Vulnerability Assessment of Arizona's Critical Infrastructure



|[pic] |10th International Conference on Short and Medium Span Bridges | |

| |Quebec City, Quebec, Canada, |[pic] |

| |July 31 – August 3, 2018 | |

Optimized Ultra-High Performance Concrete (UHPC) Decked I--Beams in Ontario

Tadros, Maher K.1,3, Sevenker, Adam1, Gardonio, Don2 and Loh, Philip2

1 e.construct.USA, LLC, USA

2 FACCA Incorporated, Canada

3 maher.tadros@econstruct.us

Abstract: Ultra-high performance concrete (UHPC) was introduced in North America about 25 years ago. Due to the high cost of the material and the limited sources of acquiring it, it has mostly been used in joints between precast elements and in few subsidized projects. In the past several years, generic mixes have emerged. The significantly reduced costs of generic mixes, and the more readily available high strength steel fibers used in the mixes, has allowed designers to begin thinking of optimized bridge products that could allow for UHPC products to be cost-competitive on an initial cost basis. Obviously, the material’s toughness and long-term durability would make it even more attractive on a life-cycle cost basis. This paper will look at the design developments of UHPC for its use in structural bridge components. The structural engineering firm, e.construct (Omaha, Nebraska, United States), has been retained by the concrete production company FACCA Incorporated (Ruscom, Ontario, Canada) to design structural components based on local interest for new developments utilizing UHPC. Through a technology transfer joint venture agreement between FACCA Incorporated and Dura Technology (Ipoh, Malaysia), the Dura UHPC is batched using local North American raw materials where available. Subsequently, e.construct has designed a decked NU 1000 girder to be installed at a new privately-owned vehicular bridge in Shanty Bay, Ontario, Canada for demonstration and evaluation.

1. Introduction

Ultra-high performance concrete (UHPC) was first introduced as Reactive Powder Concrete in the early 1990's by employees of the French contractor Bouygues (Richard 1994). When introduced, it came in two classes, Class 200 MPa (29 ksi) and 800 MPa (116 ksi). Since then, much research has been performed by the FHWA (Russell 2013) in the United States, and other countries around the world. They include Australia, Austria, Canada, Croatia, France, Germany, Italy, Japan, Malaysia, the Netherlands, New Zealand, Slovenia, South Korea, Spain, Switzerland and the United Kingdom. In the US, several states have expressed interest in introducing UHPC in their bridge projects, supported by FHWA research as well as research done by their local universities. Most notably Virginia has produced I-beams with UHPC. Iowa has built two bridges with UHPC beams and one with a UHPC deck. A significant interest has recently been directed at using UHPC in longitudinal joints between precast concrete beams. To the authors’ knowledge, it is the only application being considered in Canada in transportation engineering at this time.

It appears that the high cost of UHPC has discouraged owners from implementing use of this outstanding material in applications beyond the initial demonstration projects most of which had been subsidized by government technology implementation programs. The exception to this trend has been the significant success of the DURA Technology (DURA) in Malaysia. Over 100 bridges have been built in that country since 2010. Motivated by the success in Malaysia, a number of attempts have been made in the US and Canada to expand the implementation of UHPC beyond the recent applications in joints between precast elements.

The outcome of one of the programs is the focus of this paper. It has been sponsored by the Ontario Contractor, FACCA, Inc., and the engineering design performed by Dr. Tadros, the original developer of the popular NU I-beam, and his company, e.construct.USA, LLC. The goal was to help convert the NU I-beam to a product which fully incorporates UHPC. FACCA also engaged Dr. Jackie Voo, of the Malaysian company DURA, to give advice about implementing the technology he has successfully used in Malaysia. Thus, a strong team was formed including the original developer of the NU I-Girder, the most successful implementer of UHPC, and a versatile contractor who has been successful in precasting concrete bridge products and building bridges with them. FACCA also has the additional advantage of having the ability to design and produce steel forms for the precast products.

This article provides a summary of the steps taken to develop the UHPC Decked I-Beam (UHPC DIB). It gives a summary of the challenges faced in structural design and how they were overcome. It discusses the foundation for further developments in North America where, unlike other regions of the world, pretensioning is more cost-effective than post-tensioning.

