Shear Capacity of the Ruytenschildt Bridge

I recently presented a paper at the 2016 fib symposium in Cape Town on the shear capacity of the Ruytenschildt Bridge. The abstract of the paper is as follows:

In August 2014, the Ruytenschildt Bridge, a reinforced concrete solid slab bridge (reinforced with plain bars) in the Friesland province in the Netherlands was tested until failure. One of the goals of proof loading and testing this bridge to failure, was to study the failure mode of existing slab bridges. The combination of smaller shear capacities as prescribed by the Eurocode in combination with the heavier live load models, has raised concerns with regard to a number of existing slab bridges in the Netherlands. As the shear capacity of existing bridges is under study, the results of testing an actual slab bridge until failure are used to compare to the results of testing half-scale slab specimens in the laboratory, and the conclusions resulting from those experiments. In this paper, the results of the predictions based on the first order of approximation rating procedure from the Netherlands for shear, the Quick Scan method, as well as based on predictions of the failure mode and the average predicted capacity are compared to the experimental results. The predictions show a possibility of shear failure in the second span of the bridge. The experiment showed that both spans of the bridge failed in flexure. The observed failure mode is important, as some of the results indicate that the solid slab bridges, currently under discussion with regard to their shear capacity, fail in flexure in reality. Flexural failure is considered a ductile failure compared to the brittle failure mode in case of a shear failure.


Please find below the slides of my presentation:

Shear capacity of the ruytenschildt bridge from Eva Lantsoght

Load testing of reinforced concrete bridges in the Netherlands

I recently gave a guest lecture at my alma mater, Vrije Universiteit Brussel. You can also find some photographs of this even on the Facebook page of the group Mechanics of Materials and Constructions.

The abstract for the presentation was as follows:

As the bridge stock in The Netherlands and Europe is ageing, various methods to analyze existing bridges are being studied. Load testing of bridges is an option to study the capacity when crucial information about the structure is lacking. This information could be related to the material (for example, the effect of ASR on the capacity) as well as to the structural system (for example, the effect of restraints at the supports or transverse redistribution capacity).
When it is decided to load test a bridge, the question arises which maximum load should be attained during the experiment to approve the capacity of the bridge, and which criteria, based on the measurements during the test, would indicate that the test needs to be aborted before reaching the maximum desired load (the “stop criteria”).
A number of reinforced concrete slab bridges have been load tested over the course of the past few years. These load tests were pilot cases, in which the bridges were heavily equipped with sensors, to study the bridges’ behavior at critical positions for bending moment and shear. The test results were then extensively analyzed, and compared to the stop criteria available in the currently used codes and guidelines.
As a result of the analysis and experiments, recommendations are given for proof loading of bridges. These recommendations are important, since they will form the basis of a guideline for proof loading of existing concrete bridges that is under development in The Netherlands.

You can find the slides of the presentation here:

Load testing of reinforced concrete bridges in the Netherlands from Eva Lantsoght

Development of Stop Criteria for Proof Loading

I recently gave a presentation at IALCCE 2016, the Fifth International Symposium on Life-Cycle Civil Engineering, which was organized in Delft, the Netherlands. We organized a mini-symposium about proof load testing, which I co-chaired with some of my colleagues.

The abstract of the presentation and paper is the following:

Proof loading of bridges is an option to study existing bridges when crucial information is lacking. When proof loading is chosen, the question arises which maximum load should be attained during the test to demonstrate sufficient capacity, and which criteria, the “stop criteria”, based on the measurements during the test, would indicate that the test needs to be aborted before reaching the maximum desired load. A review of the literature identifies the stop criteria in currently used codes and guidelines. Beams sawn from the Ruytenschildt bridge were tested in a controlled way in the laboratory and analyzed with regard to the stop criteria from the literature. Recommendations are given for the future development of stop criteria for flexure and shear. These recommendations will form the basis for a guideline on proof loading of existing concrete bridges that is under development in The Netherlands.

You can find the slides of my presentation here:

Development of Stop Criteria for Proof Loading from Eva Lantsoght

Bridging the gap between one way and two-way shear in slabs

I recently gave a presentation at the ACI Convention in Philadelphia, during the joint ACI-fib symposium on punching shear. This presentation is related to the publication of an ACI Special Publication.

