Tuesday, October 21, 2014

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مجله JSEE

Spring 2011, Vol 13, No. 2

Investigation on the Potential of OSL for Dating Qanat in the Dasht-e Bayaz Region of Northeastern Iran Using the SAR Protocol for Quartz

M. Fattahi, A. Aqazadeh, R.T. Walker, M. Talebian, R.A. Sloan, and M.M. Khatib

In some parts of Iran, such as Dasht-e-Bayaz, the line of wells of the Qanat systems have been displaced by coseismic faulting. If we can date the age of these Qanat wells and measure the amount of offset, we will be able to estimate the slip-rate of the fault. The existing constraints on age of ancient Qanats in Iran are typically assigned from archaeological investigations of nearby habitation sites. We present for the first time the results of OSL dating from spoil deposits associated with the Dasht-e-Bayaz Qanat. We further explore the possibility of dating Qanat directly using the novel method of OSL. The minimum ages which are assigned to maintenance and construction of Dasht-e-Bayaz Qanat, using SAR protocol are 15.8±1.6ka and 22.1±2.7ka, respectively. Archeological investigations suggest that the Qanat ages are much younger than ages obtained by OSL. We present evidence that the SAR approach that we have chosen is operative but not relevant. The OSL method has provided ages that are consistent with stratigraphic layers in the well, but these layers were not fully bleached during construction. The single aliquot method to which dim samples we've applied in the recent research is not an efficacious way to achieve the age of Qanats and may need to test for more samples.

Full Paper

Seismic Behavior of 63kV and 132kV Substation Post Insulators with Flexible Conductors, an Experimental Approach

A.H. Khalvati, M. Hosseini, and S. Mohammadpour

Recent Earthquakes have shown that the electrical substations are very vulnerable,and direct and indirect losses resulting from their damages are highly considerable. post insulators in high-voltage substations are usually used as support for the bus bars or flexible conductors. Due to their height, low lateral stiffness and brittle materials used for the main core of such component, they have shown very poor seismic performance. In this paper, the seismic behavior of two 63kV and 132kV PIs with flexible connections to their top is studied experimentaly. Tests samples consist of individual post insulators mounted directly on the simulator platform followed by tests of complete post insulators mounted on the lattice steel structure as the support. Insulators were subjected to two different sets of inputs, first a set of sine sweeps and the second set was earthquake simulations time histories. The results of the experiments were used to verify the numerical models for further complementary assessments. The results show that they have very high frequencies and hardly can get damaged due to resonance, but the lattice steel structure decreased the natural frequencies by almost 70%, which amplifies the acceleration by %25.

Full Paper

Experimental and Analytical Investigation on In-Plane Behavior of URM Flanged Walls

M. Khanmohammadi, H. Behnam, and M.S. Marefat

The shape of most of the wall sections in existing unreinforced masonry (URM) structures have L, T, and H shapes, instead of rectangle. Limited research on the effect of return wall (flange) on their seismic behavior has been reported in the literature. The primary aim of this study is to develop a deeper understanding of in-plane response of URM walls with emphasis on return walls. The URM shear walls represent existing masonry structures with poor shear strength. An Experimental program has been conducted on four specimens with aspect ratios of 0.5 and 0.7. Two specimens designed with flanges and, for comparison, another two specimens designed without flanges. All specimens tested under constant axial force corresponding to typical 3-story buildings, and cyclic reversal displacement control loading was applied in horizontal direction. Predicted shear strength based on FEMA-356 has been compared with experimental results. An analytical model has been proposed to predict lateral response of flanged URM walls. The results emphasize on the effect of flanges when seismic assessment of non-rectangular section URM walls is considered.

Full Paper

Resilience Against Earthquakes: Some Practical Suggestions for Planners and Managers

D. Alexander

This paper offers a working definition of resilience and associated concepts, including vulnerability to earthquakes, coping, capacity and redundancy. It concludes that resilience must be set in motion and maintained by a collective effort that involves all stakeholders and people who are at risk. The paper offers ten suggestions for action in order to create a methodology for resilience against earthquakes. They are as follows. Tell people what to do in an earthquake. Develop urban search and rescue capacity on site. Reduce non-structural as well as structural hazards. Plan flexibly and make emergency planning a process, not an end. Create networks that can improve the exchange of knowledge, information and training. Encourage governance by involving different stakeholders in earthquake disaster risk reduction. Make good practice proliferate and adapt it to local circumstances. Ensure that programmes of disaster risk reduction are sustainable in the long term. Before the next major seismic event occurs, create a strategy for recovering from it. Create a culture of resilience against earthquakes, in which the problem is widely understood and taken seriously by people who are at risk or are in positions of authority.

