Email Address is required Invalid Email Address
In today’s market, it is imperative to be knowledgeable and have an edge over the competition. ACI members have it…they are engaged, informed, and stay up to date by taking advantage of benefits that ACI membership provides them.
Read more about membership
Learn More
Become an ACI Member
Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
Staff Directory
ACI World Headquarters 38800 Country Club Dr. Farmington Hills, MI 48331-3439 USA Phone: 1.248.848.3800 Fax: 1.248.848.3701
ACI Middle East Regional Office Second Floor, Office #207 The Offices 2 Building, One Central Dubai World Trade Center Complex Dubai, UAE Phone: +971.4.516.3208 & 3209
ACI Resource Center Southern California Midwest Mid Atlantic
Feedback via Email Phone: 1.248.848.3800
ACI Global Home Middle East Region Portal Western Europe Region Portal
Home > Tools > Frequently Asked Questions
Q. Do I have to use equation (c) from Table 22.5.5.1 in ACI 318-19 if my analysis shows that I don’t need to use shear reinforcement? It seems to me that if I don’t need stirrups, then Av,min=0. From that, it would follow that Av≥Av,min, so I could use equation (a) from Table 22.5.5.1, even in a slab with minimum flexural reinforcement. A. While it is correct that Av=0 in members without shear reinforcement, Av,min does not equal zero. Av,min is determined from the geometry of the design section per Section 9.6.3 in ACI 318-19. Thus, if the design section does not have shear reinforcement, Av< Av,min, and equation (c) from Table 22.5.5.1 is required. This is true even when the design section is lightly loaded and Av,min is not required. The resulting shear capacity will be less than calculated in ACI 318-14, especially if the design section has a low ρ as is likely in double-tee flanges, other precast slab elements, or cast-in-place slabs. ACI Committee 318 updated the Code provisions for shear capacity to reflect research findings on the effects of flexural reinforcement and section depth, using test data compiled and analyzed over the past two decades. Figure 1, for example, shows the impact of longitudinal reinforcing ratio on shear strength as calculated using ACI 318-14 and ACI 318-19. For further discussion of the development of the one-way shear design provisions in ACI 318-19, refer to Kuchma et al. 2019. Fig. 1: Ratio of test shear strength Vtest and nominal shear strength Vn versus longitudinal reinforcement ratio ρw, for members without Av or axial load Nu (after Fig. 5 in Kuchma et al. 2019). Note that for many of the test specimens with ρw< 0.01, Vtest/ Vn< 1.0 when Vn was calculated per either the simplified or detailed equations provided in ACI 318-14 References: ACI 318-19; ACI 318-14 Topics in Concrete: 318 Building Code
Q. Do I have to use equation (c) from Table 22.5.5.1 in ACI 318-19 if my analysis shows that I don’t need to use shear reinforcement? It seems to me that if I don’t need stirrups, then Av,min=0. From that, it would follow that Av≥Av,min, so I could use equation (a) from Table 22.5.5.1, even in a slab with minimum flexural reinforcement.
A. While it is correct that Av=0 in members without shear reinforcement, Av,min does not equal zero. Av,min is determined from the geometry of the design section per Section 9.6.3 in ACI 318-19. Thus, if the design section does not have shear reinforcement, Av< Av,min, and equation (c) from Table 22.5.5.1 is required. This is true even when the design section is lightly loaded and Av,min is not required.
The resulting shear capacity will be less than calculated in ACI 318-14, especially if the design section has a low ρ as is likely in double-tee flanges, other precast slab elements, or cast-in-place slabs. ACI Committee 318 updated the Code provisions for shear capacity to reflect research findings on the effects of flexural reinforcement and section depth, using test data compiled and analyzed over the past two decades. Figure 1, for example, shows the impact of longitudinal reinforcing ratio on shear strength as calculated using ACI 318-14 and ACI 318-19. For further discussion of the development of the one-way shear design provisions in ACI 318-19, refer to Kuchma et al. 2019.
Fig. 1: Ratio of test shear strength Vtest and nominal shear strength Vn versus longitudinal reinforcement ratio ρw, for members without Av or axial load Nu (after Fig. 5 in Kuchma et al. 2019). Note that for many of the test specimens with ρw< 0.01, Vtest/ Vn< 1.0 when Vn was calculated per either the simplified or detailed equations provided in ACI 318-14
References: ACI 318-19; ACI 318-14
Topics in Concrete: 318 Building Code
Search other resources on the ACI website for answers to technical questions