2. What is Ultra-High Performance Concrete?

There is no universal definition of UHPC or even its name. It appears that a commonly used name and definition in the US is: “UHPC-class materials are cementitious based composite materials with discontinuous fiber reinforcement, compressive strengths above 150 MPa (21.7 ksi), pre- and post-cracking tensile strengths above 5 MPa (0.72 ksi), and enhanced durability via their discontinuous pore structure” (Graybeal 2011). In Canada, the CSA includes two categories of UHPC, 120 and 150 MPa, while the MTO specifications call for 130 MPa closure strip strength. In comparison, conventional concrete is without fibers and is assumed to have compressive strength of 28 to 69 MPa (4 to 10 ksi).

The ingredients of UHPC mix vary. The early mixes generally consisted of about 700 kg/m3 (1200 pounds/yd3) of Portland cement, 25 percent of silica fume, 25 percent of silica powder, and fine sand with maximum grain size of 0.8 mm (0.03 in.). A very low water/binder ratio of 0.16-0.20 is used. For flowability, a large quantity of high range water reducer must be used. Steel fibers in the amount of about 2-2.5 percent by volume are used. The fibers are cut from very fine, 2500 MPa (360 ksi) wire. Other mixes have been developed; for example, one mix used local aggregates at a cost of about 10 percent of the early UHPC mixes (Tadros 2009). However, it does not strictly meet the 150 MPa strength definition of UHPC by FHWA, as the compressive strength is only 124 MPa (18 ksi).

3. Factors Inhibiting Widespread Use of Ultra-High Performance Concrete

The original pre-bagged product had low tolerance specifications. The steel fibers had been, and still are, the most expensive ingredient. As a result, the unit cost was relatively high. In addition, the UHPC was expected to be mixed in high-energy mixers for 8 to 17 minutes, plus another 10 minutes for loading the mixer and unloading the mix into a ready-mix truck. However, mixing of UHPC can be performed using conventional mixers, as long as high energy input is provided (Graybeal 2011). Temperature of the mix, due to increased mixing time, can be controlled through use of ice-water.

Upon placement, the product is cured for at least 48 hours of high, 90°C (194°F), temperature. Some of the original mixes were also required to be cured in high pressure chambers. This is inconsistent with standard practice of 12-16 hours over-night curing with maximum temperatures of 70°C (160°F). Loss of productivity and high materials costs could result in a premium of nearly 400 percent of the cost of conventional concrete. This sharp increase cannot be offset by the anticipated reduction in total quantities. It has been demonstrated that an optimized mix can achieve the required strength without the originally required heat or pressure curing (Wille 2011).

An effort is urgently needed in North America to publish a companion document to the Canadian Standards and AASHTO Specifications for design and construction with UHPC. Australia, France, Japan and most recently Switzerland have already published design recommendations.

4. The Malaysian Experience

The introduction of UHPC in Malaysia was started by a couple of engineers in 2006. The company DURA was co-founded by Dr. Voo after he completed his Ph.D. in Australia on UHPC under Professor Stephen Foster who had been championing UHPC in Australia. Interestingly, Australia has stagnated since the construction of its first bridge, the Shepherd Gully Creek Bridge, in 2003. The Australian experience has paralleled that in the US and Canada where small demonstration bridges were not followed by the acceptance hoped for. DURA’s pioneers started with an intensive research program from 2006 to 2010, supported by the Malaysia Public Works Department. The research program yielded important optimization factors:

1. The constituent materials were reduced to cement, silica fume, sand, superplasticizer and water. Further, relatively low cost steel fibers were identified. As a result, the original $2600/m3 ($2,000/yd3) cost was reduced to about $600/m3 ($460/yd3)

2. A large, 12 m3 (15.7 yd3) geometrical volume mixer is used. The products are sized such that they can be produced with only one batch, i.e. limited to about 20 tonnes (22 tons). There is no waiting for the next batch, no concern for differential setting time, thermal gradient or shrinkage. There are counter-intuitive benefits to making relatively small pieces. The concrete is mixed in one cycle using the large mixer. The elements can be made in a small indoors facility. They can be shipped in enclosed trucks and ship containers. They can be handled at the jobsite with small equipment.

