CEE Graduate Seminar Series Guest Speaker: Josephine Carstensen, MIT

Wednesday, January 30, 2019
12:00 pm to 1:00 pm

Location:

Floor/Room #: 
1st Floor - #115

Abstract

Topology optimization is a free-form approach to structural design in which a formal optimization problem is posed and solved using mathematical programming. It has been widely implemented, especially in the automotive and aerospace industries, for design at a range of length scales including material architectures, mechanisms and structural components. However, the number of example where topology optimization is used to design civil structures remain limited. This is despite the fact that there exist numerous prefabricated low-weight construction elements. This talk seeks to identify the barriers that impede revisiting the general design of civil components and demonstrate that new designs with improved performance can be obtained.

Although topology-optimized designs are often shown to outperform conventional low-weight designs, the optimized designs are often complex and can therefore be difficult to fabricate. However, the production of clay and cement-based construction components, such as bricks and reinforced concrete, demand shaping the elements in an initial formable stage. Combined with the recent digitalization of formwork, this suggests that clay and cement-based materials would be excellent for fabrication of topology-optimized designs. This work specifically looks at using topology optimization to design reinforced concrete elements. Reinforced concrete is a highly complex composite that consists of a concrete phase that is strong in compression and a reinforcing phase that compensates for concretes low tensile strength. Typically, steel bars are used as the reinforcement. This talk seeks to advance topology optimization of reinforced concrete on two fronts: (i) by design of the concrete phase, and (ii) by design of the reinforcing phase.

In this talk the behavior of plain concrete elements designed with different topology optimization algorithms will be experimentally evaluated. The designs are obtained using the density-based approach with a minimum length scale requirement that is implicitly imposed using a projection-based method. The elements are designed within the same design domain, but with different objectives and constraints. A standard stiffness objective is sought, and two designs are obtained by minimizing the structural weight subject to  stress constraints.

Strut-and-Tie Models (STMs) have widespread use in design of reinforced concrete structures with nonlinear stress fields. Several researchers have proposed using topology optimization to automatically generate the reinforcement layouts for STMs. In this work, the experimental behavior of RC beams designed with STMs of increasing complexity is presented. A standard STM is developed by hand, and for the same design domain two topology-optimized STMs are generated. The topology optimization is performed using the bi-linear hybrid mesh approach.

Bio

Josephine Carstensen is a lecturer in the Department Civil and Environment Engineering and the Department of Architecture at MIT. Her research revolves around the engineering question of “how we design the structures of the future?” Her research interests lie in developing and implementing novel computational design frameworks that incorporate the constraints and possibilities of the physical world. The aim is to enable design engineers to create better performing designs.

Dr. Carstensen is a Denmark-America Foundation Fellow and received her PhD from Johns Hopkins University in 2017. She holds a B.Sc. and a M.Sc. from the Technical University of Denmark.

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Cindy Bergeron
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