Precast Steel Research Articles

Enhanced Ultimate Shear Capacity of Concave Square Frustum-Shaped Wet Joint in Precast Steel–Concrete Composite Bridges

Wet joints are widely used in precast steel–concrete composite bridges to accelerate the construction of bridges, though a conventional wet joint usually has a poor ultimate shear capacity. To improve the shear capacity of the wet joint, a concave square frustum-shaped wet joint was proposed, and the failure modes and ultimate shear capacity were studied experimentally and numerically. Specimens with concave square frustum-shaped and conventional wet joints (labeled as S-SWJ and S-CWJ) were fabricated, and experiments were performed on them. The results showed that the ultimate shear capacity of S-SWJ was substantially enhanced compared to that of S-CWJ. To further explore the ultimate shear capacity of S-SWJ, the failure modes and the influences of concrete strength and shear key angle on the ultimate shear capacity were studied using a validated finite element (FE) model. Based on the FE analysis, the guidelines for obtaining a wet joint with desirable shear capacity are presented, which is useful for the design of wet joints with high ultimate shear capacity.

Calculation method of stiffness of partially fabricated steel reinforced concrete beams

In this paper, two new types of partially precast steel reinforced concrete beams are proposed by combining the advantages of steel reinforced concrete beams, high strength concrete beams and precast assembly structures. Partially fabricated steel reinforced concrete beams are composed of precast high-strength concrete shell and cast-in-place concrete core area. In order to further reduce the dead weight of the members, partially fabricated steel concrete beam sections are hollow or can be filled with thermal insulation materials. In this paper, by using the superposition method and based on the existing test results, two new stiffness calculation methods for partially prefabricated SRC beams are proposed.

Seismic collapse simulation of existing masonry buildings with different retrofitting techniques

Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake. The collapse of masonry walls may cause significant human casualties and economic losses. To maintain their integrity, several methods have been developed to retrofit existing masonry buildings, such as the constructional RC frame which has been extensively used in China. In this study, a new method using precast steel reinforced concrete (PSRC) panels is developed. To demonstrate its effectiveness, numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting, retrofitted with a constructional RC frame, and retrofitted with external PSRC walls (PSRCW). Sophisticated finite element models (FEM) were developed and nonlinear time history analyses were carried out. The results show that the existing masonry building is severely damaged under occasional earthquakes, and totally collapsed under rare earthquakes. Both retrofitting techniques improve the seismic performance of existing masonry buildings. However, it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame, while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes. The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.

Flexural Behaviour of Precast Steel Fibres Reinforces Concrete Composite Slabs with Different Shapes

Flexural Behaviour of Precast Steel Fibres Reinforces Concrete Composite Slabs with Different Shapes

Finite element analysis on connection performance of prefabricated steel joints with grouting bolt sleeve

Under the national strategy of developing vigorously the prefabricated structure, to study the prefabrication and assembly of steel reinforced concrete shear walls, but the connection performance of the precast steel frame is the key to determine whether the prefabricated structure can be carried out. To the steel joint with grouting bolt sleeve, based on the ABAQUS finite element analysis software, the anchorage length, the thickness of sleeve wall and the bolt diameter are used as the analysis parameters, and it is to be analyzed for the influence trend of the model parameters on the joint performance. The results show that the anchorage length, the thickness of sleeve wall and the bolt diameter all have a positive influence on the tensile bearing capacity, in the meantime, the rational combination can optimize the failure state and improve the tensile bearing capacity of the joints.

