International Journal of Civil Engineering
Volume:17 Issue: 8, Ausust 2019

This paper presents experimental and numerical studies on the behavior of concrete filled circular steel tubular (CFCST) members under lateral impact loading. Fourteen CFCST member specimens were designed, fabricated and tested using a Drop Hammer Impact Test Machine in a simple double-supported boundary conditions. The main parameters include the outer diameter of CFCST member, the thickness of steel tube and the height of drop hammer. The failure modes, the impact force, the impact force time history curves and the strain time history curves were investigated to evaluate the behavior of CFCST member under an impact load. A finite element analysis (FEA) model of CFCST member under lateral impact loading was established using ABAQUS software, and the accuracy of the proposed model was verified by a comparison with the test results. The response of the specimen under impact loading simulated by FEA model, matches well with the test results.

Tapered columns could be used either for architectural purposes or for structural needs to accommodate the variation of moments along the height of the column. In highway bridges, tapered columns are usually used to reduce the amount of moments that are transferred from the column base to the foundation. This paper studies slender RC columns with a linear variation in the columns’ cross section in both the principal directions of the cross section. Two slenderness ratios of 70 and 40 have been investigated in this study for RC tapered columns. Computational analysis, using the finite element (FE) method, is conducted in this study after the calibration of the reference FE models with tests that were conducted by other researches in Jenkins (Improving the design of slender, concrete columns. Doctoral dissertation, Purdue University, West Lafayette, 2015). These FE models were extended to account for different degrees of column tapering. The paper found that a minor tapering of the column (where the tapering ratio is greater than 150) is just an esthetic feature and it does not contribute to the buckling load of RC columns. In case of slender columns with a slenderness ratio of 40, the increase in the tapering of the column causes a slight increase in the buckling load of roughly 15%, as compared with non-tapered columns that have the same slenderness ratio. On the other hand, the increase in the buckling load of columns that have a slenderness ratio of 70 is about 45%. Analytical solutions based on the eigenvalue problem have also been presented to estimate the buckling load of a variety of tapering ratios.

This study aims contributing to the investigation about the shear strength of reinforced concrete members with hollow circular cross-section and ordinary concrete strength. First, a proper experimental database of tests carried out in the literature on hollow circular members is collected and analysed. Then, the few existing shear strength models from the literature or seismic codes considered suitable for hollow circular sections are discussed and compared with the experimental results. Starting from the lonely specific degrading model existing in the literature, new equations are proposed on mechanical bases for concrete, transverse reinforcement and axial load contributions to the shear strength and for the shear strength degradation due to increasing ductility demand. The new proposed model is finally validated by means of the collected experimental data. Numerical-versus-experimental comparisons show very good results in terms of predicting capacity of both maximum (not-degraded) and degraded shear strength. The relative percentage prediction error always results lower than 4% with a very limited dispersion. The proposed equations can be thus considered as a reliable improvement of existing shear strength models for the investigated structural typology.

This study presents application of a new methodology to determine the characteristics of nonlinear viscous dampers (NLVDs). It also determines the optimum retrofitting level (ORL), by providing a novel and straightforward formulation without complex calculations. Inter-story drift ratio is considered as the effective parameter to calculate the failure cost of structures and to define limit states. To determine the ORL in low, medium and high-rise steel structures, three benchmark structures with different dynamic characteristics are studied. In addition, to validate the results in different zones with various seismic hazard levels, earthquake records representing three earthquake hazard levels are used in time history analysis. Based on the numerical results from nonlinear time history analyses, this comprehensive design procedure can be efficiently used to make seismic design of steel buildings with NLVDs, thereby meeting structural performance targets for any earthquake record at any intensity. Notably, use of the comprehensive design procedure reduces inter-story drift ratio to less than 0.7 in most building stories, suggesting that the building remains in immediate occupancy state under the applied earthquake records. Further, it can efficiently reduce the life-cycle costs and establish balance between the retrofit costs and failure reduction costs once structural retrofitting is performed.

Urbanization and its further consequences and limitations, especially in arid and semi-arid regions, make societies use practices to return predevelopment conditions. In this study, stormwater runoff is aimed to comprehensively manage as a sustainable resource using the best management practices (BMPs). Potential groundwater recharge from stormwater runoff is subsequently estimated in Isfahan- the third-largest city of Iran, as the study area. To estimate the runoff volume, different watershed’s characteristics were overlaid using the Soil Conservation Service Curve Number (SCS-CN) method in the ArcGIS environment and runoff volume was calculated based on CN classes over the urban area (410 km2) in dry, normal and wet conditions. Then, according to flooding levels in the study area, three of the best management practices (BMPs) were chosen and considered as a source control method to infiltrate the calculated runoff to the zones as their potential recharges. Based on Isfahan Groundwater Model (IGM), the potential recharge volumes determined by BMPs were found to be 2.4, 11.1 and 37.5 million cubic meters per year (MCM/year) for dry, normal and wet years, respectively. These results could be a motivator for decision makers and may also change the attitudes of the managers when the optimal ways for stormwater control are addressed. Thus, it is more reasonable to primarily utilize optimal solutions to control stormwater in especially when water resources are scarce and invaluable.

