## 1 Introduction  
### Problem Specification  
From being used for transportation to being part of a water diversion system, bridge structures are widely used in human society. Bridges are used for pedestrians, roads, and railways. The construction of high-speed rail (HSR) has become increasingly popular in recent years. According to the latest Phase II report of the high-speed rail study released by AECOM, the Australian government has plans to build an east coast HSR [1]. This project will be divided into two sections, from Brisbane to Sydney (797 km in 2 h 37 min) and from Sydney to Melbourne (824 km in 2 h 44 min). The total length of these two sections is 1621 km. The construction will commence in 2027 and take around 30 years to complete the whole project. Bridge structures play a significant role in such projects.  
Bridge structures are primarily composed of a superstructure and a substructure. The construction materials used in the superstructure include reinforced concrete, prestressedconcrete, steel and composite materials, and mass timber. However, the most widely used materials are reinforced concrete and prestressed concrete. The concrete bridge decks can be either cast-in-place or precast. The construction methods include incremental launching, segmental construction, balanced cantilever, precast installation, and a Movable Scaffolding System (MSS). A variety of temporary structures, such as bridge construction equipment (BCE), are used in bridge construction including formwork system, MSS, launching gantry, cofferdam, crane platform, and temporary shoring.  
Despite extensive research into bridge construction technologies and the design of temporary structures, universal design guidelines for BCE, particularly for long-span high-speed railway bridge (HSRB) constructions, remain absent. As a cost-effective solution for continuous bridge construction, efforts to develop effective BCE design procedures persist. However, designing BCE for specific bridge projects often results in solutions that are not replicable across other projects. Current standards, heavily influenced by American, Chinese, and European construction codes, do not adequately address the unique challenges of designing BCE for Australian conditions. The lack of standardised guidelines complicates the adaptive application of BCE design across various projects, raises safety concerns, and impedes the development of economically viable solutions.  
As the application of BCE expands and their design becomes more complex, the market increasingly demands these systems to be reusable and easily transportable. BCE are transitioning from their traditional role as temporary structures to more permanent structures, elevating their significance in structural design considerations [2]. The lack of consistent design standards in the industry frequently leads to substantial unforeseen costs and increases the risk of structural failures. These issues not only affect cost efficiency but also threaten project safety and timelines [3].  
This project proposes a novel design procedure for bridge construction equipment, specifically designed for long-span high-speed railway bridge construction in Australia, employing advanced analysis methods. The focus will be on the Overhead Movable Scaffolding System (OMSS), a typical BCE used in engineering practice, though reinterpreting the design of the MSS model M1-90-S with an Organic Prestressing System (OPS), developed by BERD Company in Portugal, currently used in constructing bridge spans of up to 90 m [4]. The redesigned numerical model was simulated under various load cases to evaluate its capacity for constructing bridges spanning over 100 m and to establish a definitive roadmap for designing an OMSS for the construction of long-span, heavy bridge decks. This research complied with Australian standards throughout and bridges the gap between design codes and engineering practice.