【正文】 Emerson, Ralph Waldo 1. Present status Nowadays, there are two mainstreams in bridges development. One is the trend of extra longspan bridges, and another is the urbanization of middlespan or smallspan bridges. These two trends exactly correspond to two features of bridges. The first one is the cultural function of bridge serving as a symbol of critic or national character additional to its conventional function to support loads .The giant exposed elements of bridges inherently embody human’s strength, courage and will to conquer the river. And this is especially true in extra longspan bridges .Another obvious character of bridge is that it enables people to occupy the space owned by river. As a result ,on one hand, human attaches to the space where he originally belongs to, on the other hand he can move back and forth between banks. That makes him feel simultaneously interior and exterior, openness, freedom and protection. This experience of passengers es through the stream of plex interplay of structure itself and its surroundings. Up to now, experience accumulated on space force systems guarantees the credibility of such plex structures as cablearch structures and bridges subjected to gale. And advanced puteraided design facilitates visualization of threedimensional model of the structure under discussion. Technological restrains is loosening. At the same time, bridge aesthetics begin to thrive .Genius loci, namely, spirits of place, are desired, which are deeply rooted in the tradition of humanities. Different connects are well arranged to display a spatialtemporal sequences which arouse resonance of visitors. The maturity of bridge design technique and the emphasis on humanism and tradition are prerequisites of progress of bridge aesthetics. 2. Potential space latent in space force system Theoretical support Admittedly, conventional procedures for bridge design have a deep influence on bridge aesthetics. Because the loads on bridges are more plex than that on buildings, in the concept design stage, architecture is involved much less. And before the introduction of puteraided design software, almost all bridges were simplified into twodimension structures in order to avoid the solution of large scale linear programming. Unfortunately, this artifice has its sideeffect. It neglects bridge is a structure of threedimension who has abundant expressive forces. Consequently, the similarity between different bridges and the stiffness in their appearance occur. Then how to elicit the vigor inside bridges when we are liberated form calculation to some extent? Reverting to bridges’ original nature of a giant sculpture is an optimal choice. As a threedimension structure, bridge demands designers not only mentally to visualize a plex form from all round itself, to identify its centre of gravity, its mass, its weight, to realize its volume, as the space that the shape displaces in the air, but also the accurate expression of the internal ways to transfer loads, where lies the difference between bridges and mon sculptures. The critical step is weaving invisible load paths into the nature of bridge mold. The example below illustrates that. The oneness of aesthetics and mechanics is the logical basis for the concept advocated above. For designers, the work doesn’t rest on that primary level. Familiarity with the behavior of space force system is desired, which includes static loads distribution, structural dynamic response to winds, waves, and cozy extent for passengers. Different results e out when bridges mainy resist different loads. If bridge is mainly subjected to static loads, for an instance, the structure weight, spectators passing through it will perceive the power and the frozen movement of it. And if dynamic, for example, wind, the security springs from bridge’s protection. Analysis of examples Cablearch structure Campo Volantin Footbridge, across River Nervion, in Bilbao, Spain, tells an exact story of how a leaning arch keeps stable in the weave of cables. The construction system is a steel inclined parabolic arch with glass decking. The tortuous deck of the singlespanned