Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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REHABILITATION OF OLD NAGA-HAMMADY BARRAGE BRIDGE

Salah El-Din Sayed Mohamed

Researcher, National Water Research Center, Mechanical and Electrical Research Institute, Delta Barrage, Egypt

E-mail: Salah55333@gmail.com ABSTRACT When the Old Naga Hammady Barrage has been constructed in 1930, it had a navigation lock on the western side of the barrage. In 1993, a new navigation lock has been constructed in the western side of the old lock. Each lock has a movable bridge to allow the high ships to pass from north to south and vice versa. The bridge of the new navigation lock is suffering from technical problems pampering the bridge movement and makes it out of work. This paper studies the problems, causes and the factors affecting these problems. During this study, field inspection and measurements were carried out as well as analytical study was performed. The study concluded that the main factor affecting the bridge and causing the major problem is that the bridge is subjected to overloading due to passing heavy trucks over it although the original design is performed to carry the loads less than thirty tons. The other important factor is the bad installing of the concrete bases in the four corners. As it plays an important role for instability causing misalignment where in turn leading to breaks the various elements of the operating system in the lifting and the rotating mechanisms. To overcome the problems affecting the bridge, the study recommends a new design must be performed to the bridge and girders must be added to enable the bridge to carry seventy ton Lorries. The cam supporting system should be replaced by a sliding supporting system in the lifting mechanism and the damaged axis shafts, bearings and pinion should be replaced by new ones. Also, a good alignment and stability should be carried out for all mechanical parts. The recommended design helps safety, durability, and stability of the system. Keywords: Swing Bridge, Stability, Operating mechanism 1. INTRODUCTION The old Naga Hammady Barrage is one of the seven oldest grand barrages on the Nile in Egypt. It is located at 14 km north of the Naga Hammady railway bridge at kilo 588 from Cairo along the river. It has been constructed during the period from 1927 to 1930. It has 100 vents, each is 6 m wide. It was controlling the water levels in the area between the downstream of new Esna Barrage and the upstream of Assiut Barrage. Currently, and after constructing the New Naga Hammady Barrage, the gates of the barrage have been lifted and the barrage is not used any more for water regulation. The barrage has two navigation locks. The first lock is at the west side of the barrage. It has

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ���

80 by 16 meters chamber. The second navigation lock is constructed at the west of the first one. It has 155 by 17 meters chamber. Each lock has a movable bridge of the swing type. The swing bridge of the second lock is suffering from serious problems in the mechanical operating system. These problems cause breaks in the gearboxes, shafts and bearings, and therefore the operating system of the bridge is out of operation. This study concentrates on the problems affecting this bridge, determines the factors leading to them, and analyzes the causes of each. It also gives the solution for each problem to adjust the current situation and ensures safety and stability of the bridge. Figure 1 shows old Naga Hammady Barrage.

Fig. (1) Old Naga Hammady Barrage 2. DESCRIPTION OF THE BRIDGE 2-1- General Description The bridge is a through welded steel plate girder swing bridge. It crosses the lock from downstream. The bridge centerline is shifted from the axis line of the barrage by 4.1 meters. The bridge is designed to carry 30 ton and modified to carry 70 tons. It provides a roadway of 8 meters clear width with two sidewalks one meter wide each. The total deck width is 10 meters. The total width of the steel superstructure is 11 meters. The bridge has two unequal arms from the semi-through type construction. The radius of the long arm is 24.10 meters. The radius of the short arms is 11 meters. The total length of the bridge is 36.10 meters. The bridge provides 17 meters clear span for navigation and the distance between the two extreme bearings is 32.5 meters. The

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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roadway deck level above the turntable is + 71.37 meters and above the abutments are + 71.33 meters and + 71.27 meters. The level of the bottom of the main girder above the turn table is + 69.97 meters. The level of the top of the reinforced concrete slab supporting the turn table is + 69.15 meters. In longitudinal direction the roadway is horizontal above the turntable over a length of 10 meters from the end of the short arm. It has a slope angle of 1.5° and a slope of 0.22° at the end of the long arm. The thickness of the concrete pavement over on the carriage way is 7 centimeters. The transverse slope of the road way is 1.6°. The reinforced concrete slab of the footway depth is 200 millimeters and the transverse slope of the footway is 6.3°. Figure (2: a, b, & c) shows the bridge in case of closing (a), opening (b) and during a ship passes (c).

