پديد آورندگان :
شريفي باقرين، محمد دانشگاه تربيت دبير شهيد رجايي - دانشكده مهندسي عمران - گروه سازه، تهران، ايران , محمودي صاحبي، موسي دانشگاه تربيت دبير شهيد رجايي - دانشكده مهندسي عمران - گروه سازه، تهران، ايران , سحاب، محمدقاسم دانشگاه تفرش - دانشكده مهندسي عمران - گروه سازه، تفرش، ايران
كليدواژه :
پايش سلامت , نيروي پيشتنيدگي , تيرهاي پيشتنيده , پاسخ‌هاي استاتيكي , الگوريتم ژنتيك
چكيده فارسي :
مسئله تعيين نيروي پيشتنيدگي در تاندون‌هاي سازه هاي بتني پيشتنيده و پايش عدم تجاوز افت پيشتنيدگي از مقادير مجاز، مسئله‌اي است كه در طول دهه‌هاي گذشته محققان بسياري به آن پرداخته و روش‌هايي در اين زمينه ارائه كرده‌اند. امروزه به منظور پايش افت پيشتنيدگي، حسگرهايي پيش از نصب، در سازه هاي بتني پيشتنيده مهم تعبيه مي شود. ليكن نظر به عدم پيشبيني تجهيزاتي از اين دست در سازه هاي قديمي، پايش اين نيروها، مستلزم آزمايشات مخرب ويا غيرمخرب اما كمدقت است. لذا در اين نوشتار، روشي ارائه شده است كه بدون نياز به حسگرهاي موصوف و آزمايشات مخرب، تنها با اندازه گيري تغييرمكان هاي استاتيكي، قادر به تشخيص ميزان افت پيشتنيدگي در تاندون هاي مقطع يك تير بتني پيشتنيده مي باشد. در اين راستا الگوريتمي در محيط برنامه Python و مبتني بر الگوريتم ژنتيك و همچنين مدل سازي در برنامه تحليل اجزاي محدود فراهم شده است. مثال عددي ارائه شده در اين تحقيق نشان ميدهد، الگوريتم پيشنهادي مقادير افت پيشتنيدگي را حتي با وجود ده درصد خطاي عمدي ناشي از اندازه گيري، با دقت مطلوبي شناسايي مي كند.
چكيده لاتين :
Beam-column joints are one of the most important members of the concrete structures that are responsible
for transferring existing loads. These joints require compliance with the criteria such as the development
length of the beam and column rebar for proper operation. The lack of sufficient development length
reduces the structure's capacity and increases its deformation. This study tested three full-scale specimens
of exterior reinforced concrete beam-column joints under cyclic lateral loads. Specimens included a
control sample with an insufficient development length of the longitudinal beam rebar at the joint to the
column, the second sample with a sufficient development length through end mechanical anchorage, and
the last one with an insufficient development length strengthened with FRP fan anchors to improve the
beam-column connection. To install the FRP composite anchors, the column must first be drilled, and then
the FRP fans pass through the holes in the column and attach to the concrete surface behind the column
with a suitable adhesive. In all specimens, lateral load-displacement hysteresis diagrams, failure modes,
ductility coefficient, and stiffness were extracted and compared. This study showed that the lack of
sufficient development length leads to severe damage in the joint and the plastic hinge is not formed, and
shear cracks occur in the joint. However, in the sample with end anchorage and strengthened with FRP
fans, improvement of seismic performance, formation of plastic hinge in the beam, and the lack of
development length compensation are observed. The pinching effect in the hysteresis diagram of the
control specimen is noticed, and the maximum load capacity is much less than the others. End anchorage
of the rebar and strengthening of the specimen with FRP increases the lateral bearing capacity of the joint
by 53% compared to the control specimen; also, the residual capacity increases by about 84% and 73%,
respectively, at the end of the test (corresponding to 6% drift). The ductility of the sample with end
anchorage and the sample strengthened with FRP fan anchor is 34% and 19% higher than the control
specimen, respectively. Insufficient development length also reduces the stiffness of the control beamcolumn joint by up to 45% compared to the anchored and retrofitted specimen. Another result of
insufficient development length of rebar of the beam is the angle between beam and column. In the fixed
connections, this angle should remain constant, while in the control specimen, this angle changes
dramatically. This angle varies much less by retrofitting the connection with the FRP fan or end anchorage
of the rebar. Finally, the results of three tested samples showed that strengthening the connection with the
FRP fan anchor can effectively eliminate the lack of development length of rebar in the beams and increase
the load capacity, stiffness, and ductility of the connection
