arched architecture ceiling glass glazing roof skylight truss frame attached bolted durability durable firm frame gray grey roofing see-through steel steel roofing frame strength support trusses angles black-and-white building buildings cambodia concrete construction construction-work dangers daylight distance distant framework galvanised galvanized greyscale metal metalic monochrome multi-storey multi-story people ribbed ribbing risks risky roof-trusses safety sheeting sheets shelter sheltered structural-work structure upper-storey upper-story workmen angle-iron angled background bolts braced bracing building-construction building-site building-work color coloration colors colour colours connected connecting constructing frames house joined light metalwork New open preliminary-framework reinforced reinforcements reinforcing secure shadows solid space spacious strong sunlight unfinished