Reinforcement Pullout Research Articles

Flexure Performance of Textile-Reinforced Cementitious Composites with Novel Inclined Reinforcements.

Textile-reinforced cementitious composites have great potential to offer novel design opportunities for thin-section structures thanks to their superior material capabilities. In this work, new cementitious composites with novel reinforcement configurations are developed, which have superior mechanical properties. The cementitious composites contain inclined through-the-thickness reinforcements, and their enhanced performance on thin-section material hardening under flexural loading is demonstrated. Furthermore, a new practical FE modeling approach is proposed that involves the combined use of multiple cohesive regions and 1D reinforcement elements that pass through these regions with a bilinear material law. This approach provides a new computationally efficient modelling framework whereby reinforcement pull-out during hardening is readily captured without resorting to computationally demanding interface laws between the reinforcement and the cementititous matrix. The model can model enhanced hardening of new configurations and provides comparable results with the experimental findings. The model can be used in the modelling and design of novel cementitious composites with engineered reinforcement configurations. Overall, this study aims to open up new avenues for the smart material design of cementitious composites with novel structural reinforcements.

Microstructure, phase evolution and mechanical properties of nickel-silicon carbide reinforced Ti6Al4V alloy processed by pulsed electric current sintering

In this work, fully densified Ni–SiC reinforced Ti6Al4V matrix composites were consolidated by pulsed electric current sintering (PECS) technique. The microstructural evolution and mechanical properties of the developed composites with varying SiC contents were investigated. The microstructural study revealed in-situ precipitation of TiC, Ti5Si3 and Ti3SiC2 strengthening phases within the composites. The α colony size in the composites was notably reduced compared to the fabricated SiC-deficient samples due to the addition of SiC additive into the Ti6Al4V alloy matrix. The in-situ precipitated phases enhanced the mechanical properties of the composites. Composite reinforced with 10 wt% SiC (TNi10SiC) displayed the highest hardness value of 609.8 ± 50.9 HV0.5 among the sintered samples, translating to an increment of about 88 % compared to the unreinforced sample T. Among the sintered samples, the highest flexural strength of 2094.32 ± 97.67 MPa was obtained for the TNi5SiC composite, after which the flexural strength deteriorates with increasing SiC content as witnessed in TNi10SiC composite with the least flexural strength of 863.67 ± 71.57 MPa due to agglomeration of the reinforcement phases within the composite. Samples reinforced with 0 wt% SiC experienced a ductile fracture, and the composites containing 2.5 wt% - 5 wt% SiC content witnessed intergranular and interlamellar fractures. However, at higher SiC content, reinforcement pull-out and debonding of the agglomerated reinforcement phases predominates, and composites fail by brittle fracture.

Effect of geosynthetic reinforcement pull-out on the surface characteristics of facing blocks

The friction coefficient between the facing blocks and the geosynthetic reinforcement is one of the parameters in MSE design. To obtain this parameter, specific tests are foreseen in the standards. However the pull-out process of the geosynthetic reinforcement has an effect on the facing block surfaces. In this study the roughness of the precast concrete block elements was determined before and after the pull-out test to see the effect of the pull-out process, since the frictional behavior is a function of surface roughness. For this purpose 3D scanning was performed on block surfaces and a special macro program was coded to get a surface reading for every 0.5 mm. Since the concrete blocks used in the experiments are produced using the dry-cast method, the surfaces are not smooth and many small sized aggregate particles stick out of the average surface. As a result these extrusions break during the pull-out test. Hence, in conclusion, the roughness values have always increased after pull-out tests for both geotextile and geogrid reinforcement.

Evaluation of Construction and Demolition Waste and Other Alternative Fills for Strip-Reinforced Soil Walls

This article assesses the pullout performance of ribbed metallic strips embedded in fill soils that do not conform to conventional design criteria for mechanically stabilized earth (MSE) walls. These alternative fill soils include gravelly and sandy recycled aggregates from construction and demolition waste, artificial and natural sands, and fine-grained lateritic soil. The research included soil characterization tests and large-scale pullout tests, conducted as part of this study. The results showed that the reinforcement pullout behavior was similar for recycled, artificial, and natural sands, indicating that soil particle size played a crucial role in mobilizing the interface pullout resistance. However, in the case of recycled sand, stress concentration at the reinforcement level led to particle crushing during pullout conditions, causing this material to exhibit less efficient performance compared to other sands. The fine-grained lateritic soil demonstrated inferior behavior compared to sandy soils, despite the interparticle bonding provided by the sesquioxide coating characteristic of intensely weathered tropical soils. Finally, an analytical prediction tool based on experimental results was developed, providing an alternative method to make conjectures about the performance of different soils during the pre-design stages, particularly based on particle size attributes.