Shear behavior and shear capacity prediction of precast concrete-encased steel beams

A novel precast concrete-encased steel composite beam, which can be abbreviated as PCES beam, is introduced in this paper. In order to investigate the shear behavior of this PCES beam, a test of eight full-scale PCES beam specimens was carried out, in which the specimens were subjected to positive bending moment or negative bending moment, respectively. The factors which affected the shear behavior, such as the shear span-to-depth aspect ratio and the existence of concrete flange, were taken into account. During the test, the load-deflection curves of the test specimens were recorded, while the crack propagation patterns together with the failure patterns were observed as well. From the test results, it could be concluded that the tested PCES beams could all exhibit ductile shear behavior, and the innovative shear connectors between the precast concrete and cast-in-place concrete, namely the precast concrete transverse diaphragms, were verified to be effective. Then, based on the shear deformation compatibility, a theoretical model for predicting the shear capacity of the proposed PCES beams was put forward and verified to be valid with the good agreement of the shear capacities calculated using the proposed method and those from the experiments. Finally, in order to facilitate the preliminary design in practical applications, a simplified calculation method for predicting the shear capacity of the proposed PCES beams was also put forward and validated using available test results.

Behavior of grouped stud shear connectors between precast high-strength concrete slabs and steel beams

This study aims to examine the interface shear behavior between precast high-strength concrete slabs with pockets and steel beam to achieve accelerated bridge construction (ABC). Twenty-six push-out specimens, with different stud height, stud diameter, stud arrangement, deck thickness, the infilling concrete strength in shear pocket (different types of concrete), steel fiber volume of the infilling concrete in shear pocket concrete and casting method, were tested in this investigation. Based on the experimental results, this study suggests that the larger stud diameter and higher strength concrete promoted the shear capacity and stiffness but with the losing of ductility. The addition of steel fiber in pocket concrete would promote the ductility effectively, but without apparent improvement of bearing capacity or even declining the initial stiffness of specimens. It can also be confirmed that the precast steel-concrete composite structure can be adopted in practice engineering, with an acceptable ductility (6.74 mm) and minor decline of stiffness (4.93%) and shear capacity (0.98%). Due to the inapplicability of current design provision, a more accurate model was proposed, which can be used for predicting the interface shear capacity well for specimens with wide ranges of the stud diameters (from13 mm to 30 mm) and the concrete strength (from 26 MPa to 200 MPa).

Experimental study on shear behaviors of Partial Precast Steel Reinforced Concrete beams

An innovative Partially Precast Steel Reinforced Concrete (PPSRC) beam is presented in this paper. To study the shear behavior of PPSRC beams, static loading experiments were conducted on 10 specimens, including 4 T-beam specimens and 4 PPSRC inverted T-beam specimens together with 2 PPSRC rectangular section beams. In the tests, the shear behaviors of the PPSRC beams were emphasized. On the basis of the experiments, the failure mode and ultimate bearing capacity were thoroughly examined. The calculation methods for shear capacity are also presented in this paper. The analysis of mechanical behavior and the calculation methods presented can be used as a reference to design these innovative composite PPSRC beams and provide a significant foundation for further research.

Cyclic behavior of partially precast steel reinforced concrete short columns: Experiment and theoretical analysis

Two innovative precast steel reinforced concrete columns are presented in this paper. The partially precast steel reinforced concrete (PPSRC) column was composed of a precast outer part and a cast-in-place inner part, and the hollow precast steel reinforced concrete (HPSRC) column kept the column core hollow to further reduce the column deadweight. In this paper, six PPSRC column specimens and four HPSRC column specimens with low aspect ratios were subjected to reversal cyclic load and constant axial compression to explore the cyclic behavior, which was evaluated by the failure mode, hysteresis characteristic, stiffness degradation, energy dissipation capacity and displacement ductility. Meanwhile, the effects of section shape, axial compression, ratios of longitudinal and transverse reinforcement and concrete strength of the inner part were critically investigated. The test results indicated that the column specimens suffered flexural-shear failure mode and shear-critical failure mode according to different ratios of longitudinal reinforcement, and, in general, the PPSRC columns exhibited more satisfactory cyclic behavior than that of the HPSRC columns. When the other parameters were the same, a higher stirrup ratio and lower axial compression led to a more satisfactory energy dissipation capacity, stiffness degradation and higher displacement ductility, and the load-bearing capacity increased with increasing inner concrete strength, stirrup ratio and axial compression. Based on the test results, an analytical model was established to calculate the shear capacity of test specimens, and the proposed model was verified to be valid using a test database consisting of 66 shear-critical SRC column specimens.

