Experimental Investigation and Statistical Modeling of FRP Confined RuC Using Response Surface Methodology

Scrap tires that are dumped to landfill is a serious problem in China and rest of the world. The use of rubber in concrete is an effective environmental approach to reduce the amount of scrap tires around the world. However, the loss in compressive strength of concrete is a major drawback of rubberized concrete. In this paper, the fiber reinforced polymer (FRP) confinement technique is used to overcome the drawbacks of rubberized concrete (RuC). A total of sixty six RuC cylinders were tested in axial compression. The cylinders were cast using recycled rubber to replace, a) 0-50 percent fine aggregate volume, b) 0-50 percent coarse aggregate volume, and c) 40-50 percent fine and coarse aggregate volume. Twenty seven cylinders of the latter mix were then confined with one, two and three layers of CFRP jackets. Concrete suffered a substantial reduction in compressive strength up to 80 percent by fine and coarse aggregate replacement with rubber content. However, CFRP jackets recovered and further enhanced the axial compressive strength of RuC up to 600% over unconfined RuC. SEM was performed to investigate the microstructural properties of RuC. Statistical models were developed on the basis of experimental tests for FRP confined RuC cylinders using response surface method. The effect of variable factors; unconfined concrete strength, rubber replacement type and number of FRP layers on confined compressive concrete strength was investigated. The regression analysis was performed to develop the response equations based on quadratic models. The predicted and experimental test results were found in good agreement as the variation between experimental and predicted values were less than 5%. Furthermore, the difference between predicted and adjusted R2 was found to be less than 0.2 which shows the significance of the statistical models. These proposed statistical models can provide a better understanding to design the experiments and the parameters affecting FRP-confined RuC cylinders

Behavior and Strength Predictions for CFRP Confined Rubberized Concrete under Axial Compression

This paper presents experimental versus theoretical comparison of carbon fiber reinforced polymer (CFRP) confined rubberized concrete (a new structural material). A total of sixty six rubberized concrete cylinders were tested in axial compression. The specimens were cast using 0 to 50% rubber replacement. Twenty seven cylinders were then confined with one, two and three layers of CFRP jackets. Axial compression results of the experimental study were compared with the North American and European design guidelines. The results indicate that the addition of rubber content in the concrete leads to premature micro cracking and lateral expansion in concrete. This increased lateral dilation exploited the potential of FRP jackets. The axial compressive strength and strain values for CFRP confined RuC cylinders reached up to unprecedented 600 and 330 percent of unconfined samples. Furthermore, the current international design guidelines developed for conventional concrete confinement failed to predict the compressive strength of rubberized concrete. There is a strong need to re-evaluate the current design codes and their applicability to investigate fiber reinforced confined rubberized concrete. Moreover, the proposed equations in this research can better predict the axial compressive strength of FRP confined RuC

Error management climate and job stress in project-based organizations: an empirical evidence from Pakistani aircraft manufacturing industry

Drawing on the JD-R model, this study examines the influence of error management climate (EMC) on the job stress of frontline aeronautical employees. It also analyzes the moderating role of psychological capital (PsyCap) dimensions (i.e., hope, optimism, self-efficacy, and resilience) for the relationship between error management climate and job stress. The data was collected from 208 individuals through a questionnaire survey and was analyzed using a partial least squares structural equation modeling (PLS-SEM) approach. The results revealed that employees’ perceptions of error management climate have a significant negative impact on job stress. PsyCap optimism and PsyCap self-efficacy were found to have a negative moderating influence on the relationship between EMC and job stress. The other two dimensions of hope and resilience were found to have a moderating influence in the same direction as expected, but not at statistically significant levels. The findings of this study provide a unique perspective in realizing the part national and organizational cultures could play in either enhancing or attenuating the influence of an individual’s psychological resources such as psychological capital

Development of a cost-based design model for spread footings in cohesive soils

The use of cost-effective construction design approaches is an emerging concept in the field of sustainable environments. The design of the foundation for the construction of any infrastructure-related building entails three basic requirements, i.e., serviceability limit state (SLS), ultimate limit state (ULS), and economics. Engineering economy coupled with safety are the two main essentials for a successful construction project. The conventional design approaches are based on hit and trial methods to approach cost-effective design. Additionally, safety requirements are prioritized over the economic aspect of foundation design and do not consider safety requirements and cost simultaneously. This study presents a design approach that considers foundation construction costs while satisfying all the technical requirements of a shallow foundation design. This approach is called an optimization process in which the cost-based isolated foundation design charts were developed based on the field SPT N data. The design charts are the first of their kind for the robust design of foundations and can be used to compare the economic impact of different bearing capacity models. Furthermore, the design framework considers the quantitative impact of the different applied factors of safety values in terms of cost. The results show that Vesic’s equation yields higher values of bearing capacities than Terzaghi and Meyerhof. On the other hand, Vesic’s theory offers a 37.5% reduction in cost as compared to the conventional design approach of the foundation for isolated footing

Prediction of the rubberized concrete behavior: A comparison of gene expression programming and response surface method

