PREDICTION OF DYNAMIC RESPONSE OF A 7-STOREY MASSIVE XLam WOODEN BUILDING TESTED ON A SHAKING TABLE

Abstract

In October 2007 a series of seismic tests were carried out on a 7-storey building made of cross laminated (XLam) wooden panels in natural scale on a shaking table E-Defence in Japan within the SOFIE project. The paper presents calculation procedure, prediction of dynamic behaviour of the tested structure excited by the earthquake record "Kobe JMA 1995" and comparison between predicted, that means calculated and measured response. Due to blind prediction approach some construction details were not known before dynamic time history response calculation. Therefore some assumptions, engineering judgment and rough static analyses were needed to define all construction parts which were in modelling approach assumed as important and could have had influence on dynamic response of the analyzed structure. The most important assumptions related to the definition of the stiffness and load bearing capacity of mechanical connections, types of anchors and their positions in each floor level, were determined on the basis of static analysis where the structure was loaded with equivalent horizontal seismic forces and then were used in dynamic analysis. A mathematical model was developed in program SAP2000 where modal and time history analyses were carried out. Comparison of calculated and measured results is described and evaluated on the basis of the model assumptions and its simplification.

Full text

PREDICTION OF DYNAMIC RESPONSE OF A 7-STOREY
MASSIVE XLam WOODEN BUILDING TESTED ON A
SHAKING TABLE
Bruno Dujic 1, Klara Strus 2, Roko Zarnic 3, Ario Ceccotti 4
ABSTRACT: In October 2007 a series of seismic tests were carried out on a 7-storey building made of cross laminated
(XLam) wooden panels in natural scale on a shaking table E-Defence in Japan within the SOFIE project. The paper
presents calculation procedure, prediction of dynamic behaviour of the tested structure excited by the earthquake record
“Kobe JMA 1995” and comparison between predicted, that means calculated and measured response. Due to blind
prediction approach some construction details were not known before dynamic time history response calculation.
Therefore some assumptions, engineering judgment and rough static analyses were needed to define all construction
parts which were in modelling approach assumed as important and could have had influence on dynamic response of
the analyzed structure. The most important assumptions related to the definition of the stiffness and load bearing
capacity of mechanical connections, types of anchors and their positions in each floor level, were determined on the
basis of static analysis where the structure was loaded with equivalent horizontal seismic forces and then were used in
dynamic analysis. A mathematical model was developed in program SAP2000 where modal and time history analyses
were carried out. Comparison of calculated and measured results is described and evaluated on the basis of the model
assumptions and its simplification.
KEYWORDS: XLam, timber structure, multi-storey building, seismic analysis, full scale test, blind prediction
1 INTRODUCTION 123
Construction System Fiemme (SOFIE) is a research
project on sustainable construction aiming at promotion
of the use of timber in residential and multi-storey
buildings. The project was carried out by the Italian
National Research Council - Trees and Timber Institute
(CRN-IVALSA) under the leadership of Professor Ario
Ceccotti and the support of Trento Province in Italy. In
the scope of the SOFIE project, a series of dynamic and
seismic tests were carried out on a full scale seven-storey
1 dr. Bruno Dujič, CBD d.o.o. , Lopata 19g, 3000 Celje,
Slovenia; e-mail: bruno.dujic@cbd.si
2 Klara Štrus, University of Ljubljana, Faculty of Civil
Engineering and Geodesy, Jamova 2, 1000 Ljubljana,
Slovenia; e-mail: klara.strus@fgg.uni-lj.si
3 prof. dr. Roko Žarnić, University of Ljubljana, Faculty
of Civil Engineering and Geodesy, Jamova 2, 1000
Ljubljana, Slovenia; e-mail: roko.zarnic@fgg.uni-lj.si
4 prof. Ario Ceccotti, CNR IVALSA - CNR Trees and
Timber Institute, San Michele all`Adige, Italy Slovenia;
e-mail: ceccotti@ivalsa.cnr.it
building made of cross laminated (XLam) timber panels.
The tests were carried out using an E-Defence shaking
table at the Japanese National Research Institute for
Earth Science and Disaster Prevention (NEID) in
October 2007. It is the world’s largest and the most high-
performance seismic testing facility, which was set up
2004 in Miki near Kobe, Japan, following the 1995
catastrophic earthquake in this region. In the framework
of the SOFIE project, a research team from the Faculty
of Civil and Geodetic Engineering at University of
Ljubljana (UL FGG) led by Dr. Bruno Dujic performed a
blind prediction of the seismic response of the tested
XLam building.
2 COMPOSITION OF TESTED XLam
STRUCTURE
The tested SOFIE specimen represents an innovative
timber building system where XLam massive timber
panels are used as wall, floors and roof elements
connected by mechanical fasteners. XLam panels are
fabricated by cross-wise gluing layers of timber boards
with an average thickness of 2 to 3 cm. The panels can
reach dimensions suitable for prefabrication of one-piece
storey walls where the edges and openings for windows

