Paper in Structural Engineering International

I'm excited to announce my most recent publication, in the IABSE journal of Structural Engineering International.
After the IABSE conference in May of 2013, a number of authors were invited to submit a paper to this special edition on "Assessment, Upgrading, Refurbishment and Conservation of Infrastructures" - and we were among these.

You can access the online version of the paper here.

The abstract of the paper is the following:

Upon assessment of existing reinforced concrete short-span solid slab bridges according to the recently implemented Eurocodes that include more conservative shear capacity provisions and heavier axle loads, a number of these structures were found to be shear-critical. The results from recent experimental research on the shear capacity of slabs indicate that slabs benefit from transverse load distribution. Recommendations for the assessment of solid slab bridges in shear are developed on the basis of these experiments. A load spreading method for the concentrated loads is proposed and the applicability of superposition of loading is studied. The resulting most unfavourable position for the design trucks is provided and implemented in the so-called Dutch "Quick Scan" method (QS-EC2). Cases of existing bridges are studied with the previously used QS-VBC as well as with the QS-EC2 that includes the recommendations. As a result of the assumed transverse load distribution, the shear stress to be considered at the support based on the recommendations becomes smaller.

The keywords of this paper are: EFFECTIVE WIDTH; LIVE LOADS; LOAD DISTRIBUTION; REINFORCED CONCRETE; SHEAR; SLAB BRIDGES.

Writers' Lab: Overview of Journals on Structural Concrete and Bridge Engineering

As I was determining which journal papers I can write from my dissertation, and where to publish them I gathered a little list of interesting journals and their respective impact factors.

For those of you in my field of research, here is my list of journals and their impact factors. Note: I wrote about my Journal top 5 long time ago for PhD2Published. You can consider this a longer version, but with less additional information why I like a particular journal. The goal of this list is to inform you, and to give you an idea of where you could publish your work.

I've added the links to the author information, whenever it was possible. For TRR, you need to submit a paper for the TRB conference, and indicate you want to have it eligible for publication in TRR. The submission portal is only open between June and August 1st (the deadline for submission).

1. Transportation Research Record: IF = 0,471
2. Journal of Structural Engineering ASCE: IF = 0,955
3. Journal of Bridge Engineering (ASCE): IF = 0,623
4. ACI Structural Journal: IF = 0.667
5. Magazine of Concrete Research: IF = 0,604
6. Structural Concrete: IF = 0,395
7. Advances in Structural Engineering: IF = 0,324
8. Beton- und Stahlbetonbau: IF = 0,456
9. Cement and Concrete Composites: IF = 2,421
10. Engineering Structures: IF = 1,351
11. Materials and Structures: IF = 1,278
12. Heron: IF = 0,25
13. Structural Engineering International: IF = 0,321

Smart Materials, Made in Delft

 We’ve introduced Erik Schlangen as Professor “Experimental Micromechanics”. But what does that really mean, and where does he wants the research of his group to result in? In his own words: he wants their inventions to show up when you Google for “future materials”.


Now let’s consider for example concrete. With very simple and archaic tests, such as the slump test and the compressive test, engineers derive the properties to build our skyscrapers and bridges.



 
Nowadays, the requirements for concrete are much more complicated though. We can add steel fibers for better performance, reduce the amount of cement for a greener concrete and add retarders and superplastifiers to increase the workability. In the end, we have much more ingredients than the original sand, cement, stones with some water to make it fluid. So how representative are the very basic experiments that we use to derive the properties? Erik and his team aim at finding a way to explain how the material fails.

To explain how complex materials such as the improved concrete fail, better measurement techniques and testing machines are necessary, as well as detailed material models to support these tests. But these techniques and models not only allow the researchers to better understand existing materials – they help them to go one step further and develop better materials.

Very flexible materials, green concrete containing wood fibers, and materials that can heal themselves show us a way into the future, in which we tailor our materials to fit our requirements “a la carte”. Concrete that closes its cracks by using bacteria, and asphalt with steelwool fibers have already been invented by Erik and his colleagues, and now they are studying, amongst others, the fracture properties of graphite as used for the cores in nuclear reactors, and the properties on the interface between the stones and the cement in concrete, two different parts which can come apart.

And what will the future bring? Future materials in Google? One thing is for sure: Erik’s cheerful approach to smart materials reminds us of the eager explorations of our younger selves. Never grow up…

You can view Erik’s presentation at Civil Engineering on his professorship at Collegerama

This post originally appeared on the TEDx Delft website.

Shear and Punching 101: Distance in the codes

 I recently received a message with the following question:

Normally when we treat the problem of determination of shear stress in slabs, a critical section at a distance of half the effective depth of slab is taken from the support (like columns). Can you explain why this is recommended in many Codes?

Since I think this issue is not very clear in the background of the building codes, I'd like to share what I found while executing my literature review here.

