• Journal of KSNVE
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• v.10 no.4
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• pp.623-628
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• 2000

This paper presents the automatic plumbness measuring system form improving the accuracy and working time for plumbness measuring of semi-umbrella type hydraulic turbine generator. It is general practice that rotating shaft should run within acceptable vibration limit. In order to obtain more accurate measuring data for single stage shaft on the semi-umbrella type, plumbness approach must be established carefully and accurately. Generally, present plumbness procedure is required several calculation algorithm, laser sensor and data acquisition devices. As a result of application to actual new system it is confirmed that working time could be saved over 80% and accurate measurement data could be acquired.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.135-139
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• 2008

For deep basement construction of buildings downtown, the usage of Top-Down Method is increasing as much as ever from strong demand. One of the essential elements for the construction by Top Down Method is the pre-founded columns, which are installed in the ground and on which a building is installed. The fact that the pre-founded columns are placed in the ground makes them susceptible to its plumbness; this aspect distinguishes pre-founded columns from general columns. However, there are no criteria for erection tolerance. Therefore, field-measured-data concerning out-of-plumb of pre-founded columns in the construction field should be accumulated and investigated so that criteria and specifications for the erection tolerance of pre-founded columns may be established through the understanding of its aspects. In this paper, we investigate out-of-plumb of pre-founded columns for the construction case and analyze its aspects, and propose considerations for design and construction phase.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05b
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• pp.25-30
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• 2011

Almost prefounded columns for top-down construction certainly have construction tolerances in plan and plumbness. Therefore, it is very difficult to connect prefabricated beams to prefounded columns at each floor level after excavation by usual top-down connection method and this usual connection method leads to long construction time, increasing cost and decreasing quality. This paper presents a new method for connecting prefabricated beam to prefounded column with GROUT-JACKET CONNECTION SYSTEM consisting of sleeve, bearing-shear bands and grout. Details and illustrations of the connections and applications by GROUT-JACKET CONNECTION SYSTEM for the top-down construction are also included in this paper.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.55-60
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• 2008

Inspection of steel columns which is one of the most critical elements in construction requires trained surveyor(s). Also it takes time to handle survey device(s) delicately for accurate measurements. To improve the inspection process of steel columns, the previous studies developed the AR prototype system, ARCam, and showed that ARCam is a promising inspection device that can reduce inspection time. However, ARCam still requires a surveyor to make measurements based on his visual perception and judgment This study proposes an algorithm for automatic inspection based on ARCam. The algorithm is based on image processing and computer vision and focuses on the inspection of steel column plumbness. This method will make measurements without a surveyor's judgment. The ultimate purpose of the automatic inspection is to minimize the surveying labor, thus reducing inspection time and cost.

• Steel and Composite Structures
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• v.4 no.6
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• pp.471-487
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• 2004

Modular steel scaffolds are commonly used as supporting scaffolds in building construction, and traditionally, the load carrying capacities of these scaffolds are obtained from limited full-scale tests with little rational design. Structural failure of these scaffolds occurs from time to time due to inadequate design, poor installation and over-loads on sites. In general, multi-storey modular steel scaffolds are very slender structures which exhibit significant non-linear behaviour. Hence, secondary moments due to both $P-{\delta}$ and $P-{\Delta}$ effects should be properly accounted for in the non-linear analyses. Moreover, while the structural behaviour of these scaffolds is known to be very sensitive to the types and the magnitudes of restraints provided from attached members and supports, yet it is always difficult to quantify these restraints in either test or practical conditions. The problem is further complicated due to the presence of initial geometrical imperfections in the scaffolds, including both member out-of-straightness and storey out-of-plumbness, and hence, initial geometrical imperfections should be carefully incorporated. This paper presents an extensive numerical study on three different approaches in analyzing and designing multi-storey modular steel scaffolds, namely, a) Eigenmode Imperfection Approach, b) Notional Load Approach, and c) Critical Load Approach. It should be noted that the three approaches adopt different ways to allow for the non-linear behaviour of the scaffolds in the presence of initial geometrical imperfections. Moreover, their suitability and accuracy in predicting the structural behaviour of modular steel scaffolds are discussed and compared thoroughly. The study aims to develop a simplified and yet reliable design approach for safe prediction on the load carrying capacities of multi-storey modular steel scaffolds, so that engineers can ensure safe and effective use of these scaffolds in building construction.