and doors are cut with the use of dedicated CNC
machinery. The tested XLam structure shown in Figure 1
was 7.5 m by 15.0 m in plan, and 23.5 m in height.
Figure 1: Elevation views of the SOFIE tested 7-storey
timber building composed of cross-laminated timber
panels
2.1 STRUCTURAL DETAILS
In XLam system mostly screws (nails) and corner
brackets are used as basic mechanical connectors for
linking the timber panels into a whole structure. In
contact zones between panels, appropriate type and
length of screws are used along with steel brackets and
hold-down anchors to resist shear and uplifting forces
acting on the structure under lateral loading such as wind
and seismic action. The type, dimension, position and
number of screws, steel brackets and hold-downs are
defined by calculation where the seismic and wind forces
govern the design, where as in static analysis for gravity
loads, the majority of mechanical connectors in the
XLam system is not needed because the forces are
transferred through the contact compression zones
between the panels.
The choice of type and size of panels composing an
Xlam building depends from production parameters and
many technical and logistical parameters on construction
site. In the presented tests, the wall panels were 295 cm
in height, except the top floor, and not more than 230 cm
in width due to transport limitations, because they were
produced in Europe and shipped to Japan. Therefore, the
wall segments were connected in line with overlapped
joints. Each wall panel had a 9 cm wide and 2.7 cm deep
groove along the vertical edge for an LVL strip through
which two wall segments were mechanically connected
(Fig. 2).
Figure 2: Overlapped joints between wall segments.
In this kind of joints additionally the kinetic energy
generated in a seismic event could dissipate and
transform into other shapes of energy. With many
dispersed joints over the structure, a very high seismic
ductility can be achieved. This leads to a less rigid
structure with ductile behaviour.
XLam bending elements which compose floor
diaphragm were connected by step joints where adjacent
panels of maximum width of 230cm were overlapped by
12cm. If the panels are assembled with glue and screws,
the horizontal diaphragm can be much stiffer than the
walls. It can transfer the seismic forces through the
construction system, which allows the seismic evaluation
of the structure with rigid horizontal diaphragms.
Figure 3: Step joints between floor elements assembled
with glue and screws establish relatively rigid floor
diaphragm
2.2 MEASURING EQIPMENT FOR DYNAMIC
RESPONSE OF TESTED STRUCTURE
An important part in experimental research is the
selection of adequate measuring equipment. In dynamic
tests, the measurements of dynamic time history of the
specimen can be influenced by the movement of the
shaking platform, surrounding vibrations and noise of
the measuring equipment, which brings uncertainties
into dynamic behaviour evaluation. Therefore, an optical
displacement measuring system as target tracing system
was considered effective for capturing 3D behaviour of
the tested structure.

Additionally, conventional measuring system was used
for measuring absolute accelerations and relative
displacements (Fig. 4).
Figure 4: Some of measuring positions for 3D evaluation
of dynamic response of the structure.
For evaluation of horizontal displacements along the
height of the structure, the story drift measuring system
was used which measured relative horizontal
displacements between two floor levels. This system
consisted of two rigid wooden triangular frames attached
to floor and ceiling panels (Fig. 5). A horizontal
displacement transducer was set at the top of the lower
triangle and the target of the transducer was attached to
the upper triangle (Okabe, 2010).
Figure 5: Measuring device for story drift as relative
horizontal displacement between two floor levels.
Vertical displacements were measured at the corners of
the building using one or two displacement transducers
to capture relative displacements between walls in two
adjacent floors as opening between the upper and the
lower walls or against floor elements (Fig. 6).
Figure 6: Transducers for measuring relative vertical
displacements between wall elements in adjacent floor
levels or uplifts between wall and floor elements.
In the case of two transducers, one was set up at the wall
to the floor at the upper storey and the other was set up
at the floor to wall on the lower storey. Vertical
displacement was defined as the sum of the two
measurements.
3 DESIGN OF THE TEST BUILDING
FOR BLIND PREDICTION
Due to blind prediction approach, some construction
details were not known before the dynamic time-history
response calculations. Therefore, some assumptions,
engineering judgment and approximate static analyses
were needed to define all important construction parts,
which could influence the dynamic response of the tested
structure. The most important assumptions were related
to the definition of mechanical connections, types of
anchors and their positions in each floor level.
3.1 DESIGN OF SHEAR AND TENSION
ANCHORS
The anchoring system was set on the basis of static
design where the analyzed structure was loaded with
equivalent horizontal seismic forces. Two types of steel
brackets were designed, one for shear loads and another
for uplift or tension loads. The calculated stiffness, load-
bearing capacity and layout of anchors obtained from the
static analysis were taken into account in the dynamic
analysis.
Table 1: Input data for evaluation of seismic forces
The basic parameters used for the seismic analysis are
presented in Table 1. The period of the structure was
estimated on the basis of its height; the soil type was set
as type A assuming a rigid shake table; the behaviour
X direction
Y direction
Period T0 [s]
0.53
Soil Type
A
S - the soil factor
1.0
q - behavior factor
2
Periods [s]
Tb
0.15
Tc
0.4
Td
2.0
Design ground acceleration ag
0.82g
0.6g

