Abstract:This paper presents a state-of-the-art review on recent researches of seismic performance of steel concentrically braced frames and the seismic design methods in codes of practice of China and other countries, aiming at facilitating a safer and more cost-effective design and application of steel concentrically braced frames with single lateral resistant system. Limitations in current Chinese codes are discussed. It is pointed out that the low cycle fatigue performance of braces and their connections is not fully considered for steel concentrically braced frames, and there is no difference between the seismic design methods for structures with high ductility and low ductility. The contributions of semi-rigid connection of beam-column joints, vertical continuity of columns, and semi-rigid connection of column base bolts on the reserved capacities of steel concentrically braced frames with low ductility are neglected. To address these problems, following suggestions have been put forward. It is necessary to further investigate the low cycle fatigue life of braces and their connections and establish the seismic design principle to better match the low cycle fatigue life of braces and their connections. The capacity curve and low cycle fatigue damage of steel concentrically braced frames with high ductility should be analyzed to understand the laws of reduction level of seismic force and the demand of low cycle fatigue cumulative hysteresis energy. By combining force-based and energy-based design, a more reasonable seismic calculation method can be proposed. Structural reserved capacities for seismic resistance should be quantified to construct seismic design methods for steel concentrically braced frames with low ductility, so as to extend its application.

Abstract:To deal with the limitations of the existing constitutive relation models of confined concrete, the experimental results of confined concrete columns were collected to establish a database, including concrete strength of 19.6-158 MPa, volumetric ratio of 0.5%-7.27%, stirrup yield strength of 296-1 318 MPa, and longitudinal reinforcement ratio of 0%-5.87%. The effects of seven key parameters on the strength enhancement factor (K_c=f_cc/f_c) and deformation enhancement factor (Kε=ε_cc/ε_c) of confined concrete were analyzed. Through the unified processing and regression analysis of the data in the database, the unified equation of confined concrete stress-strain curve under axial compression was proposed, and the computation formulas of peak stress and peak strain were obtained. The prediction effects of the proposed unified equation and the existing models were compared and analyzed. Results show that the stress-strain curves obtained by the unified equation were more consistent with the experimental curves. The formulas of peak strain and peak stress had good predictive effect. From the overall verification results, it can be concluded that the model proposed in this paper is highly accurate and widely applicable.

Abstract:In order to investigate the temperature evolution of reinforced concrete top-head platform of metro under fire conditions and its impact on the structure, a scale model test was carried out under vehicle fire. The temperature evolution and distribution of the envelope and indoor space of the model room were measured. On this basis, finite element simulation analysis of the top-head floor was performed combined with layered shell model. Results show that the structure maintained intact after fire, which meets the fire resistance requirements. In addition, a high-temperature thermo-mechanical coupling calculation model for reinforced concrete floor was established, and its simulation results agreed well with test results, which further verified the reliability of the proposed method. The study can provide reference for the fire resistance evaluation of top-head platform of metro.

Abstract:To understand the influence of non-uniform corrosion on the performance of RC frame columns, the corrosion crack propagation and the distribution of corrosion products were studied. The evaluation model of the corrosion rate of longitudinal reinforcement based on the corrosion crack width was established. By introducing the corrosion influence coefficient, an equivalent strength model of corroded longitudinal reinforcement was proposed, considering non-uniform corrosion. Based on the existing test results, the relation between the corrosion rates of longitudinal reinforcement and stirrup was analyzed, and the correlation model of the corrosion rates of stirrup and longitudinal reinforcement was constructed. A concrete model confined by corroded stirrups was proposed based on the Mander model. Calculation results show that the corrosion of steel bars significantly decreased the strength of the concrete and the steel bars, and the non-uniform corrosion of the steel bars affected the mechanical properties of the steel bars. On the basis of OPENSEES and the proposed material model, a numerical model of corroded RC frame columns was established. Given the previous test data, the models proposed in this study were verified. Results show that the models achieved high accuracy, the evaluation model of corrosion rate could reflect the influence of involving factors, and the research results can be used to evaluate the performance of existing concrete structures.

