In response to the global drive towards sustainable construction, CLT has emerged as a competitive alternative to other construction materials. CLT buildings taller than 10-storeys and CLT buildings in regions of moderate to high seismicity would be subject to higher lateral loads due to wind and earthquakes than CLT buildings which have already been completed. The lack of structural design codes and limited literature regarding the performance of CLT buildings under lateral loading are barriers to the adoption of CLT for buildings which could experience high lateral loading. Previous research into the behaviour of CLT buildings under lateral loading has involved testing of building components. These studies have generally been limited to testing wall systems and connections which replicate configurations at ground floor storeys in buildings no taller than three storeys. Consequently, to develop the understanding of the performance of multi-storey CLT buildings under lateral loading, the performance of wall systems and connections which replicate conditions of those in above ground floor storeys in buildings taller than three storeys were experimentally investigated. The testing of typical CLT connections involved testing eighteen configurations under cyclic loading in shear and tension. The results of this experimental investigation highlighted the need for capacity-based design of CLT connections to prevent brittle failure. It was found that both hold down and angle bracket connections have strength and stiffness in shear and tension and by considering the strength of the connections in both directions, more economical design of CLT buildings could be achieved. The testing of CLT wall systems involved testing three CLT wall systems with identical configurations under monotonic lateral load and constant vertical load, with vertical loads replicating gravity loads at storeys within a 10-storey CLT building. The results show that vertical load has a significant influence on wall system behaviour; varying the vertical load was found to vary the contribution of deformation mechanisms to global behaviour within the elastic region, reinforcing the need to consider connection design at each individual storey. As there are still no structural design codes for CLT buildings, the accuracy of analytical methods presented within the literature for predicting the behaviour of CLT connections and wall systems under lateral loading was assessed. It was found that the analytical methods for both connections and wall systems are highly inaccurate and do not reflect experimentally observed behaviour.
Poplar laminated veneer lumber (poplar LVL) is made of fast-growing poplar veneer and structural adhesive, which owns the advantages of sustainability and stable quality. Here an innovative poplar LVL floor diaphragm is presented, mainly made up of orthogonal rib beams fitted together using L-shape steel connectors. The paper mainly deals with an experimental study on the bending behavior of the floor under transverse uniform load. Full-scale testing on eight 3.6 m × 4.8 m specimens shows that the damage phenomena of the floor mainly exhibited as the separation between the rib beams and pulling out from the rib beam for the tapping screw. Though some local damage phenomena appeared before the preset maximum loading level, the load-deflection curves basically kept linear for most of the specimens. Under the service load level of 2.5 kN/m2, the distribution of deflection and strain for the full-length rib beam substantially exhibited the characteristic of a two-way slab. In contrast, for the segmented rib beam, the situation was much more complex. Due to the parametric design of the specimens, testing results illustrated that the rib beam height played the most important role in floor stiffness. Next was the sheathing panel, while the role of segmented rib beam spacing was relatively unremarkable. At last, a revised pseudo-plate method was proposed to evaluate the maximum deflection of the novel floor, which considered the composite action by rigidity factors.
This paper presents the development of two new types of hybrid cross-laminated timber plates (HCLTP) with an aim to improve structural performance of existing cross-laminated timber plates (Xlam or CLT). The first type are Xlam plates with glued timber ribs and the second type are Xlam plates with a concrete topping. A numerical...
Point and line loads are common load cases in slabs, however their effects on timber-concrete composite (TCC) slabs are not fully known. Hence, the importance of investigating the associated structural behaviour and developing technical design rules. For this purpose, an investigation including experimental tests and theoretical analyses was performed. Five composite real scale specimens were built, each one associated with a different parameter whose effect on the load distribution was intended to be analysed. Each specimen was subjected, at a time, to point and line loads over each beam at different locations. Numerical modelling showed good agreement with experimental results and give way to a parameter study. In general, the beam over which the load was applied received the highest share of load and the distribution for the remaining beams is significantly affected by the span.
This research investigates the in-plane seismic performance of glulam frames with buckling restrained braces (BRBs) through experimental testing, numerical modelling and design approach development.
With the advancement of engineered wood products (EWPs) and digital fabrication technology, there is an increasing interest and implementation of EWPs for mid-rise and high- rise buildings (also called mass timber buildings) around the world. However, the elastic modulus of timber is only around one-third of reinforced concrete and one-twentieth of structural steel. Additionally, limited ductility is assumed during mass timber building design due to the possibility of timber’s brittle failure in tension. Seismic considerations usually govern the design of lateral force resisting systems (LFRS) in earthquake-prone countries like New Zealand. The relatively lower elastic modulus and limited ductility of timber may cause uneconomical member sizes and increase the number of LFRS (e.g. shear walls and braces). These limitations motivated this research with the main objective to improve the seismic performance of mass timber building using a timber-steel hybrid system.
Experimental tests were conducted for BRB-braced glulam frames (BRBGFs). Following the capacity design approach, BRBs were designed as ductile elements while timber members and BRB-timber interface connections were designed as non-ductile elements. Two 8 m wide and 3.6 m high full-scale BRBGFs were built and tested under cyclic loading. Dowelled connections with inserted steel plates were used in one specimen to connect the glulam members and BRBs, while screwed connections with steel side plates were used in the other specimen. The test results showed that replacing the traditional timber braces with BRBs significantly increased the energy dissipation capacity and minimized the damage in the connections as well as glulam members. The BRBGF with the dowelled connections (S-D) had more initial slips than the BRBGF with the screwed connections (S-S), but both specimens had comparable performance after the serviceability limit state (SLS) load level.
Component-based numerical models were developed in OpenSees to investigate BRBGFs with general configurations. The test data of S-D and S-S were first used to calibrate the numerical models. Then, parametric studies were conducted to investigate the influence of connection stiffness and initial slips on the cyclic performance of BRBGFs. It was shown that the component-based numerical models represented the force-drift responses, accumulated energy dissipation and BRB deformations of S-D and S-S well. When the connection relative overstrength factor os,con was over the BRB overstrength factor os,BRB, the connections were sufficiently stiff to engage BRBs. The strength and stiffness of BRBs and initial slips caused by manufacturer tolerances had a negligible effect on the ultimate strength and energy dissipation under cyclic loading.
A direct displacement-based design (DDBD) approach was developed for the BRBGF system to avoid the complicated process of numerical modelling and facilitate the application of the hybrid system. The critical parameters for extending the DDBD approach to the BRBGF system were first discussed including the displacement profile, yield drift, connection stiffness, hysteresis damping ratio and displacement reduction factor in. Then, the component-based numerical modelling method was used to build one-bay one-storey BRBGFs and verify the critical parameters by pushover analyses and nonlinear time-history analyses (NLTHA). Moreover, the DDBD approach was used to design a set of BRBGF buildings with three, six, and nine storeys. The multi-storey BRBGF models were built in the OpenSees and analysed under a set of ground motions to verify the DDBD approach. The pushover analyses showed that the stiffness of BRB-timber connections needed to be considered when estimating the yield drift of BRBGFs. The NLTHA of one-bay one-storey BRBGFs showed that the relationship between in and ductility factor µ for the Takeda fat model was also suitable for BRBGFs on the conservative side. The NLTHA results of the multi-storey BRBGF models confirmed that the DDBD approach effectively controlled the inter-storey drift ratios of the BRBGF system under seismic loads.
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