Showing 1–12 of 411 results
Ductility Demand Distribution of Asymmetric Multi-Story R/C Buildings
To evaluate the infl...ادامه/دانلودرایگان!
To evaluate the influences of the number of stories on the torsional response and ductility demand distribution in the plan and the height of plan asymmetric RC dual lateral load resistant multi-story buildings, three categories of structural models that contain 8-, 14- nd 20-stories buildings (with the wide range of eccentricity values) are subjected to an assemblage of ordinary and near-fault ground motions. The approach of modeling has been used, is more accurate for multi-storey R/C structures, because it redefines the stiffness from the strength in each time step. According to the findings, the torsional effects, decreases for high-rise structures where the lateral natural period increases
Effect of Steel Plate Jacketing of Columns in Seismic Behavior of Concrete Beam-Column Connections
Design philosophy ofادامه/دانلودرایگان!
Design philosophy of having weak beam – strong column is recommended almost in all design codes. But in some ases, in prior buildings, this philosophy is ignored. In these structures, during major earthquakes, failure mechanism would begin from columns leading to sever damages. To avoid this event, column in the connection zone must be strengthened to conduct the plastic zone to the beams. There is several ways for strengthening concrete columns and one of the efficient ways is using steel plates surrounding column in the critical zone. In this paper, using steel plates for seismic upgrading of Concrete Beam-Column connections has been investigated numerically. Effect of plate thickness, length and beam-column dimensions is taken into account. Some empirical results are used to verify the finite element approach. Analyses are conducted with the use of some modeling methods including various geometrical models and material behaviors. The results from various methods are compared and the suitable model is proposed
Evaluation of Horizontal Seismic Hazard of ABADE, Iran
This paper presentsادامه/دانلودرایگان!
This paper presents probabilistic horizontal seismic hazard assessment of Abade, Iran. It displays the probabilistic estimate of Peak Ground Horizontal Acceleration (PGHA) for the return period of 475 and 2475 years. The output of the probabilistic seismic hazard analysis is based on peak ground acceleration (PGA), which is the most common criterion in designing of buildings. A catalogue of seismic events that includes both historical and instrumental events was developed and covering the period from 840 to 2007 is used. he seismic sources that affect the hazard in Abade were identified within the radius of 150 km and the recurrence relationships of these sources were generated by Kijko and Sellevoll . Finally four maps have been prepared to indicate the earthquake hazard of Abade in the form of iso-acceleration contour lines for different hazard levels by using SEISRISK III
Experimental Investigation of Time-Dependent Effect on Shear Strength Parameters of Sand–Geotextile Interface
The time-dependent bادامه/دانلودرایگان!
The time-dependent behavior of soils has been investigated extensively using one-dimensional and triaxial tests. The phenomena associated with time effects in soils are creep, relaxation, strain rate and rearrangement effects. The engineering properties of soil are often improved significantly with the time elapse. The objective of this paper is to investigate the time-dependent effect on the shear strength parameters of sand–geosynthetic interface using large direct shear test apparatus. For this purpose, the geotextile layer has been adhered gently on a piece of wood with a thickness such that a half of the shear test box has been occupied. The other half of the box has been filled with the sand and the test has been performed. Three normal stresses of 30, 45, and 60 kPa have been applied in all tests. The shear stress has subsequently been applied in different times to the failure stage. In all tests, the shearing velocity has been kept the same. The results of these experiments show that the stiffness and friction angle of the dry sand– geotextile interface increases up to 12.6% and 3.9% at 720 minutes after the sample is poured in the mold
Flexibility based method for the extent of damage in degrading bridge structures after in-service loading
This paper presents ...ادامه/دانلودرایگان!
This paper presents a method to identify damage in bridge structures based on the flexibility matrices in the modal strain space. In the tudy by the Ritz vectors extracted from flexibility matrix, the damage is identified. The localization approach is applied to low levels of damage on the prestressed concrete girder of simply supported bridge, with a focus on using a small number of sensors and only the fundamental mode of vibration. The validity of the method is also demonstrated using experimental modal data of a plate girder from I-40 Bridge over the Rio Grande. The predictions were found to closely match the actual response of the bridges. The proposed method can detect the damage in bridge structures using a limited number of sensors and vibration modes
INFLUENCE OF FIBER REINFORCEMENT ON TRIAXIAL SHEAR BEHAVIOR OF CEMENTED SANDY SOILS
A number of triaxialادامه/دانلودرایگان!
A number of triaxial tests were conducted for evaluation of randomly distributed fiber reinforcement effects on the behavior of cemented sand. Cemented samples were prepared by addition of Portland cement up to 3% by weight and were cured for about seven days after mixture. Polypropylene fibers with a length of 12 mm were added and mixed in three different weight percentages of 0%, 0.5%, 1%. Specimens were compacted in relative densities of 50% and 70%. Consolidated drained compression triaxial tests were performed under confinements of 100, 300 and 00 kPa. Tests results indicated that addition of polypropylene fiber to cemented sandy soils increases peak and residual strength. However, ultimate dilation decreases with enhancement of fiber content in cemented soil
Investigation of the Rockfill Materials Properties Based on the Confining Pressure Effect and the Rock Type
Rockfill materials hادامه/دانلودرایگان!
Rockfill materials have been widely utilized in large structures as well as rockfill breakwaters and rockfill dams construction. Design procedure of such structures requires a rather precise estimation of geomechanical properties of such materials and hence, such properties are often evaluated with great difficulty. In this research, one of the important parameters commonly used in elasto-plastic constitutive model, namely dilation angle, is investigated by studying triaxial test results on five rockfill materials
Parametric study of concrete base isolated building in the near field earthquakes
Recently the experie...ادامه/دانلودرایگان!