The abstract of my talk was as follows:
The shear capacity of slabs under concentrated loads is particularly of interest for bridge decks under concentrated live loads. Often, one-way shear will be analyzed by considering the slab as a wide beam (without taking advantage of the transverse load redistribution capacity of the slab) and two-way shear by considering the punching area around the load. Since experiments showed that the failure mode of slabs under concentrated loads is a combination of one-way and two-way shear as well as two-way flexure, a method was sought that bridges the gap between traditional one-way and two-way shear approaches. The proposed method is a plasticity-based method. This method is based on the Strip Model for concentric punching shear and takes the effects of the geometry into account for describing the ultimate capacity of a slab under a concentrated load. The model consists of “strips” that work with arching action (one-way shear) and slab “quadrants” that work in two-way shear. As such, the resulting Extended Strip Model is suitable for the design and assessment of elements that are in the transition zone between one-way and two-way shear.

You can see the slides of this presentation here:

Bridging the gap between one way and two-way shear in slabs from Eva Lantsoght

Papers at IABMAS 2016

This year, I did not have the chance to travel to IABMAS. However, my former student Ms. Flores-Valverde traveled to IABMAS to present her thesis work as well as the paper of myself and my coauthors.

The abstract of her paper was:

An analysis and visual inspection is presented of the bridge “Quebrada de Tambura”, this study emphasizes on the visual inspection of the bridge, the elements taken into consideration for the assessment, and the relevant failure modes that can be identified throughout the process, leading to a recommendation for maintenance. In addition, CSI Bridge software is used for a case study of the bridge “Quebrada de Tambura” located in Imbabura province in Ecuador, and where possible causes for the identified failure modes are in-cluded in the model, such as settlements. Finally, the processed and analyzed information was used for the proposal for maintenance on the bridge, including the underpinning of piles and foundations, and the use of carbon fibers (CFRP) in shear-critical beams calculated by the Sika program.

The abstract of my paper was:

In August 2014, the Ruytenschildt Bridge, a reinforced concrete solid slab bridge, in Friesland, the Netherlands was tested until failure. One of the goals of the experiment is to analyze the failure mode of the slab bridge under a tandem of 4 wheel loads and to compare the capacity of the full bridge structure to the predicted results, to have an idea of the residual strength of existing bridges. The methods used are experi-mental (testing of the bridge to failure in two of its five spans) and analytical. The analytical work involved predicting the bending moment capacity, the shear capacity and the punching capacity of the bridge. In both spans, the bridge failed in flexure. The total capacity during the experiment was significantly higher than pre-dicted. The results indicate that the traditional rating procedures for shear are very conservative when applied to slab bridges that benefit from transverse load redistribution.

Here are the slides of my paper:

Shear and Moment Capacity of the Ruytenschildt Bridge from Eva Lantsoght

Son seguros los puentes por los que cruzamos?

Universidad San Francisco de Quito recently made a video highlighting my current research on load testing of bridges. You can watch it here:

Shear and moment capacity of the Ruytenschildt Bridge

My colleagues and I wrote a paper for IABMAS 2016, which was presented by my student Karen Flores.

The abstract of the presentation on the shear and moment capacity of the Ruytenschildt Bridge is as follows:

In August 2014, the Ruytenschildt Bridge, a reinforced concrete solid slab bridge, in Friesland, the Netherlands was tested until failure. One of the goals of the experiment is to analyze the failure mode of the slab bridge under a tandem of 4 wheel loads and to compare the capacity of the full bridge structure to the predicted results, to have an idea of the residual strength of existing bridges. The methods used are experi-mental (testing of the bridge to failure in two of its five spans) and analytical. The analytical work involved predicting the bending moment capacity, the shear capacity and the punching capacity of the bridge. In both spans, the bridge failed in flexure. The total capacity during the experiment was significantly higher than pre-dicted. The results indicate that the traditional rating procedures for shear are very conservative when applied to slab bridges that benefit from transverse load redistribution.

