The Effect of Lateral Loading on Civil Structures

Most civil engineering structures undergo some form of lateral load during their useful life. The load caused by an earthquake, wind, or explosion mainly causes lateral displacement of the structure. The effect of the gravitational load acting through the lateral displacement of the structure is called the P - Δ effect. This effect can cause a vicious cycle on the structural system, as the effect of gravitational load increases with increasing lateral displacement and at the same time the lateral displacement is amplified due to the gravitational load acting on them.

P delta effect - As the lateral displacement increases, the effective lateral load increases and the seismic performance decreases. The P delta effect further increases the lateral displacement, increasing the requirements on the structural system. This effect means a sharp change in the ground shearing force, overturning moment, and axial force distribution. Therefore damage will occur earlier than similar systems without significant P-delta effect. This effect is very important because the RC structure is heavier than the steel structure.

In high-rise buildings, lateral loading becomes increasingly important parameter and it is thought that it will have an important influence on the overall planning and design of the building. Side stabilization systems are often located in the central center and caution must be carefully integrated into the structure. The main lateral load is usually due to seismic load or wind. In building stability assessment, two main criteria are used: drift and acceleration. Drift is the ratio at which the building deflects beyond its height. Secondly, the important parameter is usually drift in the middle layer (floor to floor), not the drift of the whole building. The acceleration of the building is a measure of the speed at which the drift occurs, and the acceptance criterion is based on the tolerance for human movement.

Under normal conditions, the building's walls, pillars, and beams receive mainly vertical compressive loads. However, lateral loads and shear loads are generated during the earthquake, and tension and twisting forces are generated in the structural elements. These forces cause large stresses in the corners of the building and various joints. A strong joint is important to construct a structure that can withstand the shear loads during the earthquake. Since the stress concentrates at the joint between the walls, all joints must be properly prepared and reinforced. The joint of concrete must also be compressed and secured properly in order to obtain optimum strength. In unreinforced masonry joints (mortar seams as found in brick buildings) it is especially important to fix between adjacent walls.