Study on the Seismic Behavior of Structures
| Home | My Research |
Paper download
DownloadMulti-point
seismic motions based on focal mechanism and considering local site
multi-layer soil effect: theory and program implementation,
Chinese
Journal of Computational Mechanics, 2012, 29(4): 582-588.
Abstract: n this paper, a framework
for generating multi-point earthquake motion of target filed in China,
basing on focal mechanism and taking account of the spatial variability
of soil properties, is given and proposed. The main contents include:
(1) the transfer function of site including multiple soil layers is
established based on random vibration theory, (2) based on the improved
bedrock spectrum applicable to the target site in China, the variability
among different site condition is reflected by establishing the transfer
function of local site, (3) non-flat factor of site surface is considered
on the basis of previous literature, (4) explicit expression phase-angle
change by the filtration of multiple soil layers is also given for the
convenience of the subsequent program code. Then, according to the theory
framework, the visual program MEMS V2011.6 (Multi-support Earthquake
Motions Simulation Version 2011.6) is developed and run successfully.
The specific functions of the program involves the focal parameters
assignment, inputting soil parameters, calculating and displaying transfer
function of site soil with multi-layer, adjusting non-stationary parameters
and frequency, generating multi-point earthquake motion histories, verifying
the coherence of spatial seismic motions, fitting code-specified spectrum
for bridge, building and electronic facility. In addition, based on
a bridge example, the multi-point seismic motions of the target field
are generated using the program MEMS V2011.6, and the sensibility analysis
of the generated ground motions to local site effect and epicentral
distance is analyzed as well. The content in this paper involve theory
and practicability, and can provide directly reference for engineering.
Key words: multi-point earthquake motion; beck-rock spectrum;
local soil site; non-stationary; code-specified response spectrum
Seismic
damage simulation for urban buildings based on high-performance GPU
computing,
Proc. 14th Int. Conference on Computing in Civil and
Building Engineering, 2012.06. Moscow, Russia :368-369
Abstract: Refined models have been
an important development trend of urban regional seismic damage prediction.
However, the application of refined models has been limited due to their
high computational cost if implemented on traditional Central Processing
Unit (CPU) platforms. In recent years, Graphics Processing Unit (GPU)
technology has been developed and applied rapidly due to its powerful
parallel computing capability and low cost. In this paper, a simulation
method for urban regional seismic damage is developed based on GPU-CPU
cooperative computing technology, which reduces the computing time significantly.
The seismic damage simulation is then applied to a medium-sized city
using the proposed method to illustrate the unique advantages of GPU
technology in large-scale regional seismic damage simulations.
Keywords: urban regional seismic damage simulation, GPU, parallel
computing
Evaluation
of Modal and Traditional Pushover Analyses in Frame-Shear-Wall Structures
Advances
in Structural Engineering, 2011, 14(5): 815-836.
Abstract: Nonlinear
static analysis (or pushover analysis) has been widely used in the last
decade as a simplified and approximate method to evaluate the structural
seismic performance and to estimate inelastic structural responses under
severe ground motions. However most currently used pushover procedures
with invariant lateral load patterns cannot fully reflect the effect
of higher-order modes on structural dynamic responses. To overcome such
a problem, a so-called Modal Pushover Analysis (MPA) was proposed based
on the modal decoupling response spectrum method where the effect of
higher modes was considered. To date, most research on MPA has been
focused on frame structures. In engineering practice, however, most
medium-to highrise building structures are in the form of frame-shear-wall.
Therefore it is necessary to extend the current research activity to
implement the MPA to frame-shear-wall structures. In this study, two
reinforced concrete frame-shear-wall structures of 10 and 18 stories
are analyzed to evaluate the performance of the MPA method and the pushover
procedures with invariant load patterns. The evaluation is based on
the exact solutions of a nonlinear dynamic time-history analysis. The
results show that the MPA method including higher-order modes is more
accurate than the other pushover procedures. This is more evident when
estimating structural responses for high-rise structures than the medium-rise
counterparts.
Key words: nonlinear static analysis, nonlinear time-history
analysis, modal pushover analysis (MPA), frameshear-wall structures,
medium-to high-rise structures.
Spectra
of bedrock earthquake motion and improvement of bedrock displacement
input calculation model considering SSI effect,
Chinese Journal of Rock Mechanics and Engineering, 2011,
30(5): 884-892.
