Quick Start¶

This guide will get you up and running with pyRVT in just a few minutes.

Basic Usage¶

pyRVT provides several ways to work with ground motion data. Here are the most common use cases:

Creating a Motion from Fourier Amplitude Spectrum¶

import pyrvt
import numpy as np
import matplotlib.pyplot as plt

# Define frequency array (Hz)
freqs = np.logspace(-1, 2, 100)  # 0.1 to 100 Hz

# Define Fourier amplitude spectrum (g-s)
# This example uses a simple flat spectrum
fourier_amps = np.ones_like(freqs) * 0.1

# Define motion duration (s)
duration = 10.0

# Create RVT motion
motion = pyrvt.motions.RvtMotion(freqs, fourier_amps, duration)

# Calculate response spectrum
osc_freqs = np.logspace(-1, 1.5, 50)  # Oscillator frequencies
damping = 0.05  # 5% damping
resp_spec = motion.calc_osc_accels(osc_freqs, damping)

# Plot results
plt.figure(figsize=(10, 4))

plt.subplot(1, 2, 1)
plt.loglog(freqs, fourier_amps)
plt.xlabel('Frequency (Hz)')
plt.ylabel('Fourier Amplitude (g-s)')
plt.title('Input FAS')
plt.grid(True)

plt.subplot(1, 2, 2)
plt.loglog(1/osc_freqs, resp_spec)
plt.xlabel('Period (s)')
plt.ylabel('Response Acceleration (g)')
plt.title('Calculated Response Spectrum')
plt.grid(True)

plt.tight_layout()
plt.show()

Converting Response Spectrum to Fourier Amplitude Spectrum¶

import pyrvt
import numpy as np

# Define response spectrum
periods = np.logspace(-1, 1, 50)  # 0.1 to 10 seconds
resp_spec = 0.1 * np.ones_like(periods)  # Flat response spectrum at 0.1g

# Define motion duration
duration = 15.0

# Create compatible motion
motion = pyrvt.motions.CompatibleRvtMotion(
    osc_freqs=1/periods,
    osc_accels=resp_spec,
    osc_damping=0.05,
    duration=duration
)

# Get the compatible Fourier amplitude spectrum
freqs = motion.freqs
fourier_amps = motion.fourier_amps

print(f"Generated FAS with {len(freqs)} frequency points")
print(f"Frequency range: {freqs[0]:.3f} to {freqs[-1]:.1f} Hz")

Using Different Peak Factor Models¶

pyRVT includes several peak factor models. Here’s how to use different ones:

import pyrvt
import numpy as np

# Create test motion
freqs = np.logspace(-1, 2, 100)
fourier_amps = np.ones_like(freqs) * 0.1
duration = 10.0

# Compare different peak factor models
peak_models = [
    pyrvt.peak_calculators.Vanmarcke1975(),
    pyrvt.peak_calculators.BooreThompson2015(),
    pyrvt.peak_calculators.WangRathje2018(),
]

osc_freqs = np.logspace(0, 1, 20)  # 1 to 10 Hz
damping = 0.05

results = {}
for peak_calc in peak_models:
    motion = pyrvt.motions.RvtMotion(freqs, fourier_amps, duration,
                                    peak_calculator=peak_calc)
    resp_spec = motion.calc_osc_accels(osc_freqs, damping)
    results[peak_calc.__class__.__name__] = resp_spec

# Compare results
for name, resp_spec in results.items():
    print(f"{name}: Max response = {np.max(resp_spec):.3f} g")

Command-Line Interface¶

pyRVT also provides a command-line interface for quick conversions:

Convert response spectrum to Fourier amplitude spectrum:

$ pyrvt rv2fa --input-file response_spectrum.csv --output-file fourier_spectrum.csv

Convert Fourier amplitude spectrum to response spectrum:

$ pyrvt fa2rv --input-file fourier_spectrum.csv --output-file response_spectrum.csv

See the Command-line interface for more details on command-line usage.

Working with Seismological Models¶

pyRVT includes seismological models for generating Fourier amplitude spectra:

import pyrvt

# Define earthquake parameters
magnitude = 6.5
distance = 20.0  # km
duration = 10.0

# Create motion using source theory
freqs = np.logspace(-1, 2, 100)
motion = pyrvt.motions.SourceTheoryMotion(
    mag=magnitude,
    dist=distance,
    duration=duration,
    freqs=freqs
)

# Calculate response spectrum
osc_freqs = np.logspace(-1, 1, 30)
resp_spec = motion.calc_osc_accels(osc_freqs, damping=0.05)

print(f"Peak response: {np.max(resp_spec):.3f} g")

Next Steps¶

Now that you’ve seen the basics, you can:

Explore the Use as a library for more detailed examples
Learn about the Command-line interface for batch processing
Check out the API Reference for complete function documentation
See the Example usage of pyRVT for real-world applications

Key Points to Remember¶

Frequency units: pyRVT uses Hz for frequency and periods in seconds
Amplitude units: Fourier amplitudes are typically in g-s, response spectra in g
Damping: Response spectra calculations require a damping ratio (typically 0.05 for 5%)
Duration: Motion duration significantly affects peak factor calculations
Peak factor models: Different models may give different results - choose based on your application