Full Paper

Seismic Risk Analysis of Metropolitan Tehran: A Link Between Hazard Analysis, Vulnerability Assessment and Loss Estimation Studies

B. Omidvar, S. Tavakoli, and M. Eskandari

Metropolitan Tehran, as the capital, the economic and political center, and the most populated city in Iran, has a special position in earthquake preparation, mitigation and response. Tehran is vulnerable to earthquakes and is expecting a destructive earthquake with a magnitude greater than 7. In the present paper, the items of hazard analysis, vulnerability assessment, and loss estimation in respect of Tehran are introduced, and the relevant research concerning the category of physical and structural damage is investigated. The results from vulnerability assessment indicate the vulnerability of a major part of the buildings in Tehran. The results from the loss estimation indicate a high percentage of damage in the event of an earthquake in Tehran. Furthermore, based on the loss estimation results, the likely amount of debris generated and possibilities for positioning of the temporary housing are provided. The results emphasize the necessity of short-term, average-term and long-term policies for damage reduction and seismic reinforcement.

Full Paper

 

Winter 2011, Vol 13, No. 1

Characterization of Long Period Strong Ground Motion

M. Erdik, M.B. Demircioglu, K. Sesetyan, and E. Harmandar

The performance-based earthquake engineering requires reliable assessment of long-period ground motion particularly for tall buildings, base-isolated structures, long bridges, and structures that are designed to deform beyond the elastic range. The important issues involved in such assessments are: Empirical and theoretical tools for prediction of displacement response spectra; Analysis and incorporation of near fault effects; Spectrum scaling for different damping ratios and; Time domain simulation of long-period ground motion. These issues are elaborated through (1) the principles for modification of design basis spectra in the long-period range; (2) guidelines for time domain simulation of long-period ground motions; and (3) rules for selecting and scaling ground motion records to address long-period effects. This paper aims to review and discuss these issues with developments on GMPRs for peak ground displacement and 10s spectral acceleration, and example applications on earthquake hazard assessment for 10s spectral accelerations and its deaggregation in the Marmara Region, Turkey.

Full Paper

Paleoearthquakes Determination of Magnitude~6.5 on the North Tehran Fault, IranConsidering Unequal Beam Depths

H. Nazari, J.-F. Ritz, A. Ghassemi, K. Bahar-Firouzi, R. Salamati, A. Shafei, and M. Fonoudi

The North Tehran Fault is located at the southernmost piedmont of Central Alborz, north of Iran. It stands out as a major active fault menacing directly the city of Tehran, a 12 million people metropolis, and would have been the source of several major historical earthquakes in the past. The fault zone extends up to 110km and corresponds mainly to a reverse fault mostly crossing the northern suburbs of the Tehran metropolis, although NTF in its eastern part is characterized more as a left lateral strike slip active fault. We carried out a paleoseismological study of the fault zone in order to determine whether the fault was activated during the Holocene, and to define the characteristics of its activity in terms of kinematics and magnitude. Here in this paper we present only a part of our paleoseismological investigations trench TE2. Observations from two trenches dug across the North Tehran fault scarp reveal evidence for a maximum of six surface-rupturing events within the late quaternary.
According to the empirical relationships among average displacement per event and Moment magnitude [25], we can estimate six events Mw~ 6.5 associated with these ruptures in TE2 trench.

