1. Reduced equipment costs and simplified engineering requirements
2. Minimal environmental impact and cost-effectiveness in terrain with difficult access
3. Faster construction speed and lower temporary works requirements
4. Reduced foundation requirements and simplified quality control

Explanation

Answer: For bridges spanning challenging terrains or waterbodies with difficult access, conventional crane erection of girders is both cost-prohibitive and environmentally intrusive. Incremental launching—an overhead method—eliminates or minimizes the need for access and temporary supports while reducing disturbance to sensitive ecosystems below the bridge. Unlike option (a), incremental launching requires sophisticated engineering and specialized equipment. While options (c) and (d) offer certain benefits, they don't capture the primary advantages that make this method particularly suitable for challenging construction sites. 

1. To serve as both an assembly staging area and a runway for launching girders
2. To facilitate segment alignment and provide lateral stability during assembly
3. To establish the geometric control line for girder positioning and launching
4. To enable progressive assembly while providing a storage area for materials and equipment

Explanation

Answer: A launch bed serves two essential functions: it provides an assembly area for progressive girder segment construction and acts as a runway for launching the assembled structure. While other features like alignment control and storage capabilities are important, they are secondary benefits. The launch bed's key value comes from its ability to seamlessly integrate assembly and launching operations in one controlled environment, making it fundamental to successful incremental launching.

1. Cumulative stress concentrations at temporary support points
2. High wind conditions exceeding the minimum thresholds in the plans
3. Dynamic load distribution variations during segment transitions
4. Progressive geometric deviations resulting in launch path misalignment

Explanation

Answer: Geometric deviations can compound progressively during the launch, leading to system-wide misalignment and jamming if not caught and corrected early. Unlike stress concentrations or dynamic load variations which remain localized, geometric deviations accumulate gradually—making them particularly difficult to detect and address once they become substantial. Although wind conditions (option c) affect safety and load distributions (option d) impact structural behavior, the cumulative nature of geometric deviations makes them the most critical factor to monitor for maintaining proper system operation during the launching process.