Partial Interaction Models Research Articles

Tension stiffening and cracking behaviors in glass fiber reinforced polymer bar enhanced precast recycled aggregate concrete specimen

Glass fiber reinforced polymer (GFRP) bar-enhanced precast recycled aggregate concrete (PRAC) elements combine PRAC’s environmental benefits with GFRP’s corrosion resistance, making them ideal for coastal urban infrastructure. However, in-depth research on the tensile stiffness and cracking behaviors of this composite is lacking. The significant mechanical differences between GFRP bars (low modulus, high strength) and PRAC, as compared to traditional materials, raise safety concerns for widespread use. This study investigates the short-term load capacity, deformation and cracking characteristics of GFRP bar-reinforced PRAC tensile specimens through tests and analyses. The tests examine how variables like water-to-binder ratio, coarse aggregate type, recycled aggregate (RA) content and mixing methods affect the specimens' mechanical responses. Theoretical analyses, using existing equations and a partial interaction model, clarify stress-strain relationships and crack propagation under applied loads, revealing: (a) As RA content increases, PRAC shows a moderate decrease in workability and mechanical performance. The strength variability in PRAC generally falls between that of natural aggregate concrete (NAC) and conventional recycled aggregate concrete (CRAC) using RAs from construction and demolition waste, being closer to NAC. Additionally, the strength conversion relation seen in NAC applies similarly to PRAC. (b) During tension at both ends of the specimen, PRAC's resistance decreases by 24.3 % compared to NAC but is still 20.3 % higher than CRAC. (c) The number of cracks in the PRAC specimen decreases with higher RA content and basalt fibers, while the ratio of stabilized load to cracking load increases. (d) The CEB-FIP standard offers more accurate predictions of the specimen’s composite stress-strain relation, while the Chinese code excels in predicting crack width. The partial interaction model effectively predicts the specimen’s load, deformation and crack characteristics by accounting for the behaviors and bonding of both PRAC and GFRP bars.

Theoretical and numerical bonding capacity model of FRP-to-concrete joints with mechanical fastening

The coordination of multiple anchors can improve the interfacial bonding capacity of hybird bonded fibre reinforced plastic (HB-FRP) joints to concrete. But the discontinuity of the bond stress at the anchor makes it difficult to predict the bonding capacity. To solve this problem, in this study, the bonding behaviour for one anchor is derived based on the bilinear model and the threefold bond-slip model of the EB-FRP (external bonding FRP) joint and the HB-FRP joint, respectively, by using the same slip at the boundary of adjacent bonding zones. The bonding capacity of HB-FRP joints with multiple anchors is predicted. A numerical method based on the partial interaction model is proposed to predict the development of interfacial stress. The theoretical and numerical methods are mutually verified with experimental results. Finally, the influence of the bond-slip model on the bonding characteristics of the HB-FRP joints is analyzed.

Analytical approach to quantify the pull-out behaviour of hooked end steel fibres

ABSTRACT An analytical modelling approach is developed in this article to simulate the pull-out behaviour of a single straight/hooked end fibre that is embedded in concrete matrix. The partial-interaction model is used to simulate the interfacial bond between the fibre and matrix along the entire fibre length throughout all stages of loading where additional axial and frictional forces due to straightening a hook is incorporated by simulating it as plastic hinges at the apex of bends. The analytical model is presented in a concise matrix form that helps to minimise the number of solution steps for the involved individual cases and provides a monolithic simplified implementation. A significant advantage of the approach is that it does not require fitting of a smoothing polynomial to show the full-range of fibre load-slip behaviour as it simulates the forces for straightening the fibre as it pulls through a bend and directly couples this to the interfacial bond forces.

Bond-slip behavior of steel reinforced UHPC under flexure: Experiment and prediction

Ultra-high performance concrete (UHPC) is an advanced class of concrete materials that show superior mechanical and durability performance. While several studies have investigated the bond-slip behavior of steel reinforced UHPC using pullout tests, very limited information is available on the bond-slip behavior of reinforced UHPC from beam-type tests, which produce flexural stress states commonly seen in structural members. This study experimentally examines the local bond-slip behavior of reinforced UHPC using beam-end tests. The test variables include UHPC material designs (one low-cement, green UHPC mix and one typical UHPC mix), fiber volumes (0%, 0.5%, and 1.0%), cover thickness (16 mm–51 mm), steel bar sizes (16 mm–32 mm), and test ages (3 days and 50 days). A total of thirty-two tests are conducted. While the non-fiber UHPC specimens fail in a brittle manner due to splitting failure, all fiber-reinforced UHPC specimens exhibit confined splitting failure and ductile bond-slip responses. The peak bond strength is found to exhibit a linear relationship with the cover-thickness-to-bar-diameter ratio and the square root of UHPC compressive strength. Furthermore, a local bond-slip model is developed, which includes a new bond-strength prediction method that predicts the experimental results with a mean absolute error of 7.6%. Finally, this local bond-slip model is combined with a partial interaction model to explore the global bond stress variations under different embedment lengths and flexural states. Equations are proposed to predict the development length that can lead to reinforcement yielding with minimized bonded length or minimized global slip.

