# Application of Sonic Tests and Modal Identification in the Characterization of Masonry Walls
## 2 Experimental Campaign  
The SHS project (Simple Housing Solution) consists a methodology for (re)building homes and other small buildings, in a joint working system (community construction), seeking to optimize available resources and contribute to the organization of chaos installed in critical situations, such as post-disaster, post-conflict, refugee relocation, or risk mitigation. It is based on the fundamental principles for the sustainable restoration of housing declared by the United Nations Development Program (UNDP) and the International Platform for Recovery (IRP): environmental, technical, financial, and socio-organizational sustainability. The project was one of the finalists for the 2019 Sasakawa Awards, a United Nations (UN) award in the area of disasters, with impacts on several sustainable development goals. SHS-Multirisk is a spin-off project that is under development through a partnership between the Federal University of Rio de Janeiro (UFRJ) and the University of Aveiro (UA). It proposes a residence model that is simultaneously resistant to earthquakes and hurricanes, within a specific range of magnitude to be defined in the project, using simple, low-cost, and environmental-friendly construction technologies when compared to traditional alternatives or more technological, but less accessible ones. In its current phase, the first SHS-Multirisk house model [17] is being improved, aiming at more aggressive scenarios.  
The present experimental SHS campaign was performed at UA, which involved a set of six reinforced masonry soil-cement compressed earth blocks walls, with 1 m width, a height of 2.3 m and a thickness of 0.125 m. The walls have a U section and are constituted by soil-cement blocks (with two holes) in the proportion 8:1, vertical 10 mm diameter A400 steel bars (in five filled holes), horizontal 6 mm diameter A400 steel bars (in four 55 cm spaced levels, starting from the top) and soil-cement mortar in the proportion 5:1 (See Figure 2). All the specimens were built on a 60 cm height reinforced concrete base and designed with the same layout and materials, W1, W2, and W3 without plaster and W4, W5, and W6 with 3 cm of soil-cement plastering in one side of the wall.  
The dry blocks were tested according to NBR 8492:2012 [18] and showed an average compressive strength of 7.29 MPa and an average compressive strength in saturated specimens of 5.17 MPa, with coefficients of variation at around 20% in both cases. The average compressive strength of the laying mortars for the blocks and plaster was obtained by the prism test in accordance with EN1015-11:1999 [19] and showed values of around 11.70 MPa. The mean tensile stress in bending was around 2.60 MPa, representing about 20% of the compressive strength, within the expected range.  
Each row has five whole blocks or four whole blocks and two half-blocks, laid on a layer of mortar about 1 cm thick, without mortar in the vertical joints, which are alternated between the thirty rows. Holes with vertical reinforcements are filled with the same mortar used as the blocks, with manual compaction. The vertical reinforcements have an overlapping splice at mid-height, and the lower bar was anchored with a chemical anchor in the reinforced concrete footing. The horizontal reinforcements are embedded in the mortar joints. At the top of each specimen, a crown was built in reinforced concrete, approximately 10 cm high. All production of blocks and construction of masonry walls were carried out strictly by hand, without the use of electricity. This guideline was adopted to approximate as much as possible the conditions of laboratory production to those situations of project application when there is not always electricity available.