You can find the slides here:

Shear and moment capacity of the Ruytenschildt Bridge from Eva Lantsoght

Karen also presented the paper of her BSc thesis project. The abstract of this paper is as follows:

An analysis and visual inspection is presented of the bridge “Quebrada de Tambura”. This study emphasizes on the visual inspection of the bridge, the elements taken into consideration for the assessment, and the relevant failure modes that can be identified throughout the process, leading to a recommendation for maintenance.
In addition, CSI Bridge software is used for the case study of the bridge “Quebrada de Tambura” located in the Imbabura province in Ecuador, and where possible, causes for the identified failure modes are included in the model, such as settlements.
Finally, the processed and analyzed information was used for the proposal for maintenance of the bridge, including the underpinning of piles and foundations, and the use of carbon fiber reinforcements (CFRP) in shear-critical beams as calculated by the Sika program.

Afschuifcapaciteit van betonnen plaatbruggen

A bit of Dutch today :)

I recently gave a presentation with an overview of the practical recommendations that resulted from my PhD Thesis. For those of you who speak Dutch, you can find the slides below:

Afschuifcapaciteit van betonnen plaatbruggen from Eva Lantsoght

Development of a guideline for load testing in The Netherlands

At the ACI spring convention in Milwaukee, I gave a presentation on the work we are doing in Delft with regard to load testing.

The abstract of the presentation is the following:

As the bridge stock in The Netherlands and Europe is ageing, various methods to analyze existing bridges are being studied. Load testing of bridges is an option to study the capacity when crucial information about the structure is lacking. This information could be related to the material (for example, the effect of ASR on the capacity) as well as to the structural system (for example, the effect of restraints at the supports or transverse redistribution capacity).

When it is decided to load test a bridge, the question arises which maximum load should be attained during the experiment to approve the capacity of the bridge, and which criteria, based on the measurements during the test, would indicate that the test needs to be aborted before reaching the maximum desired load (the “stop criteria”).

After proof loading and testing to failure of two spans of the Ruytenschildt bridge, beams sawn from another span were tested in a controlled way in the laboratory. The results of these beams have been analyzed with regard to the stop criteria as defined by the currently used codes and guidelines.

As a result of the analysis and experiments, recommendations are given for proof loading of bridges with respect to the stop criteria. These recommendations are important, since they will form the basis of a guideline for proof loading of existing concrete bridges that is under development in The Netherlands.


You can find the slides of the presentation here:

Development of a guideline for load testing in the netherlands from Eva Lantsoght

Proof loading of existing reinforced concrete bridges in The Netherlands

I recently presented some of our TU Delft work on proof loading of bridges at a meeting of ACI Committee 342 "Evaluation of Concrete Bridges and Bridge Elements".

You can find the slides of this presentation here:

Proof loading of existing reinforced concrete bridges in The Netherlands from Eva Lantsoght

Proof loading of existing bridges

I recently gave a presentation during the IV Jornadas de Ingeniera Civil, at Escuela Politecnica Nacional in Quito.

Below you can find the slides of this presentation:

Proof loading of existing bridges from Eva Lantsoght

Application of Modified Bond Model to the capacity of Ruytenschildt Bridge

I recently gave a presentation in a session at the ACI Fall Convention on "Recent Developments in Two-way Slabs: Design, Analysis, Construction, and Evaluation". The session, in reality, turned out to be mostly aimed at shear problemns in slabs (which I enjoyed attending, of course).
This presentation combined the proof loading of the Ruytenschildt Bridge in Friesland, with my plasticity-based model that is under development.

The abstract of the presentation is the following:

The Ruytenschildt bridge in Friesland is a continuously supported concrete slab bridge, and was tested in two spans to failure in August 2014. The results of this experiment are valuable for the analysis of existing slab bridges and for analyzing the moment and shear capacity of reinforced concrete slabs and slab bridges.

Earlier analyses found that a large number of existing slab bridges in The Netherlands rate as insufficient for shear. However, these analyses did not take into account the beneficial effect of transverse load redistribution. Therefore, the Modified Bond Model was developed. This model covers beam shear, punching shear and flexure for reinforced concrete slabs.

