![]() ![]() With R-LRFD, the gain in the robustness, as reflected by the reduction in the sensitivity of the system response to the recognized but unquantified uncertainty of input parameters, is accompanied by an increase in cost. SAFETY FACTOR FOR SPOT PIER FOOTINGS FULLUnlike the reliability-based design (RBD), the user is not required to conduct a full statistical characterization of uncertain parameters. In R-LRFD, the robustness of the system response against the variation in uncertain parameters is explicitly considered. This modified RGD approach is termed R-LRFD, which stands for Robust Load and Resistance Factor Design. The recently developed reliability-based robust geotechnical design (RGD) approach is modified such that it can be integrated with the standard LRFD approach. This paper presents a novel approach for applying existing LRFD codes, with explicit consideration of design robustness, safety, and cost efficiency. However, even with LRFD, the need to reduce the variation in the predicted performance of a geotechnical system (or a geotechnical structure), referred to herein as the system response under applied loads, is still apparent. LRFD (Load and Resistance Factor Design) is becoming a design method of choice in geotechnical practice, in lieu of the factor of safety (FS)-based design approach. It is found that the design value method used to determine partial factors by FORM does not appropriately give either the partial factors or the failure probability for the case of shallow foundation design where the performance function is highly non-linear and some of the basic variables follow distributions that are far from the normal distribution. Finally, partial factors obtained using calculations based on the two bearing capacity equations are carefully reviewed. It is found that FORM gives a considerably lower failure probability than MCS. The first-order reliability method (FORM) and Monte Carlo simulations (MCS) are employed to determine and compare the 100-year failure probabilities of the shallow foundations designed. ![]() The seismic forces determined from the peaks over threshold analysis and fitted to a general Pareto distribution have been considered. The uncertainties involved in the bearing capacity equations are investigated through a comprehensive literature review. The designs obtained, using calculations based on the bearing capacity equations by Meyerhof and by Brinch Hansen as modified by Vesic, are compared. Some example cases are chosen based on a database which includes detailed information of 1869 actually constructed highway bridge pier shallow foundations in one fiscal year in Japan. This is when helicals are also used to correct compromised foundations.Partial safety factors for square footings for highway bridges resting on granular soils have been determined based on reliability analyses. Once foundations are exposed to moisture over a long period of time or construction is sited on unstable soil, structural and foundation damage becomes visible. Helical Piers and Piles are needed for numerous new and existing residential, commercial, and industrial applications and may be used when the job specifies caissons, driven piles, or micro piles. This minimizes installation time, requires little soil disturbance, and most importantly transfers the weight of the structure to load bearing soil. Instead of requiring large excavation work, they thread into the ground. Due to their design and ease to install, they are most commonly used whenever soil conditions prevent standard foundation solutions, but are starting to be used as a more cost/time effective alternative on many project. Helical piers, also known as anchors, piles or screwpiles, are deep foundation solutions used to secure new or repair existing foundations. ![]()
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