Large-Scale Testing Program for the Seismic Characterization of Dutch Masonry Structures

Abstract eng:
The evaluation of the seismic response of unreinforced masonry buildings is a popular topic all over the world. In recent years, also the Netherlands started to face seismic risk, since the induced seismicity in the north of the country considerably increased (the gas extraction started in 1963, and earthquakes have occurred since the early ‘90s, with the highest magnitude equal to 3.6 on the Richter scale experienced near Huizinge in 2012). This phenomenon has a wide impact on the built environment, which is mainly composed by unreinforced masonry. These buildings were not designed for seismic loading, and present specific characteristics such as very slender walls (a ratio height/thickness equal to 25), limited cooperation between walls and floors, and use of cavity walls, often connected by weak and corroded ties. To predict the behaviour of unreinforced masonry buildings, the use of numerical models and simple analytical design methods is required. These approaches necessitate the characterisation of the masonry at both material and structural level. An extensive large-scale testing program was performed at the Delft University of Technology to create benchmarks for the validation of the numerical and analytical models. The attention was mainly devoted to a terraced house typology, which was widely adopted for housing in the period 1960-1980. These houses were characterised by loadbearing walls of calcium silicate bricks and walls of clay bricks as outer leaves. In this framework, the paper presents an overview of the cyclic pushover tests performed on full-scale walls under either in-plane or out-of-plane loading. Seven full-scale unreinforced masonry (URM) walls were tested under in-plane loading. Two different series of solid brick masonry walls were considered: four specimens (COMP-0a, COMP-1, COMP-2, and COMP-3) were characterized by a high aspect ratio (H/B = 2.5), whereas three specimens (COMP-4, COMP-5, and COMP-6) had low aspect ratios (H/B = 0.6). Also two different configurations were considered, according to the provided boundary conditions at wall ends: cantilever walls, and double clamped walls. Five full-scale URM walls were tested in the out-of-plane direction by applying cyclic loading using a system of airbags. Two different geometries of brick masonry walls were considered: two specimens (COMP-0b and COMP-7) were characterized by a high aspect ratio and tested in a one-way spanning configuration; other three specimens (COMP-10, COMP-11, and COMP-12) had low aspect ratios and were tested in a two-way spanning configuration. All the walls were composed by solid calcium silicate masonry, except specimen COMP-10 which was made of perforated clay brick masonry. Sample COMP-12 contained a window opening, so that two asymmetric piers were determined at the sides of the window. For both the in-plane and the out-of-plane tests a description of the material properties, of the employed set-ups, and of the loading procedures is provided. An overview of the main results is presented.

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