Efficiency of Hybrid Algorithms for Estimating the Shear Strength of Deep Reinforced Concrete Beams

Earthquakes occurred in recent years have highlighted the need to examine the strength of reinforced concrete (RC) members. RC beams are one of the elements of reinforced concrete structures. Due to the dramatic increase in the population and the number of medium/high-rise buildings, in recent years, the beams of buildings have been mainly designed and executed in the type of deep beams. In this study, the artificial neural network (ANN) with optimization algorithms, including particle swarm optimization (PSO), Archimedes optimization algorithm (AOA), and sparrow search algorithm (SSA), are used to determine the shear strength of reinforced concrete deep (RCD) beams. 271 samples from experimental tests are employed to develop algorithms. The results of this study, design codes equations, and previous research are compared. Comparison between the results shows that the PSO-ANN algorithm is more accurate than previous methods. Finally, SHApley Additive exPlanations (SHAP) method is utilized to explain the predictions. SHAP reveals that the beam span and the ratio of the beam span to beam depth have the highest impact in predicting shear strength.

Regional Seafloor Topography by Extended Kalman Filtering of Marine Gravity Data without Ship-Track Information

An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topographic heights composing an undersea volcanic mount by the successive combination of large numbers of gravity measurements at sea surface using altimetry satellite-derived grids and taking the error uncertainties into account. The integration of the non-linear Newtonian operators versus the radial and angular distances (and its first derivatives) enables the estimation process to accelerate and requires only few iterations, instead of summing Legendre polynomial series or using noise-degraded 2D-FFT decomposition. To show the effectiveness of the EKF approach, we apply it to the real case of the bathymetry around the Great Meteor seamount in the Atlantic Ocean by combining only geoid height/free-air anomaly datasets and using ship-track soundings as reference for validation. Topography of the Great Meteor seamounts structures are well-reconstructed, especially when regional compensation is considered. Best solution gives a RMS equal to 400 m with respect to the single beam depth observations and it is comparable to RMS obtained for ETOPO1 of about 365 m. Larger discrepancies are located in the seamount flanks due to missing high-resolution information for gradients. This approach can improve the knowledge of seafloor topography in regions where few echo-sounder measurements are available.

Performance of full scale self consolidating concrete structural elements in shear, bond and under corrosion attack

This research program focuses on investigating the shear resistance, bond characteristics, and corrosion performance of self-consolidating concrete (SCC) compared to those of normal concrete (NC). The shear strength, cracking behavior, and deflection characteristics were tested in full-scale beams. A total of twenty reinforced concrete beams, with no shear reinforcements, were tested under mid-span concentrated load until shear failure occurred. The experimental test parameters included concrete type/coarse aggregate content, beam depth and the longitudinal reinforcing steel ratio (ρw). The beam depth ranged from 150 to 750 mm while the shear span-to-depth ratio (a/d) was kept constant in all beams, The two longitudinal reinforcing steel ratios used were 1% and 2%. The performance of SCC/NC beams was evaluated based on the results of crack pattern, crack widths, loads at the first flexure/diagonal cracking, ultimate shear resistance, post-cracking shear resistance/ductility, load-deflection response, and failure modes. Code-based equations or procedures are used to predict the crack width, first flexural cracking moment/load, and ultimate shear resistance as well as to simulate load-deflection response. The bond strength of reinforcing bars embedded in full-scale heavy reinforcing beams (4000 mm length x 1200 mm depth x 300 mm width) made with SCC was investigated and compared with that of NC. The flowability of SCC mixture through the dense reinforcement was visually monitored from a transparent formwork. The bond stress was tested for bars located at three different heights (150 mm, 510 mm, and 870 mm from the bottom of the beam) and at different concrete ages (1, 3, 7, 14 and 28 days). The bond stress-free end slip relationship, the top bar effect, and the effect of age on bond stress were investigated in both SCC and NC beams. Bond stresses predicted based on some major Codes were compared with those obtained from experiments. The corrosion of steel reinforcement embedded in full-scale SCC beams was investigated and compared to that embedded in NC beams. The corrosion performance of 400 mm width x 363 mm depth x 2340 mm length beams containing epoxy and non-epoxy coated stirrups was monitored by partial immersion in a sodium chloride solution and an impressed current. Half-cell potential tests were implemented at 25 different locations on each beam to evaluate the probability of steel corrosion along the beam length/perimeter. At the same locations where the half-cell potential tests were implemented, the chloride ion content near the bar surface was measured to study the variation of the chloride-ion penetrability along the beam length/perimeter. The mass loss and bar diameter degradation along the length of each bar were investigated at the end of the test. Predicted rebar mass loss due to corrosion based on Faraday’s law was compared with experimental mass loss for each beam.