Experimental and Finite Element (FE) Studies on the Behaviour of Horizontally Curved Composite Bridges Deck

This paper aims to study the behaviour of horizontally curved composite steel-concrete bridges deck slab and beams under static load, using experimental tests and nonlinear finite element analysis. Two different specimens were examined in the structure laboratory, one of them was horizontally curved composite deck slab and steel girders with full interaction between the concrete deck and the steel girders, while the other with partial interaction. Each specimen has three curved I-girders acted parallel connected with X shape cross frames. Linear Variable Differential Transducers (LVDT) and strain gauges were used at critical points to measure deflections and strain respectively. Three dimensional finite element (FE) models with 137119 elements were built and analysed using ANSYS software version 14. Models dimensions were 1/10 in both length and radius of curvature of the Federal Highway Administration (FHWA) full scale model. Numerical results have been compared with the experimental test results. Maximum values and distribution of both stresses and strains at top flanges, bottom flanges and the web tension zone for numerical modelling results, showed close agreement with the experimental tests results in both full and partial interaction models. Also, similar failure modes were encountered from both numerical modelling and experimental tests. Maximum deflection values obtained from numerical modelling were slightly below the experimental values and this was attributed to the stiffer numerical model. Further, mesh refinement could have increase accuracy of numerical predictions.

Steel-Concrete Composite Beams with Precast Hollow-Core Slabs: A Sustainable Solution

Industrialization of construction makes building operation more environmental friendly and sustainable. This change is necessary as it is an industry that demands large consumption of water and energy, as well as being responsible for the disposal of a high volume of waste. However, the transformation of the construction sector is a big challenge worldwide. It is also well known that the largest proportion of the material used in multistory buildings, and thus its carbon impact, is attributed to their slabs being the main contributor of weight. Steel-Concrete composite beams with precast hollow-core slabs (PCHCSs) were developed due to their technical and economic benefits, owing to their high strength and concrete self-weight reduction, making this system economical and with lower environmental footprint, thus reducing carbon emissions. Significant research has been carried out on deep hollow-core slabs due to the need to overcome larger spans that resist high loads. The publication SCI P401, in accordance with Eurocode 4, is however limited to hollow-core slabs with depths from 150 to 250 mm, with or without a concrete topping. This paper aims to investigate hollow-core slabs with a concrete topping to understand their effect on the flexural behavior of Steel-Concrete composite beams, considering the hollow-core-slab depth is greater than the SCI P401 recommendation. Consequently, 150 mm and 265 mm hollow-core units with a concrete topping were considered to assess the increase of the hollow core unit depth. A comprehensive computational parametric study was conducted by varying the in situ infill concrete strength, the transverse reinforcement rate, the shear connector spacing, and the cross-section of steel. Both full and partial interaction models were examined, and in some cases similar resistances were obtained, meaning that the same strength can be obtained for a smaller number of shear studs, i.e., less energy consumption, thus a reduction in the embodied energy. The calculation procedure, according to Eurocode 4 was in favor of safety for the partial-interaction hypothesis.

Data-Driven Corrections of Partial Lotka-Volterra Models.

In many applications of interacting systems, we are only interested in the dynamic behavior of a subset of all possible active species. For example, this is true in combustion models (many transient chemical species are not of interest in a given reaction) and in epidemiological models (only certain subpopulations are consequential). Thus, it is common to use greatly reduced or partial models in which only the interactions among the species of interest are known. In this work, we explore the use of an embedded, sparse, and data-driven discrepancy operator to augment these partial interaction models. Preliminary results show that the model error caused by severe reductions—e.g., elimination of hundreds of terms—can be captured with sparse operators, built with only a small fraction of that number. The operator is embedded within the differential equations of the model, which allows the action of the operator to be interpretable. Moreover, it is constrained by available physical information and calibrated over many scenarios. These qualities of the discrepancy model—interpretability, physical consistency, and robustness to different scenarios—are intended to support reliable predictions under extrapolative conditions.

Partial Interaction Model of Flexural Behavior of PVA Fiber–Reinforced Concrete Beams with GFRP Bars

AbstractThis paper describes experimental and analytical investigations on a highly durable composite structural system comprising polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) reinfo...

