Dynamic Properties And Application Of Steel Fiber Reinforced Self Consolidating Concrete To Segmental Bridge Columns In Moderate To High Seismic Regions
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Dynamic Properties And Application Of Steel Fiber Reinforced Self Consolidating Concrete To Segmental Bridge Columns In Moderate To High Seismic Regions
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Author : Nasi Zhang
language : en
Publisher:
Release Date : 2014
Dynamic Properties And Application Of Steel Fiber Reinforced Self Consolidating Concrete To Segmental Bridge Columns In Moderate To High Seismic Regions written by Nasi Zhang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
In this dissertation, the application of steel fiber reinforced self-consolidating concrete (SFRSCC) to precast unbonded post-tensioned segmental bridge columns in moderate-to-high seismic regions is evaluated numerically and experimentally. Drop weight impact tests are first conducted on plain concrete and steel fiber reinforced concrete (SFRC). The standard drop test recommended by the American Concrete Institute (ACI) is first conducted and a modification to this standard ACI, which involves visual inspection of first cracking and ultimate failure, is then developed. The Kolmogorov-Smirnov (K-S) test along with fitted normal and lognormal distributions are used to examine the distribution of the number of blows required to cause first cracking and ultimate failure of the concrete. The minimum sample size required to calculate the impact strength of SFRC is determined using equations available in the literature. This sample size is used in the subsequent impact study on SFRSCC specimens. The static and dynamic properties of ten groups of SFRSCC, including one group of self-consolidating concrete (SCC) without steel fibers, are studied and compared. Dramix℗ʼ ZP305, RC-65/35-BN, and RC-80/30-BP steel fiber (glued and hooked end) at a volume of 0. 25%, 0. 5% and 1% are considered in the study. The static properties are calculated using compression tests, split-tension tests and flexural beam tests. The dynamic properties are determined using the modified ACI impact test. A dynamic load sensor is installed underneath the base plate of the impact test machine to measure the relative reaction force history. The recorded reaction forces are used to develop an automated impact test method, which can circumvent visual inspections. Two large-scale (1:3. 37), precast, unbonded and post-tensioned segmental columns, one constructed with SCC and one constructed with SFRSCC (with 0. 5% of ZP305 steel fiber by volume), are tested under cyclic loading. These segmental columns incorporate shear keys at the joints. The backbone force-displacement relationships of the segmental columns are calculated from a pushover model available in the literature. The hysteretic behavior of the segmental columns under cyclic loading is also simulated by a numerical model developed on the OpenSEES platform. A single span, large-scale (1:3. 37) bridge model incorporating SFRSCC segmental columns (with 0. 5% of ZP305 steel fiber by volume) is tested on a shake table. Two types of cap beam-to-superstructure connections are considered for the bridge model: a connection using non-seismic rubber bearing and a fixed connection. The bridge model is tested for far field and near field ground motions along various directions and with increasing peak ground accelerations (PGAs). The evolution of the cumulative damage to the bridge model after each seismic test is evaluated through a system identification involving white noise excitation. A flag-shaped hysteretic model is proposed and validated through the cyclic test results obtained in this research and those available in the literature. The proposed flag-shaped model is used to predict the seismic response of the bridge model. Adding steel fibers to concrete significantly improves its impact strength and ductility. The SFRSCC segmental columns suffered less damage than the SCC columns for the same level of drift. The large-scale bridge model incorporating SFRSCC segmental columns sustained high intensity far field and near field ground motions with limited damage. The proposed flag-shaped hysteretic model can be used to simulate the cyclic behavior of segmental columns, and to provide reasonable estimates of their seismic response under strong ground motions.
