• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.23-29
• /
• 2008

Most VE operation related to construction project is progressed in stage of planing or design phase, especially in case of domestic. It is encouraging fact and if you have VE process in stage of planning and design, you'll have experience a reduction of about 70% of total saving cost in which total construction process may occurred. However, recently the work of construction in overseas increase and almost is only construction-work, except planning and design process. As this reason, VE process for construction-work phase only is demanded in high necessity. VE in construction phase comes to accomplish intensively in the part which the design change does not follow, through know-how, equipment operating method and method of temporary-structure erection at the established construction-site learned, builders will be the possibility of reduction from 3% to 10% in constructive expense. This paper describes VE performing example in OO company's construction-work phase, and propose the methodology of VE performance in the phase of construction. And also it is aimed to extending VE applications into the overseas construction enterprise.

• Structural Engineering and Mechanics
• /
• v.70 no.5
• /
• pp.639-647
• /
• 2019

The performance of precast concrete structures is greatly influenced by the behaviour of beam-to-column connections. A single connection may be required to transfer several loads simultaneously so each one of those loads must be considered in the design. A good connection combines practicality and economy, which requires an understanding of several factors; including strength, serviceability, erection and economics. This research work focuses on the performance aspect of a specific type of beam-to-column connection using partly hidden corbel in precast concrete structures. In this study, the results of experimental assessment of the proposed beam-to-column connection in precast concrete frames was used. The purpose of this research is to develop and apply the Extreme Learning Machine (ELM) for moment-rotation prediction of precast beam-to-column connections. The ELM results are compared with genetic programming (GP) and artificial neural network (ANN). The reliability of the computational models was accessed based on simulation results and using several statistical indicators.

• Advances in Computational Design
• /
• v.6 no.1
• /
• pp.55-75
• /
• 2021

The lightweight superstructure is beneficial for bridges in remote areas and emergency erection. In such weight-sensitive applications, the combination of fiber-reinforced polymer (FRP) as a material and box-beams as a structural system have enormous scope. This combination offers various advantages, but as a thin-walled structure, their designs are often governed by buckling criteria. FRP box-beams lose their stability either by flange or web buckling mode. In this paper, the web buckling behavior of simply supported FRP box-beam subjected to transverse load has been studied by modeling full box-beam to consider the effect of real state of stress (stress variation in length direction) and boundary conditions (rotational restraint at web-flange junction). A parametric study by varying the sectional geometry and fiber orientation is carried out by using ANSYS software. The accuracy of the FE models was ensured by verifying them against the available results provided in the literature. With the help of developed database the influential parameters (i.e., αs, βw, δw and γ) affecting the web bucklings are identified. Design trends have been developed which will be helpful to the designers in the preliminary stage. Finally, the importance of governing parameters and design trends are demonstrated through pedestrian bridge design.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.34 no.9
• /
• pp.11-18
• /
• 2018

As the height of the modular buildings increases, their stability becomes more and more dependent on the core. All traditional construction methods in structural concrete and steel can be utilized for cores in modular buildings but a core system with dry connection is more desirable to complete a greater degree of factory finish and faster erection of modular buildings. In order to do that, the hybrid PC(precast concrete) panel, which has a pair of C-shaped steel beams combined at the top and bottom of a concrete wall, was developed, In this study the cyclic lateral loading test on the hybrid PC panel is carried out and the panel configurations are examined to enhance the structural performance in comparison with the RC wall. Experimental results show that the strength of hybrid PC panel is about 70% of thar ot RC wall and the anchorage of vertical reinforcing bar welded to C-shaped steel beam needs to be improved.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.7
• /
• pp.147-156
• /
• 2019

The purpose of this study is to consider structural issues and analyze construction sequences when constructing hanging floors supported by Mega truss. Since suspended structures were supported by the Mega truss, vertical load on suspended structures was needed to transfer from low to high. Deflection management of structures was the primary point under construction. The results of this study were as follows; The steel structures, which has relatively lighter self-weight, were constructed upwards after the base floor steel truss erection. Concrete Placing, which has relatively heavier self-weight, were performed in two phases to minimize structure's deflection. Slab was placed downwards from the top floor to lower floor whereas column was places upwards. Deflection measurements were carried out at every construction sequences.

• Steel and Composite Structures
• /
• v.42 no.6
• /
• pp.791-804
• /
• 2022

As a type of semi-rigid connection, the top and seat angle connections are popular in current structures owing to their good cyclic performance and simple erection. However, their stiffness and load bearing capacity are relatively insufficient. This study proposes two strengthening methods to further increase the stiffness and strength of bolted-angle joints while maintaining satisfactory energy dissipation capacity (EDC) and ductility. Cyclic loading tests were conducted on six joint specimens with different strengthened angle components. Based on the test results, the influence of the following important factors on the cyclic behavior of steel joint specimens was investigated: the position of the rib stiffeners (edge rib stiffeners and middle rib stiffener), steel strength grade of rib stiffeners (Q345 and Q690), and additional stiffeners or not. In addition, the finite element models of these specimens were built and validated through a comparison of experimental and numerical results. The stiffness and bearing capacity of the bolted-angle joints could be improved significantly by utilizing the novel strengthened joints proposed in this study. Moreover, this can be achieved with almost no increase in the amount of steel required, and the EDC of this joint could also satisfy the requirements of seismic codes from various countries.

