Appendix III. A. Classification of Concrete Bridge Components

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1 Appendix III A. Classification of Concrete Bridge Components 1. Concrete beam/girder Concrete beam-type bridges normally can be classified into two types. One is the T beam bridge which is generally a cast-in-place monolithic deck and beam system. The other is the precast, prestressed beam with a cast-in-place deck. They can take various shapes, such as rectangular beam, Inverted Tee beam, 1-Beam, M-Beam and U-Beam. Concrete beams and girders are mainly load-carrying elements of bridge superstructure. 2. Deck slab Deck slab is the physical extension of the roadway across the obstruction to be bridged and it is a part of the bridge structure that has direct contact with the vehicle or live load. The main function of the deck is to distribute loads alone the bridge cross section or transversely. The deck either rests on or is integrated with a frame or other structural system designed to distribute loads along the length of the bridge or longitudinal]y. 3. Pier Piers are structures which support the superstructure at intermediate points between the end supports. A pier is also designed to sustain superstructure dead and live loads and transmit all loads to the foundation. Piers allow the total length of the bridge to be divided into variable span length. Footings, columns, and caps are the main elements of piers. Columns transmit vertical load and moment to the footing. If a single column is used, it is sometimes referred to as a stem and the unit is called a hammerhead pier. A solid wall, instead of individual columns is called as a solid wall pier. Others types of pier are pile bents and reinforced frame on pile foundation. 4. Bearing Bearings are provided over the bridge supports and they are mechanical system which transmit the vertical loads of the superstructure to the substructure. Bearings are also used to accommodate expansion and contraction movements between different parts of the structure and to damp down vibrations and minimize the effect of impact loading. Bearings can be free or fixed. Bearings allowing both rotation and longitudinal translation are called expansion bearings, and which allow rotation only are called fixed bearings. 5. Abutment/Wingwall Abutments are earth-retaining structures which support the superstructure and overpass roadway at the beginning and end of a bridge. They are provided to transmit the reaction of superstructure to the foundation, retain the earth filing and connect the superstructure to the approach roads. Abutment is normally composed of a footing, either spread or pile, a breast wall, a bridge seat, a backwall and wing walls. The common types of abutments are bank seat, retaining wall and pile bents. 6. Drainage/Gutter The drainage system in a concrete bridge can be composed of a variety of elements. Deck drains, weep tubes and scuppers can be used to carry water off the deck, while gutters drain runoff from the site and structure proper. 7. Parapet ApxIII.1

2 Parapet is the vertical wail located at the outermost edge of the bridge deck. They are provided mainly for vehicular and pedestrian and designed to take certain impact load and hence preventing vehicles from falling off the bridge. Two common types of parapet are new jersey parapet with galvanized railing and standard kerb with steel railing. 8. Pavement Surfacing or pavement forms the wearing surface of the bridge deck. The wearing surface is the portion of the deck cross section which resists traffic wear. In most instances this is a separate layer made of bituminous material. Reinforced concrete decks are typically covered with premix surfacing. The wearing course usually varies in thickness from 2 to 4 inches (51 to 102 mm). 9. Expansion joint Expansion joints are provided at joints between span members to accommodate various movements at the joints. The common types of joints are asphalt plug joint, reinforced elastomeric joint, covered gap joint and compression seal joint. The type of joint selected for a structure is generally dependent on the type and magnitude of motion the joint is required to accommodate. Deck joints can provide for longitudinal and transverse movement as well as rotation caused by thermal expansion and loading condition. 10. Slope protection/river bank Embankment or slope protection are slope fill or cut in the vicinity of the structure. The sloping faces of the embankments may be protected from the effects of erosion or scour by some form of slope protection system such as rubble pitching and gabion mattress. Slope protection could be made of dry stone or even block pavement material. The form of slope protection varies greatly dependent on specific environmental concerns and types of material readily available. 11. Headwall/Wingwall/Apron Wingwall is a side wall to the abutment to support and protect the embankment. Wingwall can be poured monolithically with the abutment backwall to form a single, integrated structure or placed a joint between the backwall and the wingwall to create the effect of the wingwall acting as a cantilever retaining wall by itself. 