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
Seismic Behavior of 63kV and 132kV Substation Post Insulators with Flexible Conductors, an Experimental Approach
A.H. Khalvati, M. Hosseini, and S. Mohammadpour
Experimental and Analytical Investigation on In-Plane Behavior of URM Flanged Walls
M. Khanmohammadi, H. Behnam, and M.S. Marefat
Resilience Against Earthquakes: Some Practical Suggestions for Planners and Managers
B. Omidvar, S. Tavakoli, and M. Eskandari
Characterization of Long Period Strong Ground Motion
M. Erdik, M.B. Demircioglu, K. Sesetyan, and E. Harmandar
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
An Optimal Distribution of Stiffness Over the Height of Shear Buildings to Minimize the Seismic Input Energy
F. Haddad Shargh and M. Hosseini
Dual Ductility Mode Shear Walls: Concept and Behavior
M.S.R. Labafzadeh and M. Ziyaeifar
Performance of Unreinforced Masonry Buildings in Canterbury Earthquakes
Rajesh P. Dhakal
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. Theinvestigated 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.
A Note on Transparency and Loss of Life Arising from Earthquakes
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.
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.
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.
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.
Constitutive Model for HSC Confined by UHS and NS Transverse Reinforcements under Cyclic and Earthquake Loadings Stress
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.
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.
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.
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.
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.
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.
صفحه 1 از 8