While 3D digital design tools have extended the reach of architectural and engineering designers within their own domains, restrictions on the use of the tools and an approach to practice whereby the architect designs (synthesises) and the engineer solves (analyses) - in that order ¡V have limited the opportunities for interdependent modes of interaction between the two disciplines during the early design phase. While it is suggested that 3D digital design tools can facilitate a more integrated approach to design exploration, this idea remains largely untested in practice. The central proposition of my research is that that 3D digital tools can enable interdependencies between crucial aspects of architectural and engineering design exploration during the early design phase which, before the entry of the computer, were otherwise impossible to affect. I define interdependency as a productive form of practice enabled by mutual and lateral dependence. Interdependent parties use problem solving processes that meet not only their own respective goals, but also those of others, by constructively engaging difference across their boundaries to actively search for solutions that go beyond the limits of singular domains. Developed through practice-based project work undertaken during my 3 year postgraduate internship within the Melbourne Australia office of the engineering firm Arup, my research explores new and improved linkages between early design exploration, analysis and making. The principal contribution of my research is to explore this problem from within the context, conditi ons and pressures of live practice. To test the research proposition this dissertation engages firstly with available literature from the fields of organisation theory and design, secondly with information gathered from experts in the field principally via interview, and lastly with processes of testing through practice-based (as opposed to university-based) project work. The dissertation is organized as follows: The Introductory Chapter outlines the central hypothesis, the current state of the discourse, and my motivations for conducting this research. I summarise the structure of my research, and the opportunities and limitations that have framed its ambitions. Chapter Two, Approach to Research and Method, details the constraints and possibilities of the Embedded Research within Architectural Practice context, within which this work has been undertaken, and describes the Melbourne office of Arup, the practice with whom I have been embedded. These contexts have led to the selection of a particular set of ethnographic research instruments, being the use of semi-structured interviews and the undertaking of practice-based studies as a participant-observer. These modes of testing are explained, and the constraints, limitations and requirements associated with them described. Within Chapter Three, Factors for Separation and Integration in Architectural and Engineering Design, I examine selected design literature to detail several factors impacting upon the historic and contemporary relationship between architects and engineers, and to introduce the problem towards which this thesis is addressed. I describe a process of specialisation that has led architects and engineers to see different aspects of a common problem, detail the historical factors for separation, the current relationship between domains and the emerging idea of increased integration during the early design phase. The aim of this section is primarily contextual - to introduce the characters and to understand why their interaction can be difficult - and investigation occurs through the concepts of specialisation and disciplinary roles. Chapter Four, Unravelling Interdependency, establishes an understanding of interdependency through the concept of collaboration. While I differentiate interdependency from collaboration because of the inconsistent manner in which the latter term is employed, the concept of collaboration is useful to initialise my understanding of interdependency because it, as opposed to the closely linked processes of cooperation and coordination, is recognised as being characterised by interdependency, and in fact is a viewed as a response specific to wider conditions of interdependency. From the literature, I identify four sites of intersection crucial to an understanding of interdependency; these are differing perceptions, shared and creative problem solving, communication and trust. These themes, which correlate with my practice experience at Arup Melbourne, are developed to introduce the concepts and vocabulary underlying my research. Chapter Five, Intersections & Interdependency between Architects and Engineers, grounds these four sites of intersection within contemporary issues of digital architectural and engineering practice. Each site is developed firstly through reference to design literature and secondly through the experiences and understandings of senior Arup practitioners as captured through my interviews. The views and experiences of these practitioners are used to locate digital limits to, and potential solutions for, interdependent design exploration between architects and engineers as they are experienced within and by practice. Through this combination of design literature and grounded experience, I extend: * the understanding of differing perceptions through reference to problems associated with digital information transfer. * the understanding of joint and creative problem solving by connecting it to the notion of performance-based design. * the understanding of communication by focussing it upon the idea of back propagating design information. * the understanding of trust by connecting it to the management and reduction of perceived complexity and risk. Chapter Six, Testing through Projects, details the project studies undertaken within this research. These studies are grouped into three discourses, characterized as Design(Arch)Design(Eng), Design|Analysis and Design|Making. As suggested by the concurrency operator that separates the two terms that constitute each of the three labels, each discourse tests how architectural and engineering explorations might execute in parallel. The section Design(Arch)|Design(Eng) reports projects that use a common language of geometry to link architectural and engineering design ideas through geometric interpretation. The section Design|Analysis reports projects in which analytical tools have been used generatively to actively guide and synthesise design exploration. The final section, Design|Making, reports projects in which the architectural and engineering design processes are synthesised around the procurement of fabrication information. Conclusions are then drawn and discussed in Chapter Seven. In evaluating the research I discuss how 3D digital design tools have enabled alternative approaches that resolve issues associated with differing perceptions, establishing common meanings, communication and trust. I summarise how these approaches have enabled increased interdependency in architect engineer interaction. Lastly, I draw together the impacts of intersecting 3D digital aspects of architectural and engineering design exploration during the early design phase, and indicate those aspects that require further analysis and research.