Journal of Constructional Steel Research 66 (2010) 198–212
Contents lists available at ScienceDirect at ScienceDirect
Journal of Constructional Steel Research journal homepage: www.elsevier.com/l www.elsevier.com/locate/jcsr ocate/jcsr
Headed steel stud anchors in composite structures, Part I: Shear Luis Pallarés a, Jerome F. Hajjar b,∗ a
Universidad Politécnica de Valencia, Valencia, 46022, Spain
b
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2352, USA
a r t i c l e
i n f o
Article history: Received 25 February 2009 Accepted 18 August 2009 Keywords: Composite construction Composite column Steel anchor Shear stud Headed stud Shear connector
a b s t r a c t
Theformula Theformula in the2005 Ameri AmericanInsti canInstitut tute e of Steel Steel Constr Construct uctionSpeci ionSpecific ficati ation on to comput compute e thestrengthof thestrengthof headedsteel headedsteel stud stud anchor anchorss (shearconne (shearconnecto ctors)in rs)in compos composite ite steel/ steel/con concre crete te struct structure uress hasbeen used used in the UnitedState UnitedStatess since since 1993, 1993, after after being being propos proposed ed based based primar primarilyon ilyon theresults theresults of pushpush-out out tests.In tests.In thepast several decades, the range of members used in composite structures has increased significantly, as has the number of tests in the literature on the monotonic and cyclic behavior of headed studs in composite construction. This paper reviews 391 monotonic and cyclic tests from the literature on experiments of headed stud anchors and proposes formulas for the limit states of steel failure and concrete failure of headed stud anchors subjected to shear force without the use of a metal deck. Detailing provisions to prevent premature pryout failure are also discussed. This paper also reviews proposals from several authors and provides recommended shear strength values for the seismic behavior of headed studs. The limit state formulas are proposed within the context of the 2005 AISC Specification AISC Specification,, and comparisons are made made to theprovisi theprovisionsin onsin theACI 318-08 318-08Buil BuildingCode dingCode,thePCI ,thePCI Handbook, Handbook , 6thEdition,and 6thEdition,and Euroco Eurocode de 4. The scope of this research research includes includes composite composite beam–colum beam–columns ns [typically [typically concrete-e concrete-encas ncased ed steel shapes shapes (SRCs) (SRCs) or concrete-filled steel tubes (CFTs)], concrete-encased and concrete-filled beams, boundary elements of composite composite wall systems, systems, composite composite connection connections, s, composite composite column column base conditions conditions,, and related related forms of composite construction. © 2009 Elsevier Ltd. All rights reserved.
1. Introduction Introduction
Headed steel stud anchors (shear connectors) welded to a steel base base and encase encased d in concre concrete te have have been been the most most common common method method for transferring forces between the steel and concrete materials in composite construction. This type of anchor has been investigated by numerous researchers worldwide. For steel and composite steel/concrete construction, the focus of the work has been predominantly on composite beams with and without a metal deck. Much less comprehensive assessment has been conducted for the streng strength th of headed headed steel steel anchor anchorss in compos composite ite compon component ents. s. For such alternative configurations, the focus of much prior work has been on reinforced or prestressed concrete construction. The main approaches regarding anchors in reinforced concrete are outlined in [1 [1] and Appendix D of ACI 318-08 [2 [2]. Recently, Anderson and Meinheit [3–5 [3–5]] developed a comprehensive research program to assess the shear strength of headed studs in prestressed concrete. As a result of this work, the 6th Edition of the PCI Handbook [6 [6] incorporated new alternative approaches for computing the shear strength of headed studs.
∗ Corresponding author. Tel.: +1 217 244 4027; fax: +1 217 265 8040. (J.F. Hajjar). E-mail address:
[email protected] address:
[email protected] (J.F.