3. Three standardized cross section shapes: pretensioned decked I-beams for short spans, segmental U-girders for medium spans, and segmental box-girder for long spans. The longest span constructed to date is 100 m (328 ft).

4. Use straight pretensioning where possible. However, most applications involve spliced post-tensioned beams, using straight bottom flange post-tensioning. The segment interfaces are match cast, with shear-keyed joints.

5. Require each batch to be tested for 1 day and 28 days average compressive (cube) strength of 70 MPa (10 ksi) and 165 MPa (24 ksi), respectively, and average tensile strength at 28 days of 25 MPa (3.6 ksi).

6. Most significantly, perhaps, is that curing is simplified such that the standard precast prestressed concrete one-day cycle is maintained. Once the strands are detensioned, the product is subjected to additional curing without losing production efficiency.

These measures have resulted in highly successful and rapidly growing UHPC bridges, with lower initial cost than conventional construction and with life expectancy far exceeding the 100 years desired by the design community. The number of completed bridges has increased from 1 bridge in 2010 to an anticipated number in 2018 of 132 bridges.

1. Example Bridge (Voo 2014)

The Sungai Nerok Bridge has three 30 m (98 ft) long spans and is 15 m (49 ft) wide. Each span has 10 beams spaced at 1.5 m (4.9 ft). Each beam was made of two identical deck bulb tee halves, Figure 1, spliced with 19-15.2 mm (0.6 in.) diameter bottom PT tendons and 4-15.2 mm (0.6 in.) top tendons. Each beam weighed 29 tonnes (32 tons). The web was only 100 mm (3.94 in.) wide. It had no reinforcing bars expect at the ends for PT anchorage. The flange connections are made with conventional reinforcement and cast-in-place UHPC closure pours.

[pic]

Figure 1: Deck bulb tee section used in the Sungai Nerok Bridge, courtesy DURA Technology

5. Conceptual Development of the FACCA Sponsored Decked I-Beam

The NU I-Girder has been successfully used on numerous bridges in the US and Canada. The largest known girder was the NU 2800 built in Calgary, Alberta to span 65 m (213 ft). Based on the author’s experience, it was felt that the number of strands was not a target for optimization. The lower weight of a reduced cross section would automatically result in somewhat fewer strands. Also, use of the 15.2 mm (0.6 in.) diameter strands would be retained in this optimization step. We definitely believe that use of 17.8 mm (0.7 in.) diameter strands would be a more suitable size for UHPC but, we decided not to emphasize this point at this time, and to allow more time for the 17.8 mm (0.7 in.) strands to be more widely available in the next several years.

A beam having the general shape of the NU I-girder was found to be a reasonable starting point. The Federal Highway Administration (FHWA) and the state of Iowa have successfully used a waffle slab deck. This inspired our team to try to use a similar ribbed slab deck system that is integral with the web and bottom flange. Several trials produced the section shown in Figure 2.

[pic]

Figure 2: 1000 UHPC Decked I-Beam with Variable Top Flange

As the team attempted to develop the shape to a family of sizes for spans up to 60 m (197 ft), we had to make the top flange large enough to accommodate the longer spans. As a result, it was decided to keep the same shape of top flange, bottom flange and web width. Thus the variables for various sizes are:

1. The total depth of 1000, 1500, and 2000 mm. Figures 2, 3 and 4, respectively.

7. The top flange width (B1) of 1000, 1500, 2000, 2500 and 3000 mm.

8. The bottom flange can be blocked out to produce a narrow bottom flange in order to save concrete volume for designs that do not require the full bottom flange.

The other series of girder shapes are shown in Figures 3 and 4.

[pic]

Figure 3: 1500 UHPC Decked I-Beam with Variable Top Flange

[pic]

Figure 4: 2000 UHPC Decked I-Beam with Variable Top Flange

6. The Demonstration Bridge

A section size was developed for a 15 m (49 ft) span would lead to a total depth of 1000 mm (39.3 in.); the shortest of the family of girders. The overall girder height of 1000 mm consists of a bottom flange similar to the NU I-Girder for placement of prestress strand, a thin web measuring 100 mm (3.9 in.) in width, and a variable width waffle deck top flange. Development of the 1000 mm girder forms and small scale testing is currently underway with plans to install a new privately-owned vehicular bridge in Shanty Bay, Ontario, Canada for demonstration and evaluation later this year. Note that the 1000 mm depth is capable of spanning longer than the 15 m span of the demonstration bridge. It was selected with the intention to have a series of sizes covering spans up to 60 m (197 ft).

