KSCE Journal of Civil Engineering

Conventionally the experimental time-settlement data from an oedometer test are analyzed by standard curve-fitting methods, Casagrande’s log t method and Taylor’s root t method. This allows determination of the end of primary consolidation parameters, (EOP) as well as coefficient of consolidation, cv. Mentioned methods use both the initial and later part of the consolidation curve and are influenced by initial and secondary consolidation effects. In this study, the settlement-time data gathered from conventional oedometer tests conducted on various cohesive soils were analyzed. To assess the validity of each cv value, the experimental results were compared with the theoretical degree of consolidation curve and quantified using the scalar error function. The predictive ability of the Terzaghi consolidation model is also discussed. Based on the comparative study it has been revealed that Casagrande and Taylor methods are insufficient to correctly determine the consolidation parameters.

The macro parameters such as cohesion and internal friction angle are usually measured on experimental test. The macro shear mechanical behaviors are determined by mesoscopic shear mechanical behaviors, which are difficult to be measured accurately on experimental test. This paper aims to study the mesoscopic shear mechanical behaviors of fully weathered coastal red sandstone (FWCRS) such as the force and displacement of rock particles, the force chain network, the microcracks and the coordination number, which can be systematically studied by discrete element software such as Particle Flow Code (PFC). This paper established models characterizing FWCRS with different rock mass stability grades by results obtained on experimental tests, and investigated the differences of their mesoscopic shear mechanical behaviors. The results show that the mesoscopic shear mechanical behaviors of FWCRS can be characterized by performing direct shear simulation and the differences among different rock mass stability grades were also revealed. As the stability increases from grade 1 to grade 5, the shear stiffness increases, the number of microcracks reduces by 48.07%, and there are significant differences in properties of shear band, development of microcrack, the coordination number and the force chain network. The research results can provide reference for the related research such as the evolution of mesoscopic shear mechanical behaviors in the failure process of rock mass in FWCRS and similar strata.

This paper experimentally studied the shear behavior of corroded post-tensioned prestressed concrete beams with full grouting. The effects of insufficient grouting in shear span on the shear behavior were also investigated. Eight beams were fabricated and divided into two groups: four beams with full grouting and four beams with insufficient grouting. Three beams in each group were subjected to accelerated corrosion. All beams were tested to failure in four-point loading. Experimental data on shear cracking, load-deflection response, shear strength and failure modes were presented. Results showed that strand corrosion accelerated the formation and propagation of diagonal crack. Insufficient grouting decreased the number of diagonal cracks. Strand corrosion degraded the post-cracking stiffness and shear strength. Insufficient grouting aggravated the propagation of diagonal crack and the degradation of post-cracking stiffness. The shear strength of corroded beam with 31.7% corrosion loss decreased by 15.44% as compared to that of the uncorroded beam. Strand corrosion loss less than 31.7% did not change the shear compression failure mode in fully grouted beams. The failure modes of locally ungrouted beams changed from shear compression failure to rupture of wires as the corrosion loss exceeded 39.6%.

The aim of this research is to obtain the bending moment and shear live load distribution factors (LLDFs) for interior girders of simply supported slab-girder bridges subjected to continuous loading, such as military tanks. The effective parameters considered in calculating the live load distribution factor were: Girders’ number and spacing, span length, slab thickness and the longitudinal to transverse ratio of deck stiffness. Over fifty 3D finite element models were created based on the existing information of bridges in the USA. An equation was obtained for the distribution factor and its validity was assessed against the numerical results. The proposed equation was compared with the AASHTO-LRFD equation for one lane of standard truck loading and also with the equation proposed by the US army corps of engineers for military vehicles. The accuracy of the equation was also verified by performing several sensitivity analyses for the parameters involved. It is concluded that the proposed LLDF equation predicts the distribution factor more accurately than the above mentioned specifications.

This paper characterizes the applied science issues related to radar-rainfall estimation in the complex mountainous terrain and presents Quantitative Precipitation Estimation (QPE) retrieved from X-band dual-polarization radar measurements. Data collected from the Hydrometeorology Testbed (HMT) in orographic (mountainous) terrain of California are used to develop and test the QPE methodology. Based on retrieved specific differential phase, rainfall estimation was performed using data obtained from the NOAA polarimetric X-band radar and evaluated using observations of the HMT ground instruments, including rain gauges. The results indicate that the technique works well for the limited number of events that are described herein.

Saturated hydraulic conductivity is one of the key parameters in soil physics and hydrological modeling. This study explores the use of Support Vector Machine (SVM) and a nonlinear statistical regression approach for the purpose of predicting the field saturated soil hydraulic conductivity (Kfield) of sandy soil based on basic soil properties of saline and alkaline soil data sets. Considering the significance of soil properties, both methods used the following levels of input soil data, which are easily measurable in the laboratory: hydraulic conductivity, clay/silt ratio, liquid limit, hydro carbonate anions, chloride ions, and calcium carbonate content. The influence of three kernel functions (linear, radial basis and sigmoid) on the performance of the SVM model was investigated. An adaptive genetic algorithm is used to determine the optimal free parameters of the SVM models. The results indicated that the SVM with the RBF model has better accuracy compared to the linear- and sigmoid-based models. The RBF model performed satisfactorily with a modeling efficiency of 0.972 and a correlation coefficient of 0.976. According to all of the performance measures, the different SVM models are a powerful tool and have better performance than statistical regression models. The excellent performance of the SVM with the RBF model demonstrated its potential to function as a useful tool for the indirect estimation of Kfield to assess maximum obtainable prediction accuracy.

This paper presents a case study of using Scan-to-BIM technology for evaluating the quantity and cost of a nuclear power plant during the decommissioning process. The study proposes a process for applying Scan-to-BIM in the dismantling stage and develops a BIM-based VPL (Visual Programming Language) to acquire accurate as-is databases that are crucial for nuclear power plants handling radioactive materials. The proposed process and system were applied to K-1 NPP (Nuclear Power Plant), the first nuclear power plant in Korea, and the results were compared to those obtained using the conventional method. The study found that errors in quantity evaluation using the conventional method ranged from around 10% to over 10 times, and were attributed to various causes such as outdated as-is drawings and limitations in expressing information in drawings. By using the Scan-to-BIM process and system, errors in quantity evaluation were significantly reduced, and the conventional method was found to have underestimated the dismantling cost by 20%. The findings of this study provide important insights for the efficient and accurate decommissioning of nuclear power plants, and demonstrate the effectiveness of the proposed method and system for evaluating the quantity and cost of a nuclear power plant during the decommissioning process.

Clustered studs are suitable for use in prefabricated steel-concrete composite beams. As a kind of shear connector, clustered studs have a non-negligible influence on the mechanical behavior of structures. Based on the theory of elasticity, prefabricated composite beams investigated via laminated plane stress problem. The load-slip curves of the shear connectors are linearly processed, and through iterative calculations, the displacement and stress distribution functions of prefabricated composite beams are obtained. Then, a model test is carried out on the positive bending moment section of prefabricated composite beams. A sampling method with front segments controlled by the load and back segments controlled by the slip is adopted. This method provides a better rate of convergence and higher accuracy than those of other methods. The test results show that when the load is small and the composite beam is in the elastic stage, the slope of the load-slip curve can be used as the shear stiffness of the clustered studs. When the load is large and the composite beam enters the plastic stage, the nonlinear shear stiffness of the studs must be considered to obtain a high-precision solution.