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

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.123-135
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• 2006

Most of all, large spatial span structures are the symbol of cities but have to get to supply the purpose of structure simultaneously, therefore their foundations are designed to get rolls of structure support, structure shape maintenance or overturn prevention, buoyancy resistance, etc. Accordingly various type foundations have been introduced, and after anchorage power is introduced for double structures shape maintenance and overturn prevention, change of anchorage power checked in the construction process is reviewed, comparing of playground case. Case1 anchors for the control of horizontal power worked outside hemisphere type roof, Case2 anchors for the overturn prevention of cantilever roof examined in this example. The examination has been executed by the analysis of anchorage power introduction process, related test results and anchorage power monitoring results for 2 examples.

• Journal of the Korean Society for Railway
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• v.6 no.4
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• pp.232-238
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• 2003

A health monitoring system becomes a very useful tool to obtain information on long term behavior of the important railway structures such as very long span and special type bridges. It can be also used to give a warning signal to the maintenance engineer when the structure shows abnormal behavior. However, due to long term use and temperature changes, the health monitoring system needs to be calibrated periodically. In this study, calibration and gauge factor readjustment process made for the health monitoring system installed in the railroad bridges and tunnel are reviewed and a few findings are updated. Future work will be concentrated on the long-term analysis of the measurement data and on the database structures so that the assessment of the structure is possible

• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.619-626
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• 2009

The use of thin-walled flexural members has proven to be a practical way to achieve the lowest cost in the construction of prefabricated long-span, low-rise building frames in steel. On the other hand, most of these structures are subjected to corrosion due to environmental exposure, which can reduce their carrying capacity. Corrosion damage is a serious problem for these structures as it causes thickness loss. That is, the class of a section (plastic, compact, non-compact, or slender) may change from one to another due to the loss of thickness of the compression flange and web due to corrosion. In this study, the effects of corrosion on thin-walled members in long-span steel frames were evaluated with regard to the moment-rotation curve, initial stiffness, maximum load capacity, stiffness in the post-maximum capacity, and energy absorption.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.67-78
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• 2004

Soil-steel bridges are made of flexible corrugated steel plates buried in the well-compacted granular soil. One kind of possible collapses of these structures could be initiated by shear or tension failure in the soil cover subjected to vehicle loads. Current design codes provide the requirements for the minimum depth of the soil cover to avoid problems associated with soil cover failures. However, these requirements were developed for short span (less than 7.7 m) structures which are made of unstiffened plates of standard corrugation (150$\times$50 m). Numerical analyses were carried out to investigate the behavior of long span soil steel bridges according to thickness of the soil cover. The span of structures were up to 20 m and deep corrugated plates (381$\times$140 m) were used. The analysis showed that the minimum cover depth of 1.5 m could be sufficient to prevent the soil cover failure in the structures with a span exceeding 10 m. Additional analyses were performed to verify the reinforcement effect of the concrete relieving slab which can be a special feature to reduce the live-load effects. Analyses revealed that the bending moment of the conduit wall with a relieving slab was less than 20% of that without a relieving slab in a case of shallow soil cover conditions.

• Wind and Structures
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• v.9 no.4
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• pp.271-296
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• 2006

The frequency of a traditional tuned liquid column damper (TLCD) depends solely on the length of liquid column, which imposes certain restrictions on its application to long span cable-stayed bridges during construction. The configuration of a cable-stayed bridge varies from different construction stages and so do its natural frequencies. It is thus difficult to apply TLCD with a fixed configuration to the bridge during construction or it is not economical to design a series of TLCD with different liquid lengths to suit for various construction stages. Semi-active tuned liquid column damper (SATLCD) with adaptive frequency tuning capacity is studied in this paper for buffeting response control of a long span cable-stayed bridge during construction. The frequency of SATLCD can be adjusted by active control of air pressures inside the air chamber at the two ends of the container. The performance of SATLCD for suppressing combined lateral and torsional vibration of a real long span cable-stayed bridge during construction stage is numerically investigated using a finite element-based approach. The finite element model of SATLCD is also developed and incorporated into the finite element model of the bridge for predicting buffeting response of the coupled SATLCD-bridge system in the time domain. The investigations show that with a fixed container configuration, the SATLCD with adaptive frequency tuning can effectively reduce buffeting response of the bridge during various construction stages.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.1
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• pp.49-54
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• 2012

The purpose of this study is to define emergency response procedures by BDMS [Building Disaster Management System] when earthquake occurs on long-span bridge structures. The study is about developing a computer-based algorithm for various earthquake intensities that works with the System. Presently, long-span bridge disaster prevention relies on closed-system centered on human intervention alone. However, this study combines IT technology and internet-based open system creating a more practical system. Additionally, assigned duties and tasks are clearly defined to all personnel involved in various disaster situations using the Active Action Diagram(AAD) techniques. Also, the design of 3-dimensional view assists to determine the appropriate initial response in times of earthquake and other disasters. The combination of the existing manual emergency response procedures and the scenario-based (IT) response system being developed will create an efficiency and fast response actions in times of emergencies.