Behaviour Of Self Consolidating Steel Fiber Reinforced Concrete Beams Under Reversed Cyclic Loading
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Author : Nima Aghniaey
language : en
Publisher:
Release Date : 2013
Behaviour Of Self Consolidating Steel Fiber Reinforced Concrete Beams Under Reversed Cyclic Loading written by Nima Aghniaey and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Of Bridge Sub Structures And Fiber Reinforced Super Workable Concrete For Infrastructure Construction
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Author : Kamal H. Khayat
language : en
Publisher:
Release Date : 2017
Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Of Bridge Sub Structures And Fiber Reinforced Super Workable Concrete For Infrastructure Construction written by Kamal H. Khayat and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Bridges categories.
The proposed research investigates the combined use of self-consolidating concrete (SCC) and fibers reinforcements to develop a novel repair material, fiber-reinforced self-consolidating concrete (FR-SCC) that can be used for the rehabilitation and strengthening of existing structures. Furthermore, the feasibility of using super workable concrete (SWC) reinforced with different types of fibers for new structural cast-in-place applications is investigated. The use of SCC matrix can greatly enhance the workability of fibrous mixtures along with incorporation of greater volume of fibers. SWC is a new type of flowable concrete with lower workability than SCC. Containing lower binder content can be more cost effective than SCC. SWC requires some mechanical consolidation energy to ensure proper filling of the formwork. Eight types of fibers, including a propylene synthetic fiber, five steel fibers and a hybrid steel and polypropylene synthetic fiber were investigated. Fibers were incorporated at a volume of 0.5% in FR-SCC and at 0.5% and 0.75% in FR-SWC. Two types of expansive agents (EA), Type G and Type K, were added to both concrete types to reduce shrinkage and enhance resistance to restrained shrinkage cracking. The optimized mixtures exhibited high workability, mechanical properties, and freeze/thaw durability. The incorporation of fibers with 4% Type-G EA in FR-SCC increased the 56-day flexural strength by up to 32%, and flexural toughness up to 23 times. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers (ST1) in FR-SCC made with 4% Type-G EA increased the elapsed time to cracking determined from restrained shrinkage ring test from 16 to 20 days compared to FR-SCC made with 0.5% ST1 fibers without EA. The use of ST1 steel fibers and 4% Type-G EA decreased the 1-year drying shrinkage by 48% compared to the reference SCC mixture without any fibers and expansive agent. In case of FR-SWC, the decrease in shrinkage was 37% compared to SWC. In addition, 20 monolithic full-scale beams were cast using different types of concrete, including conventional vibrated concrete (CVC), fiber-reinforced conventional vibrated concrete (FR-CVC), SCC, FR-SCC, SWC and FR-SWC. Twelve reinforced concrete beams were cast using CVC to fill two thirds of the beam height. They were then filled with five different types of FR-SCC and SCC to simulate beam repair in the tension zone. Findings indicated that macro fibers can be used with FR-SCC designated for repair with fiber length ≤ 2 in. (50 mm) up to 0.5% fiber volume. Macro fibers can be used with FR-SWC designated for construction with fiber length ≤ 2.6 in. (65 mm) up to 0.75% fiber volume. Fibers had great impact on structural performance of the full-scale monolithic beams. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers combined with 0.5 in. (13-mm) straight steel fibers at ratio 4 to1 (STST) with 4% Type-G EA increased toughness of FR-SWC beams by 95% compared to SWC beams and by 86% in case of 0.75% 5D fibers. Repair using FR-SCC increased the flexural capacity of the beam by 6% and the toughness by 110% in case of using 0.5% ST1 fibers with 4% Type-G EA.
