Abstract: An existing RC building in Madinah is seismically
evaluated with and without infill wall. Four model systems have been
considered i.e. model I (no infill), model IIA (strut infill-update from
field test), model IIB (strut infill- ASCE/SEI 41) and model IIC (strut
infill-Soft storey- ASCE/SEI 41). Three dimensional pushover
analyses have been carried out using SAP2000 software
incorporating inelastic material behavior for concrete, steel and infill
walls. Infill wall has been modeled as equivalent strut according to
suggested equation matching field test measurements and to the
ASCE/SEI 41 equation. The effect of building modeling on the
performance point as well as capacity and demand spectra due to EQ
design spectrum function in Madinah area has been investigated. The
response modification factor (R) for the 5 story RC building is
evaluated from capacity and demand spectra (ATC-40) for the
studied models. The results are summarized and discussed.
Abstract: Early pre-code reinforced concrete structures present
undetermined resistance to earthquakes. This situation is particularly
unacceptable in the case of essential structures, such as healthcare
structures and pilgrims' houses. Amongst these, an existing old RC
building in Madinah city (KSA) is seismically evaluated with and
without infill wall and their dynamic characteristics are compared
with measured values in the field using ambient vibration
measurements (AVM). After updating the mathematical models for
this building with the experimental results, three dimensional
pushover analysis (Nonlinear static analysis) was carried out using
commercial structural analysis software incorporating inelastic
material properties for concrete, infill and steel. The purpose of this
analysis is to evaluate the expected performance of structural systems
by estimating, strength and deformation demands in design, and
comparing these demands to available capacities at the performance
levels of interest. The results summarized and discussed.
Abstract: A capacity spectrum method (CSM), one of methodologies to evaluate seismic fragilities of building structures, has been long recognized as the most convenient method, even if it contains several limitations to predict the seismic response of structures of interest. This paper proposes the procedure to estimate seismic fragility curves using an incremental dynamic analysis (IDA) rather than the method adopting a CSM. To achieve the research purpose, this study compares the seismic fragility curves of a 5-story reinforced concrete (RC) moment frame obtained from both methods; an IDA method and aCSM. Both seismic fragility curves are similar in slight and moderate damage states whereas the fragility curve obtained from the IDA method presents less variation (or uncertainties) in extensive and complete damage states. This is due to the fact that the IDA method can properly capture the structural response beyond yielding rather than the CSM and can directly calculate higher mode effects. From these observations, the CSM could overestimate seismic vulnerabilities of the studied structure in extensive or complete damage states.
Abstract: Proof of controlling crack width is a basic condition
for securing suitable performance in serviceability limit state. The
cracking in concrete can occur at any time from the casting of time to
the years after the concrete has been set in place. Most codes struggle
with offering procedure for crack width calculation. There is lack in
availability of design charts for designers to compute crack width
with ease. The focus of the study is to utilize design charts and
parametric equations in calculating crack width with minimum error.
The paper contains a simplified procedure to calculate crack width
for reinforced concrete (RC) sections subjected to bending with axial
tensile force following the guidelines of Euro code [DS EN-1992-1-1
& DS EN-1992-1-2]. Numerical examples demonstrate the
application of the suggested procedure. Comparison with parallel
analytical tools supports the validity of result and show the
percentage deviation of crack width in both the procedures. The
technique is simple, user friendly and ready to evolve for a greater
spectrum of section sizes and materials.
Abstract: Geopolymer concretes are new class of construction
materials that have emerged as an alternative to Ordinary Portland
cement concrete. Considerable researches have been carried out on
material development of geopolymer concrete; however, a few studies
have been reported on the structural use of them. This paper presents
the bond behaviors of reinforcement embedded in fly ash based
geopolymer concrete. The development lengths of reinforcement for
various compressive strengths of concrete, 20, 30 and 40 MPa, and
reinforcement diameters, 10, 16 and 25 mm, are investigated. Total 27
specimens were manufactured and pull-out test according to EN 10080
was applied to measure bond strength and slips between concrete and
reinforcements. The average bond strengths decreased from 23.06MPa
to 17.26 MPa, as the diameters of reinforcements increased from
10mm to 25mm. The compressive strength levels of geopolymer
concrete showed no significant influence on bond strengths in this
study. Also, the bond-slip relations between geopolymer concrete and
reinforcement are derived using non-linear regression analysis for
various experimental conditions.
