The Technical File | Groundforce Groundforce Shorco | Technical File Issue 3.0 Box Struts - Multi-Box Type General description This family of struts comprises inner and outer telescopic steel box sections incorporating end rockers with a series of pin location holes along the length to provide an incrementally length adjustment facility. The end rockers allow a degree of strut articulation to facilitate a typical dig and push installation sequence. Multi-box struts are constructed out of sufficiently large box section steel so that lateral bucking is not a design limitation within the operating width range of the box. Consequently the axial resistance or capacity of these struts is limited by local effects such as shear strength of the 20mm diameter adjustment pin. A pair of standard rockers combine with a central oversleeve to increase their length and range of adjustment (Figure 1). Mini and narrow rockers permit narrower trenches and both incorporate a standard rocker, but no central oversleeve (Figure 2 and Figure 3). Design data Controlling section size for structural assessment: Mini/Std Narrow Inner Rocker 80x80x6.3 SHS, Grade S355 (50C) steel. Mini/Std Outer Rocker 100x100x6.3 SHS, Grade S355 (50C) steel. Standard Extensions oversleeves 120x120x8 SHS, Grade S355 (50C) steel. Connection between all telescopic components is by a 20mm 605M36T (EN16) Ø pin. Connection between rocker and the box panel is by a 40mm 605M36T (EN16) Ø pin. Bearing and side plates are all 10mm thick Grade S355 (50C) for both rockers. Components 1. 40mm dia. Pin and Clip (Ref. 1 Pin). 2. 20mm dia. Pin and Clip (Ref. 3 Pin). 3. Multi-Box Standard Rocker. 4. Strut Oversleeve (various sizes available). 9.5.3 Figure 1. Description Component Combination Pin to Pin Range (mm) Weight (kg) Allowable axial compressive force (kN) Allowable axial tensile force (kN) Standard - 690 o/sleeve 858 - 1258 47 +83.8 with a FOS = 1.6 (as limited by shear in the 20mm pin connections) Standard - 1190 o/sleeve 1358 - 1758 61 Standard - 1690 o/sleeve 1858 - 2258 75 Standard - 2190 o/sleeve 2358 - 2758 89 Standard - 2690 o/sleeve 2858 - 3258 103 -83.8 with a FOS = 1.6 (as limited by shear in the 20mm pin connections) Data table for standard strut combinations 2 4 1 1 2 3 3