Abstract: In this paper, the applicability
of spectra of bedrock earthquake motion and rationality of calculation
model considering soil-structure interaction (SSI) for structural seismic
response analysis are studied. Firstly, in order to obtain the spectra
of bedrock earthquake motion in China, not only the expressions of the
current spectra of earthquake bedrock motion are compared and the preferred
one is selected, but also the high-cut filter function is modified to
fit the recorded earthquake motion of target fields in China. Then,
the current SSI calculation model for structural seismic response analysis
is expounded essentially and the unnegligible problem inherent in the
model is pointed out. To solute the problem, the Massless Rigid Element
(MRE) method proposed by the authors to solute the problem inherent
in the earthquake ground displacement input model is extended and applied
to solute the corresponding problem in the current bedrock displacement
input model considering SSI effect. At last, based on the works above,
the program for generating bed-rock displacement spectrum is coded and
a soil-layers model is analyzed. The analysis results can further indicate
that the MRE method is quite applicable to the calculation model considering
SSI effect. The works of this paper belong to fundamental study and
can provide necessary reference for the relevant study of SSI effect.
Keywords: bedrock earthquake motion; Massless Rigid Element (MRE)
method; soil-structure interaction (SSI)
Multi-scale
finite element modeling and its application in the analysis of a steel-concrete
hybrid frame,
Chinese Journal of Computational Mechanics, 2010, 27(3):
469-475.
Abstract: As an effective process
to obtain appropriate balance between accuracy requirements and calculation
workloads, multi-scale calculation has been introduced into many research
fields as well as different engineering practices. In the field of structural
multi-scale finite element analysis, an important research question
is how to make the local microscopic model and structural macroscopic
model work together. To accomplish a reliable interface between microscopic
model and macroscopic model, a methodology was proposed and its constraint
equations of deformations including axial deformation, transverse deformation
and rotation were presented. With a user-defined subroutine, the multi-scale
modeling was realized in commercial finite element software and a simple
tube was calculated to verify the methodology. Based on an accurate
microscopic column-to-beam connection model validated by test, elasto-plastic
multi-scale analysis of a steel-concrete hybrid frame was carried out
and the results show that multi-scale calculation can simulated the
complex boundary condition of this connection well. The proposed methodology
meets the deformation compatibility well at the interface between different-scale
models and is applicable in engineering application.
Keywords: multi-scale; interfacial connection; finite element;
engineering application; elasto-plastic time history analysis
Evaluating
method of element importance of structural system based on generalized
structural stiffness
Journal of Architectural and Civil Engineering, 2010,
27(1): 1-6.
Abstract: A summary of existing
researches and engineering experience on element importance in the structural
systems were presented. Based on the consensus that elements transferring
more loads in the load path were generally more important in the structural
systems, the element importance index was defined as the change in generalized
structural stiffness under a certain load pattern after removing the
element from the system. Then, the generalized structural stiffness
taking into account the load pattern was proposed as a basis for evaluating
the element importance. This index was further expressed in terms of
the rate of structural strain energy change. The element importance
of a series of frame structures under gravity and horizontal seismic
load were then evaluated by the proposed method. The results show that
the method is rational, convenient for calculating, and applicable to
most structures.
Keywords: Structural safety, element importance index, generalized
structural stiffness, loading path, structural strain energy
Elasto-plastic
seismic analysis for the Beijing Automobile Museum,
Building Structure, 2009, 39(12): 118-120.
Abstract: The Beijing Automobile
Museum is a stadium structure with complex shape, which also has some
complicated steel-reinforced concrete joints to carry the columns that
sit on beams. This work uses macro-scale nonlinear finite element model
with fiber-beam-element and multi-layer-shell-element to study the elasto-plastic
static and transient seismic response of the whole structure, and micro-scale
model with continuum elements to study the elasto-plastic behavior of
the complicated joints. The loading capacities of the joints from the
micro-scale model are compared with the internal forces from the global
structural analysis. The results show that the Beijing Automobile Museum
can satisfy the seismic requirement of design fortification VIII, and
the joints have enough strength. This work provides examples for the
elasto-plastic seismic analysis of similar stadium structures.
