A Nonlinear Analysis Method for Perfomance Based Seismic Design

A Nonlinear Analysis Method for Perfomance Based Seismic Design Download File

A Simple Seismic Desiogn Strategy Based on Displancement and Ductility Compatibility
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A simple shear wall model taking into account stiffness degradation

Complex destructive phenomena take place in
reinforced concrete structures during earthquake excitations.
These include concrete cracking, interaction
effects between steel and concrete, steel yielding and
concrete crushing in compression. The damage generated
can be translated into a damage variable which takes
the local destructive effects into account in a global manner.
As damage increases within the reinforced concrete
structure, the alteration of the mechanical characteristics
yields modal characteristics changes. In this way, Chen
et al. [1] investigated the structural damage by means of
the identification method of modal changes. At a critical
damage level, they indicated that a decrease of the fundamental
frequency up to 10% can be expected for steel
beams. For reinforced concrete structures, the fundamen-
tal frequency reduction, related to the structural damage
can be significantly larger. Pseudodynamic tests carried
out at the European Laboratory for Structural Assessment
(JRC-Ispra) in fact showed fundamental frequency
reductions of more than 60% (Pegon et al. [2]). Such
fundamental frequency decrease strongly influences the
dynamic response of the structure subjected to a seismic
excitation.
In this paper, a simplified model for a particular lowrise
heavily reinforced shear wall is proposed. Its original
formulation is based explicitly on changes in fundamental
frequency according to a pertinent damage variable.
First of all, a detailed finite element analysis is
carried out with constitutive local models taking into
account the main destructive phenomena involved during
seismic excitation. The relevance of the modelling
is evaluated by comparing numerical results with experimental
available data. The following stage is devoted
to the identification of the decrease of the fundamental
frequency. This is realised by applying the finite element
modelling of the wall to a variety of ideal excitations
composed of sinusoidal cycles. The numerical results
allow to identify in a robust manner the decrease of the
fundamental frequency as a function of damage. Then,
this function is introduced in a simple dynamic uniaxial
model, expressed in terms of displacements at the top of
the wall. In the final stage, the validity of the proposed
simplified model is assessed by comparing numerical
results with experimental results in a first time, and, in
a second time, with the results issued from fine finite
element analyses for different types of seismic excitations.
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Performance of reinforced concrete buildings during, Turkey earthquake, and seismic design and construction practise in Turkey

On August 17, 1999, a Mw 7.4 earthquake occurred
on the 1500-km-long North Anatolian fault in northwestern
Turkey. The epicenter of the earthquake was near
Izmit, 90 km east of Istanbul (Fig. 1). Following the
earthquake, the Pacific Earthquake Engineering
Research Center dispatched a reconnaissance team to the
epicentral region to learn first hand about the performance
of the civil infrastructure. The geographic region
that was impacted by the earthquake was somewhat narrow
banded and centered around the fault, and stretched
from Istanbul in the west to Go¨lyaka and Du¨zce in the
east. Damage to building construction was severe and
widespread (Sezen et al. [1], Aschheim [2], Scawthorn
[3]). Estimates for economic losses were around 20
billion US dollars. The official death toll was over
17,200, with some 44,000 people injured and thousands
left homeless. Some 77,300 homes and businesses were
destroyed, and 244,500 were damaged. The majority of
deaths and injuries were in the cities of Kocaeli, Sakarya,
and Yalova.
This paper describes briefly the state-of-practice for
building seismic design and construction in Turkey, and
compares the US and Turkish codes. The performance
of the reinforced concrete frame and wall buildings and
their components during the 1999 Kocaeli earthquake is
presented, and evaluated considering the seismic design
and construction practice in the epicentral region.
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Seismic behaviour of self centring braced frame buildings with reusable hysteretic damping brace

