rcdesign

rcdesign is a Python package for analysis and design of reinforced concrete sections as per IS 456:2000, the Indian Standard code of practice for plain and reinforced concrete.

Documentation

Installation

Install from PyPI using pip

Requirements

• Python 3.7+
• numpy
• scipy
• sympy

Install from PyPI

Create a separate directory and install a virtual environment. Activate the virtual environment and install required packages. On *nix systems, do the following:

$ mkdir rcd_tutorial
$ cd rcd_tutorial
$ python -m venv ./venv
$ ./venv/bin/activate
$ python -m pip install -U pip
$ pip install rcdesign numpy sympy scipy
$ python -m rcdesign.example

On Windows, do the following:

> mkdir rcd_tutorial
> cd rcd_tutorial
> python -m venv venv
> venv\Scripts\activate
> python -m pip install -U pip
> pip install rcdesign numpy sympy scipy
> python -m rcdesign

If installation is successful, the example problems must run and you should see the output.

Install from Source on github

To install from github, clone the github repository and give it a try. If you are not familiar with the workflow for working with a source repository, follow these steps.

Preliminary checks

Check the version of Python you are using. You will require version 3.7 or later. To print the version of Python, use the command

$ python -V
Python 3.9.7

On a *nix system, you may have to type

$ python3 -V
Python 3.9.7

Clone the repository

When you clone the rcdesign repository from github, a new directory named rcdesign will be created in the current working directory. Therefore change over to a suitable directory within which to clone the repository. Clone the repository using git

$ git clone https://github.com/satish-annigeri/rcdesign.git

Change over to the directory rcdesign that is created with the command

$ cd rcdesign

List the directory contents and verify the directory structure.

Create a virtual environment

Create a virtual environment inside the rcdesign directory with the following command

$ python -m venv env

Activate the virtual environment with the command

$ source env/bin/activate
(env) $_

For Windows operating system, the command is

> env\Scripts\activate
(env) >_

Update pip with the command

(env) $ python -m pip install -U pip

Install required packages

Install required packages into the virtual environment with pip

(env) $ pip install -r requirements.txt

Run tests

Install additional packages required to run tests.

(env) pip install pytest pytest-cov nox

Run the tests with pytest

(env) $ pytest tests

Check code coverage.

(env) $ pytest --cov=rcdesign tests/

You can also use nox to run the tests. Install nox using pip, if necessary.

(env) $ pip install nox
(env) $ nox

When you are done using the virtual environment, you can deactivate it with the command deactivate at the command prompt in all operating systems.

A Simple Example

Run the built-in example with the following command.

(env) $ python -m rcdesign

Alternately, you can create the following Python script example.py, which is in fact the first example in the __main__.py file of the rcdesign package, and run the script.

from rcdesign.is456.stressblock import LSMStressBlock
from rcdesign.is456.concrete import Concrete
from rcdesign.is456.rebar import (
    RebarHYSD,
    RebarLayer,
    RebarGroup,
    ShearRebarGroup,
    Stirrups,
)
from rcdesign.is456.section import RectBeamSection

sb = LSMStressBlock("LSM Flexure")
m20 = Concrete("M20", 20)
fe415 = RebarHYSD("Fe 415", 415)

t1 = RebarLayer(fe415, [20, 16, 20], -35)
steel = RebarGroup([t1])
sh_st = ShearRebarGroup([Stirrups(fe415, 2, 8, 150)])

sec = RectBeamSection(230, 450, sb, m20, steel, sh_st, 25)
xu = sec.xu(0.0035)RECTANGULAR BEAM SECTION: 230 x 450

Check the output.

Example 1

RECTANGULAR BEAM SECTION: 230 x 450
FLEXURE
Equilibrium NA = 179.94 (k = 0.40) (ec_max = 0.003500)
   fck                             ec_max Type            f_cc   C (kN)  M (kNm)
--------------------------------------------------------------------------------
 20.00                         0.00350000    C            8.93   299.30    31.45
--------------------------------------------------------------------------------

    fy         Bars       xc       Strain Type     f_sc   f_cc   C (kN)  M (kNm)
--------------------------------------------------------------------------------
   415    1-16;2-20   415.00  -0.00457204    T  -360.87         -299.30    70.35
--------------------------------------------------------------------------------
                                                                   0.00   101.81
SHEAR
Vertical Stirrups: Fe 415 2-8 @ 150 c/c (Asv = 100.53)

