DTM Ch 25.2 - Masonry Construction test with 100% correct answers(verified for accuracy)

Seismic upgrades indicate what? That the building is pre-33 masonry construction. They are not present on post-33 masonry buildings. Where are pre-33 seismic upgrades visible? Most often they are visible from the side and read walls. What are 3 types of seismic upgrades found on pre-33 masonry construction? 1. Concrete caps on the top of parapet walls. 2. Bond beams wherever trusses contact the exterior bearing walls. 3. Rafter tie plates wherever floor joists or roof rasters contact exterior bearing walls (in flat roof buildings). Besides seismic upgrades, what other (2) factors would indicate pre-33 masonry construction? 1. Presence of your sand-lime mortar 2. King Rows (aka Header Courses) What are King Rows (aka Header Courses)? Rows of brick where only the end of each brick is visible. In pre-33 construction, the king rows connected the inner and outer withes of stretcher courses together. Where are King Rows typically placed? They are commonly placed between every 7th to 11th row of stretcher courses of brick. What is a lintel? Support for a masonry opening, usually made of steel angles or other rolled shapes singularly or in combination. They may be either straight or arched brickwork, or a steel plate. Similar to a "header" in wood frame construction. How do lintels work? They serve as a transfer beam, spanning the top of the door or window opening, carrying the weight of the structure above it horizontally to a vertical load carrying element on each end. What significantly increases the hazard of pre-33 buildings, and why? The presence of sand-lime mortar, because it does not contain any concrete and has lost its adhesion ability over time (essentially making the walls a loose stack of bricks that are no longer glued together). How can you determine the presence of sand-lime mortar? Try scraping - Sand-lime mortar will scrape away quite easily, while concrete based mortar will not. It will also often appear badly eroded due to its age. True or False: Any building with sand-lime mortar is automatically a pre-33 structure? True True or False: Seismic upgrades increase the building's resistance to earthquakes ONLY? True; They do not increase the building's fire resistance. What was a common practice on joists and rafters in older masonry buildings, that is no longer practiced today? Fire-cut joists and rafters. The fire cuts reduced the likelihood of inward wall collapse, but once a floor or roof system collapsed inwards, it frequently exerted enough outward lateral force to cause the wall to collapse outward. This caused significant damage to the fire building AND exposures. ___ reinforce the connection between exterior bearing walls and the ends of floor joists or roof rafters. Rafter tie plates What risk does the presence of rafter tie plates decrease? They decrease the risk that exterior bearing walls will peel away from the building in an earthquake, resulting in roof and floor collapse. Where do rafter tie plates occur? They occur at regular intervals along nearly the entire length of the bearing walls, at the same height(s) that the floor(s) and/or roof systems connect to the bearing walls. What is a downfall of rafter tie plates? Due to the increased strength of connection between exterior bearing walls and floor and roof systems, an inward collapse of the floors or roof from fire damage increases the likelihood of an inward exterior bearing wall collapse. Pre-33 building owners may attempt to disguise the nature of the construction by... by having the exterior walls stucco'ed over. This makes the determination of the exact construction of the building more difficult. How can you determine the construction of a building that has been stucco'ed? Usually only the front and sides of the building are stucco'ed due to the cost of the facelift. We can inspect the rear of the building, which is usually left uncovered, to determine the true style of construction. How can you tell the difference between rafter tie plates and the end of "Tie Rod & Turn Buckle" assemblies? They both exhibit flat stock steel plate w/ threaded nut through the center. But the ends of "Tie Rod & Turn Buckle" assemblies will occur at IRREGULAR intervals, and will almost always located at heights OTHER THAN FLOOR or ROOF LEVELS. Rafter Tie Plates occur at regular intervals @ roof/floor heights. The presence of "Tie Rod & Turn Buckle" assemblies is a significant indicator of what? That the building has already begun to collapse, in extremely slow motion. (unless it is associated w/ bowstring truss or a lamella roof) What are "taxpayer" type structures? Structures that have residential units over commercial or mercantile occupancies. The first floor street frontage usually consists of large glass display windows, in which the lintel over the opening was typically a small steel I-beam supporting the weight of the wall above it. What is a tactical priority if a fire burns through the 1st floor display window of a "taxpayer" structure? Apply cooling streams to the lintel I-beam. If the fire burns through the window, the I-beam will overheat and possibly buckle, causing collapse of the wall above it. If a "taxpayer" structure's display window lintel I-beam fails, what type of collapse can you expect to occur? Because the beam is supported by 2 or more posts/columns, a 90-degree or inward/outward collapse may occur (rather than the curtain fall normally associated with un-reinforced masonry). In "taxpayer" structures, where are the doorways leading to residential units normally located? Where are secondary means of egress? In the front of the building; rear exit or rear fire escape. In taxpayer structures, if the doorway leading to residential units is blocked by fire and rear exit is not available, what are two ways you could evacuate residents? 1. Ladder the second floor near to, or directly over the fire. 2. Ladder the roof of an adjacent building and cross to the roof of the involved building, making access through the penthouse. What are indicators that collapse is about to occur? 1. Creaking or rumbling sounds 2. Crackled or bulging walls 3. Cracks which continue to grow 4. Water or smoke escaping through cracks 5. Twisted or warped columns or I-beams 6. Floors or the roof sagging 7. Floor joists or roof rafters pulling out of their attachments What should you do if operations MUST occur in area where collapse indications are found? Cease operations until shoring can be placed. What is the cheapest way to dress up a building? Installing a new drop ceiling. In some cases you may find more than one. What are two hazards of drop ceilings? 