Incremental Dynamic Analysis Method Research Articles

Performance-based seismic assessment of steel frames using endurance time analysis

The current performance-based seismic assessment procedure can be computationally intensive as it requires a large number of time history analyses (THA) each requiring time intensive post-processing of results. This study proposes the endurance time analysis (ETA) method as an alternative method to THA and incremental dynamic analysis (IDA). ETA is a time history based dynamic pushover procedure that applies a set of gradually intensifying acceleration functions to the structure and monitors the performance of the building accordingly. In this paper, the application of ETA in the seismic assessment of multistory steel concentrically braced frames is compared with THA and IDA methods. Moreover, the progressive failure of the frames is investigated using the ETA method. The results of this analysis show that ETA can estimate THA as well as IDA, with considerably less computational effort.

Response modification factor of the frames braced with reduced yielding segment BRB

In this paper, overstrength, ductility and response modification factors are calculated for frames braced with a different type of buckling restrained braces, called reduced yielding segment BRB (Buckling Restrained Brace) in which the length of its yielding part is reduced and placed in one end of the brace element in comparison with conventional BRBs. Forthermore, these factors are calculated for ordinary BRBF and the results are compared. In this regard incremental dynamic analysis (IDA) method is used for studying 17 records of the most known earthquakes happened in the world. To do that, the considered buildings have different stories and two bracing configurations: diagonal and inverted V chevron, the most ordinary configurations of BRBFs. Static pushover analysis, nonlinear incremental dynamic analysis and linear dynamic analysis have been performed using OpenSees software. Considering the results, it can be seen that, overstrength, ductility and response modification factors of this type of BRBF(Buckling Restrained Braced Frame) is greater than those of conventional types and it shows better seismic performance and also eliminates some of conventional BRBF's disadvantages such as low post-yield stiffness.

Optimal topology design of replaceable bar dampers of a reticulated shell based on sensitivity analysis

In this study, a method for control of reticulated shells is proposed and its practicality is demonstrated. The control is implemented by replacing selected bars of the shell with passive viscoelastic dampers. By applying the eigenvalue perturbation technique and the earthquake spectrum concept, the sensitivities of various topologies of the shell are analyzed, and the optimal topology is determined by taking their symmetries into consideration. The results of this research show that common damper topologies are not effective for all types of responses and recorded earthquakes. The optimal topology identifi ed requires a minimal number of dampers for each type of earthquake record. The displacement control effect of the dynamic responses of the optimal topology is 10%–20%; the acceleration control effect is also about 10%–20%; and the axial force control effect is as much as 30%–45%. Furthermore, the incremental dynamic analysis (IDA) method is used to investigate the stability of the controlled shell. The results show that the dynamic stability of the controlled shell is well preserved when it is vibrated under vibration and is better than the uncontrolled shell. The ultimate load increased by 10% and the elements entered into the plastic stage when the peak acceleration reached 580 Gal, which is 200 Gal larger than the uncontrolled shell.

Analysis of the Collapse of Long-Span Reticulated Shell Structures Under Multi-Dimensional Seismic Excitations

The collapse processes of three typical long-span reticulated shell structures were simulated using nonlinear dynamic finite element analysis under strong seismic excitations. The plastic kinematic hardening model, which considers failure stain, was adopted for simulating steel. Both geometric and contact nonlinearities were considered in this study. The three failure states—i.e., dynamic local bucking, dynamic overall buckling, and whole collapse—were identified in accordance with the analysis results. Taking the Schwedler reticulated shell structure as an example, seismic waves were applied to the structure in three directions. The critical loads were obtained by the incremental dynamic analysis method (IDAM), and some critical state indices were obtained according to the dynamic responses. The results showed that all the critical indices need to be considered simultaneously in order to judge the dynamic collapse states.

Nonlinear seismic assessment of steel moment frames using time–history, incremental dynamic, and endurance time analysis methods

A recent method in the seismic assessment of structures is Endurance Time Analysis (ETA). ETA is a time–history-based dynamic pushover procedure, in which structures are subjected to gradually intensifying acceleration functions called Endurance Time Acceleration Functions (ETAFs), and their performances are evaluated based on the equivalent intensity level that they can endure while satisfying required performance goals. In this paper, the accuracy of the ETA in the seismic assessment of steel moment resisting frames is compared with the Time History Analysis (THA) and Incremental Dynamic Analysis (IDA) methods. For this purpose, a set of mid-rise and high-rise frames were selected as a case study. Three sets of second generation ETAFs were used as input in the ETA method, and seven scaled ground motions were used for THA and IDA. It was found that ETA can estimate THA results in an equivalent target time, and also the general trend of IDA curves, with acceptable accuracy, while ETA requires considerably less computational effort in comparison with THA, and, especially, the IDA method.

