The memories on this page are contributions by friends, relatives and assistants of Hans Ziegler, who wrote their memories in English. Please switch to german (DE) to read more in Hans Ziegler's mother-tongue.

Our weekly meeting took place in Ziegler's office at 8:00 on a day when there was no lecture at this hour. Ziegler sat at his desk near the window of the high-ceilinged room, opposite him were the other two professors. Usually there were only a few administrative items to discuss because most other subjects had been dealt with in his efficient way. One morning one of the assistants was not present, (he was the one assistant who already had a family). Ziegler had somebody phone him then and there. "We now have our meeting here", and we all heard this long drawn "oh", "oooh" in the otherwise perfectly silent room. We sat there in silence, Ziegler hardly moving and transfixing a point on his desk, until about 40 minutes later, Donald turned up. Then Ziegler straightened a bit and said: "Gentlemen, I have nothing. Do you have anything ?" "---" "Thank you.". I do not think any other words were lost later.

Hans Ziegler told me this story three times and amused himself each time tremendously. I am telling it here, not in order to offend colleague F. B., but to demonstrate the special humour of Hans Ziegler with an example:

The colleague F. B. had a regular Professorship for Ground Mechanics at the Institute of Geotechnics. He was asked by Hans to act as a co-referee for a dissertation. F. B. agreed without hesitance. Expert conversations about mechanics can hardly be avoided in such common efforts of helping a candidate to find his path to the doctorate. However, one has to know that Hans Ziegler insisted meticulously on the fundamentals of science all his life and that he under no circumstances permitted confusions of terms, not even by colleagues. An impulse is by no means the same as a velocity, velocity is not the same as rapidity, rapidity is not an impulse moment, an impulse moment is not a force moment, a force moment is not the same as energy, energy is not a working cycle and a working cycle is not a working efficiency, etc. The face of Hans Ziegler darkened each time, when his interlocutor did not master the fundamentals. It did not matter whether his partner was a student, an assistant, an ordinary or a non ordinary professor. The colleague F. B. happened to fall over this stumbling block several times, until Hans Ziegler took the decision to never again involve F. B. in an expert conversation. However meetings between professors were on one hand unavoidable and on the other hand F. B. was a very communicative person. Hans Ziegler had to find a solution. He seized his slightly entangled colleague from head to feet until his glance fell on the oversized footwear of the size of 48. “Which shoe size do you really wear”? Hans Ziegler asked now at every occasion of a possible conversation. Now F. B. had to find arguments and excuses for his abnormal appearance.

For heaven’s sake, why can a lonely specialist of road construction not have giant slippers?

To Professor Hans Ziegler I am owing a lot. In his mechanics lectures for engineers, physicians and mathematicians in the middle of the 1950’s he was conveyed fundamental insights and a deeper understanding of basic relationships and, moreover, respective capabilities, from which I was profiting and “feeding” all my life. To his lectures, Ziegler always came very punctually and well prepared for them. In those days, it was still a custom that the students welcomed the professors by a short but distinct applause when they appeared in a lecture hall of the main building of the ETH. That was done knocking by the right hand fist – fingers down – on the desk, and simultaneously drumming by feet on the hollow wooden floor, both about 5 to 8 times and with a frequency of about 3 Hertz. In the case of Professor Ziegler we especially liked to do that, because for every lecture he had a clear concept and learning aim, and he was always well prepared – we felt or at least had a presentiment for the high quality of that what will be presented, and we were thankful for that. His first action was always to divide each of the two large blackboards, being movable in height and one above the other, by vertical chalk lines into four fields of equal width. In the course of the lecture, the fields were filled up continuously by chalk notes. Finally, when in the last field Ziegler had written the lowest line and had set clearly audible the respective period – the recess bell was ringing, indicating the termination of all lectures going on, then in the building. No, of course, it was inverse: Professor Ziegler was so precise and disciplined, and the whole lecture was so well planned, that he put the period after the last chalk sentence some seconds before the recess bell began to ring, the official end of the lecture. However, that was “only” the didactic frame. For Ziegler, yet more important than the precise adherence to the given time, was the clear definition and consequent application of all essential terms. The – unspoken – creed was: choose terms deliberately, give them clearly defined contents and use them stubbornly – hence for instance never use synonyms at any time. Every lecture given by Ziegler was a brilliant masterwork in regard to both didactics and contents. His lectures – as well as his famous books – were so crystal clear, totally transparent and interwoven by a bright light of understanding.