Performance of full scale self consolidating concrete structural elements in shear, bond and under corrosion attack

This research program focuses on investigating the shear resistance, bond characteristics, and corrosion performance of self-consolidating concrete (SCC) compared to those of normal concrete (NC). The shear strength, cracking behavior, and deflection characteristics were tested in full-scale beams. A total of twenty reinforced concrete beams, with no shear reinforcements, were tested under mid-span concentrated load until shear failure occurred. The experimental test parameters included concrete type/coarse aggregate content, beam depth and the longitudinal reinforcing steel ratio (ρw). The beam depth ranged from 150 to 750 mm while the shear span-to-depth ratio (a/d) was kept constant in all beams, The two longitudinal reinforcing steel ratios used were 1% and 2%. The performance of SCC/NC beams was evaluated based on the results of crack pattern, crack widths, loads at the first flexure/diagonal cracking, ultimate shear resistance, post-cracking shear resistance/ductility, load-deflection response, and failure modes. Code-based equations or procedures are used to predict the crack width, first flexural cracking moment/load, and ultimate shear resistance as well as to simulate load-deflection response. The bond strength of reinforcing bars embedded in full-scale heavy reinforcing beams (4000 mm length x 1200 mm depth x 300 mm width) made with SCC was investigated and compared with that of NC. The flowability of SCC mixture through the dense reinforcement was visually monitored from a transparent formwork. The bond stress was tested for bars located at three different heights (150 mm, 510 mm, and 870 mm from the bottom of the beam) and at different concrete ages (1, 3, 7, 14 and 28 days). The bond stress-free end slip relationship, the top bar effect, and the effect of age on bond stress were investigated in both SCC and NC beams. Bond stresses predicted based on some major Codes were compared with those obtained from experiments. The corrosion of steel reinforcement embedded in full-scale SCC beams was investigated and compared to that embedded in NC beams. The corrosion performance of 400 mm width x 363 mm depth x 2340 mm length beams containing epoxy and non-epoxy coated stirrups was monitored by partial immersion in a sodium chloride solution and an impressed current. Half-cell potential tests were implemented at 25 different locations on each beam to evaluate the probability of steel corrosion along the beam length/perimeter. At the same locations where the half-cell potential tests were implemented, the chloride ion content near the bar surface was measured to study the variation of the chloride-ion penetrability along the beam length/perimeter. The mass loss and bar diameter degradation along the length of each bar were investigated at the end of the test. Predicted rebar mass loss due to corrosion based on Faraday’s law was compared with experimental mass loss for each beam.

Strengthening of Continuous Reinforced Concrete Deep Beams with Large Openings Using CFRP Strips

To accommodate utilities in buildings, different sizes of openings are provided in the web of reinforced concrete deep beams, which cause reductions in the beam strength and stiffness. This paper aims to investigate experimentally and numerically the effectiveness of using carbon fiber reinforced polymer (CFRP) strips, as a strengthening technique, to externally strengthen reinforced concrete continuous deep beams (RCCDBs) with large openings. The experimental work included testing three RCCDBs under five-point bending. A reference specimen was prepared without openings to explore the reductions in strength and stiffness after providing large openings. Openings were created symmetrically at the center of spans of the other specimens to represent 40% of the overall beam depth. Moreover, finite elements (FE) analysis was validated using the experimental results to conduct a parametric study on RCCDBs strengthened with CFRP strips. The results confirmed reductions in the ultimate load by 21% and 7% for the un-strengthened and strengthened specimens, respectively, due to the large openings. Although the large openings caused reductions in capacities, the CFRP strips limited the deterioration by enhancing the specimen capacity by 17% relative to the un-strengthened one.

Effect of Stirrup Spacing and Polypropylene Fiber Ratio on Behavior of Reinforced Concrete Beams

In this study, the effect of the change of stirrup ratio and polypropylene (PP) fiber ratio on the behavior of reinforced concrete beams was investigated. The variables of this study consisting of without stirrup, spacing up to 20 %, 40 % and 80 % of beam depth as stirrup spacing and 0.125 % and 0.500 % of the weight of reinforced concrete beam were used as PP fiber ratios. In the context of experimental study, 1/2 scaled 12 reinforced concrete beams were tested with 4-point bending mechanism. In the light of the obtained data, the load-displacement, stiffness and energy absorption graphs were plotted. The results were interpreted comparatively. According to the results, it is observed that the PP fiber additive significantly changed the behavior of the reinforced concrete beams, and the fiber effect decreased in proportion to the increase of the stirrup rate. It has been observed that the cracks spread more to the beam surfaces with the increase of PP fibers. In addition, the increase in the fiber ratio especially in the non-stirrup beams increases the bending capacity.