Keywords: Beijing Automobile Museum, seismic resistance, elasto-plastic
analysis, joint loading capacity
Seismic
performance evaluation using nonlinear time history analysis with three-dimensional
structural model for a hybrid frame-core tube structure,
Journal of Building Structures, 2009, 30(4): 119-129
Abstract: Accurate prediction for
the structural nonlinear behaviors is important to the structural safety
assessment against earthquakes. Some new models, which are used to establish
three-dimensional structural model for nonlinear time history analysis
under strong earthquakes, are presented. In these models, the material
stress-strain relationship can be connected directly with the force-displacement
behavior of the structural elements, such as beams, columns, shear walls
and core tubes, so that the complicated coupled axial force-bending
moment-shear force behaviors, as well as the corresponding cycle behaviors,
can be properly simulated. With the secondary development user subroutines,
convenient p re and post process functions and extinct nonlinear capacity
of general purpose FEA software of MSC. MARC, the spatial seismic responds
of structures can be simulated in detail. A practical hybrid frame-core
tube structure was analyzed with dynamic time-history analysis based
on these models and the complicated seismic behaviors of the structure
were simulated. According to the analytical results under ground motions
with different intensities, the exterior frame and the core tube made
up of four sub-tubes in this structure can form effective dual seismic
resistant system which has three seismic fortification lines: coup ling
beam, sub-tubes and exterior frame.
Keywords: hybrid frame-core tube structure; fiber model; multi-layer
shell element; nonlinear analysis; seismic performance
Seismic
performances and failure mode analysis of hybrid frame-core tube structures,
Building Structure, 2009, 39(04): 1-6.
Abstract: Frame-core tube system
is a type of structure which is widely used in the high-rise buildings.
In this paper, the seismic behaviors are analyzed and the rational failure
mode of this structure system is discussed. And it is proposed that
by controlling the yielding mechanism and failure mode of the core tube
based on the idea of the capacity design method and making sure the
outer frame has sufficient loading carrying capacity and ductility at
the same time, the seismic performance of the frame-core tube structure
will be improved and multiple seismic fortification lines can be established.
A practical frame-core tube hybrid structure is analyzed with pushover
method and dynamic time-history analysis respectively as an example.
The analytical results show that the reasonably designed frame-core
tube structure can form effective dual seismic resistant system which
has three seismic fortification lines: coupling beam, sub-tubes and
outer frame. Besides, the structure system has adequate energy dissipation
ability and can achieve the rational failure mode.
Keywords: frame-core tube structure, failure mode, seismic performance,
seismic fortification lines
Influence
of post-yielding stiffness to seismic response of building structures,
Journal of Building
Structures, 2009, 30(2): 17-29.
Abstract: The accurate prediction
of elasto-plastic structural response is necessary for establishing
the performance based seismic design method of building structures.
The influence of post-yield stiffness of structures on the dispersion
of elasto-plastic structural response is studied based on a large number
of elasto-plastic time-history analysis of single-degree-of-freedom
(SDOF) and multi-degree-of-freedom (MDOF) systems. The analytical results
show that: for SDOF systems with moderate or long vibration periods,
the maximal elasto-plastic displacements and the corresponding dispersions
will not obviously change with larger post-yield structural stiffness.
On the contrary, the maximal elasto-plastic displacements and the corresponding
dispersions will obviously reduce by larger post-yield stiffness for
SDOF systems with short vibration periods. And for MDOF systems with
larger post-yield stillness, the ductility factors and energy dissipations
will trend to be evenly distributed, together with obvious smaller dispersions
of maximal elasto-plastic inter-story drift. At the end of this paper
the engineer measures to increase the structural post-yield stiffness
is discussed and three typical examples are demonstrated to illustrate
the methods of building up a hardening-type structure from the structural
systematic level consideration.
Keyword: earthquake, inelastic response, inelastic system, post-yielding
stiffness, discreteness, performance based design
Finite
element analysis and engineering application of RC core-tube structures
based on the multi-layer shell elements
China Civil Engineering journal, 2009, 42(3): 51-56.
Abstract£ºAs one of the
most widely used lateral resistant structures, reinforced concrete (RC)
core tube consists of diverse members and appears spatial mechanical
behaviors. Therefore, how to accurately simulate the RC tubes for the
whole process of nonlinear behaviors is an important problem in seismic
analysis of structures. Based on the multi-layer shell element, the
whole process simulation of a pseudo-static testing on RC core tubes
is presented in the paper. By correct modeling of the key parts (such
as walls, coupling beams, reinforcement), the numerical model is able
to simulate the spatial behavior of the tube as well as the complicated
nonlinear behaviors such as the yielding and shear failure of coupling
beams, cracking of the tube and so on. Results from the simulation match
well with those from the tests. Using the proposed core-tube model,
an elastoplastic analysis for a practical framed core-tube structure
is conducted, to illustrate the implementation of proposed model in
real structures. The tube model based on multi-layer shell is helpful
in the elasto-plastic analysis of high-rise building under severe earthquakes.
