Numerical Study of the Bond Strength Evolution of Corroded Reinforcement in Concrete in Pull-Out Tests

The corrosion of rebars in reinforced concrete structures impacts their geometry (diameter and ribs) and mass, damages the concrete at the interface between the two materials, deteriorates the bond strength, and causes the cracking of the concrete cover. In the following study, a 2D numerical model of the pull-out test is presented in order to study the impact of corrosion on the bond strength. Several parameters are investigated: the embedment depth, the rebar’s diameter, and the width of the concrete cover. The model reproduces the slip of the rebar and the failure through the splitting of concrete. It integrates an interface between the two materials and a concrete damage model that simulate the deterioration of concrete in compression and tension. The results obtained are validated with experimental data from the literature. Moreover, a parametric study is carried out to determine the impact of the embedment depth, the diameter of the rebar, and the concrete cover on the bond strength. The present study confirms that a greater embedment depth increases the pulling load. The study also confirms that the rebar’s diameter impacts highly the loss of bond between the rebar and the concrete cover. Lastly, the final main result of this paper is that the width of the concrete cover slows the loss of bond strength between the two materials.

No demonstrated link between sea-level and eruption history at Santorini

Previous studies have suggested a link between rates of sea-level variation and eruptions globally [McGuire et al., 1997], with Satow and coauthors [2021] presenting the first detailed comparison between sea-level change and eruptive history for a single island-volcano. They use robust, high-resolution ages for volcanic deposits at Santorini, combined with a 2D numerical model to correlate sea-level reduction with volcanism. Lowering sea level reduces overburden pressure and is predicted to increase tensile stress in the magma chamber roof, leading to diking and eventually eruption. Having independently reproduced their results, we disagree with the numerical model for three main reasons: (1) predictions of stress distribution and magnitudes caused by sea level change are solely dependent on the size and boundary conditions of the 2D model; (2) minor changes to the model dimensions, dimensionality (2D to 3D), and/or addition of a mantle analogue, removes correlation between sea level and eruptions; and (3) crustal loading conditions at the volcano absent from the model are more significant than sea level change.

Analysis of Spring-in Deformation in L-shaped Profiles Pultruded at Different Pulling Speeds: Mathematical Simulation and Experimental Results

Peculiarities of the pultrusion manufacturing process lead to the occurrence of spring-in deformations, whereas their value depends on the pulling speed. In this article experimental and numerical analysis was carried out for glass fiber/vinyl ester resin 75 × 75 × 6 mm L-shaped profiles pultruded at pulling speeds of 200 and 600 mm/min. Spring-in angles of produced profiles were determined on the same day of manufacturing when profiles cooled down to room temperature. Higher pulling speeds provoked increased values of spring-in. 2D numerical model accounting for thermo-chemical and mechanical composite’s behavior during pultrusion was implemented in ABAQUS software. Cure Hardening Instantaneous Linear Elastic (CHILE) constitutive law was used to describe matrix resin Young’s modulus evolution. Since both unidirectional (UD) rovings and fabric material were utilized, effective mechanical properties of UD and fabric layers were calculated in accordance with Self-Consistent Field Micromechanics (SCFM) approach. Spring-in angles determined within experimental and numerical studies were compared and a good correlation was found: the errors were 12.6% and 6% for the pulling speed of 200 and 600 mm/min, respectively.

2D thermo-mechanical-chemical coupled numerical models of interactions between a cooling magma chamber and a visco-elastic host rock

<div> <p>A recent focus of studies in geodynamic modeling and magmatic petrology is to understand the coupled behavior between deformation and magmatic processes. Here, we present a 2D numerical model of an upper crustal magma (or mush) chamber in a visco-elastic host rock, with coupled thermal, mechanical and chemical processes, accounting for thermodynamically consistent material parameters. The magma chamber is isolated from deeper sources of magma (at least periodically) and it is cooling, and thus shrinking. We quantify the changes of pressure and stress around a cooling magma chamber and a warming host rock, using a compressible visco-elastic formulation, considering both simplified idealized and more complex and realistic geometries of the magma chamber.</p> </div><div> <p>We present solutions based on a self-consistent system of the conservation equations for coupled thermo-mechanical-chemical processes, under the assumptions of slow (negligible inertial forces), visco-elastic deformation and constant chemical bulk composition. The thermodynamic melting/crystallization model is based on a pelitic melting model calculated with Perple_X, assuming a granitic composition and is incorporated as a look-up table. We will discuss the numerical implementation, show the results of systematic numerical simulations, and illustrate the effect of volume changes due to temperature changes (including the possibility melting and crystallization) on stress and pressure evolution in magmatic systems.</p> </div>

Comparison of EPS Geofoam and Stone columns in heave reduction of expansive soils

To reduce the swell pressures in expansive soils usually granular piles are used, but due to lack of availability there is need of a material which is highly compressible and economical also. EPS Geofoams are obtained by expanding the polystyrene polymer which is a by-product obtained from the petroleum industry. As the drainability of the Geofoam is very less a layer of Geocomposite is surrounded over the geofoam especially for allowing the drainage. So, the mechanism involved in the study is that whenever a saturated soil swells in vertical direction this Geofoam will give room to accommodate the lateral swell which leads to reduction in the vertical heave and Geocomposite will dissipate the excess pore pressure generated during swelling of the soil. In the present study an attempt was made to predict the performance of EPS Geofoam and Geocomposite in reducing the soil heave due to constant infiltration. A two dimensional (2D) numerical model was developed using GEOSTUDIO 2012 to predict the behaviour of the swelling soil due to the inclusion of Geofoams as well as stone columns. Generally coupled and uncoupled analysis are performed to study the behaviour of the swelling soil but as the uncoupled analysis is more advantageous than coupled analysis it is performed in the present study.

Timescales of successful and failed subduction: insights from numerical modelling

Summary The relatively short duration of the early stages of subduction results in a poor geological record, limiting our understanding of this critical stage. Here, we utilize a 2D numerical model of incipient subduction, that is the stage after a plate margin has formed with a slab tip that extends to a shallow depth and address the conditions under which subduction continues or fails. We assess energy budgets during the evolution from incipient subduction to either a failed or successful state, showing how the growth of potential energy, and slab pull, is resisted by the viscous dissipation within the lithosphere and the mantle. The role of rheology is also investigated, as deformation mechanisms operating in the crust and mantle facilitate subduction. In all models, the onset of subduction is characterized by high lithospheric viscous dissipation and low convergence velocities, whilst successful subduction sees the mantle become the main area of viscous dissipation. In contrast, failed subduction is defined by the lithospheric viscous dissipation exceeding the lithospheric potential energy release rate and velocities tend towards zero. We show that development of a subduction zone depends on the convergence rate, required to overcome thermal diffusion and to localise deformation along the margin. The results propose a minimum convergence rate of ∼ 0.5 cm yr−1 is required to reach a successful state, with 100 km of convergence over 20 Myr, emphasizing the critical role of the incipient stage.