Study on Progressive Collapse of RC Structures
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DownloadProgressive
collapse resistance demand of RC frame structures based on energy method
(I): beam mechanism,
Journal of Building Structures, 2011, 32(11): 1-8.
Abstract£ºThe key issue
of progressive collapse (PC) design method is to determine the PC resistance
demand of the structures with members removed due to accidental action.
The empirical parameters that are adopted in the design methods of the
existing codes are difficult to reasonably consider the effect of nonlinear
and dynamic behavior during the PC process of building structures due
to its weak theoretical basis. A theoretical framework of the PC resistance
demand analysis for RC frame structures is established based on the
energy conservation principle. In this framework, the relationship between
the nonlinear dynamic and linear static PC resistance demands for RC
frame structures with beam mechanism to resist PC is derived. The influences
of nonlinear and dynamic behaviors are comprehensively considered so
that the nonlinear dynamic PC resistance demands can be obtained using
the linear static analysis. At last, the empirical parameters in existing
codes are discussed and the proposed demand relationship based on the
energy conservation principle is validated through numerical examples.
Keyword£ºRC frame structure,
progressive collapse, beam mechanism, resistance demand relationship,
energy conservation principle
Progressive
collapse resistance demand of RC frame structures based on energy method
(II): catenary mechanism,
Journal of Building Structures, 2011, 32(11): 9-16.
Abstract£ºThe key issue
of progressive collapse (PC) design for RC frame structures at large
deformation stage is to calculate the PC resistance demand of the structures
under catenary mechanism. The existing design codes for PC design are
unsafe because of ignoring the effect of nonlinear dynamic behavior
of PC resistance demand under catenary mechanism. According to the theoretical
framework of the PC resistance demand analysis based on the energy conservation
principle, the relationship between the nonlinear dynamic and nonlinear
static PC resistance demands for RC frame structures under catenary
mechanism is derived. And the theoretical method to calculate the PC
resistance demand of RC frame structures under catenary mechanism is
established. At last, the proposed method describing the PC resistance
demand relationship of RC frames with catenary mechanism is validated
through numerical examples.
Keyword£ºRC frame structure, progressive collapse,
catenary mechanism, resistance demand relationship, energy conservation
principle
An
improved tie force method for progressive collapse resistance design
of reinforced concrete frame structures
Engineering Structures, 2011, 33(10): 2931-2942.
Abstract: Progressive collapse of structures refers to local damage due to occasional and abnormal loads, which in turn leads to the development of a chain reaction mechanism and progressive and catastrophic failure. The tie force (TF) method is one of the major design techniques for resisting progressive collapse, whereby a statically indeterminate structure is designed through a locally simplified determinate structure by assumed failure mode. The method is also adopted by the BS8110-1:1997, Eurocode 1, and DoD 2005. Due to the overly simplified analytical model used in the current practical codes, it is necessary to further investigate the reliability of the code predictions. In this research, a numerical study on two reinforced concrete (RC) frame structures demonstrates that the current TF method is inadequate in increasing the progressive collapse resistance. In view of this, the fundamental principles inherent in the current TF method are examined in some detail. It is found that the current method fails to consider such important factors as load redistribution in three dimensions, dynamic effect, and internal force correction. As such, an improved TF method is proposed in this study. The applicability and reliability of the proposed method is verified through numerical design examples.
Study
on the Progressive Collapse Mechanism of RC Frame Structures,
Building Science, 2011, 27(5): 12-18.
Abstract: The progressive collapse
(PC) mechanism of two typical non-integrated slab and integrated cast-in-situ
slab reinforced concrete (RC) frames, with different seismic fortification
levels, is analyzed by the nonlinear dynamic alternate path (AP) method.
Firstly, the two representative PC modes are summarized and it is found
that the insufficient lateral stiffness of columns leads to propagation
of collapse in horizontal direction. And then, the PC resisting contribution
of framed beams at different locations of the frames is studied by analyzing
the mechanical response of the frames with initial damage occurring
at different locations. Results indicate that all beams are able to
provide PC resistance by beam action but only the continuous beams,
with enough horizontal constraint at both ends, are able to provide
PC resistance by catenary action. At last, the influence of slabs and
seismic design on PC resistance of the two RC frames is discussed by
analyzing the PC law of RC frames.
