# Experimental and Numerical Analysis of an Innovative Combined String-Cable Bridge
## 1 Introduction  
Suspension bridges are viewed as exceptional bridges and have been known in the world for more than one century. They are famous not only for their excellent architectural expression but also for having one of the longest spans in the world [1; 2; 3; 4; 5; 6]. These bridges have a wide range of applications, from efficient automobile and railway bridges to graceful pedestrian bridges [7; 8; 9; 10; 11; 12; 13]. Original solutions are being developed using so-called rigid cables [14]. It is necessary to note that the creation and design of bridges is related to the maintenance of these structures [15]. When designing and building a bridge, it is necessary to take into account the complex condition monitoring of the structures of such bridges, including suspension and cable-stayed bridges [16; 17; 18]. This is necessary in order to ensure the functionality and operation of existing and designed bridges [19]. It is necessary to properly select and evaluate the capabilities of the equipment and software used for this purpose [20; 21], for example, a vibration control strategy for cable-stayed-suspension hybrid bridges [20; 22]. Long-term monitoring of bridges generates a huge amount of data that must be efficiently processed [21; 23]. It is especially important, based on the collected research data, to preliminarily determine the costs of the bridge monitoring process during the projected design service life of the bridges because, at first glance, structural solutions that are rational according to the selected criteria do not always ensure sustainable and long-term exploitation of bridges. Monitoring problems can also be determined by the features of the structural system of bridges [18]. Therefore, attention should be paid to effective bridge structures such as suspension bridges [24]. Among suspension pedestrian bridges, it is necessary to single out stress-ribbon bridges, which have the lowest structuralheight [25; 26]. Although such bridges have been known for several centuries, their wide application began in the 6 th decade of the last century [27; 28]. Futuristic solutions to apply stress-ribbon constructions to long-span automobile bridges were even presented [25; 29]. It is necessary to note that there are two automobile bridges of this type in Uruguay [30]. Two structural solutions of stress-ribbon bridges currently dominate: stress-ribbons of prestressed reinforced concrete [25; 26; 31; 32] and stress-ribbons of metal strips [27; 28; 33; 34]. These solutions have two common disadvantages (negative effects): high tensile forces due to their relatively small initial sag; and a curved shape, which is not always well suited for traffic realization. There are also known two-chord suspension systems, where the upper element consists of a beam of slight curvature or a straight stiffness, which perfectly meets the operational requirements of the bridge, and the lower element is designed from a cable that performs a supporting function [35; 36]. Both strips are tensioned and fixed to anchor foundations. The increased construction height of such bridges creates the conditions for lower total tensile forces in the anchor foundations. It must be noted that beneath the graceful appearance of stress-ribbon bridges lies their complex behavior, which can cause unwanted operational issues. These bridges are primarily sensitive to the effects of asymmetric traffic loads. This causes significant dis-placements of kinematic origin [25; 37]. There are detailed calculation methods for such stress-ribbon bridges that evaluate the static and dynamic behavior of such structures [38; 39]. In such bridges, the so-called \"rigid cable\" was introduced, which stabilizes the initial shape of the bridge with its bending stiffness [35; 40]. It is necessary to note that bridge designers are looking for innovative solutions to increase the efficiency of such bridges and other transport structures, and, over the last decade, so-called string bridge and transport structures have been developed [41; 42; 43].