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Reinforced concrete dapped-end connections are susceptible to formation of inclined cracks at the reentrant corner under service conditions. As these connections also work with high shear stresses, they require a high amount of reinforcement to ensure sufficient load-bearing capacity. To deepen the understanding of this topic, an experimental campaign of eight large-scale dapped-end connections featuring diagonal reinforcement is presented. These specimens, which are among the largest available in the literature, are similar in size to the dapped ends typically used in bridges. The test series captures both flexural and shear failures of dapped ends. The crack displacements, crack patterns, and elongation of main reinforcement are reported, with 56 continuous measurements of deformations. The test results of this study are used in conjunction with a similar study on specimens with orthogonal reinforcement to investigate the impact of reinforcement layout. For the same amount of dapped-end reinforcement, specimens with diagonal reinforcement are considerably stronger than the corresponding connections with orthogonal reinforcement. For both reinforcement layouts, the crack widths exceeded typical code provisions under service conditions. Keywords: dapped-end connections; diagonal reinforcement layout; flexural failures; reentrant corner cracks; shear failures.

This paper presents a numerical model of an integrated 3D casing-cement-formation system, to evaluate the mechanical tensile and shear failure of the cement at the casing-cement interface as the pressure and temperature conditions of the formation and borehole vary during production. The model which includes the formation pressure, unlike others proposed, was developed by stages under finite element discretization and compared to analytical models. Results show that increasing the formation temperature increases the probability of tensile and shear failure in the cement, while increasing the wellbore temperature decreases these probabilities. On the other hand, the decrease in the well pressure reduces the probability of shear failure and increases the tensile failure. In the case of formation pressure, the opposite occurs.

An experimental program was conducted to study the effects of using 0.7 in. (17.8 mm) diameter prestressing strands on the performance of pretensioned concrete I-girders under shear-critical loading. Four full-scale Texas bulb-T girders (Tx-girders) with different concrete release strengths, member depths, shear span-depth ratios, and strand patterns were tested. The mild-steel reinforcement in the specimens was detailed according to the common practice in Texas for girders fabricated using conventional, smaller-diameter strands. All specimens exhibited considerable strand slip prior to failure. In three of the specimens, shear failure also resulted in prominent horizontal cracking at the interface between the web and the bottom flange. However, distributed yielding of the stirrups was confirmed in all specimens, indicating shear-tension failure. The capacities of all specimens were conservatively estimated using the general procedure in the AASHTO LRFD Bridge Design Specifications and the detailed method in ACI 318-14 provisions. Keywords: 0.7 in. (17.8 mm) strands; anchorage-induced shear failure; development length; horizontal shear failure; pretensioned; transfer length.

Due to the high depth to span ratio, shear stresses in deeps impose the need for careful design of shear strength. The shear strength of any reinforced concrete beam is the sum of its sectional strength and web reinforcement strength. Steel bar stirrups are the typical reinforcing material up to date for such a purpose; however, many studies were conducted to evaluate the use of other materials or different configurations to increase the shear strength of deep beams. In this research, closed-form steel plates (gagger plates) were used as alternative shear reinforcement in experimental deep beams. Three beams were cast and tested in four-point bending to investigate this possibility. The first was kept as a reference beam as it was reinforced with conventional closed stirrups, while the rest two beams were reinforced with 4 mm thick and 20 mm wide gagger plates. One with in-plane configuration, where the 20 mm side was aligned in the plane of the beam section, while the third beam was reinforced with out-of-plane gagger plates. Based on the test results, the mechanical behavior of beams with steel plates was noticeably improved compared to the reference beam with conventional stirrups. The in-plane configuration was superior to the out-of-plane and reference beams in strength, service stiffness, ductility, and toughness.

Conducting research on steel fiber-reinforced concrete (SFRC) beams without stirrups, particularly the SFRC beams with high-strength concrete (HSC) and high-strength steel (HSS) reinforcing bars is essential due to the limitation of test results of high strength SFRC beams with high strength steel reinforcing bars. Eight shear strength prediction equations for analysis and design of the SFRC beam derived by different researchers are summarized. A database was constructed from 236 beams. Accordingly, the previous shear strength equations can be evaluated. Ten high-strength SFRC beams subjected to monotonic loading were prepared to verify the existing shear strength prediction equations. The equations for predicting shear strength of the SFRC beam are proposed on the basis of observations from the test results and evaluation results of the previous shear strength equations. The proposed shear strength equation possesses a reasonable result. For alternative analysis and design of the SFRC beams, ACI 318-19 shear strength equation is modified to consider steel fiber parameters.

