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Assessing Precision of Commercial Ultrasonic Instrument in Detecting Hole and Imperfection in Concrete Bridge Decks
, M.Sc. Thesis Sharif University of Technology ; Joghataie, Abdolreza (Supervisor)
Abstract
The conventional methods in concrete are usually divided to destructive and nondestructive tests. Among these, nondestructive tests are more preferable because they don’t damage the structure or at least the damage doesn’t significantly affect its performance. According to precision of estimation of concrete conditions, nondestructive tests have different levels. These tests on concrete bridge decks range from chain drag to more developed test like Ground Penetration Radar in concrete The optimum ease of use, cost and the precision of results of Ultrasonic Pulse Velocity (UPV) test compared with other nondestructive methods have made it a most widely used method. The precision of results of...
Numerical Analyses for Flexural Behavior of Bridge Deck Strengthened with Frp Sheets Using Partially Bonding System
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor)
Abstract
During times, reinforced concrete sturctures might need to be strengthened due to environmental factors, material properties, design errors or changes indesign guidelines.Fibre-reinforced-polymer (FRP)composites are prominentmaterialsfor this purpose. Externally full bonding systemhas been widely used for flexural strengthening of reinforced concrete sturctures with FRP. However, the drawback of using this strengthening system is the high reduction of structure's deformability.In this research, partially bonding system used in finite element modeling of a bridge’s deck to increase deformability compared to full bonding system. Results showed that not only deformability but also load...
Performance Evaluation of Reinforced Concrete Bridge Deck Strengthened with FRP Laminates
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
According to key importance of bridges in transportation system vital routes, a need to study and survey of bridges against destructive factors exist. Among these, bridges with concrete deck are widely used. One of the most important factors in destruction of these bridges is steel reinforcements corrosion and destruction of bridge deck. So in order to reduce the aggregation of reinforcements in critical sections and performance improvement of deck beams, a reinforcing substance which is not only resistant against corrosion but benefits from high resistance and stiffness is implemented.In this research the case studied bridge is simulated by finite elements software in two cases; reinforced...
A parametric study on optimal shape of buckling restrained knee bracing frames
, Article 5th International Conference on Advances in Steel Structures, ICASS 2007, Singapore, 5 December 2007 through 7 December 2007 ; Volume 3 , 2007 , Pages 356-361 ; 9789810593711 (ISBN) ; Mofid, M ; Sharif University of Technology
2007
Abstract
This paper is concerned with the development of buckling-restrained knee bracing frames for seismic design and retrofit of steel frame structures. Analytical models based on the new nonlinear finite element modeling of the system for the moment and shear yielding mode were developed in a structure with buckling-restrained knee-braces. Parametric study was performed with new and practical parameters of the system describing the specification of the system in elastic and inelastic behavior; and the results are shown in form of the appropriate graphs and charts. This study makes an offer to a simple design technique for this type of structure with a bilinear approach, using a nonlinear finite...
Experimental and numerical study on choosing proper pulse shapers for testing concrete specimens by split hopkinson pressure bar apparatus
, Article Construction and Building Materials ; Volume 125 , 2016 , Pages 326-336 ; 09500618 (ISSN) ; Naghdabadi, R ; Ashrafi, M. J ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Dynamic behavior of concrete specimens is investigated experimentally and numerically by split Hopkinson pressure bar (SHPB) tests. In order to accurately determine dynamic properties of brittle materials such as concrete, specimens should be subjected to particular pulse loading that can be generated by using pulse shapers. Choosing proper pulse shaper dimensions helps to obtain dynamic stress equilibrium, achieve constant strain rate and minimize pulse oscillation in the concrete specimens. To this end, SHPB tests are performed for concrete specimens and effective parameters on shaping pulses such as striker bar velocity, diameter and thickness of the pulse shaper are studied...
Predictive equations for shear link modeling toward collapse
, Article Engineering Structures ; Volume 151 , 2017 , Pages 599-612 ; 01410296 (ISSN) ; Dolatshahi, K. M ; Sharif University of Technology
Abstract
In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise...
Two novel shear fuses in moment resting frames
, Article Journal of Constructional Steel Research ; Volume 144 , May , 2018 , Pages 198-210 ; 0143974X (ISSN) ; Dolatshahi, K. M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Based on the code specifications, in moment-resisting frames the span-to-depth ratio has to be larger than a minimum value to make sure of adequate plastic hinging at beam-ends. This provision poses a restriction on the use of deep beams with short spans, especially for the framed-tube system in tall buildings. In this paper, a new energy dissipation method is introduced for moment-resisting frames by modifying the mid-span of the beam by two different methods, resulting in: (i) Perforated Shear Links (PSLs) and (ii) Slit Shear Links (SSLs). The links dissipate energy through shear yielding of the web, weakened by perforation or slitting, respectively. A thorough study is conducted on the...
Investigation of the fracture resistance in hoop wound composites modified with two different reactive oligomers
, Article Materials and Design ; Volume 30, Issue 8 , 2009 , Pages 3048-3055 ; 02641275 (ISSN) ; Bagheri, R ; Haddadpour, H ; Motamedi, P ; Sharif University of Technology
2009
Abstract
Rubber modification of hoop filament wound epoxy composites was investigated using amine-terminated butadiene acrylonitrile (ATBN) and carboxyl-terminated butadiene acrylonitrile (CTBN) oligomers. Both mechanical and physical properties of modified composites were investigated and the morphology of the samples was studied via scanning electron microscopy. Results indicated that, when added to the epoxy matrix, ATBN effected a superior increase in toughness, yet a more severe decline in compressive and flexural strength, compared to CTBN. In contrast, in the case of composite samples, incorporation of ATBN led to more favorable mechanical properties, from the viewpoint of both toughness and...
Use of rubber modification technique to improve fracture-resistance of hoop wound composites
, Article Materials and Design ; Volume 30, Issue 6 , 2009 , Pages 1976-1984 ; 02641275 (ISSN) ; Khademi, V ; Bagheri, R ; Haddadpour, H ; Kouchakzadeh, M. A ; Farsadi, M ; Sharif University of Technology
2009
Abstract
Toughness improvement of an epoxy resin and respective hoop wound composite were investigated systematically using amine-terminated butadiene acrylonitrile (ATBN) liquid rubber. Rubber modification improves fracture toughness of epoxy resin with slight reduction in the glass transition temperature (Tg), flexural and compressive properties of resin. Impact resistance of composite is improved by rubber modification similar to modified resin. Interlaminar shear strength (ILSS), compressive modulus and strength, and flexural strength of composite decreased slightly with rubber modification. To interpret the data, the void content of composite samples was determined and the damaged surfaces of...