Long-term Sustained Loading Research Articles

Flexural behavior of long-term loaded RC beams strengthened by ultra-high performance concrete

This study aims to investigate the flexural behavior of reinforced concrete (RC) beams strengthened with ultra-high-performance concrete (UHPC) after being loaded with long-term sustained loads for more than 20 years. Seven RC beams, originally fabricated in 1998, are categorized as the one-time pouring unnotched beam (Overall beam), one-time pouring notched beam (Notched beam), and two-time pouring beam (Repaired beam). These RC beams were firstly tested under the effect of long-term sustained loads which lasted 23.6 years. Subsequently, notched beams were strengthened using UHPC (hereafter named as Strengthened beam), which are tested under four-point bending test to investigate the significance of strengthening using the UHPC. Long-term load effects on the flexural performance of RC beams, including creep, cracking, concrete carbonization, and steel rebar corrosion were tested and analyzed. Test results showed that the maximum carbonization depth was less than the concrete cover depth and the steel rebars corrosion was among 1.51–2.47%, which indicates that the steel rebars inside the beam are well protected and are almost free of rust. The bearing capacity of the strengthened beams were increased by 24.6–48.6% compared with that of the Notched beam, which emphasizes the significance of strengthening using the UHPC. The displacement ductility of the strengthened beams was decreased by 82–94% compared with that of the Overall beam, however no brittle failure was observed during the test. It is worth mentioning that the internal changes, caused by the long-term sustained loading, could not be completely changed by adopting UHPC strengthening, while the stiffness reduction caused by long-term loading considerably influenced the flexural behavior of the UHPC strengthened beams. In addition, more attention shall be paid to the UHPC-NC vertical interface which remarkably affected the flexural performance of the Strengthened beams.

Re-Analysis of Historical Data and Model Calibration of Duration of Load Effect on Structural Timber

The duration of load (DOL) effect in structure timber refers to the degradation of strength and stiffness that occurs under long-term continuous loading. This paper investigated the DOL effect in structure timber using DOL tests and DOL damage models. Based on the empirical-fitted formulae, the DOL coefficients were derived for three long-term sustained loads in bending, tension perpendicular to grain, and shear parallel to grain, and the results were compared and analyzed with the Madison equation, Gerhards model, Nielsen model, and Foschi and Yao model derivations to verify the applicability of the DOL empirical model and the three DOL damage models. The results show that based on the historical data of the DOL tests, the Madison empirical formula was found to be better applied to the derivation of DOL coefficients under the bending and tension perpendicular to grain long-term sustained loading, and the derivation of DOL coefficients under shear loading is not satisfactory. Among the three DOL damage models, the Foschi and Yao model was better than the Gerhards and Nielsen models for fitting the DOL test results under bending, tension perpendicular to grain, and shear parallel to grain. The DOL coefficients derived based on the Foschi and Yao model are more comparable to test results and resemble those derived from the Madison formula.

Life-cycle based structural performance of long-span CFST hybrid arch bridge: A study on arch of Pingnan Third Bridge

Long-span concrete-filled steel tubular (CFST) hybrid arch bridge is one of the optimal solutions for large-span bridge construction, where the construction process and long-term sustained loading may affect the structural performance during its life-cycle. The trussed CFST hybrid arch of the Pingnan Third Bridge in China with a main span of 575 m was taken as a benchmark case to numerically determine the life-cycle based structural performance of long-span CFST hybrid arch bridge, and the construction process and long-term service period were considered. The accuracy of the numerical method was validated with the in-situ measured records of the real bridge and a series of available laboratory tests. Thereafter, the life-cycle based working mechanism of the trussed CFST hybrid arch was investigated. Parametric investigations were also carried out to evaluate the influence of key parameters on the load-bearing capacity of the hybrid arch structure. Furthermore, the resistance of the structure was examined using GB/T 51446–2021. It is shown that the simulated results agree well with the in-situ measured and experimental data. The stress redistribution exists in the CFST chord during construction and long-term service phases. The influence of CFST chords is significant to the load-bearing capacity of hybrid arch as the core concrete plays a prominent role, while the effects of the web (brace) strength and web (brace) - to - chord diameter ratio are limited. It is recommended to use GB/T 51446–2021 for resistance prediction of the long-span CFST hybrid arch bridge.

