CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18

4.9 m x 4.9 m in size were tested with a variety of sheathing-to-stud connections,
stud material, stud spacing, stud-to-plate connections, as well as
sheathing material and thickness. Findings and observations from this project
are anticipated to be useful for development of design guidelines for
tall walls subjected to seismic loads in wood design codes and standards.
Some of the design recommendations are given bellow:
(a) Tall-walls with both, SPF and LSL studs can be effective lateral load
resisting systems. Stud tables for dimensional lumber and some engineered
wood products such as laminated veneer lumber spaced at 305
mm, 406 mm and 610 mm on center subjected to wind loads are given
in the "Tall Wall Workbook" (CWC, 2007);
(b) From a cost competitive point of view, tall walls with engineered
wood product studs, such as LSL, should be used with larger stud
spacing (1.2 in and larger) and thicker sheathing (up to 28.6 mm). The
larger stud spacing per se, was not found to be detrimental to the tall
wall performance against lateral loads, without the presence of significant
simultaneously applied vertical load;
(c) Use of thin (9.5 mm) sheathing should be avoided in combination
with studs made of denser wood products such as LSL, due to the increased
presence of nail pull-through the sheathing failure mechanism.
Such mechanism doesn't allow for full potential of the nailed
connections to be developed. On the other hand, nails in tall walls
made with 25.4 mm thick plywood were able to develop three or more
plastic hinges during testing, thus providing the wall with high lateral
load capacity and energy dissipation;
(d) Tall walls may be designed as blocked or unblocked. Blocked tall
walls, especially in case with engineered wood studs, are more cost
effective per unit of shear resistance;
(e) For lumber stud walls, use of higher strength lumber or engineered
wood products for the top and bottom plates is recommended to resist
the induced uplift and anchorage loads;
(f) For walls with a stud spacing larger than 610 mm, top plate deformation
between the studs shall be checked, as it may become an issue,
especially when transferring large gravity loads in case when roof
joists are placed perpendicular to the wall line;
(g) Stud-to-plate connections are of great importance for the overall performance
of tall walls. An arrangement consisting of off-the-shelf dual
hurricane ties and a hanger proved to be an efficient and costeffective
solution for the stud-to-plate connections, for both, site built
and prefabricated tall walls. Use of asymmetrical stud to plate connections,
such as single tie or custom made connectors that connect the
non-sheathed side of the stud only, should be avoided in high seismic
zones due to susceptibility of the studs to torsional failure;
(h) Attention should be paid to the design of the anchoring devices for tall
walls, so that they can efficiently transfer the load to the foundation,
without damaging the bottom plate. For example large plate washers
may be used to prevent splitting of the bottom plate;
(i) The effect of vertical load (in the amount of 20kN/m) on a tall wall
with dimensional lumber studs resulted in a slight increase in the lateral
load capacity, ductility and energy dissipation compared to a nonvertically
loaded wall with similar properties;
(j) Application of gypsum wallboard on the other side of the wall increased
the stiffness and the lateral load capacity of the tall wall. The
maximum load, however, occurred at displacement drifts lower than
in equivalent shearwalls without gypsum boards. For walls with LSL
studs for example, the maximum load occurred at a drift of 1.8% for
wall without gypsum vs. 1.2 % for wall with gypsum wallboards. The
ultimate displacement drifts, however, occurred at relatively similar
drift levels (1.9 % vs. 2%);
(k) Test results suggest that tall walls with wood-based panel on one side
and a gypsum wallboard on the other should be assigned a lower ductility-related
force modification factor (Rd factor) than tall walls with
wood-based panels only. A similar provision is already introduced in
the Canadian Standard for Engineering Design in Wood for standard
shearwalls.
41-15-5 P Scläddle, H J Blass
Behaviour of prefabricated timber wall elements under static and cyclic
loading
Introduction
Prefabricated Timber Wall Elements (PFTE) represent a simple, easy to
handle and sustainable construction system. In a current research project at
Universität Karlsruhe the PFTE building system is tested under both vertical
and horizontal loading to determine its shear wall capacities. For this
purpose a new testing assembly for vertical and horizontal loads able to
produce various boundary conditions was installed at Universitdt Karls-
CIB-W18 Timber Structures – A review of meeting 1-43 5 SPECIAL ACTIONS page 5.27