World Journal of Engineering and Technology, 2013, 1, 33-38
Published Online November 2013 (
Open Access WJET
Experimental Investigation of Progressive Collapse of
Steel Frames
Kamel Sayed Kandil1, Ehab Abd El Fattah Ellobody2, Hanady Eldehemy1*
1Department of Civil Engineering, Faculty of Engineering, Menoufiya University, Shibin El Kom, Egypt; 2Department of Structural
Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt.
Email: *
Received August 20th, 2013; revised September 20th, 2013; accepted September 25th, 2013
Copyright © 2013 Kamel Sayed Kandil et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This paper reports two new tests conducted to augment available data highlighting the structural performance of mul-
tistory steel frames under progressive collapse. The investigated steel frames had different geometries, different
boundary conditions, different collapse mechanisms, different damping ratios and different connections. Overall, the
paper addresses how multistory frames would behave when subjected to local damage or loss of a main structural
carrying element. The obtained results can form a data base for nonlinear finite element models. The deformations of
the investigated steel frames and failure modes under progressive collapse were predicted from the finite element
analysis, with detailed discussions presented.
Keywords: Experimental Investigations; Finite Element Model; Progressive Collapse; Steel Frames
1. Introduction
Existing multistory steel frames may be severely dama-
ged owing to collapse of its main structural elements
such as columns, beams, structural walls or bracing
members. The collapse may occur as a result of explo-
sions, blast or terrorist attacks. The damage or loss of a
main structural carrying element leads to progressive
failure of a significant part of the building or the whole
building. As a result of the damage or loss of a main
structural carrying element, the primary load-resisting
system leads to redistribution of forces to the adjoining
members. Due to the redistribution of forces, the stresses
within the remaining structural elements such as other
columns and beams would be changed and if the stresses
exceed the yield stresses of the element it fails. This
failure can continue from an element to another and
eventually the building collapses. This failure is defined
as progressive collapse of the multistory buildings. The
initial collapse of the structural elements that initiates the
overall collapse is sudden and dynamic involving
significant geometric and material nonlinearities.
Steel frames are commonly used as efficient main
structural supporting systems in multistory buildings.
However, up to date, the detailed behavior of steel
frames under progressive collapse is rarely found and
there is a lack of information regarding the design of
steel frames to overcome progressive collapse leading to
the current investigation. Full-scale tests investigating
progressive collapse of steel frames are quite costly and
Also, numerous simplified analysis methods are found
to evaluate the potential of progressive collapse such as
linear static, nonlinear static, linear dynamic and nonli-
near dynamic analyses. Marjanishvili (2004) [1] discus-
sed the advantages, disadvantages, limit and performance
of each analysis method. It showed that the analysis
methods varied from a simplest but very conservative
linear analysis method to a sophisticated but most precise
and realistic nonlinear dynamic analysis method. Based
on Marjanishvili (2004) [1], the analysis results of the
numerical investigations showed that the nonlinear
dynamic analysis is easy to be conducted and provides
the most precise solution. Also, it showed that the linear
static analysis resulted in unconservative solution
following the failure criteria of the linear static analysis
that was specified by GSA guidelines (2003) [2].
Conducting a complex 3-D nonlinear dynamic analysis is
time-consuming but provides accurate results.
*Corresponding author.
Experimental Investigation of Progressive Collapse of Steel Frames
Nonlinear 3-D finite element models were developed
using nonlinear software to conduct the analyses of steel
frames under progressive collapse. For progressive colla-
pse analysis, a nonlinear static analysis method employs
a stepwise increment of amplified vertical loads which
can be referred to as a vertical pushover analysis. The
force redistribution within the steel frames under pro-
gressive collapse was investigated in this study and the
failure modes were predicted. Progressive collapse is of
particular concern since it may be disproportionate, i.e.,
the collapse is out of proportion to initial local failure.
After the progressive and disproportionate collapse of the
Ronan Point apartment tower [3], prevention of progres-
sive collapse became one of the main concerns of struc-
tural engineers, and code-writing bodies and governmen-
tal user agencies attempted to develop design guidelines
and criteria that would reduce or eliminate the suscep-
tibility of buildings to this form of failure. These efforts
tended to focus on improving redundancy and alternate
load paths, to ensure that loss of any single component
would not lead to a general collapse. Improved local
resistance for critical components and improved conti-
nuity and interconnection throughout the building (which
can improve both redundancy and local resistance) can
be more effective than improved redundancy in many
instances. Through an appropriate combination of im-
proved redundancy, local resistance and interconnection,
it would be possible to greatly reduce the susceptibility
of buildings to disproportionate collapse [2].
