Ultra-high Performance Concrete Panels Research Articles

Repairing of Reinforced Concrete T- section Beam with Web Opening Subjected to Torque by Using Ultra- High Performance concrete (UHPC)

Abstract Due to harsh weather factors, overloading, poor design, and material defects, reinforced concrete (RC) constructions’ early degradation has grown significantly over the last few decades. RC element repair is crucial to improving existing structures’ service life. Also, the transverse openings are frequently utilized in beams in modern structures to supply the service pipes. Because stresses are concentrated in a limited region above and below the opening, the presence of openings in concrete beams causes cracks to grow around the openings. Repairing, maintaining, and upgrading structural elements may be among the most important issues in civil engineering applications. This paper studies the effect of the presence of an opening and repairing of reinforced concrete T-section beam with web opening was subjected to torsion by using ultra-high performance concrete panels with a thickness of 20mm; The experimental work included casting seven beams: one beam without an opening and another beam with an opening, and five rest beams were repaired with UHPC panels in different locations. The results show the effect of an opening by decreasing the ultimate torque and increasing the ultimate angle of twist. The increase in ultimate torque for repairing beams compared to the control beam reached 153%, and a decrease in ultimate twist angle for repairing beams compared to the control beam reached 98%.

Numerical and Experimental Studies on Crack Resistance of Ultra-High-Performance Concrete Decorative Panels for Bridges

This study develops a new type of decorative bridge panel by ultra-high-performance concrete (UHPC) based on the project of the Guangyangwan Bridge. First, the numerical analysis was carried out using MIDAS and ABAQUS to find the critical position of the bridge and decorative panels. The numerical results showed that the last concrete cantilever segment had the greatest vertical deflection, and the corresponding panel had the greatest stress response. Based on the numerical results, this study conducted a series of full-scale, self-balanced bending tests to examine the crack resistance of six UHPC panels and six glass fiber-reinforced concrete (GRC) panels with varying curved section thicknesses (from 25 to 40 mm). The experimental results indicate that, due to the high strength of the UHPC matrix and the wall effect of steel fiber distribution, the crack resistance of UHPC panels is significantly superior to that of GRC panels. UHPC panels possessed superior stiffness and ductility, while GRC panels showed brittle fracture when the curved section thickness reached 34 mm. The uniaxial tensile cracking strength of UHPC with a steel fiber volume fraction of 1.6% was 14.7% greater than that of GRC with a glass fiber volume fraction of 5%. At the same curved section thicknesses, UHPC decorative panels exhibit cracking loads and ultimate loads that are 64.3% to 123.0% and 29.2% to 115.0% greater than GRC panels, respectively. Hence, UHPC is more suitable to produce ultra-thin decorative panels for bridges that are subjected to severe environmental action and external forces.

Performance of Fiber-Reinforced Ultra-High-Performance Concrete Incorporated with Microencapsulated Phase Change Materials

In the era of environmental concerns, many attempts were proposed to optimize energy efficiency for buildings and consequently reduce their carbon footprint. As a sustainable approach, it is a promising solution to incorporate phase change materials (PCMs) in construction materials (i.e., ultra-high-performance concrete (UHPC)) to increase its thermal storage capacity and reduce the operation energy. However, incorporating microencapsulated phase change materials (MPCMs) into cementitious materials negatively impacts the fresh and hardened properties. UHPC’s improved mechanical strength allows for the creation of slimmer and lighter structures, which may result in less demand in concrete manufacturing and fewer emissions. Hence, the properties of UHPC incorporated with MPCMs (MPCM-UHPC) need more investigations. To fill the gap in the literature about the lack of information about MPCM-UHPC performance, this paper provides a comprehensive work to study the mechanical, thermal, and impact resistance properties of (MPCM-UHPC). Proportions of 5% and 10% of MPCMs were incorporated as a replacement of sand by volume. Proportions of 0.5%, 1.0%, and 1.5% of micro steel fiber reinforcement were used as a percentage of the mixture’s total volume. The results revealed the importance of fiber reinforcement in compensating for the negative effect of MPCMs inclusion for improving the thermal properties. Increasing the amount of MPCMs enhanced the thermal performance of the produced UHPC panels through the ability to absorb and release the energy during the phase change process.

