El+Paso+Civic+Center+Lamellar+Tearing+Failure

El Paso Civic (Convention) Center Lamellar Tearing Failure El Paso, Texas, 1972 by Xiaodong Jiang, BAE / MAE, AE 537, Pennsylvania State University, 2014

// Keywords: El Paso Civic Center, compression ring girder, box girder, diaphragm plate, lamellar tearing, steel welding, steel plate, brittle fracture, shrinkage, Grand Coulee, Atlantic Richfield, AISC, hidden crack, inclusion, hydrogen, through-thickness strain //

=Abstract= toc

In 1972, a lamellar tearing problem occurred on the compression ring girder of the El Paso Civic Center project. Later, the American Institute of Steel Construction and the American Welding Society developed a series of research studies to discover this steel material deficiency. Based on those studies, the AISC and American Welding Society created several design recommendations and fabrication standards for preventing lamellar tearing from happening. This case study includes the introduction of El Paso Civic Center case, the lamellar tearing mechanism, the affecting factors, two similar lamellar tearing cases, some prevention recommendations of lamellar tearing, and the case study conclusion.

=Introduction=

The Case
In 1972, weld cracks were found in the steel plate of the compression ring girder in the El Paso Civic Center project. This problem was reported by ENR associate editor Richard Kielar on July 27, 1972 (Construction Disasters, p. 255). The cause of failure was determined to be lamellar failure, which is a form of brittle fracture behavior of welding occurring in rolled steel pates. In March of 1975, the project was overdue, and the city of El Paso was sued by McKee, the general contractor, for $2.3 million; the city was also sued by sixteen subcontractors and the project's architects. Later, the city sued the structural engineer, the American Institute of Steel Construction (AISC) //, // and also the steel supplier for the same $2.3 million and an additional $247,603. Eventually, the parties negotiated a compromise; a collective $1 million was paid to the general contractor, McKee, and subcontractors.

The failure of El Paso Civic Center’s compression ring girder was the first well known lamellar tearing failure. However, it was not the last. Similar disasters also happened at the 52- story Hancock Tower Chicago project, the electric power transmission towers at the U.S. Bureau of Reclamation's third powerhouse at Grand Coulee Dam, Colorado, and King Street Bridge.


 * = [[image:failures/building-google.JPG width="613" height="300"]] ||
 * = Figure 1: El Paso Civic Center (Photo Credit: Google Map) ||

Influence
The architectural engineering and construction public was shocked by the discovery of El Paso Civic Center's lamellar tearing failure. Later, the American Institute of Steel Construction (AISC), American Welding Society, and the steel supply companies developed a series of research projects to study this kind of material deficiency. They also created a series of design requirements and process standards to prevent steel structures from developing lamellar tearing problems.

=Lamellar Tearing=

Lamellar tearing is a kind of material brittle fracture that occurs on the plane parallel to the rolled surface of steel elements (or perpendicular to the plane of rolling). In structural engineering, lamellar tearing most often occurs beneath the highly restrained welding joints of thick steel members especially thick plates which have a thickness over 1.5 inches. Lamellar tearing is usually not visible until the steel weld joint fails.

Origin of Lamellar Tearing
Steel experiences thermal expansion due to the heat of welding. Steel joint's shape is formed under thermal expansive force. Once the expanded steel cools, the internal thermal expansive force changes to internal shrinkage force and results in internal tensile stress in the steel. If a welded steel member, such as a steel plate, with a thickness over 1.5 inches, is thick enough the internal tensile stress (due to shrinkage) could exceed its fracture stress limit and cause microscopic gaps to be formed in the steel plate, known as lamellar tearing. Once such a steel plate is loaded, the gaps can expand and cause structural failure.

Factors of Lamellar Tearing
Lamellar tearing can be effected by several different factors, which include the material inclusion, lamination, hydrogen, banding, matrix embrittlement, temperature, among others.

//Inclusion//
Components of steel play important roles of steel property. Nonmetallic inclusion have essential effects to lamellar tearing. Typically, the inclusions involved in steel are silicates, sulfides, Si-AL de-oxidation, and other oxides. Such inclusions have different microscopic properties than steel. During and after the process of welding. steel and inclusions react differently; the result of the different behaviors is a low ductility and brittle behavior of steel, which is the source of lamellar tearing. In real world, inclusions in steel cannot be 100% eliminated due to economic consideration. Cost and cleanness of steel are influenced by the route followed during steel making and the best route is one which would provide, at a minimum cost, the least harmful inclusions as regards their type, size, shape, and distribution ( S. Ganesh and R.D Stout, 1976).

