Practical Construction Research Articles

Influence of fiber type on the mechanical performance and fracture mechanism of fiber reinforced concrete under coupled static-dynamic compression

As a high-performance building material, fiber-reinforced concrete (FRC) has attracted garnered significant interest in practical engineering construction. However, the effect of coupled static-dynamic loading on the dynamic response of FRC remains far from understood, which seriously limits its wide application. In this study, a series of coupled static-dynamic loading tests are conducted on four types of FRC specimens using the modified split Hopkinson pressure bar (SHPB) system, and the influences of static pre-stress and strain rate on the mechanical performance of FRC under coupled static-dynamic loading are systematically analyzed. The experimental results indicate that static pre-stress generally reduces the dynamic strength and energy dissipation density, but increases the total strength and fragmentation degree of FRC. As the pre-stress ratio increases from 0 to 0.6, the dynamic strength of FRC decreases ranging from 12 to 25 %, and the total strength increases ranging from 12 to 34 %. The failure features of FRC specimens changes from tensile failure mechanism to tensile-shear mixed mechanism with increasing the static pre-stress. Combining the scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) techniques, the microscopic structure and fracture mechanisms of FRC specimens are revealed, and the underlying influencing mechanisms of the static pre-stress, strain rate and fibers are further discussed. The axial pre-stress exerts a dual effect on FRC: enhancement by compacting primary voids as well as attenuation by stimulating secondary microcracks. The strain rate dominates the mechanical performance of FRC under coupled static-dynamic loading, and the influence of pre-stress is diminished by higher strain rates. In addition, the fiber incorporation strengthens the concrete pore structure by bridging action and crack inhibition, resulting in superior mechanical performance compared to normal concrete under coupled static-dynamic loading conditions.

Reinforcing mechanisms review of the graphene oxide on cement composites

Abstract By virtue of the abundant oxygen-functional groups, ultra-high specific surface area and superior mechanical properties, graphene oxide (GO) has been proven as one of the outstanding candidates in cement composites. Compared with the traditional cement pastes, the GO-reinforced cement composites exhibit benefits in pore structure, mechanical properties, and durability. In addition, the abundant oxygen-containing functional groups on GO can promote the hydration rate of cement and combine with hydration products to fill the pores. To further improve the performance of GO-reinforced cement composites and promote the application of composites in practical engineering, it is necessary to comprehensively understand the reinforcing mechanisms of GO on cement composites. In this work, the enhancement mechanisms of GO to improve hydration, nucleation effects, mechanical strengthening mechanisms, antiseepage mechanisms and pore-filling effects of GO are systematically revealed. The optimal dosage range of GO mixing in the current study is calculated by considering the factors of mechanical property and microscopic characterization, but the economic cost also needs to be considered in future development studies. This review will promote the application of the more cost-effective and high-performance GO-reinforced cement composites in practical construction engineering.

Finite Element Analysis of the Structural Behavior of a Corroded Pipe Culvert

The stress analysis of buried pipe culverts is a complex task, and accurately characterizing the deterioration of mechanical properties caused by corrosion poses significant challenges. In this study, the finite element analysis software PLAXIS 3D was employed to construct a numerical simulation model of a pipe culvert. By varying the stiffness and thickness of either the entire structure or specific sections, different degrees of corrosion were simulated to investigate the influence of various cross-sectional shapes on corrosion effects. Multiple experimental controls were set to analyze both the bearing capacity and deformation characteristics under different conditions. The findings reveal that different levels of corrosion have distinct impacts on the deformation behavior of pipe culverts. Overall corrosion has the most significant effect on the overall deformation, while crown and middle corrosion show a similar effect on stiffness-related deformations. In contrast, invert corrosion has minimal impact on the stiffness-related deformation. Corrosion affects circular and elliptical pipe culverts similarly. However, the circular pipe culvert is evidently influenced by overall corrosion more significantly than the elliptical ones due to the combined effects from overall and local corrosion in their deformations. Through finite element numerical simulation, it can be used as a reference for practical engineering design and construction.

