Shoring and Reshoring for Multistory Concrete Buildings-Chapter 5 of ACI 347.2R-05, Guide for Shoring-Reshoring of Concrete Multistory Buildings (PDF)

Chapter 5 of ACI 347.2R-05, Guide for Shoring-Reshoring of Concrete Multistory Buildings (PDF)

Pdf Summary

The article discusses the complexities of shoring and reshoring in the construction of multistory concrete buildings. A key resource for navigating these complexities is the ACI Committee 347’s “Guide for Shoring/Reshoring of Concrete Multistory Buildings (ACI 347.2R-05)”. This guide aids construction professionals in developing safe, economical construction schedules by addressing critical questions such as whether two or three levels of reshoring are necessary, and evaluating the safety of stripping forms.<br /><br />In construction, enabling the reuse of formwork is economical but must not compromise safety. For multistory buildings, where standardization reduces the number of forms, early stripping is crucial to maintain construction pace. Shores and reshores are vital, with shores supporting formwork and reshores distributing loads over several floor levels upon removal of the original formwork.<br /><br />The load distribution during construction is influenced by various factors, such as the stiffness of shores relative to slabs, which impacts how loads are carried. An engineering analysis must consider both load distribution and the early-age load capacity of the building structure to avoid deflections or, worse, progressive collapse.<br /><br />Early-age concrete strength significantly impacts construction schedules. The construction loads must not exceed the slab's strength at any given time. If exceeded, alternatives include changing the shoring system or using high-early-strength concrete.<br /><br />Serviceability is another concern, as excessive early loads can cause cracking and deflections, affecting long-term structural performance. Compliance with ACI 318-05 standards and close coordination between engineers and contractors are advised for managing deflections.<br /><br />The article includes a detailed example of two-way slab construction, demonstrating the evaluation of load distribution and slab capacity under various conditions. This illustrates the importance of selecting an appropriate shoring system and construction schedule to ensure both safety and economy in multistory concrete construction projects.

Keywords

shoring

reshoring

multistory concrete buildings

ACI Committee 347

formwork reuse

load distribution

early-age concrete strength

serviceability

construction schedules

two-way slab construction