Structural systems designed with conventional seismic design approach dissipate seismic energy by
incurring ductile inelastic response in selected regions. Such a seismic design strategy may not be
appealing from a life cycle cost perspective, especially for high seismic regions, where costly repairs
are often required after moderate earthquakes. After the 1994 Northridge earthquakes, growing
interests are given to a more logical seismic design approach, which involves energy dissipation
through supplemental damping system or fuse-type energy-dissipating devices. In such systems, the
main structural system is intended to have little or no damage while supplemental damping devices
are designed directly for energy dissipation and can be replaced if damaged during earthquakes.
Examples of such energy dissipation devices include friction damper, buckling-restrained brace
and many other types of passive or active structural control devices [1].
Buckling-restrained braces (BRB), which are capable of yielding in both tension and compression,
have been developed to overcome the buckling problem of conventional braces in concentrically
braced frames [2, 3]. BRB frame has been used extensively for seismic applications in Japan
after the 1995 Kobe earthquake and is also gaining popularity in the United States after the 1994
Northridge earthquake. BRB frames are desirable for seismic design and rehabilitation for their
superior ductile performance. Non-linear dynamic analyses by Sabelli et al. [2] have shown that
the behaviour of BRB frames is comparable and often better than that associated with conventional
concentrically braced frames and moment frames. However, several potential problems such as
tendency of BRBs to yield under frequent earthquakes have been identified for BRB frame by
a few researchers [2, 4]. Costly repair after moderately strong earthquakes might be necessary
due to these problems. For example, large residual displacements may exist in a BRB frame
after moderate earthquakes, necessitating closure of the building while costly repairs are being
carried out.
Recently, an alternative seismic resisting system with self-centring hysteretic behaviours has
received considerable interests (e.g. [5–7]). A flag-shaped hysteresis loop is typical of such selfcentring
systems with energy dissipation capability. Self-centring systems have the ability to control
damage and to reduce (or even eliminate) residual structural deformation. This is important since
residual structural deformation is emphasized as a fundamental complementary parameter in the
evaluation of structural (and non-structural) damage in the performance-based seismic design and
assessment approach [8].
Although several self-centring structural systems using post-tensioned high strength steel bars
or tendons have been proposed [5, 6, 9], special metals such as superelastic shape memory alloys
(SMA) possess a self-centring hysteretic behaviour which can be utilized to construct self-centring
braced frame systems. However, without pre-tensioning, superelastic SMA would most likely
remain linearly elastic and thus no energy dissipation would occur under frequent earthquakes.
SMA-based energy dissipation devices have recently attracted a great attention from civil engineering
researchers for seismic response control applications (e.g. [10–17]). Hodgson and Krumme [10]
proposed a SMA damping device with a centre-tapped configuration, in which the superelastic
wires are loaded to the middle of its superelastic strain limit when the device is constructed. This
centre-tapped configuration allows the device to dissipate energy in both push and pull directions.
Dolce et al. [13] tested Nitinol-based devices with full re-centring and good energy dissipation
capabilities. The kernel component of such a device consists of two groups of Nitinol wire loops—a
re-centring group of Nitinol wires with pre-strain and an energy-dissipating group of pre-tensioned
superelastic Nitinol wires, which are mounted on two concentric tubes. Their full-scale brace,
which was designed for a maximum force of 200 kN and has a double flag-shaped hysteretic
loop, can be used as a bracing element in framed structures. The ability of these SMA braces to
control the seismic response of RC framed structures was assessed through shaking table tests of a
1
3.3 -scale, 3-storey, two-bay RC plane frame, which was designed for low seismicity and low ductility
[14]. Their experimental results have shown that the SMA braces can provide performances
at least comparable to those provided by steel braces, while having an additional self-centring
feature.
This paper presents a special hysteretic damping device termed reusable hysteretic damping
brace (RHDB) with inherent self-centring behaviour and enhanced energy dissipation capacity.
A new type of self-centring braced frame system can be established by combining the concepts
of braced frames and self-centring system using RHDB. A seismic performance study of steel
concentrically braced frames with RHDBs, which is based on non-linear time history analysis of
RHDB frames, is the focus of this paper. The non-linear dynamic analysis involves a 3-storey and
6-storey concentrically braced frames subjected to design basis earthquake and frequent earthquake
ground motions for California.
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Prediction of elastic displacement response spectra in Europe and the Middle East

