Abstract: Currently there are many use of threaded reinforcing
bars in construction fields because those do not need additional screw
processing when connecting reinforcing bar by threaded coupler. In
this study, reinforced concrete bridge piers using threaded rebar
coupler system at the plastic hinge area were tested to evaluate seismic
performance. The test results showed that threads of the threaded rebar
coupler system could be loosened while under tension-compression
cyclic loading because tolerance and rib face angle of a threaded rebar
coupler system are greater than that of a conventional ribbed rebar
coupler system. As a result, cracks were concentrated just outside of
the mechanical coupler and stiffness of reinforced concrete bridge pier
decreased. Therefore, it is recommended that connection ratio of
mechanical couplers in one section shall be below 50% in order that
cracks are not concentrated just outside of the mechanical coupler.
Also, reduced stiffness of the specimen should be considered when
using the threaded rebar coupler system.
Abstract: The Composite Shear Walls (CSW) with steel encased
profiles can be used as lateral-load resisting systems for buildings
that require considerable large lateral-load capacity. The aim of this
work is to propose the experimental work conducted on CSW having
L section folded plate (L shape steel made-up sections) as
longitudinal reinforcement in boundary regions. The study in this
paper present the experimental test conducted on CSW having L
section folded plate as longitudinal reinforcement in boundary
regions. The tested 1/3 geometric scaled CSW has aspect ratio of 3.2.
L-shape structural steel materials with 2L-19x57x7mm dimensions
were placed in shear wall boundary zones. The seismic behavior of
CSW test specimen was investigated by evaluating and interpreting
the hysteresis curves, envelope curves, rigidity and consumed energy
graphs of this tested element. In addition to this, the experimental
results, deformation and cracking patterns were evaluated, interpreted
and suggestions of the design recommendations were proposed.
Abstract: This study aims to evaluate the effective size, section
and structural characteristics of circular hollow steel (CHS) damper.
CHS damper is among steel dampers which are used widely for
seismic energy dissipation because they are easy to install, maintain
and are inexpensive. CHS damper dissipates seismic energy through
metallic deformation due to the geometrical elasticity of circular shape
and fatigue resistance around connection part. After calculating the
effective size, which is found to be height to diameter ratio of √3,
nonlinear FE analyses were carried out to evaluate the structural
characteristics and effective section (diameter-to-ratio).
Abstract: The goal of the paper is to highlight the effect of the
building design and epicentral distance on the storey lateral
displacements, for several reinforced concrete buildings (6, 9 and 12
stories). These structures are subjected to seismic accelerations from
the Boumerdes earthquake (Algeria, May 21st, Mw = 6.8). Using the
response spectrum method (modal spectral approach), the analysis is
performed in both longitudinal and transverse directions. The
building design is expressed through the fundamental period and
epicentral distance is used to represent the earthquake effect variation
on storey lateral displacements and interstory drift for the considered
buildings.
Abstract: This paper presents development results of usage of
C-OTDR monitoring systems for rail traffic management. The COTDR
method is based on vibrosensitive properties of optical fibers.
Analysis of Rayleigh backscattering radiation parameters changes
which take place due to microscopic seismoacoustic impacts on the
optical fiber allows to determine seismoacoustic emission source
positions and to identify their types. This approach proved successful
for rail traffic management (moving block system, weigh- in-motion
system etc.).
Abstract: This paper deals with the study of reflection and
transmission characteristics of acoustic waves at the interface of a
semiconductor half-space and elastic solid. The amplitude ratios
(reflection and transmission coefficients) of reflected and transmitted
waves to that of incident wave varying with the incident angles have
been examined for the case of quasi-longitudinal wave. The special
cases of normal and grazing incidence have also been derived with
the help of Gauss elimination method. The mathematical model
consisting of governing partial differential equations of motion and
charge carriers’ diffusion of n-type semiconductors and elastic solid
has been solved both analytically and numerically in the study. The
numerical computations of reflection and transmission coefficients
has been carried out by using MATLAB programming software for
silicon (Si) semiconductor and copper elastic solid. The computer
simulated results have been plotted graphically for Si
semiconductors. The study may be useful in semiconductors,
geology, and seismology in addition to surface acoustic wave (SAW)
devices.
