Two-way Slab Systems Research Articles

EVALUASI KINERJA STRUKTUR RANGKA BETON BERTULANG BALOK LEBAR DENGAN DISTRIBUSI BEBAN PELAT SATU DAN DUA ARAH

A reinforced concrete frame building system using wide beams is a solution for buildings with limited heights to get a larger number of stories, a higher distance between stories, and flexibility in installing architectural elements and MEP. This analytical study was conducted to evaluate the behavior and performance of open-frame structures with wide beams for one-way and two-way slab system conditions. This study was carried out using a structural analysis program by applying linear and nonlinear analyzes to four models of a five-story structure with square columns, which varied in beam dimensions and slab systems. The variations considered are normal beam with one-way slab system (1wSN), normal beam with two-way slab system (2wSN), wide beam with one-way slab system (1wSW), and wide beam with two-way slab system (2wSW). All structural elements are designed to follow and meet the criteria of the Indonesian Building Codes, which are then followed by a non-linear static pushover analysis to obtain the performance of each structural model. The results of the analysis show that a structure with wide beams has greater deformation than a structure with normal beams with a faster achievement of collapse conditions so that the ductility of the structure also becomes lower. This is caused by the stiffness of the wide beam-column joints is lower than that of the normal beam-column joints. The use of one-way or two-way slab systems on structures with wide beams does not have a significant effect

Geometry and restraint effects on the bending behaviour of the glass fibre reinforced polymer sandwich slabs under point load

The behaviour of structural glass fibre reinforced polymer (GFRP) composite sandwich slab was investigated under static point load. In this paper, the effects of dimensions aspect ratio, skin fibre orientations, overall thickness, boundary restraints, and boundary conditions on the static behaviour of the GFRP slab were presented. It was found that the ultimate load of the fibre composite sandwich slab is reducing with increasing panel dimension aspect ratio. The experimental results also showed that the fibre orientation of the skin has an effect on the failure mode and stiffness of the slab. As expected, the flexural stiffness of 18mm thick slab is higher than the 15mm thick slab. Finally, the restraint conditions did not affect much on the failure load and stiffness of the one-way and two-way slab systems.

긴장재배치에 따른 PT 이방향 슬래브의 거동에 대한 해석적 연구

본 논문에서는 이방향 포스트텐션 슬래브의 다양한 텐던의 배치에 따른 효과를 분석하기 위해서 유한요소법에 기반한 해석적 연구를 수행하였다. 등분포된 텐던의 배치에서부터 기둥의 중심선에 인접하게 배치되는 형태까지 연구범위를 설정하였고, 유한요소해석 상용 프로그램인 SAP에서 제공하는 휨-평면 요소를 사용하여 모델링을 하였다. 텐던 프로파일에 근거한 등가하중을 텐던 배치에 따라서 적용하였으며, 사용 하중 상태에서의 처짐과 순수 모멘트를 결정하기 위해 텐던에 대한 등가하중에 일반적인 중력하중이 부가되었다. 또한 해석 결과와 실험결과를 비교 분석하였다. In this paper, the FE analysis results are presented to evaluate the effects of various tendon layouts on the performance of post-tensioned concrete two-way slab systems. Various arrangements from uniform cable layouts to closely banded arrangements adjacent to column centerlines are considered. The slab is modeled using plate-bending elements in the software package SAP. Equivalent loads based on cable profiles are applied to the slab according to the tendon layout. Moment fields and deflected shapes are compared for the various tendon patterns. Gravity loads are applied in the usual way and superimposed on the results from the equivalent tendon loads to determine net moments and deflections at service load levels. In addition to a study of tendon layouts, the finite-element model is compared with experimental results.

Computer Program for Exact Analysis of Flat Slabs and Beam-Supported Slabs

Two-way slab structures, owing to their economical and architectural advantages, are used extensively in civil engineering. In addition, these systems not only resist gravity loads and transfer them to the columns, but also sometimes in combination with other structural members make a lateral resisting system. Elastic analysis of equivalent frame method is a precise and comprehensive method which is widely used for analysis of two-way slab structures. Because of non-prismatic sections of slab-beams and columns, carry over and stiffness factors and fixed end moments of members with constant moment of inertia could not be used. Some tables have presented these values for different types of the slab-beams, columns and torsional members. Due to low precision of these tables and complicated and time-consuming procedure of equivalent frame method, precise analysis of two-way slab systems using equivalent frame method including stiffness degradation in all members, using slope-deflection equations, in the form of a prepared software is pursued in this research. Two analyses of example structures were performed and the efficiency and accuracy of the program were verified by comparing the hand-calculated results, results of a finite element approach and the developed computer program's results, which shows some differences in the support moments.