factor q = 2, the highest value allowed in Eurocode 8
(EC8) for timber structures with glued elements; and
design ground accelerations in two directions were set
from the Kobe earthquake record.
The total mass of the structure of 253.4 tons was defined
as dead load calculated on the basis of the building
geometry with additional 30 tons as long term and live
loads, which were placed into the tested structure in the
form of steel blocks fixed at each floor level. For
calculation of equivalent seismic forces, the weights
were concentrated at each floor level (Table 2), where
the weight of the bottom part of the ground floor walls
was assumed to be transferred directly into foundation.
Table 2: Weight at each floor level and its distance from
the shaking platform
According to Eurocode 8, the base shear force was
calculated according to the following equation:
 
WTSF db  0
(1)
where Sd(T0) is the ordinate of the design spectrum at
period T0 and W is the total weight of the building. From
the period calculation defined on the basis of building
height, the structure period T0 was assumed as 0.53s,
therefore the ordinates of the design spectrum in both
directions were set as:
ggS xd 77.0
53.0 4.0
25.2
0.182.0
,







(2)
ggS yd 57.0
53.0 4.0
25.2
0.160.0
,







(3)
Seismic force, when taking into account Sd in both
global directions, is:
kNtsmF xb 31924.25381.977.0 2
,
(4)
kNtsmF yb 14074.25381.957.0 2
,
(5)
The total base shear is 1923kN in X direction and
1407kN in Y direction. Looking at these values it should
be emphasized that the response of the structure was
assumed with limited capability to dissipate energy -
medium capacity or ductility class medium (DCM). As
XLam timber structures are not included into EC8 yet,
the q-value for buildings with glued (cross laminated)
timber elements require very conservative seismic
analyses and cannot be assigned in ductility class high
(DCH) even though the main mechanical fasteners in
dissipative zones are able to deform plastically for at
least three fully reversed cycles at a static ductility ratio
more than 6 without more than a 20% reduction of their
resistance which corresponds to DCH.
Table 3: Seismic forces (kN) at each floor level in X and
Y direction
Considering the values of shear forces at floor levels and
moment equilibriums at rotation of the structure around
the compression lines in X and Y directions, calculations
returned results of shear and up-lift forces at each floor
level as presented in Table 4. Moment equilibriums were
taken into account according to eq. (6) and (7).
0
20,7,76,65,54,43,32,21,1  xx
x
xxxxxxx lH
l
WhFhFhFhFhFhFhF
(6)
0
20,7,76,65,54,43,32,21,1  yy
y
yyyyyyy lH
l
WhFhFhFhFhFhFhF
(7)
Table 4: Cumulative shear and up-lift forces at each floor
level in X and Y directions
Uplift forces are evaluated only at levels where they are
present as tension values. On the basis of compression
forces at different levels, activated friction forces were
taken into account to reduce the number of shear
anchors. They were calculated according to the
following equation:
NkF frfr 
(8)
where kfr is friction coefficient and N is vertical force as
weight of the structure at each floor level.
The average value for the friction coefficient in the case
of wood-steel and wood-wood sliding contact was set as
0.4. With this friction coefficient the total activated
friction forces at different floor levels were evaluated.
Additionally, friction forces were evaluated per linear
meter of the wall as ratio of the wall lengths in both
directions and presented in Table 5, where W is the
weight of the tested structure at a given floor level, Ffr,tot
is the total activated friction at the floor level, ltot is total
length of full wall segments at the floor level, lx in ly are
Floor
zi [m]
Wi [kN]
zi∙Wi [kNm]
1
3.1
480.6
1490
2
6.2
476.8
2956
3
9.3
469. 6
4367
4
12.4
452.7
5613
5
15.5
430.1
6667
6
18.6
90.3
1680
7
22.1
28.8
636
∑
23409
Seismic Forces
Direction X
Direction Y
F1
122
89,5
F2
243
178
F3
359
263
F4
461
337
F5
548
401
F6
138
101
F7
52,3
38,3
Shear
force [kN]
X
direction
Y
direction
Up-lift
force [kN]
X
direction
Y
direction
S0
1923
1407
H0
504
1016
S1
1800
1317
H1
293
673
S2
1558
1140
H2
114
370
S3
1199
877
H3
< 0
134
S4
738
540
H4
< 0
6
S5
190
139
H5
< 0
< 0

