Establishment of performance‐based seismic design factors for precast concrete floor diaphragms

Abstract

This paper presents an analytical study used to establish design factors for a new seismic design methodology for precast concrete floor diaphragms. The design factors include diaphragm force amplification factors Ψ and diaphragm shear overstrength factors Ω v . The Ψ factors are applied to the ASCE7-05 diaphragm design forces to produce diaphragm design strengths aligned to different performance targets. These performance targets are based on diaphragm detailing choices, and include: (i) elastic diaphragm behavior or (ii) limiting inelastic deformation demand on the diaphragm reinforcement (connectors between precast units or reinforcing bars in a topping slab) to within their reliable deformation capacities. The Ω v factors provide overstrength relative to the diaphragm bending strength for capacity protection against shear failure. The analytical study was performed by conducting nonlinear time history analyses of a simple evaluation structure, of which the dimensions and structural properties were varied. The analytical model used in the study is constructed and calibrated on the basis of extensive physical testing. The analytically obtained values of the diaphragm design factors are presented as functions of the geometric and structural properties of the building. The design factors presented here have been verified through evaluation of a set of realistic precast prototype structures. The diaphragm design methodology is currently in the codification process. Original language EnglishPages (from-to) 675-698

Seismic-Resistant Precast Concrete Structures: State of the Art

“…With regard to precast floor diaphragms in the United States, the ASCE/SEI 7-16 (ASCE 2016) standard adopted two new sections (i.e., Sections 12.10.3 and 14.2.4) based on significant updates to diaphragm design in the 2015 NEHRP provisions (BSSC 2015). ASCE/SEI 7-16 Section 12.10.3 presents an alternative determination of the diaphragm design force based on rational methods, whereas Section 14.2.4 contains options for the seismic design of diaphragms based on Zhang and Fleischman (2016). Because of the recent nature of these developments, the "Floor Diaphragms" section of this paper includes a detailed treatment of this topic.…”

“…ASCE/SEI 7-16 Section 14.2.4 contains specific seismic design provisions for precast diaphragms and a connector qualification protocol, in addition to applicable seismic design requirements from ASCE/SEI 7-16 and ACI 318-14 Section 18.12. The precast seismic provisions in Section 14.2.4, based on Zhang and Fleischman (2016), relate structural parameters and diaphragm connection classification to the appropriate R s factor. Diaphragm connections are classified as high-deformability, moderatedeformability, and low-deformability elements based on testing, with more deformability permitting a higher R s factor (and thus lower design force).…”

Group Pile Effect on Temperature Distributions inside Energy Storage Pile Foundations

“…A quarter of the pile and surrounding soil with a thickness equal to s/2 was cut out because of the symmetric plan of the group pile foundation, as shown in Figure 5a. Then, it is modeled as 2D plane strain elements in the general-purpose finite element software Abaqus FEA (see Figure 5b), one of typical 2D simplifications used in structural simulations [27]. Symmetry boundary conditions were applied as there is no heat flux passing through the boundaries.…”

Development of diaphragm connector elements for three-dimensional nonlinear dynamic analysis of precast concrete structures

“…The design methodology employs design force factors indexed to diaphragm performance targets. These design factors are calibrated using nonlinear time history analyses (NLTHAs) of three-dimensional finite element (3D-FE) models of precast structures under suites of earthquakes representing different levels of seismic hazard (Zhang and Fleischman, 2015). Unlike the distributed force transfer in monolithic floor slabs that serve as diaphragms in reinforced concrete (RC) structures for instance (Moehle et al, 2010), forces in precast diaphragms are transferred at the discrete connector locations.…”