pycba.utils.parse_beam_string#

parse_beam_string(beam_string)[source]#

This function parses a beam descriptor string and returns CBA input vectors.

The beam descriptor string uses a specific format: spans lengths in float are separated by single characters describing the terminals of that beam element. The terminal characters are:

  • P - pinned (effectively the same as roller, but retained for visualisations)

  • R - roller (can occur at any terminal)

  • E - encastre (i.e. fully-fixed) - can only occur at beam extremity

  • F - free (e.g. cantilever end) - can only occur at beam extremity

  • H - hinge - can only occur internally in the beam

Examples of beam strings are:

  • P40R20R - 2-span, 60 m long, with pinned-roller-roller supports

  • E20H30R10F - 3-span, 60 m long, encastre-hinge-roller-free

Complex beam configurations may not be describable using the beam string.

The function returns a tuple containing the necessary beam inputs for pycba.analysis.BeamAnalysis: (L, EI, R, eType)

Parameters:

beam_string (str) – The string to be parsed.

Raises:

ValueError – When the beam string does not meet basic structural requirements.

Returns:

(L, EI, R, eType) –

In which:

  • L is a vector of span lengths.

  • EI is A vector of member flexural rigidities (prismatic).

  • R is a vector describing the support conditions at each member end.

  • eType is a vector of the member types.

Return type:

tuple(np.ndarray, np.ndarray, np.ndarray, np.ndarray)

Example

This example creates a four-span beam with fixed extreme supports and an internal hinge.

beam_str = "E30R30H30R30E"
(L, EI, R, eType) = cba.parse_beam_string(beam_str)
ils = cba.InfluenceLines(L, EI, R, eType)
ils.create_ils(step=0.1)
ils.plot_il(0.0, "R")