Empirical equations are presented for the prediction of displacement response ordinates for damping ratios
of 2, 5, 10, 20 and 30% of critical and for response periods up to 4 s, using 532 accelerograms from the
strong-motion databank from Europe and the Middle East. The records were all re-processed and only
employed for regressions at periods within the usable range, defined as a fraction of the filter cut-off
and depending on the instrument type (digital or analogue), earthquake magnitude and site class. The
equations can be applied to predict the geometric mean displacement and pseudo-acceleration spectra
for earthquakes with moment magnitudes (M) between 5 and 7.6, and for distances up to 100 km. The
equations also include style-of-faulting and site class as explanatory variables. The predictions obtained
from these new equations suggest that earlier European equations for spectral displacements underestimate
the ordinates at longer periods as a result of severe filtering and the use of the spectral ordinates at periods
too close to the filter cut-off. The results also confirm that the period defining the start of the constant
displacement plateau in the Eurocode 8 (EC8) spectrum is excessively short at 2 s. The results not only
show that the scaling factor defined in EC8 for estimating the spectral ordinates at damping ratios different
from 5% of critical are a good general approximation, but also that this scaling varies with magnitude and
distance (reflecting the influence of duration) and also displays a mild dependence on response period.
Copyright q 2007 John Wiley & Sons, Ltd.
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Simplified Estimation of Economic Seismic Risk for Buildings

Seismic risk enters into several important real-estate decision-making processes:
purchase of investment property, performance-based design of new structures, seismic
rehabilitation of existing buildings, and decisions regarding the purchase of earthquake
insurance, for example. In such situations, it matters who the decision makers are, how
they make decisions, what aspects of seismic risk most concern them, how long their
planning horizon is, and other parameters. We focus on one of the more common seismic
risk decision situations: the purchase of existing commercial property by real-estate
investors in seismic regions. (The most common situation is probably purchasing a home
in seismically active regions.)
Economic seismic risk to these properties is assessed every time the property
changes hands, on the order of every five to ten years. By contrast, a building is designed
and built only once. Thus the most common opportunity for market forces to
bring about seismic-risk mitigation for commercial properties is at times of sale. Anecdotal
evidence suggests that these are mostly missed opportunities: risk is typically not
mitigated, even in more vulnerable buildings.
This can be partly explained by considering the context in which seismic assessments
are performed. During virtually every sale of an existing commercial building, the
buyer assesses the building’s investment value using a financial analysis that considers
revenues and expenses, rent roll, market leasing, physical condition, and other property
information. The investor makes his or her bidding decision based on projected income
and expenses, using one or more of the economic performance metrics of net present
value, net operating income, cashflow, internal rate of return, and capitalization rate.
The input to this financial analysis is typically provided by a real-estate broker representing
the seller, whose figures the investor checks and modifies during a duediligence
study. Many of the inputs are known values—number, duration, and income
from current leases, for instance—but many are uncertain. Vacancy rates, market rents,
and other important parameters fluctuate significantly and unpredictably, leading to substantial
uncertainty in the future economic performance of a property. In the face of
these uncertainties, the bidder usually estimates investment value using best-estimate inputs
and then again with deterministic sensitivity studies to probe conditions that would
lead to poor performance (higher future vacancy rates, for example). The future cost to
repair earthquake damage is not one of the parameters the bidder uses in the financial
analysis. This is important: seismic risk is not a market quantity.
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On the characteristics of ground motion rotational components using Chiba dense array data