Abstract: This paper investigates the viability of using carbon
fiber reinforced epoxy composites modified with carbon nanotubes to
strengthening reinforced concrete (RC) columns. Six RC columns
was designed and constructed according to ASCE standards. The
columns were wrapped using carbon fiber sheets impregnated with
either neat epoxy or CNTs modified epoxy. These columns were then
tested under concentric axial loading. Test results show that;
compared to the unwrapped specimens; wrapping concrete columns
with carbon fiber sheet embedded in CNTs modified epoxy resulted
in an increase in its axial load resistance, maximum displacement,
and toughness values by 24%, 109% and 232%, respectively. These
results reveal that adding CNTs into epoxy resin enhanced the
confinement effect, specifically, increased the axial load resistance,
maximum displacement, and toughness values by 11%, 6%, and
19%, respectively compared with columns strengthening with carbon
fiber sheet embedded in neat epoxy.
Abstract: Self-compacting concrete (SCC) developed in Japan
in the late 80s has enabled the construction industry to reduce
demand on the resources, improve the work condition and also
reduce the impact of environment by elimination of the need for
compaction. Fuzzy logic (FL) approaches has recently been used to
model some of the human activities in many areas of civil
engineering applications. Especially from these systems in the model
experimental studies, very good results have been obtained. In the
present study, a model for predicting compressive strength of SCC
containing various proportions of fly ash, as partial replacement of
cement has been developed by using Fuzzy Inference System (FIS).
For the purpose of building this model, a database of experimental
data were gathered from the literature and used for training and
testing the model. The used data as the inputs of fuzzy logic models
are arranged in a format of five parameters that cover the total binder
content, fly ash replacement percentage, water content,
superplasticizer and age of specimens. The training and testing results
in the fuzzy logic model have shown a strong potential for predicting
the compressive strength of SCC containing fly ash in the considered
range.
Abstract: The paper presents a plastic analysis procedure based
on the energy balance concept for performance based seismic retrofit
of multi-story multi-bay masonry infilled reinforced concrete (R/C)
frames with a ‘soft’ ground story using passive energy dissipation
(PED) devices with the objective of achieving a target performance
level of the retrofitted R/C frame for a given seismic hazard level at
the building site. The proposed energy based plastic analysis
procedure was employed for developing performance based design
(PBD) formulations for PED devices for a simulated application in
seismic retrofit of existing frame structures designed in compliance
with the prevalent standard codes of practice. The PBD formulations
developed for PED devices were implemented for simulated seismic
retrofit of a representative code-compliant masonry infilled R/C
frame with a ‘soft’ ground story using friction dampers as the PED
device. Non-linear dynamic analyses of the retrofitted masonry
infilled R/C frames is performed to investigate the efficacy and
accuracy of the proposed energy based plastic analysis procedure in
achieving the target performance level under design level
earthquakes. Results of non-linear dynamic analyses demonstrate that
the maximum inter-story drifts in the masonry infilled R/C frames
with a ‘soft’ ground story that is retrofitted with the friction dampers
designed using the proposed PBD formulations are controlled within
the target drifts under near-field as well far-field earthquakes.
Abstract: Aerated concrete is a load bearing construction
material, which has high heat insulation parameters. Walls can be
erected from aerated concrete masonry constructions and in perfect
circumstances additional heat insulation is not required. The most
common problem in aerated concrete heat insulation properties is the
humidity distribution throughout the cross section of the masonry
elements as well as proper and conducted drying process of the
aerated concrete construction because only dry aerated concrete
masonry constructions can reach high heat insulation parameters.
In order to monitor drying process of the masonry and detect
humidity distribution throughout the cross section of aerated concrete
masonry construction application of electrical impedance
spectrometry is applied. Further test results and methodology of this
non-destructive testing method is described in this paper.
Abstract: Corrosion inhibitors are widely used in concrete
industry to reduce the corrosion rate of steel rebar which is present in
contact with aggressive environments. The present work aims to
using Zamzam water from well located within the Masjid al-Haram
in Mecca, Saudi Arabia 20 m (66 ft) east of the Kaaba, the holiest
place in Islam as corrosion inhibitor for steel in rain water and
simulated acid rain. The effect of Zamzam water was investigated by
electrochemical impedance spectroscopy (EIS) and Potentiodynamic
polarization techniques in Department of Civil Engineering - IUT
Saint-Nazaire, Nantes University, France. Zamzam water is
considered to be one of the most important steel corrosion inhibitor
which is frequently used in different industrial applications. Results
showed that zamzam water gave a very good inhibition for steel
corrosion in rain water and simulated acid rain.
