ATC/SEAOC Training Seminars

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29 Νοε 2013 (πριν από 4 χρόνια και 10 μήνες)

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1

ATC/SEAOC Training Seminars



Supplemental Material


Session 3

The Load Path in

Wood Frame Construction

Prepared by John R. Henry, P.E.

Senior Staff Engineer

International Conference of Building Officials

2

The Code Philosophy


The Purpose:


“The purpose of the earthquake provisions is primarily to
safeguard against major structural failures and loss of life,
not to limit damage or maintain function.” (Section 1624)



A Specific Detailing Requirement:


“Seismic and Wind Design. When the code prescribed wind
design produces greater effects, the wind design shall
govern, but
detailing requirements and limitations
prescribed in this section and referenced sections shall be
followed. (Section 1626.3)



3

UBC Section 1605:

“The Jewel in the Crown”


Rationality:


“Any system or method of construction to be
used shall be based upon a rational analysis in
accordance with well
-
established principles of
mechanics.”




Complete Load Path:


“Such analysis shall result in a system which
provides a
complete load
-
path
capable of
transferring all loads from their point of origin
to the load
-
resisting element.”


4

Specific Connection Requirements:

Seismic Zones 2, 3 & 4


Anchorage of roof to walls and columns, and of walls and
columns to foundations to resist uplift and sliding (Section
1605.2.3)



Concrete and masonry walls shall be anchored to all floors,
roofs, and other structural elements which provide support
for the wall. (Section 1605.2.3)



The anchorage shall provide a
positive direct
connection
between the wall and floor or roof (Section 1633.2.8)

5

Specific Connection Requirements:

Seismic Zones 2, 3 & 4


Connections which resist seismic forces are to be designed
and
detailed on the drawings

(Section 1633.2.3)



All parts of a structure shall be interconnected and
connections shall be capable of transmitting the seismic
force induced by the parts being connected. (Section
1633.2.5)



A positive connection for resisting a horizontal force acting
parallel to the member shall be provided for each beam,
girder, or truss. (Section 1633.2.5)



6

Specific Connection Requirements

Seismic Zones 2, 3 & 4



Collector elements shall be capable of transferring the
seismic forces originating in other portions of the building
to the element providing resistance to those forces
(Section 1633.2.6)



Diaphragms supporting concrete or masonry walls shall
have continuous ties or struts between diaphragm
chords. Added chords may be used to form
subdiaphragms to transmit the anchorage forces. to the
main cross
-
ties. (Section 1633.2.9 item 4)

7

Specific Connection Requirements

Seismic Zones 2, 3 & 4



In seismic zones 3 and 4 anchorage (of concrete or
masonry walls) shall not be done accomplished by the
use of toenails or nails subject to withdrawal nor shall
wood ledgers or framing be used in cross
-
grain bending
or cross
-
grain tension, and the continuous ties required
(above) shall be in addition to the diaphragm sheathing.
(Section 1633.2.9 item 5)



In addition, in seismic zones 3 and 4, diaphragm to wall
anchorage using embedded straps shall have the straps
attached to or hooked around the reinforcing steel or
otherwise terminated so as to effectively transfer forces
to the reinforcing steel. (Section 1633.2.8)

8

Wood Connection Requirements:


Connections and anchorages shall be provided
between the diaphragms and resisting elements.
(Section 2315.1)



All boundary members proportioned and spliced
where necessary to transmit direct stresses.
(Section 2315.3 & 2315.4)



In Seismic zones 3 & 4, collector members
provided to transmit tension and compression
forces and detailed to distribute the shearing
stresses (Section 2315.5.2)

9

Wood Connection Requirements:


Openings in diaphragms shall be fully detailed
on the plans and shall have their edges
adequately reinforced. (Section 2315.1)



Perimeter members at openings provided and
detailed to distribute the shearing stresses
(Section 2315.5.2)



In seismic zone 3 and 4, exterior exit balconies
and stairs shall be positively anchored to the
primary structure. (Section 2320.13)

10

Specific Foundation

Connection Requirements

Seismic Zones 3 & 4:


The foundation capable of transmitting design
base shear and overturning forces from the
structure into the supporting soil. (Section
1809.2)



Connection of superstructure elements to
foundation adequate to transmit design forces
to the foundation the forces for which the
foundation. (Section 1809.3)