Design for earthquake-resistent reinforced concrete structural walls (original) (raw)
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Design for earthquake-resistant short RC structural walls
The application of the compressive force path method for the design of earthquake-resistant reinforced concrete structural walls with a shear span-to-depth ratio larger than 2.5 has been shown by experiment to lead to a significant reduction of the code specified transverse reinforcement within the critical lengths without compromising the code requirements for structural performance. The present work complements these findings with experimental results obtained from tests on structural walls with a shear span-to-depth ratio smaller than 2.5. The results show that the compressive force path method is capable of safeguarding the code performance requirements without the need of transverse reinforcement confining concrete within the critical lengths. Moreover, it is shown that ductility can be considerably increased by improving the strength of the two bottom edges of the walls through the use of structural steel elements extending to a small distance of the order of 100 mm from the wall base.
Seismic design of structural concrete walls: an attempt to reduce reinforcement congestion
Magazine of Concrete Research, 2007
Non-linear finite-element analysis is used for a comparative study of the behaviour of two types of structural concrete walls: walls W1 with a value of the shear span-to-depth ratio between 1 and 2; and walls W2 with a value of the above ratio larger than 2. The walls, which are subjected to static (monotonic and cyclic) and dynamic (seismic excitation) loading, have the same geometry and vertical reinforcement details but differ in the horizontal reinforcement arrangement, the latter designed either in compliance with the earthquake-resistant design clauses of current codes or in accordance with the method of the compressive force path. The results obtained indicate that adopting the latter method yields significantly more efficient design solutions without compromising the code performance requirements.
Numerical modelling and capacity design of earthquake-resistant reinforced concrete walls
1993
Reinforced concrete structural walls constitute an important unit for the resistance of buildings against seismic action. In order to successfully design structures against earth¬ quakes, it is therefore of interest to develop a numerical model which simulates the typical behaviour of these units. This report is concerned with numerical models intended to be used in analysis of complete buildings, with focus on capacity designed multi storey buildings. A major part of the report is devoted to the development of a new macro model which simulates the highly nonlinear behaviour of structural walls based upon relatively simple kinematics and physical behaviour. The formulation of a macro element is presented. As a complement to the macro model, a micro model is derived with which it is attempted to treat the behaviour of the different material components of a structural wall in a relatively detailed manner, yet also based upon physical observations. The models are implemented into a general finite element code and extensive tests are presented including comparisons with experimental data. An important part of the report deals with the capacity design of structural walls. Performance checks are carried out on capacity designed walls by means of the newly developed macro model. It is shown that the dynamic curvature demand in the plastic hinge may be different than suggested in the existing capacity design procedure, when varied over different wall aspect ratios. It is further shown that during nonlinear time history analysis flexural yielding may frequently take place in the upper storeys of the wall which are intended to remain elastic, when the existing capacity design procedures are used. It is also shown that the dynamic shear forces may be larger than anticipated by existing capacity design assumptions. An improved distribution of flexural strength over the height of the wall is proposed, which clearly reduces the risk of unintended yielding in the upper storeys.
Proceedings of the 15th World Conference on Earthquake Engineering, 15th WCEE 2012, 2012
One important aspect of seismic design of buildings with a dual reinforced concrete structural system is the lateral stability of structural walls, when they face this danger basically due to flexural overstrain. The deep excursion in the yield region of the boundary parts of bearing walls increases dramatically their flexibility and since at the same time they are liable, because of the earthquake vibration, to a reversing axial loading (tension-compression), their lateral stability is at stake. The possibility of failure because of lateral instability is limited significantly with the proper choice of an adequate thickness, which is specified by (most) modern seismic codes as a percentage of the height of the bottom storey. The current work investigates one of the most basic parameters affecting the stability of structural walls, which is (apart from the wall thickness) the ratio of the longitudinal reinforcement of the boundary edges of load-bearing walls. The present work is experimental. It has to be noted that in order to examine experimentally the influence of the longitudinal reinforcement ratio, 11 test specimens of scale 1:3 simulating the boundary edges of structural walls were used. These specimens were reinforced with different longitudinal reinforcement ratios (varying from 1,79% to 10,72%). The degree of tension strain which was applied was the same for all specimens and equal to 30‰. The present article tries to investigate the influence of the ratio of longitudinal reinforcement to the ultimate bearing capacity of test specimens.
