PSI - Issue 5

Rachel Martini et al. / Procedia Structural Integrity 5 (2017) 1108–1115 Martini et al/ Structural Integrity Procedia 00 (2017) 000 – 000

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block, from the direct configuration test. The sonic test resulted in characteristic values of propagation velocities of the sonic waves in the analyzed walls, with these results obtained values of Young's modulus that supported the mechanical tests. In this way, it is highlighted that the synergy of the tests provides more coherent results for future correlations with the mechanical data. Both NDTs used presented coherent and related results, one technique corroborating the results of the others. The correlation between mechanical parame ters and NDTs’ results will be investigated resorting to artificial neural networks’ techniques (ANN), which is the next step of this work. © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of ICSI 2017. the next step of this work. he Authors. Published by Elsevier B.V. © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of ICSI 2017

Keywords: correlation; mechanical parameters; geophysical method.

1. Introduction

The masonry is composed of a material obtained by heterogeneous association of resistant parts interconnected by mortar to obtain a monolithic assembly. Despite the fact that stone, when not too much weathered and fractured, is a material that has resistance capacity and stiffness to compression, it is known that the set stone/mortar does not have good compression characteristics. The bedding stones mode and the poor properties of the agglomerate material are factors that determine the final performance of this composite structure. Thus, it is proposed to use non-destructive testing for characterization of historic buildings and obtain information regarding the mechanical parameters. The interesting historical buildings are material assets that make up the Urban Environmental Heritage. Due to historical and cultural value that these buildings represent, the maintenance and rehabilitation work is important to keep the appreciation of history. The preservation of buildings classified as historic and cultural heritage is of social interest, as it marked the history of society. Considering the object of research as a historic building, it is not recommended to use destructive investigative techniques. For civil engineering purposes as NDT (non-destructive testing) research option, this paper focuses on the application of geophysical methods, namely GPR (ground penetrating radar) and sonic tests as well as artificial neural networks. The GPR comprises a control unit and transmitting and receiving antennae that emits electromagnetic pulses at a high frequency rater into de subsurface and receives reflected echoes from the considered area, under the form of radargrams (Davis and Annan, 1989). The sonic tests are performed with an instrumented hammer and accelerometers for body and surface waves reception, namely P, R and/or S. Through this work, it is possible to understand the behavior of two-leaf masonry walls by relating the parameters of NDT with mechanical properties. Complementary to the application of NDT's, destructive tests were made on the laboratory experimental walls, like compression tests to obtain compression resistance values, Young's modulus and Poisson's ratio. These data will be correlated with the results of NDT's with the assistance of artificial neural networks (ANN), allowing to obtain mechanical properties through NDT's.

2. Materials and Methods

Working with a controlled environment, some studies in experimental masonry built walls were carried out in LESE (Laboratório de Engenharia Sísmica e Estrutural) in November/2014. All of the five tested walls have the same dimensions with a height of 1.75m, a thickness of 0.55 m and a width of 0.90 m (Tab. 1). The tested stone masonry are made of granite coming from the north of Portugal and the mortar composed of hydrated lime, clay and water.

Table 1. Characteristics of the walls Designation Dimensions

Characteristics

PP1 and PP5

two-leaf regular (two cross block) two-leaf regular (one cross block) f reg

PP2 PP3 PP4 PP3

1.75 x 0.90 x 0.55 m x 0.90 x 0.55 m

two-leaf regular and irregular (one cross block) two-leaf regular and irregular (no cross block)