State-of-the-Art on Technological Developments and Adaptability of Prefabricated Industrial Steel Buildings

Compared to traditional onsite steel construction, prefabricated industrial steel construction (PFISC) saves time, money, and resources. It results in sustainable steel structures that use fewer resources and are better for the environment. Despite their advantages, the private sector favors creating high-rise buildings in an old-fashioned way. In order to encourage the adaptability of prefabricated industrial steel buildings (PFISBs) in high-rise structures, this study critically evaluates the adaptable solutions offered in the literature on the recent developments, structural performances, present difficulties, and future potential. In mid-rise and low-rise structures, PFISC is frequently used. In research and case studies, PFISBs have proven to perform admirably under various adverse conditions, including in the event of an earthquake, wind, blast, impact, fire, collapse, and long-term sustained loads. The use of potential research solutions, the “Top-down” strategy, and the resolving of problems such as the structural-based design guidelines, column stability, discontinuous vertical and horizontal diaphragms, cluster columns and beams effect, damage-free and innovative inter- and intra-modular connections, high strength-to-weight modules, numerical simulation, and transportation will help PFISBs to become more widely accepted in high-rise structures. Compared to other materials, steel has recently demonstrated great promise for the construction of PFISBs. Additionally, China plans to increase their PFISC to 30% by 2026, Australia to 15% by 2025, and North America to over 5% by 2023, proving that it is a reasonable response to future urbanization concerns.

Effect of creep on the strength of high strength concrete-filled steel tubes

High strength concrete filled steel tubes (HSCFSTs) are being increasingly used as columns in tall buildings, bridges, and other critical infrastructure and complex structural systems. Very little research has been done to study the performance of these columns under long-term sustained loads where creep effects take place, and no study exists on the long-term performance of these columns under eccentric sustained loads at the large scale. Six large scale (2700 mm height) HSCFSTs were tested in this paper under sustained eccentric compression for a period of five months. After that, the columns were tested to failure and their performance was compared to another six companion HSCFSTs that were kept unloaded for the same time period. A decrease of about 13% in the load carrying capacity was observed after creep. It was also observed that creep significantly changed the force distribution between steel and concrete. A study of the force redistribution showed that the force carried by the steel increased by >50% of its initial value.

Short- and Long-Term Prestress Losses in Basalt FRP Prestressed Concrete Beams under Sustained Loading

The favorable mechanical properties of basalt fiber–reinforced polymer (BFRP) bars, such as their excellent strength-to-weight ratio, resistance to corrosion, lower environmental impact, and electromagnetic neutrality, make them attractive for internal reinforcement of concrete elements with specific service requirements. Prestressing has emerged as a possible method for limiting the deflections and cracking of BFRP-reinforced flexural RC elements. However, long-term behavior of such structural members has not yet been investigated extensively. Therefore, this paper aims to give information on long-term behavior and prestress losses of pretensioned BFRP-reinforced concrete beams based on the collected experimental data. The testing program includes long-term analysis of six BFRP concrete beams pretensioned to different prestress levels—namely, 20%, 30%, and 40% of the ultimate tensile capacity of the bars. The monitored testing stages included initial tensioning of the bars, casting and curing of concrete, transfer of prestressing force to the concrete, long-term unloaded phase after transfer, sustained-loading application, long-term sustained loading phase, unloading, and final destructive testing, conducted in a controlled indoor environment. During all phases of the testing, strain levels in the BFRP bars and deflections were continuously monitored. The results of continuous strain monitoring show that the average loss of strain over the period of initial 90 days of unloaded monitoring was 7% of the initial strain. During the following 6 months of monitoring under sustained loading, an additional 0.3% reduction was recorded on average. The loss was dependent on the initial strain.

Performance of steel-reinforced concrete-filled square steel tubular members under sustained axial compression loading

Steel-reinforced concrete-filled steel tubular (SRCFST) members have been used in the construction owing to the superior structural performances, and are usually subjected to sustained loads during their service period. The study aims to evaluate the structural behaviour of SRCFST columns under long-term sustained load. Twenty square SRCFST columns were designed and tested to investigate the influence of sustained load on the compression behaviour. Various parameters, namely, long-term load ratio, steel ratio of profiled steel and slenderness ratio are considered to evaluate their influences on the creep in sustained load, failure mode, load-deformation curve and load–strain relation of the SRCFST columns respectively. Furthermore, the finite element (FE) model was established via software ABAQUS and its reliability was verified. The results indicate that the long-term load ratio has slight effect on the ultimate strength of SRCFST specimens. When considering the long-term load, the ultimate strength of SRCFST stub columns under axial compression nearly remains unchanged, while the load-carrying capacity for long columns actually decreases. Finally, a simplified calculation method considering long-term loading effect for the load-carrying capacity index of SRCFST columns under axial loading is proposed through parametric regression.