(a) (b) (c)

Fig. (2) Naga Hammady Bridge 2.2. Bridge Material The material of the steel in the bridge is mild steel of grade 37 – 3 according to DIN 17100. 2.3. The Bridge Construction The steel structure of the bridge consists of two main girders, cross girders and stringers. The main cross girders and main stringers are diagonal girders. The reinforced concrete deck slab is supported by stringers and cross girders. The counter weight is made of cast iron blocks having geometrical shapes 7.2 ton/m3. The structure of the bridge is supported by a circular girder, rolling bearing. All steel girders are welded constructions. The connections of the main girders are welded joints. The two main girders spaced at 10.5 meters. The normal cross girders are spaced at 3.2 meters while the two normal stringers are spaced at 2.8 meters. These normal stringers are welded over the circular girder; the main girders are connected with the two main cross girders which are connected together with the two main stringers to constitute a girder system for distributing loads over the circular girder and the diagonal girders. The main cross girder has a box cross section: The main stringers are diagonal beams. The circular girder supports the structure at sixteen points, evenly distributed along its centerline. Each corner of the bridge is ended by curved cross girders at the long arm.

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ���

The bearings and the gearboxes of the swing system are fastened to the bottom of the straight end of the cross girders respectively. For wind bracing, there is lateral bracing between the two main girders on the long arm, and on the short arm, cross girder at the end of the counter weight side and cross girder at the end of the long arm. The counter weight is made of cast iron blocks and has a designed weight of about 215 tons. The reinforced concrete slab has a thickness of 16 centimeters on the roadway and 10 centimeters on the walkway and over the turntable the thickness is 15 cm. The total weight of the steel super structure above the circular girder is 136 tons [1]. 2.4. The Bridge Mechanical System 2.4.1 The Lifting Mechanism There are four supports at the four corners of the bridge for carrying and moving the bridge up and down. The operating mechanism for supports' operation is a cam system. It consists of two electric motors which drive the lifting mechanism. Each motor is connected to a gear box. Each gearbox has two outputs. Each output is connected to a shaft coupled with connectors to a cam. The cam is in contact with a concrete base. The cam rotates around an axis which gets its movement through the lifting operating mechanism. Each end has a locking hand to lock the bridge from moving during settling the bridge for crossing people and cars safely. The lifting process for the bridge supports could also be done manually. 2.4.2 The Rotating Mechanism The rotation group rotates the bridge by an angle 90° for opening and closing the navigation lock for navigation purposes. This rotation process could be done manually by four persons or electrically by using two electric motors. Each motor is attached to a gearbox fixed to the abutment. The gearbox in coupled to a pinion. The pinion is meshing with a rack has a circular shape. Each rack is a quarter of circle. The two racks are opposite to each other. 3. FIELD INSPECTIONS AND MEASURMENTS The different parts of the bridge were visually inspected, where the breaking and failure were found mostly in the bearings, gearboxes and shafts. Deflection measurements were carried out. Electrical measurements were carried out at the operating switch gears under the bridge and in the control room.

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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3.1. Visual Inspection a. From the visual inspection that has been carried out on the structure of the bridge,

the following observations were noticed: 1- Cracks and breaks are found in the concrete slab or deck of the bridge due to

passing of heavy trucks. 2- Three concrete parts were put on the slab for supporting it. 3- The constitution stones below supports are broken and the bonding concrete is

failed. 4- The level of the concrete surface contacting with the cam are moving down by

35 mm in the eastern supports. 5- Due to the moving down of the eastern supports, the left arms of the main

girders were moved down by 35 mm, so, the lifting mechanism can not be operated.

6- The ending cross girders are subjected to creeping stress leading to some welding between the ending girders and the fixed areas from the east and west sides.

7- Two concrete counter weights 2×2×2.5 m3, 12.5 tons were placed on the western side to compensate the deference in weight due to creep.

8- These counter weights solved the problem of not moving temporary for two years. After this period, the bridge return back to stop working.

Figure 3 shows a bridge deck where Figure 3 (a) shows a failed part replacement of the slap where Figure 3 (b) shows the lock of the bridge.

(a) (b)

Fig. (3) The bridge deck b. From the visual inspection that has been carried out on the lifting mechanism, the

following observations were noticed: 1- All lifting mechanisms at the four supports are out of work due to

instability which causes over loading in the operating system preventing them from the lifting motion.

