Time History Etabs

[Victorino Eagle]

Timehistory analysis provides for linear or nonlinear evaluation of dynamic structural response under loading which may vary according to the specified time function. Dynamic equilibrium equations, given by K u(t) + C d/dt u(t) + M d2/dt u(t) = r(t), are solved using either modal or direct-integration methods. Initial conditions may be set by continuing the structural state from the end of the previous analysis. Additional notes include:

Nonlinear modal time-history analysis, also known as Fast Nonlinear Analysis (FNA), is generally more accurate and efficient than direct-integration time-history analysis. The accuracy of FNA depends upon the sufficiency of suitable mode shapes, similar to how direct integration requires small enough time steps to accurately characterize dynamic behavior.

Damping is handled differently between these two analysis methods. FNA limits proportional damping at the frequency extremes to 0.99995 that of critical, while direct integration uses mass- and stiffness-proportional damping in which damping at very low and very high frequencies may exceed critical.

Results may be sensitive to physical parameters, loading conditions, and the analytical technique applied, especially with irregular structures and advanced nonlinear systems. Since FNA is an accurate and efficient analysis method, it may be worthwhile to apply this technique to a series of models which simulate variable computational scenario. For example, foundation springs and substructure may be included, then omitted, to provide a comparison study.

The project is going to be an ASCE 41 non-linear dynamic analysis and has had geotech engineers involved in picking out ground motion that represent similar ground motions that the faults near this building may produce.

Converting from time history to response spectrum can be done in ETABs, but post processing the data is kinda difficult, I can't seem to find a way to programmatically access the response spectrum curves that ETABs produces.

You can find the code to make plots like these on my github:

The required data format is a .txt file that is separated with returns and tabs. I have heard not all geotechs provide their time history data in this manner, so if you want to use this, you may have to edit.

Starting into this, I thought this process involved using fourier transforms to transition from the time domain to the frequency domain, I clearly had forgotten my structural dynamics. Reading chapter 5 of Chopra and getting some guidance from fellow engineer Bryant, I was able to recreate the Newmark method outlined in the Chopra book. Adding a whole bunch of for loops later, some awesome plots popped out.

Great job! We've been wanting a tool like this for so long that I'd considered making it myself. During my research, I stumbled across this blog right around the time you were looking for testers a few months ago.

The inability of a building to withstand deviations due to earthquake strength exceeding the required safe limit is one of the factors causing the collapse of the building. Mitigation efforts that can be made to overcome the impact of earthquakes include evaluating the performance of building structures. In this study, the Faculty of Medicine building at Indo Global Mandiri University was evaluated using the time history analysis method using ETABS V.18. The results of the analysis showed that for the El Centro (1940), Mentawai-West Sumatra (2007), and Chihuahua (2010) earthquakes, based on the value of inter-level drift and maximum inter-level drift on the effect of planned earthquake loads, the service limit performance was fewer than 0.017 meters and the ultimate limit performance was fewer than 0.080 meters, so it has met permit requirements according to the Indonesian standard (SNI 1726-2019) and is included in the safe category. Based on the performance of ATC-40 obtained for the El Centro (1940) and the Mentawai-West Sumatra (2007), it produced the performance level of the structure "Immediate Occupancy", while when subjected to the load of the Chihuahua (2010), it produced the performance level of the structure "Damage Control".

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Complete description of this function is provided in a PDF file. Two examples will help you to use this function for either base excitation load (earthquake) or time-variant forces on DOFs.

There is a new feature in this function which will let you limit modal analysis only to desired number of modes. For example, there is a 50-DOF structure. However, you want to do time history modal analysis only for first 7 modes not all the modes.

I am a beginner in Ansys. I've only started working on the software for the past four months. Now, I am working on a study using linear time history. One of my goals in this study is to compare the results from the linear time history I initiated in Ansys to other structural analysis software like Etabs to validate the results.