A Beam Test Study on the Bond Performance between Epoxy-Coated Reinforcement and Geopolymer Concrete

An epoxy-coated reinforcement geopolymer concrete structure with good durability and energy-saving properties can be formed by combining epoxy-coated reinforcement and geopolymer concrete. The bond strength is the precondition for the two to work together. In this paper, 13 beam specimens (11 epoxy-coated reinforcements and 2 ordinary deformed reinforcements) were designed to investigate the influence of the strength of geopolymer concrete, diameter of the reinforcement, bonding length and type of reinforcement on the bond performance between reinforcement and geopolymer concrete. The test results show that the ultimate bond strength of the epoxy-coated reinforcement (ECR) and geopolymer concrete decreased by 7.32% and 14.76%, respectively, when the rebar diameter increased from 14 mm to 16 mm and then to 20 mm. The ultimate bond strength between ordinary threaded reinforcement and geopolymer concrete was slightly higher than that between ECR and geopolymer concrete. When the length of the bond section is small or the concrete strength is low, the beam specimen is prone to the failure of the reinforcement pullout. The specimen with the larger reinforcement diameter is prone to concrete splitting failure. However, the specimens with medium bond length and small reinforcement diameter suffered from pull-out failure after concrete splitting. In this paper, based on the test data, the bond-slip constitutive model of ECR and geopolymer concrete was established, and the bond-slip curve obtained by this model was in good agreement with the measured curve. In addition, the calculation formula of the ultimate bond strength between ECR and geopolymer concrete was also proposed in this paper, which can provide theoretical reference for the engineering application of geopolymer concrete.

Mathematical model for the reinforced concrete with nonlinearity behaviour of bond

The article developed a mathematical model describing the deformation of reinforced concrete, taking into account its adhesion to reinforcement. The model consists of three layers: concrete, contact layer, reinforcement. The contact layer surrounding the reinforcement takes into account the complex deformation of the concrete when interacting with the profiled reinforcement. Arguments are presented for criteria that determine the transition of concrete, reinforcement and contact layer to limit states. A diagram of testing of reinforced concrete specimen has been proposed and a procedure for processing experimental data, which allow you to determine the bond parameters. Equations that bind the mechanical characteristics of the contact layer with two the bond parameters of concrete with reinforcement are obtained. The developed model was used in the numerical solution of the problem of static pull-out of reinforcement from concrete. The calculation of the finite element method showed a good correspondence with the experimental data, including during plastic deformation of the reinforcement. This shows the correctness of theoretical provisions and developed mathematical algorithms used to model the deformation of reinforced concrete.

Investigation of soil deformation characteristics during pullout of a ribbed reinforcement using X-ray micro CT

Steel-strip reinforced earth walls stabilize through the pullout resistance of the reinforcements. Soil dilation during the pullout of ribbed reinforcements may contribute to the evolution of pullout resistance; however, few studies have clarified this mechanism by investigating how soils behave with increasing pullout displacement. The ribs of the reinforcements enhance the pullout resistance, although the influence of the rib dimensions on the evolution of pullout resistance with increasing pullout displacement has not been sufficiently revealed. In the present study, a triaxial pullout apparatus is developed and pullout tests are conducted using ribbed reinforcements with different rib-inclination angles under isotropic stress. The displacement and strain fields in the soils during the pullout of the reinforcements are investigated by X-ray micro CT and a digital image correlation technique. It is found that larger rib-inclination angles provide higher pullout resistance at an early stage of the pullout because of the higher bearing resistance related to the more significant soil densification above the ribs. With increasing pullout displacement, the reinforcements with different rib-inclination angles come to behave as almost one in the same since a rigid soil wedge related to the passive soil failure is generated above the ribs. This tendency results in similar soil deformation characteristics and pullout resistance levels for every reinforcement beyond the soil failure state, although the rib-inclination angles are different.