Abstract: In this paper, a summary of analytical and
experimental studies into the behavior of a new hysteretic damper,
designed for seismic protection of structures is presented. The Multidirectional
Torsional Hysteretic Damper (MRSD) is a patented
invention in which a symmetrical arrangement of identical cylindrical
steel cores is so configured as to yield in torsion while the structure
experiences planar movements due to earthquake shakings. The new
device has certain desirable properties. Notably, it is characterized by
a variable and controllable-via-design post-elastic stiffness. The
mentioned property is a result of MRSD’s kinematic configuration
which produces this geometric hardening, rather than being a
secondary large-displacement effect. Additionally, the new system is
capable of reaching high force and displacement capacities, shows
high levels of damping, and very stable cyclic response. The device
has gone through many stages of design refinement, multiple
prototype verification tests and development of design guide-lines
and computer codes to facilitate its implementation in practice.
Practicality of the new device, as offspring of an academic sphere, is
assured through extensive collaboration with industry in its final
design stages, prototyping and verification test programs.
Abstract: Damage status of RC buildings is greatly influenced
by the characteristics of the imposed ground motion. Peak Ground
Acceleration and frequency contents are considered the main two
factors that affect ground motion characteristics; hence, affecting the
seismic response of RC structures and consequently their damage
state. A detailed investigation on the combined effects of these two
factors on damage assessment of RC buildings is carried out. Twenty
one earthquake records are analyzed and arranged into three groups,
according to their frequency contents. These records are used in an
investigation to define the expected damage state that would be
attained by RC buildings, if subjected to varying ground motion
characteristics. The damage assessment is conducted through
examining drift ratios and damage indices of the overall structure and
the significant structural components of RC building. Base and story
shear of RC building model, are also investigated, for cases when the
model is subjected to the chosen twenty one earthquake records.
Nonlinear dynamic analyses are performed on a 2-dimensional model
of a 12-story RC building.
Abstract: The paper presents new results concerning selection of
optimal information fusion formula for ensembles of C-OTDR
channels. The goal of information fusion is to create an integral
classificator designed for effective classification of seismoacoustic
target events. The LPBoost (LP-β and LP-B variants), the Multiple
Kernel Learning, and Weighing of Inversely as Lipschitz Constants
(WILC) approaches were compared. The WILC is a brand new
approach to optimal fusion of Lipschitz Classifiers Ensembles.
Results of practical usage are presented.
Abstract: Failure of typical seismic frames has been found by
plastic hinge occurring on beams section near column faces. On the
other hand, the seismic capacity of the frames can be enhanced if the
plastic hinges of the beams are shifted away from the column faces.
This paper presents detailing of reinforcements in the interior beam–
column connections aiming to relocate the plastic hinge of reinforced
concrete and precast concrete frames. Four specimens were tested
under quasi-static cyclic load including two monolithic specimens
and two precast specimens. For one monolithic specimen, typical
seismic reinforcement was provided and considered as a reference
specimen named M1. The other reinforced concrete frame M2
contained additional intermediate steel in the connection area
compared with the specimen M1. For the precast specimens,
embedded T-section steels in joint were provided, with and without
diagonal bars in the connection area for specimen P1 and P2,
respectively. The test results indicated the ductile failure with beam
flexural failure in monolithic specimen M1 and the intermediate steel
increased strength and improved joint performance of specimen M2.
For the precast specimens, cracks generated at the end of the steel
inserts. However, slipping of reinforcing steel lapped in top of the
beams was seen before yielding of the main bars leading to the brittle
failure. The diagonal bars in precast specimens P2 improved the
connection stiffness and the energy dissipation capacity.
