Ultimate Bearing Capacity Research Articles

A study of stone arch bridge’s flood reliability through a surrogate model approach

Europe’s historic masonry arch bridges are culturally and economically significant, but their long-term safety must be ensured. Scour effects are the most common cause of collapse, so it is necessary to carry out structural assessments to mitigate the risk and prevent potential failures. In this study, a metamodel-based method was used to determine the probability of failure of an existing stone arch bridge in Portugal due to local and contraction scour on the abutments. Non-linear finite element analysis supported the calculation of the reliability index, which took into account the soil-structure interaction and the failure mechanism. The variables with the greatest influence on the load-carrying capacity of the structure were identified and a surrogate model was implemented. Fragility curves were then derived based on the surrogate model, using scour depth as a measure of intensity and load factor as an engineering requirement parameter. The results of the study indicate that the load capacity of the numerical model is compromised when the scour depth of 1.5 m reaches the base of the foundation. As a result, stability problems and settlements are observed in the model. At a depth of 2.5 m, the soil reaches its ultimate bearing capacity.

Reliability analysis of the cast-in-place bored pile with different defects

The defects of the cast-in-place bored piles heavily influence their integrities and bearing capacities. The bearing capacity and reliability index of the cast-in-place bored piles with different defects were studied using the finite element method. The accuracy of the numerical model is verified by the field test results of an in situ cast-in-place bored pile. Parametric studies are conducted to investigate the toe debris, mud cake, and necking and bulging defects on the ultimate bearing capacities of the cast-in-place bored piles. The results indicate that maximum reduction in the ultimate bearing capacities of the cast-in-place bored pile was observed, with the ultimate bearing capacity of the toe debris defect decreased by 17%, that of the mud cake defect decreased by 19%, that of the necking defect by 6.1%, and that of the pile bulging defect increased by 40.9%. The minimum reliability index can be 0.81 when the diameter of the pile necking defect is 0.2 m. The maximum reliability index can be 3.63 when the diameter of the pile necking defect is 2.0 m.

Ultimate bearing capacity of T-shaped retrofitting diagonal members for angle steel transmission towers

Collapse of steel latticed transmission towers under strong winds is a significant safety concern for power systems. Attaching additional members to the tower members can enhance the wind resistance of transmission towers. To establish systematic retrofitting schemes and methods for predicting the ultimate bearing capacity of T-shaped retrofitting diagonal members, static experiments and finite element analysis on various cross-sectional dimensions and member lengths were utilized in this study. The experimental results indicate that retrofitting can effectively increase the bearing capacity of diagonal members. Finite element models are developed and verified based on the discussion of load-displacement curves and failure modes. The finite element analysis reveals that the increase in capacity achieved by reducing connector spacing is relatively small when compared to the ultimate bearing capacity obtained with the spacing of two connectors, and the arrangement of connectors at both ends meets the requirement of connector spacing. The relationship between the retrofitting bearing capacity and the slenderness ratio of diagonal members can be divided into two linear stages, which correspond to different failure modes. Furthermore, a λk coefficient method based on the axial compression equation is proposed to predict the ultimate bearing capacity of T-shaped retrofitting members. The bearing capacity based on the λk method shows agreement with finite element analysis results.

Finite element analysis of deterioration of axial compression behavior of corroded steel-reinforced concrete middle-length columns

Abstract The corrosion problem of steel-reinforced concrete (SRC) columns in coastal areas is becoming increasingly severe and needs to be solved urgently. This study established a numerical analysis model for SRC middle-length columns considering corrosion effects. The bond–slip constitutive relationship between corroded steel and concrete was established. It was found that when the rust rate is low, the bonding stress of SRC columns is slightly increased compared to those without corrosion. The ultimate and residual bonding stress will decrease significantly when the rust rate exceeds 1.5%. The comparison between the numerical analysis model and the experimental results shows that the establishment of the model is reasonable. Subsequent parameter analysis showed that for corroded SRC mid-length columns, the larger the slenderness ratio of the component, the faster the decrease in axial compression performance. The rust rate increased from 0 to 30%, and the axial compression performance of SRC columns decreased significantly. When the rust rate exceeded 30%, the axial compression performance of concrete columns tended to stabilize. A formula for calculating SRC middle-length columns’ ultimate bearing capacity considering corrosion effects has been proposed.

