Accurately predicting the installation resistance is of great benefit to a rational and economical design of foundations. This research performs a large-deformation finite-element analysis to ...investigate the effect of soil stiffness on the end bearing resistance in uniform clay. Different types of geotechnical structures and foundations, e.g., cone penetrometer, strip foundation, bucket foundation, and deep piled foundation are considered. Results show that soil stiffness has a negligible impact during shallow penetration but becomes pronounced at deep penetration. It is found that for strip footings, effect of soil stiffness is minimal, whereas the end bearing resistances of CPT and deep piled foundation with a partial plug are highly dependent on the soil stiffness. For a rough pile foundation, the resistance factor Nc,pf increases by approximately 30% as soil rigidity Ir increases from 50 to 500. For a bucket foundation, the effect of soil stiffness on the end bearing resistance falls between that of “shallow” and “deep” foundations. Based on the numerical results, empirical expressions are proposed to predict the end bearing resistance factor accounting for the effect of soil stiffness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper presents an experimental program investigating the behavior of high strength steel connections consisting of one bolt in double shear. A total of 24 bolted connections fabricated from ...three grades of high strength steel with the nominal yield strengths of 550MPa, 690MPa and 890MPa were tested. The effects of end distance, edge distance and steel grade on the bolt bearing behavior were evaluated. The bolt hole elongation due to bolt bearing on high strength steel plate was measured and its implication on the plate bearing resistance was discussed. The test results were compared with Eurocode 3 and AISC 360-10 predictions and it was found that Eurocode 3 could be used conservatively to predict the bolt bearing resistance on high strength steel with nominal yield strength up to 890MPa whereas AISC 360-10 method tends to overestimate the bearing resistance of the bolted connection. A regression analysis was performed based on the test data and those from the literature so that a more general method was proposed to predict the bolt bearing resistance on normal strength and high strength steel plate. Splitting failure was observed as a transitional failure mode between tearout failure and net cross-section failure. Splitting failure showed a lower resistance than the bolted connection with tear-out failure, therefore, a reduction factor was proposed to improve the prediction. The upper and lower boundaries of end distance to edge distance ratio for splitting failure were theoretically derived and experimentally verified.
•Experimental study on bolt bearing behavior of high strength steel plate was conducted.•24 bolted connections made from 550MPa, 690MPa and 890MPa steels were tested.•The effects of end distance, edge distance and steel grade were evaluated.•The boundaries for splitting failure were theoretically derived and verified.•Eurocode 3 and AISC 360-10 were calibrated against the experimental results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Multi-bolt high strength steel connections in tandem were tested and simulated.•Full-range load-distribution pattern were analyzed.•Bearing behavior of an individual bolt among the bolt group was ...investigated.•A nonlinear ultimate bearing resistance model was proposed.•Suggestions related to current design codes were given.
This paper presents an experimental and numerical investigation on the bearing behavior of multi-bolt high strength steel connections in single bolt line. Three grades of high strength steel with nominal yield stress of 550 MPa, 690 MPa and 890 MPa were used to fabricate thirty lap connections with two or three bolts. It is found that the deformation capability of high strength steel plate near bolt hole is sufficient to meet the deformation demand of compatibility in multi-bolt connection even with an intended bolt hole misalignment of 2 mm for M24 high strength bolt. The comparison with Eurocode3 and AISC 360-16 is conducted. When no partial or safety factors are considered, the original formulae of Eurocode3 already has sufficient safety while AISC 360-16 gives unsafe predictions. Numerical models were established and verified by test results. With the obtained results, the full-range distribution of internal load among different bolts can be divided into four stages. Features for each stage are summarized and the effect of bolt hole misalignment on the distribution pattern is evaluated. Numerical analysis results indicate that, behavior of an individual bolt in multi-bolt connection may be influenced by surrounding bolts. The formation of critical yielding band between different bolts may explain this influence. Based on the experimental and numerical analyses, this paper proposed a new ultimate bearing resistance model for multi-bolt connections. The proposed model is capable of describing the nonlinearity in the ultimate bearing resistance of multi-bolt connection and achieves improved predicting accuracy compared to classical models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
This paper presents a numerical investigation on the bearing behavior of single-bolt connections with high strength steels in double shear. To simulate the phenomenon of accumulation damage shown in ...the post-peak behavior of bolt bearing and investigate the failure mechanism of tearout and splitting, the framework of ductile metal damage was used in the numerical model. The model was verified against the test results of bolted connections between high strength steel members. With the validated numerical model, a saddle-shaped distribution of the equivalent plastic strain was observed around the bolt hole, which explains the initiation and propagation of the fracture. A pure shear stress band, which is coincidence with the shear fracture in the experiments, was observed in the numerical analysis. In addition, the reduction of ultimate bearing resistance in splitting failure is explained by the increasing of lateral tensile stress at the tip of plate end with the decrease of edge distance. An extensive parametric study of 513 specimens was carried out to evaluate the effect of edge distance and end distance on ultimate bearing resistance. The boundary between tearout and splitting failure was established based on the distribution patterns of lateral tensile stress around the plate end. Finally, a new formula for predicting the ultimate bearing resistance with consideration of splitting failure was proposed.
•Single-bolt connections made from high strength steels were simulated.•The framework of ductile metal damage was adopted in the numerical model.•The mechanism of shear fracture was revealed.•The reduction of ultimate bearing resistance in splitting failure was explained.•A new formula considering splitting failure was proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Improved test methodology for connection with bolt pre-tension was presented.•Full-range distribution of triaxial stress field near bolt hole was analyzed.•Proportions of friction force and bearing ...force were investigated.•A trade-off between ultimate resistance and bearing resistance was discovered.•Comparisons with current codes were presented.
