1627
Structure-Soil Massif System Behavior Features Under Static & Dynamic Loads
Les particularités du comportement du système edifice-sol avec des efforts statiques et
dynamiques.
Taranov V.G., Aleksandrovych V.A.
KNAME, 12 Revolutsia st., Kharkiv, Ukraine
Luchkovskyi I. Ia., Plashchev S.A.
KhNUCA, 40 Sums`ka st., Kharkiv, Ukraine
Kornienko N.V., Areshkovych O.O.
KNUCA, 31 Povitroflotsky Avenue, Kyiv, Ukraine
ABSTRACT: The effect of existence of the critical time of loading on structures that contact with soil due to rheological properties of
concrete and soil is identified in the thesis. Settlement of foundations under dynamic load has been analyzed in the paper. Dynamic
Hereditary creep theory suggested to forecast foundations settlements under dynamic load. The approximate convergence of
experimental and theoretical data, obtained by means of hereditary creep theory, has been found out.
RÉSUMÉ : Au cours du travail il est révélé un effet d'existence d’une durée critique de charge des charpentes qui sont en contact avec
le sol, à cause des propriétés rhéologiques du béton et du sol. Dans cet article est analysé l’abaissement des foundations aux efforts
dynamiques. L’emploi de la théorie héréditaire du fluage est considéré pour la provision de l’abaissement des fondations aux efforts
dynamiques. On a découvert une concordance très proche des donnés théoriques obtenues a l’aide de la théorie héréditaire du fluage
avec des donnés expérimentales.
KEYWORDS: soil, foundation, vibrocreep.
1 CRITICAL TIME OF LOADING A “BASE-
FOUNDATION” SYSTEM DEFORMING OVER TIME
The stress-strain state of the “base-foundation” system at the
initial instant corresponds to an elastic structure on elastic
foundation, and when further deformed by a constant external
load – to the same structure, but with long-term modules of the
foundation and base materials. At that, А.R. Rzhanitsyn
(Rzhanitsyn 1949), along with other authors, assumes that the
worst values of forces in the foundation structure manifest
themselves from the elastic-instantaneous solution and the creep
theory solution at time t→∞, maximal distant from the loading
moment. In (Luchkovskiy 2000), using the Winckler model as
an example, we showed that due to different creep leak rates in
the foundation structure (concrete) and the base, the worst
forces manifest themselves in some, short enough, time after the
start of the foundation loading, which is the «critical time of
loading» of the «base-foundation-structure» system.
In order to generalize regularities of the revealed
phenomenon for the soil base, possessing a distributive
capability, we shall deal with the base, having selected as a
model the discrete model (Luchkovskiy 2000), developed by us
(flat variant).
We take into account rheological properties of the
foundation structure and the base using algebraization of
integral equations of the creep theory (Luchkovskiy 2000),
(Ulitskiy 1967). For example, when using assumptions of the
«ageing» theory and stress function
f[σ]
of the form
f[σ ]=σ+β·σ
2
(1)
the time module of deformation of the uniaxially deformed
material Е
t
can be presented as the relation
,
2 2 1
2
0
0
0
t
t
t
t
E
E
(2)
In the research below we assume:
For foundation concrete – φ
∞
=3.0, b=0.04 day
-1
; β=0;
E
b
=23000МPа;
For base soil
–
φ
∞
=2.0, b=0.325 day
-1
;
β=5МPа
-1
;
E
0
=10МPа.
We have sequentially considered three processes of
deformation of the «base-foundation» system:
when taking into account linear creeping of the foundation
material;
when nonlinear creeping of the base soil shows up;
at simultaneous creeping of foundation and soil body
materials.
All calculations are made numerically for different time
moments of sustained applying of constant load. At that, in the
interval 0≤t≤20 of the day, calculations were made every other
day, after that – every 10 days during half a year.
Long-term stiffness B
t
of the foundation beam with
unilateral reinforcement А
s
=40cm
2
with a cross-section of
b=1m; h=0.35m, was found using the formula obtained by
I.I. Ulitskiy (Ulitskiy 1967)
,
3
0
0 0
t
x
h hsEsA tB
(3)
The time variation of concrete and soil creeping properties,
presented in Fig.1, shows that the base creep rate is
considerably higher than the concrete creep rate, which
determines the nature of variation of the stress-strain behavior
of the contacting system. If, according to relation (see Eq. 2),
the foundation and base stiffness is presented as