Abstract: This paper focuses on the dynamic behavior of
reinforced concrete (RC) slabs. Therefore, the theoretical modal
analysis was performed using two different types of boundary
conditions. Modal analysis method is the most important dynamic
analyses. The analysis would be modal case when there is no external
force on the structure. By using this method in this paper, the effects
of freely and simply supported boundary conditions on the
frequencies and mode shapes of RC square slabs are studied. ANSYS
software was employed to derive the finite element model to
determine the natural frequencies and mode shapes of the slabs.
Then, the obtained results through numerical analysis (finite element
analysis) would be compared with the exact solution. The main goal
of the research study is to predict how the boundary conditions
change the behavior of the slab structures prior to performing
experimental modal analysis. Based on the results, it is concluded
that simply support boundary condition has obvious influence to
increase the natural frequencies and change the shape of the mode
when it is compared with freely supported boundary condition of
slabs. This means that such support conditions have the direct
influence on the dynamic behavior of the slabs. Thus, it is suggested
to use free-free boundary condition in experimental modal analysis to
precisely reflect the properties of the structure. By using free-free
boundary conditions, the influence of poorly defined supports is
interrupted.
Abstract: The purpose of this study is to compare Self
Compacting Concrete (SCC) and Conventional Concrete (CC) in
terms of their capillary water absorption. During the comparison of
SCC and CC, the effects of two different factors were also
investigated: concrete strength class and curing condition. In the
study, both SCC and CC were produced in three different concrete
classes (C25, C50 and C70) and the other parameter (i.e. curing
condition) was determined as two levels: moisture and air curing. It
was observed that, for both curing environments and all strength
classes of concrete, SCCs had lower capillary water absorption values
than that of CCs. It was also detected that, for both SCC and CC,
capillary water absorption values of samples kept in moisture curing
were significantly lower than that of samples stored in air curing.
Additionally, it was determined that capillary water absorption values
for both SCC and CC decrease with increasing strength class of
concrete for both curing environments.
Abstract: This work is focused on the study of valuation of
recycled concrete aggregates, by measuring certain properties of
concrete in the fresh and hardened state. In this study, rheological
tests and physic-mechanical characterization on concretes and
mortars were conducted with recycled concrete whose geometric
properties were identified aggregates. Mortars were elaborated with
recycled fine aggregate (0/5mm) and concretes were manufactured
using recycled coarse aggregates (5/12.5 mm and 12.5/20 mm). First,
a study of the mortars was conducted to determine the effectiveness
of polycarboxylate superplasticizer on the workability of these and
their action deflocculating of the recycled sand. The rheological
behavior of mortars based on fine aggregate recycled was
characterized. The results confirm that the mortars composed of
different fractions of recycled sand (0 /5) have a better mechanical
properties (compressive and flexural strength) compared to normal
mortar. Also, the mechanical strengths of concretes made with
recycled aggregates (5/12.5 mm and 12.5/20 mm), are comparable to
those of conventional concrete with conventional aggregates,
provided that the implementation can be improved by the addition of
a superplasticizer.
Abstract: Asphaltic concrete for pavement construction in India
are produced by using crushed stone, gravels etc. as aggregate. In
north-Eastern region of India, there is a scarcity of stone aggregate.
Therefore the road engineers are always in search of an optional
material as aggregate which can replace the regularly used material.
The purpose of this work was to evaluate the utilization of
substandard or marginal aggregates in flexible pavement
construction. The investigation was undertaken to evaluate the effects
of using lower quality aggregates such as over burnt brick aggregate
on the preparation of asphalt concrete for flexible pavements. The
scope of this work included a review of available literature and
existing data, a laboratory evaluation organized to determine the
effects of marginal aggregates and potential techniques to upgrade
these substandard materials, and a laboratory evaluation of these
upgraded marginal aggregate asphalt mixtures. Over burnt brick
aggregates are water susceptible and can leads to moisture damage.
