NONLINEAR static methods are simplified procedures in which the problem of evaluating the maximum expected response of a MDOF system for a specified level of earthquake motion is replaced by response evaluation of its equivalent SDOF system. The common features of these procedures are the use of PUSHOVER ANALYSIS to characterize the structural system. In PUSHOVER ANALYSIS both the force distribution and the target displacement are based on the assumptions that the response is controlled by the fundamental mode and that the mode shape remains unchanged after the structure yields. Therefore, the invariant force distributions does not account for the change of load patterns caused by the plastic hinge formation and changes in the stiffness of different structural elements. That could have some effects in the outcome of the method depending on different structural parameters. This paper introduces an ADAPTIVE PUSHOVER ANALYSIS method to improve the accuracy of the currently used PUSHOVER ANALYSIS in predicting the seismic-induced dynamic demands of the structures. Comparison of the common PUSHOVER analyses, ADAPTIVE PUSHOVER analyses and TIME-HISTORY analyses performed for a number of multiple-bay, short and high-rise steel structures, demonstrates the efficiency of the proposed method.

NONLINEAR static procedure (NSP) is a common technique to predict seismic demands on various building structures by subjecting a monotonically increasing horizontal loading (PUSHOVER) to the structure. Therefore, the PUSHOVER ANALYSIS is an important part of each NSP. Accordingly, the current paper aims at investigating the efficiency of various algorithms of lateral load patterns applied to the structure in NSPs. In recent years, fundamental advances have been made in the NSPs to enhance the response of NSPs toward NONLINEAR TIME HISTORY ANALYSIS (NTHA). Among the NSPs, the philosophy of "ADAPTIVE procedures" has been focused by many researchers. In the case of utilizing ADAPTIVE procedures, the use of incremental force vector considering the effects of higher modes of vibration and stiffness deteriorations is possible and seems that it can lead to a good prediction of seismic response of structures. In this study, a new ADAPTIVE procedure called energy-based ADAPTIVE PUSHOVER ANALYSIS (EAPA) is implemented based on the work done by modal forces in each level of the structure during the ANALYSIS and is examined for steel moment resisting frames (SMRFs). EAPA is inspired by force-based ADAPTIVE PUSHOVER (FAP) and story shear-based ADAPTIVE PUSHOVER (SSAP). FAP has applied modal forces directly into load patterns; SSAP, on the other hand, has implemented the energy method in system`s capacity curve for measuring the equivalent movement. EAPA has enforced the concept of energy directly in load pattern; so that by using the modal forces-movements an energy-based ADAPTIVE algorithm is obtained. Hence, the effects of higher modes, deterioration in stiffness and strength, and characteristics of a specific site are incorporated and reflected in applied forces on the structure. Results obtained from the method proposed a desirable accordance with the extracted results from NTHA over the height of the structure.

Design sensitivity ANALYSIS is a necessary task for optimization of structures. Methods of sensitivity ANALYSIS for linear systems have been developed and well documented in the literature; however there are a few such research works for NONLINEAR systems. NONLINEAR sensitivity ANALYSIS of structures under seismic loading is very complicated. This paper presents an analytical sensitivity technique for Reinforcement Concrete Moment Resisting Frames (RCMRF) that accounts for both material and geometric NONLINEARity under PUSHOVER ANALYSIS. The results of proposed method are compared with the results of finite difference method. A three-story, two bays moment frame example is used to illustrate the efficiency of the method. This technique can be very useful and efficient for optimal performance-based design of RC buildings.

In this paper, the seismic behavior of three intermediate moment-resisting concrete space frames with unsymmetrical plan in five, seven and ten stories are evaluated by using PUSHOVER ANALYSIS. In each of these frames, both projections of the structure beyond a reentrant corner are greater than 33 percent of the plan dimension of the structure in the given direction. The performance of these buildings has been investigated using the PUSHOVER ANALYSIS. Results have been compared with those obtained from non-linear dynamic ANALYSIS.

In the conventional design and ANALYSIS methods affecting parameters (loads, materials' strength, etc) are not set as probable variables. Safety factors in the current Codes and Standards are usually obtained on the basis of judgment and experience, which may be improper or uneconomical. In technical literature, a method based on NONLINEAR static ANALYSIS is suggested to set Reliability Index on strength of structural systems. In this paper, a method based on NONLINEAR Dynamic ANALYSIS with rising acceleration (or Incremental Dynamic ANALYSIS) is introduced, the results of which are compared with those of the previous (Static PUSHOVER ANALYSIS) method and two concepts namely Redundancy Strength and Redundancy Variations are proposed as an index to these impacts. The Redundancy Variation Factor and Redundancy Strength Factor indices for reinforced concrete frames with varying number of bays and stories and different ductility potentials are computed and ultimately, Reliability Index is determined using these two indices.

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.

Having very simplicity, NONLINEAR static procedures (NSPs) are the most popular tools for estimation of structural capacity. These approaches construct a graphic display of the overall structural response via a PUSHOVER curve. The overall response of the system provides a direct simulation of the building as single degree of freedom (SDOF) system that simplifies the design and evaluation of the structure. In this research, the first step in any NONLINEAR static ANALYSIS or in other words perform a PUSHOVER ANALYSIS has been studied. Applied lateral load to the structural model not only affects the overall responses of the structure through structural capacity curve, but also directly affects the local responses of the structure. In order to evaluate these lateral loads, steel buckling restrained braced frame structures are examined by advanced modal PUSHOVERs. Next, the results of these PUSHOVER analyses will be compared with NONLINEAR TIME HISTORY ANALYSIS as the most accurate method. Finally, the most efficient method in this particular structure is introduced. The ANALYSIS conducted in these structures shows that the lateral load pattern based on story shears offers a good prediction of the maximum response of the concentrically buckling restrained braced frame buildings.

One of the simplified methods, which is progressing and completing every day, is a NONLINEAR static ANALYSIS that can directly evaluate the performance of a structure in any limit state and provide information about the NONLINEAR behavior of the structure, and it also does not have the complexity of NONLINEAR dynamic ANALYSIS. In this study, the structural responses of NONLINEAR static procedure (NSP) based on standard 2800 were compared with ASCE 41-13 code and displacement-based ADAPTIVE PUSHOVER (DAP) method in three models of reinforced concrete structures including the 3, 7 and 10 story with medium ductility. In order to study the accuracy of NONLINEAR static ANALYSIS and seismic behavior of structures, NONLINEAR TIME HISTORY ANALYSIS (NTHA) which is the most accurate method in seismic assessment of structures was conducted. The results show that in 3 and 10 story the NSP according to standard 2800 with forces distribution obtained from the spectral dynamical ANALYSIS is more accurate than other NSPs in evaluating of story drifts ratio and maximum displacement along the height of buildings. In 7 story, displacement-based ADAPTIVE PUSHOVER (DAP) method can be estimated story drift ratio more precisely. In 3 and 10 story, the NSP based on 2800 with forces distribution obtained from the spectral dynamical ANALYSIS, can estimate the mean story drifts with a lower percentage error. According to the results, in each three model the uniform distribution of NONLINEAR static procedure (NSP) based on standard 2800 estimates the story drifts with less accuracy and high error. As a suggestion, NONLINEAR static ANALYSIS based on uniform distribution can be eliminated from the standard 2800.