Effects of variation in loading protocol on the strength and deformation capacity of ductile reinforced concrete beams

Abstract

Summary Understanding the impact of prior earthquake damage on residual capacity is important for postearthquake damage assessment of buildings; however, interpretation of such impact is challenging when based on tests using traditional reversed‐cyclic loading protocols. A new loading protocol, consisting of a dynamic earthquake displacement history followed by quasi‐static reversed‐cyclic loading to failure, is presented as an alternative to traditional simulated seismic loading protocols. Data are analyzed from a set of 12 nominally identical ductile reinforced concrete beams that were tested by using variations of this protocol and traditional reversed‐cyclic and monotonic protocols. Differences in the cycle content of the earthquake displacement histories applied to the test specimens allowed for the effects of load history variation below 2.2% drift to be isolated. It is found that such variation had no effect on the beam deformation capacities. The effects of dynamic loading rates are also analyzed and compared against control quasi‐static specimens. Relative strength increases due to dynamic loading are found to be more significant at yield than at ultimate. Dynamic loading rates led to modest reductions in the beam deformation capacities, but the presence of causality between these variables remains uncertain.

Closure to “Proposed Updates to the ASCE 41 Nonlinear Modeling Parameters for Wide-Flange Steel Columns in Support of Performance-Based Seismic Engineering” by Dimitrios G. Lignos, Alexander R. Hartloper, Ahmed Elkady, Gregory G. Deierlein, and Ronald Hamburger

“…1(b)], the expected loading cycles may not differ that much from those of a standard symmetric-cyclic loading protocol. Similar conclusions hold true for reinforced concrete members (Marder et al 2018).…”

Quantification of the reduction factors of seismic capacity for damaged RC column members using the experiment database

“…Marder et al 14 . proposed a new “earthquake‐then‐cyclic protocol” as an alternative to traditional static loading protocols.…”

Quantifying the Effects of Epoxy Repair of Reinforced Concrete Plastic Hinges

“…Previous research [15] has shown that the number of loading cycles applied at or below 2% drift does not typically result in a reduced deformation capacity in ductile plastic hinges, based on tests of beams and columns with length (or height) to depth ratios of 2.2 to 5.7 (note that this study did not consider the effects of epoxy repair or strain ageing). This is further evidenced in Fig.…”

“…Analysis using the test results was not included in the data paper [12]. Information on the influence of loading protocol on beam response is included in Marder et al [15], while this paper is focused on epoxy repair of damaged plastic hinges. Three specimens (named LD-1-R, LD-2-R, and LD-2-LER-R, where "-R" denotes these as repaired) were repaired following initial damaging earthquake-displacement history loadings.…”

“…LD-1 and LD-1-R) exhibited different damage patterns following the initial earthquake loadings. The authors attribute this to inherent uncertainty in the development of damage in reinforced concrete plastic hinges, and more information is provided in [15]. [8,11], exterior and interior beam-column subassemblies [9,10], and bridge columns [21].…”