An experimental study of composite effect on the behaviour of beam-column joints subjected to impact load

[EN] This paper presents an experimental study on structural behaviour of composite beam-column joints under a middle column removal scenario. Specimens were subjected to impact loads from an MTS drop-weight testing machine. Two joints with welded unreinforced beam flange and bolted web connections were designed per AISC 360-10. One of the beam-column joints had a thicker composite slab. The joints were restrained by pinned supports at two beam ends, which were connected to rigid A-frames to represent boundary conditions from adjacent structures. Test results indicated that the composite slab significantly affected the impact force due to an increase of inertia. However, other structural responses (especially displacement of the middle column) decreased due to increase of stiffness contributed by the thicker composite slab. The finding was that increasing thickness of composite slab can increase the resistance of composite joint significantly due to increased composite effect. More experimental studies were conducted to investigate other types of joints.Chen, K.; Tan, KH. (2018). An experimental study of composite effect on the behaviour of beam-column joints subjected to impact load. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 905-912. https://doi.org/10.4995/ASCCS2018.2018.6952OCS90591

Behaviour of steel and composite beam-column joints subjected to quasi-static and impact loads

[EN] The behaviour of steel and composite beam-column joints was investigated in this paper. A test programme on typical beam-column joints subjected to quasi-static and impact loads was presented. A comparison of different connections was conducted and composite slab effect was investigated. Based on the test results, a component-based modelling approach was proposed and validated. Basic nonlinear springs of beam-column joint models were developed. Mechanical properties of the nonlinear springs were defined based on either current design codes or models proposed by previous researchers. Good agreement with test results was achieved by the component-based models.Chen, K.; Tan, KH. (2018). Behaviour of steel and composite beam-column joints subjected to quasi-static and impact loads. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 29-38. https://doi.org/10.4995/ASCCS2018.2018.7140OCS293

Effect of unprotected interior beams on membrane behaviour of composite floor system in fire, I: Experimental investigation

A number of previous studies on tensile membrane action have been conducted and they are very valuable towards understanding the behaviour of isolated slabs as well as of floor assemblies. However, the role of unprotected interior beams in the development of TMA still has not clearly determined. This paper presents an experimental study on the effect of unprotected interior beams on the behaviour of composite floor assemblies in fire. The experimental observations and results of two one-fourth scale composite slab-beam systems, 3.15 m by 3.15 m in plan, subjected to transient-heating test are presented.The test results show that the presence of interior beams can reduce the slab deflection and greatly enhance the slab load-bearing capacity. The interior beams have a major role in helping the slab in passing through the ‘transition’ stage, and thus the slab can mobilize more tensile membrane forces. Without the interior beams, the compressive ring failure may occur resulting in a little contribution from TMA in the slab load-bearing capacity

Effect of unprotected interior beams on membrane behaviour of composite floor system in fire, II: Numerical assessment

The authors’ companion paper presented the observations and results from two one-forth scale composite beam-slab systems tested in fire. This paper introduces the numerical assessment based on these experimental results. A non-linear finite element model is developed using ABQUS/Explicit to simulate the specimen behaviour. Material properties at elevated temperatures are assumed to vary according to EN 1994-1-2 (2005). The FE model was first validated with the test results, and then was used to examine the effect of unprotected interior beams on tensile membrane action. It is found that the numerical predictions agree well with the test results. The presence of interior beams significantly affects the magnitude as well as the distribution of stress of the slab elements, i.e. mesh reinforcement and concrete slab. The part with maximum tensile force is not necessarily at the slab centre. It may be part of the concrete slab above the edge beams. Shortcomings of the numerical model in predicting the failure modes are indicated

Numerical study on steel-concrete composite floor systems under corner column removal scenario

[EN] This paper evaluates the robustness of steel-concrete composite floor systems subjected to Corner Column (CC) removal scenario based on numerical simulations. Firstly, a FE model is statically analysed subjected to a CC removal scenario, yielding the static load-displacement curve, the failure mode and load-transfer mechanisms. These results are compared with those of composite floor systems under an Internal Column (IC) removal scenario. Besides, the FE model was dynamically analysed by six times under the respective six levels of loads by suddenly removing the corner column. The dynamic displacement-time responses under all levels of loads were obtained. Six pairs of load versus peak displacement constitute the pseudo-static response, to assess the load-carrying capacity and ductility of this composite floor system subjected to a sudden corner-column-removal scenario. Lastly, dynamic increase factors (DIFs) are obtained through comparing the quasi-static and pseudo-static responses, which is further compared with DIF under IC scenario.Fu, QN.; Tan, KH. (2018). Numerical study on steel-concrete composite floor systems under corner column removal scenario. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 897-904. https://doi.org/10.4995/ASCCS2018.2018.6941OCS89790

Square reinforced CFST column to RC beam joint subjected to lateral loading: An investigation using finite element analysis

[EN] Concrete-filled steel tube (CFST) columns have been applied popularly in recent years, where they were connected with reinforced concrete (RC) beams or steel beams in a building. This paper proposes a joint system which connects the square reinforced concrete-filled thin-walled steel tube (RCFTWST) column and RC beam. In the joint system, reinforced bars are located in the square CFTWST column, and stiffeners are welded at adjacent sides of the square steel tube. Besides, the panel zone is strengthened by internal diaphragms. A finite element model (FEM) based on software ABAQUS was developed to evaluate the behavior of the proposed joint system under lateral loading, and parametric analysis was carried out. Based on the analysis results obtained from FEM, some important parameters were chosen. And two specimens were tested under combined axial compression and low-cyclic lateral load to assess the seismic performance of the proposed joint system. The axial load level was chosen as the parameter. Test results showed that all tested specimens performed well up to 5% drift and can satisfy the seismic requirements of “strong-joint weak-component”. In addition, the finite element model (FEM) is verified by comparing with the experimental results. The results can be well predicted by the model.The authors greatly appreciate the financial supports provided by the National Natural Science Foundation of China (nos 51378068 & 51438001), Chongqing Research Program of Basic Research and Frontier Technology (no. cstc2016jcyjA0284) and China Scholarship Council. The opinions expressed in this paper are solely of the authors, however.Zhou, Z.; Gan, D.; Zhou, X.; Tan, KH. (2018). Square reinforced CFST column to RC beam joint subjected to lateral loading: An investigation using finite element analysis. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 449-456. https://doi.org/10.4995/ASCCS2018.2018.7136OCS44945

Punching Tests of Double-Hooked-End Fiber Reinforced Concrete Slabs

Ten (10) high-strength concrete slabs reinforced with new type of steel fibers, the double hooked-end steel fibers, were tested under punching shear loads. The strength of the concrete fc varied from 80 to 100 MPa. The fiber content Vf varied from zero to 1.2%. Two different values of flexural reinforcement ratios ρ (= As/bd) of 0.9% and 1.4% were chosen for this test program. The experimental results showed that the use of double hooked-end steel fibers in the concrete enhances slab performance significantly in many ways. As the fiber volume or fiber content Vf increased, the flexural stiffness of the slab throughout loading history also increased, while both the deflections and crack widths decreased considerably. At the ultimate load stage, the punching shear strength increased by up to 156% compared to non-fibrous concrete slabs. The increase in punching shear strength is significantly higher than the increase introduced by conventional single hooked-end steel fibers. The ductility of the slabs was also significantly improved. Comparisons between design methods with experimental results show that the design method by Concrete Societys TR-34 performs very well. Another method that was based on the yield line theory overestimates the strengths of the slabs. Model Code 2010 method also overestimates the punching shear strengths. Finally, some relevant design recommendations are given