Chapter 12 - Structural Systems Flashcards
Most newer construction are of _______ construction
post and beam
What can post and beam structures be made of?
Steel, concrete, or timber columns (posts) supporting a grid of beams on which the flooring is applied
4 types of structural systems:
- Steel
- Concrete
- Masonry
- Load bearing walls
Two most common steel structural systems
- beam-and-girder
- open-web joist
In the beam-and-girder system, large members, called _______, span between columns and smaller _____ are framed into them. The ______ span shorter distances because they carry the weight of the _____.
girders beams
girders beams
Typical spans for beam and girder system
25 to 40 feet
What happens on top of the beam and girder steel framing?
covered with steel decking, which spans between the beams. concrete topping is poured over the decking
Where is beam-and-girder most commonly used?
mid to high-rise office buildings
What is a downfall of beam and girder system?
limited space between the bottom of the girder and the suspended ceiling. adding ductwork or recessed light fixtures should be reviewed
In a ________ system, joists span between beams or bearing walls
open-web steel joist
Open-web steel joist system can span
20 to 144’
what goes on top of a the beam-and-girder system?
steel decking spans between joists and a concrete slab is poured on top of the decking
Where do you see open-web steel joists?
one-story or low-rise buildings with wide column spacing
what’s an upside of open-web steel joists?
mechanical and electrical service ducts, pipes, and conduit can easily be run between the web members. suspended ceilings and other lightweight interior elements can also easily b hung from the bottom of the joists
Two main types of concrete structural systems
Cast-in-place and precast
What is cast-in-place concrete?
concrete is poured into forms where it hardens before the forms are made
What is precast concrete?
components are usually formed in a plant and shipped to the job site, where they are set in place and rigidly connected to form the structure
Most cast-in-place concrete systems utilize only mild steel reinforcing set in the formwork before the concrete is placed. However, sometimes concrete is ________
post-tensioned
What is post-tensioned?
steel cables within the concrete are tightened after the concrete sets, creating extra compression forces in the beam or slab
If a slab is post-tensioned, what can you not do?
penetrate the slab for pipes or conduit
Five basic types of cast-in-place concrete systems
- beam-and-girder
- concrete joist
- flat plate
- flat slab
- waffle slab
Beam-and-girder
similar to the steel system. slab is poured with the beams
Concrete joist system
concrete members spaced 24 or 36 inches apart. because the joists are close together, it is more difficult to drill holes for small pipes and conduit
flat plate construction
floor slab is designed and reinforced to transfer loads directly to the columns which generally do not exceed 25’ spacing used when floor to floor height must be kept to a minimum difficult to drill these types of floors because of closely spaced reinforcing
Flat slab construction
similar to flat plate except drop panels (increased slab thickness around columns) are used to increase strength
waffle slab system
(two-way joist system) can provide support for heavier loads at slightly longer spans. often left exposed and lighting is integrated into the coffers.
Three types of pre-cast concrete floors
- single tee
- double tee
- hollow-core slab
advantage of single and double tee?
easy and fast to erect single and double team members simultaneously serve as beam AND floor decking
____ is generally limited to load bearing walls
masonry
Because masonry is so expensive, it is usually used as _______
a veneer over wood stud walls or over concrete block walls
Concrete block is the common term for ______
concrete masonry unit (CMU)
Most common CMU size?
8”x8”x16” nominal (actual dimensions are 3/8” less than nominal to count for mortar)
A load bearing wall may be ___,___,or____
concrete, masonry, or wood framing
Load bearing walls are used more in commercial or residential?
residential
Load bearing walls in commercial construction are normally where?
the core
Load bearing walls in residential construction are normally where?
exterior, especially under eaves of the roof
If you need to cut into a load bearing wall for something like a door, what needs to be done?
a double header or lintel needs to be added at the top of the opening
A ________ is a force acting on a building element
building load
Three major load types:
gravity, lateral, and dynamic
What are gravity loads?
