A constructive method is given for obtaining cospectral vertices in undirected graphs, along with an operation that preserves this construction. We prove that the construction yields cospectral vertices, as well as strongly cospectral vertices under additional conditions. Furthermore, we generalize cospectral vertices to the case of the graph Laplacian and provide an analogous construction.
Abstract Precast segmental tunnel linings are structurally vulnerable due to the presence of mechanical joints between segments. However, the lack of detailed design guidelines for these joints has led to limited recognition of the need to evaluate their structural performance. Consequently, most previous studies have focused primarily on the behavior of single segments. Although some research has addressed jointed segments, the majority employed straight-type specimens that fail to capture the actual curvature of tunnel linings. As a result, the influence of joint and segment geometry on the structural response of tunnel linings remains insufficiently quantified, and ultimate failure modes—essential for ultimate limit state design—have not been adequately discussed. To fill this gap, this study conducted full-scale experiments on both single and jointed segments, including arch-type and straight-type geometries. The objective was to examine how segment joints and geometries affect structural responses and to identify the ultimate failure modes of jointed segments. The results revealed that jointed segments exhibited distinct behaviors compared with single segments, governed by joint rotation and local stress concentration. Their response progressed through three stages—bolt contact, joint surface contact, and concrete crushing. The ultimate failure pattern varied with moment direction, with cone-shaped failure developing under sagging, whereas only intrados crushing occurred under hogging. Axial force and geometry influenced stiffness and post-cracking performance, with arch-type segments showing stiffness recovery after cracking and demonstrating superior performance to straight-type segments. These findings contribute to a more comprehensive understanding of tunnel segment behavior.
Systems of building construction. Including fireproof construction, concrete construction
Abstract Research on concrete recycling has led to the discovery of many processes for recycled concrete aggregate (RCA) treatment, each with its pros and cons on quality improvement, resource requirements, or scalability. This study aimed to propose a technique that combines two methods (mechanical grinding and acidic soaking) for mortar removal and improves the quality of RCA so as to realize a zero-waste, highly efficient, few-hours-long single-step process which we call acid milling. A quantitative comparison of aggregate and final concrete quality has been performed between each separate method. The proposed method shows about 57% relative improvement of aggregate quality for water absorption and density, while the concrete experiment shows up to 10% relative improvement for the compressive and flexural strengths compared with the untreated RCA concrete. This study paves the way for an efficient and sustainable concrete recycling process to be applied on a large scale.
Systems of building construction. Including fireproof construction, concrete construction
Ismail B. Mustapha, Muyideen Abdulkareem, Taha M. Jassam
et al.
Abstract Concrete compressive strength is usually determined 28 days after casting via crushing of samples. However, the design strength may not be achieved after this time-consuming and tedious process. While the use of machine learning (ML) and other computational intelligence methods have become increasingly common in recent years, findings from pertinent literatures show that the gradient-boosting ensemble models mostly outperform comparative methods while also allowing interpretable model. Contrary to comparison with other model types that has dominated existing studies, this study centres on a comprehensive comparative analysis of the performance of four widely used gradient-boosting ensemble implementations [namely, gradient-boosting regressor, light gradient-boosting model (LightGBM), extreme gradient boosting (XGBoost), and CatBoost] for estimation of the compressive strength of quaternary blend concrete. Given components of cement, Blast Furnace Slag (GGBS), Fly Ash, water, superplasticizer, coarse aggregate, and fine aggregate in addition to the age of each concrete mixture as input features, the performance of each model based on R 2, RMSE, MAPE and MAE across varying training–test ratios generally show a decreasing trend in model performance as test partition increases. Overall, the test results showed that CatBoost outperformed the other models with R 2, RMSE, MAE and MAPE values of 0.9838, 2.0709, 1.5966 and 0.0629, respectively, with further statistical analysis showing the significance of these results. Although the age of each concrete mixture was found to be the most important input feature for all four boosting models, sensitivity analysis of each model shows that the compressive strength of the mixtures does increase significantly after 100 days. Finally, a comparison of the performance with results from different ML-based methods in pertinent literature further shows the superiority of CatBoost over reported the methods.