Damage Criteria of Steel Frame Structures Based on Damage Constitutive Model for Steel

The damage criteria of steel frame structure for fiber level, member level and story level are proposed. The fiber level damage criteria is directly defined by the developed steel damage model, the damage criteria of steel member is averaged through all the fibers of the member, and the story level, the damage criteria is defined as the weighted average value of the members, which the weighting factor is defined as the first several relative frequencies increase of residual structure after the evaluated member was demolished. As a numerical example, the damage process of a 9-story benchmark steel frame is analyzed through IDA (Incremental Dynamic Analysis) method in term of structural global damage index, and the damage distribution of each story is proposed as well.

Performance evaluation of different types of steel moment resisting frames subjected to strong ground motion through incremental dynamic analysis

Comparative studies on seismic performance for various types of steel moment resisting frames subjected to near field and far field earthquakes are performed through Incremental dynamic analysis (IDA) method in this study. Near field earthquake has a pulse like effects on the structures. It imports immediate force in very short duration to buildings. Therefore, destructive effects of surge energy are not negligible. Four intensity indices are used, namely, peak acceleration (PGA), spectral acceleration at the structure’s first-mode period (Sa(T1, 5%)), spectral acceleration at the structure’s nth effective-mode period (Sa(Tn, 5%)) and the Spectral velocity at the structure’s first-mode period (Sv(T1, 5%)). Numerical results illustrate that the intensity measure parameters related to ground velocity and the higher mode-related parameters present better correlation with the seismic responses of near source ground motion for given systems. The higher mode-related parameters are more suitable for tall systems subjected to near field earthquakes. Moreover, the chosen parameters Sa(Tn, 5%) and Sv(T1, 5%) of near-fault impulsive ground motions enhance the performance of intensity measure of corresponding conventional parameters, i.e. Sa(T1, 5%). A comparison for the special and intermediate steel moment resisting frames is made as regard to performance using IDA method. A more efficient performance is observed for the special moment resisting frames compare to intermediate ones.

Seismic Fragility Analysis of SRC Frame Structures

With the rapid development and extensive application of SRC (steel reinforced concrete) frame structures, the study on seismic fragility of SRC structure under earthquakes seems rather important. The seismic fragility of the SRC frame structures is studied by the method of Incremental Dynamic Analysis (IDA) in this paper. IDA method is conducted on 9 storey SRC frame structure to obtain the IDA curves of this model. Meanwhile, the seismic fragility of the model is analyzed to get the fragility curve. The result shows that IDA can describe the quantitative relationship between the exceeding probability of different states and damage degree of the target.

Free-Spanning Submarine Pipeline Response to Severe Ground Excitations: Water-Pipeline Interactions

Submarine pipelines are usually laid unburied. Free spanning may be caused in the line by seabed unevenness, topology changes, scouring, or sand waves. In seismically active areas, the free spannings are prone to severe ground excitations. This article deals with the seismic performance of the submarine pipeline free spanning, and the water/pipeline interaction during the event is its focal point. For this, a numerical finite-element model has been used. Results from a conventional added mass approach have been examined against those from a more elaborate coupled acoustic-structural model. With the coupled system the surrounding seawater, pipe body, seabed, and free spanning have all been incorporated into the model. Both random earthquake and harmonic excitations have been considered. A time domain incremental dynamic analysis (IDA) method has been used to evaluate the pipeline performance. Effects from type, frequency, intensity, and direction of excitation and the free-span length on the pipeline response have been investigated. In most cases, the added mass approach has been found to provide more conservative predictions (in some cases up to 60%) for the free-spanning seismic response in comparison to those obtained from the acoustic method. For the earthquake excitations, the predictions obtained from each of the two methods have been more consistent as compared to the results obtained for harmonic excitations.

Seismic Vulnerability of Long-Span Continuous Rigid Frame Bridge with High Pier Based on Fiber Model and IDA Method

The failure behavior and the vulnerable position of the rigid frame bridge are analyzed by nonlinear response analysis, based on incremental dynamic analysis (IDA). The damage index, applying for long-span continuous rigid frame bridge with high pier, is studied. The seismic vulnerability problem of the whole bridge is analyzed by fiber model. The strain was used for damage index of piers. The displacement was used for damage index of bearings. According to the studies above, the fragility curves are established based on integral performance of the bridge.

