Experimental Study on Tensile Mechanical Properties and Reinforcement Ratio of Steel–Plastic Compound Geogrid-Reinforced Belt

The steel–plastic compound geogrid has been widely used as a new reinforcement material in geotechnical engineering and other fields. Therefore, it is essential to fully understand the mechanical properties of steel–plastic compound geogrid-reinforced belts to utilize steel–plastic compound geogrids efficiently. In this study, tensile mechanical tests of steel wire, polyethylene geogrid belt, and steel–plastic compound geogrid-reinforced belt were conducted with respect to the tensile mechanical properties of steel–plastic compound geogrid-reinforced belts. In addition, the minimum reinforcement and optimal reinforcement ratios of steel–plastic compound geogrid-reinforced belts were summarized. The results showed that the steel–plastic compound geogrid-reinforced belts possessed an incongruent force of the internal steel wire during the tensile process. The tensile stress–strain curve of the steel–plastic compound geogrid-reinforced belt can be divided into the composite adjustment, steel wire breaking, and residual deformation stages. The tensile strength of the steel–plastic compound geogrid-reinforced belt is proportional to the diameter and number of steel wires in the reinforced belt. The minimum and optimum reinforcement ratios of steel wire in the steel–plastic compound geogrid-reinforced belt were 0.63% and 11.92%, respectively.

Refined strength prediction of concrete 2D bottle-shaped struts

For better strength prediction using strut-and-tie models (STM), it is essential to use reliable strength parameters of the model components; e.g., struts, ties, and nodes. Among all the elements of the STM, the strength of the bottle-shaped struts is not well quantified. The purpose of this study is to develop more accurate formulas for the calculation of the effectiveness factors for 2D bottle-shaped struts, that are unreinforced, reinforced with minimum reinforcement, and reinforced with sufficient transverse reinforcement. The nonlinear finite element analysis, with the aid of the software ABAQUS, has been utilized in this study, which has been verified against experimental tests. The study has been carried out for grades of concrete varying from 20 to 100MPa, and for bearing plate to width ratio varying from 0.1 to 0.9. The obtained formulas for the effectiveness factors of bottle-shaped struts are functions of the concrete strength, which is not the case with the ACI 318-19 provisions. These formulas have been verified against experimental tests and have been compared with the ACI 318-19 provisions. The predictions based on these formulas are more accurate than those based on the ACI 318-19 provisions. Also, the results from these formulas are always on the safe side. On the other hand, the ACI 318-19 provisions lead to unsafe results in the case of high-strength concrete and very conservative results for the case of unreinforced struts from normal-strength concrete.

Thick Reinforced Concrete Walls Subjected To Non-Uniform Restrained Shrinkage

Several researchers have studied the behavior of reinforced concrete walls under restraint shrinkage, which demonstrate the variation of the degree of restraint with different Length/Height ratios. In general, concrete standards and codes of practice recommend a minimum amount of reinforcement for shrinkage effects. This research investigates the response of thick reinforced concrete walls subjected to restraint shrinkage. The parameters studied are the thickness of reinforced concrete walls, and non-uniform distribution of shrinkage along the Length\Height and through the thickness of the wall. This study uses the non-linear finite element method to simulate the cracking behavior of the concrete and to predict tensile stresses in the reinforcement in the vicinity of Cracks. Moreover, this study investigates the influence of reinforcement ratio and compares the results with well-known concrete standards and codes of practice. It is concluded that the non-uniform shrinkage through the thickness of the wall may have significant impact on the cracking behavior of thick concrete walls. In addition, as expected, higher reinforcement ratio results in lower tensile stresses in the reinforcement. The thesis also provides guidelines for minimum reinforcement ratio.

Thick Reinforced Concrete Walls Subjected To Non-Uniform Restrained Shrinkage

Several researchers have studied the behavior of reinforced concrete walls under restraint shrinkage, which demonstrate the variation of the degree of restraint with different Length/Height ratios. In general, concrete standards and codes of practice recommend a minimum amount of reinforcement for shrinkage effects. This research investigates the response of thick reinforced concrete walls subjected to restraint shrinkage. The parameters studied are the thickness of reinforced concrete walls, and non-uniform distribution of shrinkage along the Length\Height and through the thickness of the wall. This study uses the non-linear finite element method to simulate the cracking behavior of the concrete and to predict tensile stresses in the reinforcement in the vicinity of Cracks. Moreover, this study investigates the influence of reinforcement ratio and compares the results with well-known concrete standards and codes of practice. It is concluded that the non-uniform shrinkage through the thickness of the wall may have significant impact on the cracking behavior of thick concrete walls. In addition, as expected, higher reinforcement ratio results in lower tensile stresses in the reinforcement. The thesis also provides guidelines for minimum reinforcement ratio.