Systems of building construction. Including fireproof construction, concrete construction
Irina F. Zenkova, Vladimir A. Sorokin, Irina O. Vinogradova
The article considers the issues of ensuring the implementation of certain areas (types) of activities in the field of fire safety, as well as provides an overview of the current changes in the regulatory legal acts of the Russian Federation governing them, the program of risks prevention of harm (damage) to legally protected values in the implementation of Federal state licensing control (supervision) of activities in the field of fire safety for 2024. The article also contains legislative norms, entering into force not earlier than in 2025, that establish the procedure for qualification confirming of persons engaged in fire safety activities.
Systems of building construction. Including fireproof construction, concrete construction
Abstract In this paper, we present an investigation of the performance of reinforced concrete (RC) columns under combined bending loads and various axial forces using a finite element method (FEM) model developed with the ABAQUS finite element program, verified with actual experimental values. In the experimental study, we applied combined bending loads and various axial forces to four RC members. Two RC members were subjected to vertical cyclic loads using displacement control with 0% axial force, while the other two were tested with vertical cyclic loads, one with 10% axial force, and the other with 20% axial force. The axial force load was applied using a specially designed setup. The experimental results of the RC members include observations of final failure mode, ductility, and axial load–bending moment interaction curves (P–M correlation curves). The experimental study confirmed that as the axial force increased, cracks in the RC columns concentrated at the center of the column. The yield strength increased by 55% when the axial force ratio was 10%, and 106% when the axial force ratio was 20%. The maximum strength increased by 28% with a 10% axial force ratio, and 50% with a 20% axial force ratio. However, ductility tended to decrease as the axial force increased, reducing by 26% with a 10% axial force ratio and 60% with a 20% axial force ratio. The analytical study produced results consistent with the experimental research, showing similar numerical trends. Finally, when comparing theoretical values, experimental results, and analytical results using P–M correlation curves, we found that the experimental value has a safety rate of 18% compared to the theoretical value. The experimental and theoretical result values were similar. Therefore, it has been demonstrated experimentally and analytically that the current design has a safety value of about 18% for the performance of the actual structure.
Systems of building construction. Including fireproof construction, concrete construction
Abstract This paper investigates the progressive collapse potential of eight-story reinforced concrete framed buildings with several atypical structural configurations and compares results with a typical structural configuration. The alternative load path mechanism, the linear-static analysis procedure amplified by dynamic increase factors, and the demand capacity ratio criterion limits from the U.S. General Services Administration guideline were used to evaluate the vulnerability of the different atypical and typical framed structures. Variations in bay size, plan irregularity, and closely spaced columns were used to represent the atypical structural configurations. The extracted demand-capacity ratio (DCR) of the global structural response showed that the demand-capacity ratio for the longitudinal frame with short-span beams had a larger DCR than the transverse frame with longer beam spans with significant potential for progressive collapse. Furthermore, atypical building configurations with closely spaced columns failed by shear and showed the highest DCR limits. In addition to the global structural response, the local member end actions were also evaluated. The evaluation showed that the critical atypical frame configuration with closely spaced columns had a 91% and 127% maximum shear force and support bending moment value difference, respectively, when compared to a baseline typical frame configuration.
Systems of building construction. Including fireproof construction, concrete construction
Motahereh Nasehi Ghashouieh, Mohsen Malekinejad, Mohammad Amiri
Abstract The performance of cement-based materials depends on the characteristics of solid particles at the nano-scale or nanometer porosities in the interfacial transition zone between cement particles and aggregate. Heat significantly affects the properties of these particles and the connection between them. Accordingly, the present study seeks to investigate the effect of nano-silica on the strength parameters of sand–cement mortar at high temperatures. In this regard, the sand–cement mortar was prepared by replacing 5, 10, and 15 percent of cement with nano-silica. The specimens were subjected to temperatures of 25, 100, 200, 400, 600, and 800 °C after curing at the ages of 3, 28, and 90 days. The effect of high temperatures on the physical and mechanical properties of sand–cement mortar was analyzed using macro-structural tests of compressive strength, loss in weight, and water absorption, and microstructural tests of X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that the macro-structural behavior of sand–cement mortar highly depends on the microstructure and changes in cement nanostructures during heat treatment. Primary portlandite and C–S–H nanostructure were destroyed at 600 °C, and alite, belite, and β-wollastonite were formed at 800 °C. Adding nano-silica improved the strength properties of sand–cement mortar against heat, so the compressive strength of 28-day specimens containing 15% nano-silica increased from 13.9 to 19.2 MPa at a temperature of 800 °C.
