Development of underwater housings for the deep sea made of ultra-high performance concrete (UHPC) and long-term testing at the Arctic Sea
The aim of this research is the design and analysis of underwater housings made of ultra-high performance concrete (UHPC) within the Helmholtz Alliance “ROBEX” (robotic exploration of extreme environments) [1]. Due to the extremely corrosive maritime environment, mainly expensive materials such as titanium, ceramics, special stainless steel and aluminum are used so far for the construction of temporary and permanent research stations to guarantee long-term deployment. In this project the suitability of high-strength concrete with compressive strength up to 210 MPa for underwater pressure housings and constructions is examined to provide a low cost and durable alternative especially for large housings in future.
Sealing systems for low-cost and corrosion-free pressure housings made of ultra-high performance concrete (UHPC)
The article is about the development of a sealing system for pressure housings made of ultra-high performance concrete (UHPC), which has been developed within the Helmholtz Alliance “ROBEX” (robotic exploration of extreme environments) [1]. Several kinds of sealing systems according to the material properties of concrete have been designed so far and the amount of aluminum or titanium needed has been continuously reduced to minimize the manufacturing costs. Also a new metal-free sealing based on epoxy has been designed. The developed sealing systems made of aluminum, titanium or epoxies have been tested experimentally in pressure tanks in-situ. The sealing systems also have been simulated numerically with ANSYS 16 and the nonlinear material law multiPlas law 14 (Menetrey-Willam) by Dynardo. Advantages and disadvantages of these systems are shown in the paper.
Modeling of plain concrete structures based on an anisotropic damage formulation
In this contribution, a strain-based constitutive law for concrete within the framework of continuum damage mechanics is proposed. The model allows for the multi-axial simulation of predominantly tensile loaded plain concrete structures. A second-order integrity tensor is chosen as the internal damage variable to consider the phenomenon of load-induced anisotropy. The model is implemented in the finite element method. Hence, a fracture-energy based regularization approach is included to overcome the mesh-dependence of the computational results. The proposed model is applied to the simulation of well-known experiments with plain concrete specimens, which are often used to demonstrate the applicability of damage constitutive laws. In this context, attention is focused especially on problems regarding the accurate implementation of the complex loading and boundary conditions. Oversimplifications are discussed and proposals for a more realistic involvement of the test setups in finite element models are submitted.