Download presentation

Presentation is loading. Please wait.

Published byChase Boyle Modified over 3 years ago

1
Mechanical response of shallow foundations - Some experimental/theoretical and numerical issues: monotonic and cyclic loading Introduction Prof. ing. Claudio di Prisco

2
**Outlook of the presentation**

Indice Outlook of the presentation Introduction Failure mechanisms and punching The macro-element concept Cyclic soil-structure interaction: constitutive modeling observations A simplified approach

3
**Definitions: shallow foundations**

GEOMETRIES Shallow (B/H>4) and deep foundations (B/H<4) Strip footings Mat foundations Grid foundations Lancellotta e Calavera, 1999

4
**The soil-structure interaction**

Statically determinate interaction Redundantly constrained interaction

5
**The soil structure interaction**

What are the consequences? Irreversible differential settlements, damage to the structure energy dissipation 3 Dt 1 2 4 Dynamic structural response Soil- foundation interaction site amplification Depending on topography and stratigraphy

6
**1. The pseudo-static approach: the rigid-plastic approach**

Static equivalent horizontal load: step 2 is disregarded whereas step 4 is abruptly simplified. A design pseudo-static distribution of forces is applied to the structure, additional loads H and M are applied on the foundation and new limit conditions have to be accounted for In this perspective the design of the shallow foundation under inclined and eccentric loads become essential

7
**Failure mechanisms: the interaction domain in quasi static conditions**

Failure mechanisms: small scale 2D experimental test results (drained and undrained conditions, cohesive and granular soils) Nova e Montrasio, 1988

8
**Punching mechanisms and 2nd order effects**

Lancellotta e Calavera, 1999 Lancellotta, 1993

9
**The limit analysis and the Prandtl mechanism**

Rigid-plastic mechanical behavior of the material Associated flow-rule Mohr-Coulomb failure criterion The kinematic limit analysis approach Nova, 2008 Lancellotta, 1993

10
**The Terzaghi bearing capacity equation for vertical and centered loads**

The Terzaghi Theory The Terzaghi bearing capacity equation for vertical and centered loads Lancellotta, 1993

11
**Inclined and eccentric loads: Brinch-Hansen coefficients**

H/M V Lancellotta, 1993

12
**The interaction domain for rigid shallow footings**

MONOTONOUSLY INCREASING LOADING To each point belonging to the failure locus a distinct failure mechanism corresponds Difficulty in defining the failure locus when loose sand strata are concerned Extension to rectangular footings Extension for D/B>0 m = M/ψBVMAX, h = H/μVMAX ξ = V/VMAX

13
**Elasto-plastic finite element numerical analyses**

Centered vertical load Centered inclined load Tochnog perfect elasto-plastic numerical analyses

14
The uplift Shirato et al. 2007

15
**The uplift of rigid shallow foundations**

16
**THE EXPERIMENTAL TEST SERIES**

GENERALISED STRESS PATHS Inclined LOADS INTERACTION DIAGRAMS Rigid strip footing Dense sand B 0.5B LOAD CONTROLLED TESTS THE EXPERIMENTAL TEST SERIES

17
**DENSE SAND, vertical loading**

Failure mechanism in unreinforced dense sand layer Failure mechanism in unfastened reinforced dense sand layer

18
**H/V = 0.1 v [mm] V [ kPa] Unreinforced Unfastened reinforced**

20 40 60 80 100 120 140 5 10 15 25 30 35 45 50 55 65 v [mm] V [ kPa] Unreinforced Unfastened reinforced fastened reinforced 2 4 6 8 10 12 14 5 15 20 25 30 35 40 45 u [mm] H [ kPa] H/V = 0.1

19
**INTERACTION DIAGRAMS EXPERIMETNAL DATA and NUMERICAL INTERPOLATION**

Unreinforced loose sand Unfastened reinforced loose sand Sabbia sciolta non rinforzata Sabbia sciolta rinforzata con geosintetici non allacciati 6 10 8 4 6 H [kPa] H [kPa] 4 2 2 20 40 60 80 100 120 140 10 20 V [kPa] 30 40 50 V [kPa] Fastened reinforced loose sand Sabbia sciolta rinforzata con geosintetici allacciati 25 INTERACTION DIAGRAMS 20 15 H [kPa] 10 5 EXPERIMETNAL DATA and NUMERICAL INTERPOLATION -20 20 40 60 80 100 120 140 160 180 200 V [kPa]

20
**Truss elements Numerical simulations Tochnnog finite element code**

elasto-perfectly plastic constitutive model Truss elements Non associated flow rule (y = 0)

21
**The visco-elastic approach**

Dt 1 2 4 K =k() ? = () ?

22
**PWRI experimental test results,2005**

M - curves PWRI experimental test results,2005 Loose sand stratum Dense sand stratum FOOTING UPLIFT

24
**Ispra Laboratory Elsa di Elsa di (Pedretti, 1998)**

Cross section Plan view

29
A simplified approach A symmetric generalised stress-paths

Similar presentations

OK

Januar 2005 S M T O T F L 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25.

Januar 2005 S M T O T F L 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on unity in diversity symbol Ppt on eye os mean Ppt on question tags for youtube Ppt on world environment day posters Ppt on building information modeling salary Best ppt on minerals and energy resources Ppt on area of trapezium math Ppt on various layers of the earth Ppt on personality development for mba students Ppt on natural resources class 8