Systems of building construction. Including fireproof construction, concrete construction
The construction of modified equations is an important step in the backward error analysis of symplectic integrator for Hamiltonian systems. In the context of partial differential equations, the standard construction leads to modified equations with increasingly high frequencies which increase the regularity requirements on the analysis. In this paper, we consider the next order modified equations for the implicit midpoint rule applied to the semilinear wave equation to give a proof-of-concept of a new construction which works directly with the variational principle. We show that a carefully chosen change of coordinates yields a modified system which inherits its analytical properties from the original wave equation. Our method systematically exploits additional degrees of freedom by modifying the symplectic structure and the Hamiltonian together.
Abstract This research proposed the modular prefabricated permanent formwork system made of ultra-high-performance concrete (UHPC). Two kinds of modular formwork shapes were designed: the flat formwork and the ribbed. The experimental investigation on the axial compression performance of the composite columns that consist of the normal strength concrete (NSC) core and the modular UHPC permanent formwork was demonstrated. Compared with the flat formwork, the ribbed formwork exhibited better bonding with the NSC core. As observed from the test results, the composite column with the ribbed formwork presented a similar axial behavior as the NSC column with a slight improvement in ultimate loads. Therefore, the modular UHPC ribbed permanent formwork could be regarded as the additional cover to the conventional NSC column. In addition, the finite element analysis (FEA) model was also developed to simulate the composite columns numerically. The predicted capacities agreed with the experimental results, which validated the numerical models. The crack pattern estimated by the FEA model revealed that the interaction between the permanent formwork and the inner concrete introduced many tiny cracks to the concrete core. However, as protected by the UHPC permanent formwork, the overall durability of the composite columns can still be enhanced.
Systems of building construction. Including fireproof construction, concrete construction
Josep Ramon Lliso-Ferrando, Isabel Gasch, Ana Martínez-Ibernón
et al.
Abstract Chloride-induced rebar corrosion is one of the main causes of damage in reinforced concrete structures (RCS). Chloride attacks lead to depassivation creating pits, which can imply major losses of sections. The current generated at these spots (microcell) is contributed by the current produced between corroded and uncorroded areas (macrocell). The influence of both currents has been deeply investigated based on solution studies, which do not actually represent the behaviour of concrete-embedded elements. The studies about macrocell currents in solution are interesting to analyse this phenomenon quickly and simply. However, they must not be interpreted as the reality of RCS because this requires studies using rebars embedded in concrete. The performed experimental plan verified this fact. In addition, another objective of this study was to analyse the influence of concrete’s electrical resistance and the limiting effect of the cathode/anode surface (Cs/As) ratio on macrocell currents in solution and in concrete. For this study, specimens manufactured using concretes with different properties were used: standard concrete (SC), high-performance concrete (HPC), very high-performance concrete (VHPC) and ultra-high performance-fibre reinforced concrete (UHPFRC). The conclusions show how the Cs/As ratio plays a key role in regulating macrocell current intensity, but what really governs this phenomenon is concrete resistivity because it regulates the participation of a bigger or smaller cathode surface. The influence of this parameter as a limiting factor of macrocell currents is fundamental, especially in high resistivity concretes like VHPC and UHPFRC.
Systems of building construction. Including fireproof construction, concrete construction
Contract review is an essential step in construction projects to prevent potential losses. However, the current methods for reviewing construction contracts lack effectiveness and reliability, leading to time-consuming and error-prone processes. While large language models (LLMs) have shown promise in revolutionizing natural language processing (NLP) tasks, they struggle with domain-specific knowledge and addressing specialized issues. This paper presents a novel approach that leverages LLMs with construction contract knowledge to emulate the process of contract review by human experts. Our tuning-free approach incorporates construction contract domain knowledge to enhance language models for identifying construction contract risks. The use of a natural language when building the domain knowledge base facilitates practical implementation. We evaluated our method on real construction contracts and achieved solid performance. Additionally, we investigated how large language models employ logical thinking during the task and provide insights and recommendations for future research.