Abstract:To study the seismic behavior and influencing factors of reinforced ultra-high performance concrete (UHPC) columns, by taking carbon fiber reinforced polymer (CFRP) sheet winding, steel strength, and shear span ratio as variables, tests were carried out on an ordinary steel reinforced UHPC column, an ordinary steel reinforced UHPC column wound with CFRP sheet, and three high-strength steel reinforced UHPC columns under low frequency cyclic loads. The failure mode, load-displacement curves, ductility, and energy dissipation capacity of the specimens were analyzed. Results show that the ductility and energy dissipation capacity of the reinforced UHPC columns with shear span ratio of 1.5-4.0 were good. Under CFRP sheet winding or large shear span ratio, the failure mode of the specimens changed from shear compression failure to bending shear failure, and the ductility was significantly improved. The bearing capacity and ductility of the specimens were improved by increasing the strength of the longitudinal steel and stirrups of the UHPC columns. The working capacity of the ordinary stirrups was poor after cracking, so it is suggested that the shear members of UHPC should be reinforced with stirrups with yield strength above 600 MPa. Based on the truss-arch model, the calculation formula of shear capacity of reinforced UHPC columns was established by taking account of the tensile contribution of steel fibers and the influences of axial compression ratio and shear span ratio. The calculated values agreed well with the test results, which can provide reference for the design of UHPC structures.

Abstract:To reveal the effect of additional end anchorage on the bond behavior of carbon fiber reinforced polymer (CFRP)-to-concrete interface, the debonding process model of CFRP-to-concrete bonded interface subjected to temperature variation was established by means of analytical theory. Based on the interfacial bonding theory and bi-linear bond-slip constitutive, a series of analytical models were deduced, including the distributions of interfacial slip, interfacial shear stress, and CFRP axial stress. The calculation models of load-slip curve and interfacial debonding load were also given. By comparing the experimental and numerical results, the correctness of the analytical models was verified, and parametric analysis was then carried out. Results show that compared with external bonded interface, the end anchorage increased the interfacial debonding load and effectively decreased the interfacial slip and shear stress caused by temperature variation. Besides, CFRP axial stress increased when subjected to the same temperature variation, which enhanced the strength utilization of the CFRP material. For CFRP-to-concrete bonded interface with end anchorage, the bearing capacity of the interface increased with increasing temperature before the temperature reached the glass transition temperature of adhesives. The decreasing temperature led to the premature interfacial debonding at the load end of the bonded interface, which reduced the interfacial bearing capacity. Further, when the thickness or modulus of the CFRP material increased, the effect of temperature variation on the bond behavior was more significant.

Abstract:End anchorage is an effective measure to control the debonding of CFRP-to-concrete bond interface and improve the interface bearing capacity. To study the debonding process of CFRP-to-concrete interface with end anchorage, the exponential bond-slip model was introduced to establish analytical models. The distribution expressions of interfacial slip, bond stress, CFRP axial strain and stress were obtained. The proposed models were well verified by experimental results. Based on the analytical models, the calculation methods of the maximum bond force, effective bond length, and debonding load were established, and the influence of different bond lengths on the mechanical behaviors of the interface during the debonding process was analyzed. Results show that the effective bond length of the bonded interface with end anchorage was longer than that of the external bonded interface. The debonding load decreased with the increase of the bond length, approaching the ultimate bearing capacity of the external bonded interface. When the bond length was long, there was little difference between the debonding load and the maximum bond force, and the end anchoring force was small. When the bond length was short, the end anchorage would bear the load earlier, and the debonding load was close to the CFRP breaking load.

Abstract:The composite components composed of thin-walled metal tubes and foam materials have advantageous energy dissipation capability. In this study, aluminum foam-filled 6082-T6 aluminum alloy circular tubes were proposed as energy absorption composite components in building structures. Twenty groups of empty aluminum tubes and aluminum foam-filled composite tubes with different dimensions were tested under axial static compressive load to investigate the deformation behavior, failure mechanism, and energy absorption capacity of aluminum foam-filled 6082-T6 aluminum alloy circular tubes. Experiment results show that the specimens exhibited three failure modes under axial compression, including splitting failure, symmetry folding and splitting failure, folding and splitting and irregular deformation failure. Filling aluminum foam could effectively improve the deformation capacity of the components, prevent irregular deformation failure, and enhance their energy absorption capacity. Finite element (FE) model was established based on LS-DYNA, and parametric study was carried out. It shows that the peak crush load and energy absorption capacity of the tubes increased with the increase in the thickness and diameter of the tubes. Moreover, instability of the tubes was observed from the numerical results when the ratio of height to diameter exceeded a certain value, while filling aluminum foam could increase the critical height to diameter ratio of the components.