Keywords: concrete frame; progressive collapse mechanism; nonlinear
dynamic alternate path analysis
Study
on progressive collapse-resisting capacity of RC frame structures based
on pushdown analysis,
Journal of Shenyang Jianzhu University (Natural Science),
2011, 27(1): 10-18.
Abstract£ºhe law of the
progressive collapse (PC) -resisting capacity of the typical reinforced
concrete (RC) frames is analyzed to provide a reference for PC design
and researches. The PC-resisting capacity of the typical non-integrated
slab and the integrated cast-in-situ slab reinforced concrete (RC) frames,
with different seismic fortification levels, is compared by the nonlinear
static Pushdown method. It is found that the uncoordinated development
of internal forces of beams on different stories leads to the lower
PC-resisting capacity of the frame when multi-storey frame beams commonly
resist PC. The PC-resisting capacity of the frame under the beam action
and catenary action is dominated by the flexural capacity and tensile
capacity of frame beams respectively. After seismic design, the PC-resisting
capacity of the frame under the beam action is significantly enhanced
but the capacity of the frame under the catenary action is improved
slightly. The PC-resisting capacity of the frame under the beam action
is significantly enhanced by integrated slab but for the capacity of
the frame under the catenary action the enhancement extent relates to
the effective flange width of slabs.
Keywords£ºoncrete frame; progressive collapse-resisting
capacity; nonlinear static Pushdown analysis; seismic design; slab
Influence
of slabs on the progressive collapse behavior of structures,
Sichuan Building Science, 2010, 36(2): 5-10.
Abstract£ºThe progressive
collapse of the building structures due to accidents has become a hot
research topic of civil engineering all around the world. Floor or roof
slab, as one of major structural elements, has important contribution
to the integration of structures, and therefore could greatly enhance
the progressive collapse resistance of structures. But the influence
of slabs was not taken into consideration in the existing research work
or design specifications. In this paper, mainly referring to the design
process proposed in DoD 2005, the collapse processes of two typical
Chinese 8-story reinforced concrete (RC) frames with and without slabs
respectively are simulated and compared. Then the influence of slabs
on the progressive collapse behavior of structures is studied and the
result proofs that the slabs can greatly improve the progressive collapse
resistance of structures.
Key words£ºprogressive collapse; slabs; concrete frame;
simulation;
Design
method on the progressive-collapse-resistance of RC frames,
Building Structure, 2010, 40(2): 1-7.
Abstract: This paper firstly introduced
the design objectives and corresponding specifications of the progressive-collapse-prevetion
in different codes of foreign countries. Based on a number of calculations,
with the consideration of the actual structures designed according to
Chinese codes, and the design objectives for Chinese structures, the
design methods for the progressive-collapse-prevention of Chinese RC
frame structures are proposed in this paper, which include conceptual
method, tie force (TF) method and alternative path (AP) method, together
with corresponding detail design requirements.
Keywords: frame structure, progressive-collapse-resistance, tie
force method, alternative path, detail design
Verification
and analysis on foreign progressive collapse prevention design methods
of RC frame structures,
Building Structure, 2010, 40(2): 8-12.
Abstract£ºCurrently,
the progressive collapse of the building structures due to accidents
has become a serious threat to the public safety. Since the collapse
of the Ronan Point Tower in United Kingdom in 1968, North America and
Europe have conducted more than 40 years of research to this issue and
developed corresponding design codes and design guides, such as GSA
2003, DoD 2005 and EuroCode 1. However, codes in China have not yet
provided details on the resistance of progressive collapse. Mainly referring
to the design process proposed in DoD 2005, the capacity to resist progressive
collapse of a typical Chinese 8-story reinforced concrete (RC) frame
is analyzed. Then the frame is redesigned with the tie force method
and the alternate path method proposed in DoD 2005 to provide examples
for the progressive collapse prevention design for Chinese engineers.
And some problems when applying foreign codes to Chinese buildings are
pointed out.
Keywords£ºprogressive collapse;
concrete frame; tie force method; alternate path method
Simulation
of Structural Collapse with Coupled Finite Element-Discrete Element
Method
Proc. Computational Structural Engineering, Yuan Y, Cui
JZ and Mang H(eds.), Jun. 22-24, 2009, Springer, Shanghai:127-135.
