Concrete pier

A typical large three-phase ferroalloy furnace using prebaked carbon electrodes is shown in Eigure 4. The hearth and lower walls where molten materials come in contact with refractories are usually composed of carbon blocks backed by safety courses of brick. In the upper section, where the refractories are not exposed to the higher temperatures, superduty or regular firebrick may be used. The walls of the shell also may be water-cooled for extended life. Usually, the furnace shell is elevated and supported on beams or on concrete piers to allow ventilation of the bottom. When normal ventilation is insufficient, blowers are added to remove the heat more rapidly. The shell also may rest on a turntable so that it can be oscillated slightly more than 120° at a speed equivalent to 0.25—1 revolution per day in order to equalize refractory erosion or bottom buildup. 

Furnace Design. Modem carbide furnaces have capacities ranging from 45,000 t/yr (20 MW) to 180,000 t/yr (70 MW). A cross-section of a 40 MW furnace, constmcted in 1981, having a 300 t/d capacity is shown in Figure 2. The shell consists of reinforced steel side walls and bottom. Shell diameter is about 9 m and the height to diameter ratio is shallow at 0.25 1.0. The walls have a refractory lining of 0.7 m and the bottom has a 1-m layer of brick topped by a 1.5-m layer of prebaked carbon blocks. The steel shell is supported on concrete piers and cooling air is blown across the shell bottom. A taphole to withdraw the Hquid carbide is located at the top of the carbon blocks. 

The main value of the counterforce technique is that it requires only half the explosive needed to accomplish the same result using standard formulas and placement. For example, a 14 inch diameter timber which requires 3% pounds of plastic explosive to cut conventionally can be sheared in two with counterforce charges of % pound each. Reinforced concrete piers 2 feet by 2 feet which can be broken conventionally by 17 pounds of explosive can be broken by counterforce charges of 4 pounds each. 

Mushroom- The unacceptable occurrence when the top of a caisson concrete pier spreads out and hardens to become wider than the foundation wall... 

Even at densities of the order of 5 Amp/m the possible hydrogen-induced cracking does not favor electrochemical method of chloride removal from prestressed concrete structures. Pilot scale treatments showed it to be feasible and simple to treat full-sized reinforced-concrete bridge members, although difficult to conduct the treatment on concrete piers. One of the main difficulties is to predict the duration of treatment to reach the chloride levels to acceptable levels where corrosion is under control. Preliminary studies suggested a total charge of 600-1,500 A-h/m with a total treatment time of 10-50 days. 

In this paper, the current seismic retrofitting systems for reinforced concrete piers/columns and bridge-falling prevention systems at the abutments and piers in Japan were studied. The application of epoxy resin for both systems was investigated and discussed. Furthermore, seismic design and construction for newly built structures were also introduced. 

Seismic Retrofit of Existing Concrete Piers/Columns... 

Damages of concrete piers as shown in Fig. 1(a) were caused by lack of flexural capacity or shear capacity of existing structures against seismic forces. Particularly, extensive damages were observed at the base part of the pier and at the termination of longitudinal re-bars at mid-height. Therefore, in piers with inadequate lateral reinforcement, it is imperative to provide additional external confinement to insure ductility of the piers. 

Typical jacketing methods as shown in Fig. 2 are adopted for the reinforcement to compensate the structural deficit of the concrete piers [2]. The jacketing methods were decided by considering the following factors increase of dead-weight, working space, clearance limit, duration of construction, and maintenance, as described in Fig. 3. 

Steel Jacketing Method. Concrete piers/columns are covered by steel plate in steel jacketing method as shown in Fig. 2 (b) and Fig. 4. The characteristics of this method [3] are represented by the following points. 

Figure 3 Flow chart to decide jacketing method for concrete pier...

Figure 4 Steel jacket attachment for concrete piers with rectangular shape...

Carbon/Aramid Fiber Sheet Jacketing Method. The application of carbon/aramid fiber sheet for the reinforcement of concrete pier is adopted when restricted conditions are present on site, such as no permit of sectional increase due to clearance limit or weight increase on the foundation. The sheet in longitudinal direction is effective to increase the flexural strength and the sheet in transverse direction acts as lateral reinforcement to raise the shear strength. Particularly the fiber sheet is concentrically bonded at the termination of longitudinal rebar at the mid-height. 

In order to install these devices, steel bolts are anchored in existing concrete pier/abutment by use of epoxy resin, as shown in Fig. 8. The minimum thickness of steel bracket is 22mm and the length of bore hole is 15 times more than diameter of anchoring rebar. Two types of epoxy resins, namely liquid resin and grease type resin, as shown in Table 1 are used for the anchoring. 

Figure 8 Attachment of bracket to concrete pier/abutment...

In this study, the current seismic retrofitting for concrete piers/columns and bridge falling prevention systems after the Great Hyogo-Ken Nanbu Earthquake in Japan were introduced and discussed. The main results corresponding to polymers are summarized as follows ... 

Three types of jacketing methods using either reinforced concrete, steel or fiber as seismic retrofit to increase the flexural and shearing strength, and ductility of existing concrete piers are adopted. For steel jacketing method, liquid epoxy resin is effectively used for injection in the space between steel jacket and concrete piers. 

Horizontal tanks are supported by steel saddles mounted on concrete piers. Top plates of the saddles are welded to the shell of the tank and span at least 120° of the circumference of the tank. 

Shiotani T, Nakanishi Y, Iwaki K, Luo X, Haya H (2006) Evaluation of reinforcement in damaged railway concrete piers by means of acoustic emission, Journal ofAE 23 260-271... 

In order to know accelerations due to the train passage, accelerometers were placed in the gravity (vertical or axial) direction on the concrete pier. The frequency response of the accelerometer (750WI, TEAC) was from 3... 

Fig. 14.20. AE sensor array and 3-D source locations of AE events in a concrete pier.

Shiotani T, Nakanishi Y, Iwaki K, Luo X, Haya H (2006) Evaluation of reinforcement in damaged railway concrete piers by means of acoustic emission. AEWG, Journal of Acoustic Emission 23 260-271 Yuyama S, Okamoto T, Shigeishi M, Ohtsu M (1994) Quantitative evaluation and visualization of cracking process in reinforced concrete by a moment tensor analysis of acoustic emission. ASNT, Materials Evaluation 53 751-756... 

Fujino, Y., Hashimoto, S., and Abe, M. (2005). Damage analysis of Hanshin expressway viaducts during 1995 Kobe earthquake. I Residual inclination of reinforced concrete piers . Journal of Bridge Engineering, 10(1) 45-53. 

Ikeda, S., Nonaka, S., Hirose, S., and Yamagushi, T. (2002). Seismic performance of concrete piers prestressed in the critical section . In Proceedings of the First FIB Congress, Osaka, Japan, 47-48. 

Masukawa, J., Akiyama, H., and Saito, H. (1997). Retrofit of existing reinforced concrete piers by using carbon fiber sheet and aramid fiber sheet . In Proceedings of the Third International Symposium on Non-Metallic (FRP) Reinforcement for Concrete Structures, Vol. 1. 

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