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ��

2- The heights of the four bases which the cams contact with are not on the same level, so, the lifting motion couldn't be operated simultaneously.

3- Breaks were found in different locations in the body of the gearboxes and bearings. Some of these breaks were welded and broken again.

4- All transmission shafts and transmitters were unstable. 5- The limit switches for stroke ending were out of work [2].

Figure 4 (a, b & c) show the western supports cam system lifting mechanism. Figure 5 (a, b & c) show the eastern supports cam system lifting mechanism.

(a) (b) (c)

Fig. (4) Western supports

(a) (b) (c)

Fig. (5) Eastern supports c. From the visual inspection that has been carried out on the swing (opening and

closing) mechanism, the following observations were noticed: 1- The operating mechanism is out of work due to instability which causes

over loading in the operating system preventing them from the swing motion.

2- Crakes were found in the concrete foundation of the bridge on which the axis of rotation of the bridge is fixed.

3- Breaks were found in different locations in the body of the gearboxes and bearings. Some of these breaks were welded and broken again.

4- The base of the southern motor is broken and the pinion attached with this motor has wear in its teeth due to the instability.

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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5- The limit switches for stroke ending were out of work [2]. Figure 6 (a) shows the circular girder and the circular rake in the rotating (swing) mechanism.

(a) (b)

(c) (d)

(e) (f)

Fig. (6) Swing mechanism

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ���

Figure 6 (b) shows the circular girder and the circular rake in the rotating (swing) mechanism and the counter weights. Figure 6 (c) shows part of the circular rake meshing with the pinion in the rotating (swing) mechanism. Figure 6 (d) shows part of the circular girder and part of the circular rake meshing with the pinion and the motor axis of rotation in the rotating (swing) mechanism. Figure 6 (e) shows the part of the circular rake meshing with the pinion and the motor axis of rotation in the rotating (swing) mechanism. Figure 6 (f) shows the electric motor in the rotating (swing) mechanism. 3.2. Deflection Measurements Deflection measurements were carried out using an electrical dial gauge at the main girders. During measurements, a load more than 30 tons has been considered to be used in all cases, dead load and live load. The accuracy of the electrical dial gauge is 0.01 mm and it is located at a reference plant at 0.5 meters from the rollers. The values of deflection at left and right girders are shown in Table (1).

Table (1) Values of deflection at the left and right girders

Value of deflection at distance 0.5 meter from the girder Girder/Loading Dead Load

(mm) Live Load

(mm) Left 2 3

Right 1 1.5 4. ANALYTICAL ANALYSIS A structure analysis using sap 2000 is performed and the numerical model for the bridge during closing is shown in Figure (7). The numerical model study shows that maximum stresses 4000 kg/cm2 were found on the circular girder. The allowable stress is 1400 kg/cm2 [3]. The maximum stress is greater than allowable stress. So, the bridge must be supported by additional girders and stiffeners to carry the excess in loads [4].

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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Fig. (7) The numerical model of the bridge during closing process

5. DISCUSSIONS The field inspection and measurements show that the greatest factor causes the problem is the kind of supports. The operating system used is the cam system. It is a good lifting system if it is accurately installed. The concrete bases in the four corners should be at the same level. The inequality in the base levels in the four supports is the main reason for causing the bridge to be out of work. The inequality in the base levels caused creep in the ends of the bridge. The creep causes failure in the concrete bases leading to increase the creep. The deflection resulting from the creep caused misalignment in the axis and shafts of the lifting system. This misalignment makes the operating system instable. This instability caused the failure which showed in the body of the gearboxes and bearings and the wear which appears at the teeth pinion. The cam supporting system should be replaced by a sliding supporting system to overcome the difference in the levels of the bases. There is an important factor affecting the bridge stability and caused the problem of the bridge. This factor is the overloading due to the heavy trucks passes. The bridge is designed to support 30 tons but more than 70 tons pass. These overloads increase the values of the bending moment. This increase in the bending moment increases the values of creep stress which causes a deflection in the main girders and stringers. The creep affects also the cross girders.

