International Journal of Advanced Structural Engineering
Volume:12 Issue: 3, Autumn 2022

Numerical Investigation of the Effect of Concrete Injection on the Concrete Joints of the Arched Dam, Under the Applied Stresses    Abstract  Investigating the safety of dams is of great importance given their critical role in the industry and economy of countries and the catastrophic consequences of their failure. Hence, the present paper examines the impact of incomplete contraction joint injection in the Karun 4 double-curvature arch dam as a case study. In this article, the Abaqus 6.12 finite element software was used to model and analyze 3 numerical models of the Karun 4 dam. These models consist of a linear, integrated, and homogeneous model and two nonlinear models considering the nonlinear behavior resulting from two different types of common contraction joints in the dam's body. The results indicated that a lack of injection led to a significant increase in the maximum principal stresses (MPa) at the upstream section of the dam, such that a large part of this section, which originally worked under compression, is now under tension. The tensile stresses at the upstream abutment and the downstream crest also increased. Moreover, a lack of injection considerably increased the vertical compressive stresses between the contact surfaces (µ). These stresses were increased almost twofold near the injection stop level such that the stresses between monolith zero and one increased from a maximum of 5.13 under complete injection to 11.3. According to the results, with an increase in the joint thickness under the absence of joint injection, considerable amounts (of stress) are added to the maximum principal stresses, minimum principal stresses, dam displacement, and the vertical compressive force between the contact surfaces.

Considering the importance of the performance of buried concrete pipes under external loads and the role played by concrete specifications and pipe thickness in this regard, the current study analyzed the failure rate and response of concrete pipes buried in three types of soil to a TNT blast load using the Lagrangian-Eulerian method in the nonlinear dynamics software LS-DYNA. The results show that the presence of fluid in the pipe generates an internal pressure, which reduces the deformation of the pipe under the blast load. It was also found that the higher the P-crush of the concrete pipe, the smaller the strain and displacement generated under the blast pressure. In thicker pipes, sometimes the damage is limited to the outer sections of the shell, and the pipe remains usable. However, in thinner pipes, damage often affects both inner and outer surfaces of the shell, rendering the pipe unusable. The plastic strain generated in Specimen 1 in Soil Type 1 is 85% higher than the acceptable plastic strain of the concrete pipe. Moreover, this value is 87% for Soil Type 2 and 85% for Soil Type 3.

Fiber reinforced concretes due to their acceptable performance on structural members have been evaluated in many research. Planty of materials have been used in combination with the concrete and caused researcher focused on the concrete compressive strength. In this experimental regard, effects of three types of fibers such as Glass, Carbon and double hook steel on tensile strength, compressive strength and slump of standard concrete samples have been investigated. Four various weight ratios for any of these fibers are used (0.5, 1.0, 1.5 and 2% of cement weight). Analysis is done on the 7 and 28 days of concrete age and a simple concrete sample is existing to compare with fiber concrete samples. Results showed that in all dosage of Glass and Steel, compressive strength is increased but in samples with carbon fibers in 1.5 and 2% is decreased. Tensile strength in all used dosage of fibers is increased. Slump values of all fiber samples are decreased and maximum decrease experienced in glass fiber samples.

In this paper, cost and weight optimization for reinforcement cantilever concrete retaining wall is investigated using intelligent water drops algorithm (IWDA). The algorithm capability was compared with that of others in the literature. A computer program has been developed to analyze reinforced concrete cantilever retaining walls using the IWDA algorithm. The results show that the IWDA algorithm is able to optimize retaining walls from viewpoints of cost and weight. The effect of the wall geometry has been investigated by considering four types of T-shape walls in order to discover the influence of contributing variables on objective functions. It has been found that backfill slope, unit weight and friction angle are important parameters affecting retaining wall cost and weight. Also, the Coulomb method in computing lateral earth pressure on retaining walls leads to lower cost and weight for retaining walls than the Rankine method. In general, optimizing retaining walls may lead to approximately 44 percent saving.

The increasing production of construction waste on the one hand and the use of concrete as a widely used material in the construction industry, on the other hand, has always led researchers to reuse construction waste in concrete. Among the recycled materials that can be used in concrete, we can mention porcelain ceramic and recycled concrete. In the present study, these two types of recycled aggregates (recycled porcelain ceramics and recycled concrete) alone and together in different percentages of 20%, 40%, and 60% are used as the replacement of coarse aggregates in concrete with a strength of more than 50 MPa and high flowability. Slump test, compressive and flexural strength, water absorption, and water penetration tests have been performed on 150 samples made in 10 mixing designs along with an SEM test. The results showed that all the mixing designs had slumps of more than 180 mm. The compressive strength of the control sample averaged 60 MPa and the samples containing recycled aggregates averaged 68 MPa. Also, by combining two types of recycled aggregates, both the 7-day and 28-day strength increased with increasing replacement percentage with a linear trend. The highest increase was 28% for porcelain aggregates and 17% for combined recycled aggregates. In addition, the water penetration rate in the samples containing the combined recycled aggregates showed a significant decrease compared to the control sample. In the SEM test, it was observed that the samples containing the combined aggregates had a thicker and denser matrix.

The use of hybrid fibers in concrete has attracted wide attention in recent years. Using hybrid fibers with different elasticity moduli increases the strength and ductility of fiber reinforced concrete (FRC). In addition, hybrid fibers improve the shear strength of FRC beams significantly. The previous studies have shown that the hybrid use of fibers leads to a phenomenon, called synergy. However, the effect of combining hybrid fibers with stirrups is scantly studied and continues to main unknown. In this study, the effects of stirrups, concrete compressive strength, polypropylene fibers, steel fibers, and their hybrids on the shear strength of FRC beams are investigated. For this purpose, 24 FRC beams were tested in an experimental program. Experimental results show that samples with hybrid fiber have the highest shear performance. Additionally, a new model for simulating these beams' shear strength is presented, using genetic programming technique. The proposed model precisely predicts sample performance. The R2 for this model was 0.868, which is a suitable value due to the complexity of the problem.