Bending Capacity Research Articles

Structural behaviour and construction of a monumental ice structure

This paper investigates the use of ice-based materials combined with Fiber-Reinforced Polymer (FRP) to enhance the bending capacity of ice sculptures. Through three-point bending tests and ABAQUS simulations, the study analyses the mechanical behaviour of GFRP and cellulose ice, both separately and together. The results show that FRP improves tensile resistance while cellulose ice adds mass and ductility. An ABAQUS simulation with a layered shell partially captures the mechanical behaviour but has limitations in modelling beyond the elastic phase due to assumptions of perfect connection and material failure. Applied to a monumental sculpture by artist KAWS, incorporating a steel framework, GFRP mould, and ice-based material, the study confirms the potential of combining FRP and cellulose ice to achieve improved structural performance in ice-based sculptures.

Study on the bending behavior of CFRP-confined square concrete-filled steel tubes reinforced with internal latticed steel angles

The bending mechanical properties of FRP-confined square concrete-filled steel tubes (CFST) reinforced with internal latticed steel angles, including the failure modes, characteristic curves and characteristic mechanical parameters of tested specimens, were investigated through experiments in this paper. The bending mechanisms were also analyzed using an established finite element model, including the analysis of the bending moment borne by each component, the distributions of contact pressure between different components at the mid-span section, and the distributions of the neutral axis under the bending capacity. The key influential parameters, including the tensile strength and thickness of the FRP, were also examined. The results indicate that the FRP has almost no influence on bending stiffness, however, it enhances the yield bending moment and bending capacity to a certain extent. It was also found that the enhancement decreases as the width of steel tube increases, and the influence of FRP is more profound before reaching the peak load. The calculation formulas for the bending capacity were developed using the superposition method and numerical fitting method. Analysis of their accuracy shows that the formulation using the superposition method yields relatively accurate and safe prediction results, with the prediction errors of less than 20 %.

Theoretical and experimental studies on the bending properties of glued laminated timber manufactured with Chinese fir

China has been increasingly promoting the use of prefabricated timber structure buildings in recent years. However, unlike other countries, China lacks a diverse range of local tree species and engineered wood products suitable for load-bearing components in timber structures. This shortage poses a risk to the sustainable development of timber structures in China. This issue is addressed in this study, which focuses on the development and manufacture of glued laminated timber (GLT) using Chinese fir from plantation forests. The dynamic elastic modulus of 549 laminae was evaluated using the FAKOPP stress wave approach. A total of 28 laminae were randomly selected from Classes I, II, and III to assess the influence of stress grading on bending performance. This study included an analysis of failure modes, bending capacity, and the prediction model for bending stiffness of GLT with different layups and cross-sectional heights. The findings showed that the dynamic elastic modulus of the laminae followed a normal distribution. The bending strength and modulus of elasticity of finger-jointed laminae across different grades were 29.59 MPa to 37.05 MPa and 8.13 GPa to 10.94 GPa, respectively. The mechanical properties of both same-grade and mixed-grade composition GLT manufactured from Chinese fir met the TCT28 (MOR≥28 MPa, MOE≥8000 MPa) and TCYD24 (MOR ≥ 24 MPa, MOE ≥ 8000 MPa) garde requirements in GB/T26889, respectively. Failure modes in the GLT specimens typically began at the knots or finger joints of the bottom layer laminae. The cross-sectional height had no significant effect on the modulus of elasticity of GLT but exerted a significant effect on bending strength. The prediction model for bending stiffness, developed using the transformed section method, agreed with the experimental results. The outcome of this research provides a scientific and data-driven foundation for the application of Chinese fir in the field of structural materials.