Abstract: The seismic risk mitigation from the perspective of
the old buildings stock is truly essential in Algerian urban areas,
particularly those located in seismic prone regions, such as Annaba
city, and which the old buildings present high levels of degradation
associated with no seismic strengthening and/or rehabilitation
concerns. In this sense, the present paper approaches the issue of the
seismic vulnerability assessment of old masonry building stocks
through the adaptation of a simplified methodology developed for a
European context area similar to that of Annaba city, Algeria.
Therefore, this method is used for the first level of seismic
vulnerability assessment of the masonry buildings stock of the old
city center of Annaba. This methodology is based on a vulnerability
index that is suitable for the evaluation of damage and for the
creation of large-scale loss scenarios. Over 380 buildings were
evaluated in accordance with the referred methodology and the
results obtained were then integrated into a Geographical Information
System (GIS) tool. Such results can be used by the Annaba city
council for supporting management decisions, based on a global view
of the site under analysis, which led to more accurate and faster
decisions for the risk mitigation strategies and rehabilitation plans.
Abstract: An adaptive nonparametric method is proposed for
stable real-time detection of seismoacoustic sources in multichannel
C-OTDR systems with a significant number of channels. This
method guarantees given upper boundaries for probabilities of Type I
and Type II errors. Properties of the proposed method are rigorously
proved. The results of practical applications of the proposed method
in a real C-OTDR-system are presented in this report.
Abstract: This study presented to reduce earthquake damage and
emergency rehabilitation of critical structures such as schools, hightech
factories, and hospitals due to strong ground motions associated
with climate changes. Regarding recent trend, a strong earthquake
causes serious damage to critical structures and then the critical
structure might be influenced by sequence aftershocks (or tsunami)
due to fault plane adjustments. Therefore, in order to improve seismic
performance of critical structures, retrofitted or strengthening study
of the structures under aftershocks sequence after emergency
rehabilitation of the structures subjected to strong earthquakes is
widely carried out. Consequently, this study used composite material
for emergency rehabilitation of the structure rather than concrete and
steel materials because of high strength and stiffness, lightweight,
rapid manufacturing, and dynamic performance. Also, this study was
to develop or improve the seismic performance or seismic retrofit of
critical structures subjected to strong ground motions and earthquake
aftershocks, by utilizing GFRP-Corrugated Infill Panels (GCIP).
Abstract: The present research work investigates the seismic
response of reinforced concrete (RC) frame building considering the
effect of modeling masonry infill (MI) walls. The seismic behavior of
a residential 6-storey RC frame building, considering and ignoring
the effect of masonry, is numerically investigated using response
spectrum (RS) analysis. The considered herein building is designed
as a moment resisting frame (MRF) system following the Egyptian
code (EC) requirements. Two developed models in terms of bare
frame and infill walls frame are used in the study. Equivalent
diagonal strut methodology is used to represent the behavior of infill
walls, whilst the well-known software package ETABS is used for
implementing all frame models and performing the analysis. The
results of the numerical simulations such as base shear,
displacements, and internal forces for the bare frame as well as the
infill wall frame are presented in a comparative way. The results of
the study indicate that the interaction between infill walls and frames
significantly change the responses of buildings during earthquakes
compared to the results of bare frame building model. Specifically,
the seismic analysis of RC bare frame structure leads to
underestimation of base shear and consequently damage or even
collapse of buildings may occur under strong shakings. On the other
hand, considering infill walls significantly decrease the peak floor
displacements and drifts in both X and Y-directions.
Abstract: The principle of the seismic performance evaluation methods is to provide a measure of capability for a building or set of buildings to be damaged by an earthquake. The common objective of many of these methods is to supply classification criteria. The purpose of this study is to present a method for assessing the seismic performance of structures, based on Pushover method; we are particularly interested in reinforced concrete frame structures, which represent a significant percentage of damaged structures after a seismic event. The work is based on the characterization of seismic movement of the various earthquake zones in terms of PGA and PGD that is obtained by means of SIMQK_GR and PRISM software and the correlation between the points of performance and the scalar characterizing the earthquakes will developed.
