Side Towers Research Articles

Comparison and Selection of Multiple Construction Schemes for the Large-Span and Heavy-Load Transfer Truss

The main building of Zone II of Zhanjiang Bay Laboratory R&D Building adopts a steel frame–core tube shear wall structure system, with a 53.4 m large-span and heavy-load-transfer truss on the fourth floor. In order to propose the optimal construction and installation scheme for the large-span and heavy-load-transfer truss, the simplified model, single model, and 3D model are utilized to compare Scheme 1 with rigid connection and Scheme 2 with elastic connection and rigid connection. After completing the construction of the underground layer and towers on both sides, in Scheme 1, the fourth-floor transfer truss is directly connected to the towers on both sides in a rigid manner. Subsequently, the support at the bottom of the transfer truss is removed, allowing for layer-by-layer construction. The transfer truss remains rigidly connected to both side towers throughout. On the other hand, in Scheme 2, initially, the transfer truss is connected to both side towers through upper chords and diagonal bars before being constructed upwards until reaching the sixth floor. Once formed as a whole with two floors above using large diagonal tie rods, lower chords of the large-span and heavy-load-transfer truss are then connected with another diagonal bar to establish a rigid connection between the transfer truss and towers; thereafter, upward construction continues. Following completion of constructing a seven-story large diagonal tie rod, whereupon removal of support at the bottom of the conversion truss occurs, subsequent layer-by-layer construction takes place accordingly. It has been observed that employing Scheme 2 can enhance stress distribution within core barrel shear walls as well as transfer trusses while ensuring deflection and stress levels meet requirements for the large-span and heavy-load-transfer truss, thereby rendering structural stress more rationalized, leading to significantly improved overall safety.

Seismic control of a long-span triple-tower suspension bridge using hysteretic steel damper

The seismic performance of a long-span triple-tower suspension bridge is a critical consideration in engineering communities. To promote a better seismic design, this paper presents a parametric study on the structural seismic control using hysteretic steel dampers. The finite element model is firstly established, and an introduction to the mechanical properties of the E-shaped hysteretic steel damper is made. Then, a seismic analysis is conducted under uniform earthquake excitations. Considering the effect of wave passage, the performance of hysteretic steel dampers in seismic control is further analyzed. The results indicate that the travelling wave effect greatly affects seismic responses. Increasing the damper elastic stiffness can effectively reduce the relative displacement between the main girder and either the left or the central tower. This treatment is effective for the right tower only when the wave velocity is among 400–1600 m/s, while it makes little contribution in other ranges. At an arbitrary wave velocity, increasing the damper elastic stiffness would cause minor changes to the shear forces of side towers, while its influence on the central tower is significant. A reasonable damper design for the long-span triple-tower suspension bridge depends on an essential prior evaluation of the wave velocity based on soil conditions.

Comparative Analysis of Buffer and Damper Positions for Increasing the Seismic Performance of Suspension Bridge

In this research, a finite element model is established to investigate effective seismic control schemes for a self-anchored suspension bridge (SASB) with three towers. Nonlinear dynamic analyses are conducted to evaluate the seismic performance of SASB with different layout schemes of viscous dampers and buffers, which were installed in longitudinal direction and transversal direction, respectively. The responses of the SASB designed with 10 seismic control schemes are compared to ascertain suitable seismic schemes for SASBs. The results show that the number and location of lateral buffers have an important impact on the dynamic characterization of the SASB, especially for the first lateral mode and lateral fundamental frequency. To effectively increase the seismic performance of SASBs with three towers, mounting buffers between the side towers and the main girder of SASBs is an appropriate scheme. The viscous dampers can effectively decrease the dynamic reaction of the towers and longitudinal deformation of the girder under earthquake excitations. The plan involves the installation of dampers between the main concrete stiffening girder and the side towers as the optimal longitudinal seismic scheme for the SASB. The study offers important insights into the seismic design of SASBs with three towers.

