StructurePoint - spSlab Features

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Features

spSlab User Interface

Start Screen

Main Window

Tables Window

Reporter Window

Print/Export Window

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Analysis & Design

Analysis Methods

Equivalent Frame Method (EFM) of Analysis

spSlab utilizes the Equivalent Frame Method for the analysis and design of two-way slab systems, i.e. a slab system consisting of approximately rectangular panels with the ratio of longer-to-shorter span within a panel not exceeding 2.0, per American (ACI 318) and Canadian (CSA A23.3) concrete codes.

Slab Beams

The moment of inertia of the slab beam elements between the faces of the columns (or column capitals) is based on the uncracked section of the concrete including beams or drop panels. The moment of inertia from the face of the column (or capital) to the centerline of the column (or capital) is considered finite and is dependent on the transverse dimensions of the panel and support.

Columns

The computation of the column stiffness is more complicated as it utilizes the concept of an equivalent column. The stiffness of the equivalent column is affected by both the flexural stiffness of the columns and the torsional stiffness of the slabs or beams framing into the columns.

All applied loads are input as unfactored loads. There are no limitations imposed on the ratio of dead to live loads in the Equivalent Frame Method. Results of gravity load and lateral load analyses may be combined, however, the effects of cracking and reinforcement on stiffness must be accounted for in the lateral load analysis.

Load Patterns

The analysis of floor systems requires the consideration of several loading configurations. To cover different loading scenarios the program generates live load case based on the following load patterns.

Column and Middle Strip Widths

ACI and CSA codes define the width of the column strip on each side of the column centerline as being one-fourth of the smaller of either the transverse or the longitudinal span. These widths are printed as part of the design results.

Two-Way (Punching) Shear

Two-way (punching) shear check considering the effects of columns (rectangular, round), drop panels, column capitals, longitudinal beams, transverse beams, and slab bands can be performed.

Punching Shear Check Around Columns

Punching Shear Check Around Drop Panels

One-Way (Beam) Shear Calculations

One-way (beam) shear check considering the effects of drop panels, column capitals, longitudinal beams, transverse beams, and slab bands can be performed.

Slab Shear Capacity Check by Considering Drop Panel Contribution

Design Methods

Area of Reinforcement

The program calculates the required area of reinforcement (top and bottom) based on the values of bending moment envelope within the clear span. For rectangular sections with no compression reinforcement, the design flexural strength of the column strip, middle strip and beam must equal the factored design moment.

Concentration and Additional Reinforcement

spSlab computes the fraction of the unbalanced moment, that must be transferred by flexure within an effective slab width (a band) equal to the column width plus one and one-half the slab or drop panel depth (1.5h) on either side of the column.

Structural Integrity Reinforcement

In continuous beams, including longitudinal beams in two-way slab systems, spSlab and spBeam produce, in design mode, reinforcement that satisfies ACI requirements for structural integrity. For the CSA code, the program also performs calculation of the amount of integrity reinforcement at slab column connections in design mode.

Corner Reinforcement

The amount of corner reinforcement is calculated from the moment per unit width intensity corresponding to the maximum positive moment in span. The code allows the corner reinforcement to be placed at top and bottom of the slab in bands parallel to the sides of the slab edges.

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Results Output

Graphical Output

Diagrams

The graphical output is organized into diagrams that may be viewed, printed, exported or added to Report.

Internal Forces

This graphical view displays the internal shear force, the internal bending moment and the torsional moment diagrams for ultimate load envelope or any individual ultimate load combinations.

Moment Capacity

This graphical view displays the design strips moment capacity diagrams for any span. For beams designed/investigated per CSA A23.3-14/04, longitudinal reinforcement capacity due to combined M-V-T action is also displayed.

Shear Capacity

This graphical view displays the design strips one-way shear (and torsion) capacity diagrams for any span.

Deflection

This graphical view displays instantaneous deflection diagrams for any span.

Reinforcement

This graphical view displays the design strips flexural and shear reinforcement diagrams for any span.

Tabular Output

The Tabular Output can be accessed through both the Tables Module and the Reporter Module. The Tables Module allows users to view and export output data at any stage of model development, while the Reporter Module is used for creating, exporting, and printing customized reports once the design is complete. Both modules share the same output sections, with a few distinctions: the Reporter Module includes additional sections for cover, contents, and screenshots, while the Tables Module includes a Solver Messages section to display warnings or error messages generated during model execution.

Tables Module

Reporter Module

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Advanced Features

Deflections

Instantaneous Deflections

Instantaneous deflections are obtained directly by the program from elastic analysis of the defined system for three load levels. The first corresponds to dead load only, the second corresponds to dead load plus sustained part of live load only, and the third corresponds to dead load plus live load on all spans (total deflection).

Long-Term Deflections

The program estimates additional long-term deflection in structural members due to creep and shrinkage, addressing time-dependent behaviors that affect serviceability.

Deflections of Two-Way Systems

Calculation of deflections of reinforced concrete two-way slabs is complicated by a large number of significant parameters such as: the aspect ratio of the panels, the vertical and torsional deflection of supporting beams, the stiffening effect of drop panels and column capitals, cracking, and the time-dependent nature of the material response. The program uses an approximate method consistent with the equivalent frame to estimate the column and middle strip deflections. More information about this method can be found in Section 2.3.10.4. in spSlab Manual.

Shear Strength of Concrete Slabs with Openings

Concrete floor openings are routinely placed on design drawings and are factored into the initial analysis and design calculations. However, when openings are needed in existing floor slabs after they have been placed into service, the investigation of the beam shear and punching shear must be done carefully to maintain the floor load carrying capacity and avoid costly and labor-intensive reinforcement of the floor slab.

Slab opening effect is evaluated by reducing the perimeter of the critical section by a length equal to the projection of the opening enclosed by two-lines extending from the centroid of the column and tangent to the opening.

The following figure provides generic guidance for a designer with regards to permitted opening locations and dimensions. A designer needs to consider the distance between the opening and concentrated load or reaction area in addition to this generic guidance as outlined in ACI 318 and CSA A23.3.

Two-Way Joist (Waffle) Slab Design Approach and Methodology

Two-way joist slab often called two-way ribbed slab or waffle slab is an economical floor system when the spans are long and/or loads are high. Waffle slab analysis and design is similar to the procedure used with flat plates except that special considerations need to be taken into account to reduce the complexity of calculations needed when using exact geometry of the two-way joists. More information about this topic can be found in this Technical Article.

Structural Integrity Requirements

Enhancing redundancy and ductility is necessary in the event of damage to a major supporting element resulting from an abnormal shock or blast loading event. Minor changes in reinforcement detailing typically result in substantial enhancement in the overall integrity of a structure by confining the resulting damage to a small area and improving the resistance to progressive collapse. More information about this topic can be found in Section 2.4.4. in spSlab Manual and this Technical Article.

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Modeling with Templates

Utilizing Templates is a quick and simple option for new models in spSlab. The user can select from a set of pre-defined templates and edit their properties for simple and quick model generation.

Each template focuses on a particular slab or beam system with a specific loading pattern. The user can edit the geometric dimensions of the system, applied loads, boundary conditions, and material properties. Other system specific options may also be available for some templates.