Out-of-plane shaketable testing of unreinforced masonry walls in two-way bending

Abstract

Five half-scale unreinforced clay brick walls were subjected to out-of-plane shaketable testing, in order to verify whether wall behaviour observed in a previous test campaign involving quasistatic cyclic loading of full-scale walls could be considered representative under dynamic loading. The walls tested in the present study all had identical dimensions and support conditions which included translational support at their top and bottom edges and fixed support at their vertical edges. Three of these walls contained a window opening, and three were subjected to vertical precompression. An extensive number of individual runs were performed on every wall, comprising three basic types of input motion: pulses, harmonic excitation and realistic earthquake motions. The tests confirmed the main behavioural trends observed in the quasistatic cyclic test study, including attainment of a peak load capacity during the initial sequence of cracking, good post-cracking strength, substantial hysteretic energy dissipation, degradation of strength and stiffness with increasing size and number of cycles, and agreement between the overall cracking patterns. A discussion of the observed behaviour is provided by considering similarities and, where observed, the differences between the two studies and also between the five walls tested in the present study. As a means of standardising comparisons of key features of the measured force–displacement response of the half-scale shaketable test walls versus the full-scale cyclic test walls, theoretical predictions of ultimate strength and post-cracking strength are undertaken using simplified analytical methods utilising idealised collapse mechanisms. Predictions of the ultimate strength which allow for the tensile bond strength of the masonry show good correlation with the results of both test studies. The predicted post-cracking strength envelope is shown to be conservative within the range of deformations achieved in both sets of tests.

Appendices

Appendix 1: Supplementary material

Supplementary material can be found online at the following DOI:

http://doi.org/10.4225/55/5a0138124b6c0

The material provided consists of two files. The first is a document (120 pages) containing additional detail relating to these tests, including:

• Material test methods and results,

• Test run naming convention,

• Earthquake input motions,

• Basic data processing,

• Cyclic response analysis,

• Data filtering,

• Force-displacement graphs,

• Cracking pattern photographs, and

• Description of attached data (unprocessed and processed).

The second file is a ZIP file containing unprocessed and processed time-domain data for each of the test runs undertaken.

Appendix 2: Results of quasistatic cyclic tests (Griffith et al. 2007)

The purpose of this appendix is to provide selected results of the quasistatic cyclic test study reported in Griffith et al. 2007 as a reference for comparison of the results observed in the present tests.

Only walls S1–S5 from the quasistatic cyclic test study are considered here as they are the full-scale equivalents of the half-scale test walls D1–D5 tested in the present study. The reader is referred to the original paper for additional information including material properties, test procedure, and results for the remaining three walls (S6–S8).

2.1 Cracking patterns

Cracking patterns exhibited by walls S1–S5 at the conclusion of testing are shown in Fig. 16.

Fig. 16

Cracking patterns at the conclusion of quasistatic cyclic tests as reported in Griffith et al. 2007. The illustrations show an unfolded view of the walls including returns. Severe exhibiting a higher degree of damage or spalling cracks are highlighted as thick lines whilst cracks with lesser damage are shown as thin lines. Graphics remain copyright of John Wiley & Sons, Ltd. (2006); used with permission from Wiley. a Wall S1 (σ _vo  = 0.10 MPa), b Wall S2 (σ _vo  = 0 MPa), c Wall S3 (σ _vo  = 0.10 MPa), d Wall S4 (σ _vo  = 0.05 MPa) and e Wall S5 (σ _vo  = 0 MPa)

2.2 F-Δ capacity curves

Figure 17 provides for each wall S1–S5 a plot of the F-Δ behaviour as well as hysteretic damping ratio (ξ) computed using the same approach as in the present study [refer Eq. (9)]. For reference, the predicted load capacities calculated using the analytical techniques described in Sect. 5 are also plotted.

Fig. 17

F-Δ behaviour and hysteretic damping for quasistatic cyclic test walls S1–S5 as reported in Griffith et al. 2007. Also shown are analytical capacity predictions including: ultimate strength λ _u (thick dashed line), residual strength from rigid body rocking λ _ro (thin solid line, x-intercept at δ _ro ), and residual strength inclusive of horizontal bending friction λ _ro  + λ _ho (thin dashed line). a Wall S1 (σ _vo  = 0.10 MPa), b Wall S2 (σ _vo  = 0 MPa), c Wall S3 (σ _vo  = 0.10 MPa), d Wall S4 (σ _vo  = 0.05 MPa) and e Wall S5 (σ _vo  = 0 MPa)