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FEASIBILITY OF CASTING NEW RCC SLAB ON TOP OF EXISTING BRIDGE SLAB

 
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ronnie_singh
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PostPosted: Thu Oct 24, 2019 5:52 pm    Post subject: FEASIBILITY OF CASTING NEW RCC SLAB ON TOP OF EXISTING BRIDGE SLAB Reply with quote

Concrete slab bridge having 4 nos. of span, each 10.7 m long in the middle span and 10.4 m at the end span. i.e 10.4, 10.7, 10.7, 10.4 respectively resting on two longitudinal beam (400550 mm) i.e on both side of bridge width. For each span the longitudinal beams are connected by just one cross beam (150150 mm). This bridge across the barrage is almost 40 years old and need repairing and maintenance. The bridge slab and beams are in good condition except for the railing portion on both side is damage (i.e plaster n embedded rcc steel). In this condition is it advisable to cast 300 mm thick rcc slab on top of the existing slab. The weight of the proposed/new slab is around 30 tonne per span). kindly educate or share your knowledge regarding the feasibility of sustained loading on the existing slab. will the beam be able to sustain the proposed loading on top of existing load?. PFA in pdf for bridge


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mjnasar
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Joined: 26 Jan 2003
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PostPosted: Sun Oct 27, 2019 1:56 pm    Post subject: Reply with quote

hi,

the idea seems good

As the increase in load can be compensated by
increase in strength due to combined action of nslab concrete & existing beams ( acting Tee beams )  

this aspect should be studied before increase in load ( laying 300mm thk concrete )

and

there must be shear studs like reinforcement ( horizontal shear ) to insure the section act as one (with existing beam & slab and New concrete )

regards
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ronnie_singh
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PostPosted: Sun Oct 27, 2019 6:59 pm    Post subject: so sir, what would you suggest Reply with quote

so sir, what would you suggest ?. proposed rcc slab or skin reinforcement or just wearing coat as a repairing. will it be safe to superimposed another load in the form of integrated slab considering the age factor of the bridge ?.
N.B only the sizes of the structure is known. rest is unknown.
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bkkk
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Location: Tamil Nadu

PostPosted: Thu Oct 31, 2019 2:35 pm    Post subject: Rehabilitation of bridge. Reply with quote

Dear sefian,

You have mentioned that only railings on both sides are damaged . Why you need to go for repair of the slab.?. However, If you need to repair the slab , you can put a CC wearing coat with nominal reinforcements to  cater to secondary stresses.

Dr.Venkateswaran
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ronnie_singh
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PostPosted: Thu Nov 07, 2019 6:00 am    Post subject: Re: Rehabilitation of bridge. Reply with quote

bkkk wrote:
Dear sefian,

You have mentioned that only railings on both sides are damaged . Why you need to go for repair of the slab.?. However, If you need to repair the slab , you can put a CC wearing coat with nominal reinforcements to  cater to secondary stresses.

Dr.Venkateswaran


thank you sefian, for your valuable suggestion. i was expecting the same.
why?, Because i was under immense pressure from my superior to carry out the execution without proper investigation or evaluation just to solve an urgent matter. in spite of their persistent instruction, i stood firm to my decision not to proceed after giving possible explanation, citing personal investigation, consultation with professors, experts and fellow sefians.
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spsvasan
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PostPosted: Sun Nov 17, 2019 5:14 am    Post subject: Re: FEASIBILITY OF CASTING NEW RCC SLAB ON TOP OF EXISTING BRIDGE SLAB Reply with quote

ronnie_singh wrote:
Concrete slab bridge having 4 nos. of span, each 10.7 m long in the middle span and 10.4 m at the end span. i.e 10.4, 10.7, 10.7, 10.4 respectively resting on two longitudinal beam (400550 mm) i.e on both side of bridge width. For each span the longitudinal beams are connected by just one cross beam (150150 mm). This bridge across the barrage is almost 40 years old and need repairing and maintenance. The bridge slab and beams are in good condition except for the railing portion on both side is damage (i.e plaster n embedded rcc steel). In this condition is it advisable to cast 300 mm thick rcc slab on top of the existing slab. The weight of the proposed/new slab is around 30 tonne per span). kindly educate or share your knowledge regarding the feasibility of sustained loading on the existing slab. will the beam be able to sustain the proposed loading on top of existing load?. PFA in pdf for bridge