dead loads and live loads
Examples of dead loads
columns, beams, exterior and interior walls, floor, chandelier, and mechanical equipment
only time interior designer needs to consult structural regarding dead loads is
if unusually heaving partitioning (like masonry walls) or heavy equipment is being added
live loads include
the weight of people, furniture, and other movable equipment
lateral loads include
wind loads and earthquake loads
if a building is in a high-risk area for earthquakes, certain interior elements need to be detailed to resist earthquake forces. examples include
partitions that are tied to the ceiling, suspended ceilings, ductwork, lights, sprinklers, bookcases, storage cabinets, lab equipment, and access floor
when a force is applied suddenly, it’s called an _____
impact load
when a load is applied suddenly or changes rapidly, it is called a ________
dynamic load
examples of dynamic loads
cars moving in a parking garage, elevators traveling in a shaft, or a helicopter landing on a building
Interior partitions in commercial construction that attach to the structural floors above or the perimeter of the building, should be designed with _______
slip joints to allow the building to move without putting pressure on the partitions
Large building movements are accommodated by ______
expansion joints
2 rules for expansion joints
- don’t put partitions over them 2. don’t cover them up with finish materials
Easiest cast-in-place concrete to penetrate with a core drill?
beam-and-girder and one-way pan joists
One of the most common types of floor and roof construction?
concrete on metal deck
Can you do core drills in concrete on metal deck?
yes
Actual size of 2x4 wood studs?
1.5” x 3.5”
________ are horizontal repetitive members used to support the floor
joists
The space between joists is spanned with ______ or ______ 5/8” or 3/4” sub-flooring
plywood or particleboard sub flooring in prep for the finish flooring
______ is nailed to the outside of the stud wall to stiffen the wall and provide a nailing base for the exterior finish material
sheating
When openings for doors and windows are framed in wood construction, they are framed at the top with ______
lintels (also called headers)
Standard sizes for window and door headers?
double 2x4 , 2x6, or 2x8
For two-story wood construction, _____ framing is used
platform framing
Platform framing uses
wood studs on a sole plate and a double top plate at the ceiling level
If stronger members than 2x4s or 2x6s are needed, ______ can be used
glue-laminated wood members or glulams
What are glulams?
built up from a number of individual pieces of lumber, which are glued together and finished under factory conditions for use as beams, columns, purlins, and other structural components think covenant
when are glulams used?
heavy load/long spans unusual structural shapes are required and appearance is a consideration
What is a cricket?
saddle-shaped projection on a sloping roof used to divert water around an obstacle
The amount of slope of a roof is designated by its ______
pitch
roof pitches are in _____” increments
12 inches
example: 5/12 pitch
5” of rise for every 12” of horizontal projection
a machine used to cut a small opening in a concrete floor for conduit or poke-through electrical outlets
core drill
in a high-rise building, the wall generally used as part of the stucture of the building and surrounding the common building services, such as elevator and stairway shafts, toilet rooms, mechanical rooms, and the like
core wall
a stud above a door opening or below a windowsill
cripple stud
light-gage sheets of steel that are ribbed, fluted, or otherwise stiffened by the shape for use in constructing a floor or roof
decking
a mixture of portland cement, water, and sand containing enough water to allow it to be poured or pumped into joints, spaces, and cracks within masonry walls
grout
a framing member that crosses and supports the ends of joists, transferring the weight of the joist to parallel joists. these are used to form openings in wood-framed floors
header
a horizontal structural member over an opening that carries the weight of the wall above it
lintel
a piece of timber laid horizontally
purlin
the plywood or particleboard covering placed over exterior studding or rafters of a building that provides strength and a base for the application of wall or roof cladding
sheathing
a horizontal wood member that serves as the base for the studs in a stud partition
sole plate
a wood member in a floor or roof used to support a header
trimmer
a structural beam of steel having a shape whose cross section resembles the letter H. A ____ beam has wider flanges than an I-beam. These are used for beams as well as columns because their shape gives them approximately equal strength in both direction
wide-flange beam