In this study, a robust three-dimensional finite element (FE) model has been developed for reinforced concrete beams strengthened in shear with near surface mounted (NSM) carbon fibre reinforced polymer (CFRP) rods. The FE models were developed and validated against existing experiments and presented various nonlinear constitutive material laws and interfacial relations. A detailed parametric study was performed to investigate the effects of various parameters on the performance of strengthened member. It was shown that increasing the concrete compressive strength (fc′) from 20 to 50 MPa, leads to an increase in the beam’s ultimate load and contribution of NSM CFRP reinforcement. While for NSM reinforcement ratio (ρf), the ultimate load slightly increased when ρf is 0.14–0.22%, and then increased by 11% in average when ρf increased to 0.28%. Varying the percentage of existing steel stirrups (ρsw) from 0.11 to 0.36%, leads to an increase in ultimate load from 8 to 15% compared to the control un-strengthened specimen. However, the further increase in ρsw (more than 0.36%) caused a reduction in the contribution of NSM CFRP technique because of the changing in the failure mode. The distance between existing steel stirrups and NSM reinforcement does not affect the behaviour. In addition, the model predictions were used to evaluate several design formulas available in the literature for this technique. It was found that some theoretical equations were conservative as long as the governing failure mode is shear.

Despite its importance, little research, has studied schedule reliability from resource management perspective. This paper studies the association between the task–agent relationship and the reliability of project schedule. Four case studies are presented to examine the effect of task–agent relationships. To do so, the tasks are categorized into two groups according to their relationships with agents: single-agent and multi-agent. The groups are then compared in terms of mean lateness, lateness variance, and schedule reliability. To measure the schedule reliability, the formulations are adapted from the production and manufacturing literature to the context of design and construction. The results show that the schedules of single-agent tasks are more reliable than multi-agent tasks. Statistical tests uphold the significance of this difference, especially in design projects, as well as the projects with similar contexts. It is argued that single-agent tasks take advantage of role clarity, autonomy, and KSA (knowledge, skill, abilities) conformity. In addition, in view of promise theory, single-agent tasks are less subject to agents-in-the-middle effect and benefit from locality. The findings are of practical value to consulting firms, especially design team managers who seek to maximize innovation, competency and quality outcome.

This study aims to investigate the influence of construction schemes for non-compensatory composite indicators by multiplicative utility functions on the flood vulnerability assessment. The flood vulnerability outcomes are evaluated and compared for the 231 administrative districts in the Republic of Korea, based on the two composite indicators by different aggregation schemes from the three assessment components such as exposure, sensitivity, and coping, presented in The IPCC Third Assessment Report. The one scheme uses the coping component having a negative functional relationship with vulnerability as a divisor, and the other scheme employs the lack of coping component in the opposite concept to coping as a multiplier. As a result of comparison analysis, some districts show markedly large differences in the flood vulnerability ranking orders by the two different aggregation schemes using the same proxy variables. For robustness of flood vulnerability assessment outcomes, it is necessary to compile a non-compensatory composite indicator under the condition that all constituent assessment components have the same directional elasticity to vulnerability. This study can help to select a proper aggregation framework in constructing flood vulnerability indicators to provide useful information for supporting policy and decision-making on complex issues.

The present study was aimed at identifying driving behaviors and driving skills (i.e., ordinary violations, lack of experience errors, positive behaviors, lack of attention errors, dangerous errors, aggressive violations, perceptual-motor skills, and safety skills) in a large sample of young, middle-aged, and elderly tourists as specific subgroups of drivers based on combinations. Additionally, drivers’ risk-driving behaviors and skill deficits in terms of driving violations and errors, and traffic rule violations and accident involvements as measured by the Driver Behavior Questionnaire and the Driver Skill Inventory were evaluated. To this end, the questionnaires were completed by 681 participant drivers with three age subgroups (age < 30, age 30–40, age > 40), who had traveled to Baneh city in Iran. Based on a cluster analysis of driving behaviors and driving skills variables, five easily understandable drivers’ subgroups were investigated as safe drivers with low self-confidence, unsafe, and offensive drivers, safe, and skillful drivers, unsafe, and relatively unskilled drivers, and unskilled and relatively unsafe drivers. The drivers differed in terms of self-reported accident involvement, attitudes toward traffic safety and risk perception, and driving violations and errors. Finally, based on annual intentional and unintentional accidents and fines, the clusters were ranked. Then, the clusters were evaluated and analyzed statistically. The results indicated that unsafe and offensive cluster is the first unsafe subgroup among clusters. Safe and skillful cluster is classified as the safest subgroup among clusters.

This study experimentally explores the behaviour of recycled aggregate concrete-filled steel tubes (RACFST) subjected to axial compression loading. Twenty-four RACFST specimens were tested to failure. For comparison purpose, tests were also performed on 12 normal concrete-filled steel tube (NCFST) specimens, three steel tubes and one specimen of recycled aggregate concrete. Obtained results showed that the RACFST demonstrates distinct mechanical properties, such as much higher strength, avoiding early buckling of steel and spalling of concrete, in comparison to steel tube and recycled aggregate concrete. This may result from mutually beneficial interaction between the steel tube and concrete. More importantly, in comparison to NCFST, RACFST exhibited marginally lower mechanical properties, similar scatter at peak stress and yet lower degradation after peak stress. Quantitative details of these comparisons are reported in the current paper, providing insightful information on the potential use of RACFST.