HomeMy WebLinkAbout10 Abbe Road (7) J
EINGINEERIN
RP RIN
August 23, 1994
John Collins
Building Inspector
South Windsor, CT 06074
REGARDING: Charbonneau House
Dear John:
Please be advised that all bracing indicated on our shop drawings is required
to complete the design. Where bracing is shown on non-repetive members, the
installation of a 1 x 4 "T" brace to 90% of the web length is acceptable to
prevent failure.
Installation of bracing is the responsibility of the installer. (See excerpt
from Truss Plate Institute. )
Sincerely,
Malcolm R. White, Jr.
Sales Engineer for
TRUSS ENGINEERING CORP.
MRW,Jr. :iel
MANUFACTURERS OF ROOF & FLOOR TRUSS SYSTEMS 181 Goodwin Sb*M P.O. Box 27 Indim Omherd, Map.01151 Tel.413-543-1298
IF
Truss Plate Institute HIB-91 Truss Plate Institute HIB-91
contractor. Thus,the Truss Plate Institute,Inc.expressly 2.2.4 Overloading roof or floor trusses before permanent
disclaims any responsibility for damages arising from bracing and/or sheathing have been installed. Most
the use,application or reliance on the recommendations common overloads are stacks of plywood placed on
and information contained herein by building designers, trusses before the trusses are properly braced,
builders,installers,and others. 2.2.5 Overloading roof or floor trusses after installation
2. GENERAL is completed. Most commonly,stacks of materials,such
as concrete blocks,plywood,drywall,roofing gravel,or
2.1 Structural performance depends on the trusses being other building materials intended for use during� construction,tend to apply loads beyond the capacity of
installed vertically,in-plane,and at specific spacing,and
being properly fabricated and braced. However carefully the system,
metal plate connected wood trusses are designed and 2 2 6 Improper or unauthorized field alterations of
fabricated, there are many critical phases regarding trusses,(See section 11)
safety including loading,shipping,receiving,unloading,
storing, installation and bracing of trusses. By far the 2 2 7 Installation of broken,damaged, or improperly
majority of wood truss related accidents occur during repaired trusses,(See section 11)
truss installation,and not as a result of improper truss
design or fabrication. During the critical stages of 2 2 8 Improper truss alignment before bracing,
construction,structural performance may be compromised
if proper handling,installation,and bracing criteria are
ignored. If ignored,the collapse of the structure may 2.2.9 Improperly engineered or installed wall structures,
i
result, which at best is a substantial loss of time and �materials,and at worst could result in loss of life. 2 2.10 Failure to provide during the installation process
i special bracing that conforms to truss design assumptions.
2.2 Major causes of metal plate connected wood truss
collapses during the critical construction phase are as 2 3 The builder,building contractor,licensed contractor,
erector or erection contractor is responsible for the
follows: proper handling and installation of metal plate connected
! 2.2.1 Inadequate and/or improperly located temporary wood trusses and will henceforth be referred to as the
! bracing, installer.
woo
2.2.2 Improperly installed and/or inadequate bracing, !�
i
connections,
I
! 2.2.3 Improper and/or inadequate connections to
supporting structure, «�
i 2 3
Truss Plate Institute HIB-91 i
Truss Plate Institute HIB-91 s
13.2.3.1 LATERAL BRACES
13.2.2 BOTTOM CHORD CEILING PLANE
t
During truss design, individual members are checked
This permanent bracing is required to maintain the for buckling,and permanent lateral bracing is specified
� truss design spacing and to provide lateral support to as required for each truss member. The building designer
thebottomchordtoresistbucklingforcesintheeventof should specify how this permanent lateral bracing is to
reversal of stress due to wind uplift or unequal roof or be anchored or restrained to prevent lateral movement
floor loadings. should all truss members, so braced, tend to buckle
I together as shown in Figure 34. This may be accomplished
For multiple bearing trusses or cantilever conditions, by:
portions of the bottom chord become compression �
members and should be braced laterally to resist buckling a) Anchorage to solid end walls (Figure 35);
in the same manner as the top chord of simple span 011111111110
trusses. 4@111" b) Permanent diagonal bracing in the plane of
r" the web members ,Figure 36);or
Permanent bracing in the plane of the bottom chord is
also designed to transfer lateral forces due to wind or 0111111111101, c) Other means as determined by the building
seismic loads into side walls,shear walls,or other resisting 0100designer. s
structural elements. Permanent diagonal braces between owet j
continuous permanent lateral bracing serve to stabilize � Sheathing
T
the bottom chord. It is recommended that one complete 01111101141 i
Compression Webs:
bay of permanent diagonal bracing be installed at each 010111110 before and after
i end of any building,and additional such bays be located 1 1 I buckling. i
1011110,
at specified intervals not to exceed 20 feet. Figure 28 ' I
illustrates the use of permanent bracing in the plane of > > 1
� Unrestrained continuous
the bottom chord. permanent lat-
eral bracing maintains j
See Appendix C for a recommended sequence of installing spacing,but may cause
bracing components. unstable lateral buckling
$ p I ' ' of all web members at the }
' ' l same time. li
13.2.3 WEB MEMBER PLANE
Bearing for
This permanent bracing is designed to hold the trusses 4111111111101 trusses
in a vertical position and to maintain the design spacing. 011111111110
In addition,permanent lateral bracing may be required 40 +
Figure 34 Web members could buckle together if not
to shorten the buckling length of a web member. .111111A property restrained.
ei" 67
66 �M