The Determination of Pullout Parameters for Sand with a Geogrid

The concept of designing mechanically stabilized earth (MSE) walls is divided into internal and external stability review methods, and one of the design factors required in internal stability analysis is the frictional characteristics between soil and geogrids for civil engineering applications. Typical methods for evaluating the frictional characteristics between soil and geogrids include the direct shear test and pullout test. It is desirable to apply the pullout test to geogrid reinforcements for pulling out geogrids embedded in soil, to measure both the surface-frictional force and passive resistance at the same time. Pullout parameters can be significantly affected by confining the stress and tensile strength of reinforcements. In general, the pullout parameters tend to be overestimated for low confining stresses in the pullout test, and underestimated for high confining stresses. Therefore, to address these issues, this study aims to evaluate the influence of the confining stress and the tensile strength of a geogrid reinforcement in the pullout test, and to propose a reasonable method for obtaining practical pullout parameters. Based on the pullout tests, the maximum pullout force depending on the tensile strength of the geogrid reinforcement was measured for one-third of the reinforcement tensile strength, and it was ruptured when pullout force greater than the maximum pullout force was exerted. Furthermore, it was observed that, in the reinforcement pullout test, pullout force was measured in the whole area of the reinforcement at a confining stress smaller than one-half of the tensile strength of the grid. As a result, the effective confining stress method considering only the confining stress at which the reinforcement is fully pulled out to develop the pullout characteristics can be a practical method for obtaining pullout parameters without regard to the reinforcement tensile strength.

Numerical investigation of reinforcement pullout resistance effects on behavior of geosynthetic-reinforced soil (GRS) piers

In this study, three-dimensional numerical analyses were carried out to investigate the effects of reinforcement pullout resistance including facing connection strength on the behavior of geosynthetic-reinforced soil (GRS) piers under a service load condition. Three different piers were investigated in this study, which simulated different levels of reinforcement pullout resistance. Each pier had two cases with different reinforcement stiffness J and reinforcement spacing Sv but the same ratio of J/Sv. Numerical results showed that reinforcement pullout resistance had a significant effect on the behavior of GRS piers. When the pullout mode prevailed, the case with small Sv and low J had smaller lateral facing displacements and vertical strain of the pier under the same applied pressure as compared to the case with large Sv and high J when the ratio of J/Sv was kept constant. When the pullout mode did not prevail, two cases with the same ratio of J/Sv showed similar performance despite different combinations of Sv and J were used. To more effectively mobilize reinforcement strength and improve GRS pier performance, small reinforcement spacing or high-strength facing connection should be considered when sufficient reinforcement pullout resistance cannot be guaranteed otherwise.

Enhanced strength and toughness of silicon carbide ceramics by graphene platelet-derived laminated reinforcement

To exploit the application of silicon carbide in complex-shaped and large-scale ceramic components, graphene platelet (GPL) was chosen as the reinforcement to develop silicon carbide ceramics by reactive sintering at 1700 °C. The effects of GPL content on the microstructure, phase composition and mechanical behaviors of reaction bonded silicon carbide ceramics were studied. Bulk density of the composites decreased with the increase of GPL contents because of the agglomeration of GPL. During reactive sintering, the GPL reacted with molten silicon to form laminated reinforcement, which brought about some toughening mechanisms including crack bridging, reinforcement pullout and reinforcement delamination. At the GPL content of 1.0 wt%, the flexural strength and fracture toughness of the composites reached the peak values of 436 MPa and 5.7 MPa m 1/2 , respectively. Thus, this work provides a path to prepare high-performance silicon carbide ceramics by reactive sintering and graphene platelet. • Graphene platelet was chosen in the reactive sintering of SiC ceramics. • Graphene reacted with molten silicon to produced laminated reinforcement. • Step-by-step fracture by graphene improved fracture toughness of SiC ceramics.