Puente extradosado sobre el Río Barrow. Diseño y análisis estructural del proceso constructivo, control geométrico y asistencia técnica durante la construcción

En esta comunicación se presentan los elementos de diseño asociados a la ejecución del puente sobre el rio Barrow en New Ross, Irlanda. Con dos luces principales de 230 m en una configuración de puente extradorsal de tres torres, incluyendo el paso sobre el río Barrow con un canal de navegación en activo y una longitud total de 890 m distribuida en 9 vanos, los procesos constructivos del puente han sido determinantes para la optimización del proyecto. Para ello se han empleado dos procesos constructivos diferentes:
 
 Los viaductos de acceso en ambos lados de los vanos principales extradosados se han construido en dos fases desde el punto de vista seccional. El núcleo del cajón mediante cimbra semi rígida al suelo para el núcleo central y una segunda fase mediante un carro de alas para los voladizos transversales y losas/puntal prefabricados.
 
 Los dos vanos principales se han construido mediante voladizos sucesivos en la pila central y frente de voladizo único en las pilas laterales, en ambos casos, con carros de sección completa. Debido a la asimetría de las torres y los planos de atirantamiento (18 cables en la pila central y 8 cables en las pilas laterales) los voladizos en cada vano no son simétricos, encontrándose el punto de cierre a 140 m de la pila central y 90 de las laterales lo que requirió especial cuidado en el diseño de las fases de cierre. Asimismo, en su máxima longitud de voladizo, la pila central alcanzó 140 m en hormigón soportado por cables extradorsales, lo que constituye un récord del mundo en esta configuración

System-based probabilistic evaluation of longitudinal seismic control for a cable-stayed bridge with three super-tall towers

The system fragility method was used to evaluate the seismic structural systems and seismic mitigation devices for a cable-stayed bridge with three super-tall towers. Firstly, a three-dimensional numerical model of a four-span cable-stayed bridge with middle-tower height of 332 m was simulated using OpenSEES, which accounted for the material and geometric nonlinearities; 80 actual ground motions were chosen for conducting time history analysis. Secondly, the fragility curves of the components and the system were derived using general fragility theory and Product of the Conditional Marginal theory, respectively. Then, three longitudinal seismic structural systems were evaluated. Finally, under the optimal seismic structural system, the optimal parameters of the longitudinal fluid viscous damper and cable restrainer were obtained using the response surface method, and the mitigation effects of the fluid viscous damper and the cable restrainer with optimal parameters were compared using fragility curves. The results show that different structural systems and mitigation devices have significant influence on the damage control of displacement and stay cable force. The super-tall tower cable-stayed bridge with a partial constraint system of the consolidated middle tower and floating side towers has the lowest damage probability; and the longitudinal fluid viscous damper and cable restrainer can achieve a certain mitigation effect, however, the fluid viscous damper has better effect. Therefore, the partial constraint system and fluid viscous damper should be used in the longitudinal direction of the multiple super-tall-tower cable-stayed bridge.

Inadequacy of plume rise information to predict the ground level pollutant concentration in vicinity of small cooling towers

Dispersion of pollutant emitted from cooling towers is investigated to discover the pollution concentration distribution at the ground level. The objective is to find the proper arrangement of the cooling towers leading to a lesser concentration of pollutant on the ground. This can be very useful for sustainable development of areas in vicinity of the towers. Comprehensive plume rise data available in the literature has greatly helped to understand how an exhaust plume disperses in a cross wind. In this article, it is shown that the concentration of pollutant on the ground deduced from the plume rise behavior differs from what obtained via direct calculation. The maximum concentration of pollutant on the ground is found to occur once towers are placed in tandem. That is in contrast with what is inferred from the behavior of plume rise. For side by side towers, the plume rise occurs at a lower altitude which can mislead one to conclude that more pollutant would reach the ground surface. The evolution of vortices is employed to explain such discrepancy between the results of direct calculation and those deduced from the plume rise behavior. Similar discussions are presented for square and diamond configurations of multi-flue sources.