Abstract. Structural progressive
collapse is a great threat to life safety and therefore it is necessary
to study its mechanism in detail. Numerical simulation is significant
to study the whole process of progressive collapse in structural level.
Since collapse is a complicated procedure from continuum into discrete
fragments, numerical model should be competent in nonlinear deformation
before collapse and breaking and crashing of fragments after collapse.
Coupled Finite element-discrete element method on simulating structural
progressive collapse is proposed to meet the requirements. Relatively
accurate models, such as fiber model and multi-shell shell model, are
introduced to construct the finite element model of structure. In the
analysis, the failed finite elements will be removed and replaced with
granular discrete elements according to the criteria of equivalent total
mass and volume so that the impacting and heaping of fragments can be
taken into account. The sample with the coupled method shows that this
method not only possesses the advantages of finite element method but
also simulates the behavior of fragments well.
Keywords: Finite element, discrete element, coupling calculation,
progressive collapse, numerical model.
Study
on design method to resist progressive collapse for reinforced concrete
frames
Engineering Mechanics, 2008, 25(Sup.2): 150-157.
Abstract: This paper summarizes
the major design methods and classification-design systems in foreign
codes to resist progressive collapse. And then the alternate path (AP)
method and tie force (TF) method in the progressive design for reinforced
concrete (RC) frames are studied. Firstly, based on the analyzing the
nonlinear dynamic AP method, the principle and design factors of the
linear static AP method are analyzed, and moreover, design factors suitable
for Chinese structures are suggested. Secondly, the inapplicability
of the TF method in foreign codes to enhance Chinese RC frames is studied.
The calculating model of foreign TF method is improved and a TF method
considering space load paths is suggested. Both the linear static AP
method and the TF method suggested by this paper are verified by design.
Key words: reinforced concrete frame; progressive collapse design;
nonlinear dynamic alternate path method; linear static alternate path
method; tie force method
Study
on the design methods to resist progressive collapse for building structures
Proc. 10th Int. Symp. on Structural Engineering for
Young Experts, Oct. 2008, Changsha:478-483.
Abstract: Since the collapse of
the Ronan Point Tower in United Kingdom in 1968, the progressive collapse
resistance of building structures has attracted a global attention.
Important foreign design codes have developed their specifications for
building structures to resist progressive collapse, but the related
research is still lack in China. This paper presents a series of researches
by the Department of Civil Engineering in Tsinghua University on progressive
collapse resistance of building structures. The existing design methods
are briefly summarized, and two major design methods, which are alternate
path (AP) method and tie force (TF) method, are proposed together with
feasible procedure and carefully studied factors that are suitable for
Chinese structures. The effects of each proposed methods are verified
with nonlinear dynamic simulations and the additional cost due to progressive
collapse resistance design is compared.
Keywords: building structure; progressive collapse design; nonlinear
dynamic alternate path method; linear static alternate path method;
tie force method
Application
of fiber model for progressive collapse analysis of reinforced concrete
frames,
Proc. 12th Int. Conf. on Computing in Civil and Building
Engineering, Oct. 2008, Beijing, CDROM
Abstract£ºThe progressive collapse
of the building structures due to accidents has become a hot research
topic of civil engineering all around the world. The researches and
designs on progressive collapse are based on accurately simulation for
the failure process of whole structural systems. However, due to the
complicated material and geometric nonlinearity and large computational
workload in collapse simulation for a real reinforced concrete (RC)
structure, normal finite element (FE) analysis with solid elements are
not feasible in collapse researches. Hence, a fiber beam model is proposed
in this work to simulate the collapse of RC frame. The fiber beam model
is firstly verified with a collapse test of a planar RC frame. And then
following the design process proposed in DoD 2005, the collapse processes
of two typical Chinese 8-story RC frames with and without slabs respectively
are simulated and compared. The influence of slabs on the progressive
collapse behavior of structures is studied and the result proofs that
the slabs can greatly improve the progressive collapse resistance of
structures.
Keywords£ºfiber model; progressive collapse; simulation;
reinforced concrete frame; slabs
Simulation
for concrete structures under various disasters: model development and
engineering application
Proc. 2nd Int. Forum on Advances in Structural Engineering,
Oct. 2008, Dalian: 653-660.
