Applied Knowledge

Richard Galli, PE Becomes Associate Principal and Co-Owner of Stone Security Engineering

New York, New York (March 22, 2016 ) – Stone Security Engineering, P.C., the woman-owned small business specializing in protecting people and property from accidental and manmade hazards, announced today that Mr. Richard Galli, PE is now an Associate Principal and co-owner of the company.

“This is a major milestone for Stone, and moves us one step closer to our goal of sharing ownership with our core team of dedicated engineers.  Richard is a talented engineer who brings a fantastic client-focused excellence to the team.   This translates to high quality analysis and successful projects for all involved.  I am incredibly pleased to have Richard join us in ownership.”  Hollice Stone, President and Founder

Mr. Galli  brings an impressive breadth of experience in the fields of security and safety design to the firm. His recent projects have included a new Veterans Administration Medical Center, an existing IRS facility, an international NGO compound in Helmand, Afghanistan, blast testing of innovative materials and building element configurations, and detailed design and analysis of doors, windows, and curtainwalls.  Rich has participated in more than 100 successfully completed projects related to blast, progressive collapse, and fragment evaluation and mitigation for government and industrial sector clients. The scope of these new construction or retrofit design projects has ranged from feasibility studies and conceptual designs to detailed design and construction administration support.  Richard received his Bachelor and Master of Science degrees in engineering from George Washington University in Washington, DC in 2006 and 2011, respectively, and is a licenses Professional Engineer in Virginia and New York.

Stone Security Engineering remains a small woman-owned business, even with our expanded ownership structure.

Stone Security Engineering, P.C., is an internationally recognized specialty engineering consulting business with offices In New York City and Washington, DC with focus on blast resistance, security and safety engineering and design, predicting and mitigating hazards from explosions, fires and toxins; assessing security and blast vulnerability; research and development, testing and training. Our engineers have participated in multi-hazard vulnerability, threat, and risk assessments for more than 200 facilities around the world and abnormal loading design for more than 300 buildings and structures. The company’s web site (www.StoneSecurityEngineering.com) contains more information.

WeWork ‘Creator’ Article

I want to thank WeWork ‘Creator’ Magazine for writing such a nice article on us.   Check it out here

SDOF vs FEA

When looking at structural design or analysis for response to blast loading, there are two basic analytic approaches that are commonly implemented: Dynamic Single-Degree-of-Freedom Analysis and Dynamic Finite Element Analysis.

Dynamic Analysis

Dynamic analysis is used when dealing with blast loads.  This type of analysis assumes that the load is applied instantaneously (or nearly so), generally with a finite duration (in the range of milliseconds).  Strength Increase Factors (SIFs) and Dynamic Increase Factors (DIFs) are applied to the static material values to account for:

  • Average expected strength, as opposed to published minimum values (SIF)
  • Strain rate strength enhancement, which can be relatively high, for example, for some grades of steel (DIF)

Dynamic analysis typically yields a displacement response that reaches a maximum value, then decreases with time (as opposed to a static analysis that reaches a steady state solution).  The response may oscillate multiple times depending on the blast load and loaded component characteristics.

Dynamic Single-Degree-of-Freedom (SDOF) Analysis

SDOF analysis is a simplified analytic technique, which is the most common dynamic approach used when investigating blast resistance.  In this approach, a structural component is represented as an SDOF model and is assigned equivalent properties of a spring-mass system (e.g., mass, stiffness, and resistance) to approximate component bending response.  This simplified system is typically used to calculate the displacement of the center point of the element (e.g., beam, column, wall).  The figure below shows graphically how the system is being simplified.

SDOF

The results of the SDOF analysis are generally defined in terms of support rotation and ductility.  The calculated maximum rotation and ductility are then compared to pre-determined response limits to translate the analytic results to damage levels (e.g., superficial, moderate, heavy, and hazardous) and then to overall Levels of Protection (e.g., Low, Medium, and High).  There are numerous industry reference documents that provide this correlation of analytic results to damage levels.  Some widely-used documents include:

SDOF analysis allows for rapid analysis of individual building components, which means that it is well-suited to blast vulnerability assessments of existing buildings and for use during initial and final design phases.  It allows multiple variations of calculations to be run in order to converge on a cost-effective and constructible solution that meets the applicable protective design requirements.

Finite Element Analysis

FEA is another approach to blast resistant design.  Dynamic FEA is a high fidelity technique in which the structural component or system is broken down into a large (but finite) number of discrete elements.  The analysis entails simultaneous equations being solved at different time steps, thereby allowing various parameters (e.g., deformation, stress) along the component (as opposed to a single deflection value in an SDOF analysis) to be determined and visualized throughout the response cycle.

The figure below shows an example of FEA output.

FEA_t03

FEA is generally not called for when analyzing simple building elements/systems for far-field blast loads (i.e., blasts that are far enough away to develop uniform loading over the face of the element/system being analyzed).  FEA can be a useful tool when looking at close-in explosions and/or complex configurations that act as multi-degree-of-freedom systems.  If FEA analysis is used, it is most appropriate once the design is well-developed, and not expected to vary significantly as the design process goes forward.  This is because the FEA approach is often time-consuming (and, in following, costly).  FEA assumes a far more detailed understanding of how a specific building is constructed than is commonly available for blast assessments or during the schematic and early design development phases of a project.