Semi‐analytical solution for ultimate bearing capacity of smooth and rough circular foundations on rock considering three‐dimensional strength

AbstractThis paper proposes a semi‐analytical solution for the ultimate bearing capacity qu of both smooth and rough circular shallow foundations on rock mass. Specifically, a three‐dimensional (3D) Hoek–Brown (HB) is adopted, in conjunction with equilibrium equations under axisymmetric conditions, to derive the governing equations. The method of characteristics is utilized to solve the stress and failure characteristics mesh to determine the qu. The proposed solution is verified by using it to analyze test foundations. Comparison with an HB criterion‐based solution is performed to highlight the importance of 3D strength. Furthermore, parametric studies are performed to investigate the effects of rock mass properties (intact rock constant , geological strength index GSI, intact rock unconfined compressive strength σc) and foundation diameter (B) on the qu, failure surface size, and vertical stress distribution on the foundation base. The results indicate that ignoring the 3D strength and the rock mass weight would lead to underestimation of qu. Besides, the ultimate bearing capacity factor (ratio of qu to σc) increases with , GSI and B but decreases with . The failure surface size is significantly affected by , GSI, B, and rock mass unit weight. The stress distribution on the foundation base has higher variance (higher possibility of stress concentration) at smaller , GSI, and larger B, rock mass unit weight.

Effects of Prestressing Magnitude and Position on Seismic Performance of Unbonded Prestressed Concrete Beams

To study the effects of the jacking stress level, height and strength ratio of the prestress tendons (λ) on the seismic performance of unbonded prestressed concrete (UPC) beams, six UPC beams and one reinforced concrete (RC) beam were tested under cyclic loads. The hysteretic characteristics, skeleton curves, ductility properties, energy dissipation capacity, strain distribution of reinforcement and self-centering capability of the specimens were studied and discussed. Numerical parameter analysis was also carried out by using OpenSees. The results indicate that three failure modes of UPC beams under cyclic loading were observed, namely the tension-failure mode involving a broken rebar, the compression-failure mode involving concrete crushing and the balanced failure. By considering the influence of the prestress position and magnitude, the modified reinforcing index ω was proposed to determine the failure mode. The ω is suggested to be less than 0.3 to ensure sufficient ductility. The effective stress level is linearly and positively related to the stiffness from cracking to yield Kcr and the ultimate bearing capacity of the UPC beam under cyclic loading. The stiffness of the UPC beam is slightly larger than that of the RC beam before yielding, and significantly greater than that of the RC beam after yielding. Due to the large strength reserve after yielding, the integrated seismic performance of the UPC beam is similar to that of the RC beam. When the λ was unchanged, the increase in the relative height of the prestressed tendons αh is beneficial for the overall performance factor F, ductility and crack control. The stiffness degradation performance depends on the λ but is independent of the αh. The total energy dissipation of the non-tensioned UPC specimen was 59% higher than that of the RC beam. The cumulative total energy dissipation of the tensioned UPC specimen was only 13% lower than that of the RC beam with the same number of cycles, indicating that the UPC specimen had a considerable energy dissipation capacity.

Experimental Study on the Flexural and Shear Performance of Concrete Beams Strengthened with Prestressed CFRP Tendons

To investigate the influence of external prestressing with carbon fiber-reinforced polymer (CFRP) tendons on the flexural and shear performance of reinforced concrete beams, a total of six simply supported beams with a length of 3.5 m and two two-span continuous beams with a length of 7 m were studied. The influences of the prestressing level of CFRP tendons, the pattern of straight-line and flexural reinforcement of externally prestressed CFRP tendons, and the existence of initial cracks in the beams on the flexural bearing capacity of the reinforced beams were explored through modeling tests. The calculating equation for anticipating the ultimate flexural bearing capacity of concrete beams reinforced with externally prestressed CFRP tendons was modified based on the test results. The findings indicate that the flexural bearing capacity of the test beams was significantly enhanced through both flexural and straight-line reinforcement. Specifically, the ultimate flexural bearing capacity of the simply supported beams exhibited improvements of approximately 160% and 170%, respectively, whereas the ultimate flexural bearing capacity of the continuous beams was enhanced by approximately 113% through the reinforcement of flexural arrangement. Additionally, the shear resistance capacity of the concrete beams was notably improved through the flexural arrangement reinforcement, and the shear resistance capacity of the beams exhibited a substantial increase as the prestressing level of the CFRP tendons increased. The flexural moments in the vicinity of the support point of the reinforced beam exhibited an increase ranging from 41.7% to 112.5% when the stirrup strains started to escalate rapidly. Additionally, the rigidity of the test beams showed a close correlation with both the prestressing level and the existence of initial cracks.

