This research includes a numerical study using Finite Element Method aims to
evaluate the ability and accuracy of using Non-destructive Impact Response Method in the
assessment of length and cross-sections of intact concrete pile (not deformed) in
both time
and frequency domains. Therefore, an appropriate numerical model depends on the
modeling of both impact force (impulsive load) and distributing medium (pile + soil) and
insert them in computing software ABAQUS was carried out. The numerical model was
verified corresponding to field measures obtained from literature review and the results
showed good agreement between measures and numerical results. Furthermore, the model
was applied on a typical example in order to study vibration distribution in the pile due to
impulsive load applied on pile top. Mechanical response curve of intact pile was obtained.
Then, both of length and cross-section area of the pile were determined. Finally,
parametrical study of most important factors (stiffness of soil surrounding the pile and
length of pile embedded in the soil) effect on vibration distribution resulted from impulsive
load applied on pile top. The parametrical study was carried out in two domains; first one
was time domain depending on the direct analysis of particle displacement and velocity
and the second was frequency domain depending on analysis of pile mechanical response
curve. The results of this research enables to use the proposed numerical model to
numerically obtain the time history of particle displacement and velocity in addition to the
curve of mechanical response computed in the pile top and forms reference diagrams
which is used later to compare with similar diagrams resulted from field test of executed
piles. As a result, pile integrity test and detecting of defects in the piles if any. In addition,
the limits of the use of both analysis methods adapted in research and choose the best
between them according to the case study.
طريقة العناصر المنتهية
Finite element method
اختبار سلامة الأوتاد
تجارب الصدم غير المخربة
السجلات الزمنية للإهتزازات
تابع قابلية الحركة
منحني الإستجابة الميكانيكية للوتد
المجالين الزمني و الترددي
Pile Integrity Test
impulsive load
nondestructive impact tests
vibration time history
mobility function
pile mechanical response curve
time and frequency domains
ABAQUS
المزيد..
This research studies the behavior of the soft story in RC structures using
static analysis and dynamic analysis, where studying models of RC
structures containing soft story where this story results from increased
hieght of story than the rest st
orys, was conducted static analysis using
Nonliner pushover analysis and dynamic analysis using Nonliner time
history analysis
Response spectrum analysis and equivalent static analysis is widely used by
engineers and engineering offices to estimate buildings and structures response
to earthquakes. But performance based procedures to evaluate buildings and new
designs acco
rding to Syrian code and other international codes require response
analysis using smallest of earthquake records, where we can estimate
engineeringdemandparameters(EDPs)—
floordisplacements,storydrifts,memberforces,memberdeformations,etc.—
ofbuildingsandspecialstructuressubjectedtogroundmotions, consecutively to
verify required performance criteria.
Theserecordsshouldbeproperlyselectedandscaledincompliancewithsitespecifichazardconditionstoestimate
(EDPs) and ensure that they verify
―expected‖ median demands.
In this study, background, selection procedures compatible with Syrian
code, and review of most scaling methods were introduced. The structural
response was studied by comparing displacements due to response spectrum
analysis, scaled records using PGA, and synthetic time histories records in time
domain and frequency domain (generated according to Syrian response
spectrum). Tow three-dimensional models of real buildings in Lattakia city were
used as study cases, the results obtained by 20 analysis processes. The results
show that analysis using synthetic records compatible with Syrian code give
noticeably less displacements estimates comparing with response spectrum
analysis and analysis using records scaled by PGA scaling.
: Nonlinear response history evaluation is becoming a practical tool due to availability of high performance computing and recommendations of the new seismic guidelines, and due to the increase of available strong ground motion database. When testing
the selected and scaled ground motions, it’s a standard procedure to use the time history analysis to validate the results in terms of structural responses and their variation. this proves the efficiency of the presented procedure.
In this study the selection and scaling criteria of real time history records to satisfy the Syrian design code are discussed. Ten set of records have been selected and scaled, every set consists of seven records of available real records, to match the Syrian design spectra. The resulting time histories are investigated and compared in terms of suitability as input to time history analysis of civil engineering structures, by mean of time history analyses of SDOF systems which are conducted to examine the efficiency of the scaling method in reducing the scatter in structural response. The nonlinear response of SDOF systems is represented by bilinear hysteretic model. Assuming 5 different Periods, α=3% post-yield stiffness, a number of 700 runs of analysis are conducted. And a number of 280 runs of analysis are conducted for MDOF systems.
Design ground motions are typically prescribed by smooth response spectra. Engineers often prefer to use a time history that matches the target design spectrum rather than evaluate a structure for a sit of time histories that are representative of th
e target spectrum in an ensemble average.
Generally, scaling actual time histories to match a given design spectrum can be made by two preferred methods: First, ground motions uniform scaling in time domain which is simply scaled up or down the ground motion uniformly to best match the target spectrum within a period range of interest, without changing the frequency content. Second, spectral matching in time domain which produces only localized perturbations on both the time history and the its response spectrum, where small adjustments can be made to a time history to change its response spectrum from jagged to smooth, if done properly the resulting time history can be “realistic”.
The realistic nature of a time history should be judged in the time domain in terms of the non stationary character of acceleration, velocity and displacement, for that the effectiveness of the two methods is examined by applying them to adjust actual earthquake time histories to much the design spectra while minimizing perturbations on their characteristics.
The procedures are utilized to scale 15 set of records, every set consists of seven records of available real records to match the Syrian design spectra. The resulting time histories are investigated and compared in terms of suitability as input to time history analysis of civil engineering structures
The European Standard, the New Zealand Standard, the U.S. Standard, the Syrian Standard and the Iranian Standard define a criterion for selecting ground motion records for time-history analysis by similarity between the seismological signature of ear
thquakes used for the analysis and those earthquakes that are expected to happen at the given location. But these standards follow different methodologies. The New Zealand Standard proposes that the spectrum of each selected record should match the design spectrum over a range of periods related to the fundamental period of the structure investigated. The energy of at least one of these record’s spectra must exceed the energy of the design spectrum. The European Standard recommends that the average spectrum of the selected records should be always higher than 90% of the design spectrum in a defined range of periods, and the value of the average spectrum at period equal zero should be larger than the value of the corresponding design spectrum. The U.S. Standard, also the Syrian and the Iranian Standard; advise that in a defined range of periods, the average spectrum of the selected records should be 40% and higher than the code spectrum.
This study illustrates the differences between selecting approaches, and how these differences affect the resulting ground motion records. Some resulting recommendations for record selecting procedures are presented, and advised to be used in addition to the Syrian Standard recommendations.