Innovative accelerated construction method for Yushan Bridge, China

To overcome poor construction conditions, shorten construction time and improve project quality, the construction of Yushan Bridge in China is a fully industrialised, based on prefabrication of key components, site installation. The navigation span of the Yushan Bridge has a main span of 260 m and is the world's first segmented precast steel–concrete composite continuous-beam bridge. A new type of steel–concrete composite segment (a girder that connects the concrete box girders and the steel box girders) is used to ensure the bearing capacity and precision of closure. Thickened-edge U-shaped ribs and ultra-high-toughness concrete pavings are employed together to improve the durability of the orthotropic deck. A single-pile and single-column foundation is fully employed, with a maximum diameter of the steel composite pile (a pile that is outside is steel pipe, and the interior is filled with concrete) of 5 m. It is found that the construction time is reduced by 40%, the wave flow force is decreased by 80%, the scouring depth is decreased by 20% and the cost is reduced by 30% compared with group pilings. In addition, this method avoids durability problems of the pile cap due to group pilings. The use of a prefabricated exterior shell with cast-on-site concrete for the interior pier-top blocks of the 50 m non-navigation span solves the problems associated with the bearing force, durability, construction availability and quality control of the pier-top block.

Behavior of partially precast steel reinforced concrete columns under eccentric loading

This paper provides an insight into the behavior of partially precast steel reinforced concrete (PPSRC) column and hollow precast steel reinforced concrete (HPSRC) column subjected to eccentric loading. Nine PPSRC columns and five HPSRC columns were tested to examine the effects of the loading eccentricity, the difference of the cast-in-place concrete strength and flange shear studs on the performance of both kinds of specimens. The failure modes, axial load versus deflection curves as well as the strains of the steel section and the concrete were emphatically investigated. The test results demonstrated that the precast concrete and the inner concrete worked well in resisting the bending and the axial loading, the mechanical performances of HPSRC column and PPSRC column were comparable during the test, though the bearing capacity of the PPSRC column was slightly higher than that of the HPSRC column. Higher compression strength of the inner concrete and smaller eccentricity led to higher bearing capacity and the shear studs had no significant effect on the structural behavior of PPSRC column and HPSRC column. In addition, with the increase of eccentricity, the influence of concrete strength on bearing capacity decreased gradually. Moreover, the plane-section assumption was proved to be valid, and a rational calculation for predicting the sectional capacity of the PPSRC and HPSRC column was proposed on the basis of the experimental results.

A Hybrid Fuzzy Group Multi-Criteria Assessment of Structural Solutions of the Symmetric Frame Alternatives

Structural designers that design buildings use different criteria to select the frames’ materiality and structural solutions. Very often, the primary test is the cost of construction. Sometimes, solutions are determined by the terms of structure, architectural preferences, technological needs, fire safety requirements, environmental conditions, exploitation costs over the life of the building, ecological aspects, and experience, etc. This paper proposes an approach for analyzing the structural elements of buildings taking into account the impact on the environment using jointly incorporating subjective and objective aspects. The objective to combine the most important criteria into a single unit and carry out the overall assessment could be done by giving each variable a weighted value and perform a so-called multi-criteria analysis. This article shows the efficiency of the structural solution of the one-story building. The case study presents an investigation and comparison of five possible symmetrical structural solutions by multi-criteria assessment methods: The analysis of three steel frameworks differs majorly due to the beam-column characteristics, as well as precast RC frame structures case and combined steel beams and RC columns frame option. Possible solutions must meet all the essential requirements of the building, including mechanical resistance and stability. The obtained results show a broad assessment of the structural solutions of the building.

