Design Of Bolted Connections Research Articles

ВПЛИВ РАДИАЛЬНОГО НАТЯГА БОЛТІВ НА ХАРАКТЕРИСТИКИ НДС МОДЕЛЕЙ З'ЄДНАНЬ ЕЛЕМЕНТІВ КОНСТРУКЦІЙ ЛІТАКА

To study the effect of radial bolt tension on the VAT characteristics of the bolted connection elements of aircraft structures, calculations are carried out using the finite element method, which is based on experimental verification using a model of the bolted connection design with tension. The constructed model is verified by the test of bolted connections, based on the reliability of the three-dimensional model of elastoplastic analysis by the finite element method. A model of the analysis of the influence of the design parameters of the bolted connection for six different tension values was created. A comparative analysis of the influence of different tension values on the nature of the VAT distribution, the initial stiffness and the load-bearing capacity of the bolted connection design was carried out. The results of the study showed that the stress distribution and their concentration can be changed when applying the appropriate fit with tension. At a tension value of 1.5 % of the bolt diameter, the initial stiffness and bearing capacity increase by 14.1 % and 9.33 %, respectively.

Seismic behavior of an innovative bolted connection with dual-slot hole for modular steel buildings

Although a significant advantage for modular steel buildings (MSBs) is suitable for rapid construction, the unexpected installation error and initial defects of components in the construction site may lead to the failure of rapid assembly or even connection between modules. Aiming at the error sensitivity problem of module splicing, this paper proposes a new type of bolted connection with dual-slot hole and two kinds of connection strengthening methods, including diagonal brace strengthening and flange strengthening. To proceed, tests on four full-scale connections with cyclic loads were performed for seismic behavior. The test results presented the specimens’ failure mode, strength and stiffness properties, ductility, and energy dissipation capacity. Following that, the finite element model was validated against test data, and the influence of slot hole size and displacement effect was discussed. Finally, the hysteretic model was given. The results indicated that the proposed connection has reliable load-bearing, stable energy dissipation, and fast splicing capacity. The connection may be classified as semi-rigid type according to the stiffness feature for the structural behavior of MSBs. Both diagonal brace and flange strengthening can effectively improve the connections’ load-bearing capacity but weaken the energy dissipation capacity. The research results could serve as an effective reference for the inter-module bolted connection design of MSBs.

EFFECTIVENESS VALIDATION ON EXISTING DESIGN EQUATIONS FOR THE SUSTAINABLE DESIGN OF MASONRY BUILDING RETROFITS

Due to the unsatisfactory performance of MS544-5 in estimating the design capacity of bolted timber connections, this present study was initiated to validate the existing predictive equations used by the Malaysian Standard (MS544-5). An evaluation of the European Yield Model (EYM) equation was also done to provide an optimal design equation for the bolted connection design in local hardwood. To verify these two sets of equations, a series of bolted timber connection tests was conducted on Nyatoh hardwood. Nyatoh was chosen as its strength makes it ideal for use as structural timbers, either as roof rafters or floor joists in masonry building constructions. The bolted timber connection tests conducted involved eight types of bolt configurations and the tests on each configuration was done in sets of 10 specimens. The experimental values obtained were then compared with the predictive equations of MS544-5 and EYM to examine their effectiveness. From the comparison, it was found that the prediction values given by MS544-5 were overly conservative with an average effective ratio of 0.34 while the EYM had an average effective ratio of 1.09. Thus, the use of EYM equations was recommended for the sustainable retrofit design development of Malaysian masonry buildings.

