Technical Articles


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Flexural Effective Stiffness for Individual Columns

Author: StructurePoint (SP)

Year: 2017

Pages: 1

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In consideration of slenderness effects in an individual column design by Moment Magnification Method, ACI 318-14 utilizes the effective flexural stiffness, (EI)eff, of a column section to calculate the critical buckling load, Pc. The designer may utilize any of the options for (EI)eff for individual columns in ACI 318, section 6.6.4.4.4 given the available input data at the given design stage and desired level of accuracy.


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Comparison of Concrete Two-way Slab Analysis Methods

Author: StructurePoint (SP)

Year: 2017

Pages: 2

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Two-way concrete slabs are analyzed using one of three method: Direct Design Method (DDM), Equivalent Frame Method (EFM), and Finite Element Method (FEM). A comparison of general limitations, drawbacks, advantages, and cost-time efficiency of each method is presented to assist structural engineers to determine which method to use based on the project complexity, schedule, and budget.


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Constructing Mat Slab

Author: StructurePoint (SP)

Year: 2017

Pages: 4

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Corn Products International is replacing a worn-out coal-fired power plant with a building a state-of-the-art power plant that will burn high-sulfur Illinois coal and meet all current emissions requirements. Corn Products use PCAMats to design a 4.5 foot thick reinforced mat slab consisting of 3819 cubic yards of concrete.


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Modeling Construction Joints Structural Foundations in spMats

Author: StructurePoint (SP)

Year: 2017

Pages: 1

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In structural mat foundations and slabs on grade, construction joints are typically required to transfer vertical shear force between adjacent concrete placements. Transfer of moments across the joint may or may not be required. There are two possible ways to model a construction joints in pcaMats to analyze and design a concrete foundation where only shear is transferred and moment is not.


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Soil Sub-Grade Modulus

Author: StructurePoint (SP)

Year: 2017

Pages: 2

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Soil bearing capacity, soil compressibility, and soil modulus of subgrade reaction are various measures of strength-deformation properties of soil. The allowable soil bearing capacity is the maximum pressure that can be permitted on foundation soil with adequate safety against soil rupture or excessive settlement. Another soil characteristic, compressibility of cohesive soils, determines the amount of long-term settlement under load.


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Foundation Slabs Supported by Dissimilar Soils

Author: StructurePoint (SP)

Year: 2017

Pages: 3

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An existing L-shaped foundation slab (supported by Soil 1) will undergo expansion (supported by Soil 2). On the expansion side, the soil subgrade modulus is 100 kcf because the contractor could not match the soil properties under the existing foundation slab, which is 200 kcf. spMats v8.10 software program is utilized to investigate the impact of the dissimilar soils on the alculated bearing pressure for the combined foundation as well as other design parameters such as displacement, bending moments, and required reinforcement.


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Slabs on Grade with Single Layer of Reinforcement

Author: StructurePoint (SP)

Year: 2017

Pages: 2

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Ground supported slabs are frequently designed with a single layer of reinforcement. Such slabs are referred to as membrane slabs, floating slabs, or filler slabs and range in thickness from as little as 4 to 8 inches depending on the supported loads. In warehouses and storage facilities such slabs are subjected to concentrated point loads from storage rack posts or forklift wheel loads.


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Finite Element Mesh Density Influence on spMats Model Results

Author: StructurePoint (SP)

Year: 2017

Pages: 3

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Structural engineers routinely ask us about the influence of mesh density on the results obtained from spMats models. In any Finite Element Analysis (FEA), individual finite elements can be visualized as small pieces of a structure and particular arrangements of these elements is known as a mesh. Mesh density in FEA is defined as the number of elements used in modeling a given structure.


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Concrete Type Classification Based on Unit Density

Author: StructurePoint (SP)

Year: 20017

Pages: 1

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spSlab Program updated the unit density values for concrete types used historically to better correlate with the more detailed definitions introduced in ACI 318-08 while maintaining the unit density values pertaining to previous editions of ACI 318.


