Text

ĐỒ ÁN

Tổng hợp các đồ án mẫu dành cho sinh viên chuyên ngành xây dựng.

DRAWING LIBRARY

Bộ sưu tập các bản vẽ mẫu Autocad,Revit,Max các biệt thự,chung cư và các công trình dân dụng khác.

DISSCUS

Cùng nhau thảo luận những chủ đề liên quan đến xây dựng

GALLERY

Kho Sách Nói Audio Book,Hình ảnh,Video dùng cho giải trí

YÊU CẦU TÀI LIỆU

Để lại yêu cầu về tài liệu mà bạn đang cần.Nếu được,tài liệu sẽ gửi đến bạn sớm nhất có thể.

NOTE Đóng lại

Thứ Hai, 21 tháng 11, 2011

BEAM DESIGN

In the design of concrete beams, SAFE calculates and reports the required areas of reinforcement for flexure, shear, and torsion based on the beam moments, shear forces, torsion, load combination factors, and other criteria described in this section. The reinforcement requirements are calculated at each station
along the length of the beam.




Beams are designed for major direction flexure, shear, and torsion only. Effects resulting from any axial forces and minor direction bending that may exist in the beams must be investigated independently by the user.

The beam design procedure involves the following steps: 
  •  Design flexural reinforcement 
  • Design shear reinforcement 
  • Design torsion reinforcement 

1. DesignFlexural Reinforcement

The beam top and bottom flexural reinforcement is designed at each station along the beam. In designing the flexural reinforcement for the major moment of a particular beam, for a particular station, the following steps are involved:
  •  Determine factored moments
  •  Determine required flexural reinforcement
1.1 Determine Factored Moments:
In the design of flexural reinforcement of concrete beams, the factored mo- ments for each load combination at a particular beam station are obtained by factoring the corresponding moments for different load cases, with the corre- sponding load factors.
The beam is then designed for the maximum positive and maximum negative factored moments obtained from all of the load combinations. Calculation of bottom reinforcement is based on positive beam moments. In such cases the beam may be designed as a rectangular or flanged beam. Calculation of top re- inforcement is based on negative beam moments. In such cases the beam may be designed as a rectangular or inverted flanged beam.

1.2 Determine RequiredFlexural Reinforcement

In the flexural reinforcement design process, the program calculates both the tension and compression reinforcement. Compression reinforcement is added when the applied design moment exceeds the maximum moment capacity of a singly reinforced section. The user has the option of avoiding compression reinforcement by increasing the effective depth, the width, or the strength of the concrete. Note that the flexural reinforcement strength, fy , is limited to 80ksi (ACI 9.4), even if the material property is defined using a higher value.

The design procedure is based on the simplified rectangular stress block, as shown in Figure 2-1 (ACI 10.2). Furthermore, it is assumed that the net tensile strain in the reinforcement shall not be less than 0.005 (tension controlled) (ACI 10.3.4) when the concrete in compression reaches its assumed strain limit of 0.003. When the applied moment exceeds the moment capacity at this de- sign condition, the area of compression reinforcement is calculated assuming that the additional moment will be carried by compression reinforcement and additional tension reinforcement.

The design procedure used by SAFE, for both rectangular and flanged sections (L- and T-beams), is summarized in the text that follows. It is assumed that the design ultimate axial force does not exceed (0.1 f' c Ag) (ACI 10.3.5), hence all beams are designed for major direction flexure, shear, and torsion only.

1.2.1 Design of Rectangular Beams

In designing for a factored negative or positive moment, M(i.e., designing top
or bottom reinforcement), the depth of the compression block is given by a (see
Figure 2-1), where,

To be continued....
 

TOP-DOWN Construction Method In Ducat Moscow.


