Title: Flexural Behavior of Two-Span Lightweight Aggregate Concrete T-Beams

Author(s): Keun-Hyeok Yang, Ju-Hyun Mun, Si-Jun Kim, and Hye-Jin Lee

Publication: Structural Journal

Volume: 117

Issue: 2

Appears on pages(s): 267-276

Keywords: ACI 318-14; ductility; lightweight concrete; moment redistribution; two-span beams

DOI: 10.14359/51721368

Date: 3/1/2020

Abstract:
The present study examined the flexural performance of continuous two-span lightweight aggregate concrete (LWAC) T-beams. A total of 12 two-span beams were prepared considering full-scale dimensions that can be typically observed in beams of mid- to low-rise buildings. The test parameters for each group of all-LWAC and sand-LWAC beams were the compressive strength of concrete (fc′) and amount of longitudinal tensile reinforcement (As) in accordance with the minimum and maximum amounts specified in the ACI 318-14 code provisions. The reliability of the equivalent rectangular stress block and degree of moment redistribution (β) recommended in the code provisions was ascertained for the present beams through a comparison of the measured ultimate load capacity and moment redistribution. The test results showed that the ACI equivalent stress block gives a conservative result for all the beams in estimating the ultimate load capacity of two-span LWAC beams, although this conservatism decreases as As increases. The present two-span LWAC T-beams exhibited a lower displacement ductility ratio than simply supported normal weight concrete (NWC) beams of the same longitudinal reinforcement index (ωs). Thus, the fib model and ACI 318-14 equations overestimated the β values of the LWAC T-beams. Overall, the maximum As specified in the ACI 318-14 provision for preventing brittle failure of beams needs to be reduced for LWAC beams to achieve design requirements equivalent to those of NWC beams.