Showing papers on "Dynamic load testing published in 1972"

Soil Resistance Predictions From Pile Dynamics

Abstract: The present work extends the application of the force and acceleration records to the calculation of the distribution of soil resistance along the pile. It also shows how the records are used to predict the magnitude of dynamic resistance that the soil applies to the pile, an important factor in choosing efficient hammer characteristics. A method for obtaining a more accurate simplified prediction of total static bearing capacity is also presented. It should be emphasized that the aforementioned predictions are all made from measurements at the pile top only. The work is correlated by presentation of results for 24 pile tests which include construction static load tests as well as specially instrumented load test piles. The application of these results can have considerable impact on foundation costs. Static load tests are very costly and time consuming. In Ohio a single test on a service pile using tension reaction piles (also service piles) typically costs $3,000 to $5,000. This static test provides much useful information about the particular pile which was tested. However, due to variability of soil properties the information may be of less value for other piles in the structure. This is reflected in the large factors of safety commonly used for piles. The proposed dynamic measurements methods can be applied to a substantial number of service piles at less than the cost of a single static load test. The dynamic analysis herein differs from the general dynamics problem in which either the boundary force or acceleration record is given as input and the other record calculated as output. In the present dynamic analysis, both force and acceleration are shown and thus one of the two records can be viewed as redundant information. The second record is, therefore, used in the present analysis to give information on pile resistance effects; e.g., in the absence of soil resistance, the acceleration at the pile top completely determines the force at the top from Newton's and Hooke's laws. The presence of resistance along the pile and at the pile tip affects the force at the top in a precise and predictable manner and makes it possible to compute t e magnitude and location of resistance forces along the pile. A simple soil resistance model is used, which consists of an elastoplastic shear resistance and a linear viscous damper. The dynamic analysis will be reviewed herein to present the basic ideas behind the work. The detailed mathematical expressions are given in Refs. 3 and 9.

Deformation and fracture of concrete subjected to dynamic load

Abstract: This is a study of the influences of loading rate (or straining rate) upon the inelastic deformation and fracture of concrete and reinforced concrete members loaded in higher rates of application than in static tests. Relations between the mean rate of loading and the mean rate of strain were derived from the results of a number of tests. From the relations, the deformations and fractures of concretes and reinforced concrete members under dynamic load can be deduced. /TRRL/

Ultimate lateral resistance of a rigid pile in cohesionless soil

Abstract: LATERAL LOAD TESTS WERE CARRIED OUT ON MODEL PILES DRIVEN IN CONHESIONLESS SOIL. THE PROPOSED METHOD FOR CALCULATING THE ULTIMATE LATERAL RESISTANCE OF RIGID PILES AVOIDS THE USE OF THE COEFFICIENT OF HORIZONTAL SUBGRADE REACTION. THIS METHOD APPLIES TO THE CASE WHEN THE SURFACE OF THE PILE IS FRICTIONLESS. COMPARISONS WITH TEST DATA INDICATE A GOOD AGREEMENT BETWEEN THE VALUES CALCULATED BY THIS METHOD AND THE VALUES MEASURED IN TESTS. THE RESIDUAL DISPLACEMENT AFTER REMOVAL OF THE LOAD IS TUDIED WITH RESPECT TO BOTH THE DIAMETER AND THE DRIVING DEPTH OF THE PILE. SEE ALSO IRRD ABSTRACT NO. 100334.

Torque shear test of cylindrical friction piles

Abstract: ALTHOUGH AXIAL LOAD TESTS ARE THE ONLY SURE METHOD FOR DETERMINING ULTIMATE BEARING CAPACITY OF INDIVIDUAL PILES, CONVENTONAL PROCEDURES ARE COSTLY AND INCONVENIENT. BECAUSE OF HIGH COSTS AND TIME, FEWER PILE LOAD TESTS ARE SPECIFIED THAN MIGHT BE USEFUL AND DESIRABLE. WHEN DEALING WITH FRICTION PILES IN VARIABLE SOIL CONDITIONS, ONE WONDERS WHETHER THE TEST LOAD-PILE LENGTH CAN BE APPLIED TO THE WHOLE JOB. THUS THE NATURAL TENDENCY IS TO DRIVE PILES "LONG" TO BE SURE OF SAFETY. HERE A SIMPLIFIED FIELD TORQUE SHEAR LOAD TEST IS PRESENTED. THE TEST DETERMINES REQUIRED PENETRATION DEPTH OF FRICTION PILES ON THE BASIS OF TORQUE SHEAR RESISTANCE MEASURED DURING CONSTRUCTION. /ASCE/