Flexural behavior of high-strength steel-precast prestressed concrete composite beams with grouped demountable bolts under hogging moment

To study the bending behavior of high-strength steel (HSS)-precast reinforced concrete (PRC) slab composite beams with grouped demountable bolts under hogging moment, single-point loading tests were carried out to evaluate the bending behavior of the five prefabricated composite beams, and the key parameters are shear connection degree, shear pocket spacing in the PRC slab, and applying precompression to the concrete or not. The test results indicate that the HSS composite beams have good overall bending behavior, and two failure modes are recorded including the flexural failure, and the concrete damage in the shear pocket region. The prestressing force can effectively increase the anti-cracking performance of the slab and slightly improve the bending behavior, while increasing the shear connection degree from 1.80 to 3.61 or the shear pocket spacing from 360 mm to 800 mm (the limit value in the AASHTO LRFD Bridge Design Specifications is 610 mm) under the same shear connection degree has a limited influence on the bending behavior, and the composite beams still have the effective composite action. The existing formulas are conservative in calculating the bending capacity of HSS composite beams but have a high degree of consistency in stiffness.

PARAMETRIC ANALYSIS OF CFRP STRIPS INTERNALLY CONFINED RC COLUMNS

Fiber-reinforced polymer (FRP) sheets has been widely used as external confinement for retrofitting and strengthening structural elements as they increase axial, shear, and bending capacity. Despite many advantages, FRPs suffer from some drawbacks such as have weak durability against thermal and harsh environment. Thus, the use of FRP strips as internal confinement was proposed so that the concrete cover can protect the FRP strips. In this study, a three-dimensional (3D) nonlinear finite element (FE) model is developed using ABAQUS software to study the cyclic behavior of carbon fiber-reinforced polymer (CFRP) strips internally confined reinforced concrete (RC) columns. A validated model was used to conduct the parametric study to investigate the effect of FE model under different intensities of axial load (i.e. 70kN, 100kN, 200kN, 300kN, and 400kN) and distances between the CFRP spirals (100mm, 150mm, 200mm, and 250mm). Results indicate that an increase in the axial force has significantly increased the stress on the surface of concrete and can lead to the rupture of CFRP strips in the column. Meanwhile, increasing the distance between CFRP strips has increased the stress at the plastic hinge area and experienced buckling of longitudinal reinforcements at 250 mm of CFRP strips.

Influence of random geometrical imperfection on loading capacity of scaffold based on stochastic numerical model

The existing data indicate that two-thirds of engineering accidents occur during construction among which engineering accidents caused by scaffold collapse account for a large proportion. Due to the complex mechanical behavior of connection and random nature of scaffold system caused by random geometrical imperfection, the reliability of scaffold system is lower than other kinds of building structures. However, the method considering the random geometrical imperfection is limited. To facilitate the analysis of random geometrical imperfection, the original numerical algorithm is proposed based on ANSYS Parametric Design Language. Through proposed method, two types of geometrical imperfections, i.e., the nodal location error and initial curvature can be automatically considered. The randomness in initial curvature includes random magnitude and random direction. The established numerical model is as close to reality as possible and the process of establishing stochastic numerical model can be automatically finished. The only work that needs to be done is to enter the dimensions of the scaffold. Except the propose of numerical algorithm, the objective of this study is to reveal the influence of geometrical imperfection on random distribution of loading capacity of scaffold system under different load conditions. The influence of random geometrical imperfection on probabilistic distribution of loading capacity is systematically investigated. The results indicated that there may be several buckling modes exist and the buckling mode occurred in actual condition is closely related to the random distribution of geometrical imperfection. The load factor of internal post (point 3) is 8 %–12 % larger than that of corner post. The load factor of side post is 4.7 %–7.2 % larger than that of corner post. The ultimate bending capacity Mu has little influence on the loading capacity of scaffold system when the initial bending stiffness ko is small enough.

Evaluasi Rasio Kapasitas Plat Lantai Jembatan Pangwa Berdasarkan Mutu Beton Aktual

