Tutorial #1: Four Sided Precast Box

Problem Overview

 A complete start-to-finish design using Eriksson Culvert will be demonstrated in this chapter.  The job is a typical precast four sided box culvert, which will be designed in accordance with the LRFD 6^th Edition Specifications. Below are the input values for the problem.

Data Preparation

Most input fields in Eriksson Culvert’s interface were designed to minimize the preliminary work that must be done by the engineer prior to running the program.

Eriksson Culvert automatically computes the self-weights of both the slab and the walls.

Entering Data

To begin the tutorial, start Eriksson Culvert by accessing it though the Programs folder of the Start menu.  Click the Start button in the lower left-hand corner of the screen, highlight the Programs folder, highlight the Eriksson Culvert icon, and click the icon.  Note that due to differing versions of Windows, some of the following screen shots may look different on your system.

The startup screen will appear, select the project titled “four-sided” and double-click to open the file.

Once the job has been loaded, a design is performed based on the the current job data, and five tabbed views are displayed, with the main view selected as the current view. This view is a graphic view of the primary data for the job. This data includes the slab clear span and clear height, calculated wall and slab thicknesses, materials properties, loads, and rebar schedule. The screen shot above shows the top of four scrollable pages included in this view.

The other views are Ratings Summary, Reinforcement Summary, and Results Graphs. A tab for a 3D Model can be added by clicking on the ‘Create 3D Model’ icon in the main toolbar (it looks like a sphere). You can access these views by clicking on their respective tabs.

Data input in Eriksson Culvert is accomplished via standard Windows dialog boxes. These are organized around logical groupings of data. Depending on whether a job was initialized using one of Eriksson Culvert’s default jobs, a previously created seed file, or some other file, a number of dialog boxes will need to be opened and the relevant changes made to the data. Dialog boxes can be opened via the menu at the top of the screen or via buttons, which are located on the toolbar.

To begin the revision process for the job we have just initialized, we will revise the descriptive information for the job. On the toolbar, located near the top of the screen, click the Project Settings dialog box button, which looks like this:

Notice that in its initial state, it contains no information other than “[New job]”.

Enter the job information shown below, using the tab key to move from field to field.

Now the bottom portion of the window is where you will set all of the design information, e.i. governing specification and the operating mode.

Our job will be in accordance with LRFD 8^th Edition Specifications, and the first pass will be in design mode.  These options happen to be the default settings for this dialog box. To accept these values, click the OK button.

In Design Mode, the program selects some or all of the slab and wall thicknesses, and fills the rebar schedule.  In Analysis mode, the user selects the slab and wall thicknesses, and sets most of the rebar sizes and spacing.

Open the Culvert Properties Dialog Box by clicking its button, which looks like this:

The culvert physical properties (clear span, clear height, etc.) and material properties are specified in the Culvert Properties dialog box. All of the culvert dimensions, including rebar covers, are entered into the two tabbed pages. The design type (3 or 4 sided) and boundary conditions are also defined in this DB.

Since we are in Design Mode, the slab and wall thicknesses are labeled as minimum values.  You may input either zero for these values, or some value greater than zero.  If you assign a value greater than zero, the program requires at least a minimum value of 3 inches for all members.  Additionally, the program also checks any minimum value greater than zero for reasonableness based on the clear span and the clear height, in order to obtain reasonable values in the design phase.

The next dialog box we will look at is the static loads dialog box.  Click on the static load dialog icon on the toolbar (it looks like a vertical point load), or select ‘Static Loads’ from the Input menu.

In the Static Loads dialog box, you specify the static loads applied to the culvert. Take a moment to review the load types and values shown above.

Click the OK button.

The next dialog box we will look at is the moving loads dialog box.  Click on the load dialog icon on the toolbar (it looks like a truck), or select ‘Moving Loads’ from the Input menu.

The live load vehicle type we will be using is an LRFD HL-93. To view the details of the live load, click the “Properties” button. Close that dialog box when you are finished viewing it.

For most design mode jobs, this is probably the extent of the input that you need.  However, for this tutorial, we will also look at the Analysis Options dialog box.  Click on the following icon to access this window:

Before we look at the results of the design, note the area at the bottom of the screen.  This is called the status bar.  The two panes at the right side of the status bar contain information about the design.  From left to right, they are defined as follows:

1. Design Mode: Indicates the mode of operation (Design or Analysis)

2. LRFD 8th Ed: Currently selected design specification

All of the data input for this job has now been addressed. At this point, completion of the design consists of viewing the calculation results and and making refinements to the input data as necessary.

Getting Results

Eriksson Culvert incorporates an extremely fast and efficient calculation engine.  On a typical PC, recalculation times are typically less than a few seconds.  This results in the ability of the program to perform real-time calculations.  That is, whenever a revision to the input data is made, calculations are automatically updated in the background, and the results are quickly made available to view in multiple formats.

The practical result of Eriksson Culvert’s method of performing calculations is that after editing the input, you can immediately view the effects on the design. As we’ll see, in addition to the main view there are three other ways to view results:

• Text report

• Ratings and reinforcement summaries

• Graphs

• 3D rendering view

Click the Text Report tab to open the detailed text report view.

This view of the results gives several pages of data.  The first pages are a reprint of the input data, followed by a complete listing of all shears and moments, along with the values at the critical sections, and the rebar schedule.  Note that in the critical section table all of the allowable values are greater than the applied values. 

The text window shows the top of the detailed text report.  This report is 8 pages in length and so will not completely fit on the screen.  Along the right-hand side of the screen there is a scroll bar that permits you to very easily and smoothly scroll and review the results. The rectangular-shaped button currently positioned at the top of the scroll bar is called the “thumb.”  You can click and hold on the thumb and move your mouse toward you to fluidly scroll down the page.  Also on the right hand side of the page is a navigation tab that allows you to easily jump to a specific portion of the output by simply clicking on a link.

Scroll the text view to the position shown below, or click on Design Results.

The text screen above has been scrolled to show the top of the third page of the text report.  The design results starts here, with the reinforcement bar schedule.

The reinforcement bar schedule is followed by the unfactored moments and shears table. Note that there are two unfactored tables.  The first is the table of all loads used in the design.  The second table is a listing of all live loads checked by the program.  This may include the design truck, the tandem load, and the lane load.

The serviceability check is next, followed by the output at the critical sections.

The last part of the printout shows the load combination results at the tenth points.

Now is a good time to obtain a printout. You can actually get a printout at anytime during the design.  (Note, however, that until the job has been saved, it does not have a filename, so “Eriksson Culvert1.etcx’ will be shown as the filename at the top of each page of each report.) To bring up the Print dialog box, click “File” then “Print” or press CTRL+P.

The ‘print options’ window will appear, which allows you to select which of the results tabs you would like to print. Just select the Text Report for now.

Saving Your Data

Saving your data permits you to recall the job at a future time for review and possible editing.

To save the data for our example, we will use the Save button or select the Save option on the File menu. Since we have not yet given this job a name, the Save As dialog box will appear.

Note that once a name has been entered, if you pick the Save option, the Save As dialog box will not appear again. So, if you desire to change the name of the job, you must actually pick the Save As option from the File menu.

Eriksson Culvert’s data files use the extension “.etcx,” which Eriksson Culvert will supply for you.  So enter “Tutorial1” as the job name and click the Save button.

To close the current job, select “Close Project” from the File menu.