Interface for the EigenvalueAnalysis Class (Was Written by Francis Thomas McKenna), Part 1:
Class EigenvalueAnalysis: public Analysis {
Public:
EigenvalueAnalysis(Domain & theDomain,
ConstraintHandler & theHandler,
Dod_Numberer & theNumberer,
AnalysisModel & theModel,
EigenvalueAlgo & theSolnAlgo,
EigenvalueSOE & theSOE,
EigenvalueSOESolver &theSolver,
EigenvalueIntegrator &theEigenIntegrator);
Virtual EigenvalueAnalysis();

Virtual int domainChanged(void);
Virtual int analyze(void);
Virtual double updateMode(int mode);
};

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Pseudo-Code for the EigenvalueAnalysis Class (Was Written by Francis Thomas McKenna), Part 2:

UpdateMode() Method: This is a method to update the nodal displacements with the values in the eigenvector for a specific mode. This is done by invoking update() on the EigenvalueIntegrator object with the correct eigenvector. The method returns the value of the eigenvalue for the specified mode.

EigenvalueAnalysis::analyze(void){
if (theDomain->hasDomainChanged() == true)
this->domainChanged();
theAlgorithm->solveCurrentStep();
analysisDone = true;
};
EigenvalueAnalysis::updateMode(int mode){
if (analysisDone == false)
this->analyze();
const Vector &ɸ = theSOE->getɸ(mode);
theIntegrator->update(ɸ);
return theSOE->getℷ(mode);
}

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Prof. Lu XZ, Prof. Xie LL, Prof. Guan H, Prof. Huang YL and Prof. Lu X. A;

Congratulations on Your Outstanding Achievement !!!

This work develops a new shear wall element model and associated material constitutive models based on the open source finite element (FE) code OpenSees, in order to perform nonlinear seismic analyses of high-rise RC frame-core tube structures. A series of shear walls, a 141.8-m frame-core tube building and a super-tall building (the Shanghai Tower, with a height of 632 m) are simulated. The rationality and reliability of the proposed element model and analysis method are validated through comparison with the available experimental data as well as the analytical results of a well validated commercial FE code. The research outcome will assist in providing a useful reference and an effective tool for further numerical analysis of the seismic behavior of tall and super-tall buildings.
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 / ε ,

Where Ec is elastic modulus of concrete in ETABS. Through the adjustment, the vibration periods of OpenSees agree well with those of ETABS.

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Prof. Y. Jiang, Prof. A. Silva, Prof. L. Macedo, Prof. J. M. Castro and Prof. R. Monteiro;

Congratulations on Your Outstanding Achievement !!!
Thank you for development of an accurate model for CFST members in OpenSees, and to access the influence of CFST members on the seismic performance of moment-resisting frames.
The use of concrete filled steel tube (CFST) member in construction practice has become widespread over recent decades. Confinement effects, that improve both the strength and ductility of the core material, as well as the constraint offered by the core to the encasing steel tube, which minimizes the influence of local buckling, are some of the advantages of these members. As a consequence, the capacity and seismic performance of structures can be improved by the use of CFST members in detriment of reinforced concrete or steel-only solutions.
Two types of beam-column elements were considered to model CFST members in OpenSees, namely Distributed Plasticity (DP) and Concentrated Plasticity (CP) models.
In order to investigate the bending behaviour of long CFST columns, 16 circular rubberized CFST specimens which, were recently tested at the University of Porto, were used to calibrate the aforementioned models.

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The 2018 NHERI SimCenter Programming Bootcamp will be held July 30 through August 3, 2018, at UC Berkeley’s Richmond Field Station.
The NHERI Computational Modeling and Simulation Center (SimCenter) is hosting a “SimCenter Programming Bootcamp.” The overall goal of the bootcamp is to train NHERI researchers in programming paradigms not covered in traditional civil engineering courseware, but which are needed to advance their capabilities with regard to simulation for natural hazards engineering. The target audience is graduate students, postdocs, and new faculty who are interested in simulating the effects of natural hazards on components, structures, and communities. By the end of the workshop, participants will have a firm grasp of how to build applications that utilize SimCenter products and run on the high-performance computing platform hosted at DesignSafe-CI. During the five-day bootcamp, participants will be instructed by and interact extensively with the SimCenter’s lead development team.
A sampling of course modules to be offered include:
- Programming in C, C++, and FORTRAN
- Developing Applications in C & C++
- Parallel Programming on HPC with MPI
- Web Application Development: UI Design & Qt
- Hands on application development
- Parallel exercises on TACC Stampede (HPC)
Each day’s agenda (8:30am – 5pm) will include instruction, the development of custom capabilities, hands-on coding exercises or roundtables, example applications, accessing HPC resources at NHERI, and discussions on working within NHERI using SimCenter products. Daily homework will be assigned. Refreshments at breaks and lunch will be provided.
An early registration fee ($150) is available until June 22, 2018. After that date, the registration fee increases to $250. Registration closes July 9, 2018 or before if the maximum number of attendees register.
Financial support Limited domestic travel, lodging, and meal support is available for need-based participants. To request financial support, email <NHERI-SimCenter@berkeley.edu> by May 25, 2018. Graduate students, postdocs, and faculty from under-represented groups are especially encouraged to attend.
This workshop is supported by NSF Award Number CMMI-1612843. Learn more about the SimCenter at https://simcenter.designsafe-ci.org
All questions and concerns may be forwarded to NHERI-SimCenter@berkeley.edu