Experimental investigation of carbon steel and stainless steel bolted connections at different strain rates

A total of 36 carbon steel and stainless steel bolted connections subjected to shear loading at different strain rates was experimentally investigated. The connection specimens were fabricated from carbon steel grades 1.20 mm G500 and 1.90 mm G450, as well as cold-formed stainless steel types EN 1.4301 and EN 1.4162 with nominal thickness 1.50 mm. The connection tests were conducted by displacement control test method. The strain rates of 10 mm/min and 20 mm/min were used. Structural behaviour of the connection specimens tested at different strain rates was investigated in terms of ultimate load, elongation corresponding to ultimate load and failure mode. Generally, it is shown that the higher strain rate on the bolted connection specimens, the higher ultimate load was obtained. The ultimate loads were averagely 2-6% higher, while the corresponding elongations were averagely 8-9% higher for the test results obtained from the strain rate of 20 mm/min compared with those obtained from the lower strain rates (1.0 mm/min for carbon steel and 1.5 mm/min for stainless steel). The connection specimens were generally failed in plate bearing of the carbon steel and stainless steel. It is shown that increasing the strain rate up to 20 mm/min generally has no effect on the bearing failure mode of the carbon steel and stainless steel bolted connections. The test strengths and failure modes were compared with the results predicted by the bolted connection design rules in international design specifications, including the Australian/New Zealand Standard (AS/NZS4600 2018), Eurocode 3 - Part 1.3 (EC3-1.3 2006) and North American Specification (AISI S100 2016) for cold-formed carbon steel structures as well as the American Specification (ASCE 2002), AS/NZS4673 (2001) and Eurocode 3 - Part 1.4 (EC3-1.4 2015) for stainless steel structures. It is shown that the AS/NZS4600 (2018), EC3-1.3 (2006) and AISI S100 (2016) generally provide conservative predictions for the carbon steel bolted connections. Both the ASCE (2002) and the EC3-1.4 (2015) provide conservative predictions for the stainless steel bolted connections. The EC3-1.3 (2006) generally provided more accurate predictions of failure mode for carbon steel bolted connections than the AS/NZS4600 (2018) and the AISI S100 (2016). The failure modes of stainless steel bolted connections predicted by the EC3-1.4 (2015) are more consistent with the test results compared with those predicted by the ASCE (2002).

On the required ductility in beams and connections to allow a redistribution of moments in steel frame structures

The structural behaviour of beam-column joints plays a critical role in the seismic response of frame structures. In the case of steel rack systems, uprights (columns) are usually 3rd or 4th class open thin-walled cold-formed steel members according to Eurocode 3, as such, local buckling occurs before the plastic moment resistance (in the case of the 3rd class) or yield stress (4th class) is achieved. Beams are usually 1st or 2nd class, so they can form a plastic hinge with the rotation capacity required from plastic analysis without reduction of the resistance (1st class) or with a limitation on the rotation capacity due to local buckling (2nd class). For this reason, only beams and connections, which can be easily equipped with additional bolts to increase their structural performance, can provide a post-elastic behaviour with energy dissipation. This paper presents and develops a method capable of evaluating the rotational capacity, or ductility, required by beams and connections to perform a plastic design. The proposed approach allows for the failure mode of the structure to be predicted starting from mechanical properties of structural members, and it is valid for both service and seismic loads. The analytical method could be applied to different structural systems and materials; in the present work it is presented with reference to industrial pallet racks. Theoretical assessment herein of the required plastic rotation for beams and connections provides useful information for bolted connection design to increase capacity of the racks with minimal additional cost.

Proposal for a Mechanics-Based Bolted Connection Design Approach for AS1720.1

The design of bolted connections for timber structures using the Australian standard AS1720, albeit being simple, could lead to unconservative solutions for some common connection configurations. The rationale for a major change in the design Clause 4.4 of AS1720 is explained by highlighting some of the faulty assumptions underlying many of the current provisions. A design approach that addresses all potential ductile and brittle failure modes is proposed. This design approach is mechanics-based and uses the compression, shear and tension strength characteristics of the various materials utilised in the connection through its density property. This paper is focused on the latest international standards implementations for bolted timber connections and proposes a significant change. The methodology proposed here is intended to contribute to the discussion and development of the next Australian timber structures standard. The method is presented and explained, and two examples are provided.