Construction Techniques for Strengthening of Dongming Yellow River Road Bridge by the Cable-Stayed System

The Dongming Yellow River Highway Bridge (75+7×120+75 m), is a large span prestressed concrete rigid frame and continuous combination beam bridge, which was the first bridge strengthened by cable-stayed system in China. Using towers and stay cable system, the main bridge was transformed to provide vertical support with superstructure. For the foundation reconstruction, bored piles were constructed as new pile foundations on both sides of the original pile foundations. After cofferdam pumping, to ensure the positioning of the protective tubes, the reinforcing bars, concrete cover and concrete piles left in the river bed were removed by using brush drilling rigs, long arm digging machines and frogmen, while the "U-tube" method was used to grout at the bottom of the piles. The diamond wire saw cutting technology was adopted to complete the transformation of the old caps and insert shear nails. Using the post-pouring strip temporary shields, the new caps and old caps were connected until the tensioning of the cables was finished. To ascertain the arrangement of the reinforcement on the floor and the prestressed reinforcement, and then stick the positioning plates on the floors, bonded rebars holes were drilled utilizing the hydraulic core drill that was made. The joists and the brackets are manufactured by the factory and assembled in the construction site. Gantry cranes and angle fine-tuning devices were used to install the joists and brackets, and then the connecting bolts were inserted. Concurrently, material was transported through the hole in the roof of the middle-span, and the steel supports within the box were installed. From the middle towers to the side towers, from the short cables to the long cables, cables were tensioned by batches and levels with constant monitoring throughout the whole process of this tensioning construction. Finally, the external prestressed strands inside the box were adjusted and the bridge deck construction was completed.

Behaviour and design of three-tower, self-anchored suspension bridge with a concrete girder

This research presents the general design of a three-tower, self-anchored suspension bridge with a concrete stiffening girder based on practical engineering. The finite-element method is adopted to explore the structural behaviour of a bridge affected by shrinkage and creep of the concrete stiffening girder. The results show that shrinkage and creep of the concrete stiffening girder have a major effect on the mechanical behaviour of the side towers and stiffening girder. A new main cable system consisting of a prefabricated parallel wire strand (PPWS) cable with a polyethylene jacket and cold-cast anchorage is proposed to allow the main cables to be tensioned and the bridge cable force to be adjusted at any time. The experimental results of the PPWS cable show that the design and manufacture of the largest cable in China are safe and reliable. Moreover, the numerical simulation results for a new cable clamp connecting two main cables to a single hanger indicate that its design is reasonable. Furthermore, the anti-corrosive properties of the special cable system are investigated. The behaviour results as well as some key design technologies of this bridge style in the study provide valuable knowledge for its future application.

Seismic response analysis of self-anchored suspension bridge with multi-tower

Seismic performance of a self-anchored suspension bridge with three-tower were investigated. A three-dimensional nonlinear finite element model of the bridge was developed using Sap2000. Nonlinear time history analysis was conducted using Fast Nonlinear Analysis Method (FNA), while beam-column effect and nonlinear behavior of bearing and damper were taken into consideration. The analyze results showed that the middle tower was more vulnerable compared with the two side towers; there existed risk of buckling of composite beam, and the most vulnerable part lied near steel-concrete composite segment. Viscous dampers were effective to reduce seismic response of towers as well as girders.

Investigation of Influence Factors of Wind-Induced Buffeting Response of a Six-Tower Cable-Stayed Bridge

This paper presents an investigation of the wind-induced buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A three-dimensional finite element model for the Jiashao Bridge is established using the commercial software package ANSYS and a 3D fluctuating wind field is simulated for both bridge deck and towers. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects including the difference in the longitudinal stiffness between the side towers and central towers, partially longitudinal constraints between the bridge deck and part of bridge towers, self-excited aerodynamic forces, and the rigid hinge installed in the middle of the bridge deck. The analytical results can provide valuable references for wind-resistant design of multispan cable-stayed bridges in the future.