Rotational motions (torsional and rocking) induced by seismic waves have been essentially
ignored for a long time, first because rotational effects were thought to be small for man-made
structures [1], and second because sensitive measuring devices were not available until quite recently.
The benefits of the determination of rotational motion in seismology and engineering are
still under investigation (e.g. [2, 3]). In seismology, rotational motions can provide accurate data
for arrival times of SH waves and, in the near-source distance range, rotational motions might
provide more detailed information on the rupture processes of earthquakes [3]. Rotational motions
could also be used to better estimate the static displacement from seismic recordings, identifying
translational signals caused by rotation [2].
In engineering, dynamic response estimation of structures subjected to earthquake-induced base
excitations is often simplified by ignoring the rotational components. This has been a widely
accepted practice in engineering community, mainly caused by the lack of recorded strong motion
accelerograms for these motions. Many structural failures and the damage caused by earthquakes
can be linked to differential and rotational ground motions. Torsional responses of tall buildings in
Los Angeles, during the San Fernando earthquake in 1971, could be ascribed to torsional excitation,
while rotational and longitudinal differential motions may have caused the collapse of bridges
during San Fernando (1971), Miyagi-ken-Oki (1978) [4] and Northridge (1994) [5] earthquakes.
For the first time, Newmark [6] established a simple relationship between translational and torsional
components of the ground motion. He presented a deterministic procedure for estimating the
increase in displacement of symmetric-plan buildings caused by rotational ground motions at the
base due to horizontal propagation of plane waves with a constant velocity and further explored
in the other studies [7, 8]. Several studies have shown the importance of torsional components
in seismic analysis and design of structures [6, 9–13]. The seismic design codes also prescribe
‘Accidental Eccentricity’ in design force calculations to account for the unknown torsional inputs
and unpredictable eccentricities [14, 15]. Since then, many researchers have studied the dynamic
and accidental eccentricities of structures [12, 13, 16, 17]. The significance of rocking excitations
for continuous [18] and for base-isolated structures [19] is emphasized. Furthermore, the effects of
rocking motions on dynamic response of multistorey building have been analytically investigated
and the results revealed that stiff structures, such as nuclear power plants, having short vibration
periods, might be influenced more by this component in typical earthquake excitations [20].
Although some theoretical studies [20–22] have been carried out to estimate effects of rocking
components on response of structures, no provisions are made in design codes to account for the
effect of ground rocking motion.
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Earthquake response of tall reinforced concrete chimneys

Codes of practice around the world provide conservative
guidelines for the aseismic design of tall reinforced
concrete chimneys in the belief that such structures
would behave in a brittle manner when subject to severe
earthquake excitation. This has resulted in reinforced
concrete chimneys being prohibitively expensive in
regions of high seismicity. It has recently been established
from an experimental program that reinforced
concrete chimneys respond in a moderately ductile manner
under severe reverse cycle loading through yielding
of the reinforcement in tension provided that the sections
possess a reasonable curvature capacity [1].
The results from the experimental program have been
used to develop a non linear dynamic procedure for evaluating
the inelastic response of tall reinforced concrete
chimney structures described in this paper. The procedure,
which incorporates a cantilever model with discrete
plastic hinges is used to study the response of ten
chimneys, ranging in height from 115 m to 301 m, to
severe earthquake excitation. In particular, the response
behaviour and the failure modes of these chimneys associated
with an ensemble of earthquake ground motions
is described.
Based on the non linear dynamic study, a series of
code design recommendations have been prepared which
encourage the development of ductile behaviour to dissipate
the seismic energy and prevent the formation of
brittle failure modes. These recommendations have been
incorporated into the 2001 CICIND code [2] for the
design of reinforced concrete chimneys and result in
cheaper chimneys which perform better under earthquake
excitation (CICIND is a French acronym for International
Committee on Industrial chimneys). The justification
for the selection of a structural response factor
of R=2 which reduces the seismic design forces and satisfies
both the serviceability and structural stability limit
states is presented using a deterministic approach.
Finally, a comparison of the cost and performance of a
245 m tall chimney designed to the proposed seismic
code provisions is made with the 1998 ACI 307, 1998
CICIND, 1996 EC8-3 and 1997 UBC codes of practice
[2–5].
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Behaviour of Precast Concrete Beam for Earthquake Resistance and Fast Build House using Infill Frame System

