ALVIN P. TABAR, P.E.
STRUCTURAL
EXPERTISE
Building Design
Tower-On-Podium Building
The subsequent high cost of living due to the extreme densities of the urban center drives the need to develop tower-on-podium buildings. Tower-on-podium building is a multi-level building organized around a central core with the first few floors expressed as a podium building that serve as a pedestal for the high rise residential tower(s) above. The podium component normally houses shopping malls as well as public amenities that require unobstructed spatial layout while the upper structure(s) often used as office or residential units. The layout of the podium structure can use regularly spaced columns in longer span design; while the upper structure(s) utilize the more economical shorter span design using columns, load bearing walls and central core arranged in a more congested layout. To accommodate the discontinuities between the upper and podium structures, transfer plate normally would be essential at the base of the upper structure to transfer the loads from upper floors to lower podium floors.
Transfer Plate Design & Construction
There is no code of practice or standards governing the design of transfer plate and it cannot be designed like a normal floor slab. Common practice only proposes design principles and analytical concepts involving two design approaches based on Deep Beam and Thick Plate theories. The construction of the transfer plate is normally quite difficult too. It is usually located at a high altitude on top of the podium structure and in some design it can be over-hanging from the building line. The podium structure may not be able to provide the working spaces or support for the construction of the transfer plate due to differences in floor layout. Additionally, the transfer plate is usually very large and heavy in weight with thickness ranging from 8-ft to 14-ft with 5,000 sq ft to 15,000 sq ft in size and could weigh more than 15,000 tons. My experience in the design of large-scale tower-on-podium buildings utilizing thick transfer plates will be very beneficial to the design team in carrying out its design for Tower-on-Podium Building type. I utilize advance analysis techniques in transfer plate design as early as conceptual design phase. This allows me to provide valuable input on early decisions made that influence the constructability, cost and overall performance of the building.
Mat Slab Foundation Design
Mat foundations are normally used in buildings when the soil conditions result in conventional footings or piles occupying most of the footprint of the building or in the absence of high bearing and side friction capacities of the supporting soil media at a reasonable depth beneath the footprint of the building. Mat foundations are preferred in such circumstances because of the tendency of the mat to equalize the foundation settlements. Additionally, because of continuity, mat foundations have the capacity to bridge across local weak spots in the sub-strata. Mat foundations are not only utilized whenever the underlying load-bearing stratum consists of soft, compressible material with low bearing capacity but also as a giant pile cap to distribute the building load to a cluster of piles placed under the footprint of the building.
Mat slab foundation is relatively simple to design using the finite element method (FEM) adopted in most structural concrete design programs like SAFE by Computers & Structures, Inc., which I usually use in my design or RAM Concept by Bentley and a number of other commercially available structural analysis and design software. For complicated sites such as that of the Loyola Science Center Project of The University of Scranton, the challenge is in manipulating the supporting natural soil media to achieve the desired engineering properties for a safe and efficient building support. This solution requires a high degree of ingenuity and engineering judgment or instinct on the part of the structural engineer. My years of experience in the design of mat slab foundation systems which included supporting a 40 stories concrete residential tower and an undergraduate science laboratory building atop an abandoned coal mine would be very beneficial to design teams on projects where mat slab foundation systems would be required.
BIM/IPD/VDC
BIM Implementation
The design process for all members of the project team greatly improves with the proper implementation of Building Information Modeling (BIM) in a project. My 10+ years of experience in BIM implementation on the majority of my recent projects have enabled me to offer superior-quality design, better workflow and efficient project delivery.
Benefits of BIM
Successful advancement of BIM improves efficiency, production quality on the design process and design team coordination. BIM facilitates the resolution of errors, omissions, clashes and conflicts in the documents stage before construction begins. Conflict detection reduces the number of requests for information (RFIs) and change orders, saving both time and money. It enhances visualization, client communications, and design flexibility.
IPD
Integrated project delivery (IPD) is without question a major cultural shift for A/E firms including Structural Engineering. But the transition could not happen without technology and work processes to support it. IPD technology conversation cannot just center on the technology of building information modeling (BIM) alone, it must include the equally important enabling technologies such as PIM (Project Information Management). With PIM, co-location of the architects, engineers, consultants, and general contractors in one room would no longer be required to make changes to BIM model, otherwise necessary in earlier successful IPD implementations. Having implemented PIM (using Newforma) in my recent projects allows me to participate efficiently in a team-wide collaboration regardless of team members' locations. By utilizing PIM, it not only allows me to work from my location using our IT infrastructures (no co-location), it also provided me the means to efficiently carry out project administration during the Construction Phase of the project with full electronic shop drawing review, processing of RFIs and tracking of issues and action items assigned to the construction team. My expertise in BIM coupled with my experience in successful PIM implementation would greatly benefit all members of the project team and raise the profitability to all project stakeholders in a risk and reward approach of IPD method.
Virtual Design and Construction (VDC)
As owners and construction teams are starting to engage in the full benefits of BIM, Structural BIM model must not just be a simple tool to produce printed construction documents but rather as a genuine part of multi-disciplinary performance models in a Virtual Design and Construction (VDC) environment. This requires that a structural BIM model be at an appropriate Level of Development (LOD) at certain period in the design and construction phases. My knowledge and experience in the implementation of BIM in a multi-disciplinary environment will greatly benefit any design and construction team embracing VDC that allows the resolution of problems beforehand and not lead to project delays or costly modifications.
Conceptual Design
Collaboration
The fundamental principle to a successful project is a collaborative effort by the architect and structural engineer from the very beginning of the project. It is very important that during conceptual design phase, layout of feasible structural systems already meet the design intent of the architect and the client as well as complementing with the building architecture. My years of experience in employing new framing techniques coupled with my vast knowledge in current technological advancements in structural engineering make easier the search for solutions to structural problems that not only result in cost effective structures but also harmonize with architectural layout. I have been adopting innovative design concepts through continued research for better and more efficient methods of resisting lateral and gravity loads as well as implementing framing systems geared towards reducing the impact of structural components to other building features to minimize the overall building cost.
Innovative Lateral Design Concepts
For tall buildings, the ingenuity of lateral design makes a big difference in the material quantities. With the advancements in the methods used in the analysis of structures, improvements in the predictive ability of the analysis and the reliability of computer solutions are now achievable so the interactions between structural elements that were considered minor during the pre-computer era and thus neglected can now be taken into account. Some of my prior projects represented the earliest applications of typical floor flat slabs utilized as part of the main lateral wind force resisting systems. This innovative concept is now used extensively in concrete high-rise buildings which contribute to the reduction in overall building costs.
Structural Concept Specialties:
•Team Preparation for Interviews
•Structural Concept
•Structural Peer Reviews
•Structural Value Engineering