Calculation Of Load-bearing Capacity Research Articles

Research on topology optimization strut-and-tie model and prestress construction for cable-pylon anchorage zone of Fengshuba Bridge

To address the challenges associated with accurate load-bearing capacity calculation and prestress design for the cable-pylon anchorage zone of cable-stayed bridges, a case study focusing on the Fengshuba Bridge is conducted. Utilizing the Solid Isotropic Material with Penalization (SIMP) variable density topology optimization method, a strut-and-tie model (STM) is constructed for the cable-pylon anchorage zone. This model is subsequently employed to verify load-bearing capacity of the struts and nodes within the cable-pylon anchorage zone, as well as to calculate the required quantity of circumferential prestressing tendons. Additionally, a spatial segmental finite element model is established for the cable-pylon anchorage zone to perform a detailed analysis of prestressed structural optimization. This analysis determines various structural details, including the arrangement of prestressing tendons along the height, the design for prestressing blind zones, and the quantity of prestressing tendons. Subsequently, the optimized model is subjected to stress verification. The research results indicate that the adoption of dispersed tendon arrangement results in reduced principal tensile stress within the cable-pylon anchorage zone, in contrast to the concentrated tendon arrangement. The introduction of short prestressing steel bundles within the conduit of prestressing blind zones uniformly enhances the pre-compressive stress on the cable-pylon side wall. Due to the Poisson effect of materials, it is necessary to arrange prestressing tendons appropriately within the cable-pylon anchorage zone. Arranging prestressing steel bundles according to the proposed STM and structural optimization method adequately fulfills the structural force requirements of the cable-pylon anchorage zone.

Slenderness effects on concrete-filled square steel tube columns strengthened with CFRP grid-reinforced ECC matrix

This study presents an experimental investigation aim at evaluating the slenderness effects on concrete-filled square steel tube columns strengthened with a carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite matrix. Thirteen columns were subjected to axial compression, with the studied parameters including the length-to-width (L/B) ratio, CFRP grid layer number, concrete strength grade, and width-to-thickness ratio of the steel tube. Test results revealed that slender columns experienced an increase in load-bearing capacity ranging from 27.1 % to 32.4 % after strengthening, while the ductility enhancement reached a peak of 52.0 %. A column with an L/B ratio of 5.87 exhibited slight bending deformation in a localized region upon failed, with CFRP grid ruptured at the corner. While columns with L/B ratios of 7.83 and 9.78 failed due to the loss of stability, displaying overall bending deformation. The increase in L/B ratio accelerated the loss of stability, resulting in a decrease in the ultimate load. As the L/B ratio increased from 2.97 to 5.93, 7.91 and 9.89, the ultimate loads of the strengthened columns decreased by 7.4 %, 9.2 %, and 15.4 %, respectively. A load-bearing capacity calculation model of slender strengthened columns was developed using the fiber element method. Through numerical analysis, a stability coefficient was introduced, and a simplified calculation formula was proposed to predict the stability bearing capacity.

ОЦЕНКА МЕТОДИК РАСЧЕТА ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ ПО ПРОЧНОСТИ ПРИ ДВУХОСЕВОМ ДЕЙСТВИИ ПОПЕРЕЧНЫХ СИЛ

The current design standards for reinforced concrete structures in the Russian Federation do not contain methods for calculating bending elements subjected to biaxial action of shear forces. However, methods for calculating such structures exist and are given in the works of domestic and foreign researchers, as well as in the design standards of past years. This article selects data on the results of 33 tests of beams subjected to action of biaxial shear forces. The results of selected tests were compared with the results of theoretical calculations of the bearing capacity of elements under the biaxial action of shear forces using various analytical methods. A brief overview of existing analytical techniques is provided. A comparison of test results and theoretical calculations is presented in tabular and graphical form. The purpose of the work is to identify existing methods for calculating reinforced concrete bended elements under biaxial action of transverse forces, allowing to obtain load-bearing capacity calculation results that are as close as possible to the test results.

