بررسی آزمایشگاهی رفتار اتصال‌های کف‌ستون‌ها به همرا میل‌مهارهای جوش‌شده بدون خروج از مرکزیت با استفاده از روش همبستگی تصاویر دیجیتال

نوع مقاله : پژوهشی

نویسندگان

دانشکده‌ی مهندسی عمران، دانشکدگان فنی، دانشگاه تهران، تهران

10.24200/j30.2024.63404.3271

چکیده

در اتصال‌های کف‌ستون متداول، با خمیری‌شدن میل‌مهارها و عدم تماس‌ بین ورق کف‌ستون و بتن در حین بارگذاری، پینچینگ در نمودار هیسترزیس رخ می‌دهد. هدف پژوهش حاضر، ایجاد نوعی اتصال جوشی میل‌مهار زیر ورق کف‌ستون جهت ایجاد باربری لحظه‌‌‌یی در میل‌مهارها بدون خروج از مرکزیت نسبت به ‌بال ستون است. بنابراین، جهت بررسی مقاومت، 4 نوع اتصال جوشی تحت کشش، شامل: جوش گوشه‌ی ویژه، جوش شیاری با نفوذ کامل، جوش شیاری استوانه‌‌یی، و جوش شیاری مخروطی از اتصال T- شکل طراحی‌شده مطابق با ضوابط آیین‌نامه‌ها و مدهای گسیختگی استفاده شده است. ظرفیت، نوع شکست، و میدان کرنش اتصال جوشی میل‌مهار در هر نمونه با حالت‌های مختلف به کمک روش همبستگی تصاویر دیجیتال سنجیده شده‌اند. در نتیجه، اتصال‌های جوشی تقریباً توانایی تحمل ظرفیت نهایی میل‌مهارها را داشتند و تا آخرین لحظه از بارگذاری، در حالت کشسان باقی ماندند. البته شکست میل‌مهارهای پُرمقاومت در ناحیه‌ی HAZ، پدیده‌ی مهمی است، که از طریق عملیات پیش‌گرمایش و پس‌گرمایش قابلیت کنترل دارند. همچنین جوش گوشه‌ی ویژه از لحاظ هزینه و سهولت اجرا نسبت به بقیه‌ی اتصال‌های جوشی، در اولویت اول قرار دارد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

EXPERIMENTAL INVESTIGATION OF THE BEHAVIOR OF COLUMN BASE CONNECTIONS WITH CONCENTRICALLY WELDED ANCHOR RODS USING DIGITAL IMAGE CORRELATION METHOD

نویسندگان [English]

  • I. Karami
  • S.R. Mirghaderi
  • A.R. Ghiami Azad
  • M. Ali
M.S., School of Civil Engineering, College of Engineering, University of Tehran, Iran.
چکیده [English]

Base plate connections are one of the most important connections in steel structures. Besides the moment capacity of the connection, the rotational stiffness is an equally critical property that is frequently used in design. Because of the low rotational stiffness of the column base-plate, column base-plate connections do not have enough rigidity to create perfect plastic hinges. Therefore, concentrically-welded anchor rods were used under the column base plate to transfer loads properly. In this paper, four different weld types were used to connect the anchor rods to the bottom of the base plate. In this new connection, the eccentricity between anchor rods and the steel column is removed to improve the strength and stiffness of the base plate connections. The aim of this paper is to design four different weld types according to the specifications of welding standards. Five laboratory samples with different anchor rod strengths were tested to evaluate strength and ductility of each weld type under tensile loading. Anchor rods were the weakest member in transferring tensile load in each sample and expected to fail at the end of the test. Digital Image Correlation (DIC) method was used to provide force-displacement diagram and full field strain information of each laboratory sample. DIC is a non-contact and non-destructive technique in which digital images of the point of interest (POI) of a test specimen are captured continuously using a high-resolution camera all through the test. Fortunately, experimental results were similar to DIC results. Brittle failure was observed in the samples with high strength anchor rods at the softened heat affected zone (HAZ) in the anchor rods. As a result, all the anchor rods in each laboratory sample fractured at a tensile strength higher than yield strength of the anchor rod. Therefore, to prevent the failure of anchor rods in softened HAZ area, it is recommended to design the anchor rods of the column base connections to remain elastic under cyclic loads. It was also concluded that the fillet weld had a better performance in terms of executive and economy compared to the other welds.

کلیدواژه‌ها [English]

  • Base plate connection
  • T-shape connection
  • component method
  • groove weld
  • fillet weld
  • anchor rod
  • DIC
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