Mechanized Slab Casting on Launched Steel Girders

mechanized slab casting on steel girders

Incremental launching of steel girders followed by in-place segmental casting of the concrete slab is among the fastest and most efficient construction methods for composite bridges. Twin braced I-girders are used in many countries, twin box girders provide additional redundancy if needed, and a U-girder with cast-in-place concrete slab may be selected when additional torsional stiffness is required.

Long slab segments are cast with weekly cycles and one forming carriage that shuttles back and forth along the bridge. Two span segments are cast in four subsequent spans, the first pier segment is closed, two span segments are cast in the fifth span, the second pier segment is closed, and so on. Shorter segments can be cast with daily cycles and one crew with two forming carriages: one for the span segments, and one that follows for the pier closures between long span sections.

The reinforcing cage for the concrete slab can be fabricated behind the abutment and incrementally launched with the steel girder to shorten the cycle time of the forming carriages. Monolithic pours and continuous reinforcement provide superior durability and control of cracking. If needed, the bridge can be re-decked in the future with the same sequence of operations.

With extensive illustrations and case studies, Launched Bridges (2-day course, on-site, on-demand) provides exhaustive coverage of the design, construction, technology and industry trends of steel and prestressed-concrete bridges built by incremental launching. You will learn under which circumstances is bridge launching a competitive solution, will explore the other construction methods for medium-span steel and prestressed-concrete bridges, and will compare alternatives in preparation of successful value engineering sessions.

The course explains how to control self-weight bending and shear with launch noses, temporary piers and front cable-stayed systems, and provides exhaustive coverage of their design for optimized interaction with the deck. It discusses the Reduced Transfer Matrix method for parametric launch stress analysis with a spreadsheet, web stability and lateral torsion-flexure buckling of steel girders, and launch post-tensioning, deck segmentation and the organization of the casting facilities for prestressed-concrete bridges.

For both types of bridges, the course explores geometric launchability criteria, launch bearings and guides, thrust systems and how to control the movements of the deck in uphill and downhill launching. Richly illustrated with over 300 photographs of case studies, the course is constantly top-rated for material and presentation.

The course delivers a unique wealth of knowledge, learning and insights extracted from three decades of design and construction of launched bridges and Dr. Rosignoli's three books on the topic. Integrated by the bestseller Bridge Construction Equipment (2013, ICE Publishing), the second edition of Bridge Launching (2014, ICE Publishing) and many eManuals of BridgeTech, the course provides exhaustive coverage of the topic.

Dr. Rosignoli teaches this course personally, on-demand in the offices of bridge owners, designers and constructors. Addressing the needs of bridge owners, designers and constructors, the class provides an exciting occasion for face-to-face interaction with other bridge professionals and participating in a true learning experience.

Day One:

  • Introduction
  • Launch of steel and PC bridges
  • Alternative construction methods
  • Geometry requirements
  • Launch bearings and guides
  • Thrust force and launch techniques

Day Two:

  • Control and correction of launch stresses
  • Analysis of launch stresses
  • Incremental launching of steel bridges
  • PC bridges: deck segmentation
  • PC bridges: casting stages
  • PC bridges: launch and integrative post-tensioning

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