At book launch: Author, Prof Nzengwa, analyses innovative models for modern day civil engineering.

The 293-page book was launched at the satellite campus of the University of Douala at PK 17 on Wednesday February 12, 2025. 

Prof Nzengwa in the book, presents in a variational form, very many two-dimensional models which have been developed to overcome some weaknesses of the Kirchhoff-Love and Reissner-Mindlin’s models. 

More precisely, the N-T and N models, which he explains, are particularly treated because they clearly show the impact of the change in the third fundamental form, whose contribution to the strain energy becomes important when the characteristic ratio of the shell is roughly greater than 0.3.

Transverse stresses through-the-thickness are calculated. Gradient Recovery and Strain deformation approach with Curve triangular and Shifted Lagrange elements are implemented. These new FEM appear to be memory less greedy. 

Essentiallu in civil engineering studies and or practices a “plate and shell model” refers to a structural analysis method used to study the behavior of thin, flat (plate) or curved (shell) structures, where the thickness is significantly smaller compared to its other dimensions, allowing for efficient load distribution by utilizing in-plane forces and bending resistance, often seen in elements like building floors, roofs, and tank walls; with plates being flat surfaces and shells having curvature. 

Applications of plate and shell models, he said, are used in building slabs, adding that concrete floors in buildings are often modeled as plates, roof structures.

Prof Nzengwa, however, said as time goes on, it has become difficult to design certain structures with classical models. 

“There are certain structures that can't be designed with the classical engineering methods. When they want to construct those types of structures and they have to be designed properly, such as ships, they need models to transform two dimensional structures to three. Because it will be difficult to use computer programming to calculate,” the engineering Professor said.

He went on to add: “So, people make models to fit in both. The mathematical model to bring the two-dimensional structures to be designed as three, certain models are needed based on certain hypothesis. So, in the book, classical hypnosis are presented with their limits and show how to go beyond those models and do better”.

The book, he added, examines limitations to classical models and propose innovative models for the current trends in civil engineering. 

“We have managed to make new computer methods for more safety” he added while noting that, a shell is a three-dimensional medium that can be represented by the product of a surface and an interval whose dimension is relatively smaller than that of the surface. How to predict the three-dimensional behavior of a shell by the parameters of the surface is the objective of various models found in the literature,” Prof Nzengwa detailed. 

Thin shell theory, the author intimated, is the most widely used theory in engineering by practitioners. Various models derived from this theory are presented in the book in their variational form. 

The author, through the book, also emphasizes on the need for African technological sovereignty, moving from old knowledge to new ones. 

“It is important to change the paradigm, the way of doing things. Once the new vision is clearly defined, we transform knowledge into scientific knowledge then into technological knowledge, therefore into know-how. The subject of our book is to demonstrate that our technological sovereignty is possible and that there is no sovereignty without technological sovereignty," he said 

About the author 

Prof Nzengwa who holds Doctorate in Mathematics from the Pierre and Marie Curie University, Paris VI has been teaching in Masters level, for many years now.

He equally holds Bachelor’s degree in Mathematics and Master's degree in the same specialty as well as a diploma of advanced studies in Applied Mathematics with focus on numerical analysis.

The academic has been lecturing in several institutions, including the National Advanced School of Engineering Yaounde where he was head of department.

He also ben Dean and the head of the department of construction engineering at the Ecole Nationale Supérieure Polytechnique de Douala.

He is a lover of knowledge, this explains why he had been eager to make it known that it is not enough to claim that one is an engineer, but to prove it through research work and applications in the field. 

He said if Cameroon must achieve the progress the goals of emergency and import substitution, there must be a change of mentality. 

This article was first published in The Guardian Post Edition No:3368 of Monday February 17, 2025