Astaneh (2002) [4] investigated the strength of a ty-
pical steel building and floor system to resist progressive
collapse in the event of removal of a column. They tested
a specimen of size 60 ft by 20 ft one-story steel building
with steel deck and concrete slab floor and wide flange
beams and columns. The connections were either stan-
dard shear tab or bolted seat angle under bottom flange
and a bolted single angle on one side of the web. It was
observed that after removing the middle perimeter
column, the catenary action of the steel deck and girders
was able to redistribute the load of removed column to
other columns. The floor was able to resist the design
dead load and live load without collapse. Damage to the
system was primarily in the form of cracking of floor
slab, tension yielding of the steel corrugated deck in the
vicinity of collapsed column, bolt failure in the seat
connections of the collapsed column and yielding of the
web of the girders acting in a catenary configuration.
Astaneh (2003) [5] carried out an experimental in-
vestigation of the viability of steel cable-based systems
to prevent progressive collapse of buildings. The tests
were conducted on a full-scale specimen of a one-story
building. One side of the floor of the specimen had steel
cables placed within the floor representing new construc-
tion and the other side had cables placed outside as a
measure of retrofit of the existing building. The author
claimed that the test results showed that the system could
economically and efficiently prevent progressive collapse
of the floor in the event of removing one of the exterior
Gravity load collapse of a reinforced concrete frame
was studied by Moehle and Elwood [6,7]. Their studies
found that residual axial capacity could prevent collapse
of a building although shear failure in a concrete column
had occurred. A formula using a shear-friction model
was suggested to simulate additional axial load capacity
after shear capacity was exhausted [6,7]. The study [6]
also considered residual capacity of adjacent elements in
analyses after a component fails and leads to redistri-
bution of the applied loads.
Most flat plate buildings are prone to progressive col-
lapse (Hawkins (1979)) [8]. Punching shear failure in a
flat plate building was often observed even before
yielding of the bottom reinforcement of slabs occurred.
Mitchell and Cook (1984) [9] found that punching shear
failure at exterior columns had a low possibility of
leading to progressive collapse. However, unless conti-
nuous bottom reinforcement through a column or good
anchorage was provided, tension membrane by slabs was
not effective and could lead to catastrophic failure.
Proper detailing of slab reinforcement at a column sup-
port enabled a damaged slab to hang from its support.
Therefore, well detailed flat slab buildings were capable
of resisting additional loads even after punching failure
at a support region occurred.
A study by Malvar (2005) [10] reported behavior un-
der blast load and suggested appropriate retrofit schemes.
Both specific local resistance and alternate load paths
were considered to rehabilitate the building. Although
the suggested retrofit schemes were not necessarily appli-
cable to all concrete buildings, the fundamental retrofit
concepts to prevent progressive collapse were defined.
The study recommended that exterior frames can be re-
habilitated by providing specific local resistance using
steel jacketing or wrapping with fiber material. Interior
frames can be supported by developing load paths using
adjacent components.
There is a lack of full-scale tests reported in the litera-
ture on progressive collapse of steel frames because they
are quite expensive and time-consuming. Therefore, nu-
merous small-scale tests were reported in the literature
on progressive collapse. The small-scale tests can be con-
ducted in labs and the result is considerable savings in
time and money. Efforts to develop comprehensive and
progressive collapse-resistant specifications have been
hindered by a lack of both experimental and analytical
information about progressive collapse, leading to the
current investigation. On the experimental front, the rate
of loading and the scale of the problem, i.e., which in-
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Experimental Investigation of Progressive Collapse of Steel Frames 35
volve a full system, have made testing difficult. On the
other hand, numerical simulation is a challenging task
because the collapse process involves modeling compo-
nent and system behavior across several length scales.
The main objective of this study is to conduct two new
small-scale tests to augment available data on progres-
sive collapse of steel frames and to use the results in de-
veloping nonlinear 3-D finite element models.
