Journal of engineering and construction management

Abstract This study investigates the effect of foundation flexibility on the lateral force distribution of moment frames and shear walls. This distribution has been represented in terms of shear-moment ratio that are developed in columns, and normalized by the fix base shear and total first story moments, respectively. Four nonlinear moment resisting frames, in different heights including 5-story, 10-story, 15-story and 20-story, with nonlinear shear wall are considered, and nonlinear static analysis are performed in the fixed and flexible bases by Opensees. BNWF approach has been employed to account foundation flexibility due to soil structure interaction. Footings are modeled as beam column elements, and soil foundation interface is modeled by closely spaced, independent nonlinear spring elements. Based on the obtained results in this study, for all the investigated frames the normalized shears and moments in the first story in flexible condition are higher than the fixed base, meaning that the greatest effect due to foundation flexibility is related to forces corresponding to the first story. Foundation flexibility reduces the shear wall's stiffness and therefore, lower forces are carried out by the wall. As a result, the extra forces are developed in frames elements.

Abstract Masonry buildings constructed with stone and lime have historically served as vital components of architectural heritage across diverse cultures and regions. The durability, sustainability, and aesthetic qualities of these structures are intrinsically linked to the materials and techniques employed in their construction. However, many of these buildings face challenges posed by environmental factors, seismic activity, and deterioration due to age. This research aims to provide a comprehensive overview of contemporary methods for improving masonry buildings made with stone and lime. It highlights the significance of integrating both traditional and innovative techniques to enhance structural integrity, energy efficiency, and longevity while preserving historical value. The study examines methods such as the use of lime-cement mortars, natural hydraulic lime, and fiber-reinforced composites, as well as advanced analytical techniques for assessing structural performance. Through a synthesis of scientific literature and empirical studies, this work aims to elucidate the multifaceted approaches available for the preservation and enhancement of stone and lime masonry buildings, ultimately contributing to the discourse on sustainable construction practices and heritage conservation. The findings are expected to inform practitioners, researchers, and policymakers engaged in the restoration and rehabilitation of historic masonry, ensuring that these structures continue to endure for future generations.

Abstract Impulse waves are among the natural phenomena that are caused by the impact or transfer of energy from a mass to still water. These waves are widely observed in nature and engineering environments and have multiple effects on the surrounding structures and environments. Masses’ sliding into still water is one of the common situations in creating impulse waves that can occur in different scenarios, such as floods, landslides or sudden entry of materials into water. In recent years, many researches have been conducted in this field, each of which has investigated specific aspects of this phenomenon. The importance of studying impulse waves, especially in the fields of marine engineering and environmental protection, is clearly visible. These waves can cause serious damage to marine structures and aquatic ecosystems, and for this reason, a more accurate understanding of their characteristics and behavior can be effective in better design and more appropriate management of these environments. This article was written with the aim of providing a comprehensive framework for future research in this field. Presenting a comprehensive review of the studies conducted in the field of impulse waves caused by the sliding of masses into still water. In this regard, the results of various tests, data analysis and comparison of the results will be discussed.

Abstract The unsafe behavior of workers is one of the management problems in construction projects, which leads to the reduction of safety performance and the creation of accidents, and then to the reduction of the productivity of construction projects. The main goal of the current research was to provide a structural model to investigate unsafe behaviors and then their impact on the safety performance and productivity of the construction industry. In order to achieve this main goal, unsafe behaviors and factors affecting them were identified through the research background and then classified, and then a theoretical model of the relationship between latent variables was created. According to the results of the research, the identified variables have been classified into 6 main groups: behavior of workers and executive teams, safety performance, productivity of construction projects, knowledge, skill and experience of managers, infrastructure problems and safe conditions of the Construction workshop. The relationship between each of the research variables was also investigated and analyzed and validated through structural equation modeling in PLS software. Also, according to the general findings of the research, safety behaviors of workers and executive teams, safety performance and then project productivity are factors that affect each other and their simultaneous effect should be combined with other research variables such as the knowledge, skills and experience of managers and Investigate infrastructure problems. Managers' lack of experience in management decisions in the safety sector is effective on the safety behaviors of workers on the site and can have direct and indirect effects on causing accidents and reducing safety performance in the project. On the other hand, the creation of safety problems can lead to stoppages or long-term delays and other problems in construction projects, the effects of which should be investigated indirectly and totally in this research.