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The probabilistic seismic hazard analysis (PSHA) is composed of the following steps:
1. Identification of all earthquake sources, both faults and areal regions, capable of producing damaging ground motions to a site.
2. Characterization of the distribution of earthquake magnitudes. The cumulative distribution function is computed for the magnitudes of earthquakes that are larger than some minimum magnitude Mmin and smaller than the upper bound of earthquake magnitudes in a region Mmax due to the finite size of the source faults:

FM(m) = P(M ≤ m|Mmin < M < Mmax)

3. Characterization of the distribution of source-to-site distances associated with potential earthquakes. For a given earthquake source, it is assumed that earthquakes will occur with equal probability at any location on the fault.
4. Prediction of the resulting probability distribution of ground motion intensity by a prediction model, as a function of predictor variables such as the earthquake’s magnitude and distance.
5. Combination of uncertainties in earthquake magnitudes, source-to-site distances and ground motion intensity, using the total probability theorem.

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Spectral Shapes of the Records (Professor Laura Eads, Stanford University):

A common method of incorporating spectral shape is to use the ratio of spectral acceleration at a given period to the spectral acceleration at the fundamental period (Sa(T1)), to improve the estimation of peak interstory drift ratios of nonlinear systems.
Spectral shape is an important consideration when choosing which ground motions to use for response history analysis. As demonstrated by previous studies the spectral shape of a record can significantly influence the nonlinear response of a structure; however, the spectral shape can also influence the linear response of a multiple degree of freedom structure when using records scaled to a common Sa(T1) because of higher-mode effects. Design codes often have provisions about the spectral shapes of the records used in response history analysis. For example, ASCE 7-10 (2010) requires that the average spectrum of records used in two-dimensional response history analysis cannot be less than the design spectrum between a period range of 0.2·T1 and 1.5·T1.
Recognizing that spectral shape can play an important role in nonlinear structural response, the Design Ground Motion Library (Power et al. 2007), which contains acceleration histories suitable for response history analysis of various structures in California, evaluates the spectral shape of a potential record on both (1) the mean squared error of spectral ordinates over a period band with respect to a target spectrum and (2) the slope of the record’s spectrum over the period band versus the slope of the target spectrum over the same period band.

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Thank You Professor Laura Eads🌷🌷, for Your Substantial Researches, All OpenSees Communities Love You.🙏🌹🙏

This Equation Is Mine and You Should Consider/Control It Frequently🌷🌹🌷

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Questions?

Dear Afshin, I am studying for a PHD at the University of Michigan. Thank you for best contents. So, I really think you have two mistakes !!

1- First you tell me that what is cause of gravity?
2- Why do you frequently consider/declare we do not have a constant time in the OpenSees? Also, which time do you mean? analysis time, ground motion time or both?
Thank you.

Answers :
1- The gravity forces are beause of Higgs boson. As you know in the universe, the gravity is too weak. Out of the four fundamental physical forces in the universe_gravity, electromagnetism, the strong force, and the weak force—gravity is by far the weakest. It's so weak that, for instance, a pair of tiny magnets can easily overcome the gravitational pull of the entire Earth.
The Higgs boson, discovered in 2012, is thought to be directly correlated to the strength of gravity. The more mass in the Higgs boson, the stronger gravity would be for all matter in the universe. So essentially, the question "Why is gravity so weak?" is the same as, "Why doesn't the Higgs boson have more mass.
The new theory attempts to answer that question by arguing that after the Big Bang, a bunch of different Higgs bosons were created, each with a different mass. The Higgs bosons with large masses were unstable, so they decayed and broke apart into smaller Higgs bosons. Over time, all the heavier Higgs bosons decayed into lighter and lighter versions, until only the lightest possible kind of Higgs boson was left. That extremely light Higgs boson is the one the LHC discovered in 2012.

2- I frequently consider/declare we do not have a constant time in the OpenSees, because contrary to popular belief, time is not an independent variable, however it is a dependent and sophisticated variable. Time of each mass depends to the Higgs boson and coordinate of the mass in the structure.🌷🌷

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