Environmental sustainability and adaptation to climate change are two of several reasons floating structures are of great interest. Their resilience toward rising water levels and the possibility they allow to avoid additional land use are two specific factors that have influenced a flourishing of studies on floating structures and also several applications, for example in the transport field or in food and energy production. Moving from land to water implies taking care of a new complex environment throughout all the phases of the construction and during the whole life cycle of the structure. It is necessary to take care of the marine environment since the early phases of the conceptual design of the structure, to really consider the environment as one of the decisional information on the best-suited solution for each specific case, avoiding later costly mitigation measures and using the possibility to create environmental benefits with the change. The working party WP 1.2.3 of TG 1.2 of Fib presents in the present paper the potential environmental risks and potential benefits for concrete floating structures to promote an increased awareness of the marine environment with the involvement of different expertise from the early phases of the project.

Awareness of design risks is essential for preparing integrated design and construction tenders as decisions in this phase can have serious consequences once the project is awarded. The practice of multi-criteria decision analysis (MCDA) promises to support contractors in dealing with risks in the decision-making process. However, due to limited time and resources in a tender, risks involved in design alternatives are often overlooked and the selection of alternatives is mainly based on the decision-makers’ knowledge and experience. This raises the question how decision makers can become aware of the risks in the tender phase of projects. Following a design science research approach three interventions to raise risk awareness are identified and validated in the context of an infrastructure tender in the Netherlands. These interventions are (1) a general list of defined criteria to identify those criteria that correspond with the characteristics of the tender; (2) mapping identified project risks on criteria and assign a bandwidth score; (3) evaluation of the quality of the decision process by scoring elements of decision quality. Based on these interventions three design rules are proposed to increase the transparency of decision problems and the understanding of choices and, by doing so, create awareness for risks involved in design alternatives.

Design decision-making in infrastructure tenders is a challenging task for contractors due to limited time and resources. Multi-criteria decision analysis (MCDA) promises to support contractors in dealing with this challenge. However, the ability of MCDA to ensure decision quality in the specific context of infrastructure tenders has gained little attention. By undertaking a longitudinal case study on early design decisions in a tender for a design-build project in the Netherlands the relationship between MCDA and decision quality is investigated. The case results show that in the early tender phase the decision making very much relies on the experience and knowledge of engineers. If MCDA is inappropriately used in such a context it can create impressions of soundly underpinned evaluations of design options while neglecting uncertainties and leading to low-quality decision. Although MCDA defines the “what” is required for structuring the decision problem, it does not support decision-makers in the “how” to do it. The explicit consideration of decision quality elements in MCDA can support the “how” and can create awareness for decision makers concerning importance, scope and uncertainty of criteria.