What type of concrete structure is considered very bad for shoring?

Precast concrete structures are often considered very challenging when it comes to shoring due to their inherent characteristics. Unlike cast-in-place concrete, precast components are manufactured off-site and then transported to the construction location. This can result in a lack of continuity in the structural elements, which may lead to unpredictable load transfer and stress points.

The individual precast elements are typically designed to support themselves during transportation and placement, but once the connection points are stressed or compromised during a structural collapse, they can become unpredictable in terms of stability. This unpredictability makes it difficult to safely implement shoring strategies, since the connections between pieces may have failed or may be more vulnerable compared to elements in a monolithic structure.

Furthermore, the connections in precast systems may require specific engineering considerations that are not easily managed under emergency conditions, making shoring efforts more complex and hazardous. In summary, the disconnected nature of precast elements and their potential for unpredictable behaviors under load make them less suitable for shoring applications in the context of a structural collapse.