Influence of structural system measures on the dynamic characteristics of a multi-span cable-stayed bridge

A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cable-stayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

A case study of a high end residential condominium building acoustical design and field performance testing

A high end multi-owner condominium building complex consists of 314 units configured in a central tower with a 39-story central core, as well as 21 and 30 story side towers. A series of project specific acoustical design considerations related to condominium unit horizontal and vertical acoustical separation as well as background noise control for building HVAC systems were developed for the project construction documents and later field tested to confirm conformance with the acoustical design criteria. This paper presents the results of these building wide field tests as well as a discussion of pitfalls encountered during design, construction, and post-construction.

Seismic performance and its favorable structural system of three-tower suspension bridge

Due to the lack of effective longitudinal constraint for center tower, structural stiffness of three-tower suspension bridge becomes less than that of two-tower suspension bridge, and therefore it becomes more susceptible to the seismic action. By taking a three-tower suspension bridge-the Taizhou Highway Bridge over the Yangtze River with two main spans of 1080 m as example, structural dynamic characteristics and seismic performance of the bridge is investigated, and the effects of cable\'s sag to span ratio, structural stiffness of the center tower, and longitudinal constraint of the girder on seismic response of the bridge are also investigated, and the favorable structural system is discussed with respect to seismic performance. The results show that structural response under lateral seismic action is more remarkable, especially for the side towers, and therefore more attentions should be paid to the lateral seismic performance and also the side towers. Large cable\'s sag, flexible center tower and the longitudinal elastic cable between the center tower and the girder are favorable to improve structural seismic performance of long-span three-tower suspension bridges.

Experimental study of dynamic interaction between group of intake towers and water

Dynamic test with scaled model of a group of intake towers was performed to study the dynamic interaction between water and towers. The test model consists of intake tower or towers, massless foundation near the towers and part of water to simulate the dynamic interaction of tower-water-foundation system. Models with a single tower and 4 towers were tested to find the different influences of the water on the tower dynamic properties, seismic responses as well as dynamic water-tower interaction. It is found that the water has little influence on the resonant frequency in the direction perpendicular to flow due to the normal force transfer role of the water in the contraction joints between towers. By the same effect of the water, maximum accelerations in the same direction on 4 towers tend to close to each other as the water level increased from low to normal level. Moreover, the acceleration responses of the single tower model are larger than the group of towers model in both directions in general. Within 30m from the surface of water, hydrodynamic pressures were quite close for a single tower and group of towers model at two water levels. For points deeper than 30m, the pressures increased about 40 to 55% for the group of towers model than the single tower model at both water levels. In respect to the pressures at different towers, two mid towers experienced higher than two side towers, the deeper, the larger the difference. And the inside hydrodynamic pressures are more dependent on ground motions than the outside.

Shaking Table Test of Multi-Tower Self-Anchored Suspension Bridge

As a new kind of bridge structure, multi-tower self-anchored suspension bridge (MSSB) has complicated mechanical characteristics. So far, the research on dynamic performance of MSSB is limited to theoretical and numerical simulation. Based on the first three shaking table system in China, shaking table test of MSSB is carried out. The modal test and seismic excitation test show that the performance of fundamental mode shape is anti-symmetric vertical bending vibration of girder, coupling with longitudinal bending vibration of middle tower. Seismic response of middle tower is greater than side towers. At last, 3D finite element model of test specimen is established and test process is numerical simulated by FEM. Simulated result is agreed well with test record.

Sedimentology and depositional history of the travertines outcropping in the Poseidonia-Paestum archaeological area

The travertines on which the ancient town of Paestum was built about 2,600 years ago, have been investigated to restore the original sedimentary environment of these freshwater limestones formed during the Late Pleistocene–Holocene in the southern sector of the Sele River plain. For this purpose, the few present outcrops of travertine have been analysed from a palaeoenvironmental point of view, integrating the morphology and the sedimentology of the substrate with the information on the textural patterns of the blocks forming the town walls, some of which have a clear similarity with the outcropping substrate. The Paestum travertines can be distinguished into two sedimentary units: the lower Paestum travertines (LPT) which formed between Late Pleistocene (75,000 years BP) and the Early Holocene, and the upper Paestum travertines (UPT) formed during Late Roman to Medieval times. The UPT reached various meters of thickness within the southern and western part of the town, obstructing completely its western entrance, Porta Marina, with its flanking side towers, and were largely removed during archaeological excavations that started in the 1930s. A possible mechanism for this fossilization calls for a process of progressive upward growth of an incrustation barrier within the door, while the calcariferous waters were flowing out from the town at increasing heights.

