Abstract in English:Abstract The severe damage of precast concrete wall structures that have been recorded in the past earthquake has led to the innovation of the rocking wall concept which can demonstrate free or minimum damage aftershock of an earthquake. Furthermore, extensive research works have been well conducted in the past three decades on the establishment of precast rocking wall systems, designs, details, and techniques. Despite this extensive development, little attention has been devoted to investigate the interaction between the rocking wall systems and the flooring diaphragm. The historical perspective on the development of rocking wall systems over the past few decades in the precast concrete structures is presented. Subsequently, the limited research works on the interaction of precast rocking wall to the floor diaphragm are described. Apart from that, this paper attempts to highlight the application of rocking wall systems in the context of precast connection for the precast load-bearing structures. In this contribution, the precast rocking wall-floor connection for precast load-bearing structures is proposed and presented in this paper.
Abstract in English:Abstract A greater number of structures are being built with flat reinforced concrete slabs because they offer several advantages. However, many designers are still unsure about the type of slab that has the best structural performance and which building codes provide the best strength estimates. This study presents nonlinear computer simulations of 16 flat reinforced concrete slabs under symmetrical punching: 4 solid slabs, 4 waffle slabs with wide beams, and 8 waffle slabs with different numbers of ribs supported in the solid area of the slab. Geometric longitudinal reinforcement ratios ranged from 0.45% to 1.97%. The results showed that solid and beamed slabs are more resistant, and normative estimates overestimate their strengths, while the opposite outcome was found for waffle slabs, whose estimates provided in the codes were rather conservative. The most accurate code was EC2, followed by ACI 318 and NBR 6118.
Abstract in English:Abstract To analyze thin and thick plates, the paper presents two rectangular finite elements with high accuracy. In these elements, the proposed formulations of the displacement field utilize the Bergan-Wang approach, which depends only on one variable: the plate lateral deflection. This approach ensures that shear-locking problem will not happen as thickness decreases. The degrees of freedom of the proposed elements are twenty-four for the first element and it is named BWRE24, while the second one has thirty-six degrees of freedom and is named BWRE36. To evidence the efficiency of the two elements, a series of numerical examples for an isotropic plate subjected to various loadings and with different boundary conditions have been analyzed. Very good results are obtained suffering no numerical difficulties in case of very thin plates.
Abstract in English:Abstract The use of near-surface mounted (NSM) Glass fiber reinforced polymer (GFRP) bars is one of the most popular and effective techniques for strengthening reinforced concrete (RC) beams. This paper presents an experimental research program to study the flexural strengthening of RC beams comparing two areas of bottom tensile reinforcing steel and three development lengths of NSM GFRP bars. The beam test results indicated that the beam flexural strength increased up to 110% and 58% for the cases of low and high tensile reinforcing steel ratios, respectively. The effect of the tensile reinforcing steel area on the critical value of the development length of NSM GFRP bars was also investigated. It was found that decreasing the axial stiffness ratio, reduced the strengthening efficiency and the critical development length of the NSM GFRP bars. Finally, a 3D Finite Element (FE) model using ANSYS was constructed and was validated using the experimental results. Good agreement was seen between experimental and FE model results.
Abstract in English:Abstract Excavation of tunnels produces a redistribuition of stresses and induces deformations in the rock mass around the tunnel’s cross section. In the case of elasto-plastic behavior of rock mass, plastic zones may appear. It is important to quantify the influence of this zone on the overall response of the tunnel. In this paper, we deduce a fully analytical solution in terms of displacements and stresses around a circular deep tunnel. The aim here is not to replace a 3D numerical calculation. This kind of analytical calculation are only useful to have a good understanding of the tunnel behavior in the preliminary phases of the project. For example, to perform parametric studies useful to choosing good parameters to introduce in a 3D numerical calculation. A homogeneous and isotropic rock mass is considered. For elasto-plastic behavior, the Tresca’s constitutive model with associate flow rule and Mohr-Coulomb’s constitutive model with non-associate flow rule are considered. For both, the idealized stress-strain curve presents a linear istropic hardening law. A geostatic-hydrostatic state of initial stresses and infinitesimal strains is assumed. The analytical solutions are compared with the FEM solutions demonstrating excellent agreement.
