Tuesday, June 5, 2012

Attending Presentations in Week-10

Dr. Primerano asked me to clarify that we want you to attend three presentations by students in other sections. You’ll have an excellent opportunity to see the wide variety of projects undertaken by your classmates.

We elected not to require presentations in our sections, substituting the bridge testing in Week-9 in its stead. However, becoming familiar with presentations as both an observer and a presenter is an important skill for all engineers.

Monday, June 4, 2012

Week-10 Presentations - Why We're Not Making Them

Question:

Why don't we have a presentation time for our project? I don't mind that we don't have to do that extra work, but I'm curious about your reasoning on this decision.

Response:

My belief when putting together this course was that the week-10 presentations didn't make sense for our sections for the following reasons:

Everybody is doing the same thing in our sections, whereas other sections have more varied projects. I felt it would become boring to everyone to hear the same issues addressed many times.
I asked a considerable effort of you in putting together the weekly posts as well as the assignments. Making the last week a lighter load seemed like a good idea.

I'd be glad to hear from the class if you think adding the presentations another time would be beneficial.

Jim Mitchell

Wednesday, May 30, 2012

COMP2 - Final Results

See the following link for the comp 2 results: https://docs.google.com/spreadsheet/ccc?key=0Aq9AvRYJR07tdFpoRExuUlpGcVZMa2VONm8zZjdxemc

Group highlighted in Red had the lowest cost-to-strength ratio.

Group highlighted in orange had the smallest deviation between predicted and actual failure.

Tuesday, May 29, 2012

Comp-2 Corrections

Question 1

I believe there is an error in the COMP2 description where it says "When you have completed your initial WPBD design you'll submit the results to an online spreadsheet including....". I believe it should say Knex instead of WPBD, correct?

Response

You are correct. I have corrected the page to reflect that.

Question 2

… only one person per group needs to turn in the COMP2 right? Or do all the members of the group have to complete/submit it?

Response

Yes. Only one person per group needs to submit Comp-2

Wednesday, May 23, 2012

Refining Bridge Design

I've had two good questions about refining your bridge designs that may be of general interest.

Q1 - Why does an "X" type arrangement fail when using the Hopkins "Bridge Designer".

Response:

Probably the best answer is that you have created a "redundant" structure with an "X". You can test that by removing one leg of the X and probably it will work as in the example above. If you add the member from the lower left to the center of square so you have a complete "X" Bridge Designer won't calculate it because you have an unnecessary or "redundant" member.

Q2 - Additional Analysis

Throughout the project, I have been replicating the Knex bridge on WPBD as an extra load test. But thinking about what you said today after lab, I realize that's not the best way to test our truss. What at-home methods do you suggest would be best to see if the truss is stable?

Response:

Unfortunately you're running up against the limits of the tools you will understand in your first year. There are indeed many tools for additional analysis and testing, but to use them effectively you need the knowledge that you'll gain in your more advanced courses. WPBD and Bridge Designer have to make simplifying assumptions that your real bridges violate. Let's hope this is your incentive to continue learning.

Units for Results

At 10:47pm the day before the assignment was due I was asked the following question.

“Is it ok if we converted pounds to newtons and feet to meters to do the calculations?”

Response

You may work internally in any units you wish, but results should always be shown in the units of the country in which you work unless told otherwise. If I were working in almost anyplace other than the US then newtons and meters would be the appropriate units. In our backward (in terms of units) country we still use feet, inches and pound-force and expect to see them in the results.

Wednesday, May 16, 2012

A3 - Part-5 Clarification

Question:

Did you say that only one group member needed to complete task 5 for Assignment 3? It asks us to use Bridge Designer to model our Knex Truss, and right now only one member of our group has the bridge with them.

Response:

You only have to perform the "Bridge Designer" analysis once in each group. Each member, however, is to include the results of the analysis (part #1) and perform part #2 of Task 5 individually, though you're welcome to coordinate with your team members.

Monday, May 14, 2012

An Interesting Discussion

I had an exchange with a student who was unhappy about our policy of being timely with the submissions. It led, I’m happy to say, to a more fruitful discussion about the differences between the WPBD software and the Knex experience. Below is a portion of that exchange in chronological order with my latest response added via this blog

JEM

I did read your blog entry and appreciated your thoughtfulness about the difference between a Knex and a “real” bridge. I’d add to what you wrote that there’s a significant difference between WPBD and Knex in that WPBD is 2-D only (no torsional effects considered). In that system the gusset plates are perfect connectors as well – which is hardly the case with the Knex

