namespace/module/Model/Checkout/LayoutProcessorPlugin

...

<?php

namespace Namespace\Module\Model\Checkout;

class LayoutProcessorPlugin
{
/**
 * @param \Magento\Checkout\Block\Checkout\LayoutProcessor $subject
 * @param array $jsLayout
 * @return array
 */

public function afterProcess(
    \Magento\Checkout\Block\Checkout\LayoutProcessor $subject,
    array  $jsLayout
) {
    $jsLayout['components']['checkout']['children']['steps']['children']['shipping-step']['children']
            ['shippingAddress']['children']['shipping-address-fieldset']['children']['street'] = [
        'component' => 'Magento_Ui/js/form/components/group',
        'label' => __('Street Address'),
        'required' => true,
        'dataScope' => 'shippingAddress.street',
        'provider' => 'checkoutProvider',
        'sortOrder' => 60,
        'type' => 'group',
        'additionalClasses' => 'street',
        'children' => [
                [
                'component' => 'Magento_Ui/js/form/element/abstract',
                'config' => [
                    'customScope' => 'shippingAddress',
                    'template' => 'ui/form/field',
                    'elementTmpl' => 'ui/form/element/input'
                ],
                'dataScope' => '0',
                'provider' => 'checkoutProvider',
                'validation' => ['required-entry' => true, "min_text_len‌​gth" => 1, "max_text_length" => 255],
            ],
                [
                'component' => 'Magento_Ui/js/form/element/abstract',
                'config' => [
                    'customScope' => 'shippingAddress',
                    'template' => 'ui/form/field',
                    'elementTmpl' => 'ui/form/element/input'
                ],
                'dataScope' => '1',
                'provider' => 'checkoutProvider',
                'validation' => ['required-entry' => false, "min_text_len‌​gth" => 1, "max_text_length" => 255],
            ]
        ]
    ];
    return $jsLayout;
    }
}