Final answer:
For economically efficient construction, concrete structural members should be sized using the dimensions specified by the engineer, taking into account various criteria, constraints, and considerations for safety, durability, and costs.
Step-by-step explanation:
When sizing concrete structural members for economic construction, it is generally best to use the dimensions specified by the engineer. These dimensions take into account various criteria and constraints, including economic aspects, physical loads of the structure like compression and shear loads, the potential for thermal expansion and stress, and the need for stable foundations and framing systems.
Engineers are tasked with designing structures that are practical and must consider natural, internal, and man-made systems, as well as future systems, to ensure the structures are safe, durable, and economical. The dimensions provided by the engineer will reflect all these considerations and will likely result in the most economically efficient dimensions for the construction without compromising on safety and integrity.