Novel constitutive model of UHPC under impact and blast loadings considering compaction of shear dilation

Based on the framework of elastic-plastic-hydrocode concrete model, this study established a novel constitutive model of ultra-high performance concrete (UHPC) for impact and blast loadings considering the compaction of shear dilation. First, the established UHPC model is introduced, including five parts: (i) the dynamic failure strength surface, which is divided into tensile, compressive, and tensile-to-compressive regions and considers the Lode-dependence and strain rate effect; (ii) equation of state (EOS) that accounts for the nonlinear volumetric compaction; (iii) damage of strength, which contains independently described tensile and compressive strength hardening or softening formulae; (iv) damage of stiffness for depicting the compaction of shear dilation; (v) plastic flow rule, where the radial return algorithm is adopted for updating stress and an independent plastic potential function is employed to model the shear dilation. Then, parameters of the established UHPC model are systematically calibrated according to tests and empirical suggestions, and are further validated by conducting single element tests under varying loading paths. Through simulating the tests of reinforced UHPC beams/columns and UHPC filled steel tubes under drop hammer impact and reinforced UHPC panels under field explosion, it demonstrates that both the damage patterns and deflection-time histories of UHPC members are precisely reproduced by the established UHPC model. Furthermore, based on comparative simulations, it shows the compaction of shear dilation is critical for predicting the structural residual deflection of reinforced UHPC members. This study discloses a possibility to establish a constitutive model of concrete suitable for impact and blast scenarios with a wide range of strain rate and hydrostatic pressure.

Numerical investigation on dynamic performance of reinforced ultra‐high ductile concrete–ultra‐high performance concrete panel under explosion

AbstractUltra‐high ductile concrete (UHDC) is known for ultra‐high tensile ductility, and ultra‐high performance concrete (UHPC) has ultra‐high compressive strength. Reinforced UHDC–UHPC panels that are made of UHDC and UHPC (i.e., hybrid panels) are expected to have excellent blast‐resistance capacity. However, only limited research is devoted to study the dynamic performance of the panels under explosion. To further investigate the dynamic performance of such kind of composite structural system, numerical simulations are carried out through LS‐DYNA. The developed material models are used for describing the mechanical properties of UHDC, UHPC and steel bars at high strain rate. Based on the corresponding field blast test results, the feasibility and accuracy of the adopted finite element models are validated. Furthermore, parameter analysis is applied for investigating the effects of scale distance, reinforcement ratio and concrete type on the dynamic performance. It is concluded that the maximum deflection of reinforced UHDC–UHPC panels reduces with increasing scale distance and reinforcement ratio. Reinforced UHDC–UHPC panels possess excellent blast‐resistance capacity in comparison with reinforced concrete panels.

Calibration of KCC model for UHPC under impact and blast loadings

Ultra-high performance concrete (UHPC) is a promising material for both civil and military protective structures against the potential impact and blast loadings. However, the existing numerical simulation studies related to the material model calibrations for precisely describing the dynamic behaviors of UHPC structural members under both impact and blast loadings are limited, and the calibration procedures are also not in consensus. This paper aims to propose a comprehensive Karagozian & Case Concrete (KCC) model parameter calibration procedure and reliable parameter generation method to well predict the dynamic behavior of UHPC members subjected to dynamic loadings. First, the failure surface, equation of state (EOS), damage evolution and strain rate effect parameters were comprehensively calibrated based on the existing experimental and analytical data of UHPC, and general guidelines on the determination of key KCC model parameters for UHPC are given. Then, the numerical simulations with both the autogenerated and the calibrated parameters were carried out to predict the dynamic response and damage evolution of UHPC members, i.e., reinforced UHPC beam and column, UHPC-FST beam, and reinforced UHPC panel, under drop hammer impact and field explosion. By comparing the test data, the validation of the proposed parameter generation approach is verified. The present work can provide helpful references for designing and evaluating the UHPC structural members under potential impact and blast loadings.