Keywords£ºCore tube, Finite element, Multi-layer shell,
Elastoplastic calculation, Seismic Analysis
Comparative
evaluation of pushover analysis and modal pushover analysis with invariant
spatial earthquake load
Journal of
South China University of Technology (Natural Science Edition), 2008,
36(11): 121-128.
Abstract: Nonlinear static analysis
procedure is now widely used as a simplified effective method for estimating
the inelastic responses of structures under severe ground motions. Based
on structural dynamics theory, the modal pushover analysis (MPA) procedure
is proposed to consider effect of the higher structural response modes,
which is equivalent to standard response spectrum analysis for elastic
systems. Although the MPA procedure is common in structural engineering
practice, there are few researches on comparative evaluation of pushover
analysis and MPA procedure with invariant spatial earthquake load. Herein,
MPA and pushover procedures are estimated to compare with incremental
nonlinear dynamic time history analysis with invariant spatial earthquake
load for a six-story and a ten-story. It is indicated that the both
pushover and MPA procedures give good prediction for inelastic roof
displacements, especially the MPA procedure. Whereas, the estimation
of the maximum story drift of structure needs to be improved and requires
further more investigation.
Key words: nonlinear static analysis, nonlinear time history
analysis, modal pushover analysis, RC frame, fiber model
Nonlinear
static analysis for frame-shear-wall structures
Earthquake Resistant Engineering and Retrofitting, 2008,
30(6): 41-48.
Abstract: Nonlinear static analysis
(or pushover analysis) has been widely used recently as a simplified
method to evaluate the structural seismic performance and estimate inelastic
structural responses under severe ground motions. But most traditional
pushover procedures, which have fixed lateral load patterns that are
major based on first structural modal, can not reflect the effect of
the higher modal on the structural dynamic response. To overcome this
problem, Chopra et al. has proposed a new pushover procedure which is
referred as modal pushover analysis (MPA) based on the modal decoupling
response spectrum method to consider the effect of the higher mode.
Currently, most MPA research is focused on frame structures. In this
paper, the problem of MPA when it is implemented in frame-shear-wall
structures is high lighted together with proposed solution method. An
eighteen story reinforced concrete frame-shear-wall structure is used
as an example to benchmark the accuracy of traditional pushover method
and MPA method. The structural responses with MPA method and traditional
pushover methods are compared with the results of incremental nonlinear
dynamic time history analysis, which shows that MPA procedure gives
better prediction for inelastic responses of the structure.
Keywords: nonlinear static analysis, nonlinear time history analysis,
modal pushover analysis, RC frame-shear-wall structure
Study
on ensuring the strong column-weak beam mechanism for RC frames based
on the damage analysis in the Wenchuan Earthquake
Building Structure,
2008, 38(11): 52-59.
Abstract: Typical earthquake damages of RC frames in the Wenchuan earthquake are reviewed with some brief analyses. Special attentions are given to the absence of the preferable damage mode of RC frames known as the ¡°strong column-weak beam¡± mechanism. Analysis is conducted in depth in order to discover the underlying reasons for this adverse phenomenon in the following aspects: influence of the partitions and floor slabs, possible reasons for under-estimating the strength and stiffness of frame beams, reasons for the over-reinforcement of frame beams, factors that may weaken frame columns, structural model changing under stronger earthquake, the difference of reliability of columns and beams under different load stages and so on. Suggestions of ensuring the ¡°strong column-weak beam¡± mechanism for RC frames are proposed for the reference of future design practice and code revision.
Multiscale
finite element modeling and its application in structural analysis
Journal of Huazhong University of Science and Technology
(Urban Science Edition), 2008, 25(4): 76-80.
Abstract: A methodology to connect
microscopic finite element model to macro model is proposed, which is
important to carry out multiscale finite element analysis (FEA) of stuctures.
Both the theory and the verifying example show that the methodology
meets the deformation compatibility well at the interface between different-scale
models. Based on the methodology, a precise microscopic finite element
model is implanted into a macro frame structure model to form a multiscale
model. In the end, a further example of application is given.
