Материал: Scientific Herald of the Voronezh State University of Architecture and Civil Engineering

Scientific Herald of t he Voronezh State University o f Architecture and Civil Engineering. Construction and Architecture

Fig. 2. Strengths applied to a support sla b:

а) two r ows of anchor bolts are stretched, the slab is compressed under the right cap; b) support slab is compressed under both c aps;

Ft, l, Rd is a tensile loa on the left part of the sup port slab;

is a compressive str ength on the right part of the support sla ;

Fig. 2 (end). Strength applied to the support slab:

c)a r ow of anchor bolts is stretc hed, the slab is compressed under the right cap;

d)the same as “b” but the tension areas of the slab reach the edges

96

Fig. 3. Scheme of the failure of the support slab:

а, h) plastic areas are joined together; b) plastic areas reaches the transverse and longitudinal sides of the support slab;

c, g) the same for the transverse one; d) round plastic zones; e) angular plastic zones; f) rectangular plastic zones

2. Solution of the problem

2.1. Determining the compressive resistance of the joints as a minimum of the function [5, 7]:

97

Scientific Herald of the Voronezh State University of Architecture and Civil Engineering. Construction and Architecture

without considering extra forces at

where m is the distance between plastic hinges and the axis of the bolt (for a welded column m ec 0,8ac 2 , ac is the height of the leg of the weld; ec is the distance between the axes of the compressed bolts to the column cap; for a rolled beam m ec 0,8r , n is the distance be-

tween the extra strength Q and axes of the bolts ≤1,25m); d is the diameter of the plate; Lbef is the effective length of anchor bolts:

Lbef 8db tg tep tn / 2,

where db is the diameter of anchor bolts; tg is the thickness of the base between the support slab and the upper one with the foundation base; tn is the thickness of the plate; Mpl,1, Rd, Mpl,2, Rd are plastic bending moments of the support slab corresponding to the first and second failure mechanisms:

where leff is the effective length of the compressed zone of the support slab:

leff min 4m 1, 25ex ; 4 m; 0,5b; 2m 0,625ex 0,5w;2m 0,625ex eep ; 2 m 4eep ; 2 m w ;

tep is the thickness of the support slab; fy, ер is the bending resistance of the support slab material;

γМо is the coefficient: γМо = 1; w is the distance between two axes of bolts; b is the thickness of the support slab; ex, eep are geometrical characteristics (Fig. 3, 4); Ft, Rd, b is a calculated compressive resistance of anchor bolts:

As is the area of the longitudinal section of tensile bolts; fub is the tensile resistance of bolts; γМb = 1,1 is the coefficient.

98

Fig. 4. Denotation of the sizes used in the calculation of the column: а) of a rolled section; b) of a welded section

2.2. Compressive resistance of the joints [1, 7]:

where fj is the compressive resistance of concrete under concentrated axial loads determined according to the European Standard [1]:

where fck is the compressive resistance of concrete; a, b is the width and length of the support slab (Fig. 5);

99

Scientific Herald of the Voronezh State University of Architecture and Civil Engineering. Construction and Architecture

bc, c are the sizes specified according to Fig.5; Mc, Rd is a plastic moment in the column considering the shear and axial strengths (according to the European Standard [2]):

at e = Msd/Nsd > zc, r:

Fig. 5. Sizes of the column base:

а) position of the column on the support slab; b) position of the effective compressed zone on the support slab

2.3. Bending resistance of the column base [1, 7]:

rc is the distance between the centre of the compressed zone to the neutral line:

rc h2c c b2eff .

100