Cast-in-place and prefabricated UHPC jackets for retrofitting shear-deficient RC columns with different axial load levels

Ultra-high performance concrete (UHPC) is a new class of concrete materials that features high strength, ductility, and damage tolerance. This study experimentally evaluated three new UHPC jacketing strategies for retrofitting shear-deficient reinforced concrete (RC) columns, including cast-in-place UHPC jackets with or without steel bar mesh and prefabricated UHPC panels with steel bar mesh. The steel mesh had a high nominal yielding strength of 550 MPa. The impact of different axial load levels on the seismic performance of the retrofitted columns was also explored. Two control columns and five retrofitted columns were tested under lateral displacement reversals. Results showed that while all retrofitting methods enhanced the strength capacity of the shear-deficient column, the UHPC jacketing without steel mesh failed to improve the shear-critical behavior and drift capacity of the column. With the inclusion of high-strength steel mesh in the UHPC jacket, the control columns’ brittle shear failure was significantly improved. The proposed novel UHPC jacketing method with on-site installation of prefabricated UHPC panels showed comparable seismic retrofitting performance to the cast-in-place UHPC jacketing. In addition to the experimental study, suitable strength models, which can reasonably evaluate the strength and failure mode of the RC columns retrofitted using the proposed UHPC jackets, were suggested.

Experimental investigation of pull-out and shear behavior of lifting sockets in precast UHPC panels

The increasing demands and needs of human beings reveal the need to increase the performance of construction techniques and materials in the construction sector. Recently, the use of ultra high performance concrete (UHPC) on building facades has been increasing due to their superior mechanical and physical properties. Since UHPC products are relatively heavy, it is important to examine the lifting apparatuses for safety. In this study, pull-out and shear behavior of lifting sockets embedded in UHP precast panels produced in real geometry and dimensions were investigated. UHPCs consist of two different mixtures as A and B. Two different types of lifting sockets with the trade names RD and TF were used. Pull-out and shear test results proved that lifting sockets are sufficient as safety in both mixtures. The results obtained can contribute to the literature in this area and provide insight into the reliable lifting and handling procedure of precast facade panels.

Ultra-high performance concrete building wall panels engineered to resist windborne debris impact

Ultra-high performance concrete (UHPC) is proven to provide superior performance, in terms of both strength and durability, compared to conventional concrete. While the response characteristics of UHPC have been extensively explored under conventional loads, there is a gap in the literature concerning how UHPC can be employed as a protective system against windborne debris impact. This is of particular interest because windborne debris has been the primary source of damage to building envelopes during extreme wind events. To investigate the performance of UHPC wall panels subjected to windborne debris impact, a set of high-fidelity finite-element models were developed in the current study. Upon validating the models using the experimental test data, numerical simulations were conducted to assess the performance of a variety of UHPC wall panels under windborne debris impact. The UHPC wall panels under consideration had a wide range of thicknesses, i.e., from 76.2 mm to 203.2 mm, and were modeled both without and with embedded steel rebars. As for impact scenarios, both lumber and pipe projectiles were considered with a range of velocities, spanning from 10.0 m/s to 70.0 m/s. This holistic matrix of simulations helped characterize various response measures, including the type and extent of damage to the UHPC wall panels individually and in comparison to their normal-strength concrete (NSC) counterparts. The investigations were then extended to evaluate the UHPC and NSC wall panels under a set of pass/fail criteria prescribed by the relevant codes and standards for basic and enhanced protection wall systems. The wealth of data generated through this study was finally employed to develop a set of closed-form equations for predicting the mean impact force that the UHPC wall panels are expected to experience, given the mass and velocity of the debris object. This is expected to facilitate the design of this emerging category of wall panels, especially in the regions that witness a high risk of windborne debris impact.

