Timber-steel Hybrid Research Articles

Steel–Timber Hybrid Buildings: A Comparative Life Cycle Assessment Study of Global Warning Potential Impacts

Mass timber buildings are gaining momentum, as they are seen as an environmental alternative to conventional concrete and steel structures, and they are also being used for mid- and high-rise buildings. This study conducted a comparative LCA analysis of 20- and 40-story building structures made with different combinations of steel and mass timber. The results show that, even disregarding the environmental benefits of the sequestered biogenic carbon by using a 0/0 approach, timber-based structures result in a roughly 25% lower Global Warming Potential (GWP) impact than steel- or hybrid-based equivalent solutions. The results show that the contribution of steel does not bring any GWP advantage (an average increase of 20% is reported); however, steel–timber hybrid structures may still be the only viable solution to attain greater heights. This study also evidences that materials with lower GWP in their production phase can present a viable solution even when long transportation is required, highlighting the importance of the production phase to reach environmental targets.

Seismic performance of a six-story timber moment-resisting frame with timber-steel hybrid beam-to-column joints

Seismic performance of a six-story timber moment-resisting frame with timber-steel hybrid beam-to-column joints

Analysis of Construction Process and Suggestions for Key Construction Measures for Large-Span Spherical Reticulated Steel-Timber Hybrid Structures—Taking the Guangzhou Nano Center Circle Project as an Example

Analysis of Construction Process and Suggestions for Key Construction Measures for Large-Span Spherical Reticulated Steel-Timber Hybrid Structures—Taking the Guangzhou Nano Center Circle Project as an Example

Experimental investigation into the lateral performance of post-tensioned steel-timber hybrid frame with tension-only braces

Experimental investigation into the lateral performance of post-tensioned steel-timber hybrid frame with tension-only braces

Shear performance of glued and screwed timber-steel composite connections for composite timber-steel beams

Shear performance of glued and screwed timber-steel composite connections for composite timber-steel beams

Long-Term Comparative Life Cycle Assessment, Cost, and Comfort Analysis of Heavyweight vs. Lightweight Construction Systems in a Mediterranean Climate

Massive construction systems have always characterized traditional architecture and are currently the most prevalent, straightforward, and cost-effective in many Mediterranean countries. However, in recent years, the construction industry has gradually shifted towards using lightweight, dry construction techniques. This study aims to assess the effects on energy consumption, comfort levels, and environmental sustainability resulting from the adoption of five high-performance construction systems in a multi-family residential building: (i) reinforced concrete structure with low-transmittance thermal block infill; (ii) reinforced concrete structure with light-clay bricks and outer thermal insulation; (iii) steel frame; (iv) cross-laminated timber (CLT); (v) timber-steel hybrid structure. To achieve this goal, a multidisciplinary approach was employed, including the analysis of thermal parameters, the evaluation of indoor comfort through the adaptive model and Fanger’s PMV, and the quantification of environmental and economic impacts through life cycle assessment and life cycle cost applied in a long-term analysis (ranging from 30 to 100 years). The results highlight that heavyweight construction systems are the most effective in terms of comfort, cost, and long-term environmental impact (100 years), while lightweight construction systems generally have higher construction costs, provide lower short-term environmental impacts (30 years), and offer intermediate comfort depending on the thermal mass.

Experimental and parametric study on friction-type high-strength bolted connections between steel frames and cross-laminated timber infill walls

Experimental and parametric study on friction-type high-strength bolted connections between steel frames and cross-laminated timber infill walls

Influence of the joining technique on the structural behaviour of hybrid timber-steel cross-sections

ABSTRACT Timber as construction material has a long tradition and is increasingly coming into focus as a renewable material in the planning and construction of buildings. Nevertheless, there are mechanical limitations, especially for multi-storey buildings or large spans. In order to enable large spans with small cross-sections, steel and timber can be combined in a hybrid cross-section for bending beams. In this case, the performance of the hybrid component decisively depends on the bond of the individual cross-sections. The aim of this publication is to compare and investigate different joining techniques for an efficient bond between timber and steel. Small-scale specimens were used to investigate different bonding methods: dowel-type fasteners, punched metal plate fasteners (PMPF) and adhesive bonds between timber and steel. Adhesive bonded specimens exhibited stiff but brittle behaviour. The adhesive bond remained intact in all tests, while shear failure could be detected in the timber. Adhesive bonds exhibited 93 times the stiffness of dowel fasteners and 5.5 times the stiffness of PMPF. The load carrying capacity increased by approximately 80% compared to dowel-type fasteners and 30% compared to PMPF, demonstrating the superior suitability of adhesive bonds for high performance timber-steel hybrid sections.

