•Single-sided push-out tests on the boltedshear connectionswith various connection configurations.•Effects of bolt arrangements, concrete types and fibres are studied.•Deformation characteristics of ...the proposed connections are obtained and compared.•Fibre-reinforced high strength concrete is able to improve both strength and ductility of the proposed connections.•Contributions of steel blocks and unthreaded bolt shanks at bolt roots are also established.
In recent years, composite beams with simple on-site assembly using high performance steel and concrete are widely promoted in many parts of the world. It is proposed to use high strength steel bolts to be embedded with fibre-reinforced high strength concrete to form effective shear connections between steel beams and concrete slabs. In order to assess the structural behaviour of these shear connections, a pilot study in the form of a systematic experimental investigation was conducted, and a total of 17 single-sided push-out tests were carried out with shear connections of three different connection configurations. Details of the experimental investigation together with key test results of the bolted connections are thoroughly described in this paper, including shear resistances, failure modes and load-slippage curves.
It was demonstrated that the proposed bolted shear connections with various connection configurations, concrete types and bolt arrangements were able to provide a wide range of shear resistances applicable for construction of large composite structures. Moreover, the use of high strength concrete reinforced with steel fibres and steel blocks was shown to be able to improve both strength and ductility of these shear connections at large deformations. The measured shear resistances of these connections were compared with the design resistances to BS EN 1994-1-1, and a reasonable comparison was found for many of these shear connections. This pilot study provides important test data and insights on the structural behaviour of these bolted shear connections which will facilitate further experimental and numerical investigations for development of complementary design rules to cover the use of fibre reinforced high strength concrete and steel blocks for effective engineering applications.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The paper presents the results of tests on single shear bolted connections of cold-formed steel sections with a wall thickness of 4 mm made with standard fully threaded M16 grade 8.8 bolts. The tests ...were performed for connections with washers and without washers. The obtained results were referred to earlier studies of analogous connections using blind fasteners Huck BOM R16. The failure mode was identified, the load capacity and stiffness were compared, and a method to determine the non-linear load-displacement characteristics of such connections was proposed. The effect of stiffness of joints on structural response of exemplary cold-formed steel frame was shown.
•AE could monitor the transition of mechanical mechanism of GFRP–UHPC hybrid beams.•AE signals with high peak frequencies could reflect the plastic deformation of HSBs.•The intensive degrees of ...b-value points in distinct loading stages are different.•AE intensity analysis could quantitatively assess the damage degree of the specimen.
The failure of glass fiber reinforced polymers (GFRP)–ultra-high performance concrete (UHPC) hybrid beams originate from its mechanical mechanism transition, which is reflected in the plastic deformation of its components. The plastic deformation could be sensitively detected using acoustic emission (AE) technique. In this study, AE technique was utilized to monitor the mechanical mechanism transition of the GFRP–UHPC hybrid beam through the push-out test of a bolted shear connection specimen. Results showed that AE parameters could reflect the damage transition of the push-out specimen from qualitative and quantitative perspectives. First, the variation characteristics of AE hits, energy, and ringing counts were remarkably discernible in the three loading stages of the specimen. And the plastic deformation of high-strength bolts could be identified by the increase in AE signals with high peak frequencies. Besides, the mechanical mechanism transition of the specimen could be distinguished by the intensive degrees transition of b-value points in the different loading stages. Finally, the boundary values of the historic index H(t) and severity (Sr) were proposed to quantitatively evaluate the damage degree of the specimen. AE technique provides a possibility of safety warning for the GFRP–UHPC hybrid beams because of its ability to effectively identify the mechanical mechanism transition.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension (specified as category A and category D connections acc. to EN 1993-1-8) are ...essentially based on the regulations for carbon steel bolted connections. However, bolts made of stainless steels have in principle a different load bearing behaviour compared to carbon steel bolts and should be investigated systematically and considered in the design rules. For this reason, research activities have been carried out within the German research project “Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36” (IGF-No. 20651 N). Herein, experimental investigations and a literature review into the load bearing behaviour under pure tension and single-shear has been carried out to evaluate the resulting shear coefficients α for austenitic and duplex stainless steel bolts of property classes 50 to 12.9 as a basis for implementation in the revision of EN 1993-1-4. Furthermore, a reliability analysis according to EN 1990, Annex D has been carried out to prove the partial safety factor of γM2 = 1.25 for connections. On this basis, new shear coefficients α could be proposed which allow a more economical design of non-preloaded bolted shear connections.
Display omitted
•Revised design rules for shear bearing resistance of bolting assemblies made of stainless steel for implementation in EN 1993-1-4.•Literature review and own experimental investigations regarding the shear load bearing behaviour of stainless steel bolts.•Deviating load bearing behaviour of bolting assemblies made of stainless steel compared to that of bolting assemblies made of carbon steel.•Reliability analysis acc. to EN 1990 to prove the applicability of γM2 = 1.25 for bolted connections.•New shear coefficients α could be proposed for a more economical design.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper investigates the effects of bolt threads on the initial and final stiffnesses of double-shear bolted connections through laboratory tests and finite element (FE) analyses. Nineteen ...specimens composed of 4.7 mm and 8.0 mm thick structural steel plates with bolt diameters of 20 mm and 30 mm having varying end distances are studied. The investigation, which involves shank and thread bolted connections, has found that the threads reduce the initial stiffness but increase the final stiffness. The FE analysis shows that the reduction in the initial stiffness is due to the bolt threads cutting into the connected plate, increasing the initial displacement. However, the same factor moderates the softening behaviour of a thread bolted connection as it approaches its ultimate capacity. The FE simulation shows that in certain cases this newly discovered phenomenon is caused by the threads restraining the crimpling of the plate material downstream of it. The present modelling technique significantly improves the simulation results of bolted connections tested by independent researchers, compared to their own modelling techniques including that which attempts to simulate the thread effects by reducing the diameter of the bolt model. The “elastic” stiffness values obtained from the present laboratory tests are compared against the Eurocode's provision based on the ASTM definition, and ad hoc stiffness formulae are proposed for shank and thread bolted connections.