2. Model Description
The model is one tenth (1/10) scale, the frame consists of
two bays of 0.5 m in two directions with 0.4 m for the
height of the story. The slab is welded to the beam and
the beams-to-connections are welded also to make a rigid
connection. A superimposed load of 250 kg/cm2 is ap-
plied for each floor. The small scale beams and columns
are selected from commercial shapes. A hollow box sec-
tion of dimensions 200 × 200 × 15 mm is selected for
both columns and beams and for bracing system an equal
angle 300 × 300 × 30 mm is selected. The steel frame is
assumed to be built on fixed conditions such that no soil
interaction or differential settlements need to be consi-
dered. The steel frames are designed for gravity loads
only according to the Egyptian Code. Testing a small
scale structure, hence, needs to pay a special care in plan-
ning stage to guarantee obtaining an accurate model. The
steel frame is tested in two cases. The first one, edge
column was removed and a dynamic load was applied on
the frame as simulation of explosions, accidental over-
load, etc. The second one, internal column in the frame
was removed followed by static collapse test under con-
trolled displacement with the help of a hydraulic jack,
see Figure 1 for viewing the model after adding super
imposed loads and is connected with instrumentations. It
was considered that the columns were removed before
the test. Observations of the building response following
columns removal are presented.
Figure 1. The model after adding super imposed loads.
3. Test Instrumentation Used
The instrumentations used in the test include a display
unit (laptop computer), data transmissions unit, transmis-
sion cables, and concentrated load applied on the re-
moved column by a hydraulic jack. Five specifications of
strain gauges are placed in different positions of the
frame so that the concentrated load and the dynamic re-
sponse, including strain and displacement of the frame,
can be measured. The strain gauges attached to the colu-
mns are universal general purpose strain gauges with a
resistance of 120 ± 0.3% Ohms, and have a strain range
of ± 3%. They measure the strain in the vertical direction
caused by the compressive and tensile forces. A set pro-
cedure is used to install the strain gauges on each column.
The displacement of the frame in the vertical direction at
the end of the failed column is measured using dial
Case1: Edge Column Rem oved
Since no vibration can occur at all unless dynamic
loads are applied to the frame, a concentrated load by a
hydraulic jack is used to vibrate the frame. The model is
subjected to a concentrated load at the edge column re-
moved = 20 Kn for constant time = 7 sec., then removed
after that. Strain gauges also are fixed at the other col-
umns, see Figure 2.
The output of maximum lateral deflection will be
shown in Figure 3, it was observed that the maximum
lateral deflection for the edge column in the first floor
was 35 mm at 2 sec., immediately after the concentrated
load is applied. After 2 sec., the maximum lateral deflect-
tion has fixed value at the end of the test (at the 7 sec.) 34
mm. This meant that the maximum deflection for the
column will be in the first time of the applied load then
fixed for a few sec. For the comparison between the ex-
perimental test and with the data get from sap 2000
analysis, the maximum lateral deflection for the edge
column removed after applied load in the experimental
test is higher than in the analysis by 16.6%, that is due to
Column 4
Column 3
Column 2
Column 1
Column 5
Figure 2. The fixed places of strain gauges for edge column
Open Access WJET
Experimental Investigation of Progressive Collapse of Steel Frames
the fixation points of the steel frame in the analysis is
more specific so, get small value than the experimental
The strain for the different columns after applied load
in the experimental test is shown in Figure 4. It was ob-
served that the column No.2 near the edge of column
removed having high value of strain than other columns
this meant that the deformation of the column per unit of
the original column is higher than the column No.3 and
No.1 which having tension values. The column No.3 and
No.1 almost having the same values of column No.4 and
No.5 but having compression values, which meant that
the maximum deformation and the redistribution of
forces would be the maximum for the columns around
the area of the removed column.
Case 2: Internal Column Removed
Load redistribution of the frame occurred after the bot-
tom center column is removed. The measured and calcu-
lated results showed that the frame experienced only
elastic deformations after the loss of the bottom column.
Then a hydraulic jack is used to apply monotonically in-
creasing static load to check the ultimate load, failure
mechanism and the collapse-resistant behavior of the mo-
del frame, the static test setup. The displacement is con-
trolled during the test, Figure 5. The model is subjected
to a concentrated load, increasingly with time for 7 sec.,
0 1 2 3 4 5 6 7 8
Time in Sec.
Max. deflecti on in mm
deflection (mm) from experimental
deflection (mm) from analysis
Figure 3. The maximum lateral deflection for edge column
strain col. 1
0 1 2 3 4 5 6 7 8
Time in Sec.
strain col. 2
strain col. 4 strain col. 3
strain col. 5
Figure 4. The strain for different columns for edge column
until the column is damaged. A dial gauge is fixed at the
column which is removed to measure the deflection. And
strain gauges also were fixed at the other columns as in
Figure 6. The steel frame columns and beams damaged
and the resisting load of the frame decreased rapidly.