In the course of my later activities as a professor at the ETH, Professor Ziegler was always a luminous example for me in regard to didactics. Of course, in my own lectures, I never reached his clearness and transparency. However, in addition, I yet owe him something completely different and much more important. Nearly one and a half decade after “taking delight” in the mechanics lectures, and after some years working as a practising engineer and a manager of a contractor company, – as well as after writing a fortunately well done and widely known PhD dissertation about the application of the theory of plasticity to concrete structures – at the age of 34 years I was appointed to an assistant professorship for structural concrete at ETH. Thus I became a junior colleague of my admired former teacher. And it was a great honour for me, that after a certain time Professor Ziegler offered the familiar form of “you” to me. Subsequently, we occasionally discussed the need for continuous and lifelong learning by professors, and about the possibility of taking up completely new fields of teaching and research. Thereby Hans Ziegler said to me in his well known direct manner: “If you want to learn something really new, you simply announce a lecture about a subject in which you are interested, but of which you not yet know anything. Then you know what you have to do!”

At that time, professors had to inscribe the titles of their intended lectures into a questionnaire of the vice-chancellor half a year before the beginning of the relevant semester. In the 1970’s first of all only sporadically, but then more and more – questions about vibration and earthquake behaviour and the relevant safe design of structures came to the ETH from engineering professionals in practice. However, my altogether older professorial colleagues in the Institute of Structural Engineering were already engaged with other subjects and commitments. Although I yet barely knew anything about these subjects, I got interested in the really challenging questions from practice where people won’t get anywhere; and I recognised a chance to learn new things, to introduce myself into a yet not much developed field of science and to help to advance it. In these circumstances, the former tip of Hans Ziegler was – of course, in a spiritual sense – invaluable and a stupendous encouragement. In the fall of 1978 I was writing onto the questionnaire of the vice-chancellor the four words “Seismic Design of Structures” with 2L and 1E, i.e. 2 hours lectures and 1 hour exercises a week. Then, I really knew what I had to do in the remaining half year before the beginning of the summer semester – it became an unbelievable day (and especially night) race against time. Later, I created the new lecture series “Vibration Problems of Structures” as well, and with the help of numerous excellent collaborators and PhD students, I was permitted to create and develop at the ETH the scientific field of “Structural Dynamics and Earthquake Engineering” to a nice degree, and finally, in the 1990’s, have a worldwide recognition. Without the “insolent” tip of my fatherly colleague I never would have had the courage. Many, many warm thanks to Hans Ziegler!

Already as a five year old Hans tended to books far more than to sports.
One day a visitor found him in tears, sitting in front of the doorway of the Ziegler house.
“Why for heaven’s sake are you crying” asked the visitor.
The simple answer was:” I have to go out and play ball”

After his first lecture at Brown University, having arrived in the US few weeks before, Hans Ziegler came home totally puzzled and said to Erika:
“Imagine, those students call me Hans!”

Hans and Erika went skiing for a week or two with their assistants on several occasions, which for everybody were happy and relaxed days filled with sports, entertainment, as well as the occasional discussion among experts.

Such vacations usually took them to modest guesthouses in remote alpine ski resorts. On arrival, the Professor checked in by signing the register as “Hans Ziegler, Mechanic” – to which one of his assistants reacted by designating himself as “the mechanic apprentice”.

