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New research results on wet‐on‐wet bonded wood‐concrete composite ceilings Timber‐concrete composite ceilings (TTC ceilings) combine the positive mechanical properties of the materials timber and concrete and use these as a building element in a structurally optimized manner. A well‐planned and executed TTC ceiling has good sound and fire protection properties as well as a low tendency to vibrate. Visible wood on the bottom side of the ceiling is valued by User and architects in many ways. The biggest advantage of TTC ceilings compared to classic reinforced concrete ceilings is the reduction in the required concrete volume. The CO2 emissions are correspondingly lower. The simultaneous reduction of the slab's own weight also has a positive effect on the foundation. This article presents new research results for the production of a TTC ceiling using wet‐on‐wet bonding. Based on shear tests performed with slip‐block tests, essential mechanical properties of the bond and its boundary conditions for a successful implementation are presented. Subsequently, structural tests on bonded TTC ceiling elements with a span of up to 8 m will be presented. In the last section of this article, future challenges of rigidly connected TTC ceilings from concrete shrinkage and climatic influences are discussed. [ABSTRACT FROM AUTHOR]

New connection design with reinforced polymer concrete for FRP and timber Decisive for the load bearing capacity, economic efficiency and the design of slender timber constructions or fiber‐reinforced plastics (FRP) are usually the joints. This paper presents a novel connection concept for timber framework constructions. An important feature is a reversible assembly option. Another advantage is the transmission of high stresses without cross‐sectional enlargements. The concept is based on a force transmission through interlocking of toothes in combination with GRP reinforced polymer concrete. Due to its excellent bonding properties with wood and FRP, its load capacity and its free formability, the material enables the development of a completely new joining technology. Using the example of a rigid longitudinal joint, the potentials and challenges of the new construction method with regard to detail development and analysis are demonstrated and discussed. For the novel, cold‐cast connection node extensive numerical and experimental load tests will be presented. Also presented are approaches of a computer‐aided geometry generation and production of the node (rapid prototyping) as well as further development strategy for the overall concept. [ABSTRACT FROM AUTHOR]

New results for epoxy resin based polymer fine concrete with and without GFRP reinforcement Similar to cement‐bound concrete, polymer concrete is a heterogeneous mixture of aggregate and matrix. A substitution of the cement by epoxy has major effects to the mechanical and chemical properties as well as the manufacturing process. Based on its high load capacity under compression and tensile, good chemical resistance, good bond with many materials and short curing time, polymer concrete is used mainly for cement concrete repair and in highly aggressive environment. Technical approvals for polymer concrete are usually limited to compression stresses or limited structural specifications. The ongoing research aim to a cold‐cast detachable connection in rod constructions made of slender timber or GFRP sections. This paper presents properties of unreinforced and reinforced polymer fine concrete based on epoxy. Based on several tests, the properties of different polymer fine concrete and the qualitative influence of the main components aggregate, matrix and air pores are shown. The mechanical properties under bending are presented in the second part. Furthermore, a material model for determining the modulus of elasticity of polymer concrete based on the composition of the polymer concrete is presented. [ABSTRACT FROM AUTHOR]

In den vergangenen Jahrzehnten wurden zahlreiche Untersuchungen zum Trag- und Verbundverhalten von faserverstärkten Holzquerschnitten durchgeführt. Das Hauptaugenmerk lag dabei auf Glas- und Kohlenstofffaserverstärkungen im Verbund mit Brettschichtholzträgern größeren Querschnitts. Im Zuge eines Forschungsprojekts zu kleinen Gitternetztonnenschalen wurden an der TU-Berlin faserverstärkte Fichtenholzquerschnitte geringer Querschnittsgröße mit Glasfaser- oder Kohlenstofffaserverstärkungen untersucht. In dem vorliegenden Beitrag werden die Ergebnisse zum Trag-, Verbund- und Verformungsverhalten dieser kleinteiligen Lamellenquerschnitte vorgestellt. Im Vergleich zu den bekannten Verstärkungen von Brettschichtholz werden hier sehr hohe effektive Bewehrungsgehalte erreicht. Gleichzeitig ist die zur Verfügung stehende Verbundfläche zwischen Holz und Faserverstärkung deutlich größer. The efficiency of fibre reinforced timber lamellas with reduced hight In recent decades the load bearing mechanisms and composite action of fibre reinforced timber beams were investigated in several research projects, with a focus on the reinforcement of larger timber sections, mainly gluelam beams, with a glass or fibre reinforcement glued to the bottom side of the beam. In contrast, the efficiency of a fibre reinforcement for slender timber lamellas was assessed in a recent research project at the Technische Universität Berlin. The load bearing capacity, composite action and the displacements were tested in different test setups and are presented in this paper. In comparison with the previous research, which concentrated on reinforced gluelam beams, the reinforcement ratios are quite high in the current research project. At the same time the area provided for the bond between timber and fibre reinforcement is comparably higher. [ABSTRACT FROM AUTHOR]