Long-term behavior of CFRP plates under sustained loads

This paper studies the long-term behavior of carbon fiber–reinforced polymer (CFRP) plates under sustained loads. Two typical loading conditions, CFRP plate loading controlled by displacement constraints and force constraints, are studied. The first section investigates the prestress loss of the CFRP plate when it is loaded via displacement constraints, which serves as a prestressed system applied for prestressed structures. Short- and long-term measurements show that the prestress loss of CFRP is caused by material creep, temperature change, and CFRP and anchorage slippage. When the CFRP prestress level is 5.0%–12.3%, the average prestress loss after 42 days is 5.1%. The second section investigates the permanent deformation of the CFRP plate with curved anchorages caused by creep under a certain sustained load (i.e., controlled by force constraints), which serves as a suspension bar or cable applied for determinate structures. The creep strain-to-time relationship, creep rate, and residual strength were obtained. The creep strain-to-time relationship strongly depends on the stress level applied; the creep coefficient is less than 10.94% and the residual strength is greater than 80% of the initial tensile strength after 1000 h. The findings show the effectiveness and reliability of these two typical cases of CFRP plates under long-term sustained loads.

Reinforced concrete slabs strengthened with externally bonded carbon fibre-reinforced polymer strips under long-term environmental exposure and sustained loading. Part 1: Outdoor experiments

Carbon fibre-reinforced polymers (CFRPs) can be used to increase the load-bearing capacity of concrete bridge deck slabs and their lateral cantilevers. In this study, experiments were performed to explore the long-term performances of loaded RC slabs strengthened on the top surface using non-prestressed and prestressed externally bonded (EB) CFRP strips. A real bridge application was simulated by applying mastic asphalt on the top surface. The effects of four years of outdoor exposure to elevated temperatures and solar radiation were considered. The results show that specimens strengthened with non-prestressed EB CFRP strips exhibit satisfactory behaviours, but a substantial increase in strain is shown in the CFRP strips over time. A slab strengthened with prestressed EB CFRP strips anchored with a so-called gradient anchorage experiences premature failure, owing to elevated temperatures and sustained loads.

Investigation of long-term tension stiffening mechanism for ultra-high-performance fiber reinforced concrete (UHPFRC)

Ultra-High-Performance Fiber Reinforced Concrete (UHPFRC) is promptly emerging concrete that has ultra-high compressive strength, and its ductile properties are ensured in the addition of steel fibers. Steel fibers in UHPFRC feature strain-hardening characteristics and exert the damage pattern as intimately spaced narrow cracks. The tensile performances of reinforced concrete elements are closely interrelated with the bonding interactions between the reinforcing rebars and concrete. Since the UHPFRC exhibits different tensile behavior and cracking behavior from traditional strength concrete, it is crucial to analyze the tension stiffening mechanism and cracking propagation of UHPFRC elements in long-term serviceability limit. This study presents the time-dependent tensile behavior of reinforced UHPFRC, especially on the instantaneous and sustained tension stiffening mechanism and post-cracking behavior for the long term. A newly designed testing rig was adopted to introduce the novel testing method. The testing rig was designed in a way to overcome the limitations in applying the sustained tensile loads found in the critical literature review. This novel testing method includes the design of the testing frame for intensive sustained tensile loads application, specimen preparations, and installations. To investigate the long-term tension stiffening mechanism, different types of sustained tensile loads, i.e., 20 kN, 40 kN, 60 kN, and 80 kN, were considered. The applied sustained tensile loads were ascertained from different percentages of cracking load (40 kN) of reinforced UHPFRC derived from the 28-day instantaneous tension stiffening test. Crack width and crack spacing of reinforced UHPFRC specimens were determined for both instantaneous and sustained tensile loads. Notably, crack propagation was considerably affected by the long-term sustained tensile loads compared to instantaneous tensile loads. The autogenous and drying shrinkage strains were 392 micro-strains (µɛ), and 170 µɛ, respectively, at 180-day, where the total shrinkage strain of 562 µɛ significantly influenced the time-dependent tension stiffening behaviors of UHPFRC. A maximum total average concrete strain of 3500 µɛ was found for the sustained tensile load of 80 kN at 180-day. In addition, the material properties of UHPFRC, such as compressive strength, splitting tensile strength, and modulus of elasticity tests, were also conducted, and the maximum compressive strength of 160 MPa was reported at 120-day.

