抄録
In reinforced concrete (RC) buildings, RC walls are often used as outer walls and inner walls. This wall has the effect of increasing the strength and rigidity of adjacent columns and beams. However, the column/beam to which these walls are attached has complicated shape and arranging reinforcements as compared with a single column beam member, and it is not easy to evaluate strength and rigidity. For this reason, in recent RC buildings, a structure gap is provided between column/beam and adjacent RC walls. It is common to direct designs to behave and design without considering an increase in strength and rigidity by these walls as much as possible.
It is certain that it is one solution of earthquake-resistant design to frequently use the structural gap and to ensure the required seismic performance by expecting the ductility by bringing the behavior of the building closer to the moment frame. However, in the case of the past earthquake damage, cases where damage was not escaped but expected to be tough, but there were cases where the damage was remarkably damaged, and based on the fact that the strength type building like the so-called wall type structure is less damaged, It is desirable that a design that effectively utilizes the walls and secures the strength and rigidity of buildings to ensure necessary earthquake resistance performance while suppressing damage is also a promising option. For that purpose, no structural gap is provided. Establishment of a simple design method for buildings expected to increase strength and rigidity by RC walls is required.
In this paper, the author evaluated the ultimate flexural strength of the RC beams with spandrel walls when performing earthquake-resistant design by load-carrying capacity calculation.
1) In view of the fact that the beams with spandrel walls tend to deteriorate immediately after reaching the maximum flexural strength, it is desirable to secure the required horizontal strength of the building due to the ultimate flexural strength lower than the actual strength. On the other hand, for the shear design and the collapse mechanism guarantee design, an ultimate bending strength formula that can evaluate the upper limit of the actual strength is also desired.
2) Assuming the compressive stress distribution of concrete to be a triangle distribution, considering the tension force of the compression side beam reinforcement based on the compatibility of the strain, proposed the approximate expression formula for evaluating the lower ultimate flexural strength (equation (5)). It was confirmed that the lower limit of strength can be well evaluated.
3) Approximate expression formula (equation (6)) for evaluating the upper ultimate flexural strength based on perfect plasticity theory was proposed. In this formula, we confirmed that the upper limit of the actual strength of the beams with spandrel walls can be evaluated roughly by considering the influence of the local compressive strength of the concrete considerably by the constraint of the concrete.