//Lamination //
Welding lamination could create the weak sections of welding. When large loads are applied to a welding joint, the weak sections of welding could fail and form opening at the center of lamination, which can further cause lamellar tearing.

//Hydrogen//
As the number one enemy of welding, hydrogen can also cause lamellar tearing. Hydrogen-included cracking in the heat-affected zone (HAZ) of the base or parent metal is another leading factor responsible for occurrences of lamellar tearing in modern steel construction (Seth Mayer, 2012). In a welding environment, hydrogen is inevitable. The reason for that is not only the moisture from the environment, but most importantly, moisture is contained within the electrode coating. During welding procedures, due to high temperature of welding, the hydrogen atoms are atomized from water molecules. However, the atomized hydrogen is not stable. After welding, hydrogen molecules are reformed and results in a decreased volume change of gas in the weld joint. Therefore, the internal pressure drops down while external pressure, atmospheric pressure is not changed. The internal pressure creates stress in the welding inclusion as well as the shrinkage stress that acts at the same time. The result is that rearing occurs in the lamination.

= Cause and Explanation of El Paso Civic Center Failure =

Size of Members
The cause of El Paso Civic Center building failure was determined to be a lamellar tearing problem that occurred on the 4.6' x 2' (in cross section) box girder of the 138-foot-diameter compression ring girder (shown on the figures 2 and 3). Such a large compression ring girder was made up of 25 separated box girders. To finish the connection between the exterior face of 2 1/2" - 3" flange plate and protruded 1" diaphragm plate the original design used normal fillet welds for strength requirements. However, there was a hidden problem of the design; lamellar tearing could occur inside the welding joint.

During plate welding, the heat of welding caused steel to expand. After the welding cooled down to natural temperature, the volume of steel shrunk after the shape of steel was expanded and formed. Therefore, shrinkage forces caused internal tensile stress in the joints. If the thicknesses of plates were larger than 1.5", lamellar tearing could happen (Ross, Steven S. 1984). Unfortunately, in the El Paso Civic Center project, the thicknesses of flange plates were 2 1/2" - 3", which means the internal tensile stress due to shrinkage exceeded steel fracture limit. At such state, steel no longer performed with plastic behaviors but brittle behavior (fracture) instead. Eventually, the internal tensile stress tore the micro-structure of steel apart (known as lamellar tearing) and formed gaps in the joints. The result of the internal gaps was that the entire compression ring girder could not carry as much gravity load as designed. Once the structure of the compression ring girder was constructed and started to carry gravity loads, hidden cracks developed and the failure of the compression ring girder was inevitable.

Drawing (Image Credit: Xiaodong Jiang ||< Figure 3: 3-D Section View of Box Girder (Image Credit: Xiaodong Jiang) ||
 * < [[image:compression-ring-girder.JPG width="272" height="331" align="right"]] ||< [[image:img011.jpg width="394" height="338"]] ||
 * < Figure 2: Compression Ring Girder Plan View

Hidden Cracks
Unlike other steel failure issues, lamellar tearing is generally not visible and can cause sudden failures. In the case of El Paso Civic Center, the hidden cracks were caused by lamellar tearing after the welding connections cooled (see figure 4). Cracks developed progressively in the box girder, and eventually caused the compression ring girder to fail. Welding Cooled (Image Credit: Xiaodong Jiang) ||
 * [[image:hidden-cracks.JPG width="300" height="242"]] ||
 * Figure 4: The Hidden Cracks in Flange Plate After

= Redesign and Reconstruction =

The redesign of the compression ring girder removed the damaged diaphragm plates and replaced them with weld material (see figure 5). "Part of the diaphragm and portion of the flange plates affected by the original fillet welds had been cut out and replaced with weld material fill, depicted with gray shading" (Seth M. Moyer, 2012). It took the general contractor, Robert E. McKee, Inc., $150,000 on the quality control of reconstruction. It also took El Paso city's public works department a similar amount of money on ultrasonic inspection of the welding joints (Ross 1984, p.260).

with Weld Material (Image Credit: Seth Moyer) ||
 * [[image:SMM - Lamellar Tearing - Image 4.jpg]] ||
 * Figure 5: Diaphragm and Damaged Flange Plate Material has been Removed and Replaced

=Similar Lamellar Tearing Cases=

The Twin 52-Story Atlantic-Richifield Towers
Author: Seth Moyer, BAE/MAE 2012 Link: http://failures.wikispaces.com/Lamellar+Tearing+Overview+and+Failures+Cases

"The 52-story twin towers in Los Angeles, California tallied $400,000 worth of repairs due, partly, to the effects of lamellar tearing (Ross 1984, p. 256). Delayed cracks were detected at the column spandrel connections and nearly ten percent of the spandrel/beam flange connections were damaged. The cracks developed in the plate base metal as well as within the welds themselves. Both the column and spandrel members that experienced material failures were made up of very heavy elements, all 1 1/2 inches or thicker. However, lamellar tearing was not the only kind of cracking failure that occurred in the steel members. In an extremely unusual manner, the ASTM A-36 mild steel that was used in the fabrication of the column and spandrel members behaved in a brittle, rather than ductile, way (Kaminetzky 1991, p. 244)."

