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Current US seismic guidelines indicate that ground acceleration of 0.10g or greater is likely to produce plastic structural response, yet they require that an elastic seismic analysis be performed for all multi-span bridges located in regions deemed likely to sustain such ground acceleration. The relative superstructure–substructure displacements obtained from an elastic analysis of typical bridges located in a low–moderate seismic zone are usually in the range of 2.5–10 cm. The design code presents an empirical formula which approximates the upper limit of displacements due to plastic response. This formula typically gives displacements in the range of 37.5–60 cm. Since the requirement of the use of the empirical formula is predicted on the assumption of plastic response, an assessment of its validity is warranted. The primary objectives of this paper are to determine if plastic response is a real possibility for earthquakes of low to moderate magnitude (i.e. acceleration coefficient, A=0.10–0.20g) and further to examine if the empirical displacement formula is suitable for bridges in those seismic zones. [Copyright &y& Elsevier]

This paper describes and discusses the vibration serviceability of the innovative prestressed cable-reinforced concrete truss (i.e., prestressed cable RC truss, PCT for abbreviation) floor system subjected to heel-drop impact loading, based on the theoretical and experimental studies. In the theoretical analysis, the PCT floor system is idealized as an anisotropic rectangular plate with four built-in edges and the weighted residual method was used. A field test was carried out to investigate the dynamic characteristics of the PCT floor system and to validate and demonstrate the convergence of the theoretical solution. As a result, the experimental results agree well with the theoretical ones. The decrease of vibration is dramatic in the direction perpendicular to the PCT girder and is at a slower rate along the direction of the girder. The investigated PCT floor system has a low fundamental natural frequency (<4 Hz) with low damping ratio (≈2%). According to one standard of vibration criteria, the innovative floor system exhibits satisfactory vibration perceptibility. [ABSTRACT FROM AUTHOR]

Feiyun Pavilion is located in Shanxi Province, China. It is a classic example of ancient wooden pavilions and one of the primary national cultural assets, which was rebuilt more than 500 years ago. During recent years, the structural deterioration and degeneration of Feiyun Pavilion have accelerated due to inefficiencies in maintenance and management. The main structure is apparently off-plumb and in danger of collapse. With special financial required, the state Administration of Cultural Heritage asked the local Cultural Relic Protection Unit to contact historians, researchers, and engineers to restore this particular ancient structure. This paper presents the necessary assessment data, evaluation method, and the preferred solution for retrofitting and strengthening this historical timber building. [ABSTRACT FROM AUTHOR]

The time-dependent safety assessment and reliability analysis of a structure depends primarily on the corrosion model that directly affects the calculation accuracy. The three-dimensional non-contact surface topography instrument was used to study the corrosion morphology under urban industrial atmospheric exposure conditions and the dry/wet cycle accelerated corrosion test. The evaluation indices of the proposed corrosion model were study, including pit shape, pit depth, pit diameter–depth ratio, etch pit distribution, and thickness. Time-dependent mathematical models between these parameters and the corrosion degree are discussed. The pit depth distribution follows the normal distribution and a probability distribution model related to the rust ratio is established. There is a certain relationship between the thickness loss and etch pit depth. A corrosion model suitable for the common Q235 steel used in civil engineering in an acid rain corrosion environment is proposed. The applicability of the corrosion model is verified through the machine-simulated corrosion on the same batch of structural steel. • There is a certain relationship between the thickness loss and etch pit depth. • Time-dependent mathematical models of the corrosion level are discussed. • A corrosion model suitable for Q235 steel in an acid rain corrosion environment is proposed. • The applicability of corrosion model is verified via the machine-simulated corrosion. [ABSTRACT FROM AUTHOR]

The objective of this work is to analyze the high-cycle fatigue performance of the corroded base material without joints. Constant-amplitude axial tensile fatigue tests were conducted on 55 specimens obtained from the various environments. The infrared thermography was used to track the surface temperature of the specimens. When the corrosion degree is close, the accelerated corrosion test can simulate the atmospheric corrosion to predict the fatigue performance. The mechanism of discreteness of fatigue damage was analyzed from the perspective of energy dissipation. The S-N curves suitable for the Q235 steel in the acid rain corrosion environment are developed. [ABSTRACT FROM AUTHOR]