• Wind and Structures
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• v.17 no.3
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• pp.317-343
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• 2013

When evaluating flutter instability, it is often assumed that incident wind is normal to the longitudinal axis of a bridge and the flutter critical wind speed estimated from this direction is most unfavorable. However, the results obtained in this study via oblique sectional model tests of four typical types of bridge decks show that the lowest flutter critical wind speeds often occur in the yaw wind cases. The four types of bridge decks tested include a flat single-box deck, a flat ${\Pi}$-shaped thin-wall deck, a flat twin side-girder deck, and a truss-stiffened deck with and without a narrow central gap. The yaw wind effect could reduce the critical wind speed by about 6%, 2%, 8%, 7%, respectively, for the above four types of decks within a wind inclination angle range between $-3^{\circ}$ and $3^{\circ}$, and the yaw wind angles corresponding to the minimal critical wind speeds are between $4^{\circ}$ and $15^{\circ}$. It was also found that the flutter critical wind speed varies in an undulate manner with the increase of yaw angle, and the variation pattern is largely dependent on both deck shape and wind inclination angle. Therefore, the cosine rule based on the mean wind decomposition is generally inapplicable to the estimation of flutter critical wind speed of long-span bridges under skew winds. The unfavorable effect of yaw wind on the flutter instability of long-span bridges should be taken into consideration seriously in the future practice, especially for supper-long span bridges in strong wind regions.

• Wind and Structures
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• v.29 no.4
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• pp.279-297
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• 2019

Strong winds threaten the safety of vehicles on long-span bridges considerably, which could force traffic authorities to reduce speed limits or even close these bridges to traffic. In order to maintain the safe and economic operation of a bridge, a reasonable evaluation of the driving safety on that bridge is needed. This paper aims at carrying outdriving safety analyses for three types of vehicles on a long-span bridge in crosswinds by considering the aerodynamic interference between the bridge and the vehicles based on the wind-vehicle-bridge coupling vibration analysis. Firstly, CFD numerical simulations along with previously obtained wind tunnel testing results were used to determine the aerodynamic force coefficients of the three types of vehicles on the bridge. Secondly, the dynamic responses of the bridge and the vehicles under crosswinds were simulated, and based on those, the driving safety analyses for the three types of vehicles on the bridge were carried out for both cases considering and not considering the aerodynamic interference between the vehicles and the bridge. Finally, the effect of the aerodynamic interference on the safety of the vehicles was investigated. The results show that the aerodynamic interference between the bridge and the vehicles not only affectsthe accident critical wind speed but also the accident type for all three types of vehicles. Such effects are also different for each of the three types of vehicles being studied.

• Wind and Structures
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• v.34 no.5
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• pp.421-435
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• 2022

To investigate the non-Gaussian properties of fluctuating wind pressures and the error margin of extreme wind loads on a long-span curved roof with matching and mismatching ratios of turbulence integral scales to depth (L_u^x/D), a series of synchronized pressure tests on the rigid model of the complex curved roof were conducted. The regions of Gaussian distribution and non-Gaussian distribution were identified by two criteria, which were based on the cumulative probabilities of higher-order statistical moments (skewness and kurtosis coefficients, S_k and K_u) and spatial correlation of fluctuating wind pressures, respectively. Then the characteristics of fluctuating wind-loads in the non-Gaussian region were analyzed in detail in order to understand the effects of turbulence integral-scale. Results showed that the fluctuating pressures with obvious negative-skewness appear in the area near the leading edge, which is categorized as the non-Gaussian region by both two identification criteria. Comparing with those in the wind field with matching L_u^x/D, the range of non-Gaussian region almost unchanged with a smaller L_u^x/D, while the non-Gaussian features become more evident, leading to higher values of S_k, Ku and peak factor. On contrary, the values of fluctuating pressures become lower in the wind field with a smaller L_u^x/D, eventually resulting in underestimation of extreme wind loads. Hence, the matching relationship of turbulence integral scale to depth should be carefully considered as estimating the extreme wind loads of long-span roof by wind tunnel tests.