Experimental investigation on the effectiveness of lateral restrainers to the vertical steel in reinforced masonry walls under axial compression

Reinforced masonry (RM) walls are mostly used in low to mid rise residential/industrial buildings in cyclonic and seismic regions. They are conventionally constructed with grout embedded vertical steel reinforcements positioned in the middle of the hollow blocks. However, these reinforcing bars are rarely detailed with lateral restrainers, which are considered essential in the design standards to avoid buckling of the vertical bars. This research investigates the effectiveness of lateral restrainers to the axial compres-sion resistance of RM by testing of 128 walls under concentric and eccentric compression with different reinforcement configurations. The tested walls (190 mm thick x 600 mm wide) consisted of various types of detailing with and without lateral restrainers, grout strengths (25-50 MPa), and three heights (800 mm, 1400 mm and 2400 mm). Two walls were constructed and tested for each configuration, out of which one was tested to determine the ultimate strength and the other tested to acquire ultimate strength, axial deformation of the wall, axial strain in the steel bars and strain on the surfaces of the face-shell. The experimental results revealed that the grout has significantly contributed to the axial capacity, whilst the lateral restrainer reinforcement detailing had no significant effect on either the steel strain development or on the overall strength of the RM walls. Under concentric compression, the strain measurements in the vertical steel bars indicated that irrespective of the absence or presence of the lat-eral restrainers, the vertical bars remained under compression throughout the loading history with no evidence of buckling. Effects of slenderness and eccentricity were also evaluated for the RM walls under compression. It can be concluded from this research that the RM walls designed and constructed without lateral restrainers to resist cyclonic and seismic forces need not be treated as unreinforced masonry (URM) for compression if the vertical bars are surrounded by well compacted grout. (c) 2021 Elsevier Ltd. All rights reserved.