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To explore the supporting performance of oblique piles (OPs) used in pit excavation, a field test was performed at a foundation excavation using OPs with various inclination angles. Then, numerical models using the finite-element method were established and validated on the basis of the field test result. A novel arrangement of oblique‒vertical alternating piles (OVAPs) was proposed as the retaining structure for excavation. The displacements of the pile top, internal forces of the pile body, earth pressures on the pile body, and soil deformation were observed and studied. The results indicated that both pile inclinations and arrangements had an effect on the supporting performance of oblique piles. Furthermore, four effects were summarized to explain the advantages and working mechanisms of OP and OVAP arrangements used in retaining structures. Finally, a force analysis of oblique supporting piles in the foundation pit was conducted and a simplified formula was derived and applied to calculate the bending moments of pile bodies under different working conditions. [ABSTRACT FROM AUTHOR]

Tunneling in urban environments is challenging due to the number of pipelines to cross, which may adversely impact the pipelines due to tunneling-induced ground settlement. An adequate vertical separation distance between the bottom of the pipeline and tunnel crown is not always possible, and a minimum volume loss may be difficult to achieve due to subsurface conditions encountered and tunneling methods available. Therefore, the impact to the existing pipelines from tunneling needs to be assessed to mitigate the risk. Considering gap formation beneath the existing pipeline explicitly and a limiting overburden loading acting on the pipeline, this study proposes a design-oriented analytical approach to estimate the upper bound of the maximum bending moment of the pipeline induced by tunneling. A dimensionless quantity, namely, the overburden loading factor defined as the ratio of overburden loading and the minimum required loading to eliminate the gap, is introduced to evaluate the extent of gapping, by which gap formation can be predicted. The effect of pipe-soil interaction, which reduces the maximum bending moment in the pipeline, is considered by conducting nonlinear Winkler-based finite element analyses with varying stiffness factors. The design chart and table are presented to provide a more accurate estimation of the maximum bending moment, especially for greater stiffness factors. It is demonstrated for small overburden loading and stiffness factors, i.e., wider gaps, a perpendicular crossing may not always be the worst-case scenario. As illustrated by the partially supported beam model, the effect of the increase in the unsupported span is greater than the effect of the reduction of the curvature of the settlement trough for these cases. Design examples are provided to demonstrate the analytical procedure step-by-step, and a comparison with previous studies is made. It is demonstrated with reasonable conservatism for small to moderate stiffness factors, the proposed design-oriented analytical approach can straightforwardly predict the maximum bending moment in pipelines. It is common to cross beneath an existing buried pipeline in the proximity for any tunneling project in urban areas due to the restrictions of underground space, soil conditions, right-of-way, and construction costs, etc. Considering gap formation beneath and an ultimate overburden loading on the existing pipeline, this study can be used to estimate the maximum bending moment in the existing pipeline due to ground settlement induced by tunneling, especially in the preliminary stage when the soil information is unavailable. The analytical procedure can be easily implemented by hand calculation or a spreadsheet, and more accurate results can be found with the aid of a chart and table provided when the soil information is available. The results obtained can assist the tunnel practitioners to determine an adequate separation distance, intersection angle, and an appropriate tunneling method to minimize the impact to the existing pipeline. Three detailed design examples are provided in the Appendix to illustrate the procedure step-by-step. [ABSTRACT FROM AUTHOR]

Design methods for corrugated steel culverts in current design standards consider the circumferential force in culvert walls (i.e., hoop thrust) to be the dominant load-carrying mechanism in these structures. However, recent studies have shown that bending moment, rather than thrust, is often the more dominant response for corrugated steel culverts under shallow burial conditions and vehicle loading. In addition, 2D finite element analyses have historically been unable to effectively capture the effects of discrete surface loads, such as wheel loads, on the response of buried metal culverts. To investigate these issues, the bending moment and thrust responses from an experiment involving an elliptical corrugated steel culvert under shallow burial conditions and simulated vehicle loading are compared with the bending moment and thrust estimates from the Canadian bridge design code and CANDE-2019 (a commonly used public domain finite element software package) and the thrust estimates from the American AASHTO LRFD bridge design code (which does not consider moment directly). The comparisons show that the Canadian code and CANDE-2019 models with a fine mesh and the continuous load scaling elasticity-based method appear to be the most effective for the investigated culvert and loading, while there is a need to modify the American AASHTO LRFD code to consider moment more directly. In addition, the results suggest that, under these conditions, the current approaches for estimating the peak bending moment response are more effective compared with the approaches for estimating the peak thrust response. [ABSTRACT FROM AUTHOR]

