Assessment of the asphalt mixtures properties subjected to a flexural strength

Fatigue cracking by loading is one of the main mechanisms of damage to asphalt mixtures in service. Several studies worldwide have been conducted to try to understand the response that hot-mix asphalt undergo under this mechanism of damage. Despite the above, the fatigue phenomenon in asphalt mixtures is still not fully understood. The current research hypothesizes that the response under repeated loading of asphalt mixtures in fatigue tests can be more clearly understood through the one obtained under monotonic loading. For this reason, this study presents the results of the first phase of the research in which beams of asphalt mixtures were subjected to flexion using monotonic loads. The above, to correlate the evaluated properties with those obtained in a second phase where the response of the beams under repeated load (fatigue) will be measured. Beams made of two hot-mix asphalt mixes, two asphalt contents, and two different thicknesses were subjected to flexural strength tests. From the tests, the modulus of rupture, the maximum monotonic load that supports the beams in the failure state, the displacement in the failure state, and the relation between load and displacement were obtained. As a general conclusion of the study, it was obtained that the response experienced by the beams subjected to monotonic load has a broad correlation with the reported in the reference literature.

Resistance under Marshall monotonic load for asphalt concrete mixtures

The dense hot MDC-19 type asphalt mixes are considered, by the “Instituto Nacional de Vías” in Colombia, as continuous grading asphalt mixes (asphalt concrete). These constitute most of the surface course, in the structures of in-service pavements, being the object of study and research in different projects to ensure their durability. In the present investigation, unlike other investigations, the mechanical behavior under Marshall monotonic load was studied in the laboratory between MDC-19 dense type asphalt mixtures, comparing plant-produced and laboratory-produced asphalt mixtures. To carry out this process, samples of uncompacted asphalt mixtures were taken, produced in four fixed plants, with which Marshall-type briquettes were compacted. Likewise, samples of mineral aggregates and asphalt cement were obtained from the same plants, which constitute the mixtures raw material produced there. With these materials, briquettes with the same characteristics were mixed and compacted. Subsequently, the resistance under Marshall monotonic load was determined on the briquettes manufactured in plant and laboratory. The optimal asphalt cement content was compared between plant and laboratory- produced mixtures. An increase in Marshall Stability was found in the briquettes made with plant-produced mixtures, while these required a greater amount of asphalt cement for their production.

Experimental study of fixed-ended RC deep beams under cyclic and monotonic loading

Reinforced Concrete (RC) deep beams are commonly used in structural design to transfer vertical loads when there is a vertical discontinuity in the load path. Much experimental research has been conducted on simply supported deep beams, yet only a few research is carried out using monotonic loads. In this paper, an experimental investigation is conducted to study fixed-ended reinforced concrete deep beams under cyclic and monotonic loads. Five specimens were experimentally tested. The specimens have similar geometry but different reinforcement details. Four specimens were tested under cyclic load and one specimen under monotonic load for observing the deflection of the mid-span where the load is applied, crack patterns, failure modes, and shear strengths. The results show that the web reinforcements are more effective than longitude bars in fixed-ended RC deep beams to increase their shear capacity.

Parametric study of I-shaped shear connectors with different orientations in push-out test

A great deal of research has been conducted to improve the understanding of the behavior of new types of shear connectors. This article presents the study of I-shaped connectors behavior under monotonic load welded in four different orientations in order to get the position which gives the high shear strength and the best ductility. For this purpose, eight push-out test specimens with I-shaped shear connectors with different orientations and dimensions were tested in C20/25 and C30/37 concrete classes. The load-slip behavior and failure modes of the tested connectors are presented and discussed. Furthermore, a non-linear 3D finite element modelling of the push-out test is performed in order to further investigate the influencing parameters on the I-shaped connectors behavior. Hence, a parametric study is carried out by using the established 3D finite elements model to study the influence of concrete strength, connector’s steel grade, reinforcements, height and length of the connector. Both experimental and numerical results show that there is a privilege orientation for which the shear strength of an I-shaped shear connector is significantly higher than that of all other tested orientations.

Behaviour of Precast Concrete Beam-to-Column Connection with SHS Hidden Corbel Subjected to Monotonic Load

Beam-to-column connection is the most critical part of a precast concrete (PC) structure as it governs the integrity of the entire structure. In this study, a beam-to-column connection with square hollow section (SHS) hidden corbel was developed. A full-scale test was conducted on eleven T-subframe specimens with various configurations to investigate the behaviour of the connection under an incremental static load. The behaviour of the connection was evaluated in terms of the moment-rotation response and the mechanical properties were obtained by using the beam-line method. Due to the extensive usage of steel elements, the PC connect possessed a higher ultimate strength than the reinforced concrete (RC) connection. The moment resistance of the connection was largely contributed to by the hidden corbel embedded in the beam and column. However, the PC connection gave a lower stiffness, which resulted in a larger rotation deformation than the RC connection, and thus lowered its design strength. The PC connection was classified as semi-rigid and partial strength, and only specimen PC-3 was considered feasible for PC structures.

Behavior of Curved Steel-Concrete Composite Beams Under Monotonic Load

The paper develops a numerical investigation on the behavior of steel-concrete composite beam curved in plan to examine the effect of the various parameters. Three-dimensional finite element analysis (FEA) is employed using a commercial software, ABAQUS. The geometric and material nonlinearities are utilized to simulate the composite beam under a monotonic load. The FEA efficiency has been proved by comparing the numerical results with experimental tests obtained from previous literature, including load-deflection curves, ultimate load, ultimate and failure deflection, and cracks propagation. The validated models are used to assess some of the key parameters such the beam span/radius ratio, web stiffeners, partial interaction, concrete compressive strength, and steel beam yield stress. From the obtained results, it is noticed that the span/radius of curvature ratio influences the loading capacity, the beam yielding (i.e. the beam yield at an early stage) when the span/radius ratio increases and inelastic behavior developed early of the beam due to the torsional effect. The presence of web stiffeners with different locations in the curve composite beam affected the shear strength. The web twisting and vertical separation at the beam mid-span are observed to decrease as the number of the stiffeners increase due to the decrease in the beam torsion incorporating with transferring the failure to the concrete slab. Furthermore, the partial interaction and steel beam yield stress developed in this study appear to have a remarkable effect on beam capacity.

Effect of filling steel tube chords by concrete on the structural behaviour of composite truss girders

In this study, three specimens of Warren truss girders composite with concrete deck slab were tested experimentally under a central monotonic load to study the effect of the existence of concrete inside the chords. The load capacity, deflection, slip between the concrete slab and steel tube, and failure modes were reported. Both chords were filled with concrete to the first specimen, only the lower chord was filled with concrete and the upper chord remained hollow to the second specimen and both chords were kept hollow in the third specimen. The result indicated that the existence of concrete inside the chords has a significant effect on the load capacity, failure pattern, and the slip. The steel tubes of the upper chord filled by concrete prevent surface plasticity failure of the upper chord under loading and increase the ultimate load by 6.68 %. Also, filling the lower chord with concrete prevents the surface plasticity failure in the supports zone and caused an increase in the ultimate load by 39.59 %. The slip at the end of the specimen of two chords filled with concrete is less by 71% than the end slip of specimen of hollow top chord and higher by 46.8 % than the specimen of two hollow chords.