Figure 7 shows the maximum lateral deflection gets
from sap 2000 analysis case is higher than the one get
from experimental test by 27%, the difference between
the analysis and the experimental due the rate of loading
and the scale of the problem, i.e. that it involves a full
system, has made testing difficult. From Figure 7, the
maximum lateral deflection gets at the ultimate load ca-
pacity 50 KN for the case of loading where the load is
applied increasingly with time the maximum deflection
would be measured and get around 35 - 36 mm. The
strain for the different columns after applied load is
shown in Figure 8. It was observed that the column No.1
near the damaged column having higher value of strain
Figure 5. The model of internal column removed.
Column 2
Column 1
Column 3
Figure 6. The fixed places of strain gauges for internal col-
umn removed.
Open Access WJET
Experimental Investigation of Progressive Collapse of Steel Frames 37
than other columns that meant that the deformation of the
column is higher than the other columns and having ten-
sion value and for column No. 3 has tension value and
for column No. 2 having the compression value. The
failure mode for internal column removed presented in
Figure 9.
4. Nonlinear Analysis
A nonlinear structural problem is one in which the buil-
deflection (mm) from analysis
0 10 20 30 40 50 60
Load (Kn/mm
Max. deflection in mm
deflection (mm) from experimental
Figure 7. The maximum lateral deflection for internal col-
umn removed.
Load (Kn/nm
0 5 10 15 20 25
strain col. 1
strain col. 2
strain col. 3
Figure 8. The strain for different columns for internal col-
umn removed.
Figure 9. The failure mode for internal column removed.
ding’s stiffness changes as it deforms. All physical buil-
dings exhibit nonlinear behavior. Linear analysis is a
convenient approximation that is often adequate for
design purposes. There are three sources of nonlinearity
in structural mechanics simulations: material nonlinearity,
geometric nonlinearity, boundary nonlinearity. Most me-
tals have a fairly linear stress/strain relationship at low
strain values; but at higher strains the material yields, at
which point the response becomes nonlinear and irrever-
sible this source is defined as material nonlinearity. For
geometric nonlinearity is related to changes in the geo-
metry of the building during the analysis. Geometric
nonlinearity occurs whenever the magnitude of the dis-
placements affects the response of the building. This may
be caused by large deflections or rotations. Finally boun-
dary nonlinearity can occurs if the boundary conditions
change during the analysis. For linear analysis, the two
primary source are the stress/strain relationship & the
deformation behavior. The stress is assumed to be di-
rectly proportional to strain and the structure deforma-
tions are proportional to the loads.
In this paper, the linear analysis material and geo-
metric are carried out.
5. Finite Element Model
A finite element model of the analyzed frame has been
created by sap 2000; the beams and columns element
defined as frame section and were divided into number of
subdivided elements as shown in Figure 10. The frame
has two equal spans in two directions. In this report, two
cases are considered: a removal of an edge column, and
internal column. The slabs are also divided as in Figure
10 to subdivided slabs The self-weight for two cases is
considered and a superimposed load of 250 kg/cm2 is
Figure 10. Finite element model of the analyzed frame in
SAP 2000—element numbers.
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Experimental Investigation of Progressive Collapse of Steel Frames
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applied for each floor. The superimposed load is modeled
as a uniformly distributed linear load applied to the slab.
The columns would be fixed end conditions. The linear
static analysis is carried out for two cases.
6. Conclusion
This study has reported two tests conducted on steel
frames under progressive collapse. The tests have aug-
mented previous investigations on this field and provided
detailed information regarding the behavior of the frames
when subjected to a significant loss of main structural
elements such as column. The test results were com-
prised of failure modes, time-displacement relationship
and stresses in the adjacent elements. The tests results
were used to verify nonlinear finite element models de-
veloped in this study. Also, existing information previ-
ously analyzed by other researchers has been used to
verify the finite element models. The comparison be-
tween the experimental results and the existing results in
the literature with finite element results obtained in this
study showed that the developed model simulates the
behavior of steel frames well. It showed that the maxi-
mum lateral deflection measured for the edge-col-
umn-removed case was higher than that when predicted
numerically because the fixation points of the steel frame
were not fully rigid. It also showed that the column adja-
cent to the removed column underwent higher strains
than other columns, which implied the redistribution of
forces from the removed column to the nearest columns.
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