Introduction
Definition of a structure = “A structure is a physical system used to direct
loads from one place to another.’’
Important for structures:
- System used
- Materials
- Forces acting on the structure
- Load-bearing subsurface
History
In the course of history there was a shift from compressive systems to a
combination of compressive and tensive systems. This relates to the
development of materials.
Structural systems
Structural systems:
- Compression
o Columns, walls and arches
- Tensive
o Columns and cables
- Bending
o Walls, beams and floors
- Portal frames
o Fixed beams and columns
Structural materials
Material categories:
- Natural materials
o Known and very old
o Stone and timber
- Artificial produced materials
o Produced in factories
o Steel and aluminum
- New materials
, o Not yet understood
- Old materials
o Replaced with artificial materials
o Iron
Reinforced concrete = Concrete strengthened with rebar to take tensile
stress.
Timber has hardwood (deciduous) and softwood (coniferous). Softwood
grows faster, thus cheaper, thus most used.
Masonry (=metselen) includes: Bricks, natural stone and concrete blocks.
All can handle compression and minor tension.
Aluminum is much lighter than steel. The production process is however
energy consuming, which makes it more expensive than steel.
Stress-weight-ratio (SWR) shows the maximum allowed length of a
material.
Strength and stiffness are the most important properties of a material.
Strength (ULS) shows the possibility of collapse. Stiffness (SLS) shows the
possibility of reformation.
Structural safety
A structure is safe when the loads acting on the structure (Sd, design load)
are smaller than the resistance of the structure (Rd, design strength). ->
Sd < Rd
Since loads aren’t always the same. -> Engineers show that the chance of
failure is 10-6 or less.
Not all building functions require the same reliability. So every type of
building has its own reliability class. (Choosing a higher class is always
allowed).
Reliability classes:
1. Structures with no people present during bad weather.
2. All other buildings (Family house).
3. Structures with great financial impact and (human) damage if it
collapses.
Loads (Eurocode)
Load types:
, - Permanent (dead) loads are constantly weighing on a structure.
- Variable (live) loads are not always working on a structure (People,
snow etc.).
o Quasi permanent (Instantaneous)
o Extreme (Rarely happens)
- Accidental loads are usually loads that occur with disaster
(Earthquake).
Since live loads differ, a structure must be able to withstand the extreme
value of a variable. So for example, the highest wind speed from the last
50 years. -> Eurocode
Load combinations:
- Fundamental combinations
o Permanent load
o One extreme live load
o Other quasi permanent live loads
- Accidental combinations
o Permanent load
o Quasi permanent loads
o Accidental loads
The chances of accidental loads and an extreme live load happening at
the same time are neglectable. Thus two load combinations.
The design process
The design process starts after getting a Program of Requirements.
1. Research the site
2. Designing alternatives
3. Preliminary design: Basic dimensions and material choice.
4. Determine loads: Dead and live.
5. Calculating: Connections and material strength.
6. Designing elements and details
Difference between designing and analyzing
Analyzing refers to calculating a structure with known loads. The analysis
proves that a structure is strong enough.
Design refers to the process of determining dimensions or the amount of
rebar in columns and beams. -> Designing of members. And the amount
of bolts or length of a weld -> Designing of details.
Definition of a structure = “A structure is a physical system used to direct
loads from one place to another.’’
Important for structures:
- System used
- Materials
- Forces acting on the structure
- Load-bearing subsurface
History
In the course of history there was a shift from compressive systems to a
combination of compressive and tensive systems. This relates to the
development of materials.
Structural systems
Structural systems:
- Compression
o Columns, walls and arches
- Tensive
o Columns and cables
- Bending
o Walls, beams and floors
- Portal frames
o Fixed beams and columns
Structural materials
Material categories:
- Natural materials
o Known and very old
o Stone and timber
- Artificial produced materials
o Produced in factories
o Steel and aluminum
- New materials
, o Not yet understood
- Old materials
o Replaced with artificial materials
o Iron
Reinforced concrete = Concrete strengthened with rebar to take tensile
stress.
Timber has hardwood (deciduous) and softwood (coniferous). Softwood
grows faster, thus cheaper, thus most used.
Masonry (=metselen) includes: Bricks, natural stone and concrete blocks.
All can handle compression and minor tension.
Aluminum is much lighter than steel. The production process is however
energy consuming, which makes it more expensive than steel.
Stress-weight-ratio (SWR) shows the maximum allowed length of a
material.
Strength and stiffness are the most important properties of a material.
Strength (ULS) shows the possibility of collapse. Stiffness (SLS) shows the
possibility of reformation.
Structural safety
A structure is safe when the loads acting on the structure (Sd, design load)
are smaller than the resistance of the structure (Rd, design strength). ->
Sd < Rd
Since loads aren’t always the same. -> Engineers show that the chance of
failure is 10-6 or less.
Not all building functions require the same reliability. So every type of
building has its own reliability class. (Choosing a higher class is always
allowed).
Reliability classes:
1. Structures with no people present during bad weather.
2. All other buildings (Family house).
3. Structures with great financial impact and (human) damage if it
collapses.
Loads (Eurocode)
Load types:
, - Permanent (dead) loads are constantly weighing on a structure.
- Variable (live) loads are not always working on a structure (People,
snow etc.).
o Quasi permanent (Instantaneous)
o Extreme (Rarely happens)
- Accidental loads are usually loads that occur with disaster
(Earthquake).
Since live loads differ, a structure must be able to withstand the extreme
value of a variable. So for example, the highest wind speed from the last
50 years. -> Eurocode
Load combinations:
- Fundamental combinations
o Permanent load
o One extreme live load
o Other quasi permanent live loads
- Accidental combinations
o Permanent load
o Quasi permanent loads
o Accidental loads
The chances of accidental loads and an extreme live load happening at
the same time are neglectable. Thus two load combinations.
The design process
The design process starts after getting a Program of Requirements.
1. Research the site
2. Designing alternatives
3. Preliminary design: Basic dimensions and material choice.
4. Determine loads: Dead and live.
5. Calculating: Connections and material strength.
6. Designing elements and details
Difference between designing and analyzing
Analyzing refers to calculating a structure with known loads. The analysis
proves that a structure is strong enough.
Design refers to the process of determining dimensions or the amount of
rebar in columns and beams. -> Designing of members. And the amount
of bolts or length of a weld -> Designing of details.
