45179_towardssaferschoolconstruction_0 2015 - Page 88

Some hazard-resistant construction techniques Some of the key hazard-resistant construction techniques that community members can learn to identify are shown below. Construction workers will need more detailed guidance provided by well-qualified engineers. Earthquake shear ties: Reinforcing steel shear ties, shown here in red, loop around the reinforcing bars in columns and beams. The shear ties allow columns and beams to bend but not crumble apart in earthquakes. To be effective in earthquakes, shear ties need to be closely spaced where columns and beams intersect. The ends of the shear ties also need to be bent so they point inward at a 45 degree angle towards the center of the column or beam. Concrete mix proportioning: Exact measurements of cement, sand, gravel and water ensures concrete mixed on-site meets design specifications. Tie-down straps: Simple metal straps that attach roof trusses to wall frames help keep roofs from blowing off in high winds. Fire-resistant materials: Removing flammable vegetation on the ground and trimming lower branches of trees can lessen the intensity of fires near school buildings. Non-flammable metal or clay roofs can further protect schools as wildfires sweep across a site. SECTION III: CONSTRUCTION Deformed steel bars: When reinforcing steel has bumps and deformations, concrete grips to it better than when the steel bars are smooth. Foundation anchors: Plates or bars connecting columns or walls to the foundation help keep a school building from sliding off its foundation in high winds, fast-flowing water or earthquakes. Technical specifications for hazard-resistant construction ar e addressed in the International Building Code for many materials. For local materials not well covered by this code, see the guidance documents listed in the Resources for safer design box in the Community Design Stage section. 79