Title: A Tall Building Engineer’s Perspective on Specifying Modulus of Elasticity (MOE)

Author(s): Robert C. Sinn

Publication: Web Session

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Date: 11/20/2018

Abstract:
Nearly all tall and supertall buildings today have structural systems composed of a mixture of steel and concrete elements or are entirely configured in cast-in-place high strength concrete. This represents a fundamental shift in the engineering of such structures compared to those in the late 1960’s into the early-1980’s. Significant developments in high strength concrete mixture proportioning along with improvements in adjacent technologies such as admixtures and cement replacement, concrete pumping, placing, consolidation and testing have all helped to bring about the current state of the structural system evolution for high-rise buildings. It should not be surprising that as the systems became more dependent on reinforced concrete instead of steel, structural engineers have begun to be more attendant in specifying not only the strength of the concrete required for resisting gravity and lateral loads in tall buildings, but also the stiffness. The taller the design, the more lateral wind load effects tend to govern the structural engineering; requiring dependable stiffness characteristics to ensure appropriate performance. This presentation will focus on some of the earliest testing and specification for MOE in tall buildings such as that for the Trump Tower in Chicago, completed in 2007, up until the present time on ultra-tall towers such as the Jeddah Tower in Saudi Arabia, now under construction. The focus will be on the structural engineer’s perspective of the need for properly specifying and ensuring appropriate MOE levels that are achievable and cost-effective for such challenging structures.