Ducat Place III

SỔ TAY GIÁM SÁT THI CÔNG

HỒ SƠ ĐỊA CHẤT 1 VÀI KHU VỰC Ở TP.HCM

Tôi vừa sưu tầm được hồ sơ địa chất của 1 số khu vực ở Tp.HCM như Bình Chánh,Tân phú,Quận 7....Rất hữu ích cho các đơn vị thi công móng mà không có hồ sơ địa chất hoặc các công trình đã thi công ở khu vực đó để làm cơ sở cho việc tính toán và thi công.




TỔNG HỢP MỘT VÀI MẪU NHÀ DÂN DỤNG





4.5*14m                                  Download

4.5*16m                                  Download

4.7*11.7m                               Download

7*17m                                     Download

10*18m                                   Download

4.5*15                                     Download


4.8*13                                     Download 

[ĐỒ ÁN] TỔNG HỢP ĐỒ ÁN CHO SINH VIÊN XÂY DỰNG PART.4




Đồ án tốt nghiệp khoa XD - Thiết kế khách sạn 9 tầng 1 tầng hầm ở Nha Trang
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Đồ án tổ chức thi công

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Đồ án nền móng công trình

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Mẫu đồ án tốt nghiệp khoa XD - Thiết kế và tính toán nhà chung cư thấp tầng (Bản FULL)
Gửi tặng các bạn 1 bộ luận đồ án tốt nghiệp khoa XD khóa 99-04 chuyên đề thiết kế nhà chung cư thấp tầng , cực kỳ đầy đủ bao gồm:

1. Phần kiến trúc:
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Đồ án đường 3: Thiết kế nút giao thông thành phố

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Đồ án tốt nghiệp khoa cầu đường - Thiết kế đường giao thông

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Đồ án tốt nghiệp khoa cầu đường: Thiết kế tính toán cầu qua sông 240m
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Một số đồ án mẫu thiết kế Tổ chức thi công nền đường ôtô (4 mẫu đồ án tất cả)

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[Support for CAD] Một vài chương trình hỗ trợ cho CAD

1.Speed Cad: Phần mềm tăng tốc cho CAD
2.TKXD30-Hỗ trợ vẽ cad nhanh hơn:
TKXD30 Bản đầy đủ - Cập nhật đến 12/2010 (Copy - không cần cài đặt)
Link Download (có hướng dẫn):
Có thể chạy được trên:
- Windows XP/ Windows Vista/ Windows 7
- AutoCAD 2007/2008/2009/2010 (đang test trên 2011 và 2012)
Bản này có thể thay thế tất cả các bản đã Upload từ trước tháng 12/2010.
3.Lisp Cad QKHS:
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link down: Download
keygen: Download

Bộ tiện ích này làm thay đổi lệnh C (vẽ đường tròn) thành CI, và lệnh CO (Coppy) thành lệnh C. Tiện hơn đó vì lệnh Coppy dùng nhiều hơn lệnh vã đường tròn. Và các đường ghi kích thước từ F1->F9.



Deep Foundation Design.


Description:




Chapter 1
Introduction
Purpose
Applicability
Scope
References
General Design Methodology
Types of Deep Foundations
Selection of Deep Foundations
Site and Soil Investigations


Chapter 2
Design Stresses
Constraints
Factored Loads
Structural Design of Driven Piles
Structural Design of Drilled Shafts


Chapter 3
Vertical Loads
Design Philosophy
Driven Piles
Drilled Shafts


Chapter 4
Lateral Loads
Description of the Problem
Nonlinear Pile and p-y Model for Soil
Development of p-y Curve for Soils
Analytical Method
Status of the Technology


Chapter 5
Pile Groups
Design Considerations
Factors Influencing Pile Group Behavior
Design for Vertical Loads
Design for Lateral Loads
Computer Assisted Analysis


Chapter 6
Verification of Design
Foundation Quality



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Thank you for your attention.

Concrete Design Group(Excel Files)



Here are some files excel to help us calcul Concrete in construction.