Development And Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Applications
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Author : Fodhil Kassimi
language : en
Publisher:
Release Date : 2013
Development And Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Applications written by Fodhil Kassimi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
The use of self-consolidating concrete (SCC) in the concrete industry in cast-in-place applications, including repair applications, is growing given the various advantages offered in both fresh and hardened states. The present study deals with the design and performance of fiber-reinforced self-consolidating concrete (FR-SCC) as a repair material of concrete infrastructure. The study also considers the use of various steel and synthetic fibers (five fibers in total) that were used to produce FR-SCC and fiber-reinforced self-consolidating mortar (FR-SCM) that can be employed for structural and non-structural repair applications. The study evaluates the effect of material properties and mixture composition of the fibrous concrete and mortar on workability, mechanical, visco-elastic, durability, and structural behavior. The investigation that is presented in this thesis included the testing of 28 full-scale beams under four-point flexural loading. The majority of these beams were repaired by casting concrete to fill a relatively thin section along the tension zone of the beams. The repair technique was based on the FR-SCC characteristics including the maximum fiber volume and length. This technique required mixtures of high range of fluidity. The optimized FR-SCC and FR-SCM mixtures exhibited excellent flow characteristics along the 3.2-m long beams without blockage, segregation, nor debonding at the interface of repair-substrate concrete. Based on the structural characteristics of the composite beams, the overall performance of the beams repaired using the FR-SCC and FR-SCM was similar or higher (up to 2.6 times) than that of monolithic beams made with conventional vibrated concrete (CVC). The use of optimized FRSCC mixtures enabled the replacement of 50% of the tension steel reinforcement in repair sections; i.e., the number of bars in the tension zone decreased from three bars to two bars with the addition of fibers in the SCC without mitigating structural performance. The degree of prediction of crack width, cracking load/moment, ultimate loads, and deflection of various FR-SCC and FR-SCM mixture was evaluated using several design and code models. The results indicate that these code models can provide safe predictions for crack and ultimate loads, as well as crack width of FR-SCC. The deflection of FR-SCC is unsafe but predictable by these code models. In total, 18 large-scale beams were tested in four-point for flexural creep. FR-SCC incorporating steel fibers combined with expansive agent provided overall performance up to 10 times of that obtained with CVC with the same fiber type and volume. The cracking under constant load was reduced by 60% to 80% using self-consolidating fibrous mixtures made with or without expansion agents, compared to SCC without fibers. The best combination to reduce the cracking potential when the restrained shrinkage ring test was employed was obtained with SCC mixtures made with steel fibers and expansive agent. Models were elaborated to predict the time-to-cracking for FR-SCC and FR-SCM mixtures based on mixture modulus of elasticity and drying and autogenous shrinkages. The project involved extensive testing of highly flowable fibrous materials to determine drying shrinkage (nearly 260 prisms), modulus of rupture (nearly 180 prisms), as well as compressive and splitting tensile strengths and elastic modulus (nearly 2100 cylinders). Based on the results, models were proposed to predict these key material properties that affect the performance of FR-SCC and FR-SCM used in repair applications. In addition to FR-SCC, the investigation also was set to evaluate the feasibility of using fiber-reinforced superworkable concrete (FR-SWC) in construction and repair applications. Such highly flowable concrete that requires limited vibration consolidation can represent some advantages over FR-SCC (lower admixtures demand, lower risk of segregation, greater robustness, lower formwork pressure, etc.). The energy needed to ensure proper consolidation, using either vibration or rodding, applied on samples made with FR-SWC was determined. The energy requirement took into consideration the development of mechanical properties, the resistance to segregation, and the development of proper surface quality. The study also demonstrated the higher overall structural performance of optimized FR-SWC compared to the corresponding FR-SCC mixtures. The findings of the thesis on the design and performance of highly workable fiber-reinforced cementitious materials should facilitate the acceptance of such novel high-performance material in infrastructure construction and repair applications.
Self Consolidating Concrete For Precast Prestressed Concrete Bridge Elements
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Author : Kamal Khayat
language : en
Publisher: Transportation Research Board
Release Date : 2009
Self Consolidating Concrete For Precast Prestressed Concrete Bridge Elements written by Kamal Khayat and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Bridges categories.
At head of title: National Cooperative Highway Research Program.
Performance Of Steel Fibre Reinforced Concrete Columns Under Shock Tube Induced Shock Wave Loading
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Author : Russell P. Burrell
language : en
Publisher:
Release Date : 2012
Performance Of Steel Fibre Reinforced Concrete Columns Under Shock Tube Induced Shock Wave Loading written by Russell P. Burrell and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Blast effect categories.