Mechanical Properties of Microsteel Fiber Reinforced Concrete and Its Gradient Design in the Partially Reinforced RC Beam

Effects of two kinds of microsteel fibers were employed in reinforced concrete (RC) with different fiber volumes fraction. The RC beam was partially reinforced by microsteel fiber reinforced concrete (MSFRC) based on the idea of gradient design. Flexural performances were specially investigated. Results show that microsteel fiber highly strengthened and toughened the concrete matrix. With the same fiber volume content, the concrete reinforced by Type I fiber was generally better in strength compared with that of Type II, while the bending toughness was substantially improved. The bending strength of the concrete reinforced by microsteel fiber in partial section of tensile region was comparable to that in whole section. Based on the traditional strength theory, the critical MSFRC layer depth of in the partially reinforced RC beam was about 0.3 times of the beam depth, which possessed the same crack resistance ability with the beam composed of MSFRC in the whole section. Compared with that of the reference beam, the cracking load of the partially reinforced beam was enhanced by 119%, and the ratio of the cracking moment to ultimate moment improved by 91%. Moreover, the width and height of the cracks in the partially reinforced beam developed much slower than those in the reference beam, and the steady state in which all cracks emerged appeared later; meanwhile, the crack spacing in the pure bending region was smaller, and the number of cracks in the bending-shear region was less, which means that the partially reinforced beam is of excellent properties to resist cracking and bending. Finally, the calculation formula of the bearing capacity of the partially reinforced beam was proposed, which was in good agreement with experimental results.

Field Investigations of Underwater Mounds Formed by Hopper Dredge Discharges in a Coastal Environment

In a coastal environment, this paper investigated the formation process and the cumulative shape of subaqueous mounds formed by hopper dredged discharges. Hydrological observations and field tests were performed to examine the flow features and ultimately generated morphology characteristics. A high-precision digital elevation model (DEM) was established by multi-beam depth sweeping (MBDS) in the experiment. Particular attention was paid to the formation of the mounds, the three-dimensional shape and the influence factors. The field measurements showed that the mounds were roughly symmetrical in space, and the tidal current, though of weak strength, played a certain role in shaping the profiles. Cone and volcanic cone mound tops were observed, featuring the main top shapes. The height and covered area of the mounds were proportional to the amount of dumped sediment, and they were also affected a lot by the water depth. The results of superimposed tests showed that the second placement over the existing mound resulted in a similar overall shape, but there was pronounced movement around the mound; additional discharged volumes at the same location mainly increased the mound height. The field tests provided a reference for understanding the sediment dumping in other similar coastal areas.

Analytical and Experimental Investigation on Slip-in Gusset Plate Connection for Double C-channel Sections of Cold-formed Steel

Background: Beam-column connections are one of the most important parts of each building, which influence local/global behaviour of structures under vertical and lateral loads. From a practical point of view, a desirable connection is one that can be implemented conveniently in the construction site. For this reason, the connection with the gusset plate and bolts is one of the most commonly used connections to join structural members together. The application of this type of connection with cold-formed steels has not gotten enough attention in the literature and needs more investigation. Objective: The objective of this study is to evaluate the behaviour of the gusset plate connection with cold-formed steel sections based on its moment-rotation relation obtained experimentally when the beam depth is varied. Methods: Three specimens were built with three different depth of beams (i.e. 200, 250, and 300 mm) and constant depth of column (i.e. 300 mm). A same size gusset plate with a thickness of 10 mm was used for all the connections. A Full-Scale Isolated Joint test (FSIJ) was conducted as a testing method in this study to investigate the behaviour of the connection. Results: Three distinct modes of failure were distinguished based on observations in the experiments. Moreover, the obtained results implied that there is a meaningful difference between experimental and analytical results for moment capacity and rotational stiffness of the tested connections. Likewise, the results showed that the beam depth in this joint should be limited to have a ductile connection when the column depth is constant. Conclusion: The moment capacity of the tested connections was analytically underestimated by Eurocode 3 relative to the experimental results with an average amount of 75%, while the connection rotational stiffness overestimated by the analytical results with an average of 74%.