The test results are now to compare to the predictions with the Modified Bond Model. Since the Modified Bond Model is independent of the failure mode, the maximum load that is found can be directly correlated to the maximum tandem load in the experiment. Comparing the test results on the bridge with the predictions based on the Modified Bond Model shows good correspondence. The results are also compared to a new proposal for vmin, the minimum shear stress at which shear failure takes place. For smaller value, a moment failure takes place.

While the presented results only show a comparison between 2 tests on an existing bridge and the proposed Modified Bond Model, the results indicate that the Modified Bond Model can become a useful tool for design and analysis of reinforced concrete slabs based on the principles of the theory of plasticity.

You can find the slides here:

Application of Modified Bond Model to the capacity of Ruytenschildt Bridge from Eva Lantsoght

The road to breaking bridges and stereotypes

I was recently asked to give a presentation about myself and my scientific successes at WISE (Women in Science and Engineering) at Universidad San Francisco de Quito.
Talking about myself is not really my strength - I ended up spending way more time on putting this presentation together than what I spend on a typical research presentation. Toothing my own horn is just not my thing. So I decided to tell my story as an academic nomad, and to infuse it with bits and pieces of my adventures in music, and to report on the gender imbalances at the different universities where I studied.

The final result, a presentation titled "The road to breaking bridges and stereotypes", is here:

The road to breaking bridges and stereotypes from Eva Lantsoght

Improved formulation for compressive fatigue strength of concrete

I recently traveled to Leipzig, Germany to present a paper at the 4th International Conference on Concrete Repair, Rehabilitation and Retrofitting. The research I presented was the result of the project I worked on during Summer 2014 in Delft, where we had a small research project to come up with an improved formulation for concrete under fatigue for the Dutch National Annex to Eurocode 2-2.

The abstract of the paper is as follows:

Understanding the behavior of concrete in fatigue is essential for understanding the behavior of concrete bridges subjected to repeated loads. The Dutch National Annex to the Eurocode prescribes a different expression for the Wöhler curve for compression fatigue than the Eurocode itself, and does not have a smooth transition for 106 load cycles. A new expression for concrete in compression fatigue is thus necessary. This new expression should be valid, yet not overly conservative, for high strength concrete. Therefore, a database of experiments on (ultra) high strength concrete tested in compressive fatigue is used to validate the new proposal. A proposal for the assessment of the fatigue strength of existing structures is prepared. For design, a simplified method is proposed. An expression for the fatigue strength of concrete under compression, suitable for high strength concrete, is now available, which can replace the previous fatigue expressions used in The Netherlands.

The presentation I gave is shown here:

Improved formulation for compressive fatigue strength of concrete from Eva Lantsoght

Reliability-based expression for the shear capacity of reinforced concrete slabs under concentrated loads close to supports

My co-authors and I recently presented a paper at the 25th ESRA conference, ESREL, the European Safety and Reliability Conference. I was happy to see our work accepted for presentation at a conference that is not only civil engineering. In the paper, the reliability analysis that we used to derive a new formula for shear in slabs under loads close to supports is highlighted.

The abstract of the paper is as follows:

In bridge engineering, the effect of heavy trucks is modeled as concentrated loads, often close to the support. For slab bridges, this loading case results in large shear stresses. Typically, the code provisions for shear do not take into account the beneficial effect of transverse load redistribution in slabs. A new expression that follows the safety philosophy of the Eurocodes is based on the principles of structural reliability. Experimental results and the Eurocode 2 expression for shear are used as a starting point. The enhancement factor that describes the influence of transverse load redistribution is sought. Monte Carlo simulations are run to determine the necessary enhancement factors so that the associated reliability index is conform the safety format, i.e. the Repair Level for assessment of solid slab bridges. Finally, a formula is proposed for the shear capacity of slabs under concentrated loads close to supports.

No slides this time, as I was unable to present the work myself due to the lack of funding for my trip, and I won't place slides online that are not my own (my colleague who presented the work also developed the presentation).

PhD Talk for AcademicTransfer: How to prepare for your first conference

This post is part of the series PhD Talk for AcademicTransfer: posts written for the Dutch academic career network AcademicTransfer, your go-to resource for all research positions in the Netherlands.

These posts are sponsored by AcademicTransfer, and tailored to those of you interested in pursuing a research position in the Netherlands.

