Post on 23-Dec-2015
Principles of Joints & Sealants
Chapter 9
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Joint patterns & details
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building Joints result from need to
Work with materials that can be easily fabricated, transported and assembled on site
Allow for field adjustments Accommodate differing changes in size
between different materials Make a secure connection Articulate building surfaces
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Types of joints
Static joints provide non-moving connection between building components
Dynamic joints (Movement Joints) make connections while allowing for movement of the components
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building separation joints
Continuous joints that completely separate parts of a building from each other
Accommodates effects of movements of building as a whole
Prevent stresses created in one part of a building from transferring to other parts.
Typically1 1/2 inch - 2 inch wide, every 250 ft.
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Typical locations of building separation joints
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Two adjacent columns at separation
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building separation: double columns in concrete frame
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building separation: double columns in steel frame
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building separation at single column
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Building separation at single column
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Seismic Joint
Assure that one building segment does not collide with another during an earthquake
Accommodate mostly horizontal movement Typically wider than a building separation
joint, with width increasing with height
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Typical seismic or separation joint cover
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Factors in sizing movement joints
Thermal movement Moisture movement Elastic deformation and creep Construction tolerances Sealant (if used)
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Restrained & unrestrained joints
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Thermal movement
Occurs in all components Generally most critical type of movement Coefficient of Thermal Expansion (), property of a
material
t (change in length) = L (t)
t is a function of Annual temperature range Temperature at the time of construction
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Approximate value for selected materials
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Northern US: typical temperature gradient
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Southern US: typical temperature gradient
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Problem: Determine joint width between 100 ft.
segments of brick masonry wall
t (minimum joint width) = L (t) L = 100 ft = 1,200 int = 80ºF = 4.0 x 10-6
minimum joint width = (4.0 x 10-6)(1,200)80 = .320 in
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Moisture movement
Some materials expand on absorption of water or water vapor In some materials (brick), expansion is permanent Some materials return to original shape when
dried
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Elastic deformation & creep
Creep is incremental deformation of a component caused by sustained loading.
Significant in concrete and masonry
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Connection between spandrel beam and non-loadbearing infill wall must account for deflection
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Tolerances
Material tolerances are the allowable variation in size from unit to unit
Construction tolerances are a function of quality control during construction. Small tolerances require good construction quality and supervision
Other tolerances include foundation settlement, story drift, chemical processes and freeze-thaw
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Total joint dimension
Width of Joint
Width based on temperature, moisture and other movement + Tolerances=
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Joint sealants
If a joint sealant is used, its movement ability must also be considered
Joint sealants are categorized by movement ability (class 50 has +/- 50% movement ability
Width of Sealed Joint
Width based on temperature, moisture and other movement
+ Tolerances= 100 Sealant Class
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Detailing movement joints
Expansion joints Control (shrinkage) joints
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Brick expands over time - expansion joint required
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Concrete masonry shrinks over time - Control joint required
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Components of a sealed joint
Substrate Primer
Improve adhesion of sealant to substrate
Sealant back-up (backer rod) control depth and shape of sealant allows for tooling sealant
Bond breaker Prevents adhesion where not required
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Untooled and tooled joints
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Effect of bond breaker on sealed joints
Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.
Joint sealants
Preformed tapes Perform as sealants only when under pressure
Caulks First generation sealants, dough-like materials, rarely used
Elastomeric sealants Synthetic polymers, most commonly used in construction Vary in performance characteristics
Movement ability Water vapor permeability Abrasion resistance Chemical resistance Durability Substrate compatibility Paintability