A coupled creep and damage model of concrete considering rate effect

From experimental perspective, it is well-known that relationship between concrete creep and loading level is nonlinear at middle and high loading levels. This nonlinear characteristic is considered to be closely related to micro-crack propagation and damage accumulation in concrete during creep. It has also been revealed in experiments that the strength of concrete under long-term sustained loading is significantly lower than that under static loading test, which can also be ascribed to the nonlinear characteristic (micro-crack propagation and damage accumulation) under long-term sustained loading. Focused on the nonlinear creep of concrete at middle and high loading levels, a coupled creep and damage model considering rate effect is constructed at meso-scale in this study. In the coupled creep and damage model, the creep behavior of concrete is characterized using B3 model and rate effect is taken into account by modifying Mazars damage model via intensity amplification factors DIFs. The presented model is validated through comparisons with experiment results from literatures. The dynamic damage mechanism and nonlinear creep mechanism are comprehensively analyzed and discussed using the model. It is proven that the presented model is capable of characterizing the nonlinear creep and creep failure of concrete at medium and high loading levels. The consideration of rate effect in calculation shows better results and the characterization of its role on the creep evolution is correct and essential.

Assessment of Concrete Filled Steel Tubular Members: An Experimental Review

In this world with rapid development, durable and fast construction techniques lead to the invention of composite materials that are robust and advantageous over conventional materials. Recently invented Concrete-filled steel tubular members are the composite members used in civil engineering works to replace conventional steel and concrete members. This paper deals with an overview of the experimental performance of various types of composite members such as columns, short columns, stub columns, beam-columns, and slender columns deals with various loads such as axial compression, flexural load, cyclic bending, long-term sustained load, torsional load, and impact load. Effects due to the variation in the parameters like steel and concrete strength, diameter to thickness ratio, axial load level, shapes of tubes of these composite members on load-carrying capacity, flexural stiffness, ductility, torsional capacity, and cyclic performance of these members are discussed in this paper. The future scope is mentioned for study related to these composite members in the paper.

RC slabs strengthened with externally bonded CFRP strips under long-term environmental exposure and sustained loading. Part 2: Laboratory experiments

This investigation consists of two parts (outdoor and laboratory experiments). The first part described RC slabs strengthened with prestressed and non-prestressed CFRP strips; these slabs were loaded and exposed to an outdoor environment for four years. It was found that the elevated temperatures reached in the adhesive did not significantly affect the service behaviour of non-prestressed EB CFRPs, but could lead to the failure of the prestressed system.In the second part of the discussion, laboratory experiments are presented. Failure tests were performed to determine the ultimate strengths of the slabs. The results demonstrate that long-term exposure (thermal cycles and sustained load) does not affect the load-carrying capacity of the strengthened RC elements. Furthermore, an additional slab with an identical strengthening configuration was tested after being subjected to thermal cycles under a heavy sustained load under laboratory conditions, allowing us to better understand and verify the results obtained during the long-term experiments.

Experimental and numerical study of long-term behaviour of timber-timber composite (TTC) connections

Long-term sustained load (push-out) tests under an indoor uncontrolled environment were conducted on twelve specimens (in seven groups/types) of Timber-timber composite (TTC) joints with up to two identical specimens of each TTC joint type. The TTC joints were fabricated by connecting either Laminated veneer lumber (LVL) or Glued laminated timber (GLT) joists to Cross laminated timber (CLT) slab panels. Types of joists (LVL and GLT), size of coach screw shear connectors, type of shear connection (screws with or without adhesive) between the joists and CLT slab thickness and orientation (i.e., lengthwise, or crosswise) with respect to the loading direction were the main variables in the experimental program. The laboratory tests revealed that the creep coefficient after 420 days is in the range of 1.05 to 3.90 and the CLT slab orientation has minor and CLT thickness has major influence on the creep coefficient of TTC joints (for a given service load over loading capacity ratio). A creep model was calibrated against the experimental slip-time curves and the model was used to predict the creep coefficient for the 50-year design life of the structure. It was shown that more than 50% of the creep in the TTC joints occur in the first year of loading. Additionally, a 3D coupled Finite element (FE) model implemented as user defined subroutines in ABAQUS/Standard was validated against the long-term test results and accordingly input parameters for coupled long-term FE analysis of the LVL-CLT and GLT-CLT joints (with screw shear connectors) are recommend. The validated FE model was used to further confirm effect of the CLT panel thickness and orientation on the long-term slip-time and creep coefficient of the TTC joints.

