OBJECTIVES
David Lodge Lighting Ltd (DLLL) was commissioned by SDLS to undertake structural design calculations for 12 stainless steel catenary wires spanning between building façades along Chaloner Street, Guisborough. These wires were required to support MaxiLED Large Globe Series (DMX RGBW) festoon lighting as part of a decorative lighting upgrade within the town centre. The objective was to calculate tension loads at each building fixing point, select suitable catenary wire specifications, and provide guidance on load assumptions under wind conditions relevant to the site’s coastal proximity.
WORK CARRIED OUT
Using SDLS drawings and lighting specifications, DLLL performed detailed structural calculations to determine the required wire tension loads for each span. The calculations considered the weights of each part of the system including the festoon lighting, electrical cables and catenary wire ropes. They also considered the site specific wind conditions according to BS EN 1991-1-4:2005+A1:2010 and developed the catenary forces due to wind and ice loading.
A 5mm diameter 7×7 stainless steel wire rope, compliant with EN 12385-4, was selected for its strength, durability, and performance under projected loads. The structural assessment included all 12 spans, calculating individual forces for each end of the catenary wires due to asymmetrical fixing heights. Festoon lighting mass, wind surface area, and spacing were factored into the catenary calculations, with all tension results compiled into a detailed summary and schematic plan.
CHALLENGES
A key challenge was the asymmetric fixing point heights across the street, which required careful calculation of the relative sag heights and specific catenary forces at each end of each span. The lowest point of each catenary was checked to ensure that the minimum clearance height above ground level was provided for passing traffic.
As no ‘as-built’ span lengths or fixing point design information were provided, DLLL derived span lengths dimensions directly from plan drawings. This introduced a need for cautious assumptions ensuring conservative load assessments for safety.
RESULTS
DLLL successfully completed structural assessments and design calculations for all 12 festoon lighting spans. The recommended 5mm stainless steel wire met the safety and performance criteria, with working loads and tension forces clearly communicated for each span and fixing point. The project provided SDLS with the necessary design input to proceed with the decorative festoon lighting installation, ensuring both aesthetic impact and structural reliability. By providing clear calculation outputs and a schematic summary, DLLL enabled safe execution of the design while highlighting the need for further assessment of the building façade fixings by others.