12. Culvert Culvert is element in bridge structure which used as a stream crossing or underpass. Culverts are normally covered by embankment material and designed to support the dead load of soil arid as well as live load of traffic. A culvert is designed to transport discharge or runoff away from bridge structure and must be able to handle the water flowing through a channel at any particular time without exceeding the headwater depth allowable. When a culvert ceases to function, possible flooding can be quite destructive and consequently create quite an expense. Should malfunctions occur, embankments, roadways, and nearby property can be subjected to extensive damage. B. Inspection of Deterioration Effects for Each Concrete Bridge Component Deterioration Effects in Concrete Beam/Girder Cracking, spalling, corrosion of reinforcement and abnormal vibration are deterioration effects normally found in a concrete beam. Cracking in concrete beam can be detected in various patterns such as map cracking. diagonal cracks and vertical cracks. Diagonal cracks indicate an incipient failure. whereas vertical cracks may indicate an excessive degree of stressing in flexure. The size and distribution of cracks should be noted and some attempts made to determine their penetration, if cracking is severe. ApxIII.2

3 Spalling may occur due to the friction from movements and high edge pressure at bearing. Corrosion of reinforcement in concrete beam can sometimes be detected with the indications of inadequacy of concrete beam cover which appear as rust stains on the surface of concrete. Abnormal vibration can be detected by standing on the midspan of the superstructure when vehicles pass. If any abnormal vibration in concrete beam detected, the rating should be ranked as critical based on the JKR Condition Rating B.1.Deterioration Effects in Concrete Deck Slab Cracking, spalling, corrosion of reinforcement and water leak are most common deterioration effects found in concrete deck slab. Cracking and spalling typically proceeds from the top of the deck down through the slab to the bottom. Map cracking is normally found in concrete deck slab. Cracking can be a reflection on characteristics of the material and workmanship such as shrinkage cracking and also serious structural implications which can vary from failure of main reinforcing members to shear of main seating and anchorage Spalling in concrete deck slab may take the form of circular or oval depressions. Corrosion of slab reinforcement may leads to surface discolouration of the concrete and in extreme cases to cracking. Water leaking in concrete deck is usually detected on the soffits of decks and takes the form of staining, effloresence at cracks and formation of stalactites in extreme cases. B.2.Deterioration Effects in Concrete Pier Cracks, spalling, corrosion of reinforcement, wear/abrasion, material deterioration, tilt/settlement and scouring can cause critical defects in concrete pier. The principles causes of deterioration to a concrete bridge pier are very similar to that of an abutment. However, a pier is often more prone to some of the effects listed above than an abutment because of its location at intermediate support points. The removal of material from under pier s foundation by water channel flow. often associated with scour is also known as undermining or undercutting. When scour occurs at a specific localised point in a pier, it is known as local scour. If scour takes place over a large area of a pier, it is known as general scour. As material is removed from under a substructure s foundation, the entire component will begin to settle. B.3.Deterioration Effects in Bearing Bearing which become corroded, clogged with debris or fail to function as originally designed such as loose connections and deformation can induce high stresses and potentially lead to failure of an individual span or an entire bridge structure. Corrosion in a bridge bearing can lead to it becoming locked. This can results in the creation of abnormal large stresses at the support points as well as inhibiting the natural movement of the structure. Steel bearing should also be inspected to ensure they are oriented properly that all bolts and anchorages are secure. Rocker and roller steel bearings are especially susceptible to a build-up of debris in their moving elements. Roller nest and underside of rocker bearing are extremely susceptible to collecting debris. Collection of debris at the moving elements will limit the untended movement of bearing Settlement of piers can result in bearing becomes destabilise and undergoing loading conditions which the element was not designed for (deformation in bearing). Besides, the cumulative effect of vehicle impact and thermal expansion and contraction can lead to excessive bearing deformation or even collapse of the span B.4.Deterioration Effects in Abutment ApxIII.3