Experimental investigation and simulation analysis of cast-steel joints under vertical pressure

The joint made of cast steel is frequently utilized within a treelike column structure to ensure a smooth transition. It is of great significance in ensuring the overall structural safety, but currently, the mechanical property and bearing capacity of this type of joint cannot be fully understood. This study investigates the load characteristics of three-forked cast steel joints through concrete experiments, finite element analysis, and regression method formula derivation, filling the gap in mechanical properties and calculation formulas of forked cast steel joints. Initially, a comprehensive model of the cast-steel joint, sourced from a practical engineering, underwent vertical load testing. Detailed scrutiny of stress distribution and vertical displacement of the tested joint was conducted based on the experimental outcomes. Subsequently, a finite element model of the tested joint was constructed using SolidWorks and subjected to analysis via ANSYS. The numerical findings were juxtaposed with experimental data and extrapolated to encompass other parametric scenarios. Ultimately, a regression analysis method was employed to derive a calculation formula for the load-carrying capacity of branch-bearing cast-steel joints. The regression analysis method can accurately obtain the load-bearing capacity calculation formula for tree-shaped joint models and can be extended to determine corresponding branch and main pipe dimensions, as well as the deviation angle between branches and the main pipe, under known load conditions. This improves design efficiency and accuracy. Comparative analysis reveals a substantial concurrence among experimental, finite element analysis, and formula-based predictive outcomes. The maximum error between experimental results and those obtained from finite element analysis is 9.02%. The maximum error between the results calculated using the load-bearing capacity formula derived from regression methods and those from finite element analysis is only 1.9%.

Concrete and reliability of existing prestressed bridge structures

A large number of post-tensioned concrete bridges were built in the second half of the last century. They have often been insufficiently maintained during their lifetime (usually around 50 years). Nowadays, these structures exhibit significant deterioration, mainly due to leakages and also due to various other deficiencies such as a small concrete cover. Their load-bearing capacity needs to be verified. This paper focuses on estimating the load-bearing capacity calculation of existing post-tensioned concrete bridges. In the engineering practice, this is carried out using the partial factor method according to the currently valid standards (Czech standards ČSN and the Eurocodes), which often impose more stringent requirements than the original standards. The partial factor method then often leads to low load-bearing capacities. This study deals with the bridge for which a very low load-bearing capacity has been determined. For this reason, a comparative probabilistic analysis was performed, allowing for a better description of the uncertainties in the resistance and load effect variables. The probabilistic approach appears to be less conservative and yields a higher load-bearing capacity.

Model uncertainties in action effects and load bearing capacity calculation in statically indeterminate reinforced concrete structures

AbstractFor the dimensioning and assessment of structures, it is common practice to compare action effects with sectional resistances. Extensive studies have been performed to quantify the model uncertainty on the resistance side. However, for statically indeterminate systems, the model uncertainty in the calculation of action effects has not been properly investigated yet. The aim of this article is to contribute in quantifying the model uncertainty in action effects and load bearing capacity calculations for reinforced concrete structures, accounting for the type of mechanical model used and for various failure modes. To collect a sufficient amount of data and perform statistical analyses, the experimental response of statically indeterminate systems is obtained with a simple and effective technique which allows using experimental results available in literature. Finally, on the basis of a parametric analysis and case studies, practical implications are discussed and recommendations are given concerning the implementation in the partial safety factor format.

Flexural behavior and load-bearing capacity calculation methodology for wooden beams strengthened using aluminum plates attached with self-tapping screws

ABSTRACT To investigate the flexural failure mode and behavior of wooden beams strengthened using aluminum (Al) plates, which were attached with self-tapping screws and structural adhesive, ten specimens were tested in bending. The experimental parameters were the thickness of the bottom Al plate, the longitudinal and transverse grain spacing of the self-tapping screws. The experimental results revealed that (1) compared with unreinforced beams, the reinforced beams exhibited ultimate load capacity and displacement ductility coefficients that were 18.4%–54.3% and 6.4%–43.1% higher, respectively; (2) for the same Al plate thickness in the tensioned area, the initial stiffness of the reinforced wooden beams increases as the longitudinal grain spacing of the screw grains decreases; (3) the plane-section assumption was satisfied by the strain in the middle section of the Al plate-reinforced wooden beam along the height; (4) the strains at the same position in the wooden beam and Al plate were similar, thus indicating that the wooden beam and Al plate behaved collectively. Furthermore, a formula was proposed for calculating the flexural capacity of an Al plate-reinforced wooden beam, thus providing a valuable reference when designing wooden beam reinforcements.