Experimental study on axial compressive behavior of steel tube‐reinforced recycled aggregate concrete composite columns with steel bars

AbstractIn this paper, five specimens were designed to test under monotonic static loading to study the axial compression performance of steel tube‐reinforced high‐strength recycled aggregate concrete composite columns with steel bars. The design parameters for these specimens include the type of concrete, the sectional shape of the steel tube (circular or square), and the internal structure of the core column, specifically the presence or absence of cross‐shaped tie bars in the square steel tube. The effects of different parameters on the axial load–displacement curve, bearing capacity, and ductility were analyzed. The test results show that the failure of all specimens was caused by the concrete cover spalling of outer reinforced concrete, which occurred after the longitudinal strain of the steel tube exceeded the yield strain. The ultimate bearing capacity of the recycled aggregate concrete (RAC) specimen is higher than that of the natural aggregate concrete (NAC) specimen, but the latter has a more robust deformation performance. Furthermore, under the condition of the same steel tube cross‐sectional area and similar material strength, the bearing capacity and deformation capacity of specimens with circular steel tubes are higher than those of specimens with square steel tubes. A similar conclusion was also obtained for square steel tube specimens with cross‐shaped tie bars. Finally, four international design methods were applied to estimate the axial compression capacity of 40 composite columns, as detailed in this paper and other sources.

Ultimate Bearing Capacity Analysis of Pipelines under Water Hammer

Ultimate Bearing Capacity Analysis of Pipelines under Water Hammer

Experimental study and numerical analysis on the axial compression performance of CFRP strip reinforced round-end aluminum alloy tube concrete column

Round-end aluminum alloy tube concrete columns had good durability and were very economical, but the low strength and elastic modulus of aluminum alloy led to the need for improvement in performance. This paper proposes carbon fiber reinforced plastic (CFRP) strip reinforced round-end aluminum alloy tube concrete (CREAC) columns and investigates their mechanical properties under axial compression loads. A total of eight specimens were tested, including seven CFRP reinforced specimens and one control specimen. The effects of the width, spacing, and number of layers of CFRP strips on the axial compression performance of CREAC under the same amount of CFRP were studied. The experimental results indicate that the main failure modes of the specimen are the buckling of round-end aluminum alloy tubes and the fracture of CFRP strips. The CFRP strip can significantly improve the ultimate bearing capacity of the specimen, with a maximum increase of 15.3% in the test range. When the amount of CFRP is the same, as the number of CFRP strips decreases, the bearing capacity and ductility deteriorate. Increasing the width and thickness of CFRP strips significantly improves ductility. On the basis of the validated finite element model, parameter analysis was conducted, and the calculation method for stability coefficients was fitted. A calculation method for axial compression bearing capacity suitable for CREAC was proposed, with a maximum error of less than 1% between the predicted results and experimental results.

Enhancing bonding behavior between basalt fiber-reinforced polymer sheets and concrete using resin pre-coating method and multi-wall carbon nanotubes