4 Like any other components of concrete bridges, abutments are susceptible to the ravages of deterioration. The types of deterioration can occur in an abutment are cracks. spalling, corrosion of reinforcement, wear/abrasion, material deterioration, tilt/settlement and scouring. Cracks in abutment can develop as a result of a wide variety of situations. Vertical cracking in an abutment backwall can often be initiated by different settlement of the abutment. Cracks can also be induced by deformation loads such as shrinkage. Another cause of cracking, particularly in old structures is the use of poor concrete mix or inadequate reinforcement Abutments also suffer from surface deterioration problems by the presence of spalling and wear/abrasion. A variety of factors can lead to surface deterioration in abutments such as corrosive materials being sprayed onto exposed concrete, poor concrete mix, poor aggregates or thermal expansion. Some of the major stability problems for an abutment which could potentially arise are different settlement or other vertical movement, lateral movement or rotation movement in abutment. Different settlement can arise from problems with the soil such as consolidation or soil bearing failure. Another factor which can initiate the stability problems in abutment is scour. Generally, this is more a problem for piers than for abutments. B.5.Deterioration Effects in Drainage/Gutter Drainage is an important for inspection where corrosion, blocked drainage and inadequate pipe length for flowing water can cause a good deal of damage to a concrete bridge. The clogged inlet and inadequate drainage pipe length is a major problem which causes the overflow to the deck slab. Water stains on beam, slabs, piers, columns and abutments may indicate leaky pipes, filled gutters or inadequate drainage system. The most common problem with the bridge drainage system is the accumulation of debris in a pipe or channel. A substantial amount of debris may go into the drainage and trap inside the drainage at various strategic points. Therefore, the drainage should be checked for their cleanliness and operational efficiency. B.6.Deterioration Effects in Parapet The main deterioration effects in parapets are corrosion (for steel railing), impact damage and loose connections. Corrosion of parapets and guardrails are subject to splash from road vehicles and may therefore be in a fairly aggressive corrosion environment. The signs of deterioration or rusting should be carefully checked and special attention should be paid to the region around the base of the supporting posts. The greatest danger, with regard to bridge railing is if the units has been subjected to impact as a result of traffic accident. Such impact could damage the rail itself or loosen its anchorages. The nature and extent of the damage should be recorded and the various components should be carefully inspected for any signs of inadequacy of strength. B.7.Deterioration Effects in Pavement Pavement or wearing surface should be inspected for general forms of pavement distress, which range from cracking, potholing and rutting for asphalt surfaces to cracking and spalling for concrete surfaces. Cracking can take many forms depending on the nature of the failure and on the characteristics of the particular surfacing material. Cracking of pavement surfaces happen in a wide variety of patterns, ranging from isolated single cracks to an interconnected pattern extending over the entire pavement surface. The crack types found in asphalt pavement are block cracks, crescent shaped, crocodile cracks, diagonal cracks, longitudinal cracks, meandering cracks and transverse cracks. The crack types found in concrete pavement are block cracks, corner cracks, diagonal cracks, longitudinal cracks, meandering cracks and transverse cracks. ApxIII.4

5 Potholes are bowl-shaped depressions in the pavement surface resulting from the loss of wearing course and base course material. They are generally have sharp edges and nearly vertical sides at the top of the hole. Potholes are produced when traffic abrades small pieces of the pavement surface allowing entering water. These spots disintegrate because of the weakening of the base course or poor quality surfacing. Free water collecting in the hole and the underlying base accelerates its development. Rutting is a longitudinal and relatively smoothly shaped deformation at the wheel path. Wet weather ruts tend to be steep sided and reflect the impression of the tire into the road surfaces. Rutting of pavement is caused by inadequate wet strength. of sub-grade or pavement layer, wear by attrition due to traffic or erosion of surface material and excessive loose material of pavement. B.8.Deterioration Effects in Expansion Joint The main deterioration effects at expansion joints of concrete bridge are abnormal spacing, different in level, abnormal noise, water leak, pavement crack and rupture. Inadequate space for the expansion joint to function under the prevailing temperatures will cause abnormal spacing in expansion joint. Clearance may be lost due to unforeseen or accidental movement taking place in the foundations, substructures and superstructures. It may also result from the wrong setting of joints during construction period. These defects may lead to restrictions on movements of the joint and introduce stresses into the bridge structure. As a result of this, the joints may become excessively large and thereby presenting a hazard to traffic. A joint may displace relatively to the other and cause difference in level of expansion joints or irregularity of vertical profile in joints, and if this displacement is excessive it will cause additional impact forces under traffic loading. Leakage