• Structural Engineering and Mechanics
• /
• v.65 no.2
• /
• pp.183-190
• /
• 2018

The prestressed concrete (PSC) technology that was first developed by Freyssinet has significantly improved over the past century in terms of materials and structural design in order to build longer, slender, and more economic structures. The application of prestressing method in structures, which is determined by the pre-tension or post-tension processes, is also affected by the surrounding conditions such as the construction site, workforce skills, and local transportation regulations. This study proposes a prestressed concrete girder design based on a hybrid segment concept. The adopted approach combines both pre-tension and post-tension methods along a simple span bridge girder. The girder was designed using newly developed 2400 MPa PS strands and 60 MPa high-strength concrete. The new concept and high strength materials allowed longer span, lower girder depth, less materials, and slender design without affecting the lateral stability of the girder. In order to validate the applicability of the proposed hybrid prestressed segments girder, a full-scale 35 m girder was fabricated, and experimental tests were performed under various fatigue and static loading conditions. The experimental results confirmed the feasibility of the proposed long-span girder as its performance meets the railway girder standards. In addition, the comparison between the measured load-displacement curve and the simulation results indicate that simulation analysis can predict the behavior of hybrid segments girders.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.229-236
• /
• 2022

In this study, a model experiment and field experiment was conducted to introduce the optimal tensile force when constructing a non-open cut tunnel according to the ground conditions of sandy soil. CMR (Concrete Modular Roof) method is economical because of the high precision and excellent durability, and corrosion resistance, and the inserted parts can be used as the main structure of a tunnel. In addition the CMR method has a stable advantage in interconnection because the concrete beam is press-fitted compared to the NTR (New Tubular Roof) method, and the need for quality control can be minimized. The ground conditions were corrected by adjusting the relative density of sandy soil during the construction of non-open cut tunnels, and after introducing various tensile forces, the surface settlement according to excavation was measured, and the optimal tensile force was derived. As a result of the experiment, the amount of settlement according to the relative density was found to be minor. Furthermore, analysis of each tensile force based on loose ground conditions resulted in an average decrease of approximately 22% in maximum settlement when the force was increased by 0.8 kN per segment. Considering these results, it is indicated that more than 2.0 kN tensile force per segment is recommended for settlement of the upper ground.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.33-36
• /
• 2008

The present, most of bridges have been constructed with RC piers in Korea. But the construction of bridges with RC piers is limited to certain working environment and weather that give rise to some series trouble such as weak constructability, quality deterioration and rising of the cost of construction. For this reason, the construction tend to focus on the developing of more effective and economical construction methods. Of all methods, prefabricated precast segment piers have been examined more extensively, it has become a solution of some problems like traffic congestion that usual site placing methods have. The Korea government has the already issued specification earthquake effect. But the existing seismic specification are inapplicable to bridges with prefabricated precast segment piers. This study analyzes structural behabviors of the RC model, prestressted pier moel, the prefabricated precast segment pier with no shearduct model and the prefabricated segment piers with shearduct and changed post tensioning force.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.6
• /
• pp.905-913
• /
• 2017

To design segment lining, loads such as self weight, vertical load, horizontal load, ground reaction, water pressure, backfill grouting pressure et al. have to be considered. Earth pressure and water pressure are the major factor to design segment lining such as concrete strength, segment thickness and amount of rebar et al. To analysis earth pressure and water pressure acting on segment lining, filed monitoring and back analysis are performed in this study.

• Structural Engineering and Mechanics
• /
• v.87 no.3
• /
• pp.255-272
• /
• 2023

Spatial cable systems can provide more transverse stiffness and torsional stiffness without sacrificing the vertical bearing capacity compared with conventional vertical cable systems, which is quite lucrative for long-span earth-anchored suspension bridges' development. Higher economy highlights the importance of refined form-finding analysis. Meanwhile, the internal connection between the lateral and vertical sags has not yet been specified. Given this, an analytic algorithm of form-finding for the earth-anchored suspension bridge with spatial cables is proposed in this paper. Through the geometric compatibility condition and mechanical equilibrium condition, the expressions for cable segment, the recurrence relationship between catenary parameters and control equations of spatial cable are established. Additionally, the nonlinear general reduced gradient method is introduced into fast and high-precision numerical analysis. Furthermore, the analytic expression of the lateral and vertical sags is deduced and discussed. This is very significant for the space design above the bridge deck and the optimization of the sag-to-span ratio in the preliminary design stage of the bridge. Finally, the proposed method is verified with the aid of two examples, one being an operational self-anchored suspension bridge (with spatial cables and a 260 m main span), and the other being an earth-anchored suspension bridge under design (with spatial cables and a 500 m main span). The necessity of an iterative calculation for hanger tensions on earth-anchored suspension bridges is confirmed. It is further concluded that the main cable and their connected hangers are in very close inclined planes.