We first met the Ziegler family in the fall of 1963 when Hans had been invited to MIT for an academic year as the Hunsaker Professor in the Department of Aeronautics and Astronautics. Hans was a brilliant academician in the fields of mechanics and thermodynamics. His Minta Martin lecture presented in February of 1964 was one of the most scholarly in the history of the lecture. While at MIT Walt had expressed to Hans our interest in coming to Switzerland and Hans obtained an invitation to spend the academic year 1966 – 67 at ETH as a visiting professor.
His secretary had found a beautiful chalet for us for a very reasonable rent in Kusnacht overlooking the Zurichsee. It was an enchanted year for us. There were many social activities with the Professors, the Assistants and their families. Hans and Walt would often go for a beer together to chat about how things were going. On the first of these chats Hans explained to Walt that in Switzerland it would be considered discourteous for Walt to call him Hans around the office. This later became obvious when Sally was dancing at an après ski event with some of the assistants who were about her age. They still called her “Frau Professor” while dancing together.
On February 11, 1967 we went with the Zieglers and the Wehrlis to the AMIV ball and won a bottle of wine. Two weeks later the whole group went together for a ski week in the area around St. Moritz. On the first day of skiing Hans put a pair of skins on his skis and led the group on a climb to the top of the mountain to get warmed up. In the evening we all ate dinner together around a huge banquet table. There was a great deal of wine consumed, but only after the first toast. We laughed at Hans one evening when we saw him, perhaps by mistake, take a sip before the toast. After dinner we danced many Swiss dances that were all new to us, and we had fun teaching the Swiss to do American square dances. Walt had to do the calling which was the only time he ever did. Some days we would dance at après ski parties at the Chesa Veglia. On the last day of skiing Walt buried the bottle of wine from the AMIV ball in the snow at the side of the slope and stopped there on a later run with the group to dig it out and uncork it. Hans was thrilled. He said that was the sort of thing they did when his horse riding group went out for a ride.
We of course stayed in touch with Hans and Erika throughout the remainder of their lives. We so appreciated all that Hans had done for us that we named our second son Hans when he was born in 1969.

Hans had a sabbatical leave from his duties at the ETH every seven years. The last three of those leaves were spent at universities in the U.S. Thus he spent each of those academic years (September to June) as follows:
1956 - 1957, Brown University (Providence, Rhode Island);
1963 - 1964, Massachusetts Institute of Technology (Cambridge, Massachusetts)
1970 - 1971, Ohio State University (Columbus, Ohio)

I first met Hans in the winter of 1964, when I was a young Associate Professor of Engineering Mechanics at Ohio State.. We knew of his tremendous research in mechanics, especially in the subject of elastic stability. We also knew that he had been at Brown, and was currently at MIT. Our Department Chairman, Charles T. West (whom we called “Skip”) invited him to come to us to give a lecture. But we had more than the lecture in mind. We agreed that, if we liked Hans (that is, pleasant, not a pain), we would try to get him to spend his next leave with us, seven years later.

His beautiful lecture (all of his lectures were very clearly organized and carefully presented) at Ohio State was attended by approximately 50 graduate students and faculty members, mainly from engineering, but also several from mathematics and physics. It was about elastic stability. Afterwards, three of us from the Engineering Mechanics faculty (Skip West, Francis Niedenfuhr and I) took Hans to a good restaurant for dinner. The dinner conversation only confirmed what we already knew from private conversations with him earlier----that he was not only a very intelligent man, but also very kind and sensitive. After some lengthy chit-chat, we told him at dinner that we hoped he would spend his next leave with us. To our pleasant surprise, he said that he would like to. But first he would have to discuss it with his family. He said they all had a vote!

Skip then went to the Dean of our Graduate School of the university, and got permission to offer Hans a special Distinguished Visiting Professorship (at a good salary) for the academic year 1970-71. Within a few months Hans accepted, and we were all happy. But 1970 was six years away, and we hoped that his visit would indeed come to pass.

My family and I spent the entire summer (early June to early September) of 1966 in Europe. We spent the month of August in Interlaken, where two of my mountain climbing friends were in the hospital, recovering from an avalanche we had on the Eiger. We decided that we should drive to Zurich for a day. So I called the ETH beforehand to see if Hans was there. But the switchboard operator there thought I asked for Professor Siegler, not Ziegler, and connected me with him. We had a rather strange chat (and I thought his voice was different) but he agreed to meet me at about 13:00 on the desired day. When I showed up, we had never seen each other before! We both laughed, and he called Hans (whom he did not know), who was in Ruschlikon. Hans cut short his afternoon nap, and drove to his office to meet me. In spite of this difficult meeting situation, we had a pleasant and long conversation. Interestingly, he also said then that in 1970 he would be 60, that his father had died of a heart attack at that age, so he could not ABSOLUTELY GUARANTEE that he would be able to join us in 1970! And he was serious. One more example of his integrity. And this certainly satisfied me!

