Probabilistic fiber element modeling of reinforced concrete structures

A computational model based on a stochastic fiber element model is developed in this study. This model can be utilized for probabilistic evaluation of reinforced concrete (RC) members. The stochastic fiber element model is developed by combining the conventional fiber element formulation and the midpoint method for random field representation, to account for spatial variability of material and geometrical properties within a structural member. Three verification examples show the capability of the developed model in estimating the nonlinear structural behavior including softening. As an application of the developed computational model, a probabilistic strength analysis of a RC column is conducted in terms of the axial load-bending moment interaction. An approach of evaluating RC structural systems using the developed probabilistic computational model is also presented.     

State of the art in damage information modeling for RC bridges – A literature review

In Germany, bridges have an average age of 40 years. A bridge consumes between 0.4% and 2% of its construction cost per year over its entire life cycle. This means that up to 80% of the construction cost are additionally needed for operation, inspection, maintenance, and destruction. Current practices rely either on paper-based inspections or on abstract specialist software. Every application in the inspection and maintenance sector uses its own data model for structures, inspections, defects, and maintenance. Due to this, data and properties have to be transferred manually, otherwise a converter is necessary for every data exchange between two applications. To overcome this issue, an adequate model standard for inspections, damage, and maintenance is necessary. Modern 3D models may serve as a single source of truth, which has been suggested in the Building Information Modeling (BIM) concept. Further, these models offer a clear visualization of the built infrastructure, and improve not only the planning and construction phases, but also the operation phase of construction projects. BIM is established mostly in the Architecture, Engineering, and Construction (AEC) sector to plan and construct new buildings. Currently, BIM does not cover the whole life cycle of a building, especially not inspection and maintenance. Creating damage models needs the building model first, because a defect is dependent on the building component, its properties and material. Hence, a building information model is necessary to obtain meaningful conclusions from damage information. This paper analyzes the requirements, which arise from practice, and the research that has been done in modeling damage and related information for bridges. With a look at damage categories and use cases related to inspection and maintenance, scientific literature is discussed and synthesized. Finally, research gaps and needs are identified and discussed.     

Nonlinear analysis of reinforced concrete structures

For the prediction of yield and failure of concrete under combined stress, a generalization of the Mohr-Coulomb behavior is made in terms of the principal stress invariants. The generalized yield and failure criteria are developed to account for the two major sources of nonlinearity: the progressive cracking of concrete in tension, and the nonlinear response of concrete under multiaxial compression. Using these criteria, incremental stress-strain relationships are established in suitable form for the nonlinear finite element analysis.For the analysis of reinforced concrete members by finite elements, a method is introduced by which the effect of reinforcement is directly included. With this approach, the stress-strain laws for the constituent materials of reinforced concrete are uncoupled permitting efficient and convenient implementation of a finite element program. The applicability of the method is shown on sample reinforced concrete analysis problems.     

Minimum-cost design of reinforced concrete structures

The aim of this paper is to obtain minimum-cost designs of reinforced concrete structures in conformity with the requirements of the Australian Standard AS3600-1988. The minimum cost structure is such that all its appropriate functional states (stability, strength, serviceability, durability and fire resistance) are within the allowable performance limits. The total cost minimized includes the costs of concrete, reinforcing steel and framework. The minimum-cost problem is formulated as a non-linear programming problem whose solution is attempted by two techniques. Several numerical examples of multi-span beams and of columns are given using a computer package developed in standard FORTRAN77. The sensitivity of the minimum-cost designs to variations in the relative cost of formwork is also studied.     

Minimum cost design of reinforced concrete structures

The aim of this paper is to demonstrate how the traditional design process can be imitated mathematically to arrive at designs of reinforced concrete structures which conform to the requirement of the new Australian Standard AS3600-1988 and are the least expensive to construct. The total cost includes the costs of concrete, reinforcing steel and formwork. The minimum cost problem is formulated as a non-linear programming problem whose solution is attempted by two techniques. Several numerical examples of multi-span beams and of columns are given using a computer package developed in standard FORTRAN 77. The sensitivity of the minimum cost designs to variations in the relative cost of formwork is also studied.     