The demonstration bridge will be a two lane 9.8 m (32 ft) wide bridge with a single span of 14 m (46 ft). It will consist of four 1000 mm deep girders at 2475 mm (8 ft) spacing. The decked section eliminates deck forming at the bridge site. Instead, the girders will be joined together with three longitudinal UHPC closure pours. The typical joint detail, Figure 5, consists of a 200 mm (7.9 in.) wide gap with an additional 50 mm (2.0 in.) keyway in each girder flange. The keyways ensure load transfer from one flange to the other and the 200 mm wide gap allows for splicing of transverse reinforcement within the joint for deck continuity. It is important to note that the development length and rebar splice length in UHPC is reduced significantly because of the concrete’s material properties. The 150 mm (5.9 in.) splice detail provided is adequate for reinforcement up to 20M (#6) bars (Graybeal 2014).

[pic]

Figure 5: Typical Joint Detail

The integrated deck (top flange) incorporates details of a waffle slab to minimize the quantity of UHPC material. The transverse ribs are spaced at 500 mm (19.7 in.) to house the transverse deck reinforcement and the longitudinal rib locations are based on bridge geometry.

The web has the most significant impact on concrete quantities and girder weights. In some applications in Ontario, typical girder products have webs 150 mm or wider. This product has a web which is reduced to only 100 mm providing just enough space for a single leg vertical bar (stirrup) with sufficient cover on each side; should shear reinforcement be required. For the bridge layout and the load conditions of the demonstration bridge it was found that the beam ends require some conventional reinforcement for local effects due to prestressing, but otherwise no additional shear reinforcement is required.

The bottom flange is designed to be able to hold up to 60 – 15.2 mm (0.6 in.) diameter strands at 40 mm (1.57 in.) spacing, or up to 42 – 17.8 mm (0.7 in.) diameter strands at 50 mm (2.0 in.) spacing. Each girder of the demonstration bridge will only require 14 – 15.2 mm (0.6 in.) diameter prestressed strands. Later, it was decided to block out 215 mm (8.5 in) on each side of the bottom flange from 810 mm (31.9 in.) wide down to 380 mm (15.0 in.). This resulted in two benefits: (1) less UHPC material is required reducing production cost and product weight and (2) the prestress strands are concentrated near the web area reducing local stress distribution and avoiding possible cracking due to splitting forces.

1. Beam Design

In service conditions, design codes allow for tensile stresses in concrete to be as high as 7.5√f’c for concrete without fibers. Current codes use a simple formula based on concrete compressive strength. If code limits were applied to UHPC with 150 MPa (21.75 ksi) compressive strength without consideration of the fibers, the acceptable tensile strength of the UHPC would be approximately 7.5 MPa (1.1 ksi). Testing has shown that with inclusion of fibers in UHPC, tensile strengths over 25 MPa (3.6 ksi) can be obtained.

For the decked girder in the demonstration bridge, design was limited to 10 MPa (1.5 ksi) at the time of release and 15 MPa (2.18 ksi) final. Concrete stress at the time of release showed no strand debonding was required. Additionally, the stresses under service load conditions did not control the design. Instead, design was controlled by flexure at ultimate load conditions.

The benefit of UHPC in flexural design takes advantage of its high compressive strength coupled with the concrete’s tensile strength to allow in some applications for lower amounts of mild reinforcing. For compression, the traditional rectangular stress block design appears to be adequate although the ultimate strain of 0.003 may be too conservative. The high compressive strength results in a small compression block which can be used to reduce section dimensions and optimize products. More important to the design is the tensile strength provided by the fibers. The need for mild reinforcing may be able to be reduced by utilizing the strength of the fibers.

The flexural strength design in the longitudinal direction was performed the same as a typical precast prestressed member. The additional strength gain due to the UHPC fibers was conservatively ignored. This simplified the analysis at a cost of only a couple of prestressing strands.

