【正文】 ses,several structural analyses were performed to accurately capture the behavior of this plex bridge. For the serviceload analysis,which includes live,temperature,and wind loads,the engineers used SAP2020, a puter program created and maintained by Computers amp。the probability that it will be exceeded within 50 years is 2 pencent and within 100 years,4 persent. Because of uncertainty about the direction from which the seismic waves would approach the site, a single response spectruma curve showing the mathematically puted maximum response of a set of simple damped harmonic oscillators of different natural frequencies to a particular earthquake ground accelerationwas used to characterize mitions in two mutually orthogonal directions in the horizontal conduct a timehistory analysis of the bridge’s multiple supports,a set of synthetic motions with three ponentslongitudinal,transverse,and verticalwas developd using an iterative ground motions from an earthquake in Chile in 1985 were used as “seed”motions for the sythesis process. A time delay estimatethat is,an estimate of the time it would take for the motions generated by the SEEand FEE earthquakes to travel from one point to the nextwas create using the assumed seismic wave velocity and the distance between the piers of the an assumed was velocity of approximately ,a delay on the order of half a second to a second is appropriate for a bridge 1 to 2km long. Soilfoundation interaction studies were performed to determine the stiffness of the soil and foundation as well as the seismic excitation measurement that would be used in the dynamic studieswere conducted by means of soilpile models using linear and nonlinear soil layera of varying equivalent pile lengths in the studiesthat is, the lengths representing the portions of a given pile that would actually be affected by a given earthquakeinduced ground motionranged such a threedimensional model,there are six ways in which the soil can resist the movement of the lpile because of its stiffness:throngh axial force in the three directions and through bending moments in three the bridge site contains so many layers of varying soil types,each layer had to be represented by a different stiffness matrix and then analyzed. Once the above analyses were pleted,the International engineerstaking into consideration the project requirements developedby the owenerevaluated several different concrete cablestayed number of structural systems were investigated,the main variables,superstructure cross sections,and the varying support conditions described above. The requirement that the evevation of the deck be quite high strongly influenced the tower the proposed deck elevation of more than 80m,the most economical tower shapes included singleand dualmast towers as well as “goal post”towersthat is,a design in which the two masts would be linked to each other by crossbeams. Ultimately the engineers designd the bridge to be wide with a 420mlong cablestayd main span,two 200mlong side spansone on each side of the main spanand approach structures at the ends of the side the east side there is one 46m long concrete approach structure,while on the west side there are three,measuring 60,60,and 66m,for a total bridge length of 1, side spans are supported by four piers,referred to,from west to east,as ,P3,and P4. The bridge deck is a continuous singlecell box girder from abutment to abutment。 A construction method that would not cross the canal at any time or interrupt canal operationa in any way. Because of the bridge’s long main span and the potential for strong seismic activity in the area,no single building code covered all aspects of the the team from . Lin International determinded which portions of several standard bridge specifications were applicable and which were following design codes were used in developing the design criteria for the bridge， it is standard specifications for highway bridge ,16th ed,1996 It was paramount that the towers of the cablestayed structucture be erected on land to avoid potential ship collision and the need to construct expensive deep foundation in water. However, geological maps and boring logs produced during the preliminary design phrase revealed that the east and west banks of the canal, where the towers were to be located, featured vastly different geologicaland soil conditions. On the east side of the canal, beneath shallow layers of overburden that rangs in consistency from soft to hard, lies a block of basalt ranging from medium hard to hard with very closely spaced engineers determined that the basalt would provide a petent platform for the construction of shallow foundation for tower, piers, and approach structures on this side of west side, however,featured the infa mous Cucaracha Formation, which is a heterogeneous conglomerate of clay shale with inclusions of sandstone, basalt,and ash that is prone to landslide. As a sudsurface stratum the Cucaracha Formation is quite stable,but it quickly erodes when exposed to the elements. The engineers determined that deep foundations would therefore be needed for the western approach structure,the west tower,and the western piers. Before a detailed design of the foundationa could be developed,a thorough analysis of the seismic hazards at the site was required,The