Introduction This is the tenth issue of the Journal of Construction Business and Management, a combination of the regular issue and a special issue of selected papers from Construction Business and Project Management CBPM 2021 conference proceedings. This issue contains five blind double peer-reviewed articles by seventeen scholars in Nigeria, South Africa, and Malaysia covering strategic management, environmental pollution, compliance with building standards, dispute resolution, and performance management. Despite the difference in the topics, one of the key issues highlighted by the papers is the emphasis on improving education and awareness in the industry to address the issues identified in the papers. Following this introduction is the discussion of the papers, after which the conclusion follows. Discussion of the papers Compliance with construction regulations, standards and codes is fundamental to improving the key performance indicators, by implication, project performance (Umeokafor et al. 2022). Further, this means that it has implications for project risks. While developed countries still record compliance issues which have resulted in tragic events such as the Grenfell fire incident, the developing ones are not left behind, demonstrated to be worse in many indicators. Opawole, Alao, Yusuf, Adu and Ofoetan (2022) examine one of the major issues in building construction in Nigeria, construction materials-related building collapse. Using survey questionnaires, the authors assess the determinants of compliance with concreting materials standards in building projects in Nigeria, using one of the country's major cities, Lagos, as a case study. Being site-based and non-site based, the factors are in six categories, regulation, procurement, capacity, technical, performance and skills components. Production quality control, non-compliance with specified concrete mix, low concrete grade and supervision by incompetent persons are among the site-based factors. However, non-site-based ones include procurement policies and regulatory frameworks in efficiency and professionalism. It was also found that non-compliance with the national standards results in rework, project delays, additional costs, and environmental issues. To improve the quality of buildings through compliance with concreting materials and reduce or eliminate building collapse, the regulatory policies and enforcement mechanism, competencies and training, and ethical standards of stakeholders require more attention. While the generalisation of the findings is limited to Lagos state, given that it is one of the states with a high volume of construction, the study is, at least, indicative of what happens in major cities in Nigeria, such as Abuja and Port-Harcourt. The second paper, by Rambaruth, Adam and Krishna (2022), on strategic management in construction small and medium enterprises (SMEs), addresses another pertinent issue. SMEs outnumber the large enterprises, the heart of the economies of countries. Yet, they face challenges, which in many cases are different from their large counterparts, for example, limited access to funds and competent persons. Many of these SMEs in construction lack strategic planning, one of the factors for early failure (Rambaruth et al., 2022). Many policies, strategies and studies are informed by large enterprises' views and contexts, overlooking the SMEs. Consequently, the authors examine the determinants of a company's decision to adopt a strategic plan, the role of strategic planning in improving a company's performance, and the challenges associated with a strategic plan in place. Using the eThekwini region of South Africa as a case study, the study found that key factors for strategic management in the construction SMEs examined include increased productivity, the quest to gain competitive advantage and improved decision-making. It was good to find that most of them adopted strategic management practices to improve business performance. The authors conclude that one of the ways of improving strategic management in construction SMEs is through improved education and awareness education and broadened skills curriculum by the government. Government and tertiary institutions can also integrate strategic management into SME training programmes. The need for education and awareness, consistent with the recommendations of Opawole et al. (2022), highlights the need for more attention to education and training in the construction and property industry. Graduate architects are the future of tomorrow in the profession; they are yet to pass the professional examination but hold a master's degree in Architecture. The need to exploit education to improve the construction industry's performance is furthered in the third paper by Tiew, Hashim and Zolkafli (2022). Tiew et al. (2022). investigate the major performance barriers that graduate architects encounter in project implementation. These factors are skills-based, poor project documentation management, lack of soft skills, inadequate quality assessment management, and a shortfall in design management. While it highlights the areas the universities can focus on, adequately integrating them into the curricula is consistent with the recommendations of Opawole et al. (2022) and Rambaruth et al. (2022) in this issue. While education empowers the learners with knowledge, the process may have implications for their health and the environment. Addressing educational issues that have consequences for the environment and students' health