But he did survive to 1970. Erika and he (and Cornelia?) came by ship across the Atlantic Ocean that summer. They said that he had had a minor heart attack while on the ship! So his health was a serious matter. Our Department secretary had found a simple, but nice, house for them on the north side of Columbus. And Hans was given an office next to mine. So they were comfortable.

They spent a pleasant year with us. Hans taught a graduate level class on advanced dynamics and one on elastic stability. As I recall, Cornelia took some undergraduate classes at Ohio State. Erika, as always, read a lot. We socialized a bit together, but not a great deal. None of us collaborated with research with Hans that year because his interest had changed to thermomechanics (with a strong emphasis upon advanced thermodynamics), and none of us had any capability in this. Once a week he went horseback riding at an estate north of Columbus which belonged to a former German aristocrat (von Bredow). As a former officer in the Swiss cavalry, this was a genuine pleasure to Hans. And it resulted in a memorable incident.

One evening in the spring that year we received a call from Erika saying that Hans was home in bed, feeling terribly. She was afraid he was having a heart attack. We called a doctor for him, and drove over there ourselves, which was only a half mile from us. Hans was lying in bed, apologizing for his poor state. He said he had been horseback riding that afternoon, but afterwards was feeling some sharp pains. The doctor diagnosed that the pain was due to a minor separation in his ribs. After returning the horse to the stable, Hans was brushing him clean, as usual. The horse bumped him against the wall, causing the rib separation, which is a painful thing! Hans and we laughed about that many times afterwards.

During that year, Hans got to know me well, and also my technical work, especially the two books I had recently completed (Vibration of Plates and Vibration of Shells, which became classics). In the late spring he asked if I would be interested in coming to the ETH for a year as Visiting Professor. I said definitely yes. He contacted Max Anliker there, who approached the ETH administration, and got their approval. So it was all set for my family and me to spend the academic year there in 1972 – 1973.

It certainly was an interesting academic year for me in Zurich. On the fun side, I went to the Munich Olympics for one week and did a significant amount of skiing and mountain climbing. At the ETH I taught two graduate level courses, and wrote two technical papers which became well known and cited by others many times. And, of course, I became acquainted with the faculty members and assistants (graduate students) of Hans’ Fachgruppe fuer Mechanik. I was surprised by the lack of research activity among the faculty members (other than Hans). Hans continued to work intently on his thermomechanics research, and was frustrated that a few well-known international researchers disagreed with his results.

Trudi Achenbach was the secretary for the Fachgruppe. She typed the two research papers for me, in the course of which we became well acquainted. As the year went on our affection for each other grew. After I returned to Ohio in the autumn of 1973, I felt increasingly strongly that I did not want to continue my life without her. In November I asked her to marry me. Although she had significant doubts about it, she agreed. My wife (Jo) agreed very reluctantly to the necessary divorce. Then I wrote lengthy letters to approximately ten of my friends, including Hans, explaining the situation. I expected Hans to be upset about the news. He soon wrote back that my letter “was the biggest shock he received since the death of his father”. Nevertheless, he respected Trudi, accepted the news, and said he wanted us to continue to be friends. Both Erika and he treated Trudi with genuine warmth in the years afterwards.

And now another significant aspect of Hans’ life relative to mine began. In the winter of 1971one of my Ph. D. (doctoral) students (Lynn Wells) had finished his dissertation research. I had invited Hans to be one of the faculty members of Lynn’s final examination committee. This involved reading the dissertation, approving it, and taking part in the oral examination over it. Hans participated, and thus became acquainted with Lynn. Lynn soon after moved to Boulder, Colorado, gave up his staff scientist position with a large company, and became interested in purchasing and developing for sale and profit a large (three square miles) tract of land near Glen Haven, Colorado. In the winter of 1972 he had asked me to fly to Colorado during our spring break in March, and look at the land with him. I did, and agreed that it was a beautiful piece of land, which should appeal to a lot of people. I also agreed to approach some of my friends on the Ohio State faculty about investing in the project. The purchase was finalized in 1972, and the place was named “The Retreat”.