END-OF-LIFE CARE: A CRITICAL-REFLEXIVE REVIEW OF HOSPITAL PRACTICES

The objective of this study was to reflect on the principles of autonomy and dignity of the person, relating them to health ethics in hospital practices. The individual has the opportunity to plan their health care in advance through advance directives. In the doctor-patient relationship, this principle is fundamental, replacing the former authority of the doctor with consideration of the patient as an active participant in the treatment process. However, some doctors face difficulties in discussing end-of-life issues due to factors such as personal discomfort, lack of time, insufficient training, limited resources, or the perception that patients may feel uncomfortable. In this sense, we present a theoretical and practical construction of these principles and their benefits in quality of life. Although there is no law regulating advance directives in Brazil, the Federal Council of Medicine published Resolution 1995/2012, which guides advance care planning to facilitate the work of the health team when faced with complex ethical dilemmas from the beginning to the end of life, as the basis for shared care decisions.

Bending Test of Rectangular High-Strength Steel Fiber-Reinforced Concrete-Filled Steel Tubular Beams with Stiffeners

To better understand the bending performance of rectangular high-strength steel fiber-reinforced concrete (HSFRC)-filled steel tubular (HSFRCFST) beams with internal stiffeners, ten beams were subjected to a four-point bending test. The primary considerations were the strength grade of the HSFRC, the steel fiber content, the internal stiffener type, and the circular hole spacing of the perfobond stiffener. The moment–curvature and flexural load–deflection curves were calculated. The mode of failure and the distribution of cracks of the infill HSFRC were observed. The presence of steel fibers greatly improved the bending stiffness and moment capacity of HSFRCFST beams, with the optimal effect happening at a steel fiber content of 1.2% by volume, according to the experimental findings. The type of stiffener influenced the failure modes of the exterior rectangular steel tube, which were unaffected by the compressive strength of the infill HSFRC. On the tension surface of HSFRCFST beams, the crack spacing of the infill HSFRC was virtually identical to the circular hole spacing of perfobond stiffeners. When the circular hole spacing was between two and three times the diameter, the perfobond stiffener worked best with the infill HSFRC. The test beams’ ductility index was greater than 1.16, indicating good ductility. The test beams’ rotational capacities ranged from 6.26 to 13.20, which were greater than 3.0 and met the requirements of the specification. The experimental results demonstrate that a reasonable design of the steel fiber content and the spacing between circular holes of perfobond stiffeners can significantly improve the bending resistance of rectangular HSFRCFST beams. This provides relevant parameter design suggestions for improving the ductility and bearing capacity of steel fiber-reinforced concrete beams in practical construction. Finally, a design formula for the moment capacity of rectangular HSFRCFST beams with stiffeners is presented, which corresponds well with the experimental findings.

Vibration Analysis of the Bow Bridge With and Without the Soil Foundation

Abstract. Earthquakes can impart the phenomenon of resonance, where the frequencies of seismic waves align with a bridge's natural frequency, causing amplification of vibrations that can lead to structural failures. Aiming to accurately predict potential vulnerabilities posed to the bridge when subjected to earthquakes, this research presents a vibration analysis of the Bow Bridge. Two models, which simulate the Bow Bridge with and without soil foundation, are conducted to investigate the bridges natural frequencies and mode shapes under soilless and soiled conditions. The research result shows that the average vibration frequency in a soiled environment is much lower than that in a non-soil environment, intuitively proving the mitigation of soil environment to bridges vibration frequencies. Based on the agreeable data output, this research demonstrates the feasibility of modeling in the prediction of practical construction.