Abstract Application of high strength concrete (HSC) is an effective way to reduce the column size in high-rise and large-span structures, resulting in more available floor space. The concern on the brittleness of HSC can be alleviated by providing some confinement to it. To this end, carbon fiber reinforced polymer (CFRP) and steel tube are found to be very effective. This paper presents experimental and theoretical studies on the axial behavior of CFRP-steel composite tubed HSC columns. Totally, 25 specimens were tested to investigate the influences of CFRP layers, diameter-to-thickness ratio of steel tube, and concrete strength on the load bearing capacity and deformation behavior of such composite members. The observed failure modes, stress-strain relationships, stresses of steel tubes, and deformations of concrete are discussed. The experimental results indicate that with enough CFRP sheets the load bearing capacity and deformation behavior of core concrete are significantly improved, especially the ductility of specimens with concrete strength of 105 MPa. Calculation methods for the axial load bearing capacity of a CFRP-steel composite tubed HSC column are presented and discussed. [ABSTRACT FROM AUTHOR]

Under the action of complex earthquake loads, the elastic-plastic local buckling of a concrete-filled steel tubular column will most likely occur in the steel tube, which is difficult to be simulated using the traditional fiber beam-column finite element model. In this paper, 30 steel specimens with two strength grades, Q235 and LYP160, were prepared and tested considering various cyclic loading paths to obtain the hysteretic stress-strain relations and the elastic-plastic buckling behavior of steel material, aiming to develop an effective uniaxial constitutive model of steel material considering elastic-plastic buckling. Based on the available Légeron Model, Gomes and Appleton Model (GA Model), and Dhakal and Maekawa Model (DM Model) for determining the stress-strain relation of steel material considering the elastic-plastic buckling behavior, a comparison analysis was made between the test results and the predicted results. It is found that the buckling behavior of the steel in compression after yielding cannot be simulated well by Légeron Model; the compressive buckling stress and compressive strength of the steel with buckling behavior predicted by GA Model agrees well with the test results; and the unloading stiffness of the steel in tension and compression can be well predicted by DM Model. [ABSTRACT FROM AUTHOR]

In this paper, the causes and mechanisms of residual loads are described and discussed. Methods for measuring pile residual loads in the field are summarized and compared. Specifically, a driven pile and a bored pile were selected to show the effects of residual loads on skin frictions and toe resistances. The results indicate that the skin friction in the upper pile portion and the vertical compressive stiffness of the test piles are overestimated, while the toe resistance is underestimated, if the residual loads are ignored. [ABSTRACT FROM AUTHOR]

The tubed steel-reinforced-concrete (TSRC) column can be interpreted as a special steel-reinforced-concrete (SRC) column where the reinforcement cage is replaced with an outer encased thin-walled steel tube for confining the concrete core. In this study, seven circular TSRC columns using high-strength concrete ( f cu , 150 = 97.6 MPa) were tested under combined constant axial compression and lateral cyclic load. Two primary system parameters, the axial load ratio and the arrangement of shear studs, were considered in this test. The test results indicate that the TSRC specimens exhibit excellent ductility and plastic deformation ability. The deformation of the steel section develops coherently with the high-strength concrete for both the specimens with shear studs on the steel section and those without, due mainly to the confinement from the steel tube. The lateral strength, ductility, and deformability of the circular TSRC specimens are not effectively enhanced by installing shear studs on the steel section. The axial load-moment interaction diagrams of the specimens were developed according to the ACI and EC4 methods. The predictions from the EC4 method appear to better match with the experimental results. [ABSTRACT FROM AUTHOR]