1 Two Way Slab Two-Way Slab Design Based on ACI 318-08 using Finite Element Method
2 Voided Biaxial Slab Voided Two-Way Slab Design Based on ACI 318-08
3 Anchorage to Concrete Base Plate and Group Anchors Design Based on ACI 318-08 & AISC 360-05
4 Anchorage to Pedestal Anchorage to Pedestal Design Based on ACI 318-08 & AISC 360-05
5 Circular Column Circular Column Design Based on ACI 318-08
6 Concrete Column Concrete Column Design Based on ACI 318-08
7 Super Composite Column Super Composite Column Design Based on AISC 360-05 & ACI 318-08
8 Special Shear Wall - CBC Special Concrete Shear Wall Design Based on ACI 318-05 / CBC 07 Chapter A
9 Ordinary Shear Wall Ordinary Concrete Shear Wall Design Based on ACI 318-08
10 Concrete Pool Concrete Pool Design Based on ACI 318-08
11 Corbel Corbel Design Based on IBC 09 / ACI 318-08
12 Coupling Beam Coupling Beam Design Based on ACI 318-08
13 Deep Beam Deep Beam Design Based on ACI 318-08
14 Concrete Development & Splice Development & Splice of Reinforcement Based on ACI 318-08
15 Equipment Mounting Design for Equipment Anchorage Based on IBC 09 / CBC 10 Chapter A
16 Existing Shear Wall Verify Existing Concrete Shear Wall Based on ASCE 41-06 / CBC 10 / IBC 09
17 Friction Shear Friction Reinforcing Design Based on ACI 318-08
18 Pipe Concrete Column Pipe Concrete Column Design Based on ACI 318-08
19 PT-Concrete Floor Design of Post-Tensioned Concrete Floor Based on ACI 318-08
20 Punching Slab Punching Design Based on ACI 318-08
21 Concrete Slab Concrete Slab Perpendicular Flexure & Shear Capacity Based on ACI 318-08
22 Voided Section Capacity Voided Section Design Based on ACI 318-08
23 Concrete Diaphragm Concrete Diaphragm in-plane Shear Design Based on ACI 318-08
24 SMRF - ACI Seismic Design for Special Moment Resisting Frame Based on ACI 318-08
25 Special Shear Wall - IBC Special Reinforced Concrete Shear Wall Design Based on ACI 318-08 / IBC 09
26 Suspended Anchorage Suspended Anchorage to Concrete Based on IBC 09 / CBC 10
27 Tiltup Panel Tilt-up Panel Design based on ACI 318-08
28 Wall Pier Wall Pier Design Based on CBC 10 / IBC 09
29 Beam Penetration Design for Concrete Beam with Penetration Based on ACI 318-08
30 Column Supporting Discontinuous Column Supporting Discontinuous System Based on ACI 318-08
31 Plate Shell Element Plate/Shell Element Design Based on ACI 318-08
32 Transfer Diaphragm - Concrete Concrete Diaphragm Design for a Discontinuity of Type 4 out-of-plane offset irregularity
33 Silo/Chimney/Tower Design Concrete Silo / Chimney / Tower Design Based on ASCE 7-05, ACI 318-08 & ACI 313-97
34 Concrete Beam Concrete Beam Design, for New or Existing, Based on ACI 318-08


Source:www.engineering-international.com

Foudation Design Group (Excel file)



