Concrete Tower Research Articles

Assessment on the 2014 Jure Landslide in Nepal – a disaster of extreme tragedy

The landslides kill many people every year in Nepal and in the Himalayan region, which devastates society in the local area. A famous living memory of an example of landslide induced devastation was the landslide at Tinau river that took place in early September 1981 damming the river completely, which breached after few days causing huge flood downstream. The flood swept away concrete tower of the Tinau Hydropower Project, two suspension bridges, one concrete bridge at Butwal, part of Butwal city was completely damaged and many hundred people lost their life. Similarly, on the night of 2nd August 2014 (02:30 AM), a huge landslide, famously known as “Jure Slide”, took place along Sunkoshi River valley on Araniko Highway that connects Kathmandu with Tibet. The landslide killed 156 people who were on sleep in their houses, savaged 120 houses, partially damaged 37 more, dammed Sunkoshi river creating an artificial dam of approximately 50 m high and an approximately 3 km long reservoir was formed. A huge flood occurred after partial breach of the dam damaging barrage structures of the Sunkoshi Hydropower Project located about one kilometre downstream from the slide area. It took over two months to drain artificially created reservoir. The main aim of this manuscript is to describe and evaluate Jure landslide. Critical aspects on the causes of landslide will be highlighted giving emphasis on topography, geology, rock mass, monsoon, and earthquake.

Influence of external loads to wind turbine tower

One of the most important parts of a wind turbine is a tower. There are various designs of the wind turbine towers, and they are most often made of steel pipes, lattice towers or concrete towers. In order to increase energy density to meet the growing electricity needs, larger wind turbine projects have been developed. Larger wind turbine towers can generate more electricity, but such large sizes also create higher costs in terms of development and maintenance. This research sets up a model of a wind turbine tower, where the load to the tower is calculated by its relation to the wind velocity. Analytical approach coupled with a finite element method (FEM) is used to analyse the distribution of tower stresses under these loads. The fatigue analysis of the column is performed using the load from its own weight, the weight of the housing and the distribution of the wind velocity. The effects of different loads are also compared. The results show that the main loads of the tower are the wind force acting on the area of ??rotation of the wind turbine blades and the moment caused by the uneven wind velocity. Construction is modelled using SolidWorks modelling package, where the analysis was performed using FEM in ANSYS software. As a result of the analysis, the stress distribution in the support was determined and compared with analytical calculations.

Torsional load-bearing capacity of half-shell segments for prestressed concrete towers

This article deals with the torsional load-bearing behaviour of concrete half-shell structures. The analogy between the bending stressed tension members according to second order theory and torsional members with warping hindered cross-section leads to a significantly simplified calculation of the additionally occurring warping stresses. This eliminates the need for the laborious solution of complex differential equations of the classical torsional warping theory to determine the load-bearing behaviour of warped cross-sections. The load redistribution approach projects the global torsion load of the segment tower onto the individual half-shell. The combination of the two approaches enables the analytical calculation of the torsional load-bearing behaviour of the concrete half-shell construction as a function of the global torsional moment and the system variables of the half-shell.The objective is to investigate and describe the torsional load-bearing behaviour of segmented half-shell structures in an engineering model. Compared to closed circular ring segments, the vertical joints have a significant influence, especially on the torsional rigidity. In order to determine the horizontal joint bearing capacity of these innovative constructions, it is essential to understand the load transfer of the torsional load. The presented approach allows to separate the individual effects of the load transfer in half-shell constructions from each other and thus to identify the factors influencing the torsional load-bearing behaviour.

Seismic Damage of Submerged Intake Tower under the Sequence of Mainshocks and Aftershocks

ABSTRACT Reinforced concrete intake towers are considered as main hydraulic structures constructed in dams’ reservoirs, connected to the dam or as a separate structure. If an intake tower is damaged, the powerhouse or downstream of the dam may experience serious problems. In this research, the influence of mainshock-aftershock seismic sequences is studied on real intake tower. The intake tower of Encino dam is modeled by using the finite element method. The dynamic time history analyses are conducted with the real as-recorded earthquakes and the nonlinear behavior of concrete and steel bars is considered. The tower is modeled with reservoir and foundation, and their interactions are considered. The earthquake records are applied to the tower in three cases: (i) one horizontal component, (ii) two horizontal components, and (iii) two horizontal components with vertical component. The main dynamic responses of the tower including relative deflections and nonlinear material responses are presented. The obtained results are discussed, and the influence of the main shock-aftershock sequences are thoroughly examined.