Full Paper

An Optimal Distribution of Stiffness Over the Height of Shear Buildings to Minimize the Seismic Input Energy

F. Haddad Shargh and M. Hosseini

Based on Housner's assumption, the average input energy from earthquakes to a building modeled as a single degree of freedom (SDOF) system, is related mainly to total mass of the building. Thus, based on the above premise for low damping and relatively long period systems, the seismic input energy per unitmass of the system (SDOF or MDOF) is mainly related to the ground motion features.The present study attempts to analytically reveal the range of validity of these assumptions in linear systems and to find an optimal stiffness distribution over the height of high-rise shear linear buildings to minimize the seismic input energy. To accomplish this objective, it is shown from the spectral standpoint that input energy spectra generally is a function of the natural period of vibration, so the input energy is further related to the stiffness of structure, the mass, damping ratio and ground motion characteristics. Subsequently, it is demonstrated that for low to moderate height (up to 20 stories) shear type structures, the optimal distribution of stiffness obeys a parabolic form, while for taller structures, this form is a bell-shaped function.

Full Paper

Dual Ductility Mode Shear Walls: Concept and Behavior

M.S.R. Labafzadeh and M. Ziyaeifar

Shear walls are among the most common lateral load resisting systems, which are not recognized as efficient ductile structural components. Using any opening in the wall leads to disperse the inelastic behavior across the height of the wall and employ both flexural and shear ductility capacity of the system at the base and around the openings, respectively. Simple models were utilized to study the role of large openings in inelastic dynamic behavior of shear walls. Despite the constant total input energy, the amount of dissipated energy at the lower part of these walls is decreased to about two-third the value of ordinary shear walls. Consequently, the ductility demand diminished in the plastic hinge at the base and the required reinforcement detailing becomes simpler. However, marginal gains observed in the structural response such as base shear, base moment, inter-story drift and story displacement. Furthermore, to obtain the crack patterns and the ductility of the walls, static inelastic analyses were carried out using accurate finite element models. The results reveal that despite a small reduction in the strength of shear walls with openings, the crack patterns distribute more uniformly, and the ductility increases as the opening becomes larger.

Full Paper

Technical Note

Performance of Unreinforced Masonry Buildings in Canterbury Earthquakes

Rajesh P. Dhakal

This paper describes the impact of the 4th September 2010 and the 22nd February 2011 Canterbury earthquakes on masonry buildings. Christchurch and the surrounding areas have more than a thousand old buildings built of unreinforced brick and stone masonry. Several unreinforced masonry (URM) buildings were damaged (some very severely) in the September earthquake; whereas the February earthquake caused severe damage (many collapsed) to most URM buildings in Christchurch; requiring them to be demolished. As expected, retrofitted URM buildings generally performed better, but in the February earthquake several retrofitted buildings were also severely damaged. URM buildings with perimeter walls partially anchored using small and sporadic anchor bolts not extending to the full perimeter and height of the walls suffered severe damage. On the other hand, URM buildings that were systematically retrofitted to avoid the perimeter walls from detaching from each other and from the floor and roof sustained the severe shakings of the February earthquake with only minor damage.

Full Paper

 

Fall 2010, Vol 12, No. 3

A Note on Transparency and Loss of Life Arising from Earthquakes

N. Ambraseys

This note was prompted by the earthquake of 12 January 2010 in Haiti, which is not the only earthquake in recent years in which hundreds of thousands of people have been killed, in contrast to the near-zero death toll caused by earthquakes of the same magnitude elsewhere (viz.New Zealand 03.09.10). The Haiti earthquake raises several points that must be addressed in any realistic attempt to mitigate the loss of life arising from earthquakes, in particular the question of whether this enormous difference in human losses is almost entirely due to houses having been poorly constructed due to corrupt practices that allowed poorly sited and constructed houses to be built in seismic regions.

Full Paper

Experimental Evaluation of Cover Plate and Flange Plate Steel Moment - Resisting Connections Considering Unequal Beam Depths

B.H. Hashemi and R. Ahmady Jazany

This paper presents the differences of cyclic behavior in Special Moment Resisting Frames (SMRF) with unequal beam depths which can be affected by connection detailing arrangements. The studied connection detailing arrangements consist of continuity plate arrangements such as straight or inclined continuity plates, coverplate and flange plate connection and haunch connection systems at the shallow beam side which can create some alternatives to connect shallow beams and deep beams with columns. In spite of probable occurrences of this special case in current engineering practice, codes do not take these especial cases into consideration. Six full scale beams to column sub-assemblages were tested to investigate the cyclic behavior for this special case i.e. unequal beam depths. Experiments show that the mentioned connection detailing arrangements could achieve performance discriminations ranged between story drift ratios of at least 4% to 6% radians before experiencing 20% strength degradation. Using a specific combination of flange plate connection with the haunch connection system, the crack propagation at the deep beam bottom flange which is observed in most of the connection detailing arrangements for this special case is eliminated.