Prioritization of Personal Protective Equipment Plans for Construction Projects Based on an Integrated Analytic Network Process and Fuzzy VIKOR Method

The risk of both fatal accidents and non-fatal injuries in the construction industry is significantly high in most countries. To reduce this construction safety risk, the proper use of personal protective equipment (PPE) is one of the major measures on the jobsite. In this research, in order to comprehensively assess the PPE plans, a three-phase framework was proposed to identify the optimal solution for PPE planning from a set of alternatives. As a result, four main criteria and fifteen sub-criteria were identified based on a systematic literature review, and a decision-making model integrating the analytic network process (ANP) and VIekriterijumsko KOmpromisno Rangiranje was developed. As the assessment information in the survey was incomplete and vague, the fuzzy sets theory was adopted to transform the linguistic terms into fuzzy numbers for evaluation. The model further calculated the weight of each criterion and prioritized the potential PPE plan alternatives. Finally, the presented model was implemented in a case study to verify its feasibility and applicability for practical construction management. The proposed method enables the selection of the most compromising solution as the optimal PPE plan. This research assists decision-makers and safety planners at construction workplaces to improve the overall safety performance and reduce accident risks, which significantly contributes to construction safety management and practice.

Practical Construction and Reflection on the Curriculum Development of Early Childhood Education Programs in Vocational Colleges

As society's demands for the quality of early childhood care services continue to rise, the construction of early childhood education programs in higher vocational colleges has become increasingly crucial. Scientific course design not only affects students' professional skill development but also has a profound impact on the overall advancement of the early childhood care industry. This paper first analyzes the definition and characteristics of early childhood education programs and outlines the theoretical framework for course construction. Next, it provides a detailed discussion of the practical aspects of constructing early childhood education programs in higher vocational colleges, including curriculum design, teaching methods, and evaluation mechanisms, as well as the implementation and management of practical teaching. Finally, based on actual conditions, the paper explores the challenges and issues encountered during the course construction process and proposes suggestions and strategies for improvement.

Practical Verifiable Time-Lock Puzzle: Pre- and Post-Solution Verification

A time-lock puzzle encapsulates a secret message such that the receiver needs to perform a sequential computation, which takes a specified amount of time, to recover the message. Time-lock puzzles can be used in various scenarios, such as sealed-bid auctions, fair contract signing, and so on. The time required to generate a time-lock puzzle and the time needed to solve it are asymmetric, making the verification of a time-lock puzzle crucial. Before solving the puzzle, the solver needs to verify the validity of the puzzle to avoid computing invalid time-lock puzzles. After the puzzle has been solved, it is essential for a third party to confirm the correctness of the solution. This paper proposes a framework for time-lock puzzles, providing both pre-verification and post-verification functionalities, and outlines the security requirements of this framework. Furthermore, we present a practical construction based on iterated squaring in the RSA group and analyze the security of the specific construction. Finally, we implement this construction in Python and demonstrate its efficiency in different settings when implemented in practice.

Construction 4.0 implementation for performance improvement: an innovation management perspective

Purpose The emergence of Construction 4.0 technologies provides an impetus for radical change and rejuvenates the interest of stakeholders in addressing long-standing performance issues in the construction sector. However, construction firms struggle to implement Construction 4.0 technologies for performance measurement and improvement. Therefore, the purpose of this research is to develop a conceptual model of innovation management for implementing Construction 4.0 that guides and facilitates the strategic transformation of construction firms. Design/methodology/approach A conceptual model of innovation management is presented, and the findings are synthesised based on a literature review, 20 semi-structured interviews, two focus group discussions, three workshops, expert consultation and observations on three digitally-enabled projects. Data were inductively analysed using thematic analysis. Findings The analysis of empirical data revealed: (i) Four scenarios that could lead the industry to different futures, based on the extent of research and development, and the extent of integration/collaboration; (ii) Construction 4.0 capability stages for a sustained implementation route; (iii) Possible business model configurations derived from servitisation strategies; and (iv) Skills management challenges for organisations. Research limitations/implications First, the empirical data was only collected in the UK with its unique industry context, which may limit the applicability of the results. Second, most of the research data comes from the private sector, without the views of public sector organisations. Third, the model needs to be further validated with specific data-driven use cases to address productivity and sustainability issues. Practical implications Successful Construction 4.0 transformation requires a concerted effort of stakeholders, including those in the supply chain, technology companies, innovation networks and government. Although a stakeholder’s action would depend on others’ actions, each stakeholder should undertake action that can influence the factors within their control (such as the extent of collaboration and investment) and the outcomes. Originality/value The conceptual model brings together and establishes the relationships between the scenarios, Construction 4.0 capability stages, business models and skills management. It provides the first step that guides the fuzzy front-end of Construction 4.0 implementation, underpins the transformation to the desired future and builds long-term innovation capabilities.