Moisture damage is the progressive loss of functionality of the
material owing to loss of the adhesion bond between the asphalt
binder and the aggregate surface. Hence zycosoil as an anti striping
additive were evaluated in this study. This study summarizes the
results of the laboratory evaluation carried out to investigate the
properties of asphalt concrete prepared with zycosoil modified over
burnt brick aggregate. Marshall specimen were prepared with stone
aggregate, zycosoil modified stone aggregate, over burnt brick
aggregate and zycosoil modified over burnt brick aggregate. Results
show that addition of zycosoil with stone aggregate increased
stability by 6% and addition of zycosoil with over burnt brick
aggregate increased stability by 30%.
Abstract: The main objective of the study is focused in
producing slag based geopolymer concrete obtained with the addition
of alkali activator. Test results indicated that the reaction of silicates
in slag is based on the reaction potential of sodium hydroxide and the
formation of alumino-silicates. The study also comprises on the
evaluation of the efficiency of polymer reaction in terms of the
strength gain properties for different geopolymer mixtures.
Geopolymer mixture proportions were designed for different binder
to total aggregate ratio (0.3 & 0.45) and fine to coarse aggregate ratio
(0.4 & 0.8). Geopolymer concrete specimens casted with normal
curing conditions reported a maximum 28 days compressive strength
of 54.75 MPa. The addition of glued steel fibres at 1.0% Vf in
geopolymer concrete showed reasonable improvements on the
compressive strength, split tensile strength and flexural properties of
different geopolymer mixtures. Further, comparative assessment was
made for different geopolymer mixtures and the reinforcing effects of
steel fibres were investigated in different concrete matrix.
Abstract: Using ETABS software, this study analyzed 23
buildings to evaluate effects of mistakes during construction phase on
buildings structural behavior. For modelling, two different loadings
were assumed: 1) design loading and 2) loading due to the effects of
mistakes in construction phase. Research results determined that
considering traditional construction methods for buildings resulted in
a significant increase in dead loads and consequently intensified the
displacements and base-shears of buildings under seismic loads.
Abstract: Columns have traditionally been constructed of
reinforced concrete or structural steel. Much attention was allocated
to estimate the axial capacity of the traditional column sections to the
detriment of other forms of construction. Other forms of column
construction such as Concrete Filled Double Skin Tubes received
little research attention, and almost no attention when subjected to
eccentric loading. This paper investigates the axial capacity of
columns when subjected to eccentric loading. The experimental axial
capacities are compared to other established theoretical formulae on
concentric loading to determine a possible relationship. The study
found a good correlation between the reduction in axial capacity for
different column lengths and hollow section ratios.
Abstract: Paper presents a study about dynamic effects obtained
from the dynamic load testing of the city highway bridges in Latvia
carried out from 2005 to 2012. 9 prestressed concrete bridges and 4
composite bridges were considered. 11 of 13 bridges were designed
according to the Eurocodes but two according to the previous
structural codes used in Latvia (SNIP 2.05.03-84). The dynamic
properties of the bridges were obtained by heavy vehicle passing the
bridge roadway with different driving speeds and with or without
even pavement. The obtained values of the Dynamic amplification
factor (DAF) and the bridge natural frequency were analyzed and
compared to the values of built-in traffic load models provided in
Eurocode 1. The actual DAF values for even bridge pavement in the
most cases are smaller than the value adopted in Eurocode 1. Vehicle
speed for uneven pavements significantly influence Dynamic
amplification factor values.
Abstract: The thermo-mechanical behaviour of concrete energy
pile foundations with different single and double U-tube shapes
incorporated was analysed using the Comsol Multi-physics package.
For the analysis, a 3D numerical model in real scale of the concrete
pile and surrounding soil was simulated regarding actual operation of
ground heat exchangers (GHE) and the surrounding ambient
temperature. Based on initial ground temperature profile measured in
situ, tube inlet temperature was considered to range from 6oC to 0oC
(during the contraction process) over a 30-day period. Extra thermal
stresses and deformations were calculated during the simulations and
differences arising from the use of two different systems (single-tube
and double-tube) were analysed. The results revealed no significant
difference for extra thermal stresses at the centre of the pile in either
system. However, displacements over the pile length were found to
be up to 1.5-fold higher in the double-tube system than the singletube
system.
Abstract: In this paper, the effect of admixtures on the tensional
strength of concrete in Urmia-lake water have been investigated. We
made different types of concretes with the ratio of w/c and replaced
different percentages of micro-silica, air-entraining, super plasticizer,
corrosion-inhibiting, and caulk with two types of cement I and II as
well as investigating in both ordinary water and Urmia-lake water.
The tensional strength was investigated on these samples.