Calculation of ultimate bearing capacity of concrete-filled double steel tubular under compression based on the unified strength theory

Concrete-Filled Steel Tube (CFST) components are widely used in the engineering field due to their superior performance. However, the actual stress state of CFST components under axial compression is complex. As a result, calculations for CFST components are often simplified using material equivalent assumption formulas and empirical equations to determine their load-bearing capacity. These simplifications require the introduction of many coefficients and mechanical performance indicators, and the actual material principal stresses are not adequately considered. This approach weakens the completeness of the theory and adds to the burden of experimental research.The aim of this work is to develop a load-bearing capacity calculation formula for Concrete-Filled Double Steel Tubular (CFDST) components that considers the different stress states of the inner and outer steel tubes, the core concrete, and their interface interactions. This formula is designed to be convenient for engineers to understand and use. By comparing the results of this formula with experimental data collected from domestic and international scholars, it is evident that the results of this formula closely align with the collected experimental data. This validation confirms the accuracy and effectiveness of the formula developed in this paper. Furthermore, when compared with existing axial compression load formulas for CFDST, the formula presented in this paper demonstrates good accuracy. The research results provide a convenient and accurate calculation formula for the axial compression load-bearing capacity of CFDST components, bridging the gap between theoretical derivation and practical application.

Mechanical behavior of CFRP confined seawater sea-sand recycled concrete-filled circular aluminum-alloy tube columns under axial compression

This paper presents an experimental study and theoretical analysis of the mechanical behavior of CFRP-confined seawater sea-sand recycled concrete-filled circular aluminum-alloy tube short columns (CFRP-CFAT) under axial compression. A total of 12 circular cross-section specimens were tested, including 4 concrete-filled circular aluminum-alloy tube (CFAT) specimens and 8 CFRP-CFAT specimens. The effects of the number of CFRP layers, the thickness of the aluminum tubes, and the strength of the concrete were investigated. The test results indicate that CFRP can effectively delay or even suppress the local buckling of aluminum alloy tubes and significantly improve the ultimate load capacity of the specimens, and the enhancement is approximately linear with the number of CFRP layers. Based on the experimental results, a modified axial strain-lateral strain response model for core concrete is proposed. In addition, a new analysis-oriented model applicable to circular CFRP-CFAT short columns is established and compared with the test results for verification. Meanwhile, the CFRP-CFAT ultimate load-bearing capacity calculation method is proposed based on the superposition theory and the analysis-oriented model. The predicted results are in high consistency with the experimental results.

Anti-progressive collapse performance of prefabricated RC column-steel beam substructure with unbounded prestressed tendons

The anti-progressive collapse experiment on the prefabricated reinforced concrete column-steel beam (short title: PRCS) substructure with top-seat angles was conducted using the quasi-static loading method. Experimental results showed that the top-seat angle started the first yield and was followed by fractures, and the test finally ended with the tearing of the web at the connection part. The top-seat angle is the weakest and earliest plastic-damage part. On this basis, unbonded prestressed tendons were used instead of top-seat angles to enhance the anti-progressive collapse performance. The finite element modeling method verified by the experimental results was to analyze the anti-progressive collapse performance of the PRCS substructure with unbonded prestressed tendons (short title: UPT-PRCS). The results showed that the use of unbonded prestressed tendons instead of top-seat angles can effectively enhance the initial resistance and the ultimate bearing capacity, prolong the catenary action, and enhance the anti-progressive collapse performance. In addition, the load-bearing mechanism of the UPT-PRCS beam–column substructure was analyzed theoretically, and a load bearing capacity calculation formula suitable for progressive collapse was deduced. The theoretically calculated load-bearing capacities were compared with those computed from the finite element method, with the largest difference of 3.7%.

Improving Calculation of Load-Bearing Capacity for Steel Tubular Piles, with Consideration for Experience Gained from Constructing a Crossing Over the Kerch Strait

Improving Calculation of Load-Bearing Capacity for Steel Tubular Piles, with Consideration for Experience Gained from Constructing a Crossing Over the Kerch Strait

Combined soil foundation analysis based on ultimate limit state

The paper defines an updated method for “soil – reinforced concrete foundation” calculation that takes into account their mutual interaction. In this method, both the foundation structure and the footing structure are represented by a rigid-plastic model, which makes it possible to determine the bearing capacity of the system. This method eliminates the possibility of destruction of the reinforced concrete foundation from punching to the exhaustion of its bearing capacity. It further presents the results of the test conducted by the authors at Novocherkassk School for Soil Mechanics Research to validate the theoretical calculations attained with the use of the proposed method, as well as the results of tray testing of reinforced concrete foundation models. The calculation of the bearing capacity by the modernized method gives values close to the results of experimental studies. The authors discuss the challenge of determining the strength of sand base, which is known to affect the calculation of load-bearing capacity, and further propose a solution that uses piecewise linear limit line of shear strength of soil and has been developed in an attempt to increase the accuracy of calculations.

