1、AC1 ITG-3-04 Emerging Technology Series Report on Bridge Decks Free of Steel Reinforcement Reported by AC1 Innovation Task Group 3 ACI encourages the development and appropriate use of nau and emerging technologies through the publication of the Emerging Technology Series. This series presents infor
2、mation and recommendations based on available test data, technical reports, limited experience with field applications, and the opinions of committee members. The presented information and recommendations, and their basis, may be less fully developed and tested than those for more mature technologie
3、s. This report identijes areas in which information is believed to be less fully developed, and describes research needs. The professional using this document should understand the limitations of this document and exercise I judgment as to the appropriate application of this emerging technology. Joe
4、 Gutierrez Chair Gerald H. Anderson Andrzej S. Nowak This document outlines procedures for the design of bridge dech free of steel reinforcement and requirements for design and installation of straps to restrain rotation of edge beams to achieve arching action in a deckslab. Keywords: arching; bridg
5、e; composite action; corrosion; deck slab; fiber- reinforced concrete; reinforcement-free; transverse confinement; transverse constraint. AC1 Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This
6、 document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility
7、for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the ArchitectEngineer to be a part of the contract documents, they shall be restat
8、ed in mandatory language for incorporation by the ArchitectEngineer. It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. AC1 does not make any representations with regard to health and safety
9、issues and the use of this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations, including but not limited to, United States Occupational Safety and Health Administration (OSHA) health
10、and safety standards. Harold R. Sandberg Steven L. Stroh PREFACE The concept for the design of a steel-free bridge deck slab described in this report is patented. Therefore, use of the information in this document may require payment of royalties to the owners of the patents. At the time of printing
11、, the United States and the United Kingdom have granted a patent for the steel-free cast-in-place bridge deck slabs, with a patent pending in Canada. The steel-free precast slab is also patented in the United States, and the global patent is pending. Interested parties are invited to submit informat
12、ion regarding the identification of an alternative(s) to this patented item to AC1 Headquarters. Your comments will receive careful consideration at a meeting of the responsible standards committee, which you may attend. The American Concrete Institute takes no position respecting the validity of an
13、y patent rights asserted in connection with any item mentioned in this report. Users of this report are expressly advised that determination of the validity of any such patent rights, and the risk of infringe- ment of such rights, are entirely their own responsibility. The inventor of the reinforcem
14、ent-free bridge deck concept described in this report sponsored preparation of the report and provided reimbursement to the authors to assist in recovery of their costs and expenses related to travel to meetings; however, none of the authors received an honorarium. AC1 ITG-3-04 became effective Sept
15、ember 10,2004. Copyright O 2004, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or vis
16、ual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. ITG-3-1 ITG-3-2 AC1 COMMITTEE REPORT Conclusions from research conducted since the document was first written are included in Appendixes B and C. CON
17、TENTS Chapter .ti-Introduction, p. iTG-3-2 1.1-Purpose 1.2-Scope and objectives 1.3-Further research needs Chapter 3-Design methodology, p“ ITG-3-3 3.1-Composite action 3.2-Beam spacing 3.3-Slab thickness 3.4-Diaphragms 3.5-Haunches 3 .6-Transverse confinement 3.7-Strap spacing 3.8-Strap size 3.9-St
18、rap connection 3.10-Strap connection in negative moment regions 3.1 1-Edge stiffening 3.12-Reinforcement for transverse negative moment 3.13-Reinforcement in longitudinal negative moment 3.14-Fibers in concrete 3.1 5-Crack control Chapter 4-Materiaiq p. mx-7 Chapter 5-Special considerations, p. ITG-
19、3-8 5.1-Transverse edge stiffening 5.2-Skew angle 5.3-Concrete parapet connection 5.4-Cracking 5.5-Splitting stresses 5.6-Provisions for safety 5.7-Fatigue resistance of deck slabs Chapter the Crowchild Trail Bridge in Calgary, Alberta; the Waterloo Creek Bridge in British Columbia; and the Lindquis
