WRITTEN Testimony BY
Dr. Ronald J. Massa
Before the House Subcommittee on Public Buildings and economic development
Washington, D.C. JUNE 4, 1998
Mr. Chairman, Members of the Sub-Committee, Ladies and Gentlemen.
Concerns about the safety of our public buildings and their occupants are most strongly motivated today by two issues. First, the tragic explosives attacks on the World Trade Center and the Murrah Federal Building clearly indicate that terrorism is here in America, It is not just alive and well in far away places with strange sounding names. Second, like our public buildings, terrorism is likely to remain here for a long time reflecting the social and political diversity and mental health of this and future generations.
In spite of recent publicity raising concerns about biological, chemical and radiological weapons potentially in the terrorist arsenals, the high explosive bomb -- particularly the large improvised bomb carried to the site in a vehicle -- will long remain the weapon of choice of politically motivated terrorists, misguided zealots and deranged persons alike.
Bombs are easy to make. They can be easily transported in a clandestine manner. A 1000 pound high explosive bomb could require as little as 10 cubic feet of cargo space -- a package less than 3 feet on a side which will fit in a van or station wagon. They can be detonated when the bomber is far away with little likelihood of immediate apprehension.
Even with modern building codes and construction techniques, a relatively small bomb can make tons of building materials a part of the weapon -- rather than a component of the defense. Yes, the bomb offers many advantages to the terrorist.
Government has a serious and continuing obligation to protect its employees, visitors to public buildings and even people walking or working in the neighborhood when, and if, its facilities become magnets for bomb attacks. Unlike rifles which can be pointed directly at the target, the bombs destructive force propagates in all directions involving an entire neighborhood of buildings and people.
Even more important than protecting the public from the consequences of bomb attacks on public buildings, government has to set an example for the private sector in adopting technically meaningful and cost effective approaches to meeting these same responsibilities.
Most of the major buildings in our country are privately owned and managed. These buildings are often the neighbors of public buildings which might be targeted for bomb attack. In many instances, these private buildings could be the target of such attacks; public buildings could be the neighbors which are unfortunately involved. Any remedial measures adopted by the government must make sense for entire neighborhoods -- public and private buildings alike.
Recent history can provide important guidance in how we can implement large scale bomb defense measures -- measures which can be effectively applied to both public and private buildings. The Murrah Federal Building, the Dhahran bombing, the Bishopsgate bombing in London and the San Isidro bombing in Lima and scores of other bombings around the world all tell a similar story -- begin your bomb defense with architectural glass.
The consistent bad news is that glass is the single greatest source of both building damage and human injury in urban bomb attacks. Glass places everyone in the neighborhood at risk of injury, not just the occupants of targeted buildings.
But the glass news is not all bad. It is technically and economically feasible to mitigate glass effects, in both new and existing buildings as opposed to making structural changes in those buildings or significantly increasing enforced stand-off distances around them.
Measures which mitigate the effects of failed glass in bomb attacks must protect both the occupants of buildings and people outside of buildings on sidewalks or streets. In many urban bomb attacks more passersby are at risk than occupants of targeted buildings. In urban bomb attacks many people can be fatally injured at great distances from the detonation -- people who would have survived uninjured but for falling or flying glass.
Whatever measures are taken to reduce glass hazards in public and private buildings, they should last as long as present glazing -- essentially for the life of the building. Short term remedial measures, such as window films, should be subjected to life cycle cost analysis before they are adopted. Our goal should be to replace or harden ordinary window glass with a material as easy to maintain as present glazing.
Whatever glazing solutions we adopt must apply to both existing buildings (through retrofit) and to new buildings (through design and analysis). Both existing and new buildings must be protected in a cost effective manner. It is entirely possible that "one size will not fit all" and that different solutions will apply to different buildings.
In fact, we must develop a "Glass Plan" for each building. A Plan based on science, on test results and on site specific analyses consistent with our growing experience base with glass performance in actual explosives attacks.
