Shear Behavior of Prestressed Concrete Girders and Structural Health Monitoring Using Fiber Bragg Grating Sensors PDF Download
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Author: Aadit Kapadia
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages :
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Book Description
This research deals with six Prestressed girders that were tested to observe the shear behavior and investigate the failure mode. Three of the girders had a top slab of eight inches and were constructed with TXDOT specifications. The other three were constructed without the top slab with AASHTO specification. These were tested for bond slip behavior and with minimum reinforcement. The primary objective was to investigate the type of failure in all the girders. It was found that all of them failed in web shear and none in bond slip. One of the girders also had Fiber Bragg Grating sensors on the inside surface to observe localized bond slip. This was compared to the global slip given by the conventional sensors which led to conclusions about using those sensors instead of the conventional ones for structural health monitoring.
Author: Aadit Kapadia
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages :
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Book Description
This research deals with six Prestressed girders that were tested to observe the shear behavior and investigate the failure mode. Three of the girders had a top slab of eight inches and were constructed with TXDOT specifications. The other three were constructed without the top slab with AASHTO specification. These were tested for bond slip behavior and with minimum reinforcement. The primary objective was to investigate the type of failure in all the girders. It was found that all of them failed in web shear and none in bond slip. One of the girders also had Fiber Bragg Grating sensors on the inside surface to observe localized bond slip. This was compared to the global slip given by the conventional sensors which led to conclusions about using those sensors instead of the conventional ones for structural health monitoring.
Author: David P. Gustafson
Publisher:
ISBN:
Category : Girders
Languages : en
Pages : 173
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Author: 張穩二
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ISBN:
Category :
Languages : en
Pages : 0
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Author: Padmanabha Rao Tadepalli
Publisher:
ISBN:
Category : Fiber-reinforced concrete
Languages : en
Pages : 352
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Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: David Paul Gustafson
Publisher:
ISBN:
Category : Girders
Languages : en
Pages : 350
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Author: Dhiaa Mustafa T. Al-Tarafany
Publisher:
ISBN:
Category :
Languages : en
Pages : 412
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Implementation of the spliced girder technology in bridges has been growing in recent years. Increased girder lengths can now be realized by splicing shorter precast segments to produce a long span. The research conducted in this dissertation is focused on an evaluation of spliced girders using a three dimensional finite element analysis. The project consisted of a series of tests that were conducted in two phases. In Phase I, the effect of post-tensioning ducts on the shear behavior and strength of prestressed concrete girders was evaluated. In Phase II, the focus was on the behavior of cast-in-place splice regions between precast segments. Since a limited number of full scale beams could be tested, a three-dimensional advanced finite element program is an effective alternative to expensive tests. The parameters considered were grout to girder concrete strength ratio, splice to girder concrete strength ratio, concrete shear key detailing, coupler diameter, duct to web width ratio, shear span to depth ratio, and concrete shrinkage losses. The findings are described in detail. Using the experimental and analytical results, it was found that the grout to concrete strength ratio for grouted ducts should not to be less than 0.3. The effect of increasing the duct diameter to web width ratio from 0.43 to 0.57 was minimal. Splice to girder concrete strength ratio should be greater than 0.6. The addition of a shear key had no effect on the shear capacity of the girder. The coupler diameter in the splice region had no effect on the behavior of the spliced girder for coupler diameter to web width ratio up to 0.55. Including concrete shrinkage in the analysis slightly improved the correlation with observed response.
Author: John Cunningham Stone
Publisher:
ISBN:
Category : Strength of materials
Languages : en
Pages : 228
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Author: Anwer Al-Kaimakchi
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages : 0
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Prestressed concrete is used in structures because of its versatility, adaptability, and durability. Durability of prestressed concrete bridges in extremely aggressive environments is of increasing concern because of corrosion of the carbon steel strands that are typically used for prestressing. Concrete is a permeable material where chloride ions can penetrate through and reach the internal reinforcement and carbon steel strands are highly susceptible to corrosion. Thus, prestressed concrete bridges located in areas with high exposure to environmental factors (e.g., marine environments) deteriorate due to corrosion of carbon steel strands. For example, Florida has a long coastline, with many concrete bridges over coastal water. Among the 12,518 bridges in Florida, 6,303 are prestressed concrete, and almost half of them are older than 40 years. One solution to overcome the early deterioration of coastal bridges is to use corrosion-resistant strands, such as Duplex High-Strength Stainless Steel (HSSS) strands.HSSS strands have high corrosion resistance and are an alternative to carbon steel strands in concrete bridges in extremely aggressive environments. The growing interest in using stainless steel strands has led to the development of the ASTM A1114. In 2020, ASTM A1114 was released as a standard specification for low-relaxation, seven-wire, Grade 240, stainless steel strands for prestressed concrete. Stainless steel is made from different alloys compared to carbon steel, and thus the mechanical properties of stainless steel strands are fundamentally different than those of carbon steel strands. The most significant difference is in the guaranteed ultimate strain: the value for stainless steel strands is only 1.4%. Several departments of transportation (DOTs) have already used or allowed the use of HSSS strands in prestressed piles. As of 2020, a total of 17 projects have used stainless steel strands, a majority of them in piles. Those projects are in areas with high exposure to environmental factors. The use of HSSS strands in flexural members has been hindered by the lack of full-scale test results, structural design approaches, and/or design guidelines. The main concern in using HSSS strands in flexural members is their low ductility. Concrete members prestressed with HSSS strands, if not properly designed, might fail suddenly without adequate warning. There have been no attempts to address this problem in full-scale research studies. The goals of this research project were to investigate the use of HSSS strands in flexural members and to develop design guidelines that could be used by bridge engineers. A total of thirteen (13) 42-ft-long AASHTO Type II girders were designed, fabricated, and tested in flexure or shear. Ten (10) girders were prestressed with HSSS strands, while the other three (3) were prestressed with carbon steel strands and served as control girders. This research program included experimental activities to determine the mechanical and bond strength characteristics, prestress losses, and transfer length of 0.6-in-diameter HSSS strands. Twenty HSSS strands from two spools were tested in direct tension. A stress-strain equation is proposed for the 0.6-in.