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ���

6. RECOMMENDED SAFE DESIGN The following design represents the optimum calculation parameters for safety of the bridge to carry 70 ton loads. The results of the calculations are summarized as follows: Total load Q = 4905000 N Diameter of circular roller path D = 9.8 m Number of rollers = 40 The torque due to rolling friction of the rollers Md1 = 103005 Nm Sliding friction due to pressure of rollers, acting in outward direction S = 280285.7 N

Sliding resistance on the face of rollers, with relation to the circumference of rollers Md2 = 39352.11 Nm Sliding friction due to the weight of roller cage on roller axles [5] M3 = 2575.125 Nm

The moment due to the acting of wind on the bridge is M4 M4 = 217649.1 Nm

The total rolling resistance moment Md = Md1 + Md2 + M3 + M4 = 362581.33 Nm Adding 10% for neck bearing friction = 36258.13 Nm

The overall moment = 398839.4 Nm Toothed rim and roller's pinion calculations

The force acting on a tooth is F = Ft/cos� = 45511.27 N The torque on the roller's pinion Torque = 8339.488 Nm The force acts on the first spur gear transmission is F = 22326.3 N Calculations of main shafts

1. Pinion shaft 1 The overall stress is:

� � � σ� � = 2323.854 MPa 2. Shaft of first back gear The diameter of shaft is 90 mm

The overall stress is�σ� � = 2481.957 MPa 3. Shaft of spokes The diameter of shaft is 80 mm

Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt

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Computation of the conical rollers [6]

The total load = 13636.36 kg

Computation of the lower circular roller path

The tensile load of roller track, bσ , is calculated as:

34999.0bEIE

WP

ub =σ

The pressure between concrete and rail is:

32

2813.0bIE

EPW u

c =

where:

P = load due to rollers = 13636.36 kg E = modulus of elasticity for steel Eu = modulus of elasticity for concrete I = moment of inertia of the cross section of roller track Wc = Moment of resistance of the cross section of roller track

Roller track loadings

Bending stress of roller track � σ�= 1360.734 N

Contact pressure between roller track and concrete P = 114.7297 N

7. CONCLUSION AND RECOMMENDATION According to the field inspections and measurements and theoretical analysis, there are some factors that cause the problems which make the bridge out of work. These factors can be summarized as follows:

• Inequality in the base levels in the four supports. • Overloading from the passes of the heavy trucks. • The creep affects on the main girders and cross girders. • The misalignment in the operating shafts. • The instability in the operating components.

The following recommendations should be implemented for safety and good rehabilitation of the bridge structure:

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Fourteenth International Water Technology Conference, IWTC 14 2010, Cairo, Egypt ���

• Adjust the levels of the foundation and the bases of the axis of rotation of the bridge and the bases of supports.

• Redesign the slab; the girders, the bases and the counter weight of the bridge to carry live load 70 tons.

• Reinstall the bridge with the supporting girders. • The cam supporting system should be replaced by a sliding system to

overcome the difference in the base levels. • The rollers should be tested and change the damaged ones in addition to

adding the ones according to the new design. • All spindles, shafts, bearings, couplings and gearboxes should be replaced. • The western pinion should be replaced. • Good installation for all operating components should be carried out. • Stability should be insured in all directions. • Electrical motors should be tested and the damaged ones should be changed. • Electrical cables should be installed instead of the old ones. • The measuring gauges and other elements in the switch gears should be tested

and the damaged ones should be replaced. REFERENCES [1] BSMU, "Data Book of Naga Hammady Barrage", Technical Data Book, Barrages

Safety Mentoring Unit, Reservoirs and Grand Barrages Sector, Ministry of Water Resources and Irrigation, Egypt, 1996.

[2] CRI, "Study the Rehabilitation of Naga Hammady Bridge Lock and Asuit Culvert Gates", Technical Report, Construction Research Institute, National Water Research Center, Egypt, 2009.

[3] MERI, "Study the Rehabilitation of Naga Hammady Bridge Lock and Asuit Culvert Gates", Technical Report, Mechanical and Electrical Research Institute, National Water Research Center, Egypt, 2009.

[4] Nazeeh Asad Younan, "Irrigation Engineering", Part 1 and Part 2, Faculty of Engineering, Alexandria University, Egypt, 1996-1.

[5] Nazeeh Asad Younan, "Regulators", Faculty of Engineering, Alexandria University, Egypt, 1996-2.

[6] Egyptian Code for Irrigation and Drainage, 2001.