Elementos compuestos RC-HPFRC

@article{Zanuy2022,
title = {Experimental determination of sectional forces in impact tests: Application to composite RC-HPFRCC beams},
author = {Carlos Zanuy and Gonzalo S D Ulzurrun and Manfred Curbach},
doi = {10.1016/J.ENGSTRUCT.2022.114004},
issn = {0141-0296},
year = {2022},
date = {2022-04-01},
journal = {Engineering Structures},
volume = {256},
pages = {114004},
publisher = {Elsevier},
abstract = {The impact response of concrete structures differs significantly from the quasi-static behaviour due to strain rate influence on mechanical properties, formation of inertia forces and local damaging mechanisms. The time-variable acceleration of the impacted element leads to inertia forces which produce a time-dependent distribution of shear forces and bending moments. The failure mode of impacted elements is significantly affected by the distribution of sectional forces and a detailed study of such forces is therefore convenient for a full understanding of impact mechanics. One of the most extended approaches to study experimentally the impact behaviour of reinforced concrete (RC) beams is with the help of instrumented drop weight testing machines. Such facilities usually incorporate dynamic load cells to measure the support reactions and the impact force. Though the resulting inertia force can be derived by difference of reactions and impact force, its distribution cannot be determined, which is necessary for the estimation of sectional forces. In the present paper, an experimental methodology based on digital image correlation (DIC) supported by a high-speed and high-resolution camera is presented. The proposed methodology provides an accurate estimation of inertia forces which allows deriving the time-dependent evolution of shear forces and bending moments. The methodology is applied to an experimental campaign consisting of RC beams strengthened with a thin layer of high-performance fiber-reinforced cement composite (HPFRCC). The impact response of composite RC-HPFRCC elements is analyzed by examining the shear forces and bending moments at the critical sections. The implemented DIC-based methodology allows understanding the critical instants of the tests which lead to shear cracking. Moreover, a shear strength model is presented to estimate the capacity of studied RC-HPFRCC elements.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Zanuy2021,
title = {Evaluation of Impact-Critical RC Beams Strengthened with a Bottom Layer of HPFRCC},
author = {Carlos Zanuy and Alejandro García-Sainz},
url = {https://www.tandfonline.com/doi/abs/10.1080/10168664.2021.1965944},
doi = {10.1080/10168664.2021.1965944},
issn = {16830350},
year = {2021},
date = {2021-01-01},
journal = {Structural Engineering International},
publisher = {Taylor & Francis},
abstract = {One of the most hazardous consequences of impacts on concrete structures is the high tendency to develop shear or punching failures, with debris generation and associated flying fragments split out...},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Zanuy2020,
title = {Composite Behavior of RC-HPFRC Tension Members under Service Loads},
author = {Carlos Zanuy and Pedro Javier Irache and Alejandro García-Sainz},
url = {https://www.mdpi.com/1996-1944/14/1/47/htm https://www.mdpi.com/1996-1944/14/1/47},
doi = {10.3390/MA14010047},
issn = {1996-1944},
year = {2020},
date = {2020-12-01},
journal = {Materials 2021, Vol. 14, Page 47},
volume = {14},
number = {1},
pages = {47},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {A significant increase of the use of high-performance fiber-reinforced concrete (HPFRC) to strengthen reinforced concrete structures (RC) has been noted for the past few years, thereby achieving composite RC-HPFRC elements. Such a technique tries to take advantage of the superior material properties of HPFRC in the ultimate and service load regimes. Many of the existing works on RC-HPFRC elements have focused on the strength increase at the ultimate load state and much less effort has been devoted to the serviceability response. The in-service performance of RC structures is governed by the behavior of the tension chord, which determines the crack pattern (crack widths are critical for durability) and deformations. The presence of HPFRC is supposed to improve serviceability due to its strain-hardening and tension-softening capacities. In this paper, the experimental analysis of composite RC-HPFRC tension members is dealt with. Specimens consisting of a RC tie strengthened with two 35 mm thick HPFRC layers have been subjected to loads in the service range so that the deformational and cracking response can be analyzed. The HPFRC has been a cement-based mortar with 3% volumetric amount of short straight steel fibers with a compressive and tensile strength of 144 MPa and 8.5 MPa, respectively. The experiments have shown that RC-HPFRC has higher stiffness, first cracking strength and reduced crack widths and deformations compared to companion unstrengthened RC. To understand the observed behavioral stages, the experimental results are compared with an analytical tension chord model, which is a simplified version of a previous general model by the authors consisting of 4 key points. In addition, the influence of time-dependent shrinkage has been included in the presented approach.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Zanuy2020b,
title = {Impact Resisting Mechanisms of Shear-Critical Reinforced Concrete Beams Strengthened with High-Performance FRC},
author = {Carlos Zanuy and Gonzalo S D Ulzurrun},
url = {https://www.mdpi.com/2076-3417/10/9/3154/htm https://www.mdpi.com/2076-3417/10/9/3154},
doi = {10.3390/APP10093154},
