Within the context of efficient and sustainable design of buildings a trend towards lightweight structures, e.g. timber structures, is recognizable. This trend implies the necessity of being able to predict serviceability and comfort as well as sound transmission in order to fulfill vibroacoustic requirements. To generate reliable prediction methods, the transfer of energy between building components has to be investigated. Therefore, a detailed understanding of the modeling of the building components, e.g. walls or ceilings, is compulsory. In the low frequency range the Finite Element Method (FEM) is a convenient tool to predict the vibroacoustic behavior. However, without appropriate post-processing it is limited due to the sensitivity of the results at higher frequencies. In the mid-frequency range a sufficient number of modes per band enables the use of statistical methods like the Statistical Energy Analysis (SEA). It delivers averaged results and thus copes with the sensitivity. As both techniques have a restricted validity regarding the frequency range, averaging techniques of the SEA are applied in the post-processing of the FEM to obtain an adapted hybrid approach, the Energy Flow Analysis. This contribution will focus on the Finite Element Model of the building components out of cross laminated timber modeled as orthotropic plates. The Young’s modulus of wood is perpendicular to the fiber comparatively low, which leads to low velocities of longitudinal and shear waves. Hence, at high frequencies thickness-stretch and thickness-shear modes play an important role. These can be activated already at low frequencies within the stiffness controlled region of their amplification function. Hence, their non-resonant contribution can be identified evaluating the potential energy compared to the kinetic one. This phenomenon is verified with the help of solid elements - in comparison with shell elements - by varying the points of excitation across the thickness. Moreover, the dimensions will be modified as well as the junction by inserting an elastic layer. Whereas the SEA is typically not able to represent through-thickness effects of plate-like structures, the energy flow between a wall and a ceiling will be investigated using the hybrid approach.
Experimental tests of a composite concrete-cross-laminated timber (CLT) floor system were conducted. The floor system was constructed with 5-ply CLT panels (6.75 in. thick) made composite with a 2.25 in. thick reinforced concrete topping slab. Four series of tests were performed using different specimen configurations and laboratory testing methods. Tests included: (1) Comparative one-way bending tests (CB) to evaluate the performance of alternative shear connectors used to join the concrete slab to the CLT panel; (2) Orthotropic stiffness and strength tests (OS) to evaluate the elastic orthotropic stiffness of the deck system and provide strength results for weak-axis bending and negative moment strength; (3) Full-scale system performance tests (FS) of a continuous floor span to establish strength at realistic span lengths and the influence of continuity; and (4) Long-term deformation tests (LT) to investigate creep deflections of the composite concrete-CLT floor system considering positive and negative bending influences.
Results include overall strength, elastic stiffness values, deformation capacity, slip deformations along the concrete-CLT interface, predicted neutral axis locations in the composite concrete-CLT systems, and connection deformations.