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Abstract

Block tearing is a failure mode of steel connections based on rupture of material. In this paper, a numerical model is developed to capture fracture initiation and progression until failure in steel angles connected by one leg using single row of bolts. It was realized using Gurson-Tvergaard-Needleman porous material model, which can accurately trace the behaviour of steel at plastic and ultimate range. Obtained results are validated on laboratory test results in global and local terms. Stress distribution along the failure paths in the gross and net area subjected to shear and tension was investigated for different geometrical arrangements of connections. Observation of rupture mechanisms allowed to compare the design procedures given in Eurocode 3 with connections behaviour. Results of analysis indicate that both plastic stress distribution in gross shear area and ultimate stress distribution in net shear area can limit block tearing resistance, which is consistent with the newest code provisions.
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Authors and Affiliations

Edyta Bernatowska
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. Rzeszow University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2 Street, 35-084 Rzeszow,
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Abstract

In civil engineering structures, steel angles are often used as tensioned elements, because of their ease of fabrication and assembly. For practical reasons, angles are usually connected only by one leg, using a single row of bolts, and rupture of weakened section usually determines a joint capacity. Also, eccentricity affects the distribution of stresses in the net section and hence its load capacity. Assessment of ultimate resistance is a completely different issue compared to the well-known and established problems of plastic resistance and requires advanced material modelling. The paper presents a numerical simulation of net section failure of tensioned angles, made of structural steel grade S275, taking into account ductile initiation and propagation of fracture using the Gurson–Tvergaard– Needleman damage model. Extensive parametrical analysis of ultimate tensile resistance was performed with a wide range of parameters. The typical and well-recognised failure modes were observed as net section fracture and block tearing. Also, an additional failure mode, classified as limited block tearing, has occurred which is not considered in current design provisions. The paper describes the impact of individual geometrical properties of the joint (numbers of bolts, connection length, and distance from the edge of the connected leg to the center of the fastener hole) on the apparent failure form and the resistance obtained.
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Authors and Affiliations

Edyta Bernatowska
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2, 35-084 Rzeszów, Poland
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Abstract

Joints in cold-formed steel framing structures are usually designed as bolted lap type ones with a gusset plate. Unlike the end-plate joints in hot-rolled structures, the load in such joints is transferred through shearing of the bolts and bearing of the material. The prediction of their structural properties may be problematic in viewof unfavourable influence of the hole clearance and hole ovalization resulting from low bearing resistance of thin walls. A few experimental programmes showed that these issues lead to a different behaviour of the whole joint comparing to common end plate type. These concerns may be particularly important for joints under variable loading, which are prone to deterioration of structural properties. The testing programme conducted by the authors was focused on their behaviour under monotonic and cyclic loading with attention to a potential drop of resistance and stiffness. Monotonic tests revealed quite similar course of the joints’ response. In view of high deformability of the specimens at the intermediate stage of each monotonic test, plastic moment resistances of joints were associated with the initial part of the moment-rotation curves and were multiple times lower than maximum moments obtained in the experiments. The quantities of deterioration of structural properties were determined based on cyclic tests. Drop of resistance and stiffness was observed for several levels of loading range, but the trend of decrease varied for each property. Application of the DIC technique allowed one to identify qualitatively and quantitatively the sources of joint deformability.
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Authors and Affiliations

Rafał Budzinski
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. RzeszowUniversity of Technology, Faculty of Civil and Environmental Engineering and Architecture, Al. Powstanców Warszawy 12, 35-959 Rzeszów, Poland

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