Guidelines for Shear Strengthening of Beams Using Carbon Fibre-Reinforced Polymer (FRP) Plates

The fundamental aim of this work is to give clear guidelines for the process of strengthening reinforced concrete beams using FRP materials. Types and methods of FRP construction are described in general. FRP properties and their effect on strengthening are illustrated. Experimental results obtained from an earlier study are utilized in this research to present a reasonable model for strengthening. The experiments investigated the shear behaviour of reinforced concrete beams strengthened by the attachment of different configurations and quantities of CFRP using epoxy adhesives. Two types of CFRP materials were used. These are pultruded and prepreg materials. A general comparison between results is carried out showing the best configuration for strengthening. In this paper, it is clearly stated that moderate surface treatment for concrete before FRP bonding is sufficient to allow FRP to do its job in a proper way. In general, it is adequate to remove all laitance and loose material by hand or machine abrading, followed by degreasing with a detergent and rinsing clean

Design and implementation of car rental system

When someone wants to rent a car, the customer will usually think twice about the company from which they want to rent. The decision will be based on factors such as good rates, quality and customer service. The service the company representative offers the client should be fast, clear and accurate. This goal cannot be achieved without an informative system that will enable the customer representative to answer the various questions the client might have

Performance Modelling and Evaluation of Active Queue Management Techniques in Communication Networks. The development and performance evaluation of some new active queue management methods for internet congestion control based on fuzzy logic and random early detection using discrete-time queueing analysis and simulation.

Since the field of computer networks has rapidly grown in the last two decades, congestion control of traffic loads within networks has become a high priority. Congestion occurs in network routers when the number of incoming packets exceeds the available network resources, such as buffer space and bandwidth allocation. This may result in a poor network performance with reference to average packet queueing delay, packet loss rate and throughput. To enhance the performance when the network becomes congested, several different active queue management (AQM) methods have been proposed and some of these are discussed in this thesis. Specifically, these AQM methods are surveyed in detail and their strengths and limitations are highlighted. A comparison is conducted between five known AQM methods, Random Early Detection (RED), Gentle Random Early Detection (GRED), Adaptive Random Early Detection (ARED), Dynamic Random Early Drop (DRED) and BLUE, based on several performance measures, including mean queue length, throughput, average queueing delay, overflow packet loss probability, packet dropping probability and the total of overflow loss and dropping probabilities for packets, with the aim of identifying which AQM method gives the most satisfactory results of the performance measures. This thesis presents a new AQM approach based on the RED algorithm that determines and controls the congested router buffers in an early stage. This approach is called Dynamic RED (REDD), which stabilises the average queue length between minimum and maximum threshold positions at a certain level called the target level to prevent building up the queues in the router buffers. A comparison is made between the proposed REDD, RED and ARED approaches regarding the above performance measures. Moreover, three methods based on RED and fuzzy logic are proposed to control the congested router buffers incipiently. These methods are named REDD1, REDD2, and REDD3 and their performances are also compared with RED using the above performance measures to identify which method achieves the most satisfactory results. Furthermore, a set of discrete-time queue analytical models are developed based on the following approaches: RED, GRED, DRED and BLUE, to detect the congestion at router buffers in an early stage. The proposed analytical models use the instantaneous queue length as a congestion measure to capture short term changes in the input and prevent packet loss due to overflow. The proposed analytical models are experimentally compared with their corresponding AQM simulations with reference to the above performance measures to identify which approach gives the most satisfactory results. The simulations for RED, GRED, ARED, DRED, BLUE, REDD, REDD1, REDD2 and REDD3 are run ten times, each time with a change of seed and the results of each run are used to obtain mean values, variance, standard deviation and 95% confidence intervals. The performance measures are calculated based on data collected only after the system has reached a steady state. After extensive experimentation, the results show that the proposed REDD, REDD1, REDD2 and REDD3 algorithms and some of the proposed analytical models such as DRED-Alpha, RED and GRED models offer somewhat better results of mean queue length and average queueing delay than these achieved by RED and its variants when the values of packet arrival probability are greater than the value of packet departure probability, i.e. in a congestion situation. This suggests that when traffic is largely of a non bursty nature, instantaneous queue length might be a better congestion measure to use rather than the average queue length as in the more traditional models

Effect of Jordanian Steel Blast Furnace Slag on Asphalt Concrete Hot Mixes

Significant quantities of slag are generated as waste materials or by-product from steel industries. They usually contain considerable quantities of metals. In this study, steel slag obtained from a steel factory in Jordan was used in Asphalt Concrete Hot Mixes (ACHM). Marshall specimens were prepared with 100% lime stone dense graded aggregates at 4.5, 5, 5.5 and 6% bitumen contents by weight of aggregate to serve as control specimens. Another set of Marshall specimens with 100% Steel Slag Aggregates (SSA) and another set with a combination of limestone and (SSA) were prepared using the same grading and bitumen contents. Test results showed a reduction in the Optimum Bitumen Content (OBC) and an increase in density and stability values for specimens prepared with 100% (SSA). A decrease in the flow, Percentage of air voids (Pav), and Voids in Mineral Aggregates (VMA) values - but in compliance with the recommended values by the Asphalt Institute- was observed in specimens prepared with 100% (SSA)

Steady State Response and Stability of an Elastically Restrained Tapered Beam

An analytical method for the study of the nonlinear forced vibrations and their stabilities of an elastically restrained tapered cantilever beam due to a direct periodic excitation is developed. The method of harmonic balance is used to study the steady state frequency response of the beam system for different values of physical parameters such as the root translational and rotational stiffness and the beam taper ratio. Results are presented for the first three modes of vibration. The stability of the frequency response for some selected values of the physical parameters is investigated, i.e. the regions on the frequency response curves at which the solution may bifurcate and then culminate into chaos. The qualitative features of the solutions are studied and identified using phase plane, Poincare maps and Fast Fourier Transform. The results are presented, discussed and conclusions on the elastically restrained tapered beam nonlinear dynamics are drawn

Properties of tube and fitting scaffold connections under cyclical loads

The standard design procedure for tube and fitting connections assumes that the connections are only subjected to non-cyclical loads. This paper presents the results of experimental tests and theoretical calculations of the moment-rotation capacities of three common connections – sleeve couplers, swivel couplers and right-angled couplers. The results show that under a cyclic side load, such as that occurring by wind loading, looseness affects the capacity of the connections. For all three types of coupler looseness is shown to be relatively high which will reduce the stiffness of the connection under side loads. For sleeve couplers the effects of axial load in the tubes also affects the coupler stiffness and the maximum bending capacity of the joint. This implies that the common European code BS EN 74-1 for the connection should be changed to consider the loss in stiffness and maximum side load capacity under axial loads and looseness which are ignored in the standard. The standard assumption for right-angled and swivel couplers is that the connection can be assumed to be rigid about an axis normal to the plane containing the two tubes being joined. This is shown to be incorrect as the connections are shown to have stiffnesses about this axis which is of a similar order to the stiffnesses about the other axes