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The test results on the performance of carbon fiber-reinforced polymer (CFRP)-confined reinforced concrete (RC) columns under axial compression load are presented in this study. Twelve slender CFRP-confined circular RC columns with a diameter of 200 mm were divided into two groups. Six specimens with different slenderness ratios of 12, 20, 32, 40, 48, and 56 were contained in each group. The experimental results demonstrated the circumferential CFRP wrap was effective in enhancing the ultimate axial load of slender CFRP-confined circular RC columns compared with unwrapped RC columns. The experimental investigation also showed that the slenderness of the specimens had important influences on the axial compressive behavior, and the axial bearing capacity of slender CFRP-confined circular RC columns decreased as the slenderness ratio increased. In order to predict the load-carrying capacities of slender CFRP-confined circular RC columns, a formula was proposed and the prediction agreed with the experiments. The slenderness of slender CFRP-confined circular RC columns was recommended to be less than 26.5 in practical engineering.

The present work deals with the performance of screw piles constructed in gypseous soil of medium relative density; such piles are extensively used in piles foundations supported structures subjected to axial forces. The carrying capacity and settlement of a single screw pile model of several diameters (20, 30, and 40) mm inserted in gypseous soil is investigated in the present study. The gypsum content of soil used in tests was 40%. The bedding soil used in tests was prepared by raining technique with a relative density of 40%. A physical model was manufactured to demonstrate the tests in the laboratory. The model of screw pile has been manufactured of steel with a total length of 500 mm and helix diameters of 20, 30, and 40 mm continuous over the embedded depth of pile (400 mm). The results of tests showed decreasing the ratio of length to diameter (L/D) resulted in a higher axial carrying capacity of screw piles and low corresponding settlement.

Grouted connections are commonly used in marine engineering, especially on oil platforms, cross-sea bridges, and offshore wind power turbines. The prediction methods for axial carrying capacity of grouted connections with shear keys and their application ranges in current codes were analyzed in this paper. The calculated results by using different codes were compared based on a practical grouted connection between steel piles and the jacket foundation of a wind turbine. The research team conducted axial compression tests on seven specimens, collected a wide range of experimental results to establish a database, and finally compared the standard calculation results with the experimental results. The study indicates that the axial strength of grouted connections predicted by different methods is distinct. The calculation formula of the British Health and Safety Executive (HSE, 2002) has obvious limitations; specifically, with increased shear keys, strength is overestimated, resulting in insecure design outcome of structures. The results calculated by the Norwegian Det Norske Veritas (DNV, 2013) are generally consistent with the experimental results, in which the reduction effect of multiple shear keys was considered. The prediction method of the American Petroleum Institute (API, 2007), which undervalues the bearing performance of connections, is excessively conservative. The method of the combined Norwegian and German Det Norske Veritas–Germanischer Lloyd (DNV-GL, 2016) has wider applicability and is safe, reliable, and economical.

A finite element model is described in this paper, which investigates the behavior of CFS built-up un-lipped channel sections, connected back to back with the help of intermediate web fasteners, subjected to axial load. Finite element package ABAQUS was used to develop the model for built-up columns, which were validated against the test results reported by the authors recently on another paper. Material non-linearity and initial imperfections were included in the FEA model. A parametric study was conducted using the validated FEA model to investigate the effect of screw spacing on axial strength. Axial strengths obtained from the FEA model were compared against the AISI&AS/NZS design strengths; obtained comparisons showed that the AISI&AS/NZS standards were un-conservative for stub and short columns which failed by local buckling whereas the standards were over-conservative for columns failed through overall buckling.

The paper presents the progressive collapse analysis of structures, focusing on the impact of the initial conditions (particularly initial velocity) and the damage. It proposes a method that calculates the residual axial load capacity and damage of columns based on their strain profile and considers the effects of multiple blast locations. The methodology involves the conventional design of a three-story moment-resisting frame, selecting blast parameters, calculating blast pressures, and performing structural and progressive collapse analyses. The findings reveal that the Alternate Load Path Method (APM) overestimates the capacity compared to a benchmark blast–structure interaction analysis, especially when unsuitable initial conditions and damage properties are used. To address this limitation, the paper concludes the recommendations for incorporating appropriate initial conditions and damage considerations for a relatively accurate progressive collapse analysis.

The individual effects of the main reinforcement corrosion and stirrup corrosion on the axial compressive behavior of reinforced concrete (RC) columns were evaluated through axial compression tests on 10 full-scale short columns. The primary experimental parameters were the corrosion location and the corrosion ratio of the steel bar. The electrochemical accelerated corrosion method was applied on nine of the columns, including three columns corroded in the main reinforcement, three columns corroded in the stirrup, and three columns corroded in both the main reinforcement and stirrup. The full-field displacement of the column and strain of concrete were evaluated using a non-contact 3D-DIC (digital image correlation) technique. The results indicated that, with the increase in the main reinforcement corrosion ratio, the width of the longitudinal corrosion crack increased. The transverse corrosion cracks appeared when the stirrup corrosion ratio is larger than 8%, and the increase in stirrup corrosion ratio increased the crack number, but had little effect on the crack width. Compared to the non-corroded RC column, the peak load of specimens with main reinforcement corrosion ratios of 8.02%, 9.01%, and 19.27% decreased by 10.53%, 13.56%, and 19.77%, respectively, and that of the specimens with stirrup corrosion ratios of 7.08%, 12.33%, and 24.36% decreased by 11.59%, 12.07%, and 17.15%, respectively. The axial-compressive-load-carrying capacity of RC columns decreased almost linearly as the corrosion ratio of the main reinforcement increases, while it exhibited an approximately bilinear degradation as the corrosion ratio of the stirrups increases. The stirrup corrosion ratio had less effect on the axial compressive loading capacity of the RC column when it was larger than 7.5%. A model for calculating the axial-compressive-load-carrying capacity of the corroded RC short columns was developed based on the impact mechanisms of the corroded main reinforcement and stirrups on the columns’ axial compressive behavior. The calculated results closely matched the test data, demonstrating that the proposed model can reliably predict the residual load-carrying capacity of corroded columns.