Abstract:To eliminate the adverse effect of the additional rigidity of infilled wall on its frame and make full use of the strong deformation capacity and good ductility of concrete filled steel tubular (CFST) frame, the structural measures of reserving the gaps between CFST column frame and infilled wall as well as the flexible connection between infilled wall and steel beam were adopted. A full-scale two-story two-span frame infilled wall specimen was tested under low frequency repeated loads to verify the reliability of the flexible connection and investigate the seismic performance and interaction mechanism of CFST column frame-integral assembled infilled wall. Based on the test, the damage evolution process of infilled wall, the deformation performance of CFST column frame and connection, and the seismic performance of the structure were analyzed. Results show that the hysteretic curve of the overall structure was full, and the energy dissipation capacity of the structure was strong. When the ultimate displacement angle reached 1/41, the structure still had stable bearing capacity and good ductility. The flexible connection between the assembled infilled wall panel and the frame weakened the load transferred from the frame to the infilled wall panel, and delayed and reduced the damage of the integral assembled infilled wall. The integral assembled infilled wall and fabricated steel frame were connected reliably as a whole by the flexible connection, exerting the advantages of strong deformation capacity and good ductility of the CFST frame. In the later stage, the overall structure exhibited stable bearing capacity, good seismic performance, and safety reserve under earthquake load.

Abstract:To study the stress mechanism of grouted sleeve lapping connectors for rebars with large diameters, a total of 36 lapping connectors were tested under uniaxial tensile load. The failure modes, bearing capacity, ductility, and sleeve strain of the connectors were investigated. Test results show that with the same relative lapping length, the yield strength and ultimate load of the specimens increased with the increase of the rebar diameter. Meanwhile, specimens with larger lapping lengths had better initial stiffness and ductility. At the early stage of loading, the sleeve was in longitudinal tensile state, and at the late loading stage, it was in longitudinal compression state. The conversion load of longitudinal sleeve strain from tension to compression increased gradually with increasing lapping length. With the increase of the lapping length, the longitudinal tensile strain of the sleeve near the rebar increased during the loading process, while the longitudinal compressive strain of the sleeve in the far side of the rebar decreased under ultimate load. At the early stage of the loading process, the circumferential strain in the middle of the sleeve was larger than that in the edge section. When the ultimate load was reached, the circumferential strain of the sleeve in the edge section was smaller than that in the middle section due to the shedding of the grout at the end of the specimens. The force transmission path and mechanical mechanism of the connectors were analyzed. The distribution and development of longitudinal sleeve stress were analyzed based on the curve of rebar-concrete bond stress, and results show that the sleeve was in longitudinal tensile state at the early stage of loading and in longitudinal compression state at the late loading stage, which was consistent with test results. The calculation formulas for the ultimate bond strength and critical lapping length of grouted sleeve lapping connectors were proposed based on the test data. The research lays theoretical foundations for the application of such connectors.

Abstract:To study the progressive collapse of a prefabricated reinforced concrete frame structure (PRCS) with steel tube bolted connection, three full-scale prefabricated long columns were tested. First, a simplified prefabricated column model was proposed by using the multi-stage linear plastic connection element in SAP2000. The column-column joint was simulated and compared with test results. Then, a six-story PRCS connected by steel tube bolted bars and a six-story cast-in-place reinforced concrete frame structure (CRCS) were analyzed by removing column method. Four working conditions were removed, namely, the corner column, the long side middle column, the short side middle column, and the inner column of the first floor. The internal force and displacement time history curve of key components were obtained after removing the columns. Lastly, the collapse mechanisms of PRCS and CRCS were analyzed through Pushdown curves. Results show that the multi-stage linear plastic connection element well simulated the prefabricated column-column joint, and the simulation value was consistent with the test value. Under design load, the failure of the inner column had the greatest impact on the PRCS, and its displacement was 72.2% larger than that of the CRCS. By analyzing the Pushdown curves, it was found that when the corner column was damaged, the bearing capacity of the PRCS under beam mechanism was the lowest, which was 25.4% less than that of CRCS, and the lowest bearing capacity was 33.1% less than that of CRCS when the inner column was damaged. Finally, the section size and reinforcement of the inner and side columns and their adjacent beam members that are needed to be strengthened, as well as the thickness of the outer steel tube, were obtained to improve their rigidity. Therefore, this paper can provide reference for the collapse resistance design of the subsequent engineering application of such prefabricated structures.