• Headed stud-steel block connectors (HSBCs) are proposed to be used in prefabricated steel-concrete composite bridge beams. • Shear behavior of HSBCs with UHPC grouting material in precast concrete slabs is experimentally studied by full-scale push-out testing. • Large shear stiffness, high shear capacity, and sufficient deformability are verified by the tests for the HSBCs. • Sufficient longitudinal spacing is required to guarantee the shear performance of the HSBCs. • Ultimate shear capacity of HSBCs contributes from both the steel block and headed studs. Full-scale push-out tests of 13specimens were conducted to study the shear behavior of the headed stud-steel block connectors (HSBCs) in prefabricated steel-concrete composite bridge beams, where the key parameters of steel block height, longitudinal connector spacing, presence of oblique rebars in the precast slab, and grouting material were considered. The objective was to develop large shear stiffness, high shear capacity, and sufficient deformability of the connectors in prefabricated steel-concrete composite bridge beams. The results from the push-out tests reveal: two main failure modes the compression failure in the concrete slab and the shear failure in the grouting material and concrete slab; and the HSBC has large shear stiffness, high shear capacity (≈1500kN), and sufficient deformability. Based on the analysis of the shear extrusion dimension of the grouting material and concrete slab, the shear inclination ratio was found approximately to be 1:5, which agrees well with the stipulation specified in the EC4. The height and spacing of HSBCs are the two principal parameters affecting the shear capacity and failure mode of the specimens. By comparing the measured shear capacities of the HSBCs with those calculated by the design formulas for steel blocks and headed studs as specified in the EC4, it is shown that the steel block and headed studs can work together to resist the force between the precast concrete slab and the steel beam. [ABSTRACT FROM AUTHOR]

• Square CFST columns up to 1000 mm in width were tested under axial compression. • The difference in strength between the different thicknesses of steel tube used in the tests was only 18 MPa. • The effects of size and width-to-thickness ratio on the steel tube stresses were discussed. • A axial bearing capacity model considering the size effect was proposed for square CFST columns. In this study, eight specimens with the sectional widths (B) of 200–1000 mm and the width-to-steel tube thickness ratios (B / t) of 40 and 50 were tested to failure under axial compression to investigate the size effects of square concrete-filled steel tubular (CFST) short columns, specifically those on the failure mode, composite elastic modulus, peak axial strain, peak axial stress, ductility index, strength index, and stress development. The test results indicate that the peak axial stress, ductility index, and strength index decrease with the increasing specimen size, while the failure mode and composite elastic modulus maintain relatively steady. Under the peak axial load, the longitudinal to yield stress ratio of steel tubes increases with the increasing specimen size, while the trend of transverse to yield stress ratio is opposite. The size effect on the transverse stress in the steel tube reduces the tube confinement effect, thus degrades the compressive strength of the core concrete. Compared to the test results, both the EC4 and the GB50936 codes are unconservative in predicting the strength of large square CFST columns. Therefore, a model considering the ratio of width to thickness (B / t) and specimen size is proposed to evaluate the axial bearing capacity of square CFST short columns. [ABSTRACT FROM AUTHOR]

The circular tubed-reinforced concrete (TRC) column is a kind of special concrete-filled steel tube (CFST) columns, in which the outer thin-walled steel tube does not pass through the beam-column joint and thus can avoid the direct transfer of an axial load and maximize the confinement effect from the steel tube. Although the columns possess high load-carrying capacities and good ductility performance in seismic zones, there is a possible decrease in the axial bearing capacity of the TRC column to RC beam connections due to the discontinuity of the column tube, which is a particular concern to engineers. To compensate for the discontinuity of the column tube, strengthening stirrups, a tube with rectangular openings, and horizontal haunches are adopted in the connection zone as Type A, Type B, and Type C connections, respectively. Nine connections aforementioned and four reference circular TRC columns were tested under axial compression. The experimental results show that Type B and Type C connections are effectively strengthened, while Type A connection needs further strengthening because of the lower axial bearing capacity than the reference columns. A finite element (FE) model was developed to simulate the behavior of connections under axial compression. The predicted load-stain curves are in good agreements with the measured ones. A theoretical model for predicting the axial bearing capacities of the connections which is based on the confined concrete theory and local compression theory is proposed. [ABSTRACT FROM AUTHOR]

• Based on the test results, a refined finite element model was established for the push-out test of SSGCs. • Parametric analysis was carried out through the finite element model, and the factors affecting the static performance of the specimen were analyzed. • The stiffness of the SSGCs at the elastic stage was theoretically analyzed by using the thrust pile comprehensive stiffness method. A refined finite element (FE) model was established to simulate the push-out test of shear stud group connectors (SSGCs). The failure phenomena and interface shear-slip curves obtained by the FE model were compared with the test results and found to be in good agreement. The verified FE model was then used in a parametric analysis, considering the concrete strength, stud diameter, stud height, stud spacings (longitudinal and transverse), strength of grouting material, and number of shear studs in a SSGC. Based on the Winkler foundation model and the comprehensive stiffness principle of thrust piles, a theoretical calculation formula for the stiffness of SSGCs was obtained, considering the concrete material, stud diameter, and number of shear studs in a SSGC. The calculation formula was verified with the test results and fitted with the FE analysis results. [ABSTRACT FROM AUTHOR]