Seismic Response Analysis of Multi-Span Cable-Stayed Bridge

Based on the dynamic characteristics analysis results of a precise three-dimensional finite element model, the earthquake responses of the bridge are analyzed in this paper. The influences of cable local modes and stabilizing cables on the seismic response are investigated by using different mode combinations and different models. It is found that the influence of cable local modes is negligible on the side towers while significant and not negligible on the main tower; the influence of the stabilizing cables is significant and not negligible on side towers, while minor and negligible on the main tower. As for the deck displacements, the influence of cable local modes is minor and negligible, while that of longitudinal stabilizing cables is significant and not negligible.

Influence of Stabilizing Cables on Seismic Response of a Multispan Cable‐Stayed Bridge

Abstract: A recent trend in the design of long‐span bridges is multispan cable‐stayed bridges with three or more towers. A critical problem of multispan cable‐stayed bridges is the stabilization of the central tower(s), which has resulted in increasing application of stabilizing cables. The Ting Kau Bridge in Hong Kong is one of a few multispan cable‐stayed bridges adopting stabilizing cables ever built. In this article, the dynamic properties of multispan cable‐stayed bridges with stabilizing cables and the effect of stabilizing cables on bridge seismic response are studied by referring to the Ting Kau Bridge. Based on a validated 3D finite‐element model, modal analysis is conducted which shows that the longitudinal stabilizing cables bring about a number of global modes with strong modal interaction among the deck, towers, and cables. The seismic response and internal force in the central tower are found to be much larger than those in the side towers. The longitudinal stabilizing cables are very effective in reducing the internal force in the central tower generated by longitudinal earthquake excitation, but insignificantly affect the seismic response in the bridge deck and side towers. As a whole, the stabilizing cables act favorably in the reduction of seismic response of the bridge.

Portals of the Church of Saint Nicholas in Bari

The Church of Saint Nicolas in Bari, in southern Italy, is known as a church of great renown and importance, in view of the fact that it was built to receive the remains of Saint Nicholas, which are still kept in the church?s crypt, in the part of the building from where its construction began, at the end of the XI century. This church played a highly significant role in the creation of the specific, Romanic style of architecture in this region, so several important buildings were constructed using the basic typological and stylistic characteristics of the Church of Saint Nicholas. It was built as a triple-naved basilica with a transept and a dome designed at the intersection of the main nave and the transept, and the specific rendition of the altar section, with side towers and a flat facade wall that encloses the inner apse was applied in a similar manner on several churches in Apulia. Its great renown in the Christian world is well-known, reflected both in the strong connection between the churches in Bari and Kotor, and through the donations by the medieval Serbian rulers, among which is the large icon of Saint Nicholas, a gift from Stefan Decanski, which is still preserved in the church?s crypt. The importance of this and the other churches in Apulia was undoubtedly one of the factors that have led to discussion in literature about the question of their possible influence on architectonic creation in related artistic fields, including the monuments of the Raska stylistic group, particularly in connection with the architectural and sculptural plastics on portals because of the similarity of some of the shapes and motives in the stonemasonry...

PROTECTION FOR THE FORTH ROAD BRIDGE: Corrosion‐free Cables for 100 Years

This suspension bridge, with its main span of 3,300 ft., is expected to be opened in 1963. It will be the largest in Europe and the fourth largest in the world. A number of interesting improved techniques will be used in protecting it from corrosion and, in particular, the post‐tensioning cables which anchor the side towers to the base rock are expected to last over a century.