Dear Er.Ronnie Singh

Since the bridge is about 40 years old, it is prudent to inspect the bottom of the bridge carefully. If corrosion is observed in the soffit of the slabs and the beams, remedial actions may be taken along with remedial actions for the handrails

S.P.Srinivasan
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spsvasan
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PostPosted: Mon Nov 18, 2019 1:53 am    Post subject: Re: FEASIBILITY OF CASTING NEW RCC SLAB ON TOP OF EXISTING BRIDGE SLAB Reply with quote

spsvasan wrote:
ronnie_singh wrote:
Concrete slab bridge having 4 nos. of span, each 10.7 m long in the middle span and 10.4 m at the end span. i.e 10.4, 10.7, 10.7, 10.4 respectively resting on two longitudinal beam (400550 mm) i.e on both side of bridge width. For each span the longitudinal beams are connected by just one cross beam (150150 mm). This bridge across the barrage is almost 40 years old and need repairing and maintenance. The bridge slab and beams are in good condition except for the railing portion on both side is damage (i.e plaster n embedded rcc steel). In this condition is it advisable to cast 300 mm thick rcc slab on top of the existing slab. The weight of the proposed/new slab is around 30 tonne per span). kindly educate or share your knowledge regarding the feasibility of sustained loading on the existing slab. will the beam be able to sustain the proposed loading on top of existing load?. PFA in pdf for bridge



Dear Er.Ronnie Singh

Since the bridge is about 40 years old, it is prudent to inspect the bottom of the bridge carefully. If corrosion is observed in the soffit of the slabs and the beams, remedial actions may be taken along with remedial actions for the handrails

S.P.Srinivasan



Dear Er.Ronnie Singh

In continuation of my ealier posting, even if corrosion cracks are not visible in the bottom surfaces, half cell potentials should be measured to check whether corrosion cracks are imminent

S.P.Srinivasan
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ronnie_singh
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Joined: 24 Oct 2019
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PostPosted: Tue Nov 19, 2019 6:41 pm    Post subject: Re: FEASIBILITY OF CASTING NEW RCC SLAB ON TOP OF EXISTING BRIDGE SLAB Reply with quote

spsvasan wrote:
spsvasan wrote:
ronnie_singh wrote:
Concrete slab bridge having 4 nos. of span, each 10.7 m long in the middle span and 10.4 m at the end span. i.e 10.4, 10.7, 10.7, 10.4 respectively resting on two longitudinal beam (400550 mm) i.e on both side of bridge width. For each span the longitudinal beams are connected by just one cross beam (150150 mm). This bridge across the barrage is almost 40 years old and need repairing and maintenance. The bridge slab and beams are in good condition except for the railing portion on both side is damage (i.e plaster n embedded rcc steel). In this condition is it advisable to cast 300 mm thick rcc slab on top of the existing slab. The weight of the proposed/new slab is around 30 tonne per span). kindly educate or share your knowledge regarding the feasibility of sustained loading on the existing slab. will the beam be able to sustain the proposed loading on top of existing load?. PFA in pdf for bridge



Dear Er.Ronnie Singh

Since the bridge is about 40 years old, it is prudent to inspect the bottom of the bridge carefully. If corrosion is observed in the soffit of the slabs and the beams, remedial actions may be taken along with remedial actions for the handrails

S.P.Srinivasan



Dear Er.Ronnie Singh

In continuation of my ealier posting, even if corrosion cracks are not visible in the bottom surfaces, half cell potentials should be measured to check whether corrosion cracks are imminent

S.P.Srinivasan



Thanks for the valuable suggestion, The concerned authority have already taken the remedial action by casting 100 mm thick skin reinforcement on top of the existing slab and repairing of railing etc.
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