RampCalc0.1 – Parametric input for ramp in FE.

This program calculate data of beam, col and slab for ramp. It creates CSV file that can be used in sap2k or any FE package. It requires gnuoctave/matlab to work. You can download it from here:

Scripts Info:

  1. spiral.m = calculate and plot ramp in octave/matlab
  2. beams.m  = calculate data of beam for ramp to be used in FE
  3. cols.m    = calculate data of columns for ramp to be used in FE
  4. slabs.m   = calculate data of triangular slab for ramp to be used in FE

Background Theory:

Circle plot requires x = r*sin(t) and y = r*cos(t) where t increments from 0 to any given radians. If we increment z from 0 to given height h with some increment, and plot with x and y of a circle,  we will get a 3D spiral curve. Two such spiral curve can be used to calculate data point for ramp. Below is the sample code. You can run this by copy and paste directly in gnu octave or matlab or  create script out of it.

Ramp plot in octave
Ramp plot in octave

By using, beams, cols and slabs script function, csv data will be created that can be formatted as per any finite element code. Here I formatted it for sap2K.

Ramp view in sap2k
Ramp view in sap2k

A spreadsheet with sample sap2k format is attached with this code. Below is video tutorial explaining usage of this code:

 

Location of Construction Joint

Following points are helpful to provide construction joint in RC Slab, Beam and Raft Foundation:

  1. Construction joint shall be provided preferably at a location where stress are zero.
  2. Construction joint is provided at one-third or end of support.
  3. Also provide key and rebar to transfer shear stress if shear stress is not zero at point of construction joint.
  4. Provide construction joints as minimum as possible.
  5. Construction joint shall not be left on discretion of contractor. It must be approved by designer.

Definition:

Construction joints are placed at the end of a day’s work. In slabs, they may be designed to permit movement and/or to transfer load. Often in reinforced concrete a conscious effort is made to clean the joint and bond the next day’s work.[1].

Explanation:

The number of construction joints in concrete structures should be minimized. If construction joints are necessary to facilitate construction, it is normally aligned perpendicular to the direction of the member. For beams and slabs, construction joints are preferably located at about one-third of the span length. The choice of this location is based on the consideration of low bending moment anticipated with relatively low shear force. However, location of one-third span is not applicable to simply supported beams and slabs because this location is expected to have considerable shear forces and bending moment when subjected to design loads. Sometimes, engineers may tend to select the end supports as locations for construction joints just to simplify construction. [2].

Construction joint is not preferred at midspan. When formwork removed from construction pours (delay in next pouring) and the beam (or slab) has had to cantilever from the previous support to the new construction joint. Also, joints at midspan do not typically work for post-tensioned construction. you need to accommodate anchorages and at approx 1/3 span works best. [3].

You need to provide a joint with key and rebars crossing the joint. In raft footing, at construction joint, shear force may not be minimum/zero. Hence you will have to leave dowels from one pour to another pour to transfer shear. You may calculate area of reinforcement required based on permissible shear stress as 0.45 fy. [4].

You can have your opinion and suggestion in comment box below.

Reference:

  1. CADMAN
  2. A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
  3. eng-tips
  4. sefindia.org

Additional Reference:

  1. ACI 302.1, “Guide for Concrete Floor and Slab Construction,” ACI Manual of Concrete Practice.
  2. “Slabs on Grade,” ACI Concrete Craftsman Series, American Concrete Institute, Detroit, Mi.
  3. “Cracks in Concrete: Causes, Prevention, Repair,” a collection of articles from Concrete Construction Magazine, June, 1973.

Classificaiton of Load with respect to Time

Static:

A static load is time independent. It’s value is constant w.r.t time.
 

Dynamic:

A dynamic load is time dependent and for which inertial effects cannot be ignored.
 

Quasi-Static/Pseudo-Static:

A quasi-static/pseudo-static load is time dependent but is “slow” enough such that inertial effects can be ignored. Note that a load quasi-static for a given structure (made of some material) may not be quasi-static for another structure (made of a different material).
 

Quasi-Dynamic/Pseudo-Dynamic:

In pseudo-dynamic loading, inertia and damping properties are simulated while stiffness properties are acquired from the structure. It is displacement based load given to structure in pseudodynamic (PSD) test. The pseudodynamic (PSD) test method is a displacement-based experimental technique that is used to simulate the seismic response of structures. PSD utilizes feedback signals from a test structure in a numerical integration algorithm to sequentially solve the equations of motion to determine command displacements. The command displacements are imposed on a test structure using hydraulic actuators.