1 Free Standing Wall Free Standing Masonry & Conctere Wall Design Based on TMS 402-08 & ACI 318-08
2 Eccentric Footing Eccentric Footing Design Based on ACI 318-08
3 Flagpole Flagpole Footing Design Based on Chapter 18 of IBC & CBC
4 Masonry Retaining Wall Masonry Retaining / Fence Wall Design Based on TMS 402-08 & ACI 318-08
5 Concrete Retaining Wall Concrete Retaining Wall Design Based on ACI 318-08
6 Masonry-Concrete Retaining Wall Retaining Wall Design, for Masonry Top & Concrete Bottom, Based on TMS 402-08 & ACI 318-08
7 Concrete Pier Concrete Pier (Isolated Deep Foundation) Design Based on ACI 318-08
8 Concrete Pile Drilled Cast-in-place Pile Design Based on ACI 318-08
9 Pile Caps Pile Cap Design for 4, 3, 2-Piles Pattern Based on ACI 318-08
10 Pile Cap Balanced Loads Determination of Pile Cap Balanced Loads and Reactions
11 Conventional Slab on Grade Design of Conventional Slabs on Expansive & Compressible Soil Grade Based on ACI 360
12 PT-Slab on Ground Design of PT Slabs on Expansive & Compressible Soil Based on PTI 3rd Edition
13 Basement Concrete Wall Basement Concrete Wall Design Based on ACI 318-08
14 Basement Masonry Wall Basement Masonry Wall Design Based on TMS 402-08
15 Basement Column Basement Column Supporting Lateral Resisting Frame Based on ACI 318-08
16 MRF-Grade Beam Grade Beam Design for Moment Resisting Frame Based on ACI 318-05
17 Brace Grade Beam Grade Beam Design for Brace Frame Based on ACI 318-08
18 Grade Beam Two Pads with Grade Beam Design Based on ACI 318-08 & AISC 360-05
19 Circular Footing Circular Footing Design Based on ACI 318-08
20 Combined Footing Combined Footing Design Based on ACI 318-08
21 Boundary Spring Generator Mat Boundary Spring Generator
22 Deep Footing Deep Footing Design Based on ACI 318-08
23 Footing at Piping Design of Footing at Piping Based on ACI 318-08
24 Irregular Footing Soil Pressure Soil Pressure Determination for Irregular Footing
25 PAD Footing Pad Footing Design Based on ACI 318-08
26 Plain Concrete Footing Plain Concrete Footing Design Based on ACI 318-08
27 Restrained Retaining Wall Restrained Retaining Masonry & Concrete Wall Design Based on TMS 402 & ACI 318
28 Retaining Wall for DSA /OSHPD Retaining Wall Design Based on CBC 10 Chapter A
29 Tank Footing Tank Footing Design Based on ACI 318-08
30 Temporary Footing for Rectangular Tank Temporary Tank Footing Design Based on ACI 318-08
31 Under Ground Well Under Ground Well Design Based on ACI 350-06 & ACI 318-08
32 Stud Bearing Wall Footing Footing Design for Stud Bearing Wall Based on IBC 09 / ACI 318-08
33 Wall Footing Footing Design of Shear Wall Based on ACI 318-08
34 Fixed Moment Condition Fixed Moment Condition Design Based on ACI 318-08
35 Flood Way Concrete Floodway Design Based on ACI 350-06 & ACI 318-08
36 Lateral Earth Pressure Lateral Earth Pressure of Rigid Wall Based on AASHTO 17th & 2009 IBC
37 Shoring Sheet Pile Wall Design Based on IBC 09 / CBC 10 / ACI 318-08
38 Composite Element Durability Composite Element Design Based on AISC 360-05 & ACI 318-08

Share with you all of my excel files which I collected.Leave me your comment below if the links have problems.
Enjoy it!

Source:  www.engineering-international.com

Chủ Nhật, 20 tháng 11, 2011

Importance of Classification of Cracks


Cracks in a building are like ailments in human body. The building gets weaker and weaker if the cracks are not treated properly. The cracks give an impression of faulty and poor quality work. Moisture penetrates through the cracks and deteriorates the external facade as well as the internal facade. For determining a treatment procedure for the cracks, cracks have to be classified depending on its cause and nature. Different types of cracks have to be treated in different ways depending on its nature of occurrence.

Cracks in Buildings
In my earlier articles, I have discussed major and minor causes of cracks. Studying these causes also help in the classification of cracks.

The classification of cracks is based on various factors:

  1. Direction of the cracks
  2. Extent of the cracks
  3. Width of the cracks (if tapers)
  4. Width of the cracks
  5. Depth of the cracks
  6. Alignment of the cracks
  7. Sharpness of the edges
  8. Cleanliness
  9. General

Direction of the cracks

  1. Vertical
  2. Horizontal
  3. Diagonal
  4. Straight
  5. Toothed
  6. Variable and irregular
The materials trough which crack passes should be recorded.