Influence of continuous elastic lateral restraints on beams and beam-columns of steel-timber hybrid structures in fire

Influence of continuous elastic lateral restraints on beams and beam-columns of steel-timber hybrid structures in fire

Sustainable and Efficient Structural Systems for Tall Buildings: Exploring Timber and Steel–Timber Hybrids through a Case Study

The paper focuses on tall timber buildings. The major aim of this paper is to identify the most sustainable and efficient structural system to increase the height of timber buildings, also considering steel–timber hybrid structures. First of all, a brief review of tall buildings’ evolution is presented to understand why tall timber buildings are considered nowadays and which are the most adopted structural solutions. Then, the case study of the tallest timber building in the world is selected and utilized as an archetype. Once the model has been validated, seven alternative structural systems are considered by varying the horizontal load resisting system and preserving the same member cross-sections as the reference building. The variants are tested and compared in terms of material consumption, vibration characteristics and lateral load response. Using the best structural system, the height of the building is increased, pushing the structures beyond the current limits and identifying the most efficient option. The idea is to preserve the column cross-sections and balance the increase in gravity loads due to the additional floors by replacing the concrete floors with timber counterparts. With the same structural system, equivalent steel–timber hybrid solutions are finally tested and compared in terms of sustainability to timber-only counterparts and to the original project. The results of analyses show that the use of steel elements combined with timber can lead to optimized and sustainable structural solutions.

Linear vs nonlinear structural vibration behavior of steel-timber composite building elements

Composite structures including wood are increasingly coming into focus due to rising demand for sustainability and, at the same time, high-rise buildings, and long-span components. In this context, steel-timber hybrid building elements are gaining more attention since they offer sufficient load-carrying properties. However, such lightweight structures increase vibration levels and sound transmission. Accurate understanding of the structures is therefore indispensable. Consequently, herein, a novel steel-timber composite building element is studied concerning its vibrational behavior numerically and experimentally. Especially the influence of the joints between steel and timber components is investigated by considering nonlinear behavior due to frictional effects. Therefore, amplitude-dependency regarding eigenfrequencies and damping properties as well as multi-harmonic responses are studied. Hence, nonlinearities are revealed by slight amplitude-dependency and the occurrence of higher harmonics.

Experimental testing of post-tensioned steel-timber hybrid frames equipped with energy-dissipating braces

Experimental testing of post-tensioned steel-timber hybrid frames equipped with energy-dissipating braces

Numerical investigation of lateral behaviour of steel‐timber hybrid frames

AbstractThis paper examines the response of steel‐timber hybrid (STH) lateral stability systems for medium‐rise buildings. A ten‐storey baseline STH structure was designed to codified procedures and compared with a steel‐concrete composite structure. Detailed numerical models were constructed in which specific constitutive representations were assigned to steel‐timber and timber‐timber connections. Parametric investigations on the STH structure were carried out in which the cross laminated timber panel layups, timber shear wall length, and connection characteristics were modified. The study indicated that the STH structure had larger lateral deformations compared to the steel‐concrete structure, both within code limits. For the same design loads, the reduction in self‐weight from the steel‐concrete structure to the STH structure was 73.1%, whilst the floor depth was reduced by 17.2%, respectively. Parametric studies showed that the lateral response of STHs is generally improved with the effective thickness of the timber infill panel and is influenced by the panel layup. Increasing the shear wall length generally enhances the lateral stiffness, yet the overall performance is reduced with the increase of panel connections. The reduction in self‐weight, member sizes and replacement of the concrete with timber led to a reduction in embodied carbon of more than 32.7% whilst achieving similar structural performance.