Experimental investigation on shear behavior of high-strength friction-grip bolt shear connectors in steel-precast UHPC composite structures subjected to static loading

Steel-precast ultra-high-performance concrete (UHPC) composite structures with high-strength friction-grip bolt (HSFGB) shear connectors offer several advantages, such as shortening the onsite construction time, making it possible to replace deteriorated components rapidly, and improving structural durability. However, there is limited investigation on steel-UHPC composite structures with HSFGB shear connectors. Addressing this issue, this study presents a systematic experimental study on shear behaviors of HSFGB shear connectors in steel-precast UHPC composite structures by conducting 18 push-out tests. The major considered parameters are the slab concrete type, bolt grade, bolt diameter, slab thickness, pretension force, and arrangement of the shear connectors. Test results demonstrated that the shear capacity and friction resistance can be enhanced with increasing in the bolt grade and bolt diameter. In addition, there was no reduction in the shear strength of each bolt as the shear connectors were arranged in a group, and even with the spacing decreased to 80 mm. Moreover, it was recommended that the HSFGB and UHPC can be optimally utilized with a 75-mm-thickness prefabricated UHPC panels. Finally, more accurate formulas were developed for predicting the shear capacity and the load-slip relationship of HSFGB shear connectors in steel-precast UHPC composite structures, which provided feasible design approaches for engineers.

Seismic performance of full-scale UHPC-jacket-strengthened RC columns under high axial loads

Ultra-high-performance concrete (UHPC) is a class of concrete materials that have high strength and ductility capacities. This study developed two UHPC jacketing methods to improve the seismic performance of shear-deficient RC columns in mid- to high-rise buildings without enlarging the cross-section of the columns. In the first method, the original concrete cover was replaced with a cast-in-place UHPC jacket that was reinforced by steel bar mesh. To simplify the on-site construction process, the second method utilized prefabricated UHPC panels incorporating steel bar mesh. The performance of the proposed strengthening methods was evaluated using cyclic loading tests on three full-scale RC columns with a high axial load demand. The test results showed that the developed UHPC jacketing methods improved the lateral strength and drift capacity of the shear-deficient column by at least 40% and 30%, respectively. They also reduced the residual displacement of the column by 65%-80%. Compared to the cast-in-place jacketing, the discontinuity in the prefabricated UHPC jackets inhibited full composite action of the jacketing, thus reducing the retrofitting efficiency. In addition to the experimental study, evaluation methods were proposed to evaluate the strength and behavior of the retrofitted columns.

Development of Thermoplastic Composite Reinforced Ultra-High-Performance Concrete Panels for Impact Resistance.

In order to improve flexural and impact performance, thin panels of steel fiber-reinforced ultra-high performance concrete (UHPC) were further reinforced with external layers of continuous fiber-reinforced thermoplastic (CFRTP) composites. CFRTP sheets were bonded to 305 × 305 × 12 mm UHPC panels using two different techniques. First, unidirectional E-glass fiber-reinforced tapes of polyethylene terephthalate glycol-modified (PETG) were arranged in layers and fused to the UHPC panels through thermoforming. Second, E-glass fiber woven fabrics were placed on the panel faces and bonded by vacuum infusion with a methyl methacrylate (MAA) polymer. Specimens were cut into four 150 mm square panels for quasi-static and low-velocity impact testing in which loads were applied at the panel centers. Under quasi-static loading, both types of thermoplastic composite reinforcements led to a 150–180% increase in both peak load capacity and toughness. Impact performance was measured in terms of both residual deformation and change in specimen compliance, and CFRTP additions were reduced both by 80% to 95%, indicating an increase in damage resistance. While both reinforcement fabrication techniques provided added performance, the thermoforming method was preferable due to its simplicity and fewer specialized tool requirements.

