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Showing 56 results for Type of Study: Technical Note

M. Naderi,
Volume 4, Issue 2 (6-2006)
Abstract

This paper introduces an innovative partially destructive method, called “Twist-off”, for the assessment of in situ concrete strength. In this method a 40mm diameter metal probe is bonded to a concrete surface by means of a high strength epoxy resin adhesive. To measure the concrete compressive strength, a torque is applied using an ordinary torque-meter and the maximum shear stress at failure is used to estimate the cube compressive strength by means of a calibration graph. The relationship between the results of this new method and compressive strengths of concrete cores is also presented in this paper. The average coefficient of variation of the results of this method was seen to be of the order of 8 percent and the correlation coefficients of its comparative results with concrete cube and core compressive strengths were found to be 0.97 and 0.90 respectively. In order to assess the performance of this method on site, tests were undertaken on a number of buildings. Although the method was found to perform well but with some of the structures tested, the differences between the strengths of sample cubes and estimated in situ compressive strength of concrete were seen to be significant.
M. Mazloom, A.a. Mehrabian,
Volume 4, Issue 4 (12-2006)
Abstract

The objective of this paper is to present a new method for protecting the lives of residents in catastrophic earthquake failures of unreinforced masonry buildings by introducing some safe rooms within the buildings. The main idea is that occupants can seek refuge within the safe rooms as soon as the earthquake ground motions are felt. The information obtained from the historical ground motions happened in seismic zones around the globe expresses the lack of enough safety of masonry buildings against earthquake. For this potentially important reason, an attempt has been made to create some cost-effective seismic-resistant areas in some parts of the existing masonry buildings, which are called safe rooms. The practical method for creating these areas and increasing the occupant safety of the buildings is to install some prefabricated steel frames in some of their rooms or in their halls. These frames do not carry any service loads before earthquake. However, if a near field seismic event happens and the load bearing walls of the building destroy, some parts of its floors, which are in the safe areas, will fall on the roof of the installed frames consequently, the occupants who have sheltered in the safe rooms will survive. This paper expresses the experimental and theoretical work executed on the steel structures of the safe rooms for bearing the shock and impact loads. Finally, it was concluded that both the strength and displacement capacity of the steel frames were adequate to accommodate the distortions generated by seismic loads and aftershocks properly.
A. Yeganeh Bakhtiary, A. Ghaheri, R. Valipour,
Volume 5, Issue 1 (3-2007)
Abstract

Determination of allowable free span length plays a crucial role in design of offshore pipelines. The seabed intervention cost and safety of an offshore pipelines project are largely influenced by pipelines free spanning during the project life time. Different criteria are proposed by both the current designing guidelines and researchers there is however lack of comprehensive assessment of independent parameters affects the design length of free span. In this note, it is intended to investigate the effects of seabed formation along with axial force on Natural Frequency of offshore pipelines. Based on this assessment a new simple formula is proposed. Finally, to evaluate the result of this study, the allowable free span length of Qeshem Island pipelines is calculated as a case study and compared with those of the DNV (1998) and ABS (2001) guidelines and the modal analysis.
S.a. Naeini, R. Ziaie-Moayed,
Volume 5, Issue 2 (6-2007)
Abstract

Series of undrained monotonic triaxial tests and cone penetration tests were conducted on loose silty sand samples to study correlation between undrained shear strength of silty sands (Sus) and piezocone test results. CPT tests were conducted at 27 silty sand samples in calibration chamber. The results indicate that, in low percent of silt (0-30%), as the silt content increases, the undrained shear strength (Sus) and cone tip resistance (qc) decreases. It is shown that, fines content affects undrained shear strength (Sus) and cone tip resistance (qc) similarly. On the basis of obtained results, equations were proposed to determine the normalized cone tip resistance (qc1n) and undrained shear strength (Sus) of silty sand in term of fines content. Finally based on those equations, a correlation between normalized cone tip resistance and undrained shear strength of silty sand is presented. It is shown that the normalized undrained shear strength and normalized cone tip resistance of loose silty sands (F.C. <30%) decreases with increase of silt contents.
A. Haddad, Gh. Shafabakhsh,
Volume 5, Issue 2 (6-2007)
Abstract

