Civil Engineering Dimension (E-Journal)
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Evaluation of Crack Initiation Points of Load-Carrying Cruciform Welded Joints Based on Effective Notch Stress Approach
Get PDFFor fatigue assessment, recently effective notch stress (ENS) approach is accepted as a valid alternative to fracture mechanics approaches in Japan. However, at least one study showed that the fatigue assessment at weld root of load-carrying cruciform welded joints based on ENS approach does not capture the influence of plate thickness, weld size and weld penetration. Consequently, there are still uncertainties about the fatigue assessment. This paper discusses the evaluation method of the joints based on ENS approach. Effects of weld size, weld penetration, and plate thickness on ENS are determined by using fine-meshed FEM analyses. Validity of this method is determined by comparing the evaluation results with fracture mechanics approach. It is shown that results from this method are comparable to those of the previous study and the results seem to be conservative when ratio of weld penetration to plate thickness becomes smaller and plate thickness becomes larger
Analyses of Steel Bridge Circular Columns using Fiber Model considering Local Buckling
Get PDFOne of the most concerned problems for analytical estimation of ultimate strength and ductility of steel bridge columns is the consideration of local buckling. Stress-strain curves with softening behavior to include local buckling in fiber model analysis method were proposed by several researchers. However, accuracy of those models is still relatively low. As a consequence, most steel bridge designs have been done using fiber model analysis method without consideration of local buckling. In order to improve the analytical response estimation of steel bridge columns, a fiber model analysis method considering local buckling is proposed in this study. In this method, multi-fiber elements were used to model the local buckling length to simulate local buckling deformation. The proposed method shows good results not only for estimating peak strength but also post-peak strength compared to previous experimental results. However, further research should be directed to improve the accuracy of the deformation modes
Effect of Rigidity of Plinth Beam on Soil Interaction of Modeled Building Frame Supported on Pile Groups
Get PDFThis paper presents the effect of rigidity of plinth beam on a model building frame supported by pile groups embedded in cohesionless soil (sand) through the results of static vertical load tests. The effect of rigidity of plinth beam on displacements and rotation at the column base and also shears and bending moments in the building frame were investigated. In the analytical model, soil nonlinearity in the axial direction is characterized by nonlinear vertical springs along the length of the pile (t-z curves) and at the tip of the pile (Q-z curves) while in the lateral direction by the p-y curves. Results revealed that, shear force and bending moment values which were back calculated from the experimental results, showed considerable reduction with the reduction of the rigidity of the plinth beam. The response of the frame from the experimental results is in good agreement with that obtained by the nonlinear finite element analysis
Experimental Investigation of the Effects of Reverse Bending and Straightening Process on Carbon Steel Bars used for Civil Engineering Applications
Get PDFThis paper presents an experimental investigation of the effects of reverse bending and straightening process on the mechanical properties of a typical carbon steel bar used for civil engineering applications. Twenty four specimens each were used for the metallogarphy, microhardness and tensile tests. The investigation revealed that the reverse bending and straightening process has no significant effect on the bars’ through-thickness microstructure and hardness. However, the reverse bending and straightening process reduces the yield load, ultimate load, and displacement at fracture of the bars by 4.27%, 2.58%, and 18.62% respectively. These results highlight the need to take into consideration the effects of the previous loading history of the bars/wires, particularly the reduction in the displacement at fracture and consequently, the ductility of the bars/wires in the design and fitness for purpose assessment of components made from them, since the bars/wires could experience high strain during installation and in service due to overloads
An Evaluation of Factors Predisposing Building Elements to Variation in Nigeria
Get PDFThe construction industry has been consistently criticized for poor performance in attaining clients’ requirements. The study, thus, assessed the factors predisposing building elements to variation with a view to providing cost-design information that enhance construction project delivery, that is, on-time completion of project within budget. The building elements considered in this study include substructure, frame, upper floors, and roof. Data were collected using well-structured questionnaires administered on professionals in consulting firms, contracting firms, and client organizations in Lagos metropolis. Data analysis was done using descriptive and inferential statistics. The results of the analysis revealed nine factors through factor analysis that predispose substructure to variation, seven factors predispose frame, six factors predispose upper floors, and seven factors predispose roofs to variation during construction process in Nigeria
