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Long-term performance of post tensioned cross laminated timber (CLT) shear walls: hygro mechanical model validation and parametric analysis

Zeng Xiuzhi, He Minjuan, Li Zeng, Luo Qi

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e68, 1--18

EN

Post-tensioned cross-laminated timber (CLT) shear wall structure is an innovative solution of earthquake resilient structures. The prestressing force of post-tensioned CLT shear walls remarkably affect the structural seismic performance. Due to the time-dependent elastic, creep, and environmental deformation of wood, the prestressing force will change over the service life of the structure. In this study, a hygro-mechanical numerical model for simulating the time-dependent performance of post-tensioned CLT shear walls was established. Moisture diffusion analysis, time-dependent deformation calculation and prestressing force updating were incorporated in the proposed model, which was further validated based on experimental results. Subsequently, a series of parametric analysis was conducted to study the effect of various material properties, geo metric characteristics, environmental conditions and prestressing forces on the long-term performance of post-tensioned CLT shear walls. The analytical results of the key parameters such as the CLT shear wall dimension, the initial prestressing force, and the environmental temperature and relative humidity were presented and discussed. Practical suggestions for enhancing the long-term safety of post-tensioned CLT shear wall structures were proposed.

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Experimental investigation on the influence of lamination aspect ratios on rolling shear strength of cross-laminated timber

Sun Xiaofeng, He Minjuan, Li Zheng

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e22, 2022

EN

Cross-laminated timber (CLT) as one novel engineered massive wood is prone to the rolling shear failure, due to its configuration characteristics of orthogonal orientation of adjacent layers. For comprehending its rolling shear behavior and clarifying the influence of the lamination aspect ratios on the rolling shear strength, pseudo-static monotonic rolling shear tests were conducted on the CLT specimens with aspect ratios ranging from 2.54 to 9.40, based on a modified planar shear test method. Their rolling shear strength or rolling shear resisting capacity was calculated with respect to the influence of the aspect ratios. The damage modes of the rolling shear specimens were analyzed considering the influence of their lamination width. The effect of the lamination width and that of the lamination thickness on the rolling shear strength were investigated, respectively. Besides, in the case of different aspect ratios, the strength modification factor defined as the ratio between the design rolling shear strength to the design parallel-to-grain shear strength of the outermost laminations was provided, which can facilitate the estimation of the rolling shear strength. Considering the influence of the aspect ratios, both the regression equations of the strength modification factor and the predictive equations of the rolling shear strength were proposed. It is found that a highly positive linear correlation exists between the rolling shear resisting capacity and the aspect ratio. The damage modes of the CLT rolling shear specimens depend on their lamination width; besides, when the lamination width increases from 184 to 235 mm, little improvement can be identified for the rolling shear resisting capacity. Meanwhile, larger thickness of the CLT transverse laminations can result in less CLT rolling shear strength. Overall, the proposed equations are capable of predicting the rolling shear strength of CLT fabricated with the SPF lumber. The study can contribute to the comprehension on the CLT rolling shear behaviors and provide reference values for mitigating the possibilities of CLT rolling shear damages in engineering design.

3

Mechanical performance of glulam beam-to-column connections with coach screws as fasteners

He Minjuan, Li Minmin, Li Zheng, He Guirong, Sun Yongliang

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

180--196

EN

The mechanical performance of beam-to-column connections plays an essential role in the design of post-and-beam glulam structures. This paper presents an investigation into the mechanical performance of glulam beam-to-column connections with coach screws as fasteners. A series of monotonic and reversed cyclic loading tests were conducted on the beam-to-column connections with coach screws, and the failure modes, moment-resisting capacity, stiffness, ductility and energy dissipation of the connections were analyzed. Results showed that the use of coach screws was an effective way to increase the initial stiffness, ductility and energy dissipation of the glulam beam-to-column connections. The strength of coach screws and glulam members was fully developed, and the moment-resisting capacity of the beam-to-column connections was improved due to the adoption of the coach screws. It was noted that the rotational deformation and energy dissipation of the beam-to-column connections was mainly governed by the mechanical performance of the screwed connections. Moreover, a separating analytical method and a finite element model were established for the tested glulam beam-to-column connections, and results indicated that the stress distribution, deformation and moment–rotation relationships of the connections can be predicted efficaciously versus the test results.

4

Bolted joints for small and medium reticulated timber domes: experimental study, numerical simulation, and design strength estimation

Shu Zhan, Li Zheng, He Minjuan, Chen Fei, Hu Chao, Liang Feng

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

131--154

EN

This paper proposes a new type of bolted glulam joint for small-span and medium-span reticulated timber dome structures. The joint fastens the timber elements and the angled slotted-in steel plates together with steel bolts. Reasonably simplified experiments were designed and conducted to understand the mechanical properties of the proposed joint. Finite element models were also developed and calibrated with the tested results. A four-line model was provided to explain the mechanical properties of the joints, which were observed from the tests and simulations. To facilitate the future use of the proposed joint, theoretical derivations were provided to estimate its mechanical features. According to the estimation equations, bilinear moment–rotation curves could be easily obtained for the joints with different wood species, member sizes, joint designs, and/or bolt diameters. Finally, full-size structural models were created to investigate the static stability of K6 single-layered reticulated timber domes with the proposed joints. The influences on the ultimate structural stability capacity from the span, the rise-to-span ratio, the joint model (i.e., stiffness), the initial geometric imperfection introduced from the construction, and the load distribution were systematically investigated.