Full Paper

Experimental Study on Seismic Behavior of Conventional Concrete Bridge Bents

M.K. Bahrani, A. Vasseghi, A. Esmaeily, and M. Soltani

This paper presents the results of an experimental study conducted to assess the seismic response of the commonly used multicolumn bridge bents constructed in Iran. Observing the real performance of the bent, capturing undesirable failure modes, and verifying current code requirements are the main goals of this study. A 30% scaled specimen was designed, constructed and tested under simulated earthquake loads. The results indicate that the joint failure and slippage of longitudinal column reinforcement within the joints are the predominant failure modes under lateral cyclic loading. Such failure modes adversely affect the energy-absorbing capacity by a significantly pinched hysteresis response. Slippage of the column's longitudinal bar is the main contributing factor for the pinched hysteresis response. Based on the test results, AASHTO requirements for development length of the column's longitudinal bars inside the cap-beam is unnecessarily long, and it can be reduced considering the confinement effects of transverse reinforcement. Test results also indicate that the displacement capacity of bridge bents calculated by the AASHTO approximate equation may be unconservative.

Full Paper

Stability of Railroad Tracks under the Effects of Temperature Change and Earthquake

F. Arbabi and M. Khalighi

One of the major causes of train accidents is derailment due to axial or lateral buckling of the track. This problem is more prominent in continuously welded rails (CWR), which are now very common because of their advantages of reduced noise and damage and more comfortable rides. As for the effect of earthquakes on track buckling, the axial force they induce seems to be much less than that of temperaturechange as well as those caused by tractive action and braking of locomotives. This does not mean that earthquakes cannot have a detrimental effect on railroad tracks. Their main cause of damage is the large reduction they may produce in the lateral resistance of ballast due to shaking of the ballast bed. This paper deals with the problem of axial and lateral buckling of CWR and the effects of earthquakes and temperature change on the stability of the track. A three-dimensional macro-element is used to model the track. A program, developed in Mathcad environment, is used to conduct a series of parametric studies. The results show that the simple sinusoidal form often used for determining buckling loads of tracks is only valid for totally homogeneous tracks, a rather rare situation. It was ascertained that the buckled shapes observed in practice are due to local inhomogeneities of the track.

Full Paper

Constitutive Model for HSC Confined by UHS and NS Transverse Reinforcements under Cyclic and Earthquake Loadings Stress

M. Bastami

In this paper, a cyclic constitutive model is developed for high-strength concrete (HSC) confined by ultra-high-strength and normal-strength transverse reinforcements (UHSTR and NSTR), with the intention of providing efficient modeling for the member and structural behavior of HSC in seismic regions. The model for HSC subjected to monotonic and cyclic loading, comprises four components; an envelope curve (for monotonic, cyclic and earthquake loadings), an unloading curve, a reloading curve, and a tensile unloading curve. It explicitly accounts for the effects of concrete compressive strength, the volumetric ratio of transverse reinforcement, yield strength of ties, tie spacing, and tie pattern. The proposed envelope curve models for confined HSC cover four options; namely, (1) rectangular (square) cross section with NSTR, (2) circular cross section with NSTR, (3) rectangular (square) cross section with UHSTR, and (4) circular cross section with UHSTR. Comparisons with test results showed that the proposed model provides a good fitting to a wide range of experimental results. The configuration of transverse reinforcement had a particularly large effect.

Full Paper

 
 

Spring and Summer 2010, Vol. 12, No. 1 & 2

Seismic Situation's Probability Prediction in Greater Caucasus During the Period 2005-2025

O. Varazanashvili and N. Tsereteli

This paper presents probabilistic prediction of seismic situation along the structural-tectonic zones of the axial part and the southern slope of Great Caucasus. It is an important problem, because large earthquakes (M>6) occur frequently in this area. As usual, the calculated probabilities of occurrence of large earthquakes give more condensed information. As it was expected, conditional probabilities of a future earthquake is small immediately after previous shock and it increases with the time passed after the last earthquake. To solve this problem, the spatial distribution and frequency of occurrence of large earthquakes is studied. In particular, it was found that epicenters of earthquakes with M>6 are distant from each other in this zone on the average distance of 100km. On the basis of maximum seismic activity in these areas, the average periods of recurrence of large earthquakes have been identified. By using a time-dependent model of seismicity, some segments and subsegments of the structural-tectonic zones and conditional probabilities of occurrence of large earthquakes for the period 2005-2025 were calculated. Studies have shown that areas with a high probability of occurrence of large earthquakes deserve priority in controlling the seismic situation.