Local site conditions have a strong effect on ground response during earthquakes. Two important soil parameters that control the amplification effects of seismic motions by a soil column are the soil hysteretic damping ratio and shear wave velocity. This paper presents the results of in situ damping ratio measurements performed using continuous surface wave attenuation data at a site in Semnan University campus and analysis used to obtain the near surface soils damping ratio profile. Once the frequency dependent attenuation coefficients are determined, the shear damping ratio profile is calculated using an algorithm based on constrained inversion analysis. A computer code is developed to calculate the shear damping ratio in each soil layer. Comparisons of the in situ shear damping ratio profile determined from continuous surface wave with cross hole independent test measurements are also presented. Values of shear damping ratio, obtained using continuous surface wave measurements, were less than the measured using cross hole tests, possibly because of the higher frequencies used in cross hole tests.
S.n. Moghaddas Tafreshi, Gh. Tavakoli Mehrjardi, S.m. Moghaddas Tafreshi,
Volume 5, Issue 2 (6-2007)
Abstract

The safety of buried pipes under repeated load has been a challenging task in geotechnical engineering. In this paper artificial neural network and regression model for predicting the vertical deformation of high-density polyethylene (HDPE), small diameter flexible pipes buried in reinforced trenches, which were subjected to repeated loadings to simulate the heavy vehicle loads, are proposed. The experimental data from tests show that the vertical diametric strain (VDS) of pipe embedded in reinforced sand depends on relative density of sand, number of reinforced layers and height of embedment depth of pipe significantly. Therefore in this investigation, the value of VDS is related to above pointed parameters. A database of 72 experiments from laboratory tests were utilized to train, validate and test the developed neural network and regression model. The results show that the predicted of the vertical diametric strain (VDS) using the trained neural network and regression model are in good agreement with the experimental results but the predictions obtained from the neural network are better than regression model as the maximum percentage of error for training data is less than 1.56% and 27.4%, for neural network and regression model, respectively. Also the additional set of 24 data was used for validation of the model as 90% of predicted results have less than 7% and 21.5% error for neural network and regression model, respectively. A parametric study has been conducted using the trained neural network to study the important parameters on the vertical diametric strain.
Mohammad Reza Kavian Pour, H.r. Masoumi ,
Volume 6, Issue 3 (9-2008)
Abstract

Hydraulics of stepped spillway is a very complicated phenomenon, as it consists of a two phase flow passing through a set of designed steps. The steps increase the rate of energy dissipation taking place on the spillway face. Turbulence, flow aeration and energy dissipation are the main tasks in the design of such structures. This study consists of the experimental investigation to determine the energy dissipation over stepped spillways. Experiments conducted at Water Research Institute on two physical models of the Siyah Bisheh stepped spillways in Iran. To develop a more generalized expression, the results of previous investigations were also considered in our study. Therefore, a wide range of variables were taken into account to estimate the energy dissipation along the non-uniform flow regime. Assuming the energy dissipation along the uniform flow regime to be equal to the vertical displacement of the jet, the total energy lost was calculated. A comparison of the results with those of measurements showed a regression of 0.92 for the total energy dissipation, which is one of the features of the present method for estimating of the energy dissipation, compared with the previous investigation.
A. Kaveh, M. Najimi,
Volume 6, Issue 3 (9-2008)
Abstract

In this paper, the Rayleigh's quotient and the inverse vector iteration method are presented. The latter approach helps to obtain the natural frequencies and mode shapes of a structure. Inverse vector iteration method with shifting enables to determine the higher modes. Some basic theorems of linear algebra are presented and extended to study the free vibration of structures. The variation theorems are presented for predicting the eigenvalues and eigenvectors of the modified structures. These theorems reduce the number of cycles of the iterations used for calculating the eigenvalues and eigenvectors of the modified structures. Finally, an example is solved to show the ability of the present approach.
M. Mazloom, A.a. Mehrabian,
Volume 7, Issue 4 (12-2009)
Abstract

Pullback test has no scrupulous theoretical establishment. It is based on the hypothesis that the response of

the structure can be related to the response of an equivalent single degree-of-freedom (SDOF) system. This implies that

the response is controlled by a single mode. In fact, the steel frame of each safe room, which is introduced within the

unreinforced masonry buildings for protecting the lives of residents in catastrophic earthquake failures, contains a

SDOF structural system. In pullback test, the steel frame carries its gravity load first, and then it will be pushed under

an incremental lateral roof displacement pattern, which is imposed to its center of mass. This paper expresses the

results of 13 pullback tests executed by the authors on the steel frames of safe rooms. The results show that pullback

test is a practical method for seismic performance evaluation of safe rooms. Also the performance of these frames

located in a collapsing three storey masonry building is presented with favorable conclusions. In fact, the results of

pullback test of the safe room located at the ground-floor level were compared with the requirements of Iranian code

for seismic resistant design and it was concluded that the steel frame had an acceptable performance against seismic

effects.