Abstract:To solve the unfavorable deformation problems of asymmetric RC frame-prefabricated shear wall (AFPSW) structures under earthquake excitation, such as inter-story drift concentration and plane torsion, a seismic strengthening method of attaching external rocking frame was proposed to improve the seismic performance and damage deformation capacity of the AFPSW structure. The dynamic equation of the structural system was derived, the deformation control mechanism was revealed, and the corresponding design method was put forward for rocking frame. To verify the proposed method, the AFPSW finite element model was established and verified based on shaking table test. On the basis of the model, nonlinear dynamic time-history analysis was conducted, and the deformation modes, damage states, and performance improvement of the AFPSW structure with and without reinforcement were investigated. Results show that the drift concentration factor N_DCF and torsion of the strengthened structure were reduced by 20.9% and 53% respectively under peak ground acceleration of 0.62 g, which greatly improved the unfavorable deformation of the structure and reduced the damage level of the system.It indicates that the dynamic equation of the structure was correctly deduced, and the proposed reinforcement design method is effective, which can remarkably improve structural uniformity and seismic performance.

Abstract:With time series data of base bending moments and forces simultaneously measured by high frequency force balance (HFFB) wind tunnel test of 1 000 kV ultra-high voltage (UHV) substation frame in uniform flow, terrain A, and terrain B, the power spectrum density (PSD) and statistical characteristics such as mean value, root mean square (RMS), kurtosis, and skewness of aerodynamic coefficients of the whole substation frame and segment models were compared and analyzed. The influence rules of wind direction, terrain type, and other factors on the wind load characteristics were investigated, and the proportional relationship of aerodynamic force coefficient characteristic between the overall model and segment models of the substation structure under different flow fields was discussed. Results show that taking segment model A as an example, the ratio of mean values of C_x in uniform flow field, terrain A, and terrain B landforms at 0° wind direction was 1∶[KG-2mm]1.58∶[KG-2mm]1.57 and that of its RMS values was 1∶[KG-2mm]1.60∶[KG-2mm]1.59. Correspondingly, the ratios of mean values and RMS values of C_y were 1∶[KG-2mm]7.0∶[KG-2mm]7.57 and 1∶[KG-2mm]1.53∶[KG-2mm]1.30, respectively. Contrastive analysis of the overall model and various segment models demonstrates that in the uniform flow field at 90° wind direction, the ratios of mean values and RMS values of C_x for the overall model and four segment models were 1∶[KG-2mm]0.02∶[KG-2mm]0.26∶[KG-2mm]0.22∶[KG-2mm]0.38 and 1∶[KG-2mm]0.06∶[KG-2mm]0.37∶[KG-2mm]0.32∶[KG-2mm]0.41, respectively. While the ratios of mean values and RMS values of C_y were 1∶[KG-2mm]0.46∶[KG-2mm]0.57∶[KG-2mm]0.43∶[KG-2mm]0.69 and 1∶[KG-2mm]0.47∶[KG-2mm]0.58∶[KG-2mm]0.44∶[KG-2mm]0.70, respectively. The most unfavorable wind direction and design wind load of 1 000 kV UHV substation frame were determined by comprehensive comparative analysis of time and frequency domains, which provides reference for engineering design.

Abstract:Standing seam metal roof systems are widely used in large-scale buildings such as factories, stations, and stadiums, while they are prone to have local and overall damages under strong wind due to the characteristics of lightweight and flexibility. It is crucial to study the wind-induced response and failure mechanism of standing seam metal roof systems, so as to improve their wind-resistance performance. Full-scale tests and numerical simulation were conducted to investigate the wind-induced response of standing seam metal roof systems, which includes the process of deformation, local buckling, and final failure. The displacement, failure modes, and ultimate bearing capacity of roof panel at different stages were studied under increasing wind loads. Results show that the failure mode of standing seam metal roof systems was the clip separation from seam. Local buckling was observed before the failure, which resulted in the global deformation of the roof panel. The clip force near the local buckling increased rapidly after the occurrence of the local buckling and caused the clip separation. The proposed finite element method can not only simulate the whole process of standing seam metal roof systems subjected to wind pressure but also predict failure modes and ultimate bearing capacity precisely.