Extent of the cracks

The cracks usually occur at starting and finishing points i.e. across the openings, passes round the edges of the materials or cracks close to the ground – passing through dpc (damp proof course) or confined above or below.

Width of the cracks (if tapers)

Mark the end of the crack
Direction of taper
(It is important to note the humidity of the day. Some cracks widen and close during the day due to thermal changes)
This is necessary for remedial work.

Width of the cracks

It can be measured through instruments and tell-tale signs. The changes in the length of the cracks should be noted.

Depth of the cracks

Figuring out or measuring the actual depth of the crack is irrelevant, but how many of the materials of the wall have cracked is important to detect.
For example, Just point film may have cracked which is not a very serious crack. A piece of very fine wire may be used to detect the fine crack.

Alignment of the cracks

A note should be taken of the levels of the materials on the two sides of the crack, one side sometimes being forward of the other can be done by feeling with the finger tip, passing it across the crack in both direction, when any direction in the level is readily apparent.
Alignment indicated whether the crack has been produced by a straight pull, or with a tensile force or as with a diagonal pull as with a shear action.

Sharpness of Edges

Most cracks have sharp edges but they may be rounded or roughened if the sides of the cracks have been brought together by compressive forces or by vibrations. Badly broken edges will often be indicative of initial compressive forces.

Cleanliness

Examine the cracks with magnifying glass for the following reasons:
  • Brightness of the sides of the cracks
  • The presence of dust, algae, insects etc
  • The presence of decorative materials (example, Paint on the sides of the crack)

General

Observe the crack over a period of time to know whether it is static or altering in size and if bows are there, measure the extent of bow.