Construction-specific spatial information reasoning in Building Information Models

In recent years, there have been significant advances in modeling technology for object-oriented building products. However, the building models are still lacking of providing construction-specific spatial information required for construction planning. Consequently, construction planners visually analyze building product models and derive geometric characteristics such as bounded spaces and exterior perimeter to develop detailed construction plans. Such a process presents fragmented information flows, from building product information to construction planning, that rely on subjective decisions of construction planners. In order to overcome these drawbacks, this research proposes a geometric reasoning system that analyzes geometric information in building designs, derives the construction-specific spatial information, and uses the information to assist in construction planning. The scope of presented work includes detecting work packages formed by faces during construction, such as large work faces and bounded spaces, and using information in the work packages directly to support planning of selected indoor construction activities. The main features of the proposed system named Construction Spatial Information Reasoner (CSIR) include a set of relationship acquisition algorithms, building component relationship data structure, and interpretation of the relationship to support detailed construction activity planning. The relationship acquisition algorithms identify adjacency between building components that is stored in the relational data structure. Then, acquired adjacency relationships are transformed into a set of graphs that represent work packages. To implement the proposed approach, CSIR utilized a commercially-available Building Information Modeling (BIM) platform and the algorithms were imbedded to the BIM platform. For validation, CSIR was tested on a real commercial building. For interior ceiling grid installation activities, CSIR successfully detected existing work packages and analyzed the spatial characteristics impacting construction productivity. The major contribution of the presented research would be to enable a realistic analysis of building geometric condition that is not possible in current BIM and a seamless information flow from building product information to construction process plans. These can potentially reduce current manual and error-prone construction planning processes. Limitations and future research suggestions are also presented.     

Design optimization of 3D reinforced concrete structures

This paper presents a computer-based method for the optimal design of three-dimensional reinforced concrete (RC) skeletal structures having members subjected to biaxial moments, biaxial shears and axial loads. The width, depth and area of longitudinal reinforcement of member sections are taken as the design variables. The optimality criteria (OC) method is applied to minimize the cost of the concrete, steel and formwork for the structure. The primary focus of the paper concerns fundamental issues related to the formulation of design performance constraints on combined axial load, biaxial moments and biaxial shears. An example problem is solved with and without account for biaxial shear constraints to illustrate their influence on the design.     

BIM 和GIS 的空间语义数据集成方法及应用研究

随着数字城市和智慧城市的建设发展,建筑信息模型(BIM)和地理信息系统(GIS)的集成被广泛研究和应用。目前的集成研究主要是通用数据标准IFC 和CityGML 之间的空间和语义转换,但由于应用领域和空间尺度等差异,存在信息错误和丢失、几何语义信息耦合度低、应用拓展性差等问题。为此提出了一种兼顾三维实体对象和地理空间对象的三维城市数据模型,研究了BIM 和GIS 的空间和语义数据的提取、处理和转换方法,设计了BIM 和三维GIS 的集成应用框架并在三维可视化平台上进行验证和初步应用。该方法可实现BIM和GIS 信息在几何、语义、精度上的完全融合,避免了传统的数据转换带来的信息缺失,在多尺度的空间和语义信息分级存储和加载显示方面存在着优势,有利于实现大规模、高精度的建筑和城市信息的高效集成。     

Fuzzy set based crack diagnosis system for reinforced concrete structures

This paper presents a computer assisted crack diagnosis system for reinforced concrete structures which aids the non-expert to diagnose the cause of cracks at the level of an expert in the general inspection of structures. The system presented adapts fuzzy set theory to reflect fuzzy conditions, both for crack symptoms and characteristics which are difficult to treat using crisp sets. The inputs to the system are mostly linguistic variables concerning the crack symptoms and some numeric data about concrete and environmental conditions. Using these input data and based on built-in rules, the proposed system executes fuzzy inference to evaluate the crack causes under consideration. The built-in rules were constructed by extracting expert knowledge, primarily from technical books about concrete and concrete cracks. We implemented the proposed system in a computer program with a graphic user interface for actual utilization in practical business fields. When applied to cracks actually diagnosed by experts, the proposed system provided results similar to those obtained by experts, and we expect that this system can be used as an effective crack diagnosis tool for both experts and non-experts in the regular inspection of RC structures.     

