Abstract
Preserving reservoir safety has recognized to be important for the public where a vast majority of dams are located upstream of greatly populated cities and industrialized areas. Buckling, floatation and cavitation have caused failure in the spillway gates and conveyance features during past catastrophic events; showed their vulnerability and need for regular inspection along with reviewing design calculations to ensure the spillway meet current design standards. This paper investigates the hydraulic and structural consideration of dam\'s spillway by evaluating the data of Karkheh Dam\'s. Discharge capacity, flood routings and cavitation damage risk were main features for hydraulic considerations where hydrostatic and hydrodynamic forces and stability conditions were considered in structural considerations.
Key Words
spillway radial gate; hydrodynamic forces; hydrostatic forces; westergaard\'s theory
Address
Iman Faridmehr: South Ural State University, 454080 Chelyabinsk, Lenin Prospect 76, Russian Federation, Russia
Mohammad Javadi Jokar,
Mohammadreza Yazdanipour and Ali Kolahchi: Production Operation Company of Karkheh Dam Hydropower Plant, Andimeshk, Khuzestan, Iran
Abstract
One way to provide safe buildings and to protect tenants from the terrorist attacks that have been increasing in the world is to study the behavior of buildings members after being exposed to dynamic loads. Buildings behaviour after being exposed to attacks inspired researchers all around the world to investigate the effect of impact loads on buildings members like slabs and to deeply study the properties of High Performance Concrete. HPC is well-known in its high performance and resistance to dynamic loads when it is compared with normal weight concrete. Therefore, the aim of this paper is finding out the impact of dynamic loads on RPC slabs\' flexural capacity, serviceability loads, and failure type. For that purpose and to get answers for these questions, three concrete slabs with 0.5, 1, and 2% steel fiber contents were experimentally tested. The tests results showed that the content of steel fiber plays the key role in specifying the static capacity of concrete slabs after being dynamically loaded, and increasing the content of steel fiber led to improving the static loading capacity, decreased the cracks numbers and widths at the same time, and provided a safer environment for the buildings residents.
Abstract
In present study, Operational Modal Analysis (OMA) was employed to carry out the dynamic and vibration analysis of the threshing unit of the combine harvester thresher as a mechanical component. The main study is to find the causes of vibration and to decrease it to enhance the lifetime and efficiency of the threshing unit. By utilizing OMA, structural modal parameters such as mode shapes, natural frequencies, and damping ratio was calculated. The combine harvester was excited by engine to vibrate different parts and accelerometer sensor collected acceleration signals at different speeds, and OMA was utilized by nonparametric and frequency analysis methods to obtain modal parameters while vibrating in real working conditions. Afterwards, finite element model was designed from the thresher and updated using the data obtained from the modal analysis. Using the conducted analyses, it was specified that proximity of the thresher pass frequency to one of the natural frequencies (16.64 Hz) was the most important effect of vibration in the thresher. Modification process of the structure was carried out by increasing mass required for changing the natural frequency location of the first mode to 12.4 Hz in order to reduce resonance and vibration of the thresher.
Key Words
structural modification; operational modal analysis; vibrations; thresher
Address
Hamed Ghafarzadeh Zare and Ali Maleki:Department of Mechanical Engineering of Biosystems, Shahrekord University, Iran
Ali Maleki: Department of Mechanical Engineering, University of Kashan, Iran
Majid Lashgari: Department of Mechanical Engineering of Biosystems, Arak University, Iran
Abstract
One method of retrofitting concrete structures is to use fiber reinforced polymers (FRP). In this research, the shear, torsional and flexural strengthening of self-compacting reinforced concrete (RC) girders are fulfilled with glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) materials. At first, for verification, the experimental results were compared with numerical modeling results obtained from ABAQUS software version 6.10. Then the reinforcing sheets were attached to concrete girders in one and two layers. Studying numerical results obtained from ABAQUS software showed that the girders stiffness decreased with the propagations of cracks in them, and then the extra stresses were tolerated by adhesive layers and GFRP and CFRP sheets, which resulted in increasing the bearing capacity of the studied girders. In fact, shear, torsion and bending strengths of the girders increased by reinforcing girders with adding GFRP and CFRP sheets. The samples including two layers of CFRP had the maximum efficiencies that were 90, 76 and 60 percent of improvement in shear, torsion and bending strengths, respectively. It is worth noting that the bearing capacity of concrete girders with adding one layer of CFRP was slightly higher than the ones having two layers of GFRP in all circumstances; therefore, despite the lower initial cost of GFRP, using CFRP can be more economical in some conditions.
Address
Moosa Mazloom: Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
Morteza Mehrvand: Department of Civil Engineering, University of Science and Culture, Tehran, Iran
Pardis Pourhaji: Department of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
Azim Savaripour: Department of Civil Engineering, Islamic Azad University of Sirjan, Sirjan, Iran
Abstract
Digital Image Correlation technique (DIC) is a non-contact optical method for rapid structural health monitoring of critical infrastructure. An innovative approach to DIC is presented using QR (Quick Response) code based random speckle pattern. Reinforced Cement Concrete (RCC) beams of size 1800 mm X 150 mm X 200 mm are tested in flexure. DIC is used to extract Moment (M) – Curvature (k) relationships using random speckle patterns and QR code based random speckle patterns. The QR code based random speckle pattern is evaluated for 2D DIC measurements and the QR code speckle pattern performs satisfactorily in comparison with random speckle pattern when considered in the context of serving a dual purpose. Characteristics of QR code based random speckle pattern are quantified and its applicability to DIC is explored. The ultimate moment-curvature values computed from the QR code based random speckled pattern are found to be in good agreement with conventional measurements. QR code encrypts the structural information which enables integration with building information modelling (BIM).
Key Words
DIC; Speckle Pattern; QR Code; Moment-Curvature; Reinforced Cement Concrete (RCC)
Address
B. Murali Krishna, T.P. Tezeswi, P. Rathish Kumar, K. Gopikrishna, M.V.N. Sivakumar and M. Shashi: Department of Civil Engineering, National Institute of Technology Warangal, Telangana, India-506004