Experimental and numerical studies on dynamic behavior of reinforced UHPC panel under medium-range explosions

This paper aims to study the blast-resistant behavior of one-way simply-supported reinforced ultra-high performance concrete (UHPC) panels through field tests and numerical simulations. Firstly, by designing a box-like blast loading apparatus, both three reinforced UHPC panels and three reinforced normal strength concrete (NSC) control panels were fabricated and tested under medium-range explosions from end-detonated cylindrical charges with different scaled distances (0.5~1.0 m/kg1/3). The valuable data including the explosion-induced incident and reflected overpressure-time histories, deflection- and acceleration-time histories, as well as the post-blast damage of panels were obtained and assessed experimentally. The superiority of UHPC as a blast-resistant material was proved quantitatively by comparison with NSC. Then, the corresponding 3D finite element (FE) model was established by adopting the program LS-DYNA, both the blast loadings induced by the medium-range explosions and the constitutive model parameters of UHPC were mainly concerned. The applicability of the CONWEP method in predicting the blast overpressures was verified, but the prediction precision declines with the decrease of scaled distance since the influences of charge shape and detonation point enhanced accordingly. Moreover, based on the systematic static and dynamic mechanical tests data, the parameters of Karagozian & Case concrete (KCC) model describing the strength surface, equation of state (EOS), damage evolution, and strain rate effect of UHPC were calibrated. Finally, the present FE model, numerical algorithm and the calibrated model parameters were fully verified by comparing the numerical results with the test data, which could provide reference for the evaluation and design of UHPC structures under blast loadings.

Structural behavior of ultra‐high performance (fiber‐reinforced) concrete compression struts subjected to transverse tension and cracking

AbstractStruts and stress fields with transverse tension and cracks parallel to the direction of compression lead to a reduction of compressive strength in reinforced concrete structures. Biaxial tests on fine‐grained ultra‐high performance concrete (UHPC) and ultra‐high performance fiber‐reinforced concrete (UHPFRC) panels additionally reinforced with steel bars show that this reduction in compressive strength is already pronounced even with small transverse tensile strain and crack widths, but stabilizes for larger tensile strain. A reduction could also be observed with regard to compressive stiffness of the struts, which behave quasi‐linear under compressive loading. Basically, the UHPFRC panels show less reduction in strength and stiffness than the UHPC panels. Compared with the results obtained from the tests on normal‐strength reinforced concrete panels and fiber‐reinforced concrete panels, the reduction of compressive strength is only little larger for UHP(FR)C. Based on the test results, a proposal for modeling the stress–strain behavior of UHP(FR)C in compression–tension stress state is provided.

Fully-scale test and analysis of fully dry-connected prefabricated steel-UHPC composite beam under hogging moments

A fully dry-connected prefabricated composite beam is proposed that satisfies the requirements for accelerated bridge construction. The fundamental prefabricated structural elements are the ultra-high-performance concrete (UHPC) panels and the main steel beams, which are connected by bolting and welding. Onsite wet construction is completely removed. To investigate the crack resistance and bending behavior of the novel fully dry-connected composite beam, two full-scale specimens were tested. The crack development, slippage between the UHPC panel and the steel beam, load–deflection response, and the strain distribution were monitored. An adequate bolting torque applied to the high-strength bolts connecting the concrete panels and the steel beam is important in guaranteeing the composite action of the composite beam. Based on tests, a numerical model was configured in ABAQUS that delivered good agreement with test results. The division of the UHPC panels and the layout of the bolts were investigated through parametric analysis. The division did not evidently change the load–deflection response, but fewer panels may result in better crack resistance. With the larger spacing between the bolts, the overall stiffness and crack resistance had evident deterioration.

Finite element study of headed shear studs embedded in ultra-high performance concrete

A novel bridge repair method has been developed to strengthen steel bridge girders with section loss due to end corrosion. The repair comprises of welding headed shear studs to the non-corroded portion of the web plate and encasing them in ultra-high performance concrete (UHPC) to create an alternate bearing load path. The interaction between the headed studs and the UHPC panels is crucial in the force transfer. Therefore, a careful study is needed through high-fidelity finite element analysis to complement the experimental results. This paper presents the development of a model in Abaqus finite element software that enables capturing the behavior of studs embedded in UHPC. The model was validated using a series of experimental results from push-out tests with headed shear studs welded onto a thin web plate. Experimental results from push-out tests performed on stud diameters of 12, 16 and 19 mm and two levels of eccentric loadings were used to calibrate the modeling methodology. The model explicitly considers effects of material damage, contact between the studs and UHPC, and the precise geometry of the weld collar of studs. After validation, design parameters such as interaction of in-plane torsion and direct shear, and limits for web thickness-to-stud diameter ratio were studied to compliment the experimental data. The results are expected to inform engineers about the design of this novel repair method. In addition, this paper may enable future finite element studies on the performance of studs in UHPC.