20、t Bridge in British Columbia, which is on a forestry road and incor- porates a precast slab. A reinforcement-free precast slab has also been used in the reconstruction of a wharf structure in Halls Harbour, Nova Scotia. The research conducted on reinforcement-free deck slabs in Canada over the past
21、12 years is reported in the tech- nical literature (hcaioi: 10.1) along with the histories of bridges incorporating the new concept. Lhs listing of the published papers referenced in this document. In addition to the work done in Canada, research on the reinforcement-free deck slab is also being con
22、ducted in the United States (Seible et al. 1998) and Japan (Matsui et al. 2001). 1.3-Further research needs While the reinforcement-free bridge deck design leads to elimination of the problem of corrosion from steel reinforce- ment, it also raises several other concerns. Those concerns relate to the
23、 possibility that significant longitudinal cracking will be observed over time, and other types of cracks may lead to serviceability problems. Another area of concern is the potential for deterioration of the steel straps due to corrosion and the lack of their protection from a possible fire or impa
24、ct. To address this issues, Appendices a, 6, and i) provide supplemental information and list areas of additional research that should be considered to answer the afore- mentioned concerns. CHAPTER 2-DEFINITIONS AND ABBREVIATIONS AFRl-aramid fiber-reinforced polymer. CFRl-carbon fiber-reinforced pol
25、ymer. fibers-small-diameter filaments of materials of relatively high strength, which can be glass, carbon, aramid, or low- modulus polymer. FRC-fiber-reinforced concrete; a fiber-reinforced composite in which the matrix is portland-cement concrete, and in which the fibers are discontinuous and unif
26、ormly and randomly distributed. FRl-fiber-reinforced polymer; a fiber-reinforced composite with a polymeric matrix and continuous fiber reinforcement. fiber volume fraction-the ratio of the volume of the fibers to the volume of the fiber-reinforced composite. GFRP-glass fiber-reinforced polymer. low
27、-modulus fibers-fibers of thermoplastic polymer with a moduli of elasticity less than 1450 ksi (10 GPa), such as nylon, polyolefii, polypropylene, and vinylon. matrix-the continuous material in a fiber-reinforced concrete or polymer component that contains aligned or randomly distributed fibers. mul
28、tispine bridge-a box-girder bridge in which the bottom flange is discontinuous in the transverse direction. RC-reinforced concrete. reinforcement-in this document, this term refers to bars that are added to concrete to enhance its tensile strength. Bars provided for only crack control are not referr
29、ed to as reinforcement. strap-a linear component of steel, FRP, or other material used to provide external transverse confinement in the rein- forcement-free bridge deck slabs. CHAPTER 3-DESIGN METHODOLOGY The design methodology employing the concept described in this report relies mainly on transve
30、rse straps (Fig. 3.1 through 3.3), which may be made of steel, connected to the top flanges of adjacent girders for preventing their outward relative displacement; such displacement would normally occur when a load is applied on the slab between two girders. A combination of flange restraint against
31、 lateral movement and the cracking of concrete at the bottom of the slab leads to the formation of a shallow arch in the slab with the straps acting as ties. The degree of lateral restraint provided by the straps controls the relative lateral movement of adjacent girders and governs the ultimate loa
32、d at which the slab fails in punching. The failure load can be several times greater ITG-3-4 AC1 COMMITTEE REPORT t, (min 3 in i5 mm) Fig. 3.1-Haunch between the deck slab and top of the supporting beam. -steel strap welded to top flanges of supporting beams Fig. 3.2-Transverse confinement by direct
33、ly connected straps. Fig. 3.3-Illustration of transverse confinement by partially studded straps. than the load that causes flexural cracking of the slab, and is markedly greater than the failure load of an RC slab having the same dimensions. The design guidelines that follow are for cast-in-place a
34、nd precast bridge deck slabs in accordance with the load and resistance factor design (LRFD) format of the AASHTO Specifications (1998). This method for designing bridge deck slabs can be modified suitably to address slabs of other structures, such as parking garages and marine wharves. A cast-in-pl