• The proposed sphere fitting algorithm's accuracy is less than 0.15 mm and its fitting time is 0.6 s. • The efficiency and accuracy of the proposed central axis extraction method are improved by 20% and 95%. • The central axis is involved in the verticality of end face and bending assessment. • Validation experiments were conducted on 46 space frame components. Space frame components (SFCs), mainly spherical joints and cylindrical tubes, are characterized by their large number. The dimensional quality assessment (DQA) of SFCs relies on manual measurements, which are subjective and inefficient. Since the surface of SFCs is mainly curved, many DQA items are hardly achieved by manual measurements. As the terrestrial laser scanning (TLS) can record accurate point cloud data of SFCs, it is widely used in the construction industry for DQA. This study proposes an automated method for DQA on SFCs based on TLS, including the component recognition, geometric parameter estimation, and DQA. A feature-based method is applied for component recognition. The geometric parameter estimation algorithms for spherical joints and cylindrical tubes are proposed. The effectiveness of the proposed method is verified by comparing the proposed algorithms with other algorithms and by conducting the validation experiment on 13 spherical joints and 33 cylindrical tubes. [ABSTRACT FROM AUTHOR]

• An automatic flatness quality assessment for building indoor acceptance is proposed. • Convert the building indoor point cloud segmentation task into a geometric feature-based segmentation problem. • The DBSCAN is used on point cloud slice for obtain the room contours. • A RANSAC-based multi-line detection algorithm is proposed to detect lines in the room contour. • The 2D continuous wavelet transform and an improved simulated manual method are used to inspect the flatness of each structure in building indoor scene automatically. For building indoor acceptance, flatness is an important metric. Traditionally, the flatness quality assessment (FQA) relies on manual labor, but manual inspection is random, error-prone, inefficient and non-repeatable results. With the development of terrestrial laser scanning (TLS) technology, it is becoming possible to resolve the above issues. In this paper, a fully automatic building indoor acceptance approach for FQA via TLS is proposed, which consists of indoor segmentation and FQA. First, the indoor segmentation is performed using the geometric features of the indoor point cloud. Then, the FQA is carried out using the two-dimensional continuous wavelet transform and simulated manual method. Manual and simulated inspections are performed on the same inspection points. The results show that the simulated manual method is rigorous than the manual method. Furthermore, the validity and efficiency of the proposed approach is proved by running two tests on point cloud data obtained from two as-built dwellings. [ABSTRACT FROM AUTHOR]

• Bond mechanism and failure mode of rebar embedded in HECC were investigated by direct pullout test. • Influence laws of various parameters on bond behavior were evaluated. • A calculation equation for the average bond strength of HECC was proposed. • The design anchorage length of the rebar embedded in HECC was suggested based on a reliability analysis. Steel-polyethylene hybrid fiber engineered cementitious composites (HECC) featuring relatively high tensile strength and ductility, high elastic modulus, and high temperature resistance, making it an ideal alternative material under severe loading conditions. To understand the bond behavior between the HECC and rebar, direct pullout tests were conducted to systematically investigate the effects of rebar diameter d , anchorage length l a , and cover thickness c on the bond performance. The experimental results indicate that the variation of bond strength with d is not apparent; l a affects negatively while c influences positively on the average bond strength; and the critical c for HECC is about 4 d. Additionally, the bond strength of HECC specimen is obviously higher than that of ECC and stirrups-confined concrete due to the crack-bridging effect of hybrid fibers at different scales. As noted, the ductility of HECC specimens is comparable with that of stirrups-confined concrete specimens, indicating that stirrup can be partially replaced when HECC is used which can simplify construction. Then, a calculation equation for the average bond strength of HECC is proposed, and the critical anchorage length of the rebar embedded in HECC is about 40% less than that embedded in ECC. Lastly, the design anchorage length of the rebar embedded in HECC is suggested based on a reliability analysis which is much smaller compared with the minimum embedment length of rebar in concrete predicted by the existing standards, providing a useful reference for reinforced HECC structural design. [ABSTRACT FROM AUTHOR]