Pullout Behavior of Different Geosynthetics—Influence of Soil Density and Moisture Content

Geosynthetics have increasingly been used as reinforcement in permanent earth structures, such as road and railway embankments, steep slopes, retaining walls and bridge abutments. The understanding of soil-geosynthetic interaction is of primary importance for the safe design of geosynthetic-reinforced soil structures, such as those included in transportation infrastructure projects. In this study, the pullout behaviour of three different geosynthetics (geogrid, geocomposite reinforcement and geotextile) embedded in a locally available granite residual soil is assessed through a series of large-scale pullout tests involving different soil moisture and density conditions. Test results show that soil density is a key factor that affects the reinforcement pullout resistance and the failure mode at the interface, regardless of geosynthetic type or soil moisture content. The soil moisture condition may considerably influence the pullout response of the geosynthetics, particularly when the soil is in medium dense state. The geogrid exhibited higher peak pullout resistance than the remaining geosynthetics, which is associated with the significant contribution of the passive resistance mobilised against the geogrid transverse members to the overall pullout capacity of the reinforcement.

Pullout response of strengthened geosynthetic interacting with fine sand

This research describes results of pullout tests performed on two new systems to reinforce the fine-grained silica sand classified as SP in the Unified Soil Classification System. The first system is composed of geogrid on which transverse steel bars are tied to make a 3-D strengthened geogrid, here called Geogrid-Bar (GGB). In the second system, plastic push pins are attached to geocomposite and a strengthened geocomposite is made, here called Geocomposite-Pin (GCP). Eighteen pullout tests were conducted with the soil relative density of 80% revealed that the use of GGB and GCP systems causes the reinforcement pullout resistance to increase by about 37% and 46%, compared with normal planar geogrid and geocomposite, respectively.

Corrosion Effect on Reinforcement Pull-Out Bond Strength Characteristics of Corroded and Coated Members in Concrete

Corrosion Effect on Reinforcement Pull-Out Bond Strength Characteristics of Corroded and Coated Members in Concrete

PHAETHON: Software for Analysis of Shear-Critical Reinforced Concrete Columns

Earthquake collapse of substandard reinforced concrete (RC) buildings, designed and constructed before the development of modern seismic design Codes, has triggered intense efforts by the scientific community for accurate assessment of this building stock. Most of the proposed procedures for the prediction of building strength and deformation indices were validated by assembling databases of RC column specimens tested under axial load and reversed cyclic lateral drift histories. Usually a column structural behavior is assessed by considering all involving mechanisms of behavior, namely flexure with or without the presence of axial load, shear and anchorage. In the present paper a force-based fiber beam/column element was developed accounting for shear and tension stiffening effects in order to provide an analytical test-bed for simulation of experimental cases such as the lightly reinforced columns forced to collapse. Their peculiar characteristics are the outcome of the shear – flexure interaction mechanism modeled here based on the Modified Compression Field Theory (MCFT) and the significant contribution of the tensile reinforcement pullout from its anchorage to the total column’s lateral drift. These features are embedded in this first-proposed stand-alone Windows program named “Phaethon” -with user’s interface written in C++ programming language code- aiming to facilitate engineers in executing analyses both for rectangular and circular substandard RC columns.

Transverse Pullout Response of Smooth-Metal-Strip Reinforcements Embedded in Sand

The pullout resistance of reinforcement is an important parameter in the design of reinforced earth structures. Existing design procedures consider the pullout resistance of reinforcement from axial pull. However, the kinematics of failure clearly establish that the reinforcement is pulled obliquely along the slip surface. The response of reinforcement to oblique pull is equivalent to an application of axial and transverse components of oblique pull. In this study, details are provided of a novel experimental test setup used to examine the response of smooth-metal-strip reinforcement subjected to transverse pull at one end. A large-size test chamber of dimensions (length, width, and depth) with an arrangement to conduct transverse pullout of reinforcement is developed. The pullout response of smooth-metal-strip reinforcements to transverse pull is obtained for three different normal stresses of 17, 52, and 87 kPa. Transverse pullout resistance factors of smooth-metal-strip reinforcements corresponding to different transverse displacements of the reinforcement are proposed and found to range from 0.6 to 2.9, corresponding to transverse displacements of 20–30 mm.

