The Boumerdes 2003 earthquake which has devastated a large part of the north of Algeria has raised questions about the adequacy of framed structures to resist strong motions, since many buildings suffered great damage or collapsed. To evaluate the performance of framed buildings under future expected earthquakes, a non linear static pushover analysis has been conducted. To achieve this objective, three framed buildings with 5, 8 and 12 stories respectively were analyzed. The results obtained from this study show that properly designed frames will perform well under seismic loads.

An experimental study is conducted on three ½ scales, single-story, single-bay, frame specimens. The first specimen was a reinforced concrete frame with solid-brick infill. The second specimen was a reinforced concrete frame with hollow clay perforated-brick infill. The last specimen was a reinforced concrete frame without any infill. These three specimens were tested by pseudostatic method. Different response parameters are investigated and results are compared with those resulted from analytical approach. The results of the experimental and analytical studies indicate that use of masonry infill increases the lateral stiffness of the reinforced concrete frame. The increase in the stiffness is almost the same for both types of infill considered in this study. Use of masonry infill also increases the ultimate strength of the reinforced concrete frame. However, the strength of the frame in the case of hollow clay-block decays much faster in compare with frame infilled with solid clay-bricks because of a faster rate of failure in hollow blocks. Using masonry infill increases the energy dissipation capability of the reinforced concrete frame. In the case of frame with solid clay-bricks infill, a much more uniform distribution of damages is observed in columns. Comparisons with analytical approach show that analytical method provides a good estimation of initial stiffness of solid-brick infill but its estimations of initial stiffness of perforated-brick infill and inelastic response of both types of masonry infill frames are not in good agreement with the experimental results.

Historically regular buildings perform better in earthquake than irregular buildings which are prone to damage during earthquake. But due to functional and architectural requirements irregularity in structure is unavoidable. While trying to understand the seismic response of irregular structure many researches attempt by using nonlinear static pushover analysis. Performance point in pushover analysis may evaluate the capacity and demand of overall structure. But the response of individual member in the structure with reference to its capacity and the demand that exist in the member needs in depth study. This paper reports results of such study on three different structures. The members so identified are modified so that the structure not only satisfies performance point requirement but also at local level all the members have enough capacity that far exceeds the demand requirement.

The strength and ductility of concrete are improved under multi-axial compressive stress due to confinement effect. Some effective parameters for concrete confinement are longitudinal and transverse steel reinforcement. Some stress-strain relations for confined concrete with steel reinforcement have been proposed by different researchers. In this paper, various stress strain models with considering the steel confinement effect are reviewed briefly and used for simulating the lateral behavior of on an experimental reinforced concrete frame. Envelope curves, tension damage, yielding patterns, ductility ratio and energy absorption of the frames are discussed. Results from the finite element analysis compared with experimental findings show that in the case of lateral load and displacement, the analytical models which were presented by Fafitis et al. and Muguruma et al. had more compatibility with experimental results and the difference is less than 10%. Energy absorption of the model which was proposed by Khaje Samani & Attard had the most compatibility with experimental results and difference is about 1%.

Elevated water tanks supported by the reinforced concrete (RC) Staging are classified as inverted pendulum structures. These are considered as structures of high post-earthquake importance and should remain functional after the seismic events. National codes of various countries recommend Force-Based Design (FBD) procedure for water tank staging, which does not ensure nonlinear performance level for a given hazard. Therefore, it becomes necessary to design these structures with a performance-based design approach like Direct Displacement-Based Design (DDBD). Many design engineers consider that the behavior of frame staging of the elevated water tank is similar to the building's frame and generally adopt the same design principles for both types of structures. However, the seismic behavior of the building frame is significantly different from frame staging due to the absence of diaphragm action at the bracing level and concentrated mass at the top level only. Therefore, it may not be rational to utilize the same DDBD procedure of the building's frame for the design of frame staging of the elevated water tanks. The present study proposes some modification in existing DDBD procedure (used for the design of frame building) based on the nonlinear time history analysis of twenty meters high RC frame staging with four different configurations. The modifications are proposed in terms of inelastic displacement profile, design displacement, effective height, and effective mass calculation. Further, the performance of the same RC frame staging designed using the proposed DDBD procedure has been assessed using nonlinear static and dynamic analyses to verify the suitability of proposed modifications.

The seismic strengthening methods are very important in earthquake-prone countries. Steel divergent bracing with replaceable link beam tied in steel frame and embedded in a concrete frame is a new method for a concrete frame strengthening. That is low cost and easy repairable after an earthquake.In this article six concrete frame strengthening methods have been investigated, including X-bracing, reverse chevron bracing, divergent bracing with concrete link beam, divergent bracing with steel link beam connected to steel columns in the steel frame, divergent bracing with steel link beam connected to the steel frame and with steel columns between those two, divergent bracing with steel link beam connected to the steel frame. All strengthening models are attached to concrete frames by a steel frame surrounding them . These models are investigated by ETABS and PERFORM-3D softwares. In concrete frame strengthed by steel divergent bracing with steel link beam, the base shear is decreased about 20%, steel consumption decreased to 40% in 6-story, and 15% in 14- and 20-story compared to X-bracing, and the existing to allowable stress ratio decreased to 50% in 6-story, to 40% in14-story and 35% in 20-story. As the structure's height is increased, the interaction between the frame and the brace, and the lateral force in the frames increased. Nonlinear static and dynamic analysis have shown more elastic hardness, ductility, behavior coefficient, and base shear in strengthed concrete frame with divergent bracing with steel link beam connected to the steel frame model than others.

Reinforced concrete frame buildings designed before 1970, often have inadequate lateral resistance and must be assessed and upgraded. These frames in addition to low lateral resistance were poorly detailed. Their common characteristics are: 1- low reinforcement ratio in the columns, 2-discontinuous positive monet reinforcement in the beam-column joints, 3- little or no confinement in joint core, 4- lap splices in columns are typically located in the potential honge region near by floor levels. Six reinforced concrete frames by three bays (three frames at three stories and other three frames at five stories) with overall span length 13.0 m designed and analyzed under Tabas, Naghan and Manjil earthquakes. Results show high lateral displacement and sever damage in columns. Therefore these frames are not able to resist the expected probable earthquakes in most cities of Iran.

One of seismic retrofitting approach of reinforced concrete (RC) frames is using structural steel brace elements. In current paper some existing moment resisting RC frames with intermediate ductility was designed to withstand seismic loads which were predicted by second edition of Standard No. 2800. In other to evaluate rehabilitated RC frames, models were loaded according to third edition of Standard No. 2800. Analyses of frames show stress ratio in most of columns were exceeded allowable value. Selected RC frames were rehabilitated using concentric inverted V-brace elements. Retrofitted frames were evaluated based on Seismic Rehabilitation Code for Existing Building in Iran. Also formation of plastic hinges and provided performance levels were investigated. Displacement control plastic hinges and performance levels of nonlinear modeling criteria were extracted from Seismic Rehabilitation Code. Results present formed plastic hinges with their performance levels and discus about used seismic retrofitting approach efficiency for hazard level of 10% earthquake probability of acceptance in 50 years.