Final answer:
The correct answer to when vertical stabilizer plates must be equipped is (c) When specified by the project engineer, who assesses various factors for the structural design. Engineers adjust building designs for factors like wind and seismic activity, using systems like tuned-mass dampers for stability.
Step-by-step explanation:
The question relates to the use of vertical stabilizer plates in column construction. The correct answer is (c) When specified by the project engineer. Vertical stabilizer plates are not solely based on the discretion of the operator, the height of buildings, or specific weather conditions like windy days. Decisions surrounding these structural components are primarily determined by the project engineer, who takes into account various factors such as building design, the structural load of the building, prevalent wind patterns, seismic activity, and other environmental conditions in the building's location.
As buildings are built taller, they behave similarly to inverted pendulums and can oscillate due to forces such as winds and earthquakes. Engineers must design systems to control these oscillations, such as the tuned-mass damper used in the Comcast Building. This includes considering the varying value of gravitational acceleration (g) at different heights, which slightly affects the weight of materials at the top of a very tall building compared to the first floor. This aspect is particularly relevant for very tall structures like those approaching the height of the Comcast Building in Philadelphia, Pennsylvania, to maintain their structural integrity and safety over time.