Analysis of Laterally Loaded Long or Intermediate Drilled Shafts of Small or Large Diameter in Layered Soil
Strain wedge (SW) model formulation has been used for evaluating the response of a single pile or a group of piles in layered soils to lateral loading. The SW model approach provides appropriate prediction for the behavior of an isolated pile and pile group under lateral static loading in layered soil (sand and/or clay). In this study, the authors extend the capability of the SW model to predict the response of laterally loaded large diameter shafts considering 1) the influence of shaft type on the lateral shaft response; 2) the nonlinear behavior of shaft material and its effect on the soilshaft-interaction; 3) developing partial or complete liquefaction in the surrounding soil profile based on far and near-field induced porewater pressure; and 4) vertical side shear resistance along the shaft wall that has a significant contribution to the lateral shaft response.
Improving the stability of bridge column rebar cages during construction
Rebar cages are the skeletons of reinforced concrete columns formed by connecting the longitudinal to the transverse reinforcement with tie wire connections. The collapse of several bridge rebar cages recently showed the need to establish guidelines to enhance the lateral stability of these temporary structures. The results of experimental and analytical studies on the stability of bridge column rebar cages are presented in this paper. An experimental investigation was conducted on two full-scale rebar cages to determine their lateral behavior and to calibrate nonlinear computational models. Using these calibrated models, the effects of various cage parameters on the lateral stability of rebar cages were investigated. Based on this investigation, it was concluded that the internal bracings provide the significant component of the cage lateral stiffness and strength. Guidelines to improve the lateral stability of column rebar cages are proposed.
THE STEADY STATE OF DEFORMATION
The steady state of deformation for any mass of particles is that state in which the mass is continuously deforming at constant volume, constant normal effective stress, constant shear stress, and constant velocity. The steady state of deformation is achieved only after all particle orientation has reached a statistically steady-state condition and after all particle breakage, if any, is complete, so that the shear stress needed to continue deformation and the velocity of deformation remain constant. The similarities and differences between steady-state deformation and the current use of the term critical state are described. A special undrained triaxial test on a sand is presented to demonstrate clearly that a special flow structure exists during steady-state deformation, which is quite different from the initial structure, and which is credited to a nonrandom, i.e., statistically oriented, arrangement of the sand grains.