DVD-Ebook tiếng anh cho xây dựng


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METHODS OF CRACK REPAIR

Introduction
Following the evaluation of the cracked structure, a suitable repair procedure can be selected. Successful repair procedures take into account the cause(s) of the cracking. For example, if the cracking was primarily due to drying shrinkage, then it is likely that after a period of time the cracks will stabilize. On the other hand, if the cracks are due to a continuing foundation settlement, repair will be of no use until the settlement problem is corrected.
This chapter provides a survey of crack repair methods, including a summary of the characteristics of the cracks that may be repaired with each procedure, the types of structures that have been repaired, and a summary of the procedures that are used.
Epoxy injection
Cracks as narrow as 0.002 in. (0.05 mm) can be bonded by the injection of epoxy. The technique generally consists of establishing entry and venting ports at close intervals along the cracks, sealing the crack on exposed surfaces, and injecting the epoxy under pressure. Epoxy injection has been successfully used in the repair of cracks in buildings, bridges, dams, and other types of concrete structures (ACI 503R). However, unless the cause of the cracking has been corrected, it will probably recur near the original crack. If the cause of the cracks cannot be removed, then two options are available.
One is to rout and seal the crack, thus treating it as a joint, or, establish a joint that will accommodate the movement and then inject the crack with epoxy or other suitable material. With the exception of certain moisture tolerant epoxies, this technique is not applicable if the cracks are actively leaking and cannot be dried out. Wet cracks can be injected using moisture tolerant materials, but contaminants in the cracks (including silt and water) can reduce the effectiveness of the epoxy to structurally repair the cracks.
The use of a low-modulus, flexible adhesive in a crack will not allow significant movement of the concrete structure. The effective modulus of elasticity of a flexible adhesive in a crack is substantially the same as that of a rigid adhesive because of the thin layer of material and high lateral restraint imposed by the surrounding concrete. Epoxy injection requires a high degree of skill for satisfactory execution, and application of the technique may be limited by the ambient temperature.
Clean the cracks. The first step is to clean the cracks that have been contaminated; to the extent this is possible and practical. Contaminants such as oil, grease, dirt, or fine particles of concrete prevent epoxy penetration and bonding, and reduce the effectiveness of repairs. Preferably, contamination should be removed by vacuuming or flushing with water or other specially effective cleaning solutions.
  • Seal the surfaces. Surface cracks should be sealed to keep the epoxy from leaking out before it has gelled. Where the crack face cannot be reached, but where there is backfill, or where a slab-on-grade is being repaired, the backfill material or sub base material is sometimes an adequate seal. A surface can be sealed by applying an epoxy, polyester, or other appropriate sealing material to the surface of the crack and allowing it to harden. If a permanent glossy appearance along the crack is objectionable and if high injection pressure is not required, a strippable plastic surface sealer may be applied along the face of the crack. When the job is completed, the surface sealer can be stripped away to expose the gloss-free surface. Cementitious seals can also be used where appearance of the completed work is important. If extremely high injection pressures are needed, the crack can be cut out to a depth of 1/2 in. (13 mm) and width of about 3/4 in. (20 mm) in a V-shape, filled with an epoxy, and struck off flush with the surface.
  • Install the entry and venting ports. Three methods are in general use:
a. Fittings inserted into drilled holes. This method was the first to be used, and is often used in conjunction with V-grooving of the cracks. The method entails drilling a hole into the crack, approximately 3/4 in. (20 mm) in diameter and 1/2 to 1 in. (13 to 25 mm) below the apex of the V grooved section.
