As the height of building increases, effect of shear lag also becomes considerable in the design of high-rise buildings. In this paper, shear lag effect in tall buildings of heights, i.e., 120, 96, 72, 48 and 36 stories of which aspect ratio ranges from 3 to 10 is studied. Tube-in-tube structural system with façade bracing is used for designing the building of height 120 story. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads. Different geometric patterns of bracing system are considered. The best effective geometric configuration of bracing system is concluded in this study. Lateral force, as wind load is applied on the buildings as it is the most dominating lateral force for such heights. Wind load is set as per Indian standard code of practice IS 875 Part-3. For analysis purpose SAP 2000 software program is used.

Today, many strategies have been proposed to improve the behavior of tall buildings under seismic load. Drifts, torsion, and structure period are essential parameters affecting high-rise building behavior. In addition, the stress concentration at the end wing of shear walls is another critical subject in high-rise buildings, which was resolved using end shear walls. The end shear wall connects the end of two shear walls in high-rise buildings without opening. In this study, a new end shear wall connects the end of shear walls in a high-rise building with regular openings (ESWO). Therefore, two 30-story RC buildings with and without end shear walls with opening were modeled by a nonlinear time history analysis under seismic load. The drift was decreased by 49% in a 30-story building with a new end shear wall. Moreover, the residual displacement of 30-story buildings with end shear walls with opening was decreased by 67%.. The time history nonlinear analysis investigation indicated that the end shear walls with opening declined the maximum displacement by 62% in tall buildings by Open Sees software. The reduction of the standard deviation of data increased the confinement in 30-story drifts in the X and Y directions by end shear walls with opening. Based on the results, the performance of the end shear walls with the opening was appropriate in the seismic behavior of high-rise buildings.

This study targets the behavior of shear buildings equipped with tuned liquid column dampers (TLCD) which attenuate dynamic load-induced vibrations. TLCDs are a passive damping system used in tall buildings. This kind of damper has proven to be very efficient, being an excellent alternative to mass dampers. A dynamic analysis of the structure-damper system was made using the software DynaPy, developed in the research process. The software solves the equations of motion through numeric integration using the central differences method. The simulations results obtained with DynaPy showed that the use of TLCD can reduce the dynamic response significantly for both harmonic excitations and random excitations.

Flat-slab building structures exhibit significant higher flexibility compared with traditional frame structures, and shear walls (SWs) are vital to limit deformation demands under earthquake excitations. The objective of this study is to identify an appropriate finite element (FE) model of SW dominant flat-plate reinforced concrete (R/C) buildings, which can be used to study its dynamic behavior. Three-dimensional models are generated and analyzed to check the adequacy of different empirical formulas to estimate structural period of vibration via analyzing the dynamic response of low- and medium-height R/C buildings with different cross-sectional plans and different SW positions and thicknesses. The numerical results clarify that modeling of R/C buildings using block (solid) elements for columns, SWs, and slab provides the most appropriate representation of R/C buildings since it gives accurate results of fundamental periods and consequently reliable seismic forces. Also, modeling of R/C buildings by FE programs using shell elements for both columns and SWs provides acceptable results of fundamental periods (the error does not exceed 10%). However, modeling of R/C buildings using frame elements for columns and/or SWs overestimates the fundamental periods of R/C buildings. Empirical formulas often overestimate or underestimate fundamental periods of R/C buildings. Some equations provide misleading values of fundamental period for both intact and cracked R/C buildings. However, others can be used to estimate approximately the fundamental periods of flat-plate R/C buildings. The effect of different SW positions is also discussed.

Nowadays with development of urbanity, request for dwelling has increased extremely. In all the cases the steel structures as for the high speed of construction have a special status. Among the defect of steel buildings than concrete type is higher cost of construction. Hence, occasionally the fabricators with a view to imparting of advantage of both the construction speed and some deal decreasing providing cost of steel lateral bracing, use the steel buildings with reinforced concrete shear wall as lateral bearing system. Hence, study in the field of analysis and design of this structure system seems necessary. At present, one of the most important goals of earthquake engineers is predicting of the structures behavior versus future earthquakes. Today, it has become evident that structures designed on the basis of the existing regulations sustain extensive damages in under intense earthquakes. Thus, performance-oriented design as a method based on acceptance of expected displacement and ductility has been considered. In earthquake engineering, it is imperative to determine the capacity and the seismic demand of the structure in terms of performance. The performance assessment of nonlinear systems is a complex task requiring appropriate analytical methods suitable for modeling the behavior of the structure against the earthquake. The incremental dynamic analysis is an analytical tool which can be used to assess performance in earthquake engineering. This method is able to estimate the seismic demand and limit states of the capacity of a structure under seismic loading using suitable records scales to several levels. Utilizing this method, one can attain better understanding of the behavior of a structure from elastic to destruction conditions. In the present research, dynamic analysis of the time history and the robust software OpenSees have been employed considering the geometric nonlinear effects of materials for seven buildings having 3, 6, 9, and 12 stories and two plans. The structures under consideration are analyzed using incremental dynamic analysis and the robust Opensees software subsequent to the design phase and considering the designed sections, gravity loading characteristics and specifications and seismic parameters. Then, graphing the cluster curves and IDA quantiles the buildings under consideration are assessed. Although the results of this study indicate better performance of the moderate structures in comparison to the short and rise structures, it seems that the proper height of a structure with respect to the characteristics of the soil of its construction site and the parameters of the resonance and damping between the structure and the soil (the effect of soil and structure interaction) and the frequency content of the acceleration records of the first mode in the region. The seismic intensity estimation parameter (which is considered in this study, the first-mode spectral acceleration) is a determinant factor in reflecting the behavior of the earthquake acceleration record applied to the structure. In order to conduct a detailed study with the IDA analysis, it is necessary to select the severity criterion in a way that best describes the content of the selected accelerogram. In spite of the relative advantage of the Spectral Spectrum Parameter (Sa) on the maximum acceleration (PGA), it still seems that this parameter is not a complete representation of record content.