• Structural Engineering and Mechanics
• /
• v.82 no.3
• /
• pp.313-323
• /
• 2022

Steel laminated elastomeric bearings are commonly used in bridge structures to control displacements and rotations and transfer forces from the superstructure to the substructure. Proper knowledge of design, fabrication and erection procedures is important to ensure stability and adequate structural performance during the lifetime of the bridge. Difference in elevations sometimes leads to large size gaps between the bearing and the girder which makes the grout thickness that is commonly used for leveling deviate beyond standards. This paper investigates the structural response of High Strength Fiber Reinforced Cementitious (HSFRC) thin plinths that are used to close gaps between bearing pads and precast girders. An experimental program was developed for this purpose where HSFRC plinths of different size were cast and tested under vertical loads that simulate bridge loading in service. The structural performance of the plinths was closely monitored during testing, mainly crack propagation, vertical reaction and displacement. Analytically, the HSFRC plinth was analyzed using the beam on elastic foundation theory as the supporting elastomeric bearing pads are highly compressible. Closed form solutions were derived for induced displacement and forces and comparisons were made between analytical and experimental results. Finally, recommendations were made to facilitate the practical use of HSFRC plinths in bridge construction based on its enhanced load carrying capacity in shear and flexure.

• International Journal of Korean Welding Society
• /
• v.3 no.1
• /
• pp.34-38
• /
• 2003

It has been used many kinds of horizontal butt-welding methods at block-to-block erection stage in shipbuilding companies. For examples, some companies use conventional FCAW process with one side or both sides groove joint welding, others use carriage with torch holder type mechanized welding method. Although lots of efforts were done until now, some problems in quality and productivity still remain in ship's hull welding. In this study, we have attempted to raise productivity and quality on horizontal position of welding with following 3 items. 1) Prepare groove condition with no root gap for making easy fit-up work. 2) Develop improved MAG (100% $CO_2$ gas shielding) welding process with solid wire for making sound root bead from one side. 3) Develop and apply quite new automatic welding carriage. The stability of new welding process was confirmed by conducting mechanical tests of weldments to verify the soundness of weldments.

• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.65-69
• /
• 2015

The aim of this paper is to identify and rank the main causes of fall accidents from scaffolding according to their relative importance as perceived by project managers and site engineers in construction projects in the Gaza Strip. A total of 50 questionnaires were distributed to project managers and site engineers, 35 questionnaires were received yielding 70% response rate. A total of 33 factors that cause fall accidents in scaffolding were identified through a literature review and consolidated by a pilot study. These factors were categorized into six groups: factors related to erection, factors related to the staff (Scaffolders), factors related to loads, factors related to the personal safety, factors related to the workers behavior, factors related to the personal competencies. The results indicated that factors related to the workers behavior are the major factors that caused fall accidents from scaffolds. The results revealed that the top ranked factors which caused falls accidents from scaffolding were: absence of personal protective equipment (PPE), missing ladders, wind loads, disguised the design code, lack of proper assembly or inspection, overhead tools and materials, climbing and neglect using ladders, lack of guardrails, missing bracing and working during fatigue. These findings would help contractors to understand the top factors that caused fall accidents so that they can take them into consideration in safety planning in order to minimize the possibility of their occurrences.

• Anatomy and Cell Biology
• /
• v.56 no.4
• /
• pp.421-427
• /
• 2023

Bladder exstrophy is a rare congenital condition of the pelvis, bladder, and lower abdomen that opens the bladder against the abdominal wall, produces aberrant growth, short penis, upward curvature during erection, wide penis, and undescended testes. Exstrophy affects 1/30,000 newborns. The bladder opens against the abdominal wall in bladder exstrophy, a rare genitourinary condition. This study is vital to provide appropriate therapy choices as a basis to improve patient outcomes. This study may explain bladder exstrophy and provide treatment. Epispadias, secretory placenta, cloacal exstrophy, and other embryonic abnormalities comprise the exstrophy-spades complex. The mesenchymal layer does not migrate from the ectoderm and endoderm layers in the first trimester, affecting the cloacal membrane. Embryological problems define the exstrophy-aspidistra complex, which resembles epimedium, classic bladder, cloacal exstrophy, and other diseases. Urogenital ventral body wall anomalies expose the bladder mucosa, causing bladder exstrophy. Genetic mutations in the Hedgehog cascade pathway, Wnt signal, FGF, BMP4, Alx4, Gli3, and ISL1 cause ventral body wall closure and urinary bladder failure. External factors such as high maternal age, smoking moms, and high maternal body mass index have also been associated to bladder exstrophy. Valproic acid increases bladder exstrophy risk; chemicals and pollutants during pregnancy may increase bladder exstrophy risk. Bladder exstrophy has no identified cause despite these risk factors. Exstrophy reconstruction seals the bladder, improves bowel function, reconstructs the vaginal region, and restores urination.