Influencing factors on creep displacement assessment of bonded fasteners in concrete

The long-term sustained load behaviour of bonded fasteners in concrete is tested and assessed in accordance with European Assessment Documents (EADs) 330087 and 330499. In these EADs, the measured displacements during sustained loading are projected to a 50-year working life using a power-law regression and extrapolation combining an initial displacement δ0 and a time-dependent creep term a∙tb. The projection of sustained load displacement data is sensitive to methods for determining and employing the initial displacement, data sampling choices for regression, and the length of testing. To illustrate these sensitivities, six sustained load tests with an extended test duration of 300 days and high displacement measurement frequency were conducted and numerically investigated. The aim of this paper is to address and verify the influence of various parameters on the displacement projection. In particular, the determination of the initial displacement, sampling window, and their proper use in the application of the Findley power-law method for creep displacement extrapolations are evaluated. To that end, different scenarios are assessed varying the time step between the displacement measurements, the size of the time window of measured displacements used for the regression analysis and use of the initial displacement in regression. A final check on the appropriateness and conservatism of the use of a power-law regression is proposed. Based on this analysis, proposals for the assessment of long-term displacement of bonded fasteners in concrete under sustained load are made.

Long-Term Creep and Shrinkage Behavior of Concrete-Filled Steel Tube.

A concrete-filled steel tube (CFT) combines the advantages of concrete and steel in construction and structural applications. However, research on the time-dependent deformation of the CFT under long-term sustained loading are still limited, particularly for stress transfer between the steel tube and concrete due to creep. This study investigated the creep behavior of CFT over a long period of 400 days. The creep and shrinkage strain of CFT was significantly lower than those of concrete that was not confined within a steel tube. The vertical strains of the steel tube and concrete core were almost identical, and it was shown that they were well bonded and acted as a composite. The vertical stress of steel increased by 32.7%, whereas the vertical stress of concrete decreased by 15.8% at 375 days. The stress transfer is notable and cannot be neglected in CFT design. Moreover, the results of creep and shrinkage were compared to prediction values of the B4 model and B4-TW model to verify their validity.

Study on long-term performance and flexural stiffness of recycled aggregate concrete beams

The incorporation of recycled concrete aggregate (RCA) will unfavorably affect the performance of concrete. The aim of this paper is to investigate the long-term performance of recycled aggregate concrete beams for a period of 3045 days and the bending behavior of test beams after sustained load is removed. Three different replacement ratios of RCA (0%, 50% and 100%) are the main parameters. The experiment observes the crack spacing of RAC beams is larger than that of natural aggregate concrete (NAC) beams during the long-term loading. Compared with the control specimen, the long-term deformations of RAC beams are greater and have hysteresis, which is attributed to the fact that creep and shrinkage of RAC have more significant time-dependence. The RAC beam shows a larger deflection recovery value after the long-term load is removed, and long-term creep effect and sustained load value of specimens may be responsible for this result. The RAC beams exhibit more significant stiffness degradation characteristics in flexural test. In addition, the modified equation is proposed to evaluate the reload short-term stiffness of the RAC beams after exposure to sustained loading.

Long-term performance of lightweight aggregate reinforced concrete beams

The results of long-term sustained flexural loading tests of 17 large scale reinforced concrete beams fabricated with lightweight aggregate (LWAC) having a density of 1800 kg/m3 are presented. Deflections, strains and crack widths were recorded over a period of 30 years. Subsequently, each beam was tested to failure. The observations are compared to US, European and Chinese standard provisions for long-term concrete behaviour and LWAC concrete design. The dominant conclusion drawn from this study is that, accounting for reduced material properties, the long-term behaviour of LWAC exhibits no differences from that of normal weight concrete (NWC). Existing provisions for addressing long-term behaviour of NWC may be applied to LWAC and remain suitably conservative. Experimental results confirmed the beneficial effects of the presence of compression reinforcement or a wider compression flange (tee beam). Creep effects on deflection and compression strains were more pronounced that those on maximum measured crack width. The paper presents extensive data accumulated over the 30 year long-term load study reported.

