Journal of Constructional Steel Research 65 (2009) 531–541 Contents lists available at ScienceDirect Journal of Constructional Steel Research journal homepage: www.elsevier.com/locate/jcsr Behavior of bolted top-seat angle connections in fire Amir Saedi Daryan ∗,1 , Mahmood Yahyai 2 Civil Engineering Department, K.N. Toosi University of Technology, Iran article info Article history: Received 26 December 2007 Accepted 15 July 2008 Keywords: Bolted angle connection Experimental study Elevated-temperature behavior Rotation–temperature curves Fire abstract Beam-to-column connections have been found to be of great significance in influencing structural behavior at ambient and elevated temperatures. When steel-framed structures are subjected to fire, the load bearing capacity is decreased and the behavior of the joints is of particular concern. Observations from full-scale fire tests and damaged structures confirm that connections have a considerable effect on the stability time of structural components in fire. The cost of high temperature tests on the broad range of connections used in practice means that their influence is not well detailed in current design codes. The paucity of data also limits the effective use of numerical models developed to simulate the behavior of complete structures at elevated temperatures. In this study, 12 full-scale tests were conducted at elevated temperatures on two types of bolted angle beam-to-column connections in order to investigate their resistance to fire. The failure modes and deformation patterns of these specimens were studied and the results are shown as rotation–temperature curves. In addition, the influence of different parameters such as thickness of the angles, the grade of bolts, and other geometrical and mechanical characteristics of the connections were studied. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction Structural steel frames consist of beams and columns connected together. The structural performance of the complete frame is affected by the behavior of the joints, which should be considered in any global analysis of the structure. In conventional analysis and design of steel and composite frames, beam-to-column connections are assumed to behave either as ‘pinned’ or as fully ‘rigid’ joints [1]. Although the pinned or rigid assumption significantly simplifies analysis and design procedures, in practice, the actual joint behavior exhibits characteristics from a wide spectrum between these two extremes. The difference between the two simplified joint types is that pin joints have rotational stiffness while rigid joints display flexibility. Designers may choose a more accurate representation of joint behavior for analysis and design, but many adopt simplified economical methods. Although these simplified approaches are sufficient for designs at ambient temperatures, when steel-framed structures are subjected to fire the behavior of the joints within a frame exerts an even greater influence on overall response. If ∗ Corresponding author. Tel.: +98 2122749398; fax: +98 2122749399. E-mail addresses: amir_saedi_d@yahoo.com (A. Saedi Daryan), m_yahyai@yahoo.com (M. Yahyai). 1 Ph.D. Student of Earthquake Session of Civil Engineering Department, K.N. Toosi University, Tehran, Iran. 2 Assistant Prof. of Civil Engineering Department, K.N. Toosi University, Tehran, Iran. the behavior of these connections is not considered properly, the analysis may misrepresent the performance of a structure during a fire. As steel structures are widely used in buildings and are sensitive to fire, researches have been focused on studying the influence of high temperatures on the behavior of steel structures. The traditional method for fire protection is to use fire-resistant coatings, which increase the cost and time of construction [2]. To minimize the need for coatings, extensive experimental and analytical studies of the effects of temperature on structures seem to be necessary. Tests can be conducted either on individual members or the whole structure. For this purpose, some tests have been focused on the influence of temperature on the response of structural connections. The tests conducted by CTICM [3] in 1976 investigated the performance of high strength bolts at elevated temperatures. British Steel [4] also carried out two tests in 1982 on a moment-resisting connection. Experimental studies were also conducted by Lawson [5] and Leston-Jones [6], however, these tests only provided useful data for a limited range of conditions using relatively small section sizes. In 1999, Al Jabari et al. [7] Conducted 20 experimental tests on five types of structural connections at elevated temperatures. In 2006, Wei-Yunj et al. [8] conducted a full-scale test on four connections at elevated temperatures. In addition to the studies conducted on connections, other experimental tests have been conducted to specifically study the behavior of bolts, which are a major component of structural connections. Kirby [9] conducted a series of experimental tests in 1995 to determine the strength degradation of grade 8.8 bolts in a temperature range from 300 0143-974X/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcsr.2008.07.021