Performance-Based Plastic Design (PBPD) method has been recently developed to achieve the enhanced response of structures to earthquake. To reach this goal, several ways have been suggested. In this paper, the schemes of calculating base shear in the (PBPD) procedure will be studied. Two techniques of determining base shear will be used. The base shear of two steel moment frames will be found by these two processes. By using the difference between the input energy and the elastic strain energy to obtain the plastic energy, the plastic design is then performed to detail the frame members in order to achieve the intended yield mechanism and behavior. The inelastic seismic behaviors of the four frames were studied through nonlinear static and dynamic analyses. These two suggested techniques and their comparisons have not been proposed yet. This kind of plastic design has three main parts. Calculating base shear is the first and important portion. The second part consists of the member plastic design for flexible behavior. To design elastic members by using column trees is the third and last part. Throughout this study is devoted to present two methods for calculating base shear. The moment frames will be investigated in this article.

Application of the base-isolation systems, as a means to limit the seismic-induced response of structures, has attracted the attention of many engineers and researchers. Due to their importance, the Uniform Building Code (UBC) has incorporated a special section for the seismic analysis and design of base-isolated structures since its 1991 edition. The present work investigates the vertical distribution of the lateral seismic force for base-isolated structures provided by the 1997 edition of UBC (UBC97). Different 6 and 8-story, 3-D base-isolated structural models with LRB isolators are considered, having a variety of effective periods and effective damping ratios. The UBC97 analysis procedure for the base-isolated structures is used to determine the minimum lateral seismic force and its vertical distribution for different floors. Since the number of stories above the isolation interface is more than four for the considered isolated structural models, the response spectrum analysis is used, considering the equivalent linear properties for isolation systems. Also, the UBC97 recommended that the 5%-damped design spectra be properly modified to account for the actual modal damping ratios of an isolated structure. Extensive nonlinear dynamic analyses were performed for 8 types of LRB isolators, using appropriately normalized earthquake accelerograms recorded on SA and SB soil profiles. Both the superstructure and the isolators are allowed to behave nonlinearly, in order to evaluate the seismic induced demand shear force on different floors. The peak base center and corner displacements, maximum base and story shear forces and the maximum inter-story drifts are determined for different base-isolation systems and earthquake records. The results, together with their mean and mean plus one standard deviation values are used for the evaluation of UBC97 response spectrum analysis procedures for these buildings. The results indicate that the UBC97 suitably predicts the seismic lateral forces for base-isolated buildings. However, it does not provide a good estimate of the shear force distribution over the height, especially for the highly damped base-isolation systems. Furthermore, the number of columns per story that behaved nonlinearly during the time history analyses is included for comparison.

RC coupled shear walls are known as one of the best and popular lateral load resisting structural systems. Most of the structural design codes have no seismic design considerations for base shear and fundamental vibration period. In current study finite element models were generated to provide a reliable data base to estimate the base shear and fundamental period. The differences between the behavior of in-plane and out-of-plane actions in these systems were investigated. In the final stage corrective coefficients will present according to analyses results. More accurate estimation of the demand makes more resistant structures against wind and earthquake loads.

Current seismic codes assume a triangular distribution of base shear for isolated buildings similar to their fixed base counterparts. In this paper the validity of such distribution is investigated for isolated structures having electrometric isolators. So different models of isolation systems are selected that cover a wide range of electrometric isolators with low to high stiffness and damping. The results of non-linear time-history analysis on these models show some conservatism in code-specified distribution compared with the observed distribution of story forces. Also a new formula is proposed instead of the triangular distribution to make a better estimation of real behavior of seismic isolated buildings.

Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins has an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS) between targis (a ceromer) and two alloys (noble and base metal) was studied and the effect of thermocycling on the bond investigated. Materials and Methods: In this experimental study, alloys samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the alloys. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance.Result: The studied alloys did not differ significantly, when the samples were not thermocycled (P=0.136) but after thermocycling a significant difference was observed in SBS of resin to different alloys (P=000.1). Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003). There was a significant difference in SBS before and after thermocycling in noble alloys (P=0.009), but this was not true in base metals (P=0.29). Maximum SBS (19.09 Mpa) belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa) was seen in Degubond 4 after thermocycling. Conclusion: The effect of thermocycling in reducing bond strength of resin to metal depends on the type of alloy. The noble metal studied is significantly affected by thermal tensions.

Based on experience of past earthquakes, irregularity in building is one of the major cause has been damages to structures. One of these irregularities is the discontinuity of vertical elements such as displacement of position of shear wall in height, considering that in design versus lateral forces, the forces applied to buildings should be transferred from the point of their effect through the whole system to the ground, and the path of forces must be completed. Where, there is an interruption in the normal transition of forces, problems have occurred. Weak story or torsion effects created in floor of building. In multi-story buildings, columns and shear walls must be positioned along each other. With considering the limitations of codes and architectural requirements, there is a question in minds of engineers that it is possible to violate this common rule and to design discontinued shear wall in height. Although, Iranian code No. 2800 (Ver. 4) warned against the design and use of buildings with discontinues shear wall and recommended these types of systems should not be applied. Therefore, in this research, the seismic behavior of irregular flexural concrete frames in terms of discontinuity in shear wall have been evaluated. Also, building coefficient of behavior, displacement control an irregularity effects in seismic behavior of frames have been considered. What is important in this research, moving the shear wall in which floor can have the least effect on structural response. In this study, models analyzed under nonlinearity statically condition with using SAP 2000 program.

Recently, scientists developed the seismic rehabilitation of structures and their points of view were changed from strength to the performance of structures. Nonlinear Static Procedure (NSP) or pushover analysis is a new method that is chosen for its speed and simplicity in calculations. “Seismic Rehabilitation Code” & FEMA356 considered this method. Result of this analysis is a target displacement that is the base of the performance of the structures. Exact recognition of this displacement could develop the workability of pushover analysis. Although Nonlinear Dynamic Analysis can exactly apply the seismic ground motions, it consumes time, costs very high and is more difficult than other methods. So it is not applicable as much as NSP. A Coefficient used in NSP for determining the target displacement (C2, Stiffness and Strength Degradations coefficient) is applicable for correcting the errors due to eliminating the stiffness and strength degradations in hysteretic-cycles. In this study, three concrete frames with shear walls have been analyzed by several accelerations. After comparing pushover analysis with dynamic analysis, calculated C2 was comprised with values in rehabilitation codes.