1. Katedra za metalne konstrukcije
NELINEARNI ODZIV NA POTRESNO OBTEŽBO JEKLENIH OKVIRJEV Z NESIMETRIČNIMI VIJAČENIMI STIKI S ČELNO PLOČEVINO
Peter Skuber
Mr. Chairman, ladies and gentlemen I will present the results of our research on
BEHAVIOUR OF UNSYMMETRIC BOLTED CONNECTIONS SUBJECTED TO DYNAMIC LOADING

2. STATIČNA OBTEŽBA
The unsymmetric bolted end-plate connections are primarily suitable to resist gravity bending moments in non-sway frames. They can be used also in low-rise sway frames in non-seismic regions or for moderate wind loading, where moments from gravity loads prevail.
This type of connections was in the past sometimes used also in seismic regions. For instance in Slovenia. Old Slovenian codes, which are still in force in parallel with Eurocode 8, have implicitly incorporated a behaviour factor 5 or even more. Such behaviour factors require fully ductile design. In order to get an insight into the behaviour of those connections, a small testing program was elaborated.
To analyse earthquake resistance of frames containing unsymmetric bolted end-plate connections the hysteretic behaviour of connections was established from the test results and then the non-linear dynamic analysis was performed.

3. POTRESNA OBTEŽBA

4. SLOVENSKI STANDARD ZA POTRESNO VARNO GRADNJO (1980)
The tests were run under displacement control following the sinusoidal pattern with constant amplitude of approximately two times the yield displacement. The constant frequency of 0.5 Hz was applied. To simulate the effect of the gravity loading the static displacement causing the bending moment equal to 30 % of the beam plastic moment was introduced before dynamic loading. The preloading certainly caused tension at the stronger part and favourable compression at the weaker part of the connection, as in real frame situation.

5. IZBIRA STIKOV NA POTRESNO NEVARNIH PODROČJIH
NEPRAVILNO
On the picture we see the test specimen geometry. Typical beam-column assembly. M20 bolts in the connections were of grade 10.9 and half of the full preloading was applied. The connections were designed as full-strength and rigid except the column-web panel which did not confirm these requirements.
PRAVILNO

6. ZNAČILNOSTI NUMERIČNEGA MODELAF M
poškodovani
stik x t
histerezna
ovojnica Fu
Nesimetrični stik
“pinching” efekt
Porušitev vijakov

7. NIHAJNI ČAS (s)
AKCELEROGRAMI

8. SPEKTRI POSPEŠKOV
PRILAGODITEV SPEKTROV NA PROJEKTNI POSPEŠEK PGA = 0.3 g

9. Geometrija in obtežba za enoetažni okvir
Stalna in lastna
Spremenljiva
Sneg :
gk = 3.6 kN/m2
qk = 3.0 kN/m2
sk = 1.4 kN/m2
Veter
Potres
vref = 25 m/s
PGA = 0.3g, q = 5
B = 5.0 m
Razdalja med okvirji
IPE 400
HEA 320
L = 8.0 m
Sini M p1 p2 F u2 u1
Ovojnica
Modeliranje stika z Histerezno ovojnico
Mejne
rotacije
(mrad) S
ini =
50 K
(togi stik)
16.7 K
(delno togi stik.)
5.6 4 45 5 . 7 8 11

10. Rezultati za enoetažni okvir
umax/h * 10 -2
Poškodbe
Kobe, PGA = 0.2 g, Sini = 50 K
0.78
elastično
Kobe, PGA = 0.3 g, Sini = 50 K
1.17
male
1.18
Kobe, PGA = 0.4 g, Sini = 50 K
1.58
velike
2.17
Porušitev vijaka
(levi stik)
Kobe, PGA = 0.5 g, Sini = 50 K
2.35
5.12
(oba stika)
Kobe, PGA = 0.3 g, Sini = 50 K,
Brez prednapetja
1.43
Kobe, PGA = 0.2 g, Sini = 16.7 K
0.97
elastične
Kobe, PGA = 0.3 g, Sini = 16.7 K
1.46
1.55
Kobe, PGA = 0.4 g, Sini = 16.7 K
2.19
3.31
Kobe, PGA = 0.55 g, Sini = 16.7 K
3.27 /
Porušitev stika
Kobe, PGA = 0.2 g, Sini = 5.6 K
1.52
Kobe, PGA = 0.3 g, Sini = 5.6 K
2.03
2.08
Kobe, PGA = 0.4 g, Sini = 5.6 K
2.53
4.98
Simetrični polnonosilni stik
2.16

11. Diagram Moment – čas za levi in desni stik
levi stik
Diagram Moment – čas za levi in desni stik
porušitev vijakov
desni stik
Čas (s)
porušitev vijakov
KOBE
Sini = 50 K
PGA = 0.5 g
Čas (s)

12. SPEKTER POSPEŠKOV PRILAGOJEN ZA PGA = 0,1 g, 5 % DUŠENJE
NORTHRIDGE
NIHAJNI ČAS (s)

13. Diagram Moment – čas v poškodovanih stikih
Porušitev stika pri
PGA = 0,3 g

14. NAJVEČJI ZASUKI ETAŽ PRI RAZLIČNI POTRESNI OBTEŽBI (PGA = 0,1 g)
številka etaže
Največji zasuki etaže (mrad)

15. ZAKLJUČKI
BOLŠE OBNAŠANJE OBRAVNAVANIH OKVIRJEV KOT JE BILO ZA PRIČAKOVATI TUDI V PRIMERU PORUŠITVE VIJAKOV NA ENI STRANI STIKA
POVEČANJE ROTACIJSKE KAPACITETE PO PORUŠITVI VIJAKOV NA ŠIBKEJŠI STRANI STIKA
KONSTRUKCIJA POSTANE BOLJ PODAJNA – ZMANJŠANJE POTRESNIH SIL
PREDNAPETJE ZARADI VERTIKALNE OBTEŽBE DELUJE UGODNO
MODEL UPOŠTEVA SAMO MOMENTNO OBREMENITEV. VPLIV OSNE IN STRIŽNE SILE JE LAHKO VELIK ŠE POSEBEJ PO PORUŠITVI VIJAKOV NA ENI STRANI STIKA