International Journal of Civil Engineering最新文献

Buckling restrained braces (BRBs) enhance energy dissipation and ductility considerably by preventing the buckling of steel braces under cyclic loads during earthquakes and, thus, the strength degradation caused by buckling. This paper introduces and discusses the development of BRBs made with an elastomer known as phase change material (PCM), which has superior ductility and faster-filling properties than commonly used mortar while being approximately 50% lighter. BRBs filled with PCM have high ductility and good energy dissipation. To verify the seismic performance of the PCM BRB, axial brace tests and subframe tests were conducted. Using PCM as the filler in the axial tests ensured a stable tension and compression ratio (below 1.5), as recommended by the AISC provisions, and the core material fully withstood axial loads for six cycles beyond 1.5delta_bm. Global buckling occurred after 2.0delta_bm under compression, at which point the experiment was terminated.

This study experimentally investigated the behavior of reinforced recycled aggregate concrete (RAC) beams under monotonic and cyclic loadings to identify the advantages and shortcomings of RAC in reinforced concrete beams. Five RAC specimens and one normal aggregate concrete (NAC) specimen were tested to failure. The concrete compositions of RAC and NAC were similar; however, the coarse aggregate of RAC was recycled coarse aggregate, while that of NAC was normal stone coarse aggregate. Results indicated similarities in the failure modes of RAC and NAC beams. Compared with NAC beams, the yield and ultimate load-carrying capacities of RAC beams were only 2.6% and 8.9% lower, respectively. The cyclic loading effect negligibly induced strength degradation but decreased ductility by 9.1%. However, the yield deflection and yield stiffness of RAC beams were 22.9% higher and 30% lower than those of NAC beams, revealing their shortcomings. The above results emphasized the potential use of RAC in structural members by addressing the high deformation characteristic of RAC (e.g., modifying the concrete composition to increase the compressive strength of RAC). The nonlinear analytical method of NAC beams, in which the fiber model and the finite element method were finally combined, can be used for RAC beam analysis with acceptable accuracy.

The complex mechanical behaviours of steeply inclined and layered surrounding rock in strong and active fault zones result in control measures that cannot adapt to asymmetric squeezing tunnel and are still unsolved. Hence, the Yuntunbao Tunnel was taken as an example to study this issue based on geological survey and indoor and outdoor tests. The results showed that strong geological structures and abundant groundwater undoubtedly deteriorate the mechanical properties of rocks containing many water-sensitive minerals, approximately 45%. The stepwise growth of deformation characteristics before reaching the rock peak strength and the gradient to abrupt failure characteristics after reaching the rock peak strength are determined via triaxial cyclic and static load tests. According to field test results, the unilateral squeezing deformation is severe and greater than 1.5 m, the average extent of the excavation loosening zone is approximately 10 m, and the highest deformation rate reaches 12 cm/d. The gradual and sudden changes in tunnel deformation are demonstrated to be consistent with the postpeak deformation characteristics of layered rock in indoor tests. Moreover, the steel arch exhibits composite failure characteristics of bending and torsion. Finally, reliable and practical controlling measures are suggested, including the optimised three-bench excavation method with reserved core soil, advanced parallel pilot tunnel, long and short rock bolts, and large lock-foot anchor pipe. Compared with tunnel deformation before taking measures, the maximum convergence deformation is reduced from 2.7 to 0.9 m, and the bearing force of the primary support is also reasonable and stable.

This study aimed to evaluate the mechanical properties and PTFE (Polytetrafluoroethylene) coated membrane strength reduction coefficients of the original cable-membrane connection of a double-layer orthogonal cable-membrane structure. First, two kinds of membrane connections applicable to the double-layer orthogonal cable-membrane structure were introduced. Subsequently, considering the influence of the membrane configuration, 36 loading specimens were designed to carry out tensile experiments on the cable-membrane connection. By examining the experimental results, the failure mechanism of the connections was revealed. The connection failure loads at different membrane angles and configurations were tested, and the corresponding load—displacement curves were obtained. Furthermore, the factors affecting the connection mechanical properties were analysed, and the relationship between membrane stress and strain was deduced. Finally, the membrane strength reduction coefficient corresponding to the proposed connections was calculated, and the suggested value was given to provide a basis for designers applying the connection. The results show that the mechanical properties of the connection are affected by a variety of factors, including the membrane angle, membrane configuration, connection method, and material properties. The reduction factors of the different connections are as follows: the clamping connection factor is 0.35, the biting connection membrane with long ridges and short ridges is 0.25, and the biting connection without reinforcement membranes is 0.2.