Abstract: The use of energy dissipation systems for seismic applications has increased worldwide, thus it is necessary to develop practical and modern criteria for their optimal design. Here, a direct displacement-based seismic design approach for frame buildings with hysteretic energy dissipation systems (HEDS) is applied. The building is constituted by two individual structural systems consisting of: 1) a main elastic structural frame designed for service loads; and 2) a secondary system, corresponding to the HEDS, that controls the effects of lateral loads. The procedure implies to control two design parameters: a) the stiffness ratio (α=Kframe/Ktotal system), and b) the strength ratio (γ=Vdamper/Vtotal system). The proposed damage-controlled approach contributes to the design of a more sustainable and resilient building because the structural damage is concentrated on the HEDS. The reduction of the design displacement spectrum is done by means of a damping factor (recently published) for elastic structural systems with HEDS, located in Mexico City. Two limit states are verified: serviceability and near collapse. Instead of the traditional trial-error approach, a procedure that allows the designer to establish the preliminary sizes of the structural elements of both systems is proposed. The design methodology is applied to an 8-story steel building with buckling restrained braces, located in soft soil of Mexico City. With the aim of choosing the optimal design parameters, a parametric study is developed considering different values of હ and . The simplified methodology is for preliminary sizing, design, and evaluation of the effectiveness of HEDS, and it constitutes a modern and practical tool that enables the structural designer to select the best design parameters.
Abstract: A reliability-based methodology which uses structural demand hazard curves to consider the increment of the ductility demands of structures with tilting is proposed. The approach considers the effect of two orthogonal components of the ground motions as well as the influence of soil-structure interaction. The approach involves the calculation of ductility demand hazard curves for symmetric systems and, alternatively, for systems with different degrees of asymmetry. To get this objective, demand hazard curves corresponding to different global ductility demands of the systems are calculated. Next, Uniform Exceedance Rate Spectra (UERS) are developed for a specific mean annual rate of exceedance value. Ratios between UERS corresponding to asymmetric and to symmetric systems located in soft soil of the valley of Mexico are obtained. Results indicate that the ductility demands corresponding to tilted structures may be several times higher than those corresponding to symmetric structures, depending on several factors such as tilting angle and vibration period of structure and soil.
Abstract: Optical radiation emitted from a metal-coated fiber tip apex at liquid-air interface was measured. The intensity of the output radiation was strongly depend on the relative position of the tip to a liquid-air interface and varied with surface fluctuations. This phenomenon permits in-situ real-time investigation of nano-metric vibrations of the liquid surface and provides a basis for development of various origin ultrasensitive vibration detecting sensors. The described method can be used for detection of week seismic vibrations.
Abstract: Predicting the collapse potential of a structure during
earthquakes is an important issue in earthquake engineering. Many
researchers proposed different methods to assess the collapse
potential of structures under the effect of strong ground motions.
However most of them did not consider degradation and softening
effect in hysteretic behavior. In this study, collapse potential of
SDOF systems caused by dynamic instability with stiffness and
strength degradation has been investigated. An equation was
proposed for the estimation of collapse period of SDOF system which
is a limit value of period for dynamic instability. If period of the
considered SDOF system is shorter than the collapse period then the
relevant system exhibits dynamic instability and collapse occurs.
Abstract: The design philosophy of building structure has been
changing time to time. The reason for this is because of an increase of
human inertest, an improved building materials and technology that
will impact how we live, to speed up construction period and natural
effect which includes earthquake disasters and environmental effect.
One technique which takes in to account the above case is using a
prefabricable structural system. In which each and every structural
element is designed and prefabricated and assembled on a site so that
the construction speed is increased and the environmental impact is
also enhanced. This system has an immense advantage such as: reduce
construction cost, reusable, recyclable, speed up construction period
and less environmental effect. In this study, it is tried to present some
of the developed and evaluated structural elements of building
structures.