Effects of Non-Plastic Fines Content on Cyclic Resistance and Post Liquefaction of Sand-Silt Mixtures Based on Shear Wave Velocity

F. Askari, R. Dabiri, A. Shafiee, and M.K. Jafari

The cyclic resistance, shear wave velocity and post-liquefaction behavior of saturated Firoozkooh sand with different percentages of non-plastic silt are evaluated. Cyclic triaxial and resonant column tests performed on reconstituted samples prepared in laboratory utilizing undercompaction method. The data obtained from this study along with other existing data were transferred to the field and compared with the field performance curves based on shear wave velocity proposed by Andrus and Stokoe-2000. Then, to observe post-liquefaction behavior of the mixtures, volume change and pore pressure dissipation were measured. Tests results exhibit a clear trend among cyclic resistance, shear wave velocity and post-liquefaction behavior of specimens. In addition, the laboratory results indicated that using the existing field-based correlations may overestimate the cyclic resistance of the Firoozkooh sand-silt mixtures when silt content is 60%. For clean sand and the specimens with up to 30% fines, results of this study are fairly consistent with Andrus and Stokoe correlations. Increasing fines content would increase the final post-liquefaction volumetric strain.

3D Topography Effects on Amplification of Plane Harmonic Body and Surface Waves

B. Omidvar, M. Rahimian, T. Mohammadnejad, and A.R. Sanaeiha

In this paper, three-dimensional scattering of plane harmonic SH, SV, P, and Rayleigh waves by surface topographies is investigated by using a boundary element method in frequency domain. It is shown that for exact evaluation of surface ground motions in topographies all efficient parameters such as geometry of the region, mechanical properties of the surrounding geological materials (density, Poisson's ratio, and shear modulus), wave type, azimuth and angle of incidence, as well as stimulation frequency must be taken into account altogether. Furthermore, the results emphasize the need for three-dimensional modeling of irregularities. Most of the topographies in the nature are composed from the simple shape. Based on this fact, four problems are considered in order to study the effects of the shape of the topography on the surface ground motion amplification. In order to assess the accuracy and efficiency of the proposed formulations for the computation of the surface displacement field amplification, several problems are considered. The
investigated problems are hemispherical canyons, elliptical-shaped canyons, hemispherical hills and rectangular cube canyons.

Experimental Study on Flexural Strengthening of RC Columns with Near Surface Mounted FRP Bars

M. Sarafraz and F. Danesh

The effectiveness of FRP jackets for increasing the compression strength, shear strength and ductility of reinforced concrete (RC) columns was demonstrated in many studies, but the influence of FRP jacketing on the flexural capacity of columns is minimal. In this paper, a new retrofit method, which utilized near surface mounted (NSM) fiber reinforced polymer (FRP), was studied aiming to improve the flexural capacity of RC columns subjected to bending and compression. This technique is based on bonding fiber reinforced polymer (FRP) bars into grooves cut in the cover of RC columns. For this purpose, five reinforced concrete column specimens were designed, constructed and subjected to constant axial compression and lateral cyclic loading. In addition, the strengthened columns were wrapped with carbon composites to satisfy seismic detailing requirements. The test results show that by using the NSM technique, the flexural strength and lateral load capacity of the columns increase significantly. The test results were also compared with the results obtained from the analytical study that was conducted based on strain compatibility. A good agreement between analytical and experimental results was observed.

