What Is Precast Structure Calculation?

Precast reinforced concrete structures are erected by assembling columns, beams, purlins and panel elements produced in a factory on site. In single-storey, wide-span industrial buildings, roof beams are mostly pinned to columns, truss-type beams whose depth varies along their length are used, and the roof cover may not behave like a rigid slab.

TBDY 2018 Chapter 8 defines the design of connections in these structures, Annex 8B the modeling of the roof plane with equivalent braces, and 4.3.6 different structural system coefficients for the upper and lower parts in buildings with an intermediate floor. In buildings with overhead cranes, crane loads, seismic forces on façade panels per Chapter 6 and foundation sliding are also part of the design.

StatiCAD links these requirements to the general analysis workflow with tools specific to precast buildings: connections are designed with the forces obtained from the analysis, and every calculation creates a record that goes into the calculation report.

What Does StatiCAD Do in Precast Structures?

The entire workflow of a precast industrial building, from modeling to connection design.

Nonprismatic and Precast Sections

  • Nonprismatic beams: a section varying along its length in a single member, with true stiffness variation
  • Linear, parabolic and cubic stiffness variation; double-pitched (gable) roof beam
  • Parametric section templates: Precast I, Precast T, Precast U, box and trapezoid
  • Transfer to SAP2000 with precast section definitions

Pinned Connections and Roof Diaphragm

  • Release the ends of selected beams with a single command (M2 + M3)
  • TBDY Annex 8B: modeling a trapezoidal sheeting or sandwich panel roof with equivalent brace pairs
  • Equivalent axial stiffness, brace force capacity and applicability conditions
  • Rigid or semi-rigid diaphragm options; exact solution of the rigid diaphragm in roofs with thousands of nodes

Overhead Crane and Additional Masses

  • Crane girder design forces from wheel reactions
  • Automatic writing of vertical force, horizontal force and eccentricity moment onto columns
  • Automatic definition of the four crane load cases (X+, X−, Y+, Y−)
  • Entering façade panel and crane bridge masses as additional seismic mass only

Different R and D (TBDY 4.3.6)

  • Different response modification and overstrength factors for the lower part in buildings with an intermediate floor
  • Automatic calculation of the ν factor from storey weights, or manual entry
  • Lower part internal forces, shear capacity calculations and relative storey drifts with the corrections of the code

Connection Design (TBDY Chapter 8)

  • Pinned (dowel) connection: overturning, starter bars and dowel shear
  • Moment-resisting connection with wet joint on top and welded at the bottom: continuity reinforcement, weld and moment capacities
  • Purlin and gutter beam connections: dowel shear-friction, fillet weld and purlin buckling
  • Demands are taken from the analysis results of the selected beam with one click

Façade Panel, Foundation Sliding and Beam Reinforcement

  • Façade panel equivalent seismic load (TBDY Chapter 6)
  • Foundation sliding check (TBDY 16.8.4)
  • Automatic reinforcement calculation in polygon, precast and nonprismatic RC beams
  • True section outline, cover and reinforcement layout in beam cross-section drawings

How Does It Work?

  1. Define the sections: rectangular columns, precast templates and nonprismatic roof beams.
  2. Draw the columns and beams; release the roof beam, purlins and gutter beams with a single command.
  3. Set the roof diaphragm; generate the Annex 8B equivalent braces for trapezoidal sheeting or sandwich panel cover.
  4. Enter the overhead crane loads, façade panel and crane masses; set the different R and D in a building with an intermediate floor.
  5. Run the analysis; design the connections with the analysis forces and get the report.

Reports

Precast calculations are added to the general calculation report:

  • “Precast Connection Design (TBDY Chapter 8)” page: demand, capacity, ratio and result for each connection
  • Summary of inputs and intermediate results for each record, sources of demand and capacity
  • Nonprismatic section definitions in the section reports
  • Reinforcement of polygon and nonprismatic beams in the detailing drawings and quantity take-off
  • Turkish or English report

Verification

The precast features were developed and compared on the example building (40×75 m, with an intermediate floor, 200 kN overhead crane) in the book “Analysis and Design of an Example Precast Concrete Industrial Building per TBDY-2018” by the Turkish Precast Association.

The Annex 8B, overhead crane, different R and D, connection, façade panel and foundation sliding calculations were compared with the numerical examples in the book; the results match exactly except where the program applies the code on the safe side. When the same finite element model was built independently in SAP2000 v27, the periods came out within 1%.

Details of the verification studies (Knowledge Base)

Codes and Standards

TBDY 2018 Chapter 8 TBDY 2018 Annex 8B TBDY 2018 4.3.6 TBDY 2018 Chapter 6 TBDY 2018 16.8.4 TS 500
Which edition? The precast tools (connection design, Annex 8B braces, overhead crane loads, different R and D, precast templates) are included in StatiCAD Ultimate. The nonprismatic section definition is available in all editions.

Frequently Asked Questions

How is a nonprismatic roof beam modeled?

The beam is defined as a single member with a section varying along its length: the start and end sections, segment lengths and the form of stiffness variation (linear, parabolic, cubic) are entered. A double-pitched gable roof beam is defined with two segments. The analysis, SAP2000 transfer and reinforcement calculation use the nonprismatic section automatically.

Should the roof diaphragm be taken as rigid?

The default assumption is a rigid diaphragm. For roofs with trapezoidal sheeting or sandwich panel cover, the shear stiffness of the roof plane can be modeled with equivalent brace pairs per TBDY Annex 8B. In this case, it is recommended that you also run the rigid diaphragm solution for comparison.

How are overhead crane loads defined?

The wheel reactions from the manufacturer’s table, wheel spacing, dynamic factor and crane girder span are entered. The program calculates the crane girder design forces, defines the four crane load cases and writes the vertical, horizontal and eccentricity loads onto the selected columns. Load combinations including the crane are defined by the user.

Do I have to enter the forces manually for connection calculation?

No. After the analysis, select a single beam and use the “Take from selected beam” button to transfer the forces at the relevant end of the beam to the connection window. Each calculation creates a connection record and goes into the report.

Which StatiCAD edition includes it?

The precast tools are included in StatiCAD Ultimate; the nonprismatic section definition is available in all editions. The precast data of a project prepared in Ultimate is preserved in the file.

Related Pages

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