Civil Engineering

Erratum to: Bayesian Networks-based Shield TBM Risk Management System: Methodology Development and Application This erratum is published to notify an error of a reference which was cited in-text, but not mentioned in the references section. See revised reference below: Errata: Jung, J. H., Chung, H., Kwon, Y. S., and Lee, I. M. (2019). “An ANN to predict ground condition ahead of tunnel face using TBM operational data.” KSCE Journal of Civil Engineering, Vol. 23, No. 7, pp. 3200–3206, DOI: https://doi.org/10.1007/s12205-019-1460-9. The original article has been corrected.

A Study on Coupled Wall System with Post-tensioned Steel Truss Coupling Beams: Concept and Performance Evaluation Abstract In order to improve the seismic behavior of coupled shear wall structures, a new type of post-tensioned steel truss coupling beam (PSTCB) is developed in this paper. The PSTCB is composed of chord members, two diagonal buckling-restrained energy dissipaters and diagonally placed post-tensioned tendons. The energy dissipaters are expected to serve as fuses and can be quickly repaired after earthquake. Furthermore, the residual drift of the coupling beam can be reduced by the application of post-tensioned tendons in the diagonal direction. In the PSTCB, the post-tensioned tendons are anchored at outer ends of the wall piers. According to the Chinese code, an 11-story coupled wall structure was designed and the numerical model was developed in PERFORM-3D software. The seismic behaviors of the hybrid coupled wall system with PSTCBs (HCW-P), the hybrid coupled wall system with replaceable steel truss coupling beams and concrete coupled wall system with reinforced concrete coupling beams were evaluated and compared under maximum considered earthquake. Results showed that the HCW-P can achieve excellent lateral strength, stiffness, and ductility as well as reduce the residual displacements of the structure after earthquake.

Noise and Vibration Mitigation Performance of Damping Pad under CRTS-III Ballastless Track in High Speed Rail Viaduct Abstract This study proposes a frequency domain vehicle-track coupling model for the CRTS (China railways track system)-III type damping track system based on the two-dimensional vehicle-track-viaduct coupling model, and utilizes dynamic compliance method to determine the dynamic compliance for the vehicle and track systems. The accelerations for the viaduct are hereinafter obtained and are compared between CRTS-III damping track system and conventional CRTS-III track system, and the structure-borne noises for near field and far field of the viaduct are assessed with finite element method (FEM). The acoustic contribution rates for the substructures of the viaduct to the near-field and far-field noises are analyzed. The results reveal that in comparison with the conventional CRTS-III system, the CRTS-III damping track system can mitigate the viaduct acceleration peak with 69.9%, and mitigate the average acceleration with 60.4%. The near field and far field noise measurement points are captured for the CRTS-III damping track system, the sound pressure levels decline by 8.15 dB and 8.36 dB, respectively. The acoustic contribution rates for the viaduct top plate reach 65.28% and 68.30%, respectively. The viaduct top plate thus becomes the major noise source and the damping track system can effectively mitigate the structure-borne noise of the viaduct.

Improvement of Pullout Loads by Variation of Two Load Points in Anchorage System Abstract Multiple compression type anchors were developed to relive the problem of uneven exertions of bond stress across the bond lengths of existing anchors. Unlike existing anchors, these anchors can have different lengths of strand to adjust the spacing of load points between anchors and also can have different orders of tensions of anchors to ensure even exertions of bond stress across the bond length. The spacing of load points and the order of tensions are considerations that can affect the pullout load of anchors because interference effects between anchors vary with them. However, existing studies have investigated the pull-out characteristics of anchors without considering the aforementioned factors. In this study model tests were conducted to investigate the pull-out characteristics of multiple compression type anchors that vary with the spacing of load points between anchors and the order of tensions. Through the results of the study on the pull-out characteristics of two load points of anchorage system, it was identified that interference effects between anchors varied with the spacing of load points between anchors and the order of tensions to affect the pullout load.

Influence of Vehicle Load Mode on the Response of an Asymmetrically-Loaded Deep Excavation Abstract At present, the research on the influence of vehicle load mode on response of asymmetrically-loaded deep excavation is limited. Based on a deep excavation which is adjacent to the expressway and is subjected to the asymmetric load induced by the weight of embankment and the vehicle load together, this paper presented several vehicle load conversion methods firstly. Then a numerical modelling was performed to simulate the response of deep excavation considering the above methods. Next, a field monitoring of response of deep excavation was performed to verify the simulation results. By comparing the simulated and monitored results, the optimum vehicle load mode was recommended. The results indicate that the vehicle load has a considerable influence on the response of deep excavation. For this study, the equivalent thickness of soil layer method and the improved equivalent thickness of soil layer method are recommended to treat the vehicle load. This paper also analysed the influence factor of the improved equivalent thickness of soil layer method and found the improvement effect of this method rapidly decreases with the increase of retaining wall height. For a very high retaining wall, the improvement effect of this method is limited.