Reference:

  1. IMECHANICA
  2. ASCE
  3. PSD

 

 

Understanding Retrofitting, Repair, and Strengthening

In Structural Engineering, retrofitting, repair and strengthening of structure are most commonly used words. It is important to distinguish them and defined them for better understanding.

Retrofitting: Retrofitting is the bringing the structure back to its original strength after damage + further increase in its strength to make it more strong than before.


Repair: Repair is bringing back the structure to its original strength after damage.


Strengthening: Strengthening is increase in strength of structure which is not damaged.

Lectures on Steel Structures

Following are lectures on Steel Structures.

Instructor: Prof. Dr. Akhtar Naeem Khan

Lecture 1 – Design Philosophies

Lecture 2 – Introduction to Steel Structures

Lecture 3 – Design Loads

Lecture 4 – Bolted Connections

Lecture 5 – Welded Connections

Lecture 6 – Tension Members

Lecture 7 – Miscellaneous Topics

Lecture 8 – Compression Members

Lecture 9 – Compression Members Problems

Lecture 10 – Beams

Lecture 11 – Beams Problems

Lecture 12 – Composite Beams

Lecture 13 – Plate Girders

Lectures on Advanced Structural Analysis I

Following are course content on Advanced Structural Analysis I

Course Intructor: Prof. Dr. Shahzad Rahman

Course Outline

Lectures

Lecture 1: Overview of Bernoulli-Euler Beam Theory, Theory of Torsion, Static Indeterminancy, Kinematic Indeterminancy

Lecture 2: Slope-Deflection Method

Lecture 3: Virtual Work Principles

Lecture 4: Moment Distribution Method

Lecture 5: Modifications in Moment Distribution Method

Lecture 6: Moment Distribution Method – Frame with Side Sway

Lecture 7: Compatibility Method of Analysis

Lecture 8: Matrix Analysis of Structures

Lecture 9: Matrix Analysis / Stiffness Method

Lecture 10: Matrix Analysis / Stiffness Method Contd.

Lecture 11: Matrix Analysis / Stiffness Method – Static Condensation

Lecture 12: Approximate Analysis

Lecture 13: Matrix Analysis – Member Releases

Labs

Introduction to SAP2000

Assignments

Assignment 1: Slope and Deflection of Beam

Assignment 2: Displacements in Truss

Assignment 3: Solving Beam using Moment Distribution Method

Solution of Assignments

Exam

Mid Term Exam Paper

Solution of Mid Term Paper

Final Term Exam Paper and Solution

Lectures on Introduction to Finite Element Analysis

Following are course content for Introduction to Finite Element Analysis –  FEA.

Course Intructor: Prof. Dr. Shahzad Rahman

Introduction to FEA

Very Informative lectures on FEA are also available on Youtube.

Lectures

Course Outline

Lecture 1: Overview of Finite Element Method – FEM, Historical Background and its Application

Lecture 2: Method of Weighted Residual, Least Square, Collocation, and Galerkin

Lecture 3: General derivation of Finite Element Equilibrium Equations

Lecture 4: Development of Stiffness Matrix for a Beam Element

Lecture 5: Some rules governing relationship between Global and Local Coordinates

Lecture 6: Comments on Numerical Integration

Lecture 7: Error and Convergence in FEM

Assignments

Assignment 1: Bar Element Problem

Assignment 2: Beam Problem

Assignment 3: Thick walled cylinder Problem

Solution of Assignments

Note: Solution of Assignment 1 is in Lecture 2. There is excellent solution of axial bar problem using FE and comparing with Exact Solution plot along with matlab code in here.

Solution of Assignment 2

Solution of Assignment 3

Exams

Midterm Exam Paper

Final Term Paper

Solver based on Direct Stiffness Method

DSM-SOLVER is based on Direct Stiffness Method.  Direct Stiffness Method is implementation of Finite Element Method. It is available in two flavors. One is octave/matlab while other is scilab script and distributed under GNU/GPL v2.0 license.

GNU Octave is free clone of matlab. It is fully compatible with matlab.

Scilab is an open source, cross-platform numerical computational package and a high-level, numerically oriented programming language. Scilab is alternative to matlab.

You can download the source-code of DSM-OCTAVE-SOLVER or  DSM-SCILAB-SOLVER. To understand how this script works,  read the document provided along with the source files. Consider the following example:

scilab dsm example
Example Problem

The above example can be solved in one of the two scripts explained as under:

For Octave/Matlab example, first define some input variables as:

 

To run the program, you need to update the directory to src folder, then, write following:

Note that truss2d has same code as that of frame 2d. You can get pretty accurate result for trusses by considering it as frame.

 

For SCILAB example, the input matrices and command for making var01.bin as provided in the preproc.sce file are:

To run the program, you need to update the directory to src folder, then, write following: