Prefabricated structures have been developed and tested over many years internationally and in Hong Kong, China. However, their domestic expansion and development have only gained momentum in recent years. This growth is partly driven by the evolving domestic economic environment, which emphasizes development, upgrading, and reform. Additionally, it reflects earlier research efforts and the previous lack of national regulatory standards in this field.
Previously, it was challenging to assess the seismic performance and safety of prefabricated structures, which resulted in low consumer confidence and hindered their wider adoption.
Through ongoing discussions and research involving industry experts and academics, theoretical and experimental analyses of new connection methods—both dry and wet—have been conducted. The introduction of mature, advanced international experiences has gradually addressed these issues. Notably, the concept of “equivalent cast-in-place” has played a key role in resolving design challenges for prefabricated structures, becoming a convincing argument for consumers.
By nature, the connections between components in prefabricated structures represent a potential weak point compared to cast-in-place constructions. This has long complicated the selection of an appropriate mechanical model for structural design.
However, extensive experimental analysis and engineering practice have shown that by applying stricter and more suitable node design measures than those used in cast-in-place structures, the mechanical performance differences between prefabricated and cast-in-place structures can be minimized. In essence, a strong node design strategy ensures that prefabricated structures exhibit overall structural behavior comparable to cast-in-place ones, a principle known as “equivalent cast-in-place.” This allows designers to utilize cast-in-place structural analysis models and design methods for prefabricated buildings.
The strong node design in prefabricated structures is mainly achieved through two approaches:
First, engineering mechanics criteria such as the mechanical properties and durability of materials are set more stringently than for cast-in-place structures. A common practice is to use non-shrinkage expansion grouting mortar within sleeve connections at prefabricated nodes. This mortar typically has a strength grade one level higher than the concrete used in the connected prefabricated components, ensuring that the overall connection performance matches or exceeds that of cast-in-place nodes.
Second, during the design phase, structural safety margins are enhanced by increasing load effect factors, reducing material design strengths, and implementing appropriate construction measures.
By applying these strong node design methods, the inherent weaknesses at prefabricated node connections are effectively compensated, enhancing structural integrity. Consequently, the well-established design theories and methods developed for cast-in-place structures can be confidently applied to prefabricated buildings.
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