of water through joints is one of the major effects found in expansion joint. In many cases, joints are designed with open gaps through which water and debris can fall. Debris, stone and other foreign material will restrict the joint from moving freely and cause the deterioration of the joint filler material, which will result in water leaks into the substructure. Pavement cracking at joints also one of the common deterioration effects found in expansion joint. Loosening of expansion joints such as breaking of bolts, joint components and seating may cause cracks developing between the joints and the surfacing. The extent of cracking should be taken as an indication of the need for a local repair of the surfacing. Rupture is the deterioration occurs at rubber seal components of bridge expansion joint. Rupture could result in the damage of supported bridge beam soffit at pier head which is supporting the joints. B.9.Deterioration Effects in Slope Protection/River Bank Slope protection or embankment of concrete bridges are susceptible to the deterioration such as scouring, erosion and material loose/disintegration. Scouring occurs at embankment of bridges as a result of an obstruction such as accumulation of debris to the flow of water in the stream bank. Erosion is the gradual wearing away or removal of material by surface drainage or wind. Sources of surface drainage potentially leading to erosion are leakage through expansion joints onto the embankment, runoff around the ends of wing walls, discharge from deck drains directly above the embankment and abutment and wing wall subdrains discharging onto the embankment. Erosion detection on embankment should be limited within 30 m surrounding the structure. Material loss/disintegration at the slope protection area refers to the splitting, spalling and disintegration of the slope protection material such as masonry, rubble pitching. The course of the ApxIII.5

6 occurrence are due to abrasion and weathering, actions of acids, sulphates or chlorides which present in water flow, movement and vegetation growth or the loss of strength to the mortar joint. B.10.Deterioration Effects in Headwall/Wingwall/Apron Basically the deterioration effects in headwall/wingwall/apron are similar with the effects in abutment. The deterioration effects found in headwall/wingwall/apron are cracking, spalling, corrosion of reinforcement, wear/abrasion, tilt/settlement, material deterioration and scouring. The explanation of the characteristic for each effect can be referred to the explanations for deterioration effects in abutment. B.11.Deterioration Effects in Culvert The most common types of deterioration effects found in culvert are cracking, spalling, corrosion of reinforcement, wear/abrasion, material deterioration, water leak, tilt/settlement, silting, scouring and inadequate size of culvert. Hairline cracks in the invert of culvert indicates that the steel reinforcement in the concrete culvert has accepted part of the tensile stress. Transverse cracks may be signs of poor soil support. Spalling may be caused by differential movement or corrosion of the reinforcing steel and may be detected visually or by tapping with a hammer. Good quality concrete culvert will be resistant to wear from clear water traveling at high velocity as long as the flow is uniform and direction of the flow is not abruptly changed. Small holes, imperfections or misalignment of the floor or sides may lead to damage as a result of water turbulence. In general, the abrasion resistance of concrete culvert increases as the strength of the concrete is increased. Leakage in concrete pipe culvert may be caused by water exfiltration or water infiltration. Exfiltration occurs when joint allows water flowing through the culvert pipe to leak into the supporting soil and this will cause serious misalignment or culvert pipe failure. When surrounding water tables are higher than the culvert invert, infiltration may occur where water may seep into the culvert and cause settlement and misalignment by removing fine grained soil from the backfill. Silting is the raising of the stream/river bed or the narrowing of the stream/river channel due to deposition of material by the stream/river and usually results in the transport sediment capacity of the stream/river to decrease. Steep culverts tend to minimize the problem of water backing up but the increase the possibility of erosion at the outlet because of the high flow velocity. Flat culverts tend to cause silt and debris deposits to in the barrel. The problem of silting is particularly happening to box culverts, which often have a low gradient. There are two common types of scour damage in concrete culverts that are scour at the inlet and scour at the outlet end. Scour at the inlet end of concrete culvert is a result of turbulence when more water is collected at the inlet and than can be rapidly discharge by the culvert. Possible causes are that the waterway opening is too small or the entrance is choked with silt or debris. Scour at the outlet of concrete culvert is caused by a rapid uncontrolled discharge of a large volume of water onto an outlet streambed due to the steep slope of the culvert which increases the velocity of the flow greater than the normal. ApxIII.6