No abstract

ABSTRACT:The size effect or scaling phenomenon is a fundamental problem when dealing with fracture of geomaterials. Concrete is considered as one of world's most widely used construction materials. The design in civil engineering of structural concrete should take into account the size effect when extrapolating the experimental tests at laboratory scale to structures with large dimensions. The size effect is generally investigated on the nominal strength which is an important parameter for design in civil engineering. However, the fracture characteristics are also considered in structural concrete codes. The limitation of cracking (crack width, crack length , etc. ) are important aspects to consider in order to guarantee a safe conception. This paper deals with a numerical analysis of size effect on the nominal strength and on the cracking characteristics in concrete beams. Numerical simulations of geometrically similar notched beams of various sizes are performed using a mesoscopic approach with an isotropic damage model. In order to properly describe the cracking process, a post processing method based on the fracture energy regularization is adopted. The size effect on crack-opening and crack length evolution is investigated by comparing the numerical results with experimental data obtained by digital image correlation technique. The numerical results prove the ability of the mesoscopic approach to describe the size effect on the global behavior and the local behavior of concrete. The numerical investigation reveals the existing of a size effect on the cracking process evolution.

 ðàìêàõ ïîäõîäà ìåçîìåõàíèêè ïðîâåäåíî ìîäåëèðîâàíèå ðàçðóøåíèÿ êâàçèõðóïêèõ ìàòåðèàëîâ, ïîäîáíûõ áåòîíó. Ïðåäñòàâëåí äåòàëüíûé àíàëèç èçìåíåíèÿ äëèíû çîíû ïðåäðàçðóøåíèÿ â õîäå îáðàçîâàíèÿ òðåùèí. Ðàññìîòðåíà âçàèìîñâÿçü ìåaeäó äëèíîé çîíû ïðåäðàçðóøåíèÿ è ðàñêðûòèåì òðåùèíû.  õîäå èñïûòàíèé íà òðeõòî÷å÷íûé èçãèá áàëîê ñ ðàçëè÷íûìè íàäðåçàìè èññëåäîâàíî èçìåíåíèå çîíû ïðåäðàçðóøåíèÿ ñ òî÷êè çðåíèÿ ýâîëþöèè êàñàòåëüíûõ íàïðÿaeåíèé ñöåïëåíèÿ âäîëü òðåùèíû. Ñ èñïîëüçîâàíèåì ïîíÿòèé ìåõàíèêè óïðóãîãî ðàçðóøåíèÿ âû÷èñëåíî ïðèðàùåíèå äëèíû òðåùèíû. Ïîêàçàíà íåëèíåéíàÿ âçàèìîñâÿçü ìåaeäó äëèíîé çîíû ïðåäðàçðóøåíèÿ è äëèíîé òðåùèíû íà ìåçîóðîâíå. Íà îñíîâå ïîëó÷åííûõ çíà÷åíèé ïðèðàùåíèÿ äëèíû òðåùèíû ïîêàçàíî, ÷òî R-êðèâàÿ çàâèñèò îò ðàçìåðà îáðàçöà è êîíôèãóðàöèè íàäðåçà.

No abstract