Effects of foundation pit excavation on adjacent metro stations and shield tunnel structures: a study on horizontal displacement

PurposeThe aim of this study is to investigate the horizontal displacement effects of foundation pit excavation on adjacent metro stations and shield tunnel composite structures. It seeks to develop a theoretical calculation method capable of accurately assessing these engineering impacts, aiming to provide practical assistance for engineering applications.Design/methodology/approachThis study introduces a model for shield tunnel segments incorporating rotation and misalignment, considering the constraints of metro stations. It establishes a displacement model for tunnel-station combinations during foundation pit excavation, deriving a formula for calculating station-proximal tunnel horizontal displacements. The method's accuracy is validated against field data from three engineering cases. The research also explores variations in tunnel displacement, inter-ring shear force, misalignment and rotation angle under different spatial relationships between pits, tunnels and stations.FindingsThis study models uneven deformation between stations and tunnels due to bending stiffness and shear constraints. It enhances the misalignment model with station-induced shear effects and introduces coefficients for their mutual interaction. Results show varied responses based on pit-station-tunnel positioning: minimal displacement near pit edges (coefficients around 0.1) and significant effects near pit centers (coefficients from 0.4 to 0.5). “Whip effect” from station constraints affects tunnel displacement, shear force, misalignment and rotation, with fluctuations decreasing with distance from excavation areas.Originality/valueThis study demonstrates significant originality and value. It introduces a novel displacement model for tunnel-station combinations considering station constraints, addressing theoretical calculations of horizontal displacement effects from foundation pit excavation on metro stations and shield tunnel structures. Through validation with field data and parameter studies, the concept of influence coefficients is proposed, offering insights into variations in structural responses under different spatial relationships. This research provides crucial technical support and decision-making guidance for optimizing designs and facilitating practical construction in similar engineering projects.

Numerical analysis of a deep and oversized group excavation: A case study

Group excavations are composed of several individual excavations adjacent to each other with simultaneous or successive construction sequences (CS), which are distinctive from individual excavation in terms of the performance of excavation. In this study, a hyper-scale 3D finite element model was established to investigate the deformation behavior of a diaphragm wall system retaining a deep and oversized group excavation (DOGE) in Shanghai soft clay deposits. The numerical model simulated the practical construction stages and sequences, and it was verified by a series of comparisons with field measurements. Based on the numerical model, the spatial effect of the performance of DOGE in the process of excavation stages was investigated in this study, which cannot be addressed by limited field measurements. Furthermore, the effects of partition walls and CS on the deformation control were discussed to provide practical suggestions for oversized and deep excavations. The results indicate that the employment of bi-partition walls to divide the oversized excavation into several small pits and mono-partition walls and cross walls to further divide the pits near the metro lines into smaller ones, was proved to have significant effectiveness in controlling the wall deflection and protecting the adjacent metro line. For the partition wall, the magnitude and direction of the wall deflection primarily depended on the initial excavation, while the influence of subsequent excavation activities proved insignificant. Thus, it should be noted that the effect of the initial excavation should be especially concentrated. The findings can help optimize similar DOGE engineering.

