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The construction industry generates significant timber waste, particularly from formwork systems, posing environmental and economic challenges. To promote resource recycling and sustainable construction, this study investigates the feasibility of utilizing recycled composite wood joists, fabricated from construction waste timber, polypropylene, polyester thread, and fibre composite bands, as the secondary joists in concrete formwork systems. Through theoretical analysis and on-site experiments, the load-bearing performance of the composite joists was evaluated under equivalent loads corresponding to concrete slabs of varying thicknesses. The results demonstrated that the deflection trends of the joists aligned closely with theoretical predictions, with a maximum deflection of 5.65 mm recorded under 4th load mode. The composite joists met the deformation standards (≤4 mm) for slabs up to 200 mm thickness, which can meet the relevant specifications for formwork construction. The study concludes that the recycled composite wood joist is a viable, eco-friendly alternative for secondary joists in formwork systems, contributing to sustainable construction practices by repurposing construction waste.

Purpose This paper aims to present an evaluation of comparative fire resistance on traditional and engineered wood joists used in the construction of floor systems in residential housing. Design/methodology/approach Fire resistance experiments were carried out on four types of wood joists, namely, traditional lumber, engineered I-joist, castellated I-joist and steel/wood hybrid joist, used in traditional and modern residential construction. The test variables included type of wood joist, support conditions and fire protection (insulation). Findings Results from these tests indicate that webs of engineered I-joists and castellated I-joists are highly susceptible to fire, and failure generally occurs through the burn-out of the web. In addition, engineered I-joists have much lower fire resistance than traditional solid joist lumber. The application of an intumescent coating on an engineered I-joist significantly enhances its fire resistance and yields a similar level of fire resistance as that of a traditional lumber joist. Originality/value The presented fire tests are unique and provide valuable insight (and information) to the behavior and response of four types of wood joists when subjected to gravity loading and fire conditions.

This study investigates the optimization of the design of timber floor joists, taking into account the self-manufacturing costs and the discrete sizes of the structure. This non-linear and discrete class of optimization problem was solved with the multi-parametric mixed-integer non-linear programming (MINLP). An MINLP optimization model was developed. In the model, an accurate objective function of the material and labor costs of the structure was subjected to design, strength, vibration and deflection (in)equality constraints, defined according to Eurocode regulations. The optimal design of timber floor joists was investigated for different floor systems, different materials (sawn wood and glulam), different load sharing systems, different vertical imposed loads, different spans, and different alternatives of discrete cross-sections. For the above parameters, 380 individual MINLP optimizations were performed. Based on the results obtained, a recommended optimal design for timber floor joists was developed. Engineers can select from the recommendations the optimal design system for a given imposed load and span of the structure. Economically suitable spans for timber floor joists structures were found. The current knowledge of competitive spans for timber floor joists is extended based on cost optimization and Eurocode standards.

To realize the unmanned production of precision planetary cycloidal reducer planetary frame finishing, the design of this paper focuses on the robot loading and unloading system for RV reducer planetary frame finishing, and the structural dimensions of the end robot of the system are calculated in detail. The load-bearing parts of the truss affect the strength and stiffness of the whole truss system, and the ANSYS Workbench software is used to perform the static finite element analysis of the truss. The simulation results show that the maximum total deformation of the joist beam is about 0.403mm, which can effectively meet the overall loading and unloading accuracy requirements. The maximum local stress value of the joist is 5.5 MPa, the yield stress of Q235 is 235 MPa, the tensile strength is 375-460 Mpa, which meets the strength requirement, and the automatic loading and unloading system of the joist is determined to meet the design requirements.

The current study investigates the influence of timber-to-concrete connection types on the behaviour of timber–concrete composite (TCC) structures employing metal web timber joists. Two groups of laboratory specimens were prepared, each comprising four samples with push-joisted beams joined by oriented strand board (OSB) and cast with a concrete layer. One group utilised compliant timber-to-concrete connections via perforated steel tape angles, while the other employed rigid connections through epoxy adhesive and granite chips. The specimens, consisting of two 1390 mm long beams of grade PS10 timber, were tested under three-point bending. Experimental results and finite element analyses demonstrated that specimens with compliant connections exhibited 14–16% greater maximum vertical displacements but only a marginal 1.79% reduction in load-carrying capacity compared to those with rigid connections. Findings indicate that connection compliance markedly affects stiffness and deflection but has a minor impact on ultimate strength. These insights can guide optimisation of TCC members with metal web joists, balancing structural performance and design requirements in sustainable timber construction.

The literature identifies concrete and steel as the primary contributors to embodied carbon in building structures and highlights a strong relationship between sustainability and structural system geometry. However, existing studies predominantly focus on one-way systems and flat slabs, while research on two-way joist slabs remains limited and often centred on strength optimisation. In particular, there is a lack of systematic life cycle comparisons of alternative beam configurations within this system. This gap is critical, as early-stage design decisions largely determine the environmental impact of structural systems. This study presents a comprehensive, span-dependent evaluation of four beam configurations, namely Without Beam, Internal Beam, Perimeter Beam, and Full Beam, for reinforced concrete two-way joist slabs used in office buildings. A parametric framework was developed using Eurocode-compliant structural design and nonlinear finite element modelling to assess 36 span combinations ranging from 4 × 4 m to 14 × 14 m. Material quantities were extracted from the final designs and converted into embodied carbon values using cradle-to-gate (A1–A3) emission factors derived from the ICE database. The results demonstrate that beam configuration has a significant influence on embodied carbon and construction cost. For spans below approximately 8 m, beamless systems provide the most material-efficient solution. For spans exceeding approximately 10 m, full-beam configurations offer improved structural efficiency and reduced embodied carbon due to enhanced stiffness and load distribution.