Abstract in English:Abstract A hybrid finite-discrete element method is proposed to model the rock fracture under various loading conditions. The key component of the hybrid method, i.e. transition from continuum to discontinuum through fracture and fragmentation, is introduced in detail. An empirical relationship between the static strengths and the dynamic strengths derived from the dynamic rock fracture experiments is implemented in the hybrid method to model the effect of loading rate. The hybrid method is calibrated by modelling the Brazilian tensile strength (BTS) test, uniaxial compressive strength (UCS) and notched Brazilian dis tests. Then the hybrid method is employed to model the dynamic rock fracture process in UCS and BTS tests. The proposed method has well modelled the dynamic rock fracture and fragmentation processes and captured the effect of loading rate on rock strengths. It is concluded that the hybrid finite-discrete element is a valuable tool to study the dynamic rock fracture as it takes the advantages of the continuum and discontinuum based method, and considers the effect of loading rate.
Abstract in English:Abstract Passenger safety and low fuel consumption rate are the most important factors that need to be considered when designing modern transportations. This study validates the crash behavior and optimum values of foam-filled structures under the dynamic oblique impact using the Weibull distribution. The optimization method aimed to absorb maximum energy with minimum peak crushing force. Furthermore, the metamodel and optimization techniques such as RBF and NSGA-II were used to ensure accurate validation of the Weibull distribution method. The result showed that the finite element model is comparable to the experimental data in the reference, while the metamodel method, which is directly verified, affects optimization results. The Weibull distribution method shows that the optimum value and the simulation have good accuracy or R2> 0.85.
Abstract in English:Abstract Numerical simulation plays a crucial role in today’s aviation industry. Modern computers with the latest commercial FE codes have fueled the triumph of establishing simulation as a prerequisite of aerostructure part design from micro modeling of materials to large-scale structural analysis. In this current research paper, a Mooney-Rivlin material model of ballistic gelatin with Lagrange code is analyzed as a potential candidate for the computational bird model to simulate bird strike case studies. To investigate the practicability, the model is compared with other established Lagrange and SPH EOS models for both rigid and deformable body impacts along with experimental data found in the literature adopting explicit solver Ansys Autodyn. Despite some discrepancies found during rigid body impacts, deformable plate impacts confirm the robustness of the model with significantly faster computation time. Besides, the biggest criticism of the Lagrange model, mesh distortion problem as fluid during bird strike case studies is efficiently tackled by adopting the node erosion algorithm as an effective technique to solve Lagrange bird models without affecting the outcome of the solutions.
Abstract in English:Abstract Intermediate crack (IC) debonding failure is one of the common bending failure forms of fiber-reinforced polymer (FRP)-strengthened reinforced concrete (RC) beams. In this paper, a new prediction model for IC debonding in FRP-strengthened RC beams is proposed based on fracture mechanics and cohesive zone model (CZM), which takes into account the coupling effect of many parameters and has the advantages of high precision and simple expression. The nonlinear behavior of FRP-strengthened RC beams and the influence of flexural cracks are reasonably considered in this model, whereas all existing analytical models based on the CZM neglect this effects. To verify the accuracy of this model, we established a database containing 248 test data from the existing literature. By comparing the differences between the predicted and experimental results, we analyzed the causes of the error and established a semiempirical model. To test the reliability of the model, it is evaluated using the database constructed in this paper together with four representative strength models. The results show that the semiempirical model has a high accuracy.
Abstract in English:Abstract The interaction between water and structure will inevitably lead to the hydrodynamic pressure, which could change the dynamic behavior of the wind turbine tower under earthquake action. Based on the Morison hydrodynamic theory, a simplified calculation method of hydrodynamic pressure was proposed, and the effects of different water depths and hydrodynamic pressure on the seismic behavior of the wind turbine tower is investigated. The main results include: wind turbine tower in deep water is sensitive to water, and the deformation and energy dissipation capacity of the wind turbine tower are decreased affected by the hydrodynamic pressure; the influence of hydrodynamic pressure on the acceleration and displacement is related to the high frequency components of the seismic wave, and the effect of hydrodynamic pressure on the internal force, displacement, and acceleration increases with the increasing of the water depths under different earthquakes. Finally, a shaking table test is carried out, and the experimental results are in good agreement with the calculated results using our proposed method.