Thermal conductivity enhancement of epoxy by a 3D Si3N4 crystal rod/grain skeleton fabricating from photovoltaic silicon waste

Silicon nitride (Si3N4) is one of the preferred fillers for the preparation of high thermal conductivity polymer composites because of its intrinsic high thermal conductivity and good electrical insulation. To maximize the thermal conductivity enhancement effect of the fillers in the composites, it is necessary to pre-construct a three-dimensional (3D) thermally conductive filler network. Herein, surfactant foaming was applied to pre-construct a 3D Si-containing framework from photovoltaic silicon waste (PSW), which was subsequently transformed into a porous skeleton consisting of Si3N4 rods and grains by in-situ nitridation reaction sintering. And finally, thermal conductive Si3N4/epoxy (EP) composites were fabricated after infiltrating EP into the network skeleton. When the filler content of Si3N4 was 41.00 vol%, the obtained Si3N4/EP composite showed the highest thermal conductivity of 2.99 W·m-1·K-1, which was 13.95 times higher than that of pure EP. Tests on running CPU and heating table showed that the Si3N4/EP substrate had excellent heat dissipation performance compared to the pure EP substrate. The 3D continuous network formed by "bridging" between two different morphologies of Si3N4 microcrystals contributed to providing effective multi-directional heat transfer paths and thereby improving the thermal conductivity of the composites. Overall, the low cost of raw silicon source originating from industrial waste as well as the simple and practical construction of heat-conducting filler network demonstrate the promising application of the Si3N4/EP composites fabricated in our work.

TBM Advanced Geological Prediction via Ellipsoidal Positioning Velocity Analysis

Traditional seismic wave-based tunnel advanced geological forecasting techniques are primarily designed for drill and blast method construction tunnels. However, given the fast excavation speed and limited prediction space in tunnel boring machine (TBM) construction tunnels, traditional methods have significant technical limitations. This study analyzes the characteristics of different types of TBM construction tunnels and, considering the practical construction conditions, identifies an effective observation system and data acquisition method. To address the challenges in advanced forecasting for TBM construction tunnels, a method of ellipsoid positioning velocity analysis, which takes into account the constraints of three-component data directions, is proposed. Based on the characteristics of the advanced forecasting observation system, this method compares the maximum values on the spatial isochronous ellipsoidal surface to determine the average velocity of the geological layer rays, thereby enabling accurate inversion of the spatial distribution ahead. Utilizing numerical simulation, a model for the advanced detection of typical unfavorable geological formations is established by obtaining the wave field response characteristics of seismic waves in three-dimensional space, and the velocity structure of the model is retrieved through this velocity analysis method. In the engineering example, the fracture property, water content, and weathering degree of the surrounding rock are predicted accurately.

Parameter optimisation of the ventilation system for an underground power space using a hybrid model

The ventilation system is one of the essential safety systems in underground power spaces. Over the years, active ventilation has been widely employed for heat dissipation in underground power spaces. In operation, high-power equipment generates significant heat, necessitating sufficient heat dissipation for smooth and efficient functioning. The effectiveness of the ventilation system is influenced by airflow, making aerodynamics a crucial aspect of studying underground power spaces. This study establishes a comprehensive hybrid model (a combination of physical and data-driven models) representing underground power spaces. Ansys Fluent and MATLAB are used to simulate and calculate temperature fields for various structures. The physical model employs model order reduction to achieve efficient computation without compromising accuracy. For the data-driven model, a genetic neural network is developed for multifactor nonlinear optimisation to evaluate and analyse thermal behaviour within the space. The integrated hybrid model enables efficient and high-precision calculations for the underground power space’s ventilation system. The research outcomes provide a theoretical foundation for practical construction and design schemes of underground power spaces, contributing significantly to ensuring their safety and optimal functionality in real-world applications.

Empirical comparative study of new field-cast foamed cement insulation systems

In practical building construction, simply judging the insulating performance of the material by its thermal conductivity is not fully comprehensive. Therefore, the study used the “four identical tests” to compare the effects of insulation materials on energy consumption and indoor comfort in actual buildings. New field-cast foamed cement and extruded polystyrene plate insulation materials with lower thermal conductivity are used in Test Houses 1 and 2. The test houses' indoor temperature and energy consumption were monitored. Comparison of two Test Houses shows that, during the heating shutdown, Test House 2 daily temperature dropped 0.5 °C more than Test House 1. Conversely, Test House 2 exhibits a 5.97 % higher temperature fluctuation during heating than Test House 1. Under normal and heating conditions, Test House 2 consumes 2.2 kW h and 1.6 kW h less energy on average than Test House 1, with energy fluctuation rates 13.54 % and 9.33 % higher, respectively. Although the energy consumption of Test House 1 experimental room using the new type of field-cast foamed cement is slightly higher, it exhibits better temperature stability during the heating period, significantly improving indoor comfort. Moreover, it demonstrates good energy-saving potential and durability, making it a better choice for building insulation.

