Preliminary performance-based design of a post-tensioned glue-laminated timber frame

Post-tensioned timber joints have been studied at the ,nstitute of Structural Engineering at the ETH =urich. A post-tensioned beam-column timber joint has been developed using glued laminated timber with local hardwood reinforcement. 2nly a single straight tendon is placed in the middle of the beam and post-tensioned to restrain the rotation of the joint. 1o additional steel elements are used. The developed joint is characterised by a high degree of pre-fabrication and easy assembly on site. The glue-laminated timber moment-resisting frame featuring this joint shows great potential for timber frame structures especially for multi-storey buildings. Robust performance-based design criteria are a necessity for a s uccessful market implementation of the proposed system. A simplified analytical model was developed in order to predict the structural performance of the post-tensioned timber connection and facilitate preliminary performance-based design. This model was implemented in 2penSees using a bi-linear rotational spring approach. The model was verified against an analytical model and validated against tests on a post-tensioned timber joints under gravity loading and under horizontal loading. Moreover, a complex numerical model was developed using 2penSees to check the accuracy of the proposed preliminary design model. The preliminary design model was used to design fictitious moment-resisting post-tensioned glue-laminated timber frame structures using the loads prescribed in the Swiss code. The design process showed that neither the gravity loads nor the seismic load controlled the design. The design was governed by the lateral deformations due to wind. Based on this finding it is recommended to focus further research on increasing the connection stiffness or on adding additional structural elements to address the seismic performance of post-tensioned timber frames in regions of high seismicity

Charney Hall Redesign Using Cross-Laminated Timber

Santa Clara University’s new law building, Charney Hall, was constructed in 2018 using steel and concrete, but was redesigned by this team using Cross-Laminated Timber (CLT) and Glue- Laminated Timber (glulams). Charney Hall is a non-symmetric, incongruent structure with large open rooms up to 6,000 square feet. Glulams are made of several parallel planks of wood glued together with structural epoxy to obtain higher strength in the longitudinal direction. CLT panels are similar to glulams, but the longitudinal grains of wood planks are oriented in perpendicular layers in order to increase strength along the weak and strong axes of the member. These engineered wood products capture the strength and longevity of steel and concrete while lowering the environmental impact during the manufacturing and construction process, so the purpose of this design was to show the applicability of these materials in the United States. The completion of this design required an understanding of product information and material properties provided by manufacturers such as Structurlam along with an understanding of the fire, seismic, and safety research that a few organizations, such as Portland and Oregon State Universities, have conducted. This structural redesign included the design of the gravity system by way of the glulam beams and columns and the CLT floor diaphragms. It also included the design of CLT shear walls for the lateral system and a few poignant connection designs

Theoretical and experimental structural studies of historical Latin-American laminated planked timber arches

This article describes a first group of theoretical and experimental works undertaken at the Polytechnic University of Madrid. One major purpose is to obtain a structural model for the assessment of historical Latin-American vertically laminated planked timber arches built by the Spanish, mainly in the XVII and XVIII centuries. Many of those constructions still stand and represent a notable historical heritage. Pedro Hurtado recently presented his Ph. D. thesis on historical and construction topics. A structural study was then undertaken. This step of the structural research focussed on static analysis, most especially the deformation in the connection system. This article describes part of this first structural research. Even though it is still at a basic level, it shows reasonable agreement with the experimental results. Further static analytical models are been now developed and implemented. The next stage will address the dynamic problem, even though improvements will be made also in the constitutive equations

Vibrational Modal Frequencies and Shapes of Two-Span Continuous Timber Flooring Systems

Based on classic vibrational bending theory on beams, this paper provides comprehensive analytical formulae for dynamic characteristics of two equal span continuous timber flooring systems, including frequency equations, modal frequencies, and modal shapes. Four practical boundary conditions are considered for end supports, including free, sliding, pinned, and fixed boundaries, and a total of sixteen combinations of flooring systems are created. The deductions of analytical formulae are also expanded to two unequal span continuous flooring systems with pinned end supports, and empirical equations for obtaining the fundamental frequency are proposed. The acquired analytical equations for vibrational characteristics can be applied for practical design of two-span continuous flooring systems. Two practical design examples are provided as well

Reliability analysis of a glulam beam

The present case study is an example of the use of reliability analysis to asses the failure probability of a tapered glulam beam. This beam is part of a true structure built for a super market in the town of Kokemaki in Finland. The reliability analysis is carried out using the snow load statistics available from the site and on material strength information available from previous experiments. The Eurocode 5 and the Finnish building code are used as the deterministic methods to which the probabilistic method is compared to. The calculations show that the effect of the strength variation is not significant, when the coefficient of variation of the strength is around 15% as usually assumed for glulam. The probability of failure resulting from a deterministic design based on Eurocode 5 is low compared to the target values and lower sections are possible if applying a probabilistic design method. In fire design, if a 60 min resistance is required, this is not the case according to Eurocode 5 design procedures, a higher section would be required. However, a probabilistic based fire analysis results in bounds for the yearly probability of failure which are comparable to the target value and to the values obtained from the normal probabilistic based design. (C) 2006 Elsevier Ltd. All rights reserved

Flexual buckling of structural glass columns. Initial geometrical imperfection as a base for Monte Carlo simulation

In this paper Monte Carlo simulations of structural glass columns are presented. The simulation was performed according to the analytical second order theory of compressed elastic rods. A previous research on shape and size of initial geometrical imperfections is briefly summarized. An experimental analysis of glass columns that were performed for evaluation of equivalent geometrical imperfections is mentioned too

Seismic Response of a Platform-Frame System with Steel Columns

Timber platform-frame shear walls are characterized by high ductility and diffuse energy dissipation but limited in-plane shear resistance. A novel lightweight constructive system composed of steel columns braced with oriented strand board (OSB) panels was conceived and tested. Preliminary laboratory tests were performed to study the OSB-to-column connections with self-drilling screws. Then, the seismic response of a shear wall was determined performing a quasi-static cyclic-loading test of a full-scale specimen. Results presented in this work in terms of force-displacement capacity show that this system confers to shear walls high in-plane strength and stiffness with good ductility and dissipative capacity. Therefore, the incorporation of steel columns within OSB bracing panels results in a strong and stiff platform-frame system with high potential for low- and medium-rise buildings in seismic-prone areas

The Design of a semi-prefabricated LVL-concrete composite floor

This paper describes the design of a novel semi-prefabricated LVL-concrete composite floor that has been developed in New Zealand. In this solution, the floor units made from LVL joists and plywood are prefabricated in the factory and transported to the building site. The units are then lifted onto the supports and connected to the main frames of the building and to the adjacent units. Finally, a concrete topping is poured on top of the units in order to form a continuous slab connecting all the units. Rectangular notches cut from the LVL joists and reinforced with coach screws provide the composite action between the concrete slab and the LVL joists. This system proved to be an effective modular solution that ensures rapid construction. A design procedure based on the use of the effective flexural stiffness method, also known as the “gamma method” is proposed for the design of the composite floor at ultimate and serviceability limit states, in the short and long term. By comparison with the experimental results, it is shown that the proposed method leads to conservative design. A step-by-step design worked example of this novel semi-prefabricated composite floor concludes the paper

Fire analysis of steel frames with the use of artificial neural networks

The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress-strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature-displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies. (c) 2007 Elsevier Ltd. All rights reserved