Precast prestressed concrete bridge girders, however, are only prestressed in the longitudinal direction, the direction of traffic on a bridge. Thus, rebar must be used in the transverse direction, across the width of the cross section. Flexural design in the transverse direction was found to benefit more from the fiber strength. The deck design is discussed further in its own section.

Unlike in flexural design where the benefits of the fibers are outweighed by prestressing strand, UHPC provides huge benefits to a member in shear design. In a typical design, shear is resisted in part by the concrete, in part by steel reinforcement and in part by any vertical prestress force which may be present. In UHPC there becomes an additional component with the existence of fibers making it possible to completely remove, or at least greatly reduce, the amount of mild steel shear reinforcement.

Since current design specifications do not provide any provisions for shear design using UHPC, design procedures refer to the publications by Crane (2010) and Graybeal (2005) to account for the shear capacity due to the fiber contribution in which a rupture residual stress, frr, equal to 6.9 MPa (1000 psi) is recommended. The rupture residual stress is taken as the extreme fiber tensile stress carried between first cracking and a crack width of 0.3 mm during a modulus of rupture test. This fiber resistance was considered in design by adding the Vf to the factored shear resistance in CSA Article 8.9.3.3 as shown:

[1] Vr = Vc + Vs +Vp + Vf

In which the total shear resistance is arithmetic sum of the shear resistance provided by the concrete, reinforcing steel, the component of the effective prestressing force, and the post-crack fiber strength, respectively.

Where,

[2] Vf = φcbvdvfrrcotθ

It was found that the inclusion of fiber strength for the specific load conditions of the demonstration bridge can be used to completely remove all vertical shear reinforcement within the web except for requiring some conventional reinforcement at the beam ends for strand local effects.

Horizontal interface shear design considered the fiber resistance in a similar manner. The fiber rupture residual stress, frr, was added to the factored shear resistance on the plane in CSA Article 8.9.5.1 by treating it the same as the mild steel reinforcement stress, σ, in CSA Article 8.9.5.3. The limit imposed on the shear resistance of 6.5 MPa (0.95 ksi) or a quarter of the concrete compressive strength was ignored. It is not believe that this limit should be enforced when designing with UHPC.

[3] v = φc(c + μ(σ + frr))

Principal tensile stress checks have traditionally been used to verify the adequacy of webs of segmental concrete girder bridges. This check has recently been introduced to bridge types other than segmentally constructed bridges. For this reason, the diagonal tension in the web at the critical location (L = dv cot θ) was analyzed. For the demonstration bridge, the largest tensile stresses were found to occur in the web of the girder just above where the 100 mm web begins to transition into the curved fillet of the top flange and that the maximum tensile stresses resulted in much less than the assumed allowable stress of 15 MPa.

2. Deck Design

The UHPC waffle deck slab is designed to be cast integrally with the girder having concrete ribs spanning in transverse and longitudinal directions. The width of transverse and longitudinal ribs was chosen based on the side cover requirements for the reinforcement with tapering of the rib for easy removal of panel formwork. The reinforcement needed to resist the design wheel loads is provided in the ribs along both directions. The reinforcement required in the transverse direction determines the transverse rib spacing. The longitudinal rib spacing is determined by the bridge layout and the girder spacing. It has been recommended to limit the transverse spacing to 300 mm (11.8 in.) in order to maintain one rib underneath a wheel at all times and limit any local damage to the flat plate and control cracking of the panel under service loads. However, pending full-scale testing, the authors believe that utilizing the material properties of the UHPC can allow the rib spacing to be increased to 500 mm (19.7 in.).

The thickness of the UHPC flat plate connecting the ribs at the top of the UHPC waffle deck panel is determined by the punching shear capacity of the plate between the ribs, cover requirements of top transverse and longitudinal reinforcement, and any anticipated surface wearing over time. With the limited data available on the punching shear capacity of UHPC, a 75 mm (2.95 in.) thick flat plate is provided to prevent a punching shear failure between the ribs for the design truck load. Based on an experimental test completed at Iowa State University (Aaleti 2013), the punching shear capacity of a 63 mm (2.5 in.) thick UHPC plate was found to be 6.9 MPa (1000 psi). This result yields a punching shear capacity of 890 kN (200 kips) under a typical truck tire dimensions of 250 mm by 600 mm (10 in. by 24 in.).