Frictional Resistance of Closely Spaced Steel Reinforcement Strips Used in MSE Walls

AbstractFrictional resistance between soil and steel reinforcements develops as a result of relative displacement at the soil-reinforcement interface and is typically characterized using interface shear or reinforcement pullout tests. The soil-reinforcement interaction between uniformly-graded soils and metal reinforcements has been well-characterized. However, the interface response of well-graded gravelly soils and ribbed steel strips is primarily based on lower-bound estimates of pullout resistance using databases of single isolated reinforcement pullout tests. Increases in horizontal stresses that develop in tall mechanically stabilized earth (MSE) walls are often accounted for in design by reducing the reinforcement spacing; however, the effect of possible frictional interference between closely spaced inextensible reinforcements has not been explored. Two reinforcement pullout apparatuses have been developed to study the soil-reinforcement interaction and effect of reinforcement proximity in a well-...

Size and shape effect in the pull-out of FRP reinforcement from concrete

Scaling phenomena in the progressive debonding between fiber reinforced polymer (FRP) strips and concrete substrate are examined on the basis of single lap shear tests, considering different bond lengths and widths. To capture a stable post-peak response of the FRP-concrete joint, the slip between the concrete support and the reinforcement strip, measured at the reinforcement end using a clip gage, was selected as feedback control signal during the tests. This allowed a quasi-static stable fracture propagation in the descending branch until complete load relaxation and debonding. Experimental tests were simulated by means of 2D and 3D finite element analyses adopting two different approaches. At first, a numerical model based on linear elastic materials with all non-linearities concentrated at the interface was assumed. It clearly revealed the inability to recognize all the aspects of the debonding process. Then, a different numerical model, based on a non-linear constitutive model for concrete and perfect adhesion between all the materials, was adopted.

Numerical modeling of reinforcement pull-out and cover splitting in fire-exposed beam-end specimens

The behavior of bond between reinforcement and concrete at high temperature is numerically investigated considering both pure bond failure and splitting of concrete. To this end, a transient three-dimensional thermo-mechanical model utilizing temperature dependent microplane model as the constitutive law for concrete is employed. Two heating types are considered to simulate the exposure conditions in a slab and in a beam, namely one-sided and three-sided heating, according to the ISO 834 standard fire curve. The results clearly show that for realistic concrete cover, confinement and fire exposure, the concrete splitting almost always governs the bond behavior. The common pull-out mechanism works only if the concrete cover is very high (largely exceeds the values used in the practice) and/or the temperature gradients are rather low. The results further indicate that the beam-end test specimen offers a suitable setup to investigate the pull-out behavior of reinforcement under high temperatures accounting for different influencing factors.

Ultrasonic guided waves for monitoring the setting process of concretes with varying workabilities

Quality of mature concrete can be judged a great deal by monitoring its properties at the time of pouring. However, modern day concrete varies greatly in composition and rheology that result in considerable variation in setting behaviour. This paper demonstrates an ultrasonic, in-situ guided wave monitoring technique for studying the setting characteristics of freshly poured concrete with varying workabilities. The solidification and curing of freshly poured concrete is monitored through the propagation of ultrasonic waves in embedded steel reinforcing bars. As concrete solidifies and cures, more wave energy escapes into the surrounding solidifying concrete resulting in signal attenuation. Two types of concrete specimens are prepared – one with moderate slump (80mm) named as Conventional Concrete (CC) and other with high slump (675mm) referred as Self-Compacting Concrete (SCC) and are monitored with carefully selected ultrasonic signal patterns. Destructive tests such as compressive strength and reinforcement pullout strength are also performed at different stages of setting of the two concrete types. Relationships for estimating the strengths from ultrasonic tests are developed. The ultrasonic guided waves are very promising for discerning the early age characteristics of concrete with varying workabilities.

Pull-out of textile reinforcement in concrete

Textile Reinforced Concrete (TRC) has emerged as a promising novel alternative offering corrosion resistance and both thinner and light-weight structures. Although TRC has been extensively researched, the formalization of experimental methods and design standards is still in progress. The aim of this work was to extract local-bond behaviour from pull-out tests of basalt and carbon TRC and utilize these in both simple (1D) and advanced models (3D) to yield the global structural behaviour. The simulation results from the 1D and 3D models are able to simulate the complex behaviour of TRC with a reasonable level of correlation.