High-performance reinforced concrete structures: Brittleness size-scale effects高性能钢筋混凝土结构：脆性尺度效应

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Brittle solids show an unstable structural behaviour after the peak load that is represented by the negative slope in the load-displacement softening response. This means that the load must decrease to obtain a stable crack propagation. In extremely brittle cases, crack propagation occurs suddenly with a catastrophic drop in the load carrying capacity, since the load-displacement softening branch assumes a virtual positive slope. If the loading process is controlled by the displacement, the curve presents a discontinuity, and the representative point drops onto the lower branch with negative slope. In this case, both load and displacement must decrease to obtain a controlled crack propagation. Such a phenomenon, the so-called snap-back instability, was deeply investigated with reference to crack growth in quasi-brittle materials (cementitious composites). In the framework of Linear Elastic Fracture Mechanics, the cusp catastrophe represents the classical Griffith-Irwin instability for very brittle and initially cracked structural elements. This report includes two parts as follows: Part I deals with Nonlinear Fracture Mechanics models (in particular, the Cohesive Crack Model to describe strain-localization in both tension and compression) and their peculiar consequences: fold catastrophes (post-peak strain-softening and snap-through instabilities) or cusp catastrophes (snap-back instabilities) in plain or reinforced structural elements. Part II deals with the brittle behaviours of high-performance reinforced concrete beams for rather weak or strong reinforcement percentages. In the former case, the loading drop is due to tensile concrete cracking, whereas in the latter it is due to compression concrete crushing at the opposite beam edge. For the former case, an analytical model is introduced (the Bridged Crack Model) that is able, through a peculiar rotational compatibility condition, to deduce the redundant closing forces applied by the longitudinal reinforcement to the crack faces. On the other hand, introducing a numerical model where concrete is considered as a cohesive softening material in both tension and compression, we can obtain a double size-scale brittle-ductile-brittle transition.

      Alberto Carpinteri教授是欧洲科学院工程部主任、国家级人才、讲席教授，欧洲科学与艺术院院士。于1976年获得意大利博洛尼亚大学核工程博士学位，1981年获得数学博士学位。曾任意大利都灵理工大学结构工程系主任、结构工程研究生院创始院长。现为汕头大学土木与智慧建设工程系讲席教授。

      Carpinteri教授是包括欧洲科学院、国际工程院、都灵科学院和美国土木工程师学会在内的多个学院和专业机构的研究员。曾任欧洲科学院工程部部长，也曾兼任过国际断裂大会、欧洲结构完整性学会、国际混凝土和混凝土结构断裂力学协会、意大利断裂组、国家计量研究所等多个科学协会和研究机构的主席。Carpinteri教授为国际理论与应用力学联合会大会委员会成员、实验力学学会执行委员会成员、11种国际期刊编委会成员、《Meccanica》国际期刊主编、《智能建筑与可持续城市》国际期刊名誉编辑。发表国际期刊论文500多篇，谷歌学者H指数为91，Scopus H-索引为66。

      Carpinteri教授获得过RILEM颁发的Robert L’Hermite奖章、ESIS颁发的Griffith奖章、ASTM颁发的Swedlow纪念讲座奖、ICF颁发的Paul Paris就职金质奖章、俄罗斯科学院工程博士荣誉Causa、SEM颁发的Frocht奖、广东省的“珠江人才计划”和美国材料与试验协会颁发的乔治·欧文奖章等众多国际荣誉和奖项。