Numerical Investigation of Steel-LVL Timber Composite Beams

in ce/papers (2022, August 31)

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies ... [more ▼]

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies showed that timber can be used as an alternative to the concrete slab in hybrid structures. However, the knowledge in steel-timber composite flooring systems is still very limited. This contribution presents numerical investigations of steel-LVL timber composite beams. The load deformation behaviour was determined through 3D finite element models. The design resistance of the composite beams was estimated analytically through a strain-controlled approach. The results of this study show that the resistances obtained in the numerical models and the strain-controlled approach are in good agreement. Moreover, obtained deflections and slip values were given at ultimate load. [less ▲]

Discussion of an algorithm to transfer arbitrary shear connector load-slip curves into an effective shear resistance

in Kolloquiumsband - 23 DASt-Forschungskolloquium (2022, February 22)

The RFCS research project REDUCE (Project No. 710040) investigated dismountable shear connections with preloaded bolts. These connectors have in most cases a slip capacity greater than 6 mm and show a ... [more ▼]

The RFCS research project REDUCE (Project No. 710040) investigated dismountable shear connections with preloaded bolts. These connectors have in most cases a slip capacity greater than 6 mm and show a monotonic increasing nonlinear load-slip behaviour without plastic plateau and failure of the bolt in shear. Current design procedures of steel-concrete composite beams are largely based on the implementation of headed shear studs, which exhibit a rather different load-slip behaviour with a pronounced plastic niveau. Thus, a question turned out, which compression force can be activated by the shear connection in the concrete girder of a composite beam and how can the respective ultimate bending capacity be determined. Hence, this contribution presents an analytical algorithm to estimate the occurring compression force in the concrete girder when demountable shear connectors are used. The proposed algorithm bases on the actual measured load-slip curve of the shear connection and the expected slip along the beam, which is estimated for each single connector to later determine the compression force in the concrete girder. In addition to the explanation of the “general algorithm”, assumptions for practical use have been made for the slip distribution to simplify the calculation of the compression force and an effective shear resistance P_Rd,eff. [less ▲]

Design models for predicting the resistance of headed studs in profiled sheeting

in Steel and Composite Structures (2022), 42(5), 633-647

This paper presents the results from reliability analyses of the current Eurocode 4 (EN 1994-1-1) and AISC 360-16 design models for predicting the resistance of headed stud shear connectors within ... [more ▼]

This paper presents the results from reliability analyses of the current Eurocode 4 (EN 1994-1-1) and AISC 360-16 design models for predicting the resistance of headed stud shear connectors within profiled steel sheeting, when the ribs are oriented transverse to the supporting beam. For comparison purposes, the performance of the alternative “Luxembourg” and “Stuttgart” model were also considered. From an initial database of 611 push-out tests, 269 cases were included in the study, which ensured that the results were valid over a wide range of geometrical and material properties. It was found that the current EN 1994-1-1 design rules deliver a corrected partial safety factor γM* of around 2.0, which is significantly higher than the target value 1.25. Moreover, 179 tests fell within the domain of the concrete-related failure design equation. Notwithstanding this, the EN 1994-1-1 equations provide satisfactory results for re-entrant profiled sheeting. The AISC 360-16 design equation for steel failure covers 263 of the tests in the database and delivers γM*≈2.0. Conversely, whilst the alternative “Stuttgart” model provides an improvement over the current codes, only a corrected partial safety factor of γM*=1.47 is achieved. Finally, the alternative “Luxembourg” design model was found to deliver the required target value, with a corrected partial safety factor γM* between 1.21 and 1.28. Given the fact that the Luxembourg design model is the only model that achieved the target values required by EN 1990, it is recommended as a potential candidate for inclusion within the second generation of Eurocodes. [less ▲]

Numerical Investigation of Steel-LVL Timber Composite Beams

in Proceedings of the XIII Steel and Composite Construction Conference (2021, November 25)

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies ... [more ▼]

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies showed that timber can be used as an alternative to the concrete slab in hybrid structures. However, the knowledge in steel-timber composite flooring systems is still very limited. This contribution presents numerical investigations of steel-LVL timber composite beams. The load deformation behaviour was determined through 3D finite element models. The design resistance of the composite beams was estimated analytically through a strain-controlled approach. The results of this study show that the resistances obtained in the numerical models and the strain-controlled approach are in good agreement. Moreover, obtained deflections and slip values were given at ultimate load. [less ▲]

Numerical study on design rules for minimum degree of shear connection in propped steel-concrete composite beams

in Engineering Structures (2021), 241

This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the ... [more ▼]