Grand Coulee Transmission-Line Towers
"In the wake of the AISC meeting, the Bureau of Reclamation stopped construction on twenty transmission-line towers meant to bring water from a new Grand Coulee powerhouse" (Ross 1984 p. 260). At that moment, even though only one tower had been erected and detected to have a lamellar tearing problem, lamellar tearing later happened on another twelve constructing transmission-line towers. Unlike the El Paso Civic Center's thick steel plate issue, in the Grand Coulee powerhouse's transmission-line towers, the cracks were detected on the steel plates with the thickness range from 3/8" to 1 1/16". At that point in time, there was no previous record that showed lamellar tearing could happen in such thin plates.

Lamellar tearing cracks were detected on the box girder and column legs. Similar to El Paso Civic Center, the cracks were also found on the diaphragm plates part of the box girders and columns legs. Redesign and reconstruction were inevitable to the Grand Coulee transmission-line towers. Eventually, the U.S. Bureau of Reclamation paid $950,000 for the old towers, and another $952,000 to rebuild them (Ross 1984, p.260).

= Prevention =

It is very important to understand the potential steel strength deficiency of welding in order to prevent structures from developing lamellar tearing. American Institute of Steel Construction, AISC, and American Welding Society have carried out a series of research studies about lamellar tearing. They developed prevention recommendations relative to design, detail, and fabrication. Properly designed, detailed and fabricated steel is necessary to avoid highly restrained joints, which is important and effective relative to lamellar tearing prevention (Steel Construction Manual, 14th edition, p.2-42).

Design and Detail
Design and detail is the first stage of welding. If the design and details are wrong, nothing can be done correctly. The American Institute of Steel Construction (AISC) provides the improved detailing guideline in AISC (1973) and also Steel Construction Manual (14th Ed.). Figure 6 shows three improved welding details compared to susceptible weld details. Similar image are also provided in Steel Construction Manual (14th Ed.) and other steel organizations' documents and online sources, such as TWI website. In addition to joint details, the design and details of steel plate shall meet the standard provided on ASTM A770. (Image Credit:American Institute of Steel Construction) ||
 * Figure 6: Susceptible and Improved Details of Welding

Fabrication
To prevent lamellar tearing from happening, fabrication procedures shall be done carefully and correctly. There are several fabrication processes that can help to prevent lamellar tearing, such as preheating, buttering, peening, specification of electrodes and temperature monitoring.

**Prevention Recommendations** Many organizations have their own version of recommendations on lamellar tearing. In general, the prevention recommendations are based on the factors of lamellar tearing. The following recommendations are summarized by the stages of welding:

1. Design Phase
 * Limit the size and number of tack welds.
 * Design the minimum size of weld that would meet the design requirements.
 * The larger size it is, the larger internal stress would occur and might cause the gaps in a joint.
 * Adjusting and arranging welding and other types of connections to avoid through-thickness strain. (also see ASTM A770)
 * Determine and limit the sulfur levels (less or equal to 0.005%).
 * Because research studies from AISC and American Welding Society show that limiting the sulfur content below 0.005% can greatly reduce the lamellar tearing (also see Welding Defect, Wikipedia)
 * Select electrodes which provides the lowest yield strength for strength requirement of welding.
 * Because electrodes with lower yielding strength have better ductility while the high-strength electrodes are brittler.
 * Specify the preheating of the base metal.
 * Required preheating is to ensure that the HAZ (Heat-Affect Zone) micro-structure hardness levels are within the NACE MR0175 requirements. (also see //"Understand Hydrogen Failures//", AWS).

2. Fabrication Phase
 * Keep electrode original packaging until ready to use (Seth M. Moyer, 2012).
 * Because intact packaging can minimize the source of hydrogen from environment.
 * Old or surplus electrodes which are re-baked must not be utilized in joints where lamellar tearing is a concern (Seth M. Moyer, 2012).
 * This is also to minimize the environment effects to the electrodes.
 * Monitoring the temperature during preheating and welding processes.
 * This is to ensure that the finished weld joint would produce acceptable micro-structure and hardness levels. (also see // "Understand Hydrogen Failures // ", AWS).