35、ace or precast slab supported on beams satissling the conditions set forth as follows need not be analyzed except for negative transverse moments due to loads on the overhangs and concrete parapets. 3.1-Composite action beams in the positive moment regions of the beams. The deck slab should be compo
36、site with parallel supporting The composite action of the deck slab with the supporting beams provides the necessary confimement in the longitudinal direction of the beams (Bakht, Mufti, and Jaeger 1998). The condition for the composite action in the positive moment regions should be considered in c
37、onjunction with Srcriw .? 1 O, which deals with the composite action in the negative moment regions. For precast deck slabs, the longitudinal confinement can be provided within the panel itself, elim- inating the need for the composite action (Mufti, Banthia, and Bakht 2001). A deck slab supported o
38、n multispine box girders without external bracing experiences significant transverse moments under eccentric live loads. Such transverse moments cannot be dealt with by the arching action in the slab. Accordingly, neither cast-in-place nor precast deck slabs without reinforce- ment should be used on
39、 multispine box girders unless the box girders are prevented from excessive relative rotation by means of suitable bracing between them. 3.2-Beam spacing The spacing of the supporting beams, S, should not exceed 12 ft (3.7 m). The largest spacing of the supporting beams of RC deck slabs designed by
40、the empirical methods of AASHTO is 13.5 ft (4.11 m). Cast-in-place and precast deck slabs have been tested in the laboratory with a beam spacing of up to 13.1 ft (3.99 m). To be conservative, however, the maximum spacing of bridge girders is limited to 12 ft (3.7 m). The spacing can be increased if
41、approval is obtained from the authority having jurisdiction over the bridge. The approval process can be facilitated by conducting tests on full-scale models. The spacing of the girders for the frst reinforcement steel-free deck slab was 8.9 ft (2.71 m). Before this slab was built, its full-scale mo
42、del was tested to failure (Newhook and Mufti 1996a). Subsequently, precast deck slabs with beam spacing of 11.5 ft (3.51 m) were tested at full-scale in the laboratory and implemented in the field (Sargent, Mufti, and Bakht 1999). As noted in Chnpici. 7, the precast slab of a marine structure is sup
43、ported on beams at a spacing of 13.1 ft (3.99 m). The use of beam spacing greater than 12 ft (3.7 m) should be based on tests of full-scale models and not on the basis of analysis alone. 3.3-Slab thickness The deck slab thickness t should be at least 6.5 in. (165 mm), and should not be less than 315
44、, where S is the spacing of the supporting beams, in inches (mm). To predict the failure load of deck slabs under concen- trated loads, an analytical model was developed by Mufti and Newhook (1998b). The limiting ratio of beam spacing to slab thickness required in this condition was partially estab-
45、 lished by using this method, which has been validated with experimental results. Also according to this method and veri- fied by experiment, even a 6 in. (1 50 mm) thick slab provides sufficient strength to the deck slab supported on beams spaced at 6.6 ft (2.01 m) (Bakht and Lam 2000). To be conse
46、r- vative, however, a minimum slab thickness of 6.5 in. (165 mm) was used. Structures that are not subjected to heavy vehicular BRIDGE DECKS FREE OF STEEL REINFORCEMENT ITG-3-5 Y loads, such as parking garages, can have thinner slabs, but only after confirmatory tests on full-scale models have been
47、conducted. 3.4-Diaphragms Unless justified by rigorous analysis, the supporting beams should be connected with transverse diaphragms, or cross-frames, at a spacing of not more than 26 ft (7.9 m). The transfer of wheel loads to beams remote from the live loads takes place primarily through the transv
48、erse flexural action of the deck slab. For most bridges, the transverse moments induced in the deck slab by this mechanism are positive, with tension occurring at the bottom of the slab. For such cases, the transverse moments are sustained by the straps at the underside of the precast and cast-in-pl
49、ace deck slabs. In certain cases, an eccentrically placed vehicle may induce small negative transverse moments in the deck slab, resulting in tension in the top surface of the slab that might lead to longitudmal cracks at its top surface. To accommodate such cases, this condition requires the provision of transverse diaphragms. This requirement is very conservative and can be superseded after additional analytical investigation. Another reason for providmg the diaphragms, or cross-frames, is to provide additional redundancy in the bridge against failure of one of the girders. The condit