This article reviewed the effect of decreasing quality of concrete in the vehicle deck on Pangwa bridge located in Trienggadeng, Pidie Jaya district, Aceh Province. The bridge deck was planned to use concrete with a quality of 30 MPa, however in practice, it was estimated that only 18.8 MPa was achieved. Based on the actual concrete quality, this article reported a reanalysis of the bending and shear capacity ratio. Structural analysis was carried out using SAP2000 software referring to engineering design data. The stages include modeling the bridge as a space frame steel construction with a deck using reinforced concrete material, loads calculation, internal force analysis, and checking the structural capacity. Load calculations and load combinations refer to the standard Loading for Bridges (SNI 1725: 2016). The bridge deck was analyzed as a one way slabs using D16-150 reinforcement with steel grade fy = 320 MPa. The loads taken into structure analysis include: self weight, additional dead load, truck load, and wind load. Based on the loads on the bridge, it is estimated that the possible forces arising from certain conditions are calculated based on the ultimate load combination of Strength-I, Strength-II, Strength-III, Strength-IV and Strength-V according to the provisions of SNI 1725-2016. Based on the results of the structural analysis recapitulated from the value of the load combination, the maximum and minimum moments were 388.68 kN.m and -391.22 kN.m while the maximum shear force were 169.60 kN. The planned bending capacity was 396.303 kN.m (design) and was achieved at 365.568 kN.m (actual) or 7.75% less than the ultimate moment. The pons shear force arising on the bridge deck was Vu = 169.6 kN with pons shear capacity, ØVn = 874.895 kN in the design data and was achieved by 703.811 kN (actual). Based on the results of these calculations, it can be concluded that Pangwa bridge still meets the level of safety for the use as a vehicle traffic lane.

Experimental investigation on seismic performance of CHS T-joints in salt spray environment

This paper aims to investigate the seismic performances of circular hollow section (CHS) T-joints with different regions of corrosion damage. A total of seven CHS T-joint specimens with various corrosion degrees were applied to conduct the quasi-static tests of brace axial cyclic loading, and the effects of corrosion damage on the hysteresis behavior and failure mode were discussed. Experimental results indicated the brace corrosion only had a slight influence on the seismic performance of CHS joints, while the corrosion difference on two sides of the brace might cause an additional bending moment and damage accumulation to accelerate the plastic collapse of the connection zone. Compared with the corrosion on the brace, the resistance of CHS joints was more susceptible to the corrosion located in the chord wall, resulting in the axial cyclic carrying capacity and stiffness of CHS joints significantly decreasing with the increase of chord corrosion level. However, the increasing corrosion on the chord would affect the final fracture behavior and fracture position, so the total energy dissipation and deformation of CHS joints presented a complicated and nonlinear degradation trend. In addition, corrosion damage simultaneously had an impact on reducing the bending capacity of the chord, and this phenomenon not only caused the differences between the degradation rates of axial tensile and compressive strength of CHS joints but also affected the failure mechanism and local deformation of CHS joints under the brace axial cyclic loading.

An analytical model of longitudinal joints in the segmental lining of shield tunnels with considering geometric nonlinearity

The previous mechanical analysis on the longitudinal joint of segmental linings commonly used the plane section assumption, in which the strains on the normal section are linearly and continuously distributed. This was proven to be overidealized according to a series of full-scale tests in existing literatures. In this paper, the nonlinear characteristics of deformation behavior for longitudinal joint were investigated with emphasis on the geometric nonlinearity of joint. A new analytical model of longitudinal joint was proposed with considering the geometric nonlinearity via employing the local plane section assumption to describe the strain distribution of joint section. The effectiveness of the proposed model was validated and parametric study (e.g. loading cycles and peak bending moment) was conducted. The results indicated the geometric nonlinearity of longitudinal joint refers to the increase area of free surface for the joint section. This nonlinearity will cause the discontinuous change of contact state which can be intuitively charactered by the height of concrete compression zone. Without considering the geometric nonlinearity, the area of concrete compression zone and bending capacity of the joint are overestimated by 45% to 100% based on the calculation result of the verification case. The increasing load cycles and peak load value deteriorate the deformation recoverability and ultimate capacity of joints. The degree of geometric nonlinearity is intensified with the increase of load cycles and peak load value but it can be alleviated if the concrete in external edge contact during overloading process.

Experimental and numerical investigations on the bending capacity of cold-formed steel box headers

The study investigates the bending strength of tracks of box headers beyond AISI, which considers the capacity of individual channels alone. Both experimental and FEM are used, and the results are compared to AISI. The findings highlight tracks' significant role in the overall bending capacity. AISI is found to be conservative by 34% to 152%. Failure mode is different from code theoretical expectations for a single channel. Fastener close spacing marginally improves the capacity, while side fasteners offer significant enhancement, but track widening limits this enhancement. A modification to AISI is proposed considering track strength, with outcomes showing good accuracy.

