Research on seismic resistance of combined system bridge of cable-stayed bridge and irregular arch

The evaluation of the elastic modulus of recycled concrete is one of the focuses of civil engineering and structural engineering, which is not only related to the stability of building structures but also related to the resource utilization of concrete. Therefore, based on the IRSM method in mesoscale, a novel model for predicting the elastic modulus of recycled concrete is proposed which has the advantages of being low-cost and high-precision, amongst others, compared to theoretical and experimental methods. Then, the influence of coarse aggregate, contact surface, gelling material, and air bubbles on the elastic modulus of recycled concrete is studied. The IRSM model includes four processes: Identification, Reconstruction, Simulation, and Monte Carlo, which can accurately reconstruct the geometric characteristics of coarse aggregate, efficiently reconstruct the coarse aggregate accumulation model, and quickly analyze the elastic modulus of concrete, as well as fully consider the nonuniform characteristics of coarse aggregate distribution and shape. Compared with the experimental results, the error is less than 5%, which verifies the rationality of the IRSM method. The results of the parametric analysis show that the influence of each factor on the elastic modulus of concrete in descending order is elastic modulus of cement, elastic modulus of coarse aggregate, content of coarse aggregate, content of air voids, elastic modulus of contacting surface, and thickness of contacting surface, and the corresponding Pearson’s Coefficients are 0.688, 0.427, 0.412, −0.269, 0.188, and −0.061, respectively, in which the content of air voids and thickness of contact surface have a negative effect on the elastic modulus of concrete. These influences mainly affect the deformation resistance (elastic modulus) of concrete through “force chain” adjustment, including the force transfer effect, number of paths, and integrity.

Concrete structures are often in different humidity conditions that have a significant impact on the elastic modulus of concrete, therefore, systematic research on the evolution of the law of concrete elastic modulus under different humidity conditions is needed. In this study, the variation laws of the water saturation of concrete specimens with strength grades C15, C20, and C30 were obtained, and then the influence laws of the water saturation on the concrete axial compressive strength were carried out, and the prediction model of elastic modulus of concrete with respect to water saturation was constructed. The results showed that the water saturation of concrete with strength grades C15, C20, and C30 increased with an extension of immersion time, and the water saturation showed an approximately linear rapid growth within three soaking hours, reaching 47.56%, 71.63%, and 47.29%, respectively. Note, the concrete reached saturation state when the soaking time was 240 h. The axial compressive strength with strength grades C15, C20, and C30 decreased with increased water saturation, and the axial compressive strength of saturated concrete decreased by 27.25%, 21.14%, and 20.76%, respectively, as compared with the dry state concrete. The elastic modulus of concrete with strength grades C15, C20, and C30 increased with increased water saturation, and the elastic modulus of saturated concrete was 1.18, 1.19, and 1.24 times higher than those of dry concrete, respectively.

The elastic modulus of concrete is one of the most important parameters in the analysis and design of concrete structures. However, determining the elastic modulus in civil structures using core-drilled samples is time-consuming and labor-intensive. Additionally, the elastic modulus of Ultra-High Performance Concrete (UHPC) varies significantly depending on its composition. This paper proposes an improved, non-destructive application to identify the elastic modulus of UHPC materials in in-service structures. The elastic modulus is estimated through calibration between a numerical model and experimental UHPC plate vibration test results, using frequency and mode shapes. This calibration involves solving an inverse problem using optimization techniques such as Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Cuckoo Search, and the YUKI algorithm. Updating the plate characteristics is made possible by the development of numerous iterations, where each iteration updates the elastic modulus, thickness, and width values in the term to find the best solution. The highest accuracies compared to experimental data natural frequency values were found in models updated by GA, PSO, YUKI, and Cuckoo algorithms, with errors of 10.77%, 6.58%, 6.87%, and 6.87%, respectively. An experimental sample was tested to determine the elastic modulus of the UHPC, and the proposed application showed a 0.55% error compared to the experimental value. Thus, the estimated elastic modulus value is highly accurate.