Dynamic-Instability Mechanism of Double-Layer Spherical Shell under Harmonic Loading

Based on dynamic instability theory, by incremental dynamic analysis method, large-scale parameters-analysis is carried on double-layer Kiewitt shell under harmonic loading，with weight effects and double non-linear effect calculated and Failure-amplitude is determined. Further exploring on the relationship between excitation frequency changes and failure-amplitude and between initial imperfection effect and load reduction are also conducted.

Seismic Performance Evaluation of SRC Frames Based on Incremental Dynamic Analysis

Incremental dynamic analysis (IDA) is an effective method for evaluation of seismic performance of building structures. Based on the principle and characteristics of IDA method, evaluation steps of investigating deformation and ductility of steel reinforced concrete (SRC) structures under increasing earthquake loading are put forward. Limit states of different performance levels for structures are connected with IDA curve slope whose decrease amplitude is determined according to current test data. Based on the proposed constitutive model of steel and concrete, a regular steel reinforced concrete frame structure is analyzed with IDA method, and distribution of story drift angle and ductility for four performance levels are investigated. The calculation results show that the SRC frame has better seismic performance when subjected to random earthquake waves.

Evaluation of ASCE-41, ATC-40 and N2 static pushover methods based on optimally designed buildings

Alternative static pushover methods for the seismic design of new structures are assessed with the aid of advanced computational tools. The current state-of-practice static pushover methods as suggested in the provisions of European and American regulations are implemented in this comparative study. In particular the static pushover methods are: the displacement coefficient method of ASCE-41, the ATC-40 capacity spectrum method and the N2 method of Eurocode 8. Such analysis methods are typically recommended for the performance assessment of existing structures, and therefore most of the existing comparative studies are focused on the performance of one or more structures. Therefore, contrary to previous research studies, we use static pushover methods to perform design and we then compare the capacity of the outcome designs with reference to the results of nonlinear response history analysis. This alternative approach pinpoints the pros and cons of each method since the discrepancies between static and dynamic analysis are propagated to the properties of the final structure. All methods are implemented in an optimum performance-based design framework to obtain the lower-bound designs for two regular and two irregular reinforced concrete building configurations. The outcome designs are compared with respect to the maximum interstorey drift and maximum roof drift demand obtained with the Incremental Dynamic Analysis method. To allow the comparison, also the life-cycle cost of each design is calculated; i.e. a parameter that is used to measure the damage cost due to future earthquakes that will occur during the design life of the structure. The problem of finding the lower bound designs is handled with an Evolutionary type optimization algorithm.

Seismic evaluation of existing RC frames with wide beams using an energy-based approach

This paper investigates the seismic performance of existing reinforced concrete frames with wide beams mainly designed for gravity loads, as typically found in the seismic-prone Mediterranean area before the introduction of modern codes. The seismic capacity is evaluated in terms of the overall amount of input energy that the frame can dissipate/absorb up to collapse. This approach provides a quantitative evaluation that can be useful for selecting and designing an appropriate retrofit strategy. Six prototype frames representative of past construction practices in the southern part of Spain are designed, and the corresponding non-linear numerical models are developed and calibrated with purposely conducted tests on wide beamcolumn subassemblages. The models are subjected to sixteen earthquake records until collapse by applying the incremental dynamic analysis method. It is found that the ultimate energy dissipation capacity at the story level is markedly low (about 1.36 times the product of the lateral yield strength and yield displacement of the story), giving values for the maximum amount of energy that the frame can dissipate which are from one fourth to half of that required in moderate-seismicity regions.

Evaluating effectiveness and optimum design of isolation devices for highway bridges using the fragility function method