Briefing: Dynamic mode couplings of railway composite track slabs

Steel–concrete composite railway track slabs are a financially viable alternative for the modular construction of railway slab tracks and for the replacement of resilient timber transoms on railway bridges, and design and experiments have been carried out to investigate their technical feasibility. Extended findings based on dynamic eigenvalue analyses of a precast steel–concrete composite slab panel for a track support structure are presented in this paper. The natural frequencies of the railway composite slab were investigated using the finite-element package Abaqus. Dynamic eigenmodes were then extracted using the Lanczos method. Modal cross-over phenomena were clearly observed when the design mass of the track slab was changed. This paper highlights the unprecedented dynamic mode coupling effects on composite track slabs over a railway bridge. This insight can be used to improve practical noise- and vibration-control technologies through composite material design, resulting in quieter railway track slabs.

Precast Steel Reinforced Concrete Wall Structure Enabling Random Construction of Gate-type Frameworks

都内の地上5階地下2階の商業建物において，大小9つの門型ユニットが平面・立面ともにランダムに組み合わされた建築計画を実現するため，SRC壁柱＋梁Sの門型架構にコア耐震壁を組み合わせた構造システムを考案した。また，現場の施工性向上を目的としてSRC壁柱にPCaを採用した。課題となる各PCa壁柱の接合部については，応力伝達を考慮した配置やディテールを検証することで極力シンプルとする計画とした。本稿では，これらの構造計画および施工計画について報告する。

Post-fire test of precast steel reinforced concrete stub columns under eccentric compression

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

Theoretical and experimental study on shear strength of precast steel reinforced concrete beam

With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

Proposed Shear Load-transfer Curves for Prebored and Precast Steel Piles

Proposed Shear Load-transfer Curves for Prebored and Precast Steel Piles

Experimental study on seismic performance of partially precast steel reinforced concrete columns

This paper aims to develop two kinds of innovative precast steel reinforced concrete columns, which are partially precast steel reinforced concrete (PPSRC) columns and hollow precast steel reinforced concrete (HPSRC) columns. Both the two kinds of composite columns have precast reactive powder concrete (RPC) shells, and the PPSRC column has a cast-in-place column core. In this paper, a series of cyclic loading tests on 10 column specimens subjected to combined static axial loading and cyclic lateral loading were carried out to explore their seismic performances. All specimens were evaluated by the failure modes, hysteresis characteristics, strength and stiffness degradation, energy dissipation capacity and ductility. The effects of section shape, stirrup spacing, axial compression and concrete strength of cast-in-place inner-part were investigated in details. The experiment results indicated that the PPSRC columns exhibited more satisfactory seismic behavior than the HPSRC columns in terms of hysteretic behavior, strength degradation, ductility and energy dissipation, while their bearing capacities were almost identical under low axial compression. Steel fibers could effectively prevent the cracked concrete from spalling, therefore, the encased steel shape was efficiently confined by the surrounding concrete during the entire test process. Higher stirrup ratio and lower axial compression of the column leaded to more satisfactory energy dissipation capacity, stiffness degradation and higher ductility. Based on the plastic stress theory, the seismic bending moment capacity analysis was conducted, and the results obtained form the formulas agreed well with those from the experiments.

Analysis of Bearing Capacity and Safety Factor of Dynamic Load Test of Prebored and Precast Steel Pile

Analysis of Bearing Capacity and Safety Factor of Dynamic Load Test of Prebored and Precast Steel Pile

Pseudo-dynamic tests on masonry residential buildings seismically retrofitted by precast steel reinforced concrete walls

A retrofitting technology using precast steel reinforced concrete (PSRC) panels is developed to improve the seismic performance of old masonry buildings. The PSRC panels are built up as an external PSRC wall system surrounding the existing masonry building. The PSRC walls are well connected to the existing masonry building, which provides enough confinement to effectively improve the ductility, strength, and stiffenss of old masonry structures. The PSRC panels are prefabricated in a factory, significantly reducing the situ work and associated construction time. To demonstrate the feasibility and mechanical effectivenss of the proposed retrofitting system, a full-scale five-story specimen was constructed. The retrofitting process was completed within five weeks with very limited indoor operation. The specimen was then tested in the lateral direction, which could potentially suffer sigifnicant damage in a large earthquake. The technical feasibility, construction workability, and seismic performance were thoroughly demonstrated by a full-scale specimen construction and pseudo-dynamic tests.