Corrosion of Steel Reinforcements in Fly Ash- and Kaolin-based Geopolymer Concrete Immersed in Distilled Water and ASTM Seawater
Get PDFCorrosion behavior of steel bar in fly ash- and kaolin-based geopolymer concrete immersed in aggressive media of distilled water and ASTM seawater was compared to Portland cement concrete having similar mix design. An accelerated corrosion by applying 3 V potential on the steel bar was performed to obtain reasonable test results in a relatively short time. The potential and pH of the immersing media were measured from day 1 to day 10 and then plotted on Pourbaix diagram to predict passivation or corrosion state. At day 10, steel bar in Portland cement concrete were in corroded state both in distilled water and seawater. The best corrosion performance was for kaolin- based geopolymer concrete in which at day-10 the steel bar was passivated in both media. Steel bar in fly ash- based geopolymer concrete was passivated in distilled water but corroded in seawater
Torsional Strength Prediction of RC Hybrid Deep T-Beam with an Opening using Softened Truss Model
Get PDFThis paper presents an analytical study to predict the torsional behavior of reinforced concrete (RC) hybrid deep T-beam with opening and to compare to the experimental results. The RC hybrid deep T-beam was cast with normal weight concrete web and light weight concrete flanges. Based on the Softened Truss Model and Bredt’s theory, a new equation was derived and proposed to show the relationship between compression strut of light weight concrete and normal weight concrete. Based on the experimental results of cracking angles and curvature equation of light weight concrete and normal weight concrete, a new equation was also proposed to show the relationship between strain diagram of light weight concrete and normal weight concrete. The analytical results show that the prediction of maximum torque capacity of the beams are close to the experimental results, except the prediction of twist angle which are larger than the experimental results
Effect of Coarse Aggregate Sizes and Replacement Levels on the Strength of Palm Kernel Shell (PKS) Concrete
Get PDFThe maximum coarse aggregate size used in concrete can impact on its strength. An investigation of the effect of coarse aggregate size and replacement level of granite with palm kernel shell (PKS) on the compressive and tensile strengths of PKS concrete were investigated. Mix proportion by weight of 1:1½:2 with w/c of 0.50 were used. All samples were tested at 7 and up to 90 days. Results showed that both compressive and splitting tensile strengths increased with increase in aggregate sizes. Both strengths however decreased with increase in replacement levels of granite with PKS. Optimum replacement level of granite with PKS was 25% with compressive and tensile strengths of 22.97 N/mm2 and 1.89 N/mm2 respectively at maximum coarse aggregate size of 20 mm. However, at 50% PKS content, which results in lightweight concrete, compressive strength was 18.13 N/mm2 which is above the minimum value of 17 MPa for lightweight concrete
The Effects of Water Content Variation on Adhesion Factor of Pile Foundation in Expansive Soil
Get PDFSeasonal change causes variations in soil moisture content. On expansive soil, this condition influences soil moisture content in the active zone, which is approximately in five meters depth. The water content variation induces the changes in soil characteristics and these changes have an impact to adhesion factor of piles. The main objective of this research is to investigate the influence of water content variations on adhesion factor of piles. A series of laboratory experiments were conducted considering water content variations. A pile model made of concrete was penetrated to soil sample which was placed in a cylindrical tube of diameter about 15 times the diameter of the pile model. The pile model was loaded until failure to investigate the friction capacity. The results showed that the change of water content have great impact to adhesion factor of piles and its friction capacity decreased up to eight times from drying to wetting condition
Seismic Behavior of Fatigue-Retrofitted Steel Frame Piers
Get PDFFatigue retrofit works have been conducted on severely fatigue damaged beam-to-column connections of existing steel frame bridge piers in Japan. It is clear that retrofit works provides additional stiffness but the significance on the seismic behavior of steel frame piers is not clear. Since fatigue retrofit works have become prevalent, the effect of fatigue retrofit works on the seismic behavior of steel frame piers need to be understood. The objective of this study is therefore to investigate these effects of the retrofit work, especially installation of bolted splices, which is the most common technique. Elasto-plastic finite element earthquake response analyses were carried out. It is shown that the existence of bolted splices may increase seismic demand on the piers when plastic hinge zone is located on the beam. In addition, longer bolted splices using low yield strength steel are proposed to overcome this problem and are shown to give beneficial effects