Mechanical Behavior of the Novel Gradient Concrete Tower of a Cable-Stayed Bridge

In this paper, the novel gradient concrete is innovatively applied to the bridge towers of Chizhou Yangtze River Bridge to solve the cracking and insufficient durability problems of concrete towers. Fiber-reinforced concrete is used in the outer functional area of the bridge tower, to significantly improve its crack resistance during construction and service. Moreover, the integrated design of anti-cracking and mechanical properties of tower materials is achieved. To study the performance of the novel functional gradient concrete (FGC) tower, the mechanical properties of the FGC tower material are tested, and the overall finite element stress is analyzed. Based on the material properties, the mechanical behavior of the cable-stayed bridge tower is studied. The temperature and stress of the FGC tower during the generation of the hydration heat are compared with that of the ordinary concrete tower. The crack resistance of the FGC tower is analyzed by the finite element method. The results show that the FGC tower has good mechanical properties and durability for the cable-stayed bridge towers.

Discussion on the Design of Cable Tower Grouping-Anchorage System of Cable-Stayed Bridge

Cable Tower Grouping-Anchorage-System of Cable-Stayed Bridges is a new type of anchorage system, which is only used in Chi-Zhou bridge in An Hui province in domestic. In order to understand the behavior characteristics and the design methods, took Chi-Zhou Bridge as an example. Firstly, the propaedeutics were introduced, and then the finite element models of the whole bridge were built in six different cases and parameters sensitivity were analyzed which included cables layouts, agglomeration forms and steel beams design. Then took introduced the beam-column stiffness ratio, studied the stiffness matching between concrete tower and steel beam and clarified the influence of grouping, agglomeration and stiffness ratio on the whole bridge. Some design suggestions were stated. The results showed that the Grouping-Anchorage-System is more advantageous on the lateral stability and torsion resistance of the whole bridge; The steel beams are the key point of design because of the stress complexity. Changing the length of the steel beam will bring about changes in the local stress and changing the space between steel beams will bring about changes in the whole bridge. Considering the layout spaces and detailing requirements, the length of steel beams should be reduced as much as possible, so as to improve the efficiency of stay cables, which is beneficial to the whole bridge stress and economy.

Structural calculation analysis and design of a Towering concrete building

This Towering building is a concrete tower with a height of 199. 10m and an octagonal plane, with a complex structure. The structure is calculated as a whole through the programs of two different mechanical models, the calculation results are relatively close, and the control indicators meet the requirements of relevant specifications and regulations. This article introduces and analyzes the structural system, structural calculation and analysis methods, seismic performance objectives, and overall calculation results of the project, and details the design of the steel tower.

Analysis of tower foundation of long span single tower cable stayed bridge

The pylon is an important stressed structure in the single pylon cable-stayed bridge. The rationality of bearing platform and pile foundation of pylon foundation is one of the key research contents in the design of single pylon cable-stayed bridge. The main bridge of Tarim bridge in Xinjiang is a single tower double span cable-stayed bridge with span arrangement of (41 + 168 + 168 + 41) m and total height of cable tower of 125m. Arc shaped concrete tower columns are adopted. The stress of cable tower foundation is complex. The stress analysis of foundation scheme is one of the key problems of this project. In this paper, the geological conditions, structural stress, economic rationality, construction convenience and other factors are comprehensively considered, the different foundation types are compared and analyzed, the reasonable foundation type and layout type are determined, and the stress of the pile and cap structure of the main tower foundation is calculated and analyzed. Through the solid finite element model, this paper analyzes the influence of the stiffness deformation of pile cap on the stress of pile group foundation. The calculation results show that the stress of dumbbell shaped pile cap is more reasonable than that of rectangular foundation pile cap, and the number of pile foundation and the calculated pile length are reduced in varying degrees. By adjusting the pile foundation arrangement under dumbbell shaped foundation, the stress of pile foundation can be more uniform, which can be used as the foundation for similar projects. The foundation design provides reference and reference.

