Chybiński Marcin, Polus Łukasz
Institute of Building Engineering, Faculty of Civil and Transport Engineering, Poznan University of Technology, Piotrowo 5 Street, 60-965 Poznan, Poland.
Materials (Basel). 2022 Jul 30;15(15):5271. doi: 10.3390/ma15155271.
This paper presents the first experimental study of the load-slip behaviour of aluminium-timber composite bolted connections reinforced with toothed plates. The effectiveness of the strengthening was evaluated in laboratory push-out tests. The push-out test samples consisted of laminated veneer lumber panels, aluminium alloy I-beams, and bolts (grade 8.8 10 mm × 125 mm and 12 mm × 135 mm bolts, grade 5.8 10 mm × 125 mm and 12 mm × 135 mm bolts). A group of 16 specimens had toothed plates as additional reinforcement, while 16 specimens had no reinforcement. The impact of the bolt diameter (10 and 12 mm) and bolt grade (5.8 and 8.8) on the behaviour of the connections was also analysed. The values of the ultimate load and the slip modulus for the bolted connections with grade 8.8 10 mm and 12 mm bolts and with grade 5.8 12 mm bolts reinforced by toothed-plate connectors were comparable to the values for the non-reinforced connections. This was because, in the case of grade 8.8 10 mm × 125 mm and 12 mm × 135 mm bolts and grade 5.8 12 mm × 135 mm bolts, the laminated veneer lumber (LVL) slabs split both in the reinforced and non-reinforced connections. The toothed-plate connectors reduced timber destruction in the bearing zones in the LVL slabs. However, they did not protect the LVL slabs against splitting. Therefore, the impact of the toothed plate connectors on the stiffness and strength of the bolted connections with grade 8.8 10 mm and 12 mm bolts and with grade 5.8 12 mm bolts analysed in this paper was found to be negligible. In the case of grade 5.8 10 mm bolts, the LVL slabs did not split. The mean slip modulus of the connections with grade 5.8 10 mm bolts reinforced with toothed plate connectors was 2.9 times higher than that of the non-reinforced connections. However, the strength of the connections with grade 5.8 10 mm bolts was 1.2 times lower after reinforcing. This was because the shanks of the bolts were sheared faster in the reinforced connections than in the non-reinforced connections as a result of the bolt shanks being under the bearing pressure of the aluminium flange, the LVL slab, and the toothed-plate flange. This situation did not occur for the remaining connections because they had a higher strength (grade 8.8 bolts) or a larger diameter (12 mm), and their bolts were less prone to cutting off. The investigated load-slip curves of the reinforced bolted connections can be used for designing and numerical modelling of aluminium-timber composite beams with this type of connection.
本文介绍了对带齿板加固的铝木复合螺栓连接的荷载-滑移行为的首次试验研究。通过实验室推出试验评估了加固的有效性。推出试验样本包括单板层积材面板、铝合金工字梁和螺栓（8.8级10 mm×125 mm和12 mm×135 mm螺栓、5.8级10 mm×125 mm和12 mm×135 mm螺栓）。一组16个试件有齿板作为额外加固，而16个试件未加固。还分析了螺栓直径（10 mm和12 mm）和螺栓等级（5.8和8.8）对连接性能的影响。对于由齿板连接件加固的8.8级10 mm和12 mm螺栓以及5.8级12 mm螺栓的螺栓连接，其极限荷载和滑移模量值与未加固连接的值相当。这是因为，对于8.8级10 mm×125 mm和12 mm×135 mm螺栓以及5.8级12 mm×135 mm螺栓，在加固和未加固连接中，单板层积材（LVL）板均发生了开裂。齿板连接件减少了LVL板承压区的木材破坏。然而，它们并未保护LVL板免于开裂。因此，本文分析得出，齿板连接件对8.8级10 mm和12 mm螺栓以及5.8级12 mm螺栓的螺栓连接的刚度和强度的影响可忽略不计。对于5.8级10 mm螺栓，LVL板未开裂。用齿板连接件加固的5.8级10 mm螺栓连接的平均滑移模量比未加固连接的高2.9倍。然而，加固后5.8级10 mm螺栓连接的强度降低了1.2倍。这是因为在加固连接中，螺栓杆在铝翼缘、LVL板和齿板翼缘的承压作用下，比在未加固连接中更快地被剪断。其余连接未出现这种情况，因为它们具有更高的强度（8.8级螺栓）或更大的直径（12 mm），且其螺栓更不易被剪断。所研究的加固螺栓连接的荷载-滑移曲线可用于此类连接的铝木复合梁的设计和数值模拟。
