NL1000848C1 - Lattice-work girder - Google Patents

Abstract

The girder (1) comprises top and bottom bars (6, 7) running in its lengthwise direction and joined by diagonal ones (8) at nodal points (9). The intervals between these points are determined by the lengths of the top and bottom bars. The lengths of the top and bottom bars are determined by formulae taking account of the total overall length and their distance apart in the vertical direction. The girder can form a calculation basis for the design of a girder with solid walls and containing illumination holes if desired.

Description

Truss girder and solid wall girder based on that truss girder.

The invention relates to a lattice girder with top and bottom bars running in the longitudinal direction of the beam, and these connecting diagonals, wherein said bars and diagonals come together in nodes at their ends. The invention also relates to a solid wall beam, optionally with lighting holes in its web field, constructed on the basis of a lattice beam according to the present invention as a design simplification thereof.

The object of the invention is to provide a lattice girder and a solid wall girder that can be derived from it, with optimum strength with minimum use of material.

To this end, the present invention proposes a lattice girder, a so-called comb girder, which has a geometric, regular distribution of the nodes between the top and bottom bars, respectively. With the present invention it is possible to design the box girder in such a way that the pressure-loaded diagonals per unit area, possibly including instability surcharge, are loaded as heavily as the tensile bars, for example the diagonals, so that they both have the same profile can be executed.

On the basis of the lattice analogy in concrete beams or the fold distribution in the body of steel plate beams, the lattice beam according to the present invention can serve as the basis for an optimal design of a concrete beam or a steel plate beam.

Versions are possible in which the diagonals are of constant length, so that the top edge and / or the bottom edge of the lattice girder according to the invention will be curved.

In the following, the invention is further elucidated with reference to illustrative exemplary embodiments, with reference to the annexed drawings. In the drawings, Figures 1-8 schematically show in side view various lattice girders according to the present invention. The lattice girder 1 is supported vertically at 2 and 3 and horizontally supported at 4.

As a result, the balance of the lattice girder 1 is always statically determined. However, statically indefinite equilibrium situations (see e.g. fig. 8) are also possible for beam 1. The beam 1 is supported on vertical 5, which may be omitted 1000848 2. The beam 1 is composed of top bars 6, bottom bars 7 and diagonals 8. The interconnection of those bars 6, 7 and 8 is made in nodes 9.

The drawings furthermore show in broken lines 5 how the course of the diagonals is mutually coordinated at a common intersection. Furthermore, the parameters a1f a2 ....., an; b1 # b2, ....., bn _.,; Η, P and Q. The value for these parameters can be derived from the following formulas I to V: 10

I a1 + a2 + a3 + a4 + .. + an = L

II b.j + b2 + b3 + .. + bnl = L

III b1 / a1B (H + Q) / Q

bk / ak = (H + Q) / Q

IV b, / a2 = (H + P) / P

bk / ak + 1 = (H + P) / P

VS = ((H + P) / P) / ((H + Q) / Q) where: 20 · L = Total length of the bars 6 and 7 av a2, ..., a = Lengths of the bottom bars 7 1 respectively t / mnb ^, b2 b_n = Lengths of top bars 6 1 up to and including -1 n = Number of bottom bars 7 25 k, m = Variables k = 1, 2, ..., n; m = 1,2, ..., n-1 and k + m = <n H = Height measure distance between parallel edges of bars 6 and 7 P = Height measure intersection point p to 30 bottom bar 7 Q = Height measure distance intersection point q to top bar 6

s = Constant depending on heights P and Q

/ a2 '···' *> i '^ 2' ‘'"' ^ n-1 DD

35 depending on s

Usually the parameters L, H, p and Q will be chosen depending on the desired design. From this, the lengths 1 00 0 8 4 8 3 for the different top bars 6 (av a2, ....., an) and bottom bars 7 (b · ,, b2, .... bn_1) and thus the location of the nodes 9 and the orientation of the diagonals 8 are determined, starting from the above formulas I to V. For this purpose, those formulas I to 5 V can be combined and converted as follows:

Formula I and IV L-al = L (P / (H + P)) aj = L (1 - (P / (H + P))) = L (H / (H + P)) 10 Formula 1 and III L - an = L (Q / (H + Q)) an = L (l- (Q / (H + Q))) = L (H / (H + Q))

Formula I, III and IV a 1 / an = (H + Q) / (H + P) 15 Formula I, III, IVenV 1 / s = ((H + Q) / (H + P)) * (P / Q) a! / an = (Q / P) * (1 / s)

Formula III and IV a, / a2 - s a2 / a3 = s * k / a k * l = s 20 a. / A, = s a 1 / a n = s η-Ί

Formula I, III, IV and V βη / an = (Q / P) * (1 / s) = s n_1 25 Q / P = s n s - (Q / P 1 1 1 "

Formula I, III and IV a / a + a2 / an + a3 / an + ^ ♦ ... ♦ an / an = L / an 30 snJ | ♦ s3 + s2 + s ♦ 1 = L / an 1 Ση sk_1 = 1 + s + s2 + s3 + ... + sn-1 = (s * sn_1 - 1) / (s- 1) f-Lsn - 1 ) / (s -1)

Formula III and IV b., / T> 2 = s b? / b, = s 35 b η / b η_η = s n ~ 2

Formula II. III and IV b./b ♦ b2 / b + b ^ b ^ ♦ b ^ / b ^ = U

sn + ... + s * + s + i = L / b, ^ 1 In 1 sk 1 = 1 + s + s2 + ... + sn '2 - (s * sn' 2 - 1) / (s -1) -—Ls_n '1 - i) / (s - i)

Formula I, II, III and IV L / bf) _1 = (L / an -1) * (1 / s) ^ For Q / p <1 A mirror symmetric result is achieved with respect to Q / p> 1. Figure 7 shows the situation Q / ρ = ^ For all other figures, Q / p> 1.

1000848 4

Naturally, further embodiments belonging to the invention are also possible. Furthermore, based on the design of the lattice girder according to the present invention, it is possible to derive, for example, a full wall girder, for instance from concrete. The rod-shaped diagonals 8 are then, for example, presented as tensile and compression bars, of the reinforcing steel and the concrete, respectively. Also, starting from a lattice girder according to the present invention, it is possible to choose an optimal pattern of lighting holes for a full wall girder. In an optimal design, the lighting holes may not be crossed by the course of the diagonals 8.

1000848

Claims (2)

Truss beam, with top bars (6) and bottom bars (7) running in the longitudinal direction of the truss beam (1), and the top bars (6) and 5 bottom bars (7) connecting diagonals (8), with adjacent top and bottom bars respectively and diagonals converge in respective nodes (9), which nodes (9) have a spacing substantially corresponding to the length of the respective top bar (6) or bottom bar (7), and the length of those top bars (6) and lower bars (7) is determined by the following formulas: I a ^ + a2 ♦ a3 + a ^ + .. + an = L II b., + b2 + b3 + .. + bn-1 = L 15 III b / a1 = (H + Q) / Q bk / ak = (H + Q) / Q IV b1 / a2 = (H + P) / P bk / ak + 1 = (H + P) / PV s = ({ H + P) / P) / ((H + Q) / Q) 20 where: L = Total length of bars 6 and 7 a1, a2 an = Lengths of bottom bars 7 1 to 25 b1, b2 bn_1 = Lengths from top bars 6 1 to n -1 n = Number of bottom bars 7 k, m = Variables k = 1,2, ..., n; m = 1,2, ..., n-1 and k + m = <n H = Height measure distance between parallel edges 30 of bars 6 and 7 P = Height measure distance intersection point p to bottom bar 7 Q = Height measure distance intersection point q to top bar 6 35 s = Constant depending on height P and Q 3- | r & 2 "" * "" ^ 2 "·" "^ n-1 depending on s 1000848 Full wall beam, optionally equipped with lighting holes in its web plate, wherein the design of the web and / or the location of the lighting holes is chosen on the basis of the design of the corresponding lattice beam as schematization according to claim 1, 5 used as simplified calculation model for the design of the full-wall beam. 1000848