It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete. The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.
Investigation Of Fiber Reinforced Self Consolidating Concrete
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Author : Michael Carey Brown
language : en
Publisher:
Release Date : 2010
Investigation Of Fiber Reinforced Self Consolidating Concrete written by Michael Carey Brown and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Self-consolidating concrete categories.
The rising cost of materials and labor, as well as the demand for faster construction, has prompted development of cheaper, faster alternatives to conventional building techniques. Self-consolidating concrete (SCC), a high performance concrete characterized by its ability to flow without segregation under its own weight, promises to speed construction while reducing the need for skilled labor. However, experience has shown that SCC may be prone to shrinkage cracking, which may compromise its durability. In conventional concrete, fiber reinforcement has been used to control cracking and increase tensile and flexural strength. This study evaluated the feasibility of fiber-reinforced SCC (FR-SCC) for structural applications. Tests were conducted in the laboratory to assess the fresh and hardened properties of FR-SCC containing various types and concentrations of fibers. The results indicated that an SCC mixture can be prepared for use in transportation facilities that combines the properties of a high flow rate and some residual strength that would be beneficial for crack control. The residual strength is contributed by the internal fibers and provides load-carrying capacity after initial cracking of the concrete. At optimum fiber additions, FR-SCC mixtures can have the same fresh concrete properties as traditional SCC mixtures. FR-SCC also demonstrated a considerable improvement in the residual strength and toughness of a cracked section, which is expected to lead to the control of crack width and length. The improved performance of the FR-SCC cracked section indicated that it can be expected to have more durability in service conditions than would an identical SCC with no reinforcement. The study recommends that the Virginia Department of Transportation's Structure & Bridge Division evaluate FR-SCC in field applications such as link slabs and closure pours in continuous concrete decks; formed concrete substructure repairs; or prestressed beams where end zone cracking has been an issue. In such applications, construction with FR-SCC has the potential to be faster than with SCC, as traditional steel reinforcement may be reduced or eliminated, yielding reduced labor and materials costs for reinforcement placement. Enhanced public and worker safety may result from the reduction of overall construction time and required maintenance of traffic. The next step toward implementation of this technology would involve coordination with VDOT's Materials Division and Structure & Bridge Division to create special provisions or standard specifications regarding the use of FR-SCC and to identify candidate projects for field trials.
Seismic Performance Of Stainless And Conventional Steel Energy Dissipation Bars In Precast Segmental Bridge Columns
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Author : Yihui Zhou
language : en
Publisher:
Release Date : 2011
Seismic Performance Of Stainless And Conventional Steel Energy Dissipation Bars In Precast Segmental Bridge Columns written by Yihui Zhou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
The use of stainless steel reinforcing bars in seismic applications has recently attracted much attention in the civil engineering community due to its superior material properties, including high corrosion resistance and high specific strength. However, as with all new materials, a number of shortcomings are unavoidable, such as high initial costs, unknown low-cycle fatigue behavior, uncertain ductility properties and unidentified bond-slip behavior between the embedded bar and grouted duct in precast concrete element for use in segmental bridge members. The performance of precast segmental post-tensioned concrete bridge columns in seismic regions has been investigated by many other researchers. Mild steel energy dissipation bars (ED bars) that were continuous across the column segment joints were added into the columns to increase the hysteretic energy dissipation capacity.^In phase Iexperimental study, mechanical properties and low-cycle fatigue behavior of Talley S24100, Talley 316LN, Talley 2205 and Arminox UNS S32304 stainless reinforcing steel, A706 carbon black reinforcing steel, and MMFX II high strength, corrosion resistant reinforcing steel were investigated. Talley S24100 was found to obtain the highest ductility and the best low-cycle fatigue performance among the steels investigated. Therefore, compared to A706, Talley S24100 was considered to be the superior substitute material for ED bars. Succeeding phase II and phase III study on the bond-slip response of stainless steel reinforcing bars in grouted ducts of precast concrete element was then carried out with a focus on the influence of various duct/bar diameter ratios and different embedment lengths.^A seriesof monotonic pull-out and tension cyclic tests were conducted to investigate the constitutive bond-slip relationship between the bar and duct confined grout and their further applications under seismic loadings. Results showed that for A706 and Talley S24100 steels, both the duct/bar diameter ratio and embedment length influenced the bond-slip behavior in the monotonic pull-out tests. A one-dimensional nonlinear bond spring model exhibited a good performance in simulating the test results. In addition to the conventional bond-slip model, an "end-slip model" is also proposed in this study to describe the loaded end slip behavior of a bar anchored in grouted duct with a relatively deep embedment (12,16and 24 db). Each bond-slip and end-slip model has a five segment structure (each segment is linear). Recommended design equations were developed for development lengths for A706 and Talley S24100 reinforcing steels, respectively.^The local ED bar strains at different column top drift levels were investigated.