Student

I would like to to thank you for taking the time to read and provide feedback regarding my worthless blog entry. While I did write that the differences are endless, (thankfully in this situation did not waste my time in further elaborating on these due to the fact that it is now resulting in a zero) I did like the specific portions you added and for the most part agree with them. I agree very much with your statement about the gusset plates in WPBD; they can be connected at any desired angle and are also never a point of failure, making them "perfect" connectors. While you are correct in saying that WPBD does not consider torsional effects, I would have to say the same goes for the K'Nex as well. The only reason that bridges in class were experiencing this twisting effect was due to the fact that the applied force was attached to the uppermost portion of the bridge. In WPBD the loads (dynamic in this case, unlike the static type used on the K'Nex bridges) are being applied at the same elevation as the bridges anchor points, not allowing for much torsion on the bridge. In the lab the bridges were tested by having the load applied from a point higher than that of the anchor points, causing the tall flimsy bridges to twist and fail. The use of cross members is another large portion of this, but for the sake of time and possible material for this weeks blog post I will end my thoughts here.

JEM – New Response

In any real bridge the loadings are always uneven. The torsional effects are thus ones that must be considered and were important in your Knex designs, leading to failures in several cases. In WPBD the single truck crossing a two-lane bridge would have asymmetrically loaded the bridge and thus torsional effects would have mattered, but were ignored by the software.

Wednesday, May 9, 2012

Week-6 - Bridge Testing - Lessons Learned

Your Results - You can see the spreadsheet here

Lessons About the Rules

The SPAN is 24" - NOT the length of your bridge
- Your bridge must be longer than 24" to allow the supports at the end
- The next bridge will require a SPAN of 36"
The Width of your bridge matters

For your last bridge the width must be at least 3.5"

Vehicles should be able to drive across the bridge

For your last bridge there must be a "tube" at least 3" wide x 2" high - continuous

You can only contact the supports at one level at each end

For the next bridge we will span between the tables, a plywood surface.
There will not be the "V" to take advantage of from the sawhorses

No one will be penalized this time for not meeting the requirements, except it must span 24" - there was no grade for this testing. There will be for week-9

Lessons about Bridge Building - Your Observations

Most failures occurred at gusset plates
There were unexpected failure modes - e.g. twisting
Long pieces passing through gusset pieces helped some groups

Tuesday, May 8, 2012

Calculating Triangle Angles and Trigonometric Values

To analyze a truss there is often a good deal of trigonometry involved to calculate the components of forces. To make things simpler (I hope), I’ve created a simple excel spreadsheet that will allow you to calculate angles, sines, cosines, and tangents if you know the length of the legs of any triangle. This should ease the calculation burden somewhat. You might well wish to use this sheet as a starting point to make your truss calculations even readily modifiable.

Here’s the link to the spreadsheet.

Download the spreadsheet to Excel to see the diagram that explains the notation.

Friday, May 4, 2012

Week-6 Bridge Results Recording

Before you leave the lab in Week-6 we’d like you to record the results of your bridge test along with the characteristics of your bridge. We’ve set up the linked Google Docs Form to submit it.

We’ll show the results in class or summarize them in the blog.

Note that this form is very much like the one you’ll be asked to complete for week-9 to PREDICT the results for your final bridge.

Thursday, May 3, 2012

Late submissions to Bb Vista

Over the past few weeks Dr. Mitchell, Deepak, and I have noticed a large portion of our inboxes dedicated to students either forgetting to submit their course assignments on Bb Vista, submitting the wrong links, or something related. We have decided that we will no longer allow for corrections to submissions or submissions of assignments, blog posts, and etc past the due date times as set forth on Bb Vista.

This will go into affect officially next week. To help avoid problems in your assignment submissions, take note of the following:

Stay Up to Date:There is something due every week in Bb Vista for our course. The Bb Vista assignments don't show up however until a week before they are due. You should be checking the course Bb Vista site every week to stay updated on everything.
Check your Hyperlinks: Make sure you check your hyperlinks before you submit them. A lot of you end up submitting links to the blog post editor or to the blog post preview. These will not work for anyone except for you. Try following the hyperlinks in a different browser, or even following them after signing out of your Google account.
Resubmissions Before Due Date: If you submit early and notice a mistake, you can still take your assignment, modify, and resubmit. This will only work however if it is done before the assignment due date. I've set it up in Bb Vista so that every single one of your assignments is due on a Wednesday at 9AM. The only variable is the week in which each assignment is due.

If you have trouble submitting or if Bb Vista is acting strangely, feel free to email anyone of us before the due date and we will gladly assist.

Bridge over CSX Tracks–Photos

You can see the photos I took this morning when the bridge was put in place over the CSX tracks.

