فهرست مطالب مهدی ایزد پناه

Surrounding the central core of a concrete component by means of an internal or external factor such as transverse reinforcements, carbon and polymer fibers and steel sheets causes confinement for the concrete. Confining generally improves the strength and ductility of concrete components. As a result of boosting the local performance of elements, the overall performance of structure is made progress. Recently, tending to build irregular structures has been increasing. The presence of irregularity in the structure has always been one of the challenges faced by engineers.  In this investigation, the influence of confinement phenomenon on the seismic performance (damage level and behavior factor) of the moment resisting reinforced concrete frames with vertical irregularity is assessed. To do so, 31 moment resisting frames with vertical irregularity are categorized in four classes including 3-, 6-, 9- and 12-story and the roof displacement-base shear curves of them are acquired using pushover analysis. The capacity curve of each frame is achieved in two states including neglecting the confinement effect and considering it. The outcomes indicate that not only can confining improve the seismic performance of structures but also it can decrease the imposed damage of structures. In other words, comparing the capacity curves of each frame with/without confining effect shows that taking the confinement effect leads to improving the secant stiffness and strength of the frame. Furthermore, due to confinement effect, lateral load carrying capacities of the frames are boosted and the considered damage levels are achieved in higher base shear and roof displacements in comparison with the state that confinement is not considered. The observed values of damage levels indicate that the influence of confinement for higher frames is more significant and the maximum base shears for the frames with the confining action is around 3-19% higher than those of the frames without confinement effect. For 3-story frames, considering confinement effect leads to improving 3.9, 3.6 and 2.9% in damage levels of DL, SD, and NC. For 6-story frames these values are 6.9, 9.5, and 6.8% respectively. Taking confinement effect results in improving 18.25, 11.8, and 14.6% in damage levels of DL, SD, and NC and 14.3, 14.2, and 13.3% improvement for 12-story frames. Comparing the behavior factors in the two states demonstrates that considering confining effect improves the mean values of behavior factors around 10.4%. In addition, the observed values of behavior factors show that the differences between the amounts of behavior factors (with/without confinement effect) for the frames with more stories are higher. It is manifested that type of irregularity plays significant role on the seismic behavior of the moment-resisting reinforced concrete frames. Comparing the analytical behavior factor obtained in the current study with the prescribed value of behavior factor in Iranian seismic code shows that although the proposed value of Iranian seismic code is conservative for low-rise frames, this value is not met for high-rise frames.

The moment-resisting steel frame building is highly used due to their advantages such as, high speed construction coupled with appropriate strength and ductility. The main advantage of this system is related to architectural considerations and the possibility of creating openings within all spans. Connections play an outstanding role in the seismic responses of this structural system. The connections are generally assumed to have a rigid behavior in analyzing and designing of the moment-resisting steel buildings. Studying of the previous investigations indicates that the assumption of rigid behavior for the beam-to-column connections is not always correct and can bring about a significant error in the responses. In this study, behavior factor of moment-resisting steel frames considering joint flexibility is evaluated. To do so, some intermediate moment-resisting steel frames with various number of stories and bays including 1-bay, 1- and 2-story frames, 2-bay, 2-, 4-, 6-, 8-, and 10-story frames, 3-bay, 3-, 6-, 9-, and 12-story frames and 4-story, 2-, 6-, 10-, and 14-story frames are designed regarding Iranian seismic code and Iranian national building code for designing steel structures. After that, the capacity curves of these frames are achieved using pushover analysis once considering rigid connections and again taking joint flexibility into consideration using OpenSees software. To model the nonlinear behavior of connections, one zero-length rotational spring is assigned to each end of beam members. Then, the behavior factor of each frame is calculated using the recommended procedure of FEMA-P695. The outcomes show that for the frames with rigid connections, the acquired behavior factors are almost close to 5 (which is the prescribed behavior factor in Iranian seismic code for the intermediate moment-resisting steel frames). Furthermore, for the frames with semi-rigid connections (60%), the behavior factors are close to 5 as well. For 10-story 2-bay, 12-story 3-bay, and 14-story 4-bay frames the prescribed behavior factor in Iranian seismic code does not meet. For these frames, the ratio of height to total-span that is known as the slenderness coefficient of the frame is higher than others, so these frames fall into slender frames. Results show that for the frames with semi-rigid connections (60%), despite of decreasing the over-strength factors in some cases, their ductility increased, therefore, the behavior factors are achieved higher than those of the frames with rigid connections. All in all, it is observed that the nonlinear behavior of connections can significantly affect the seismic behavior of the moment-resisting steel frames. Comparing the behavior factors calculated in this investigation with the prescribed value of this factor in code 2800 showed that for the frames with rigid connections, 80% of the obtained behavior factors are higher than 5. For frames with semi-rigid connections (80% and 60%), 0%, and 66% of the behavior factors meet the proposed value of code 2800, respectively. Regarding the observations, it is recommended that the influence of joint flexibility be considered in assigning a value of behavior factor to design the moment-resisting steel frames.