A modified equivalent frame method for lateral load analysis

The equivalent frame method (EFM) was developed for two-way slabs as a simple approximate method. Current design codes (ACI 318-05, Eurocode 2 and BS 8110) permit the EFM for the analysis of two-way slab systems under gravity loads, as well as lateral loads such as seismic loads. The EFM, however, was developed based on a semi-empirical formula, derived from the behaviour of two-way slab systems under gravity loads. This study shows that the EFM is not appropriate in accurately predicting the response of two-way slab systems under lateral loads. To improve the EFM under lateral loads, this study proposes a modified equivalent frame method (MEFM). To verify the MEFM, an idealised two-storey flat plate frame is considered and analysed by both the MEFM and elastic finite-element (FE) analysis for estimating slab moments and lateral drifts. Analysis results obtained from the conventional EFM and effective beam width method (EBWM) are also compared. The lateral stiffness, based on the proposed MEFM, was also compared with experimental data.

Applicability of Code Design Methods to RC Slabs on Secondary Beams. Part I: Mathematical Modeling

The behavior and the appropriate method of analysis for two-way slab systems supported by a grid of main and secondary beams are not fully understood. The overall objective of this two-part study is to investigate the applicability of the ACI code methods for evaluation of design moments for such slab systems. This part analyzes five beam-slab-systems of different configurations through the code and finite element procedures. One slab system was without secondary beams while the remaining four have secondary beams with bearing beam- to-slab depth ratios from 2.6 to 5. The secondary beams were found to reduce the floor weight by upto 30 % when the five slab systems were of equal stiffness. However, achieving slab-systems of equal stiffness is not straightforward and cannot be evaluated from section properties only. It was found that derivation of equal stiffness of the slab systems based on section properties alone resulted in an error of 38 % in computed deflection. In beam-slab systems, the rib projection of the beam poses a modeling challenge. Two options were considered: physical offset with rigid link option or equivalent beam option in which the size of the beam was increased to compensate for the rib offset. In this part the study, the advantages and drawbacks of both modeling approaches are discussed.

Deflection Control of Two-Way Reinforced Concrete Slabs

Limitation of midpanel deflection is an essential performance design of two-way slab systems. Two alternative design procedures for deflection control are presented in this paper. One procedure with fewer parameters is written in a format of the minimum thickness requirements. The other, allowing more flexibility in choices, involves the direct calculation of midpanel deflections. Both procedures suggested herein are simple; however, various factors influencing deflections of two-way slab systems (i.e., loading intensity, slab geometrical configuration, material properties, cracking phenomenon, slab discontinuity, long-term effects, and allowable deflection limits) are also considered. These techniques are provided with illustrative examples as well as comparisons with both the available experimental data and ACI 318-89 being made.

Practical Estimation of Two-Way Slab Deflections

The calculation of the deflection of a reinforced concrete element is usually troublesome, and is even more problematic for two-way slabs than for beams. An algebraic equation was developed in this paper for estimating the midpanel deflections of the two-way slab systems subjected to uniform gravity loads. The proposed method was initially derived from the differential equation of plate and then calibrated using the results of finite-element analyses to estimate the elastic deflections of interior panels. The proposed procedure was further directed toward the general problem concerning progressive cracking of concrete, varied boundary conditions due to discontinuity of slab, and long-term effects. The resulting expression provides a more accurate representation of the midpanel deflection than does the simpler method outlined in the ACI Committee 435 report. The adequacy of the proposed procedure was checked by comparing calculated deflections with experimental data reported in previous literature, and sat...

An expert system for the design of post-tensioned flat plates

This paper describes an expert system for the structural design of post-tensioned concrete flat plates. A brief review of prestressed concrete theory and design procedures for two-way slab systems is presented, and the expert system shell is described. The shell used to develop the expert system is one designed for business applications, and the objective of this study was to investigate the feasibility of using it for engineering design applications. As an illustrative example, the program is used to design a four-bay by three-bay floor system.