Performance based earthquake evaluation of reinforced concrete buildings using design of experiments

Seismic resiliency of new buildings has improved over the years due to enhancements in seismic codes and design practices. However, existing buildings designed and built under earlier codes are vulnerable and require a performance-based screening and retrofit prioritization. The performance modifiers considered are soft story, weak story, and the quality of construction, which are collated through a walk down survey. The building evaluation is performed through a pushover analysis, and performance objective are obtained through initial stiffness of the pushover curve. Using a design of experiments technique, a reliable system input-output relation has been identified and used to evaluate the performance criteria at untried design points (i.e., buildings with different modifier values). The proposed method of performance based evaluation is illustrated through consideration of the different structural deficiencies on a typical six-storey reinforced concrete building in Vancouver. Through the designed experiments, the main and interaction effects of the performance modifiers have also been studied.     

Design optimization of 3D reinforced concrete structures having shear walls

This paper presents a computer-based method for the optimal design of three-dimensional Reinforced Concrete (RC) structures having beams subjected to shear force and bending moment, columns subjected to biaxial moments, biaxial shears and axial loads, and shear walls subjected to pure shear. Regarding the beams and columns, the design variables are the width, depth and area of longitudinal reinforcement of member sections. The design variables for the shear walls are the thickness of the wall, the area of vertical reinforcement, horizontal distance between the vertical stirrups, the area of horizontal reinforcement, vertical space between the horizontal stirrups, and the area of vertical flexural reinforcement. The Optimality Criteria (OC) method is applied to minimize the cost of the concrete, steel and formwork for the structure. ACI code [1] provisions concerning the strength and ductility of beams, columns and shear walls are taken as constraints. The constraints also impose upper and lower bounds on the dimensions of beams and columns, and on shear wall thickness, reinforcement area and the maximum and minimum vertical and horizontal spaces between the stirrups of the shear walls. Sensitivity analysis is conducted for both internal forces and the capacities of the sections of the beams, columns and shear walls. The features of the design method are illustrated by a solved example.     

Automatic design and planning of scaffolding systems using building information modeling

Considering their significant impact on construction projects, scaffolding as part of the temporary facilities category in construction must be thoroughly designed, planned, procured, and managed. The current practices in planning and managing scaffolding though is often manual and reactive, especially when a construction project is already underway. Widespread results are code compliance problems, inefficiency, and waste of procuring and managing material for scaffolding systems. We developed a rule-based system that automatically plans scaffolding systems for pro-active management in Building Information Modeling (BIM). The scope of the presented work is limited to traditional pipe and board scaffolding systems. A rule was prepared based on the current practice of planning and installing scaffolding systems. Our computational algorithms automatically recognize geometric and non-geometric conditions in building models and produce a scaffolding system design which a practitioner can use in the field. We implemented our automated scaffolding system for a commercially-available BIM software and tested it in a case study project. The system thoroughly identified the locations in need of scaffolding and generated the corresponding scaffolding design in BIM. Further results show, the proposed approach successfully generated a scaffolding system-loaded BIM model that can be utilized in communication, billing of materials, scheduling simulation, and as a benchmark for accurate field installation and performance measurement.     

