Behaviour of composite haunched beam connection
Introduction
Strong demand for large column-free space in buildings in recent times has necessitated further research into the behaviour of haunched beams since they are considered to be an efficient and economical form for long span construction [1], [2]. Haunched beams are designed by assuming a rigid moment connection between the beams and columns [3]. Depth and length of a haunch are chosen so that they result in an economical method of transferring moment into the column and in a reduction of beam depth to a practical minimum. Haunched composite beams in which steel beams are designed to act in conjunction with a concrete slab of definite width could result in shallow beams, provide a long unobstructed space for services and increase speed of construction. The haunch can be designed to provide sufficient rotation capacity of the connection that will permit a redistribution of the moment and thus mobilise a full sagging capacity of the beam resulting in an economical design. Researchers [4], [5], [6], [7], [8], [9] have proposed design methods for composite beams, simple or continuous. Required and available rotation capacities for a section have been considered and the accuracy of the prediction method assessed by comparing the theoretical and experimental results. A comprehensive guideline has been proposed [10] for the design of semi-continuous composite beams in braced frames where special attention is given to the effects of joint rotational stiffness. Tests were carried out [11], [12] in order to calibrate analytical models [13] and to investigate rotation and moment capacities in composite beams. Local buckling and moment redistribution in composite beams have also been studied [14], [15]; it has been concluded that the redistribution of elastic bending moment allowed by Eurocode 4 [16] is safe, economical and reflects the real behaviour of two-span composite beams. For beams continuous over more than two spans, the method is believed to be slightly conservative. Extensive investigations [17], [18] into the behaviour of composite connections and continuous composite frames have shown that properly designed and detailed composite connections are capable of providing moment capacity up to the full hogging resistance of the beam. It has also been concluded that elastic analysis assuming full continuity is not acceptable for composite frames because it fails to meet the moment capacity requirement at the support section and it is over conservative for sections within the span. Despite the detailed studies on composite beams, information available on composite haunched beams that can be designed similar to continuous beams is limited. Recent works [19], [20] have shown that haunch is sufficiently stiff to assume such connections at the toe are restrained when a full depth stiffener is provided on both sides of the web. In order to study further the application of haunch connections in long-span composite construction a study has been undertaken by the authors on the behaviour of haunch connections. Sub-assemblies of composite haunch beams have been tested to examine the moment rotation characteristics and the failure modes of these connections. The object of this paper is to report on the experimental results obtained from the present study of haunch connections. The experimental program is described in detail and the results for ultimate moment capacity of the tested connections are given.
Section snippets
Test specimens
Connection specimens were designed with reference to a building plan layout shown in Fig. 1. Based on global elastic analysis for typical design load of an office block (Refer to Beam 3/A-E), the point of contraflexure was found to be at about 2 m from the column centreline (Column C3). Joint specimens of cruciform section were used to simulate the internal joint. A 120 mm thick floor slab was made from normal weight concrete designed to 30 N/mm2. The cross-sectional area of slab reinforcement
Joint ultimate moment, Mu
The ultimate moment resistance of a joint Mu is equal to the peak value of the moment–rotation characteristic as shown in Fig. 7. For a full strength composite haunch joint, the moment capacity of the haunch connection has to be greater or equal to the hogging moment capacity of the composite section at the haunch toe. The capacity of the haunch connection is calculated as follows.
Results and discussion
The ultimate moment obtained from the experiments along with those predicted by the method given in Section 3 for all the test specimens are summarised in Table 4. Also, the experimental values are compared with the predicted results. Extensive measurements were made for strain and displacement at various locations in the test specimens. However, only typical results at selected locations are presented for discussion. Detailed discussion is presented in the following sections for each of the
Conclusions
Experiments on composite haunch connections are described and results corresponding to ultimate moment capacity, moment-rotation characteristic and rotation capacity are presented. These connections are classified as a full strength rigid connection in accordance with Eurocode 4. It is confirmed by the test results which show that the measured moment capacity for all connections is larger than the plastic capacity of the beams and rotation in all tests was very small, less than 2 miliradian.
Acknowledgements
The investigation presented in this paper is part of the research program on Composite Construction for long span structures being carried out in the Department of Civil Engineering, National University of Singapore. The work is funded by a research grant (RP 930648) made available by National University of Singapore. The support from Yongnam Engineering & Construction (Pte) Ltd, Singapore who supplied the test specimens is gratefully acknowledged.
References (22)
- et al.
Determination of rotation capacity requirements for steel and composite beams
Journal of Constructional Steel Research
(1995) Local Buckling in Class 2 continuous composite beams
Journal of Construction in Steel Research
(1997)Design development in long span flooring system in the UK
A resource book for structural steel design and construction
(2001)- et al.
Design of haunched composite beam in buildings
(1989) - et al.
Ultimate strength of continuous composite beams
Journal of The Structural Division
(1976) Semi-rigid composite construction
Journal of Constructional Steel Research
(1990)- et al.
Available rotation capacity in steel and composite beams
The Structural Engineer
(1991) - et al.
Composite beams
A new design method for continuous composite beams
Structural Engineering International
(1996)
Practical design guidelines for semi-continuous composite braced frames
International Journal of Steel and Composite Structures
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Experimental studies on composite haunch beams
2012, Journal of Constructional Steel ResearchCitation Excerpt :The details of the beam are summarized in Table 3. The steel material used is the same as the one employed in the joint tests [23]. Specimens were not painted or coated with any chemical.
Testing of composite steel top-and-seat-and-web angle joints at ambient and elevated temperatures, Part 1: Ambient tests
2011, Engineering StructuresCitation Excerpt :The initial gradient of the moment–rotation curve defines the initial rotational stiffness of a joint. However, despite voluminous experimental data of composite semi-rigid joints, most of the experimental works conducted were focused on the behaviour of composite joints with flush or extended end-plates, or flange or web cleats [3,4,6–9]. The experimental works on the composite steel TSW angle joints are relatively limited to 1994 [10–13].
Seismic Behavior Investigations of the Haunched Joint with Ribbed Anchor Webs in CFDST Structures
2023, Advances in Civil EngineeringLoading Capacity Calculation of Integrated Precast Slab and Column Panel Using Cold-formed Steel
2021, Journal of Physics: Conference SeriesDamage effect on experimental modal parameters of haunch strengthened concrete-encased composite column–beam connections
2020, International Journal of Damage Mechanics