The design of the longitudinal beam did not consider the fiber strength of the UHPC as the strength gained from the fibers did not provide significant savings toward the reduction of prestressing strand. However, the waffle deck is conventionally reinforced and does not benefit from prestressing like the longitudinal direction. Therefore, the fiber strength was taken into account for flexural strength design.

The procedure described in the FHWA Report (Aaleti 2013) was utilized to determine the nominal moment capacity of a beam. This procedure requires an iterative process and depends on the assumed method of failure (compression or tension controlled). The flexural analysis showed that 20M (#6) bars at 500 mm (19.7 in.) spacing at the bottom of the ribs, see Figure 6, satisfies transverse positive moments due to the design truck. For negative moment, it was determined that the fiber capacity was adequate assuming a relatively low resistance factor. However, for the sake of redundancy, and pending full-scale testing, it was decided to also include 20M (#6) bars at 250 mm (9.8 in.) spacing in the top of the deck.

[pic]

Figure 6: Typical Deck Cross Section (Section A)

7. Future Developments

The authors have developed a series of UHPC Decked I-Beam sizes for possible use for spans ranging from 15 to 60 m, see Fig. 7. Three standard depths are proposed: 1000, 1500 and 2000 mm. The forms for the bottom flange and web would be the same for all shapes, with an extension block added for beams deeper than 1000 mm. The member width will depend on the total bridge deck width. It was decided to develop span capacities for top flange widths of 1000, 1500, 2000, 2500 and 3000. In actual design, any width between these standard values is possible by adjusting the rib slab blockout lengths and by blocking out the top flange edges.

Because of the high cost of UHPC materials, it was decided to have the option to block out the edges of the bottom flange to create a width of 380 mm instead of the full width of 810 mm. This decision would be made by the bridge designer based on the total number of strands required.

It should be recognized that use of 0.7 in. (17.8 mm) diameter strands would add about 35 percent prestressing force per strand, and a commensurate amount of span capacity. However, this paper only deals with 0.6 in. (15.2 mm) strands as an interim solution until the larger size strand becomes more readily available on the market.

Based on preliminary design, it was determined that the 1000, 1500 and 2000 mm deep beams can span up to 37 m, 48 m, and 59 m (121 ft, 157 ft, and 194 ft), respectively. These span limits are based on satisfying serviceability and strength limit state requirements in CSA. It should be cautioned however, that use of UHPC results in lighter members that could have more critical vibrations under vehicular traffic than conventional concrete bridge beams. Although, the spans given here were checked for deflection using AASHTO Code provisions and were found to satisfy the (span/800) live load deflection limit, no studies have been undertaken relative to vibration characteristics.

Another UHPC product, a hollow box shape, is in the development stages and is intended to provide very shallow structural depth while maintaining good deflection/vibration behavior. It will serve as an alternate to the conventional concrete adjacent box beam system if shallow depth is critical. However, because of the anticipated hollow box shape of the product, it will be harder and more expensive to make than the Decked I-Beam product. More information will be presented when development is complete.

8. Recommendations and Conclusions

Following the design of the demonstration bridge, it was concluded that the proposed shape satisfies the design criteria as currently known for UHPC. The bottom flange can house more strands and have longer span capacities. The web width is only 100 mm, while this theoretically meets design requirements it should be tested experimentally for shear and diagonal tension behavior and for stability during unbalanced erection loading.

Summarized below are some specific areas that might be worth further research for a variety of reasons, such as precast production, cost savings or code development.

1. According to FHWA, UHPC should not see load application below 100 MPa (14 ksi) compressive strength. This includes transfer of the strand forces at the time of release. The time required to reach 100 MPa may require the product to remain in the precast bed for several days slowing production turn-around.

2. Tensile strength at release used in calculations was assumed to be proportional to compressive strength gain. According to FHWA, tensile strength within UHPC develops faster than compressive strengths, but no guidance is provided. While debonding of strand was not required in this example with the proportional tensile strength assumption, future products may require debonding unless guidance for using higher tensile strengths is developed.

3. Limited data is available on the punching shear capacity of UHPC. Additional data on punching shear may allow the deck “plate” thickness to be reduced, leading to a significant reduction in the amount of UHPC material required.

