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.

Explosive strength evolution of Romanian professional rugby players – Backs

The purpose of this study is to highlight the evolution of the explosive strength in the 4-year interval of the backs compartment and the level of adaptation to the game requirements. The hypothesis in this study is that the explosive strength of the lower limbs in rugby backs developed during the past 4 years, trying to keep up with the higher needs in the first Romanian league. Explosive power was measured using the ‘Just Jump System’, which is a plyometric test mat on which the players conducted a set of three tests: squat jump, control movement jump and free jump. The forwards significantly improved their explosive strength in a 4-year period. Although the total body mass got bigger, the players managed to improve their lower limbs’ explosive strength; this fact proves a good physical adaptation to the requirements of the rugby game. Keywords: Power, jump.

Interaction between Cement Clinker Constituents and Clay Minerals and their Influence on the Strength of Cement-Based Stabilized Soft Clay

The strength of cement stabilized clay is less than that of concrete and mortar and shows a distinct variability owing to the existence of various clay minerals. To better understand the cement-clay reactions and the strength generation, two artificial clays with the unique clay mineral and major strength-producing constituents of cement clinker were investigated via mechanical, compositional, and microstructural analyses. Results show that C3A-stabilized clay gains strength rapidly in the first three days, but this favourable tendency vanishes over time. After 90 days of curing, the strength of C3S-stabilized clay is about four times that of the corresponding C3A-stabilized clay, indicating the remarkable long-term stabilization efficiency of C3S. Furthermore, clay minerals primarily draw into strength evolution in the reaction process. Despite that bentonite is more reactive than kaolin as long as the highly alkaline conditions persist, it has a higher probability to flocculate into large aggregates during the mixing process, which may impair the reaction efficiency and even brings adverse stabilization effects, suggesting the importance of uniformity control.

Spatial Distribution of Slip and Stress Changes in Contained Laboratory-Generated Earthquakes with Heterogeneous Initial Stress

<p>Earthquake ruptures arrest due to either encountering a barrier with high fracture energy or entering unfavorable stress conditions. Our large-scale laboratory earthquake experiments use heterogeneity in initial stress to confine the rupture within a 3-m long saw-cut granite fault. All earthquake processes, i.e., initiation, propagation, and arrest, were spontaneous and contained within the simulated fault. We proposed an analytical crack model to fit our experimental measurements and to better constrain the features in the spatial distribution of both slip and stress changes. Similar to natural earthquakes, laboratory measurements show coseismic slip that gradually tapers near the rupture tips. Measured stress changes show roughly constant stress drop in the center of the ruptured region, a maximum stress increase near the rupture tips, and a smooth transition in between, in a region we describe as the earthquake arrest zone. In our experiments, the earthquake arrest zone is more than one order of magnitude wider than the cohesive zone described by fracture mechanics. We propose that the transition in stress changes and the corresponding linear taper observed in the slip distribution are the result of rupture termination conditions primarily controlled by the initial stress distribution and are not related to the fault strength evolution. We also performed dynamic rupture simulations that confirm how arrest conditions can affect slip distribution and static stress changes, especially near the tip of an arrested rupture. If applicable to larger natural earthquakes, this distinction between the earthquake arrest zone resulted from heterogeneous initial stress and a cohesive zone that depends primarily on strength evolution has important implications for how seismic observations of earthquake fracture energy should be interpreted.</p>

The large-scale troughs on Asteroid 4 Vesta are opening-mode fractures

<p>The Dawn mission at Asteroid 4 Vesta revealed two sets of enormous linear structures. Both sets are troughs—linear, negative-relief landforms—with one spanning around at least two-thirds of the equator and the other set incompletely preserved in the northern hemisphere. A previous study evaluated the cross-sectional geometries of the troughs and interpreted them as analogous to grabens, which are landforms caused by normal faults. However, for the troughs to be large-scale opening-mode fractures, i.e., joints, was heretofore not considered. To distinguish between normal faulting and jointing, we investigated the map patterns, cross-sectional geometries, and variations of relief and width along the length of these troughs. Relief and width are meaningful measurands that causally relate to the vertical displacement of faults or aperture of joints, respectively. Their distributions along the trough length should thus reveal differences in fracturing behavior. In addition, we derived strength-depth profiles to characterize the rheologic structure of Vesta’s lithosphere and determine the predicted fracturing behavior in its brittle regime.</p><p>We mapped all large-scale troughs on Vesta, including four equatorial and two northern troughs, and no map patterns diagnostic for faulting were identified. The troughs are bounded by scalloped rims and mainly show V- and bowl shapes in cross-section. The variation of reliefs of the two-opposing trough-bounding scarps reveals that the relief maxima for each of the investigated troughs are located off-center, and at different locations along the trough they bound. In contrast, we found that both the individual and cumulative variations in trough width have their maxima near the center of the trough. These map patterns and geomorphologic characteristics are largely inconsistent with the mechanics of graben formation but instead point to an origin by opening-mode fracturing. Moreover, our calculations of lithospheric strength evolution that enable assessments of fracturing behavior reveal that Vesta’s lithosphere has been dominated by a thick brittle portion throughout its history. Solutions to the Coulomb criterion considering a range of strengths properties of intact to fractured basaltic materials are in support of jointing as the major fracturing mode in at least the upper ~14 km of Vesta’s lithosphere.</p>