Picasaweb Photos

Wednesday, May 2, 2012

Truss Bridge Installation Wednesday Night and Thursday AM May 2nd and 3rd

Here’s a news release from the Schuylkill River Parks Alliance that may be of considerable interest to this class. It’s tonight and tomorrow morning!

Truss of Connector Bridge

The delivery of the truss portion of the bicycle-pedestrian bridge that will span the CSX tracks between Locust and Spruce streets is supposed to be delivered overnight Wednesday, May 2nd into the early morning of Thursday, May 3rd. The Philadelphia Streets Department will use the Swift Reach telephone system to notify residents along the route. The contents of the message is below in italics.

Rockport, the contractor, expects that it will take approximately one hour to assemble the truss Thursday morning, then it is going to set the bridge into place between 8:30 AM and 9:00 AM.

The telephone Swift Reach message from the Streets Department:
Philadelphia Departments of Streets and Parks & Recreation is pleased to announce the delivery of the new Truss Bridge that will soon connect the Schuylkill River Park between Spruce and Pine Streets to the Schuylkill River Trail. Truss bridge is scheduled to arrive at the project site on late Wednesday night into early Thursday morning. Bridge will be escorted to the project site by Philadelphia Truck Enforcement unit and transported on two (2) oversized hauling trucks. In order to safely make the move, temporary parking restrictions will be posted along the trucking route, and will be effective from Wednesday, May 2nd at 10pm through Thursday, May 3rd at 7am. No parking signs will be posted at the intersections of Washington Avenue and 22nd Streets and 22nd and Locust Streets, as well as along Locust Street between 22nd and 25th Streets.

Tuesday, May 1, 2012

Truss Bill of Materials Typo Correction

Question:

I think there is an error in the excel spreadsheet that calculates the bridge cost. The member length after 1.25 should be 2.125 instead of 1.125 correct?

Response:

Indeed there is a typo in the Truss Bill of Materials. Part #2 should be 2.125” in length rather than the 1.125” indicated in the description.

I corrected it on the server at about 7:15 on 5/1/2012

The cost is still correct.

Wednesday, April 25, 2012

Real Bridges – California’s New Bay Bridge

This video from Science Friday isn’t directly about trusses (but notice the use of trusses in the construction), but it’s interesting to see the kinds of things that engineers incorporate to make bridges safe.

As the video indicates, the previous bridge in this location failed during the 1989 Loma Prieta earthquake.

Note the time scale for big projects of this sort – it’s 23 years since the failure and the replacement is just about to open.

Tuesday, April 24, 2012

Blog Addresses for Students in Prof. Mitchell’s Bridge Sections

Below are the blog addresses of the students in these sections, sorted by last name. This list was generated from the A1 assignment submission so there are some blog addresses missing, either because no blog URL was submitted, or the editing URL rather than the published URL was submitted.

“Not Available” means that the URL submitted was the editing URL – only the owner can see that
A blank URL means no URL was submitted.

You can see the blog by clicking the URL. To find the particular post of interest you will need to:

Use the “labels” that (we hope) each student applied
Scroll through the blog.

Name URL of Blog

Tuesday, April 17, 2012

Posting Mechanism

Question:

Last week for the teamwork post my group posted them as comments on our "Weekly post" page. For the A1 assignment we have to make a post and title it and when ever we try to make a post it always goes to our home page. How should we go about posting it?

Response:

Without looking at your blog I cannot be certain about this answer, but it sounds to me as though you're probably doing the correct thing. The idea behind a blog is that the latest post is always at the top of the list, with previous posts following on the page. To see previous posts you can:

Scroll down the main page - usually a limited number of posts will be scrollable
Search the blog for key words
Use the "labels" (sometimes called "tags") to click and see the posts with those labels
Use the chronology to show those posts happening at a given time.

Note that you don't want to "comment" on a previous post, you want to create a new post each time. You add comments only when you want the comment to stick with the post as a comment.

To get the URL of your specific post:

Display the post on your page - that's what happens usually when you "publish" your post or search for it
Click on the title of the post

That displays that post only, with the URL in the "Location Bar"

Copy the URL from the location bar

Saturday, April 14, 2012

Comp-1 = A1 Survey – Please complete this survey of your design results

Updated 4/17/2012 4:05PM to make it clear this is the Comp-1 assignment.

In the week-3 lab we’ll be reviewing the results of your A1 designs and then each team will develop an improved design in class.
To allow us to compare the designs and perhaps draw some inferences we’re asking you to complete a Google Docs survey that documents some aspects of bridge that you’ve designed, as well as the URL of your A1 blog post.
You’ll receive a very similar email asking you to do the same thing. This post is just a readily accessible place to go to the survey.

Link to Survey - This is the Comp-1 survey

You’ll be able to see the results in spreadsheet form here.