I performed linear time history in Ansys through modal and transient analysis, and I'm looking for the displacement of the structure when subjected to acceleration. However, I am having a hard time matching the results of Ansys with Etabs.

I have tried to make the loads similar in Etabs and Ansys and have successfully matched the results of the modal analyses from each software after several attempts. But the results in the transient analysis are still far from each other. Since I am more familiar with Etabs, I am sure that I have performed the linear time history analysis well in that software.

However, Ansys has a different interface and features than Etabs. I am not sure whether I have performed the analysis well in Ansys because it produces small values compared with Etabs, especially while using the transient analysis.

I think that perhaps, the analysis settings in the transient analysis of Ansys have something to do with the discrepancy between the results. I believe there is a need to input the correct time step. However, I am still having trouble defining such value. Can anyone please help me?

Our new Taylor Damped Moment FrameTM (TDMFTM) procedure simplifies the design process for new buildings by eliminating the need for nonlinear time-history analysis and peer review. This more prescriptive approach decouples special steel moment frame design from the damper frame, allowing for easier analytical models and improved coordination with Taylor Devices.

Damper Properties are determined through a prescriptive approach. The damping constant, C, is easily determined for each damper. The velocity exponent, alpha, is fixed at 0.4. The process is easily implementable into spreadsheets

The document provides a step-by-step guide for conducting a time-history seismic analysis using SAP2000 software. It details how to:1) Download recorded earthquake accelerograms from the PEER database, such as one from the 1940 Imperial Valley earthquake. 2) Upload the selected accelerogram file into SAP2000 and define it as a time history function.3) Assign the accelerogram to a time history analysis case and run the dynamic analysis.4) View and analyze results like envelopes of axial forces, moments, and time histories of displacements.Read less

Based on the refined ETABS Benchmark model of a 606m mega-tall building (provided by Prof. Xilin Lu and Prof. Huangjun Jiang from Tongji University (Lu et al., 2015a)), the corresponding models of OpenSees are established and provided here (Figure 1). The modeling method proposed by Lu et al. (2015b) is adopted for this building.

Two mesh schemes are considered, which results in two models: Model 1 and Model 2. Model 1 is relatively coarse, which has 27220 nodes. The coupling beams and shear walls of Model 1 is subdivided to generate Model 2, which has 81572 nodes. The shear walls and coupling beams are simulated using ShellMITC4 in OpenSees.

There are some differences in defining the elastic modulus of concrete in ETABS and OpenSees, which will affect the calculated vibration periods. When we conduct the modal analysis, the elastic modulus of concrete material in OpenSees should be adjusted following the equation Ec=2fc/e0, where Ec is elastic modulus of concrete in ETABS. Through the adjustment, the vibration periods of OpenSees agree well with those of ETABS.

Note that the commercial software package MSC.Marc has been widely used in nonlinear analyses of super-tall buildings and well validated. The corresponding models are also established in MSC.Marc (denoted as Model1M and Model2M, respectively). Through the comparison between the time history analysis results of OpenSees and MSC.Marc, the reliability of the OpenSees models is validated.

The El-Centro ground motion, which is scaled to a value of PGA of 220 cm/s2 (i.e., the MCE level ground motion of this building according to the Chinese code), is firstly used to conduct the time history analysis of Model1 and Model1M. Note that both CPU and GPU solvers (Tian et al. 2015) are used to perform the time history analysis to validate the reliability and facilitate different researchers to use these models. If you want to use the CPU version model, please use dynamiccpu.tcl, else please use dynamicgpu.tcl in the zip files.

The time history curves of the roof and the envelope of inter-story drift are presented in Figure 2. Good agreements are observed. In addition, the time history results obtained from CPU and GPU are also compared in Figure 3. The results are identical, thus validating the reliability of the GPU solver.

Then, the time history analysis of Model2 and Model2M are also performed. The time history curves of the roof and the envelope of inter-story drift are presented in Figure 4. Good agreements are also observed, thus validating the reliability of Model2.

3a8082e126