictable, measurable, and, sometimes, guaranteed services. Network administrators and architects can better achieve this performance from network by managing delay, delay variation (Jitter), bandwidth provisioning, and packet loss parameters with quality of service (QoS) techniques. As the concept of converged network is being widely used today where all types of traffic are required to be sent and transmitted on the same wide area network (WAN) link. Hence different applications need to be differentiated and treated according to their sensitivity to business. QoS is the suitable answer and method to solve this issue and make sure that each traffic type will be treated differently using various mechanisms of QoS. In this research different types of traffic that represent different applications are generated in WAN and local area network (LAN) where various techniques of QoS are implemented. Network performance is indicated by capturing different parameters on real time such as, delay, jitter, packet loss, and bandwidth. Based on results obtained, a set of recommendations is concluded for each QoS mechanism highlighting the suitable traffic type for this technique to be used for along with appropriate network locations for this technique to be implemented.
نسرين عادل بن لطيف (2011)

Abstract

Finite element method is used to analyze the flexural vibrations of beams using Galerkin approach for both Bernoulli and Timoshenko theories.The methodology is started by integral formulation of the partial differential equations for the physical problem, and then the element stiffness, mass matrices and load vector have been obtained. Free vibrations analysis is used for the predictions of natural frequencies and mode shapes for, first flexural vibrations by classical theory, second flexural vibrations by including the effect of shear deformation and rotary inertia in the analysis. Finally, the axial and torsional vibrations, in addition to flexural vibrations, in both transverse and lateral directions together have been taken into consideration, thus the finite element equations and the element stiffness, mass, and load vector matrices have been developed for axial, torsional, and flexural vibration together.The natural frequencies are tabulated for all classical types of classical boundary conditions. The mode shapes corresponding to the natural frequencies were presented graphically. The exact solutions and results obtained by other standard methods are used for comparison with the current numerical results. The forced vibrations were introduced for the analysis of dynamic behavior of beams under several types of loading. The finite element code with Taylor series method and mode superposition for the Bernoulli and Timoshenko beams has been carried out. Numerical results are presented in the form of comparisons between the Bernoulli and Timoshenko and demonstrate how the effect of shear deformation reduced the displacement response with increasing the excitation frequency, excitation amplitude, and length of the beam. Comparisons are made with the exact and existing classical methods and checked with those obtained IVusing standard methods (ANSYS package) and are found in good agreement. It should be noted that all models of beams have always convergence to the correct solution.
أمنة احمد القلفاط (2009)

Abstract

Fire is one of the greatest risks for every building and particularly for high-rise buildings. Usually, a building fire causes not only hazard to the occupants in a floor, but also a possible threat to the occupants in other floors and in particular to those located at upper storeys, with rising temperature and with killer smoke. Fire simulation can be performed using software packages designed for such a task. The fire simulation can often include aspects of hazard identification, fire growth and smoke movement, egress assessment, structural fire performance, sprinkler and fire detection system design, and smoke management system specification.The present thesis examines the up-to-date technologies available within the context of fire engineering simulation. This work gives an overview of available software packages that are used today in fire engineering simulation. It presents the procedure of fire simulation inside a high-rise building by using an advanced computer program named the Consolidated Model of Fire Growth and Smoke Transport ) CFAST for short. The CFAST program simulates fire action by calculating fire gases, the evolving distribution of smoke and temperature throughout a building during fire. This computer program is based on solving a set of equations that predict the state variables such as pressure and temperature. These equations are derived from the conservation equations for energy mass and the ideal gas law. It is important to know that the resulting errors, which might result, does not come from these equations, but rather they come from numerical analysis representation of the equations or from the simplifying assumption.
خالد عبد الونيس السكوري (2010)