3. Detection Phase
 * Ultrasonically check base metal for extent and location of laminations for critical welds.
 * This is to ensure the completed welding joints have no potential lamellar tearing problem.

= Conclusion =

The El Paso Civic Center lamellar tearing failure was an engineering disaster and caused a large economic loss back in the 1970s; however, since this accident, the structure engineering and construction field started to realize the importance of welding details and lamellar tearing prevention. After the lesson of El Paso Civic Center, the welding design and construction were able to be improved. Eventually, lamellar tearing rarely happens in modern steel construction.

In conclusion, to design a building with lamellar tearing considerations, the structure designer should carefully specify the details of base metal, welding, welding electrodes and any other details that relate to lamellar tearing prevention. As a part of the prevention process, welding operators shall carefully follow the specified requirements of welding, because the problem of lamellar tearing is hidden beneath the surface of the welding and base metal. Finally, ultrasonic checks should be required for all critical weld connections.

=Annotated Bibliography=

This article introduces lamellar tearing issue and refers lamellar tearing issue to EI Paso Civic Center.
 * Concrete Construction Staff, (April 1, 1974). "A problem in structural Steel." Concrete Construction.**
 * <[]> (October 3, 2014)**

This book introduces the lamellar tearing issue of El Paso Civic Center and provides improved detail to protect connection from lamellar tearing problem.
 * Kaminetzky, Dov. (1991). Design and Construction Failures: Lessons from Forensic Investigations. New York: McGraw-Hill. pp. 243-44. **

This book provides a detailed introction of lamellar tearing issue of El Paso Civic Center.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Ross, Steven S. (1984). Construction Disasters: Design Failures, Causes, and Prevention. New York: McGraw-Hill. pp. 255-66. **

It is a report reference of material variables effects to lamellar tearing.
 * S. Ganesh and R.D. Stout (1976), "Material Variables Affecting Lamellar Tearing Susceptibility in Steels", Welding Journal, November 1973, Research Supplement, Page 341-55** **<[]> (October 3, 2014)**

It is a report reference of fabrication procedure effects to lamellar tearing
 * E.J. Kaufmann, A.W. Pense and R.D. Stout (1981), "An Evaluation of Factors Significant to Lamellar Tearing", Welding Research, March 1981, Page 43-49 < **** []>(October 3, 2014) **

This wiki page introduces the overview of lamellar tearing issue and provides some lamellar failure cases.
 * "Lamellar Tearing and Failures Cases" (2012), Seth M. Moyer, Failure Cases Wiki. ** ** <http://failures.wikispaces.com/Lamellar+Tearing+Overview+and+Failures+Cases> **** (October 3, 2014) **

TWI provides the introduction of lamellar tearing and examples with good design details.
 * "Defects - Lamellar Tearing.",** **TWI** **<****[]**> **(October 3, 2014)**

It is the webpage of WeldCor Supplies Inc., and it also provides an introduction of lamellar tearing.
 * "Lamellar Tearing", WeldCor Supplies Inc. <[]> (October 23, 2014)**

<span style="color: #252525; font-family: Arial,Helvetica,sans-serif;">It is Wikipedia's brief introduction about all kinds of welding defect, which include lamellar tearing.
 * " Welding Defect", Wikipedia <http://en.wikipedia.org/wiki/Welding_defect#Lamellar_tearing** **> (December 2, 2014)**

It is the American Welding Society's introduction about hydrogen failures and prevention, it also relates to lamellar tearing.
 * "Understand Hydrogen Failures", AWS <@http://www.aws.org/wj/jan04/still_feature.html> (December 2, 2014)**

This standard specification provides a through-thickness tension testing of steel plate for special applications. The appendixes portion of this standard specification provides the reference information about lamellar tearing and points out the through-thickness ductility requirements for welding.
 * ASTM A 770-A770M - 86 (Reapproved 2001). "Standard Specification For Through-Thickness Testing of Steel Plate For Special Applications", ASTM.**

= Additional Resource and Reference =

It is a report reference of weldability for susceptibility to lamellar tearing
 * R.P. Oates and R.D. Stout (1973), "A quantitative Weldability Test for Susceptibility to Lamellar Tearing", Welding Journal, November 1973, Research Supplement ,**Page **481-557** **[|<http://www.aws.org/wj/supplement/WJ_1973_11_s481.pdf]>** **(October 3, 2014)**

This report provides a scientific study of the joint restraint effect on lamellar tearing susceptibility in steel plates.
 * L. Malik and B.A. Graville. (1979). Effect of Joint Restraint on Lamellar Tearing Susceptibility in Steel Plates. <[]>****(October 3, 2014)**