-diameter HSSS strands, which satisfied all ASTM A1114 requirements. The minimum and average bond strengths, following ASTM A1081, of six 0.6-in.-diameter HSSS strands were 15.8 kips and 17.9 kips, respectively. The minimum and average experimental ASTM A1081 bond strengths were 23.4% and 19.8% greater than the recommended values by PCI Strand Bond Task Group. The maximum measured transfer length of 0.6-in.-diameter HSSS strands was 21.5 inches, which was less than the value predicted by AASHTO LRFD Bridge Design Specifications' equation for carbon steel strands. Experimental flexural and shear results showed that the post-cracking behavior of girders prestressed with HSSS strands continued to increase up to failure with no discernible plateau. The behavior is attributed to the stress-strain behavior of the HSSS strands. Also, flexural results revealed that, although HSSS strands have low ductility and all composite girders failed due to rupture of strands, the girders exhibited large reserve deflection and strength beyond the cracking load and provided significant and substantial warning through large deflection, as well as well-distributed and extensive flexural cracking, before failure. A non-linear analytical model and an iterative numerical model were developed to predict the flexural behavior of concrete members prestressed with HSSS strands. Although the analytical model gave better predictions, the iterative numerical approach is slightly conservative and is easier to use for design - designers prefer to use an equation type of approach to perform preliminary designs. Numerical equations were developed to calculate the nominal flexural resistance for flexural members prestressed with HSSS strands. The proposed equations are only valid for rectangular sections. In the case of flanged sections, iterative numerical approaches were also introduced. Because HSSS strand is a brittle material, the design must consider the strain capacity of the strand and must be balanced between flexural strength and ductility. Based on the flexural design philosophy for using carbon steel strands in prestressed concrete girders, along with experimentally-observed behaviors and analytical results for concrete members prestressed with HSSS strands, flexural design guidelines were developed for the use of HSSS strands in flexural members. For I-girders, rupture of strands failure mode is recommended by assuring that concrete in the extreme compression fiber reaches considerable inelastic stresses, at least 0.7f_c^'. For slab beams (e.g. Florida Slab Beam), crushing of concrete failure mode is recommended by assuring that the net tensile strain in the HSSS strand is greater than 0.005. The recommended maximum allowable jacking stress and stress immediately prior to transfer are 75% and 70%, respectively. A resistance factor of 0.75 is recommended for both rupture of strand and crushing of concrete failure modes. AASHTO equations conservatively estimated the measured transfer length and prestress losses of 0.6-inches-diameter HSSS strands. The ACI 318-19 and AASHTO LRFD conservatively predicted the shear capacity of concrete girders prestressed with HSSS strands.
Author: Roya Alirezaei Abyaneh
Publisher:
ISBN:
Category :
Languages : en
Pages : 190
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Prestressed concrete girders are commonly fabricated with 0.5-in. (12.7-mm) or 0.6-in. (15.2-mm) diameter prestressing strands. Recent interest in the use of larger (0.7-in. (17.8-mm) diameter) strands has been driven by potential benefits associated with reduction of the required number of strands and fabrication time, or potential increases in the workable range of prestressed concrete girders (i.e., greater capacities and span capabilities). A limited number of experiments on full-scale specimens with 0.7-in. (17.8-mm) diameter strands have shown that the load-carrying capacity and strand transfer length of specimens with 0.7-in. (17.8-mm) diameter strands can be conservatively estimated using existing AASHTO LRFD provisions. However, performance at prestress transfer requires further investigation to ensure that application of the strands with standard 2-in. (50-mm) spacing and conventional concrete release strength does not increase the end-region cracking that is characteristic of prestressed girders. It must be verified that the development of such cracks does not stimulate anchorage-driven or premature shear failures prior to yielding of the shear reinforcement. Previous research lacks in monitoring of reinforcement stresses and evaluation of end-region cracking which has long been a durability concern. A reliable finite element model that captures the behavior of the specimen at prestress transfer with consideration of performance from construction stages, over the course of the service life, and up to the ultimate limit state can provide key insight into the suitability of using of 0.7-in. (17.8-mm) diameter strands. Further, it could serve as an economical tool for the investigation and proposal of efficient end-region reinforcing details to reduce concrete cracking and enhance durability. Finite element analyses of prestressed I-girder end-regions encompassing cracking and long-term creep- and shrinkage-induced damage, especially in girders fabricated with large diameter strands, have been limited. This research program assessed the limitations of 0.7-in. (17.8-mm) diameter strands at prestress transfer up to limit state response and investigated measures for enhancing the serviceability of the girders through finite element analyses using the commercial software, ATENA 3D. The finite element study was complemented with a full-scale experimental program which was used to validate the numerical results. This paper lays out a validated procedure for modeling the construction stages of prestressed girders and load testing. The model was then used as a tool for investigating alternative end-region reinforcement details for improved end-region serviceability. The most promising options are presented for consideration in further experimental studies and future implementation