Examination of the behavior of structures in past earthquakes shows that the asymmetric torsion has been one of the causes of severe vulnerabilities. Considering the advantages of modern seismic design methods in which energy dissipation additives such as dampers are used to control the responses in an earthquake, it is possible to control the seismic torsion in the structure. However, recent earthquakes have shown that concrete structures are damaged by earthquakes, making them very difficult and even impossible to repair. For this reason, after relatively severe earthquakes, these buildings have been damaged and destroyed, and in order to reuse the structure, it is necessary to spend a lot of time and money due to the extent of damage to the structure, and this issue creates a new idea to limit damage. In this way, buildings can be exploited more quickly by replacing damaged elements. One of the new methods to improve the seismic performance of concrete buildings is the use of systems that limit damage to the structure. Among these methods, we can mention systems with rocking motion, in which the main building behaves elastically so that the energy absorption and nonlinear performance occur only in certain parts of the building that have been predicted. Therefore, in this study, a new system has been introduced using the mechanism of cradle movement in the shear walls of the structure, transmits damage to the structural fuses and makes the concrete structure safe in earthquake and after, and very repairable. Precise details of connections, design and nonlinear analysis of this system have been done in ABAQUS and SAP2000. The solid element was used to model the rocking system in ABAQUS and concrete damage palsticity model was used to modeling the concrete, which is used to model the nonlinear behavior of concrete. The contact between the steel bolts and the concrete shear wall is simulated using the contact element.The concrete shear wall in this method remains in the elastic range, but the dampers connected to the shear wall due to the elevation of the shear wall absorb most of the seismic force. It should be noted that the system reversibility is provided by post-tensioned cables. The torsion in the structure is of the concentrated mass type and the exit from the 5%, 10% and 20% axes is applied in the concrete structure. The results show that the use of this new system in comparison with concrete structures without it effectively reduces the damage to the structure and the concrete structure remains intact and by changing the retraction force of retracted cables seismic torsion control is performed. Also, the functional levels of the structure remain in the IO area. The use of a controlled rocking motion system significantly reduces axial force in structural members by about 30%. Post-tensioned cables in the cradle drive system have a more than 70% effect on reducing the deformation of the structure and then the flow damper is placed. According to the written DEMATEL code, the tensile strength and stiffness of the structure and the stiffness of the Gap element are the most effective; besides, the vibration mode and displacement of the structure are the most effective factors in controlled rocking motion. The use of a new repairable shear wall with rocking motion has caused the vibration mode to dominate the structure of the first vibration mode and the distance between the torsion mode, and the first and the second modes are very large.

The objective of this article is to present a new method for identifying the damage location in a multi-story shear building by direct model updating method. In this regard, structural perturbation matrices should be determined that are directly defined as the discrepancy between mass and stiffness matrices of undamaged and damaged structures. As a result of expanding the dynamic orthogonality conditions, mass and stiffness perturbation matrices are formulated by the initial information of undamaged structures as well as the structure’s modal parameters before and after the occurrence of damages. These matrices cannot easily detect the damage site. Therefore, a more explicit determination of damage location is performed dividing the amount of change in these matrices’ diagonals by the physical properties of undamaged structure. This modification facilitates the damage localization process and yields precise and preferable results in comparison with applying classical methods such as natural frequencies, mode shapes and structural properties changes. Subsequently, the applicability and effectiveness of the proposed damage detection method are verified numerically and experimentally. For numerical verification of the proposed methods, a six-story shear building is utilized as a discrete system. Then, the experimental verification of proposed methods is conducted detecting the location of damages in a simple laboratory frame. It can be deduced that the proposed damage localization method can reliably detect and also localize the structural damage.

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Recently, with progress in earthquake engineering and design of structures, the performance-based seismic design is becoming more popular. However, finding the optimum structure that satisfies the performance limitation of this method is a hard task. In this study, the applicability of endurance time method in optimal performance-based design is evaluated using uniform deformation theory. First, shear building structures are optimized for a set of records, representing a specified seismic hazard level using time-history analysis and uniform deformation theory. This is done for a different number of stories ranging from 5 to 15. In addition, different target ductilities are used for uniform deformation procedure ranging from 1 to 8. Sets of ground motions used in this study are obtained from the SAC project and represent different seismic hazard levels. The results show that the optimized structure for a specific seismic hazard level does not necessarily show appropriate performance at other seismic hazard levels. However, the performance of optimized structures for another set of ground motions with the same seismic hazard level is satisfactory. Consequently, using a try-and-error process, the structure's performance is improved to a certain extent; however, it is not yet ideal and also the stiffness of the structure increases. This process is time-consuming and insufficient for engineering application. Therefore, endurance time method is utilized to find optimal structures with a proper performance at different seismic hazard levels. ETA40g acceleration functions are used since they are more compatible with the ground motions used before. The results of endurance time method are compared with those obtained for ground motions. It is shown that the results of endurance time analysis are consistent with those obtained from time history analysis of the set of records. Distribution of story shears and deformations are compatible in two methods. Finally, an effective technique is presented in which the structural performance is simultaneously improved at all seismic hazard levels.