بررسی رفتار لرزه ای اتصالات تیر به ستون بتن آرمه ساخته شده از کامپوزیت های سیمانی مسلح الیافی توانمند (HPFRCC)

نویسندگان
فرزین مولودی 1
علی خیرالدین 2
علی همتی 3
1 دانش آموخته کارشناسی ارشد سازه، دانشکده مهندسی عمران، دانشگاه سمنان، ایران
2 استاد، دانشکده مهندسی عمران، دانشگاه سمنان، ایران
3 استادیار، گروه مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران
چکیده
کامپوزیت های سیمانی مسلح الیافی توانمند (HPFRCC) به مصالحی شامل ملات سیمانی با سنگ دانه های ریز و الیاف اطلاق می شود. ویژگی شاخص این مصالح، آن است که برخلاف بتن معمولی و بتن الیافی، تحت بارگذاری کششی، رفتار سخت شوندگی کُرنشی از خود بروز می دهد. در این مقاله، پس از معرفی این مصالح، با استفاده از روش اجزای محدود، میزان تأثیرگذاری کاربرد مصالح HPFRCC در عملکرد اتصال تیر به ستون، بررسی شده است. به همین منظور، نتایج تحقیقات آزمایشگاهی انجام شده توسط چاو در دانشگاه میشیگان، مبنای صحّت سنجی مدل اجزای محدود قرار گرفته است. تأثیرگذاری پارامترهای مختلف اتصال تیر به ستون، نظیر: طول ناحیه مصالح HPFRCC در تیر، طول ناحیه مصالح HPFRCC در ستون، مقاومت فشاری بتن و مصالح HPFRCC، فاصله بین خاموت ها در تیر و ستون، به صورت تکی و یا ترکیبی، در مدل مبنا، بر روی عملکرد اتصال، بررسی شده است. نتایج بدست آمده، نشان داد که مقاومت حداکثر، مقاومت تسلیم و نسبت شکل پذیری اتصال تیر به ستون در صورتی که مصالح HPFRCC در بخشی از تیر یا ستون (به همراه چشمه اتصال) استفاده شده باشد، نسبت به اتصال تیر به ستون بتن مسلح معمولی، به ترتیب 36.9، 10.4 و 53.1 درصد بیشتر است. همچنین نتایج بدست آمده نشان داد که اثر پارامتر مقاومت فشاری بتن معمولی و مصالح HPFRCC، تأثیر قابل ملاحظه ای بر نسبت شکل پذیری اتصال داشته است؛ به طوری که نسبت شکل پذیری اتصالِ با بتن 35 مگاپاسکال، نسبت به اتصال مبنا (دانشگاه میشیگان)، 40.7 درصد بیشتر است.

کلیدواژه‌ها

عنوان مقاله English

Investigation of the Seismic Behavior of Reinforced Concrete Beam-column Connections Made of High Performance Fiber Reinforced Cementitious Composites (HPFRCC)

نویسندگان English

farzin moludi 1
Ali Kheyroddin 2
Ali Hemmati 3
چکیده English

Investigation of the Seismic Behavior of Reinforced Concrete Beam-column Connections Made of High Performance Fiber Reinforced Cementitious Composites (HPFRCC)
In recent years, the use of the HPFRCC materials has been taken into consideration in order to construct safe structures against earthquake. High performance fiber reinforced cementitious composites (HPFRCC) refer to the materials, including cement mortar with fine aggregates and fibers. The distinctive feature of the materials is that they exhibit strain hardening behavior under tensile loading unlike normal concrete and fiber reinforced concrete. The HPFRCC materials can be used for seismic retrofitting of structural components, construction of structural fuses and in areas susceptible to degradation in structures, such as beam-column connections and shear wall interface beam. As the beam-column connections are considered as one of the points of damage in concrete flexural frames, the use of the HPFRCC materials in the beam-column connections, which have high strength and ductility, can lead to the formation of the structures with higher strength and ductility compared to the conventional concrete structures. This study first introduces the materials and then determines the effect of the use of the HPFRCC materials in the beam-column connection performance. Therefore, the results of laboratory studies conducted by Chao at University of Michigan were used to verify the finite element model. The effect of the different parameters of beam-column connection, including HPFRCC materials length area in the beam, HPFRCC materials length area in the column, compressive strength of concrete and HPFRCC materials, the distance between stirrups in the beam and the distance between stirrups in the column, individually or combined, and performance of connection were investigated in the base model. The results showed that maximum strength, yield strength and ductility ratio of beam-column connection, if the HPFRCC materials are used in some parts of the beam or column (with panel zone), are respectively 36.9%, 10.4% and 53.1% greater than the beam-column connection made of reinforced concrete. Furthermore, the concrete compressive strength parameter has a significant effect on the connection ductility ratio so that the ratio of ductility of the connection with 35 MPa concrete is 40.7% greater than the base connection (University of Michigan). It is notable that in the laboratory connection of the University of Michigan where the HPFRCC area length in the beam is twice the beam depth (711.2 mm), the reduction of the HPFRCC area length just in the beam led to the 40.7% increased ductility ratio of the connection from twice the beam depth (711.2 mm) to the length equal to the beam depth (355.6 mm) compared to the base connection (University of Michigan) while it had minimal effect on connection strength. Moreover, the use of the HPFRCC area just in the column led to the 50.1% increased ductility ratio of the connection compared to the base connection (University of Michigan). The results indicated that when HPFRCC materials were used in the beam, the use of the HPFRCC materials in the column did not have a significant effect on the strength and ductility ratio of the connection.
Keywords: HPFRCC, Reinforced Concrete, Beam-Column connection, Seismic Behavior, Ductility.

کلیدواژه‌ها English

HPFRCC
reinforced concrete
Beam-column connection
Seismic behavior
ductility
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مهندسی عمران مدرس
دوره 17، شماره 3
مرداد و شهریور 1396
صفحه 213-226