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Description
DURA® UBG – U bridge girders are prefabricated using the revolutionary composite material of ultra-high performance concrete and high-carbon-high-tensile steel fibers (UHPdC). It is an excellent solution for bridge engineers looking for a cost effective, fast construction, light-weight and high-durability option for bridge span range of 16 to 60 m.

Figure 1 gives an example of a single span bridge with a total bridge span of 40 m and total width of 15 m. The proposed bridge consists of two 2.5 m wide walkways (parapet inclusive). The intermediate portion of the bridge consists of 3 notional lanes carriageway and is 10 m wide. If using Dura method, only THREE pieces of DURA® U1750BG are needed to composite with a 200 mm thick cast in-situ R.C. slab. The DURA® U1750BG are spaces 5 m apart c/c. In contrast, if using conventional method, seven pieces of the super tee girders are needed in order to has similar structural performance.

Figure 1: Example of a 15m wide and 40 m single span highway bridge
ubg-1-method

Features
  • The UHPdC used for DURA® UBG has characteristic compressive strength range between 120 to 140 MPa; characteristic flexural strength of 20 MPa and characteristic cracking strength of 7.5 MPa.
  • DURA® UBG eliminate the used of conventional steel reinforcing bars and stirrups, except at regions where jointing detail are required for composite construction. All steel fibers used are made from high carbon steel wires with tensile strength of minimum 2300 MPa.
  • Except DURA® U1000BG is pretensioned girder, DURA® U1250BG, U1750BG and U2250BG are assembled using post-tensioning methods on several segmental pieces of the same kind. For example, Figure 2 shows a 40 m span DURA® U1750BG generally composed of five segments (i.e three identical 8 m long intermediate segments and two 8 m long anchorage segments). Each 8 m long intermediate segment and each 8 m long anchorage segment weight approximately 17 tons and 20 tons, respectively.
Figure 2: Segmental detail of DURA® U1750BG
ubg-2-tensioning

Figure 3: Cross-sectional detail of DURA® UBG
ubg-3-crosshead

Table 1: Technical Data for Prestressed DURA® U Bridge Girders
    Unit UBG1000 UBG1250 UBG1750 UBG2250 UBG2750
Prestressing Method     Pre-Tension Post-Tension
Nominal Length L m 16 ~   22 23 ~   36 37 ~ 51 52 ~   64 65 ~   75
Nos. of Segment   pcs 1 2 ~ 3 5 ~ 7 8 ~   10 10 ~   14
Weight W kN/m 6.7 11.8 21.2 25 27
Sectional Area Ag x 103   mm2 283 517 909.3 971.5 1099
Neutral Axis ytop mm 589 745 1019 1379 1679
ybot mm 411 505 731 871 1071
Moment of Inertia Ixx x 109   mm4 35.2 102.1 338.1 648.18 1104.36
Section Modulus Ztop x 106   mm3 59.81 137.13 331.66 470.20 657.75
Zbot x 106   mm3 85.55 202.08 462.75 743.78 1031.14
Web Thickness BW mm 150 200 300 200 200
Girder Depth D mm 1000 1250 1750 2250 2750

Advantages of DURA® UBG

  • The total number of prestress DURA® UBG needed can be halved when compared to conventional designs (refer to Figure 1). Thus, immediate savings for the superstructural cost can be attained;
  • At least 20% of immediate savings can be attained for the substructure and foundation cost due to the lighter superstructure (especially on difficult ground condition);
  • Indirect cost saving may be realized where shallower bridge beams are needed. Figure 1 shows the conventional super T girders has a total depth of 2400 mm whereas the DURA® method has a total depth of 1950 mm. The reduction of girder depth can lead to indirect cost saving resulting from minimal cut and fill of the embankment or approach bridge levels.
  • DURA® bridge system is at least 3 times more durable than conventional method as the UHPdC used consist significant amount of discrete high strength steel fibers to stitch cracks (if any) and the girders are designed based on uncracked approach at SLS (thus significantly increasing the life span of the infrastructure);
  • Ease of handling (due to ultra-light weight when compare to conventional beams) and fast in construction;
  • Due to the absence of conventional steel reinforcements, DURA® girders can be designed and produced in much slenderer and efficient sections, with no concern for classical issues such as minimum concrete cover, to prevent corrosion of steel reinforcement;
  • No waterproofing needed as DURA® is a highly impermeable material.
  • Its natural high quality finish due to the ultra-packed nature of the concrete matrix eliminates the need for painting or protective coating (thus leading to further long term savings in cost). Micro-organism such as mould and algae will also not grow easily on this surface;
  • DURA® UBG is a highly GREEN product which supports the visionary of sustainable construction by reducing the overall CO2 emission, primary energy consumption and global warming potential of at least 25%.


 

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