Displacement of a vertical pile group subjected to lateral loads

Abstract: PRESENT THEORIES DEALING WITH THE BEHAVIOR OF PILES SUBJECTED TO LATERAL LOADS USE THE COEFFICIENT OF HORIZONTAL SUBGRADE REACTION. IN THE CASE OF PILE GROUPS SUCH COEFFICIENTS ARE OF NO USE, WHICH IS THE REASON WHY A HYPOTHESIS HAS BEEN MADE OF AN ELASTIC HALF-SPACE BY MEANS OF THE INTEGRATION OF MINDIN'S EQUATIONS. A RIGOROUS ANALYSIS OF THE ANALYTICAL PROCESS HAS BEEN MADE, WHICH ALLOWS THE STUDY OF SYMMETRIC AND ASSYMETRIC PILE GROUPS. THE ABOVE HYPOTHESIS ENABLES THE BUCKLING OF A PILE WITHIN A GROUP TO BE ANALYZED. THE CONCEPT OF EFFICIENCY HAS BEEN INTRODUCED AND CAN BE OF GREAT UTILITY TO THE DESIGNER. A SERIES OF MODEL TESTS ON PILES IN SANDY SOIL HAVE BEEN CARRIED OUT TO DETERMINE THE EFFICIENCY OF A 3 X 3 PILE GROUP WITH DIFFERENT SPACING AND SOIL DENSITY. /TRRL/

Effects of Shearing Force and Rotary Inertia to Dynamical Behaviours of Thin Cylindrical Shells Subjected to Impulsive Inner Pressures

Abstract: Behaviours of dynamical stresses and bending moments acting in the cantilevered thin cylindrical shells subjected to impulsive inner pressure are investigated. Cylinder is assumed to be elastic and inner pressure to be expressed as step function with respect to time. In this analysis, shearing force and rotatory inertia are taken into consideration. Relationships between dimensions of a cylinder and dynamic load factors with respect to hoop stress at free end and bending moment at clamped end are studied. From the results of analysis, it became evident that the values of dynamic load factors with respect to hoop stress at free end for the case where two factors are taken into consideration are much different from those for the case where these are neglected.

Bearing capacity of cyclically loaded piles

Abstract: THE BEARING CAPACITY OF DRIVEN PRECAST CONCRETE AND TIMBER PILES HAS BEEN INVESTIGATED AT FOUR DIFFERENT TEST SITES IN SWEDEN (UPPSALA I, UPPSALA II, BJOERKTORP, AND GULLBERGSMOTET). THE PILES WERE DRIVEN INTO A DEEP LAYER OF NORMALLY CONSOLIDATED CLAY AND SUBJECTED TO CYCLIC LOADS AT SUCCESSIVELY HIGHER LOAD LEVELS. THE TEST WAS TERMINATED AT THE LOAD LEVEL AT WHICH THE DEFLECTION INCREMENT FROM EACH LOAD CYCLES STRATED TO INCREASE. THIS LOAD LEVEL IS DEFINED HEREIN AS THE CRITICAL LOAD. IT IS CONSIDERED THAT A PILE CAN RESIST AN INDEFINITE NUMBER OF LOAD CYCLES WITHOUT FAILURE IF THE INTENSITY OF THE CYCLIC LOADING IS LESS THAN THE CRITICAL LOAD. THE MEASURED CRITICAL LOADS WERE COMPARED WITH CALCULATED VALUES FOR EACH SITE. /AUTHOR/

Illumination activated transistor relaxation oscillator

Abstract: An illumination activated circuit for supplying power from an oscillatory source to a load. A light sensitive device is arranged in the output circuit of the source such that the signal provided by the source to the load is initiated only when illumination above a certain intensity is received by the device, the device being in effect a dynamic load for the source.

Comparison between measured and calculated stresses and strains in flexible road structures

Abstract: At two full-scale flexible road structures of a test track extensive measuring programmes were carried out to determine stresses and strains in structures under controlled dynamic load conditions. A rail guided load vehicle, driven automatically, enabled the application of defined rolling loads of a single lorry wheel in the range between 0.5 and 2.0 tons. For testing the influences of loading time (speed) and environmental conditions, the load device was run on each test structure in the speed range between 5 and 50 km/h, and during all seasons of the year at asphalt temperatures between 0 deg C and 30 deg C. Radial strains (longitudinal and transverse) and vertical strains in the asphalt layer, and vertical stresses in the unbound base and the soil were measured at different levels of depth in the structures. The applied transmitters (strain gauges, pressure cells) had been tested successfully in situ for years. The two investigated road structures with a total thickness of the asphalt of 22 cm differed only in the stability properties of the asphalt base materials. Therefore direct comparisons could be made between the two structures under the same conditions. As a general result, the differences between radial strains in the asphalt were bigger than the differences between the vertical stresses in the unbound base and in the soil For the comparisons between measured and calculated values a so-called values a so-called effective dynamic stiffness modulus of the asphalt materials was introduced which accounts for the material properties, the temperature and the "effective" loading time. The numerical data were calculated by the computer programme BISTRO, which is based on the theory of elasticity for multilayer systems. The dynamic moduli of the materials were determined in the laboratory by a known vibration method, and in situ by the wave porpagation method. The best correlations between measured and calculated values were found for strains in the lower part of the asphalt layer and for the stesses in the unbound base and the soil, even when the stiffness conditions for the asphalt layer were low at asphalt temperatures of 30 deg C. When asphalt temperatures exceeded 25 deg C, maximum tensile strains were observed in the middle part of the asphalt pavements at the interface of two layed asphalt courses.

