With the introduction of new concrete materials, a renaissance is occurring in how structural engineers deal with building stiffness. This paper will discuss how advanced admixtures, as well as new and better aggregates being imported into major cities such as Los Angeles and San Francisco are significantly improving the capabilities of concrete ready-mix companies to supply cutting edge mixes capable of achieving Modulus of Elasticity (MoE) greater than building code standards.
Understanding these advances will allow high-rise designers to take advantage of these higher quality materials, resulting in lower cost structures. The history and applicability of the equations in ACI 318 and in ACI 363 will be discussed. MoE affects not only how much a building will sway under lateral loads, but also the deflection of slabs. While it has not been common practice to specify MoE for slabs, some jurisdictions are requiring that this be done, as well as tested. The paper will discuss the pros and cons of this approach.
Is it important for the design professional to specify MoE? There can be significant cost impacts to doing so if the designer is unfamiliar with the effect on mix design. This will be discussed in detail. Discussion will also focus on the important mix design characteristics of MoE, the effect of time on MOE, and what to be cognizant of throughout construction. Case studies of recent and current projects will be presented.