The Defense – my experience

On June 14th, I passed my PhD defense, and I promised to write a blog post replying the question “What was it like to defend?”.

Most of all, it went so quickly. Only during a few moments, I realized of what I was actually doing up there, and the weight of my words – most moments, I simply focused on answering the questions.

I was frankly curious to see what my committee members would ask me.

Immediately after the defense, I received my diploma, which was yet another moment to remember.

It was quite an experience to defend my work in front of my friends and family, and with a committee of knowledgeable people. I started with a 20 minute presentation only for friends and family. Afterwards, the actual defense was 1 hour sharp, and the committee members could ask their questions – members from “far” went first and received most time, and the last was my promotor. In fact, I was half-way through answering my promotor’s first question when the beadle came in to mark the hour.

During the first question I was quite nervous. It was a rather long question, and I did make notes, but I found it difficult to address all the elements that he summed up in his question (and at one point I had difficulty reading what I had scribbled down as one of the points that came up).

But then, after talking through the first 10 minutes, I felt more relaxed, and I realized that I really do know my topic inside out – and that there are elements on which I might have a different opinion than some of my committee members, and that they find that perfectly fine as long as I have a good reason for thinking that way.

During the defense, I spent some time discussing the Modified Bond Model with the first committee member*, who uttered his serious doubts about it, and with the fourth committee member, who mostly wanted me to explain why the results for the slab strips appear to be unsafe – a question that was easily tackled by showing the difference between the pure one-way behavior in the strips as compared to the two-way (or combined one-way and two-way) behavior in the wider specimens that we tested.

The other questions that came up during the defense were about the mechanism of shear transfer, and their relative importance, which I discussed with the second committee member (a more theoretical question), the use of finite element calculations and their practical applications, the difference between plain and ribbed bars (plain bars were used until the mid 1960s, and we also tested slabs reinforced with plain bars to compare to undeformed bars), the proposition about the cracked specimens that turned out to have a surprisingly large residual capacity and the link between the Modified Bond Model and the Hillerborg model.

After the defense itself, the committee left for 15 minutes, and then they came back to give me my diploma, and for the speech of my promotor.

When all was said and done, we had a reception, and in the evening I hosted a dinner in a restaurant in Delft, to celebrate the very end of my PhD studies.

* My defense was public, and you can see the list of committee members in my dissertation, but I can imagine that not everybody likes having their name up on the internet, so I’ve decided to just number my committee members for this post.