lengths of full wall segments in each direction, Ffr/m is
friction per meter of wall, Ffr,x(y) is activated friction in X
or Y direction and Ffr,v is activated friction in each node
of FEM at the floor level.
Table 5: Activated friction forces at the bottom of each
floor level in X and Y directions
For anchorage system it was assumed that commercial
hardware would be used, such as, for example, HTT22
for hold downs, with max. 32 nails or screws on strap,
and BMF 90×48×3×116 for shear anchors, with max. 18
nails or screws on strap. The design load-bearing
capacity per nail/screw of ø4/60 mm according to EC5
is:
kN
kNkR
R
m
k
nd 2.2
3.1 1.16.2
mod
,





(9)
On the basis of this value, the hold-down capacity and
shear capacity were defined. For shear anchors, it was
assumed that they could contribute also to prevent up-lift
load. On the basis of this assumption, the number of
anchors and their positions at each floor level were
defined. In Figure 7, placement of hold-downs and shear
anchors at different floor levels is presented, where
coloured notations represent:
Hold-downs for up-lifting forces in Y direction
Hold-downs for up-lifting forces in X direction
Shear anchors for shear loads in Y direction
Shear anchors for shear loads in X direction
a) ground floor – LEVEL 0
b) 1st Floor – LEVEL 1
c) 2nd Floor – LEVEL 2
d) 3rd Floor – LEVEL 3
e) 4rd Floor – LEVEL 4
f) 5th Floor – LEVEL 5
Figure 7: Placement of hold-downs and shear anchors at
different floor levels
When the number of hold-downs was set in different
loading directions, the contribution of the nearest hold-
downs on perpendicular walls was taken into account as
actively resisting in secondary shaking direction. This
assumption is fulfilled when connection between
perpendicularly connected walls is strong and stiff
enough to transfer this reaction force into the hold-down
placed on the wall oriented in the other direction.
3.2 MECHANICAL PROPERTIES OF XLam
PANELS
The structure was built of 5-layer cross laminated panels
of three different thicknesses. The wall thickness in the
first two storeys was 14.2 cm, in the third and fourth
At the
bottom of
floor level
W
[kN]
Ffr,tot
[kN]
ltot
[m]
lx
[m]
ly
[m]
Ffr/m
[kN/m]
Ffr,x
[kN]
Ffr,y
[kN]
Ffr,v
[kN]
0
2486
994
58
32
26
17.1
547
445
4.3
1
2009
803
66
36
30
12.2
438
365
3.0
2
1525
610
66
36
30
9.2
333
277
2.3
3
1055
422
66
36
30
6.4
230
192
1.6
4
585
234
66
36
30
3.5
128
106
0.9
5
150
59
56
32
24
2.7
35
25
0.3