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Equivalent Frame Method Design Factors for Moment Distribution

Author: StructurePoint (SP)

Year: 2017

Pages: 2

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To calculate the factored moments using the moment distribution procedure it is necessary to determine moment distribution factors and fixed-end moments for the equivalent frame members (columns and slab-beam members). The designer is required to take into account the non-prismatic nature of equivalent frames and to account for the variation in the moment of inertia along the axis of the slab-beam between supports. With the increasing use of computers for two-way slab analysis by the Equivalent Frame Method, programs such as spSlab take into account the combination of the exact geometry of column elements, torsional members, and slabbeams to complete the structural analysis and determine the design moments without the need for design aids.


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Structural Wall Reinforcement Design Considerations

Author: StructurePoint (SP)

Year: 2017

Pages: 2

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Structural walls are frequently designed with out of plane loads and two curtains of reinforcement. spWall has an option for design of walls with two curtains of reinforcement as well as one curtain of reinforcement to accommodate various needed wall thicknesses. The proper consideration of this condition as provided by spWall is important to ensure the successful performance of compression reinforcement in the wall section.


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Reinforced Concrete Floor Systems (2 PDH)

Author: David Fanella, Iyad Alsamsam

Year: 2005

Pages: 8

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Reinforced concrete floor systems can provide an economical solution to a wide variety of situations. Numerous types of nonprestressed and prestressed floor systems are available to satisfy virtually any span and loading condition, see Figure 1. Selecting the most effective system for a given set of constraints can be vital to achieving overall economy, especially for low- and mid-rise buildings and for buildings subjected to relatively low lateral forces where the cost of the lateral-force-resisting system is minimal.


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Post-Tensioning for Two-Way Slabs (1 PDH)

Author: Amy Reineke Trygestad

Year: 2005

Pages: 8

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Every major metropolitan area is getting a facelift. Old buildings are being renovated and converted, while new construction continues to add to the skyline. Downtown living is more popular than ever, and with residential construction, two-way post-tensioned flat plates are the structural system of choice. Learn the basics of post-tensioning two-way slabs in this compact article.


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Structural Integrity Requirements (1 PDH)

Author: M. E. Kamara, Mike Mota

Year: 2006

Pages: 8

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Structures capable of safely supporting all conventional design loads may suffer local damage from severe, local abnormal loads, such as explosions caused by gas or industrial liquids, vehicle impact, or impact of local effects from very high winds such as those recorded in tornadoes. Generally, such abnormal loads or events are not design considerations. However, basic structural intergrity is an essential feature for limiting dissporportionate damamge and utlimately achieveing building resilience, durability, and serviceability


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Engineering Mass Concrete Structures (1 PDH)

Author: John Gajda, Iyad Alsamsam

Year: 2006

Pages: 8

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Mass concrete is all around us. Traditionally, mass concrete has been associated with dams and other extremely large placements. This is no longer the case. Larger placements for economy and the use of concretes with high cement contents for durability and rapid strength gain mean that an increasing number of concrete placements must be treated as mass concrete. Learn the basics of mass concrete spcification and mitigation techniques of damaging effect of excessive heat of hydration.


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Torsion Design of Structural Concrete Based (1 PDH)

Author: M. E. Kamara, B. G. Rabbat

Year: 2007

Pages: 8

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Upon reading the article and completing the quiz, the reader should be able to understand the behavior and design of structural concrete members subjected to torsion. The article presents the American Concrete Institute Building Code (ACI 318) design provisions and detailing requirements for torsion design.


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Strut-and-Tie Model for Structural Concrete Design (1 PDH)

Author: Attila Beres, B. G. Rabbat

Year: 2007

Pages: 8

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This article sponsored by StructurePoint discusses the strut-and-tie model in concrete structures. Upon reading the article, the reader should be able to understand the basic principles and the related ACI 318-05 Code requirements for Strut-and-tie modeling, analysis, design and detailing of deep beam members in buildings and bridges.


