Pantex ^® Lattice Girders 

Field of application 

Pantex ^® Lattice Girders have been developed for special demands in the field of tunneling. The Pantex ^® System has been extensively tested and successfully used for numerous tunnel projects throughout the world. Contrary to standard steel sections (solid-web girders, irrespective of the shape), Pantex ^® Lattice Girders are entirely integrated in the shotcrete lining.

Thus, the reinforced lining forms a homogeneous composite structure without unconsolidated areas. Porous zones and shotcrete spray shadows can be avoided. The overall result is a tunnel lining that significantly reduces ground deformations and prevents the ingress of water.

Pantex ^® Lattice Girders ensure immediate support in the excavation area. The load-bearing characteristics of Pantex ^® Lattice Girders have been proven by testing procedures which were carrried out to examine significant static load conditions. These experiments have confirmed the stability and high load-bearing capacity even when not bonded into the shotcrete layer. This is an important criterion for immediate ground support, particularly during the curing time of the shotcrete. 

Integral part of the shotcrete lining reinforcement 

Pantex ^® Lattice Girders exhibit an excellent interconnection with the shotcrete layer. The quality of the bond between shotcrete and Pantex ^® Lattice Girders is essentially determined by the mechanical properties of the shotcrete (compressive and tensile strength) and the lattice girder geometry.

The excellent interlocking of Pantex ^® Lattice Girders with shotcrete has been determined by several pull-out tests in terms of characteristic curves. These consolidated findings allow to include the Pantex ^® Lattice Girders into the design of the shotcrete layer according to the reinforced concrete concept. 

Bars, Stiffeners 

All load-bearing elements are produced according to the particular demands in tunneling:

• High strength
• Great deformability
• Well suited for welding
• Steel grade: Reinforcing or construction steel BSt 500 according to DIN 488-1 

Connections 

• Flat steel or angle steel St 37-2 or St 52-3 according to DIN 17100, depending on the girder type
• Bolts are provided in matched quality (e.g. 8.8 according to DIN 267-3) 

Quality Control 

All quality features are defined according to the theory of quality control as 5%-quantile of the basic population considering a statistical probability of W = 0,9. Materials and manufacturing of Pantex ^® Lattice Girders (particularly the welding work) are continuously controlled both by self-monitoring and external quality control. 

Main advantages for the use of Pantex ^® Lattice Girders 

• Immediate support in the excavation area
• Utilization as a template when applying shotcrete
• Easy and quick assembling, simple handling
• Optimum bond and interconnection with the shotcrete lining
• Simple adjustment and shaping to the excavation geometry
• Optimum bearing for spiles and lagging boards
• Spiles can be installed both above and through Pantex ^® Lattice Girders

Pantex ^® Lattice Girders / 3 Bars

Three bars, aligned with stiffeners, are assembled to form a girder. Thereby, the single bar can, depending on the requirements, either be arranged on the inner or outer side relative to the curvature, fitting the specific excavation geometry.

The stiffeners (also known as "spiders") reduce local buckling lengths of the bars and provide, besides a high normal and bending moment resistance, an assured transfer of the normal forces even before the shotcrete has been applied.

 ¹⁾ Cross-sectional area of the bars

Pantex ^® Lattice Girders / 4 Bars

Four bars, aligned with stiffeners, are assembled to form a girder. Due to the design of the 4-bar girder, an adjustment to fit the specific excavation geometry can easily be accomplished.

The stiffeners reduce the local buckling lengths of the bars and provide, besides a high normal and bending moment resistance, an assured transfer of the normal forces even before the shotcrete has been applied.

¹⁾ Cross-sectional area of the bars

Pantex ^® Lattice Girders / Wallplate Beams

4-bar-girders are also used as longitudinal wall plates for heading advances. They serve as bearing and template for the arch assembly.

At the same time, they can be considered as statically effective reinforcement for the base beams. The frontal connection is bending resistant.