This study presents methods for establishing allowable stresses in steel, concrete, and timber piles using load/resistance factor concepts. These methods take into account not only the material properties of the pile itself but also the individual effects of long term loads, driving stresses and drivability, imperfections in form or material and various environmental conditions which tend to reduce pile capacity. Using the results of the study, changes in Section 4, Division 1 of the AASHTO Standard Specifications for Highway Bridges, are proposed. The study is limited to the design of the pile as a structural member.

Load transfer data are presented for six piles embedded in sand. The data were adjusted to account for residual loads caused by driving in order to arrive at the true variation of skin friction with depth. Residual loads of 25 to 48 tons were observed for conventionally driven piles, whereas the load for a pile driven with a vibratory hammer did not exceed the weight of the driver. Friction during compression was found to exceed that during tension by 30 percent. An average lateral earth pressure coefficient of 1.1 was observed, with a value of 0.75 being observed for a jetted pile. The data indicate that conventional hammers may compact the soil below the pile tip and improve point bearing capacity. Skin friction adjacent to the pile tip was found to be significantly lower than for other parts of the pile.

Factors controlling the static, long-term, and dynamic structural strength of pile sections are delineated and discussed for timber, concrete, and steel piles. It is shown that current design stresses for steel and concrete are reasonable, but that timber design stresses equal or exceed long-term constant load ultimate stresses. Reasonable limits to dynamic driving stresses are recommended. Other sources of load and stress in piles are discussed along with pile strength reducing factors; many of these factors are not now considered in design. It is concluded that the normal current pile-to-soil factor of safety of 2.0 is reasonable, and that pile structural factors of safety should always exceed the pile-to-soil factor of safety. It is also concluded that normal factors of safety should not be lowered until the profession attains a higher level of competence in inspection of pile installation.

Static and dynamic one-dimensional compression tests were performed on each of ten 5-inch undisturbed shelby tube soil samples taken from the site of Operation Snowball at the Suffield Experimental Station. The maximum stresses attained were generally in the 390 to 1,300 psi range. The results of the tests are presented in the form of plots of axial stress versus axial strain, constrained modulus versus axial stress, and radial stress versus axial stress. The dynamic modulus observed for the upper 13 feet of the soil profile has a minimum value of approximately 3,000 psi, and is approximately twice the static value. Between the depths of 13 feet and 23 feet, moduli values ranging from 18,000 to 24,000 psi are applicable at the 100 psi stress level. Below a depth of 23 feet, the estimated water level, the constrained modulus is considered equal to that of water--300,000 psi. An airblast-induced ground motion prediction was made for a range of 250 feet from a 500-ton TNT explosion. A peak transient surface displacement of 4.6 inches was computed for a time of 39 milliseconds after arrival of the shock front at the ground surface. Because of differences between the laboratory and field loading histories, and the strain rate sensitivity of the soil, the computed displacement is probably from 50 to 100 percent of the actual displacement. (Author).

Lateral load tests were performed on four 4-ft-diameter drilled piers extending through water bearing granular overburden and terminating in shale bedrock. Depth of overburden varied from 10 to 43 ft. The tests involved piers with both bell and socket bases. Electric resistance strain gages were used to measure strains at the reinforcing steel, and furnished data from which bending moments were determined. It was concluded that: (1) drilled piers are capable of resisting lateral loads of large magnitude, (2) soil embedment is very effective in attenuating moments caused by lateral loads, (3) bell and socket bases effectively resist lateral loads for short drilled piers terminating in rock, (4) lateral load resistance of long drilled piers is not influenced by the base conditions, and (5) cyclic loading causes deflections to double and moments to increase 20 to 50 percent, approximately, compared to the values for the first cycle of load.

Static, rapid and dynamic one-dimensional compression tests were performed on four different sands at each of three different initial relative densities. The maximum stresses attained were generally 10,000 psi or higher, except for a low-pressure dynamic test series which attained stresses from 1,000 to 1,500 psi. The results of the tests are presented in the form of plots of axial stress versus axial strain, constrained modulus versus axial stress, and radial stress versus axial stress; grain size distribution curves are also presented for each specimen for both the before- and after-test conditions. The static data were compared to Hendron's static data or the same four sands; general agreement was noted, although the compressibility was consistently somewhat higher than observed by Hendron. The radial stresses were also somewhat lower; however, the discrepancies are probably a function of the test devices and the manner of performing the test. Crushing of the sand grains was very pronounced for the coarse sands, especially the angular sand, and had an overwhelming effect on the stress-strain relationship. Consideration of sand-grain contact stresses provides a qualitative explanation for the observed behavior.