Bolt pre-tension is regularly used in the practical case of bearing-type connection. Due to confinement of lap plates, complicate triaxial stress field can be observed near bolt hole, which may affect bearing behavior of the whole connection. Currently, investigations on the related issues are limited. To fill this research gap, this paper presents a combined experimental and numerical study on high strength steel single-bolt connections with bolt pre-tension. Results reveal several meaningful recognitions on the bearing behavior of connection with bolt pre-tension. Firstly, the effect of bolt pre-tension on the final tearout failure mode is negligible. Secondly, distribution of triaxial stress field initiates with a circular pattern and gradually shrinks to a localized pattern between shear fracture lines at ultimate resistance of the connection. Thirdly, out-plane confinement will limit the piling-up of plate material in front of bolt, which will reduce the related bearing resistance. However, increasing bolt grade is still beneficial to the whole connection due to a trade-off between ultimate resistance of the connection and related bearing resistance. Comparison with current code is further conducted. It is found that current Eurocode3 has adequate design safety for connection with bolt pre-tension while extra safety is needed for current AISC 360-16.
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Geogrid–soil interaction is a key issue to describe geogrid reinforcement mechanisms. In order to investigate the geogrid–soil interface behaviour, both experimental and numerical pullout tests have ...been carried out with modified geogrid samples embedded in granular soil. In the laboratory tests, two different failure modes have been observed depending on the number of geogrid transverse members in this study. Obviously, the maximum pullout resistance increased with increasing number of geogrid transverse members. In the numerical investigations, discrete element software PFC2D has been used. The geogrid–soil interaction under pullout loads has been investigated not only by the qualitative force distributions along the geogrid and in the specimen but also by the quantitative geogrid force, displacement and strain distributions along the geogrid with different numbers of geogrid transverse members. The numerically obtained contributions of transverse members to the total pullout resistance have been used to explain the different failure modes in the laboratory pullout tests. Based on the Fourier Series Approximation (FSA) method, reorientations of contacts and forces in the specimen were presented at different clamp displacements. Moreover, normal stress distributions in the geogrid plane, which is a decisive parameter that can only be evaluated indirectly in the experimental pullout tests, have been obtained directly using the FSA method in the numerical modelling. The experimental and DEM investigation results in this study provide researchers an improved understanding of the geogrid–soil interaction under pullout loads.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study presents a detailed numerical investigation of 7075-T6 and AA-6086 high-resistance aluminium alloy channel-shaped members with strengthened web holes in web crippling. A nonlinear finite ...element (FE) model was developed and validated against the test results reported by the authors and other researchers. The material properties of 7075-T6 and AA-6086 high-resistance aluminium alloy were also obtained from the literature. Utilising this validated model, an extensive parametric study including 1296 models was carried out. This study examined both cases with clamped and unclamped flanges, and the variables were web thickness, bearing lengths, diameter of web holes, stiffener lengths, internal corner radii, and grades of aluminium alloys. Given the absence of existing standards for calculating the web load-bearing resistance of such members with strengthened web holes, the numerical results obtained from the parametric study were used to develop new design formulas with new coefficients through regression analysis. The design strengths calculated by the proposed design formulas were then compared against the FE results. Finally, a reliability analysis was also performed, demonstrating that the proposed design formulas can accurately predict the web load-bearing resistance for these members.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
With the aim of proposing possible solutions for seismic-resistant Automated Rack Supported Warehouses (ARSWs), this paper studies the possibility of considering plastic ovalization of the ...diagonal-to-upright bolted connection to increase the global seismic performance.
In the transversal direction of the structure, so-called cross-aisle direction, diagonals are connected to the upright through a single bolt, and the leading failure mechanism of the connection is plastic ovalization, due to the low thickness of the diagonal element. The bearing resistance is usually far lower than the resistance of the element. Given the difficulties of increasing the bearing resistance without also increasing the resistance of the element, the idea is to exploit the ductility associated to the plastic ovalization and to design all the other members of the upright frame to be over-resistant with respect to that. The actual behaviour of the diagonal-upright system is validated through the execution of an experimental campaign where tensile and compression monotonic tests are performed, as well as cyclic ones, both on short and full-length elements. Various configurations of the connections are tested to see how the geometric parameters (i.e., dimension of the holes for the connection and their position) affect the resistance of the connection and the behavior of the diagonal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
•Non-homogeneous masonry walls including an AAC layer are mechanically characterized.•The interaction between masonry and AAC layer has a positive impact on the resistance.•Strength of the thermal ...layer can be derived from tests on duplets.•Conclusions are valid for centric and eccentric loading.
An experimental research on the resistance of composite masonry walls is presented. The composite specimens considered herein are load-bearing masonry walls comprising two types of masonry units (i.e. regular masonry units with one layer of thermal break elements). The focus regarding the thermal elements has been put on isolation layers made of aerated autoclaved concrete (AAC). The research included extensive laboratory experiments on small and medium scale of homogeneous and composite specimens (stacked blocks and masonry wallets) under uniaxial compression load with and without eccentricity. The experimental results show that the interaction between masonry and thermal elements has a positive influence on the local bearing resistance of the thermal break layer because of the stiffening brought by the upper masonry layers. Based on this observation, interaction factors are proposed. In addition, results indicate that the global strength reduction due to eccentricity showed to be slightly more severe for composite walls in comparison with the homogeneous specimens.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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