H.m. Noh, Y.o. Cho,
Volume 8, Issue 1 (3-2010)
Abstract

In this paper, the processes which are currently under development in South Korea, concerning railway

safety management system are introduced. Railway safety management system in South Korea is briefly presented,

making particular attentions to Systems Engineering Management Plan (SEMP). To make huge national R&D projects

successful, systematic management process is essential. In this respect, detailed applying SEMP on railway safety

management system of South Korea is discussed including Systems Engineering process and Verification and

Validation procedures. Furthermore, a computer-aided systems engineering tool (Cradle) is used in order to make the

management process more easily controllable.


M. Mazloom ,
Volume 8, Issue 3 (9-2010)
Abstract

 According to the Iranian code of practice for seismic resistant design of buildings, soft storey phenomenon happens in a storey when the lateral stiffness of the storey is lower than 70% of the stiffness of the upper storey, or if it is lower than 80% of the average stiffness of the three upper stories. In the combined structural systems containing moment frames and shear walls, it is possible that the shear walls of the lower stories crack however, this cracking may not occur in the upper stories. The main objective of this research is to investigate the possibility of having soft storey phenomenon in the storey, which is bellow the uncracked walls. If the tension stresses of shear walls obtained from ultimate load combinations exceed the rupture modulus of concrete, the walls are assumed to be cracked. For calculating the tension stresses of shear walls in different conditions, 10 concrete structures containing 15 stories were studied. Each of the structures was investigated according to the obligations of Iranian, Canadian, and American concrete building codes. Five different compressive strengths of 30, 40, 50, 60, and 70 MPa were assumed for the concrete of the structures. In other words, 150 computerized analyses were conducted in this research. In each analysis, 5 load combinations were imposed to the models. It means, the tension stresses of the shear walls in each storey, were calculated 750 times. The average wall to total stiffness ratios of the buildings were from 0.49 to 0.95, which was quite a wide range. The final conclusion was that the soft storey phenomenon did not happen in any of the structures investigated in this research. 


M.e. Poorazizi, A.a. Alesheikh,
Volume 9, Issue 1 (3-2011)
Abstract

Air pollution is a serious challenge in densely populated cities. It poses a significant threat to human health, property and the environment throughout the developed and developing parts of the world. Real-time air quality monitoring and public access to related information are the key components of a successful environmental management. Mashups can be customized to adequately address the monitoring of such geographically oriented challenges. The growth of mashups has been accelerated by Web 2.0 technologies. The integration of Web 2.0 and GIS (Geographic Information System) has been highlighted by the second generation of Internet-based services that emphasizes on online information collaboration and sharing among users. The main objective of this paper is to assess, design and develop a Web 2.0 thin client application called Tehran Air Quality Reporter. The application uses Google Maps API (Application Programming Interface), Web GIServices (Geographic Information Services), and AJAX (Asynchronous JavaScript and XML) to disseminate real-time air quality information through internet. Such information can improve the decisions of the pertinent environmental organizations as well as urban settlers. The software also utilized DOM (Document Object Model) and JavaScript functionalities for handling the response events and providing flexibility and more interactivity. The developed Geo Mashup includes geospatial maps and features, standard business charts, node and link displays, as well as custom visual displays. All visualization components run in any web browsers and provide a user friendly environment.
M. Mahmoudi, M. Zaree,
Volume 9, Issue 1 (3-2011)
Abstract

Inelastic deformation of structural components is generally acceptable in seismic design. In such behavior, the strength of structures increases while plastic hinges are formed in members frequently. The strength revealed during the formation of plastic hinges is called "overstrength". Overstrength is one of the important parameters in the seismic design of structures. The present study tries to evaluate the overstrength of the concentrically steel braced frames (CBFs), considering reserved strength, because of members post-buckling. As such, a static nonlinear (pushover) analysis has been performed on the model buildings with single and double bracing bays, different stories and brace configurations (chevron V, invert Vand X-bracing). It has been realized that the number of bracing bays and the height of buildings have a low effect on reserve strength due to brace post-buckling. However, these parameters have a profound effect on the overstrength factor. These results indicate that the overstrength values for CBFs, proposed in seismic design codes, need to be modified.