Calculation method for the axial load-bearing capacity of steel pipe-to-sleeve grouted connections

The existing axial load-bearing capacity calculation method for the steel pipe-to-sleeve grouted connections is introduced. It is proposed that by considering the tensile strain of a grouting material along the inner cyclic direction of the sleeve reaching its ultimate tensile strain as the limit state, the limit load-bearing capacity calculation model of the steel pipe-to-sleeve grouted connections is established via:1.) the deformation coordination relationship among the cyclic strain of the sleeve, steel pipe and the grout; 2.) the overall static equilibrium of the grout; and 3.) the three-way constitutive relationship of the grout. The calculation model has a wide application range and strong applicability, In addition, the proposed model is used to calculate the axial load-bearing capacity of 82 sets of steel pipe-to-sleeve grouted connection specimens in the literature, and the calculated values agree well with the experimental values.

STRUCTURAL ASSESSMENT OF THE BRIDGE № M 044 AT THE END OF RYBNIČNÁ STREET ABOVE THE ROAD II/502 BRATISLAVA-PEZINOK

Abstract. The paper is focused on the results of the survey and diagnostics of the bridge № M 044 at the end of Rybničná street above the road II/502 Bratislava-Pezinok in the Slovak Republic. The article is the result of the cooperation between the Department of Concrete Structures and Bridges of the Slovak Technical University in Bratislava and the Department of Reinforced Concrete Structures and Transport Facilities of the Odessa State Academy of Civil Engineering and Architecture within the framework of the National Scholarship Program of the Slovak Republic. Data were obtained to assess the technical condition of the structures and the bridge as a whole. As a result of the inspection, the type of destruction of each structural element of the frame and superstructure was determined. A study on the content of chloride-ionic contamination of concrete and non-destructive tests of strength parameters was carried out. A detailed research analysis of the results and recommendations for processing the reconstruction has been proposed. In accordance with the valid regulations, due to the significant deformation in the horizontal plane, the cause of which is not known and due to the gradual loss of the bearing function, we evaluate the construction, and technical condition by the degree: VI ‒ very bad, and immediate reconstruction is required. The service life of the bridge is mainly affected by corrosion and displacement of the bearings, as well as contamination of concrete with chlorides from sanding salts and corroded bearings. Corrosion of the reinforcement in the horizon of 5 years can negatively affect the load-bearing capacity of the bridge and there is also an increased risk of falling pieces of the covering layer of the reinforcement on the road leading under the bridge. The following actions are strongly recommended: replace all bearings; reconstruct the waterproofing of the bridge, roadway, drainage system, expansion join on support no. 4; consider the installation of asphalt expansion joins over support no. 1 and piers no. 2 and 3; clean the entire surface with high-pressure water and apply a remedial coating, that would slow down the corrosion of the reinforcement; renew the areas with the delaminated cover layer with a repair compound. The conclusions about the calculation of load bearing capacity are based on the current technical condition of the bridge found during diagnostics (08/2021). During further operation, it is necessary to pay attention to the state of prestressing and possible opening of joints at the contact of beam segments.

Research on the Seismic Performance of Highly Durable Concrete Structures with Corrosion-resistant Reinforcing Steel Materials

The combination of high durability concrete and GFRP reinforcement for infrastructure construction in the South China Sea can meet its durability requirements under high temperature, high humidity, high salt spray and high radiation environment. Due to the frequent seismic activities in the South China Sea, it is imperative to study the bearing capacity and seismic performance of GFRP reinforced high-durability concrete components and structures. The authors first analyzed the load-bearing performance of GFRP reinforced highly durable concrete beams and established the correction formula for its load-bearing capacity calculation based on the research results. Then the seismic performance of the GFRP reinforced high durability concrete structural members is studied. The seismic damage of the new structure and components is studied by analyzing the hysteresis curve, skeleton curve, stiffness degradation and other parameters. The time course curves and inter-layer displacement angles of GFRP reinforced high durable concrete structure are studied by adjusting the reinforcement type and concrete type, and finally the seismic performance of GFRP reinforced high durable concrete structure is obtained.