Bending behaviour of surface corroded and perforated corroded steel tubes repaired by laser cladding additive manufacturing

In recent years, laser cladding (LC) technology has been increasingly applied and investigated for repairing damaged surface on metal structural components. However, there are limited experimental studies on the bending behaviour of the LC repaired steel components. And an effective repair method for the perforated corroded steel components is still lacking, therefore, this paper introduces a novel LC repair method for such steel tube. Four-point bending tests were conducted on four specimens, including one intact steel tube (IT), one surface corroded steel tube (SCT), one surface corroded steel tube repaired by LC (SRT), and one perforated corroded steel tube repaired by LC (PRT) to verify the effectiveness of the LC repair methods by evaluating their structural performance in terms of bending capacity, rotational stiffness, and ductility. The experimental results showed that the bending strength and rotational stiffness of the SRT and PRT can be fully restored and even slightly higher than those of the IT. The strain analysis indicated that the LC repair method can significantly reduce stress/strain concentration caused by surface corrosion and perforation corrosion. The experiments were replicated numerically by means of finite element (FE) analysis and parametric studies were performed to investigate the effect of different factors on the bending behaviour of the PRT and SRT. Furthermore, design formula for predicting the elastic bending capacity of the LC repaired steel tube was developed.

Study of the flexural behavior of UHPC-HPC composite beams strengthened with BFRP sheet after chloride secondary erosion

To solve the issue of insufficient durability of reinforced concrete (RC) structures, a new structure of ultra-high performance concrete (UHPC)-high performance concrete (HPC) composite beam was designed, and the flexural performance of the composite beam strengthened with basalt fiber reinforced polymer (BFRP) after pre-damage was investigated. Results indicate that main cracks are formed and developed after the secondary erosion of chloride salt, leading to three forms of failure modes of the beams: BFRP sheet fracture and concrete crushing, BFRP sheet debonding and concrete crushing and BFRP sheet debonding. The test beam failure process can be classified into three stages: linear elasticity, crack development and yield. The maximum cracking and ultimate loads increased by 27.9 % and 35.8 %, respectively. The crack load growth rate of the beam decreased after 7 days (d) of secondary chloride salt erosion. The formula for calculating the peel strength of the UHPC-HPC composite beam was modified. The calculated bending capacity of the beam agrees well with the measured value. This study provides a reference for enhancing the lifespan and calculating the flexural bearing capacity of structures in corrosive environments.

Comparison of analytical models for shear strength estimation of steel plate girders

Web shear buckling of steel plate girders limits their load-carrying capacity in bending. Several analytical models have been suggested in the literature to estimate the shear capacity of plate girders. This paper presents a critical evaluation of several of these analytical models using the data of experimentally tested plate girders available in the literature. It was found that these analytical models make a conservative estimation of critical buckling strength for plate girders with larger slenderness and/or aspect ratios. Although the predicted ultimate shear strength varied across the different analytical models, no particular trend was identified to show that the aspect and/or slenderness ratios influenced the shear strength. A parametrically conducted analysis indicated that the threshold slenderness ratio (to cause buckling in the web panel) decreases with increasing yield strength and aspect ratio. The paper proposes simplified guidelines for the preliminary sizing of steel plate girders by avoiding shear buckling. It has been shown that the sizes of plate girders determined using the proposed guidelines satisfy design requirements for both flexure and shear.

Experimental study of ultra-high-performance fibre-reinforced concrete (UHPFRC)-encased CFST short columns under axial and eccentric compression