Dynamic load factors for plastic deformation of hexagonal subassembly cans.

Abstract: Abstract The dynamic plastic deformation of a hexagonal subassembly duct subjected to an internal step pulse is computed for various wall thicknesses and pulse magnitudes. The results are compared to the corresponding plastic deformations of a duct loaded by static internal pressures of the same magnitudes as the step pulses. It is shown that the dynamic deformations exceed the static deformations by factors of 1.7 to 2.0. The results for deformation across flats cover a range of several wall thicknesses for pressures as high as twice the yield load of an undeformed can. The time duration of the dynamic response is also determined.

Capacity of pile anchors

Abstract: EXPERIENCE WITH PILING FOR HIGHWAY STRUCTURES HAS INDICATED A NEED FOR POSITIVE ANCHORAGE OF PILES TO THE SUBSTRUCTURE TO RESIST UPLIFT FORCES. SIX TYPES OF PILE ANCHOR DEVICE, TWO FOR USE WITH STEEL PILES AND FOUR FOR USE WITH TIMBER PILES, WERE CAST IN CONCRETE BLOCKS DESIGNED TO SIMULATE BRIDGE FOOTINGS AND TESTED USING BOTH STATIC AND CYCLIC LOADS TO DETERMINE THE PULL OUT CAPACITY OF THE PILE TO FOOTING CONNECTION. THE RESULTS FROM EACH ANCHOR WERE COMPARED WITH THE DESIRED ALLOWABLE LOAD CAPACITY OF 40% OF THE PILE BEARING CAPACITY AND ALSO WITH THE RESULTS FROM A COMPARABLE STEEL OR TIMBER PILE CONTROL SPECIMEN THAT WAS IDENTICAL TO THE TEST SPECIMEN IN ALL RESPECTS EXCEPT THAT IS CONTAINED NO ANCHOR DEVICE. IT WAS FOUND THAT THE CONTROL SPECIMENS TOGETHER WITH ONE OF THE ANCHOR TYPES WERE SUBJECT TO SUDDEN FAILURES NEAR THEIR ULTIMATE LOAD. ALL OF ULTIMATE AND HAD LOAD CAPACITIES GREATER THAN THE CORRESPONDING CONTROL SPECIMEN AND GREATER THAN 40% OF THE BEARING CAPACITY OF THE CORRESPONDING PILE TYPE. EXCEPT FOR ONE ANCHOR TYPE, ALL ANCHORS WERE CAPABLE OF RESISTING AT LEAST 100 CYCLES OF LOADING (AT A 0.1 CPS LOAD RATE) FROM 0 KIPS TO A LOAD EQUAL TO 40% OF THE BEARING CAPACITY OF THE PILE. ALL ANCHORS THAT WERE RELOADED STATICALLY AFTER CYCLIC LOADING DEMONSTRATED STATIC RELOAD CAPACITIES IN EXCESS OF 40% OF THE BEARING CAPACITY OF THE PILE. /FHWA/

Sheet pile anchors: design reviewed--the importance of flexibility in the design of sheet pile anchors in sand

Abstract: DETAILS ARE GIVEN OF MODEL AND FIELD TESTS CARRIED OUT TO DETERMINE THE SAFE LOAD ON A SHEET PILE ANCHOR. RESULTS SHOW THAT THE SAFE LOAD IS LIKELY TO BE CONSIDERABLY LESS THAN THAT ESTIMATED FROM DESIGN CALCULATIONS ASSUMING THE ANCHOR TO BE COMPLETELY RIGID. THE REASONS FOR THE REDUCTIONS IN LOAD ARE OUTLINED. TOGETHER WITH THE EFFECTS OF TIE ROD LEVEL AND RELATIVE DENSITY OF THE SAND ON THE BEHAVIOR OF THE ANCHOR. /TRRL/

Dynamic load force calibrating system and a method for its use in a motion test system

Abstract: A dynamic load force calibrating device is provided in which the displacement of one moving member to which a driving force is being applied relative to a following member to which it is resiliently coupled and to which an adjustable load force is being applied is compared to a reference displacement representative of a desired load force to dynamically verify thereby the amount of load force being applied.