Abstract:To explain the mechanisms of non-Gaussian features of wind pressure of the chamfered corner square cylinder, the flow around a sharp corner square cylinder and a chamfered corner square cylinder was investigated by large eddy simulation (LES) method with various wind angles at a Reynolds number of 2.2×10⁴. The effect of corner modification on the non-Gaussian features of wind pressure was analyzed. Based on the instantaneous flow information, the influences of corner modification on extreme wind pressure were discussed and the corresponding flow mechanisms were studied. Results show that the non-Gaussian regions of the sharp corner square cylinder mainly occurred at the rear corner of the lateral surface and the leeward surface. There were no noticeable non-Gaussian features at shear layer reattachment regions (i.e., separation bubble regions). Chamfer modification could significantly decrease the non-Gaussian regions at the rear corner of the lateral surface and the leeward surface. Flow mechanisms for the occurrence of the extreme wind pressure could be divided into two types, i.e., attached vortex mechanism at rear corner of the lateral surface and Karman vortex mechanism at the leeward surface. Compared with sharp corner square cylinder, chamfer modification made the separated shear layer closer to the cylinder, produced a weaker Karman vortex, and caused weaker (or even the disappearance of) attached corner vortices, leading to a decrease of extreme wind pressure and smaller non-Gaussian regions.

Abstract:To ensure that the structures in different regions have the same collapse probability under earthquakes, uniform risk spectra are investigated in this paper. First, the uniform hazard spectra of Xi’an region were obtained through probabilistic seismic hazard analysis, and the uniform risk spectra were obtained through risk integral method. By comparing the uniform hazard spectra with the uniform risk spectra, it was found that seismic design based on the uniform hazard spectra resulted in different collapse probabilities of structures under earthquakes. Then, the uniform risk spectra in Xi’an region were constructed through analytical method, and the uniform risk spectra obtained by risk integral method and analytical method were compared. It was found that the difference in the uniform risk spectra was small if the seismic hazard of the site was well described by the seismic hazard function. Finally, the effects of the logarithmic standard deviation (β) of seismic fragility on the uniform risk spectra, risk coefficient (R_c), and coefficient among risk-targeted ground motions were analyzed. Results show that β had little effect on the uniform risk spectra of maximum considered earthquake, while it had significant effect on the uniform risk spectra of design basis earthquake and very rare earthquake when β was less than or equal to 0.7 and greater than 0.7, respectively. When β was less than 0.7, R_c decreased with the increase of β, while R_c increased with the increase of β when β was greater than or equal to 0.7. The effect of β on the coefficient between the risk-targeted very rare earthquake and design basis earthquake was greater than that on the coefficient between the risk-targeted maximum considered earthquake and design basis earthquake.

Abstract:To analyze the multi-physical field and multi-phase coupling effects in complex geotechnical engineering, it is necessary to construct a general constitutive theoretical framework for unsaturated double-porosity media. First, double-porosity media was regarded as the nested superposition of two single-porosity media, and an energy conservation equation for unsaturated double-porosity media was derived from classical mixture theory based on the internal relations between strain and pore deformation of each component. Then, the general potential constitutive equations were established under small strain condition for unsaturated double-porosity media on the basis of the mechanical behaviors of conjugate quantity pair. As an application of the general potential constitutive equation, the potential function was adopted as a quadratic polynomial of strains, and it was supposed that each conjugate quantity was independent of each other. Thus, an isotropic linear elastic model of unsaturated double-porosity media was established, and model parameters were determined by experimental data. When unsaturated double-porosity media was degenerated into saturated double-porosity or unsaturated single-porosity media, the proposed model was degenerated into corresponding existing model. The general potential constitutive equation obtained in this paper can provide guidance for the specific modeling of unsaturated double-porosity media, and the linear elastic constitutive model can be used to formulate corresponding consolidation governing equation.

