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Requirements
Process
Form
Methodisch construc%ef ontwerpen Ontwerpparameters
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Probleemdefini%e HelJ van de oplossing Einstein is quoted as having said that if he had one hour to save the world he would spend fiLy-‐five minutes defining the problem and only five minutes finding the solu%on
Oplossing Oplossingsrich6ng: 1. Probleemdefini%e op onderdelen 2. Samenhangend oplossingsniveau 3. Overtollig onderzoek 4. Ontbrekend onderzoek 5. Produc%eplanning
Artificial entelligence
Current state of SE
Start of written history
Chapter 3
Methodical approaches on structural design
Origin of mankind
40
Timeline
Methodical approaches on structural design
Figure 3.1: Timeline the past by studying the design process of famous ancient architects.
3.1 3.1.1
Structural design from past to present Timeline
In the search for an appropriate design methodology we can learn from famous ancient architects, present-day excellent structural engineers and on going developments as shown in figure 3.1. Structural engineering is the profession that deals with the frame work or skeleton of parts of the built environment such as buildings, bridges, towers, and tunnels. Originally engineering was a military activity. As time passed, the benefit of engineering in non-military activities was recognised and engineering subsequently divided into Military engineering and Civil engineering. Soon other disciplines as Mechanical engineering, Structural engineering, Environmental engineering, and others developed from Civil engineering. In the search for an appropriate design methodology we can learn from
The following requirements will be considered in the research: It is of great importance finding clearly stated design methodologies or at least design philosophies. At a time that sophisticated design tools were surely not available. Particularly excellent engineers are of interest who have competence in multiple fields, especially in the field of structural, architectural and civil engineering. Or excellent engineers, who worked in an interdisciplinary team, and had the interests and the skills to look “out of the box”. And above all, the accessibility of reliable information, straight or based upon personal writings. The objective is to find one or more viable design methods, not to strive for completeness. The following famous architects are researched on: • Vitruvius Pollio, Marcus (1st century BC), probably not excellent, but active in multiple fields and one of the few engineers writing
12.1 Deformation Ultimate Limit State For a short beam, the shear deformation is in general: ˆ V δbending = GA
151
152
Design parameters deformation uniform load q
(12.3)
!
!
H h
l
And in this specific case: δshear
Fl = GA
H (12.4)
The transition from “short” to “long” depends on the bending versus shear stiffness of the material. The transition slenderness can’t be determined by an equilibrium of foregoing shear and bending formulae, because the abstraction of bending is based upon long beam theory and the transition slenderness is beyond the validity range of this theory. Experimental results indicate the approximated transition slenderness as listed in table 12.1: Transition slenderness hl -ratio for short to long beams Beam type Concrete Steel Simply supported 2 5 Cantilevered 1 2.5
Approximated loads: Nmain, max = H <
Nweb, max =
1 2 2 qd l
(12.5)
h
� � qd · npanel − 12 · l sin α
(12.6)
Displacement due to shear deformation:
Shear deformation in cantilevered trusses
Because of the stocky dimensions, the displacement at the cantilevered end of the truss will be dominated by shear deformation, rather than bending deformation. Realising this, the design in the Serviceability Limit State should focus on shear deformation and the corresponding required section properties of the web members.
"!
Figure 12.2: Shear deformation in a cantilevered truss
δ = npanel ·
An example of a usual present-day cantilevered parallel chord building design is showed in figure 12.2.
l
l
Table 12.1: Transition slenderness for short to long beams
12.1.3
Δ !
q l
Nweb, k · lweb EAweb · sin α
= npanel ·
qk ·(npanel − 12 )·l sin α
·
��
l npanel
EAweb · sin α
�2
+ h2 ≤ δrequired (12.7)
Required section property:
Aweb, max ≥
qk ·(npanel − 12 )·l sin α
·
��
l npanel
�2
δrequired · E · sin2 α
+ h2 (12.8)