CAPACITY
Mu = 101.81 kNm
Vu = 156.83 kN

================================================================================

Example 2

RECTANGULAR BEAM SECTION: 230 x 450
FLEXURE
Equilibrium NA = 136.21 (k = 0.30) (ec_max = 0.003500)
   fck                             ec_max Type            f_cc   C (kN)  M (kNm)
--------------------------------------------------------------------------------
 20.00                         0.00350000    C            8.93   226.56    18.02
--------------------------------------------------------------------------------

    fy         Bars       xc       Strain Type     f_sc   f_cc   C (kN)  M (kNm)
--------------------------------------------------------------------------------
   415         2-16    35.00   0.00260065    C   347.70   8.93   136.23    13.79
   415         2-16   380.00  -0.00626432    T  -360.87         -145.11    35.38
   415         3-16   415.00  -0.00716367    T  -360.87         -217.67    60.68
--------------------------------------------------------------------------------
                                                                -226.56   109.85
                                                               =================
                                                                   0.00   127.87
SHEAR
Vertical Stirrups: Fe 415 2-8 @ 150 c/c (Asv = 100.53)

CAPACITY
Mu = 127.87 kNm
Vu = 156.19 kN

Contribute

Contributions are welcome. Contributions can be in a variety of forms:

1. Bug reports
2. Additional features
3. Documentation
4. Additional examples

Links

• Documentation: Documentation
• PyPI release: 0.4.0
• Github repository: https://github.com/satish-annigeri/rcdesign

What rcdesign can and cannot do

At present rcdesign can do the following:

1. Analyse reinforced concrete rectangular and flanged sections subjected to bending and shear as per the Limit State Method according to IS 456:2000, the Indian standard code of practice for plain and reinforced concrete. This calculates the ultimate strength of the section in bending and shear depending on the materials, section size and main (longitudinal) and shear reinforcement.
2. Analyses reinforced concrete rectangular sections subjected to axial compression and bending about one axis parallel to the first (usually the short) edge, as per limit state method of IS 456:2000.
3. Represent stress strain relationship for:
   1. concrete in flexure as per IS 456:2000 (38.1),
   2. concrete under axial compression and flexure as per IS 456:2000 (39.1),
   3. reinforcement bars:
      1. mild steel bars with well defined yield point
      2. cold worked deformed bars
4. Represent layers of reinforcement bars placed parallel to the edge of the section at a given distance from the compression (or tension edge). Bars can be of different diameters but must be of the same type.
5. Represent group of layers of reinforcement bars. All bars in agroup must be of the same type and layers of reinforcement must be placed parallel to the edge of the section.
6. Represent group of shear reinforcement in the form of vertical stirrups, inclined stirrups and bent-up bars.

Rectangular and flanged sections must be of a given grade of concrete. Main (longitudinal) reinforcement to resist bending must be provided as a single group of reinforcement layers, possibly with one or more layers in the compression zone in addition to one or more layers in the tension zone. However, since the position of the neutral axis is dependent on the section size and the amount and location of main reinforcement, whether a layer of reinforcement lies in the tension zone or the compression zone will be known after an analysis of the section.

At present, rcdesign cannot do the following:

1. Cannot design sections, either for bending, shear and torsion or for axial compression with or without bending about one or both axes.
2. Cannot verify whether the section meets the detailing requirements of IS 456:2000 (26).
3. Cannot analyse or design sections as per Working Stress Method of IS 456:2000 (Annexure N).
4. Cannot design reinforced concrete elements such as beams and columns. At present, the scope of the package is restricted to analysis and design of sections of beams and columns. This is a distant goal, but no promises.

Some or all of the above features will be gradually included. Contributions in accomplishing these are welcome.

Current Status

The package is in early development and may undergo backward incompatible changes. It has undergone testing of the current code base. Limited examples have been solved and verified by hand. Test coverage is currently 100% (excepting the example script).

Classes

The following classes have been implemented:

1. A class LSMStressBlock to represent the stress block for concrete in compression under limit state of flexure, as well as limit state of combined axial compression and flexure as per IS 456:2000.
2. A class Concrete to represent concrete.
3. An abstract class Rebar to represent reinforcement bars. Two derived classes RebarMS and RebarHYSD to represent mild steel bars and high yield strength deformed bars, respectively.
4. A class RebarLayer to represent a single layer of reinforcement bars, defined as a list of bar diameters and the distance of the centre of the bars from the nearest edge. A class RebarGroup to represnt a list of layers of reinforcement bars.
5. An abstract class ShearReinforcement to represent shear reinforcement. Two derived classes Stirrups and BentupBars to represent vertical/inclined stirrups and bent up bars, respectively.
6. A class ShearRebarGroup to represent a group of shear reinforcement bars.
7. A class RectBeamSection to represnt a reinforced concrete rectangular beam section. A derived class FlangedBeamSection to represnt flanged sections subejcted to flexure and shear, derived from RectBeamSection.
8. A class RectColumnSection* to represent a reinforced concrete rectangular coulmn section subjected to combined axial compression and bending about one axis.