Bring your Bridge Design with you

As the survey notes, you’ll want to modify your bridge design in class so please bring your file with you:

On a flash drive
On a web site such as Google Docs or DropBox
Email it to yourself

Thursday, April 12, 2012

Introducing myself - Jay Bhatt - your engineering librarian

My name is Jay Bhatt and I am your engineering librarian.

Increased cognizance of online handbooks, encyclopedias, and various online databases such as ASCE Digital Library, and Engineering Village, is extremely important for you in order to successfully complete your design projects. To assist you with this, I have created Engineering Reference Assistance page which can be accessed by going to:

http://www.library.drexel.edu/engineering

You can also set up an appointment with me for more in depth research consultations. Here is how you can do so:

http://www.library.drexel.edu/blogs/englibrary/reference-assistance-for-engineering/
and click on 'Book a Reference Consultation' to set up a meeting time

You can also email me at bhattjj@drexel.edu or call me at 215 895-1873 and set up a meeting with me. My office is in room 132 in the Library.

I have also created a web page for Bridge Design Resources that I think you will find it very useful during the course of this term for your design projects.

This page can be accessed from: http://www.library.drexel.edu/blogs/englibrary/2012/04/05/bridge-design-resources/

Looking forward to meeting with you all.

Wednesday, April 11, 2012

Field Inspection - Week-3 Discussion Alternate Topic

Those who wish to substitute the following for the discussion portion of the week-3 blog entry may do so. Understand that you still include the notebook entries on what you did and what you're going to do.

Field Inspection

Safely visit a truss bridge, take photos, make observations on its function and its status. By status we mean.

Its overall condition
Whether the traffic loads on it appear too great, too little, or about right
Any particular problems you observe, particularly with respect to the truss portion of the bridge

Include the photos in your blog entry as well as your observations.

Tuesday, April 10, 2012

How to Capture and Post Images

This post was created to show you how to capture and post images to your blog. I used a PC (Windows-7) so some of the information is PC-specific.

Tools

Windows-7 has a built-in screen capture tool - "Snipping Tool"

On a home machine just searching for snipping
On a "locked down" Drexel machine in which searching isn't available you may be able to go to windows help (F1 when on the desktop) and search for "snipping". In the help that comes up there will be links to the snipping tool.

You can also use PrintScreen - which has good instructions on how to use it.
There are many good, free screen capture utilities. One that I use is PicPick

How to Add an Image - How I created the image above

I'll assume you have access to Snipping on a PC - other programs will be similar

Get the image you want to capture on your screen - e.g. the bridge design
Start the program Snipping

If it's already started create a new snip from its menu

The screen will go white
Draw around the area you want to capture
That will capture it to the program Snipping

Save the image to a file somewhere where you can get it again

I used the default "png" format to create the image above

Open Blogger and put the cursor where you want the image to appear.
Click on the link of the image in Blogger for to upload it to your blog - see below

Accept it within blogger

Tuesday, April 3, 2012

WPBD Registering to Local Contest

Registering for the West Point Bridge Designer Contest

Our contest ID is DUPA - Please register as individuals

Here are the instructions from the authors of WPBD on how to set up your copy so you're scores will be entered in our "Local Contest".

(1) Instruct all of your students to register for the West Point Bridge Design Contest at http://bridgecontest.usma.edu/login.htm. If any of your students are not “eligible contestants,” as defined by the WPBDC rules, that’s OK. They can still register in the “Open Competition.” (Anyone in the world can enter the Open Competition, though there are no prizes associated with this category.)

(2) On the final page of the web registration system (the same page on which teams are asked to provide their e-mail address and password), your students will see a text box labeled, “If you are participating in a local contest organized by your school, a local engineering association, or other organization, enter your Local Contest Code here." Students should enter the Local Contest Code in this text box.

(3) The website will check that the code is a valid one and will post a confirmation on the Team Home Page.

(4) If a contestant has already registered and did not enter the Local Contest Code at the time of registration, he or she can add it at any time by logging into the Team Home Page.

(5) Once your project or contest is underway, you can view your own Local Contest Scoreboard on the following web page:

http://bridgecontest.usma.edu/standings/local/DUPA.htm

Wednesday, March 28, 2012

About This Blog

We'll use this blog as home base for all information related to our two sections of ENGR-103. It has all the assignment information, grading information that you’ll need. We’ll also use it to post Official announcements and answer questions that are raised throughout this term.

We advise you to subscribe to it via an RSS reader such as Google Reader. That way you won't have to go into VistaBB to get information though you’ll still have submit assignments there. There are many, many blogs available on interesting topics. A good place to search for others that may interest you is Technorati.