Abstract: Background:Solid-web I-joists are some of the most commonly used engineered wood products in residential and commercial buildings for floor and roof assemblies. Web openings, which are required to accommodate services in a building, can reduce the shear capacity and structural integrity of the joists. Open-web joists, which do not require modifications on-site, can overcome this problem.Objective:The objective of this study is to create an all-timber open-web joist product utilising engineered timber with reduced environmental impact compared to existing I-joist products. Joists are manufactured by combining latticed web-components made from Laminated Veneer Lumber (LVL) with solid timber flanges. The structural performance of these novel joists is investigated. Methods:Bending and shear tests were carried out on latticed LVL-webbed I-joists of two different depths, namely, 241 mm and 305 mm. The load-displacement behaviour and failure mode were recorded. The characteristic bending moment and shear force capacity are compared to that of commercially available I-joist products manufactured with a solid web.Results:Failure of the I-joists was found to occur in the web, good load capacities were achieved and the response was predominantly linear elastic to failure. Joists manufactured using PRF adhesive were found to outperform those manufactured using UF adhesive. Conclusion:The latticed LVL web I-joists compared favourably with similar-sized solid-web I-joists with regard to moment and shear capacity and have been shown to be a suitable alternative to commercially available I-joists that can also facilitate openings for services without adversely affecting the structural integrity of the joist.
Abstract: Background:Structural members subjected to strong earthquakes undergo stiffness and strength degradation. To predict accurately the seismic behaviour of structures, nonlinear static methods of analysis have been developed in scientific literature. Generally, nonlinear static methods perform the pushover analysis by applying a monotonic lateral load. However, every earthquake input is characterized by several repeated loads with reverse in signs and the strength and deformation capacities of structures are generally related to the cumulative damage. This aspect is neglected by the conventional monotonic approaches, which tend to overestimate the strength and stiffness of structural members.Objective:This paper aims to investigate the possibility that the Cyclic Pushover Analysis (CPA) may be used as a tool to assess the seismic behaviour of structures. During the CPA, the structure is subjected to a distribution of horizontal forces that is reversed in sign when predefined peak displacements of the reference node are attained. This process repeats in cycles previously determined in a loading protocol.Methods:To investigate the effectiveness of the CPA in predicting the structural response, a steel moment resisting frame is designed as a case study building. A numerical model of this frame is developed in OpenSees. To examine the influence of the loading protocols on the seismic response, the CPA is run following the ATC-24 and the SAC protocols. Additionally, the seismic demand of the case study frame is determined by a Monotonic Pushover Analysis (MPA) and by Incremental nonlinear Dynamic Analysis (IDA).Results and Conclusions:The following results are obtained:• Despite the differences between the SAC and the ATC-24 loading protocols, the CPA applied according to those two protocols led to almost the same structural response of the case study frame.• The CPA showed the capability of catching the stiffness and strength degradation, which is otherwise neglected by the MPA. In fact, given a base shear or peak ground acceleration, the CPA leads to the estimation of larger displacement demands compared to the MPA.• During long (or medium) duration earthquakes, the CPA was necessary to estimate accurately the response of the structure. In fact, at a PGA equal to 1 g, the CPA estimated the top displacement demand with an error lower than 10%, while the MPA underestimated it by 18%.• The importance of considering the cyclic deterioration is shown at local level by the damage indexes of the frame. In the case of long earthquakes, given a top displacement of 600 mm (corresponding to a PGA equal to 1 g), the CPA estimated the damage indexes with an error equal to 12%.
Abstract: Objective:For the purpose of inexpensive and accelerated creation of corrosive resistive load bearing environments, the concept of combing pre-placed aggregate construction methods with Inorganic Polymer (IP) binder was explored.Methods:In this study the concept of combing pre-placed aggregate construction methods with Inorganic Polymer (IP) binder was explored by using laboratory scale experiments.Conclusion:Laboratory scale experiments demonstrate mechanical properties of the constructed bed as well as provide a useful range of component ratios, and ascertain the optimal operating conditions.
Abstract: Background:Reinforced concrete beam-column connections provided with wide beams are widely used in the European residential building stock. Several seismic codes indicate some limitation to be applied to this kind of reinforced concrete buildings due to their reduced performances with respect to those provided with conventional beams.Objective:The paper is focused on improving the knowledge of wide beam-column joints, highlighting the key degradation mechanisms affecting them, mainly related to slip phenomena of beam rebars, especially the rebars placed outside the column width.Methods:The behavior of wide beam-column joints has been evaluated by means of both experimental tests under cyclic loading and accurate nonlinear finite element analyses. The FE models predicted satisfactorily experimental results, thus enabling to carry out additional numerical analyses aimed at checking the effect of the longitudinal reinforcement amount in the beam member.Results:Experimental results show that wide beam-column joints conforming to the Italian seismic code do not exhibit a sufficiently ductile behavior due to damage in the non-confined concrete region, where beam rebars external to the joint core are anchored. Numerical simulations allowed to monitor bond slip of beam rebars as a function of the applied global displacement, showing differences between bars placed inside and outside the column width.Conclusion:Numerical simulations showed that different behavior is expected in case additional beam rebars are placed either inside or outside column width. In the first case, higher peak load and ductility values can be achieved, provided that the amount of beam reinforcement is not high enough to shift damage towards the column or cause high shear stress to the joint core and its consequent fragile failure.
Abstract: Background:Some typologies of masonry constructions ( towers or walls with openings) can be reasonably studied through simple beam or frame-like models. For these structures, shear mechanisms often play an important role inducing failure and collapse.Objective:The paper presents an enriched beam model for studying the in-plane response of masonry walls. Initially formulated for masonry columns, towers and masonry slender structures in general, the model is now modified in order to also capture the shear failure mechanisms, in addition to the flexural ones.Methods:Starting with a one-dimensional no-tension model, a strength domain in the plane of the axial and tangential stress of the beam has been added, which has been defined by limiting both the stress shear component with respect to any possible direction and the main compressive stress.Results:The model, implemented in the FEM computational code MADY, allows for short computational times in studying the response of single panels as well as walls with openings.Conclusion:Comparisons with some experimental results from literature and some numerical results from more refined 2D models show the effectiveness and accuracy of the model’s predictions in terms of global and local response.
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