As the development of unconventional oil and gas resources goes deeper, the stimulation of reservoirs goes deeper year by year. Flow in longer wellbores poses a challenge to the stability of drag-reduction performance of fracturing fluid. However, at present we have limited understanding of the mechanism of drag-reduction damage caused by shear flow, especially the microscopic mechanism. Therefore, in this work, the variation pattern of drag reducer solution performance with shear rate has been analyzed by using a high precision loop flow drag test system. The test results show that there is a critical shear rate for the performance damage of the drag reducer solution, and high strength shear flow and cumulative shear flow time are the main factors leading to the performance degeneration of the drag reducer. Based on the nanometer granularity distributions, rheological properties and microscopic structures observed with a transmission electron microscope of drag reducer solutions subjected to shear flows of different velocities, it is confirmed that the damage to the microscopic structure of the solution is the main reason leading to its performance degeneration. The destruction of the microscopic structure causes the drag reducer solution to degrade in non-Newtonian characteristics, so it becomes poorer in its capability of reducing turbulent dissipation and drops in drag-reduction capability. This research can provide a reference for improving and optimizing drag-reduction capability of fracturing fluid.

The present study pertains to the effects of transverse opening diameters and shear reinforcement ratios on the shear and flexural behavior of RC beams with two web openings across different spans, i.e., a single opening in each half-span. Within the scope of the study, a total of 12 RC beams with five different opening diameter-to-beam depth ratios (0, 0.20, 0.27, 0.33, 0.40, and 0.47) and two shear reinforcement ratios were tested to failure under four-point bending. The load capacities, ductilities, rigidities and energy dissipation capacities in the elastic and plastic ranges of beam behavior were compared. Furthermore, the load capacities of the beams were compared to the existing analytical shear strength formulations in the literature. The test results indicated that whether an RC beam with openings has adequate or inadequate amounts of shear reinforcement, the frame-type shear failure becomes much more pronounced with increasing opening diameter. The reductions in the load capacity and modulus of toughness with increasing opening diameter are more considerable in the presence of inadequate amounts of shear reinforcement, while the beam ductility is less affected in shear-deficient RC beams with openings as compared to the ones with adequate shear reinforcement.

Shear cracking behaviour of fibrous self-compacting concrete of normal and high strength grade (M30 and M70) is presented here. Two stirrup diameters (6mm ∅ and 8 mm ∅) with a constant steel fiber content of 38 kg/m (0.5% by volume of concrete) were selected for the present study. The size of the beam was fixed at 100x200x1200mm. The clear span of the beam 1100mm, was maintained throughout the study. A total of 16 shear-deficient beams were tested under three point loading. Two stirrup spacing (180mm and 360 mm) are used for the shear span-to-depth ratio (a/d = 2). Investigation indicates that initial cracking load and ultimate load increased as the area of shear reinforcement increased by increasing the diameter of stirrup. It was also noted that the failure mode was modified from brittle shear failure to flexural-shear failure in the presence of fibers. The mechanical behaviour of SFRSCC was improved due to the combined effect of stirrups and steel fibers. The stiffness, toughness, and deflection of the beams increased when compared to SCC beams without fibers. The experimental results were compared with existing models available in literature, and the correlation is satisfactory.

One-way slabs under concentrated loads may fail by one-way shear, two-way shear, flexure, or a combination of these modes. This paper reviews shear and punching shear-failure mechanisms of one-way slabs under concentrated loads tested from the literature and investigates the accuracy of different approaches to predict the ultimate capacity for such slabs using the ACI code expressions. A database with 160 test results was evaluated. Shear and concentrated loads measured at failure were reviewed according to parameters such as the load position, slab width, and reinforcement ratios. The load position and slab width play a marked influence on the failure mechanism and tested loads. The analyses improved the understanding of the main parameters influencing the behavior of one-way slabs under concentrated loads. Finally, the proposed effective shear width expression enables accurate shear capacity predictions using the ACI code expressions.