Recently the experience of recent near source earthquakes such as Northridge, Kobe and Tabas earthquakes have shown that the structures re more vulnerable in the near source earthquakes. This has also shown in many studies. The main reason for that is due to a strong and long period velocity pulse which generates in the near-field (NF) earthquakes. Base isolation systems are one of the methods for reducing the damage and vulnerable in the near source earthquakes, seismic isolation system increase period of vibration which reduce seismic force and the amount of energy transferred into the structure. In this paper, a parametric study has been carried out to study the behavior of based isolated concrete buildings in the near source earthquakes. One base isolated concrete building with 6 stories is considered. The behavior of selected structure has been studied using nonlinear dynamic analysis under three near and three far field (FF) earthquake recorders. A parametric study of various value of stiffness for the base isolation has been studied as well. The results have shown that the responses of building in the NF are very much than FF earthquakes, and the use of base isolation system reduces the base shear and story acceleration of building in NF in contrast FF, but displacement increased. Also the parametric study on the stiffness of base isolation showed that, decreasing stiffness of isolator’s causes the base shear and story acceleration reduced, but this subject for story displacements is not valid
Static Response of Reinforced Soil Retaining Walls with Modular Block Facing
Effect of backfill cادامه/دانلودرایگان!
Effect of backfill compaction, reinforcement connection type, geogrid-soil interface properties, and facing inclination on static response of Geosynthetic Reinforced Soil Walls (GRSW), was investigated using finite difference method. The numerical simulation of wall was included sequential construction of the wall. Backfill soil was modeled with Elastic-plastic Mohr–Coulomb model and modular block was modeled with elastic model. Results include the facing displacement, maximum load reinforcement and lateral earth pressure. Numerical results show the magnitude of lateral displacement decrease with increasing facing inclination and compaction load, the maximum reinforcement load increased significantly with an increase in compaction load. It was found that finite difference procedure was able to simulate the static response of GRS wall ery well
آلودگي صوتي تهديدي جدي براي سلامت انسان
يكيازمهمترين آلايندههاي زيست محيطي استكه در ابعاد مختلف سلامتي انسان را به مخاطره مياندازد بدين. منظور اين تحقيقبهارتباط بين اين آلودگي و
عوارض ناشي از آن در ابعاد جسماني و رواني پرداخته .است عامل صدا ، انسان و ساير موجودات زنده را از بين نميبرد بلكه باعث ضعف شنوايي ، ناشنوايي و ناراحتي هاي عصبي ميگردد معمولا شدت صدا را با واحدي به نام دسي بل نشان ميدهند براي سنجش صداها نسبت . log آنرا تعين ميکنند تحقيقات نشان مي دهد كه از دست دادن شنوايي با سن افراد در جوامع صنعتي ديده مي شود صداهاي شديد كوتاه مدت در انسان باعث ناشنوايي موقت ميشود نياز به صنعت در جوامع گوناگون، ايجاد كارخانه ها و صنايع توليدي مختلف را به دنبال داشته است. صنعتي شدن نيز سبب گرديده تا نيروي انساني شاغل در تماس هميشگي با وسايل ماشيني و تجهيزات قرار گيرد. اثرات ناشي از استفاده گسترده از وسايل ماشيني و تجهيزات صنعتي به صورت مواجهه انسان كند ها با مخاطرات گوناگون در محيط كار خودنمايي ميکند.
آناليز استاتيكي سيستم تركيبي قاب محيطي، هسته مركزي و كمربند خرپايي در برابر نيروهاي جانبي در سازه هاي بلند
يكي از مناسبترين سيس...ادامه/دانلودرایگان!
يكي از مناسبترين سيستمهاي مقاوم در برابر بارهاي جانبي در سازه هاي بلند سيستم تركيبي قاب محيطي، هسته مركزي و كمربند خرپايي ميباشد. كمربند خرپايي در تركيب با قاب محيطي و هسته مركزي همانند يك فنر خمشي در تركيب با تير طره عمل ميكند. در اين مقاله با در نظر گرفتن توابع جابجايي محوري براي ستونها و نوشتن رابطه انرژي، روابطي براي تنش هاي موجود در ستونها در ارتفاع بيان شده است. سپس با مينيمم كردن تغييرمكان جانبي بالاي سازه محل بهينه كمربند خرپايي به دست آمده است. در ادامه دقت نتايج روش پيشنهادي با روش آناليز كامپيوتري مقايسه گرديده است.
آناليز تغيير شكل و پايداري تاثير نيروهاي پيش تنيدگي مهار هاي اصطكاكي در سازه هاي نگهبان انعطاف پذير در خاك هاي رسي سفت تا سخت
در سازه هاي نگهبان م...ادامه/دانلودرایگان!
در سازه هاي نگهبان مسلح شده با مهار هاي اصطكاكي، الگوي تغيير شكل بسيار پيچيده بوده و با تئوري توزيع فشار هاي رانكين يا كولمب سازگار نميباشد. در اين تحقيق اثر نيروي پيش تنيدگي مهار هاي اصطكاكي بر تغيير شكل ها و ضريب اطمينان پايداري در يك ديواره در خاك رسي سفت تا سخت و در حالت خشك كه سيستم حائل جانبي آن متشكل از شمع نگهبان و مهار هاي اصطكاكي بوده، بررسي شده و نتايج در انتها ارائه شده است. نتايج تحليل بيانگر آنست كه استفاده از حد پايين نمودار فشار از لحاظ اقتصادي و عملي براي نوع خاك بررسي شده مطلوب تر از حد بالاي نمودار فشار خواهد بود.