b. Bonded flush fitting. When the cracks are not V grooved , a method frequently used to provide an entry port is to bond a fitting flush with the concrete face over the crack. The flush fitting has an opening at the top for the adhesive to enter and a flange at the bottom that is bonded to the concrete.
c. Interruption in seal. Another system of providing entry is to omit the seal from a portion of the crack. This method can be used when special gasket devices are available that cover the unsealed portion of the crack and allow injection of the adhesive directly into the crack without leaking.
  • Mix the epoxy. This is done either by batch or continuous methods. In batch mixing, the adhesive components are premixed according to the manufacturers instructions, usually with the use of a mechanical stirrer, like a paint mixing paddle. Care must be taken to mix only the amount of adhesive that can be used prior to commencement of gelling of the material.
  • Inject the epoxy. Hydraulic pumps, paint pressure pots, or air-actuated caulking guns may be used. The pressure used for injection must be selected carefully. Increased pressure often does little to accelerate the rate of injection. If the crack is vertical or inclined, the injection process should begin by pumping epoxy into the entry port at the lowest elevation until the epoxy level reaches the entry port above. For horizontal cracks, the injection should proceed from one end of the crack to the other in the same manner. The crack is full if the pressure can be maintained. If the pressure can not be maintained, the epoxy is still flowing into unfilled portions or leaking out of the crack.
  • Remove the surface seal. After the injected epoxy has cured, the surface seal should be removed by grinding or other means as appropriate.
  • Alternative procedure. For massive structures, an alternate procedure consists of drilling a series of holes [usually 7/8 to 4-in. (20 to 100-mm) diameter] that intercepts the crack at a number of locations. Typically, holes are spaced at 5-ft (1.5-m) intervals. Another method recently being used is a vacuum or vacuum assist method.
There are two techniques: one is to entirely enclose the cracked member with a bag and introduce the liquid adhesive at the bottom and to apply a vacuum at the top. The other technique is to inject the cracks from one side and pull a vacuum from the other. Typically, epoxies are used; however, acrylics and polyesters have proven successful.
  • Routing and sealing
Routing and sealing of cracks can be used in conditions requiring remedial repair and where structural repair is not necessary. This method involves enlarging the crack along its exposed face and filling and sealing it with a suitable joint sealant  (Fig. 3.1). This is a common technique for crack treatment and is relatively simple in comparison to the procedures and the training required for epoxy injection. The procedure is most applicable to approximately flat horizontal surfaces such as floors and pavements. However, routing and sealing can be accomplished on vertical surfaces (with a non-sag sealant) as well as on curved surfaces (pipes, piles and pole).
Routing and sealing is used to treat both fine pattern cracks and larger, isolated cracks. A common and effective use is for waterproofing by sealing cracks on the concrete surface where water stands, or where hydrostatic pressure is applied. This treatment reduces the ability of moisture to reach the reinforcing steel or pass through
the concrete, causing surface stains or other problems.
The sealants may be any of several materials, including epoxies, urethanes, silicones, polysulfides, asphaltic materials, or polymer mortars. Cement grouts should be avoided due to the likelihood of cracking. For floors, the sealant should be sufficiently rigid to support the anticipated traffic. Satisfactory sealants should be able to withstand cyclic deformations and should not be brittle.
The procedure consists of preparing a groove at the surface ranging in depth, typically, from 1/4 to 1 in. (6 to 25 mm). A concrete saw, hand tools or pneumatic tools may be used. The groove is then cleaned by air blasting, sandblasting, or water blasting, and dried. A sealant is placed into the dry groove and allowed to cure. A bond breaker may be provided at the bottom of the groove to allow the sealant to change shape, without a concentration of stress on the bottom (Fig. 3.2).