Fire Performance of Steel-Timber Hybrid Beam Section

Slim-floor-type of steel-timber hybrid floor systems which use steel beams contained within the depth of the cross-laminated timber (CLT) floor slab offer many benefits, but there is still very little research available on the fire resistance performance of these systems. In the study presented in this paper two furnace tests and numerical simulations have been conducted to investigate the thermal profiles of the steel member and CLT slabs and to obtain information on the temperature development and charring of the hybrid beam section when it is exposed to standard fire conditions. Also, the effects of intumescent fire protection on temperatures and charring performance were investigated. Numerical 2D thermal simulations for unprotected and protected cases were conducted using SAFIR software, and the agreement between experiments and numerical-analysis predictions were in general very good. The results show that intumescent protection reduces the temperatures of the steel and CLT components as well as charring depth significantly, and the start of charring at CLT slab support may be delayed if intumescent paint protection thicker than that required for the load bearing steel member is used. The result also showed that CLT temperatures exceed 100°C already in the early stages of the fire which decrease the strength and stiffness properties of CLT much before the start of charring. Therefore, the fire design of the CLT slab support should not only consider the char depth and residual cross-section analysis but also the reduction in strength.

Experimental Investigation on Self-Centering Steel-Timber Hybrid Beam-Column Connections

Self-centering heavy timber frames rely on the self-centering beam-column timber connections to limit damage and provide the recentering capability. However, low compressive strength and stiffness perpendicular to the grain of the timber columns have long been a design challenge, which yields low initial post-tensioning forces and possibly a significant loss of post-tensioning forces over the building service life. To address this issue, this paper proposes a new design solution for the self-centering steel-timber hybrid beam-column connections, in which the timber column is replaced by a steel-timber composite column. Cyclic tests were conducted on four beam-column connection specimens with post-tensioning. During the gap-opening, the composite column provided a stiff foundation to the timber beam. The hysteretic curves of all four connections were in a flag shape. Compared with self-centering beam-column timber connections that had the same geometry and material properties, the proposed connection had a larger connection stiffness and an improved efficiency of dissipating energy. After the cyclic loading, the loss of post-tensioning force of the proposed connection was also lower than that of the counterpart timber connections.

Direct displacement-based design of steel-timber hybrid structure with separated gravity and lateral resisting systems

Steel-timber hybrid structure can bring the benefits of timber and steel together in a more effective way. In this paper, a steel-timber hybrid structure with separated gravity and lateral resisting systems (ST-SGLRS) was proposed, and an iterative direct displacement-based design method was developed for this type of structure. Design examples revealed that the direct displacement-based design method with appropriate iterative steps is feasible for the design of steel-timber hybrid structures with separated gravity and lateral resisting systems. Furthermore, four steel-timber hybrid structures were designed based on the proposed design method, including 6-story, 9-story, 12-story structures with deformable steel-timber connections and a 9-story structure with rigid steel-timber connections, and corresponding OpenSees structural models were generated. Static and dynamic analyses were performed on the models to calibrate the structural performance. Comparing with the analytical result, it is found that the post-yield stiffness of the structure with deformable steel-timber connections decreased less than the structure with rigid steel-timber connections. As the earthquake intensity increased, the inter-story drift of the structure with rigid steel-timber connections increased rapidly. Besides, the residual inter-story drift of the structure with rigid steel-timber connections was generally larger than that of the structure with deformable steel-timber connections, indicating that the deformable connections contribute to the structure's ability to recover after a large earthquake. Finally, the seismic performance of the calibrated structures considering far-field and near-field earthquakes and impulse effect was evaluated via the probabilistic seismic demand analysis method. It is found that the maximum inter-story drift and the residual inter-story drift exceedance probabilities of the structures under near-field pulse-like earthquakes were larger than those under near-field no-pulse and far-field earthquakes. The research outcome aims to provide a fundamental basis for the design and engineering application of steel-timber hybrid structures with separated gravity and lateral resisting systems.

