Issue 51

M.G. Masciotta et alii, Frattura ed Integrità Strutturale, 51 (2020) 423-441; DOI: 10.3221/IGF-ESIS.51.31 425 experimental counterpart allows to verify the reliability of the non-standard numerical procedure adopted to simulate the evolution of the dynamic behavior of settled masonry arches with reasonable accuracy. E XPERIMENTAL T ESTING he segmental masonry arch investigated in this work was built and tested in the structural laboratory of the Institute of Bio-Sustainability of the University of Minho (Guimarães, Portugal). The small-scale arch was progressively damaged by applying uniform increasing displacements at one support and, after each displacement stage, dynamic tests were performed to measure the dynamic response of the system and follow its stiffness degradation due to the occurrence of structural damage. Finally, in order to gain a better insight into the failure mechanisms of masonry arches on spreading support, displacements were increased up to collapse, allowing to analyze the hinge position throughout the development of the mechanism as well as to estimate the ultimate displacement of the arch. Description of the arch and static damage tests The arch specimen consists of four rows of 39 brick units (100x75x50 mm 3 ) assembled with staggered lime mortar joints and it is characterized by a nominal span of 1900 mm, a springing angle of 40°, a nominal net rise of 430 mm and a 75 mm radial thickness (Fig.1). The structure is symmetrically loaded with two lime bags of 25 kg each (corresponding to about 50% of the arch weight), aiming at reproducing the weight of backfill material typical of masonry arch bridges, and is supported by two concrete abutments, one fixed to the floor by bolts (left support) and the other set on a simple system with lateral roulette wheels (right support) featuring a movable springing along the horizontal direction. With the aim of investigating the support settlements effects on the dynamic behavior of the segmental arch, a displacement- controlled test is carried out to induce five unrecoverable Damage Scenarios (DSs). Outward movements in horizontal direction are imposed to the right support with a hydraulic jack, whose displacement is simultaneously measured by a Linear Variable Displacement Transducer (LVDT). Additionally, two LVDTs are used to control the uniform sliding of the movable support and two LVDTs are employed to measure the arch displacements at the keystone and left springer, respectively (Fig.1a). (b) (a) (c) Figure 1: Arch specimen: (a) geometry with test layout; (b) view of the test apparatus; (c) static scheme. Increasing displacement rates are applied in five stages up to reaching a final value of 3 mm (Tab.1). the scope of the experimental test in this first phase is to cause very little visual damage to the arch so as to quantitatively assess the effects that incipient settlement-induced cracks can have on its global dynamic behavior. It is noted that the typical experimental T