My knowledge base does not contain specific documentation on A-frame structures, including load-bearing capacity and fall protection measures. However, I can provide general safety guidelines based on industry best practices for derricks and scaffolding, which share structural similarities.

An "A-frame derrick" is a derrick in which the boom is hinged from a cross member between the bottom ends of two upright members spread apart at the lower ends and joined at the top; the boom point secured to the junction of the side members, and the side members are braced or guyed from this junction point. [1]

General safety tips for erecting scaffolding include:

• Referring to local occupational health and safety regulations and standards for design and assembly requirements.
• Choosing the right scaffold system for the job.
• Erecting all scaffold parts according to the manufacturer's instructions.
• Selecting scaffold according to height required, type and duration of work, range of weather conditions, weight of workers, materials, and equipment, location, and requirements for pedestrian traffic.
• Erecting scaffold on a base that will support all the loads that will be applied including materials and equipment.
• Making sure the backfill is compact and level and replacing mud and soft soil with gravel or crushed stone.
• Providing adequate sills for scaffold posts and use base plates.

[3] When installing guardrails, consider the following:

• Install guardrails consisting of a top rail 1 m (40 inches) above the platform.
• A midrail about halfway between the platform and the top rail on the inside of the posts.
• A toe board 100 mm (4 inches) high fastened to the inner side of posts.
• Posts and rails capable of withstanding a force of at least 900 N (200 lb.) applied at any point, or withstanding any load likely to be applied.

[2] To ensure stability of the scaffold, do not allow the ratio of scaffold height to base width to exceed 3 to 1 unless the scaffold is tied into a structure, stabilized by guy wires, or secured by outriggers or stabilizers to maintain the ratio. [2]