Methods

Following funcationality has been implemented for the different classes:

1. LSMStressBlock: Calculation of the following:

   1. strain distribution,
   2. stress for a given strain,
   3. stress at a specified distance $x$ from neutral axis,
   4. area of stress distribution between two locations $x_1$ and $x_2$ from neutral axis, and
   5. moment of stress block between the two locations with respect to depth $x_u$ of the neutral axis.

   These are implemented for both the following cases:

   1. Flexure
   2. Combined axial compression and bending about one axis.

2. Concrete: Calculation of design stress $f_d$, shear stress $\tau_c$ and maximum shear stress $\tau_{c,max}$.

3. RebarMS and RebarHYSD: Stress for a specified value of strain and design stress.

4. RebarLayer: Area of bars in a layer.

5. RebarGroup: Calculation of the sum of the following values aggregated after calculating the values individually for each layer:

   • Area of reinforcing bars in the group,
   • Force in reinforcing bars in the group, in tension and in compression,
   • Moment of force in reinforcing bars in the group about the neutral axis, in tension and in compression

6. RectBeamSection and FlangedBeamSection: Calculation of:

   • Total compression force and the corresponding moment about the neutral axis for a specified neutral axis location $x_u$, considering concrete in compression and compression reinforcement bars, if present,
   • Total tension force and the corresponding moment about the neutral axis due to a group of tension reinforcement bars,
   • Position of the neutral axis $x_u$, calculated iteratively to satisfy equilibrium,
   • Shear force capacity of a section for a given shear reinforcement in the form of vertical or inclined stirrups,
   • Spacing of vertical or inclined stirrups for a given design shear force

7. RectColumnSection: Calculation of:

   • Total axial compression force and bending moment about the neutral axis for a given position of the neutral axis.

Testing

Testing has been implemented using pytest and unit tests have been implemented for the following classes:

1. ConcreteLSMFlexure and Concrete
2. RebarMS and RebarHYSD
3. RebarLayer and RebarGroup
4. ShearReinforcement and Stirrups
5. RectBeamSection and FlangedBeamSection
6. RectColumnSection

Code coverage through tests using pytest-cov at the current time is 100%, excepting the example script and the methods that implement __repe__() and report().

Analysis of rectangular and flanged beam sections with and without compression reinforcement, for flexure and shear, has been completed. Several examples have been solved and verified by hand to consider different cases.

Analysis of rectangular column sections for combined axial compression and bending about one axis has been completed. An example has been solved and verified by hand.

Automated testing can be done using. Check to ensure that nox is installed using the command

(env) $ nox --version
2021.6.12

If required, install nox with the command:

(env) $pip install nox

Documentation

Documentation is available here. Any advise or help on documentation is welcome.

Future Plans

Immediate plans include the design of sections:

1. Design of rectangular and flanged sections subjected to bending, shear and torsion.
2. Write user and API documentation using Sphinx.
3. Design of rectangular column sections.
4. Detailing of rectangular beam sections subjected to bending, shear and torsion.
5. Design of rectangular column sections subjected to combined axial compression and bending.
6. Implementing a stress block to represent working stress method.

Long term plans include:

1. Design and detailing of reinforced concrete elements such as beams, columns, slabs, footings, retaining walls etc.
2. Calculation of deflections of elements.
3. Design and detailing of reinforced concrete structures, including detailing of joints (very far into the future, if at all).

References

1. IS 456:2000 Indian Standard Code of Practice for Plain and Reinforced Concrete (Fourth Revision), Bureau of Indian Standards, New Delhi, 2000.
2. SP:24 (S&T)-1983 Explanatory Handbook on Indian Standard Code of Practice for Plain and Reinforced Concrete (IS 456:1978), Bureau of Indian Standards, New Delhi, 1984.
3. SP 16:1980 Design Aids for Reinforced Concrete to IS:456-1978, Bureau of Indian Standards, New Delhi, 1980.