The Launching Gantry for precast segment erection:
After NRS entered the segmental market, expressions like "glue-as-you-go" and "turnaround" have been well recognised world-wide as cost & timesaving solutions for erecting segmental bridges. The implementation of a hinged Gantry solution has proven successful erection of spans down to 75m horizontal radius. This is applicable for both overhead and underslung gantries, and for both span-by-span and balanced -cantilever erection methods. A specially designed gantry crane is used to travel through the kinked hinges.
Design & Flexibility:
NRS can offer gantries for both overhead and underslung erection.
The design of our advanced equipment has been improved and optimized over the years, based on our wealth of experience from the various projects carried out, leading to the present systems, which is light weight, easy to assemble, practical, supported by internationally known hydraulic and cranage systems and most important, efficient in operation. The gantries can be re-used on other projects, too. Using hinges to go thru curves of as little as 75m, increases the contractor's possibility to re-use the gantry later on, almost independently of the next project's radii.
Services:
Our strong technical support team can offer services at various levels:
- Partial delivery:
- design, know-how & construction engineering
- hydraulic equipment
- launching equipment
- Complete delivery
- Consultancy & supervision
- experienced supervision
and consultation during fabrication, assembly & operation.
Hinged Gantries:
Throughout the last years, several contractors have chosen to use the special NRS - Gantries for their challenging segmental bridge projects. With horizontal radii down to 130m and span length up to 50m, the use of the special kinked overhead Gantry has proven to be very successful. For other challenging segmental projects contractors have chosen the special Hinged Underslung Gantry. Some of the Gantries supplied have up to 12 hinges and are capable of erecting simply supported spans up to 63m and horizontal radii down to 75m.
Glue-As-You-Go:
One of the special segment erection methods executed with Gantries supplied by NRS is the "glue-as-you-go" procedure for wet joint segmental bridges. This method allows a limited pre-loading of the gantry, avoiding the time consuming double handling of all the segments.
- Normally one to three segments are preloaded to the Gantry at one end of the span.
- The erection of the span starts from the other end, starting with the first segment as a guideline for the remaining segments.
- Each new segment is temporary stressed to the previous erected segment by means of temporary tension bars. This is mainly to obtain a minimum contact pressure between the segments (curing of the epoxy glue).
- When using a overhead Gantry, the last segments of the span are equipped with wider suspension beams, allowing the last segment to be turned inside the previous suspended segment.
- The whole span is finally adjusted to the
correct level (vertically) and alignment (transversally) by the Gantry,
and the permanent stressing operation can take place.
How to support/suspend:
To support the segments during erecting, hydraulic cylinders are used at underslung Gantries, while segments are suspended by means of tension bars directly to overhead Gantries.
