Brandverhalten von Brettsperrholz

Fire behaviour of cross‐laminated timber Cross Laminated Timber (CLT) is currently used in modern timber structures for load‐bearing wall, floor or roof elements as a high quality, innovative and cost‐effective structural element. Careful planning and implementation ensures the safe use of CLT in buildings with increased fire protection requirements and in accordance with the requirements of building‐design standards (e. g. EN 1995‐1‐1 and EN 1995‐1‐2) [1, 2]. Worldwide, many fire tests with CLT have been per‐formed to investigate the influence of different cross‐sectional build‐ups and various adhesives on the fire resistance of CLT floor and wall elements. This paper gives an overview of the extensive investigations, main outcomes are summarized and recommendations on the fire design of CLT elements are given. The investigations show that an adequate data base exists to reliably describe the fire behavior of CLT.     

The investigation of the tensile behaviors of single L‐joint type bonded with adhesive and rivet

In this study, tensile behaviour of single “L” type joints was investigated experimentally and numerically. Aluminium pieces with 2 mm, 3 mm and 4 mm thicknesses were used as joint materials. Overlap lengths were chosen as 10 mm, 15 mm and 20 mm. Joints were executed with two different rivets as steel and aluminium and 3 M 2216 epoxy based adhesive. Experiments were carried out by means of Shimadzu universal testing machine with 5 kN load cell. While the numerical study was carried out, using ANSYS Workbench, finite element analysis program, models were formed with the same properties as experimental works. Results showed that the samples with 20 mm overlap length had the highest strength of all models. Models with steel rivet had higher strength than models with aluminium rivets for all overlap lengths.     

Forming limit evaluation of adhesive bonded sandwich steel sheets and numerical prediction

In the present work, the effect of hardener to resin ratio of epoxy adhesive on the formability of adhesive bonded steel sheets has been studied. Forming limit curve has been evaluated by hemispherical dome tests at predefined strain-paths. They are predicted by finite element simulations using strain mapping method. Cohesive zone model has been used to model the interface between skin and adhesive core. An improvement in the forming limit of sandwich steel sheets has been observed when the hardener to resin ratio is changed from 0.6 : 1 to 1 : 1 due to the improved plasticity of adhesive core layer at 1 : 1 ratio as compared to others. The forming limit of sandwich sheet made at 1 : 1 ratio is equivalent to base steel sheet of same thickness and grade. This shows the potential use of sandwich sheet in place of base steel sheet. The forming limit curve predictions agree well with experimental data for base sheet, while reasonable agreement is observed in case of sandwich sheet. Numerical prediction of interface delamination show insignificant influence of hardener to resin ratio on the onset of delamination and significant effect of strain-paths.     

Visko‐elastisches Verhalten von Holz‐Klebstoff‐Verbindungen unter zyklischer Zug‐Druck‐Belastung

Visco‐elastic behavior of bonded wood under cyclic tensile and compression loading In the present contribution, a test method is used to simulate the static, cyclic loading of adhesive joints due to swelling and shrinking of the wood and to demonstrate the plastic deformation in the low load range. For tensile shear specimens prepared from beech wood and bonded with three different adhesives (MUF, PRF, PUR), the elastic behavior under cyclic tensile and compression loading was investigated and the loss and storage of energy was determined. All tested adhesives showed viscose parts even at a very low load level of 3 MPa. At a load level of 7 MPa, the PRF joints revealed a more elastic behavior than the other. The increased loss energy determined for the PUR bonding indicates a softening of the adhesive joint.