Rough set algorithm for crack category determination of reinforced concrete structures

Rough set theory is a new mathematical approach to imprecision, vagueness and uncertainty in data analysis. This paper presents a new approach to rough set theory in determining the category of crack causes for insufficient and imprecise crack characteristics observed in regular inspection of concrete structures. The categories of crack causes are classified into four classes, that is, (1) concrete material, (2) construction work, (3) service and environmental factors, and (4) structure and applied loads. The crack characteristics include time of formation, shape, regularity, cause of concrete deformation, and range. The decision table was constructed considering crack characteristics as condition attributes and the categories of crack causes as decision attributes. A minimal decision algorithm for this decision table was generated on the basis of rough set theory; the algorithm is equivalent to the original decision table, but requires minimum subsets of condition attributes. It turned out in determining the category of crack causes that, “time of formation” had the most important influence among crack characteristics, and “shape” could be omitted with the least influence on diagnosis.     

Behavior of reinforced concrete structures predicted by the finite element method

With current nonlinear analysis computer capabilities, considerable strides are being made in developing procedures, the utilization of which, allows one to analyze reinforced concrete structures while taking into account cracking and other characteristics of the constituent materials. Objective of the analyses is the determination of displacements as well as concrete and steel forces at various stages of loading. Cracking and the consequent loss of tensile strength is a major characteristic that must be modeled in any program for the analysis of reinforced concrete members. The three basic approaches have been employed by various investigators to account for tension cracking are discussed. Advantages and problems associated with these approaches are discussed. The formulation used to delineate compressive stress characteristics of concrete is evaluated. Solution procedures are described. Peculiarities required of solution methods in order to be suitable for the analysis of reinforced concrete systems are noted.     

电子信息管理平台构建过程分析

电子信息管理平台是当今组织重要的一项管理工具,构建高效的信息管理平台对于提升企业管理水平和管理效率具有重要意义。本文阐述了建立电子信息管理平台前的准备工作和电子信息管理平台的设计开发过程。     

BIMQL – An open query language for building information models

In this paper we present the on-going development of a framework for a domain specific, open query language for building information models. The proposed query language is intended for selecting, updating and deleting of data stored in Industry Foundation Classes models. Even though some partial solutions already have been suggested, none of them are open source, domain specific, platform independent and implemented at the same time. This paper provides an overview of existing approaches, conceptual sketches of the language in development and documents the current state of implementation as a prototype plugin developed for the open source model server platform bimserver.org. We report on the execution of example test-cases to show the general feasibility of the approach chosen.     

Finite element analysis of reinforced and prestressed concrete structures including thermal loading

This paper describes the application of finite element techniques to the solution of nonlinear concrete problems. Reinforced concrete thick plates and shells are first considered for which both a perfect and strain-hardening plasticity approach are employed to model the compressive behaviour. A dual criterion for yielding and crushing in terms of stresses and strains is considered, which is complemented with a tension cut-off representation. Degenerate thick shell elements employing a layered discretisation through the thickness are adopted and both reduced and selectively integrated 8-node serendipity and heterosis elements are considered.Thermal loading of prestressed concrete structures is also considered which necessitates the inclusion of time effects in the analysis. The technique described in this paper involves concurrently solving an uncoupled set of equations within a time interval to provide both the displacement and temperature increments. A two-level time stepping scheme is employed to predict temperature changes within a time interval and elasto-viscoplastic material analysis is performed using an explicit forward-difference scheme incorporating an equilibrium iteration procedure. The constitutive model for the concrete is essentially identical to that employed for the plate and shell analysis.Numerical examples are presented for both types of analysis and comparison is made with experimental results whenever possible. Additionally, results for thermal loading are presented which indicate that a full transient thermal-mechanical analysis is sometimes essential in order to obtain a realistic structural response.     

Asymptotic modeling of quasi-brittle interfaces

This study deals with the damage modeling of quasi-brittle interfaces such as the mortar/brick interfaces present in masonry walls. For this purpose, a model is developed based on a bulk model presented by Gambarotta and Lagomarsino, which takes the damage to the mortar joint into account. A quasi-fragile damage interface model is introduced using an asymptotic technique. This model memorizes some of the geometrical and mechanical characteristics of the interface, such as the thickness, elastic coefficients, normal and tangential stress, and the damage variable. Numerical simulations are performed using the Gyptis finite element software: academic cases involving traction and shear loads are presented.