When our "homework" is completed, laminated glass, protecting us from trauma injury as our car windshields for more than 60 years, will emerge as the only practical choice for new construction. Note that in the highly technical and cost competitive worldwide auto industry, we dont use polycarbonates, other plastics or filmed glass. There must be a good reason why!
Actually there are many reasons why and many of them apply equally well to building glazing. Strength. lifetime, ease of maintenance and post breakage behavior are some of them.
Consider a nominal 1/4" thick laminated glass window lite made of two 1/8" thick sheets of annealed glass bonded together with heat and pressure by a tough, 0.030" thick polyvinyl butyral (PVB) interlayer. [Use shirtail to make points here] This glass looks and feels like any other piece of window glass of the same thickness. If we subject this laminated glass lite and an ordinary lite of window glass to blast overpressures beyond their nearly identical breaking points, both will crack and break. Once they crack under blast loads, the similarity between the ordinary window glass and laminated window glass ends dramatically.
The ordinary window glass will fail catastrophically breaking into large sharp pieces which will fly into the building on which they are installed and fall to the ground outside the building. These sharp glass shards, traveling up to 100 feet per second, can and will kill or maim many in the vicinity of an explosives attack on a building glazed with ordinary window glass.
The laminated glass will also crack, but it will remain in one piece tenaciously clinging to its frame. It may release some powdered glass at the crack sites, but there will be no significant flying or falling glass and few, in any, injuries. As the attack on the glass becomes more and more severe, either through the use of a larger explosive charge or detonation at a reduced standoff distance, the laminated glass will reluctantly leave its frame in one piece or a few pieces of less destructive potential than ordinary window glass.
Of course this laminated glass performance should not surprise us. It is quite similar to what happens if we throw a brick at an automobile windshield with increasing velocity. The windshield will crack and require replacement, but the occupants of the car will escape injury until the attack severity is many times greater that the attack severity which would break ordinary window glazing.
Why isnt laminated glass used in all of our buildings -- particularly our public buildings which might be at particular risk of bomb attack? This question is best answered in two parts. First, in new buildings it is difficult to believe that laminated glass is not the universal glazing choice. While the acquisition cost of laminated glazing might increase overall construction cost by a percent or so, in addition to bomb, hurricane, earthquake and forced entry protection, the laminated glazing will also provide sound and heat isolation and aesthetic effects such as colored and reflective glazing.
Laminated glass should be the architectural glazing choice in all new construction -- particularly landmark public buildings.
Second, let us look at installing laminated glass in existing buildings. We must begin by recognizing the natural reluctance to re-glaze existing buildings. The prospect of removing a perfectly good piece of glass that can last another 50 years sounds like a needlessly expensive remedy. However, we must also recognize that if re-glazing is not done, only short term solutions are available. With such solutions, such as remedial window film, life cycle cost and performance both become important and should be carefully considered. There may not be a short term solution which is either technically comparable to laminated glass or less expensive.
We recommend that a proper "Glass Plan" be prepared for each public and/or private building under consideration. These glass plans will provide site specific guidance on how a multiplicity of non-permanent solutions (shields, drapes, screens, plastic film, etc.) and permanent solutions such as laminated glass or glass removal can assist in glass damage and injury mitigation. Such guidance could materially reduce the overall cost of protecting window glazing by using only those remedial measures which are effective at each location on the building.
The performance of window glazing in an explosives attack is not a great mystery. Many decision makers have witnessed glazing performance tests and demonstrations such as those conducted at the DoD Force Protection Equipment Demonstration (FPED) at Quantico, Virginia last fall. We saw clearly that laminated glass protects both building occupants and neighbors from flying and falling glass and prevents blast energy from entering a building through failed architectural glazing.
Other materials can provide, in whole or in part, these same benefits. But none of them offers the combination of effectiveness, low cost and ease of maintenance over the life of the building as laminated glass -- the same laminated glass which has been protecting us from glass injuries in thousands of automobile accidents for scores of years.
Lets learn from the past. Lets do it right based on science and engineering rather than perception. Lets do it now. Lets do it with the best and most versatile material -- laminated glass.