This paper presents the derivation and validation of a mechanics-based finite element for the analysis of shear-critical slender reinforced concrete beams and columns. The element can capture the load-deformation behavior associated with axial loads, bending moments, and shear in uncracked or cracked reinforced concrete using only a small number of degrees of freedom and easily measurable input parameters: the gross cross-section dimensions and steel and concrete material stress/strain curves. The element is specifically derived to represent the full reinforced concrete cross section (i.e., one element is required over the depth of a member) and consists of four nodes, with two translational degrees of freedom (DOFs) per node. This formulation facilitates modeling the interface regions between walls or joint regions, beams, or columns and lowers the numerical complexity and number of decisions that the user must make. The element shows improvements to results from design codes when validated against experimental results for 782 beams without shear reinforcement and 167 beams with shear reinforcement taken from the literature. By reducing the number of degrees of freedom, the element will allow relatively rapid two-dimensional (2D) nonlinear analyses of full reinforced concrete buildings. [ABSTRACT FROM AUTHOR]

The inherent variability of soil parameters noticeably influences geotechnical structures such as piled-raft foundations. In this research the application of random fields is extended to a stochastic analysis of a piled-raft foundation embedded into an elastoplastic soil a problem that is known as complicated soil-structure interaction. For this purpose a stochastic framework is developed using a random finite-element method (RFEM) by coupling the random field theory and a finite-element-based program coded in MATLAB to model the stochastic plane strain piled-raft foundation behavior. The analysis is performed deterministically and then extended to the stochastic context to consider the spatial variability of Young's modulus friction angle cohesion and unit weight of the soil media. The stochastic responses of the piled-raft foundation such as displacement axial force bending moment and shear force are assessed. The stochastic analysis shows that implementation of the uncertainties of soil parameters leads to more influence on the raft differential settlement compared to the other responses. Variation of the horizontal and vertical correlation length has a more considerable effect on the coefficient of variation (COV) of the bored piles' responses compared to those of the raft. Based on the COV of the piles and raft load contribution it is demonstrated that the heterogeneity of the soil has more influence on the raft. Furthermore it is found in all realizations that the main percentage of the load is carried by the bored piles. [ABSTRACT FROM AUTHOR]

The damage to pipelines from submarine landslides or debris flows has been vastly reported. In this paper, the behavior of pipelines is investigated through analytical and numerical analyses. A refined analytical method is first brought forward by improving the tension assumption. The pipeline is divided into different segments based on loading conditions, and the continuity of displacement, inclination angle, bending moment, and shear are all preserved. Then numerical analysis by vector-form intrinsic FEM is carried out by further considering the axial soil resistance at the sliding zone. The numerical analysis demonstrates that the initial negative pipeline displacement is a threat to pipeline safety because of the large increase in bending moment. The axial tension is closely related to the location of the landslide impact and the initial pipeline configuration. The variations in displacement and tension with time are also investigated in the parametric analysis. [ABSTRACT FROM AUTHOR]

Three-dimensional finite element analyses were performed to study the behavior of piles in sloping ground under undrained lateral loading conditions. Piles of different diameter and length in sloping cohesive soils of different undrained shear strength and several ground slopes were considered. Based on the results of the finite element analyses, analytical formulations are derived for the ultimate load per unit length and the initial stiffness of hyperbolic p-y curves. New p-y criteria for static loading of piles in clay are proposed, which take into account the inclination of the slope and the adhesion of the pile-slope interface. These curves are used through a commercial subgrade reaction computer code to parametrically analyze the effect of slope inclination and pile adhesion on lateral displacements and bending moments. To validate the proposed p-y curves, a number of well documented lateral load tests are analyzed. Remarkable agreement is obtained between predicted and measured responses for a wide range of soil undrained shear strength and pile diameter, length, and stiffness. [ABSTRACT FROM AUTHOR]

A family of interaction expressions are developed for steel elliptical hollow sections (EHSs) subjected to combinations of axial force, biaxial bending moments, torsion, and bimoments. The formulation is based on kinematically admissible strain fields within the context of the upper bound theorem of plasticity. The interaction relations derived successfully capture the effect of confining radial strains present at welded end sections, as well as sections that are free to deform in the radial direction away from end welded sections. The interaction expressions developed consist of a set of elliptical integrals which are cast in a dimensionless form applicable for EHS of general geometries. An iterative solution technique is developed to solve the resulting nonlinear relations. The applicability of the resulting interaction relations for conducting the cross-sectional check is illustrated through examples. A comparison with shell finite-element analysis results illustrates the validity of the interaction relations derived. [ABSTRACT FROM AUTHOR]

This paper presents a study on the strength and behavior of cold-formed steel Z-sections with simple and complex stiffeners subjected to major axis bending. The study involved both experimental and numerical investigations, in which a series of specimens were examined. All specimens were failed by the combined mode of shear and moment. The results from the investigations were analyzed and compared with the combined moment and shear strengths predicted by international design rules. The suitability of the design rules in predicting the combined capacity of Z-section with complex stiffeners was assessed through a reliability analysis. [ABSTRACT FROM AUTHOR]