Repair of concrete
            The bond breaker may be a polyethylene strip or tape which will not bond to the sealant. Careful attention should be applied when detailing the joint so that its width to depth aspect ratio will accommodate anticipated movement (ACI 504R).
Stitching
Stitching involves drilling holes on both sides of the crack and grouting in    U-shaped metal units with short legs (staples or stitching dogs) that span the crack as
shown in Fig 3.3. Stitching may be used when tensile strength must be reestablished across major cracks. The stitching procedure consists of drilling holes on both sides of the crack, cleaning the holes, and anchoring the legs of the staples in the holes, with either a non shrink grout or an epoxy resin-based bonding system.
Repair of concrete
Additional reinforcement
  • Conventional reinforcement
Cracked reinforced concrete bridge girders have been successfully repaired by inserting reinforcing bars and bonding them in place with epoxy. This technique consists of sealing the crack, drilling holes that intersect the crack plane at approximately 90 deg (Fig. 3.4), filling the hole and crack with injected epoxy and placing a reinforcing bar into the drilled hole. Typically, No. 4 or 5 (10 M or 15 M) bars are used, extending at least 18 in. (0.5 m) each side of the crack. The reinforcing bars can be spaced to suit the needs of the repair. They can be placed in any desired pattern, depending on the design criteria and the location of the in-place reinforcement.
Repair of concrete
  • Pre stressing steel
Post-tensioning is often the desirable solution when a major portion of a member must be strengthened or when the cracks that have formed must be closed (Fig. 3.5). This technique uses pre stressing strands or bars to apply a compressive force. Adequate anchorage must be provided for the pre stressing steel, and care is needed so that the problem will not merely migrate to another part of the structure.
Repair of concrete
Drilling and plugging
Drilling and plugging a crack consists of drilling down the length of the crack and grouting it to form a key (Fig. 3.6).
Repair of concrete
This technique is only applicable when cracks run in reasonable straight lines and are accessible at one end. This method is most often used to repair vertical cracks
in retaining walls. A hole [typically 2 to 3 in. (50 to 75 mm) in diameter] should be drilled, centered on and following the crack.
 The grout key prevents transverse movements of the sections of concrete adjacent to the crack. The key will also reduce heavy leakage through the crack and loss of soil from behind a leaking wall. If water-tightness is essential and structural load transfer is not, the drilled hole should be filled with a resilient material of low modulus in lieu of grout. If the keying effect is essential, the resilient material can be
placed in a second hole, the fiat being grouted.
Gravity Filling
Low viscosity monomers and resins can be used to seal cracks with surface widths of 0.001 to 0.08 in. (0.03 to 2 mm) by gravity filling. High-molecular- weight methacrylates, urethanes, and some low viscosity epoxies have been used successfully. The lower the viscosity, the finer the cracks that can be filled. The typical procedure is to clean the surface by air blasting and/or water blasting. Wet surfaces should be permitted to dry several days to obtain the best crack filling.
Water blasting followed by a drying time may be effective in cleaning and preparing these cracks. Cores taken at cracks can be used to evaluate the effectiveness of the crack filling. The depth of penetration of the sealant can be measured. Shear (or tension) tests can be performed with the load applied in a direction parallel to the repaired cracks (as long as reinforcing steel is not present in the core in or near the
failure area). For some polymers the failure crack will occur outside the repaired crack.
Grouting
  • Portland cement grouting
Wide cracks, particularly in gravity dams and thick concrete walls, may be repaired by filling with Portland cement grout. This method is effective in stopping water leaks, but it will not structurally bond cracked sections. The procedure consists of cleaning the concrete along the crack; installing built-up seats (grout nipples) at intervals astride the crack (to provide a pressure tight connection with the injection apparatus); sealing the crack between the seats with a cement paint, sealant, or grout; flushing the crack to clean it and test the seal; and then grouting the whole area. Grout mixtures may contain cement and water or cement plus sand and water, depending on the width of the crack.
However, the water-cement ratio should be kept as low as practical to maximize the strength and minimize shrinkage. Water reducers or other admixtures may be used to improve the properties of the grout. For small volumes, a manual injection gun may be used; for larger volumes, a pump should be used. After the crack is filled, the pressure should be maintained for several minutes to insure good penetration.
  • Dry packing
Dry packing is the hand placement of a low water content mortar followed by tamping or ramming of the mortar into place, producing intimate contact between the
mortar and the existing concrete. Because of the low water-cement ratio of the material, there is little shrinkage, and the patch remains tight and can have good quality with respect to durability, strength, and water tightness.
Dry pack can be used for filling narrow slots cut for the repair of dormant cracks. The use of dry pack is not advisable for filling or repairing active cracks.
Before a crack is repaired by dry packing, the portion adjacent to the surface should be widened to a slot about 1 in. (25 mm) wide and 1 in. (25 mm) deep. The slot should be undercut so that the base width is slightly greater than the surface width.
To minimize shrinkage in place, the mortar should stand for 1/2 hour after mixing and then should be remixed prior to use. The mortar should be placed in layers
about 3/8 in. (10 mm) thick. Each layer should be thoroughly compacted over the surface using a blunt stick or hammer, and each underlying layer should be scratched
to facilitate bonding with the next layer. The repair should be cured by using either water or a curing compound. The simplest method of moist curing is to support
a strip of folded wet burlap along the length of the crack.
Overlay and surface treatments
Fine surface cracks in structural slabs and pavements may be repaired using either a bonded overlay or surface treatment if there will not be further significant movement across the cracks. Unbounded overlays may be used to cover, but not necessarily repair a slab. Overlays and surface treatments can be appropriate for cracks caused by one-time occurrences and which do not completely penetrate the slab.
  • Surface treatments
Low solids and low-viscosity resin-based systems have been used to seal the concrete surfaces, including treatment of very fine cracks. They are most suited for surfaces not subject to significant wear. Bridge decks and parking structure slabs, as well as other interior slabs may be coated effectively after cracks are treated by injecting with epoxy or by routing and sealing. Materials such as urethanes, epoxies, polyesters, and acrylics have been applied in thickness of 0.04 to 2.0 in. (1 to 50 mm), depending on the material and purpose of the treatment. Skid-resistant aggregates are often mixed into the material or broadcast onto the surface to improve traction.
  • Overlays
Slabs containing find dormant cracks can be repaired by applying an overlay, such as polymer modified Portland cement mortar or concrete, or by silica fume concrete. Slabs with working cracks can be overlaid if joints are placed in the overlay directly over the working cracks. In highway bridge applications, an overlay thickness as low as 1-1/4 in. (30 mm) has been used successfully. Suitable polymers include styrene butadiene or acrylic latexes. The resin solids should be at least 15 percent by weight of the Portland cement, with 20 percent usually being optimum.

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