Cohesive soil, as soil lumps within the sand matrix of the Gangetic alluvial plain, exerts a significant influence on the dynamic properties of sand deposits, as extensively documented in prior research. This study aimed to describe the intricacies of microstructural changes and re-distribution of pore sizes resulting from the effects of loading and wetting. To gain a comprehensive understanding, microstructural characterization of Indo-Gangetic alluvial soil was performed using two advanced analytical techniques, mercury intrusion porosimetry and scanning electron microscopy. The collapse behavior of Sone river sand samples mixed with varying proportions of soil lumps was studied using a series of oedometer test. A decrease in the collapse potential (CP) trend was observed with each increase in the sand percentage. The CPs were estimated as 16.39% and 10.07% for alluvial sand containing 70% and 40% collapsible lumps, respectively. The micrographs and differentiation in pore morphology were used to describe the microstructural evolution of lump-sand mixture due to saturation and loading. This study highlights the pivotal role played by the collapsible soil lumps within the sand matrix. Initially, these lumps possess an open structure, characterized by cementation bonds that interconnect clay-coated silts and sand aggregates. However, these cemented bonds are susceptible to disintegration under the influences of loading and wetting, ultimately triggering collapse in the soil matrix. After the collapse, soil particle re-arrangement occurs, and the initial open structure in soil lumps transforms into a dense structure. Microstructural change is dependent on stress levels. With increasing stress levels, higher inter-aggregate pores or macro-pores evolve into small sized intra-aggregate pores or micro-pores. This study contributes to the literature by providing both qualitative and quantitative insights into soil collapse and valuable guidelines for comprehending the intricate microstructural alterations that occur within alluvial sand containing these unique lumps.

A fundamental requirement for analysing timber structures under fire is to consider the degradation of material properties with temperature. Therefore, the objective of this study is to propose a model that accounts for the variation of the thermo-physical properties, the development of char, and its evolution with temperature. This model integrates a sequential coupling of heat transfer analysis with structural response. The degradation of the material properties is accounted for through the regulatory approach recommended in Eurocode 5. The stress analysis employs an elasto-plastic model with nonlinear isotropic hardening. Implementation of the model is achieved within the Abaqus suite of finite element software using external subroutines. The model's predictions align well with experimental data, accurately reproducing both thermal and structural responses. Specifically, the model accurately predicts temperature profiles, displacements, and the depth of the charred layer, which initiates above 300 °C. Additionally, for rectangular sections, it was observed that exposure of all faces to fire results in a non-rectangular residual section. Furthermore, employing the temperature-dependent thermal property curves suggested by EC5 yields satisfactory results when predicting the fire resistance of softwood timber structures.

The pavement texture wavelength and mean texture depth (MTD) of the pavement macrotexture significantly affect functional performance. However, owing to its higher correlation with the wavelength, the Exposed Aggregate Concrete Pavement (EACP) texture was evaluated based on the MTD and exposed aggregate number (EAN) in the same location. The MTD contributes significantly to road surface friction and tire-pavement noise and is vital for anti-sliding and noise reduction. Conventional methods for MTD measurement require considerable human effort when the sample size is large and sensitive to the operator. Furthermore, it is time-consuming to measure the MTD together with the EAN. Recently, image-based estimation has become a new trend, owing to its economy and convenience. Therefore, this study aimed to estimate the MTD of the EACP pavement surface texture at an image-based level as an alternative measurement approach simultaneously within the EAN location. Initially, the image acquisition was created based on aerial photography. Subsequently, photogrammetry was used to reconstruct a high-resolution point cloud of the pavement texture. Subsequently, the MTD was estimated analytically from image-based point clouds. Experiments were conducted at over 60 locations in three field tests of the EACP in South Korea. The MTD results showed good agreement and a higher correlation between the image-based and sand-patch test (SPT) methods. The image-based method showed results higher than the SPT with a value of 22%. Therefore, the developed method can be used to estimate the MTD using the established regression equation.