storeys it was 12.5 cm and in the upper storeys it was
8.5 cm. The thickness of all floor panels was 14.2 cm,
and the roof panels were 8.5 cm thick.
Mechanical characteristics of XLam panels were not
known; therefore, the thickness of different layers and
mechanical properties (E-moduli) were estimated on the
basis of experimental tests done at ULFGG on XLam
KLH system (Dujic 2005, 2008) and homogenized into
one layer of orthotropic material by taking into account
rolling shear of the middle layers by the method with
composition coefficients proposed by Blaß, 2004 (Fig.8).
Figure 8: Homogenisation of multi-layer panel with wood
fibres oriented in different directions into homogeneous
orthotropic material
The simplification of the multi-layer XLam material
using homogenisation was necessary for the numerical
analysis by FEM where orthotropic shell elements were
used for modelling the panels. The values of E-moduli
were defined for walls in two plane directions while for
bending XLam elements, such as floor and roof panels,
E-moduli were defined for the perpendicular to plane
direction (Table 6).
Table 6: E-moduli of homogeneous orthotropic material
representing deformation characteristics of 5-layer XLam
panels of different thicknesses
4 NUMERICAL ANALYSIS
A numerical model was developed in the finite element
program SAP2000 - Nonlinear 9, to carry out the modal
and time-history analyses. An attempt was made to
develop an exact model of XLam wall assembly which
would take into account realistic mechanical properties
of all constituent elements. Results of racking tests
performed at UL FGG served for the model verification
(Dujic 2005, 2006).
The model was composed of orthotropic shell elements
and longitudinal spring elements simulating behaviour of
the main mechanical connectors and anchors. Envelope
curves obtained from cyclic tests performed at UL FGG
were incorporated in the model as responses of multi-
linear springs (Fig. 9 and 10).
Figure 9: Envelope and load bearing capacity of the shear
anchor with 12 nails of ø4/60 mm when acting in shear (a)
and when acting as hold down (b)
Figure 10: Envelope and load bearing capacity of the
hold-down with 22 nails of ø4/60 mm for prevention of up-
lifting of the panel (a) and its contribution as friction
element for prevention of shear sliding (b)
Multi-layer XLam structural elements (walls, floors,
roof) were taken into account as homogeneous
orthotropic material with mechanical characteristics
calculated according to the method with composition
coefficients (Blaß, 2004);the E-moduli are presented in
Table 6.
In the numerical model, overlapped joints were not taken
into account, as position and connection details were not
defined when analysis for blind prediction was
performed.
Figure 11: Numerical model of XLam tested structure for
blind prediction of dynamic response
E-moduli of XLam plates [kN/m2]
Plate loading
E-moduli
142
125
85
In plane
direction
E0,ef =
9.68 ∙ 106
9.3 ∙ 106
7.7 ∙ 106
E90,ef =
3.33 ∙ 106
3.7 ∙ 106
5.3 ∙ 106
Perpendicular to
plane direction
E0,ef =
10.1 ∙ 106
10 ∙ 106
E90,ef =
2.9 ∙ 106
2.95 ∙ 106
-40
-30
-20
-10
0
10
20
30
40
-0 -0 -0 -0 0 0,01 0,02 0,03 0,04
Pomik [m]
Sila [kN]
Trenje v vsaki
točki KE
Force [kN]
Displacement [m]
shear
anchor
envelope of
cyclic response -
friction is taken
into account
-120
-100
-80
-60
-40
-20
0
20
40
0 0,01 0,02 0,03 0,04
Pomik [m]
Sila [kN]
Force [kN]
Up-lift [m]
shear
anchor
-120
-100
-80
-60
-40
-20
0
20
40
60
80
0 0,01 0,02 0,03 0,04
Pomik [m]
Sila [kN]
Force [kN]
hold-
down
Up-lift [m]
-5
-4
-3
-2
-1
0
1
2
3
4
5
-120 -80 -40 0 40 80 120
Pomik [m]
Sila [kN]
Force [kN]
Displacement [m]
friction;
hold-
down
shear
anchor
Hold
down