Keywords: multiscale calculation, interface connection, finite
element, engineering application£¬elasto-plastic time history
analysis
Study
on the influence of post-yielding stiffness to the seismic response
of building structures
Proc. the 14th World Conference on Earthquake Engineering,
October 12-17, 2008, Beijing, China, CDROM.
ABSTRACT: The response dispersion
of structures under strong earthquakes significantly restricts the implementation
of performance based seismic design. Besides the variation of earthquake
inputs, the inelastic characteristics of structures themselves are also
the influence factors on the seismic response dispersion of structures,
in which the post-yielding stiffness is key parameters. In this paper
the inelastic time-history analysis of numbers of SDOF and MDOF systems
are studied to investigate the influence of post-yielding stiffness
on the inelastic seismic response and the dispersion. The analytical
results show that, (1) for SDOF system, the larger positive post-yielding
stiffness will result in smaller the maximum displacement and especially
the residual displacement, (2) for the MDOF system, the larger positive
post-yielding stiffness results in more uniform distribution of hysteresis
energy dissipation and the smaller variation of the maximum inelastic
story drift. Hence, the larger of the positive post-yielding stiffness
will result in a better control of structural performance under earthquake,
so that the performance based design can be easier implementation. The
methods to increase the post-yielding stiffness and some practical examples
are finally presented in this paper.
KEYWORDS: inelastic seismic response, post-yielding stiffness,
dispersion, performance based design
Analysis
on Building Seismic Damage in Wenchuan Earthquake
Journal
of Building Structures, 2008, 29(4): 1-9.
Abstract: On May, 12, 2008, an earthquake
with a magnitude of 8.0 happened in Wenchuan, Sichuan Province. The
earthquake resulted in a large number of collapses and damages of buildings,
and brought huge loss to the people's lives and properties. This paper
gathers the building seismic damage data in major disaster area from
the investigation work of the civil and structural groups of Tsinghua
University, Xinan Jiaotong University and Beijing Jiaotong University.
The data are classified according to structural type, construction time,
earthquake intensity and function of usage. The characters of building
seismic damage in this earthquake is analyzed with typical building
damage cases, and the lessons are concluded on structural type selection,
structural design and construction management and so on.
Keywords: Wenchuan earthquake, Seismic damage analysis, seismic
damage cases
Influence
of the inter-story post-yield stiffness to the variance of seismic response,
Engineering Mechanics, 2008, 25(7): 133-141.
Abstract:
The remarkable discreteness of seismic response of structures under
strong earthquakes significantly restricts the implementation of performance
based seismic design. Response variation may be caused by the variant
ground motions and the seismic capabilities of structures. Based on
numerical simulations, the influence of structural stiffness after yielding
on the inelastic seismic response for multi-degree of freedom (MDOF)
structural systems is discussed. By avoiding degradation of structural
stiffness after yielding, damage concentration in structures may be
prevented which would also reduce the discreteness of inelastic seismic
responses. Moreover, it is studied that structures with higher stiffness
after yielding are more effective to control the seismic performance
of structures, that will achieve the aims of performance based seismic
design.
Key words: earthquake response; inelastic MDOF system; stiffness
after yielding; discreteness; performance based design
Seismic
nonlinear analytical models, methods and examples for concrete structures
Engineering Mechanics, 2006, 23(sup. II). 131-140.
Abstract: Structures will enter
nonlinear stage in strong earthquake, precisely prediction for the nonlinear
behavior of reinforced concrete (RC) structures in earthquake is important
to assess the aseismic safety of the structures. This paper presents
the programs recently developed by the Civil Engineering Department
of Tsinghua University, which include the fiber model based the program
THUFIBER for RC frames, the program NAT-PPC for prestressed concrete
(PC) frames, and multi-layer shell element based shear wall program.
These programs can connect the nonlinear nodal force/nodal displacement
relationship of elements directly with the nonlinear stress/strain relationship
of materials. So complicated cycle behaviors and coupled axial force-biaixal
bending-shear behaviors of the RC structures can be correctly simulated.
And furthermore, with the convenient pre/post process and nonlinear
capacity of common finite element software, these programs not only
can precisely simulate the spatial structural nonlinear seismic response,
but also can simulate some extreme nonlinear problems such as blast
or collapse. The precision and the capacity of the programs are illustrated
in this paper with a series of researches and applications.