There is a crucial problem of premature debonding failure in fiber-reinforced polymer (FRP) sheet external bonding reinforcement for concrete structures. Using anhydrous ethanol as solvent instead of acetone, the effect of resin pre-coating (RPC) technique with neat resin-ethanol solution and multi-wall carbon nanotubes (MWCNTs)-resin-ethanol solution on the bonding behavior of the FRP-concrete joints was investigated by single-shear tests. Experimental results indicated that RPC technique significantly enhanced the bonding properties, especially when the pre-coating was MWCNTs-resin-ethanol solution. In the case of using neat epoxy resin as adhesive, compared with the control specimens without RPC treatment, the ultimate bearing capacity, ultimate global slip, maximum bond stress and interface fracture energy of the basalt fiber-reinforced polymer (BFRP)-concrete joints using RPC treatment with MWCNTs-resin-ethanol solution increased by 32.6 %, 48.4 %, 68.3 % and 88.8 %, respectively. MWCNTs could be seen in scanning electron microscopy (SEM) images of the fracture surface, which indicated that they could penetrate into the concrete and the crack bridging and pull-out of MWCNTs could enhance the interfacial adhesion of the FRP-concrete joints. Compared with the RPC treatment using the restricted acetone, the RPC treatment with MWCNTs-resin-ethanol solution can more significantly enhance the bond properties of the interface between concrete and FRP sheet, and it is suitable for large-scale practical engineering applications on site. This study demonstrated the great promise of the RPC technique with MWCNTs-resin-ethanol solution toward practical engineering application in reinforcement and repair of concrete structures.

Static performance of precast concrete arches with carbon fiber reinforced polymer reinforcement

In this paper, static performances of a new precast concrete arch system with carbon fiber reinforced polymer (CFRP) reinforcement were investigated. Varied concrete strengths and segment types of precast concrete arches were tested. The results show that the increase of concrete strength can improve the bearing capacity of the precast arches with CFRP reinforcement. The ultimate bearing capacity of the precast arches segmented at the arch vault with CFRP reinforcement can reach or even exceed that of complete arches, while the precast arch segmented at the shoulder had lower ultimate load. A theoretical analysis method was proposed to predict the failure and bearing capacity of the precast concrete arches with CFRP reinforcement, which were found to be in close agreement with the experimental result.

Axial compressive behavior of pre-damaged concrete-filled square steel tube columns repaired with section circularization and CFRP composites

This study focused on repair treatments for the effective reuse of damaged concrete-filled square steel tube (CFSST) columns with carbon fiber-reinforced polymer (CFRP) composites. Forty specimens were designed to investigate the effects of pre-damage levels, section circularization, and the number of CFRP layers on the compressive behavior of the repaired CFSST columns. Test results indicated that the method of section circularization and CFRP wrapping effectively restored the degraded initial axial stiffness of the pre-damaged CFSST columns and increased the ultimate bearing capacity of the pre-damaged CFSST columns by 49–180 % compared to their undamaged condition. Considering the influence of the pre-damage level and the contribution of section circularization, the ultimate bearing capacity calculation model was suggested for predicting the compressive behavior of the repaired CFSST columns. The experimental results and collected test data have well verified the accuracy and applicability of the calculation model.

Seismic Performance of U-Shaped Connection for Prefabricated Steel Plate Shear Wall

In this investigation, a U-shaped connection (U-C) was introduced for a prefabricated steel plate shear wall with beam-only connections. This design replaces a portion of shear bolts with tension bolts to enhance bolt efficiency and reduce the overall bolt count, and it is suitable for a prefabricated high-rise steel structure. Four 1/3 scale specimens were designed, and an array of performance aspects including failure modes, hysteretic behavior, skeleton curves, energy dissipation capacity, stiffness degradation, and key performance indicators were systematically investigated through a combination of quasi-static tests and finite element analyses. The results showed that the combination arrangement of tensile and shear bolts in U-C effectively reduced the usage of bolts used and reduced installation costs; under low cycle reciprocating loads, the ultimate bearing capacity and energy dissipation capacity of a beam-only-connected prefabricated steel plate shear wall with U-shaped connection (BPSW-U) had slightly decreased compared with the prefabricated steel plate shear wall with discontinuous cover-plate connection (DCPC). Nevertheless, the BPSW-U excelled in preserving the integrity of the frame beams, channeling structural plastic deformations primarily into the infilled steel plate. This design feature ensures that post-earthquake functionality recovery can be achieved by simply replacing the infilled steel plate.