1. Each installation adds additional weight that the building was not originally designed to support. 2. The create void spaces, increasing the risk of internal expansion, which may be difficult to detect. If a truck crew cuts a heat hole and reports heavy fire in the attic, but the interior crews have opened the ceiling and have not found fire, what should they suspect/do? They should suspect multiple drop ceilings and continue opening upward until they reach the underside of the roof. If an interior crew reports heavy fire in the attic, but a heat hole in the roof yields little or no heat or smoke, what should the truck crew suspect/do? They should suspect multiple drop ceilings and continue to breach downward until the fire is found. In most cases, all types of masonry occupancies (besides apartments due to their interior bearing walls) utilized ____________ construction in order to achieve the large expanses of open space inside the building. Define characteristics of the construction. some form of roof truss construction; They were built with unprotected structural steel, heavy timber, or a combination of wood and metal materials. One of the most common types of heavy timber truss (and the most prevalent of the structures that yield an arched shape to the roof) is the ____ ____ truss. Ribbed Arch Truss What is approximate burn time of a heavy timber ribbed arch truss? Approximately 20 minute burn time In almost all cases of ribbed arch truss roofs, what might be found at each end of the roof? Why is this important? A small "hip" section, running from the truss nearest the end wall to that end wall. If the roof is seriously compromised due to age/rot/fire damage/overloading, an alternative method of ventilating is to place openings in the "hip" sections at each end and positive pressure ventilate across the interior of the roof. What should truck crews on a truss roof do if the decision is made to "go defensive"? Place a heat hole over the fire if possible, but back up one truss bay before cutting a hole. If a ribbed arch truss begins to fail, what is the safest course of action for crews operating on the roof? Travel perpendicular to the trusses back toward their escape route, rather than towards a sidewall. Traveling perpendicular to the failing truss shortens the distance traveled to a temporary safe point over the adjacent truss (since most trusses are no more than 20-30 ft apart) True or False: a bowstring truss is the same as a ribbed arch truss? False! There is a critical distinction between the two since they behave very differently under fire conditions. What are the 3 types of arched roof supports? 1. Ribbed Arch Truss 2. Bowstring Truss 3. Lamella Arch What is a bowstring truss? A truss with a heavy timber top chord and a Tie Rod & Turnbuckle bottom chord (tensile member) (unprotected structural steel). At what temperature does steel begin to elongate? 850 degrees Fahrenheit. What happens when a bowstring truss begins to elongate due to heat on the bottom chord? The elongation reduces resistance to outward (lateral) thrust created by the weight of the roof on the top chord, and may eventually result in failure of the truss. What is the risk category and approximate failure time of an arched roof supported by bowstring trusses? high risk; approximate fail time of 10 minutes. What ventilation strategy should you consider on an arched roof supported by bowstring trusses? Cutting ventilation openings in the hip sections at each end, and horizontally cross ventilating. What is a Lamella Arch (AKA Summerbell Roof)? An arch shaped roof in which the truss construction is replaced by an "eggcrate" style interconnecting series of 2X materials, which forms the support for the sheathing. The outward (lateral) thrust created on the walls is resisted by tie rods and turnbuckles. Hence, it has the same limitations as the bowstring truss roof. Do Lamella Arche roofs usually have the hip section at each end? No, with one exception at the S.E. corner of E 3rd & Alamitos. What is a general rule to determine a roof is a Lamella Arch? If the building has an arched roof but is lacking hip sections at the end, it is normally a Lamella roof (with the exception at E 3rd & Alamitos) At what percentage of roof damage should you expect a complete roof collapse in a Lamella Arch? 10-20% How many Lamella roofs are in Long Beach (that we know about)? 7 Lamella Roofs that we know about Other than arched roof, what is another type of roof support that can be found in masonry construction? Steel I-beams with conventional rafters spanning between them. If interior operations are required on a masonry building with a roof supported by steel I-beams and conventional rafters, what should be a tactical priority? Placing cooling streams on the steel I-beams, just like you would do on the steel lintels over display windows in taxpayer occupancies. As a truck company working on a roof with several different rooflines or pitches in the occupancy, what should you do for each roofline? Repeat your "diagnostics" for each roof, in order to insure you know what type of roof you are working on. This is due to the possibility that the building may have been built in stages, with different types of roof for each stage. By code, how are reinforced masonry walls built? Cells of concrete block bearing walls are to be concrete filled, and steel reinforcement bars (rebar) are required in at least every 3rd cell. True firewalls have a ___ that extends at least ___ft above the roof surface, and ___ft out from any sidewalls (if those sidewalls are of combustible construction) Parapet; 2ft; 1ft What are Fire Division Walls? Walls that subdivide an occupancy into separate fire zones, from foundation to roof. They are frequently made from the reinforced masonry. What is the difference between Firewalls and Fire Division Walls? Firewalls have a parapet that extends at least 2ft above the roof surface and 1ft out from sidewalls. Fire division walls do not have parapet walls above the rooflline or sidewall extensions. What must be present whenever there is an opening in a fire rated wall? A fire rated automatic closing door must be present to protect any openings in a firewall. What are the 2 closing mechanisms for the automatic closing doors in fire rated walls? 1. Fusible link/counterweight. 2. Electro-magnetic type. What should fire attack teams do if they need to operate through an automatic closing door in a fire rated wall? They should insure that the door is blocked open enough to prevent their hose from being pinched off if the door is activated and closes.