One of the most widely used among the existing methods proposed by the codes for the seismic analysis of structures is linear static analysis. Several methods have been presented for determining the static lateral load pattern. In spite of the simplicity of the existing procedures, their accuracy is not desirable, especially for structures in which the influences of higher modes are significant. In this study, a new method is developed to improve the lateral load pattern in linear static analysis. To achieve the proposed lateral load distribution, firstly, the average response of structure subjected to some earthquakes is acquired. Then, regarding the dynamic of structures, the static lateral load pattern compatible with the average response is developed. Eventually, to derive a straightforward and hands on lateral load distribution, using a statistical study, some relations coupled with a graph are developed. Since the proposed method is developed based on the structural responses resulting from linear dynamic analysis (time-history analysis), it is shown that the suggested way despite its simplicity and efficiency, presents appropriate accuracy in predicting the response of the structures subjected to seismic excitations. The developed method is evaluated for a set of structures with different fundamental periods. Results show that the method gives higher accuracy in comparison with the static method of Iranian standard 2800 and FEMA 356. Also the developed procedure can be considered as an appropriate technique for determining lateral load distribution in seismic codes.

Although infill panels are considered as non-structural elements in analysis and design process of building frames, these members may significantly affect the seismic performance of the frames. Nowadays, tendency to design and construct the irregular buildings has increased. Behavior factor plays an important role in the seismic design of buildings. Seismic codes usually present the same Behavior factor for the regular and irregular lateral load-carrying systems. In this investigation, the influence of masonry infill walls on the behavior factor of the vertically irregular moment resisting reinforced concrete frames was evaluated. To do so, 3-, 6-, 9- and 12-story moment resisting reinforced concrete frames with various types of vertical irregularities were considered. These frames were assessed with/without considering the influence of infill walls. The capacity curves of the frames were derived using incremental dynamic analysis using 14 acceleration ground motions and then the behaviour factors were achieved. Outcomes demonstrated that infilled frames present higher response modification factors and more efficiently performance in lateral load-carrying rather than bare frames. Furthermore, it was shown that vertical irregularity affects the seismic responses and the behavior factor of moment resisting reinforced concrete frames. Eventually, two approximate relations were developed to acquire the response modification factors of bare- and infilled- vertically irregular moment resisting reinforced concrete frames.

because thoracolumbar region is highly exposed to serious impairments, the different aspects of treatment in this region have been largely evaluated.Non-operative treatment in the situations not involved in neurologic impairments, has shown satisfying results. Body jacket and Jewett orthoses are among one of the Non-operative choices of treatment which there is a gap in the literature about their ability to restricting motion in the thoracolumbar region. Although more efficient orthosis in restricting movement of different parts of vertebral column have been mentioned by orthotics text, those preferences have not been achieved by scientific studies and precise biomechanical evaluation between different motion planes. The purpose of this research is to determine the degree of differences between two orthosis and non-orthosis option in restricting thoracolumbar movements. this is a before and after interventional experimental study performed in the research center of Isfahan rehabilitation college with the benefit of motion analysis equipment. All participants including 10 male university students with average age of (23±3) who had no history of musculoskeletal impairments as well as osteoporosis performed 6 motion including flexion-extension-left lat flex-right lat flex-left rot-right rot in the 3 positions(1-with body jacket orthosis-2-with jewett orthosis-3-no orthosis)and meanwhile range of motion was recorded. Variance analysis as well as kruskall-walis analysis was performed in the confidence interval of 95%by SPSS19 software, to statistically analyzing the data. Resuls:according to this research, there are significant differences between three interventions in the movements of forward flexion-lateral flexion and rotation in the thoracolumbar region(p=0/000).However, when it comes to sagittal plane movements in the upper thoracic region there is no difference between two orthoses and no orthosis option(p=0/124) according to the results of this study, body jacket orthosis plays an important role in restricting motions of thoracolumbar region in the frontal plane (lateral flexion), although, jewett orthosis is more efficient to control transverse plane movements (rotation) than body jacket. two orthoses have similarly shown more effectiveness in controlling sagittal plane movements in the thoracolumbar region in comparison with non -orthosis situation.

Determination and prediction of damage imposed on the structures is one of the most important topics related to the performance based design. In this regard, the standards regarding the performance based design have introduced some levels & limitations. The main objective of this research is to evaluate these levels by comparison of damage indices calculated from dynamic & pushover analysis. IN addition, performance of ABA & 2800 codes in limiting damage of structures is evaluated. For this purpose, seven earthquake records, which are appropriate for site effects under consideration, are selected & scaled in such a way that average response spectrum of them has minimum difference with Iranian code 2800 design spectrum. then damage analysis is performed on several reinforced concrete moment resisting frames. Results represented that drift criterion introduced by standards such as FEMA273 & ATC40 can lead to incorrect results in determination of seismic performance of structures. it was illustrated that ABA & 2800 codes have proper performance in limiting damage of structures at Life Safety level.