0143-974X/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcsr.2009.08.009
Resear Research ch on headedstuds headedstuds in compos composite ite struct structure uress extend extendss back back to the1950’s.A the1950’s.A brief brief summa summary ry is presen presentedhere.The tedhere.The first first push-o push-out ut test for studying the behavior of headed studs was conducted by Viest [ Viest [7 7], who performed 12 tests at the University of Illinois with varying ratios of effective depth-to-stud diameter (h ( hef /d), where base to theundersid theunderside e of thestud head. head. hef is thestudheightfromits base Viest [7 [7] observed three types of failure: steel failures, where the stud diameter reached its yield point and failed; concrete failures, where the concrete surrounding the headed stud crushed; and mixedfailures that included included failure failure of bothmaterials. bothmaterials. Furthermor Furthermore, e, Viest Viest propos proposed ed oneof thefirstformulasto thefirstformulasto assessthe assessthe shear shear streng strength th of headed studs of composite structures (see Table (see Table 1). 1 ). Drisco Driscoll ll and Slutte Slutterr [8] propos proposed ed a modifi modificat cation ion of Viest’ Viest’ss equation ( equation (Table Table 1) 1) and observed that the total height-to-diameter ratio ( ratio (h h/d) for studs embedded in normal-weight concrete should be equa equall to or larg larger er than than 4.2 4.2 if the the full full shea shearr stre streng ngth th of the the anch anchor or had to be developed. Chinn and Steele [9 [ 9,10 10]] developed push-out tests on lightweight composite slabs. Davies [ 11 11]] studied group effects for several headed studs in push-out tests. Mainstone and Menzies [ Menzies [12 12]] carried out tests on 83 push-out specimens covering the behavior of headed anchors under both static static and fatigue fatigue loads. Goble [13 13]] investigated the effects of flange thickness on the strength of composite specimens. Topkaya et al. [ 14 14]] tested 24 specimens in order to describe the behavior of headed studs at early concrete ages.
199
L. Pallarés, J.F. Hajjar / Journal of Constructional Steel Research 66 (2010) 198–212 Table 1 Proposed equations for headed steel anchor strength in composite structures.
Notation
Area of the headed stud anchor As Av g . (µ) Average Coefficient for shear strengths C v C .O.V . Coefficient of variation Modulus of elasticity of the concrete E c Secant modulus of elasticity of concrete E cm Diameter of the headed stud anchor d Specified compressive strength of the concrete f c Average measured compressive strength of the f cr concrete Specified splitting tensile strength of concrete f c ,sp Yield stress of the steel f s Specified minimum tensile strength of a stud shear F u connector Height of the stud h Effective embedment depth anchor hef Coefficient to compute pryout by ACI 318-08; it kcp equals 1 for hef 1 in, then Q nv = 5df c f √ f 932d Long studs (h/d > 4.2): Q nv = A √ 222hd f Short studs (h/d < 4.2): Q nv = A Steel failure: Q nv s = As f s Concrete failure: Q nv c = 0.0157hdf c ,sp + 6.80 Q nv s = 0.5 As f c E c 4.5, even though steel failure often occurs in those tests. In Proposal 4 (Fig. 6(d)) (which is similar to the concrete formula of PCI 6th Edition) and in ACI 318-08 (Fig. 6(e)), prediction of the type of failure typically matches better with the actual failure mode. However, the results of using the minimum of the steel and concrete formulas tend to be unnecessarily conservative for hef /d > 4.5, and the prediction may be reasonable based upon
checking only the steel formula, as mentioned above, due to the limited cases with concrete or mixed failures and the reasonable predictions made for those specific cases using the steel formula. While Table 9 and Figs. 5 and 6 include tests with both normal-weight and lightweight concrete, to be conservative, all of the recommendations discussed so far in this section could be limited to the use of normal-weight concrete. This is because for lightweight concrete, 35% of the tests have h ef /d > 4.5, whereas
209
L. Pallarés, J.F. Hajjar / Journal of Constructional Steel Research 66 (2010) 198–212 Table 8 Summary of test failure for several hef /d ratios.
# tests
S.F.a
C.F.b
M.F.c
Comments
251 140 224 167 69 322 43 348
184 18 182 20 63 139 42 160
51 63 29 85 6 108 1 113
16 54 13 62 0 75 0 75
73.33% failed in the steel 87.14% failed in the concrete or mixed failure 81.25% failed in the steel 88.02% failed in the concrete or mixed failure 91.30% failed in the steel 56.83% failed in the concrete or mixed failure 97.67% failed in the steel 54.02% failed in the concrete or mixed failure
201 75 187 99 50 236 33 253
164 9 158 11 49 120 32 137
28 41 16 53 1 68 1 68
13 20 13 35 0 48 0 48
81.59% failed in the steel 81.33% failed in the concrete or mixed failure 84.49% failed in the steel 88.89% failed in the concrete or mixed failure 98.00% failed in the steel 49.15% failed in the concrete or mixed failure 96.96% failed in the steel 45.84% failed in the concrete or mixed failure
50 65 37 68 19 86 10 95
24 9 24 9 14 19 10 23
23 22 13 32 5 40 0 45
3 34 0 27 0 27 0 27
60.00% failed in the steel 83.63% failed in the concrete or mixed failure 64.86% failed in the steel 86.76% failed in the concrete or mixed failure 73.68% failed in the steel 77.90% failed in the concrete or mixed failure 100% failed in the steel 75.78% failed in the concrete or mixed failure
All tests hef /d 4.00 hef /d