In this paper, the aim is to discuss the applicability of polyethylene terephthalate fiber-reinforced polymer (PET FRP) in DSTC structures. PET FRP can improve the strength and stability of structures by providing constraints for concrete. Herein, experimental and response surface analyses of the axial compressive properties of PET FRP–concrete–steel double-skin tubular stub columns (DSTCs) based on 26 DSTC specimens subjected to axial compression testing are presented. The height of each DSTC specimen is 600 mm, the outer diameter is between 305 and 315 mm, and the thickness of the added concrete is 43 mm. The main parameters are the number of layers on the PET FRP, the compressive strength of the concrete, and the thicknesses of the steel tubes. The experimental results show that the ultimate load and ultimate axial strain can be significantly increased by increasing the number of PET FRP layers, reaching 27.34% and 28.79%, respectively. When the compressive strength of the concrete increases from C30 to C40, the ultimate load and ultimate axial strain values of the DSTCs increase by 12.54% and 8.99%, respectively. In addition, as the thickness of the steel tube increases from 6 to 8 mm, the ultimate load and ultimate axial strain increase by 34.95% and 118.90%, respectively. These results indicate that the introduction of PET FRP significantly improves the overall performance of DSTCs. Increasing the number of PET FRP layers helps to limit the circumferential strain of DSTCs. P6-S8-C40 has the best ultimate load-bearing capacity and ultimate axial strain capacity, which reach 3356.18 kN and 0.1992, respectively. The main purpose of this paper is to study the influences of the PET FRP thickness (in different layers), steel tube thickness, and concrete strength on the properties, damage mode and damage process of DSTCs.

This paper presents an innovative method to include creep deformations in the prediction of time to corrosion-induced cover cracking. Using experimental results, creep and cracking criteria used in this method are verified. It is argued in the paper that the cover cracking problem under corrosion is close to a relaxation problem and the conventional creep formulations based on the effective elastic modulus cannot be adopted. It is found in the paper that accurate consideration of creep deformation would lead to about 30–40% longer time to cover cracking when compared to no consideration of creep deformations whilst for the currently practiced methods, the time can be up to 200% longer, which is unconservative in predicting time to cover cracking. Results in this paper open the debate on modelling of creep in the analysis of corrosion-affected structures and serve as an important step towards the accurate prediction of corrosion-induced concrete cracking.

Improving driving behaviour can be a fruitful intervention to improve traffic safety. This paper proposes a method to determine a driving behaviour score (DBS) for each driver based on their driving history. For this purpose, a fuzzy inference system (FIS) was used to calculate DBS for every driver between 0 and 1. The input variables for this model are the frequency and severity of previous crashes, near-crash situations, and aberrant driving behaviours. The calculated DBS can then be applied in implementing usage-based insurance schemes. The proposed method is used for a case study in Kerman (Iran). For this purpose, 40 young drivers were recruited in an experiment to record their previous history of crashes, aberrant driving behaviours, as well as surrogate safety measures while driving on a specific route. According to the results, DBQ is a useful indicator to measure a driver's level of safe driving style since it considers the history of crashes, near-crash incidents and dangerous driving behaviours. In this study, DBQ was primarily affected by the frequency of previous crashes. In Iran, drivers with dangerous driving behaviours pay the same insurance premium as those with relatively safer driving habits. Due to the disregard of a complete driving history, the insurance premiums determination process is not fair. According to this paper, usage-based insurance pricing can become fair and dependent upon a driver's behaviour by using DBQ.