Modelling of FRP-concrete bonded interfaces containing FRP anchors

Anchors made from fibre-reinforced polymer (FRP) composites can be used to delay the propagation of debonding cracks and enhance the deformability of FRP-to-concrete bonded interfaces. This paper presents a model for FRP anchors that is calibrated from tests on FRP-to-concrete joints anchored with FRP anchors. The anchor model is incorporated in a partial interaction model in order to simulate the behaviour of such anchored joints. Simulations of the relationship between load and slip compare favourably with tests results. Simulations also accurately represent the distribution of strain along the length of the FRP plate for FRP-to-concrete joints anchored with a single as well as multiple FRP anchors. The simulations are then extended to include the distributions of bond stress and slip along the FRP plate and they ultimately lead to a better understanding of the influence of anchors upon FRP-concrete bonded interfaces. Parametric studies are finally reported and they demonstrate the influence of the key FRP anchor model parameters.

Influence of plate length and anchor position on FRP-to-concrete joints anchored with FRP anchors

This paper presents the details of an experimental and analytical study that addresses the influence of fibre-reinforced polymer (FRP) anchors upon the strength and behaviour of FRP-to-concrete bonded interfaces. Single-shear joints are utilised to represent the bonded interface. The primary variables under consideration are (i) the influence of anchor position in relation to the loaded end of the joint, lanc, (ii) the length of plate between the anchor and the unloaded plate end, lend, and (iii) total length of plate, lfrp. These variables, which have received limited direct attention to date by the research community, are important parameters for understanding the influence of concrete cracking upon the behaviour of the FRP strengthening systems containing anchorage devices. The results of forty-one anchored joints and two unanchored control joints are presented and it is shown that lend is more influential than lanc. Details of a partial interaction model are also presented and the model is shown to adequately replicate the load, slip and strain distribution responses of a selected test joint.

Analysis of FRP-to-concrete interfaces using a displacement driven partial interaction model

Fibre-reinforced polymer (FRP)-to-concrete bonded interfaces are susceptible to bond failure in the concrete at the interface. This paper presents the details of a partial interaction model that is capable of analysing such bond failure in FRP-to-concrete joints. The model is driven by displacing the slip between the FRP and concrete at the loaded end of the joint and is thus able to capture unloading of the bonded interface. Such unloading is due to a reduction in the available length of the bonded plate on account of progressive plate debonding. A bond stress versus slip model is calibrated from test results and incorporated into the partial interaction model. Predictions of strain, bond stress and slip along the length of the bonded plate are produced and the results are found to correlate with test measurements. Finally, parametric studies on a typical joint enable insights to be gained on the parameters used to define the bond-slip model.

Mechanics Model for Simulating RC Hinges under Reversed Cyclic Loading.

Describing the moment rotation (M/θ) behavior of reinforced concrete (RC) hinges is essential in predicting the behavior of RC structures under severe loadings, such as under cyclic earthquake motions and blast loading. The behavior of RC hinges is defined by localized slip or partial interaction (PI) behaviors in both the tension and compression region. In the tension region, slip between the reinforcement and the concrete defines crack spacing, crack opening and closing, and tension stiffening. While in the compression region, slip along concrete to concrete interfaces defines the formation and failure of concrete softening wedges. Being strain-based, commonly-applied analysis techniques, such as the moment curvature approach, cannot directly simulate these PI behaviors because they are localized and displacement based. Therefore, strain-based approaches must resort to empirical factors to define behaviors, such as tension stiffening and concrete softening hinge lengths. In this paper, a displacement-based segmental moment rotation approach, which directly simulates the partial interaction behaviors in both compression and tension, is developed for predicting the M/θ response of an RC beam hinge under cyclic loading. Significantly, in order to develop the segmental approach, a partial interaction model to predict the tension stiffening load slip relationship between the reinforcement and the concrete is developed.

Vertical shear interaction model between external FRP transverse plates and internal steel stirrups

A convenient and proven technique for increasing the vertical shear capacity of reinforced concrete beams is to externally bond fibre reinforced polymer (FRP) to the sides of the beam with the fibres orientated in the transverse or vertical direction. The FRP, which can be in the form of pultruded plates or applied in the wet lay-up procedure, acts as external FRP stirrups resisting vertical shear in the same way as the conventional internal steel stirrups. However, internal steel stirrups are ductile as they are both fully anchored and can yield, which is in contrast to external FRP stirrups that can debond in a brittle fashion and do not yield. Hence, there is no guarantee that the peak vertical shear forces that can be resisted by the steel stirrups and by the transverse FRP plates coincide. In this paper, a partial-interaction model has been developed that quantifies the vertical shear interaction between transverse FRP plates and steel stirrups.