Keywords: reinforced concrete, seismic, nonlinear, fiber model,
shear wall, multi-layer shell
Elasto-plastic
Analysis for A Steel Frame-Core Wall Structure
Sichuan Building Science, 2008, 34(3): 5-10.
Abstract: Structures will enter
nonlinear stage during strong earthquakes. Hence accurate prediction
for the structural nonlinear behaviors is important to the safety and
loss assessment during earthquakes. This paper reviews the existed nonlinear
analytic models for structures and presents some novel models for structural
nonlinear analysis that recently developed by the Tsinghua University.
With these models, the material stress-strain relationship can be connected
directly with the force-displacement behavior of the structural elements.
So that the complicated coupled axial force-bending moment-shear force
behaviors can be properly simulated, as well as the corresponding cycle
behaviors. With the secondary development user subroutines, convenient
pre and post process functions and extinct nonlinear capacity of general
purpose FE software of MSC.MARC, the spatial seismic responds of structures
can be precisely simulated. A steel frame-core wall structure with an
eccentric tube is analyzed with static pushover and dynamic time-history
analysis to demonstrate the applications of the new models.
Keywords: nonlinear analysis, structure, seismic, fiber model,
shear wall, multi-layer shell
Introduction
of Robustness for Seismic Structures
Building Structures, 2008, 38(6): 11-15.
Abstract:The concept of robustness
of structures is firstly introduced in this paper. And importance with
enough robustness for seismic structures in preventing collapse of the
structures under strong intensity earthquake attack is discussed. Then
the approaches to increase the robustness of seismic structures, including
structural systems, strength and ductility of structure, failure modes
and redundancy, are suggested.
Keywords: seismic structure; robustness; structural systems;
integrity; failure mode; strength; ductility; redundancy elements.
Study
on lateral load patterns of pushover analysis using incremental dynamical
analysis for RC frame structures
Journal of Building
Structures, 2008, 29(2): 132-140.
Abstract: In this research, the nonlinear
static p rocedures with different lateral load patterns were compared
by using incremental dynamical analysismethod based on a six2storey
and a ten2storey RC frame fibermodel. For each story of different frames,
the inter2story shear force vs. drift curves computed by pushover analysis
by using different lateral load patterns and time history analysis with
a series of earthquake records on the design site have been compared
to give a rational lateral load pattern of pushover analysis. Finally,
for a whole frame structure, the lateral load pattern choice was suggested,
that is,
uniform load pattern was better for the stories near foundation; load
pattern with the story heights taken into consideration was suitable
for the mid stories and the SRSS pattern or Chinese Code pattern was
suitable for upper stories. It is also shown that the nonlinear static
p rocedure gives a safe estimation of the inelastic seismic response
statistically for regular RC frames with good numerical stability.
Keywords: RC frame; fiber model; pushover analysis; incremental dynamic
analysis; inter-storey shear force and drift relation
Abstract: Precise prediction for
the hysteretic behaviors of reinforced concrete (RC) column under seismic
load is important to assess the safety of RC structures under earthquake.
Due to the overturning moment in the earthquakes, besides being subjected
to seismic lateral forces, RC columns also experience variable axial
loads. Therefore the influence of variable axial forces must be taken
into account when to study the hysteretic behaviors of RC columns under
cyclic loads. In this paper, a numerical analysis model based on a fiber
model program have been validated firstly through the rational hysteretic
simulations of two RC columns under various patterns of axial loads,
Then a frame column has been simulated under various patterns of variable
axial loads by numerical method. The analytical results indicate that
the variety of axial loads has considerable effect on the hysteretic
behaviors of RC columns. Because of the randomness of axial loads and
to facilitate carrying on experimental researches and analyzing earthquake-resistant
behaviors for RC structures, a equivalent fixed axial load method is
put forward to determine the seismic behaviors of RC column in structures
under earthquake.