This study presents a comprehensive experimental programme and analysis of ultra-high-performance fibre-reinforced concrete (UHPFRC)-encased concrete-filled steel tube (CFST) columns subjected to axial and eccentric compression. Twelve short columns were tested, with six of them utilising UHPFRC encasement while the other six employing normal strength fibre-reinforced concrete (FRC) encasement for comparison purpose. The study focused on the effects of load eccentricity ratio, concrete encasement type, and steel tube configuration. Key findings from the test results including failure modes, load-deflection behaviour, moment-curvature relationships and curvature ductility were examined. The findings showed that UHPFRC-encased CFST columns exhibited significantly enhanced strength and bending capacity, while FRC-encased columns showed remarkable ductility. A notable shift in failure mode was observed with increasing load eccentricity ratio, transitioning from crushing of concrete to compression, and then to balanced failure. Furthermore, applicability of prevalent design codes such as EC4, AIJ, and ACI 318 in calculating the peak loads of UHPFRC- and FRC-encased CFST columns was assessed. The plastic stress distribution methods in EC4 and AIJ overestimated peak loads, while ACI 318's strain compatibility approach accurately predicted FRC-encased columns but not UHPFRC-encased columns. To address this, modifications of the parameters α and β were incorporated into the ACI design method to reflect the relative brittle nature of UHPFRC, resulting in accurate predictions.

Combined axial load-biaxial bending interaction method for L-shaped CFSP shear walls

This paper reports the development of axial load and biaxial bending interaction method for L-shaped concrete-filled steel plate (CFSP) composite shear walls based on fiber section analysis model using the uniaxial constitutive relationship of materials. Owing to the complex interaction between the two perpendicular wall limbs (web and flange) of an L-shaped shear wall, the contour shape of the My-Mz curve is asymmetric. Linear transformation was employed to reduce the asymmetry of the contour shape, eliminate the influence of dimension, and perform parametric analysis. The analysis results indicate that when 0° ≤ θ(neutral axis angle) ≤ 90°, the influence of width-to-thickness ratio (hw1/bw) and shape coefficient (γ) on the coefficient that controls the contour shape (α) was negligible. The effect of shape coefficient (γ), steel content ratio (ρ), compressive strength of unconfined concrete (fc0), and yield strength of steel plate (fyp) on α is not significant for −180° ≤ θ ≤ −90°. Further, simplified equations were suggested to determine α. The axial load-moment interaction curve expressions for distinctive loading directions were determined by establishing the calculation method for the curve's characteristic points (axial load capacity, bending capacity, boundary points). Subsequently, the characteristic points were combined with the contour shape of the axial load-moment interaction curve derived by fitting the finite element simulation data to generate the axial load-moment interaction curve equations. A design approach was finally formulated based on the equations for the biaxial moment capacity curve and the axial load-moment interaction curves of the characteristic loading directions.

Bend behavior of CFRP grid fabrics UHPC panels with serpentine connectors: Experiments, simulations and calculation formula

CFRP-UHPC panel is an essential type of lightweight concrete structure that can be applied in many cases, such as protective structures, warehouses, and offshore structures. However, further research is needed to achieve the CFRP grid fabrics widely applied in concrete structures. This work proposes a CFRP-UHPC panel with serpentine connectors and conducts three/four-point bending tests, DIC, and finite element methods to reveal its bend behavior. This work also presents the formula for calculating the ultimate moment, considering the stress-strain relationship of UHPC and the interaction of CFRP grid fabrics-UHPC. In summary, this work reveals the failure mechanism of CFRP-UHPC panels with serpentine connectors and proposes a formula for calculating bending capacity.

Static and fatigue behavior of concrete bridge deck slabs reinforced with BFRP and steel bars

Using Fiber-reinforced polymer (FRP) has proved great promise as an alternative to conventional steel in bridge constructions owing to its high tensile strength and corrosion resistance. However, using Hybrid reinforced concrete (RC) slabs displayed enhanced stiffness, narrower crack width and larger bending capacity compared with FRP-RC slabs. This paper studies the static and fatigue performance of concrete bridge deck slabs reinforced with hybrid basalt-FRP (BFRP) and steel bars. The main parameters were the effective reinforcement ratio, the FRP-to-steel bars ratio Af/As, and the fatigue limit. The test results exhibited that superior fatigue behavior was achieved in the hybrid-RC slabs because the hybrid bars can better distribute the load and reduce stress concentration. In addition, the fatigue life growths with increasing the effective reinforcement ratio while reverse trend was observed when increasing Af/As ratio. In addition, increasing the upper fatigue load limit deteriorates the slab stiffness and significantly reduces the fatigue life. A regression analysis has been performed and revealed that the concrete deck slab can withstand 2 million cycles after fatigue loading of an upper fatigue load limit of 34 % of its ultimate static capacity.