If these posts raise your interest in working as a researcher in the Netherlands, even better - and feel free to fire away any questions you might have on this topic!

Today's post is about preparing yourself to attend and (I am assuming) to present at your first academic conference. I'm assuming you have written your paper (if you haven't done so yet, check out how I write my conclusions), and your request has been approved - now, all that remains to be done, is to "just" go and attend the conference.

1. Request a travel budget

I think it's inherently wrong that we're so often tacitly assumed to be forking out (part of) the money ourselves to attend conferences. Asking an underpaid PhD student to pay a registration fee of 1000 USD at a conference is so far away from the gist of why we are practicing science and want to exchange our ideas. Most universities do have travel budgets you can apply to. Some of these additional scholarships are more unbiased, in other cases you might just need to write a letter to an Important Person and hope he reads this on a good day and helps you with the expenses. By all means, the system at Delft University of Technology is fair and straightforward: if you have the approval to travel, they take care of all your expenses (including the cost of food while you are away).

2. Book in advance

Many conferences have early-bird registration fees. Avoid additional costs by booking as early as possible (by the same token: apply for travel funding as early as possible). Similarly, your flight ticket and hotel registration may be cheaper when you book in advance - and you avoid the unpleasant situation of not finding spots on the flight or in the hotel of your choice anymore as the date of your conference approaches. Booking early is part of being well-prepared.

3. Study the conference schedule

Now that you know that you are going for sure, it is time to outline your itinerary for the days of the conference. Make sure you read all the information of the conference, and know where and when to register (pro tip: try to register as early as possible to avoid unpleasant surprises, such as a payment that did not go through and your registration that did not get processed).
Read the titles of all presentations to familiarize yourself with the topics, and mark which presentations you want to see. Note that sometimes presentations only are remotely related to the topic of the session, so don't let yourself be guided too much by the topic of the session. Plan to ask questions after the presentations as well.

4. Identify who to talk to

From the conference schedule, identify who is carrying out research related to yours, and make sure you attend these presentations. Try to talk with the presenter after his/her presentation, so you can introduce yourself to him/her. Also identify in the scientific committee if there are senior researchers you would like to talk to - often the members of the scientific committee will attend the conference as well.

5. Plan some downtime

Conferences are exhausting, so it is a good ideas, especially for your first conference, to identify when you could have a little bit of downtime. If your conference schedule is packed with dinners until midnight and sessions that start at 8 am, you will be running on -say- 6 hours of sleep, which for many of us is not enough. Factor in the fact that attending conference presentations is like a scaled-up version of attending lectures, and you know you need your full concentration to benefit from attending the sessions. Often as well, you will be jetlagged and tired from traveling to the conference, so that doesn't help either to keep your attention sharp. Don't neglect self-care when traveling.

6. Pack your clothes

When packing your bag, travel light - just take the clothes you are planning to wear for the days of the conference, a spare shirt in case you spill your coffee, workout clothes if you think you can squeeze in some exercise, and comfortable clothes for your flight. You can find an overview of what I typically take to a conference here. Keep in mind as well that sometimes you might be traveling to a warm destination, but the AC in the conference venue might be turned to arctic. Similarly, you might be heading to Snow Capital in January, and find that the heating is set to boil you alive. The solution: take some layers.

7. Explore the city

Plan in advance when you will have time to see something of the city, and what you are going to visit. Keep in mind that the conference is your main goal, but that the chance that you will return to the city of the conference in the next years might be small. A good strategy is to arrive early: you will have a day to see something of the city, register for the conference, and if your flight gets delayed you only miss out on the touristing part and will not have your attendance at the conference in peril.

8. Go with your presentation ready

You will not have time to make your presentation during the conference. Go well-prepared and have your presentation ready, and practiced. I typically make my presentation 2-3 weeks in advance so that I can send it to my co-authors for approval. I also (still, after all these years!) practice my presentation until I have a good feeling for the time I have available. Keep in mind as well that if, for example, your conference has 4 presentations per hour, you will not speak for 15 minutes. You'll need to calculate the time for getting introduced, sometimes the time for getting the computers up and running, and time for questions. For this case, prepare a presentation of 10-12 minutes. You don't want to be the person taking too much time (especially not before the coffee or lunch breaks, when everybody wants to go eat, drink something or just take a break). Many conferences will ask you to send/upload your presentation in advance. By all means, check in the speaker ready room if your presentation is in the system, and if everything comes on the screen as you intended it to (different versions of powerpoint sometimes move things around - correct that before you are up on the stage to present).
If you feel insecure about presenting your (early) work to some of the top researchers in your field, you can practice power-posing to boost your self-confidence.