Bolt Thread and Head Fillet Stress Concentration Factors

Linear finite element analysis (FEA) was performed to determine stress concentration factors for the threads and the bolt head fillet in a bolted connection. The FEA models consisted of axisymmetric representations of a bolt and two circular steel plates each 20 mm in thickness. The bolts studied were 8, 12, 16, 20, and 24-mm-dia grade 10.9 metric bolts with the standard M thread profile. The threads were modeled at both the minimum and maximum allowable depths. The fillet between the bolt shank and bolt head connection was modeled at its minimum radius. Each bolt was loaded to its proof strength. A comparison is made to stress concentration factors typically used in bolted connection design. Stress concentration factors in the head fillet were 3.18, 3.23, 3.63, 3.58, and 3.90 for the 8, 12, 16, 20, and 24-mm bolts, respectively. Thread stress concentration factors were highest in the first engaged thread and decreased in each successive thread moving toward the end of the bolt. Stress concentration factors for the shallow thread models ranged from 1.17 to 4.33, 0.87 to 4.32, 0.83 to 4.67, 0.87 to 4.77, and 0.82 to 4.82 for the 8, 12, 16, 20, and 24-mm bolts, respectively. Likewise, stress concentration factors for the deep thread models ranged from 1.18 to 4.80, 0.88 to 4.80, 0.78 to 5.12, 0.83 to 5.17, and 0.82 to 5.22 for the 8, 12, 16, 20, and 24-mm bolts, respectively. [S0094-9930(00)01402-5]

Bolted connection design for sheet steels less than 1.0 mm thick

The results of recently completed shear tests indicate that the current connection provisions set out in the AS/NZS 4600, AISI and Eurocode cold formed steel design standards cannot be used to accurately predict the failure mode of bolted connections that are fabricated from thin G550 and G300 sheet steels. Furthermore, these design standards cannot be used to accurately determine the bearing resistance of bolted specimens based on a failure criterion for predicted loads. The measured variation in bearing resistance between thin 0.42 mm G550 sheet steels and typical 1.0 mm and thicker sheet steels has been used to develop a gradated bearing coefficient method, which is dependent on the thickness of the connected materials and the size of the bolt(s) used in the connection. It is recommended that the gradated bearing coefficient formulation, the unreduced net section resistance, and the Eurocode design method for end pull-out be used in the design of bolted connections.

Simple Formula for Eccentric Bolted Connection Design

This paper develops a simple formula to calculate the strength capacity of an eccentrically loaded bolted connection. The formula is based solely on connection geometry, can include mixed connector sizes, and is shown to be suitable for skewed load cases. The formula includes computations for both high and low eccentricity connections including lap splices. The results compare favorably with experimental data and the ultimate strength method described in the American Institute of Steel Construction (AISC) manual. Because the formula is based only on connection geometry and connector sizes, strength properties can be determined for each connection. These strength properties, once calculated, allow for rapid determination of connection capacity for any eccentricity. One advantage is that connection capacity coefficients can be calculated without using the iterative approach of the ultimate strength method. Because mixed connector sizes and skewed loadings are considered, the formula provides a wider range of connection capacities than the eccentric loads on fastener groups tables in the AISC Manual of Steel Construction .

Bolted Connection Design Values Based on European Yield Model

This paper discusses the calibration of connection strengths predicted by the European yield model (EYM) to the design values for bolted connections tabulated in the 1986 National Design Specification (NDS). Predicted EYM strengths were compared with 1986 NDS design values to arrive at recommended calibration factors for two‐ and three‐member connections with wood and steel side members loaded parallel and perpendicular to grain over the design space. Design values were changed as a result of basing the bolt‐bearing strength of the wood on the specific gravity of a species. Use of Hankinson's formula with bolt‐bearing strength was found to be more expedient for loads at an angle to the grain than using the formula with design values for parallel‐ and perpendicular‐to‐grain loading. The recommended calibration factors result in some increases and decreases in design values. These factors have been incorporated into the 1991 NDS and a proposed specification for load and resistance factor design (LRFD).