Because Hans knew Lynn, I told him about Lynn’s new project. Of course, he was astounded (and perhaps a bit disgusted, as I was) that Lynn would flush his Ph. D. work down the drain, and become a land developer. Hans asked me for information about the project, including a map of the proposed roads and lots. To my surprise he said he wanted to buy some of the lots, and he wanted me to choose four for him. His only request was that they be up high, and have a LOT of trees. I told him that he should do it himself, but he insisted. So I picked out four lots up high, on the NORTH side of Bulwark Ridge, which was thick with trees. When Hans saw the lots some months later, he decided that they were too dark for him (they were — too many trees), so he chose four others on the SOUTH side of the ridge. He added a fifth one a year or two later, and the locals called him “The Baron of Bulwark Ridge!”

Erika and Hans had a very nice cabin (made of hollow logs) built for themselves on their lots. Being up high on the ridge, the well for their drinking water had to be very deep — about 550 ft (170 m). They settled happily into their cabin, and went there every summer for several weeks. Hans typically arose early in the morning, had his breakfast, put on his work clothes, and went out on the surrounding terrain (which was rather steep) to collect dead wood for the rest of the morning. He sawed each stick and each branch into a defined length, and laid it horizontally on a pile. The piles became enormous. After lunch Erika and he would take their usual nap. Then he would enjoy the later afternoons, often on the cabin porch, and have a martini or two (very dry, he said — actually, pure gin) before dinner.

He enjoyed this way of life very much. We never talked explicitly about this, but I am sure he generally liked being in the U.S., away from the “Herr Professor” demeanor and responsibilities that they expected of him in Switzerland. He was more relaxed here. And being in The Retreat in Colorado was close to being in heaven for him. Erika enjoyed The Retreat less, simply because the high altitude (7900 ft or 2400 m) gave her terrible headaches.

Trudi and I were also welcome to use the cabin. We did this many summers, usually for about three weeks each time. Sometimes we would overlap with the Zieglers’ stay, and we would all be together for a week. I enjoyed these overlap weeks very much, mainly because we thus got to know Hans and Erika even better. We would often sit out on the cabin porch in the afternoon or evening and chat. Once he made a serious proposition to me. He said: “Art, you drink too much coffee.” It’s true — when at home or at the university I probably drank about ten cups per day. He said further: “I would like to make a contract with you. You drink no coffee after 12:00 noon, and I’ll not drink any martinis before 6:00 PM.” Wow! I had to laugh at this, but nevertheless accepted the deal. And that we both did. Although he died in 1985, I’m sure he’s up there keeping an eye on me. Now I drink NO real coffee at all (unless there is nothing else), only the decaffeinated version, which I think Hans would find acceptable.

One morning in the summer of 1976 Hans and Erika were astounded to see a helicopter land near their cabin. There had been a very heavy rain there the night before. This caused raging torrents of water in the Big Thompson River canyon, which destroyed the road there, many homes, and killed more than 100 people. The Zieglers were told that they could come out then by helicopter or stay. But if they stayed, it could be many weeks before any roads were open. So they left and went back to Switzerland early. This torrential rain (14 inches in four hours in some areas) is still talked about now in 2009 by Coloradoans.

During their summers in Colorado they did a lot sightseeing locally (for example, Estes Park and Rocky Mountain National Park), elsewhere in Colorado and, as I recall, even beyond Colorado. Erika sometimes went swimming in the pool at the Stanley Hotel in Estes Park. They took walks in the Retreat often. At their ages they no longer were serious hikers. But once the four of us took a six mile (10 km) hike together to Bridal Veil Falls in RMNP, with a 1000 ft (300 m) elevation gain altogether. They both agreed that their Colorado stays were very good for Hans’ health.

Hans was generally a very serious man. His students respected him greatly, and even feared him. I was the rather casual, easy-going American, but for some reason we always seemed to get along well with each other. He told some good jokes to me that I still remember; for example, Goldberg from Brooklyn crossing the Atlantic Ocean the first time on the S.S. France.

I cannot remember exactly when Hans retired from the ETH. It was approximately 1980. ( He said he wanted to retire earlier, but they asked him to stay somewhat longer.) Upon retiring he told me that he would now spend his days “reading the classics”. I said, “Hans, you have spent your life developing tremendous scientific expertise. Are you now going to throw this all away and not do any more research?” After reading classic books for a year, he told me that he missed his research, and was going back to it, particularly his work in thermomechanics. Furthermore, he was going to approach it from a more fundamental viewpoint, using the Theory of Relativity. He did this until the end of his life, as far as I know.