Assessment of Shear Wall Quantity in Seismic-Resistant Design of Reinforced Concrete Buildings
Arabian Journal for Science and Engineering, 2012
ABSTRACT It is common to design reinforced concrete buildings with shear walls to resist seismic loads. In the present study, an easy to apply analytical method has been proposed to determine the amount of shear walls necessary to make reinforced concrete buildings seismic-resistant against moderate to severe earthquakes. The method is based on the following design strategy: (1) The total design base shear must be resisted by shear walls; (2) Equal amounts of shear walls must be placed in both orthogonal directions of the structure; and (3) The moment resisting frame elements, which are beams and columns, must independently be able to resist 25 % of the total design base shear. For such a system, the ratio of the total area of shear walls to the area of the floor plan has been obtained by equating the total design base shear to the total shear resistance provided by all shear walls in one direction. Because seismic action may occur in any direction, equal amount of shear walls is recommended to provide in the two orthogonal directions. A procedure is also presented to check the stiffness (or storey drift) requirement for the determined amount of shear walls. The complete analytical procedure was demonstrated by implementing it on a 10 storey 3-D reinforced concrete building.
The Calculation of Reinforced Concrete Walls Under Seismic Action
2002
The fact that theoretical basis and research of cast in place house building lagged behind the demands that arose in design and construction is explained by intensive development of cast in place house-building in many seismic regions of the world. The negative effect of the delay is expressed in a number of ways. First, in some cases in designing cast in place buildings specific quantities of metal were unjustifiably increased due to application of standard reinforcement principles, which had been developed using the results of research of mainly column structures. Second, the absence of justified principles of design of cast in place buildings, which incorporate both specifics of their construction and the work under loading, caused unsatisfactory behavior of such buildings during earthquakes. By the way as an example, a number of high-rise cast in place buildings in Moldova were damaged heavily during the Carpathian earthquake of 1986. The above facts explain the author’s wish to...
Seismic behaviour of RC walls: an attempt to reduce reinforcement congestion
Magazine of Concrete Research, 2011
Non-linear finite-element analysis is used for a comparative study of the behaviour of two types of structural concrete walls: walls W1 with a value of the shear span-to-depth ratio between 1 and 2; and walls W2 with a value of the above ratio larger than 2. The walls, which are subjected to static (monotonic and cyclic) and dynamic (seismic excitation) loading, have the same geometry and vertical reinforcement details but differ in the horizontal reinforcement arrangement, the latter designed either in compliance with the earthquake-resistant design clauses of current codes or in accordance with the method of the compressive force path. The results obtained indicate that adopting the latter method yields significantly more efficient design solutions without compromising the code performance requirements.
Ductile Design of Slender Reinforced Concrete Structural Walls
2014
Slender reinforced concrete structural walls are commonly used in mid- to high-rise buildings as a main lateral load resisting element in earthquake regions. Past research has shown these walls to be efficient and effective in limiting the building lateral drifts due to their large in-plane stiffness. However, the damage sustained by concrete walls in recent earthquakes have demonstrated that current design requirements of these walls may need modifications, which is further supported by a NEES experimental study completed on slender concrete walls. To further understand the behavior of concrete walls and address the shortcomings of the current design requirements, an analytical study was conducted on slender rectangular concrete walls designed according to ACI 318-11. First, a simplified computational method to estimate force-displacement response of a structural wall, utilizing the moment-curvature relationship, was developed and validated using experimental data. Next, the influe...
Earthquake Design of Buildings with Large Lightly Reinforced Concrete Walls
2014
Eurocode 8 part1 (CEN, 2004) includes some specific design provisions for buildings with large lightly reinforced concrete walls, which is an alternative way of design compared to the traditional design method with shear walls detailed to dissipate energy through hysteresis in plastic hinges at their base. This work attempts to quantify the effect of rocking of the foundations in reducing the forces acting on the vertical bearing elements in case of buildings that comply to the criteria of Eurocode 8 so that they may be designed as structures with large lightly reinforced concrete walls. A typical rectangular layout was analysed with 3, 4 and 5 storeys and for three different ground types, B, C and D. Isolated foundations were chosen for all vertical elements, so as to enable rocking of the walls. The results are discussed.
Seismic performance of lightly reinforced structural walls for design purposes
Magazine of Concrete Research, 2013
Lightly reinforced concrete walls are commonly found in low-to-moderate seismic regions such as Australia. While many theoretical analyses on lateral load–displacement of structural walls have been proposed and widely used, not many have been developed for lightly reinforced concrete walls. The lateral load–displacement behaviour and failure mechanism of lightly reinforced structural walls differ to those of heavily reinforced concrete walls, particularly in terms of tension stiffening effects, possible failure mechanisms and drift capacities. An analytical study on lightly reinforced rectangular concrete walls is presented in this paper. A parametric study was conducted to provide initial insight into the effect of four design parameters (aspect ratio, axial load ratio, transverse reinforcement ratio and longitudinal reinforcement ratio) on the ultimate displacement capacity of reinforced concrete walls. Two analytical models were developed to predict the lateral load–displacement ...