Effect of compression casting method on the compressive strength, elastic modulus and microstructure of rubber concrete

Modulus of elasticity of a material is the ratio of applied stress to the corresponding strain within elastic limit. It indicates the resistance of a material to deformation. The elastic modulus of concrete can be calculated using empirical formulae provided by different codes. These formulae are based on the relation between elastic modulus of concrete and characteristic compressive strength. The strength of concrete depends on the proportions and modulus of elasticity of the aggregate. The codes are providing formulae for the determination of elastic modulus of conventional concrete. Replacement of materials in concrete is gaining attention all over the world nowadays. The applicability of these empirical formulae for such concretes are not clear. So, evaluating the elastic modulus of concrete with replacement components become essential. In this experimental study, the modulus of elasticity of plastic aggregate concrete is evaluated. Plastic aggregate concrete refers to the concrete mixed with PET bottle waste as replacement for coarse aggregates on various proportions. 5, 10, 15% of coarse aggregate are replaced with plastic aggregates and elastic modulus is studied.

Introduction. One of the most important characteristics of asphalt concrete that characterizes its properties is the elasticity modulus. The elasticity modulus of asphalt concrete is used in the design of pavement structures to calculate its permissible elastic deflection, under the condition of shear resistance of the working subgrade layer and the layers of non-cohesive materials, as well as bending tensile strength. Problem statement. Today, the calculated value of the elasticity modulus of asphalt concrete is taken in accordance with Handbook No. 2 «Design Characteristics of Asphalt Concrete» [2]. In this Handbook, the calculated value of the elasticity modulus of asphalt concrete is given depending on the bitumen grade, temperature, type of asphalt mixture, and time of load action. Numerical design values of the elasticity modulus of asphalt concrete are provided only for asphalt concrete type B; for other types of asphalt concrete, it is proposed to reduce or increase the design value of the elasticity modulus by the value that depends on the type of asphalt concrete and temperature. Since 2020, a new standard on technical requirements for bitumen has been in force in Ukraine, which brings bitumen grades in line with the European classification [4]. At the same time, in the Handbook No. 2 [2], the calculated value of the elasticity modulus of asphalt concrete is given in accordance with the previous bitumen grades, which necessitates their adjustment.

Deterioration of mode II fracture toughness, compressive strength and elastic modulus of concrete under the environment of acid rain and cyclic wetting-drying

One of the key parameters governing the stresses due to restrained deformation, and thereby the associated risk of cracking, is the elastic modulus of concrete. The early-age evolution of the elastic modulus is intrinsically a function of the development of hydration degree. For concrete subjected to sustained loads, the elastic modulus evolves with creep and relaxation properties. Many design methods use the concept of effective elastic modulus or age-adjusted effective elastic modulus to account for such effects. The challenge with the existing approaches is the lack of in-depth knowledge and reliable test data to accurately determine creep and aging effects for predicting elastic modulus evolution under sustained loading conditions. This paper first provides a brief review of the current approaches to determine the elastic modulus evolution under sustained loading at early age. Second, a method is proposed to directly obtain the age-adjusted effective elastic modulus (Eaaef(t, t0)) evolution experimentally by utilizing an advanced Temperature Stress Testing Machine. Such evolution of Eaaef(t, t0) in a high-performance concrete subjected to a sustained tensile stress of 30% of the 3-day tensile strength is experimentally obtained. The test data are compared with the pure elastic modulus evolution. The creep and aging coefficients are derived based on the newly-measured test data. Differences between obtained early-age creep coefficients and that predicted by existing approaches are comparatively investigated. In addition, on the basis of newly-measured test data and analytical investigations, a convenient approach to determine Eaaef(t, t0) using time-dependent profiles of reduction factors is proposed.

