## 1 Introduction
The 3D geometrical models for existing bridge structures can be created in various ways depending on the capability and resource of the originator. The geometric representation comprising each structural member can be referred to as the IFC Bridge model, which aims to flexibly link geometric representations with semantic objects [10]. IFC schema can be learned and developed for the bridge information system by appropriate compiling IFC Bridge and IFC Infrastructure extensions [10]. On the other hand, recently the author of this paper and his research team have widely introduced the digital information models using the BIM technique for various types of bridges, such as cable-stayed bridge [11; 12] and prestressed concrete bridge [13; 14; 15]. The alignment-based object-oriented design philosophy appears to be essential for the creation of a bridge information model. By applying a set of parameter definitions and appropriate algorithms, the entire bridge model can be realized without any discontinuity. The parametric design concept enables designers to alter any input factors of the model in order to match the target requirements. Moreover, during its lifecycle, the digital bridge model significantly helps engineers in managing the flow of information for multiple purposes. The interoperability of the design platform allows collaborative work among various stakeholders and stages of the project. Cable modeling for suspension bridges is a major challenge for engineers. There is no unique undeformed configuration for cable structures in the stress-free state; this is because any applied tension generates lateral stiffness in the cable. Therefore, only the deformed shape of a cable structure under dead loads, which is predetermined at the design stage, is similar to the framed structures. The undeformed configuration of a frame structure is predetermined during the design process based on functional specifications and the experience of engineers. Basic analysis tools that are based on predefined undeformed configurations can be easily used to measure the displacement field under dead loads because framed structures possess an initial rigidity that is independent of the applied load. However, a specific undeformed configuration for the equilibrium state of a cable structure under a dead load has not been reported thus far. This is because the lateral rigidity of a cable,caused by the applied tension, can be considered as a distinctive mechanical property for general cable structures. Owing to its self-weight, a cable is loaded even without any externally applied loads; hence, sufficient tension should be applied to the wire to counter the self-weight in order to target the desired configuration [16; 17; 18]. The concept of an elastic catenary cable element has been widely introduced for the main cables of suspension bridges [19]. Owing to the existence of an extensive range of variables, including construction methods, temporary supports, and alteration loads, geometric control for suspension bridges is always a difficult task. Moreover, for the main cable, geometrically nonlinear effects and multiple tension loads should be considered. During the construction stage of a suspension bridge, the cable profile continually changes according to the load, leading to a change in the specific geometrical configuration of other structures such as the suspended structure and the stiffening girder. Therefore, geometric control simulations should be implemented during the construction phase to ensure that the target configuration is satisfied after the erection of the bridge [20; 21]. In this regard, a master digital bridge model is necessary; this model should be capable of extracting the suggested target configuration for each sub-process and continuously update the changes during the erection procedure in a timely manner in order to manage the specific geometrical configuration of each member. To address the abovementioned complexities associated with suspension bridges, a design strategy with multiple goals is required.