Bending Stiffness of Hybrid Wood-Metal Composite Beams: An Experimentally Validated Numerical Model

This paper presents an experimentally validated model for the computational analysis of metal-reinforced wooden composites. The model can be used in both research and in industry to effectively estimate how much a certain composite design improves the bending stiffness and strength of a hybrid metal-reinforced wooden component. A model based on computer simulations allows the prediction and analysis of the mechanical behaviour of a hybrid composite material consisting of several interconnected components made of different base materials. The model for different boundary conditions and parameters provides the correct data on stiffness, especially bending, and the associated maximum displacements. It allows for a variation of the mechanical and geometrical properties, and makes it possible to observe the initiation of irreversible change in the window-frame member. The model enables parametrical simulations to find the optimum layout of reinforcements in the window-frame member, as well as to make estimations of the maximum performance of certain designs.

Optiknot 3D—Free-Formed Frameworks out of Wood with Mass Customized Knots Produced by FFF Additive Manufactured Polymers: Experimental Investigations, Design Approach and Construction of a Prototype

Free-formed frameworks are architecturally appealing constructions. They allow for maximum creative freedom as well as for a structural optimization of the support structure. The design and construction of these kind of structures is complex however, and therefore challenging, with each frame member having an individual length, each cladding plate an individual dimension and especially each knot having an individual geometry. The result is that geometry optimization and production technology become the most important processes when striving for an economic and ecological construction. The goals of the authors are the automation of the design process by applying a parametric model and the collection of the complete complexity in the knots as well as the production of these knots without material wastage by additive manufacturing. The development process was split into three different phases: (1) Preliminary experiments determining the tension, compression and bending load-bearing behavior of the knots produced by additive manufacturing, using different polymer-based materials: ABS, ASA, PA-CF, PA6CT, PCX, PETG and a mixture of PLA and ABS. (2) Development of an automated digital workflow for the design and production of these structures by the use of a parametric approach. (3) Design, production and assembly of a full-scale prototype in the form of a free-formed shell structure spanning an area of 20 m2. The prototype was made from fumed oak wood members in combination with white stained plywood panels connected by knots produced by Fused Filament Fabrication (FFF) additive manufacturing, using polymer-based materials and screws. At the end of the contribution, a summary and an outlook on further research is given.

Buckling length of a frame member

In steel frame design, the definition of buckling lengths of members is a basic task. Computers can be used to calculate the eigenmodes and corresponding eigenvalues for the frames and using these the buckling lengths of the members can be defined using Euler's equation. However, it is not always easy to say, which eigenmode should be used for the definition of the buckling length of a specific member. Conservatively, the lowest positive eigenvalue can be used for all members. In this paper, methods to define the buckling length of a specific member is presented. For this assessment, two ideas are considered. The first one uses geometric stiffness matrix locally and the other one uses strain energy measures to identify members taking part in a buckling mode. The behaviour of the methods is shown in several numerical examples. Both methods can be implemented into automated frame design, removing one big gap in the integrated design. This is essential when optimization of frames is considered.

Finite Particle Method-Based Collapse Simulation of Space Steel Frame Subjected to Earthquake Excitation

In the process of collapse failure of the space steel frame subjected to earthquake excitation, complex behaviors often are involved, including geometric nonlinearity, material nonlinearity, fracture, contact, and collisions. In view of the unique advantages of the finite particle method to analyze complex structural nonlinear problems, this paper utilized the finite particle method as the basic means of analysis and used MATLAB software for computational analysis. This paper first derived a finite particle method-based space steel frame model, conducted static analysis and dynamic response analysis under earthquake excitation, and compared findings with ANSYS analysis results to validate reliability. This paper established the fracture criterion and failure mode of a steel frame member. Theoretical derivation and numerical simulation indicate that the finite particle method is a feasible and effective way to simulate the collapse of space steel frame structures subjected to earthquake excitation. This method provides a new approach to study the collapse and anticollapse seismic design of space steel frame structures subjected to earthquake excitation.

NONLINEAR MULTILEVEL ANALYSIS OF REINFORCED CONCRETE FRAMES

Full range analysis of reinforced concrete (RC) members covering the post-crack and post-peak regimes is important for obtaining the deformation response and failure mode of structural members. When a RC member is subject to an increasing external load, the critical sections would exhibit cracking and/or softening. Due to stress relief effect in the proximity of crack opening and plastic hinging, unloading may occur at the adjacent regions. The variable stress states of discrete sections would lead to sectional variation of stiffness, which could not be accounted for by conventional structural analysis methods. In this paper, a nonlinear multilevel analysis method for RC frames whereby the frame members are divided into sub-elements and sectional analysis is utilised to evaluate stiffness degradation and strength deterioration is developed. At sectional level, the secant stiffness is determined from moment-curvature relation, where the curvature is evaluated based on both transverse displacements and section rotations of the frame member. Unloading and reloading behaviour of concrete and reinforcing steel is simulated. In implementing the multilevel analysis, secant iteration is performed in each step of displacement increment to obtain the convergent solution satisfying equilibrium. Numerical example of RC frame is presented to demonstrate the applicability and accuracy of the proposed nonlinear multilevel analysis method.

Experimental Study on Normal-Section Bearing Capacity of Steel Reinforced High-Strength Concrete L-Shape Short Pier Shear Wall

Based on the experimental study of normal-section bearing capacity of four steel reinforced high-strength concrete (SRHC) L-shape short pier shear walls with two-way eccentric compressive load, this thesis discussed the failure pattern and working mechanism and get some general laws about normal-section baring capacity of this kind of specimens. The research results show that: the failure pattern of SRHC L-shape short pier shear wall with two-way eccentric compressive load is classified into two types-large eccentric compression and small eccentric compression; the sectional strain basically fit the plane-section assumption; steel and concrete can practically work cooperatively until the specimens are damaged and the steel of compressive region yielded; the normal section baring properties of the perforated frame member and the trussed frame member were fairly close to each other and the trussed frame has no advantage compared with the perforated one.