There are two reasons for a distance of d/2 away from the column:
- for punching, you determine the punching perimeter at a certain distance (depending on the code). There is no physical explanation for the distance itself, although researchers like to relate this distance to the inclination of the shear crack that would result from the root of column to the top of the slab where the punching cone intersects (for the case of a flat slab floor for example).
If you look at the background of the codes, for example ACI 318, you find that the chosen distance is based on a better statistical result for the resulting punching perimeter in combination with the ACI formula as compared to test results (work done by Moe, 1961 [1]).
- for shear, we assume direct transfer of the load from its point of application to the support for loads that are at a distance d/2 to d from the column (also depending on the considered code). This direct transfer is by means of a compressive strut, which is of course much stronger than a section in shear.

[1] Moe, J. (1961). Shearing strength of reinforced concrete slabs and footings under concentrated loads, Portland Cement Association Research and Development laboratories, Skokie, IL.

Fifty Shades of Concrete

My TEDx Delft Salon talk is online! 

Kick-off 3TU.Bouw

On Monday October 8th, I gave a short PhD pitch at the kick-off meeting for 3TU.Bouw Center for the Built Environment, which combines the four academic Built Environment faculties of the Netherlands. My PhD pitch (5 minutes presentation) represented the faculty of Civil Engineering and Geosciences of Delft University of Technology. The event also allowed for outreach to the public sector and the building industry of the Netherlands.

In my presentation, I gave a quick overview of the project on the capacity of existing concrete bridges and briefly discussed the research from the group of Concrete Structures, Structural Mechanics, and the cooperation with TNO and the Dutch Ministry of Infrastructure and the Environment. The end of the pitch focuses on the impact of the research: the (inter)national scientific impact of this project, as well as the broader impact on society showing how this project contributes to a more sustainable future.

I've shared my slides on SlideShare:

 

Bestaande betonnen bruggen from elantsoght

The recording of the presentation can be viewed here (at 48:30 my presentation starts):

Storify of 3TU.Bouw kickoff

Structural engineering conferences

There are a few websites I regularly check to see if there's an interesting conference coming up to which I should submit an abstract. These are:
ACI: International conferences
fib events
ASCE Conferences

After attending a few conferences, I now also receive calls for abstracts in my mailbox regularly.

Over the past two years, I've attended the following conferences:

Structural Faults and Repair
This is a conference specialized in repair and strengthening of existing structures. Case studies from practicing engineers as well as academic research are presented. It's organized in the marvelous city of Edinburgh.

fib PhD symposium in Civil Engineering
This conference is organized for PhD students, mainly for PhD students researching structural concrete. Presentations are 20 minutes, followed by 10 minutes of discussion - so there is plenty of time to go in-depth. It's also a great place to practice presenting skills among your peers.

ASCE Structures Congress
Eight parallel tracks, featuring all topics related to structural engineering... This conference bundles a vast amount of expertise and information into a few days' worth of time - planning your schedule ahead is a must! I learned a lot on bridge engineering, as I chose to mainly attend the sessions in the bridge engineering track.

fib symposium
This conference is entirely focused on structural concrete - and I was very pleased to find several entire sessions dedicated to the problem of shear in concrete. Again, with several parallel tracks, planning your schedule in advance is required.

Software review: Codeform and Codeproof

Over the past week, I’ve been trying out a software package for structural engineering which combines a traditional calculation program (Codeform) with preprogrammed spreadsheets for all Eurocodes (Codeproof). Over a 1000 prefabricated formulas are available in the Eurocode library.

When I learned about this software, I became very curious to test it out. I download the 5-days trial version and, as an example, used the predefined Codeproof sheet to calculate the shear capacity of a concrete slab under a concentrated load (as shown here).
I used the trial version which can be found at Technosoft’s website for Codeform en Codeproof.

Here are my first impressions of the software package:

Advantages

Very easy to learn

It took me only 20 minutes to turn the existing Codeproof sheet into a sheet which can be used for calculating the expected values of my experiments according to Eurocode 2. I had never used Codeform before, but it is very easy to operate.

Presentation format

The sheets are preprogrammed and look very professional with respect to their layout. In the two printscreens I took, you can see how it looks. The sheets are ready to be printed out and implemented in a report. The calculation is made clear by displaying the formulas at full, in contrast to the ‘hidden formulas’ which result from printing out Excel output.

Flexible format

Since Codeform is a very user-friendly engine, it is very easy to make changes to the existing Codeproof sheets and develop them into your own spreadsheet.

Suitable for design offices

Since this software package contains standard sheets for all Eurocodes, it is the perfect tool for design offices. No more need to spend hours on developing in-house standard spreadsheets for frequently used calculations. The interpretation of the Eurocodes has also been done and the right links to previous chapters or paragraphs were made.

Learn to use the Eurocodes

For designers abroad who are not familiar with the Eurocodes, this tool could be a great way to get acquainted with the Eurocodes. It shows you how to use the code, how to calculate with it, and how to interpret it.

Disadvantage

Dimensionless calculations

Unlike some other packages, CodeForm does not use dimenions. If you would need to switch between English and SI units, then you’ll have to add the right conversion factors yourself.


Are you curious to test out this software too? You can head to the website and use the 5-day trial of the software.