Differentiation of Displacement Factor for Stiff and Soft Clay in Additional Modulus of Subgrade Reaction of Nailed-Slab Pavement System

This paper discusses the variation of the Modulus of subgrade reaction (k) backcalculated from slab deflection basins, interactive with the location of the Falling Weight Deflectometer (FWD) load pulse, and curling of slabs due to daily temperature variations. The k-value was calculated following the AASHTO design guides procedures, while deflection basins were recorded at an interval of 3 to 4 hours along the day on an instrumented concrete pavement test section in West Virginia. The state of deformation of the slabs are continuously monitored, through dowel bar bending measurements and records of the temperature gradient profiles through the slab thickness, as well as joint openings every 20 minutes. The results indicated that the backcalculated k-values are greatly affected by the positive temperature gradient, and the least variation in (k) was found in the slab center. In order to minimize errors in back-calculations of k-values, it is recommended to perform the FWD test for recording deflection basins in the interior of the slab during late evening or in the early morning.

Download Full-text

EXCEL BASED SETTLEMENT OF BEAMS ON ELASTIC FOUNDATIONS WITH FREE-ENDS AND ARBITRARY LOADING

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2017.66 ◽

2017 ◽

Vol 4 (1) ◽

Author(s):

Amir W. Al-Khafaji ◽

Robert Jacobs

Keyword(s):

Cross Sections ◽

Engineering Practice ◽

Subgrade Reaction ◽

Variable Loading ◽

Cross Sectional ◽

Modulus Of Subgrade Reaction ◽

Elastic Foundations ◽

Arbitrary Loading ◽

Finite Differences Method ◽

Soil Modulus

The deflection of long footings placed on homogeneous and isotropic soils involves soil-structure differential equations models whose solution may not be possible for most practical problems. The analytical solution of beams on elastic foundation problem involves soil modulus of subgrade reaction and simplifying assumptions relative to applied loading. The exact solutions are available in relatively simple cases of loading, uniform cross sectional properties of the footing and constant soil modulus of subgrade reaction. Therefore, the Finite Difference Method (FDM) or Finite Element Method (FEM), are typically used to compute the deformation of beams with variable loading and geometry resting on elastic foundations with variable modulus of subgrade reaction. The finite differences method was used to solve this problem for long beams with arbitrary loading and constant cross-sections using an Excel Workbook to compute beam deflections providing both numerical and graphical output. The foundation is modeled as a long beam with free ends and a constant modulus of subgrade reaction. The proposed solution presents an efficient method involving a complex ordinary differential equation model for beams on elastic foundations encountered in engineering practice.

Download Full-text

Subgrade reaction and load-settlement characteristics of gravelly cobble deposits by plate-load tests

Canadian Geotechnical Journal ◽

10.1139/t98-044 ◽

1998 ◽

Vol 35 (5) ◽

pp. 801-810 ◽

Cited By ~ 15

Author(s):

Ping-Sien Lin ◽

Li-Wen Yang ◽

C Hsein Juang

Keyword(s):

Bearing Capacity ◽

Field Tests ◽

Load Test ◽

Subgrade Reaction ◽

Plate Load Test ◽

Modulus Of Subgrade Reaction ◽

High Rise ◽

Undisturbed Samples ◽

Load Tests ◽

Mat Foundations

This paper presents the result of plate-load tests conducted on a gravelly cobble deposit in Taichung Basin, Taiwan. The geologic formation of the gravelly cobble deposit makes it very difficult to obtain large undisturbed samples for laboratory testing. These field tests provide an opportunity to examine the applicability of existing theories on bearing capacity and subgrade reaction in this geologic formation. The modulus of subgrade reaction is of particular importance in the local practice of designing high-rise buildings on mat foundations. The results of the plate-load tests on this soil deposit are analyzed and discussed.Key words: plate-load test, gravelly cobble deposit, modulus of subgrade reaction, bearing capacity.

Download Full-text

Validation of Using Modulus of Subgrade Reaction to Consider the Soil Structure Interaction

AEI 2015 ◽

10.1061/9780784479070.056 ◽

2015 ◽

Cited By ~ 1

Author(s):

Hany Farouk ◽

Mohammed Farouk

Keyword(s):

Soil Structure ◽

Soil Structure Interaction ◽

Subgrade Reaction ◽

Modulus Of Subgrade Reaction ◽

Structure Interaction

Download Full-text

Impact of subgrade and backfill stiffness on values and distribution of bending moments in integral box bridge

Studia Geotechnica et Mechanica ◽

10.2478/sgem-2021-0001 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Andrzej Helowicz

Keyword(s):

Reinforced Concrete ◽

Parametric Analysis ◽

Bridge Structure ◽

Bending Moments ◽

Structural Elements ◽

Subgrade Reaction ◽

Bridge Design ◽

Modulus Of Subgrade Reaction ◽

The Impact

Abstract The article presents parametric analysis regarding the impact of subgrade and backfill stiffness on values and distribution of bending moments in the structural elements of a small integral box bridge made of cast in situ reinforced concrete. The analyzed parameters are the modulus of subgrade reaction under and behind the bridge structure (kv kh). At the beginning, the author presents the integral box bridge and selected parts of the bridge design. In particular, the author focuses on the method of modeling of the subgrade stiffness parameters under and behind the bridge structure, as well as their impact on the values and distribution of bending moments in the bridge structural elements. The bridge was designed by the author and built on the M9 motorway between the towns of Waterford and Kilcullen in Ireland. In conclusions, the author shares his knowledge and experience relating to the design of small integral bridges and culverts and puts forward recommendations as to further research on these type of structures in Poland.

Download Full-text