Top-down construction method in concrete structures: advantages anddisadvantages of this construction method

The construction of undergroundstructures in the traditional method, which begins withexcavation and execution of the foundation of theunderground structure, continues with the construction of themain structure from the base and ends with the completion ofthe final roof. It is known as the bottom-up method. Incontrast to this method, there is an advanced technique calledthe top-down method, which has practically replaced thetraditional construction method in large projects inindustrialized countries in recent years. Unlike the traditionalmethod, this method begins with the construction of thesurrounding walls, columns and the final roof and iscompleted by excavating and constructing the foundation ofthe underground structure. The most important advantages ofthis method include eliminating or minimizing the formworklevels, eliminating temporary bracing during excavation,creating some traffic facilities during the construction of thestructure, and the possibility of using it in limited andextensive ways. Traffic in urban spaces Despite thesenumerous advantages, unfortunately, there is still insufficientawareness of this method in our country, to the extent that itcan be said that most stakeholders in the construction industryare unaware of the existence of such a construction method.But it can be used as a very important implementation optionalongside other conventional methods in the construction ofunderground structures. Therefore, given the wideapplication capabilities of this method, this article aims topresent a method for constructing underground structuresbased on the above advanced method to the scientificcommunity of the country, examine the advantages andlimitations of this method and its effects on time. And costsand discuss its application in urban spaces. Finally, some ofthe underground structures implemented in the Ahvaz urbanrail, which are being implemented using this advancedmethod with the best knowledge, are introduced.

کلیدواژه ها:

top-down method ، bottom-up method ، underground structure ، construction method