Wilayah Indonesia mempunyai aktivitas
gempa yang cukup tinggi (puslitbang). Dampak yang
terjadi akibat gempa bumi tersebut adalah jatuhnya
korban jiwa dan keruntuhan sebagian besar bangunan,
khususnya rumah tinggal. Sebagian besar rumah yang
runtuh adalah rumah yang dibangun tanpa struktur
penguat seperti sloof, kolom, balok ring dari beton
bertulang, material yang tidak memenuhi standar dan
banyak rumah tinggal yang dibangun tanpa mengikuti
peraturan dan konsep desain bangunan tahan gempa
yang ada (Wibowo).
Untuk membantu korban tuna wisma, pemerintah
harus segera memberi bantuan berupa rumah tinggal
yang dapat dibangun secara cepat sehingga korban
dapat kembali beraktifitas dengan normal. Untuk
mengatasi masalah tersebut, maka pada penelitian ini
diusulkan rumah tahan gempa dari beton pracetak.
Sistem pracetak beton mempunyai beberapa
kelebihan seperti mutu dan bahan lebih terjamin karena
proses pembuatan di pabrik dengan control kualitas
pekerjaan yang prima, waktu pemasangan lebih cepat
dan praktis, beton dapat langsung diekspos tanpa perlu
finishing terlebih dahulu. Selain itu,
tidak perlu khawatir bahwa penggunaan elemen precast
tersebut akan mahal, karena mengingat elemen pracetak
bisa diproduksi secara massal dan seragam sehingga
elemen-elemen dalam jumlah besar bisa langsung
dicetak dan dirakit di lapangan untuk membuat suatu
perumahan se-tipe dalam jumlah banyak dalam waktu
singkat. Karena bisa mempercepat waktu pelaksanaan,
maka pasti akan menghemat biaya (Yee, 2001).
Salah satu komponen struktural bangunan adalah
balok. Balok menerima beban lentur yang menyebabkan
keruntuhan tarik dan beban geser yang dapat
menyebabkan keruntuhan getas (britlle). Desain geser
merupakan hal yang sangat penting dalam struktur
beton karena kekuatan tarik beton jauh lebih kecil
dibandingkan dengan kekuatan tekannya. Perilaku balok
beton bertulang pada keadaan runtuh geser sangat
berbeda dengan pada keruntuhan karena lentur. Balok
tersebut langsung hancur tanpa ada peringatan terlebih
dahulu.
Dalam penelitian ini akan digunakan sistem
struktur infill frame, pengertian sistem struktur infilled
frame adalah sistem struktur dimana kontribusi infill
panel (dinding atau panel pengisi rangka)
diperhitungkan dalam menahan beban lateral. Infilled
frame terdiri dari 3 komponen, yaitu rangka
(frame/skeletal structure), infill panel (bagian pengisi)
dan penghubung antara rangka dan infill
panel/pengisinya (Hoenderkamp et al,2005). Sistem
struktur ini dipilih karena banyak konstruksi rangka
gedung pada abad ke-20 ini yang dindingnya (cladding)
sengaja didesain untuk menambah kestabilan dan
kekakuan struktur terhadap beban lateral (D. V. Malick,
1967), sehingga dapat membantu rangka bahkan
mengoptimalkan dimensi rangka.
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Methodology of Seismic Hazard Analysis and Damage Assessment

Since Taiwan locates at seismic active region, seismic hazard mitigation
is always one of the most important parts in natural hazard mitigation
plans. To have effective seismic hazard mitigation plans needs
cooperation of experts in many fields. In order to accelerate the progress
in seismic loss estimation and hazard mitigation, Haz-Taiwan adopts the
methodology from HAZUS, which is developed by the scientists and
engineers in the United States. However, Taiwan has its special
construction environment and quality, seismic design codes, social and
economic activities, etc., not only the inventory data but also the
analytical models and the associated parameters need to be collected and
calibrated.
This joint project investigates methodology of seismic hazard analysis
and structural damage assessment from earthquake engineering
viewpoint. The main objective is to provide technical support, to develop
analytical models, and to calibrate associated parameters in Haz-Taiwan
program. The research topics include estimation of ground motion
intensities due to scenario earthquakes, estimation of permanent ground
deformation due to soil-liquefaction, evaluation of site-dependent seismic
demand of buildings, evaluation of capacity and fragility curves in damage
assessment of reinforced concrete buildings and multi-span continuous
bridges, and so on.
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