Recovery testing of self-centering steel-timber hybrid beam-column connections

A self-centering steel-timber hybrid beam-column connection design was proposed to improve performance of conventional self-centering timber beam-column connections. The proposed connection utilized a steel-timber composite column to prevent the wood material from being compressed perpendicular to the grain. In this paper, the recovery performance of the hybrid connection was experimentally investigated. Six specimens were prepared for the recovery testing. Three experimental variables, including the initial post-tensioning force, energy dissipator types (sliding friction and metallic yielding), and key parameters of dampers, were considered. After the first loading, the specimens reached their ultimate performance with damage. Then specimens were repaired and loaded for the second time. Five recovery indexes were calculated to quantitatively evaluate the recovery performance of hybrid connections. The effects of different variables on the recovery ability of hybrid connections were explored.

Passive fire protection of steel profiles using wood

Steel-timber hybrid structures are becoming more and more common in the construction industry. They offer high practical advantages as sustainable solutions with high load-bearing capacities and fire resistance. Wood is occasionally used as a passive protection for steel to maintain its mechanical strength as long as possible with the aim to prevent structural collapse under fire. This paper aims to analyse the thermal behaviour of hybrid steel-timber elements through experimental tests and numerical modelling. The fire tests were performed on various steel-timber combinations using T and I steel cross-sections with various wood species. A high-temperature furnace of up to 1200 °C built in the laboratory was used. The results show that wood provides a significant protection to the steel cross-section, mainly to the fully encapsulated IPE profile. Wood performed as an insulating material that significantly reduced the temperature rise in steel. The experimental results are compared to those obtained through thermal simulations using Abaqus software. The comparison shows that the numerical model can be used to evaluate the temperature increase in the steel element protected by timber in high-temperature conditions.

Vibroacoustic response of steel–timber composite elements

With the increasing demand for sustainable construction and, at the same time, for larger spans in buildings and high-rise buildings, composite timber structures are gaining more attention, and steel–timber hybrid elements offer a promising approach. Therefore, this study analyzes a novel steel–timber composite floor structure experimentally and numerically. The investigations focus on the vibrational behavior of the structures while considering nonlinearities due to frictional effects in joints. First, eigenfrequencies, damping properties, and consequently, the vibrational characteristics of the systems are determined. Then, detection of nonlinearity follows, investigating amplitude-dependent stiffness and damping and the occurrence of higher harmonics. Results reveal nonlinearities indicated by the occurrence of higher-order harmonics and slight amplitude-dependent damping. Furthermore, the influence of parameters, such as steel thickness and fastener type, on the vibrational behavior of the structures is investigated, comparing specimens of various configurations. Finally, the experimental results validate a linear Finite Element model using the commercial software ANSYS as a first approach despite the nonlinearities that occurred during the measurements. Nonetheless, further investigations could deal with nonlinear models to get more detailed insight. • Steel–timber structures are investigated in vibroacoustic terms. • Experimental and numerical methods are used. • Nonlinear effects in the joints are considered. • Low amplitude dependence and higher harmonic were detected.

Experimental and analytical study of hybrid steel-timber beams in bending

The combination of timber elements and steel beams can be of high interest for mechanical performances including instabilities and fire protection. In this paper, experiments and numerical modelling are performed to analyse the behavior of various configurations of steel-timber beams in bending. Two timber beams are connected to the web and the flanges of the steel beam. In order to define the material properties of the tested elements, each component (wood and steel) has been tested separately. Then, timber and steel beams have been connected and tested up to failure. The observed behavior shows a limited effect of hybridation in the elastic domain. However, the effect is significant at the ultimate stage. Actually, the combination of timber and steel elements improves the resistance to lateral torsional buckling and local buckling of the steel beam. The stiffness and the strength of these innovative hybrid structures are estimated at SLS and ULS respectively using approaches similar to those proposed in European design rules. The analytical values are close to those obtained from tests even with the failure reached by instability of steel element. However, it appears that for hybrid beams the calculated value of elastic critical bending moment for lateral-torsional buckling needs to be improved. These results highlight the potential of the steel-timber hybrid elements for further developments.