Abstract: Engineering structures
could be destroyed by disaster loads, such as earthquake, fire, blast
et al. In concrete structures, frames, shear walls and slabs are major
structural elements, and therefore accurate simulation for the nonlinear
behavior of them in various disasters is the key problem for the researches
on disaster resistance of concrete structures. The Department of Civil
Engineering in Tsinghua University developed fiber beam model and multi-layer
shell model for the ultimate analysis of structures. These models could
accurately simulate the nonlinear failure process of concrete structures
in earthquake, fire, blast, progressive collapse et al. And with the
high efficiency of these models, they can be used in the whole process
simulation of real large-scale complicated RC structures under various
disasters. This paper presents the principles of the models and their
typical applications in researches and practices.
Keywords: disaster simulation; fiber model; multi-layer shell
model; dynamic large deformation computation; thermal-mechanical coupled
computation
Numerical
simulation for the progressive collapse of concrete building due to
earthquake
Proc. the 14th World Conference on Earthquake Engineering,
October 12-17, 2008, Beijing, China, CDROM.
ABSTRACT : Collapse is a critical
ultimate state for buildings under earthquake. Though collapse should
theoretically be avoid for any buildings under any earthquake, it is
still very important to study the collapse behavior of buildings so
as to get a better understanding for the collapse mechanism and to find
efficient method to against it. Progressive collapse, which means that
collapse of whole building due to local weak stories or weak zones,
is a most common failure mode in earthquake. And as its collapse process
highly depends on the whole structural system, numerical simulation
becomes a major method to study it. With the fiber-beam-element model
and multi-layer-shell-element model, which is developed by Tsinghua
University for reinforced concrete (RC) frames and RC shear-walls respectively,
the extreme nonlinear behavior of RC structural elements can be properly
simulated including the cycle behavior under coupled axial force-bending
moment-shear force, the breakdown of structural elements at ultimate
states, and the contact between structural elements during the collapse.
Simple RC frames and RC frame-shear wall structures are firstly used
to demonstrate and to benchmark the capacity of the numerical model,
and real complicated buildings are analyzed to study the failure mechanism
of the structures.
KEYWORDS: progressive collapse, earthquake, numerical model,
nonlinear, reinforced concrete
Collapse
prevention of building structures: a lesson from the Wenchuan earthquake
Journal of Building
Structures, 2008, 29(4): 42-50
Abstract:
The aseismic capacity of engineering structures is the first line in
the earthquake defense system of the society. Building collapse is one
of the major earthquake devastating consequences. Damages of buildings
generally reflect the degree of earthquake disaster. As a result, the
aseismic capacity of building structures, especially their capacity
to prevent collapse, is of great importance to the overall earthquake
defense system of the society. Based on analyzing the building seismic
damage in the Wenchuan earthquake, methods to increase the overall aseismic
capacity of building structures are discussed in the framework of system
theory. Some key problems and suggestions for seismic design, especially
for increasing the capacity to prevent collapse of building structures
are proposed. It is shown that: the safety margin of building structural
systems can be divided into 3 levels: fundamental, integral and unexpected
safety margins. The overall seismic capacity and collapse prevention
of building structures are mainly determined by the integral safety
margin and unexpected safety margin. Lack of unexpected safety margin
is the main reasons of the severe building damage in Wenchuan earthquake.
The unexpected safety margin of a structural system mainly comes from
its robustness, stability and integrity. Research on the integral and
unexpected safety margins of building structures is still limited. Corresponding
requirements and specifications in current design code for building
structures need to be improved.
Keywords: Wenchuan earthquake, building seismic damage, seismic
system, collapse prevention, robustness, stability, structural system
Tie
force method for progressive collapse resistance of structures
Proc. 10th National Conference on fundamental theory
and engineering application of concrete, Aug. 2008, Dalian, 391-396.
Abstract£ºTie force (TF)
method is one of the major design methods proposed by foreign codes
to resist progressive collapse, but the related researches are still
lack in China. TF method is convenient to implement because it does
not need to calculate the response of the whole structure. However,
as too many assumptions have been set to build up this method, the empirical
factors are needed to be carefully checked to guarantee the safety of
the TF design. This paper summarized the conceptions and specifications
of TF methods in foreign codes. Then foreign TF methods were proved
to be not safety for Chinese concrete frames with nonlinear finite element
dynamic analysis. In order to explain this phenomenon, the drawbacks
in foreign TF methods were pointed out from the discussion of the fundamental
principles of TF methods. And the suggestions from these discussions
will be helpful to setup a feasible TF method in China.