Flexural behaviors of fiber-reinforced polymer fabric reinforced ultra-high-performance concrete panels

The use of fiber-reinforced polymer (FRP) fabrics as reinforcement in concrete offers several advantages, such as high tensile strength, corrosion resistance, and light weight. This paper presents experimental and mechanical studies on the flexural behaviors of FRP fabric reinforced ultra-high-performance concrete (UHPC) panels. Glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) fabrics were investigated. Mechanical properties of GFRP and CFRP fabrics, high-strength mortar, and UHPC containing micro steel fibers were experimentally evaluated. The interfacial properties between the FRP fabric and cementitious matrix were characterized using push-pull tests. The flexural performance of panels with different reinforcement configurations was experimentally evaluated. The use of GFRP or CFRP fabric enhanced the flexural properties of UHPC panels, but did not lead to any increase in the flexural strength for the panels made with high-strength mortar. A mechanical analysis is performed to understand and predict the flexural behavior of the FRP fabric reinforced UHPC panels. The proposed fabric reinforced UHPC panel is demonstrated to be promising for the development of lightweight, high-performance permanent formwork system. Such formwork can be potentially used in accelerated construction of critical infrastructure with enhanced crack resistance and extended service life.

Numerical and theoretical modelling of low velocity impact on UHPC panels

The paper presents the studies carried out on low velocity impact of Ultra high performance concrete (UHPC) panels of size 350X350X10 mm3 and 350X350X15 mm3. The panels are cast with 2 and 2.5% micro steel fibre and compared with UHPC without fiber. The panels are subjected to low velocity impact, by a drop-weight hemispherical impactor, at three different energy levels of 10, 15 and 20 J. The impact force obtained from the experiments are compared with numerically obtained results using finite element method, theoretically by energy balance approach and empirically by nonlinear multigenetic programming. The predictions by these models are found to be in good coherence with the experimental results.

Strength and Behavior of Bolted Ultra-High Performance Concrete Panel Joint with Geometric Parameter

One of the most reasonable ways to connect thin ultra-high performance concrete (UHPC) facades to building structures is bolted joints. To design the joints for the facades economically and safely, a clear investigation of the structural behavior is needed. In this study, the joint strength, failure modes and strain concentration phenomena of the bolted UHPC panels are investigated by direct tensile test. The main experimental variables are the geometric parameters, which are the width of the specimen, its thickness, and the distance from the center of the hole to the edge. Experimental results show that ductility of the joint depends on the failure mode. In addition, it is shown that the increase in the material cost of the panel, such as size and thickness, does not necessarily lead to an increase in the joint strength.

Biaxial tension–compression strength behaviour of UHPFRC in-plane elements

Ultra-high-performance fibre-reinforced concrete (UHPFRC) panel-shaped elements subjected to compression–tension loading are tested to investigate their in-plane structural behaviour under biaxial stress. Tension-stiffening and compression-softening ultra-high-performance concrete (UHPC) behaviours are analysed with and without fibre, based on the test results from 30 specimens subjected to various transverse tensile strains. The tension-stiffening bond factor of UHPC with fibre is found to be about twice that of UHPC without fibre. The compressive strength of a UHPC panel subjected to transverse tensile loading is decreased by 50 % without fibre and 30 % when the fibre is in the elastic range of the reinforcing bars. Sequential loading of biaxial stress onto UHPC is appropriate for determining the limited lower boundary for the reduction of compressive strength that characterises the transverse tensile effects of fibre reinforcement. In addition to the biaxial behaviour of the UHPC panel, the failure envelope of UHPC with and without fibre is suggested schematically by considering the existing references, and a failure envelope is proposed. The entire analytical investigation and proposed failure criteria will allow for the efficient optimisation of the geometries of UHPFRC structures.