Seismic isolation can be used as a practical method to mitigate earthquake hazards for designing new highway bridges or retrofitting existing ones. To realize a reliable and effective seismic isolation design, several important and often interacting factors should be considered, including the ground motion characteristics, structural configurations and properties, mechanical properties of isolation devices and soil-structure interaction etc. This paper adopts the performance-based evaluation approach to investigate the effectiveness and optimum design parameters of isolation devices so as to minimize the overall damaging potential of seismically-isolated bridges. Fragility functions, which define the probability exceeding a performance state at a given set of earthquake intensities, are derived using nonlinear time history analyses of typical highway bridges (conventionally designed or base-isolated) subject to a suite of 250 earthquake motions. The nonlinear models for bridge columns and isolation devices are incorporated and various combinations of isolation parameters, e.g. elastic stiffness, characteristic strength and post-yielding stiffness, representing common types of isolation devices are evaluated. Both Probabilistic Seismic Demand Analysis (PSDA) and Incremental Dynamic Analysis (IDA) methods are used and compared in generating the fragility functions. Damage criteria for both piers and isolation devices are established to relate the component response quantities to global damage states of bridges. The study shows that the mechanical properties of isolation devices have a significant effect on the damage probability of isolated bridges. By evaluating the earthquake intensity required to achieve specified damage states of base-isolated bridges, the optimum combinations of mechanical parameters of isolation devices are identified as a function of structural properties and damage states. The findings can serve as a practical guide for isolation device designs where the uncertainties with ground motions and variability of structural properties are effectively incorporated under the fragility function framework.

Evaluation of modal incremental dynamic analysis, using input energy intensity and modified bilinear curve

AbstractIn this paper, a technique for the study of nonlinear performance of structures in different levels of earthquakes is developed. In this method, the Incremental Dynamic Analysis (IDA) curves are not achieved from nonlinear dynamic analysis of multi‐degree‐of‐freedom (MDF) structure. However, the procedure of constructing these curves is based on modelling of the entire structure with several single‐degrees‐of‐freedom (SDF) structures and evaluating them through the modal pushover analysis method. An innovative idea for approximating pushover curves that is based on error distribution is introduced in this investigation. Furthermore, the total input energy applied towards the SDF oscillator, which gets converted into MDF structure, is used as intensity measure to impose the different levels of scaled earthquakes.This technique possesses all the advantages of the IDA method in studying the performance of structures in different levels of earthquake. In addition, it benefits from easy usage, high solving speed and less computational CPU time and in attendance with the modified bilinear curves. In this paper, six earthquake records have been applied over four different 4, 8, 12 and 16‐storey structures. The structural responses derived by this method, in the format of multi‐modal incremental curves, containing maximum displacement, drift, hinge rotation and hysteretic energy at the end of the earthquake, have been compared with the IDA method. Comparison of the results is found to have acceptable precision and reveals good agreement between two methods. Copyright © 2008 John Wiley & Sons, Ltd.

Probabilistic structural response assessment using vector‐valued intensity measures

AbstractMethods for using scalar and vector ground motion intensity parameters to estimate the probabilistic relationship between ground motion intensity and structural response are described and compared. Options include using regression analysis on structural analysis results from a set of unscaled (or uniformly scaled) ground motions, or fitting a probability distribution to the analysis results from scaled ground motions analysed using incremental dynamic analysis and related methods. Past methods for using scalar ground motion intensity are reviewed, and methods for utilizing improved vector‐valued intensity measures (IMs) are proposed. ‘Hybrid’ estimation methods that obtain the benefit of vector‐valued IMs using simplified techniques such as careful record selection are also discussed. The results are then combined with models for ground motion occurrence obtained from probabilistic seismic hazard analysis to compute seismic reliability, and the results obtained from the various methods are compared. In general, a tradeoff must be made between the accuracy of the functional relationship between ground motion intensity and structural response versus the number of structural analyses needed for estimation. Copyright © 2007 John Wiley & Sons, Ltd.

On the modal incremental dynamic analysis

In this article a new technique for the dynamic response of structures is investigated. This applied procedure can predict the approximate seismic performance of the structures and it is fast, inexpensive and results are reasonably acceptable. In fact, this novel method logically combines two different techniques, ‘incremental dynamic analysis (IDA)’ and ‘modal pushover analysis (MPA)’, presented by other researchers. This method will take advantage of both methodical ideas such as equivalent single degree of freedom of multi-degree structures and the implementation of different scaled level of an earthquake record to the provided equivalent SDF structure. Using this procedure, simple approximate curves that present a realistic linear and non-linear seismic behaviour of the structure due to the applied scaled level of earthquakes can easily be extracted. In this investigation, several four-, eight- and 12-storey structures are specified as the example models and are dynamically analysed. Next, three different scaled earthquakes, El Centro, Northridge and San Fernando, are applied to each example problem. The results of the presented technique, modal incremental dynamic analysis (MIDA), are then compared with the IDA method. Comparison of the results reveals good accuracy in building seismic demands evaluation. Finally, it is also shown that the MIDA method is simple enough to be carried out on most personal computers and the authors believe this technique will serve design engineers working in real design conditions. Copyright © 2005 John Wiley & Sons, Ltd.