Abstract The effects of the foundation flexibility on Structural drift has been considered in concrete moment resisting frames in this paper. The foundation flexibility influences the total base shear reaction and its distribution directly. To analysis the base shear measurement, the near-field earthquakes were used as lateral external forces. In this study three concrete moment resisting frames 7, 10 and 15 story with 22.2m, 31.8m and 41.8m height were investigate that their bays are 5.5m in all of cases. To model the flexible foundation, Beam Nonlinear Winkler Foundation (BNWF) method was used. In this method, linear inelastic springs were used in vertical and horizontal directions. After base shear measurement, the structural drifts of concrete moment resisting frames have been compared in the case of flexible and fix-based foundation. The distribution of shear base pattern and drift values in fix-based foundation are totally different from flexible-based. The difference is observed in all height level structures.

Abstract Schedule pressure is caused by various factors in construction projects, and the role of human resources performance in improving or increasing this pressure is very important and decisive. In this article, the structural equation modeling method was used to investigate the effect of program pressure on the performance of human resources working at the site of construction projects. In order to achieve this main goal, the effective variables were first identified and referenced through the research background and experts' opinion in the initial questionnaire. Also, the reliability and validity of the questionnaire created by the researcher were checked and confirmed according to Cronbach's alpha coefficient and confirmatory factor analysis. In the next stage, the theoretical model of the research is drawn and after collecting information in the case study of the research (two Ofoq engineering companies in Tehran and the Energy Industry Design and Engineering Company (EIED), civil and architecture department), a structural model for the relationship between the latent variables with each other and also The relationship between obvious and latent variables was drawn and then validated. The findings of the research were drawn in the form of 6 latent variables, schedule pressure, human resources performance, safety atmosphere and culture, training and awareness of human resources, rework and managers' decisions.As a result, indirect and total relationships as well as correlation between research hypotheses were compared and analyzed. According to the findings, the total and indirect relationships of the structural equation model have many differences with the results of the research hypotheses that have been obtained through the bootstrap test.

Abstract In recent years, metakaolin is used in concrete to improve the short-term and long-term properties of concrete. Considering the importance of compressive strength and bonding between concrete and rebar in reinforced concrete structures, a new method for evaluating bonding strength between concrete and reinforcement is presented in this research. Also, the optimal percentage of metakaolin along with steel fibers has been determined in order to achieve maximum bonding and compressive strength. In this research, 20 different mixing designs with four different percentages of metakaolin (0%, 10%, 15% and 20%) and five different percentages of steel fibers (0%, 0.75%, 1%, 1.5% and 2%) were considered and slump test on fresh concrete and compressive strength and bonding strength tests on 28-day samples were conducted. The results showed that the new method presented for measuring the bonding strength between concrete and rebar is very practical. Also, minor addition of metakaolin and steel fibers significantly reduced the compressive strength, and by increasing the percentage of fibers, the compressive strength was increased and then decreased. Also, adding metakaolin up to 15% significantly increased the bonding strength of concrete, but by increasing the amount of metakaolin up to 20%, bonding strength of concrete was decreased. On the other hand, both metakaolin and steel fiber reduced the flowability of fresh concrete. Finally, the sample containing 15% metakaolin and 1.5% steel fibers showed the highest bonding strength.

Abstract Recent studies indicate that recycled concrete aggregates (RCA) can achieve mechanical properties comparable to those of conventional aggregates, thereby facilitating their use in structural applications without compromising safety or durability. For instance, research has demonstrated that the incorporation of larger aggregates in large particle 3D concrete printing methods can significantly reduce the volume of cement required, thus contributing to lower environmental impact while maintaining structural integrity. Additionally, the utilization of supplementary cementitious materials has been shown to improve the bonding characteristics and overall performance of recycled aggregate concrete.
The review further elucidates the role of innovative recycling techniques and smart materials in augmenting the effectiveness of recycled aggregates within 3D printing processes. These advancements not only enhance the quality of the recycled materials but also promote their acceptance within the industry. Moreover, the discussion extends to the implications of regulatory frameworks and public perception, which play critical roles in influencing the widespread adoption of sustainable construction practices.
In conclusion, this literature review presents a comprehensive analysis of the current state of research on recycled aggregates in 3DCP technology, highlighting both the challenges and the significant potential for their integration in promoting sustainability within the construction sector. It concludes with insights into future trends and the necessity for ongoing research to optimize the use of recycled aggregates, positioning them as a key component in the evolution of environmentally responsible building practices. As the industry moves forward, the continued exploration of the interplay between recycled materials and advanced construction technologies will be vital in shaping a more sustainable future for concrete production and construction methodologies.