Analysis on the structural type of large-span steel truss bridge specially designed for cables

When the installation of cables and pipelines needs to go across rivers, bridges are usually adopted to support the cables and pipelines for crossing the rivers. The measure can make full use of the space resources and have no effect on the flow pattern of rivers. For this reason, analysis on the structural-type design of a large-span steel truss bridge specially used for cables has been performed. The numerical results indicate that the stayed-cable bridge with steel truss beam and concrete main tower has better performance and improved structural type caparisoned with that of the beam and arch bridges, and the construction of the major beam can be without the temporary support.

Seismic response analysis of steel–concrete hybrid wind turbine tower

The steel–concrete hybrid wind turbine tower is characterized by the concrete tubular segment at the lower part and the traditional steel tubular segment at the upper part. Because of the great change of mass and stiffness along the height of the tower at the connection of steel segment and concrete segment, its dynamic responses under seismic ground motions are significantly different from those of the traditional steel tubular wind turbine tower. Two detailed finite element models of a full steel tubular tower and a steel–concrete hybrid tower for 2.0 MW wind turbine built in the same wind farm are, respectively, developed by using the finite element software ABAQUS. The response spectrum method is applied to analyze the seismic action effects of these two towers under three different ground types. Three groups of ground motions corresponding to three ground types are used to analyze the dynamic response of the steel–concrete hybrid tower by the nonlinear time history method. The numerical results show that the seismic action effect by the response spectrum method is lower than those by the nonlinear time history method. And then it can be concluded that the response spectrum method is not suitable for calculating the seismic action effects of the steel–concrete hybrid tower directly and the time history analyses should be a necessary supplement for its seismic design. The first three modes have obvious contributions on the dynamic response of the steel–concrete hybrid tower.

An integrated GPR and geoinformatics approach for assessing potential risks of flash floods on high-voltage towers, Makkah, Saudi Arabia

Makkah city is considered as a geologically transitional region that combines topographic and terrain features of the Sarawat Mountains to the east and the coastal plain of the Red Sea to the west and it is consisted of a semi-circular plateau cut by several structural valleys that were defined by faults and cracks. The surface runoff resulting from the rainstorms over the mountainous areas lead to the occurrence of flashfloods that debouch into the tributaries of valleys towards estuaries that encompass residential areas and municipal infrastructures. The present study assesses the negative impacts of flash floods on under-construction high-voltage towers in the valleys surrounding Makkah city using topographic analysis, Ground Penetrating Radar (GPR) surveys and field checks. Topographic modeling was implemented to delineate risky zones that are vulnerable to flash floods at the intersections between major valleys in Wadi Numan and Wadi Al Sharaya Basins and high voltage power lines. The GPR results showed the presence of three geological layers of sedimentary rocks: the first surface layer (A) is composed of alluvial sediments of fine to coarse sand with a thickness of 2 m. Followed by the second layer (B) of sand and gravel, which attains 3 m thickness. The third layer (C) consists of alluvial sediments mixed with rock fragments (diorite and quartzite diorite) and extend to a depth of more than 10 m. The GPR sections indicated that the concrete tower bases are different in thickness and depth from site to other. Different protection measures for the tower bases were suggested to avoid the adverse impacts of the flash flood. The measures varied from site to site and included the establishment of soil barriers, implementation of rocky hills, the defensive collision nets system and the concrete walls system.

Mechanical Behavior of a Multisegmented Tower Anchorage Structure with an Exposed Steel Anchor Box

A tower anchorage structure with an exposed steel anchor box is commonly used for cable‐stayed bridges. Many researchers have conducted studies on this structure by considering a single segment. However, in practical engineering, the stress of multisegmented tower anchorage structure is not completely similar to that of single segment, and the forces between segments affect each other. Hence, in this study, the mechanical behavior of a multisegment anchorage structure with an exposed steel anchor box was investigated via finite element analysis. Furthermore, the load transfer path and stress distribution characteristics of the structure were investigated. The results indicate that the horizontal component of the cable force is borne by the side plate of the steel anchor box, the diaphragm, and the side wall of the concrete tower column, while the vertical component is transmitted by the steel anchor box and concrete tower column. Under the action of this cable force, the horizontal component of the cable force borne by the middle segment increases, while the components at the two end segments decrease. The vertical force is greater on the lower tower segments. The stress levels on the side plate and on the diaphragm of the steel anchor box in the middle section are high. Under the cable force load, the frame formed by the end plate and side plate of the steel anchor box expands outward. The end plate is mainly under a tensile load, and the tensile stress level on the lower section exceeds that on the upper section. A high‐stress area for the concrete tower is observed in the steel‐concrete joint. The stud group of the anchorage structure is subjected to horizontal and vertical shear forces, and no “saddle‐shaped” distribution of the stud shear is found. An optimal arrangement method for the stud group was proposed to optimize its mechanical performance.