Analysis of reinforced retaining wall failure based on reinforcement length

Reinforced retaining walls are structures constructed horizontally to resist earth pressure by leveraging the frictional force imparted by the backfill. Reinforcements are employed because they exhibit excellent safety and economic efficiency. However, insufficient reinforcement can lead to collapse, and excessive reinforcement reduces economic efficiency. Therefore, it is important to select the appropriate type, length, and spacing of reinforcements. However, in actual sites, although the stress and fracture mechanisms in the straight and curved sections of reinforced soil retaining walls differ, the same amount of reinforcements are typically installed. Such an approach can lead to wall collapse or reduce economic feasibility. Therefore, in this study, the behaviours of straight and curved sections fortified with reinforcements of various lengths (1, 3, 5, and 7 m) are predicted through a three-dimensional numerical analysis. The retaining walls are of the same height, but the reinforcement variations in the aforementioned sections influence the wall behaviour differently. Based on the results, the optimum reinforcement lengths for the straight and curved parts were selected. By installing reinforcements of different lengths in these sections, the maximum reinforcing effect with minimum reinforcement was derived. This study further found that the curved section of the wall required more reinforcements, and the reinforcement lengths for the curved and straight sections should be separately optimized.

Steel fibers for replacing minimum reinforcement in beams under torsion

This paper concerns an investigation on six large-scale Steel Fiber Reinforced Concrete (SFRC) beams tested in pure torsion. All beams had longitudinal rebars to facilitate the well-known space truss resisting mechanism. However, in order to promote economic use of the material, the transverse reinforcement (i.e. stirrups/links) was varied in the six large scale beams. The latter contained either no stirrups, or the minimum amount of transverse reinforcement (according to Eurocode 2), or hooked-end steel fibers (25 or 50 kg/m3). Material characterization were also carried out to determine the performance parameters of SFRC. The results of this study show that SFRC with a post-cracking performance class greater than 2c (according to Model Code 2010) is able to completely substitute the minimum reinforcement required for resisting torsion. In fact, the addition of steel fibers contributes to significantly increase the maximum resisting torque and maximum twist when compared to the same specimen without fibers. Moreover, SFRC provides a rather high post-cracking stiffness and a steadier development of the cracking process as compared to classical RC elements. This phenomenon improves beam behavior at serviceability limit state. The experimental results are critically discussed and compared to available analytical models as well as with other tests available into the literature.

Progressive Collapse of RC Box Girder Bridges due to Seismic Actions

Most of the recent studies focus on the progressive collapse of ordinary structures due to gravity and blast loads. A few focus on studying progressive collapse due to seismic actions, especially of bridge structures. The past major earthquakes have shown that it is possible to develop improved earthquake-resistant design techniques for new bridges if the process of damage from initial failure to ultimate collapse and its effects on structural failure mechanisms could be analyzed and monitored. This paper presents a simulation and analysis of bridge progressive collapse behavior during seismic actions using the Applied Element Method (AEM) which can take into account the separation of structural components resulted from fracture failure and falling debris contact or impact forces. Simple, continuous, and monolithic bridges’ superstructures were numerically analyzed under the influence of the severe ground motions not considering the live loads. The parameters studied were the superstructure redundancy and the effect of severe ground motion such as Kobe, Chi-Chi, and Northridge ground motions on different bridge structural systems. The effect of reducing the reinforcement ratio on the collapse behavior of RC box girders and the variation of columns height were also studied. The results showed that monolithic bridge models with reduced reinforcement to the minimum reinforcement according to ECP 203/2018 showed a collapse behavior under the effect of severe seismic ground motions. However, changing the bridge structural system from monolithic to continuous or simple on bearing bridge models could prevent the bridge models from collapse.