Equations representing stress strain values of steel rebars.

The equations are derived by third order polynomial curve fitting of the data given in SP-16 table  in Indian code.

For Fe 250:
 y = 10802254950x3 - 47811496.7x2 + 74481.40335x + 205.8829164

For Fe 415:
y = 8634745755x3 - 84776621.6x2 + 284712.3995x + 29.42076793

For Fe 500:
y = 7949113254x3 - 89302413.2x2 + 343343.7433x - 20.40632679

Working transparent Plane not shown or visible in 3d window in sap2000 / etabs ?

Go to options and click show bounding plane.

LOAD DISTRIBUTION IN ONE WAY SLAB IN SAP2000

Sap 2000 distributes one way slab load to red colored axis direction only and not towards longer edges. So you'll have to rotate your local axis of slab such that red axis points to your longer edge.

Unit weight of cement, sand, aggregate and other materials?

Unit weight of different materials like cement, sand, aggregates for engineering calculations have been provided in IS:875 (Part I)-1987. You can easily download it following google search for pdf document. IS875 Part I to Part 4 provide loads to be used for building design purpose.
IS: 875 (Part I)-1987 : Dead Loads- Unit weights of building materials and stored materials
IS: 875 (Part 2)-1987 : Imposed Loads (Live loads)
IS: 875 (Part 3)-1987 : Wind Loads
IS: 875 (Part 4)-1987 : Snow Loads
Follow this download link for legal download of all Indian (IS codes) codes.
https://law.resource.org/pub/in/bis/S03/

To prepare SAP2000 model to import in SAFE

See page 12 of https://wiki.csiamerica.com/download/attachments/8750886/Section%20Designer%20RC%20column%20and%20beam%20design.pdf?version=1&modificationDate=1331927322690&api=v2

How to create fourier frequency series from discrete x,y data?

http://www.taoxing.net/web_documents/excel.fft.pdf

What is fourier transformation?

FFT (Fast Fourier Transform) Waveform Analysis

To calculate an FFT (Fast Fourier Transform), just listen. The human ear automatically and involuntarily performs a calculation that takes the intellect years of mathematical education to accomplish. The ear formulates a transform by converting sound—the waves of pressure traveling over time and through the atmosphere—into a spectrum, a description of the sound as a series of volumes at distinct pitches. The brain then turns this information into perceived sound.

A similar conversion can be done using mathematical methods on the same sound waves or virtually any other fluctuating signal that varies with respect to time. The Fourier transform is the mathematical tool used to make this conversion. Simply stated, the Fourier transform converts waveform data in the time domain into the frequency domain. The Fourier transform accomplishes this by breaking down the original time-based waveform into a series of sinusoidal terms, each with a unique magnitude, frequency, and phase. This process, in effect, converts a waveform in the time domain that is difficult to describe mathematically into a more manageable series of sinusoidal functions that when added together, exactly reproduce the original waveform. Plotting the amplitude of each sinusoidal term versus its frequency creates a power spectrum, which is the response of the original waveform in the frequency domain. 

Reference: http://www.dataq.com/data-acquisition/general-education-tutorials/fft-fast-fourier-transform-waveform-analysis.html