Precast Segmental Post Tensioned Concrete Bridge Columns For Seismic Regions
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Author : Yu-Chen Ou
language : en
Publisher:
Release Date : 2007
Precast Segmental Post Tensioned Concrete Bridge Columns For Seismic Regions written by Yu-Chen Ou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
A simplified analytical model for static pushover analysis and a three-dimensional detailed finite element model for cyclic analysis of the proposed bridge columns are developed in this research. In addition, a stiffness degrading hysteretic model is proposed for response-history analysis. With the analytical models, a parametric study is conducted to examine the seismic performance of the proposed columns with different design parameters.
Behaviour Of High Performance Fibre Reinforced Concrete Columns Under Axial Loading
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Author : Milad Mohammadi Hosinieh
language : en
Publisher:
Release Date : 2014
Behaviour Of High Performance Fibre Reinforced Concrete Columns Under Axial Loading written by Milad Mohammadi Hosinieh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with University of Ottawa theses categories.
When compared to traditional concrete, steel fibre reinforced concrete (SFRC) shows several enhancements in performance, including improved tensile resistance, toughness and ductility. One potential application for SFRC is in columns where the provision of steel fibres can improve performance under axial and lateral loads. The use of SFRC can also allow for partial replacement of transverse reinforcement required by modern seismic codes. To improve workability, self-consolidating concrete (SCC) can be combined with steel fibres, leading to highly workable SFRC suitable for structural applications. Recent advances in material science have also led to the development of ultra-high performance fibre reinforced concretes (UHPFRC), a material which exhibits very high compressive strength, enhanced post-cracking resistance and high damage tolerance. In heavily loaded ground-story columns, the use of UHPFRC can allow for reduced column sections. This thesis presents the results from a comprehensive research program conducted to study the axial behaviour of columns constructed with highly workable SFRC and UHPFRC. As part of the experimental program, twenty-three full-scale columns were tested under pure axial compressive loading. In the case of the SFRC columns, columns having rectangular section and constructed with SCC and steel fibres were tested, with variables including fibre content and spacing of transverse reinforcement. The results confirm that use of fibres results in improved column behaviour due to enhancements in core confinement and cover behaviour. Furthermore, the results demonstrate that the provision of steel fibres in columns can allow for partial replacement of transverse reinforcement required by modern codes. The analytical investigation indicates that confinement models proposed by other researchers for traditional RC and SFRC can predict the response of columns constructed with SCC and highly workable SFRC. In the case of the UHPFRC columns, variables included configuration and spacing of transverse reinforcement. The results demonstrate that the use of appropriate detailing in UHPFRC columns can result in suitable ductility. Furthermore, the results demonstrate the improved damage tolerance of UHPFRC when compared to traditional high-strength concrete. The analytical investigation demonstrates the need for development of confinement models specific for UHPFRC.