Sharif Digital Repository

For applications such as videoconferencing, in which network resources are used for transmittingshared data, one may utilize multicasting so that resources are allocated in an efficient way. Due to the difficulties in implementing multicasting in the IP layer, designers tend to use the application layer of the OSI model to map an overlay network and implement the multicasting protocol in that layer, also known as Application Layer Multicasting (ALM). Besides the transfer of data, various concerns about the method such as application domain, group management, and routing mechanism are all handled by the ALM protocol. In this thesis, an ALMprotocol for multi-participant video conferencing in... 

Video signal has a major role in the transmission of visual information to a wide range of users in various applications. Video modeling and analysis have been of great interest in the video research community, due to their essential contribution to systematic improvements concerned in a wide range of video processing techniques. Parametric modeling and analysis of video provides appropriate means for processing the signal and mining necessary information for efficient representation of the signal. Video comparison, human action recognition, video retrieval, video abstraction, video transmission, video clustering are some of video processing applications that can get certain benefits from... 

Multiple distortion coding is a promising solution for video transmission over lossy channels. In MDC multiple descriptions of a source are generated which are independently decodable and mutually refinable. When all descriptions are available, the corresponding quality is called central quality; otherwise it is called side quality. Generally, there exist a trade-off between side and central quality in all MDC schemes. The MDC methods which provide better central-side quality trade-off are of more interest to the designers.In this thesis a new MDC scheme is introduced which has better trade-off between side and central quality. In other words, for the same central quality, it provides higher... 

Due to the expansion of Data Networks and the ubiquity of high speed Internet, new services especially multimedia services have become more popular. Video streaming is one such service, but video data are quite bulky and need to be compressed for transmission since the network has limited bandwidth. This compression is achieved through a video encoder, such as H.264, which is currently the most advanced video encoder. In addition, the network introduces lag in the form of packet loss, delay and jitter which adversely affect real-time video applications.
In this thesis, we try to answer the following question in the context of a video streaming application: what encoding parameters should... 

Bridges are among the crucial elements of transportation networks and play an important role in facilitating emergency relief efforts following earthquakes. For this reasons, they should have an appropriate performance in earthquakes; Thus, presentation of true design of bridges was necessary. Elastic design of bridges due to the earthquake is uneconomic; hence, during an earthquake, the codes permitted to structures go to their inelastic behavior domain but inelastic analysis of structures are noncommercial and the capability of detail modeling of the inelastic behavior of the material is still impossible. Therefore, designers use response modification factor to consider the inelastic... 

Numerous research is available in the literature regarding shear walls. These have considered parameters like wall cross-section, Reinforcement configuration, boundary elements, etc. In addition, seismic and wind loading behavior has been discussed. Currently, the software ETABS is used extensively in automatic design of shear walls, The programs design bases are investigated in this thesis in ragards to flexural, shear and boundary elements of shear walls under seismic loading. The attachment of wall elements to frame (column) elements is of particular interest in this study  

The application of composite systems has rapidly advanced in bridge and building construction. Shear connectors are the most basic parts of the composite systems.The connectors transfer the shear forces between the slab and the beam. They also prevent separation of the slab from the beam.
Therefore researchers have done widespread studies on the behavior of shear connectors and their load carrying capacity. Steel angles are one of the shear connectors that can be used incompositesystems. Only limited number ofstudies has investigated thebehavior of thistype of connector.
The purpose of this thesis is to investigate the behavior of angle shear connectors embedded in solid concrete... 

Lateral forces on structures are transferred to braces as tensile and compressive loads. These loads enter the beams and columns through the gusset plates. The gusset connections to the beams and columns must be such that they be able to pass the loads through themselves. So far, five analytical models have been proposed for this connection and only one of them is recommended by AISC. These models estimate the existing forces and moments on the connection. The analytical models are: model 1 (KISS), model 2 (2A-AISC), model 3 (Thornton), model 4 (Ricker) and model 5 (Richard). Among these models, only model 3 is recommended by AISC because the others are more conservative. It should be noted... 