STUDY ON BOUNDARY CONDITIONS OF GROUND ANCHORED CABLE STAYED BRIDGE WITH SINGLE INCLINED TOWER

In order to study the influence of boundary conditions at the bottom of the tower on the structural characteristics of a ground anchored cable-stayed bridge with single inclined tower, taking a bridge project as an example, the finite element model is established to study the static, dynamic and overall stability of three structural systems, namely, universal hinge connection, unidirectional hinge connection and consolidation connection, between the bridge tower and the concrete tower base. The results show that: The internal force can be reduced by universal hinge connection between tower bridge and tower base, and structural deformation can be reduced by choosing consolidation method. However, there will be huge torque and transverse bending moment at the bottom of tower, so the consolidation system should not be selected first; the dynamic characteristics of the three systems are different, but the dynamic characteristics of the main girder are basically the same. In terms of stability, the boundary conditions have little effect on the low-order instability modes of the structure, and the stability can be considered as the final factor of the structure selection.

Practical performance-based design of friction pendulum bearings for a seismically isolated steel top story spanning two RC towers

A case study of performance-based design is presented for a seismically isolated steel structure that rests on top of two adjacent high-rise reinforced concrete towers, the latter separated by means of an expansion joint. The isolation system comprises Friction Pendulum Bearings (FPBs) that are designed to accommodate two salient characteristics of the system. First, the isolated top floor is subjected to narrow-band floor acceleration histories as the ground motion excitation is filtered by the dynamic response of the supporting towers. Second, the displacement demands imposed to the FPBs are affected by the in-phase or out-of-phase movement of the supporting structures, with the latter case potentially giving rise to higher displacement capacity requirements for the bearings. In a search for a solution beyond conventional design norms, the probability of bearing failure associated with a wide range of FPB displacement capacities was determined via an explicitly risk-consistent performance-based seismic design. Overall, the case-specific design approach is shown to be able to meet any desired performance objective, consistently determining the final compromise between safety, cost-efficiency and practicability.

Seismic response of the elevated concrete water tower considering liquid–solid–soil interaction

In the present study, the elevated concrete water tower is used as the research object. In order to investigate the ground motion response law of the elevated concrete water tower with the near-field Chichi wave, the near-field no-pulse Tehachapi Pump wave and the far-field long-period Tianjin waves when the liquid–solid–soil interaction (LSSI) is considered. And the finite element calculation model of the elevated concrete water tower and foundation with different liquid storage rate was established and the dynamic time history analysis was also conducted. The calculation results demonstrate that when considering LSSI, the elevated concrete water tower exhibits different response characteristics under the action of three types of seismic waves. Under the action of pulsed seismic waves in the near field, the seismic response of the elevated water tower structure is the most intense, followed by the far-field long-period seismic wave, and the response in the near-field no-pulse seismic wave remains the least.

Updating the bearing capacity, stresses, and strain for retrofitting reinforced concrete towers of the cellular and internet system

To retrofit reinforced concrete telecommunication towers, it is necessary to update their parameters because the structure’s bearing capacity is no longer the same as at the initial moment of commissioning. Reinforced concrete columns are elements formed from the combination of two materials—steel and concrete—making them a composite material. For the calculation of induced stresses in sections of composite materials, homogenization techniques are required. Due to the slow deformation of the concrete, as a function of the rheological behavior of the material, some of the stresses that were absorbed by the homogenized concrete section are transferred to the reinforcement, causing an increase in the initially calculated values. To evaluate the stress in the reinforcement and the structural strain, an analytical mathematical procedure with nonlinear characteristics was employed to investigate a real, slender, reinforced concrete column, for which the critical buckling load was dynamically determined. A variation of loading considering the column exclusively under its self-weight up to the imminence of instability was applied. Then, by computing the equilibrium of forces and compatibility displacements, allied to the criteria for creep, shrinkage and strength of concrete present in the European Standard EN 1992‐1‐1, Eurocode 2, it was possible to verify that the induced stresses in the reinforcement steel do not produce the material yielding so that strain does not initiate the cracking process in the concrete.

