**1. Introduction**

The visual impact of an urban overpass or bridge inserted into a road network requires a careful study of its aesthetic aspect by its engineers. The importance of the aesthetic analysis of the infrastructure design in serving the public good demands special attention because of the densely built‐up nature of the site where it is to be inserted that necessarily calls for order, discipline and aesthetic values [1]. Moreover, it is also important to analyse the environmental

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

impact of a bridge, especially true of urban overpasses with regard to their more intrusive location close to areas of the pedestrian use.

Much of the public focus has been centred on several "landmark" bridges [2]. Denn [3] specifies aesthetic guidelines for bridge design, remarking that a careful and early application of aesthetic concepts can make a significant improvement in the appearance of bridges and structures. Every bridge is, to some degree, a historical document, a demonstration of struc‐ tural technique, a performance test of building materials, a comment on the values of a society which produced it and a reflection of the richness or poverty of its designer's imagination. So, the bridge designer must strive to understand the creative process, together with scientific and technical principles. The aesthetic aspects that stimulate the senses in most viewers are proportion, order, simplicity, balance, colour and texture. Design bridges must incorporate these aesthetic principles with the physical and geometric components of the structure.

In this context, the generation of three‐dimensional (3D) geometric models of bridges, which are to be designed and analysed, can play an important role. For this purpose, a computer graphic system, which enables the 3D geometric modelling of decks of the most frequent types of bridges, was developed. With this tool, the geometry of the bridge shape can be directly inserted into the computer application, using the user‐friendly interfaces with geometric parameters of the longitudinal view and cross section of the bridge deck. In this way, the description of the geometry, conceived for each case, is easily achieved. In addition, it satis‐ factorily supports a rapid definition of several suitable alternative solutions for the bridge.

In addition to the 3D model of a bridge allowing its aesthetic analysis, it also supports the creation of 4D (3D + time) interactive models simulating the construction work. In order to create interactive 4D models, simulating the sequence and progress of the construction process, techniques of virtual reality (VR) were used. The designer links each construction task, established in a Gant map, to specific 3D model components, and programs the simula‐ tion of the bridge construction process, using the VR software. The virtual interactive 4D model allows users to view and interact with these construction stages and with the equipment involved in the process.

The incorporation of VR technology into 3D geometric models allows greater realism in the simulations; it is, now, often applied in the field of engineering perhaps because VR technology constitutes a good interface and provides the possibility of finding solutions to real‐life problems in the construction field.
