LUBA RET. EX 076/077 RE-E - Laserfiche WebLink

• 4 ti.l ~t lLrl • • a^~_ =w5 HAZARDS TO THE FIRE SERVICE During a fire, any building may become inherently rt;~;~t unsafe for occupants and fire service personnel. a yn t` However, some building construction features t 4 present unique or unexpected hazards. This section Lightweight Construction Trusses are widely used in construction to span wide areas without the need for vertical supports, reducing both material and construction costs (Figure 2.24). Under ordinary conditions, trusses work well and building codes have permitted this type of construction for many years. However, trusses often fail suddenly and totally during fires. Both wood and metal trusses are made of interdependent members which all fail if one member fails. Adjacent trusses, in their weakened state, are then unable to carry the additional load and these also fail in quick succession. It is impossi- ble for crews operating at a fire to predict the time or extent of a collapse since they cannot see how many trusses are affected, which components, and to what extent. Wood trusses have less mass than solid lumber, which greatly reduces the "extra" wood compared to solid joists that burn through more slowly and provide indications to firefighters of an impending collapse. The higher surface area-to-volume ratio of trusses compared to joists allows trusses to burn more quickly. In addition, the metal gusset plates that hold wood truss components together may fail quickly as fire consumes the wood in which the gusset teeth are shallowly embedded. Many firefighters have been killed in collapses attributed to trusses, particularly wooden ones, since the 1970s. Incident commanders and/or safe- ty officers typically consider the presence of trusses in their fireground risk analysis. Marking these buildings that include trusses makes this informa- tion immediately available to firefighters. The State of New Jersey requires this as a direct result of five firefighters losing their lives in Hackensack in 1988 (Figure 2.25). Another component used to maximize construc- tion efficiency is the wooden I-beam. Similar to trusses, I-beams eliminate extra wood, thereby pro- viding less warning prior to failure under fire condi- tions. However, they lack the metal gusset connec- tion plates that appear to be at the root of many wood truss failures. discusses these hazards. wvl*~q TRUSS BOWING P,I~iJ's11fi1R"is 1!lilSfl:~~'t~i usa- airb:._,:p ':b o~a;e~.tr,.,c .d'~'~:!jud.rtn.a.eL;. pn~ad•'ime;a.ensrri nw~»'... :-iC-N"~*"U=44 irnW4QiF1c4 t:WM4*+'tva.~as'] cams astir. ilm tta¢. <41e Via ~•Qf.ur31t7 ±eES V'~i c^..e `Lr ~:rEt~ah't'4SYtw ttn'x-.Lb...v al~t6Ci+~aad~sa I+~,t!E~u~tin'`'s J _ t3.'~'T Zr+ t1: _•G'~F. ,3.3 9.•!V }l4TS 9.~Tw {'+J [di:3.T.i^:. !"'1~!•SS 2 inn" ~ . 8ibz:~is Y;h (Fig. 2.25) New Jersey truss building identification emblems. 26 0J11L"11 Occupational Safety and Health Administration 142 (Fig. 2.24) Building with wood truss construction. The adjacent finished building shows no indication from the exterior that wood trusses were used in its construction.