Abstract The effects of Soil-Structure Interaction and base flexibility on reduction of base shear has been investigated using BNWF method in this article. Investigating the effects of soil-structure interaction on the seismic behavior of the structure is depended on the soil stiffness, foundation and structure rigidity in a way that increasing or decreasing any of them will affect the base shear directly. The effects of fixed or flexible soil and foundation in changing the base shear has been investigated in this article separately. In this article three concrete moment resisting frames 7,10 and 15 story with 22.2m, 31.8m and 41.8m are investigate that their bay is 5.5m in all of cases. In these models, first the main period, then shear base are calculated. Considering to the period of the structures, the shear base decrease in every model. But the rates of reduction are different. With increasese of base flexibility the rate of reduction of shear base increasesd. To model the flexible foundation, Beam Nonlilear Winkler Foundation (BNWF) method is used. In this method, linear inelastic springs were used in vertical and horizontal directions. In addition, inelastic base with sliding allowed is used to increase the flexibility effect of foundation and to maximaxe the soil-structure interaction effect.

Abstract The phenomenon of impulse waves caused by soil mass sliding into water is one of the important issues in geotechnical and hydrodynamic engineering, which can have destructive consequences on the environment and coastal structures. These waves are widely observed in nature and engineering environments and have multiple effects on the surrounding structures and environments. These waves are caused by the sudden entry of the soil mass into the water, and their investigation is of great importance, especially using numerical methods. In this study, a comprehensive review of the numerical researches conducted in the field of impulse waves caused by landslides is presented. This article examines different numerical models, key parameters affecting wave generation and validation of numerical results compared to experimental data. Also, the challenges in the numerical simulation of this phenomenon and the proposed solutions to improve the accuracy of the modeling have been investigated. The results of this study can help to improve the understanding of this phenomenon and develop new simulation methods.

Abstract This study, firstly, gives a summary about natural ventilation and particle dispersion, and, then, presents the research reported so far in these areas. As well as these, the research methodology, the sub-grid scale model equations used in the simulation, namely, Wall-Adapting Local Eddy-viscosity (WALE), Standard Smagorinsky-Lilly Model (SSLM) and Dynamic Smagorinsky-Lilly Model (DSLM), computational domain and other requisite conditions for the simulation have been illustrated. In order to ensure of the validity of the present results, direct comparisons with available experimental results have been made. These results show that the sub-grid scale WALE model is more accurate than the other models in the simulation of the particle dispersion in a model building with natural ventilation, and SSLM sub-grid scale model estimates the least particle concentration in the building. In addition, these results illustrate that the convective flux and turbulent diffusion flux have the key role in the pollutant transportation process around the entrance of model building. Also, the influence of convective flux is more than that of diffusion flux as one moves along the length of the model building.

Abstract The purpose of this research was to identify the effective indicators in conducting "value engineering" studies in the projects of the worn-out urban fabric of North East Investment Company. For this purpose, previous studies used to identify indicators. Feebly researchers introduced 36 indicators as the main effective factors in value engineering studies. The panel of experts of this research were 20 experts from people involved, active or related to the subject of value engineering studies of Northeast Investment Company. The present study identified and prioritized value-engineering indicators in urban dilapidated fabric projects using the fuzzy Delphi model. To carry out this research, a document study used to identify the value engineering indicators in the urban dilapidated fabric projects and the fuzzy Delphi technique used to prioritize the identified indicators. The survey conducted in three stages and the results of each stage were refined. The panel of research experts included the experts of North East Investment Company. Data collection was done using the fuzzy Delphi method and by sending questionnaires in three stages. To achieve the goals of the research; First, with library studies, value engineering indicators identified in dilapidated urban fabric projects, and then by using the fuzzy Delphi method in three stages and asking for opinions through a five-point Likert scale questionnaire from 20 experts of dilapidated urban fabric projects. 36 items that got a sufficient score in the experts' consensus were determined and then the identified value engineering indicators prioritized using the opinion of experts and based on the fuzzy Delphi method.