Effect of Residual Stress on the Ultimate Bearing Capacity of Titanium Alloy Pressure Spherical–Cylindrical-Combined Shells

Titanium alloy pressure spherical–cylindrical shells enable the effective utilization of the strength of spherical and cylindrical pressure-resistant shell components. In this study, a numerical simulation of the residual stress of a titanium alloy butt-welding plate was conducted by employing sequential coupling and a temperature heat source model. The results of welding residual stress analysis agreed well with the experimental results reported in the literature. Subsequently, the welding residual stress of a titanium alloy pressure spherical–cylindrical shell was calculated and analyzed using the same method. Finally, the influence of residual stress on the ultimate bearing capacity of the shell was assessed. On the inner surface of the shell, the horizontal welding residual tensile stress, perpendicular to the weld path, exhibited a bimodal distribution. The longitudinal welding residual tensile stresses were higher than the horizontal welding residual stress. Near the weld on the outer shell surface, higher longitudinal welding residual tensile stresses existed, whereas the horizontal welding residual stress was compressive. Both the inner and outer shell surfaces exhibited significant longitudinal residual tensile stresses along the weld path, though residual compressive stresses existed on both surfaces. The influence of welding residual stress on the ultimate load-bearing capacity of the shell was minimal.

Axial compressive behavior of steel reinforced GGBS-RFBP-FA ternary composite geopolymer recycled fireclay brick aggregates concrete columns

In this study, the axial compressive behaviors of steel reinforced ternary composite geopolymer recycled fireclay brick aggregates concrete columns were investigated. The ternary binder material used in this study was produced by the combination of industrial by-products (i.e., granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. A total of 60 square steel reinforced composite columns (with a 200-mm side length and 600-mm height) were tested under axial compression. The tested variables included the mix proportion of ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC), the recycled coarse aggregate replacement ratios (0%, 30%, 50%, 70%, 100%), the longitudinal reinforcement ratios (1.13%, 2.01%), and the hoop stirrup reinforcement ratios (0.81%, 1.62%). Each group contained three identical samples. The ductility, failure mode, and axial load-bearing capacity of the columns were recorded and analyzed. The experimental results revealed that the damage progression and patterns of steel reinforced GRA-RFBAC columns were similar to those of ordinary Portland cement based recycled concrete columns. The ultimate bearing capacity of steel reinforced GRA-RFBAC columns decreased with an increasing replacement ratio of recycled coarse aggregate and increased with an increasing reinforcement ratio of longitudinal and hoop stirrups. Meanwhile, the stress-strain model of steel reinforced GRA-RFBAC columns under axial compression was proposed based on the experimental results. The present study suggests an efficient and environmental-friendly compression member.

Resistance of natural stone masonry wallettes under centred and eccentric compressive loading: Experimental and numerical approaches

Masonry walls are typically subjected to eccentric compressive loadings in common buildings. However, the design of walls towards this type of solicitation remains very empirical, often leading to oversizing the structure. This is especially true for natural stone masonry, for which experimental data are quite scarce. This paper presents an experimental campaign on 15 natural stone masonry wallettes subjected to centred and eccentric compression until failure. Different values of the eccentricity of the load, ranging from h/12 to h/4 (where h is the thickness of the wallette) were investigated, highlighting the noticeable effect of such a value on the compressive failure load. During the tests, the displacements were recorded by a Digital Image Correlation system, providing insights into the different failure mechanisms that depend on the value of the eccentricity. The so-obtained experimental failure loads are then compared to the predictions of Eurocode 6. Finally, a finite-element yield-design analysis of these tests is proposed which shows that this modelling framework is suitable to find the ultimate bearing capacity of a masonry wallette.

Combined bearing capacity of footings on geogrid-reinforced granular fill over soft clay

The current study investigates the ultimate bearing capacity of obliquely/eccentrically loaded shallow strip foundations resting on a geogrid-reinforced granular fill with limited thickness over a very soft to soft clay layer. To this end, the lower bound theorems of the finite element limit analysis (FELA) and second-order cone programming (SOCP) are effectively exploited to simulate the underlying clay deposit, geogrid layer, and granular fill along with the inclined/eccentric loading exerted on the overlying footing. The accuracy of the adopted formulations is rigorously examined through several comparisons with the results of a well-established analytical approach in the literature. A comprehensive parametric study is then conducted to properly examine the influences of the geosynthetic layer characteristics and soft clay properties on the overall bearing capacity and failure envelope of the strip footing subjected to wide ranges of inclined and eccentric loadings. The results show that placement of a geogrid-reinforced granular fill layer over the soft clayey soil significantly increases the bearing capacity of the shallow foundation. The ultimate tensile strength of the reinforcement layer and the cohesion of the underlying very soft to soft clay deposit are also observed to have considerable effects on the size of failure envelopes.

