# Experimental performance of reinforced double H-block masonry shear walls under cyclic loading

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## Abstract

Ordinary reinforced concrete block masonry shear walls have some shortcomings such as abrupt change in the grout core cross section and permeation of grout concrete resulting in reduced integrity and seismic performance of masonry structure. To overcome these issues, the authors used a special type of core-aligned block (termed as double H-block) to construct shear wall, and the seismic performance of double H-block reinforced masonry shear walls was investigated by lateral cyclic loading test. Two large-sized double H-block reinforced masonry shear walls were designed and fabricated. Two axial compression ratios and two grout ratios were considered. The failure pattern, shear strength, hysteretic energy, and ductility capacity of the walls were analyzed. The test results showed that the double H-block masonry shear wall constructed in running bond exhibited integrity, high ductility and energy dissipation capacity. The bearing capacity of H-block shear walls decreased with the reduction of axial compression ratio, while the ductility increased. A model was also proposed to predict the shear strength of the grouted double H-block based on mechanical analysis of the internally grouted concrete. The accuracy of the model was verified through 30 H-block specimens under shear tests and it was found the grout ratio had a significant effect on the shear strength of the grouted double H-block. The model proposed by the Chinese masonry code was over-conservative when the grout ratio was high. Finally, a modified shear capacity model was proposed and was found to be effective to predict the shear capacity of double H-block reinforced masonry shear wall.

## Keywords

Masonry shear wall Seismic behavior Cyclic test Failure mode## Abbreviations

- \(A_{\text{sh}}\)
Section area of the horizontal reinforcement rebar

- \(C_{1}\)
Factor considering the dowel action of the longitudinal reinforcement

- \(C_{2}\)
Factor considering the shear span ratio

- \(F_{i,\hbox{max} }^{ + } ,\,F_{i,\hbox{max} }^{ - }\)
The peak load in the push and pull direction loaded at the

*i*th multiple of the crack displacement, respectively- \(F_{\text{p}}\)
The lateral peak capacity of the shear walls

- \(K_{{_{{{\text{eff,}}i}} }}^{ + } ,\,K_{{_{{{\text{eff,}}i}} }}^{ - }\)
The lateral stiffness of the shear wall along the push and pull loading direction at the

*i*th multiple of the crack displacement, respectively- \(N\)
Compression load applied on the top of the shear wall

- \(V_{\text{c,new}} ,\,V_{\text{c,CN}} ,\,V_{\text{c,NZ}}\)
The calculated shear capacities of the shear wall, with the shear strength of the grouted concrete block masonry calculated using the new shear strength model proposed in this paper, the code suggested model of China and the code model of New Zealand, respectively

- \(V_{\exp }\)
Shear capacity of the shear wall obtained from the cyclic tests

- \(V_{\text{m}} ,\,V_{\text{N}} ,\,V_{\text{s}}\)
The contribution of grouted masonry, compression load, hozizontal reinforcement rebar to the shear capacity of shear wall, respectively

- \(X_{i}^{ + } ,\,X_{i}^{ - }\)
The displacement corresponding to \(F_{i,\hbox{max} }^{ + }\) and \(F_{i,\hbox{max} }^{ - }\), respectively

- \(b\)
Thickness of the shear wall

- \(f_{\text{b}}\)
Compressive strength of the brick

- \(f_{\text{c}}\)
Axial compressive strength of concrete prism

- \(f_{\text{cb}}\)
Mean compressive strength of concrete masonry unit

- \(f_{\text{cc}}\)
Compressive strength of concrete prism under biaxial stress state

- \(f_{\text{cg}}\)
Mean compressive strength of grout concrete

- \(f_{\text{cu}}\)
Cubic compressive strength of the grouted concrete

- \(f_{\text{g}}\)
Compressive strength of the grouted concrete block masonry

- \(f_{\text{m}}\)
Compressive strength of mortar

- \(f_{\text{mas}}\)
Compressive strength of the ungrouted concrete block masonry

- \(f_{\text{m,NZ}}\)
Mean masonry compressive strength based on the code of New Zealand

- \(f_{\text{t}}\)
Tensile strength of the concrete

- \(f_{\text{v}}\)
Shear strength of concrete

- \(f_{\text{vg}}\)
Shear strength of grouted concrete block masonry

- \(f_{\text{yh}}\)
Tensile strength of the horizontal reinforcement rebar

- \(h_{0}\)
Effective height of the transverse section of the shear wall

- \(s\)
Space between the adjacent horizontal reinforcement rebar along the vertical direction

- \(v_{\text{bm}}\)
Shear strength of grouted masonry

- \(\alpha\)
Ratio of the grout concrete section area to gross block section area

- \(\alpha_{\text{n}}\)
Ratio of net area to gross area of masonry unit

- \(\Delta_{\text{y}}\)
Yielding displacement of shear wall

- \(\Delta_{\text{u}}\)
Ultimate displacement of shear wall

- \(\delta_{\text{g}}\)
Block hole ratio, referring to the ratio of the hole section area to the gross block section area

- \(\theta\)
The angle formed between the wall axis and the strut from the point of axial load application to the center of the flexural compression zone

- \(\lambda\)
Shear span ratio of the shear wall

- \(\mu_{\Delta }\)
Ductility ratio, calculated by \({{\Delta_{\text{u}} } \mathord{\left/ {\vphantom {{\Delta_{\text{u}} } {\Delta_{\text{y}} }}} \right. \kern-0pt} {\Delta_{\text{y}} }}\)

- \(\rho_{\text{g}}\)
Grout ratio, referring to the ratio of the grout concrete section area to the hole section area

- \(\sigma_{1} ,\,\sigma_{2}\)
Principal compressive stress of the concrete

## Notes

### Acknowledgments

This research was sponsored by the National Natural Science Foundation of China (Grant Nos. 51378193 and 51408211), the Science and Technology Plan of Changsha, China (Grant Nos. CSCG-HNTF-GK20130576), the Natural Science Foundation of Hunan Province, China (Grant Nos. 2015JJ3032), the Open Fund of Hunan Province Engineering Laboratory of Bridge Structure (Changsha University of Science & Technology, Grant Nos. 14KD02), and the Fundamental Research Funds for the Central Universities through the Project of Young Teacher Growth of Hunan University (Grant No. 531107040799).

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