Increasing shear capacity within existing reinforced concrete structures (ACI 364.2T-08)

Description

Rehabilitation projects often involve the need to increase the load-carrying capacity of members within existing concrete structures that are deficient due to increased load demand associated with change of use, deficiencies in the original design or construction, or deterioration. Such strengthening often includes increasing shear capacity. Shear strengthening may also be necessary when a structure requires flexural strengthening to ensure a ductile failure mechanism in seismic loading situations. The accessibility difficulties normally encountered in concrete structures, as well as general lack of design standards, may lead to building official limitations on what strengthening may be accepted.

The following are descriptions and some examples of various tech-niques for shear strengthening. Note that, unless indicated, the shear strengthening measures described are specific to nonseismic applica-tions. Chapter 5 of ACI 546R-04 (ACI Committee 546 2004) and ACI 440.2R-02, 440.1R-06, and 437R-03 (ACI Committee 440 2002, 2006; ACI Committee 437 2003) provide additional information on structural strengthening. All shear strengthening should be performed under the guidance of a licensed engineer familiar with the selected technique.