issn = {2076-3417},
year = {2020},
date = {2020-05-01},
journal = {Applied Sciences 2020, Vol. 10, Page 3154},
volume = {10},
number = {9},
pages = {3154},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {Reinforced concrete (RC) structures typically present brittle failures by shear or punching under impact loading. High-performance fiber-reinforced concrete (HPFRC) has great potential due to its superior strength and energy absorption. The higher price and environmental cost of HPFRC compared to conventional RC can be effectively overcome by partially strengthening impact-sensitive RC members with HPFRC. To study the feasibility of this technique, HPFRC was applied as a tensile layer at the bottom of RC beams. Drop weight impact tests were carried out on beams with two values (35 and 55 mm) of HPFRC thickness, in addition to companion RC beams. Results show that the impact response can be divided into two stages: a first stage governed by local effects and shear plug formation at midspan, and a second stage governed by global beam behavior with formation of shear web cracks. A new resisting mechanism was observed for beams strengthened with HPFRC, as the strengthening layer worked similarly to a stress ribbon retaining the damaged RC and reducing fragmentation-induced debris. Such mechanism was fully achieved by the specimens with 35 mm HPFRC layer but was limited for the specimens with 55 mm HPFRC layer due to impact-induced interface debonding.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Zanuy2020a,
title = {Bending model for composite UHPFRC-RC elements including tension stiffening and crack width},
author = {Carlos Zanuy and Gonzalo S D Ulzurrun},
doi = {10.1016/J.ENGSTRUCT.2019.109958},
issn = {0141-0296},
year = {2020},
date = {2020-04-01},
journal = {Engineering Structures},
volume = {209},
pages = {109958},
publisher = {Elsevier},
abstract = {The application of a thin ultra-high performance fiber-reinforced concrete (UHPFRC) layer at the tensile side of reinforced concrete (RC) elements has lead to an efficient structural concept with promising capacities. Composite UHPFRC-RC elements have an increased bending capacity with respect to the RC member. In addition, the serviceability and durability are also improved as the composite element has higher stiffness and smaller crack widths. In order to widen the application of composite UHPFRC-RC elements, practitioners and designers need analytical and numerical tools with a sound mechanical background, if possible conceptually analogous to well-established models for conventional concrete structures. The paper starts with a discussion of the main drawbacks of existing models for UHPFRC-RC elements in bending. Secondly, new experimental basis is provided with own tests where the digital image correlation (DIC) technique is exploited to understand the crack pattern development and interfacial behaviour of UHPFRC-RC. Finally, the main goal of the paper is the proposal of a new model for UHPFRC-RC elements in bending which includes tension stiffening and the interaction at the steel-concrete and concrete-UHPFRC interfaces by means of a new composite tension chord model. The tension chord model is based on the stress transfer mechanisms between adjacent cracks, which include the explicit consideration of bond stresses between the constituent materials (i.e. steel and concrete, and UHPFRC and concrete). The compatibility condition between the UHPFRC and the RC layers is established in terms of the extension of each layer between adjacent cracks, as the classic compatibility of strains based on perfect bond assumption cannot be used upon macrocrack formation. Rather, the extension of the UHPFRC layer includes the contribution of cross-sections within the elastic, hardening or softening stages of the UHPFRC. The proposed model allows estimating the whole bending response, including calculation of crack widths and average curvatures between cracks.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Zanuy2019b,
title = {Analysis of interfacial interaction in UHPFRC-strengthened reinforced concrete beams},
author = {C Zanuy and G S D Ulzurrun and I M Díaz},
url = {https://iopscience.iop.org/article/10.1088/1757-899X/596/1/012024 https://iopscience.iop.org/article/10.1088/1757-899X/596/1/012024/meta},
doi = {10.1088/1757-899X/596/1/012024},
issn = {1757-899X},
year = {2019},
date = {2019-08-01},
journal = {IOP Conference Series: Materials Science and Engineering},
volume = {596},
number = {1},
pages = {012024},
publisher = {IOP Publishing},
abstract = {The behaviour and failure mode of reinforced concrete elements strengthened with a thin tensile layer of ultra-high performance fiber-reinforced concrete (UHPFRC) is governed by the interface interaction between the UHPFRC and conventional concrete. In order to analyze the relative displacements at the interface and its influence on the crack pattern evolution and monolithic response, digital image correlation (DIC) has been used in this contribution. With the help of DIC, the distinct stages of the behaviour of UHPFRC-strengthened beams have been correlated with the crack formation and development. Special attention has been paid to the progressive debonding due to the strain incompatibility between UHPFRC and conventional concrete when cracks develop. It is shown that the utilization of the capacity of the UHPFRC can be achieved from a certain thickness of the strengthening layer for shear-critical elements, thereby providing a gain of shear strength and ductility. In contrast, a thinner UHPFRC layer has been more beneficial for flexure-critical elements.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}