SYS_LSF-class: System Limit-State Function (SYS_LSF)
In TesiproV: Reliability Analysis Methods for Structural Engineering

SYS_LSF-class

R Documentation

System Limit-State Function (SYS_LSF)

Description

A reference-class that stores a user-defined limit-state function. The function can be written either as an **expression** ('expr') or as a **regular R function** ('func'). All random variables that appear in the function must be supplied in the 'vars' list as 'PROB_BASEVAR' objects.

Details

The method 'getLSF()' returns a **closure** that expects a numeric vector 'x' (ordered exactly like 'vars') and evaluates the limit-state function.

Sign convention: g(x) > 0 is the safe domain, g(x) = 0 the limit state and g(x) < 0 failure. All reliability methods of TesiproV use this convention.

For consistency across FORM and Monte Carlo reliability methods, limit-state functions must either accept a single numeric vector argument or explicitly named scalar arguments. The use of function(...) is not supported.

Fields

name: Optional human-readable name of the limit-state function.
expr: Symbolic expression (e.g. 'expression(f_ck - d_nom)') that is later converted to a callable function via 'ExpressionToFunction()'.
func: Actual R function implementing the limit-state equation. May be 'NULL' until defined by user or converted from 'expr'.
vars: List of 'PROB_BASEVAR' objects that provide the random variables.

Methods

ExpressionToFunction(): Transforms a valid expression into a objective function. Need the set of Variables with correct spelled names and IDs
check(): Checks all variables. You dont need to execute this, since the system object will do anyway.

Limit-State Function (LSF) API

A limit-state function must follow one of the two supported interface patterns:

function(x)

A single numeric vector argument x containing all basic variables in the order specified in vars.

Example:

    lsf$func <- function(x) {
      x[1] - sum((x[-1]^2) / seq_along(x)[-1])
    }

function(Z, Fy, M, ...)

Explicitly named scalar arguments corresponding to the variable names defined in vars.

Example:

    lsf$func <- function(Z, Fy, M) {
      Z * Fy - M
    }

The following form is not supported:

function(...)

Using ... as the sole argument leads to inconsistent behaviour between FORM-based and Monte Carlo-based reliability methods and is therefore prohibited.

For maximum robustness and compatibility across all reliability algorithms, the use of the vector form function(x) is recommended.

Author(s)

Examples

vars <- list(
  PROB_BASEVAR(Name = "f_ck", DistributionType = "norm", Mean = 30, Sd = 1),
  PROB_BASEVAR(Name = "d_nom", DistributionType = "norm", Mean = 0.2, Sd = 0.01)
)
lsf <- SYS_LSF(name = "Bending resistance", expr = expression(f_ck - d_nom), vars = vars)
lsf$ExpressionToFunction()
lsf$func(c(30, 0.2))

TesiproV documentation built on Oct. 28, 2026, 5:13 p.m.