4. Further research into prestressing local effects utilizing the tensile strength of UHPC could led to a reduction of the end bursting and strand confinement reinforcement, specifically the requirements of CSA Article 8.16.3.2.

5. A number of creep tests have indicated that the creep of UHPC is much less than conventional concrete (Russell 2013). Lower creep values will result in reduced prestress losses which can be detrimental if relied on to reduce stresses in restrained members. More testing should be performed to get a better handle on this material property.

6. The CSA ULS8 with TL-2 crashing loading does not control. The capacity provided in the deck overhang seems to justify up to a TL-4. However, testing is recommended before going to the higher level.

7. The proposed series of UHPC Decked I-Beams (UHPC-DIB) is shown to be applicable to spans up to 60 m. These shapes offer ease of production and construction and superior long term performance.

8. Efforts are underway to develop a very shallow product for short spans that meets all the deflection and vibration requirements of CSA while using shallower structural depth than the UHPC-DIB and the current conventional concrete box beams. It is expected to cost more than the UHPC-DIB but, it will be used for cases where special site requirements for structural depth must be satisfied.

Acknowledgements

The authors thank FACCA, Inc., Ontario, for financial support of the study reported in this project. The employees of FAACA have demonstrated ingenuity in creating a forming system for this unique UHPC-DIB shape that allows the product to be made in one stage without a “cold” joint. A number of MTO personnel have provided the motive behind the development of the UHPC-DIB and continuing support of the progress made so far. William Nickas, Director of Transportation at the Precast Prestressed Concrete Institute (PCI) has been an inspiration and a strong driving force for precast industry adoption of the new and exciting UHPC material in full members, not just joints. Dr. Amgad Girgis and Dr. Micheal Asaad of e.construct contributed valuable information to the development of the UHPC-DIB system.

References

American Association of State Highway and Transportation Officials (AASHTO). 2014. AASHTO LRFD Bridge Design Specifications. Washington, D.C. American Association of State Highway and Transportation Officials.

Aaleti, Sriram, Bradley Petersen, and Sri Sritharan. 2013. Design Guide for Precast UHPC Waffle Deck Panel System, including Connections. Publication No. FHWA-HIF-13-032. National Technical Information Service, Virginia, USA. 29-65.

Canadian Standards Association (CSA). 2014. Canadian Highway Bridge Design Code. Canadian Standards Association.

Crane, Charles Kennan. 2010. Shear and Shear Friction of Ultra-High Performance Concrete Bridge Girders. Georgia Institute of Technology. Atlanta, Georgia, USA.

Graybeal, Ben. 2005. Characterization of the Behavior of Ultra-High Performance Concrete. Ph.D. Thesis. University of Maryland, College Park, Maryland, USA.

Graybeal, Ben. 2011. Ultra-High Performance Concrete. TechNote, FHWA-HRT-11-038, Federal Highway Administration, McLean, Virginia, USA.

Graybeal, Ben. 2014. Design and Construction of Field-Cast UHPC Connections. Publication No. FHWA-HRT-14-084. National Technical Information Service, McLean, Virginia, USA.11-16.

Richard, P., and Cheyrezy, M.H. 1994. Reactive Powder Concretes with High Ductility and 200-800 MPa Compressive Strength, ACI, SP-144(24), San Francisco, California, USA, 507-518.

Russell, H. G. and Graybeal, B. A. Henry G. and Benjamin A. 2013. Ultra-High Performance Concrete: A State-of-the-Art Report for the Bridge Community. Publication No. FHWA-HRT-13-060, National Technical Information Service, Springfield, Virginia, USA, 171.

Tadros, M. K. and Morcous, G. 2009. Application of Ultra-High Performance Concrete to Bridge Girders. Nebraska Department of Roads (NDOR) Project Number P310, Lincoln, NE, USA, 72.

Voo, Y. L., Foster, S. J. and Hassan, M. F. 2014. The Current State of Art of Ultra-High Performance Concrete Bridge Construction in Malaysia, Proceedings of the 12th International Conference on Concrete Engineering and Technology. 12-14 Aug, Selangor, Malaysia, 95-102.

Wille, K., Naaman, A.E., and El-Tawil, S. 2011. Optimizing Ultra-High-Performance Fiber- Reinforced Concrete. Concrete International, 33(9): 35–41.

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