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TitleArchitectural Structures
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Page 1

G G Schierle Architectural Structures

Page 2

G G Schierle
Architectural Structures

Excerpts
















ISBN 0-18-195009-x

Copyright © G Schierle 1990-2006. All rights reserved

Portions of this document reproduce sections from the 2003 International Building Code,
International Code Council, Falls Church, Virginia. All rights reserved.

AISC data, copyright © American Institute of Steel Construction, Inc.
Reprinted with permission. All rights reserved

USGS data copyright © United States Geological Survey, courtesy USGS




































University of Southern California
Custom Publishing
C/O Chauncey Jemes
Los Angeles, CA 90089-2540
e-mail:[email protected]
Tel. 213-740-8946
Fax: 213-740-7686

Page 113

PART IV HORIZONTAL SYSTEMS Bending Resistant

PART IV

HORIZONTAL SYSTEMS




Part III presents structure systems, divided into two categories: horizontal, and
vertical/lateral. Horizontal systems include floor- and roof framing systems that support
gravity dead- and live load and transfer it to vertical supports, such as walls and columns.
As the name implies, vertical/lateral systems include walls, columns and various other
framing systems that resist gravity load as well as lateral wind- and seismic load.

In the interest of a structured presentation, both, horizontal and vertical/lateral systems
are further classified by type of resistance controlling the design. This also helps to
structure the creative design process. Though many actual systems may include several
modes of resistance, the controlling resistance is assumed for the classification. For
example, cable stayed systems usually include bending elements like beams, in addition
to cables or other tension members. However, at least at the conceptual level, their
designed is controlled more by tension members than by bending. Therefore they are
classified as tensile structures. Horizontal systems are presented in four chapters for
structures controlled by bending, axial, form and tensile resistance. Vertical/lateral
systems are presented in three chapters for structures controlled by shear-, bending-,
and axial resistance.












11

HORIZONTAL SYSTEMS
Bending Resistant

Bending resistant systems include joist, beam, girder, as well as Vierendeel frame and
girder, folded plate and cylindrical shell. They carry gravity load primarily in bending to a
support structure. Shear is typically concurrent with bending, yet bending usually
controls the design. Though bending resistant elements and systems are very common,
they tend to be less efficient than other systems, because bending varies from maximum
compression to maximum tension on opposite faces, with zero stress at the neutral axis.
Hence only half the cross-section is actually used to full capacity. Yet, this disadvantage
is often compensated by the fact that most bending members are simple extrusions, but
trusses are assembled from many parts with costly connections. Like any structure
system, bending elements are cost effective within a certain span range, usually up to a
maximum of 120ft (40m). For longer spans the extra cost of more complex systems is
justified by greater efficiency.

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11-1 HORIZONTAL SYSTEMS Bending Resistant


Bending Concepts
Some concepts are important for an the intuitive understanding of bending members and
their efficient design. They include the effects of span and overhang, presented in this
section. Other concepts, such as optimization and the Gerber beam, are included in the
following section.

Effect of span
The effect of the span L for bending members may be demonstrated in the formulas for
deflection, bending moment and shear for the example of a simple beam under uniform
load.

= (5/384) wL4/ (EI)
M= wL2/8
V= wL/2
where

= Maximum deflection
E= Elastic modulus
I = Moment of Inertia
L= Length of span
M= maximum bending moment
V= maximum shear force
w= Uniform load per unit length

The formulas demonstrates, deflection increases with the 4th power of span, the bending
moment increases with the second power, and shear increases linearly. Although this
example is for a simple beam, the same principle applies to other bending members as
well. For a beam of constant cross-section, if the span is doubled deflection increases 16
times, the bending four times, but shear would only double. Thus, for long bending
members deflection usually governs; for medium span bending governs, yet for very
short ones, shear governs

1 Beam with deflection = 1
2 Beam of double span with deflection = 16
3 Short beam: shear governs
4 Medium-span beam: bending governs
5 Long-span beam: deflection governs



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Page 226

24-6 MATERIAL Cable/Fabric











Mast / cable details
The mast detail demonstrates typical use of cable or strand sockets. A steel gusset plate
usually provides the anchor for sockets. Equal angles A and B result in equal forces in
strand and guy, respectively.

A Mast / strand angle
B Mast / guy angle
C Strand
D Guy
E Sockets
F Gusset plates
G Bridge socket (to adjust prestress)
H Foundation gusset (at strand and mast)
I Mast










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Page 227

24-7 MATERIAL Cable/Fabric




























1














2 3

Production process
Fabric pattern
To assume surface curvature, fabric must be cut into patterns which usually involves the
following steps:

Develop a computer model of strips representing the fabric width plus seems
Transform the computer model strips into a triangular grids
Develop 3-D triangular grids into flat two-dimensional patterns


The steps are visualized ad follows:

1 Computer model with fabric strips
2 Computer model with triangular grid
2 Fabric pattern developed from triangular grid

Pattern cutting
Cutting of patterns can be done manually of automatic.
The manual method requires drawing the computer plot on the fabric
The automatic method directs a cutting laser or knife from the computer plot

Note:
For radial patterns as shown at left, cutting two patterns from one strip, juxtaposing the
wide and narrow ends, minimizes fabric waste.

Pattern joining
Fabric patterns are joint together by one of three methods:
Welding (most common)
Sewing
Gluing


Edge cables
Unless other boundaries are used, edge cables are added, either embedded in fabric
sleeves or attached by means of lacing.

Fabric panels
For very large structures the fabric may consist of panels that are assembled in the field,
usually by lacing. Laced joints are covered with fabric strips for waterproofing.


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