•Threads reduce the initial stiffness of a bolted shear connection.•Threads increase the final stiffness of a bolted shear connection.•Threads restrain crimpling of plate material in a bolted hollow section.•An accurate finite element modelling technique is presented.•Ad hoc formulae for determining the elastic stiffness of shank and thread bolted connection.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AbstractThis study investigated the behavior of bolted shear connections for fiber-reinforced polymer (FRP)–concrete hybrid beams. Fourteen push-out tests were conducted with varying parameters of ...bolt strength, bolt diameter (dbolt), bolt-embedding length in concrete (hbolt), FRP shear strength (SFRP), and the use of ultra-high performance concrete (UHPC). Tests showed that a larger hbolt leads to smaller slip but has only a slight effect on capacity; specimens with a larger dbolt have greater capacity and smaller slip. Specimens with ordinary-strength bolts (OSBs) failed at bolt shank shear, whereas specimens with high-strength bolts (HSB) failed at FRP flange shear-out associated with a significant improvement in capacity compared with those with OSBs. The use of UHPC substantially reduced slip, but did not improve bolt capacity because the two failure modes do not occur in concrete. The prediction equations for capacity associated with these two failure modes were derived by modifying the existing equations. A salient finding in the load-slip curves of HSB specimens was three loading stages with different slopes: compacting, hardening, and softening. This was different from observations in previous studies on head studs in steel-concrete composite beams and FRP bolts/dowels in FRP-concrete hybrid beams. The load-slip curves of specimens with HSB were fitted by a trilinear model to facilitate design and analysis. Finally, design recommendations for bolted connections were formulated after parametric analysis.
This paper proposes a novel fiber-reinforced polymer (FRP)-concrete hybrid system with local ultrahigh-performance concrete (UHPC) in key parts to accelerate construction and reduce the cost of UHPC. ...Fifteen push-out specimens were tested to investigate the shear behavior of the UHPC-FRP hybrid interface embedded with bolts in a local UHPC slab. The parameters varied were the local UHPC width, types of concrete slabs, bolt diameter, bolt number and bolt embedding length in concrete. Push-out test results showed that (1) the increase in bolt embedding length substantially reduced the bearing capacity, with a maximum reduction of 25.8%; (2) the interfacial bearing capacity and rigidity increased significantly with increasing bolt diameter, while the excessive diameter may cause the failure of GFRP flange shear-out; (3) the increase of the number of bolts improved the interface performance, but decreased the efficiency of a single bolt utilization; (4) the employment of local UHPC increased the slip stiffness by 16.9%, which had similar shear performance to that of the whole UHPC slab; (5) further changing the local UHPC width had little effect on the shear performance of the push-out specimens. Finally, the calculation method of the bolt shear bearing capacity considering the influence of the embedded length was proposed by modifying the existing formula.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Compared to traditional shear keys, bolted shear connections adopted in steel-concrete composite beams or bridges provide the advantages of improved construction efficiency and rapid replacement of ...the deteriorated elements. However, current investigations on the shear performance of bolted shear connectors are quite limited. This paper explores the mechanical behavior of the advanced bolted shear connections embedded in steel and concrete composite beams. A total of 10 push-off test specimens were fabricated and carried out to determine the bolt diameter and the bolt pretension on the failure models, shear strength, initial slip load, shear stiffness, and peak slip of this advanced bolted shear connection. The experimental results demonstrate that bolt sheared off is the primary failure mode in all specimens with a small amount of concrete crushing underneath the bolts. Bolt pretension displays a negligible effect on the shear keys' failure models and the shear capacity, while the concrete spalling area increases as the bolt diameter improves. The initial slip load and the shear stiffness of the advanced bolted shear connections grow as the bolt pretension and bolt diameter increase. Based upon the existing formulae, some design recommendations are proposed for predicting this advanced bolted shear connection.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Composite steel-concrete floor systems represent a ubiquitous structural steel framing system for commercial and industrial buildings in the developed world, which exploit the strengths of reinforced ...concrete and structural steel both symbiotically and in a complementary fashion. However, as attention is being focused increasingly towards minimising emissions and maximising recycling, these composite systems are problematic for many reasons. This paper describes the results of tests on three full-scale sustainable flush end plate semi-rigid beam-to-column joints and three push-out tests with deconstructable tensioned bolted shear connectors, needed to establish the strength of the shear connection in order to design the joints. For this system, precast concrete slabs having a reduced content of ordinary Portland cement are attached compositely to the steel beam using post-tensioned high-strength friction-grip bolts that are unbolted readily at the life-cycle end of the building. This innovative connection system is proposed to circumvent the high-carbon attributes associated with the demolition of conventional steel-concrete composite framing systems. The push-out tests show that the behaviour of specimens with post-installed bolts in clearance holes is significantly different to that of members with stud shear connectors in slabs cast in situ, and the bolted connectors provide reliable and adequate shear connection to composite beams and joints with precast concrete slabs. The test results show that these composite joints have credible rotation and moment capacities within the recommendations of EC3 and EC4, and that fracture of the joint occurs after substantial rotational deformations had been achieved.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
