پديد آورندگان :
مولودي، فرزين دانشگاه سمنان , خيرالدين، علي دانشگاه سمنان - دانشكده مهندسي عمران , همتي، علي دانشگاه سمنان، واحد سمنان - دانشكده مهندسي عمران - گروه مهندسي عمران
كليدواژه :
HPFRCC , بتن آرمه , اتصال تير به ستون , رفتار لرزه اي , شكل پذيري
چكيده فارسي :
كامپوزيت هاي سيماني مسلح اليافي توانمند (HPFRCC) به مصالحي شامل ملات سيماني با سنگ دانه هاي ريز و الياف اطلاق مي شود. ويژگي شاخص اين مصالح، آن است كه برخلاف بتن معمولي و بتن اليافي، تحت بارگذاري كششي، رفتار سخت شوندگي كُرنشي از خود بروز مي دهد. در اين مقاله، پس از معرفي اين مصالح، با استفاده از روش اجزاي محدود، ميزان تاثيرگذاري كاربرد مصالح HPFRCC در عملكرد اتصال تير به ستون، بررسي شده است. به همين منظور، نتايج تحقيقات آزمايشگاهي انجام شده توسط چاو در دانشگاه ميشيگان، مبناي صحت سنجي مدل اجزاي محدود قرار گرفته است. تاثيرگذاري پارامترهاي مختلف اتصال تير به ستون، نظير: طول ناحيه مصالح HPFRCC در تير، طول ناحيه مصالح HPFRCC در ستون، مقاومت فشاري بتن و مصالح HPFRCC، فاصله بين خاموت ها در تير و ستون، به صورت تكي و يا تركيبي، در مدل مبنا، بر روي عملكرد اتصال، بررسي شده است. نتايج بدست آمده، نشان داد كه مقاومت حداكثر، مقاومت تسليم و نسبت شكل پذيري اتصال تير به ستون در صورتي كه مصالح HPFRCC در بخشي از تير يا ستون (به همراه چشمه اتصال) استفاده شده باشد، نسبت به اتصال تير به ستون بتن مسلح معمولي، به ترتيب 36.9، 10.4 و 53.1 درصد بيشتر است. همچنين نتايج بدست آمده نشان داد كه اثر پارامتر مقاومت فشاري بتن معمولي و مصالح HPFRCC، تاثير قابل ملاحظه اي بر نسبت شكل پذيري اتصال داشته است؛ به طوري كه نسبت شكل پذيري اتصالِ با بتن 35 مگاپاسكال، نسبت به اتصال مبنا (دانشگاه ميشيگان)، 40.7 درصد بيشتر است.
چكيده لاتين :
In recent years, the use of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) materials has been taken into consideration, in order to construct safe structures against earthquake. 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 normal 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 the 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 the performance of connection were investigated in the base model. Results showed that if the HPFRCC materials are used in some parts of the beam or column (with panel zone), the maximum strength, yield strength and ductility ratio of beam-column connection are respectively 36.9%, 10.4% and 53.1% greater than the beam-column connection made of reinforced concrete. Furthermore, the concrete compressive strength 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 experimental specimen 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 the 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 HPFRCC materials in the column did not have a significant effect on the strength and ductility ratio of the connection.
