بهسازی لرزه‌ای اتصالات خارجی تیر - ستون بتنی با آسیب شدید با استفاده از مصالح hpfrcc و frcm

بررسی زلزله‌های گذشته حاکی از آن است که به علت عدم رعایت جزئیات لرزه‌ای ویژه اتصالات تیر-ستون، ساز و کار ترد سازه ناشی از رفتار اتصال، اغلب منجر به آسیب‌دیدگی شدید یا حتی فروریزش ساختمان می‌گردد. گسیختگی اتصال تیر-ستون به دلیل گسیختگی برشی هسته اتصال یا لغزش آرماتور در این مکانیسم‌ها شایع است. احیا و بهسازی لرزه‌ای اتصالات خارجی تیر–ستون بتن مسلح آسیب‌دیده یکی از چالش‌های اخیر محققین است؛ لذا در این تحقیق به ارائه راهکاری جهت ارتقای لرزه‌ای رفتار اتصالات آسیب‌دیده تحت زلزله پرداخته شده است. در این راستا 3 اتصال خارجی تیر–ستون با مقیاس ½ تحت بارگذاری جانبی چرخه‌ای با دامنه افزایشی قرار گرفتند. نمونه‌های آزمایش شده شامل دو نمونه کنترلی بدون آسیب اولیه است که یک نمونه دارای جزئیات لرزه‌ای ویژه و نمونه کنترلی دیگر فاقد جزئیات لرزه‌ای ویژه است. نمونه بهسازی شده، مانند نمونه‌های کنترلی فاقد جزئیات لرزه‌ای است که ابتدا تحت آسیب شدید قرار گرفته است و سپس اقدام به احیا و بهسازی اتصال با مصالح hpfrcc و frcm شده است.نتایج آزمایش نشان می‌دهد که جایگزینی بتن آسیب‌دیده با مصالح hpfrcc سبب جابه‌جایی مفصل پلاستیک به بیرون هسته اتصال و شکل‌گیری مفصل پلاستیک خمشی در تیر و عدم آسیب هسته اتصال و بهبود پیوستگی بین بتن و آرماتور طولی شده است، همچنین میانگین بار حداکثر، ضریب شکل‌پذیری و انرژی مستهلک شده برای نمونه احیاء و بهسازی شده به طور میانگین به ترتیب %16، %17 و %56 نسبت به نمونه کنترلی دارای جزئیات لرزه‌ای ویژه بدون آسیب اولیه افزایش‌یافته است.

rehabilitation of damaged rc exterior beam-column joints with the hpfrcc and frcm materials

the reconstruction and modernization of impaired external beam-column connections in reinforced concrete constructions is presently a significant predicament for scholars and experts in the field. this predicament necessitates comprehensive research in order to formulate viable solutions and methodologies for the seismic restoration and retrofitting of these connections. consequently, the main focus of this research lies in proposing a solution to improve the seismic performance of impaired connections under earthquake-induced loading. within this specific context, it is of utmost importance to consider a comprehensive analysis of a total of three beam-column connections that were strategically positioned externally and scaled down to half their original size. these connections were then subjected to a series of cyclic lateral loading, which can be characterized by its repetitive nature and a distinct feature of an increasing amplitude. the objective of this experimental study was to evaluate the response and behavior of these connections under such loading conditions. additionally, in order to establish a reliable basis for comparison, two control specimens were included in the testing program. these control specimens, which were meticulously preserved and remained undamaged, served as benchmarks against which the subjected specimens were compared and evaluated. one of these control samples possessed seismic details that were of a unique and distinctive nature, while the other control specimen lacked the presence of such special seismic details. it is of utmost importance to note that the purpose of conducting these tests was to evaluate and assess the efficacy and effectiveness of the seismic details in their ability to withstand and resist lateral loading under cyclic conditions. furthermore, in addition to the aforementioned control specimens, one supplementary specimen was also included in the testing process. this additional specimen experienced a preliminary stage during which it was exposed to significant harm, following which it was subsequently exposed to the restoration of connections. this process of restoration involved the application and execution of materials known as high-performance fiber reinforced cementitious composite (hpfrcc) and alongside the retrofitting of the specimens with fiber reinforced cementitious matrix (frcm) and. the results and findings that were derived from the examination and analysis of the data obtained from these tests demonstrate and illustrate that the replacement and substitution of deteriorated concrete with hpfrcc substances leads to the transfer of the plastic hinge from the core of the connection, thereby establishing a flexural plastic hinge within the beam. the utilization of this methodology does not yield any unfavorable outcomes on the underlying connections, all the while enhancing the bond between the concrete and longitudinal reinforcement. as a result, the incorporation of these particular materials introduces a practical and feasible approach for amplifying the capacity of load-bearing, flexibility, energy dissipation, and stiffness of the individual components. additionally, the average maximum load, ductility factor and energy dissipation for the rehabilitated specimen increased by an average of 16%, 17% and 56%, respectively, compared to the undamaged control specimen with special seismic detailing. this particular method exhibits a significant potential for enhancing the overall structural soundness and stability of constructions.