Keywords: concrete frame structures£»progressive
collapse; design codes; tie force method
Design
Method to Resist Progressive Collapse for a Three-Story RC Frame
Journal of PLA University of Science and Technology,
2007, 8(6): 659-664
Abstract£ºCurrently,
the progressive collapse of the structures has become a serious threat
to the public safety. Since the collapse of the Ronan Point Tower in
United Kingdom in 1968, North America and Europe have researched on
this issue for more than 30 years and developed relevant design codes
and design guides, such as GSA 2003, DoD 2005 and EuroCode 1. However,
codes in China have not yet proposed in detail on the resistance of
progressive collapse. Hence, based on the design process proposed in
DoD2005, the capacity to resist progressive collapse of a typical Chinese
3-story reinforced concrete (RC) frame is analyzed. Then the frame is
re-designed with the Tie Force Method and the Alternate Path Method
proposed in DoD 2005 to provide examples for the progressive collapse
prevention design for Chinese frame structures. And some problems when
applying foreign code to Chinese buildings are pointed out.
Key words£ºprogressive collapse; concrete frame; simulation;
tie force method; alternate path method
Progressive
collapse of structures: introduction and comparison of standards
Proc. 6th National Conference on Safety Protection for
Engineering Structures. Luoyang, 2007. 195-200.
Abstract:
Currently, the progressive collapse of the structures has become a serious
threat to the public safety. Since the collapse of the Ronan Point Tower
in United Kingdom in 1968, north America and Europe have conducted more
than 30 years of research to this issue and developed relevant design
codes and design guides. However, codes in China have not yet provided
details on the resistance of progressive collapse. In this paper, the
corresponding design specifications for the progressive collapse prevention
in the main foreign design codes (e.g.,ACI 318-02£¬GSA 2003£¬DoD
2005¡¢EuroCode1¡¢BS8100) are summarized and compared.
Then, the major design methods to prevent progressive collapse are proposed
and suggestions are given for the Chinese codes.
Key words: progressive collapse codes design method
Simulation
for the Collapse of Reinforced Concrete Frame under Blast Load with
Fiber Model
Blasting, 24(2), 2007, 1-6.
Abstract: More and more attentions have been given to the simulation of collapse of structures under blast load. In this work, the collapse of a reinforced concrete (RC) frame under blast load is simulated with the fiber model based program THUFIBER, which is developed with MSC.MARC commercial finite element (FE) software. The flexural and shear failures of RC frame designed according to Chinese building codes have been considered in THUFIBER. The numerical results show that THUFIBER can correctly simulate the collapse of RC frame structure. And several important parameters are discussed with the FE model.
Keywords: blast, collapse, fiber model, reinforced concrete, finite element
Study
on the Frame and Soil Model in Collapse Analysis
Computer Aided Engineering, 2006, 15(Sup.), 417-420.
Abstract: Based on the common finite element software of MSC.Marc, with the convenient secondary development capacity, special models for reinforced concrete (RC) frame and soil are developed, in which the RC beams and columns are simulated with the fiber model based program THUFIBER, while the soil is simulated with a modified Drucker-Prager model. The computational results show that with the outstanding nonlinear capacity and secondary development function, the superstructure and soil can be properly simulated.
Key words: MSC.Marc, reinforced concrete frame, fiber model, soil model
Dynamic
Finite Element Simulation for the Collapse of World Trade Center
China Civil Engineering Journal,34(6), 2001,8~10
Abstract:
Simulation for the Collapse of World Trade Center is processed in this
paper with the finite element software of LS-DYNA. The parameters used
in the simulation are discussed with the numerical results. The simulation
is very close to the real conditions, which means that using proper
numerical model can simulate such complex problems as the collapse of
large building. The numerical results also show that the softening of
steel under fire and impact load of top floors are the two main reasons
for the collapse. If improving the steel fire-resistant ability or enhancing
the ductility of the structure, the collapse can be avoided.
Keywords: dynamic finite element, world trade center, collapse
of tall building