The use of rubber in concrete to partially substitute mineral aggregates is an effort to decrease the global amount of scrap tires. This study investigates the behavior of rubberized concrete (RC) with various replacement ratios (0–50%) by volume and replacement type (fine, coarse, and fine-coarse) using soft computing techniques. The uniaxial compressive strength (CS), elastic modulus (EM), and ductility (D) are measured, and the effect of rubber content and the rubber aggregate type on the properties of RC is investigated. Scanning electron microscopy and X-ray diffraction analyses are made to determine its microstructural and chemical composition. This article compares the efficiency of two RC models using a recently developed artificial intelligence technique, i.e., gene expression programming (GEP) and conventional technique, i.e., response surface method (RSM). Statistical models are developed to predict the CS, TS, EM, and D. The mathematical models are validated using determination coefficient (R 2) and adjusted coefficient (R 2adj), and they are found to be significant. Furthermore, both methods (i.e., RSM and GEP) are very well correlated with the experimental data. The GEP is found to be more effective at predicting the experimental test results for RC. The projected methods can be executed for any practical value of RC

Evaluation of Moisture Damage Potential in Hot Mix Asphalt Using Polymeric Aggregate Treatment

To enhance the moisture damage performance of hot mix asphalt (HMA), treating the aggregate surface with a suitable additive was a more convenient approach. In this research, two types of aggregate modifiers were used to study the effect of moisture damage on HMA. Three different aggregate sources were selected based on their abundance of use in HMA. To study the impact of these aggregate modifiers on moisture susceptibility of HMA, the indirect tensile strength test and indirect tensile modulus test were used as the performance tests. Moisture conditioning of specimens was carried out to simulate the effect of moisture on HMA. The prepared samples’ tensile strength ratio (TSR) and stiffness modulus (Sm) results indicated a decrease in the strength of the HMA after moisture conditioning. After treating the aggregate surface with additives, an improvement was seen in dry and wet strength and stiffness. Moreover, an increasing trend was observed for both additives. The correlation between TSR and strength loss reveals a strong correlation (R2 = 0.7219). Also, the two additives indicate increased wettability of asphalt binder over aggregate, thus improving the adhesion between aggregate and asphalt binder

International Journal of Environmental Research and Public Health / Analyzing the Importance of Driver Behavior Criteria Related to Road Safety for Different Driving Cultures

Driver behavior has been considered as the most critical and uncertain criteria in the study of traffic safety issues. Driver behavior identification and categorization by using the Fuzzy Analytic Hierarchy Process (FAHP) can overcome the uncertainty of driver behavior by capturing the ambiguity of driver thinking style. The main goal of this paper is to examine the significant driver behavior criteria that influence traffic safety for different traffic cultures such as Hungary, Turkey, Pakistan and China. The study utilized the FAHP framework to compare and quantify the driver behavior criteria designed on a three-level hierarchical structure. The FAHP procedure computed the weight factors and ranked the significant driver behavior criteria based on pairwise comparisons (PCs) of drivers responses on the Driver Behavior Questionnaire (DBQ). The study results observed “violations” as the most significant driver behavior criteria for level 1 by all nominated regions except Hungary. While for level 2, “aggressive violations” is observed as the most significant driver behavior criteria by all regions except Turkey. Moreover, for level 3, Hungary and Turkey drivers evaluated the “drive with alcohol use” as the most significant driver behavior criteria. While Pakistan and China drivers evaluated the “fail to yield pedestrian” as the most significant driver behavior criteria. Finally, Kendalls agreement test was performed to measure the agreement degree between observed groups for each level in a hierarchical structure. The methodology applied can be easily transferable to other study areas and our results in this study can be helpful for the drivers of each region to focus on highlighted significant driver behavior criteria to reduce fatal and seriously injured traffic accidents.(VLID)486939

Assessment of Significant Factors Affecting Frequent Lane-Changing Related to Road Safety: An Integrated Approach of the AHP–BWM Model

Frequent lane changes cause serious traffic safety concerns for road users. The detection and categorization of significant factors affecting frequent lane changing could help to reduce frequent lane-changing risk. The main objective of this research study is to assess and prioritize the significant factors and sub-factors affecting frequent lane changing designed in a three-level hierarchical structure. As a multi-criteria decision-making methodology (MCDM), this study utilizes the analytic hierarchy process (AHP) combined with the best–worst method (BWM) to compare and quantify the specified factors. To illustrate the applicability of the proposed model, a real-life decision-making problem is considered, prioritizing the most significant factors affecting lane changing based on the driver’s responses on a designated questionnaire survey. The proposed model observed fewer pairwise comparisons (PCs) with more consistent and reliable results than the conventional AHP. For level 1 of the three-level hierarchical structure, the AHP–BWM model results show “traffic characteristics” (0.5148) as the most significant factor affecting frequent lane changing, followed by “human” (0.2134), as second-ranked factor. For level 2, “traffic volume” (0.1771) was observed as the most significant factor, followed by “speed” (0.1521). For level 3, the model results show “average speed” (0.0783) as first-rank factor, followed by the factor “rural” (0.0764), as compared to other specified factors. The proposed integrated approach could help decision-makers to focus on highlighted significant factors affecting frequent lane-changing to improve road safety