Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 6 Articles
Nowadays, high-performance concrete (HPC) and ultra-high-performance concrete (UHPC) are ranked among advanced concrete\ntechnologies. The application of the mentioned advanced technologies may have potential to improve the construction efficiency\nfromseveral points of view. For instance, reducing of construction time and construction material, construction quality improving,\nenvironmental impact minimizing, and increasing of both durability and lifetime of structures as well as reducing of total\nconstruction costs may be obtained. Particular advanced concrete technologies are described and the possibilities of their utilization\nin both monolithic structures and precast units are presented in the article. The main benefits of modern methods of construction\n(MMC) based on advanced concrete technologies application in precast elements production are presented. Regarding the selected\naspects of construction efficiency assessment, a comparison of conventional and advanced concrete technologies that are applied\nin monolithic structures and precast units is made. The results of this comparison, estimated in semantic differential scale, are\npresented in the article. By the results of the comparison, the significance of applying the advanced concrete technologies in modern\nmethods of concrete structures production is demonstrated in order to improve construction efficiency...
This study presents a systematic approach for the development of an efficient steel beamsection for modular construction based on\nSix-Sigma. Although the Six-Sigma is frequently implemented in manufacturing and other service industries, it is a relatively new\nconcept in the area of building design and construction. As a first step in this approach, market studies and surveys are conducted\nto obtain the opinions of potential customers. Then the opinions of customers are converted into quality characteristics for the steel\nbeam using the quality function deployment methodology. A steel hollow flanged channel is chosen as the main modular beam\nshape, and the design concept is derived and developed by applying the Pugh matrix methodology. A pilot test was performed to\nvalidate the effectiveness of the developed beam section. The results indicated that the developed channel beam section showed\nexcellent performance and retained high accuracy in fabrication, thus resulting in a significant reduction of steel consumption....
Concrete workability, quantified by concrete slump, is an important property of a concrete mixture. Concrete slump is generally\nknown to affect the consistency, flowability, pumpability, compactibility, and harshness of a concrete mix. Hence, an accurate\nprediction of this property is a practical need of construction engineers. This research proposes a machine learning model for\npredicting concrete slump based on the Least Squares Support Vector Regression (LS-SVR). LS-SVR is employed to model the\nnonlinear mapping between the mix components and slump values. Since the learning process of the LS-SVR necessitates two\nhyperparameters, the regularization and the kernel parameters, the grid search method is employed search for the most desirable\nset of hyperparameters. Furthermore, to construct the hybrid model, this research collected a dataset including actual concrete\nslump tests from a hydroelectric dam construction project in Vietnam. Experimental results show that the proposed model is\ncapable of predicting concrete slump accurately....
This paper proposed a hybrid precast concrete shear wall emulating monolithic construction (HPWEM) that utilized grouted\nvertical connecting reinforcements and unbonded posttensioned high-strength strands across the horizontal joint for the lateral\nresistance. The grouted reinforcements with predetermined debond length were used to provide strength by tension and energy\ndissipation by yielding. The posttensioned strands were mainly employed to offer the restoring force to reduce the residual\ndisplacement by elastic extension. The overlapping welded closed stirrups improved the confinement property of the restrained\nconcrete, avoiding the brittle failure. Six HPWEM specimens, considering variables including the amounts of strands and the\ndebond lengths of grouted reinforcements, as well as one referenced cast-in-place monolithic wall specimen, were tested under\nthe low-cycle reversed lateral load. The HPWEM specimens were capable of providing strength, stiffness, ductility, and energy\ndissipation equivalent to that of the monolithic wall specimen under certain variable condition....
The shield tunnel of the Kunming subway crosses beneath the Kun-Shi Railway. Due to\nthe high requirements of railway track for settlement control, this article proposes the following\ntechnical measures for controlling the settlement based on the analysis of risks arising from the\nshield crossing railway: (1) Reinforcing the stratum of the region crossed by the shield in advance to\nachieve high stability; (2) Using a reinforced segment for the shield tunnel and increasing reserved\ngrouting holes for construction; (3) Reasonably configuring resources, optimizing construction\nparameters, strengthening monitoring and information management during the shield crossing.\nIn strict accordance with the construction plan, the shield successfully and safely crossed beneath the\nKun-Shi Railway; this provides experience that can be used in similar projects in the future....
A simplified full-depth precast concrete deck\npanel system for accelerating bridge construction (ABC) is\nintroduced and a finite element analysis (FEA) is conducted\nto investigate the static and dynamic responses of\nthis conceptual deck system. The FEA results are compared\nto those of the traditional full-depth precast concrete deck\npanel system. The comparison results show that the\nmechanical behavior of the new deck system is different\nfrom that of the traditional deck system. The concrete\ndecks in the new system act as two-way slabs, instead of\nthe one-way slab in the traditional system. Meanwhile, the\nconnections in both the longitudinal and transverse directions\nmay need to accommodate the negative moments.\nCompared to those in the traditional system, the longitudinal\nnominal stress at middle span increases a lot in the\nnew deck system and the effective flange width varies\nsignificantly. In addition, the dynamic results show that the\nimpact factor is influenced by the spacing of connections.\nFinally, some design concerns of the new deck system are\nproposed....
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