is the focus of Nkeleme, Mbamali and Shakantu (2022). The authors measured the number of combustion pollutants generated while learning and teaching in laboratories at one of Nigeria's leading universities (Ahmadu Bello University Zaria) and their effect on indoor air quality. Nkeleme et al. found that the presence of CO during the combustion is above ASHRAE 62 and NAAQS limit of 9ppm reaching up to 45ppm at some points and oxygen at the critical level, 20.9 per cent or below 20.4 per cent. The authors also found that the laboratories are congested, and inadequate ventilation systems exacerbate the discomforting effects of combustion-generated pollutants. Adequate ventilation should be provided, which is one of the paper's recommendations. The students learning environment, including the physical ones, is one of the barriers to learning; it should facilitate and support education (Cleveland and Fisher 2014). Undoubtedly, COVID-19 has socio-economic and health implications globally. However, it has increased attention on technology, mental health and some aspects of risk management in construction. Amoo, Lukman and Musa (2022) is the last paper, focussing on dispute resolution methods in construction during COVID-19, where South Africa is used as a case study. The aim is to determine their appropriateness and effectiveness. The findings demonstrate the negative implication of an interest-based approach rather than the right-based approach to resolving disputes in construction. Further, the study shows that negotiation, mediation, and conciliation were adopted to resolve unforeseen delays, claims, and added costs during the pandemic. The pandemic draws attention to pricing methods as a significant source of dispute in the supply and demand chain network during the period. It highlights the imperativeness of clear language in contracts, risk management training, communication improvement, and dynamic project schedule documentation as some conflict and dispute resolution tools post-COVID. Conclusion This issue which contains five papers from seventeen scholars in Nigeria, South Africa, and Malaysia, covers strategic management, environmental pollution, compliance with building standards, dispute resolution, and performance management. While the findings vary, one consistent key finding or implication of this is the need for education and training to improve the construction industry's performance. This is in terms of performance improvement skills of graduate architects, risk management training for those with contract and risk management responsibilities, integrating strategic management education in curricula, and building materials standard compliance training. We thank the authors for their contributions and the reviewers for their efforts to improve the quality of the papers published by the journal. The journal editorial board and panel of reviewers also play a critical part in the higher quality assurance of the manuscript and in keeping the journal on the path to attaining the expected standard and quality. Criticisms, feedback, and suggestions from readers on improving the journal's quality are also welcome. References Amoo, O. T., Lukman, Y. and Musa, N., 2022. Dispute Resolution Mathods adopted by Contractors during Covid-19 in Eastern Cape, South Africa: A Case Study. Journal of Construction Business and Management, 5(2): 54-67. Cleveland, B. and Fisher, K., 2014. The evaluation of physical learning environments: a critical review of the literature. Learning Environ Res, 17:1–28 Nkeleme, E. I., Mbamali, I. and Shakantu, W. M. I., 2022. A Measure of Combustion-Generated Pollutants in University Laboratories and its Effects on Indoor Air Quality. Journal of Construction Business and Management, 5(2): 44-53. Opawole, A., Alao, O. O., Yusuf, A. O., Adu, E. T. and Ofoetan, M. A., 2022. Evaluation of Compliance of Concreting Materials to Standards in Building Projects in Lagos State, Nigeria. Journal of Construction Business and Management, 5(2): 1-19. Rambaruth, A., Adam, J. K. and Krishna, S. B. N., 2022. Elements and Issues to Strategic Management in the Construction Industry Among Small and Medium Enterprises: A Case Study in South Africa’s eThekwini Region. Journal of Construction Business and Management, 5(2): 20-28. Tiew, S. Y., Hashim, H. A. and Zolkafli, U. K. B., 2022. Performance Barriers affecting Graduate Archite
Dmitry S. Adamov, Irina F. Zenkova, Natalia O. Shchegoleva
et al.
Annual monitoring of the effectiveness of licensing activities in the field of fire safety allows not only to evaluate the work done in this area, but also to identify existing problematic issues in this area and suggest possible solutions.
Systems of building construction. Including fireproof construction, concrete construction
This paper introduces a new systematic algorithm for constructing periodic Euclidean weaving diagrams with combinatorial arguments. It is shown that such a weaving diagram can be considered as a specific type of four-regular periodic planar tiling with over or under information at each vertex. Therefore, a weaving diagram can be constructed using two sets of cycles, one to build a tiling, and a second to define the crossing information. However, this construction method does not guarantee the uniqueness of the diagram, so we define the notion of equivalence classes of weaving diagrams using the concept of crossing-matrices. Finally, we present a classification of our periodic structures according to the minimum number of crossings on a unit cell.