Experimental Investigation of the Effect of Transverse Beams on the In-plane Behavior of Brick-Flat-Arch Roofs

H. Shakib and A.R. Mirjalili

A number of historical and residential buildings were constructed with traditional brick-flat-arch roofs. The seismic behavior of this type of diaphragms has shown that they have a poor seismic performance. Several methods were suggested to retrofit this type of diaphragms. In this research, the in-plane seismic behavior of retrofitted brick flat arch diaphragms using transverse beams is investigated with experimental models. For this purpose, four full-scale experiments of roof diaphragm were conducted under cyclic loading. The results of the two first experiments showed that non-retrofitted traditional flat arch roofs have insufficient stiffness, shear capacity and integrity. In the retrofitted models however, the transverse beams within all the spans of roof can improve the in-plane behavior of this type of diaphragm to the extent that acceptable improvement in integrity and ductility of the diaphragm was observed in retrofitted roof, but the transverse beams could not properly improve the other seismic parameters of the diaphragm such as its shear capacity and stiffness. Therefore, this retrofitting method might not be an adequate method to secure the appropriate in-plane behavior of flat-arch roofs.

An Evaluation of Disaster Preparedness in Four Major Earthquakes in Iran

Y.O. Izadkhah and K. Amini Hosseini

Iran is located in the Alpine-Himalayan seismic belt, as one of the most active tectonic regions of the world. Throughout history, the country has frequently suffered large and destructive earthquakes and experienced several major earthquakes in the past few decades. More than 70 percent of the big cities in Iran are located in the vicinity of seismic faults and in some cases, the active faults pass through the city. Therefore, earthquake preparedness can be regarded as one of the factors which can contribute to safety of various groups of citizens. In Iran, measures have been undertaken to improve the public knowledge about disasters. A review on the activities of recent two decades, reveal the gradual improvement on the trends of earthquake preparedness in the country. The aim of this paper is to evaluate the progress of disaster preparedness in four major earthquakes that has occurred in Iran including Manjil - Roudbar, 1990, Changureh-Avaj 2002, Bam 2003, and Darb-e-Astaneh-Silakhore 2006 earthquakes. At the end, recommended strategies towards promoting public awareness and education as well as professional training are presented.

Stability of Plate Girders in RBS Connections: A Numerical Approach

A. Vasseghi and A. Tajoddini

Steel moment frame connection with Reduced Beam Section (RBS) is one of several pre-qualified connections which have been proposed in FEMA 350 for use in moment resisting frame structures. Previous studies on behavior of RBS connections are limited to connections with rolled sections and design requirements have been developed for such sections. Large size rolled sections are not readily available in developing countries like Iran and steel frame structures are usually built using plate girders. In such structures the slenderness ratios of web and flanges could greatly influence the seismic performance of the RBS connection. In this paper the effect of slenderness ratios of web and flanges on the behavior of RBS connections is studied by nonlinear finite element analyses. The analyses simulate inelastic local buckling of the girder as ductility and energy dissipating capacity of the connection are directly influenced by such inelastic behavior. Twelve RBS connections with various web and flange slenderness ratios are analyzed to evaluate the effect of slenderness ratios on ductility of the connection. The results indicate that FEMA- 350 requirements for maximum slenderness ratios of web and compression flange are too conservative. Connections in which the slenderness ratios of girder web and flanges exceeded the allowable limits by up to 30 percent have shown proper ductile behavior in the analyses.

 

Winter 2010, Vol 11, No. 4

Four Earthquakes of the Sumatran Fault Zone (Mw 6.0-6.4): Source Parameters and Identification of the Activated Fault Planes

Madlazim and B.J. Santosa

Four earthquakes (Mw 6.0-6.4) which occurred at 3 major segments of Sumatran Fault Zone (SFZ) were analyzed to identify their fault planes. The events were relocated to assess physical insight into the hypocenter uncertainty. The earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and Geofon broadband IA networks. The epicentral distances of all stations were less than 10°. Moment tensor solutions of the events was performed, simultaneously with the determination of the centroid position. Joint analysis of the hypocenter position, centroid position and nodal planes of the vents indicated the Sumatra fault planes. The hypocenters of all four events clearly prefer that strikes parallel to Sumatra Island to be the fault plane in all cases. Regional moment tensor solutions of this paper along with the focal mechanisms, which represent the only double couple of moment tensor, is plotted. The MT solutions consist of all events have strike slip one fault type. The preferable seismotectonic interpretation is that the events activated Sumatra fault zone at a depth of about 14-18 km, corresponding to the interplate of Sumatra fault boundary.

