The Influence of Freezing and Thawing Process on the Bending Moment Capacity of L-Shaped Heat-Treated Wood Dowel Joints

In this work, the influence of the freezing and thawing process on the bending moment capacity of L-shaped heat-treated wood dowel joints is analysed. The parts of the joints were made of heat-treated ash (Fraxinus excelsior) wood. Half of the analysed joints were randomly divided in two groups. One group was frozen and thawed in a climatic chamber and the other group was kept in laboratory environmental conditions. The bending moment capacity was calculated by means of ultimate failure load, which was experimentally obtained. One-way analysis of variance (One-way ANOVA) was applied to figure out if there is a significant difference between the analysed groups. Based on the obtained results, it was concluded that the freezing and thawing process did not significantly affect the strength of the L-shaped heat-treated wood dowel joints.

Behavior of Non-Shear-Strengthened UHPC Beams under Flexural Loading: Influence of Reinforcement Percentage

In the present work, the structural responses of 12 UHPC beams to four-point loading conditions were experimentally and analytically studied. The inclusion of a fibrous system in the UHPC material increased its compressive and flexural strengths by 31.5% and 237.8%, respectively. Improved safety could be obtained by optimizing the tensile reinforcement ratio (ρ) for a UHPC beam. The slope of the moment–curvature before and after steel yielding was almost typical for all beams due to the inclusion of a hybrid fibrous system in the UHPC. Moreover, we concluded that as ρ increases, the deflection ductility exponentially increases. The cracking response of the UHPC beams demonstrated that increasing ρ notably decreases the crack opening width of the UHPC beams at the same service loading. The cracking pattern the beams showed that increasing the bar reinforcement percentages notably enhanced their initial stiffness and deformability. Moreover, the flexural cracks were the main cause of failure for all beams; however, flexure shear cracks were observed in moderately reinforced beams. The prediction efficiency of the proposed analytical model was established by performing a comparative study on the experimental and analytical ultimate moment capacity of the UHPC beams. For all beams, the percentage of the mean calculated moment capacity to the experimentally observed capacity approached 100%.

Behavior of Non-Shear-Strengthened UHPC Beams under Flexural Loading: Influence of Reinforcement Depth

This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high-performance concrete (UHPC) containing hybrid microsteel straight fibers and natural fine aggregates under four-point flexural loading. The experimental results revealed that the fiber pullout mechanism had a progressive pullout (collapse) mode. A highly flexural crack developed when the fiber pulling mechanism was explicitly triggered, leading to the failure of most beams. The maximum load in beams reinforced by 1.2, 1.6, and 2.0% exceeded that in beams without longitudinal reinforcement by 56, 73, and 94%, respectively. Further, bar reinforcements at 125, 115, 95, 85, and 75 mm depths led to increases of 56, 55, 73, 96, and 94% in beam load capacity, respectively. In addition, bar reinforcement at 115, 95, 85, and 75 mm depths reduced the beams’ ductility by 40, 23, 35, and 39% compared to those with 125 mm depth. All studied UHPC beams had an uncracked phase that extended to a curvature of about 7.5 × 10−6 rad, which occurred at about 10 kNm. The use of the design of experiments was exploited in this investigation to develop a prediction model for the ultimate moment capacity of UHPC beams. This prediction model took into account the sectional and material properties of UHPC beams. To carry out this analysis, a database of 25 beams, developed by other investigators, as well as the present authors, was utilized. With a mean prediction-to-test ratio of 0.92, this prediction model had a reasonable performance capacity. In turn, this model was used to generate isoresponsive surface contours that could be used for UHPC beam design.

Analysis of the Internal Mounting Forces and Strength of Newly Designed Fastener to Joints Wood and Wood-Based Panels

This study aimed to numerically and experimentally analyze the effects of internal mounting forces and selected materials on the stiffness and bending moment capacity of L-type corner joints connected with novelty-designed 3D printed fasteners. The experiments were carried out using medium-density fiberboard, high-density fiberboard, beech plywood, particleboard, and beech (Fagus silvatica L.) wood. The results showed that the joints made of beech wood were characterized by the largest bending moment capacity (12.34 Nm), while the worst properties were shown by particleboard (2.18 Nm). The highest stiffness was demonstrated by plywood joints (6.56 kNm/rad), and the lowest by particleboard (0.42 kNm/rad). Experimental studies have reasonably verified the results of numerical calculations. The test results confirmed that the geometry of new fasteners promotes the mounting forces under the assembly of the joints. It was shown that the higher the density of the materials, the greater the value of the mounting forces (164 N–189 N).