Prefabricated wood construction relies heavily on efficient material handling, yet rigging system design for floor panels remains understudied. This study introduces a novel rigging device that attaches to prefabricated wood I-joist floor panels using self-tapping screws, avoiding potential damage caused by predrilled holes in the sheathing panels and framing members. To establish allowable lifting capacities and optimal installation practices, comprehensive withdrawal tests were conducted on 114-floor panel specimens. Factors influencing withdrawal capacity, such as anchor plate placements, flange materials and width, screw type and quantity, and sheathing panel thickness, were systematically evaluated. Results indicate that withdrawal capacity does not scale linearly with screw quantity and that anchor plates with eight screws centered on the flange enhance performance by up to 20% compared to four-screw configurations. Unexpectedly, thinner sheathing panels yielded higher capacities, potentially due to increased screw penetration depth in the joist flange. In addition, anchor plate orientation, flange width, and flange materials also impact capacity. These findings provide essential data for designing reliable and efficient rigging systems in prefabricated wood construction.

In the article linear buckling analysis of a set of steel trusses braced by purlins and trapezoidal sheeting are conducted. The buckling load factor due to the height of a corrugated sheeting profile is investigated in parametric studies. The minimal height of trapezoidal sheeting required for preventing the sheeting and chords of the trusses against the buckling is obtained. Two groups of models are considered: “axial” model as a simple one and “eccentric” model as a more complex one. In the second group of models, eccentricity between the top chord of the trusses and purlins is considered, by means of equivalent beam elements. The differences between models are indicated and the results are discussed.

One-way joist slab floor systems are commonly favored in modern residential building applications due to their efficiency in architectural and structural design processes. However, a significant number of such buildings experienced heavy damage or collapse mechanisms during the catastrophic earthquakes in Türkiye since they are more vulnerable due to some uncertainties in the design and construction stages. In this regard, although well-known seismic codes such as Eurocode, IBC, and ASCE do not impose additional requirements for the design of structural systems with joist slabs, the seismic codes of some Mediterranean basin countries regulate the ductility levels, use of shear walls, and member/system-based specific requirements. In the present study, the impact of shear wall quantity on the seismic behavior of reinforced concrete buildings with one-way joist slabs was investigated in five-story structural systems, which were basically similar in terms of the slab properties and layout but have different overturning moment ratios (αM = 0.75, 0.60, 0.45, 0). In this context, a total of 88 bi-directional nonlinear time history analyses were conducted on four structural systems, which were highly representative of buildings in the earthquake zones of Türkiye, under real earthquake ground motions. Hence, the seismic behavior demands—including story displacement, inter-story drift and plastic deformations, distributions of plastic hinges, and member-based performance levels—were discussed by the overturning moment ratio that is directly associated with the shear wall quantity in the system. It can be concluded that when these buildings are jointly designed with the shear walls and frames of a high ductility level—through the capacity design principles—the stipulated performance objective can be successfully achieved. While the shear wall quantities ranging from 0.45 to 0.75 did not have a significant impact on the member-based damage across all floors, the frame-only system was found to be inadequate for controlling the lateral deformations due to insufficient stiffness under design-based seismic events.

Additional steel supporting joists (ASSJs) can effectively enhance the anti-overturning capacity of the existing solo-column concrete pier (SCP) bridges. Although the interface consists of bolt connections between steel and concrete is the crucial load-transmitting portion, the design of the interface between the ASSJ and SCP still mainly relies on practical experiences. In an actual bridge rehabilitation project with ASSJs in China, a novel connection comprising large-diameter bolts and an epoxy resin layer was adopted to overcome the shortcomings of the initial design. In this study, connections composited with large-diameter bolts and different interfacial treatments were investigated. Four push-out tests on the interfacial shear performance of steel–concrete connections were carried out. The experimental parameters encompassed the interface treatment method (barely roughened surface, smearing epoxy resin, and filling epoxy mortar) and the number of bolts (single row and double rows). The failure modes were unveiled. According to the experimental results, the interfacial treatment method with filling epoxy mortar could uniformly transfer stress between concrete and steel and improve the shear stiffness and shear resistance of the steel–concrete connections. Compared with specimens with barely roughened interfaces, epoxy mortar and epoxy resin employed at the steel–concrete interface can increase the shear-bearing capacity of connections by approximately 47.71% and 43.46%, respectively. However, the interfacial treatment method with smearing epoxy resin resulted in excessive stiffness of the shear members and brittle failure mode. As the number of the bolts increased from a single row to a double row, the shear-bearing capacity of a single bolt in the specimen exhibited approximately an 8% reduction. In addition, by comparing several theoretical formulae with experimental results, the accurate formula for predicting the shear-bearing capacity of bolts was recommended. Furthermore, the load-bearing capacity of an ASSJ in the actual engineering rehabilitation was verified by the recommended formula GB50017-2017, which was found to accurately predict the shear-bearing capacity of large-diameter bolt connectors with an epoxy mortar layer.