This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the revised rules for the minimum degree of shear connection (CEN/TC250/SC4.T3) with respect to the occurring slip. First, a non-linear 3D finite element model was developed through the software ABAQUS 2017 and validated against analytical values of the elastic stiffness and plastic bending resistance. Then, 91 configurations were analysed for different degrees of shear connection η=0.2,0.4…1.0. The span ranges from 6 to 25 m while the geometrical and mechanical properties varied within their typical field of applicability. According to both current and revised rules, 16 configurations with relatively deep beam and “weak” concrete slab exhibited allowable slip values smax significantly higher than 6 m. Therefore, the authors proposed a reduction of the maximum degree of utilization to these special cases. If the proposed reduction is included in the revised rules, none of the considered cases exhibit a slip smax higher than 8 mm while few cases have smax between 6 and 8 mm. For the ease of use, a design proposal is reformulated as a conditional reduction of the plastic bending resistance of the composite section. [less ▲]

Effective resistance of demountable shear connectors

in Proceedings of ICMS (2021, June 16)

Steel-concrete composite construction is structurally efficient but is impossible to dismount where the floor slab is permanently connected to the steel beams through traditional welded studs. This ... [more ▼]

Steel-concrete composite construction is structurally efficient but is impossible to dismount where the floor slab is permanently connected to the steel beams through traditional welded studs. This contradicts the reuse and reduce aspects of the circular economy concept which has recently been introduced to the construction industry. Within the RFCS REDUCE project, several solutions have been proposed. Demountability of the composite beams using the proposed new shear connectors has been successfully demonstrated by push-out tests and full-scale beam tests. Both experiments and numerical simulations showed that the composite beams can develop plasticity even the demountable shear connectors in solid concrete slabs failed in a brittle way. To extend the scope of Eurocode 4 and avoid uneconomic elastic design, effective shear resistance of the demountable shear connectors was defined by using a newly developed algorithm, for the calculation of the plastic moment capacity of composite sections with partial shear connection. [less ▲]

Headed studs in profiled steel sheeting transverse to the beam. Investigations on design resistance of headed stud shear connectors on the basis of the Final Draft of SC4.PT3 (April 2018)

Report (2021)

The unsafety of current design rules for novel types of open-trough deck geometries for the resistance of headed studs in profiled steel sheeting is well known [1] and it was the main reason behind the ... [more ▼]

The unsafety of current design rules for novel types of open-trough deck geometries for the resistance of headed studs in profiled steel sheeting is well known [1] and it was the main reason behind the nomination of CEN/TC250/SC4- Task SC4.T3: “Revised rules for shear connection in the presence of modern forms of profiled sheeting”. During the RFCS research project “DISCCO” (RFCS-CT-2012-00030) [1], a mechanical model was developed on the basis of a large literature study and previous studies [2, 3, 4, 5, 6] while the corresponding design equations were presented by CEN/TC250/SC4.PT3 and further enhanced during the Research Project “ShearCON” of University of Luxembourg. In order to let the current rules of EN 1994-1-1 6.6 (Eq.(2) and (3)) as unchanged as possible, the limits of its suitable field of applicability (Database B1) was investigated thoroughly by means of the statistical procedure of EN 1990 D.8 [7]. The newly proposed equations (Eq. (7) and (8)) apply only to the cases outside these limits (Database B2). In this way, the proposed solution is able to restore the level of safety to its initial value, so that the partial safety factor for the shear connection ϒV=1.25 is adequate. Conversely, the current situation (without including the new design equations) would need a much higher partial safety factor as shown below. [less ▲]

Luxembourg 2050 - Prospects for a Regenerative City Landscape : Report Phase 2

Report (2021)

Effective bending stiffness of steel-concrete composite columns with multiple encased steel profiles

in Journal of constructional steel research (2021), 181

For the structural analysis of steel-concrete composite columns, Eurocode 4 allows only cross-sections with one implemented steel profile and double symmetry. However, there are worldwide more and more ... [more ▼]

For the structural analysis of steel-concrete composite columns, Eurocode 4 allows only cross-sections with one implemented steel profile and double symmetry. However, there are worldwide more and more examples of composite columns with more than one embedded steel profiles, like for example in the International Financial Center of Hong Kong and the Ping Anh Finance Center in Shenzhen. The common practice of analysis of such columns is to use the simple Euler-Bernoulli beam theory to describe the global behaviour. But recently, performed tests reveal that the resulting deformations exceed largely the deformations predicted by the aforementioned analytical model. The presented contribution shows a modified approach to analyse the stiffness of composite columns with multiple encased steel profiles. Based on the performed laboratory tests and numerical simulations with the finite element code Abaqus®, a new method to determine the effective stiffness is proposed. It combines a modified Timoshenko beam theory with embedded Vierendeel truss model – the VTBM model. This modified method leads to a reduced value of the effective stiffness, more realistic deformations at Ultimate Limit State and thus to a more realistic assessment of the Euler's critical buckling load. •Columns used in high-rise buildings are often out of the scope of design codes.•Separated steel cores in a column's cross-section leads to an innovative hypothesis.•Transition from the Euler-Bernoulli beam theory towards Vierendeel truss behaviour.•Vierendeel-like beam behaviour confirmed in tests and finite element simulations.•Proposed novel analytical model allows for a more accurate stability analysis. [less ▲]

Luxembourg 2050 - Prospects for a Regenerative City-Landscape - Report Phase 2

Report (2021)