Construction and Practice of an Interactive Virtual English Learning Community on Campus Information Platforms

In the context of the information age, campus information platforms have gradually become essential tools for enhancing educational quality. This paper explores the construction and practice pathways of an interactive virtual English learning community based on a campus information platform, aiming to provide students with a more flexible and efficient English learning environment. By analyzing the current development of campus information platforms and interactive learning theories, this paper proposes the design principles and functional modules of the virtual learning community and elaborates on the technical architecture and practical construction pathways of the community. The research results indicate that the interactive virtual English learning community not only effectively enhances students' learning motivation and outcomes but also strongly supports the innovative practice of English education. In the future, with the development of artificial intelligence and big data technologies, virtual learning communities are expected to achieve greater breakthroughs in personalized learning recommendations and intelligent interaction.

Copper-catalyzed intermolecular formal [4 + 1] annulation of 1,5-diynes with benzocyclobutenones

The one-carbon ring expansion of benzocyclobutenones is an efficient methodology for the assembly of cyclic ketones. However, hazardous reagents or noble metal catalysts are frequently required. Herein, we disclose a copper-catalyzed intermolecular formal [4 + 1] annulation of 1,5-diynes with benzocyclobutenones, allowing the practical and atom-economical construction of diverse pyrryl 1-indanones in generally good yields under mild reaction conditions. This reaction represents an important advancement in the ring expansion of benzocyclobutenones via vinyl cation pathway.

An overview of potential excavation compensation method for tunnelling in deep rock engineering

The complicated geological environment of deep rocks poses new challenges to tunnel and mining engineering. Some thorny disasters such as large deformation of soft rock and rockburst are becoming more and more prominent. However, the classic tunnelling methods represented by the mine tunnelling method and the new Austrian tunnelling method are generally unsatisfactory in addressing these issues due to the limited self-stability of surrounding rock mass. Therefore, the excavation compensation method (ECM) with the core of active stress compensation has been proposed and applied in practical engineering construction to solve the above problems. After extensive engineering practice, the theoretical foundation, key technologies, and construction system of ECM have been established and improved. This article provides a comprehensive overview of this novel tunnelling method. In addition, its controlling effects on surrounding rock are demonstrated by two typical engineering examples. It could provide some new ideas and references for the development of future tunnelling technology.

Calculation of foam injection ratio and regulation method of muck compressibility under shield soil chamber pressure conditions

The proper compressibility of shield muck is crucial for ensuring the safety and efficiency of shield tunneling. Foam conditioning is an effective method for improving the compressibility of muck. However, the amount of foam injected in practical construction is mostly based on experience or subjective judgment. A novel foam injection ratio calculation formula was derived based on Boyle’s law and the pore pressure calculation model. This formula comprehensively considers the impact of chamber pressure, pore water, soil gradation, and existing muck conditioning parameters on foam consumption. Starting with the premise that pore foam lifts the soil skeleton, reducing the effective stress in the soil to zero, a method for regulating the compressibility of muck in shield tunnel construction sites was proposed. This method presents the advantage of accurately quantifying the amount of foam injection. Verification results from field applications confirm that optimizing the muck conditioning parameters through this new method leads to improvements in workability, permeability, and muck compressibility, meeting the requirements for efficient shield tunneling. The fluctuation of chamber pressure is reduced, lowering the risk of tool wear. Additionally, there is a reduction of 29.96 % in average total thrust and 29.82 % in cutterhead torque, with a corresponding increase in tunneling speed by 24.42 %. Furthermore, the advantages and limitations of the proposed method were discussed.