Experimental and nonlinear numerical analysis of underwater housings for the deep sea, made of ultra-high performance concrete

Abstract

The paper describes the design and analysis of underwater housings made of ultra-high performance concrete (UHPC) within the Helmholtz Alliance "ROBEX" to provide cost-efficient alternatives to expensive titanium housings. The research is related to former investigations on spherical and cylindrical shells under hydrostatic pressure made of normal strength concrete, performed from 1960 to 1980 at the Civil Engineering Laboratory, Port Hueneme, California. Several housings made of UHPC have been manufactured and the short-term implosion resistance has been determined experimentally. Since neither the mechanical equations for thin-or thick-walled shells nor the empirical equations for implosion pressure of shells made of normal strength concrete by Albertsen can describe the behavior sufficiently, two nonlinear material laws for concrete, multiPlas Law 9 (modified Willam-Warnke model) and Law 14 (Menetrey-Willam model) by Dynardo for ANSYS, have been calibrated with results from uni-and biaxial strength tests, and the results of nonlinear finite element model with ANSYS 16 have been compared. To study the long-term behavior, an in situ test is currently being performed at 2,500-m depth in the Arctic Sea.

Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

“…An in-situ test was recently carried out in the Arctic Sea at a 2500-m depth that monitored temperature and humidity inside underwater housings made of ultra-high performance concrete in order to determine alternative materials to titanium, special stainless steel and aluminum for housings (Wilhelm and Curbach 2017;ROBEX n.d.). On a laboratory scale, Wilhelm and Curbach (2017) have described that the implosion behavior of concrete housings can be simulated by empirical equations determined by Albertson (1973) modified with a nonlinear material law for concretes, which was calibrated with results from multiaxial strength tests (Hampel et al 2009;Ritter and Curbach 2015).…”

UHPC‐Druckgehäuse für Anwendungen in der Tiefsee

“…Die Lasteinleitung erfolgte über 400 Stahlborsten je Belastungsseite, um die Querdehnungsbehinderung weitestgehend zu minimieren. Entgegen wurde für beide verwendeten UHPC‐Mischungen WPE 1 und 2 eine Zunahme der zweiaxialen Druckfestigkeit ( σ 1 / σ 2 / σ 3 = 1/1/0) von 10 % am Würfel mit 10 cm Kantenlänge (Prüfalter 28 d) (Bild ) bestimmt (). Die Festigkeitssteigerung im für die Zylinderschalen relevanten Spannungsverhältnis von 1/0,5/0 betrug im Mittel 20 %.…”

“…50,2 MPa belastet (Bild ). Experiment und numerische Nachrechnung sind ausführlicher in beschrieben. Die Gehäuse in Phase II wurden von vornherein an die Geometrie des Drucktanks angepasst.…”

UHPFRC for the cast-in place reinforcement of offshore maritime signalization structures

“…Without being exhaustive, one can cite: (1) the Sakata-Mirai footbridge (variable height box girder cross section, wide circular openings, span 50 m) in Japan, prefabricated externally posttensioned box-girder UHPFRC segments, located at the mouth of a river by the sea [3] ; (2) the extension in 2008 of the Haneda airport in Japan (Tokyo harbor), with 24,000 m 3 UHPFRC in the form of prefabricated pre-tensioned ribbed slabs attached to a metallic frame [4]; (3) the completion in 2012 of one of the 4 multi-span bridges with 6 spans planned for the extension of a container unloading terminal at Port Klang in Malaysia with a locally developed and produced UHPFRC [5] for 102 12.1 m long prestressed beams, without passive reinforcement; (4) the feasibility study for the application of prefabricated elements in UHPFRC for a harbor dock in Lorient, France [6]; (5) the proposal of prefabricated UHPFRC elements for the replacement of polder flood barriers in the Netherlands, [7]; (6) the proposal for the use of UHPFRC for offshore wind turbines [8] and then for the construction of their foundations [9], and finally prefabricated UHPFRC elements assembled by post-tensioning for the towers [10]; (7), the project of wave power plants using UHPFRC floats, with a prototype plant was installed in 2005 in the North Sea as part of the "Wavestar" project [11]; (8) the UHPFRC deep sea housings developed at university of Dresden [12] currently under testing in the arctic sea, 2500 m deep; (9) the emblematic MUCEM building and footbridge in Marseille, with structural members and filigree cladding lattices made of UHPFRC, exposed to the seaside environment [13]; (9) the footbridge "Las Ovejas" in Alicante (span: 45 m), on the Mediterranean seaside, made of post tensioned UHPFRC segments (FORMEX® mix using local components) with an organic shape and transparent colored inserts, [14]; and finally (10) the very original use for offshore mussels farms of a UHPFRC grid resting on floaters, (FORMEX® mix), [15].…”