Displacement piles - classification and new methods for the calculation of bearing capacity

The paper presents technological changes concerning not only the method of construction, but also the materials used. Another aspect is the methods of calculating the load-bearing capacity and settlement of piles. With acceptance for use the PN-EN:1997-1:2008 standard in 2010, it was necessary to change the approaches applied that based on many years of experience and tradition. The best method in this case is to forecast the full load-settlement characteristics. On the basis of the collected data, a comparative analysis of particular displacement piles technologies was made. The usefulness of individual methods of load-bearing capacity calculation depending on the pile technology was determined.

Research on the Compression Behavior of Steel Reinforced Concrete Columns With Built-in Steel Tubes

In order to study the compression behavior of rectangular steel reinforced concrete columns with built-in steel tubes under different eccentric loads, three 1/10 scale specimens were designed and monotonic loading tests were carried out on them. The dimensions, steel bars and steel tube of the three specimens were the same except for the location of the loading point. The eccentricity ratios of the three specimens were 0, 0.25 and 0.5, respectively. The failure modes, load-bearing capacity and displacement characteristics of the test specimens were analyzed. According to the Chinese code, the load-bearing capacity calculation principles and methods of steel reinforced concrete columns with built-in steel tube were investigated for the comparison. The study shows that the peak vertical loads of specimens decrease and the corresponding vertical and horizontal peak displacement increase as the eccentricity increases. The load-bearing capacity calculation results from Chinese code are slightly smaller than the test result because of the unconsidered sleeve effect of the internal steel tube. The errors between them are small, and the calculation methods are beneficial to ensure the structural safety.

Experimental study on flexural behavior of damaged reinforced concrete (RC) beam strengthened by toughness-improved ultra-high performance concrete (UHPC) layer

The flexural test was conducted to investigate crack resistance, loading bearing capacity, deformation characteristics and failure modes of damaged reinforced concrete (RC) beams strengthened by reinforced ultra-high performance concrete (UHPC) layer (Abbreviated as UC). Also, their mechanical properties were compared with those of the unstrengthened RC beam (Abbreviated as I–C). Additionally, the effects of pre-damage degrees in the RC beams and three strategies for the improvement of toughness of the reinforced UHPC layer on the cracking and flexural performance of UC were discussed. The results showed that UC acted monolithically under flexure without interfacial debonding before typically flexural failure. Compared with I–C, cracking and ultimate loads of UC increased by 1.57–3.32 times and 1.72–2.21 times, respectively. The reinforced UHPC layer effectively suppressed the cracking of the RC beam, making crack width in the RC beam propagate slowly with the load. Moreover, the severer the pre-damage degree of the RC beam, the smaller improvement of the flexural performance of UC. The addition of steel wire mesh, orientation of steel fibers and moderate-temperature steam curing further improved the cracking and flexural performance of UC with the most evident improvement in the addition of steel wire mesh. Finally, the theoretical model and formula were proposed for the calculation of load bearing capacity of UC with consideration of the influence of the pre-damage degrees in the RC beams, and the experimental results verified that the theoretical formula can accurately predict the load bearing capacity of UC.

ENGINEERING METHOD FOR CALCULATING STEEL-REINFORCED CONCRETE ELEMENTS WITH FLEXIBILITY

In the article presents an engineering method for calculating compressed flexible reinforced concrete elements with sheet reinforcement over a steel cross section. The results of the calculation are compared with the experimental data. Calculation ofload-bearing capacity of reinforced concrete flexible elements with sheet reinforcement is based on the method of boundarystates. The work of specimens under load and the nature of the load-bearing capacity depending on the height and eccentricity of the effort were investigated. The proposed method of calculating compressed elements with sheet reinforcement on asteel-cross-section allows to take into account their flexibility in both axial and out-of-center application of load.

Calculation of Load-bearing Capacity of Tubula Anchor of Friction Type

The load-bearing capacity of a rod of a tubular anchor of a friction type (friction-type anchor) is determined by the nature of its interaction with the walls of the hole. The preliminary (estimated) calculation of this indicator is difficult because of the lack of information about the deformed state of the rod. The proposed interaction scheme assumes coupling only over a part of the cross-sectional profile. Force factors are represented by concentrated and distributed loads. On the basis of accepted assumptions, a mathematical model which indicates rod-hole force interaction is formed. The determination of the parameters characterizing the adopted interaction scheme is based on the solution of the obtained nonlinear equations. The physical simulation of the process of installing the anchor in the borehole model was performed. The accepted scheme of interaction of a rod – borehole is experimentally confirmed. The results of numerical simulation have large convergence with experimental data.