Abstract:Ultra-high performance lightweight concrete (UHPLC) is a kind of lightweight cement-based material with properties of high tension and compression ratio and tensile strain-hardening. To investigate the collaborative tension mechanism between UHPLC and steel before the yield point of the steel, a self-designed tensile loading system was used to conduct cyclic tensile loading. The adopted UHPLC has a density of 1 789 kg/m³, compressive strength of 63.1 MPa, ultimate tensile strain of 2.4×10^-3-2.8×10^-3, and ultimate tensile strength of 6.9-7.8 MPa. Four cyclic loading conditions were applied, i.e., tensile strains were 2.0×10^-4, 5.0×10^-4, 1.0×10^-3, and 1.5×10^-3, respectively. Test results show that the envelope curves of the cyclic tensile stress-strain curves were in high consistency with the direct tensile stress-strain curves. The residual strain, stiffness of loading, and stiffness of unloading that derived from the cyclic loading test reflected the debonding situation of the fibre at bridged micro-cracks. The larger the residual strain was, the longer the debonding length of the fibre was, which resulted in the reduction of the loading and unloading stiffness. When the cumulated tensile strain under the cyclic tensile loading was smaller than the ultimate tensile strain, the multiple cyclic loading led to a cyclic tensile action on the debonding part of the fibre. The degradation rate of the loading stiffness and the cumulated residual strain followed a power function with a fitting degree of 0.99. The stiffness of the UHPLC under cyclic tensile loading was decided by the effective length of the fibre (the debonding part) under tensile loading, which could be characterized by the cumulated residual strain.

Abstract:To study the effects of corrosion on the mechanical properties of cold-formed thin-walled steel and hot-rolled steel materials, tensile tests were conducted on cold-formed thin-walled C-shaped steel that has been in service for many years in industrial environments. By using a 3D scan handheld laser scanner, the surface morphology of the corroded steel plate was obtained, and the influence of the degree of rust on its mechanical properties was discussed. Test results were compared with corroded hot-rolled steel to analyze effects of corrosion on the surface morphology, fracture form, stress-strain curve, and mechanical properties of the two steel products. Results show that the 3D roughness parameters S_a and S_q of the corroded cold-formed thin-walled steel gradually increased with the increase of the corrosion rate, and the growth rate was higher than that of the hot-rolled steel. The elastic modulus, yield strength, ultimate strength, and ultimate strain of the corroded cold-formed thin-walled steel decreased linearly with the increase of the corrosion rate, but the elongation decreased by a quadratic curve with the increase of corrosion rate. At the same depth of rust damage, the decrease rates of elastic modulus, yield strength, ultimate strength, ultimate strain, and elongation of the cold-formed thin-walled steel were greater than those of the hot-rolled steel, which proves that the influence of corrosion on the mechanical properties of cold-formed thin-walled steel is greater than that on hot-rolled steel.

Abstract:A self-centering steel column base with buckling-restrained bar was proposed, and its stress mechanism was analyzed. The self-centering parameter (β_sc) and axial force of column were used as design parameters, and four specimens were designed and manufactured. Low cyclic loading test was conducted to compare and analyze the load transfer mechanism, self-centering capability, deformation capability, and energy dissipation capability of the specimens. Test results show that the plastic deformation of the specimens was concentrated on the buckling-restrained bars, and the seismic performance of the structure could be quickly restored by replacing the damaged buckling-restrained bars, indicating that the design intention was realized. The load-displacement hysteretic curves of the specimens were “double flag-shaped”, and the residual story drift was only 0.001 rad after unloading, which means the structure had good self-centering capability. Analysis on the displacement ductility coefficient and equivalent viscous damping coefficient showed that the structure had good deformation capability and energy dissipation capability. With the increase of β_sc, the self-centering capability of the column base increased, and the bearing capability and energy dissipation capability decreased, while the deformation capability was less affected. With the increase of the axial force of the column, the self-centering capability and bearing capability increased, and the deformation capability decreased, while the energy dissipation capability was less affected.

Abstract:To tackle the problems of strengthening and repairing ancient timber columns, this paper proposes an economic and feasible method of strengthening. Seven square timber columns were strengthened with carbon fiber reinforced polymer (CFRP) strips and steel bars to investigate changes in bearing capacity and ductility under eccentric compression, mainly considering the amount of embedded bars and the eccentricity of timber columns. Test results show that the failure of the hybrid strengthened timber column which was wrapped with a layer of CFRP strips at intervals and embedded with steel bars occurred mainly in the interval between the CFRP strips, indicating a better integrity than the unstrengthened timber columns. When the eccentricity was 0, all four sides of the timber column were destroyed; with the eccentricity increased, the timber column was destroyed only on the pressure side. Under the same eccentricity, the bearing capacity and ductility of the hybrid strengthened timber columns were improved obviously, and the extent of improvement increased with the increase of the amount of steel bars. With the same strengthening method, when the eccentricity increased from 0 to 50 mm, the bearing capacity of the timber column decreased significantly, but the ductility coefficient was little affected.