F. Hajivalie, A. Yeganeh Bakhtiary,
Volume 9, Issue 1 (3-2011)
Abstract

In this paper, a two-dimensional Reynolds Averaged Navier-Stokes (RANS) model is developed to simulate the shoaling, breaking and overtopping of a solitary wave over a vertical breakwater. Turbulence intensity is described by using a k turbulence closure model and the free surface configuration is tracked by Volume Of Fluid (VOF) technique. To validate the numerical model the simulation results is compared with the Xie (1981) experimental data and a very good agreement between them is observed. The results revealed that wave height and wave energy decrease considerably during the reflection from vertical wall, which illustrates a considerable energy lost during the impaction and wave overtopping process. The turbulence production during the broken wave interaction with vertical breakwater is very significant consequently the vertical breakwater undergoes sever turbulent and dynamic drag force.


Reza Abbasnia, Neda Mirzadeh, Kamyar Kildashti,
Volume 9, Issue 3 (9-2011)
Abstract

In recent years, different damage indexes have been introduced in engineering literature. The most prominent one among other

counterparts is the 1985 Park and Ang's damage index (DIPA), which demonstrates well calibration against experimental

results. Hence, it has traditionally had broad application in the field of structural engineering. Commonly, in DIPA relevant

parameters are assessed based on plastic-hinge approach, which is not well suited to consider the coupled response between

stress resultants (axial force and flexural moment) especially in grossly nonlinear domain. The reason is that named approach

is utilized constant shape plastic moment-curvature curve, which is not capable of varying the shape throughout loading history.

Another drawback of plastic-hinge method is the difficulty of representing precisely partial yielding of the cross-section. To

remedy the situation, the fiber discretization technique is used in this paper. Based on the fiber discretization strategy, not only

have the stiffness and strength degradation been characterized more accurately, but also the distribution of plasticity along the

plastic zone has been considered. Besides, the multi-directional effect of axial force and flexural moment is considered to assess

DI parameters. Additionally, this strategy directly incorporates the effect of transverse confinement into cross sectional

constitutive behaviour.


A. Soroush, R. Jannatiaghdam,
Volume 10, Issue 2 (6-2012)
Abstract

This paper studies thoroughly and deeply the results of about one hundred triaxial compression tests on thirty types of rockfill
materials. The materials are categorized in accordance with their particles shape (angular / rounded) and gradation
characteristics. The main tool of the study is the Hyperbolic Model developed by Duncan and Chang. The focus of the study is
on the variations of deformation modulus of the materials (Ei and Et) with confining stress (&sigma3). Features of the mechanical
behavior of the rockfill materials, as compared with the general behavior of soils, are highlighted through the exponent
parameter (n) of the Hyperbolic Model. It is shown that high confining stresses may have adverse effects on the deformation
modulus of the rockfill materials and make them softer. The particle breakage phenomenon which happens during compression
and shearing is found as the main factor responsible for the above effects and, in general, responsible for controlling the
behavior of the materials. For the rockfill materials of this study, two correlations for estimating the initial elasticity modulus (Ei)
and the internal friction angle (&phi) in terms of particles shape, confining pressure (&sigma3), and coefficient of uniformity (Cu) are
suggested.


N. Shariatmadari, S. Saeidijam,
Volume 10, Issue 2 (6-2012)
Abstract

Bentonite-sand mixture is one of the most important candidates for engineering buffer element in nuclear waste repositoriesso
the analysis of its thermo-hydro-mechanical behavior is important for design purposes.An innovative setup of classic oedometer
was used for swelling and compression study at high temperatures in this research. A fully calibration program was utilized to
include high temperature effects on measurements. This research shows that the elevation of temperature from 25 to 90◦C in
1:1bentonite-sand mixture in distilled water reduces free swelling potential and strain about 20 percent. The required time for
equalization of swelling is less in high temperature due to increasing in permeability. Also, the high temperature causes increasing
in compressibility rate and quantity for this buffer. For detection of this effect, XRD analysis showed that an increase in
temperature causes a decrease in basal spacing. So, the particles can come near to each other more than lower temperatures and
the amount of absorbed water in the microstructure of the clay is smaller.The effect of thermal history on behavior of bentonitesand
mixture has been showed and tried to clarify it. At similar stress-temperature states, thermal history causes different
deformation in samples. The highest temperature that bentonite has been experienced, controls its behavior in the next thermal
cycles.