An investigation into age-dependent strength, elastic modulus and deflection of low calcium fly ash concrete for sustainable construction

Coupled effect of coarse aggregate and micro-silica on the relation between strength and elasticity of high performance concrete

Effect of moisture and temperature on the mechanical properties of concrete

In this paper, the simple genetic algorithm (SGA) is improved by combining with the simulated annealing algorithm (SAA) for the parameter identification of a reinforced concrete (RC) frame on elastic foundation. SGA adopts parallel search strategy, which is based on the concept of "survival of the fittest" in optimization while SAA adopts a serial form and the process is endowed with time-variety probable jumping property so that local optimization could be prevented. The global searching ability is developed by combining the two methods and the new algorithm is named genetic annealing hybrid algorithm (GAHA). Modal experiments were carried out on a four-storey RC frame structural model with isolated embedded footings in laboratory. The measured natural frequencies and mode shapes have been utilized to identify the physical parameters of the frame by the proposed method. Four cases of concrete elastic modulus and foundation dynamic shear modulus are identified, and the results are compared with the usual sensitivity methods (SM). By model updating, the results show that the elastic modulus of concrete increases with respect to the storey. The identified elastic modulus of the concrete is generally larger than that found by compressive testing because the dynamic modulus of concrete is larger than the static modulus of concrete. The identified soil dynamic shear modulus also increases with the storey since the soil property depends on the pressure exerted on the soil. It is also shown that the identified results by GAHA are better than that of SM.

Test results obtained on the effect of specimen size and aggregate size on concrete compressive strength and modulus of elasticity are presented. The concrete was prepared using 4.75, 9.5, 19.0, 37.5, and 75-mm nominal maximum size aggregate. Over 600 cylinders were cast and tested for concrete compressive strength and modulus of elasticity. Four different sizes of plastic cylinder molds were used: 150 by 300 mm, 100 by 200 mm, 75 by 150 mm, and 50 by 100 mm. The testing was carried out in accordance with ASTM standards for concrete compressive strength (ASTM 39) and modulus of elasticity (ASTM C 469). The test results were presented in terms of the concrete modulus of elasticity-to-compressive strength ratio (E/f′c) versus cylinder diameter, maximum aggregate size, age at testing, among other factors. The results revealed that a size effect exists. The strength ratio was higher for the larger nominal maximum aggregate size concrete at each testing date. Hence, as the nominal maximum aggregate size decreased, the strength ratio decreased. The strength ratio followed a dished trend with respect to specimen size. For each cylinder size, as the nominal maximum aggregate size increased, the coefficient of variation increased. It was also found that for the same nominal maximum aggregate size specimens, the coefficient of variation increased as the cylinder size decreased.

As a kind of destructive natural disasters, earthquake can cause serious damage to the bridges of lifeline projects, which will bring great difficulties to the rescue and relief work. The bridge structure is complex, and people pay increasingly more attention to the research on its seismic resistance. It is very important for designers and researchers to adopt an appropriate analysis method in seismic resistance analysis. This paper briefly summarizes the hazards caused by earthquakes to long-span bridges, and introduces the calculation principles of response spectrum method and time history analysis in detail. Through the comparative study of the two commonly used seismic resistance analysis methods for bridges, it summarizes the advantages and disadvantages and the application scope of each method, providing reference for selecting suitable design methods for seismic resistance design. Lastly, it describes the future research trends of response spectrum method and time history analysis.

There are differences in each countrys design code for concrete elastic modulus that cause uncertainty in stability analysis of critical buckling load column. This paper investigates the impact of uncertainty on concrete elastic modulus for designing of critical buckling load of building column. The statistical data on materials and applied load being collected in Thailand are used together with an investigation on the uncertainty of the concrete elastic modulus in the design code from 8 countries. Finally the Monte Carlo simulation is used to find out the stability index in term of reliability index. The results show that the uncertainty of the concrete elastic modulus plays an important role in stability analysis and should be considered in the design.