Keywords: fiber model; variable axial load; concrete column;
earthquake-resistant behavior; hysteretic analysis
Numerical
Simulation for the Hysteresis Behavior of RC Columns under Cyclic Loads
Engineering Mechanics, 2007, 24(12): 76-81
Abstract£ºPrecise prediction
for the hysteresis behaviors of reinforced concrete (RC) columns under
seismic loads is important to assess the safety of RC frames and bridges
during sever earthquake. Due to the complicated material behavior and
complex external force during the earthquake, an accurate simulation
of the behaviors under seismic loads currently mainly depends on numerical
method, and more precisions are demanded for the hysteresis constitutive
laws of concrete and steel reinforcement. In this paper, a fiber model
program is developed with more precise hysteresis constitutive laws
of concrete and steel reinforcement. Two columns, which are under cyclic
compressive-bending loads, with different axial load ratios and reinforcement
ratios are analyzed and the simulation results are found agreed well
with test results.
Key words: fiber model; cyclic load; concrete column; hysteretic
relation; numerical analysis
High
Performance Simulation for Building Structures under Disaster
Proc. 1st Symp. on High Performance Computing (HPC) Technology
in Engineering Design, 2007. Dec. 11-12, Shanghai: 93-101.
Abstract: Buildings and building
clusters could be destroyed by disaster load, such as earthquake and
blast. Accurate prediction for the behavior of building structures in
various disasters provided by high-performance numerical computing is
important to structural design. The Department of Civil Engineering
in Tsinghua University developed a series of advanced numerical models
including material laws and element models. Therefore, base on parallel
computing and nonlinear methods, analyses about some extreme problems
of building structures such as collapse, overturning and the loss of
earthquake damage of urban building clusters are successfully processed.
Hence, the analyses provide important advice for disaster prevention
and mitigation.
Keywords: building structure, high-performance simulating analysis,
finite element model, progressive collapse, blast wave, urban building
clusters
Study
on the Accuracy and Applicability of the Pushover Analysis
Earthquake Resistant Engineering and Retrofitting, 30(1),
2008, 55-59.
Abstract:
The nonlinear static pushover analysis procedure is now widely used
as a simple method to estimate the inelastic seismic response for building
structures. However, the accuracy of the method still needs to be validated
because of the inherent limitation in the theory of the method. Besides,
there are some confines on the application of this method. In this paper,
a 6-storey RC frame and an 18-storey RC frame-wall structure are analyzed
with both pushover method and the incremental dynamical analysis method
respectively. The comparison between the results of the two methods
shows that the pushover method can be used only for low structures which
are controlled by the first modal shape. It is also shown that for the
structures which are influenced by the higher modal shape evidently,
pushover analysis always gives the much lower capacity result.
Keywords: pushover analysis, RC frame, frame-wall structure,
IDA
Spatial
finite element analysis for the whole-process of RC core tubes based
on the layered shell element
Proc. 11th Conf. on earthquake resistance technology
of high-rise buildings, Nov. 2007. Kunming, China, 184-189.
Abstract£ºAs the most
widely used lateral resistant structures, RC core tubes consist of various
members and perform spatial mechanical behaviors. Therefore, how to
accurately simulate the RC tubes for the whole process of nonlinear
behaviors is a significant subject in seismic analysis of structures.
Based on the layered shell element the whole process simulation of a
pseudo-dynamic testing on RC core tubes is presented in the paper. By
correct modeling of the key structural elements (such as walls, coupling
beams, reinforcements), the model is able to reflect the spatial behavior
of the tube as well as the complicated nonlinear behaviors of the yielding
and shear failure of coupling beams, cracking of the tube and so on.
Furthermore, results from the simulation match well with those from
the tests, which show the finite element model is of some help on elasto-plastic
calculation of high-rise RC tubes in severe earthquakes.
Keywords£ºCore tube, Finite
element, Layered shell, Elasto-plastic calculation, Seismic Analysis
Elasto-plastic
time-history computational model for steel frame-core wall structures
Architecture Technology, 2007, 38(sup.), 242-244.
Parametric
study of structural stiffness after yielding on inelastic seismic response
for multi-degree of freedom structural systems
Journal of Disaster Prevention and Mitigation Engineering,
27(sup.), 2007, 158-162.
Abstract: The remarkable discreteness
of seismic response of structures under strong earthquakes significantly
restricts the implementation of performance based seismic design. Response
variation may be caused by the variant ground motions and the seismic
capabilities of structures. Based on numerical simulations, the influence
of structural stiffness after yielding on the inelastic seismic response
for multi-degree of freedom structural systems is discussed. By avoiding
degradation of structural stiffness after yielding, damage concentration
in structures may be prevented which would also reduce the discreteness
of inelastic seismic responses. Moreover, it is studied that structures
with higher stiffness after yielding are more effective in controlling
the seismic performance of structures, that will achieve the aims of
performance based seismic design.