M. Heidarzadeh, A.a. Mirghasemi, S. M. Sadr Lahijani, F. Eslamian,
Volume 11, Issue 1 (5-2013)
Abstract

In a rare engineering experience throughout the world, we successfully stabilized relatively coarse materials of drain using

cement grouting. The grouting work was performed at the Karkheh earth dam, southwest Iran, and was part of the efforts to

extend the dam’s cut-off wall. Since the dam was completed, the execution of the new cut-off wall from the dam crest was

inevitable. Hence, one of the main difficulties associated with the development of the new cut-off wall was trenching and execution

of plastic-concrete wall through the relatively coarse materials of drain in the dam body. Due to high permeability of drain, the

work was associated with the possible risk of excessive slurry loss which could result in the collapse of the trench. In order to

achieve an appropriate grouting plan and to determine the mix ratio for the grouting material, a full-scale test platform consisting

of actual drain materials was constructed and underwent various tests. Results of the testing program revealed that a grouting

plan with at least 2 grouting rows and a Water/Cement mix ratio of 1/ (1.5-2) can successfully stabilize the drain materials. After

finalizing the technical characteristics of the grouting work, the method was applied on the drain materials of the Karkheh dam

body. The results were satisfactory and the drain materials were stabilized successfully so that the cut-off wall was executed

without any technical problem.


M. Gharouni Nik, M. Fathali,
Volume 11, Issue 1 (5-2013)
Abstract

Geometrical profile (roughness) of joint surfaces influences the behaviour of rock joints under shear loading. With regard to the

dilation, there are two models of direct shear test that may simulate the original loading condition existing in the location from

where the specimens have been sampled. The first model in which the normal load is constant (CNL) and the discontinuity is free

to dilate in shearing, represents typical situations such as movement of a block on a surface slope as a result of its own weight.

The second model in which the dilatancy is prohibited (VNL), simulates the condition of a block confined in a rock mass in an

underground opening. A shear test conducted under restricted normal displacement (dilation) will generally yield considerably

higher shear strength than one conducted under constant normal stress. In this research, both types of tests were conducted on

smooth and rough surfaces of specimens made from rock like material. The results of the VNL and the CNL direct shear tests on

regular teeth-shaped profile discontinuities indicates that at all levels of normal load, the linear Mohr-Coulomb criterion was not

valid for rough surfaces that subscribed to the power law equations. Increasing normal load emphasized the difference between

the results obtained from two methods, although for lower normal loads the results were nearly similar.


D. Galan, M. Marchamalo, R. Martinez-Marin, J. A. Sanchez-Sobrino,
Volume 11, Issue 2 (6-2013)
Abstract

New advances in geomatics and communications technologies are enabling the development of Automated Auscultation System for structure monitoring. In particular, Differential GPS (DGPS) technique allows real-time monitoring of structures with millimetre accuracy after an appropriate mathematical treatment. The results of real-time DGPS monitoring of a pilot dam over 15 months are presented and compared with the results of pendulums and angular collimation. DGPS monitoring was established to control two points at the top of the dam with reference to an external and stable station. Communications were critical, evolving from initial GPRS connections to more reliable ASDL line in the last months. Real-time DGPS positions were filtered to reach millimetric accuracy through Kalman filter. Two configurations of the filter were tested, one more adapted to predictable and uniform velocity deformations (low frequency) and another more suitable for sudden and large movements (high frequency). Root mean square errors were calculated taking pendulums as a reference. Results show that both DGPS and angular collimation allow monitoring with millimetric accuracy. In the last period, where communications with processing server were stable, a global accuracy of 1.44 and 1.86 mm was reached for real-time DGPS monitoring. RINEX post-processing yielded millimetric results, validating real-time observations. We can affirm that the DGPS system is very useful for dam auscultation and safety as it detects adequately absolute deformations, being a complement to existing methods which should be considered in new safety plans.

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