As the first step, non-linear analysis has been tried as
procedure of direct integration with 5% damping, but the
algorithms did not converge and the analysis could not
be concluded. The problem was in the descending
envelope parts of link elements. Therefore, two
additional simplification steps were introduced.
In the first simplification, the descending parts of the
envelopes were changed into a constant deformation part
at the highest load level of the spring (Fig. 12).
Figure 12: Simplified link elements from nonlinear to
linear representing shear anchors (a) and hold-downs (b)
The second simplification was to perform the linear time
history analysis with secant stiffness of link elements.
The stiffness was evaluated as secant line on the
envelope where the load range in the steel bracket was
assumed according to simple static analysis with
equivalent horizontal forces (Fig. 12 and Table 7).
In linear elastic analysis, damping was set as 15% of
critical to cover viscous damping, which is not taken into
account in linear elastic analysis. The viscous damping
represents the capability of energy dissipation when
springs behave in nonlinear manner.
Table 7: Values of secant stiffness (kN/m) of steel
brackets taken into account as linear springs in the model
5 CALCULATED RESPONSE
This section presents the prediction of the dynamic
behaviour of the tested structure excited by the
earthquake record “Kobe JMA 1995” and a comparison
between the predicted and the measured response.
Calculated response at the top of the model in both
directions is presented in diagrams of Figure 13. In
strong direction the calculated displacement was 14.6 cm
or about 2 cm per storey, which represents the storey
drift ratio of h/150. In weaker direction the calculated
displacement reached more than 32 cm, which represents
an average horizontal displacement of 4.6 cm per storey,
or storey drift ratio of h/65.
From comparisons of the calculated and measured
results at the top of the structure it can be seen that a
relatively good agreement was achieved. As the test
results are still under evaluation, the correlation was
done for sum of inter-storey drifts only, while local
uplifting of the wall panels at the corners are still not
evaluated and therefore not included in the presented
dynamic responses. The main problem is that the
measuring points of inter-storey drifts do not correspond
to the locations where the uplifts were measured.
However, as the XLam structure was composed of
narrow panels, the uplift values do not have important
influence on the global horizontal displacement in the
middle of the shorter direction. Also, in longer building
direction, the uplifts were absorbed and did not influence
significantly the global horizontal displacements, as the
narrow panels were locally rotated as rigid bodies
between the floor levels, and the uplift was measured as
a consequence of this local rotation.
Diagrams on Figure 13 present modelled and measured
time history responses of the structure in two main
directions at the mid-roof point. Comparison shows
relatively good agreement in traces and amplitudes
during earthquake excitation. Most of the time, the
model shows higher amplitudes. If additional horizontal
displacements due to uplifts of wall elements were
included into the global measured response at the top of
the structure, the differences would be even smaller.
Figure 13: Comparison of experimental and predicted
time history responses of tested Xlam structure in X and
Y directions
-60
-40
-20
0
20
40
60
-0,04 -0,02 0 0,02 0,04
Pomik [m]
Sila [kN]
Fnelin.
Fkor.
Flin.
Force [kN]
Displacement [m]
-150
-100
-50
0
50
100
-0,02 0 0,02 0,04 0,06 0,08
Pomik [m]
Sila [kN]
Fnelin.
Fkor.
Flin.
Force [kN]
Up-lift [m]
Hold-down
Shear Anchor
Floor level
Up-lift
Shear
Up-lift
0
11250
8000
5000
1
5250
7500
5000
2
4375
7250
5000
3
5750
4250
4
4500
3500
5
4000
3500
-200
-150
-100
-50
0
50
100
150
200
0 5 10 15 20 25 30 35 40
DG-X1 - roof level [mm]
time [sec]
X direction: test results - sum of interstorey drifts
model
test
-400
-300
-200
-100
0
100
200
300
0 5 10 15 20 25 30 35 40
DG-Y1 - roof level [mm]
time [sec]
Y direction: test results -sum of interstorey drifts
test
model
-20
-15
-10
-5
0
5
10
15
20
010 20 30 40 50
Horizontal displacement [c m]
Time [s]
14.6cm
-40
-30
-20
-10
0
10
20
30
010 20 30 40 50
Horizontal displaceme nt [cm]
Time [s]
32.2cm

6 CONCLUSIONS
In the last years, research laboratories in several
European countries have been performing research on
XLam elements, typical connections used in the XLam
systems, their construction parts and on the whole
buildings. Therefore, day by day, multi-storey buildings
made of XLam system are becoming a strong and
economically valid alternative even to their competitors
built of concrete and masonry throughout Europe.
However, design of buildings in XLam system is not yet
considered by European standards. E.g., in Eurocode 8
this constructive system is not included and no
recommendations are given regarding its seismic
behaviour.
Seismic research on the XLam system in the last few
years already showed that it is numerically manageable
and predictable and could be analyzed with basic
computational tools. As XLam panels have extremely
high in-plane stiffness and load bearing capacity,
dispersed mechanical connectors and anchors play an
important role in seismic design. They are the weakest
construction elements with ability to assure high
structural ductility.
In this paper, comparison of measured and calculated
results obtained by fully blind prediction shows, that on
the basis of geometrical sketches XLam structures could
be properly designed and accurately analyzed for seismic
load. One of the important outcomes is that the results
are stable also with variation of type and thickness of
XLam elements and with position and type of connectors
and anchors due to their abundance in the structure. With
high capability to dissipate energy through many
mechanical fasteners, another very positive property of
the XLam system is its self-centering after seismic
excitation, which could lead to a very promising future
design philosophy in seismic areas with the new no
damage design approach (NDDA).
ACKNOWLEDGEMENT
Dr. Bruno Dujič’s research work is partly financed by
the European Union.
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