Keywords: earthquake response; inelastic
MDOF system; stiffness after yielding; discreteness; performance based
design, cumulative hysteretic energy dissipation
Numerical
Simulation for the Hysteresis Behavior of Prestressed Conrete Structures
under Cyclic Loads
Earthquake
Resistant Engineering, 28(6), 2006, 25-29.
Abstract: Due to progressively using
in practical construction of prestressed concrete structures, the researches
for seismatic performance of prestressed concrete (PC) structures has
remarkable significance in engineering practice. Because of the complicated
behavior of material and loads, the precise simulation of PC structures
or members under cyclic loads has to depend on numerical model. In this
paper, a numerical analysis model for the simulation of PC member structures
has been developed on the basis of a fiber model program. A PC frame,
an unbonded PC frame and an unbonded PC column under cyclic loads are
simulated with the developed program. The comparison of the results
between simulations and tests indicates that, for the reason of using
rational hysteretic material model and exactly considering the influence
of prestressing, the numerical analysis model based on fiber models
developed in this study can accurately predict the hysteretic properties
of PC structures and can be used in the parametric analysis and mechanism
study.
Keywords: fiber model; cyclic load; prestressed
concrete; analysis method
High
strength/performance structural materials and the developments of modern
engineering structures and the design theory
Proc. 1st International Forum on Advances in Structural
Engineering, Beijing: China Building Industry Press, Beijing, 2006,
208-250.
Abstract: This paper firstly presents
the latest development of high strength/performance structural materials
in recent years. The rational applications and examples of high strength/
performance structural materials in the structural systems to obtain
high performance are discussed and presented. The positive functions
of high strength reinforcement used in reinforced concrete frame structures,
that can enhance the structural performance against earthquake and reduce
the structural seismic damage, are investigated in detail with nonlinear
pushover analysis and dynamic analysis. The results show that the high
seismic performance of the reinforced concrete frames, including a delayed
appearance of plastic hinges at the bottom story columns feet, to form
a rational failure mechanism under strong earthquake, and a small residual
displacement after earthquake that cause an easy retrofitting after
earthquake, can be obtained by replacing normal strength reinforcement
with high strength reinforcement in the columns. Finally, the development
of the safety and design theory for the structures using high strength/performance
materials are discussed.
Keywords: High strength/performance concrete;
High strength/performance steel; Engineering Structures; Structure safety;
Design theory; Accidental event; Earthquake resistance.
Nonlinear
FE model for RC shear walls based on multi-layer shell element and microplane
constitutive model
Proc.
Computational Methods in Engineering And Science (EPMESC X),
Tsinghua University Press & Springer-Verlag, Aug. 2006, Sanya, Hainan,China,
2006, CDROM.
Abstract: Nonlinear simulations
for structures under disasters have been widely focused on in recent
years. However, precise modeling for the nonlinear behavior of reinforced
concrete (RC) shear walls, which are the major lateral-force-resistant
structural member in high-rise buildings, still has not been successfully
solved. In this paper, based on the principles of composite material
mechanics, a multi-layer shell element model is proposed to simulate
the coupled in-plane/out-plane bending and the coupled in-plane bending-shear
nonlinear behaviors of RC shear wall. The multi-layer shell element
is made up of many layers with different thickness. And different material
models (concrete or rebar) are assigned to various layers so that the
structural performance of the shear wall can be directly connected with
the material constitutive law. And besides the traditional elasto-plastic-fracture
constitutive model for concrete, which is efficient but does not give
satisfying performance for concrete under complicated stress condition,
a novel concrete constitutive model, referred as microplane model, which
is originally proposed by Bazant et al., is developed to provide a better
simulation for concrete in shear wall under complicated stress conditions
and stress histories. Three walls under static push-over load and cyclic
load were analyzed with the proposed shear wall model for demonstration.
The simulation results show that the multi-layer shell elements can
correctly simulate the coupled in-plane/out-plane bending failure for
tall walls and the coupled in-plane bending-shear failure for short
walls. And with microplane concrete constitutive law, the cycle behavior
and the damage accumulation of shear wall can be precisely modeled,
which is very important for the performance-based design of structures
under disaster loads.
Keywords: shear wall, nonlinear analysis,
microplane, finite element, multi-layer shell element