Optimal structural control of tall buildings using tuned mass dampers via chaotic optimization algorithm

Tuned Mass Dampers (TMDs) are widely used to mitigate undesirable structural vibrations that result from intensive uncertain environmental phenomena. This paper deals with the optimum tuning of the free parameters of passive and active TMDs. Novel Chaotic Optimization Algorithm (COA) is used to determine the optimal parameters for the TMD systems. This algorithm has been tested on a 10‐story shear-type frame under strong seismic motions, as well as response control of wind-excited of a 76-story concrete office tower. The numerical results reveal that the tuned mass dampers with optimum parameters have good capability in attenuating the responses of the structural system under different excitations.

Behavior study of prestressed concrete wind-turbine tower in circular cross-section

In this work, we sought to study the behavior of prestressed concrete wind-turbine tower in circular cross-section. The idea was to use Genetic Algorithm to obtain a structural optimization of the projected tower. Thus, a tower with the shape of a conical section was obtained, which minimizes the appearance of stress concentrations in the structure. The tower has a tapered profile to reduce the area subjected to wind thus lower the total weight and applied moment. It will also enhance the dynamic response of the tower and improve its overall stability. Steel tubular wind turbine towers are most widely utilized for wind turbines, however, the use of concrete material is becoming more attractive for wind towers because concrete towers are more stable for buckling failure. As the turbine size is growing and the towers are rising in height, steel towers are required to be sufficiently strong and stiff, consequently leading to high construction costs. Therefore, the prestressed concrete wind-turbine tower has a reduced construction cost compared to the steel tubular wind turbine towers or the self-supporting steel truss towers with a maximum height of 150 m. For this, Computer-Aided Engineering (CAE) tools were used and a 100 m prestressed concrete tower system for a wind turbine was optimized. It is concluded that the model met all the restrictions described and represents an economy in raw material and greater simplicity of design in relation to the octagonal model used for comparison. A new structural methodology was described for the study and application of prestressed concrete to replace the steel towers currently used.

The construction process for pre-stressed ultra high performance concrete communication tower.

Towers are important structures for installing radio equipment to emit electromagnetic waves that allow radio, television and/or mobile communications to function. Feasibility, cost, and speed of the construction are considered in the design process as well as providing stability and functionality for the communication tower. This study proposes the new design for construction of segmental tubular section communication tower with ultra-high-performance fibre concrete (UHPFC) material and prestress tendon to gain durability, ductility, and strength. The proposed mix design for UHPFC in this study which used for construction of communication tower is consisted of densified Silica Fume, Silica fine and coarse Sand and hooked-ends Steel Fiber. The prestressed tendon is used in the tower body to provide sufficient strength against the lateral load. The proposed design allows the tower to be built with three precast segments that are connected using bolts and nuts. This paper presents a novel method of construction and installation of the communication tower. The advantages of proposed design and construction process include rapid casting of the precast segment for the tower and efficient installation of segments in the project. The use of UHPFC material with high strength and prestress tendon can reduce the size and thickness of the tower as well as the cost of construction. Notably, this material can also facilitate the construction and installation procedure.

An isolation case study of a vertical caisson wall directly adjacent to an underground rail vibration source

A large concrete tower planned for construction was proposed at a site immediately adjacent to underground rail. The underground rail passenger trains pass frequently at a rate of once per 2-4 min 18–20 h per day. Excavation began and a caisson wall was constructed facing the underground vibration source. Preliminary measurements were made by placing an accelerometer on the East facing caisson wall. Attenuation was required in the 20-63 Hz frequency range. An isolation layer (GenieMat DM) was added to the caisson wall. The presentation will illustrate how this was done in combination with water proofing of the foundation and other onsite complexities. Large steel tie-backs are used to hold the caisson wall in place and these were treated to prevent any direct path for vibration. Upon completion of construction, measurements are taken and the level differences are presented. Attenuation exceeded the design and building code criteria at all one-third octave bands of concern.