Full Paper

Seismic Performance of Variable Frequency Pendulum Isolator under Bi-Directional Near-Fault Ground Motions

V.R. Panchal and D.P. Soni

The dynamic response of flexible five-story building supported on the variable frequency pendulum isolator (VFPI) under bi-directional near-fault ground motions is investigated. In order to verify the effectiveness of the VFPI, the seismic responses are compared with the friction pendulum system (FPS) and variable friction pendulum system (VFPS). The response of the system with bi-directional interaction is compared with those without interaction in order to investigate the effects of bi-directional interaction of frictional forces. Moreover, a parametric study is carried out to critically examine the influence of important parameters on bi-directional interaction of the frictional forces of the VFPI. From the above investigations, it is concluded that under bi-directional near-fault ground motions, the isolator displacement in the VFPI is more than that of the VFPS and the FPS whereas the top floor absolute acceleration and the base shear are less than that of the VFPS and the FPS. Furthermore, if the bi-directional interactions of frictional forces of the VFPI are ignored, the isolator displacements will be under predicted and superstructure acceleration and base shear will be over predicted.

Full Paper

Nonlinear Analysis and Modeling of Unreinforced Masonry Shear Walls Based on Plastic Damage Model

A.A. Akbarzade M. and A.A. Tasnimi

Shear behavior and the failure modes of shear stressed masonry walls have been the subject of many investigations. In the present paper, the performance of an interface elasto-plastic constitutive model for the analysis of unreinforced masonry walls by means of micro-finite element modeling is evaluated. The micro-model is utilized to obtain the behavior of unreinforced masonry walls, based on assumption that the masonry bricks, mortar and their interface are three separate elements. In the present modeling, the behavior of bricks and mortar is assumed to comply with the plastic-damage model which is based on multiple damage variables. The behavior of the interface element is assumed to comply with the coulomb friction model having a limit on the critical shear stresses. A nonlinear analysis is performed by the application of explicit formulae in which displacements and rotations between bricks are taken into consideration. To validate the model, experimental results of masonry elements and walls is compared with the results obtained from the numerical analysis. It is concluded that the suggested model is suitable for assessing the behavior of masonry walls under vertical and horizontal loading.

Full Paper

Experimental and Analytical Studies on the Infilled Frames with Frictional Sliding Fuses

M. Mohammadi, V. Akrami, and R. Mohammadi

Experimental and analytical investigations have been conducted on a new type of infilled frames with Frictional Sliding Fuses (FSF). The results show that these infilled frames have adjustable strength and high ductility similar to other structural elements. Furthermore, the ultimate strengths and deformation capacities of such infills are much more than regular similar fuse-less infilled frames. To study the behavior of such infilled frames in out of plane direction, a specimen was loaded transversally after being failed by in-plane loadings and having the experience of 6% drift in this direction. The results reveal that the infill has sufficient strength against out of plane components of regular earthquakes. The infill with the proposed configuration of this study is modeled by finite element method, in ABAQUS, to study the influence of the fuse sliding strength on its ultimate strength. It is shown that the ultimate strength is raised linearly by increasing the sliding strength of the fuse. In summary, the results confirms that such infilled frames can be regarded engineered for their high ductility as well as the capability of being adjusted for a desired strength.

Full Paper

Seismic Monitoring of Distant Earthquakes for Studying Geodynamics and Estimating Environment's Stress

O.G. Popova and S.U. Kuhmazov

The results of long-term seismic monitoring with use of natural sources conducted in the seismic dangerous area of the Caucasus mineral waters are presented. In order to study the subsurface geodynamics and its stress state in the study area, a technique has been developed based on studying energy of converted PS waves. The analysis of obtained data allowed middle-term criteria for predicting local tectonic earthquakes to be formulated proceeding from the model within the scope of the avalanche-unsteady crack formation (AUCF) theory. It has been shown that the catastrophic far earthquakes (distance up to 7000km) with M >7.0, after which intense surface waves had been recorded in the area of Caucasus Mineral Waters, changed anisotropic properties and stress state causing the increase of local seismic activity. This shows the induced seismicity. Induced process reduces the reliability of formulated criteria. This reveals the necessity to correct the model of earthquake origin in accordance with the AUCF theory.

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