Experimental and numerical research on the performance of cast‐in‐situ concrete wet joints in closure section in precast concrete segmental bridges under cyclic loading

AbstractThe closure section of precast concrete segmental bridges (PCSBs) usually adopts the wet joint of cast‐in‐situ concrete, the width is generally 10–20 cm, and the regular longitudinal reinforcement is discontinuous, which makes the section the vulnerable part of the bridge. To explore the mechanical property of the wet joint in the closure section of PCSB under cyclic load, six wet joint specimens are tested to investigate the influence of loading mode, interface treatment mode, setting of regular reinforcement, and prestress level. The results show that the failure modes of wet joint specimens have similar characteristics, careful roughening of joint surfaces can improve the bonding effect of the new and old concrete and delay the cracking of the specimen, the cracking load of the specimen increases by 10.3% after careful roughening. When the prestress level increases from 6 to 8 MPa and 10 MPa, the stiffness of the specimens increases obviously, and the fracture development of the specimen in the loading process is improved. The cracking load increases by 21.9% and 32.8%, the shear strength increases by 9.9% and 6.6%, respectively, but the ultimate displacement decreases by 5.6% and 11.4%, respectively. Then, the finite element model of the wet joint was established and verified, the influence of shear key, concrete strength, and wet joint width are selected for parameter analysis. It is found that stress concentration is easy to occur after shear key is set, which has adverse effects on structural flexural resistance. The shear capacity of the model decreases by 22.4% and 21.5%, respectively after the setting of single and double‐shear keys, but the stiffness of the wet joint model before cracking is improved. Compared with C50 concrete model, the ultimate bearing capacity of C60 and C70 concrete models is increased by 11.5% and 24.8%, respectively. Wet joint width has little influence on the mechanical properties of wet joints in the closure section. The research results provide references for design and construction of PCSB wet joints in practical engineering.

Experimental Study on Seismic Performance of Prefabricated Columns Connected Using a Novel Dry Sleeve

Prefabricated structures are widely used because of their advantages of energy savings, environmental protection, standardization, and universality. However, due to the complex structure of the joints, it is easy to make the joint installation difficult and the prefabricated column connection unreliable, and further lead to the poor seismic performance of the structure. Therefore, a new type of dry sleeve joint with double screw sleeve without support is proposed, and the seismic performance and influencing factors of the new dry-sleeve-joint prefabricated column are studied. This study encompasses seven reinforced concrete columns characterized by cross-sectional dimensions of 600 mm × 600 mm. Among these, five specimens feature a novel dry sleeve connection, while the remaining two specimens were entirely cast-in-place. Low-cycle reversed loading experiments were conducted on all specimens to analyze and compare the damage patterns, hysteresis curves, skeleton curves, displacement ductility, energy dissipation capacity, and ultimate bearing capacity between precast and cast-in-place columns. Several parameters, including fabrication method, axial compression ratio, longitudinal reinforcement diameter, and hoop spacing, were examined. The findings demonstrated that the calculated-to-tested ratio of the ultimate bearing capacity for the prefabricated specimens was determined to be 0.62, indicating a high level of safety. The displacement ductility coefficient for each specimen ranged from 2.43 to 3.31, while the ultimate drift ratio was within the range of 1/41 to 1/33, satisfying the specified requirements for seismic performance. However, the hysteresis curve of the prefabricated specimens exhibited a pinching effect, which may be related to the existence of a weak layer on the joint surface of the post-cast section. In general, the shape of the new dry sleeve is maintained in the test, the connection form can effectively transfer the force, and the longitudinal bars can be strained and yield when the prefabricated column reaches the peak load. The new type of dry sleeve connection can be used for longitudinal reinforcement connection of reinforced concrete columns with seismic design.