Determination of Optimal Load-Resistance Factors for Gravitational Loads-Governed Limit State of Korean Bridge Design Code Abstract This paper presents an optimization scheme to determine the optimal load-resistance factors for a gravitational loads-governed limit state in the Korean Highway Bridge Design Code. The random variables in the limit state function are normalized to the total nominal load effect, and the optimization is formulated using the normalized variables. The objective function is defined as an L2-norm of errors between the design strength obtained by the load-resistance factors and the target strength evaluated by the inverse reliability analysis for the target reliability index. Two different types of optimization, reference and sequential optimizations, are proposed. The former is to determine absolute optimal load-resistance factors, while the latter is proposed to obtain the factors suitable for actual design codes. The reference optimization results in load-resistance factors that yield a more uniform reliability index than the sequential optimization. The reliability levels provided by the proposed load-resistance factors are presented in detail and compared with those obtained by the factors in the Korean Highway Bridge Design Code. It is shown that the factors in the code lead to a much higher reliability index than the target while the optimal load-resistance factors yield a reliability index within ± 5% error bounds to the target reliability index.

Degradation Model and Evaluation Criteria for the Seismic Behavior of Corrosion H-section Steel Column Abstract The cross section would be reduced and the material properties of the steel structure would be deteriorated under the corrosion environment, which will have different effects on the earthquake resistant behavior. This paper takes corroded H-steel column as the research object. Firstly, the influence on the failure mode, bearing capacity, hysteretic properties, ductility and hysteretic energy is analyzed from specific factors which consist of different width-to-thickness on flange, different height-to-thickness on web and different axial compression ratios by FEA. The results show that, the area of the hysteresis loop diminishes gradually, the bearing capacity decrease clearly, the accumulative energy dissipation and ductility coefficient decreased continuously, and the degradation laws of buckling load, peak load, hysteretic energy and ductility coefficient of corroded H-steel columns are thereby established. When the thickness of flange decreased by 30%, the peak load decreased by 32% and hysteretic energy decreased by 77%. However, the peak load decreased by 14% and hysteretic energy decreased by 40% when the thickness of web decreased by 30%. When the axial compression ratio is 0.6, and the mass loss ratio of corroded H-steel columns reached 22%, the peak load and hysteretic energy decreased by 28% and 51% respectively. Secondly, the hysteretic model of load-displacement of corroded H-steel members under cyclic loading is proposed based on the simulation results and the degradation model of characteristic point of skeleton line was given. Finally, the evaluation criteria are proposed based on the seismic performance objectives, and the classification of failure types as well as the overall performance evaluation of corroded steel members are carried out.

Impact of Jet-Grouting Pressure on the Strength and Deformation Characteristics of Sandy and Clayey Soils in the Compression Zone Abstract Jet-grouting as a soil improvement method is extensively preferred in today’s civil engineering practice. High-modulus grout columns constructed by extremely high jetting pressures displace the surrounding soil causing a densification in soil particles. Accordingly, the strength as well as the deformation characteristics of subsurface soils are relatively improved across the compression zone which is under the influence of high jetting pressure. In this study, the modification of soil properties in compression zone after jet-grouting in sandy and clayey soils is investigated by standard penetration tests (SPT) and multi-channel analysis of surface waves (MASW) performed at a couple of construction sites along established jet-grout column rows. The in-situ test results point out significant improvement of the measured parameters compared to initial values. The rate of enhancement in the compression zone is higher in sandy strata than that of clayey deposits. The strengthening of soil due to jetting pressure is validated by finite element analyses as well. Furthermore, very low shear strain values are obtained in clayey soils with respect to the improved characteristics of compression zone representing extremely low shear deformation under foundation.

Experimental and Numerical Evaluation of Reinforced Concrete Bracket Design for Supporting Middle Slab in Double-Deck Tunnel Abstract This research was conducted to evaluate the design of reinforced concrete brackets that support middle slabs in a double-deck tunnel by performing experimental and numerical analyses. The most distinctive feature of double-deck tunnel is the existence of middle slabs. Since the brackets attached to the tunnel liner sustain all the loads applied on middle slabs, it is crucial to design brackets appropriately to ensure safety against falling of middle slab, failure of tunnel liner, and associated human and material damages. The structural design of bracket was performed based on currently available design methods. Test specimens of the bracket attached tunnel liner structure were fabricated and loading tests were conducted to verify appropriateness of the design, to evaluate safety factors to damages and failures, and to find the failure mode. The numerical analysis models of the bracket attached tunnel liner structure were also developed and analyses were performed to confirm the bracket design and to evaluate the effect of bracket shape on the structural capacity of bracket. Based on the experimental and numerical analysis results, the safety factors to damage and failure of bracket were obtained to be large enough. However, since the shape of bracket may reduce the safety factors, suggestions were finally provided to improve the design of bracket for the use in double-deck tunnels.

Influence of Silane-based Impregnation Agent on the Permeability of Concretes Abstract Three types of silane-based impregnation agent (short for SIA) are used to treat the concrete surface, and the influence of water/binder (W/B) ratio, mineral admixtures, curing methods, the type and dosage of SIA on the capillary water absorption and electric flux of concretes is examined. Results show that the penetration depth of SIA increases with the increasing of the W/B ratio and SIA dosage, and is related to the type of SIA. Surface treatment by SIA can reduce capillary water absorption and electric flux of concretes, the W/B ratio and curing methods are no longer the main factor, the increasing of the SIA dosage can further improve the surface protection effect of concrete. Mineral admixtures improve the compactness of concretes, and the combined effects of surface treatment and admixtures can evidently enhance the impermeability of concrete. Different types of SIAs have different mechanisms of action on the surface treatment of concrete, and thus have different impacts on the permeability of concrete. The concrete treated by SIA2 with the effects of the penetration and the formation of surface film layer has lower permeability.