Rockbolts are widely used in the tunnels and underground mining industry for support and reinforcement of the rock mass around the perimeter of the excavation. Better understanding of the load transfer mechanisms of rockbolts could improve rockbolt technology. Current rockbolt testing generally focuses on axial loading of the rockbolt, with shear loading of rockbolts only becoming more prevalent in the last 10–15 years. This research experimentally investigated the load-carrying capacity of five new rockbolts under axial and shear loadings, of which three were friction bolts and two were yielding bolts. Testing was undertaken using high strength concrete blocks to simulate a homogenous rock mass. The yielding style rockbolts provided considerably more tensile load capacity and deformation compared to the inflatable rockbolts; however, the inflatable rockbolts have the ability to deform significantly more in shear than in tension and have similar shear deformation as the yielding-style rockbolts. This research contributes to the understanding of the performance of the new inflatable and yielding rockbolts in different loading conditions and hence provided a benchmark for comparison with other existing friction and yielding bolts. Ultimately, the addition of these new rockbolts in the ground support community would give the site engineers more options to properly select the most suitable rockbolt under varying geotechnical conditions.HighlightsThe inflatable rockbolts (Hydrabolt) performed similarly and could hold peak loads of up to 82-107 kNIn shear loading situations the inflatable rockbolt can achieve peak shear loads up to 91-121 kN.The MP1 Bolt could achieve a maximum tensile load of 273-308 kN while deforming up to 132-135 mm.PAR1 Resin Bolt achieved maximum tensile load of 232-238 kN while deforming up to 148-176 mm.The shear load capacity of the inflatable bolts is greater than the tensile load capacity.

Special-shaped concrete-filled steel tube (SS-CFST) columns can be embedded in the wall, thus preventing the columns from protruding. This feature makes it popular in steel residential buildings. This paper proposes a new special-shaped concrete-filled square steel tube (SS-CFSST) composite column composed of multiple square steel tubes connected by steel hoops to form L-, T- or cross-shaped sections. Eight specimens were tested under axial loads with section shape, construction method, slenderness ratio, steel tube thickness, and steel strength as variation parameters. The structural performance, such as failure modes, peak load, load–displacement curves, load–strain curves, and Poisson’s ratio of the steel tubes, were analyzed. The tests illustrated that the failure modes of hoop-type specimens and weld-type stub columns were mainly the local buckling of steel tubes and bending failure, and those of the weld-type slender columns were mainly overall bending failure. The load-carrying capacity of the hoop-type specimen was higher than that of the weld-type specimen with the same cross-sectional dimensions and slenderness ratio. Next, the stress–strain relationship model of core concrete in the SS-CFSST composite column was established by considering the restraint effect of the connection coincidence area of steel tubes and steel hoops on concrete. Additionally, the finite element model (FEM) of the column was established using this constitutive model. By comparing the failure modes, load–strain curves and bearing capacities obtained from the tests and FEM, the established FEM can accurately evaluate the mechanical properties of SS-CFSST composite columns with steel hoops under axial compression.

Due to their outstanding structural economy and performance, steel-reinforced concrete-filled steel tubular stub (SRCFST) columns have become increasingly popular in recent decades. The concept combines the advantages of both materials by using steel reinforcement inside a steel tube filled with concrete. The concrete filling provides additional stiffness and fire resistance, while the steel reinforcement enhances the column’s strength and ductility. This study covers the advantages of concrete-filled steel tubes (CFST) and steel-reinforced concrete-filled steel tubular stub (SRCFST) columns, highlighting their ability to save site space and exhibit high strength. The primary goal of this study is to replace conventional columns with SRCFST columns that have higher ultimate bearing capacities. The work aims to analyze the ultimate load-carrying capacity and axial compressive strength of SRCFST and CFST columns, as well as the failure mechanisms of these structures. An experimental study on the compressive behavior of SRCFST and CFST columns under axial load was conducted. The results show that SRCFST and CFST columns perform well, with the placement of steel reinforcement inside the tube significantly increasing both the ultimate bearing capacity and axial compressive strength.

To study the axial compression performance of aluminum foam-filled steel tube and empty steel tube as objects, such tubes are studied in this paper, which explores the carrying capacity and deformation behavior of aluminum foam-filled steel tube with different lengths under a quasi-static axial load through experimental research. The carrying capacity, deformation behavior, stress distribution, and energy absorption characteristics of empty steel tubes and foam-filled steel tubes are compared through finite element numerical simulation. The results indicate that, compared with the empty steel tube, the aluminum foam-filled steel tube still presents a large residual carrying capacity after the axial force exceeds the ultimate load, and the whole compression process reflects steady-state compression. In addition, the axial and lateral deformation amplitudes of the foam-filled steel tube decrease significantly during the whole compression process. After filling the foam metal, the large stress area decreases and the energy absorption capacity improves.