Bridge Function, Economy and Aesthetics

Advantage Steel, 2014

Structural Engineering International

In bridge planning, the successful translation of the many conditioning factors into a solution that meets all safety requirements while also addressing considerations such as economy and elegance is essentially a matter of conceptual design. Despite the utmost importance of that stage, which in addition to an intuitive understanding of load-bearing mechanisms calls for imagination and a sense of form and beauty, creative conceptual thinking is systematically underestimated both in engineering training and everyday practice. The resulting impoverishment of the profession stems not only from growing, need-driven and hardly reversible specialisation, but also from inexorably extensive and opaque standardisation and control. The rules for ensuring robustness reflect the increasing complexity and opacity characterising structural design codes. While the practical importance of designing and building robust structures is universally acknowledged, the codes presently in place are often vague or confusing. Cross-referencing, in turn, may lead to loops around rules that, confounding engineers, are counterproductive. At the same time, however, that lack of clarity may afford opportunities for innovative solutions by building items that ensure robustness into the conceptual design of a structure. This paper proposes an operational design process that deals appropriately with all factors of structural performance, including robustness, without compromising bridge economy or elegance. That process, which combines a number of robustness strategies, including risk-based considerations, is illustrated with a case study of a proposal submitted to a design competition for a viaduct.

This article is a critical review of the conventional wisdom on bridge aesthetics. If bridge design is to be recognized as a valid and distinct means of artistic expression, then bridges must reflect the truths that define the fundamental essence shared by all works of art, regardless of the medium of expression. By extension, for these truths to be embodied in bridges, their existence and importance must first be acknowledged in the conceptual frameworks used by designers to guide their decisions in the design process. A fundamental attribute of the essence of art is to challenge existing ideas, and hence to defy dogmatic notions of how to create art works that are in "good taste". The conventional wisdom on bridge aesthetics, however, is actually nothing more than such a set of dogmas. These include: (1) Form Follows Function (structural efficiency is a sufficient condition for aesthetic significance), (2) The Customer Is Always Right (art is not created by artists, but by the public), and (3) Architects Do It Better (the discipline of structural efficiency and the expressive potential of the flow of forces are irrelevant). The works of Maillart, Roebling, and other masters of bridge design show that designers need to be free from such dubiously founded restrictions to create works of artistic significance.

IABSE Symposium, Melbourne 2002: Towards a Better Built Environment - Innovation, Sustainability, Information Technology, 2002

The design of bridges is typically split into two, quite distinctly different stages: the design of the overall structure on the one hand; and the detailed design of the individual components on the other hand. Typically the overall design takes place on generalised and simplified models of the bridge structure. Section forces and displacements gained from such models are then used as boundary conditions for the much more detailed models used in the second stage. An integrated process whereby requirements for both design stages are incorporated into one model has in the past been made difficult or impossible by the lack of computing resources. This situation is about to change. Generally available computers will soon be powerful enough to allow such a holistic approach. This paper outlines the strategies employed in a current research project which provides the scientific background for such an integrated design approach. The outcomes of this research project are to be directly incorporated into a state-of-the-art bridge design software package. First results of this research project are documented and future developments are explained in this paper

IABSE Symposium, Venice 2010: Large Structures and Infrastructures for Environmentally Constrained and Urbanised Areas, 2010

This paper analyses how urban bridges respond to a different set of rules from road bridges when choosing its bridge type, and developing its design. While road bridges adopt one or other bridge type only based on technical restraints, cost, function and structural efficiency, with limited resulting span scopes suitable for each bridge typology. Urban bridges and footbridges can adopt these designs out of its strict span scope, as no structural predetermination exists, responding to different new factors as: aesthetics, architectural scale, landscape integration, users’ perception, urban planning flexibility, landmark or symbol creation.Examples of urban bridges design are used, including recent arch and cable stayed bridges by Arenas & Asociados. Conclusions attempt to create some simple rules for urban bridge design, as result of local conditions and architectural restraints.

This paper presents the effect of the bridge's width on the optimum design of steel bridges. I-section is considered for main girders and diaphragms. The problem of optimum cost of steel bridges is formulated as minimization of initial cost (IC) which consists of substructure cost and superstructure cost. The performance constraints in the forms of deflection, stresses, local buckling etc, are based on the AASHTO Specifications. The Sequential Unconstrained Minimization Technique (SUMT) is used to make required optimizations for costs. Orthotropic plate theory is introduced to analyse the bridge system. To demonstrate the effect of widths on the optimum design of bridges, a steel I-girder bridge with various lengths and widths were chosen. From the results of the numerical investigation and figures, it may be positively stated that the optimum design of steel I-girder bridges based on SUMT technique in this study will lead to more reasonable, economical design compared with conventional design. The main results found from this study [For bridges less than 350 m length] are that (1) There is an insignificant effect of the bridge's width on the ratio of substructure cost/ superstructure cost. (2) The number of girders required for a bridge to give optimum design ranges from two to four girders.