Lateral torsional buckling capacity of corroded steel beams: A parametric study

Thickness reduction due to uniform corrosion increases the tendency of lateral torsional buckling (LTB) of open cross-sections and it reduces the moment capacity of the beam. The effect of the various corrosion cases on the LTB moment capacity (M b,rd) of the I-beams are investigated in this paper. An analytical framework for patch corroded I-beams is introduced to provide a guideline for simulating the nonlinear lateral torsional buckling behaviour of patch corroded simple beams. Hence the effect of different corrosion scenarios to reduce the buckling reduction factor (η LT) is investigated by conducting a parametric study. Twelve different beam lengths were considered to obtain different non-dimensional slenderness ratios (λ LT) in this parametric study. The degraded buckling curves were obtained for each corrosion scenarios.

On the Limit Behaviour of Moment Resisting Connections Under Uncertainties

Moment resisting connections are mainly designed to transfer bending moments and shear forces. Generally speaking, the design strength of a moment resisting connection can be classified as full-strength (moment capacity of the connection equal to or greater than that of the connected member) or partial-strength (the moment capacity of the connection less than that of the connected member). Similar remarks can be made regarding the stiffness defining connection rigid or semi-rigid if compared to the stiffness of the connected member. In the past, full-strength connections have been widely adopted especially in moment resisting frames and their structural performance relied on the proper behaviour of welding. However, the research following the 1994 Northridge and 1995 Kobe earthquakes demonstrated the lower than expected performance of welded connections, stimulating the onset and development of pre-qualified connections to be adopted especially in seismic areas. Among these connections the most studied ones are those belonging to the Reduced Beam Section (RBS) typology, being the so-called “dogbone” connection the most adopted. The dogbone presents a bending strength and a flexural stiffness lesser than the ones of the original structural member. Recently, the authors proposed a special device suitably designed to realize an innovative moment resisting connection for steel beam elements belonging to the RBS typology. Such a device, called Limited Resistance Plastic Device (LRPD), is constituted by three different portions: the central one is devoted to the onset and development of plastic deformations and presents geometrical dimensions reduced with respect to those of the original structural member; the external ones are devoted to recover the stiffness of beam-device system to that of the original structural member and present greater geometrical dimensions. This latter remark allows to affirm that, from a connectivity point of view, the stiffness of LRPD at the column-beam interface, is greater than the one of the original structural member. Another fundamental remark is that the structural connections are intrinsically characterized by uncertainties related either to geometrical or to material ones. Usually, the effect of uncertainties is covered by the use of safety coefficients and the analyses are performed referring only to the nominal values of the geometrical and mechanical characteristics. However, in order to perform a more complete interpretation of the mechanical behaviour of the studied connections, a non-deterministic analysis approach can be used. Aim of the paper is the characterization of the structural behaviour of the referenced connections (“dogbone” and LRPD) taking into account the main geometrical uncertainties and that related to the material strength by performing suitably Monte Carlo simulations and by determining the relevant M-N domains. Starting from the described characterization, different commercial steel profiles will be considered in order to build a series of M-N domains useful to quantify the safety level and the range of usability of the two different RBS approaches. Finally, the implemented applications will lead to demonstrate the greater reliability of LRPD compared to the classical dogbone.

Assessment of the Bending Moment Capacity of Naturally Corroded Box-Section Beams

The steel constructions of mine shaft steelwork are particularly exposed to aggressive environments, which cause large, nonuniform corrosion loss throughout the steel members. A correct assessment of corrosion loss and load-carrying capacity of shaft steelwork is crucial for its maintenance and safe operation. In this article, we present the results of laboratory, numerical, and analytical investigations conducted on naturally corroded steel guides disassembled from shaft steelwork. The steel guides considered had a closed profile formed by welding two hot-rolled channel sections. Laboratory bending tests were carried out on beams with various levels of corrosion loss, corresponding to compact, non-compact, and slender cross sections. Multiple detailed measurements of the thicknesses of naturally corroded walls were used in order to reproduce their nonuniform geometry in finite element (FE) models. The results of numerical simulations of five bending tests showed good agreement with laboratory measurements and replicated the observed failure modes, therefore confirming the applicability of this modeling approach for assessing the moment capacity of highly corroded steel beams when the deteriorated geometry is known. For the purpose of generalization, a series of derived models reflecting the natural corrosion pattern was then developed, and moment capacity statistics were collected through multiple simulations. They showed that the mean moment capacity is determined by the mean wall thickness. However, the minimum moment capacity is strongly affected by corrosion loss variation, particularly for the highly corroded beams. A simplified, analytical modeling approach was also examined, providing fairly good assessments of the mean; however, the minimum moment capacity could not be estimated. This study contributes to the body of knowledge on the mechanical behavior of highly corroded hot-rolled box-section beams.