Experimental study of flexural behavior of glulam Douglas Fir beams spliced with engineered bamboo cover plates and inclined self-tapping screws

Due to the limitation of transportation and installation, long-span timber structural components need to be extended through multiple spliced joints. Among the common spliced joints, spliced beam joints with self-tapping screws have the advantages of low cross-section weakening, beautiful appearance, and convenient construction. However, the beam joints spliced by self-tapping screws have limitations in terms of bearing capacity and stiffness. To overcome these limitations, this paper proposes inclined self-tapping screw-engineered bamboo joints. In this novel joint, the high-strength engineered bamboo connection plates are used to improve the mechanical properties of spliced glulam beams. A total of thirteen glulam beams were designed. The effects of the layout and number of self-tapping screws, types of connection plates, and spliced gaps on the flexural performance of novel glulam beams were experimentally investigated through four-point bending tests. The results show that the mechanical properties of the spliced beam with parallel self-tapping screws are better than those with staggered self-tapping screws. The bending capacity of the glulam beams spliced with bamboo scrimber plates arranged in parallel increases with the increase of the number of self-tapping screws. The average bending capacity and stiffness can reach 97.3 % and 93.3 % of the intact beams, respectively. The bending capacity and stiffness of glulam beams with the same number of self-tapping screws arranged in parallel and spliced with plybamboo are lower than those of glulam beams spliced with bamboo scrimber. The gap between the spliced cross-sections of glulam beams significantly reduces the flexural mechanical properties of spliced beams, especially the stiffness.

Review of Behavior Flexural Strengthened RC Beams Using Ultra-High Performance Concrete

The use of ultra-high performance concrete (UHPC) to reinforce existing reinforced concrete (RC) structures in flexure has made great strides in research recently. In addition to creating an experimental archive, the research provided a thorough technical literature review. The effectiveness of UHPC strengthening schemes for RC beams was assessed by examining the effect of size on the flexural strengthening performance of RC members with UHPC. Various dimensions of RC elements were considered in order to understand any possible size-related effects. Factors like material strength and stiffness of the current RC members were considered because they could affect the strengthening's overall effectiveness. To comprehend how the strengthening of the UHPC would impact the overall. In order to find the most successful strategy, various UHPC strengthening configurations were examined. prior to applying the UHPC, the concrete substrate must be prepared. The experimental results from the studies under review indicate that UHPC is a promising reinforcement that can successfully provide RC beams flexural strength. The plain overlay's bending capacity increased by 20% to 60% when the thickness of the UHPC overlay was increased within the range of 30 to 50 mm. In contrast to plain overlays, the reinforced overlay resulted in a notable 40%–85% increase in flexural capacity. To assist stakeholders in making decisions, a cost comparison of UHPC with other strengthening techniques, such as carbon fiber reinforced polymers (CFRP), was provided. The study concludes by highlighting the potential of UHPC as a workable option for flexural strengthening of existing RC structures and offers insightful information for furthering the advancement and application of this technology in the building sector.

Amelioration of Flexural Performance for Reinforced Concrete Beams by Soffit Bonded High Performance Self Compacting Concrete Prisms

Abstract This paper presents a strengthening technique using a high-performance fibre-reinforced cement-based composite (HPFRCC) mixture. To evaluate the performance of this approach, two types of concrete mixtures were used one high performance and other high strength in strengthening process and compared to strengthening using CFRP laminate. The results showed that the strengthening was in the proportions (42 %, 58.03 %, 74.32 %) for (Mhs, Mcfrp, Mhp), respectively, Where the strengthening improved the bending capacity for beam (Mhp) to a greater extent of the other types and it reduced the appearance of cracks in the beam when loading until occur failure. As appeared failure modes in all elements were due to rupture in the flexure region and crush in the compression region. In addition, ductility index of the strengthened beams was acceptable and energy absorption of the strengthened samples high if compared to the reference beam Therefore, it can be said that this technology may provide a safer alternative for flexural strengthening of RC beams.