Cable-stayed bridges are the most economical solution for spans ranging from about 200 to 1000 meters. They have become more popular in recent decades due to their efficiency and appearance. The need to understand their seismic beahvior is apparent and any improvement can be useful. The main purpose of this study is to determine the effect of using three lateral cable arrangement groups namely, cross system, pulley system and spatial lateral cable system with two transversally inclined cable planes on seismic performance of cable-stayed bridges. In this research, the seismic consequences of these arrangements with interactions of key parameters like, the main span length and deck to pylon... 

The shear lag phenomenon is one of the effective factors in determining the tensile capacity of tension members. In this phenomenon, there are various factors including the size and type of the cross-section, the type of connection, the length of connection, thickness of gusset plate, etc. are effective. The previous studies which are the basis of the specification equations, have been conducted on the cross-sections with bolted and riveted connections, while no study has been conducted to determine the effects of some of these factors yet. Using numerical methods, the present study investigates and compares each of the effective parameters on shear lag phenomenon on the single and double... 

The steel-concrete composite beams are increasingly used in bridge and building construction in recent years. A shear connection between the steel and concrete should be provided to effectively transfer the shear force and to make the two materials act as a single unit. The mechanical shear connectors provide this means. They are the essential component of any composite beam system. Many studies have been performed on shear connectors and many different steel shapes have been suggested for connectors. The steel studs and channels are the most popular code accepted connectors. However, economic considerations continue to motivate the development of new products.
Present knowledge of the... 

According to recent researches, angle-shape shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. This study investigates the effect of tilted angle on capacity and behavior of angle-shape shear connectors. In this study, we consider two different tilted angles. Push-out tests consisting of eight specimens made of reinforced concrete and different angle-shapes were conducted. Specimens have tilted anglesof 112.5 and 135 degrees between the angle leg and steel beam. Two different failure modes were observed consisting of concrete crushing-splitting and angle fracture. In addition, a nonlinear finite element model of these push-out... 

In this thesis the shear strength of pipe shear connector is investigated experimentally and numerically. The numerical analysis uses a nonlinear finite element model of the push-out specimen. The specimens consist of the pipe shear connector, steel beam, concrete slab and embedded steel rebar for concrete confinement. Eight push-out specimens are constructed with different pipe sizes and concrete strength. The results are used in a finite element parametric study to evaluate the strength of such connectors for all practical ranges of pipe size and concrete strength. It is shown that pipe connectors are more effective in transferring shear forces than angle and channel and stud connectors.... 

Tension-Only Concentrically Braced Frame (TOCBF) incorporates very slender bracing members, such as single angles, that are unable to dissipate much energy in compression due to their negligible buckling strength. Alternating tension yielding and elastic compression buckling of the bracing elements result in rapid strength degradation during strong motions, which translates into deteriorating pinched hysteresis loops. Based on this unfavorable behavior, it is not recommended to employ TOCBF system for medium and high-rise buildings located in active seismic areas. However, as a result of its inexpensivity and simplicity to design, the TOCBF system is used prevalently in low-rise steel... 

Purpose of this research is evaluation of response modification factor for integral abutment bridges in longitudinal direction in which substructure and superstructure both act as a unit system in resisting of lateral loads and no expansion joints are used in them. One of the most important challenges in design of IABs, is lack of response modification factor for their seismic design in longitudinal direction. Another challenge in these bridges, is modeling of soil-bridge structure interaction that affects not only abutment and piles’ seismic performance, but deck performance too. The other challenge is lack of adequate knowledge about their behavior and seismic performance which is of great... 

This study examines the safety and economics concerns in seismic design of column splices in steel concentrically braced frames. The importance of column splices in steel frames is that in structures with high columns, due to the limited length of existing profiles or economic issues, we have to use column splices. Error in the design and implementation of the column splice can affect the stability and overall performance of the structure. In this regard, the Seismic Provisions for Structural Steel Buildings has provided rules for designing column splices in the braced frame. The purpose of this research is to evaluate the criteria presented in the regulation and obtain seismic demand and... 

Regarding available structural codes, for designing of buildings with dual lateral force resisting system which includes special moment frames and ordinary concentrically braced frames, we need to determine seismic performance factors. Seismic performance factors embraces of response modification (R), over strength (Ω0) and displacement amplification (Cd) factors. The goal of this research is to evaluate aforementioned factors using the method presented with FEMA P-695. This method represents a reliable framework to assess the seismic performance factors of various kinds of lateral force resisting systems. In this approach, first, archetypes are designed with assuming certain values for...