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Economical Concrete Formwork

Author: Amy Reineke Trygestad

Year: 2006

Pages: 1

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The key to designing economical reinforced concrete structures is not optimization of the material quantities. Rather, the key is constructability. Successful concrete building design must include consideration of the building process, sequencing, forming, shoring, and staging. Formwork consideration affect over 50% of the building framing construction cost. This article focuses on economical concrte building formwork selection.


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Concrete Building Members - Assembling Loads

Author: Amy Reineke Trygestad

Year: 2005

Pages: 5

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An essential primer on the origin of loads and combinations necessary for the analysis and design of reinforced concrete members. Detemine everything the concrete member will support and make sure you account for all loads needed for design. Article provides a summary of external and internal the engineers needs to consider in any concrete building or bridge desing project.


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Design of Concrete Structures for Fire Effects

Author: Amy Reineke Trygestad

Year: 2005

Pages: 4

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For any concrete building or structure, the governing code will require provisions to achieve a specific fire rating. Building owner may require your design to comply with stricter fire design requirements. Learn the basics of fire endurance in selection and design of reinforced concrete member design. This article will provide you a primer and basic understanding of fire effects and rating of concrete structures.


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Structural Integrity Requirements for Concrete Buildings

Author: Portland Cement Association (PCA)

Year: 2006

Pages: 6

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Concrete structures capable of safely supporting all conventional design loads may suffer local damage from severe local abnormal loads,such as explosions due to gas or industrial liquids, or vehicle impact. The ability of concrete buildings to withstand blast loads can be substantially enhanced with minor changes in reinforcement detailing. Explore ACI 318 concrete design and detailing requirements to provide continuity, redundancy, and increase ductility of concrete buildings.


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Two-day Construction Cycle for High-Rise Structures Based on Use of Preshores

Author: Jacob Grossman

Year: 1986

Pages: 5

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Classic article by a renowned engineer and formost expert in concrete floor systems. Reflecting on how New york city engineers and contractors have perfected the two-day construction cycle for flat plate and flat slab high-rise buildings. A step by step procedure to achieve construction efficiency using preshores during the stripping of primary forms and shores while maintaining safety. Must read for any concrete designer!


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Primer - Blast and Progressive Collapse Effects on Buildings

Author: Portland Cement Association (PCA)

Year: 2006

Pages: 8

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Primer introducing progressive collapse as a situation where local failure of a primary structural component(s) leads to the collapse of adjoining members, in turn leading to additional collapse. Hence, the extent of total damage is disproportionate to the original cause. Blast effects often result in a chain reaction or propagation of failures following damage to a relatively small portion of a structure.


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Design of Deep Beams - Girders

Author: Portland Cement Association (PCA)

Year: 1976

Pages: 12

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Deign of reinforced concrete deep beams, transfer girders, or coupling beams is increasingly common. This classic document with numerical design aids has been used for decades by practicing engineers. Today nonlinear analysis programs like spWall or detailed Strut and Tie models can also be used.


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Openings in Concrete Floor Slabs

Author: Portland Cement Association (PCA)

Year: 2006

Pages: 4

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Selecting locations and sizes for openings in two-way floor slabs for both new and existing structures can often be accommodated without requiring strengthening. Learn the ACI 318 provisions for selecting opening size and location in various floor slab systems and review and primer on strengthening techniques.


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Two Way Concrete Slab Punching Shear Check

Author: American Concrete Institute (ACI)

Year: 2005

Pages: 1

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When using the Equivalent Frame Method (EFM) to comply with ACI 318, should structural engineers check punching shear in two-way concrete floor slabs for biaxial moments simultaneously? Dr. Jim Wight and ACI Dan Falconer help clarify this issue in a Q&A from an issue of concrete international.


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Ultimate Load Factor Design for Spread Footing and Mat Foundations

Author: American Concrete Institute (ACI)

Year: 2010

Pages: 2

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Footing design requires load factors for calculation of pressure distribution and determination of soil contact area for all service and ultimate load combinations. Major differences between service and ultimate design conditions can exist. spMats Program users often ask about this and possible uplift? Dr. Jim Wight and ACI-318 members help clarify this issue in a Q&A from an issue of CI.