THEORY EXAMINATION (SEM–VI) 2016-17 ADVANCED CONCRETE DESIGN

ADVANCED CONCRETE DESIGN (ECE021)

Time: 3 Hours  Max Marks: 100

(Use of IS:456 & IS:3370 allowed, M20 concrete, Fe 415 steel)

SECTION–A (Short Answer Questions)

(10 × 2 = 20 Marks)

(a) Joints in water tanks

Joints in water tanks are provided to control cracking and leakage. Common types are construction joints, expansion joints, and contraction joints. These joints are usually sealed with water bars to ensure water tightness.

(b) Determination of capacity of water tank

Capacity of a water tank is determined based on population demand, per capita water requirement, storage period, and future expansion as per design standards.

(c) Live load for gathering spaces

As per IS codes, live load for gathering spaces such as halls and auditoriums is generally taken as 4 to 5 kN/m², depending on occupancy.

(d) Codes on culvert design

Culvert design in India is governed by IRC:6 (Loads), IRC:21 (RCC bridges), and IS:456 for concrete design.

(e) Building frames

Building frames are structural systems consisting of beams, columns, and slabs connected together to resist vertical and horizontal loads safely.

(f) Earthquake loads

Earthquake loads are lateral forces induced in a structure due to ground motion during seismic activity. These loads depend on seismic zone, importance factor, and structural characteristics.

(g) Seismic zone

A seismic zone is a region classified based on earthquake intensity and risk. India is divided into Zones II, III, IV, and V.

(h) Increase in seismic load from Zone II to Zone III

When moving from Zone II to Zone III, seismic load increases by approximately 1.6 times, because the zone factor increases.

(i) Wind zones in India

India is divided into wind zones with basic wind speeds of 33 m/s, 39 m/s, 44 m/s, 47 m/s, and 50 m/s.

(j) High performance concrete

High performance concrete (HPC) is concrete with high strength, durability, workability, and low permeability, achieved using mineral admixtures and chemical admixtures.

SECTION–B (Long Answer Questions)

(Attempt any FIVE – 5 × 10 = 50 Marks)

2(a) Design requirements for water tanks as per IS:3370

IS:3370 specifies that water tanks should be designed for crack control, water tightness, and durability. Permissible stresses are lower than those for ordinary RCC structures. Minimum reinforcement and proper joint detailing are mandatory.

2(b) Analysis of building frame for lateral loads

Building frames are analysed for lateral loads due to wind and earthquakes. Methods include:

Approximate methods (portal method, cantilever method)

Exact analysis using stiffness method or software
Load combinations are applied as per IS:456 and IS:1893.

2(c) Raft foundation for overhead water tank

Raft foundation is used when soil bearing capacity is low. It distributes load uniformly over a large area and prevents differential settlement. It consists of a thick RCC slab supporting staging columns.

2(d) Design of deck slab for concentrated load

Deck slab design involves calculating bending moments due to concentrated wheel loads using effective width concept. Slab thickness and reinforcement are provided based on bending and shear criteria.

2(e) Concept of exact analysis

Exact analysis considers actual stiffness of members and boundary conditions. For example, multistory frames analysed using matrix methods give accurate bending moments, shear forces, and deflections.

2(f) Codal recommendations on RCC bridge design

RCC bridges are designed as per IRC codes considering dead load, live load, impact factor, wind load, and seismic effects. Proper durability and serviceability checks are essential.

2(g) Design of deck slab in RCC culvert

The deck slab is designed for dead load, earth fill, and live load. Reinforcement is provided in longitudinal and transverse directions based on bending moment calculations.

2(h) Elements of RCC culvert and loads

An RCC culvert consists of deck slab, side walls, foundation, and wing walls. Loads include dead load, live load, earth pressure, and water pressure.

SECTION–C (Very Long Answer Questions)

(Attempt any TWO – 2 × 15 = 30 Marks)

3. Design of RCC dome of Intze water tank (250 kL)

Given:
Capacity = 250 kL                     Staging height = 22 m                           SBC = 12 kN/m²

Procedure (outline):

Assume tank dimensions based on capacity               Calculate water load and self weight

Determine dome thickness                                          Calculate meridional thrust and hoop stress

Provide reinforcement as per IS:3370

The dome is designed as a thin shell structure mainly resisting compressive forces.

4. Design moments calculation in 6-storey three-bay RCC frame

Moments are calculated using:                                    Approximate methods for preliminary design

Exact analysis using stiffness method

Steps include load calculation, distribution of lateral forces, determination of bending moments, shear forces, and deflections for beams and columns.

5. Design of single slab bridge

Given:                                                                          Clear span = 5 m
Carriageway width = 7.5 m                                          Live load = IRC Class AA

Design steps:                                                               Calculate dead load and live load

Apply impact factor                                                       Determine bending moment and shear force

Design slab thickness and reinforcement                     Check shear and serviceability

The bridge slab is designed as an RCC slab supported on abutments.