Several of our engineers ventured to Portland, OR, last week to present their papers, studies and cases at the 2015 Structures Congress. This congress is organized by the Structural Engineering Institute of the American Society of Civil Engineers.
Communication and Coordination in Residential Concrete Construction with a 2-Day Cycle
The 2-day cycle is commonly used in New York City for residential concrete projects. Given that a floor is poured every other day, instant communication and infield coordination are key to maintain the fast paced schedule and minimize mistakes. The structural engineer needs to be fully immersed in the day-to-day construction process to ensure successful and timely completion of the project. A case study of a 600,000 square feet residential concrete flat plate building will be presented to illustrate the construction process in a 2-day cycle. The typical floor plate consisted of 58 apartments with an average floor area of 700 square feet per apartment, which resulted in congestion of mechanical, electrical, and plumbing (MEP) components. As detailed coordination of the MEP trades occurred during construction, the structural engineer played a crucial role in ensuring that the placement of conduits and risers did not compromise the capacity and the integrity of the structure. Though ACI-318 provides some guidance on how to address embedded conduits and slab openings adjacent to columns and walls, the provisions were found to be insufficient when dealing with the complexities and constraints present in the project. The construction team communicated directly with the structural engineer, but a formal submittal and RFI process was also put in place for record keeping and to keep all parties informed. The case study will illustrate the common coordination problems that occur in the field, where they are likely to happen, and strategies to minimize these problems in future projects. The presentation is targeted towards structural engineers involved in building design and construction of reinforced concrete buildings. The case study and construction practices presented are from the New York City region but the ideas presented are applicable to other parts of the country. Through examination of the lessons learned, the audience can better identify potential coordination and communication issues in future projects and resolve them quickly as they arise.
Probabilistic Performance Based Design Multi-Objective Optimization for Steel Structures
By Sanaz Saadat, Charles V. Camp, Shahram Pezeshk and Christopher M. Foley
Multi-objective optimization for the probabilistic seismic performance based design of an example moment frame steel structure is presented. Direct economic and social losses associated with seismic events, which are of interest in the current recommended frameworks for the performance based design of structures, are considered in the optimization problem defined. Three optimization objectives are selected: the initial construction cost, modeled as the weight of the structural system; expected annual economic loss associated with damage resulting from seismic hazard; and expected annual social loss resulting from seismic hazard induced damage. Hazus recommended procedures are applied in the economic and social loss calculations which include the fragility functions used in the damage analyses and injury event models implemented in the social loss calculations. The multiobjective optimization method uses a non-dominated sorting genetic algorithm strategy. The optimization results for the multiple objectives are presented and discussed in the form of Pareto fronts. Engineering demand parameters implemented for the seismic loss analysis are inter-story drifts and peak floor accelerations and are obtained using inelastic time history analysis for the ground motions associated with various seismic hazard levels. To illustrate the design procedure, loss parameters are calculated for an example steel structure located in Los Angeles, CA.
Challenges and complexity of air-rights structures
Case Study: One Jackson Square
Karl also moderated a session about case studies of disproportionate collapse.
How to Succeed Without Risking It All!
Achieving success on projects can be elusive. With many technical and non-technical demands on today’s structural engineering Project Manager (PM), this session will focus on how non-technical items can produce some risky challenges during the life of a project and how a PM can successfully navigate these challenges. During the session, several tools and checklists developed by CASE will be showcased, giving PMs resources to help reduce risk factors on a project and achieve that elusive success!