Life-cycle based analytical theory of concrete-filled steel tubular structures and its applications

<p indent=0mm>Concrete-filled steel tube (CFST) is a composite structure consisting of a steel tube filled with concrete. The steel tube and its concrete core work together to carry external loads applied to the structure. Due to the interaction between the two kinds of materials, i.e., the confinement effect of steel tube on the core concrete, CFST structures can effectively delay/avoid the local buckling of the steel tube and the brittle failure of the concrete core. The superior structural properties of CFST include high strength and stiffness, good ductility, excellent seismic and fire performances, and easy construction. Therefore, CFST structures have been extensively used in large-scale constructions including industrial plants, subway stations, transmission towers, high-rise buildings, and bridges, etc. CFST structures have also offered substantial benefits on architectural appearance and engineering economy. The confinement effect in CFST throughout its service-life essentially contributes to the structural advantages, whilst it has, at the same time, brought about enormous complexities in the corresponding load-resisting mechanisms. Firstly, an in-depth understanding and accurate characterization of the confinement effect, and the development of some feasible constitutive models for the core concrete that facilitate the analysis and design of major infrastructures, becomes the key issue to be addressed. The salient loading factors in the service-life of CFST structures need to be considered in the constitutive models, such as long-term sustained load, low-cycle cyclic load and full-range fire. Secondly, the establishment of damage mechanism analysis and strength prediction models for CFST structures considering long-term sustained load, complex loading conditions, earthquake and fire becomes another key issue that needs to be resolved for the safety design of major CFST constructions. Life-cycle based damage mechanism and analytical theory of concrete-filled steel tubular structures have been investigated and established based on nearly <sc>20 years</sc> of persistent and systematic study. The design methods for the ultimate loading capacity of CFST structures were further proposed. The major research outcomes can be summarized in the following three aspects: (1) The interaction between the steel tube and its core concrete as well as the passive confinement mechanism in CFST were revealed. A general constitutive model for the confined core concrete under various stress/action conditions was established with the “confinement factor” as an essential variable. The considered actions include long-term sustained stress, cyclic load and elevated temperature. (2) Theoretical models were established to account for the damage mechanism of CFST structures under long-term sustained load and complex loading conditions. The ultimate strength of CFST members under various loading conditions was analysed, including compression, tension, bending, shear, torsion, and the combinations of different loads and load paths. The creep and shrinkage of concrete as well as the deformation of CFST under long-term sustained load were accurately simulated. (3) Theoretical models were established to simulate the damage mechanism of CFST under earthquake and full-range fire. The hysteretic properties and ductility of CFST members under low-cycle cyclic loading were revealed. The model for calculating the fire resistance of CFST columns was proposed, in which the coupling effects of loads and full-range fire were taken into account. This paper briefly reviews the development of CFST structures and outlines the life-cycle based analytical theory for CFST structures. Finally, the potential development trends of the CFST structures are discussed.

Concrete-filled steel tubes subjected to axial compression: Life-cycle based performance

This paper presents a life-cycle based finite element analysis modelling for concrete-filled steel tubular (CFST) stub columns. The effects of initial imperfections (e.g., residual stresses induced by cold forming or welding, and initial geometric imperfections), preloads during the construction process, long-term sustained loads and corrosion are considered in the modelling. To reveal the life-cycle time-dependent behaviour of CFST stub columns, influences of the above factors on the full-range load-displacement relations and the load-transfer mechanism are discussed in regard of five typical working conditions as: Case 0 - short-term loading; Case 1 - initial imperfection with short-term loading; Case 2 - initial imperfection, short-term loading followed by sustained load; Case 3 - initial imperfection, short-term loading followed by sustained load and corrosion; as well as Case 4 - initial imperfection, preload, short-term loading, sustained load and corrosion. Considering the effects of these factors, definition of the ultimate state of CFST stub columns under typical working conditions are discussed. Parametric studies are then carried out to calibrate the simplified design models for CFST stub columns at different loading cases. A database with information of 1096 CFST stub column specimens are established. Reliability analysis proves that the proposed simplified methods meet the reliability requirements in accordance with current design standards for CFST members under the five discussed cases. Partial factor for axial compressive strength of the composite section is suggested at the end of this paper.