9. Travel early

I once almost missed the first day of a conference because my first flight was delayed, I missed my connecting flight and then was put onto the waiting list. I was hoping so hard they'd find a spot for me, and just before the flight took off, I heard my name from the standby list as cleared to board. Since then, I've been traveling with a day of extra time for my long flights. I'd rather stay one night extra in the hotel, than miss the entire first day of a conference because of travel problems.

10. Have everything backed-up

Print out your boarding pass, hotel reservations and conference registration confirmation. Figure out how to get from the airport to the hotel to avoid having to pay for a cab. Print out your slides of the presentation to practice. Put all the emails about the conference, your paper, presentation and all relevant documents on a back-up for when you need them. I am not traveling with a laptop anymore, but use a Surface tablet (the device itself is so glitchy that I wouldn't recommend you getting it, but when it works, it is useful for my teaching and for having access to MS Office and the internet when traveling)

11. Plan you time before and after the conference

I once did the math to see how much time a conference really takes me - from the step of finding a suitable conference to present my work to the point of needing some extra time to recover after a conference.
Keep in mind as well that, after the conference, you don't just simply return to your office, park yourself in front of your computer and get going again. You'll need to file for reimbursement and do all the administration work. You will need to send a few emails to catch up with people you met during the conference. Your overflowing mailbox might take a day to get sorted out. You'll need to catch up in the lab to see how things are going. There'll be people who need to talk to you, mail you or phone you. You'll be tired and busy. Plan accordingly.

Paper and presentation from fib Symposium 2015

I recently presented and published a research paper at the fib Symposium in Copenhagen.

The abstract of the presentation and paper is as follows:

Slabs subjected to concentrated loads close to supports, as occurring for truck loads on slab bridges, are less studied than beams in shear or slab-column connections in punching. To predict the shear capacity for this case, the Bond Model for concentric punching shear was studied initially. Modifications to this model resulted in the Modified Bond Model, which takes into account the enhanced capacity from the direct transfer of the load to the support, is able to deal with moment sign changes as occurring near continuous supports, and can take into account the reduction in capacity, resulting from the geometry when the load is placed close to the edge. The model is then compared to the results of experiments on slabs subjected to concentrated loads close to supports. As compared to the Eurocode and the ACI code, the Modified Bond Model leads to a significantly better prediction of the experimental results. The Modified Bond Model is one of the few models available to describe the shear capacity of slabs subjected to concentrated loads close to supports and can be used for design and assessment.

The slides of the presentation are here:

Why you should study civil engineering

Every semester, I teach a seminar in the general course on sciences and engineering, to show first-year students why civil engineering is the coolest thing ever. The presentation explores the range of problems civil engineering deals with, and shows the students how civil engineers improve our daily lives day after day.

Here you can find the slides of my presentation:

Research seminar: Testing to Failure of the Ruytenschildt Bridge

Last April, I gave a presentation in the research seminar of the Politecnico of Universidad San Francisco de Quito about testing the Ruytenschildt Bridge in Friesland, and some of the first results of the analysis.

You can find the slides of the presentation here:

Applications of sound in engineering

Some time ago, I gave a short presentation about the use of sound in engineering for the college of Medicine of Universidad San Francisco de Quito.

In this presentation, you find a brief overview of how we take sound into account when we design (buildings as well as pavements), and then I go deeper into the use of sound in bridge engineering. Sound is used for the inspection of bridges (non-destructive techniques) as well as for measurements during proofloading. I used the case of the Ruytenschildt bridge which we tested in The Netherlands last summer to illustrate how acoustic emission measurements work for proofloading.

You can find the slides of the presentation here:

Sound in engineering from Eva Lantsoght