At the beginning of August, 1985 I went to the U.S. Air Force Academy in Colorado Springs to begin an academic year there as Visiting Professor. We had spent July in the cabin in the Retreat. The Zieglers came to the cabin soon after we left. One evening a few weeks later Erika phoned us from a hospital in Denver. Hans had had a heart attack and had been taken by helicopter to the hospital. It took us about one hour to drive to the hospital, where we met Erika and the doctors. The doctors told us that Hans’ condition was very bad. Hans could talk with us. He apologized to me, saying that he would not be able to be the Keynote Speaker at the Midwestern Mechanics Conference at Ohio State several weeks later! One last example of his integrity. The surgeon told Erika that the only hope he saw for Hans was to implant a pacemaker for his heart. Erika agreed, it was done, but Hans died nevertheless.

And thus Hans was gone, and Regula flew over to Denver immediately. A memorial session in remembrance of Hans was held in their cabin a few days later. We attended, along with approximately 20 neighbors from The Retreat. We all agreed that we would never forget Hans. I never have. We visited Erika in Ruschlikon for many years afterwards. But I always missed the presence there of Hans.

Memories are the seasoning of the soul bringing long lasting warmth to the spirit. A professor teaches by lecturing, writing, sharing his research etc.  This “Professor” Ziegler I did not know - but the person of Hans Ziegler, his wife Erica and family has left a lasting imprint on me as well as my family.

My husband and I were introduced to Hans and Erica at a neighbor’s house where we all had been invited for wine and cheese. It was 1979 and we had just purchased a building lot in the “Retreat”, Glen Haven, Colorado. Hans was one of the first property owners in the “Retreat”, a Colorado mountain subdivision. We all had decided this piece of land provided a perfect place for rest and relaxation from the busy lives for those professionals needing a place just to renew themselves.

When we had settled on the time frame for actually building our own retreat home, Hans & Erica graciously allowed us to stay at their cabin for a summer’s week to test our feel for mountain living - a privilege not granted to all.  This is when we really met Hans Ziegler, a Swiss gentleman with unbelievable character and spirit. We soon learned one’s actions are not only the seeds of today but also the nutrients of all the tomorrows.

Hans had organized the Ziegler cabin so well we knew we were in privileged territory.  Their handwritten “Ziegler Cabin Book” let us know quickly the instructor was in charge.  It provided many detailed instructions for opening and closing the cabin, as well as directing us to every possible solution for any problem that might arise during our stay. As we would begin the construction of our own cabin the coming year, our main motive for the week long stay was to learn and understand the challenges of mountain living.

The Ziegler cabin was on a road overlooking our lot. Every morning and evening we would walk to the outlook point on the road looking down to see where we might locate our cabin in relation to the sun’s rays.  Then we would return to the Ziegler cabin, refer to Hans’ cabin instructions and understand all the things we needed to plan. We measured room size in relation to furniture, an entry door with suitable Alpine flavor and construction details to be watched so we could pattern our cabin as Hans had efficiently done. During the year of our cabin’s construction we developed our own “Gee Cabin Book”, just like Hans had done.  It was as if Hans was personally supervising.

The first year the walls of our mountain house were up and the house barely settled we were ready to entertain.  Even though we had a hot plate to cook on and a card table on which to serve our guests, we invited Hans and Erica for a meal.  We were eager to share with them how much we had tried to follow Hans’ pattern and the influence of the “Ziegler cabin” even to our naming our mountain abode “Gee’s Mt. Haus”.

What a wonderful evening of wine, simple food, laughter and magic conversation.  Although our “Haus” was starkly completed, Hans & Erica graciously accepted our meager surroundings.  In an evening filled with stories, suggestions and recommendations, our “Haus” had been dedicated with champagne, cheese and a Swiss spirit.

Sadly the next day Hans’s heart attack was the last “Haus” imprint left for us. However, his presence has had a lasting influence. Sharing memories with Retreat friends, his daughter Regula and grandchildren has been a continuing blessing for our “Mt. Haus.” These special friendships that have been created are alive with champagne, cheese and his Swiss spirit.