• Structural Engineering and Mechanics
• /
• v.51 no.1
• /
• pp.89-110
• /
• 2014

In this study, two beam-column elements based on the Elasto-Fiber element theory for reinforced concrete (RC) element have been developed and compared with each other. The first element is based on Elasto Fiber Approach (EFA) was initially developed for steel structures and this theory was applied for RC element in there and the second element is called as Fiber & Bernoulli-Euler element approach (FBEA). In this element, Cubic Hermitian polynomials are used for obtaining stiffness matrix. The beams or columns element in both approaches are divided into a sub-element called the segment for obtaining element stiffness matrix. The internal freedoms of this segment are dynamically condensed to the external freedoms at the ends of the element by using a dynamic substructure technique. Thus, nonlinear dynamic analysis of high RC building can be obtained within short times. In addition to, external loads of the segment are assumed to be distributed along to element. Therefore, damages can be taken account of along to element and redistributions of the loading for solutions. Bossak-${\alpha}$ integration with predicted-corrected method is used for the nonlinear seismic analysis of RC frames. For numerical application, seismic damage analyses for a 4-story frame and an 8-story RC frame with soft-story are obtained to comparisons of RC element according to both approaches. Damages evaluation and propagation in the frame elements are studied and response quantities from obtained both approaches are investigated in the detail.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.265-268
• /
• 2008

In this paper behavior of U-Channel Bridge (UCB) and the slab design considering construction sequence was studied. The segments of UCB are produced in the factory and transported to the site by trailers, and the segments are fabricated in the construction field. In this sequence the supporting conditions are changed. Four steps that were the segment precasting step, the segment carrying step, the segment placed on the erection beam step, and the completion step were chosen by supporting condition. In each step model using the frame and plate elements was proposed and structural analysis was performed. Four construction steps were to be considered in the process of slab analysis. The design method of slab was proposed considering construction sequence.

• KCI Concrete Journal
• /
• v.11 no.3
• /
• pp.99-107
• /
• 1999

In designing the Prestressed concrete box-girder bridge. dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which. therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of time-dependent characteristics. In this study the creep test was carried out for four different curing ages of concrete which were applied to the Prestressed concrete structure at the construction site, and the results of test were compared with the values of creep prediction proposed by the design code. Also the creep test was performed with step-wise incremental stresses and the results were compared to the analytical values.

• Journal of the Korea Concrete Institute
• /
• v.11 no.3
• /
• pp.23-34
• /
• 1999

In designing PSC box girder bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code. In this study the creep and shrinkage test were carried out for four curing ages of concrete which was applied to the pretressed concrete box-girder bridge at a construction site, and the results of test were compared to the values of prediction by the design code. Shrinkage test shows that the test results are similar to KSCE-96 and JSCE-96 but very higher than other prediction model and creep test results are generally similar to ACI-209 and DSCE-96 but lower than other prediction models in contrast to shrinkage test.

• 한국정보통신설비학회:학술대회논문집
• /
• 2007.08a
• /
• pp.315-319
• /
• 2007

지하에 설 치된 맨홀의 구조물이 노후되거나, 내부에 수 용된 시설물로 작업 공간이 협소하여 맨홀 구조물을 대개체 할 펼요가 있을 경우, 지금까지는 대부분 현장 콘크리트 타설에 의한 방법을 사용하였다. 이러한 방법은 거푸집 시공, 콘크리트 타설, 콘크리트 양생, 거푸집 철거 등의 공정이 소요되어 공사 기간이 장기화 되고, 도심지에 위치한 맨홀인 경우에는 차량과 보행자의 통행 불편을 초래하기도 하였다. 또한, 통상적으로 사용되고 있는 프리캐스트 맨홀에 비해 시공 품질이 낮아 향후 맨홀의 운용 및 유지관리에 많은 어려움을 겪는 원인이 되기도 하였다. 본 논문에서는 이러한 문제점들을 해결하기 위해, 폴리머 콘크리트를 이용하여 하부, 벽체, 상부로 구성된 다수의 세그먼트를 생산한 후, 현장에서 이들 세그먼트를 조립하여 맨홀을 설치하는 방법을 연구하였다. 가변형 거푸집을 이용한 세그먼트 제작과 조립식 블록에 의한 관구를 사용하여 현장 적용성을 높임은 물론, 프리캐스트로 생산되는 폴리머 콘크리트 맨홀 수준의 시공 품질을 확보할 수 있도록 하였다.